Electronic Properties of Organic Solar Cells Based on CF3-Functionalized Non-Fullerene Acceptors ⊥.

Efficient exciton dissociation and charge separation at donor/acceptor interfaces as well as balanced charge transport within each phase are critical for advancing next-generation organic photovoltaics. In this work, we study a trifluoromethyl-substituted nonfullerene acceptor (NFA), Y2CF3, whose central-core fluorinated side chain modification induces favorable crystal packing and markedly improves device performance (Cho et al., J. Am. Chem. Soc., 147, 758 (2025)). Combining molecular dynamics simulations and density functional theory calculations, we comprehensively describe the electronic processes and charge transport in PM6:Y2CF3 blends and compare them to the benchmark PM6:Y6 blends. Y2CF3 shows a red-shifted singlet local exciton (1LE) energy but nearly unchanged charge transfer (1CT) energies, narrowing the 1LE-1CT gap and enabling rapid conversion as precursor of charge separated states. Enhanced electron transfer rates among Y2CF3 molecules arise from strong terminal-terminal interactions as dominantly found in the Y2CF3 crystal structure. Thermal fluctuations are found to substantially enhance the hole transport rates in PM6, narrowing the disparity between electron and hole transport. These findings clarify how targeted side chain fluorination at the NFA core can optimize packing, charge separation, transport, and OPV efficiency.