High-Efficiency Lead-Free KSnI3/CsSnI3 Dual-Absorber Solar Cells: A Numerical Modelling Approach

Halide perovskites have emerged as leading contenders for next-generation photovoltaic (PV) technology, offering exceptional optical properties, high efficiency, lightweight design, and cost-effectiveness. This study unveils a cutting-edge numerical approach to enhance efficiency in a novel dual-absorber perovskite solar cell (PSC), harnessing eco-friendly inorganic perovskite materials and precise parameter optimization. Initially, we performed comprehensive first-principles calculations of KSnI₃ and CsSnI₃, revealing their unique direct band gap characteristics of 1.82 eV and 1.26 eV, respectively. Both materials exhibit exceptional absorption coefficients exceeding 10⁵ cm^-1 beyond their band gaps, alongside minimal lattice mismatch, making them prime candidates for next-generation high-performance dual-absorber solar cells. In our proposed PSC architecture, KSnI₃ acts as the upper absorber layer, while CsSnI₃ serves as the lower absorber, complemented by ZnMgO as the electron transport layer (ETL) and NiO_x as the hole transport layer (HTL). By utilizing double-graded KSnI₃/CsSnI₃ materials, our study achieves an impressive efficiency of 30.01%, with an open circuit voltage of 1.11 V, fill factor of 78.1%, and short circuit current of 37.76 mA/cm². The simulation comprehensively examines the influence of absorber and transport layer thickness, as well as bulk and interface defect densities, on the device’s performance parameters. Additionally, it evaluates the effects of series and shunt resistances and investigates temperature variations to assess performance stability. These insights pave the way for the design and development of next-generation, high-efficiency dual-absorber solar cells.