Compact SnO 2 /Mesoporous TiO 2 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). SnO 2 has been extensively investigated as an alternative material for the traditional TiO 2 electron transport layer (ETL). The challenges facing the successful application of SnO 2 ETLs are degradation during the high-temperature process and voltage loss due to the lower conduction band. To achieve highly efficient PSCs using a SnO 2 ETL, low-temperature-processed mesoporous TiO 2 (LT m-TiO 2 ) was combined with compact SnO 2 to construct a bilayer ETL. The use of LT m-TiO 2 can prevent the degradation of SnO 2 as well as enlarge the interfacial contacts between the light-absorbing layer and the ETL. SnO 2 /TiO 2 bilayer-based PSCs showed much higher power conversion efficiency than single SnO 2 ETL-based PSCs.