In Situ Self‐Assembly of Trichlorobenzoic Acid Enabling Organic Photovoltaics with Approaching 19% Efficiency

Abstract Future industrialization of organic photovoltaics (OPVs) requires OPVs’ processing to be more energy‐efficient and streamlined. Currently, only MoO₃ and PEDOT:PSS are commonly used as the anode interface layer (AIL). The processing of MoO₃ typically involves vacuum thermal evaporation with stringent thickness requirements. PEDOT:PSS necessitates separate processing and thermal annealing at temperatures exceeding 100 °C to eliminate moisture. This work utilized 3,4,5‐trichlorobenzoic acid (3CBA) as the AIL material. The distinct advantage of 3CBA over PEDOT:PSS and MoO₃ is the in situ self‐assembly of 3CBA eliminates the need for separate solution processing, thermal evaporation, or thermal annealing. Remarkably, OPV devices incorporating PM6, BTP‐eC9, and the 3CBA AIL exhibited a superior efficiency of 18.2% compared to those with PEDOT:PSS (17.7%). By using nonhalogenated solvent, o‐xylene, to meet industrialization requirements, the devices achieved an exceptional efficiency of 18.8%, the highest reported value among devices with in situ self‐assembled interface layers. Furthermore, semi‐transparent devices with 3CBA displayed higher PCE and AVT values (13.1% and 25.7%) than their PEDOT: PSS counterparts, due to the weak absorption of the 3CBA AIL. This work contributes significantly to the high‐throughput production of OPVs by streamlining the AIL processing.