Recent progress in Y-series small molecule acceptors in polymer solar cells.

Polymer solar cells (PSCs) have emerged as a hot research topic in next-generation photovoltaic technology due to their lightweight nature, low-cost fabrication and flexible characteristics. The development of Y-series small molecule acceptors (SMAs) has significantly enhanced photovoltaic performance. This review systematically summarized recent advances in Y-series SMAs, categorized by their electron-deficient fused-ring central cores of benzotriazole (BTA), benzothiadiazole (BT) and quinoxaline (Qx) with emphasis on how molecular structure optimization strategies, including central core engineering, side-chain engineering and end-group engineering, influence optoelectronic properties, film morphology and device performance. Finally, strategies for constructing high-efficiency PSCs are proposed to advance their future development.