Ternary Cooperative Interface With Electronegative Phosphine Bridges Enables Efficient and Stable Inverted Perovskite Solar Cells

ABSTRACT Carbazole‐based self‐assembled monolayers (SAMs) are widely used in high‐performance perovskite solar cells (PSCs); however, single‐component SAMs often suffer from incomplete coverage on FTO substrates and weak interactions with the perovskite layer, leading to interfacial defects and crystallization stress. Herein, we develop a synergistic interface engineering strategy by introducing a phosphine‐based molecule, bis(4‐trifluoromethylphenyl)(4‐carboxyphenyl)phosphine (TFMP), to construct a ternary cooperative interface (Co‐SAM@TFMP) based on a co‐adsorbed self‐assembled monolayer (Co‐SAM) composed of [4‐(3,6‐dimethyl‐9H‐carbazol‐9‐yl)butyl]phosphonic acid (Me‐4PACz) and [4‐(9'‐phenyl‐9H,9'H‐[3,3'‐bicarbazol]‐9‐yl)butyl]phosphonic acid (4PABCz). In this system, the phosphonic and carboxylic acid groups are firmly anchored to the substrate, improving the integrity of the interfacial coverage. At the buried interface, TFMP acts as a molecular bridge by coordinating with Pb 2+ and stabilizing FA + , thereby suppressing interfacial defects. Furthermore, this cooperative interface alleviates crystallization stress during perovskite film growth through flexible molecular segments, promoting the formation of uniform and highly crystalline films. Ultimately, the optimized inverted PSCs achieved a power conversion efficiency (PCE) of 26.78%, and the unencapsulated devices retained 93.7% of their initial PCE after continuous operation at the maximum power point for 1200 h. This work offers a general and effective strategy for interface modulation toward high‐performance perovskite solar cells and related optoelectronic devices.