perovskite solar cell

The raw materials used and the possible fabrication methods (such as various printing techniques) are both low-cost.{{cite journal|author1=Stefano Razza|author2=Sergio Castro-Hermosa|author3=Aldo Di Carlo |author4=Thomas M. Brown |title=Research Update: Large-area deposition, coating, printing, and processing techniques for the upscaling of perovskite solar cell technology|journal=APL Materials|date=2016|volume=4 |issue=91508|page=091508 |doi=10.1063/1.4962478 |bibcode=2016APLM....4i1508R|doi-access=free}} Their high absorption coefficient enables ultrathin films of around 500 nm to absorb the complete visible solar spectrum.{{cite journal |author1=Wan-Jian Yin|author2=Tingting Shi|author3=Yanfa Yan |title=Unique Properties of Halide Perovskites as Possible Origins of the Superior Solar Cell Performance |journal=Advanced Materials|date=15 May 2014|volume=26 |issue=27|pages=4653–4658 |doi=10.1002/adma.201306281 |pmid=24827122|bibcode=2014AdM....26.4653Y |s2cid=27113056}} These features combined result in the ability to create low-cost, high-efficiency, thin, lightweight and flexible solar modules. Perovskite solar cells have found use in powering prototypes of low-power wireless electronics for ambient-powered Internet of things applications,{{cite journal|author1=Sai Nithin R. Kantareddy|author2=Ian Mathews |author3=Shijing Sun|author4=Mariya Layurova|author5=Janak Thapa|author6=Juan-Pablo Correa-Baena |author7=Rahul Bhattacharyya Tonio Buonassisi|author8=Sanjay E. Sarma|author9=Ian Marius Peters |title=Perovskite PV-powered RFID: enabling low-cost self-powered IoT sensors |journal=IEEE Sensors Journal |year=2019|volume=20|issue=1 |pages=471–478 |doi=10.1109/JSEN.2019.2939293|bibcode=2020ISenJ..20..471K |arxiv=1909.09197|s2cid=202712514}} and may help mitigate climate change.{{cite journal |last1=O’Connor |first1=David |last2=Hou |first2=Deyi |title=Manage the environmental risks of perovskites |journal=One Earth |date=November 2021 |volume=4 |issue=11 |pages=1534–1537 |doi=10.1016/j.oneear.2021.11.002 |bibcode=2021OEart...4.1534O |s2cid=244430089|doi-access=free }}

Perovskite cells also possess many optoelectrical properties that benefit their use in solar cells. For example, the exciton binding energy is small. This allows electron holes and electrons to be easily separated upon the absorption of a photon. Moreover, the long diffusion distance of the charge carrier and the high diffusivity – the rate of diffusion – allow the charge carriers to travel long distances within the perovskite solar cell, which improves the chance of it to be absorbed and converted to power. Lastly, perovskite cells are characterized by wide absorption ranges and high absorption coefficients, which further increase the power efficiency of the solar cell by increasing the range of photon energies that are absorbed.{{cite journal |last1=Chen |first1=Xiang |last2=Zhou |first2=Hai |last3=Wang |first3=Hao |title=2D/3D Halide Perovskites for Optoelectronic Devices |journal=Frontiers in Chemistry |date=2021 |volume=9 |pages=715157 |doi=10.3389/fchem.2021.715157 |pmid=34490208 |pmc=8416683 |bibcode=2021FrCh....9..679C |issn=2296-2646 |doi-access=free }}

File:CH3NH3PbI3 structure.png

The name "perovskite solar cell" refers to the ABX₃ crystal structure of the absorber materials, called perovskite structure, where A and B are cations and X is an anion. A cations with radii between 1.60 Å and 2.50 Å have been found to form perovskite structures.{{cite journal|last1=Park|first1=N.-G.|title=Perovskite solar cells: an emerging photovoltaic technology|journal=Materials Today|date=2015|volume=18|issue=2|pages=65–72|doi=10.1016/j.mattod.2014.07.007|doi-access=free}} The most commonly studied perovskite absorber is methylammonium lead trihalide (CH₃NH₃PbX₃, where X is a halogen ion such as iodide, bromide, or chloride), which has an optical bandgap between ~1.55 and 2.3 eV, depending on halide content. Formamidinium lead trihalide (H₂NCHNH₂PbX₃) has also shown promise, with bandgaps between 1.48 and 2.2 eV. Its minimum bandgap is closer to the optimal for a single-junction cell than methylammonium lead trihalide, so it should be capable of higher efficiencies. The first use of perovskite in a solid-state solar cell was in a dye-sensitized cell using CsSnI₃ as a p-type hole transport layer and absorber.{{cite journal|last1=Chung|first1=I.|last2=Lee|first2=B.|last3=He|first3=J.|last4=Chang|first4=R.P.H|last5=Kanatzidis|first5=M.G.|title=All-Solid-State Dye-Sensitized Solar Cells with High Efficiency|journal=Nature|date=2012|volume=485|issue=7399|pages=486–489|doi=10.1038/nature11067|pmid=22622574|bibcode=2012Natur.485..486C|s2cid=4420558}} A common concern is the inclusion of lead as a component of perovskite materials; solar cells composed from tin-based perovskite absorbers such as CH₃NH₃SnI₃ have also been reported, though with lower power-conversion efficiencies.{{cite web|title=Solar Researchers Find Promise in Tin Perovskite Line |author=Wilcox, Kevin |website=Civil Engineering |date=May 13, 2014 |url=http://www.asce.org/CEMagazine/ArticleNs.aspx?id=23622330855 |url-status=dead |archive-url=https://web.archive.org/web/20141006212903/http://www.asce.org/CEMagazine/ArticleNs.aspx?id=23622330855 |archive-date=October 6, 2014 }}{{cite news|title=Getting the lead out of Perovskite Solar Cells|author=Meehan, Chris |website=Solar Reviews |date=May 5, 2014 | url=http://www.solarreviews.com/news/lead-out-perovskite-solar-040514/}}{{cite journal|last1=Hao|first1=F.|last2=Stoumpos|first2=C.C.|last3=Cao|first3=D.H.|last4=Chang|first4=R.P.H.|last5=Kanatzidis|first5=M.G.|title=Lead-free solid-state organic–inorganic halide perovskite solar cells|journal=Nature Photonics|date=2014|volume=8|issue=6|pages=489–494|doi=10.1038/nphoton.2014.82|bibcode=2014NaPho...8..489H|s2cid=5850501 }}

Solar cell efficiency is limited by the Shockley–Queisser limit. This calculated limit sets the maximum theoretical efficiency of a solar cell using a single junction with no other loss aside from radiative recombination in the solar cell. Based on the AM1.5G global solar spectra, the maximum power conversion efficiency is correlated to a respective bandgap, forming a parabolic relationship.

This limit is described by the equation

:$\backslash eta\; =\; t\_s\; \backslash times\; u\; (x\_g)\; \backslash times\; v(f,\; x\_g,\; x\_c)\; \backslash times\; m(vx\_g/x\_c)$

Where

:$x\_g\; =\; V\_g/V\_s\; \backslash \; ;\; \backslash \; x\_c\; =\; V\_c/V\_s$

and u is the ultimate efficiency factor, and v is the ratio of open circuit voltage V_op to band-gap voltage V_g, and m is the impedance matching factor, and V_c is the thermal voltage, and V_s is the voltage equivalent of the temperature of the Sun.

The most efficient bandgap is found to be at 1.34 eV, with a maximum power conversion efficiency (PCE) of 33.7%. Reaching this ideal bandgap energy can be difficult, but utilizing tunable perovskite solar cells allows for the flexibility to match this value. Further experimenting with multijunction solar cells allow for the Shockley-Queisser limit to be surpassed, expanding to allow photons of a broader wavelength range to be absorbed and converted, without increasing thermalisation loss.

The actual band gap for formamidinium (FA) lead trihalide can be tuned as low as 1.48 eV, which is closer to the ideal bandgap energy of 1.34 eV for maximum power-conversion efficiency single junction solar cells, predicted by the Shockley–Queisser Limit. The 1.3 eV bandgap energy has been successfully achieved with the {{chem|(FAPbI|3|)|1−x|(CsSnI|3|)|x}} hybrid cell, which has a tunable bandgap energy (E_g) from 1.24 – 1.41 eV.{{cite journal |last1=Zong |first1=Yingxia |last2=Wang |first2=Ning |last3=Zhang |first3=Lin |last4=Ju |first4=Ming-Gang |last5=Zeng |first5=Xiao Cheng |last6=Sun |first6=Xiao Wei |last7=Zhou |first7=Yuanyuan |last8=Padture |first8=Nitin P. |title=Rücktitelbild: Homogenous Alloys of Formamidinium Lead Triiodide and Cesium Tin Triiodide for Efficient Ideal-Bandgap Perovskite Solar Cells (Angew. Chem. 41/2017) |journal=Angewandte Chemie |date=2 October 2017 |volume=129 |issue=41 |pages=12966 |doi=10.1002/ange.201708387 |doi-access=free |bibcode=2017AngCh.12912966Z }}

Multi-junction solar cells are capable of a higher power conversion efficiency (PCE), increasing the threshold beyond the thermodynamic maximum set by the Shockley-Queisser limit for single junction cells. By having multiple bandgaps in a single cell, it prevents the loss of photons above or below the band gap energy of a single junction solar cell.{{Cite book|last1=McMeekin|first1=David|last2=Mahesh|first2=Suhas|last3=Noel|first3=Nakita|last4=Klug|first4=Matthew|last5=Lim|first5=JongChul|last6=Warby|first6=Jonathan|last7=Ball|first7=James|last8=Herz|first8=Laura|last9=Johnston|first9=Michael|last10=Snaith|first10=Henry|title=Proceedings of the 11th International Conference on Hybrid and Organic Photovoltaics |chapter=Solution-Processed All-Perovskite Multi-Junction Solar Cells |date=2019-02-11|volume=3|issue=2|location=València|publisher=Fundació Scito|doi=10.29363/nanoge.hopv.2019.099|s2cid=182243452|chapter-url=https://ora.ox.ac.uk/objects/uuid:36d9096a-49f2-405c-bd42-9f2a574e8782}} In tandem (double) junction solar cells, PCE of 31.1% has been recorded, increasing to 37.9% for triple junction and 38.8% for quadruple junction solar cells. However, the metal organic chemical vapor deposition (mocvd) process needed to synthesise lattice-matched and crystalline solar cells with more than one junction is very expensive, making it a less than ideal candidate for widespread use.

Perovskite semiconductors offer an option that has the potential to rival the efficiency of multi-junction solar cells but can be synthesised under more common conditions at a greatly reduced cost. Rivalling the double, triple, and quadruple junction solar cells mentioned above, are all-perovskite tandem cells with a max PCE of 31.9%, all-perovskite triple-junction cell reaching 33.1%, and the perovskite-Si triple-junction cell, reaching an efficiency of 35.3%. These multi-junction perovskite solar cells, in addition to being available for cost-effective synthesis, also maintain high PCE under varying weather extremes, making them utilizable worldwide.{{cite journal |last1=Werthen |first1=J.G. |title=Multijunction concentrator solar cells |journal=Solar Cells |date=June 1987 |volume=21 |issue=1–4 |pages=452 |doi=10.1016/0379-6787(87)90150-5 }}

Utilizing organic chiral ligands shows promise for increasing the maximum power conversion efficiency for halide perovskite solar cells, when utilized correctly. Chirality can be produced in inorganic semiconductors by enantiomeric distortions near the surface of the lattice, electronic coupling between the substrate and a chiral ligand, assembly into a chiral secondary structure, or chiral surface defects. By attaching a chiral phenylethylamine ligand to an achiral lead bromide perovskite nanoplatelet, a chiral inorganic-organic perovskite is formed. Inspection of the inorganic-organic perovskite via Circular Dichroism (CD) spectroscopy, reveals two regions. One represents the charge transfer between the ligand and the nanoplatelet (300-350 nm), and the other represents the excitonic absorption maximum of the perovskite. Evidence of charge transfer in these systems shows promise for increasing power conversion efficiency in perovskite solar cells.{{cite journal |last1=Georgieva |first1=Zheni N. |last2=Bloom |first2=Brian P. |last3=Ghosh |first3=Supriya |last4=Waldeck |first4=David H. |title=Imprinting Chirality onto the Electronic States of Colloidal Perovskite Nanoplatelets |journal=Advanced Materials |date=June 2018 |volume=30 |issue=23 |pages=1800097 |doi=10.1002/adma.201800097 |pmid=29700859 |bibcode=2018AdM....3000097G |doi-access=free }}

File:Efficiency history of inorganic perovskites, basic structure.jpg

The highest performing perovskites solar cells suffer from chemical instability. The organic components such as methylammonium or formamidinium are the basis of the weakness. Encapsulation to prevent this decay is expensive. Fully inorganic perovskites could miminize these problems. Fully inorganic perovskites have PCE over 17%.  These high performing fully inorganic perovskite cells are created using CsPbI₃, which has a band gap similar to that of high performing OIHPs (~1.7 eV), as well as excellent optoelectrical properties. Although chemically stable, these perovskite materials face significant issues with phase stability that prevent its broad industrial application. In high efficiency CsPbI₃, for example, the photoactive black α-phase is prone to transform into the inactive yellow δ-phase, seriously inhibiting the performance, especially when exposed to moisture. This also made them difficult to synthesize at ambient temperatures as the black α-phase is thermodynamically unstable with respect to the yellow δ-phase, although this has been recently tackled by Hei Ming Lai's group, who is a psychiatrist.{{cite journal |last1=Lai |first1=Hei Ming |title=Direct Room Temperature Synthesis of α-CsPbI3 Perovskite Nanocrystals with High Photoluminescence Quantum Yields: Implications for Lighting and Photovoltaic Applications |journal=ACS Appl. Nano Mater. |date=April 27, 2022 |volume=5 |issue=9 |pages=12366–12373|doi=10.1021/acsanm.2c00732 |doi-access=free }} The challenge of stabilizing the photoactive black α-phase of inorganic perovskite materials has been tackled in a variety of strategies, including octahedral anchoring and secondary crystal growth.{{cite journal |last1=Wang |first1=Xingtao |last2=Wang |first2=Yong |last3=Chen |first3=Yuetian |last4=Liu |first4=Xiaomin |last5=Zhao |first5=Yixin |title=Efficient and Stable CsPbI 3 Inorganic Perovskite Photovoltaics Enabled by Crystal Secondary Growth |journal=Advanced Materials |date=November 2021 |volume=33 |issue=44 |pages=2103688 |doi=10.1002/adma.202103688 |pmid=34515363 |bibcode=2021AdM....3303688W |s2cid=237495330 }}{{cite journal |last1=Wang |first1=Yong |last2=Chen |first2=Gaoyuan |last3=Ouyang |first3=Dan |last4=He |first4=Xinjun |last5=Li |first5=Can |last6=Ma |first6=Ruiman |last7=Yin |first7=Wan-Jian |last8=Choy |first8=Wallace C. H. |title=High Phase Stability in CsPbI 3 Enabled by Pb–I Octahedra Anchors for Efficient Inorganic Perovskite Photovoltaics |journal=Advanced Materials |date=June 2020 |volume=32 |issue=24 |pages=2000186 |doi=10.1002/adma.202000186 |pmid=32363655 |bibcode=2020AdM....3200186W |s2cid=218493218 }}

2D perovskites are characterized by improved stability and excitonic confinement properties compared with 3D perovskites, while maintaining the charge transport properties of 3D perovskite materials. Furthermore, the 2D hybrid organic-inorganic perovskite (HOIP) structure also eases the steric restrictions on the “B” cations, as outlined by the Goldschmidt’s tolerance factor in 3D HOIPs, providing a much larger compositional space to engineer new materials with tailored properties.

HOIPs follow the same ABX₃ stoichiometry as their 3D counterparts. In this case, B is a metal cation, X is halogen anions (Cl⁻, Br⁻, I⁻) and A represents an organic molecular cation. The A-site cations are caged in a BX₆ corner-sharing octahedra network via the hydrogen bond of N-H-X between the ammonium group from the A-site cation and the halogen from octahedra. As the length of the 2D organic ion increases, the spacing between the corner sharing octahedra does as well, forming a 2D or quasi-2D structure.{{cite journal |last1=Hou |first1=Yuchen |last2=Wu |first2=Congcong |last3=Yang |first3=Dong |last4=Ye |first4=Tao |last5=Honavar |first5=Vasant G. |last6=van Duin |first6=Adri C. T. |last7=Wang |first7=Kai |last8=Priya |first8=Shashank |title=Two-dimensional hybrid organic–inorganic perovskites as emergent ferroelectric materials |journal=Journal of Applied Physics |date=14 August 2020 |volume=128 |issue=6 |pages=060906 |doi=10.1063/5.0016010 |bibcode=2020JAP...128f0906H |s2cid=225384930 |issn=0021-8979|url=https://scholarsphere.psu.edu/resources/29b8cac4-8c73-49a0-b4e7-b05af0697481 |doi-access=free }} The organic and inorganic layers are held together by Van der Waals forces. A formula of R₂A_n−1B_nX_3n+1 is used to characterize the 2D and quasi 2D structures. Here, R is the large organic cation space that separates the inorganic layers and “n” refers to the number of organic units between inorganic layers.

To achieve mechanically durable devices, a top priority is to understand the inherent mechanical properties of the materials. Like other 2D materials, mechanical properties are analyzed using computational methods and are verified using experiments.

Nanoindentation is a common technique to measure mechanical properties of 2D materials. Nanoindentation results in 2D HOIP reveal anisotropy in the Young’s modulus along different plane directions (100, 001, and 110).{{cite journal |last1=Gao |first1=Hongqiang |last2=Wei |first2=Wenjuan |last3=Li |first3=Linsui |last4=Tan |first4=Yuhui |last5=Tang |first5=Yunzhi |title=Mechanical Properties of a 2D Lead-Halide Perovskite, (C 6 H 5 CH 2 NH 3 ) 2 PbCl 4, by Nanoindentation and First-Principles Calculations |journal=The Journal of Physical Chemistry C |date=3 September 2020 |volume=124 |issue=35 |pages=19204–19211 |doi=10.1021/acs.jpcc.0c04283|s2cid=225497934 }} Gao et al. showed single-crystal (C₆H₅CH₂NH₃)₂PbCl₄ had mid-range anisotropy in these directions because of corner sharing inherent to the crystal structure. The strongest direction was the [100] direction which is perpendicular to the inorganic layers. Generally, across many 2D HOIPs, there is a dominant correlation between increased Pb-X (very common cation) bond strength and Young’s moduli.{{cite journal |last1=Sun |first1=Shijing |last2=Fang |first2=Yanan |last3=Kieslich |first3=Gregor |last4=White |first4=Tim J. |last5=Cheetham |first5=Anthony K. |title=Mechanical properties of organic–inorganic halide perovskites, CH3NH3PbX3 (X = I, Br and Cl), by nanoindentation |journal=Journal of Materials Chemistry A |date=1 September 2015 |volume=3 |issue=36 |pages=18450–18455 |doi=10.1039/C5TA03331D |issn=2050-7496}} Similarly, another nanoindentation study found that changing the A ion from organic CH₃NH₃₊ to inorganic Cs⁺ has negligible effects on the Young’s modulus, whereas the Pb–X strength has the dominating effect.{{cite journal |last1=Reyes-Martinez |first1=Marcos A. |last2=Abdelhady |first2=Ahmed L. |last3=Saidaminov |first3=Makhsud I. |last4=Chung |first4=Duck Young |last5=Bakr |first5=Osman M. |last6=Kanatzidis |first6=Mercouri G. |last7=Soboyejo |first7=Wole O. |last8=Loo |first8=Yueh-Lin |title=Time-Dependent Mechanical Response of APbX 3 (A = Cs, CH 3 NH 3; X = I, Br) Single Crystals |journal=Advanced Materials |date=June 2017 |volume=29 |issue=24 |pages=1606556 |doi=10.1002/adma.201606556 |pmid=28464367 |bibcode=2017AdM....2906556R |s2cid=19325635 |issn=0935-9648|doi-access=free |hdl=10754/623454 |hdl-access=free }} Due to the increased mechanical stability of the inorganic layers, nanoindentation finds that 2D HOIP structures with thicker and more densely packed inorganic layers have increased Young’s moduli and increased stability.

A study by Tu et al. performed mechanical properties testing on a simple lead iodide system to investigate the role of the number and the length of subunits (organic layer) on the out of plane Young’s modulus utilizing nanoindentation.{{cite journal |last1=Tu |first1=Qing |last2=Spanopoulos |first2=Ioannis |last3=Hao |first3=Shiqiang |last4=Wolverton |first4=Chris |last5=Kanatzidis |first5=Mercouri G. |last6=Shekhawat |first6=Gajendra S. |last7=Dravid |first7=Vinayak P. |title=Out-of-Plane Mechanical Properties of 2D Hybrid Organic–Inorganic Perovskites by Nanoindentation |journal=ACS Applied Materials & Interfaces |date=5 July 2018 |volume=10 |issue=26 |pages=22167–22173 |doi=10.1021/acsami.8b05138|pmid=29882400 |arxiv=1803.11277 |s2cid=206484846 }} This study found that 2D HOIPs are softer than 3D counterparts due to a shift from covalent/ionic bonding to van der waals bonding. Furthermore, increasing the number of subunits “n” from (1-5) increases the Young’s modulus and hardness until reaching 3D standard values. The length of the organic chain decreases and plateau’s the Young’s modulus. These factors can be tailored when designing perovskites solar cells for unique applications.

2D HOIP are also susceptible to the negative Poisson's ratio phenomenon, in which a material contracts laterally with stretched and expands laterally when compressed. This phenomenon is observed commonly in 2D materials and the Poisson's ratio can be modulated by changing the "X" halide in the 2D HOIP chemistry.{{cite journal |last1=Du |first1=Yuchen |last2=Maassen |first2=Jesse |last3=Wu |first3=Wangran |last4=Luo |first4=Zhe |last5=Xu |first5=Xianfan |last6=Ye |first6=Peide D. |title=Auxetic Black Phosphorus: A 2D Material with Negative Poisson's Ratio |journal=Nano Letters |date=12 October 2016 |volume=16 |issue=10 |pages=6701–6708 |doi=10.1021/acs.nanolett.6b03607|pmid=27649304 |arxiv=1607.00541 |bibcode=2016NanoL..16.6701D |s2cid=36082570 }} Halides with weaker electronegativity form weaker bonds with the “B” cation resulting in increased (in magnitude) negative poisson ratio. This leaver allows for tunable flexibility of 2D HOIPs and applications of microelectromechanical and nanoelectronics devices.

Solar cells based on transition metal oxide perovskites and heterostructures thereof such as LaVO₃/SrTiO₃ have been studied.{{cite journal |title=Oxide Heterostructures for Efficient Solar Cells |author1=Elias Assmann |author2=Peter Blaha |author3=Robert Laskowski |author4=Karsten Held |author5=Satoshi Okamoto |author6=Giorgio Sangiovanni |name-list-style=amp |journal=Phys. Rev. Lett. |volume=110 |issue=7 |page=078701|year=2013|doi=10.1103/PhysRevLett.110.078701|pmid=25166418 |arxiv = 1301.1314| bibcode = 2013PhRvL.110g8701A |s2cid=749031 }}{{cite journal |title=Device Performance of the Mott Insulator LaVO3 as a Photovoltaic Material |author1=Lingfei Wang |author2=Yongfeng Li |author3=Ashok Bera |author4=Chun Ma |author5=Feng Jin |author6=Kaidi Yuan |author7=Wanjian Yin |author8=Adrian David |author9=Wei Chen |author10=Wenbin Wu |author11=Wilfrid Prellier |author12=Suhuai Wei |author13=Tom Wu |name-list-style=amp |journal=Physical Review Applied |volume=3 |issue=6 |page=064015|year=2015|doi=10.1103/PhysRevApplied.3.064015| bibcode = 2015PhRvP...3f4015W |doi-access=free |hdl=10754/558566 |hdl-access=free }}

Rice University scientists discovered a novel phenomenon of light-induced lattice expansion in perovskite materials.{{cite web|url=http://news.rice.edu/2018/04/05/light-relaxes-crystal-to-boost-solar-cell-efficiency-2/|title=Light 'relaxes' crystal to boost solar cell efficiency|website=news.rice.edu}}

Perovskite quantum dot solar cell technology may extend cell durability, which remains a critical limitation.{{cite web|url=https://www.nwdiamondnotes.com/quantum-dot-solar-cell-market-82603/ |title=Quantum Dot Solar Cell Market Trends, Top Manufactures, Quantum Dot Solar Cell Market Demands, Industry Growth Analysis & Forecast 2026|website=www.nwdiamondnotes.com/ |url-status=dead |archive-url=https://web.archive.org/web/20211127062243/https://www.nwdiamondnotes.com/quantum-dot-solar-cell-market-82603/ |archive-date=2021-11-27}}

In order to overcome the instability issues with lead-based organic perovskite materials in ambient air and reduce the use of lead, perovskite derivatives, such as Cs₂SnI₆ double perovskite, have been investigated.{{Cite journal|last1=Ke|first1=Jack Chun-Ren|last2=Lewis|first2=David J.|last3=Walton|first3=Alex S.|last4=Spencer|first4=Ben F.|last5=O'Brien|first5=Paul|last6=Thomas|first6=Andrew G.|last7=Flavell|first7=Wendy R.|date=2018|title=Ambient-air-stable inorganic Cs₂SnI₆ double perovskite thin films via aerosol-assisted chemical vapour deposition|journal=Journal of Materials Chemistry A|volume=6|issue=24|pages=11205–11214|doi=10.1039/c8ta03133a |doi-access=free}}

Perovskite solar cells hold an advantage over traditional silicon solar cells in the simplicity of their processing and their tolerance to internal defects.{{Cite journal|title=High Defect Tolerance in Lead Halide Perovskite CsPbBr3|journal=The Journal of Physical Chemistry Letters|volume=8|issue=2|pages=489–493|last=Jun|first=Kang|date=10 January 2017|doi=10.1021/acs.jpclett.6b02800|pmid=28071911|osti=1483838 |url=https://escholarship.org/uc/item/38j557sc}} Traditional silicon cells require expensive, multi-step processes, conducted at high temperatures (>1000 °C) under high vacuum in special cleanroom facilities.[http://www.engineering.com/Blogs/tabid/3207/ArticleID/6773/Is-Perovskite-the-Future-of-Solar-Cells.aspx Is Perovskite the Future of Solar Cells?]. engineering.com. December 6, 2013 Meanwhile, the hybrid organic-inorganic perovskite material can be manufactured with simpler wet chemistry techniques in a traditional lab environment. Most notably, methylammonium and formamidinium lead trihalides, also known as hybrid perovskites, have been created using a variety of solution deposition techniques, such as spin coating, slot-die coating, blade coating, spray coating, inkjet printing, screen printing, electrodeposition, and vapor deposition techniques, all of which have the potential to be scaled up with relative ease except spin coating.{{cite journal|doi=10.1038/ncomms8586|pmid=26145157|pmc=4544059|title=High-quality bulk hybrid perovskite single crystals within minutes by inverse temperature crystallization|journal=Nature Communications|volume=6|page=7586|year=2015|last1=Saidaminov|first1=Makhsud I.|last2=Abdelhady|first2=Ahmed L.|last3=Murali|first3=Banavoth|last4=Alarousu|first4=Erkki|last5=Burlakov |first5=Victor M.|last6=Peng|first6=Wei|last7=Dursun|first7=Ibrahim|last8=Wang|first8=Lingfei|last9=He|first9=Yao|last10=MacUlan|first10=Giacomo|last11=Goriely|first11=Alain|last12=Wu|first12=Tom|last13=Mohammed|first13=Omar F.|last14=Bakr|first14=Osman M.|bibcode=2015NatCo...6.7586S}}{{cite journal |last1=Howard |first1=I. A. |last2=Abzieher |first2=T. |last3=Hossain |first3=I. M. |last4=Eggers |first4=H. |last5=Schackmar |first5=F. |last6=Ternes |first6=S. |last7=Richards |first7=B. S. |last8=Lemmer |first8=U. |last9=Paetzold |first9=U. W. |date=2019 |title=Coated and Printed Perovskites for Photovoltaic Applications |journal=Advanced Materials |volume=31 |issue=26 |pages=e1806702 | pmid=30932255 | doi=10.1002/adma.201806702|bibcode=2019AdM....3106702H | doi-access=free}}{{cite journal|doi=10.1021/jz4020162|title=Perovskites: The Emergence of a New Era for Low-Cost, High-Efficiency Solar Cells|journal=The Journal of Physical Chemistry Letters|volume=4|issue=21|pages=3623–3630|year=2013|last1=Snaith|first1=Henry J.}} All these methods seek to ensure a perovskite layer achieves full surface coverage by limiting growth rate and increasing nucleation.{{Cite journal |last1=Abbas |first1=Mazhar |last2=Zeng |first2=Linxiang |last3=Guo |first3=Fei |last4=Rauf |first4=Muhammad |last5=Yuan |first5=Xiao-Cong |last6=Cai |first6=Boyuan |date=January 2020 |title=A Critical Review on Crystal Growth Techniques for Scalable Deposition of Photovoltaic Perovskite Thin Films |journal=Materials |language=en |volume=13 |issue=21 |pages=4851 |doi=10.3390/ma13214851 |doi-access=free |pmid=33138192 |bibcode=2020Mate...13.4851A |issn=1996-1944|pmc=7663244 }}

The solution-based processing method can be classified into one-step solution deposition and two-step solution deposition. In one-step deposition, a perovskite precursor solution that is prepared by mixing lead halide and organic halide together, is directly deposited through various coating methods, such as spin coating, spraying, blade coating, and slot-die coating, to form perovskite film. One-step deposition is simple, fast, and inexpensive but it's also more challenging to control the perovskite film uniformity and quality. In the two-step deposition, the lead halide film is first deposited then reacts with organic halide to form perovskite film. The reaction takes time to complete but it can be facilitated by adding Lewis-bases or partial organic halide into lead halide precursors. In two-step deposition method, the volume expansion during the conversion of lead halide to perovskite can fill any pinholes to realize a better film quality. The vapor phase deposition processes can be categorized into physical vapor deposition (PVD) and chemical vapor deposition (CVD). PVD refers to the evaporation of a perovskite or its precursor to form a thin perovskite film on the substrate, which is free of solvent. While CVD involves the reaction of organic halide vapor with the lead halide thin film to convert it into the perovskite film. A solution-based CVD, aerosol-assisted CVD (AACVD) was also introduced to fabricate halide perovskite films, such as CH₃NH₃PbI₃,{{cite journal |last1=Ke |first1=Chun-Ren |last2=Lewis |first2=David J. |last3=Walton |first3=Alex S. |last4=Chen |first4=Qian |last5=Spencer |first5=Ben F. |last6=Mokhtar |first6=Muhamad Z. |last7=Compean-Gonzalez |first7=Claudia L. |last8=O’Brien |first8=Paul |last9=Thomas |first9=Andrew G. |last10=Flavell |first10=Wendy R. |title=Air-Stable Methylammonium Lead Iodide Perovskite Thin Films Fabricated via Aerosol-Assisted Chemical Vapor Deposition from a Pseudohalide Pb(SCN) 2 Precursor |journal=ACS Applied Energy Materials |date=26 August 2019 |volume=2 |issue=8 |pages=6012–6022 |doi=10.1021/acsaem.9b01124 |s2cid=201232856 |url=https://www.research.manchester.ac.uk/portal/en/publications/airstable-methylammonium-lead-iodide-perovskite-thin-films-fabricated-via-aerosolassisted-chemical-vapor-deposition-from-a-pseudohalide-pbscn2-precursor(bb8437bb-509e-4b81-9c8c-07e376f19bfd).html }} CH₃NH₃PbBr₃,{{cite journal |last1=Lewis |first1=David J. |last2=O'Brien |first2=Paul |title=Ambient pressure aerosol-assisted chemical vapour deposition of (CH 3 NH 3)PbBr 3, an inorganic–organic perovskite important in photovoltaics |journal=Chem. Commun. |date=2014 |volume=50 |issue=48 |pages=6319–6321 |doi=10.1039/c4cc02592j |pmid=24799177 |url=https://www.research.manchester.ac.uk/portal/en/publications/ambient-pressure-aerosolassisted-chemical-vapour-deposition-of-ch3nh3pbbr3-an-inorganicorganic-perovskite-important-in-photovoltaics(828962f8-e559-4e3b-9c06-f652ab180a53).html }} and Cs₂SnI₆.{{cite journal |last1=Ke |first1=Jack Chun-Ren |last2=Lewis |first2=David J. |last3=Walton |first3=Alex S. |last4=Spencer |first4=Ben F. |last5=O'Brien |first5=Paul |last6=Thomas |first6=Andrew G. |last7=Flavell |first7=Wendy R. |title=Ambient-air-stable inorganic Cs 2 SnI 6 double perovskite thin films via aerosol-assisted chemical vapour deposition |journal=Journal of Materials Chemistry A |date=2018 |volume=6 |issue=24 |pages=11205–11214 |doi=10.1039/C8TA03133A |doi-access=free }}

File:One-two step.jpg

In one-step solution processing, a lead halide and a methylammonium halide can be dissolved in a solvent and spin coated onto a substrate. Subsequent evaporation and convective self-assembly during spinning results in dense layers of well crystallized perovskite material, due to the strong ionic interactions within the material (The organic component also contributes to a lower crystallization temperature). Precise control of crystal growth is essential to achieve high quality perovskite films. The rate of crystallization can be controlled by a method that involves Lewis acid-base adduct formation. By adding base molecules in a stoichiometric ratio with perovskite precursors, electron pair donors such as sulfur or oxygen can, for example, make adducts with PbX₂, a strong Lewis acid. By elevating the solubility of lead halides, these acid-base adducts can slow the nucleation process and speed of crystal growth, achieving more homogeneous and performant perovskite layers.{{Cite journal |last1=Lee |first1=Jin-Wook |last2=Dai |first2=Zhenghong |last3=Lee |first3=Changsoo |last4=Lee |first4=Hyuck Mo |last5=Han |first5=Tae-Hee |last6=De Marco |first6=Nicholas |last7=Lin |first7=Oliver |last8=Choi |first8=Christopher S. |last9=Dunn |first9=Bruce |last10=Koh |first10=Jaekyung |last11=Di Carlo |first11=Dino |last12=Ko |first12=Jeong Hoon |last13=Maynard |first13=Heather D. |last14=Yang |first14=Yang |date=2018-05-23 |title=Tuning Molecular Interactions for Highly Reproducible and Efficient Formamidinium Perovskite Solar Cells via Adduct Approach |url=https://pubs.acs.org/doi/full/10.1021/jacs.8b01037 |journal=Journal of the American Chemical Society |volume=140 |issue=20 |pages=6317–6324 |doi=10.1021/jacs.8b01037 |pmid=29723475 |bibcode=2018JAChS.140.6317L |issn=0002-7863}}{{Cite journal |last1=Son |first1=Dae-Yong |last2=Lee |first2=Jin-Wook |last3=Choi |first3=Yung Ji |last4=Jang |first4=In-Hyuk |last5=Lee |first5=Seonhee |last6=Yoo |first6=Pil J. |last7=Shin |first7=Hyunjung |last8=Ahn |first8=Namyoung |last9=Choi |first9=Mansoo |last10=Kim |first10=Dongho |last11=Park |first11=Nam-Gyu |date=2016-06-20 |title=Self-formed grain boundary healing layer for highly efficient CH3NH3PbI3 perovskite solar cells |url=https://www.nature.com/articles/nenergy201681 |journal=Nature Energy |language=en |volume=1 |issue=7 |pages=1–8 |doi=10.1038/nenergy.2016.81 |issn=2058-7546}}{{Cite journal |last1=Ahn |first1=Namyoung |last2=Son |first2=Dae-Yong |last3=Jang |first3=In-Hyuk |last4=Kang |first4=Seong Min |last5=Choi |first5=Mansoo |last6=Park |first6=Nam-Gyu |date=2015-07-15 |title=Highly Reproducible Perovskite Solar Cells with Average Efficiency of 18.3% and Best Efficiency of 19.7% Fabricated via Lewis Base Adduct of Lead(II) Iodide |url=https://pubs.acs.org/doi/full/10.1021/jacs.5b04930 |journal=Journal of the American Chemical Society |volume=137 |issue=27 |pages=8696–8699 |doi=10.1021/jacs.5b04930 |pmid=26125203 |bibcode=2015JAChS.137.8696A |issn=0002-7863}} However, simple spin-coating does not yield homogenous layers, instead requiring the addition of other chemicals such as GBL, DMSO, and toluene drips.{{cite journal|title=Solvent engineering for high-performance inorganic–organic hybrid perovskite solar cells|journal=Nature Materials|volume=13|issue=9|pages=897–903 |year=2014|last1=Jeon|first1=Nam Joong|last2=Noh|first2=Jun Hong|last3=Kim|first3=Young Chan |last4=Yang |first4=Woon Seok|last5=Ryu|first5=Seungchan|last6=Seok|first6=Sang Il|doi=10.1038/nmat4014|pmid=24997740 |bibcode=2014NatMa..13..897J}} These antisolvent compounds that are completely soluble in host solvents, have high dielectric constants and boiling points tend to form superior quality films based on nucleation and substrate coverage.{{Cite journal |last1=Emrul Kayesh |first1=Md. |last2=Matsuishi |first2=Kiyoto |last3=Chowdhury |first3=Towhid H. |last4=Kaneko |first4=Ryuji |last5=Lee |first5=Jae-Joon |last6=Noda |first6=Takeshi |last7=Islam |first7=Ashraful |date=2018-10-01 |title=Influence of anti-solvents on CH3NH3PbI3 films surface morphology for fabricating efficient and stable inverted planar perovskite solar cells |url=https://www.sciencedirect.com/science/article/abs/pii/S0040609018305406 |journal=Thin Solid Films |volume=663 |pages=105–115 |doi=10.1016/j.tsf.2018.08.015 |bibcode=2018TSF...663..105E |issn=0040-6090}} Other strongly basic S-donors such as thiourea similarly improved FA-based perovskite layer formation.{{Cite journal |last1=Lee |first1=Jin-Wook |last2=Kim |first2=Hui-Seon |last3=Park |first3=Nam-Gyu |date=2016-02-16 |title=Lewis Acid–Base Adduct Approach for High Efficiency Perovskite Solar Cells |url=https://pubs.acs.org/doi/full/10.1021/acs.accounts.5b00440 |journal=Accounts of Chemical Research |volume=49 |issue=2 |pages=311–319 |doi=10.1021/acs.accounts.5b00440 |pmid=26797391 |issn=0001-4842}} Simple solution processing results in the presence of voids, platelets, and other defects in the layer, which would hinder the efficiency of a solar cell.

Another technique using room temperature solvent-solvent extraction produces high-quality crystalline films with precise control over thickness down to 20 nanometers across areas several centimeters square without generating pinholes. In this method "perovskite precursors are dissolved in a solvent called NMP and coated onto a substrate. Then, instead of heating, the substrate is bathed in diethyl ether, a second solvent that selectively grabs the NMP solvent and whisks it away. What's left is an ultra-smooth film of perovskite crystals."{{cite journal|doi=10.1039/C5TA00477B|title=Room-temperature crystallization of hybrid-perovskite thin films via solvent–solvent extraction for high-performance solar cells|journal=J. Mater. Chem. A|volume=3|issue=15|pages=8178–8184|year=2015|last1=Zhou |first1=Yuanyuan|last2=Yang|first2=Mengjin|last3=Wu|first3=Wenwen|last4=Vasiliev |first4=Alexander L. |last5=Zhu|first5=Kai|last6=Padture|first6=Nitin P.|s2cid=56292381}}

In another solution processed method, the mixture of lead iodide and methylammonium halide dissolved in DMF is preheated. Then the mixture is spin coated on a substrate maintained at higher temperature. This method produces uniform films of up to 1 mm grain size.{{Cite journal|title = High-efficiency solution-processed perovskite solar cells with millimeter-scale grains|journal = Science|date = 2015-01-30|pmid = 25635093|pages = 522–525|volume = 347|issue = 6221|doi = 10.1126/science.aaa0472|first1 = Wanyi|last1 = Nie|first2 = Hsinhan|last2 = Tsai|first3 = Reza|last3 = Asadpour|first4 = Jean-Christophe|last4 = Blancon|first5 = Amanda J.|last5 = Neukirch|first6 = Gautam|last6 = Gupta|first7 = Jared J.|last7 = Crochet|first8 = Manish|last8 = Chhowalla|first9 = Sergei|last9 = Tretiak|bibcode = 2015Sci...347..522N| osti=1579878 |s2cid = 14990570|url = https://zenodo.org/record/1231263}}

Pb halide perovskites can be fabricated from a PbI₂ precursor,{{cite journal |last1=Chen |first1=Qian |last2=Mokhtar |first2=Muhamad Z. |last3=Ke |first3=Jack Chun-Ren |last4=Thomas |first4=Andrew G. |last5=Hadi |first5=Aseel |last6=Whittaker |first6=Eric |last7=Curioni |first7=Michele |last8=Liu |first8=Zhu |title=A one-step laser process for rapid manufacture of mesoscopic perovskite solar cells prepared under high relative humidity |journal=Sustainable Energy & Fuels |date=2018 |volume=2 |issue=6 |pages=1216–1224 |doi=10.1039/C8SE00043C |url=https://www.research.manchester.ac.uk/portal/en/publications/a-onestep-laser-process-for-rapid-manufacture-of-mesoscopic-perovskite-solar-cells-prepared-under-high-relative-humidity(0028fa14-0925-4789-90ec-68a9a1fc1b75).html }} or non-PbI₂ precursors, such as PbCl₂, Pb(Ac)₂, and Pb(SCN)₂, giving films different properties.

In 2015, a new approach{{Cite journal|last1=Zhang|first1=Hong|last2=Choy|first2=C.H.Wallace|date=2015|title=A Smooth CH3NH3PbI3 Film via a New Approach for Forming the PbI2 Nanostructure Together with Strategically High CH3NH3I Concentration for High Efficient Planar-Heterojunction Solar Cells|journal=Adv. Energy Mater.|doi=10.1002/aenm.201501354|volume=5|issue=23|page=1501354|bibcode=2015AdEnM...501354Z |s2cid=97330089}} for forming the PbI₂ nanostructure and the use of high CH₃NH₃I concentration have been adopted to form high quality (large crystal size and smooth) perovskite film with better photovoltaic performances. On one hand, self-assembled porous PbI₂ is formed by incorporating small amounts of rationally chosen additives into the PbI₂ precursor solutions, which significantly facilitate the conversion of perovskite without any PbI₂ residue. On the other hand, through employing a relatively high CH₃NH₃I concentration, a firmly crystallized and uniform CH₃NH₃PbI₃ film is formed. Furthermore, this is an inexpensive approach. N-donors, such as pyridine (Py) additives have shown promise in the last few years to fabricate MAPbI₃. After spin coating PbI₂, pyridine vapor is introduced which leads to the formation of nanostructured PbI₂(Py)₂ films at room temperature. This is represented by the equation PbI₂(s)+2Py(g) ↔ PbI₂(Py)₂ (s). The second phase involves dipping the porous films into a CH₃NH₃I solution which can be represented by the equation  PbI₂.(Py)₂(s) CH₃NH₃I(aq) →CH₃NH₃PbI₃(s)+2Py(aq) where the previously intercalated pyridine molecules are replaced by CH₃NH₃I leading to a uniform morphology and full surface coverage.{{Cite journal |last1=Zhang |first1=Hong |last2=Cheng |first2=Jiaqi |last3=Li |first3=Dan |last4=Lin |first4=Francis |last5=Mao |first5=Jian |last6=Liang |first6=Chunjun |last7=Jen |first7=Alex K.-Y. |last8=Grätzel |first8=Michael |last9=Choy |first9=Wallace C. H. |date=2017 |title=Toward All Room-Temperature, Solution-Processed, High-Performance Planar Perovskite Solar Cells: A New Scheme of Pyridine-Promoted Perovskite Formation |url=https://advanced.onlinelibrary.wiley.com/doi/abs/10.1002/adma.201604695 |journal=Advanced Materials |volume=29 |issue=13 |pages=1604695 |doi=10.1002/adma.201604695 |pmid=28128871 |bibcode=2017AdM....2904695Z |issn=1521-4095}}

In vapor assisted techniques, spin coated or exfoliated lead halide is annealed in the presence of methylammonium iodide vapor at a temperature of around 150 °C.{{cite journal|doi=10.1021/ja411509g |pmid=24359486 |title=Planar Heterojunction Perovskite Solar Cells via Vapor-Assisted Solution Process|journal=Journal of the American Chemical Society|volume=136|issue=2|pages=622–625|year=2014|last1=Chen|first1=Qi|last2=Zhou|first2=Huanping |last3=Hong|first3=Ziruo|last4=Luo|first4=Song|last5=Duan|first5=Hsin-Sheng|last6=Wang|first6=Hsin-Hua|last7=Liu|first7=Yongsheng|last8=Li|first8=Gang|last9=Yang|first9=Yang|bibcode=2014JAChS.136..622C }} This technique holds an advantage over solution processing, as it opens up the possibility for multi-stacked thin films over larger areas.{{cite journal|doi=10.1038/nature12509|pmid=24025775|title=Efficient planar heterojunction perovskite solar cells by vapour deposition|journal=Nature|volume=501|issue=7467|pages=395–8|year=2013|last1=Liu|first1=Mingzhen|last2=Johnston|first2=Michael B.|last3=Snaith|first3=Henry J.|bibcode=2013Natur.501..395L|s2cid=205235359}} This could be applicable for the production of multi-junction cells. Additionally, vapor deposited techniques result in less thickness variation than simple solution processed layers. However, both techniques can result in planar thin film layers or for use in mesoscopic designs, such as coatings on a metal oxide scaffold. Such a design is common for current perovskite or dye-sensitized solar cells.

Scalability includes not only scaling up the perovskite absorber layer, but also scaling up charge-transport layers and electrode. Both solution and vapor processes hold promise in terms of scalability. Process cost and complexity is significantly less than that of silicon solar cells. Vapor deposition or vapor assisted techniques reduce the need for use of further solvents, which reduces the risk of solvent remnants. Solution processing is cheaper. Current issues with perovskite solar cells revolve around stability, as the material is observed to degrade in standard environmental conditions, suffering drops in efficiency (See also Stability).

In 2014, Olga Malinkiewicz presented her inkjet printing manufacturing process for perovskite sheets in Boston (US) during the MRS fall meeting – for which she received MIT Technology review's innovators under 35 award.{{cite web|title=Olga Malinkiewicz {{!}} Innovators Under 35|url=http://innovatorsunder35.com/innovator/olga-malinkiewicz|website=innovatorsunder35.com|date=2015|access-date=2017-08-02|archive-url=https://web.archive.org/web/20170802203850/http://innovatorsunder35.com/innovator/olga-malinkiewicz|archive-date=2017-08-02|url-status=dead}} The University of Toronto also claims to have developed a low-cost Inkjet solar cell in which the perovskite raw materials are blended into a Nanosolar ‘ink’ which can be applied by an inkjet printer onto glass, plastic or other substrate materials.[http://news.engineering.utoronto.ca/printable-solar-cells-just-got-little-closer/?_ga=1.195331948.1180808848.1486483274 Printable solar cells just got a little closer]. Univ. of Toronto Engineering News (2017-02-16). Retrieved on 2018-04-11.

In order to scale up the perovskite layer while maintaining high efficiency, various techniques have been developed to coat the perovskite film more uniformly. For example, some physical approaches are developed to promote supersaturation through rapid solvent removal, thus getting more nucleations and reducing grain growth time and solute migration. Heating,{{cite journal|doi=10.1002/aenm.201601660|title=Enhanced Efficiency of Hot-Cast Large-Area Planar Perovskite Solar Cells/Modules Having Controlled Chloride Incorporation|journal=Advanced Energy Materials|volume=7|issue=8|pages=1601660|year=2016 |last1=Liao|first1=Hsueh-Chung|last2=Guo|first2=Peijun|last3=Hsu |first3=Che-Pu|last4=Lin|first4=Ma|last5=Wang|first5=Binghao|last6=Zeng|first6=Li|last7=Huang|first7=Wei|last8=Soe|first8=Chan Myae Myae|last9=Su|first9=Wei-Fang|first10=Michael J.|last10=Bedzyk|first11=Michael R. |last11=Wasielewski|first12=Antonio|last12=Facchetti|first13=Robert P. H.|last13=Chang|first14=Mercouri G.|last14=Kanatzidis|first15=Tobin J.|last15=Marks|doi-access=free}} gas flow,{{cite journal|doi=10.1039/C6TA09565H |title=Large-area high-efficiency perovskite solar cells based on perovskite films dried by the multi-flow air knife method in air|journal=Journal of Materials Chemistry A|volume=5|issue=4|year=2017|pages=1548–1557|last1=Gao |first1=Li-Li|last2=Li|first2=Cheng-Xin|last3=Li|first3=Chang-Jiu|last4=Yang|first4=Guan-Jun}} vacuum,{{cite journal|doi=10.1126/science.aaf8060|pmid=27284168|title=EA vacuum flash–assisted solution process for high-efficiency large-area perovskite solar cells|journal=Science|volume=353|issue=6294|pages=58–62|year=2016|last1=Li|first1=Xiong|last2=Bi|first2=Dongqin|last3=Yi|first3=Chenyi|last4=Décoppet|first4=Jean-David|last5=Luo |first5=Jingshan|last6=Zakeeruddin|first6=Shaik Mohammed|last7=Hagfeldt|first7=Anders|last8=Grätzel|first8=Michael|bibcode=2016Sci...353...58L|s2cid=10488230}} and anti-solvent can all assist solvent removal. And chemical additives, such as chloride additives,{{cite journal|doi=10.1126/science.1228604|pmid=23042296|title=Efficient Hybrid Solar Cells Based on Meso-Superstructured Organometal Halide Perovskites |journal=Science|volume=338|issue=6107|pages=643–647|year=2012|last1=Lee|first1=Michael M.|last2=Teuscher|first2=Joël|last3=Miyasaka|first3=Tsutomu|last4=Murakami|first4=Takurou N.|last5=Snaith|first5=Henry J.|s2cid=37971858 |bibcode=2012Sci...338..643L|doi-access=free}} Lewis base additives,{{cite journal|doi=10.1021/acs.accounts.5b00440|pmid=26797391|title=Lewis Acid–Base Adduct Approach for High Efficiency Perovskite Solar Cells|journal=Accounts of Chemical Research|volume=49|issue=2 |pages=311–319|year=2016|last1=Lee|first1=Jin-Wook|last2=Kim|first2=Hui-Seon|last3=Park|first3=Nam-Gyu}} surfactant additive, and surface modification,{{cite journal |doi=10.1021/acsnano.6b01904|pmid=27128850|title=Induced Crystallization of Perovskites by a Perylene Underlayer for High-Performance Solar Cells|journal=ACS Nano|volume=10|issue=5|pages=5479–5489|year=2016 |last1=Wang|first1=Zhao-Kui|last2=Gong|first2=Xiu|last3=Li|first3=Meng|last4=Hu|first4=Yun|last5=Wang |first5=Jin-Miao|last6=Ma|first6=Heng|last7=Liao|first7=Liang-Sheng}} can influence the crystal growth to control the film morphology. For example, a recent report of surfactant additive, such as L-α-phosphatidylcholine (LP), demonstrated the suppression of solution flow by surfactants to eliminate gaps between islands and meanwhile the surface wetting improvement of perovskite ink on the hydrophobic substrate to ensure a full coverage. Besides, LP can also passivate charge traps to further enhance the device performance, which can be used in blade coating to get a high-throughput of PSCs with minimal efficiency loss.

Scaling up the charge-transport layer is also necessary for the scalability of PSCs. Common electron transport layer (ETL) in n-i-p PSCs are TiO₂, SnO₂ and ZnO. Currently, to make TiO₂ layer deposition be compatible with flexible polymer substrate, low-temperature techniques, such as atomic layer deposition,{{cite journal|author1=Francesco Di Giacomo|author2=Valerio Zardetto|author3=Alessandra D'Epifanio |author4=Sara Pescetelli|author5=Fabio Matteocci|author6=Stefano Razza|author7=Aldo Di Carlo|author8=Silvia Licoccia|author9=Wilhelmus M. M. Kessels|author10=Mariadriana Creatore|author11=Thomas M. Brown|title=Flexible Perovskite Photovoltaic Modules and Solar Cells Based on Atomic Layer Deposited Compact Layers and UV-Irradiated TiO2 Scaffolds on Plastic Substrates |journal=Advanced Energy Materials|year=2015|volume=5|issue=8|pages=1401808 |doi=10.1002/aenm.201401808 |bibcode=2015AdEnM...501808D |s2cid=98120094|url=https://research.tue.nl/nl/publications/flexible-perovskite-photovoltaic-modules-and-cells-rased-on-atomic-layer-deposited-compact-layers-and-uvirradiated-tio2-scaffolds-on-plastic-substrates(0ae7bf3f-5ec0-424e-99a3-6b8e61a44364).html}} molecular layer deposition,{{Cite journal|last1=Sundberg|first1=Pia|last2=Karppinen|first2=Maarit|date=2014-07-22|title=Organic and inorganic–organic thin film structures by molecular layer deposition: A review|journal=Beilstein Journal of Nanotechnology|volume=5|pages=1104–1136|doi=10.3762/bjnano.5.123 |pmc=4143120|pmid=25161845}} hydrothermal reaction,{{cite journal |author1=Azhar Fakharuddin|author2=Francesco Di Giacomo |author3=Alessandro L. Palma|author4=Fabio Matteocci|author5=Irfan Ahmed|author6=Stefano Razza |author7=Alessandra D’Epifanio|author8=Silvia Licoccia|author9=Jamil Ismail |author10=Aldo Di Carlo |author11=Thomas M. Brown|author12=Rajan Jose|title=Vertical TiO2 Nanorods as a Medium for Stable and High-Efficiency Perovskite Solar Modules|journal=ACS Nano|year=2015|volume=9|issue=8|pages=8420–8429 |doi=10.1021/acsnano.5b03265|pmid=26208221}} and electrodeposition,{{cite journal|author1=Tzu-Sen Su|author2=Tsung-Yu Hsieh|author3=Cheng-You Hong|author4=Tzu-Chien Wei|title=Electrodeposited Ultrathin TiO2 Blocking Layers for Efficient Perovskite Solar Cells|journal=Scientific Reports|year=2015|volume=5 |pages=16098|doi=10.1038/srep16098|pmid=26526771|pmc=4630649|bibcode=2015NatSR...516098S}} are developed to deposit compact TiO₂ layer in large area. Same methods also apply to SnO₂ deposition.

As for hole transport layer (HTL), instead of commonly used PEDOT:PSS, NiO_x is used as an alternative due to the water absorption of PEDOT, which can be deposited through room-temperature solution processing.{{cite journal|author1=Yi Hou|author2=Wei Chen|author3=Derya Baran|author4=Tobias Stubhan |author5=Norman A. Luechinger|author6=Benjamin Hartmeier|author7=Moses Richter|author8=Jie Min|author9=Shi Chen|author10=Cesar Omar Ramirez Quiroz |author11=Ning Li|author12=Hong Zhang|author13=Thomas Heumueller |author14=Gebhard J. Matt|author15=Andres Osvet|author16=Karen Forberich|author17=Zhi-Guo Zhang |author18=Yongfang Li|author19=Benjamin Winter|author20=Peter Schweizer|author21=Erdmann Spiecker |author22=Christoph J. Brabec|author22-link=Christoph J. Brabec|title=Overcoming the interface losses in planar heterojunction perovskite-based solar cells|journal=Advanced Materials|year=2016|volume=28|issue=25|pages=5112–5120 |doi=10.1002/adma.201504168|pmid=27144875|bibcode=2016AdM....28.5112H |s2cid=27609580}} CuSCN and NiO{{cite journal |last1=Di Girolamo |first1=Diego |last2=Matteocci |first2=Fabio |last3=Kosasih |first3=Felix Utama |last4=Chistiakova |first4=Ganna |last5=Zuo |first5=Weiwei |last6=Divitini |first6=Giorgio |last7=Korte |first7=Lars |last8=Ducati |first8=Caterina |last9=Di Carlo |first9=Aldo |last10=Dini |first10=Danilo |last11=Abate |first11=Antonio |title=Stability and Dark Hysteresis Correlate in NiO-Based Perovskite Solar Cells |journal=Advanced Energy Materials |date=August 2019 |volume=9 |issue=31 |pages=1901642 |s2cid=199076776 |doi=10.1002/aenm.201901642|bibcode=2019AdEnM...901642D |url=http://www.helmholtz-berlin.de/pubbin/oai_publication?VT=1&ID=100950}} are alternative HTL materials which can be deposited by spray coating,{{cite journal|author1=In Seok Yang|author2=Mi Rae Sohn|author3=Sang Do Sung|author4=Yong Joo Kim |author5=Young Jun Yoo |author6=Jeongho Kim|author7=Wan In Lee|title=Formation of pristine CuSCN layer by spray deposition method for efficient perovskite solar cell with extended stability|journal=Nano Energy|year=2017|volume=32 |pages=414–421|doi=10.1016/j.nanoen.2016.12.059|bibcode=2017NEne...32..414Y }} blade coating,{{cite journal|author1=Peng Qin |author2=Soichiro Tanaka|author3=Seigo Ito|author4=Nicolas Tetreault|author5=Kyohei Manabe|author6=Hitoshi Nishino |author7=Mohammad Khaja Nazeeruddin|author8=Michael Grätzel|title=Inorganic hole conductor-based lead halide perovskite solar cells with 12.4% conversion efficiency|journal=Nature Communications|year=2014 |volume=5|pages=3834 |doi=10.1038/ncomms4834|pmid=24815001|bibcode=2014NatCo...5.3834Q|hdl=10754/597000 |doi-access=free|hdl-access=free}} and electrodeposition,{{cite journal |author1=Senyun Ye|author2=Weihai Sun|author3=Yunlong Li|author4=Weibo Yan |author5=Haitao Peng |author6=Zuqiang Bian|author7=Zhiwei Liu|author8=Chunhui Huang|title=CuSCN-Based Inverted Planar Perovskite Solar Cell with an Average PCE of 15.6%|journal=Nano Letters|year=2015|volume=15|issue=6|pages=3723–3728 |doi=10.1021/acs.nanolett.5b00116 |pmid=25938881|bibcode=2015NanoL..15.3723Y|s2cid=206724479 }} which are potentially scalable. Researchers also report a molecular doping method for scalable blading to make HTL-free PSCs.{{cite journal|author1=Wu-Qiang Wu|author2=Qi Wang|author3=Yanjun Fang|author4=Yuchuan Shao|author5=Shi Tang|author6=Yehao Deng |author7=Haidong Lu|author8=Ye Liu|author9=Tao Li|author10=Zhibin Yang|author11=Alexei Gruverman |author12=Jinsong Huang|title=Molecular doping enabled scalable blading of efficient hole-transport-layer-free perovskite solar cells|journal=Nature Communications|year=2018|volume=9|issue=1|pages=1625 |doi=10.1038/s41467-018-04028-8|pmid=29691390|pmc=5915422|bibcode=2018NatCo...9.1625W}}

Evaporation deposition of back electrode is mature and scalable but it requires vacuum. Vacuum-free deposition of back electrode is important for full solution processibility of PSCs. Silver electrodes can be screen-printed,{{cite journal|author1=Thomas M. Schmidt|author2=Thue T. Larsen-Olsen|author3=Jon E. Carlé|author4=Dechan Angmo|author5=Frederik C. Krebs|title=Upscaling of Perovskite Solar Cells: Fully Ambient Roll Processing of Flexible Perovskite Solar Cells with Printed Back Electrodes|journal=Advanced Energy Materials|year=2015|volume=5|issue=15|pages=1625|doi=10.1002/aenm.201500569|s2cid=97192087|doi-access=free|bibcode=2015AdEnM...500569S }} and silver nanowire network can be spray-coated{{cite journal |author1=Chih-Yu Chang|author2=Kuan-Ting Lee|author3=Wen-Kuan Huang|author4=Hao-Yi Siao|author5=Yu-Chia Chang|title=High-Performance, Air-Stable, Low-Temperature Processed Semitransparent Perovskite Solar Cells Enabled by Atomic Layer Deposition |journal=Chemistry of Materials|year=2015|volume=7|issue=14|pages=5122–5130 |doi=10.1021/acs.chemmater.5b01933}} as back electrode. Carbon is also a potential candidate as scalable PSCs electrode, such as graphite,{{cite journal|author1=Zhiliang Ku|author2=Yaoguang Rong |author3=Mi Xu|author4=Tongfa Liu|author5=Hongwei Han|title=Full Printable Processed Mesoscopic CH3NH3PbI3/TiO2 Heterojunction Solar Cells with Carbon Counter Electrode |journal=Chemistry of Materials |year=2013|volume=3|pages=3132|doi=10.1038/srep03132|pmid=24185501|pmc=3816285|bibcode= }} carbon nanotubes,{{cite journal|author1=Zhen Li |author2=Sneha A. Kulkarni |author3=Pablo P. Boix|author4=Enzheng Shi|author5=Anyuan Cao|author6=Kunwu Fu|author7=Sudip K. Batabyal|author8=Jun Zhang |author9=Qihua Xiong|author10=Lydia Helena Wong|author11=Nripan Mathews |author12=Subodh G. Mhaisalkar |title=Laminated Carbon Nanotube Networks for Metal Electrode-Free Efficient Perovskite Solar Cells |journal=ACS Nano|year=2014|volume=8|issue=7|pages=6797–6804|doi=10.1021/nn501096h|pmid=24924308|s2cid=10097572 }} and graphene.{{cite journal|author1=Peng You|author2=Zhike Liu|author3=Qidong Tai|author4=Shenghua Liu|author5=Feng Yan|title=Efficient Semitransparent Perovskite Solar Cells with Graphene Electrodes |journal=Advanced Materials|year=2015|volume=27 |issue=24|pages=3632–3638|doi=10.1002/adma.201501145 |pmid=25969400|bibcode=2015AdM....27.3632Y |s2cid=36581768|doi-access=free}}

Toxicity issues associated with the lead content in perovskite solar cells strains the public perception and acceptance of the technology.{{cite journal |last1=Babayigit |first1=Aslihan |last2=Ethirajan |first2=Anitha |last3=Muller |first3=Marc |last4=Conings |first4=Bert |title=Toxicity of organometal halide perovskite solar cells |journal=Nature Materials |date=March 2016 |volume=15 |issue=3 |pages=247–251 |doi=10.1038/nmat4572 |pmid=26906955 |bibcode=2016NatMa..15..247B |hdl=2268/195044 |hdl-access=free }} The health and environmental impact of toxic heavy metals has been much debated in the case of CdTe solar cells, whose efficiency became industrially relevant in the 1990s. Although CdTe is a thermally and chemically very stable compound with a low solubility product (K_sp, of 10⁻³⁴) and, accordingly, its toxicity was revealed to be extremely low, rigorous industrial hygiene programmes{{cite book |chapter=First Solar's Cd Te module manufacturing experience; environmental, health and safety results |title=Conference Record of the Twenty-Eighth IEEE Photovoltaic Specialists Conference - 2000 (Cat. No.00CH37036) |year=2000 |last1=Bohland |first1=J.R. |last2=Smigielski |first2=K. |pages=575–578 |isbn=0-7803-5772-8|s2cid=121877756 |doi=10.1109/PVSC.2000.915904}} and recycling commitment programmes{{Cite web|date=2020 |title=The recyclign advantage|url=http://www.firstsolar.com/-/media/First-Solar/Sustainability-Documents/Recycling/First-Solar-Recycling-Brochure.ashx|website=First Solar}} have been implemented. In contrast to CdTe, hybrid perovskites are very unstable and easily degrade to rather soluble compounds of Pb or Sn with K_SP=4.4×10^−9, which significantly increases their potential bioavailability{{Cite journal|last1=Hailegnaw |first1=Bekele|last2=Kirmayer|first2=Saar|last3=Edri |first3=Eran|last4=Hodes|first4=Gary|last5=Cahen|first5=David|date=2015-05-07 |title=Rain on Methylammonium Lead Iodide Based Perovskites: Possible Environmental Effects of Perovskite Solar Cells|journal=The Journal of Physical Chemistry Letters|volume=6|issue=9|pages=1543–1547|doi=10.1021/acs.jpclett.5b00504 |pmid=26263309}} and hazard for human health, as confirmed by recent toxicological studies.{{Cite journal|last1=Benmessaoud|first1=Iness R.|last2=Mahul-Mellier|first2=Anne-Laure|last3=Horváth |first3=Endre|last4=Maco|first4=Bohumil|last5=Spina|first5=Massimo|last6=Lashuel|first6=Hilal A. |last7=Forró |first7=Làszló|date=2016-03-01|title=Health hazards of methylammonium lead iodide based perovskites: cytotoxicity studies|journal=Toxicology Research|volume=5|issue=2|pages=407–419|pmc=6062200 |doi=10.1039/c5tx00303b |pmid=30090356}}{{Cite journal|last1=Babayigit|first1=Aslihan|last2=Duy Thanh|first2=Dinh|last3=Ethirajan|first3=Anitha|last4=Manca|first4=Jean|last5=Muller|first5=Marc |last6=Boyen|first6=Hans-Gerd|last7=Conings |first7=Bert|date=2016-01-13|title=Assessing the toxicity of Pb- and Sn-based perovskite solar cells in model organism Danio rerio|journal=Scientific Reports|volume=6 |issue=1|pages=18721|doi=10.1038/srep18721|pmc=4725943 |pmid=26759068|bibcode=2016NatSR...618721B}} Although the 50% lethal dose of lead [LD₅₀(Pb)] is less than 5 mg per kg of body weight, health issues arise at much lower exposure levels. Young children absorb 4–5 times as much lead as adults and are most susceptible to the adverse effects of lead.{{cite book |last1=Fewtrell |first1=Lorna |last2=Kaufman |first2=Rachel |last3=Prüss-Üstün |first3=Annette |title=Lead: Assessing the Environmental Burden of Disease at National and Local Levels |date=May 2003 |publisher=World Health Organization |isbn=978-92-4-154610-2 |hdl=10665/42715 |hdl-access=free }} In 2003, a maximum blood Pb level (BLL) of 5 μg/dL was imposed by the World Health Organization, which corresponds to the amount of Pb contained in only 25 mm² of the perovskite solar module. Furthermore, the BLL of 5 μg/dL was revoked in 2010 after the discovery of decreased intelligence and behavioral difficulties in children exposed to even lower values.{{cite book |title=Preventing disease through healthy environments: exposure to lead: a major public health concern |date=2019 |publisher=World Health Organization |hdl=10665/329953 |isbn=978-92-4-003763-2 |hdl-access=free }} Recently, Hong Zhang et al. reported a universal co-solvent dilution strategy to significantly reduce the toxic lead waste production, the usage of perovskite materials as well as the fabrication cost by 70%, which also delivers PCEs of over 24% and 18.45% in labotorary cells and modules, respectively.{{Cite journal |last1=Zhang |first1=Hong |last2=Darabi |first2=Kasra |last3=Grätzel |first3=Michael |last4=Yaghoobi Nia |first4=Narges |last5=Aldo |first5=Di Carlo |last6=Amassian |first6=Aram |year=2022 |title=A universal co-solvent dilution strategy enables facile and cost-effective fabrication of perovskite photovoltaics |journal=Nature Communications |volume=13 |issue=1 |pages=89 |doi=10.1038/s41467-021-27740-4 |pmid=35013272 |pmc=8748698|bibcode=2022NatCo..13...89Z }} 50px Text was copied from this source, which is available under a [https://creativecommons.org/licenses/by/4.0/ Creative Commons Attribution 4.0 International License].

Various studies have been performed to analyze promising alternatives to lead perovskite for use in PSCs. Good candidates for replacement, which ideally have low toxicity, narrow direct bandgaps, high optical absorption coefficients, high carrier mobility, and good charge transport properties, include tin/germanium-halide perovskites, double perovskites, and bismuth/antimony-halides with perovskite-like structures.{{cite journal |last1=Ke |first1=Weijun |last2=Kanatzidis |first2=Mercouri G. |title=Prospects for low-toxicity lead-free perovskite solar cells |journal=Nature Communications |date=December 2019 |volume=10 |issue=1 |pages=965 |doi=10.1038/s41467-019-08918-3|pmid=30814499 |pmc=6393492 |bibcode=2019NatCo..10..965K |doi-access=free }}

Research done on tin halide-based PSCs show that they have a lower power conversion efficiency (PCE), with those fabricated experimentally achieving a PCE of 9.6%. This relatively low PCE is in part due to the oxidation of Sn²⁺ to Sn⁴⁺, which will act as a p-type dopant in the structure and result in higher dark carrier concentration and increased carrier recombination rates.{{cite journal |last1=Jokar |first1=Efat |last2=Chien |first2=Cheng-Hsun |last3=Tsai |first3=Cheng-Min |last4=Fathi |first4=Amir |last5=Diau |first5=Eric Wei-Guang |title=Robust Tin-Based Perovskite Solar Cells with Hybrid Organic Cations to Attain Efficiency Approaching 10 |journal=Advanced Materials|date=January 2019 |volume=31 |issue=2 |pages=e1804835 |doi=10.1002/adma.201804835 |pmid=30411826 |bibcode=2019AdM....3104835J |s2cid=53242660 }} Germanium halide perovskites have proven similarly unsuccessful due to low efficiencies and issues with oxidising tendencies, with one experimental solar cells displaying a PCE of only 0.11%.{{cite journal |last1=Krishnamoorthy |first1=Thirumal |last2=Ding |first2=Hong |last3=Yan |first3=Chen |last4=Leong |first4=Wei Lin |last5=Baikie |first5=Tom |last6=Zhang |first6=Ziyi |last7=Sherburne |first7=Matthew |last8=Li |first8=Shuzhou |last9=Asta |first9=Mark |last10=Mathews |first10=Nripan |last11=Mhaisalkar |first11=Subodh G. |title=Lead-free germanium iodide perovskite materials for photovoltaic applications |journal=Journal of Materials Chemistry A |date=24 November 2015 |volume=3 |issue=47 |pages=23829–23832 |doi=10.1039/C5TA05741H |hdl=10356/142601 |hdl-access=free }} Higher PCEs have been reported from some germanium tin alloy-based perovskites, however, with an all-inorganic CsSn_0.5Ge_0.5I₃ film having a reported PCE of 7.11%. In addition to this higher efficiency, the germanium tin alloy perovskites have also been found to have high photostability.{{cite journal |last1=Chen |first1=Min |last2=Ju |first2=Ming-Gang |last3=Garces |first3=Hector F. |last4=Carl |first4=Alexander D. |last5=Ono |first5=Luis K. |last6=Hawash |first6=Zafer |last7=Zhang |first7=Yi |last8=Shen |first8=Tianyi |last9=Qi |first9=Yabing |last10=Grimm |first10=Ronald L. |last11=Pacifici |first11=Domenico |last12=Zeng |first12=Xiao Cheng |last13=Zhou |first13=Yuanyuan |last14=Padture |first14=Nitin P. |title=Highly stable and efficient all-inorganic lead-free perovskite solar cells with native-oxide passivation |journal=Nature Communications |date=3 January 2019 |volume=10 |issue=1 |pages=16 |doi=10.1038/s41467-018-07951-y |pmid=30604757 |pmc=6318336 |bibcode=2019NatCo..10...16C |doi-access=free }}

Apart from the Tin and Germanium based perovskites, there has also been research on the viability of double-perovskites with the formula of A₂M⁺M³⁺X₆. While these double-perovskites have a favorable bandgap of approximately 2 eV and exhibit good stability, several issues including high electron/hole effective masses and the presence of indirect bandgaps result in lowered carrier mobility and charge transport.{{cite journal |last1=Giustino |first1=Feliciano |last2=Snaith |first2=Henry J. |title=Toward Lead-Free Perovskite Solar Cells |journal=ACS Energy Letters |date=9 December 2016 |volume=1 |issue=6 |pages=1233–1240 |doi=10.1021/acsenergylett.6b00499 |doi-access=free }} Research exploring the viability of Bismuth/Antimony halides in replacing lead perovskites has also been done, particularly with Cs₃Sb₂I₉ and Cs₃Bi₂I₉, which also have bandgaps of approximately 2 eV.{{cite journal |last1=McCall |first1=Kyle M. |last2=Stoumpos |first2=Constantinos C. |last3=Kostina |first3=Svetlana S. |last4=Kanatzidis |first4=Mercouri G. |last5=Wessels |first5=Bruce W. |title=Strong Electron–Phonon Coupling and Self-Trapped Excitons in the Defect Halide Perovskites A3M2I9 (A = Cs, Rb; M = Bi, Sb) |journal=Chemistry of Materials |date=9 May 2017 |volume=29 |issue=9 |pages=4129–4145 |doi=10.1021/acs.chemmater.7b01184 |osti=1494819 |url=https://www.osti.gov/biblio/1494819 }} Experimental results have also shown that, while Antimony and Bismuth halide-based PSCs have good stability, their low carrier mobilities and poor charge transport properties restrict their viability in replacing lead-based perovskites.

Recent research into the usage of encapsulation as a method for reducing lead leakage has been conducted, particularly focusing on the utilization of self-healing polymers. Research has been done on two promising polymers, Surlyn and a thermal crosslinking epoxy-resin, diglycidyl ether bisphenol A:n-octylamine:m-xylylenediamine = 4:2:1. Experiments showed a substantial reduction in lead leakage from PSCs using these self-healing polymers under simulated sunny weather conditions and after simulated hail damage had cracked the outer glass encapsulation. Notably, the epoxy-resin encapsulation was able to reduce lead leakage by a factor of 375 times when heated by simulated sunlight.{{cite journal |last1=Jiang |first1=Yan |last2=Qiu |first2=Longbin |last3=Juarez-Perez |first3=Emilio J. |last4=Ono |first4=Luis K. |last5=Hu |first5=Zhanhao |last6=Liu |first6=Zonghao |last7=Wu |first7=Zhifang |last8=Meng |first8=Lingqiang |last9=Wang |first9=Qijing |last10=Qi |first10=Yabing |title=Reduction of lead leakage from damaged lead halide perovskite solar modules using self-healing polymer-based encapsulation |journal=Nature Energy |date=July 2019 |volume=4 |issue=7 |pages=585–593 |doi=10.1038/s41560-019-0406-2 |bibcode=2019NatEn...4..585J |s2cid=189929914 |url=https://oist.repo.nii.ac.jp/?action=repository_action_common_download&item_id=1213&item_no=1&attribute_id=22&file_no=2 }}

Chemically lead-binding coatings have also been employed experimentally to reduce lead leakage from PSCs. In particular, Cation Exchange Resins (CERs) and P,P′-di(2-ethylhexyl)methanediphosphonic acid (DMDP) have been employed experimentally in this effort. Both coatings work similarly, chemically sequestering lead that might leak from a PSC module after weather damage occurs. Research into CERs has shown that, through diffusion-controlled processes, Pb²⁺ lead is effectively adsorbed and bonded onto the surface of CERs, even in the presence of competing divalent ions such as Mg²⁺ and Ca²⁺ that might also occupy binding sites on the CER surface.{{cite journal |last1=Chen |first1=Shangshang |last2=Deng |first2=Yehao |last3=Gu |first3=Hangyu |last4=Xu |first4=Shuang |last5=Wang |first5=Shen |last6=Yu |first6=Zhenhua |last7=Blum |first7=Volker |last8=Huang |first8=Jinsong |title=Trapping lead in perovskite solar modules with abundant and low-cost cation-exchange resins |journal=Nature Energy |date=2 November 2020 |volume=5 |issue=12 |pages=1003–1011 |doi=10.1038/s41560-020-00716-2|bibcode=2020NatEn...5.1003C |s2cid=228806268 |url=https://cdr.lib.unc.edu/downloads/2z10x177k }}

To test the efficacy of CER-based coatings in adsorbing lead in practical conditions, researchers dripped slightly acidic water, meant to simulate rainwater, onto a PSC module cracked by simulated hail damage. Researchers found that by applying a CER coating onto the copper electrodes of damaged PSC modules, lead leakage was reduced by 84%. When the CER was integrated into a carbon-based electrode paste applied to PSC and on the top of the encapsulating glass, the lead leakage decreased by 98%. A similar test was also performed on a PSC module with DMDP coated on both the top and bottom of the module to study the efficacy of DMDP in reducing lead leakage. In this test, the module was cracked by simulated hail damage, and placed in a solution of acidic water containing aqueous Ca²⁺ ions, meant to simulate acidic rain with low levels of aqueous Calcium present. The lead concentration of acidic water was tracked, and researchers found that the lead sequestration efficiency of the DMDP coating at room temperature 96.1%.{{cite journal |last1=Li |first1=Xun |last2=Zhang |first2=Fei |last3=He |first3=Haiying |last4=Berry |first4=Joseph J. |last5=Zhu |first5=Kai |last6=Xu |first6=Tao |title=On-device lead sequestration for perovskite solar cells |journal=Nature |date=February 2020 |volume=578 |issue=7796 |pages=555–558 |doi=10.1038/s41586-020-2001-x |pmid=32076266 |bibcode=2020Natur.578..555L |osti=1602693 |s2cid=211195242 |url=https://www.osti.gov/biblio/1602693 }}

A co-solvent dilution strategy has been reported to obtain high-quality perovskite films with very low concentration precursor solutions. This strategy substantially reduces the quantity of expensive raw materials in the perovskite precursor ink and reduces the toxic waste production by spin coating through two key routes: minimizing precursor loss during the processing of perovskite films and enhancing the lifetime and shelf-life of the inks by suppressing aggregation of precursor colloids. A PCE of over 24% for laboratory PSCs could be achieved with a co-solvent dilution to a level as low as 0.5 M. In addition, scalability of the co-solvent dilution strategy is tested via fabrication of perovskite solar modules (PSMs) with different sizes using industrial spin coating. The modules fabricated by co-solvent dilution strategy show higher PCEs and far better uniformity and reproducibility than modules prepared with conventional perovskite inks, whilst using a fraction of the precursor. Importantly, more than 70% toxic waste/solvent, perovskite raw material, and fabrication cost are projected to be reduced for module fabrication compared to the same modules made using conventional inks by industrial spin coating, and in doing so make spin coating a sustainable technique for medium scale manufacturing, for instance, for standalone modules or Si wafer-scale integration. This work shows that through judicious selection of a greener co-solvent, we can significantly reduce the usage and waste of toxic solvents and perovskite raw materials, while also simplifying fabrication and cutting costs of PSCs.

An important characteristic of the most commonly used perovskite system, the methylammonium lead halides, is a bandgap controllable by the halide content.

The materials also display a diffusion length for both holes and electrons of over one micron.{{cite journal|last1=Stranks|first1=S. D.|last2=Eperon|first2=G. E.|last3=Grancini|first3=G. |last4=Menelaou |first4=C.|last5=Alcocer|first5=M. J. P.|last6=Leijtens|first6=T.|last7=Herz|first7=L. M.|last8=Petrozza|first8=A.|last9=Snaith|first9=H. J.|s2cid=10314803|display-authors=8|date=October 17, 2013|title=Electron-Hole Diffusion Lengths Exceeding 1 Micrometer in an Organometal Trihalide Perovskite Absorber|journal=Science|volume=342|issue=6156|pages=341–344|doi=10.1126/science.1243982|pmid=24136964 |bibcode=2013Sci...342..341S |url=https://ora.ox.ac.uk/objects/uuid:5c3cd89c-98a4-4bac-b3be-6c023adc5e0a}}{{cite web|title=Oxford Researchers Creating Simpler, Cheaper Solar Cells|date=November 12, 2013 |website=SciTechDaily.com |url=http://scitechdaily.com/oxford-researchers-creating-simpler-cheaper-solar-cells/}}{{Cite journal|last1=Liu|first1=Shuhao|last2=Wang|first2=Lili|last3=Lin|first3=Wei-Chun |last4=Sucharitakul|first4=Sukrit|last5=Burda |first5=Clemens|last6=Gao|first6=Xuan P. A.|date=2016-12-14 |title=Imaging the Long Transport Lengths of Photo-generated Carriers in Oriented Perovskite Films |journal=Nano Letters|volume=16|issue=12|pages=7925–7929 |doi=10.1021/acs.nanolett.6b04235|pmid=27960525 |arxiv=1610.06165|bibcode=2016NanoL..16.7925L|s2cid=1695198}}

The long diffusion length means that these materials can function effectively in a thin-film architecture, and that charges can be transported in the perovskite itself over long distances.

It has recently been reported that charges in the perovskite material are predominantly present as free electrons and holes, rather than as bound excitons, since the exciton binding energy is low enough to enable charge separation at room temperature.{{cite journal|last1=D’Innocenzo|first1=Valerio |last2=Grancini|first2=Giulia|last3=Alcocer|first3=Marcelo J. P.|last4=Kandada|first4=Ajay Ram Srimath |last5=Stranks|first5=Samuel D.|last6=Lee |first6=Michael M.|last7=Lanzani|first7=Guglielmo|last8=Snaith |first8=Henry J.|last9=Petrozza|first9=Annamaria| display-authors = 8|title=Excitons versus free charges in organo-lead tri-halide perovskites|journal=Nature Communications|date=April 8, 2014|volume=5|page=3586 |doi=10.1038/ncomms4586|pmid=24710005|bibcode=2014NatCo...5.3586D|doi-access=free|hdl=11311/862945|hdl-access=free}}{{cite journal|author=Collavini, S.|author2=Völker, S. F. |author3=Delgado, J. L.|year=2015 |title=Understanding the Outstanding Power Conversion Efficiency of Perovskite-Based Solar Cells |journal=Angewandte Chemie International Edition|volume=54|issue=34|pages=9757–9759 |doi=10.1002/anie.201505321|pmid=26213261}}

Perovskite solar cell bandgaps are tunable and can be optimised for the solar spectrum by altering the halide content in the film (i.e., by mixing I and Br). The Shockley–Queisser limit radiative efficiency limit, also known as the detailed balance limit,{{Cite journal |title=MATLAB Program of Detailed Balance Model for Perovskite Solar Cells |doi=10.13140/RG.2.2.17132.36481 |date=November 2016 |last1=Sha|first1=Wei E. I. |journal=Photon Recycling Effect in Perovskite Solar Cells}} is about 31% under an AM1.5G solar spectrum at 1000 W/m{{sup|2}}, for a Perovskite bandgap of 1.55 eV.{{Cite journal|title = Tabulated Values of the Shockley-Queisser Limit for Single Junction Solar Cells|journal = Solar Energy|date = 2016-02-08|pages = 139–147|volume = 130|doi = 10.1016/j.solener.2016.02.015 |first = Sven|last = Rühle|bibcode = 2016SoEn..130..139R}} This is slightly smaller than the radiative limit of gallium arsenide of bandgap 1.42 eV which can reach a radiative efficiency of 33%.

Values of the detailed balance limit are available in tabulated form and a MATLAB program for implementing the detailed balance model has been written.

In the meantime, the drift-diffusion model has found to successfully predict the efficiency limit of perovskite solar cells, which enable us to understand the device physics in-depth, especially the radiative recombination limit and selective contact on device performance.{{Cite journal|last1=Ren|first1=Xingang|last2=Wang|first2=Zishuai|last3=Sha|first3=Wei E. I.|last4=Choy|first4=Wallace C. H.|year=2017|title=Exploring the Way To Approach the Efficiency Limit of Perovskite Solar Cells by Drift-Diffusion Model|journal=ACS Photonics|volume=4|issue=4|pages=934–942|doi=10.1021/acsphotonics.6b01043|arxiv=1703.07576|bibcode=2017arXiv170307576R|s2cid=119355156}} There are two prerequisites for predicting and approaching the perovskite efficiency limit. First, the intrinsic radiative recombination needs to be corrected after adopting optical designs which will significantly affect the open-circuit voltage at its Shockley–Queisser limit. Second, the contact characteristics of the electrodes need to be carefully engineered to eliminate the charge accumulation and surface recombination at the electrodes. With the two procedures, the accurate prediction of efficiency limit and precise evaluation of efficiency degradation for perovskite solar cells are attainable by the drift-diffusion model.

Along with detailed balance analysis and drift-diffusion calculations, there have been many first principle studies to find the characteristics of the perovskite material numerically. These include but are not limited to bandgap, effective mass, and defect levels for different perovskite materials.{{Cite journal|title = First-Principles Modeling of Mixed Halide Organometal Perovskites for Photovoltaic Applications|journal = The Journal of Physical Chemistry C|date = 2013-07-01|pages = 13902–13913|volume = 117|issue = 27|doi = 10.1021/jp4048659|first1 = Edoardo|last1 = Mosconi|first2 = Anna|last2 = Amat|first3 = Md. K.|last3 = Nazeeruddin|first4 = Michael|last4 = Grätzel|first5 = Filippo De|last5 = Angelis|url = https://zenodo.org/record/3424941}}{{Cite journal|title = First-principles study on the electronic and optical properties of cubic ABX3 halide perovskites|journal = Physics Letters A|date = 2014-01-10|pages = 290–293|volume = 378|issue = 3|doi = 10.1016/j.physleta.2013.11.018|first1 = Li|last1 = Lang|first2 = Ji-Hui|last2 = Yang|first3 = Heng-Rui|last3 = Liu|first4 = H. J.|last4 = Xiang|first5 = X. G.|last5 = Gong|arxiv = 1309.0070|bibcode = 2014PhLA..378..290L|s2cid = 119206094}}{{Cite journal|title = General Working Principles of CH 3 NH 3 PbX 3 Perovskite Solar Cells|journal = Nano Letters|date = 2014-01-10|pages = 888–893|volume = 14|issue = 2|doi = 10.1021/nl404252e|pmid = 24397375|first1 = Victoria|last1 = Gonzalez-Pedro|first2 = Emilio J.|last2 = Juarez-Perez|first3 = Waode-Sukmawati|last3 = Arsyad|first4 = Eva M.|last4 = Barea|first5 = Francisco|last5 = Fabregat-Santiago|first6 = Ivan|last6 = Mora-Sero| first7 = Juan|last7 = Bisquert | author-link7 = Juan Bisquert |bibcode = 2014NanoL..14..888G|hdl = 10234/131066}}{{Cite journal|title = Relativistic GW calculations on CH3NH3PbI3 and CH3NH3SnI3 Perovskites for Solar Cell Applications|journal = Scientific Reports|date = 2014-03-26|volume = 4|issue = 4467|doi = 10.1038/srep04467|first1 = Paolo|last1 = Umari|first2 = Edoardo|last2 = Mosconi|first3 = Filippo De|last3 = Angelis|pmid=24667758|pmc = 5394751|page=4467|arxiv = 1309.4895|bibcode = 2014NatSR...4.4467U}} Also there have some efforts to cast light on the device mechanism based on simulations where Agrawal et al.{{Cite book|date = 2014-06-01|pages = 1515–1518|doi = 10.1109/PVSC.2014.6925202|first1 = S.|last1 = Agarwal|first2 = P.R.|last2 = Nair| title=2014 IEEE 40th Photovoltaic Specialist Conference (PVSC) | chapter=Performance optimization for Perovskite based solar cells |isbn = 978-1-4799-4398-2|s2cid = 23608158}} suggests a modeling framework,{{Cite journal|title = Device engineering of perovskite solar cells to achieve near ideal efficiency|journal = Applied Physics Letters|year = 2015|page = 123901|volume = 107|issue = 12|doi = 10.1063/1.4931130|first1 = Sumanshu|last1 = Agarwal|first2 = Pradeep R.|last2 = Nair|arxiv = 1506.07253|bibcode = 2015ApPhL.107l3901A|s2cid = 119290700}} presents analysis of near ideal efficiency, and talks about the importance of interface of perovskite and hole/electron transport layers.{{Cite journal|title = Device modeling of perovskite solar cells based on structural similarity with thin film inorganic semiconductor solar cells|journal = Journal of Applied Physics|date = 2014-08-07|page = 054505|volume = 116|issue = 5|doi = 10.1063/1.4891982|first1 = Takashi|last1 = Minemoto|first2 = Masashi|last2 = Murata|bibcode = 2014JAP...116e4505M|doi-access = free}}

Additionally, circuit model has been developed for describing the current density-voltage characteristics of perovskite solar cells. Sun et al.{{Cite journal|title = A Physics-Based Analytical Model for Perovskite Solar Cells|journal = IEEE Journal of Photovoltaics|date = 2015-09-01|pages = 1389–1394|volume = 5|issue = 5|doi = 10.1109/JPHOTOV.2015.2451000|first1 = Xingshu|last1 = Sun|first2 = R.|last2 = Asadpour|first3 = Wanyi|last3 = Nie|first4 = A.D.|last4 = Mohite|first5 = M.A.|last5 = Alam|arxiv = 1505.05132|bibcode = 2015arXiv150505132S|s2cid = 21240831}} tries to come up with a compact model for perovskite different structures based on experimental transport data. Minshen Lin et al. proposed a modified diode model to quantify the efficiency loss of perovskite solar cells.{{Cite journal|title = Quantifying Nonradiative Recombination and Resistive Losses in Perovskite Photovoltaics: A Modified Diode Model Approach|journal = Solar RRL|date = 2013-11-02|pages = 2300722|volume = 8|issue = 1|doi = 10.1002/solr.202300722|first1 = Minshen|last1 = Lin|first2 = Xuehui|last2 = Xu|first3 = Hong|last3 = Tian|first4 = Yang (Michael)|last4 = Yang|first5 = Wei E. I.|last5 = Sha|first6 = Wenxing|last6 = Zhong|arxiv = 2311.17442}}

File:Perovskite solar cell architectures 1.png TiO₂ which is coated with the perovskite absorber. The active layer is contacted with an n-type material for electron extraction and a p-type material for hole extraction. b) Schematic of a thin-film perovskite solar cell. In this architecture in which just a flat layer of perovskite is sandwiched between two selective contacts. c) Charge generation and extraction in the sensitized architecture. After light absorption in the perovskite absorber the photogenerated electron is injected into the mesoporous TiO₂ through which it is extracted. The concomitantly generated hole is transferred to the p-type material. d) Charge generation and extraction in the thin-film architecture. After light absorption both charge generation as well as charge extraction occurs in the perovskite layer.]]

Perovskite solar cells function efficiently in a number of somewhat different architectures depending either on the role of the perovskite material in the device, or the nature of the top and bottom electrode. Devices in which positive charges are extracted by the transparent bottom electrode (cathode), can predominantly be divided into 'sensitized', where the perovskite functions mainly as a light absorber, and charge transport occurs in other materials, or 'thin-film', where most electron or hole transport occurs in the bulk of the perovskite itself. Similar to the sensitization in dye-sensitized solar cells, the perovskite material is coated onto a charge-conducting mesoporous scaffold – most commonly TiO₂ – as light-absorber. The photogenerated electrons are transferred from the perovskite layer to the mesoporous sensitized layer through which they are transported to the electrode and extracted into the circuit. The thin film solar cell architecture is based on the finding that perovskite materials can also act as highly efficient, ambipolar charge-conductor.

After light absorption and the subsequent charge-generation, both negative and positive charge carrier are transported through the perovskite to charge selective contacts. Perovskite solar cells emerged from the field of dye-sensitized solar cells, so the sensitized architecture was that initially used, but over time it has become apparent that they function well, if not ultimately better, in a thin-film architecture.{{cite journal|last1=Eperon|first1=Giles E.|last2=Burlakov|first2=Victor M.|last3=Docampo|first3=Pablo|last4=Goriely|first4=Alain|last5=Snaith|first5=Henry J.|title=Morphological Control for High Performance, Solution-Processed Planar Heterojunction Perovskite Solar Cells|journal=Advanced Functional Materials|volume=24|issue=1|pages=151–157|doi=10.1002/adfm.201302090|year=2014|s2cid=96798077|url=https://ora.ox.ac.uk/objects/uuid:c71608e0-a544-4d28-bb73-e87316f9191e}} More recently, some researchers also successfully demonstrated the possibility of fabricating flexible devices with perovskites,{{Cite journal|title = Efficient organometal trihalide perovskite planar-heterojunction solar cells on flexible polymer substrates|journal = Nature Communications|volume = 4|doi = 10.1038/ncomms3761|first1 = Pablo|last1 = Docampo|first2 = James M.|last2 = Ball|first3 = Mariam|last3 = Darwich|first4 = Giles E.|last4 = Eperon|first5 = Henry J.|last5 = Snaith|year = 2013|pmid=24217714|page=2761|bibcode = 2013NatCo...4.2761D|doi-access = free}}{{Cite journal|title = Low-Temperature Solution-Processed Perovskite Solar Cells with High Efficiency and Flexibility|journal = ACS Nano|date = February 25, 2014|pages = 1674–1680|volume = 8|issue = 2|doi = 10.1021/nn406020d|pmid = 24386933|first1 = Jingbi|last1 = You|first2 = Ziruo|last2 = Hong|first3 = Yang (Michael)|last3 = Yang|first4 = Qi|last4 = Chen|first5 = Min|last5 = Cai|first6 = Tze-Bin|last6 = Song|first7 = Chun-Chao|last7 = Chen|first8 = Shirong|last8 = Lu|first9 = Yongsheng|last9 = Liu}}{{Cite journal|last=Zhang|first=Hong|date=2015|title=Pinhole-free and Surface-Nanostructured NiOx Film by Room-Temperature Solution Process for High-Performance Flexible Perovskite Solar Cells with Good Stability and Reproducibility|url=https://www.researchgate.net/profile/Hong_Zhang174|journal=ACS Nano |volume=10 |issue=1 |pages=1503–1511|doi=10.1021/acsnano.5b07043|pmid=26688212}} which makes it more promising for flexible energy demand. Certainly, the aspect of UV-induced degradation in the sensitized architecture may be detrimental for the important aspect of long-term stability.

There is another different class of architectures, in which the transparent electrode at the bottom acts as cathode by collecting the photogenerated p-type charge carriers.

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| image1 = Expanding the standard research cycle in experimental material science.webp

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| alt1 = Expanding the standard research cycle in experimental material science

| caption1 = Schema of how the open database, interactive visualization tools, protocols and a metadata ontology for reporting device data, open-source code for data analysis, etc. can support PSC development.

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| alt2 = Development of perovskite cell efficiencies

| caption2 = Example of analysis from the database; in the initial version one can display "the performance evolution of, for example, flexible cells, cells based on CsPbI₃ or cells fulfilling any combination of constraints" with a click.

}}

The Perovskite Database is a database and analysis tool of perovskite solar cells research data which systematically integrates over 15,000 publications, in particular device-data about "over 42,400" perovskite devices. Authors described the FAIR open database site – which as of January 2022 requires signing up to access the data and uses software that is partly open source but not marked as having a free software license on GitHub{{cite web |title=Jesperkemist/perovskitedatabase |website=GitHub |date=24 January 2022 |url=https://github.com/Jesperkemist/perovskitedatabase |access-date=24 January 2022}} – as a participative "Wikipedia for perovskite solar cell research". It allows data to be filtered and displayed according to various criteria such as material compositions or component type and could thereby support the development of optimal architecture designs (including the materials used).{{cite news |title=The Wikipedia of perovskite solar cell research |url=https://techxplore.com/news/2021-12-wikipedia-perovskite-solar-cell.html |access-date=19 January 2022 |work=Helmholtz Association of German Research Centres}}{{cite journal |author1=T. Jesper Jacobsson |author2=Adam Hultqvist |author3=Alberto García-Fernández |display-authors=et al. |title=An open-access database and analysis tool for perovskite solar cells based on the FAIR data principles |journal=Nature Energy |date=13 December 2021 |volume=7 |pages=107–115 |doi=10.1038/s41560-021-00941-3 |s2cid=245175279 |issn=2058-7546|doi-access=free |hdl=10356/163386 |hdl-access=free }}

High-throughput screening of mixtures and contact layers is one development mechanism that has been used to develop relatively stable perovskite solar cells.{{cite journal |last1=Zhao |first1=Yicheng |last2=Heumueller |first2=Thomas |last3=Zhang |first3=Jiyun |last4=Luo |first4=Junsheng |last5=Kasian |first5=Olga |last6=Langner |first6=Stefan |last7=Kupfer |first7=Christian |last8=Liu |first8=Bowen |last9=Zhong |first9=Yu |last10=Elia |first10=Jack |last11=Osvet |first11=Andres |last12=Wu |first12=Jianchang |last13=Liu |first13=Chao |last14=Wan |first14=Zhongquan |last15=Jia |first15=Chunyang |last16=Li |first16=Ning |last17=Hauch |first17=Jens |last18=Brabec |first18=Christoph J. |title=A bilayer conducting polymer structure for planar perovskite solar cells with over 1,400 hours operational stability at elevated temperatures |journal=Nature Energy |date=16 December 2021 |volume=7 |issue=2 |pages=144–152 |doi=10.1038/s41560-021-00953-z |bibcode=2022NatEn...7..144Z |s2cid=245285868 |language=en |issn=2058-7546}}

{{See also|Timeline of solar cells}}

Perovskite materials have been well known for many years, but the first incorporation into a solar cell was reported by Tsutomu Miyasaka et al. in 2009.

This was based on a dye-sensitized solar cell architecture, and generated only 3.8% power conversion efficiency (PCE) with a thin layer of perovskite on mesoporous TiO₂ as electron-collector. Moreover, because a liquid corrosive electrolyte was used, the cell was only stable for a few minutes. Nam-Gyu Park et al. improved upon this in 2011, using the same dye-sensitized concept, achieving 6.5% PCE.{{cite journal|last1=Im|first1=Jeong-Hyeok|last2=Lee|first2=Chang-Ryul|last3=Lee|first3=Jin-Wook|last4=Park|first4=Sang-Won|last5=Park|first5=Nam-Gyu|s2cid=205795756|title=6.5% efficient perovskite quantum-dot-sensitized solar cell|journal=Nanoscale|volume=3|issue=10|pages=4088–4093|doi=10.1039/C1NR10867K|pmid=21897986|year=2011|bibcode=2011Nanos...3.4088I}}

A breakthrough came in 2012, when Mike Lee and Henry Snaith from the University of Oxford realised that the perovskite was stable if contacted with a solid-state hole transporter such as spiro-OMeTAD and did not require the mesoporous TiO₂ layer in order to transport electrons.{{cite journal|last1=Lee|first1=M. M.|last2=Teuscher|first2=J.|last3=Miyasaka|first3=T.|last4=Murakami|first4=T. N.|last5=Snaith|first5=H. J.|s2cid=37971858|title=Efficient Hybrid Solar Cells Based on Meso-Superstructured Organometal Halide Perovskites|journal=Science|date=October 4, 2012|volume=338|issue=6107|pages=643–647|doi=10.1126/science.1228604|pmid=23042296|bibcode=2012Sci...338..643L|doi-access=free}}{{cite web|website=RSC Chemistry world|url=http://www.rsc.org/chemistryworld/2012/10/perovskite-solar-cell-energy-loss|title=Perovskite coat gives hybrid solar cells a boost|date=October 4, 2012|author=Hadlington, Simon }}

They showed that efficiencies of almost 10% were achievable using the 'sensitized' TiO₂ architecture with the solid-state hole transporter, but higher efficiencies, above 10%, were attained by replacing it with an inert scaffold.{{cite journal|last1=Kim|first1=Hui-Seon|last2=Lee|first2=Chang-Ryul|last3=Im|first3=Jeong-Hyeok|last4=Lee|first4=Ki-Beom|last5=Moehl|first5=Thomas|last6=Marchioro|first6=Arianna|last7=Moon|first7=Soo-Jin|last8=Humphry-Baker|first8=Robin|last9=Yum|first9=Jun-Ho|last10=Moser|first10=Jacques E.|last11=Grätzel|first11=Michael|last12=Park|first12=Nam-Gyu|title=Lead Iodide Perovskite Sensitized All-Solid-State Submicron Thin Film Mesoscopic Solar Cell with Efficiency Exceeding 9%|journal=Scientific Reports|date=August 21, 2012|volume=2|page=591|doi=10.1038/srep00591|pmid=22912919|pmc=3423636|bibcode= 2012NatSR...2..591K}}

Further experiments in replacing the mesoporous TiO₂ with Al₂O₃ resulted in increased open-circuit voltage and a relative improvement in efficiency of 3–5% more than those with TiO₂ scaffolds.

This led to the hypothesis that a scaffold is not needed for electron extraction, which was later proved correct. This realisation was then closely followed by a demonstration that the perovskite itself could also transport holes, as well as electrons.{{cite journal|last1=Ball|first1=James M.|last2=Lee|first2=Michael M.|last3=Hey|first3=Andrew|last4=Snaith|first4=Henry J.|title=Low-temperature processed meso-superstructured to thin-film perovskite solar cells|journal=Energy & Environmental Science|volume=6|issue=6|page=1739|doi=10.1039/C3EE40810H|year=2013}}

A thin-film perovskite solar cell, with no mesoporous scaffold, of > 10% efficiency was achieved.{{cite journal|last1=Saliba|first1=Michael|last2=Tan|first2=Kwan Wee|last3=Sai|first3=Hiroaki|last4=Moore|first4=David T.|last5=Scott|first5=Trent|last6=Zhang|first6=Wei|last7=Estroff|first7=Lara A.|last8=Wiesner|first8=Ulrich|last9=Snaith|first9=Henry J.|title=Influence of Thermal Processing Protocol upon the Crystallization and Photovoltaic Performance of Organic–Inorganic Lead Trihalide Perovskites|journal=The Journal of Physical Chemistry C|date=July 31, 2014|volume=118|issue=30|pages=17171–17177|doi=10.1021/jp500717w}}{{cite journal|last1=Tan|first1=Kwan Wee|last2=Moore|first2=David T.|last3=Saliba|first3=Michael|last4=Sai|first4=Hiroaki|last5=Estroff|first5=Lara A.|last6=Hanrath|first6=Tobias|last7=Snaith|first7=Henry J.|last8=Wiesner|first8=Ulrich|title=Thermally Induced Structural Evolution and Performance of Mesoporous Block Copolymer-Directed Alumina Perovskite Solar Cells|journal=ACS Nano|date=May 27, 2014|volume=8|issue=5|pages=4730–4739|doi=10.1021/nn500526t|pmid=24684494|pmc=4046796}}

In 2013 both the planar and sensitized architectures saw a number of developments.

Burschka et al. demonstrated a deposition technique for the sensitized architecture exceeding 15% efficiency by a two-step solution processing,{{cite journal|last1=Burschka|first1=Julian|last2=Pellet|first2=Norman|last3=Moon|first3=Soo-Jin|last4=Humphry-Baker|first4=Robin|last5=Gao|first5=Peng|last6=Nazeeruddin|first6=Mohammad K.|last7=Grätzel|first7=Michael|title=Sequential deposition as a route to high-performance perovskite-sensitized solar cells|journal=Nature|date=July 10, 2013|volume=499|issue=7458|pages=316–319|doi=10.1038/nature12340|pmid=23842493|bibcode=2013Natur.499..316B|s2cid=4348717|url=https://zenodo.org/record/3425690}} At a similar time Olga Malinkiewicz et al., and Liu et al. showed that it was possible to fabricate planar solar cells by thermal co-evaporation, achieving more than 12% and 15% efficiency in a p-i-n and an n-i-p architecture respectively.{{cite journal|author1=Olga Malinkiewicz |author2=Aswani Yella |author3=Yong Hui Lee |author4=Guillermo Mínguez Espallargas |author5=Michael Graetzel |author6=Mohammad K. Nazeeruddin |author7=Henk J. Bolink|title=Perovskite solar cells employing organic charge-transport layers|journal=Nature Photonics |date=2013|volume=8|issue=2|pages=128–132|doi=10.1038/nphoton.2013.341|bibcode=2014NaPho...8..128M|s2cid=121301878 |url=https://zenodo.org/record/3426092}}{{cite journal|last1=Liu|first1=Mingzhen|last2=Johnston|first2=Michael B.|last3=Snaith|first3=Henry J.|title=Efficient planar heterojunction perovskite solar cells by vapour deposition|journal=Nature|date=September 11, 2013|volume=501|issue=7467|pages=395–398|doi=10.1038/nature12509|pmid=24025775|bibcode=2013Natur.501..395L|s2cid=205235359}}{{cite news |last1=Miodownik |first1=Mark |title=The perovskite lightbulb moment for solar power |url=https://www.theguardian.com/technology/2014/mar/02/perovskite-lightbulb-moment-abundant-solar-power-britain |work=The Guardian |date=2 March 2014 }}

Docampo et al. also showed that it was possible to fabricate perovskite solar cells in the typical 'organic solar cell' architecture, an 'inverted' configuration with the hole transporter below and the electron collector above the perovskite planar film.{{cite journal|last1=Docampo|first1=Pablo|last2=Ball |first2=James M.|last3=Darwich|first3=Mariam|last4=Eperon|first4=Giles E.|last5=Snaith|first5=Henry J. |title=Efficient organometal trihalide perovskite planar-heterojunction solar cells on flexible polymer substrates|journal=Nature Communications|date=November 12, 2013|volume=4 |doi=10.1038/ncomms3761|pmid=24217714|page=2761|bibcode=2013NatCo...4.2761D|doi-access=free}}

A range of new deposition techniques and even higher efficiencies were reported in 2014. A reverse-scan efficiency of 19.3% was claimed by Yang Yang at UCLA using the planar thin-film architecture.{{cite journal|last1=Zhou|first1=H.|last2=Chen|first2=Q.|last3=Li |first3=G.|last4=Luo|first4=S.|last5=Song|first5=T.-b.|last6=Duan|first6=H.-S.|last7=Hong|first7=Z. |last8=You|first8=J.|last9=Liu|first9=Y. |last10=Yang|first10=Y.|title=Interface engineering of highly efficient perovskite solar cells|journal=Science|date=July 31, 2014|volume=345|issue=6196|pages=542–546 |doi=10.1126/science.1254050|pmid=25082698 |bibcode=2014Sci...345..542Z|s2cid=32378923}} In November 2014, a device by researchers from KRICT achieved a record with the certification of a non-stabilized efficiency of 20.1%.

Continuing the trend, a new record of efficiency for a single-junction perovskite solar cell efficiency was set each year since 2015, with the most frequent record-breakers coming from KRICT and UNIST. The latest record-holders are researchers from UNIST who achieved 25.7% efficiency. There are also efforts focused on reducing energy cost, including the Apolo project consortium at CEA laboratories which aims to bring the module cost below €0.40/Wp (Watt peak).{{citation needed|date=September 2024}}

At least since 2016, the records for perovskite-silicon tandem solar cells have consistently remained higher than the ones for single-junction cells.{{cite journal |last1=Bush |first1=Kevin A. |last2=Palmstrom |first2=Axel F. |last3=Yu |first3=Zhengshan J. |last4=Boccard |first4=Mathieu |last5=Cheacharoen |first5=Rongrong |last6=Mailoa |first6=Jonathan P. |last7=McMeekin |first7=David P. |last8=Hoye |first8=Robert L. Z. |last9=Bailie |first9=Colin D. |last10=Leijtens |first10=Tomas |last11=Peters |first11=Ian Marius |last12=Minichetti |first12=Maxmillian C. |last13=Rolston |first13=Nicholas |last14=Prasanna |first14=Rohit |last15=Sofia |first15=Sarah |last16=Harwood |first16=Duncan |last17=Ma |first17=Wen |last18=Moghadam |first18=Farhad |last19=Snaith |first19=Henry J. |last20=Buonassisi |first20=Tonio |last21=Holman |first21=Zachary C. |last22=Bent |first22=Stacey F. |last23=McGehee |first23=Michael D. |title=23.6%-efficient monolithic perovskite/silicon tandem solar cells with improved stability |journal=Nature Energy |date=April 2017 |volume=2 |issue=4 |pages=17009 |doi=10.1038/nenergy.2017.9|bibcode=2017NatEn...217009B |hdl=1721.1/118870 |s2cid=43925320 |hdl-access=free }} Since 2018 the records were interchangeably broken by Oxford Photovoltaics and researchers from Helmholtz-Zentrum Berlin. In 2021, the latter achieved the best efficiency so far: 29.8%.

One big challenge for perovskite solar cells (PSCs) is the aspect of short-term and long-term stability.{{Cite journal |doi = 10.1039/C5EE00615E|title = Perovskite photovoltaics: Life-cycle assessment of energy and environmental impacts|year = 2015|last1 = Gong|first1 = Jian|last2 = Darling|first2 = Seth B.|last3 = You|first3 = Fengqi|journal = Energy & Environmental Science|volume = 8|issue = 7|pages = 1953–1968}} The traditional silicon-wafer solar cell in a power plant can last 20–25 years, setting that timeframe as the standard for solar cell stability. PSCs have great difficulty lasting that long [196]. The instability of PSCs is mainly related to environmental influence (moisture and oxygen),{{cite journal|last1=Bryant|first1=Daniel|last2=Aristidou|first2=Nicholas |last3=Pont|first3=Sebastian|last4=Sanchez-Molina|first4=Irene |last5=Chotchunangatchaval|first5=Thana|last6=Wheeler|first6=Scot|last7=Durrant|first7=James R.|last8=Haque|first8=Saif A.|title=Light and oxygen induced degradation limits the operational stability of methylammonium lead triiodide perovskite solar cells|journal=Energy Environ. Sci.|volume=9|issue=5|year=2016|pages=1655–1660|doi=10.1039/C6EE00409A|doi-access=free|hdl=10044/1/30873|hdl-access=free}}{{Cite journal|last1=Chun-Ren Ke|first1=Jack|last2=Walton|first2=Alex S. |last3=Lewis|first3=David J.|last4=Tedstone|first4=Aleksander|last5=O'Brien|first5=Paul|last6=Thomas|first6=Andrew G.|last7=Flavell|first7=Wendy R.|date=2017-05-04|title=In situ investigation of degradation at organometal halide perovskite surfaces by X-ray photoelectron spectroscopy at realistic water vapour pressure|journal=Chem. Commun.|volume=53|issue=37|pages=5231–5234|doi=10.1039/c7cc01538k|pmid=28443866|doi-access=free}} thermal stress and intrinsic stability of methylammonium-based perovskite,{{cite journal|last1=Juarez-Perez|first1=Emilio J.|last2=Hawash|first2=Zafer|last3=Raga|first3=Sonia R. |last4=Ono|first4=Luis K.|last5=Qi|first5=Yabing|title=Thermal degradation of CH3NH3PbI3 perovskite into NH3 and CH3I gases observed by coupled thermogravimetry–mass spectrometry analysis|journal=Energy Environ. Sci.|volume=9 |issue=11|year=2016|pages=3406–3410|doi=10.1039/C6EE02016J|doi-access=free}}{{Cite journal|last1=Juarez-Perez|first1=Emilio J.|last2=Ono|first2=Luis K.|last3=Maeda |first3=Maki|last4=Jiang |first4=Yan|last5=Hawash|first5=Zafer|last6=Qi|first6=Yabing |title=Photodecomposition and thermal decomposition in methylammonium halide lead perovskites and inferred design principles to increase photovoltaic device stability |journal=Journal of Materials Chemistry A|volume=6|issue=20|year=2018|pages=9604–9612|doi=10.1039/C8TA03501F|doi-access=free}}{{cite journal|last1=Juarez-Perez|first1=Emilio J.|last2=Ono |first2=Luis K.|last3=Uriarte|first3=Iciar|last4=Cocinero|first4=Emilio J.|last5=Qi|first5=Yabing|title=Degradation Mechanism and Relative Stability of Methylammonium Halide Based Perovskites Analyzed on the Basis of Acid–Base Theory|journal=ACS Applied Materials & Interfaces|volume=11|issue=13|year=2019|pages=12586–12593 |doi=10.1021/acsami.9b02374|pmid=30848116|doi-access=free}} and formamidinium-based perovskite,{{cite journal|last1=Juarez-Perez|first1=Emilio J.|last2=Ono|first2=Luis K.|last3=Qi|first3=Yabing|title=Thermal degradation of formamidinium based lead halide perovskites into sym-triazine and hydrogen cyanide observed by coupled thermogravimetry-mass spectrometry analysis|journal=Journal of Materials Chemistry A|volume=7|issue=28|year=2019|pages=16912–16919 |doi=10.1039/C9TA06058H|s2cid=197047404|url=https://oist.repo.nii.ac.jp/?action=repository_uri&item_id=1329}} heating under applied voltage,{{cite journal|last1=Yuan|first1=Yongbo|last2=Wang|first2=Qi|last3=Shao|first3=Yuchuan|last4=Lu|first4=Haidong|last5=Li|first5=Tao |last6=Gruverman|first6=Alexei|last7=Huang|first7=Jinsong|title=Electric-Field-Driven Reversible Conversion Between Methylammonium Lead Triiodide Perovskites and Lead Iodide at Elevated Temperatures|journal=Advanced Energy Materials|volume=6|issue=2|year=2016|page=1501803 |doi=10.1002/aenm.201501803|bibcode=2016AdEnM...601803Y |s2cid=101794508}} photo influence (ultraviolet light){{Cite journal|last1=Matteocci|first1=Fabio|last2=Cinà|first2=Lucio |last3=Lamanna|first3=Enrico|last4=Cacovich|first4=Stefania|last5=Divitini|first5=Giorgio|last6=Midgley|first6=Paul A.|last7=Ducati|first7=Caterina|author-link7=Caterina Ducati|last8=Di Carlo|first8=Aldo|date=2016-12-01 |title=Encapsulation for long-term stability enhancement of perovskite solar cells|journal=Nano Energy|volume=30|pages=162–172|doi=10.1016/j.nanoen.2016.09.041|bibcode=2016NEne...30..162M |hdl=2108/210706|hdl-access=free |url=https://art.torvergata.it/bitstream/2108/210706/1/Matteocci_Nanoenergy.pdf}} (visible light) and mechanical fragility.{{Cite journal|last1=Rolston|first1=Nicholas |last2=Watson|first2=Brian L.|last3=Bailie|first3=Colin D.|last4=McGehee|first4=Michael D.|last5=Bastos|first5=João P.|last6=Gehlhaar|first6=Robert|last7=Kim|first7=Jueng-Eun|last8=Vak|first8=Doojin|last9=Mallajosyula|first9=Arun Tej|title=Mechanical integrity of solution-processed perovskite solar cells|journal=Extreme Mechanics Letters|volume=9|pages=353–358|doi=10.1016/j.eml.2016.06.006|year=2016|s2cid=42992826|doi-access=free|bibcode=2016ExML....9..353R }} Several studies about PSCs stability have been performed and some elements have been proven to be important to the PSCs stability.{{cite journal |last1=Li |first1=Xiong |last2=Tschumi |first2=Manuel |last3=Han |first3=Hongwei |last4=Babkair |first4=Saeed Salem |last5=Alzubaydi |first5=Raysah Ali |last6=Ansari |first6=Azhar Ahmad |last7=Habib |first7=Sami S. |last8=Nazeeruddin |first8=Mohammad Khaja |last9=Zakeeruddin |first9=Shaik M. |last10=Grätzel |first10=Michael |title=Outdoor Performance and Stability under Elevated Temperatures and Long-Term Light Soaking of Triple-Layer Mesoporous Perovskite Photovoltaics |journal=Energy Technology |date=June 2015 |volume=3 |issue=6 |pages=551–555 |doi=10.1002/ente.201500045 |s2cid=135641851 }}{{cite journal |last1=Leijtens |first1=Tomas |last2=Eperon |first2=Giles E. |last3=Noel |first3=Nakita K. |last4=Habisreutinger |first4=Severin N. |last5=Petrozza |first5=Annamaria |last6=Snaith |first6=Henry J. |title=Stability of Metal Halide Perovskite Solar Cells |journal=Advanced Energy Materials |date=October 2015 |volume=5 |issue=20 |pages=1500963 |doi=10.1002/aenm.201500963 |bibcode=2015AdEnM...500963L |s2cid=97626956 }} However, there is no standard "operational" stability protocol for PSCs. But a method to quantify the intrinsic chemical stability of hybrid halide perovskites has been recently proposed.{{cite journal|last1=García-Fernández|first1=Alberto|last2=Juarez-Perez |first2=Emilio J.|last3=Castro-García|first3=Socorro|last4=Sánchez-Andújar|first4=Manuel|last5=Ono |first5=Luis K.|last6=Jiang |first6=Yan|last7=Qi|first7=Yabing|title=Benchmarking Chemical Stability of Arbitrarily Mixed 3D Hybrid Halide Perovskites for Solar Cell Applications|journal=Small Methods |volume=2|issue=10|year=2018|pages=1800242 |doi=10.1002/smtd.201800242|doi-access=free}}

The water-solubility of the organic constituent of the absorber material make devices highly prone to rapid degradation in moist environments.{{cite journal|last1=Habisreutinger|first1=Severin N.|last2=Leijtens|first2=Tomas |last3=Eperon|first3=Giles E.|last4=Stranks |first4=Samuel D.|last5=Nicholas |first5=Robin J. |last6=Snaith |first6=Henry J.|title=Carbon Nanotube/Polymer Composites as a Highly Stable Hole Extraction Layer in Perovskite Solar Cells |journal=Nano Letters |volume=xx|issue=x|pages=5561–8|doi=10.1021/nl501982b|pmid=25226226|year=2014|bibcode=2014NanoL..14.5561H}} The degradation which is caused by moisture can be reduced by optimizing the constituent materials, the architecture of the cell, the interfaces and the environment conditions during the fabrication steps. Encapsulating the perovskite absorber with a composite of carbon nanotubes and an inert polymer matrix can prevent the immediate degradation of the material by moist air at elevated temperatures.{{cite journal|title=Cheap solar cells tempt businesses|author=Van Noorden, Richard |journal=Nature |volume=513 |issue=7519 |pages=470 |date=September 24, 2014|bibcode=2014Natur.513..470V |doi=10.1038/513470a |pmid=25254454 |s2cid=205082350 |doi-access=free }} However, no long-term studies and comprehensive encapsulation techniques have yet been demonstrated for perovskite solar cells. Devices with a mesoporous TiO₂ layer sensitized with the perovskite absorber, are also UV-unstable, due to the interaction between photogenerated holes inside the TiO₂ and oxygen radicals on the surface of TiO₂.{{cite journal|last1=Leijtens |first1=Tomas|last2=Eperon|first2=Giles E.|last3=Pathak |first3=Sandeep|last4=Abate |first4=Antonio |last5=Lee |first5=Michael M. |last6=Snaith |first6=Henry J.|title=Overcoming ultraviolet light instability of sensitized TiO₂ with meso-superstructured organometal tri-halide perovskite solar cells |journal=Nature Communications|volume=6|page=2885|doi=10.1038/ncomms3885|pmid=24301460|year=2013 |bibcode=2013NatCo...4.2885L|doi-access=free}}

The measured ultra low thermal conductivity of 0.5 W/(Km) at room temperature in CH₃NH₃PbI₃ can prevent fast propagation of the light deposited heat, and keep the cell resistive on thermal stresses that can reduce its life time.{{cite journal|last1=Pisoni |first1=Andrea|last2=Jaćimović|first2=Jaćim|last3=Barišić|first3=Osor S.|last4=Spina|first4=Massimo |last5=Gaál|first5=Richard|last6=Forró|first6=László|last7=Horváth |first7=Endre |title=Ultra-Low Thermal Conductivity in Organic–Inorganic Hybrid Perovskite CH₃NH₃PbI₃|journal=The Journal of Physical Chemistry Letters|date=July 17, 2014|volume=5|issue=14 |pages=2488–2492|doi=10.1021/jz5012109|pmid=26277821|arxiv=1407.4931|bibcode=2014arXiv1407.4931P|s2cid=33371327}} The PbI₂ residue in perovskite film has been experimentally demonstrated to have a negative effect on the long-term stability of devices. The stabilization problem is claimed to be solved by replacing the organic transport layer with a metal oxide layer, allowing the cell to retain 90% capacity after 60 days.{{cite journal|last1=Zhang|first1=Hong|last2=Cheng|first2=Jiaqi|last3=Lin|first3=Francis|last4=He|first4=Hexiang|last5=Mao|first5=Jian|last6=Wong|first6=Kam Sing|last7=Jen|first7=Alex K.-Y.|last8=Choy |first8=Wallace C. H.|title=Pinhole-Free and Surface-Nanostructured NiOxFilm by Room-Temperature Solution Process for High-Performance Flexible Perovskite Solar Cells with Good Stability and Reproducibility|journal=ACS Nano |volume=10|issue=1|year=2016|pages=1503–1511|doi=10.1021/acsnano.5b07043|pmid=26688212}}{{Cite journal|title = Improved air stability of perovskite solar cells via solution-processed metal oxide transport layers|journal = Nature Nanotechnology|volume = 11|issue = 1|pages = 75–81|doi = 10.1038/nnano.2015.230|pmid = 26457966|first1 = Jingbi|last1 = You|first2 = Lei|last2 = Meng|first3 = Tze-Bin|last3 = Song|first4 = Tzung-Fang|last4 = Guo|first5 = Yang (Michael)|last5 = Yang|first6 = Wei-Hsuan|last6 = Chang|first7 = Ziruo|last7 = Hong|first8 = Huajun|last8 = Chen|first9 = Huanping|last9 = Zhou|year = 2015|bibcode = 2016NatNa..11...75Y}} Besides, the two instabilities issues can be solved by using multifunctional fluorinated photopolymer coatings that confer luminescent and easy-cleaning features on the front side of the devices, while concurrently forming a strongly hydrophobic barrier toward environmental moisture on the back contact side.{{Cite journal |author1=Federico Bella |author2=Gianmarco Griffini |author3=Juan-Pablo Correa-Baena |author4=Guido Saracco |author5=Michael Grätzel |author-link5=Michael Grätzel |author6=Anders Hagfeldt |author-link6=Anders Hagfeldt |author7=Stefano Turri |author8=Claudio Gerbaldi |year=2016 |title=Improving efficiency and stability of perovskite solar cells with photocurable fluoropolymers |journal=Science |volume=354 |issue=6309 |pages=203–206 |bibcode=2016Sci...354..203B |doi=10.1126/science.aah4046 |pmid=27708051 |s2cid=26368425 |hdl-access=free |hdl=11311/1000885}} The front coating can prevent the UV light of the whole incident solar spectrum from negatively interacting with the PSC stack by converting it into visible light, and the back layer can prevent water from permeation within the solar cell stack. The resulting devices demonstrated excellent stability in terms of power conversion efficiencies during a 180-day aging test in the lab and a real outdoor condition test for more than 3 months.

In July 2015, major hurdles were that the largest perovskite solar cell was only the size of a fingernail and that they degraded quickly in moist environments.{{cite journal|last1=Sivaram |first1=Varun |last2=Stranks|first2=Samuel D.|last3=Snaith|first3=Henry J.|title=Outshining Silicon |journal=Scientific American|volume=313|issue=July 2015|pages=44–46|bibcode=2015SciAm.313a..54S |year=2015 |doi=10.1038/scientificamerican0715-54}} However, researchers from EPFL published in June 2017, a work successfully demonstrating large scale perovskite solar modules with no observed degradation over one year (short circuit conditions).{{cite journal|author1=G. Grancini |author2=C. Roldán-Carmona |author3=I. Zimmermann |author4=E. Mosconi |author5=X. Lee |author6=D. Martineau |author7=S. Narbey |author8=F. Oswald |author9=F. De Angelis |author10=M. Graetzel |author11=Mohammad Khaja Nazeeruddin|title=One-Year stable perovskite solar cells by 2D/3D interface engineering|journal=Nature Communications|date=2017|volume=8 |issue=15684|page=15684|doi=10.1038/ncomms15684 |pmid=28569749|pmc=5461484|bibcode=2017NatCo...815684G}} Now, together with other organizations, the research team aims to develop a fully printable perovskite solar cell with 22% efficiency and with 90% of performance after ageing tests.{{cite web|author=Ana Milena Cruz|author2=Mónica Della Perreira|title=The New Generation of Photovoltaic Cells Entering the Market, Leitat, Barcelona, April 12, 2018 |date=April 2018 |url=https://projects.leitat.org/the-new-generation-of-photovoltaic-cells-entering-the-market/}}

Early in 2019, the longest stability test reported to date showed a steady power output during at least 4000 h of continuous operation at Maximum power point tracking (MPPT) under 1 sun illumination from a xenon lamp based solar simulator without UV light filtering. Remarkably, the light harvester used during the stability test is classical methylammonium (MA) based perovskite, MAPbI₃, but devices are built up with neither organic based selective layer nor metal back contact. Under these conditions, only thermal stress was found to be the major factor contributing to the loss of operational stability in encapsulated devices.{{cite journal|last1=Islam|first1=M. Bodiul|last2=Yanagida|first2=M.|last3=Shirai|first3=Y.|last4=Nabetani|first4=Y.|last5=Miyano|first5=K.|title=Highly stable semi-transparent MAPbI3 perovskite solar cells with operational output for 4000 h|journal=Solar Energy Materials and Solar Cells|volume=195|year=2019|pages=323–329 |doi=10.1016/j.solmat.2019.03.004|s2cid=108779926|doi-access=free}}

The intrinsic fragility of the perovskite material requires extrinsic reinforcement to shield this crucial layer from mechanical stresses. Insertion of mechanically reinforcing scaffolds directly into the active layers of perovskite solar cells resulted in the compound solar cell formed exhibiting a 30-fold increase in fracture resistance, repositioning the fracture properties of perovskite solar cells into the same domain as conventional c-Si, CIGS and CdTe solar cells.{{Cite journal|last1=Watson|first1=Brian L.|last2=Rolston|first2=Nicholas|last3=Printz|first3=Adam D.|last4=Dauskardt|first4=Reinhold H.|title=Scaffold-reinforced perovskite compound solar cells |journal=Energy Environ. Sci.|volume=10|issue=12|page=2500|doi=10.1039/c7ee02185b|year=2017}} Several approaches have been developed to improve perovskite solar cell stability.{{clarify|date=June 2021}} For instance,

in 2021 researchers reported that the stability and long-term reliability of perovskite solar cells was improved with a new kind of "molecular glue".{{cite news |title="Molecular glue" strengthens the weak point in perovskite solar cells |url=https://newatlas.com/energy/molecular-glue-strengthens-perovskite-solar-cells-stability/ |access-date=13 June 2021 |work=New Atlas |date=2021-05-10}}{{cite journal |last1=Dai |first1=Zhenghong |last2=Yadavalli |first2=Srinivas K. |last3=Chen |first3=Min |last4=Abbaspourtamijani |first4=Ali |last5=Qi |first5=Yue |last6=Padture |first6=Nitin P. |title=Interfacial toughening with self-assembled monolayers enhances perovskite solar cell reliability |journal=Science |date=2021-05-07 |volume=372 |issue=6542 |pages=618–622 |doi=10.1126/science.abf5602 |issn=0036-8075 |pmid=33958474 |bibcode=2021Sci...372..618D |s2cid=233872843 }}

As of 2021, the existing stability tests for solar panels and solar cell systems are designed solely for those containing silicon wafers. As such, these tests, produced by the International Electrotechnical Commission (IEC), have been re-evaluated for their lack of suitability. At the International Summit on Organic PV Stability (ISOS), stability checks for in-lab development of all solar cells were created, but these were not adopted by the IEC. These tests are not pass/fail criteria, rather they evaluate the various causes of solar cell stability issues to root out the problems. They are grouped into five categories: dark storage testing, outdoor testing, light soaking testing, thermal cycling testing, and light-humidity-thermal cycling testing. In these tests, the PCE and J-V data graphs of the PSCs were calculated among varying physical conditions to determine the various causes of PSC degradation.{{cite journal |last1=Khenkin |first1=Mark V. |last2=Katz |first2=Eugene A. |last3=Abate |first3=Antonio |last4=Bardizza |first4=Giorgio |last5=Berry |first5=Joseph J. |last6=Brabec |first6=Christoph |last7=Brunetti |first7=Francesca |last8=Bulović |first8=Vladimir |last9=Burlingame |first9=Quinn |last10=Di Carlo |first10=Aldo |last11=Cheacharoen |first11=Rongrong |last12=Cheng |first12=Yi-Bing |last13=Colsmann |first13=Alexander |last14=Cros |first14=Stephane |last15=Domanski |first15=Konrad |last16=Dusza |first16=Michał |last17=Fell |first17=Christopher J. |last18=Forrest |first18=Stephen R. |last19=Galagan |first19=Yulia |last20=Di Girolamo |first20=Diego |last21=Grätzel |first21=Michael |last22=Hagfeldt |first22=Anders |last23=von Hauff |first23=Elizabeth |last24=Hoppe |first24=Harald |last25=Kettle |first25=Jeff |last26=Köbler |first26=Hans |last27=Leite |first27=Marina S. |last28=Liu |first28=Shengzhong (Frank) |last29=Loo |first29=Yueh-Lin |last30=Luther |first30=Joseph M. |last31=Ma |first31=Chang-Qi |last32=Madsen |first32=Morten |last33=Manceau |first33=Matthieu |last34=Matheron |first34=Muriel |last35=McGehee |first35=Michael |last36=Meitzner |first36=Rico |last37=Nazeeruddin |first37=Mohammad Khaja |last38=Nogueira |first38=Ana Flavia |last39=Odabaşı |first39=Çağla |last40=Osherov |first40=Anna |last41=Park |first41=Nam-Gyu |last42=Reese |first42=Matthew O. |last43=De Rossi |first43=Francesca |last44=Saliba |first44=Michael |last45=Schubert |first45=Ulrich S. |last46=Snaith |first46=Henry J. |last47=Stranks |first47=Samuel D. |last48=Tress |first48=Wolfgang |last49=Troshin |first49=Pavel A. |last50=Turkovic |first50=Vida |last51=Veenstra |first51=Sjoerd |last52=Visoly-Fisher |first52=Iris |last53=Walsh |first53=Aron |last54=Watson |first54=Trystan |last55=Xie |first55=Haibing |last56=Yıldırım |first56=Ramazan |last57=Zakeeruddin |first57=Shaik Mohammed |last58=Zhu |first58=Kai |last59=Lira-Cantu |first59=Monica |title=Consensus statement for stability assessment and reporting for perovskite photovoltaics based on ISOS procedures |journal=Nature Energy |date=January 2020 |volume=5 |issue=1 |pages=35–49 |doi=10.1038/s41560-019-0529-5 |bibcode=2020NatEn...5...35K |s2cid=211544985 |hdl=1721.1/136287 |hdl-access=free }}

Overall, these ISOS tests helped determine the causes of PSC degradation, which were found to include extended exposure to visible and UV light, environmental contamination, high temperatures, and electrical biases. After 200 temperature cycles, the 2020 PSCs still retained 90% of their power, indicating that they are capable of short-term stability. Now, what remains to be researched is long-term stability, and what material advances could be applied to boost these 200 temperature cycles (days) to 20–25 years.

In 2025, the Open Solar Stability (OSS) Lab{{cite web|title=The Open Solar Stability (OSS) Lab: An Ecosystem for Testing Stability in Emerging Photovoltaics|url=https://www.emiliojuarez.es/2025/02/01/OSSLab/|website=Emilio J. Juarez-Perez|date=2025-02-01|access-date=2025-03-25}} introduced two tools specifically designed to address stability testing challenges in perovskite solar cells. The Perovskino, an open-source and low-cost maximum power point tracking (MPPT) device, was developed to accurately track performance degradation under operational conditions. Its galvanostatic approach proved particularly effective for devices exhibiting high hysteresis, a common issue in perovskite cells.{{cite journal|last1=Juarez-Perez|first1=E. J.|last2=Momblona|first2=C.|last3=Casas|first3=R.|last4=Haro|first4=M.|title=Enhanced power-point tracking for high-hysteresis perovskite solar cells with a galvanostatic approach|journal=Cell Reports Physical Science|volume=5|year=2024|pages=101885|doi=10.1016/j.xcrp.2024.101885|arxiv=2312.03124}}{{cite journal|last1=Sanz-Marco|first1=A.|last2=Jeronimo-Cruz|first2=R.|last3=Haro|first3=M.|last4=Juarez-Perez|first4=E. J.|title=Protocol for building and using a maximum power point output tracker for perovskite solar cells|journal=STAR Protocols|volume=5|year=2024|pages=103394|doi=10.1016/j.xpro.2024.103394|pmc=11532285}} The complete source code and documentation for the Perovskino are freely available on GitHub.{{cite web|title=Perovskino|url=https://github.com/ej-jp/perovskino|website=GitHub|access-date=2025-03-25}} Complementing this, the ParaSol platform, located in Zaragoza, Spain, enables long-term outdoor testing of multiple devices under real environmental conditions, while continuously tracking performance metrics, temperature, solar irradiance, and humidity. These tools represent an important advancement in standardizing stability measurements for perovskite photovoltaics by providing accessible methods for researchers to conduct comparable long-term stability studies.

Ion migration is a major issue with PSCs detrimental to their efficiency and long-term stability. Due to the soft ionic lattice of these materials, preventing the motion of halide ions (commonly I⁻, Br⁻, Cl⁻) and metal cations (Pb²⁺, Sn²⁺) under elevated temperatures is paramount. This migration can reduce charge transport efficiency and generate internal electric fields that disrupt the operation of the solar cell. Maintaining phase segregation is critical in mixed-halid cell operation, thus this mechanism serves to disrupt stability by progressively degrading this phase separation. One effective strategy to reduce ion migration is to introduce Nd3+ cations as the higher valence state provides improved ability to impede halide migration and can passivate negatively charged defects at much lower concentration than traditional dopants such as Na⁺ at much lower concentrations (0.08% compared to 0.45%). Notably, researchers showed under 2002 hours of illumination that an encapsulated PSC device maintained 84.3% of its original power conversion efficiency (PCE), while a device doped with Na⁺ under the same conditions retained 72.7% of its PCE. However, this comes at a tradeoff, where the interstitial occupation introduces lattice strain which compromises long-range ordering and stability of the main phase.{{Cite journal |last1=Zhao |first1=Yepin |last2=Yavuz |first2=Ilhan |last3=Wang |first3=Minhuan |last4=Weber |first4=Marc H. |last5=Xu |first5=Mingjie |last6=Lee |first6=Joo-Hong |last7=Tan |first7=Shaun |last8=Huang |first8=Tianyi |last9=Meng |first9=Dong |last10=Wang |first10=Rui |last11=Xue |first11=Jingjing |last12=Lee |first12=Sung-Joon |last13=Bae |first13=Sang-Hoon |last14=Zhang |first14=Anni |last15=Choi |first15=Seung-Gu |date=December 2022 |title=Suppressing ion migration in metal halide perovskite via interstitial doping with a trace amount of multivalent cations |url=https://pubmed.ncbi.nlm.nih.gov/36396958/ |journal=Nature Materials |volume=21 |issue=12 |pages=1396–1402 |doi=10.1038/s41563-022-01390-3 |issn=1476-4660 |pmid=36396958|bibcode=2022NatMa..21.1396Z |hdl=11424/284042 |hdl-access=free }}

The introduction of the Al₂O₃/NiO interfacial layer not only improves the crystalline quality of perovskite films with large grain size and enhances charge transport, but also effectively restricts the carrier recombination, but PSCs using this interface still have instability problem due to ion-migration and instability of perovskite crystals.{{Cite journal |last1=Wang |first1=Yousheng |last2=Mahmoudi |first2=Tahmineh |last3=Rho |first3=Won-Yeop |last4=Yang |first4=Hwa-Young |last5=Seo |first5=Seunghui |last6=Bhat |first6=Kiesar Sideeq |last7=Ahmad |first7=Rafiq |last8=Hahn |first8=Yoon-Bong |date=October 2017 |title=Ambient-air-solution-processed efficient and highly stable perovskite solar cells based on CH3NH3PbI3−xClx-NiO composite with Al2O3/NiO interfacial engineering |url=http://dx.doi.org/10.1016/j.nanoen.2017.08.047 |journal=Nano Energy |volume=40 |pages=408–417 |doi=10.1016/j.nanoen.2017.08.047 |issn=2211-2855}}{{Citation |last1=Getachew Alemu |first1=Anshebo |title=Recent Development of Lead-Free Perovskite Solar Cells |date=2022-12-14 |work=Recent Advances in Multifunctional Perovskite Materials |publisher=IntechOpen |isbn=978-1-80355-318-4 |last2=Alemu |first2=Teketel|doi=10.5772/intechopen.105046 |doi-access=free }} To solve the problem, perovskite/Ag-rGO composites in active layer can be used to enhance the stability of PSCs and achieve high performance simultaneously.{{Cite journal |last1=Ahmad |first1=Khursheed |last2=Kim |first2=Haekyoung |date=March 2023 |title=Improved photovoltaic performance and stability of perovskite solar cells with device structure of (ITO/SnO2/CH3NH3PbI3/rGO+spiro-MeOTAD/Au) |url=http://dx.doi.org/10.1016/j.mseb.2022.116227 |journal=Materials Science and Engineering: B |volume=289 |pages=116227 |doi=10.1016/j.mseb.2022.116227 |issn=0921-5107}} The Ag-rGO layer can act as a surface passivation layer, reducing defects and trap states at the perovskite layer's surface, which minimizes non-radiative recombination and improves performance and stability. In addition, the perovskite/Ag-rGO composite layer can act as a barrier, preventing moisture entering the perovskite layer and protecting it from degradation due to environmental effects. In the light harvesting measurements, perovskite/Ag-graphene PSCs show a higher Incident monochromatic photon-electron conversion efficiency (IPCE) value than traditional PSCs in the range of visible light.{{Cite journal |last1=Bi |first1=Enbing |last2=Chen |first2=Han |last3=Xie |first3=Fengxian |last4=Wu |first4=Yongzhen |last5=Chen |first5=Wei |last6=Su |first6=Yanjie |last7=Islam |first7=Ashraful |last8=Grätzel |first8=Michael |last9=Yang |first9=Xudong |last10=Han |first10=Liyuan |date=2017-06-12 |title=Diffusion engineering of ions and charge carriers for stable efficient perovskite solar cells |journal=Nature Communications |volume=8 |issue=1 |page=15330 |doi=10.1038/ncomms15330 |issn=2041-1723|doi-access=free |pmid=28604673 |pmc=5472713 |bibcode=2017NatCo...815330B }}{{Cite web |title=Stability Enhancement in Perovskite Solar Cells with Perovskite/SilverGraphene Composites in the Active Layer |url=http://dx.doi.org/10.1021/acsenergylett.8b02201.s001 |access-date=2023-11-20 |doi=10.1021/acsenergylett.8b02201.s001 }} The current-voltage curve of the PSCs also shows the absence of hysteresis effect which is common in traditional PSCs. Perovskite/Ag-graphene PSCs also exhibit better thermal-stability aging at 90 degree Celsius and better photo-stability under continuous light illumination. To increase thermal stability, another low-cost additive in the form of caffeine has been proposed to elevate stable operating temperature. MBAPbI₃ has been proven to be stable between 0-90C, which was improved to 196-242C after the addition of caffeine at 2-8% concentration. Caffeine forms a so-called “molecular lock” with Pb²⁺ ions which leads to a more stable crystalline structure that resists degradation at higher temperatures. By reducing the density of defects and grain boundaries, there are fewer sites for ion migration and mechanical degradation induced by thermal stress.{{Cite journal |last1=Tsotetsi |first1=Dieketseng |last2=Idisi |first2=David O. |last3=Benecha |first3=Evans M. |last4=Dhlamini |first4=Mokhotjwa |last5=Mbule |first5=Pontsho |date=2024-08-05 |title=Influence of caffeine on the crystallinity and thermal stability of MAPbI3: Experiment and density-functional theory calculations |url=https://www.sciencedirect.com/science/article/abs/pii/S0022286024007750 |journal=Journal of Molecular Structure |volume=1309 |pages=138255 |doi=10.1016/j.molstruc.2024.138255 |issn=0022-2860}} However, the open-circuit voltage V_oc and fill factor (FF) decreases as a trade-off. To address the loss in V_oc and FF, SrTiO₃/TiO₂ composite layer is chosen to overcome this low V_oc problem.{{Cite journal |last1=Duong |first1=Binh |last2=Lohawet |first2=Khathawut |last3=Muangnapoh |first3=Tanyakorn |last4=Nakajima |first4=Hideki |last5=Chanlek |first5=Narong |last6=Sharma |first6=Anirudh |last7=Lewis |first7=David A. |last8=Kumnorkaew |first8=Pisist |date=2019-06-03 |title=Low-Temperature Processed TiOx/Zn1−xCdxS Nanocomposite for Efficient MAPbIxCl1−x Perovskite and PCDTBT:PC70BM Polymer Solar Cells |journal=Polymers |volume=11 |issue=6 |pages=980 |doi=10.3390/polym11060980 |issn=2073-4360 |doi-access=free |pmid=31163696 |pmc=6631563 }} By choosing SrTiO₃/TiO₂ as light harvesting material, it is expected to achieve high stability as well as high V_oc.{{Cite journal |last1=Okamoto |first1=Yuji |last2=Fukui |first2=Ryuta |last3=Fukazawa |first3=Motoharu |last4=Suzuki |first4=Yoshikazu |date=January 2017 |title=SrTiO3/TiO2 composite electron transport layer for perovskite solar cells |url=http://dx.doi.org/10.1016/j.matlet.2016.10.090 |journal=Materials Letters |volume=187 |pages=111–113 |doi=10.1016/j.matlet.2016.10.090 |issn=0167-577X}}

Another major challenge for perovskite solar cells is the observation that current-voltage scans yield ambiguous efficiency values.{{cite journal|

last1=Snaith|first1=Henry J.|

last2=Abate|first2=Antonio |

last3=Ball|first3=James M.|

last4=Eperon |first4=Giles E.|

last5=Leijtens |first5=Tomas |

last6=Noel |first6=Nakita K.|

last7=Wang |first7=Jacob Tse-Wei|

last8=Wojciechowski |first8=Konrad |

last9=Zhang |first9=Wei|last10=Zhang|first10=Wei|

title=Anomalous Hysteresis in Perovskite Solar Cells |

journal=The Journal of Physical Chemistry Letters |

volume=5|

issue=9

|pages=1511–1515|

doi=10.1021/jz500113x|pmid=26270088|year=2014}}

{{cite journal|

last1=Unger|first1=Eva L.|

last2=Hoke|first2=Eric T. |

last3=Bailie|first3=Colin D.|

last4=Nguyen |first4=William H.|

last5=Bowring |first5=Andrea R. |

last6=Heumuller |first6=Thomas|

last7=Christoforo |first7=Mark G.|

last8=McGehee |first8=Michael D. |author8-link=Michael D. McGehee|

title=Hysteresis and transient behavior in current-voltage measurements of hybrid-perovskite absorber solar cells |

journal=Energy & Environmental Science|volume=7|issue=11|pages=3690–3698|doi=10.1039/C4EE02465F|year=2014}}

The power conversion efficiency of a solar cell is usually determined by characterizing its current-voltage (IV) behavior under simulated solar illumination. In contrast to other solar cells, however, it has been observed that the IV-curves of perovskite solar cells show a hysteretic behavior: depending on scanning conditions – such as scan direction, scan speed, light soaking, biasing – there is a discrepancy between the scan from forward-bias to short-circuit (FB-SC) and the scan from short-circuit to forward bias (SC-FB). Various causes have been proposed such as ion movement, polarization, ferroelectric effects, filling of trap states, however, the exact origin for the hysteretic behavior is yet to be determined. But it appears that determining the solar cell efficiency from IV-curves risks producing inflated values if the scanning parameters exceed the time-scale which the perovskite system requires in order to reach an electronic steady-state. Two possible solutions have been proposed: Unger et al. show that extremely slow voltage-scans allow the system to settle into steady-state conditions at every measurement point which thus eliminates any discrepancy between the FB-SC and the SC-FB scan. The steady-state conditions with extremely slow voltage-scans can be simulated by drift-diffusion solvers SolarDesign{{citation | title= SolarDesign|url= http://solardesign.cn/}} and IonMonger.{{citation | title= IonMonger|url= https://github.com/PerovskiteSCModelling/IonMonger}}

Henry Snaith et al. have proposed 'stabilized power output' as a metric for the efficiency of a solar cell. This value is determined by holding the tested device at a constant voltage around the maximum power-point (where the product of voltage and photocurrent reaches its maximum value) and track the power-output until it reaches a constant value.

Both methods have been demonstrated to yield lower efficiency values when compared to efficiencies determined by fast IV-scans. However, initial studies have been published that show that surface passivation of the perovskite absorber is an avenue with which efficiency values can be stabilized very close to fast-scan efficiencies.{{cite journal|

last1=Noel|first1=Nakita K|title=Enhanced Photoluminescence and Solar Cell Performance via Lewis Base Passivation of Organic–Inorganic Lead Halide Perovskites|

last2=Abate|first2=Antonio |

last3=Stranks|first3=Samuel D.|

last4=Parrott |first4=Elizabeth S.|

last5=Burlakov |first5=Victor M. |

last6=Goriely |first6=Alain|

last7=Snaith |first7=Henry J.| author-link7 = Henry Snaith|

journal=ACS Nano |volume=8|issue=10|pages=9815–9821|doi=10.1021/nn5036476|pmid=25171692|year=2014}}

{{cite journal|last1=Abate|first1=Antonio|last2=Saliba|first2=Michael|last3=Hollman|first3=Derek J.|last4=Stranks|first4=Samuel D.|last5=Wojciechowski|first5=Konrad|last6=Avolio|first6=Roberto|last7=Grancini|first7=Giulia|last8=Petrozza|first8=Annamaria|last9=Snaith|author-link9=Henry Snaith|first9=Henry J.|title=Supramolecular Halogen Bond Passivation of Organic–Inorganic Halide Perovskite Solar Cells|journal=Nano Letters|date=June 11, 2014|volume=14|issue=6|pages=3247–3254|doi=10.1021/nl500627x|pmid=24787646|bibcode=2014NanoL..14.3247A}}

No obvious hysteresis of photocurrent was observed by changing the sweep rates or the direction in devices or the sweep rates. This indicates that the origin of hysteresis in photocurrent is more likely due to the trap formation in some non optimized films and device fabrication processes. The ultimate way to examine the efficiency of a solar cell device is to measure its power output at the load point. If there is large density of traps in the devices or photocurrent hysteresis for other reasons, the photocurrent would rise slowly upon turning on illumination{{cite journal|

last1=Xiao|first1=Zhengguo|

last2=Bi|first2=Cheng |

last3=Shao|first3=Yuchuan|

last4=Dong |first4=Qingfeng|

last5=Wang |first5=Qi |

last6=Yuan |first6=Yongbo|

last7=Wang |first7=Chenggong|

last8=Gao| first8=Yongli|

last9=Huang | first9=Jinsong|s2cid=16131043|

title=Efficient, High Yield Perovskite Photovoltaic Devices Grown by Interdiffusion of Solution-Processed Precursor Stacking Layers|

journal=Energy & Environmental Science |volume=7|issue=8|page=2619|doi=10.1039/c4ee01138d|year=2014}}

This suggests that the interfaces might play a crucial role with regards to the hysteretic IV behavior since the major difference of the inverted architecture to the regular architectures is that an organic n-type contact is used instead of a metal oxide.

The ambiguity in determining the solar cell efficiency from current-voltage characteristics due to the observed hysteresis has also affected the certification process done by accredited laboratories such as NREL. The record efficiency of 20.1% for perovskite solar cells accepted as certified value by NREL in November 2014, has been classified as 'not stabilized'. To be able to compare results from different institution, it is necessary to agree on a reliable measurement protocol, as proposed by Zimmermann et al.{{cite journal|last1=Zimmermann|first1=Eugen|last2=Wong|first2=Ka Kan|last3=Mueller|first3=Michael|last4=Hu|first4=Hao|last5=Ehrenreich|first5=Philipp|last6=Kohlstaedt|first6=Markus|last7=Würfel|first7=Uli|last8=Mastroianni|first8=Simone|last9=Mathiazhagan|first9=Gayathri|last10=Hinsch|first10=Andreas|last11=Gujar|first11=Tanji P.|last12=Thelakkat|first12=Mukundan|last13=Pfadler|first13=Thomas|last14=Schmidt-Mende|first14=Lukas|title=Characterization of perovskite solar cells: Towards a reliable measurement protocol|journal=APL Materials|volume=4|issue=9|page=091901|doi=10.1063/1.4960759|year=2016|bibcode=2016APLM....4i1901Z|doi-access=free}} with corresponding Matlab code on GitHub.{{cite web|last1=Zimmermann|first1=Eugen|title=GitHub Repository|url=https://github.com/EugenZimmermann/matlab-keithley-jv|website=GitHub|date=2018-08-20}}

Beyond the ambiguity in determining efficiency, tracking perovskite solar cells with hysteresis at their maximum power point (MPP) presents an even greater challenge. The MPP voltage cannot be accurately determined from either the forward or reverse J-V scan due to the hysteresis effect, but rather it exists at higher voltages than either scan would suggest.{{cite journal|last1=Pellet|first1=N.|last2=Giordano|first2=F.|last3=Ibrahim Dar|first3=M.|last4=Gregori|first4=G.|last5=Zakeeruddin|first5=S.|last6=Maier|first6=J.|last7=Grätzel|first7=M.|title=Hill climbing hysteresis of perovskite-based solar cells: A maximum power point tracking investigation|journal=Progress in Photovoltaics: Research and Applications|year=2017|doi=10.1002/pip.2894}} Recent advancements have addressed this issue with an open-source galvanostatic tracker approach that can efficiently track cells with high hysteresis, rapidly finding the appropriate stabilized MPP voltage under constant illumination conditions. This method provides a more accurate means to evaluate the true operational performance of perovskite devices exhibiting significant hysteresis, helping to standardize stability testing protocols.

A perovskite cell combined with a bottom cell such as Si or copper indium gallium selenide (CIGS) as a tandem design can suppress individual cell bottlenecks and take advantage of their complementary characteristics to enhance efficiency.{{Cite journal|title = The detailed balance limit of perovskite/silicon and perovskite/CdTe tandem solar cells|journal = Physica Status Solidi A|page = 1600955|volume = 214|issue = 5|doi = 10.1002/pssa.201600955|first = Sven|last = Rühle|year = 2017|bibcode = 2017PSSAR.21400955R|s2cid = 126339380}} These types of cells have higher efficiency potential, and therefore have attracted attention from academic researchers.{{cite journal |last1=Werner |first1=Jérémie |last2=Niesen |first2=Bjoern |last3=Ballif |first3=Christophe |title=Perovskite/Silicon Tandem Solar Cells: Marriage of Convenience or True Love Story? – An Overview |journal=Advanced Materials Interfaces |date=January 2018 |volume=5 |issue=1 |pages=1700731 |doi=10.1002/admi.201700731|s2cid=139745316 }}{{cite journal |last1=Chen |first1=Bo |last2=Zheng |first2=Xiaopeng |last3=Bai |first3=Yang |last4=Padture |first4=Nitin P. |last5=Huang |first5=Jinsong |title=Progress in Tandem Solar Cells Based on Hybrid Organic-Inorganic Perovskites |journal=Advanced Energy Materials |date=July 2017 |volume=7 |issue=14 |pages=1602400 |doi=10.1002/aenm.201602400|doi-access=free |bibcode=2017AdEnM...702400C }}{{cite journal |last1=Lal |first1=Niraj N. |last2=Dkhissi |first2=Yasmina |last3=Li |first3=Wei |last4=Hou |first4=Qicheng |last5=Cheng |first5=Yi-Bing |last6=Bach |first6=Udo |title=Perovskite Tandem Solar Cells |journal=Advanced Energy Materials |date=September 2017 |volume=7 |issue=18 |pages=1602761 |doi=10.1002/aenm.201602761|bibcode=2017AdEnM...702761L |s2cid=99748711 }}

Using a four terminal configuration in which the two sub-cells are electrically isolated, Bailie et al.{{Cite journal|title = Semi-transparent perovskite solar cells for tandems with silicon and CIGS|journal = Energy Environ. Sci.|pages = 956–963|volume = 8|issue = 3|doi = 10.1039/c4ee03322a|first1 = Colin D.|last1 = Bailie|first2 = M. Greyson|last2 = Christoforo|first3 = Jonathan P.|last3 = Mailoa|first4 = Andrea R.|last4 = Bowring|first5 = Eva L.|last5 = Unger|first6 = William H.|last6 = Nguyen|first7 = Julian|last7 = Burschka|first8 = Norman|last8 = Pellet|first9 = Jungwoo Z.|last9 = Lee |first10 = Michael|last10 = Grätzel|first11 = Rommell|last11 = Noufi|first12 = Tonio|last12 = Buonassisi|first13 = Alberto|last13 = Salleo|first14 = Michael D. |last14 = McGehee |s2cid = 98057129|year = 2015|osti = 1220721|url = https://www.osti.gov/biblio/1220721}} obtained a 17% to 18.6% efficient tandem cell with mc-Si (η ~ 11%) and copper indium gallium selenide (CIGS, η ~ 17%) bottom cells, respectively. A 13.4% efficient tandem cell with a highly efficient a-Si:H/c-Si heterojunction bottom cell using the same configuration has also been obtained.{{Cite journal|title = Organic–inorganic halide perovskite/crystalline silicon four-terminal tandem solar cells|journal = Phys. Chem. Chem. Phys.|pages = 1619–1629|volume = 17|issue = 3|doi = 10.1039/c4cp03788j|pmid = 25437303|first1 = Philipp|last1 = Löper|first2 = Soo-Jin|last2 = Moon|first3 = Sílvia Martín de|last3 = Nicolas|first4 = Bjoern|last4 = Niesen|first5 = Martin|last5 = Ledinsky|first6 = Sylvain|last6 = Nicolay|first7 = Julien|last7 = Bailat|first8 = Jun-Ho|last8 = Yum|first9 = Stefaan De|last9 = Wolf|year = 2015|bibcode = 2014PCCP...17.1619L}} The application of TCO-based transparent electrodes to perovskite cells allowed fabricating near-infrared transparent devices with improved efficiency and lower parasitic absorption losses.{{cite journal |last1=Werner |first1=Jérémie |last2=Dubuis |first2=Guy |last3=Walter |first3=Arnaud |last4=Löper |first4=Philipp |last5=Moon |first5=Soo-Jin |last6=Nicolay |first6=Sylvain |last7=Morales-Masis |first7=Monica |author7-link= Mónica Morales Masis |last8=De Wolf |first8=Stefaan |last9=Niesen |first9=Bjoern |last10=Ballif |first10=Christophe |title=Sputtered rear electrode with broadband transparency for perovskite solar cells |journal=Solar Energy Materials and Solar Cells |date=October 2015 |volume=141 |pages=407–413 |doi=10.1016/j.solmat.2015.06.024|bibcode=2015SEMSC.141..407W }}{{cite journal |last1=Duong |first1=The |last2=Lal |first2=Niraj |last3=Grant |first3=Dale |last4=Jacobs |first4=Daniel |last5=Zheng |first5=Peiting |last6=Rahman |first6=Shakir |last7=Shen |first7=Heping |last8=Stocks |first8=Matthew |last9=Blakers |first9=Andrew |last10=Weber |first10=Klaus |last11=White |first11=Thomas P. |last12=Catchpole |first12=Kylie R. |title=Semitransparent Perovskite Solar Cell With Sputtered Front and Rear Electrodes for a Four-Terminal Tandem |journal=IEEE Journal of Photovoltaics |date=May 2016 |volume=6 |issue=3 |pages=679–687 |doi=10.1109/JPHOTOV.2016.2521479|s2cid=12959943 |hdl=1885/111684 |hdl-access=free }}{{cite journal |last1=Werner |first1=Jérémie |last2=Barraud |first2=Loris |last3=Walter |first3=Arnaud |last4=Bräuninger |first4=Matthias |last5=Sahli |first5=Florent |last6=Sacchetto |first6=Davide |last7=Tétreault |first7=Nicolas |last8=Paviet-Salomon |first8=Bertrand |last9=Moon |first9=Soo-Jin |last10=Allebé |first10=Christophe |last11=Despeisse |first11=Matthieu |last12=Nicolay |first12=Sylvain |last13=De Wolf |first13=Stefaan |last14=Niesen |first14=Bjoern |last15=Ballif |first15=Christophe |title=Efficient Near-Infrared-Transparent Perovskite Solar Cells Enabling Direct Comparison of 4-Terminal and Monolithic Perovskite/Silicon Tandem Cells |journal=ACS Energy Letters |date=3 August 2016 |volume=1 |issue=2 |pages=474–480 |doi=10.1021/acsenergylett.6b00254|doi-access=free }}{{cite journal |last1=Duong |first1=The |last2=Wu |first2=YiLiang |last3=Shen |first3=Heping |last4=Peng |first4=Jun |last5=Fu |first5=Xiao |last6=Jacobs |first6=Daniel |last7=Wang |first7=Er-Chien |last8=Kho |first8=Teng Choon |last9=Fong |first9=Kean Chern |last10=Stocks |first10=Matthew |last11=Franklin |first11=Evan |last12=Blakers |first12=Andrew |last13=Zin |first13=Ngwe |last14=McIntosh |first14=Keith |last15=Li |first15=Wei |last16=Cheng |first16=Yi-Bing |last17=White |first17=Thomas P. |last18=Weber |first18=Klaus |last19=Catchpole |first19=Kylie |title=Rubidium Multication Perovskite with Optimized Bandgap for Perovskite-Silicon Tandem with over 26% Efficiency |journal=Advanced Energy Materials |date=July 2017 |volume=7 |issue=14 |pages=1700228 |doi=10.1002/AENM.201700228|bibcode=2017AdEnM...700228D |s2cid=99098643 }}{{Cite journal|last1=Aydin|first1=Erkan|last2=Bastiani|first2=Michele De|last3=Yang|first3=Xinbo|last4=Sajjad|first4=Muhammad|last5=Aljamaan|first5=Faisal|last6=Smirnov|first6=Yury|last7=Hedhili|first7=Mohamed Nejib|last8=Liu|first8=Wenzhu|last9=Allen|first9=Thomas G.|last10=Xu|first10=Lujia|last11=Kerschaver|first11=Emmanuel Van|date=2019|title=Zr-Doped Indium Oxide (IZRO) Transparent Electrodes for Perovskite-Based Tandem Solar Cells |journal=Advanced Functional Materials |volume=29|issue=25|pages=1901741|doi=10.1002/adfm.201901741|hdl=10754/652829 |s2cid=145876795|url=https://research.utwente.nl/en/publications/821c565f-f497-430f-a18c-04231bab832a |hdl-access=free}} The application of these cells in 4-terminal tandems allowed improved efficiencies up to 26.7% when using a silicon bottom cell{{cite journal|last1=Ramírez Quiroz|first1=César Omar|last2=Shen|first2=Yilei|last3=Salvador|first3=Michael|last4=Forberich|first4=Karen|last5=Schrenker|first5=Nadine|last6=Spyropoulos|first6=George D.|last7=Heumüller|first7=Thomas|last8=Wilkinson|first8=Benjamin|last9=Kirchartz|first9=Thomas|date=2018|title=Balancing electrical and optical losses for efficient 4-terminal Si–perovskite solar cells with solution processed percolation electrodes|journal=Journal of Materials Chemistry A|volume=6|issue=8|pages=3583–3592|doi=10.1039/C7TA10945H|last10=Spiecker|first10=Erdmann|last11=Verlinden|first11=Pierre J.|last12=Zhang|first12=Xueling|last13=Green|first13=Martin A.|last14=Ho-Baillie|first14=Anita|last15=Brabec|first15=Christoph J.|hdl=10754/626847|hdl-access=free}} and up to 23.9% with a CIGS bottom cell.{{cite journal |last1=Shen |first1=Heping |last2=Duong |first2=The |last3=Peng |first3=Jun |last4=Jacobs |first4=Daniel |last5=Wu |first5=Nandi |last6=Gong |first6=Junbo |last7=Wu |first7=Yiliang |last8=Karuturi |first8=Siva Krishna |last9=Fu |first9=Xiao |last10=Weber |first10=Klaus |last11=Xiao |first11=Xudong |last12=White |first12=Thomas P. |last13=Catchpole |first13=Kylie |title=Mechanically-stacked perovskite/CIGS tandem solar cells with efficiency of 23.9% and reduced oxygen sensitivity |journal=Energy & Environmental Science |date=2018 |volume=11 |issue=2 |pages=394–406 |doi=10.1039/C7EE02627G}} In 2020, KAUST-University of Toronto teams reported 28.2% efficient four terminal perovskite/silicon tandem solar cells.{{Cite journal|last1=Chen|first1=Bin|last2=Baek|first2=Se-Woong|last3=Hou|first3=Yi|last4=Aydin|first4=Erkan|last5=De Bastiani|first5=Michele|last6=Scheffel|first6=Benjamin|last7=Proppe|first7=Andrew|last8=Huang|first8=Ziru|last9=Wei|first9=Mingyang|last10=Wang|first10=Ya-Kun|last11=Jung|first11=Eui-Hyuk|date=2020-03-09|title=Enhanced optical path and electron diffusion length enable high-efficiency perovskite tandems |journal=Nature Communications |volume=11|issue=1|pages=1257|doi=10.1038/s41467-020-15077-3 |pmc=7062737|pmid=32152324|bibcode=2020NatCo..11.1257C}} To achieve these results, the team used Zr-doped In₂O₃ transparent electrodes on semitransparent perovskite top cells, previously introduced by Aydin et al., which improved the near infrared response of the silicon bottom cells by utilizing broadband transparent H-doped In₂O₃ electrodes. The team also enhanced the electron-diffusion length (up to 2.3 μm) thanks to Lewis base passivation via urea. The record efficiency for perovskite/silicon tandems currently stands at 28.2%.

Mailoa et al. started the efficiency race for monolithic 2-terminal tandems using an homojunction c-Si bottom cell, demonstrating a 13.7% efficiency cell, largely limited by parasitic absorption losses.{{Cite journal|title = A 2-terminal perovskite/silicon multijunction solar cell enabled by a silicon tunnel junction|journal = Applied Physics Letters|date = 2015-03-23|page = 121105|volume = 106|issue = 12|first1 = Jonathan P.|last1 = Mailoa|first2 = Colin D.|last2 = Bailie|first3 = Eric C.|last3 = Johlin|first4 = Eric T.|last4 = Hoke|first5 = Austin J.|last5 = Akey|first6 = William H.|last6 = Nguyen|first7 = Michael D.|last7 = McGehee|first8 = Tonio|last8 = Buonassisi|doi = 10.1063/1.4914179|bibcode = 2015ApPhL.106l1105M|hdl = 1721.1/96207| s2cid=108771599 |hdl-access = free}} Then, Albrecht et al. developed low-temperature processed perovskite cells using a SnO₂ electron transport layer. This allowed the use of silicon heterojunction solar cells as bottom cells, with tandem cell efficiency up to 18.1%.{{cite journal |last1=Albrecht |first1=Steve |last2=Saliba |first2=Michael |last3=Correa Baena |first3=Juan Pablo |last4=Lang |first4=Felix |last5=Kegelmann |first5=Lukas |last6=Mews |first6=Mathias |last7=Steier |first7=Ludmilla |last8=Abate |first8=Antonio |last9=Rappich |first9=Jörg |last10=Korte |first10=Lars |last11=Schlatmann |first11=Rutger |last12=Nazeeruddin |first12=Mohammad Khaja |last13=Hagfeldt |first13=Anders |last14=Grätzel |first14=Michael |last15=Rech |first15=Bernd |title=Monolithic perovskite/silicon-heterojunction tandem solar cells processed at low temperature |journal=Energy & Environmental Science |date=2016 |volume=9 |issue=1 |pages=81–88 |doi=10.1039/C5EE02965A}} Werner et al. then improved this performance by replacing the SnO₂ layer with PCBM and introducing a sequential hybrid deposition method for the perovskite absorber, leading to a tandem cell with 21.2% efficiency.{{cite journal |last1=Werner |first1=Jérémie |last2=Weng |first2=Ching-Hsun |last3=Walter |first3=Arnaud |last4=Fesquet |first4=Luc |last5=Seif |first5=Johannes Peter |last6=De Wolf |first6=Stefaan |last7=Niesen |first7=Bjoern |last8=Ballif |first8=Christophe |title=Efficient Monolithic Perovskite/Silicon Tandem Solar Cell with Cell Area >1 cm |journal=The Journal of Physical Chemistry Letters |date=24 December 2015 |volume=7 |issue=1 |pages=161–166 |doi=10.1021/acs.jpclett.5b02686|pmid=26687850 }} Important parasitic absorption losses due to the use of Spiro-OMeTAD were still limiting the overall performance. An important change was demonstrated by Bush et al., who inverted the polarity of the top cell (n-i-p to p-i-n). They used a bilayer of SnO₂ and zinc tin oxide (ZTO) processed by ALD to work as a sputtering buffer layer, which deposited a transparent top of indium tin oxide (ITO) electrode. This change helped to improve the environmental and thermal stability of the perovskite cell{{cite journal |last1=Bush |first1=Kevin A. |last2=Bailie |first2=Colin D. |last3=Chen |first3=Ye |last4=Bowring |first4=Andrea R. |last5=Wang |first5=Wei |last6=Ma |first6=Wen |last7=Leijtens |first7=Tomas |last8=Moghadam |first8=Farhad |last9=McGehee |first9=Michael D. |title=Thermal and Environmental Stability of Semi-Transparent Perovskite Solar Cells for Tandems Enabled by a Solution-Processed Nanoparticle Buffer Layer and Sputtered ITO Electrode |journal=Advanced Materials |date=May 2016 |volume=28 |issue=20 |pages=3937–3943 |doi=10.1002/adma.201505279|pmid=26880196 |bibcode=2016AdM....28.3937B |s2cid=14643245 }} and was crucial to further improve the perovskite/silicon tandem performance to 23.6%.{{Cite journal |last1=Bush|first1=Kevin A.|last2=Palmstrom|first2 = Axel F. |last3= Yu |first3 = Zhengshan J. |last4 = Boccard |first4 = Mathieu |last5 = Cheacharoen |first5 = Rongrong|last6 = Mailoa |first6 = Jonathan P. |last7 = McMeekin |first7 = David P. |last8 = Hoye |first8 = Robert L. Z. |last9 = Bailie |first9 = Colin D. |first10 = Tomas |last10 = Leijtens |first11 = Ian Marius |last11 = Peters |first12 = Maxmillian C. |last12 = Minichetti|first13 = Nicholas |last13 = Rolston |first14 = Rohit |last14 = Prasanna |first15 = Sarah |last15 = Sofia |first16 = Duncan |last16 = Harwood |first17 = Wen |last17 = Ma |first18 = Farhad |last18 = Moghadam |first19 = Henry J. |last19 = Snaith |first20 = Tonio |last20 = Buonassisi |first21 = Zachary C. |last21 = Holman |first22 = Stacey F. |last22 = Bent |first23 = Michael D. |last23 = McGehee |date=2017|title=23.6%-efficient monolithic perovskite/silicon tandem solar cells with improved stability|journal=Nature Energy|volume=2|issue=4|page=17009|doi=10.1038/nenergy.2017.9|bibcode=2017NatEn...217009B|hdl=1721.1/118870|s2cid=43925320 |hdl-access = free }}

In the meantime, using a p-i-n perovskite top cell, Sahli et al. demonstrated in June 2018 a fully textured monolithic tandem cell with 25.2% efficiency, independently certified by Fraunhofer ISE CalLab.{{cite journal|last1=Sahli|first1=Florent|last2=Werner|first2=Jérémie|last3=Kamino|first3=Brett A.|last4=Bräuninger|first4=Matthias|last5=Monnard|first5=Raphaël|last6=Paviet-Salomon|first6=Bertrand|last7=Barraud|first7=Loris|last8=Ding|first8=Laura|last9=Diaz Leon|first9=Juan J.|date=11 June 2018|title=Fully textured monolithic perovskite/silicon tandem solar cells with 25.2% power conversion efficiency|journal=Nature Materials|volume=17|issue=9|pages=820–826|doi=10.1038/s41563-018-0115-4|pmid=29891887|last10=Sacchetto|first10=Davide|last11=Cattaneo|first11=Gianluca|last12=Despeisse|first12=Matthieu|last13=Boccard|first13=Mathieu|last14=Nicolay|first14=Sylvain|last15=Jeangros|first15=Quentin|last16=Niesen|first16=Bjoern|last17=Ballif|first17=Christophe|bibcode=2018NatMa..17..820S|s2cid=48360906|url=http://infoscience.epfl.ch/record/255651/files/Fully%20textured%20monolithic_manuscript_postprint.pdf}} This improved efficiency can largely be attributed to the massively reduced reflection losses (below 2% in the range 360 nm-1000 nm, excluding metallization) and reduced parasitic absorption losses, leading to certified short-circuit currents of 19.5 mA/cm². Also in June 2018 the company Oxford Photovoltaics presented a cell with 27.3% efficiency.Osborne, Mark (June 25, 2018) [https://www.pv-tech.org/news/oxford-pv-takes-record-perovskite-tandem-solar-cell-to-27.3-conversion-effi Oxford PV takes record perovskite tandem solar cell to 27.3% conversion efficiency] {{Webarchive|url=https://web.archive.org/web/20180724153959/https://www.pv-tech.org/news/oxford-pv-takes-record-perovskite-tandem-solar-cell-to-27.3-conversion-effi |date=2018-07-24 }}. pv-tech.org In March 2020, KAUST-University of Toronto teams reported in Science Magazine regarding tandem devices with spin-cast perovskite films on fully textured bottom cells with 25.7% efficiency.{{Cite journal|last1=Hou|first1=Yi|last2=Aydin|first2=Erkan|last3=De Bastiani|first3=Michele|last4=Xiao|first4=Chuanxiao|last5=Isikgor|first5=Furkan H.|last6=Xue|first6=Ding-Jiang|last7=Chen|first7=Bin|last8=Chen|first8=Hao|last9=Bahrami|first9=Behzad|last10=Chowdhury|first10=Ashraful H.|last11=Johnston|first11=Andrew|date=2020-03-06|title=Efficient tandem solar cells with solution-processed perovskite on textured crystalline silicon |journal=Science|language=en|volume=367|issue=6482|pages=1135–1140|doi=10.1126/science.aaz3691|pmid=32139544|bibcode=2020Sci...367.1135H|s2cid=212560453 |hdl=10754/661949|hdl-access=free}} The research teams show effort to utilize more solution-based scalable techniques on textured bottom cells. Accordingly, blade-coated perovskite based tandems were reported by a collaborative team of University of North Carolina and Arizona State University. {{citation needed|date=May 2024}} Following this, in August 2020 KAUST team demonstrated first slot-die coated perovskite based tandems, which was an important step for accelerated processing of tandems.{{Cite journal|last1=Subbiah|first1=Anand S.|last2=Isikgor|first2=Furkan H.|last3=Howells|first3=Calvyn T.|last4=De Bastiani|first4=Michele|last5=Liu|first5=Jiang|last6=Aydin|first6=Erkan|last7=Furlan|first7=Francesco|last8=Allen|first8=Thomas G.|last9=Xu|first9=Fuzong|last10=Zhumagali|first10=Shynggys|last11=Hoogland|first11=Sjoerd|date=2020-09-11|title=High-Performance Perovskite Single-Junction and Textured Perovskite/Silicon Tandem Solar Cells via Slot-Die-Coating |journal=ACS Energy Letters|volume=5|issue=9|pages=3034–3040|doi=10.1021/acsenergylett.0c01297|hdl=10754/664695|s2cid=225497627|hdl-access=free}} In September 2020, Aydin et al. showed the highest certified short-circuit currents of 19.8 mA/cm² on fully textured silicon bottom cells.{{Cite journal|last1=Aydin|first1=Erkan|last2=Allen|first2=Thomas G.|last3=De Bastiani|first3=Michele|last4=Xu|first4=Lujia|last5=Ávila|first5=Jorge|last6=Salvador|first6=Michael|last7=Van Kerschaver|first7=Emmanuel|last8=De Wolf|first8=Stefaan|date=2020-09-14|title=Interplay between temperature and bandgap energies on the outdoor performance of perovskite/silicon tandem solar cells |journal=Nature Energy|volume=5|issue=11 |pages=851–859|doi=10.1038/s41560-020-00687-4|bibcode=2020NatEn...5..851A|hdl=10754/665149|s2cid=224974516 |hdl-access=free}} Also, Aydin et al. showed the first outdoor performance results for perovskite/silicon tandem solar cells, which was an important hurdle for the reliability tests of such devices. In December 2021, KAUST team updated the champion certified PCE to 28.2%.{{Cite journal|last1=Liu|first1=Jiang|last2=Aydin|first2=Erkan|last3=Yin|first3=Jun|last4=Bastiani|first4=Michele De|last5=Isikgor|first5=Furkan H.|last6=Rehman|first6=Atteq Ur|last7=Yengel|first7=Emre|last8=Ugur|first8=Esma|last9=Harrison|first9=George T.|last10=Wang|first10=Mingcong|last11=Gao|first11=Yajun|date=2021-11-29|title=28.2%-efficient, outdoor-stable perovskite/silicon tandem solar cell|journal=Joule|volume=5|issue=12|pages=3169–3186|language=English|doi=10.1016/j.joule.2021.11.003|s2cid=244767353|issn=2542-4785|doi-access=free|bibcode=2021Joule...5.3169L |hdl=10754/674009|hdl-access=free}}

The record efficiency for perovskite/silicon tandems currently stands at 29.8% as of December 2021.Dumé, Isabelle (January 10, 2020) [https://physicsworld.com/a/tandem-solar-cells-break-new-record/ Tandem solar cells break new record]. physicsworld.com

To investigate possible all-tandem perovskite candidates in an efficient and economical way, simulation software has been implemented. Shankar et al.{{Cite journal |last1=Shankar |first1=G. |last2=Kumar |first2=P. |last3=Pradhan |first3=B. |date=2022-12-01 |title=All-perovskite two-terminal tandem solar cell with 32.3% efficiency by numerical simulation |url=https://www.sciencedirect.com/science/article/pii/S2589234722001336 |journal=Materials Today Sustainability |language=en |volume=20 |pages=100241 |doi=10.1016/j.mtsust.2022.100241 |bibcode=2022MTSus..2000241S |s2cid=252700385 |issn=2589-2347}} published a paper in 2022 detailing their use of the Solar Cell Capacitance Simulator – One Dimensional software. This software allows the user to vary device parameters and properties to optimize performance. Results from this simulation research have exhibited efficiencies as high as 30% for a band gap of 1.4 eV, which resulted from increasing the external quantum efficiency to 95% via doping the transport layer.{{Cite journal |last1=Diekmann |first1=Jonas |last2=Caprioglio |first2=Pietro |last3=Futscher |first3=Moritz H. |last4=Le Corre |first4=Vincent M. |last5=Reichert |first5=Sebastian |last6=Jaiser |first6=Frank |last7=Arvind |first7=Malavika |last8=Toro |first8=Lorena Perdigón |last9=Gutierrez-Partida |first9=Emilio |last10=Peña-Camargo |first10=Francisco |last11=Deibel |first11=Carsten |last12=Ehrler |first12=Bruno |last13=Unold |first13=Thomas |last14=Kirchartz |first14=Thomas |last15=Neher |first15=Dieter |date=August 2021 |title=Pathways toward 30% Efficient Single-Junction Perovskite Solar Cells and the Role of Mobile Ions |journal=Solar RRL |language=en |volume=5 |issue=8 |pages=2100219 |doi=10.1002/solr.202100219 |s2cid=235601081 |issn=2367-198X|doi-access=free }} Shankar et al simulated an efficiency of 32.3% by altering the material and thickness of the electron transport and hole transport layers. This simulated efficiency represents a 37% increase in simulated work so far and was obtained upon optimization of work done by Zhao et al. in two-terminal all-perovskite tandem solar cells.

In May 2016, IMEC and its partner Solliance announced a tandem structure with a semi-transparent perovskite cell stacked on top of a back-contacted silicon cell.Manners, David. (2016-05-25) [http://www.electronicsweekly.com/news/itf2016-imec-and-solliance-present-first-semi-transparent-perovskite-pv-module-2016-05/ Electronics Weekly]. Electronics Weekly. Retrieved on 2018-04-11. A combined power conversion efficiency of 20.2% was reported, with the potential claimed to exceed 30%.

In 2016, the development of efficient low-bandgap (1.2–1.3 eV) perovskite materials and the fabrication of efficient devices based on these enabled a new concept: all-perovskite tandem solar cells, where two perovskite compounds with different bandgaps are stacked on top of each other. The first two- and four-terminal devices with this architecture reported in the literature achieved efficiencies of 17% and 20.3% respectively.{{Cite journal|last1=Eperon|first1=Giles E.|last2=Leijtens|first2=Tomas|last3=Bush|first3=Kevin A.|last4=Prasanna|first4=Rohit|last5=Green|first5=Thomas|last6=Wang|first6=Jacob Tse-Wei|last7=McMeekin|first7=David P.|last8=Volonakis|first8=George|last9=Milot|first9=Rebecca L.|date=2016-11-18|title=Perovskite-perovskite tandem photovoltaics with optimized band gaps|journal=Science|volume=354|issue=6314|pages=861–865|doi=10.1126/science.aaf9717|pmid=27856902|arxiv=1608.03920|bibcode=2016Sci...354..861E|s2cid=28954845}} In addition, making formamidinium cesium lead iodide bromide perovskite into four-terminal tandem cells could achieve efficiency ranging from 19.8% to 25.2%, depending on the parameters of the measurements.{{Cite journal |date=8 Jan 2016 |title=A mixed-cation lead mixed-halide perovskite absorber for tandem solar cells |journal=Science |volume=351 |issue=6269 |pages=151–155|doi= 10.1126/science.aad5845|last1= McMeekin|first1= David P.|last2= Sadoughi|first2= Golnaz|last3= Rehman|first3= Waqaas|last4= Eperon|first4= Giles E.|last5= Saliba|first5= Michael|last6= Hörantner|first6= Maximilian T.|last7= Haghighirad|first7= Amir|last8= Sakai|first8= Nobuya|last9= Korte|first9= Lars|last10= Rech|first10= Bernd|last11= Johnston|first11= Michael B.|last12= Herz|first12= Laura M.|last13= Snaith|first13= Henry J.|pmid= 26744401|bibcode= 2016Sci...351..151M|s2cid= 206643942|doi-access= free}} All-perovskite tandem cells offer the prospect of being the first fully solution-processable architecture that has a clear route to exceeding not only the efficiencies of silicon, but also GaAs and other expensive III-V semiconductor solar cells.

In 2017, Dewei Zhao et al. fabricated low-bandgap (~1.25 eV) mixed Sn-Pb perovskite solar cells (PVSCs) with the thickness of 620 nm, which enables larger grains and higher crystallinity to extend the carrier lifetimes to more than 250 ns, reaching a maximum power conversion efficiency (PCE) of 17.6%. Furthermore, this low-bandgap PVSC reached an external quantum efficiency (EQE) of more than 70% in the wavelength range of 700–900 nm, the essential infrared spectral region where sunlight transmitted to bottom cell. They also combined the bottom cell with a ~1.58 eV bandgap perovskite top cell to create an all-perovskite tandem solar cell with four terminals, obtaining a steady-state PCE of 21.0%, suggesting the possibility of fabricating high-efficiency all-perovskite tandem solar cells.{{Cite journal|last1=Zhao|first1=Dewei|last2=Yu|first2=Yue|last3=Wang|first3=Changlei|last4=Liao|first4=Weiqiang|last5=Shrestha|first5=Niraj|last6=Grice|first6=Corey R.|last7=Cimaroli|first7=Alexander J.|last8=Guan|first8=Lei|last9=Ellingson|first9=Randy J.|date=2017|title=Low-bandgap mixed tin–lead iodide perovskite absorbers with long carrier lifetimes for all-perovskite tandem solar cells|journal=Nature Energy|volume=2|issue=4|page=17018|doi=10.1038/nenergy.2017.18|bibcode=2017NatEn...217018Z|osti=1371834|s2cid=136139811 |url=https://www.osti.gov/biblio/1371834}}

A study in 2020 shows that all-perovskite tandems have much lower carbon footprints than silicon-perovskite tandems.{{Cite journal|last1=Tian|first1=Xueyu|last2=Stranks|first2=Samuel D.|last3=You|first3=Fengqi|date=2020-07-01|title=Life cycle energy use and environmental implications of high-performance perovskite tandem solar cells|journal=Science Advances|language=en|volume=6|issue=31|pages=eabb0055|doi=10.1126/sciadv.abb0055|pmid=32789177|pmc=7399695|bibcode=2020SciA....6...55T }}

Additionally, in 2020, all-perovskite tandem efficiencies hit a new peak of 24.2% efficiency for 1 cm² solar cells. This value was measured and recorded by Japan Electrical Safety and Environment Technology Laboratories, and was reached by passivating defects at grain boundaries of the traditional lead-tin perovskite using zwitterionic molecules. These inhibit tin ion oxidation, a process which lowers the efficiency of the solar cell by increasing trap density and preventing diffusion. The introduction of zwitterionic antioxidants greatly boosts the efficiency of these devices while only permitting an additional 2% degradation. The addition of zwitterionic substances also requires using an environment rich with formamidine sulfinic acid, catalyzing the necessary reactions to permit charge to transport between the solar cells.

In November 2022, the all-perovskite tandem efficiency reached a new record of 27.4%.{{Cite journal |last1=Chen |first1=Hao |last2=Maxwell |first2=Aidan |last3=Li |first3=Chongwen |last4=Teale |first4=Sam |last5=Chen |first5=Bin |last6=Zhu |first6=Tong |last7=Ugur |first7=Esma |last8=Harrison |first8=George |last9=Grater |first9=Luke |last10=Wang |first10=Junke |last11=Wang |first11=Zaiwei |last12=Zeng |first12=Lewei |last13=Park |first13=So Min |last14=Chen |first14=Lei |last15=Serles |first15=Peter |date=2022-11-15 |title=Regulating surface potential maximizes voltage in all-perovskite tandems |url=https://www.nature.com/articles/s41586-022-05541-z |journal=Nature |volume=613 |issue=7945 |language=en |pages=676–681 |doi=10.1038/s41586-022-05541-z |pmid=36379225 |hdl=10754/685774 |osti=1900407 |s2cid=253551396 |issn=1476-4687|hdl-access=free }} This breaks the 2020 record for 1 cm² solar cells, and was achieved by a joint team from Northwestern University, University of Toronto, and the University of Toledo. This cell additionally broke the previous record for Voc for all-perovskite tandems. {{citation needed|date=May 2024}} This same cell was certified by NREL with a PCE of 26.3% and a Voc of 2.13V. This marks the “first certified all-perovskite tandem to surpass the record PCE (25.7%) of single-junction perovskite solar cells”. (AUTHOR NAMES ET AL) have found areas for improvement in the Jsc values that put 30% efficiency in the near future. {{citation needed|date=May 2024}}

Inverted perovskite solar cells (PSCs) arrange the hole-transport layer beneath the perovskite absorber, in contrast to the conventional n–i–p layout. They gained traction after demonstrating reduced current–voltage hysteresis and potentially enhanced stability. Early research showed that tuning perovskite compositions and interfaces in the p–i–n architecture improved power conversion efficiencies above 26%. This arrangement also allows simpler low-temperature processing, which supports flexible devices. As laboratory results advance, inverted PSCs are considered strong candidates for large-scale solar applications and tandem architectures.Liu, T.; Chen, K.; Hu, Q.; Zhu, R.; Gong, Q. Inverted Perovskite Solar Cells: Progresses and Perspectives. Adv. Energy Mater. 2016, 6, 1600457.

In an inverted PSC, incident light first passes through a transparent electrode and hole-transport layer before reaching the perovskite absorber. Excitons split into electrons and holes, which then migrate in opposite directions due to built-in fields and favorable band alignment. Holes move downward toward the anode, while electrons drift upward through an electron-selective layer into the metal cathode. The reduced hysteresis often observed in p–i–n devices is partly linked to limited ion migration and fewer interfacial traps on the electron-collection side. By precisely controlling energy levels and interface quality, inverted PSCs can achieve high photovoltage and stable operation under continuous illumination.Park, N.-G.; Zhu, K. Scalable Fabrication and Coating Methods for Perovskite Solar Cells and Solar Modules. Nature Reviews Materials 2020, 5, 333–350.

Controlling the perovskite film is essential for achieving both high efficiency and reliability, starting with composition engineering where multiple cations (FA+, MA+, Cs+) and halides (I−, Br−, Cl−) are combined to optimize bandgap, phase stability, and crystallinity. Among these, blending formamidinium and cesium cations has proven effective at stabilizing the black-phase perovskite at room temperature, while partially substituting lead with tin offers a path to reduce toxicity and tune the bandgap, albeit with additional doping and oxidation challenges. Additive engineering, involving molecules such as small amines, polymers, and inorganic salts, can passivate grain boundaries and suppress deep-level traps, improving both open-circuit voltage and operational lifetime. Another important strategy involves controlling solvent chemistry – binary or ternary solvents (DMF, DMSO, NMP) or ionic-liquid-based systems – to form intermediate phases that yield dense, pinhole-free films upon annealing. Intermediate adducts, in particular, promote a more controlled crystal growth that reduces defects. Researchers also utilize techniques like anti-solvent dripping, gas-quenching, and vacuum-assisted drying to tailor crystal nucleation and achieve uniform, large grains with fewer grain boundaries. Alongside compositional and solvent control, the thermal annealing profile, sometimes split into stepwise temperature ramps, can transform meta stable intermediate states into the desired perovskite phase with improved reproducibility. Because the film composition strongly affects moisture tolerance, many labs explore partial or complete removal of volatile MA+ cations to reduce the film’s sensitivity to humidity or temperature, demonstrating stable operation over hundreds of hours.

An inverted perovskite cell typically employs a hole transport layer (HTL) at the bottom and an electron transport layer (ETL) at the top, each selected to align energy levels favorably with the perovskite absorber. On the hole transport side, many devices started with PEDOT:PSS, but its acidity and suboptimal energy alignment often limit voltage and stability, prompting the adoption of alternatives like NiOx, whose wide bandgap and good thermal tolerance are advantageous. Additional doping in NiOx (for instance, Li-doping) can raise conductivity and yield higher fill factors. Organic HTLs such as PTAA or poly-TPD also appear frequently due to their solution processability and amenable energy levels, though their wetting properties need to be carefully adjusted to ensure smooth perovskite deposition. On the electron transport side, fullerene derivatives like C60 or PCBM remain the mainstream choice, known for their low trap density, excellent coverage, and strong electron affinity. These fullerene layers may be combined with a thin buffer layer, such as BCP or LiF, to block holes and protect against metal electrode diffusion. Some device designs incorporate bilayers of fullerene with metal oxide nanoparticles (SnO2 or ZnO) to enhance device stability, especially under harsh environmental conditions. Recent advances involve self-assembled monolayers or 2D material coatings that enable extremely thin yet robust interfaces, sometimes contributing to record voltage outputs. The synergy between the transport layer composition, doping strategy, and the overall device architecture can dramatically affect the PCE, making CTL optimization a critical research direction.Chen, P.; Xiao, Y.; Li, S.; Jia, X.; Luo, D.; Zhang, W.; Snaith, H. J.; Gong, Q.; Zhu, R. The Promise and Challenges of Inverted Perovskite Solar Cells. Chem. Rev. 2024, 124, 10623–10700.

Maximizing performance and stability requires careful tuning of both the top and bottom interfaces, where lattice mismatch, energy misalignment, and high defect densities frequently arise. For the bottom interface (HTL/perovskite), selecting a surface with proper wettability ensures uniform nucleation of the perovskite, which can otherwise form cracks or voids. Many labs introduce self-assembled or crosslinked molecules that bond strongly to the inorganic sublayer and simultaneously passivate grain boundaries. Alternatively, depositing ultrathin 2D or quasi-2D perovskite layers at the bottom can smooth out surface roughness and serve as a passivation barrier, thus improving open-circuit voltage. The top interface (perovskite/ETL), on the other hand, often suffers from halide vacancies or lead-rich regions that become centers for nonradiative recombination. Incorporating buckyball derivatives or halogen-containing passivation agents can mitigate such losses, while also ensuring that no direct contact occurs between metal electrodes and the absorber. Another pressing issue is controlling band bending in these interfacial regions: properly tuning doping or adding dipole layers can shift the local vacuum level to boost the cell’s built-in electric field. Molecular dopants or metal chelates introduced in the perovskite or at the interface also reduce charge-transport barriers, facilitate extraction, and potentially block ion migration. Hybrid approaches, integrating organic passivation layers with inorganic overlayers, show promise in tackling multiple challenges at once, especially under continuous illumination or elevated temperatures.

Despite enormous gains in efficiency, long-term stability remains a central topic, particularly for commercial viability, as perovskite films can degrade under moisture, oxygen, heat, and UV illumination. In inverted PSCs, the architecture can be more resilient to certain failure modes, for instance, by placing the metal electrode on top, thus reducing direct contact with halides. However, thermal stress and ionic motion within the perovskite can still lead to decomposition pathways if the film composition or interface design is inadequate. Substituting MA+ with more stable cations, such as FA+ or cesium, is a popular route to enhance thermal robustness, while interfacial modifications, such as the addition of self-assembled monolayers or alkylammonium-based capping layers, help protect against moisture. Some groups confirm that the inverted structure can pass stringent reliability tests including damp heat (85 °C/85% RH) and continuous illumination for over 1,000 hours without severe degradation. Another factor is that metal electrode materials, like silver or copper, may diffuse or react under operating conditions, prompting the use of inorganic buffer layers or barrier coatings. Adopting carbon-based electrodes or tin oxides can also help minimize corrosion or doping issues. Overall, the synergy between stable compositions, robust transport layers, and carefully passivated interfaces has led to inverted PSCs that promise to sustain output with minimal performance drop over thousands of hours.

{{Expand section|date=November 2021}}

A factory producing perovskite solar cells was opened in May 2021 in Wrocław by Saule Technologies.{{cite news |title=Warsaw solar panel firm becomes world's first to begin production of revolutionary perovskite technology |url=https://www.thefirstnews.com/article/warsaw-solar-panel-firm-becomes-worlds-first-to-begin-production-of-revolutionary-perovskite-technology-22153 |website=www.thefirstnews.com |language=en}} {{As of|2021}} there was a little manufacturing in Poland and China,{{Cite web |title=Can the most exciting new solar material live up to its hype? |url=https://www.technologyreview.com/2021/06/29/1027451/perovskite-solar-panels-hype-commercial-debut/ |access-date=2021-11-20 |website=MIT Technology Review |language=en}} but large-scale deployment was held back by the instability and shorter lifespan.{{Cite journal |last1=Schmidt-Mende |first1=Lukas |last2=Dyakonov |first2=Vladimir |last3=Olthof |first3=Selina |last4=Ünlü |first4=Feray |last5=Lê |first5=Khan Moritz Trong |last6=Mathur |first6=Sanjay |last7=Karabanov |first7=Andrei D. |last8=Lupascu |first8=Doru C. |last9=Herz |first9=Laura M. |last10=Hinderhofer |first10=Alexander |last11=Schreiber |first11=Frank |date=2021-10-01 |title=Roadmap on organic–inorganic hybrid perovskite semiconductors and devices |journal=APL Materials |volume=9 |issue=10 |pages=109202 |bibcode=2021APLM....9j9202S |doi=10.1063/5.0047616 |s2cid=240026499 |doi-access=free}} Oxford PV opened a factory in Brandenburg, Germany in 2022.{{Cite web |date=2021-07-23 |title=Oxford PV completes 100 MW factory build out |url=https://www.pv-magazine.com/2021/07/23/oxford-pv-completes-100-mw-factory-build-out/ |access-date=2024-11-04 |website=pv magazine International |language=en-US}}

However companies hope to have perovskite-on-silicon tandem products on the market with a 25-year warranty sometime in the mid-2020s.{{Cite web|title=Perovskite: the wonder crystal set to transform solar power|url=https://cosmosmagazine.com/technology/materials/perovskite-set-to-transform-solar-generated-electricity/|access-date=2021-11-20|website=cosmosmagazine.com|date=5 November 2021 |language=en-AU}} They may help to meet the high targets for new solar power in India.{{Cite journal|last1=Kajal|first1=Priyanka|last2=Verma|first2=Bhupesh|last3=Vadaga|first3=Satya Gangadhara Rao|last4=Powar|first4=Satvasheel|title=Costing Analysis of Scalable Carbon-Based Perovskite Modules Using Bottom Up Technique |journal=Global Challenges |year=2021|volume=6|issue=2|doi=10.1002/gch2.202100070 |pmid=35140980|pmc=8812919|s2cid=240476544|doi-access=free}} Building integrated photovoltaics is a possible area of commercialisation, and while there are still stability-related concerns, in 2021 a building in Lublin became the first to be clad with perovskite solar panels, which marked the first commercial use of perovskite.{{cite news |title=Ta-da! Lublin building becomes world's first to be clad in perovskite 'sun-breaker' panels |url=https://www.thefirstnews.com/article/ta-da-lublin-building-becomes-worlds-first-to-be-clad-in-perovskite-sun-breaker-panels-24376 |website=www.thefirstnews.com |language=en}}

The U.S. Department of Energy Solar Energy Technologies Office (SETO) is a government organization that is investing in the research and development of perovskite solar technologies. They have identified several key areas of improvement if perovskite solar cells are to play a part in the future of photovoltaic technologies.

The four target areas for improvement are stability and durability, power conversion efficiency at scale, manufacturability, and technology validation and bankability.{{Cite web |title=Perovskite Solar Cells |url=https://www.energy.gov/eere/solar/perovskite-solar-cells |access-date=2022-11-21 |website=Energy.gov |language=en}} The first and third points are addressed above in the Processing and Scalability sections.

Power conversion efficiency at scale remains a problem because laboratory efficiencies for small-area devices have not been proven at larger scale devices. Current small-scale devices may find use in mobile and disaster response technologies due to their light weight, flexibility, and power-to-weight ratios, but large-scale testing will be necessary before the power industry adopts this technology on the grid-level.

The technology validation and bankability area of development points to the willingness of financial institutions to collaborate with these technologies. This will require a standardization of testing protocols and an increase in field data available. The degradation of perovskite solar cells makes current PV testing methods unrealistic in predicting performance in real-world applications. To address these concerns in the adoption of perovskite technology, SETO has funded the Perovskite Photovoltaic Accelerator for Commercializing Technologies (PACT) Validation and Bankability Center. PACT will set standardized field and lab testing and conduct bankability studies to ensure that perovskite technology is ready for commercialization. SETO also published performance targets to direct research and verify that projects are relevant to the development of commercialization.

{{Portal|Renewable energy|Energy}}

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• Dye-sensitized solar cell
• Emerging photovoltaics
• Hybrid solar cell
• List of types of solar cells
• Methylammonium lead halide
• Nanocrystal solar cell
• Perovskite (mineral)
• Polymer solar cell
• Thin film solar cell
• Third generation photovoltaic cell

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