Multi-cation hybrid stannic oxide electron transport layer for high-efficiency perovskite solar cells

The performance of perovskite solar cells (PSCs) can be improved by optimizing the perovskite film quality and electron transfer layers (ETLs). In this study, high-efficient PSCs with multi-cation hybrid electron transport layer (SnO₂@Na:Cs ETL) were fabricated using continuous spin-coating. Compared to the pristine SnO₂, the power conversion efficiency (PCE) of device based on SnO₂@Na:Cs ETL have reached 22.06% (with an open circuit voltage of 1.13 V), up approximately 21%. The photovoltaic performance of the device is enhanced due to the increase in the transmission rate, electrical conductivity, electron mobility and surface state owing to the multi-cation hybrid. In addition, because SnO₂@Na:Cs ETL can significantly improve interface contact with the perovskite film and improve its crystallinity, the transport defect state and carrier transport efficiency are significantly improved at the ETL/Perovskite interface. Therefore, the open circuit voltage (V_oc) and fill factor (FF) of PSCs was significantly increased. The application of SnO₂@Na:Cs ETL provides a simple and efficient method to obtain highly-efficient PSCs.