Ethylammonium as an alternative cation for efficient perovskite solar cells from first-principles calculations.

Mixed-cation lead halide perovskites have emerged as a new class of promising photovoltaic materials for perovskite solar cells. Formamidinium (FA), methylammonium (MA), and Cs cations are widely studied in the field of mixed-cation hybrid halide perovskites. In this work, we have investigated ethylammonium (CHCHNH, EA) as an alternative cation to explore the stabilities and electronic properties of mixed MA EA PbI perovskites. The results indicate that replacing MA with EA is a more effective way to improve the stabilities of the mixed MA EA PbI perovskites except for MAEAPbI. The band gap of MA EA PbI slightly increases with from 0.25 to 1.00, which is quite different from the MA-FA mixed-cation perovskites. The results indicate that the axis distortion of the Pb-I-Pb bond angles can play a greater role in tuning the band gap. Moreover, the mixed MA EA PbI perovskites show comparable absorption abilities in the visible light region to the pure MAPbI structure. We hope that our study will be greatly helpful for further experiments to find more efficient perovskite materials in the future.