Optoelectronic properties and ion diffusion mechanism in 2D perovskites Cs3BX5 (B = Ge, Sn, and Pb; X = Cl, Br, and I): A first-principles investigation

Mitigating ion migration is a big challenge for optoelectronic perovskite materials. In this work, we investigate a novel family of layered halide perovskites Cs3BX5 (B = Ge, Sn, and Pb; X = Cl, Br, and I) by first-principles calculations. These compounds exhibit direct bandgap and small effective masses of electrons and holes. The optical absorption and spectroscopic limited maximum efficiency suggest the promising potential for these materials in solar energy conversion. The suppressed ionic conductivity has also been demonstrated by the higher energy barriers of halide ions migrations, which would be conducive to mitigate the hysteresis in perovskite solar cells.