Numerical Analysis and Parametric Optimization of Multi-Absorber Layer All-Inorganic Perovskite Solar Cells Employing Double Perovskites

All-inorganic, lead-free perovskite solar cells have emerged as promising candidates to replace the conventional photovoltaic technologies due to their superior efficiency, environmental stability, and non-toxic composition. This study introduces a novel multi-absorber solar cell architecture featuring double perovskite materials Cs₂AgBiBr₆ and Cs₂SnI₆ configured as SnO₂/Cs₂AgBiBr₆/Cs₂SnI₆/NiO stack. The dual-absorber strategy harnesses the complementary optical and electronic characteristics of the two perovskites to extend spectral coverage and enhance charge separation. Efficient carrier extraction is further supported by the integration of a high-quality electron transport layer (SnO₂) and an efficient hole transport layer (NiO), both of which contribute to reduced recombination losses. Through numerical simulations, the device is optimized for key parameters including absorber thickness, defect density, and interface energetics. The optimized structure achieves a power conversion efficiency (PCE) of 37.38%, an open-circuit voltage (Voc) of 1.15 V, a short-circuit current density (Jsc) of 36.13 mA/cm², and a fill factor (FF) of 89.46%. These results highlight the potential of double perovskite-based multi-absorber designs for developing stable, efficient, and environmentally sustainable all-inorganic solar cells.