Adhesively Bridging Co‐Self‐Assembled Monolayer and Perovskite Via In Situ Polymerization for Enhanced Stability of Inverted Perovskite Solar Cells

Abstract The strategic utilization of self‐assembled monolayers (SAMs) significantly advances the interfacial contact and power conversion efficiency (PCE) of inverted perovskite solar cells (IPSCs). However, inadequate adhesion between the SAM and perovskite layer remains a critical challenge, limiting further performance enhancement. Herein, a synergistic interface engineering strategy is introduced that combines a co‐assembly approach with in situ polymerization to optimize the buried interface of perovskite film. Specifically, 11‐Mercaptoundecylphosphoric acid (MPA) is incorporated into a SAM to form co‐SAMs, improving homogeneity and mitigating defects at the NiO x surface. Simultaneously, the ionic liquid (IL) monomer 1‐Allyl‐3‐vinylimidazolium bis((trifluoromethyl)sulfonyl) imide (AVMTF 2 ) is incorporated into the perovskite precursor. The aggregation of ILs cation at the bottom interface facilitates in situ polymerization via sulfhydryl end groups, forming the POL‐AVM polymer at the perovskite/SAM interface. This polymer enhances interfacial adhesion, regulates perovskite crystallization, and reinforces structural integrity by strongly anchoring organic cations through multiple hydrogen bonds. As a result, this synergistic strategy achieves a champion PCE of 26.25% (certified 26.04%), along with excellent long‐term stability, retaining 95.6% of its initial efficiency after 1000 h of continuous operation under the ISOS‐L‐2I protocol.