TiO₂/SnO₂ Nanocomposites as Electron Transporting Layer for Efficiency Enhancement in Planar CH₃NH₃PbI₃-Based Perovskite Solar Cells

Both TiO2 and SnO2 as electron transport layers (ETLs) are the most successful at producing high-efficiency perovskite solar cells (PSCs). Unfortunately, these layers usually require multiple treatments to improve device performance, especially for TiO2-based planar PSCs. Here, a simple, one-step, solution-based method is introduced for fabricating a TiO2/SnO2 nanocomposite ETL. Compared to a pristine TiO2 layer, partial incorporation of SnO2 nanoparticles in a thin compact TiO2 layer contributes to high electrical conductivity and suitable band-level alignment at the ETL/perovskite interface. Using the optimized TiO2/SnO2 nanocomposite ETL, methylammonium lead halide perovskite CH3NH3PbI3-based PSCs exhibit the champion efficiency of 16.8% (area, 0.13 cm2) with less current density–voltage (J–V) hysteresis, which is significantly superior to that of TiO2-based PSCs. Our work highlights that the successful use of TiO2/SnO2 nanocomposite ETL can offer an efficient method for further improvement of the performance for planar PSCs.