Review on the Application of SnO2 in Perovskite Solar Cells

SnO2 has been well investigated in many successful state-of-the-art perovskite solar cells (PSCs) due to its favorable attributes such as high mobility, wide bandgap, and deep conduction band and valence band. Several independent studies show the performances of PSCs with SnO2 are higher than that with TiO2, especially in device stability. In 2015, the first planar PSCs were reported with a power conversion efficiency over 17% using a low temperature sol-derived SnO2 nanocrystal electron transport layer (ETL). Since then, many other groups have also reported high performance PSCs based on SnO2 ETLs. SnO2 planar PSCs show currently the highest performance in planar configuration devices (21.6%) and are close to the record holder of TiO2 mesoporous PSCs, suggesting their high potential as ETLs in PSCs. The main concerns with the application of SnO2 as ETL are that it suffers from degradation in high temperature processes and that its much lower conduction band compared to perovskite may result in a voltage loss of PSCs. Here, notable achievements to date are outlined, the unique attributes of SnO2 as ETLs in PSCs are described, and the challenges facing the successful development of PSCs and approaches to the problems are discussed.