Green Solvent-Processable Trifluoromethylated π-Extended Non-Fullerene Acceptors for High-Efficiency Organic Solar Cells

Organic solar cells (OSCs) based on nonfullerene acceptors (NFAs) are promising for next-generation solar energy harvesting. However, their widespread adoption is hindered by the use of environmentally harmful halogenated solvents in processing. Here, we report a trifluoromethylated π-extended NFA, BT-BO-CF3, that offers both high performance and excellent processability in environmentally friendly solvents. The trifluoromethyl groups and extended π-system provide a narrow bandgap for increased photocurrent while enhancing solubility in the green solvent tetrahydrofuran (THF). Importantly, BT-BO-CF3 exhibits superior cosolubility with the donor polymer PTQ10 in THF, resulting in an excellent bulk heterojunction morphology without any additives. These inverted binary PTQ10:BT-BO-CF3 OSCs yield a power conversion efficiency (PCE) of 14.05% when processed from THF, dramatically outperforming the nonfluorinated BT-BO counterpart (PCE = 3.57%), and with only a ≈15% of PCE reduction versus a conventional D18:BT-BO-CF3 OSC processed in chloroform (PCE = 16.55%). Detailed characterization reveals that trifluoromethylation enhances intermolecular interactions, charge transport, and morphology in the active layer. This work demonstrates that strategic molecular design can simultaneously achieve performance while addressing processability challenges in OSCs, paving the way for more environmentally friendly manufacturing of high-efficiency devices.