Interface Modification via Rare Earth Material to Assist Hole Migration for Efficiency and Stability Promotion of Perovskite Solar Cells

Interface defect is a limiting factor of the charge dynamics and stability of perovskite solar cells (PSCs). Herein, a rare earth metal oxide cerium oxide is introduced into the interface between perovskite and spiro‐OMeTAD [2,2,7,7‐tetrakis ( N , N ‐di‐p‐methoxyphenyl‐amine) 9,9‐spirobifluorene] to passivate interfacial defects. Due to the nearest‐neighbor interaction of CeO 2 with spiro‐OMeTAD, it can accelerate the oxidization process of spiro‐OMeTAD to form a donor–acceptor complex at this interface, which can overcome the interface barrier for the high hole collecting ability. The bonding formation between lead and oxygen makes this heterojunction show metal conduction behavior at this interface. The insertion of CeO 2 between perovskite and spiro‐OMeTAD, can improve hole transferring to balance the extraction of electron and hole by their respective electrodes, for the decreased device hysteresis with the higher efficiency and improved stability. The results show that the CeO 2 ‐based PSC device achieve a power conversion efficiency (PCE) of over 24%, retaining more than 87% of the initial PCE after 2570 h of storage at 20 ≈ 30% humidity.