Synergistic Bimolecular Engineering Enables Homogeneous and Multifunctional Surfaces for High‐Performance Inverted Perovskite Solar Cells

ABSTRACT The fabrication of low‐dimensional perovskite layers via halide ammonium salts is an established surface passivation strategy for suppressing nonradiative recombination and improving the performance of perovskite solar cells (PSCs). However, conventional approaches relying solely on concentration tuning inherently face a trade‐off between defect passivation and charge transport. Herein, we introduce a synergistic bimolecular engineering (SBE) method based on choline chloride (ChCl) and phenethylammonium iodide (PEAI) to precisely control the formation and distribution of a surface 1D perovskite phase. Hydrogen bonding between ChCl and PEAI promotes uniform 1D layer formation during cation exchange, effectively decoupling passivation from transport limitations. This leads to simultaneous enhancement of defect passivation and charge carrier mobility, resulting in improved open‐circuit voltage and fill factor. Moreover, the SBE strategy enables multifunctional interface optimization, including enhanced crystallization, removal of residual PbI ₂ , and favorable energy level alignment. Consequently, the resulting inverted PSCs achieve a champion power conversion efficiency of 25.24%, substantially exceeding the 21.08% of control devices, along with enhanced operational stability. This work offers a general molecular design principle for advanced interface engineering in high‐efficiency photovoltaics.