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 (CH₃CH₂NH₃, EA) as an alternative cation to explore the stabilities and electronic properties of mixed MA_1- EA PbI₃ perovskites. The results indicate that replacing MA with EA is a more effective way to improve the stabilities of the mixed MA_1- EA PbI₃ perovskites except for MA_0.75EA_0.25PbI₃. The band gap of MA_1- EA PbI₃ slightly increases with x from 0.25 to 1.00, which is quite different from the MA-FA mixed-cation perovskites. The results indicate that the c axis distortion of the Pb-I-Pb bond angles can play a greater role in tuning the band gap. Moreover, the mixed MA_1- EA PbI₃ perovskites show comparable absorption abilities in the visible light region to the pure MAPbI₃ structure. We hope that our study will be greatly helpful for further experiments to find more efficient perovskite materials in the future.