High‐Performance Ultrathin Flexible Organic Solar Cells Through the Modification of Self‐Assembled Monolayers

Abstract Ultrathin flexible organic solar cells (OSCs) have emerged as promising a power source for wearable technologies owing to their solution‐processability, excellent mechanical flexibility, and conformability. In recent years, self‐assembled monolayers (SAMs) have garnered considerable attention in the fabrication of high‐performance thin‐film solar cells owing to their tunable interfacial properties. However, research on the application of SAMs in ultrathin flexible OSCs remains insufficient. A critical limitation arises from the aggregation of SAMs on flexible indium tin oxide (ITO) surfaces, leading to poor surface coverage. In this manuscript, a facile strategy is developed through the modification of Br‐2PACz SAMs using H‐TPAc, which enables the formation of uniform and dense SAMs on flexible ITO electrodes, thus simultaneously enhancing device optoelectronic and mechanical properties. Based on the modified SAMs, the PM6:L8‐BO:BTP‐eC9 ternary rigid and ultrathin flexible OSCs devices achieve efficiencies of 19.7% and 17.5%, respectively. The use of modified SAMs by mixing with H‐TPAc small‐molecules exhibits exceptional potential for pioneering next‐generation hole transport layer (HTL) materials and advancing high‐performance flexible organic solar cells.