CO₂ Plasma-Treated TiO₂ Film as an Effective Electron Transport Layer for High-Performance Planar Perovskite Solar...

Perovskite solar cells (PSCs) have received great attention because of their excellent photovoltaic properties especially for the comparable efficiency to silicon solar cells. The electron transport layer (ETL) is regarded as a crucial medium in transporting electrons and blocking holes for PSCs. In this study, CO₂ plasma generated by plasma-enhanced chemical vapor deposition (PECVD) was introduced to modify the TiO₂ ETL. The results indicated that the CO₂ plasma-treated compact TiO₂ layer exhibited better surface hydrophilicity, higher conductivity, and lower bulk defect state density in comparison with the pristine TiO₂ film. The quality of the stoichiometric TiO₂ structure was improved, and the concentration of oxygen-deficiency-induced defect sites was reduced significantly after CO₂ plasma treatment for 90 s. The PSCs with the TiO₂ film treated by CO₂ plasma for 90 s exhibited simultaneously improved short-circuit current (J_SC) and fill factor. As a result, the PSC-based TiO₂ ETL with CO₂ plasma treatment affords a power conversion efficiency of 15.39%, outperforming that based on pristine TiO₂ (13.54%). These results indicate that the plasma treatment by the PECVD method is an effective approach to modify the ETL for high-performance planar PSCs.