Strengthening the Hetero‐Molecular Interactions in Giant Dimeric Acceptors Enables Efficient Organic Solar Cells

Abstract Giant dimeric acceptor (G‐Dimer) is becoming one of the most promising organic solar cell (OSC) materials because of its definite structure, long‐term stability, and high efficiency. Strengthening the hetero‐molecular interactions by monomer modification greatly influences the morphology and thus the device performance, but lacks investigation. Herein, two novel quinoxaline core‐based G‐Dimers, Dimer‐QX and Dimer‐2CF, are synthesized. By comparing trifluoromethyl‐substituted Dimer‐2CF and non‐substituted Dimer‐QX, the trifluoromethylation effect on the G‐Dimer is investigated and revealed. The trifluoromethyl with strong electronegativity increases electrostatic potential and reduces surface energy of the G‐Dimer, weakening the homo‐molecular ordered packing but reinforcing the hetero‐molecular interaction with the donor. The strong hetero‐molecular interaction suppresses the fast assembly during the film formation, facilitating small domains with ordered molecular packing in the blend, which is a trade‐off in conventional morphology control. Together with favorable vertical phase separation, efficient charge generation, and reduced bimolecular recombination are concurrently obtained. Hence, the Dimer‐2CF‐based OSCs obtain a cutting‐edge efficiency of 19.02% with fill factor surpassing 80%, and an averaged extrapolated T₈₀ of ≈12 000 h under continuous 80 °C heating. This study emphasizes the importance of hetero‐molecular interaction and trifluoromethylation strategy, providing a facile strategy for designing highly efficient and stable OSC materials.