methylammonium lead halide
Methylammonium lead halides (MALHs) are solid compounds with perovskite structure and a chemical formula of {{chem2|[CH3NH3]+Pb(2+)(X−)3}}, where X = Cl, Br or I. They have potential applications in solar cells,{{Cite journal|last1=Kojima|first1=Akihiro|last2=Teshima|first2=Kenjiro|last3=Shirai|first3=Yasuo|last4=Miyasaka|first4=Tsutomu|date=2009-05-06|title=Organometal Halide Perovskites as Visible-Light Sensitizers for Photovoltaic Cells|url=https://doi.org/10.1021/ja809598r|journal=Journal of the American Chemical Society|volume=131|issue=17|pages=6050–6051|doi=10.1021/ja809598r|pmid=19366264|issn=0002-7863}} lasers, light-emitting diodes, photodetectors, radiation detectors,{{cite journal|last1=Náfrádi|first1=Bálint|title=Methylammonium Lead Iodide for Efficient X-ray Energy Conversion|journal=J. Phys. Chem. C|date=October 16, 2015|volume=2015|issue=119|pages=25204–25208|doi=10.1021/acs.jpcc.5b07876}} scintillator,{{cite journal|last1=Birowosuto|first1=M. D.|title=X-ray Scintillation in Lead Halide Perovskite Crystals|journal=Sci. Rep.|date=16 November 2016|volume=6|page=37254|doi=10.1038/srep37254|pmid=27849019|pmc=5111063|arxiv=1611.05862|bibcode=2016NatSR...637254B}} magneto-optical data storage{{cite journal|last1=Náfrádi|first1=Bálint|title=Optically switched magnetism in photovoltaic perovskite CH3NH3(Mn:Pb)I3|journal=Nature Communications|date=24 November 2016|volume=7|page=13406|doi=10.1038/ncomms13406|pmid=27882917|pmc=5123013|arxiv=1611.08205|bibcode=2016NatCo...713406N}} and hydrogen production.
Properties and synthesis
The first MALHs to be synthesized were the methylammonium derivatives {{chem2|[CH3NH3]SnX3}} and {{chem2|[CH3NH3]PbX3}}. Their potential in the area of energy conversion wasn't realized until decades later.{{Cite journal |last1=Cheetham |first1=Anthony K. |last2=Seshadri |first2=Ram |last3=Wudl |first3=Fred |date=2022-06-30 |title=Chemical synthesis and materials discovery |url=https://www.nature.com/articles/s44160-022-00096-3 |journal=Nature Synthesis |language=en |volume=1 |issue=7 |pages=514–520 |doi=10.1038/s44160-022-00096-3 |issn=2731-0582|arxiv=2207.07052 |bibcode=2022NatSy...1..514C |s2cid=250199748}}
In the {{chem2|[CH3NH3]PbX3}} cubic crystal structure the methylammonium cation ({{chem2|[CH3NH3]+}}) is surrounded by {{chem2|PbX6}} octahedra. The X ions are not fixed and can migrate through the crystal with an activation energy of 0.6 eV; the migration is vacancy assisted. The methylammonium cations can rotate within their cages. At room temperature the ions have the CN axis aligned towards the face directions of the unit cells and the molecules randomly change to another of the six face directions on a 3 ps time scale.
File:CH3NH3PbI3_crystal_growth.webm at 110 °C. The yellow color originates from the lead(II) iodide precursor.]]
File:CH3NH3PbBr3_crystal_growth.webm at 80 °C.]]
The solubility of MALHs strongly decreases with increased temperature: from 0.8 g/mL at 20 °C to 0.3 g/mL at 80 °C for {{chem2|[CH3NH3]PbBr3}} in dimethylformamide. This property is used in the growth of MALH single crystals and films from solution, using a mixture of Methylammonium halide and {{chem2|PbX2}} powders as the precursor. The growth rates are 3–20 mm3/hour for {{chem2|[CH3NH3]PbI3}} and reach 38 mm3/hour for {{chem2|[CH3NH3]PbBr3}} crystals.
The resulting crystals are metastable and dissolve in the growth solution when cooled to room temperature. They have bandgaps of 2.18 eV for {{chem2|[CH3NH3]PbBr3}} and 1.51 eV for {{chem2|[CH3NH3]PbI3}}, while their respective carrier mobilities are 24 and 67 cm2/(V·s). Their thermal conductivity is exceptionally low, ~0.5 W/(K·m) at room temperature for {{chem2|[CH3NH3]PbI3}}.
Thermal decomposition of {{chem2|[CH3NH3]PbI3}} gives methyl iodide ({{chem2|CH3I}}) and ammonia ({{chem2|NH3}}).{{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|issn=1754-5692|doi=10.1039/C6EE02016J|doi-access=free}}
:{{chem2|[CH3NH3]PbI3 → PbI2 + CH3I + NH3}}
Applications
MALHs have potential applications in solar cells, lasers,{{cite journal |last1=Deschler |first1=Felix |last2=Price |first2=Michael |last3=Pathak |first3=Sandeep |last4=Klintberg |first4=Lina E. |last5=Jarausch |first5=David-Dominik |last6=Higler |first6=Ruben |last7=Hüttner |first7=Sven |last8=Leijtens |first8=Tomas |last9=Stranks |first9=Samuel D. |last10=Snaith |first10=Henry J. |last11=Atatüre |first11=Mete |last12=Phillips |first12=Richard T. |last13=Friend |first13=Richard H. |title=High Photoluminescence Efficiency and Optically Pumped Lasing in Solution-Processed Mixed Halide Perovskite Semiconductors |journal=The Journal of Physical Chemistry Letters |date=2 April 2014 |volume=5 |issue=8 |pages=1421–1426 |doi=10.1021/jz5005285 |pmid=26269988 |doi-access=free}} light-emitting diodes, photodetectors, radiation detectors, scintillator{{cite journal|last1=Birowosuto|first1=M. D.|title=X-ray Scintillation in Lead Halide Perovskite Crystals|journal=Sci. Rep.|date=16 November 2016|volume=6|page=37254|doi=10.1038/srep37254|pmid=27849019|pmc=5111063|arxiv=1611.05862|bibcode=2016NatSR...637254B}} and hydrogen production. The power conversion efficiency of MALH solar cells exceeds 19%.
Historic references
- {{Cite journal |last=Weber |first=Dieter |date=1978 |title=CH3NH3SnBrxI3-x (x = 0-3), ein Sn(II)-System mit kubischer Perowskitstruktur / CH3NH3SnBrxI3-x (x = 0-3), a Sn(II)-System with Cubic Perovskite Structure |journal=Zeitschrift für Naturforschung B |language=en |volume=33 |issue=8 |pages=862–865 |doi=10.1515/znb-1978-0809 |issn=1865-7117|doi-access=free}}
- {{Cite journal |last=Weber |first=Dieter |date=1978-12-01 |title=CH3NH3PbX3, ein Pb(II)-System mit kubischer Perowskitstruktur / CH3NH3PbX3 , a Pb(II)-System with Cubic Perovskite Structure |journal=Zeitschrift für Naturforschung B |language=en |volume=33 |issue=12 |pages=1443–1445 |doi=10.1515/znb-1978-1214 |s2cid=93597007 |issn=1865-7117|doi-access=free}}*{{Cite journal |last=Grätzel |first=Michael |date=2014 |title=The light and shade of perovskite solar cells |url=https://www.nature.com/articles/nmat4065 |journal=Nature Materials |language=en |volume=13 |issue=9 |pages=838–842 |doi=10.1038/nmat4065 |pmid=25141800 |bibcode=2014NatMa..13..838G |issn=1476-1122}}
See also
References
{{Commons category|Methylammonium lead halides}}
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