Core‐to‐Wing Type Hybrid Dimeric Giant Molecule Acceptors With Different‐Length Ester‐Linked Alkyl Chains Enable 20.25% Efficiency Organic Solar Cells

ABSTRACT

Dimeric acceptors have recently emerged as promising giant molecule acceptors (GMAs) for organic solar cells (OSCs), but most systems link two identical monomeric units. Hybrid GMAs combining different acceptor units remain unexplored. Herein, we develop a core‐to‐wing type hybrid strategy coupling BT‐ and BZ‐core acceptor units through flexible ester‐linked alkyl chains, affording three GMAs (BTZ‐2‐2, BTZ‐2‐6, and BTZ‐2‐10). This design enables complementary absorption by combining the spectral features of BT‐ and BZ‐based monomers while preserving favorable crystallization behavior. Among them, BTZ‐2‐6 exhibits the broadest, most red‐shifted absorption, enhanced π‐π stacking, and the highest electron mobility due to the optimal length of its ester‐linked alkyl chain. The PM6:BTZ‐2‐6 binary device delivers 18.53% efficiency and retains nearly 90% of its initial efficiency after 720 h of illumination. Furthermore, the efficiency can be increased to 19.41% by replacing PM6 with D18 as the donor polymer, and further boosted to 20.25% by incorporating BTZ‐2‐6 as a third component into PM6:L8‐BO binary devices. These results demonstrate that core‐to‐wing hybrid GMAs with ester‐linked alkyl chains of different lengths provide an effective strategy for constructing high‐performance GMAs, offering new opportunities for efficient and stable OSCs.