Low‐Cost Hydroxyacid Potassium Synergists as an Efficient In Situ Defect Passivator for High Performance Tin‐Oxide‐Based Perovskite Solar Cells

Abstract Perovskite solar cells (PSCs) based on SnO 2 electron transport layers have attracted extensive research due to their compelling photovoltaic performance. Herein, we presented an in situ passivation of SnO 2 with low‐cost hydroxyacid potassium synergist during deposition to optimize the interface carrier extraction and transport for high power conversion efficiency (PCE) and stabilities of PSCs. The orbital overlap of the carboxyl oxygen with the Sn atom alongwith the homogenous nano‐particle deposition effectively suppresses the interfacial defects and releases the internal residual strains in the perovskite. Accordingly, a PCE of 24.91 % with a fill factor (FF) up to 0.852 is obtained for in situ passivated devices, which is one of the highest values for SnO 2 ‐based PSCs. Moreover, the unencapsulated device maintained 80 % of its initial PCE at 80 °C over 600 h, 100 % PCE at ambient conditions for 1300 h, and 98 % after one week maximum power point tracking (MPPT) under continuous AM1.5G illumination.