Recent Progress of Asymmetric Non-Fused Ring Electron Acceptors for Organic Solar Cells

Fused-ring electron acceptors (FREAs) have enabled high-performance organic solar cells (OSCs) owing to their rigid planar backbones and extended π-conjugation, yet their complex synthetic routes and high production costs severely hinder commercialization. As a promising alternative, non-fused ring electron acceptors (NFRAs), linked by single C−C bonds, offer advantages in synthetic simplicity, structural tunability, and cost-effectiveness. Recently, symmetry-breaking strategies have been introduced into NFRA design as a promising approach to tailor molecular conformation and electronic distribution, thereby enabling precise control over energy levels, molecular packing, aggregation behavior, and miscibility with polymer donors, which are critical for optimizing bulk heterojunction (BHJ) morphology and charge transport. This review summarizes recent advances in asymmetric NFRAs, focusing on backbone engineering, side-chain modulation, and terminal group design. The structure−property−performance relationships are highlighted, and future perspectives toward high-efficiency and low-cost OSCs are discussed.