Dual Function of Surface Alkali-Gas Erosion on SnO <sub/>2</sub> for Efficient and Stable Perovskite Solar Cells

摘要： The electrical character and interface contact of electron transport layer (ETL) play a critical role on high efficiency planar perovskite solar cells (PSCs). Here, a dual functional surface alkali-gas erosion (SAE) method is proposed based on the unique chemical properties of the amphoteric oxide. Firstly, during the SAE process, the SnO2 can react with alkaline gas slightly and the chemical reaction mechanism is elucidated, which leads to the crystal fusion of the SnO2 surface, bringing an improved electron mobility and an excellent interface contact between SnO2 ETL and perovskite layer. Secondly, SAE method introduced -NH2 group on SnO2 surface chemically can provide nuclear site of perovskite crystal and promote the growth of perovskite film, meanwhile, the -NH2 group connected chemically with SnO2 also serves as a bridge-link by replacing the organic cation at the perovskite/SnO2 interface, which effectively enhances the interfacial charge transport and the perovskite crystallinity. As a consequence, devices with SAE achieve a champion PCE of 21.10% and the average PCE is increased from 18.07% to 20.30%, which mainly results from the increase of short-circuit current density from 22.34 mA/cm2 to 24.19 mA/cm2. Moreover, the optimized devices retain 86% of its initial PCE (compared with 41% of control device) after 60 days at room temperature with 40%–50% humidity.