A Promising Nonfullerene Acceptor Containing Boron–Oxygen Heterocycle

Exploring nonfullerene acceptors (NFAs) with high luminescent structural "genes" is crucial for suppressing the nonradiative recombination in organic solar cells (OSCs). Herein, a boron-oxygen six-membered heterocycle is first employed to afford two conformationally distinct NFA isomers of CH-S and CH-C. Owing to the electron-lacking nature of boron atoms, both CH-S and CH-C demonstrate a relatively wide bandgap. Interestingly, different ring-fused pathways yield the typical S- and C-shaped molecular conformations, which not only dominate their distinctive intermolecular packing modes but also greatly exert on the fundamental luminescent and optoelectronic properties. Consequently, CH-C-based binary OSCs achieve an excellent efficiency of 11.03%, ranking among the highest values reported for wide-bandgap acceptors with absorption cutoffs below 750 nm. This work first highlights the significant potential of boron-oxygen heterocycles for constructing high-performance wide-bandgap NFAs.