Numerical optimization of TiO₂/SnO₂ bilayer electron transport layers for enhanced perovskite solar cell performance

To improve charge extraction and address UV-induced degradation in perovskite solar cells, we propose and numerically evaluate a TiO₂/SnO₂ bilayer electron transport layer (ETL) architecture. Using physics-based simulation, we systematically analyze the influence of individual and combined ETL thicknesses on key parameters. The results identify an optimal configuration of 100 nm TiO₂ and 20 nm SnO₂, which minimizes interfacial recombination and enhances electron transport. Furthermore, CH₃NH₃SnI₃ is employed as a lead-free absorber layer. Simulation results demonstrate a notable efficiency improvement upto 20.80%. The experimental results verified that the bi-layer Sn-based perovskite can achieve a conversion efficiency of 10.3%. This study highlights the potential of simulation-guided design in optimizing multilayer ETL structures and advancing environmentally friendly, high-efficiency perovskite photovoltaics.