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 (CH 3 CH 2 NH 3 , EA) as an alternative cation to explore the stabilities and electronic properties of mixed MA 1- x EA x PbI 3 perovskites. The results indicate that replacing MA with EA is a more effective way to improve the stabilities of the mixed MA 1- x EA x PbI 3 perovskites except for MA 0.75 EA 0.25 PbI 3 . The band gap of MA 1- x EA x PbI 3 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- x EA x PbI 3 perovskites show comparable absorption abilities in the visible light region to the pure MAPbI 3 structure. We hope that our study will be greatly helpful for further experiments to find more efficient perovskite materials in the future.