Methylamine Vapor Exposure for Improved Morphology and Stability of Cesium-Methylammonium Lead Halide Perovskite Thin-Films
Mixed-cation cesium-methylammonium lead halide perovskite (CsxMA1−xPbI3−xBrx) thin-films have been used to demonstrate stable and efficient perovskite devices. However, a systematic study of the Cs incorporation on the properties of the perovskite films has not been reported. In this report, impact of cesium incorporation on the minority carrier recombination lifetime of cesium-methylammonium lead halide perovskite thin-films is studied. The lifetime of the as-deposited perovskite films decreases with increasing concentration of cesium. However, mixed-cation perovskite films are more stable, showing higher lifetimes (15–20 µs) after 9 h of ambient exposure than just after deposition (6–13 µs). ‘Methylamine Vapor Exposure’ (MVE) technique was used to improve the morphology of the as-deposited film. MVE treated films are more oriented along (110) direction and were even more stable in ambient, with Cs0.10MA0.90PbI2.90Br0.10 films showing lifetime of almost 50 μs after 9 h of ambient exposure, twice the lifetime of a comparable MAPbI3 film. These results throw light on why mixed-cation cesium-methylammonium lead halide perovskite films are better for highly efficient and stable perovskite solar cells.
This work was supported under the U.S.–India Partnership to Advance Clean Energy-Research (PACE-R) for the Solar Energy Research Institute for India and the United States (SERIIUS), funded jointly by the U.S. Department of Energy (Office of Science, Office of Basic Energy Sciences, and Energy Efficiency and Renewable Energy, Solar Energy Technology Program, under Subcontract DE-AC36-08GO28308 to the National Renewable Energy Laboratory, Golden, Colorado) and the Government of India, through the Department of Science and Technology under Subcontract IUSSTF/JCERDC-SERIIUS/2012 dated 22nd Nov. 2012. The work is also supported by Department of Science and Technology (DST), Government of India, under project reference no: SB/S3/EECE/0163/2014. The last two authors would also like to acknowledge the support from PhD Fellowship and Young Faculty Research Fellowship under the Visvesvaraya PhD Scheme for Electronics and IT by Ministry of Electronics & Information Technology (MeitY), Government of India.