Auxiliary Buried‐Interface Passivation Toward Stable and Low‐Recombination‐Loss Perovskite Photovoltaics

Defects occur in the bulk perovskite and heterojunction interfaces of perovskite solar cells (PSCs). While additive and interface engineering are commonly used to passivate defects within the perovskite phase and at the interface, the interconnections between these two strategies have not been fully explored. This study introduces an auxiliary passivation approach for enhancing the performance of PSCs by passivating both the perovskite phase and the buried interface using succinimide (SID), referred to as the multilayer passivation (MLP) strategy. By adding SID to a lead iodide precursor solution and depositing it on tin oxide film, the remarkable ability of SID to coordinate with Pb 2+ through Lewis‐base coordination and bind the iodide ion with hydrogen bonds is demonstrated, thereby reducing defects within the perovskite and suppressing nonradiative recombination. Additionally, SID could passivate oxygen vacancy and hydroxyl defects on the SnO 2 surface, facilitating carrier separation and extraction. This MLP strategy enables us to achieve a power conversion efficiency (PCE) of 24.47% based on a two‐step process. Moreover, the unencapsulated devices maintain a PCE of 82% at 20 °C with 30% relative humidity after 7000 h. Overall, this study highlights the unparalleled potential of MLP strategy for enhancing the performance of PSCs.