Synergistically Regulating CBD‐SnO₂/Perovskite Buried Interface for Efficient FAPbI₃ Perovskite Solar Cells

Abstract Tin oxide (SnO 2 ) based on chemical bath deposition method (CBD‐SnO 2 ) is considered as an ideal electron transporting layer for perovskite solar cells (PSCs), however, the research on precise regulation toward CBD‐SnO 2 layer is lacking. Here, the study introduces a multifunctional molecule, potassium 2‐(N‐morpholino)ethanesulfonate (MES‐K), on the surface of CBD‐SnO 2 layer to synergistically modify the buried interface between the SnO 2 and perovskite. It is found that MES‐K introduction can passivate interfacial defects, favor the perovskite crystal growth, and improve carrier transportation. 25.14% efficiency of small‐size perovskite solar cells has been achieved with 24.45% efficiency of 1 cm 2 perovskite devices, with negligible hysteresis. Besides, unencapsulated devices based on CBD‐SnO 2 can maintain > 95% of its initial efficiency after 2000 h storage at ambient environment, and > 90% after 1000 h LED illumination.