Compact SnO₂ /Mesoporous TiO₂ Bilayer Electron Transport Layer for Perovskite Solar Cells Fabricated at Low Process Temperature

Charge transport layers have been found to be crucial for high-performance perovskite solar cells (PSCs). SnO₂ has been extensively investigated as an alternative material for the traditional TiO₂ electron transport layer (ETL). The challenges facing the successful application of SnO₂ ETLs are degradation during the high-temperature process and voltage loss due to the lower conduction band. To achieve highly efficient PSCs using a SnO₂ ETL, low-temperature-processed mesoporous TiO₂ (LT m-TiO₂) was combined with compact SnO₂ to construct a bilayer ETL. The use of LT m-TiO₂ can prevent the degradation of SnO₂ as well as enlarge the interfacial contacts between the light-absorbing layer and the ETL. SnO₂ /TiO₂ bilayer-based PSCs showed much higher power conversion efficiency than single SnO₂ ETL-based PSCs.