The pursuit of environmentally sustainable and high-efficiency solar cells has accelerated research on lead-free perovskite absorbers. In this work, a comprehensive SCAPS-1D simulation study was performed on Rb1–xCsxSnCl3 (x = 0–1) to assess the effects of compositional engineering, transport layer selection, and structural optimization on device performance. Vegard’s law-based alloying enabled bandgap tuning from 1.24 eV (RbSnCl3) to 1.52 eV (CsSnCl3). Among the alloy series, Rb0.75Cs0.25SnCl3 demonstrated the best balance between the open-circuit voltage (0.77 V) and short-circuit current density (30.39 mA/cm2), yielding a power conversion efficiency (PCE) of 19.53%. Screening of eight electron transport layers (TiO2, ZnO, IGZO, PCBM, CdZnS, CdS, SnS2, WS2) and three-hole transport layers (Cu2O, CuI, Spiro-OMeTAD) identified the ZnO/Cu2O heterocontact as the optimal transport layer combination, achieving a PCE of 20.13%. Further optimization of absorber thickness, bulk defect density, and interface defect states enhanced the PCE to 21.18%, with Voc = 0.81 V, Jsc = 30.83 mA/cm2, and fill factor (FF) = 84.12%. These findings underscore the potential of Rb–Cs mixed tin chlorides as efficient and nontoxic perovskite absorbers, offering a viable pathway toward next-generation photovoltaic technologies.
S et al. (Thu,) studied this question.