Stable lead-free perovskite solar cells: A first-principles investigation.

A suitable substitution of the lead element in lead-based halide perovskites is a feasible approach to explore lead-free perovskite material with excellent stability, tunable band gap, high optical absorption, and better photovoltaic performance. In this study, the toxic lead is replaced by mixing Ba/Si and Ba/Sn to develop environmentally friendly perovskite materials with excellent properties. MABaSnI has shown evidently improved properties in terms of structural stability and suitable band gap, which indicates that MABaSnI can become the most potential material for applications in single-junction solar cells. Moreover, MABaSnI and MABaSnI can be promising materials for the top cell in the tandem architecture due to their proper band gaps (1.70-1.80 eV). Moreover, the optical absorption coefficients of the proposed lead-free perovskites are stronger than that of MAPbI in the range of 500-800 nm. Our work can provide new insights into exploring lead-free perovskite solar cells with excellent stability and suitable band gap.