Trifluoromethoxylated Electron Acceptor Enabling Ternary Organic Solar Cells with over 20% Power Conversion Efficiency

ABSTRACT In this work, we introduce a trifluoromethoxy (OCF 3 ) group as a pseudo‐halogen terminal group design for non‐fullerene acceptors, which combines strong inductive electron‐withdrawing ability with moderate resonance donation. The as‐synthesized BTP‐OCF3, when benchmarked against its methoxy analogue BTP‐OCH3, demonstrates narrowed bandgap, enhanced light harvesting, and improved compatibility with the donor polymer PM6. As a result, PM6:BTP‐OCF3 devices deliver a power conversion efficiency of 19.04% in the binary system, further boosted to 20.27% upon ternary optimization. Morphological investigations reveal that OCF3 substitution promotes favorable molecular packing, suppresses excessive aggregation, and induces preferential vertical phase segregation, thereby facilitating balanced charge transport and reducing recombination losses. These results establish trifluoromethoxylation as a versatile terminal engineering strategy that simultaneously optimizes the electronic, morphological, and interfacial properties of NFAs, offering a new design paradigm for high‐performance organic solar cells.