Methylammonium lead halide explained

Methylammonium lead halides (MALHs) are solid compounds with perovskite structure and a chemical formula of, where X = Cl, Br or I. They have potential applications in solar cells,^[1] lasers, light-emitting diodes, photodetectors, radiation detectors,^[2] scintillator,^[3] magneto-optical data storage^[4] and hydrogen production.

Properties and synthesis

The first MALHs to be synthesized were the methylammonium derivatives and . Their potential in the area of energy conversion wasn't realized until decades later.^[5] In the cubic crystal structure the methylammonium cation is surrounded by 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.

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 in dimethylformamide. This property is used in the growth of MALH single crystals and films from solution, using a mixture of and powders as the precursor. The growth rates are 3–20 mm³/hour for and reach 38 mm³/hour for 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 and 1.51 eV for, 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 .

Thermal decomposition of gives methyl iodide and ammonia .^{[6] [7]}

Applications

MALHs have potential applications in solar cells, lasers,^[8] light-emitting diodes, photodetectors, radiation detectors, scintillator^[9] and hydrogen production. The power conversion efficiency of MALH solar cells exceeds 19%.

Historic references

• Weber . Dieter . 1978 . 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 . Zeitschrift für Naturforschung B . en . 33 . 8 . 862–865 . 10.1515/znb-1978-0809 . 1865-7117. free.
• Weber . Dieter . 1978-12-01 . CH3NH3PbX3, ein Pb(II)-System mit kubischer Perowskitstruktur / CH3NH3PbX3, a Pb(II)-System with Cubic Perovskite Structure . Zeitschrift für Naturforschung B . en . 33 . 12 . 1443–1445 . 10.1515/znb-1978-1214 . 93597007 . 1865-7117. free.
• Grätzel . Michael . 2014 . The light and shade of perovskite solar cells . Nature Materials . en . 13 . 9 . 838–842 . 10.1038/nmat4065 . 25141800 . 1476-1122.

See also

• Perovskite solar cell
• Methylammonium halide

Notes and References

1. Kojima. Akihiro. Teshima. Kenjiro. Shirai. Yasuo. Miyasaka. Tsutomu. 2009-05-06. Organometal Halide Perovskites as Visible-Light Sensitizers for Photovoltaic Cells. Journal of the American Chemical Society. 131. 17. 6050–6051. 10.1021/ja809598r. 19366264. 0002-7863.
2. Náfrádi. Bálint. Methylammonium Lead Iodide for Efficient X-ray Energy Conversion. J. Phys. Chem. C. October 16, 2015. 2015. 119. 25204–25208. 10.1021/acs.jpcc.5b07876.
3. Birowosuto. M. D.. X-ray Scintillation in Lead Halide Perovskite Crystals. Sci. Rep.. 16 November 2016. 6. 37254. 10.1038/srep37254. 27849019. 5111063. 1611.05862. 2016NatSR...637254B.
4. Náfrádi. Bálint. Optically switched magnetism in photovoltaic perovskite CH3NH3(Mn:Pb)I3. Nature Communications. 24 November 2016. 7. 13406. 10.1038/ncomms13406. 27882917. 5123013. 1611.08205. 2016NatCo...713406N.
5. Cheetham . Anthony K. . Seshadri . Ram . Wudl . Fred . 2022-06-30 . Chemical synthesis and materials discovery . Nature Synthesis . en . 1 . 7 . 514–520 . 10.1038/s44160-022-00096-3 . 2731-0582. 2207.07052 . 250199748.
6. Juarez-Perez. Emilio J.. Hawash. Zafer. Raga. Sonia R.. Ono. Luis K.. Qi. Yabing. Thermal degradation of CH3NH3PbI3 perovskite into NH3 and CH3I gases observed by coupled thermogravimetry–mass spectrometry analysis. Energy Environ. Sci.. 9. 11. 2016. 3406–3410. 1754-5692. 10.1039/C6EE02016J. free.
7. Williams. Alice E.. Holliman. Peter J.. Carnie. Matthew J.. Davies. Matthew L.. Worsley. David A.. Watson. Trystan M.. Perovskite processing for photovoltaics: a spectro-thermal evaluation. J. Mater. Chem. A. 2. 45. 2014. 19338–19346. 2050-7488. 10.1039/C4TA04725G.
8. Deschler . Felix . Price . Michael . Pathak . Sandeep . Klintberg . Lina E. . Jarausch . David-Dominik . Higler . Ruben . Hüttner . Sven . Leijtens . Tomas . Stranks . Samuel D. . Snaith . Henry J. . Atatüre . Mete . Phillips . Richard T. . Friend . Richard H. . High Photoluminescence Efficiency and Optically Pumped Lasing in Solution-Processed Mixed Halide Perovskite Semiconductors . The Journal of Physical Chemistry Letters . 2 April 2014 . 5 . 8 . 1421–1426 . 10.1021/jz5005285 . 26269988 . free.
9. Birowosuto. M. D.. X-ray Scintillation in Lead Halide Perovskite Crystals. Sci. Rep.. 16 November 2016. 6. 37254. 10.1038/srep37254. 27849019. 5111063. 1611.05862. 2016NatSR...637254B.