Efficient Planar Perovskite Solar Cells with ZnO Electron Transport Layer

Perovskite solar cells (PSCs) have experienced rapid development in the past period of time, and a record efficiency of up to 25.7% has been yielded. At present, the PSCs with the planar structure are the most prevailing, which not only can significantly simplify the device fabrication process but also reduce the processing temperature. Particularly, the electron transport layer (ETL) plays a critical role in boosting the device performance of planar PSCs. ZnO is a promising candidate as the ETL owing to its high transparency, suitable energy band structure, and high electron mobility. Moreover, ZnO is easy to be processed at a low cost and low energy. This review mainly summarized the recent advances in the application and strategic optimization of ZnO ETL for planar PSCs. The basic properties of ZnO, including energy levels, mobility, processability, trap defects, as well as chemical stability, are clearly clarified. The most available deposition means for preparing ZnO ETLs were also described briefly. Finally, we presented the challenges and guidelines for utilizing ZnO as ETL on efficient planar PSCs.