Dipolar Molecule‐Induced Molecular Bridging Strategy Modifies Acceptor Decomposition and Enhances Interfacial Charge Transport for High‐Efficiency Organic Solar Cells

ABSTRACT Perylene diimides (PDIs) are used as cathode interlayers in organic solar cells (OSCs) due to their tunable energy levels and thickness‐insensitive properties. However, ammonium‐functionalized PDIs (PDIN, PDINN, etc) can cause photoinduced degradation of acceptor materials, impairing charge transport and stability of device. Herein, we introduce a multifunctional molecular bridging strategy by incorporating chloroacetic acid into PDIN. Theoretical calculations reveal that the hydroxyl group of chloroacetic acid anchors to the fluorine groups of the Y6 acceptor via hydrogen bonding, while the chlorine atoms form dipole‐dipole interaction with the ammonium cation of PDIN. This synergy establishes a molecular bridge between the acceptors and cathode interface, effectively preventing direct contact between PDIN and the acceptor, thereby suppressing acceptor photodegradation and accelerating charge transport. Optimizing monochloroacetic acid incorporation at 1% in PDIN yields power conversion efficiencies of 19.0% and 19.6% in binary PM6:Y6 and PM6:L8‐BO OSCs. Moreover, the generality of this strategy is demonstrated by evaluating three chloroacetic acid derivatives on three different acceptors. Therefore, this work demonstrates that the strategy not only suppresses the photo‐induced acceptors degradation but also enhances charge transport, offering new insights for achieving highly efficient and stable OSCs.