Numerical Simulation and Machine Learning-Driven Engineering of K ₂ GeI ₆ Perovskite Solar Cells for High-Efficiency and Sustainable Photovoltaics

Perovskite solar cells (PSCs) have garnered significant attention due to their exceptional optoelectronic properties and potential for high power conversion efficiency (PCE). This study presents a comprehensive numerical investigation of lead-free potassium germanium hexaiodide (K2GeI6)-based double perovskite absorbers using the SCAPS-1D simulation tool. A total of 84 device configurations were explored by varying combinations of electron transport layers (ETLs) and hole transport layers (HTLs). The ITO/Ws2/K2GeI6/CuSbS2/Ni structure delivered the highest PCE of ∼28.69%. Further optimization was performed by analyzing the absorber thickness, intrinsic defect density, and the thickness and doping levels of the transport layers. The absorber layer was optimized with a thickness of 0.7 μm, an acceptor density (NA) of 1 × 1018 cm– 3, and a defect density…