High‐Efficiency Lead‐Free Hybrid Perovskite Solar Cells Integrating (FA) ₂ BiCuI ₆ and MASnI ₃ for Broad‐Spectrum Light Harvesting

This study presents a lead‐free dual‐absorber perovskite solar cell (PSC) integrating double perovskite material (FA) 2 BiCuI 6 for enhanced sensitivity and single perovskite material MASnI 3 for broad spectrum absorption resulting in enhance power conversion efficiency (PCE) of 28.31%, working at temperature 320 K while mitigating lead toxicity. The proposed device architecture is FTO/WS 2 /(FA) 2 BiCuI 6 /MASnI 3 /CuI/Ni. The (FA) 2 BiCuI 6 layer effectively absorbs visible light, whereas MASnI 3 extends absorption into the near‐infrared region (NIR). This performance surpasses many current systems and competes with the efficiency of complex tandem cells, without their associated drawbacks. The use of oxygen‐free materials, WS 2 and CuI, in the electron and hole transport layers prevents tin oxidation, boosting both stability and efficiency via facilitating efficient carrier extraction and reducing recombination losses. The device exhibits a short‐circuit current density (J SC ) of 33.43 mA/cm 2 , an open‐circuit voltage (V OC ) of 1.01 V, and a fill factor (FF) of 83.45% at series resistance 1.2 and shunt resistance 10 5 . Quantum efficiency measurements indicate 94% efficiency in the visible spectrum, with NIR efficiency decreasing from 92% to 38%. Comprehensive analysis of defect density, absorber thickness, interfacial properties, and recombination dynamics underscores the critical factors influencing device performance. This architecture not only boosts environmental resilience but also advances the development of high‐performance, sustainable solar technology.