Trifluoromethyl-substituted asymmetric non-fullerene acceptors enable non-halogenated solvent-processed indoor organic photovoltaics with an efficiency of over 30%

The emergence of Y6 and its derivatives has significantly advanced organic photovoltaics (OPVs). However, the limited design strategies for Y6-based non-fullerene acceptors (NFAs) in absorbing visible light restrict their application in indoor OPVs (IOPVs). Furthermore, the reliance on additive-assisted chlorinated solvents for processing photoactive layers poses a significant barrier to IOPV commercialization. Herein, we synthesized two IPC-ended NFAs (IPC-BBO-IC2F and IPC-BBO-IC2Cl) and two IPC1CF3-ended NFAs (IPC1CF3-BBO-IC2F and IPC1CF3-BBO-IC2Cl). These asymmetric NFAs, featuring two distinct groups at the molecular ends, demonstrated blue-shifted absorption and elevated energy levels compared to Y6, offering a promising approach to harness indoor light and achieve higher open-circuit voltages more effectively. IOPVs processed without additives and using o-xylene, based on PM6:IPC1CF3-BBO-IC2F and PM6:IPC1CF3-BBO-IC2Cl, showed high efficiencies of 26.5% and 24.2%, respectively, under 1000-lux light-emitting diode (LED) illumination. These efficiencies surpass those of IOPVs that employ IPC-ended NFAs or Y6. Moreover, ternary IOPVs based on PM6:Y6:IPC1CF3-BBO-IC2F and PM6:Y6:IPC1CF3-BBO-IC2Cl achieved notable efficiencies of 26.9% and 27.1% under 1000 lux-LED illumination and 30.2% and 29.2% under 1000 lux-fluorescent light (FL) illumination, respectively. These findings underscore the potential of the IPC1CF3 end group in the asymmetric structural modification of Y6 to enhance the performance of IOPVs using additive-free and environmentally benign solvents.