Triazine derivative as volatile solid additive for non‐halogenated solvent and thermal annealing‐free processed organic solar cells with over 18% efficiency

Abstract Volatile solid additive (VSA) has been demonstrated to be an effective strategy to optimize the morphology of the active layer for high‐performance organic solar cells (OSCs). Most of the reported OSCs with VSA are processed by chloroform (CF) and relies on thermal annealing (TA) posttreatment. However, the CF solvent problems of low boiling point, toxicity, and environmental‐unfriendly as well as increasing cost from TA restricted the large‐scale production. Here, a simple‐structured and low‐cost triazine derivative 2,4,6‐trichloro‐1,3,5‐triazine (TCT) as a VSA was introduced into PM6:BTP‐eC9‐based OSCs. Employing the TCT additive, the nonhalogenated solvent (o‐xylene) processed OSCs without TA treatment and delivered higher power conversion efficiencies (PCEs) in comparison to the TA‐treated counterpart. Benefiting from the intermolecular interactions between TCT and the active layer materials, the TCT‐treated blend films exhibited optimized morphology and enhanced crystallinity. As a result, the PM6:BTP‐eC9 OSCs achieved a champion PCE of 18.18% and fill factor (78.5%), which is among one of the most advanced nonhalogenated solvent‐processed and annealing‐free OSCs. Meanwhile, the TCT‐treated blend films also demonstrated the better photo‐stability compared to the control device. This work provides a guideline of triazine derivatives as VSA for high‐performance OSCs with TA‐free and nonhalogenated solvent‐processing treatment.