Recently progress of aromatic side chain engineering on Y6 for high performance organic solar cells

Due to the precisely tunable energy levels, structural versatility, and broad absorption spectra extending into the near-infrared region, the Y-series of nonfullerene acceptors (NFAs) have attracted a lot of attention from researchers in recent years. Among the various methods for optimizing material structure, side-chain modification is a simple and efficient way to improve the corresponding device performance of the material. Because of the large steric hindrance, the introduction of aromatic groups into the side chain is an effective method to adjust the planarity of the molecular skeleton and the morphology of the active layer. Despite the numerous reviews on the acceptor materials, there are scarcely any comprehensive summaries focusing on aromatic side chains optimized Y6 acceptors. Therefore, this paper mainly focuses on the aromatic side chain modification strategy on Y6 materials, which include the synthetic methods and research status for introducing aromatic side chains into the inner and the outer side chains of Y6-series materials. The structure–performance relationship is also comprehensively discussed, and the future design directions and challenges of Y-series NFAs are proposed.