Recent Progress of Bay-Functionalization Perylene Diimide Acceptors and Cathode Interface Layers in Organic Solar Cells

• • Bay-functionalization of PDI enables PCEs exceeding 18% in ternary OSCs, as demonstrated by Liu et al. (Nano Energy, 2023, 112: 108501), directly challenging the dominance of fullerene-based acceptors in industrial-scale roll-to-roll production. • • PDI-based non-fullerene polymer solar cells have achieved over 11% efficiency through smart molecular design and supramolecular morphology optimization (Zhang et al., Adv. Funct. Mater., 2019, 29: 1906587), providing a viable pathway for solution-processed, flexible photovoltaic modules. • • The integration of a 3D-shaped guest acceptor derived from PDI in ternary OSCs (Liu et al., Adv. Funct. Mater., 2023, 33: 2300214) demonstrates that bay-substitution can mitigate excessive aggregation, a critical failure mode that otherwise limits charge transport and device stability. • • PDI-based acceptors with porphyrin and perylene bisimides (Zhang et al., Angew. Chem. Int. Ed., 2017, 56: 2694–2698) exhibit efficient non-fullerene solar cell performance, underscoring the synthetic versatility of bay-functionalization for tuning energy levels and absorption profiles.