Optoelectronic and Thermoelectric Properties of Pb-Free Halide Inorganic Perovskites RbSnX₃ (X = Cl, Br, I) for Solar Cell Applications—A DFT Study

This study utilized Density Functional Theory (DFT) to investigate various physical properties of the three inorganic perovskites RbSnX₃ (X = Cl, Br, I) as potential materials for solar cells, and also examine the impact of halogen ion substitution. The study focused on analyzing structural, electronic, optical, and thermoelectric characteristics using the full-potential linearized augmented-plane wave (FP-LAPW) method. The exchange–correlation potential V_xc was computed employing both the generalized Perdew–Burke–Ernzerhof gradient approximation (GGA-PBE) and the modified Becke–Johnson potential (mBJ). Based on our results, it is found that the studied materials exhibit p-type semiconductor behavior with a direct band gap. By employing the mBJ corrective approximation, the gap energy values were enhanced. Besides, the calculated optical properties revealed outstanding absorption and optical conductivity of the three Rb-based perovskites, indicating their potential for optoelectronic applications. The analysis of thermoelectric/transport properties demonstrated that RbSnCl₃ perovskite exhibits higher ‘ZT_e’ (Electronic figure of merit) values, suggesting its suitability for thermoelectric devices.