Perovskite solar cells (PSCs) have garnered significant attention in the scientific community due to their rapid increase in performance. Inorganic perovskite devices have been noted for their high performance and long-term stability. This study introduces a device optimization process guided by modeling to produce high-efficiency PSCs using lead-free n–i–p methylammonium tin bromide (MASnBr3) materials. We have thoroughly examined the impact of both the absorber and interface layers on the optimized structure. Our approach utilized graphene as the interface layer between the hole transport and absorber layers. We employed zinc oxide (ZnO)/Al and 3C–SiC as interface layers between the absorber and electron transport layers. The optimization process involved adjusting the thicknesses of the absorber layer and interface layers and minimizing defect densities. Our proposed optimized device structure, ZnO/3C–SiC/MASnBr3/graphene/CuO/Au, demonstrates theoretical power conversion efficiencies of 31.97%, fill factors of 89.38%, a current density of 32.54 mA/cm2, a voltage of 1.112 V, and a quantum efficiency of 94%. This research underscores the ability of MASnBr3 as a nontoxic perovskite material for sustainable energy from renewable sources’ applications.

The quest for high-efficiency solar cells has led to significant research into lead-free perovskite materials, particularly tin-based perovskites. This study investigates the photovoltaic properties of various compositions of FASn(I_1 − xBr_x)₃ perovskites for potential application in solar cells. Computational simulations explore the influence of absorber layer thickness and bulk defect density on the performance of lead-free single-junction perovskite solar cells. Additionally, a two-terminal monolithic tandem solar cell configuration comprising FASn(I_0.75Br_0.25)₃ for the top cell and silicon for the bottom cell is proposed and analyzed. The proposed tandem device, with a 1.66 eV perovskite top cell and a 1.12 eV c-Si-based heterojunction, achieved a maximum power conversion efficiency (PCE) of 33.39%, an open circuit voltage (V_OC) of 2.04 V, a short-circuit current density (J_SC) of 21.14 mA/cm², and a fill factor (FF) of 77.26%. For comparison, the perovskite top cell alone achieved a V_OC of 1.36 V, J_SC of 20.44 mA/cm², FF of 75.51%, and PCE of 21.07%. The bottom cell under AM 1.5G illumination exhibited a V_OC of 0.68 V, J_SC of 40.36 mA/cm², FF of 80.18%, and PCE of 22.05%. Under a filtered spectrum, the bottom cell produced a V_OC of 0.67 V, J_SC of 30.46 mA/cm², FF of 79.13%, and PCE of 16.33%. This performance comparison highlights the enhanced efficiency, voltage, and overall stability provided by the tandem structure over individual cells. This examination encompassed the variation of absorber layer thickness, J-V curves under illumination, quantum efficiency, energy band diagrams, filtered spectra, and tandem photovoltaic parameters governing the conversion efficiency. The study demonstrates the potential of lead-free perovskite/silicon tandem devices, showcasing their promise for the future development of high-efficiency and stable solar cells.