Theoretical investigation of FAPbSnGeX₃ efficiency

The use of hybrid lead halide perovskites as light absorbers in photovoltaic cells have gained large interest due to their optoelectronic properties and high efficiency. However, most hybrid perovskites contain toxic lead which has a negative impact on the environment. In this work, we systematically study the structural, electronic, and optical properties of lower lead halide perovskites FAPb_0.5Sn_0.25Ge_0.25X₃ (X = I, Br, Cl), as well as discussing their photovoltaic performance (open circuit voltage (V _oc), the short circuit current density (J _sc), and the power conversion efficiency (η)) using density functional theory (DFT), and we compare these with FAPbX₃ (X = I, Br, Cl) frameworks. The compounds show a suitable band gap for photovoltaic applications, in which iodine has a lower gap value compared to chlorine. It is noteworthy that we found that lead doping by both germanium and tin in the FAPb_0.5Sn_0.25Ge_0.25X₃ (X = I, Br, Cl) materials significantly improves the adsorption coefficient and the stability of these systems compared to the FAPbX₃ (X = I, Br, Cl) systems. The calculated Jsc shows a monotonical decrease from FAPb_0.5Sn_0.25Ge_0.25I₃ to FAPbCl₃, which represents the lowest Jsc. Results reveal that FAPb_0.5Sn_0.25Ge_0.25Cl₃ demonstrates promising potential for photovoltaic application as it shows the highest efficiency. This study can help reduce the toxicity of hybrid lead halide perovskites and also raises their experimental power conversion efficiency.