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. MABa_0.125Sn_0.875I₃ has shown evidently improved properties in terms of structural stability and suitable band gap, which indicates that MABa_0.125Sn_0.875I₃ can become the most potential material for applications in single-junction solar cells. Moreover, MABa_0.50Sn_0.50I₃ and MABa_0.25Sn_0.75I₃ 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 MAPbI₃ 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.