Novel Combination of Inorganic Dual‐Absorber Perovskite Solar Cell (Cs ₂ TiI ₆ /Cs ₂ CuBiCl ₆ ): SCAPS‐1D Optimization and Underwater Analysis

Lead‐free perovskites have grasped the popularity in the research community as a potential alternative of toxic lead‐based perovskite. In this work, we have taken lead‐free double absorbers Cs 2 TiI 6 and Cs 2 CuBiCl 6 due to their stability and nontoxic nature. We have simulated the FTO/WO 3 /Cs 2 TiI 6 /Cs 2 CuBiCl 6 /Cu 2 O/Au structure with interfacial defect layer using SCAPS‐1D software. An efficiency of 17.46% along with short circuit current ( J SC ) of 17.52 mA/cm 2 , fill factor (FF) of 88.79% and open circuit voltage ( V OC ) of 1.12 V has initially been achieved in unoptimized device. Further, we have investigated effect of various factors such as thickness of absorber layers, doping density, defects energy level and operating temperature on the device performance. Optimization of these critical parameters resulted in an ≈58% improvement in device efficiency. After optimization of different parameters, maximum PCE of 27.68% with J SC of 28.99 mA/cm 2 , FF of 88.55% and V OC of 1.07 V has been achieved at temperature of 300 K and doping densities of 10 18 cm −3 . The underwater performance of the proposed PSC was evaluated at depths of up to 9 m. The Cs‐based inorganic composition ensures enhanced chemical and thermal stability, while efficiency losses at greater depths are mainly driven by moisture ingress, optical attenuation, and interfacial degradation.