Unraveling a Novel CsSnI ₃ and CsSnGeI ₃ Double Absorber Perovskite Solar Cell

The demanding need for sustainable energy solutions has driven notable progress in solar cell technology, with perovskite solar cells (PSCs) emerging as a promising option. This research introduces a novel method to boost PSC efficiency by incorporating a double perovskite active layer (DPAL) design featuring CsSnGeI 3 and CsSnI 3 having energy bandgap of 1.5 and 1.3 eV, respectively. Through comprehensive simulation and optimization applying SCAPS‐1D software, this work investigates the effects of absorber layer thickness, defect density, and doping concentration on the photovoltaic (PV) performance of the proposed PSCs. The results reveal that the DPAL structure (FTO/PCBM/CsSnGeI 3 /CsSnI 3 /Au) achieves impressive power conversion efficiency (PCE) of 31.31%, significantly surpassing single absorber designs. The optimized configuration exhibits a short‐circuit current density ( J SC ) of 35.31 mA/cm 2 , an open‐circuit voltage ( V OC ) of 1.01 V, and a fill factor (FF) of 87.63%. In comparison, CsSnGeI 3 and CsSnI 3 ‐based single absorbers achieved PCEs of 27.33% and 28.10%, respectively. These findings demonstrate the potential of the DPAL approach in enhancing light absorption, charge carrier separation, and transport. This study not only deepens the understanding of PSC design and optimization but also lays the groundwork for advanced solar cells designed to achieve higher efficiency and greater environmental sustainability.