Enhancing Organic Solar Cells Efficiency by Using Self‐assembly Monomolecular Layer with Improved Hydrophilicity and Hole Transport Capability †

Comprehensive Summary This study deliberately designs and synthesizes three HTMs: m ‐PhACz, p ‐PhACz, and p ‐DPAPCz, incorporating carbazole or diphenylamine groups linked through a benzene ring and functionalized with phosphonic acid groups. Notably, m ‐PhACz, featuring a carbazole unit and meta ‐substituted phosphonic acid, exhibits superior hole transport mobility and hydrophilicity, fostering strong intermolecular interaction with indium tin oxide. Consequently, m ‐PhACz‐based devices achieve an outstanding power conversion efficiency of 19.44%, which is much higher than p ‐PhACz (18.30%) and p ‐DPAPCz (17.38%) based ones. Our work sets a new benchmark for high‐performance OSC fabrication.