<p>Theoretical Investigation and Device Modeling of Cs<sub>4</sub>CuSb<sub>2</sub>Cl<sub>12</sub>/Sr<sub>3</sub>SbI<sub>3</sub> Dual Absorber Lead-Free Perovskite Solar Cells</p>

The performance limitations of single-absorber perovskite solar cells caused by spectral losses can be reduced by adopting dual-absorber architectures capable of harvesting a broader solar spectrum. In this study, a lead-free dual-absorber device employing Cs4CuSb2Cl12 and Sr3SbI3 as complementary absorber layers is theoretically investigated using Solar Cell Capacitance Simulator in 1D simulation tool. The effects of absorber thickness, defect density, and doping concentration on photovoltaic performance are systematically analyzed. The optimized dual-absorber device achieved a maximum theoretical power conversion efficiency (PCE) of 35.22%, which is higher than the 30.11% obtained for the single-absorber Cs4CuSb2Cl12 device under near-ideal defect conditions. Under realistic defect densities, the simulated device exhibited a PCE of 21.19%. The results identify absorber defect density as the dominant factor governing device performance due to trap-assisted recombination. A temperature-dependent analysis was also performed to evaluate realistic operating conditions. These findings provide simulation-guided insights for the design of stable and efficient lead-free dual-absorber perovskite solar cells.