SCAPS‐1D Numerical Simulation and Optimization of Lead‐Free CsSnBr ₃ /MgHfS ₃ Dual‐Absorber Perovskite Solar Cells

To overcome the toxicity limitations of lead‐based perovskite solar cells (PSCs) and the efficiency constraints inherent to lead‐free alternatives, this study presents a novel lead‐free PSC architecture incorporating CsSnBr 3 /MgHfS 3 dual‐absorber layers. This material combination offers unique advantages: the type‐II heterojunction with favorable band alignment (CBO = 0.07 eV) effectively suppresses interfacial recombination, while the complementary bandgaps enable broad spectral coverage from 360 to 870 nm. Key device parameters—including absorber layer thickness, charge transport layer materials, bulk and interfacial defect densities, back electrode work function, and operating temperature—are systematically optimized using SCAPS‐1D to maximize the synergistic light harvesting enabled by the complementary bandgaps of CsSnBr 3 (1.8 eV) and MgHfS 3 (1.43 eV). Under optimized conditions, the simulated device achieves a theoretical power conversion efficiency of 29.04% at 320 K ( V OC = 1.22 V, J SC = 27.54 mA/cm 2 , FF = 86.45%), marking a 50.3% improvement over the baseline PCE of 19.32%. The systematic optimization framework and physical insights provided here offer valuable guidance for the experimental development of high‐performance lead‐free perovskite solar cells.