Streamlined Y6‐Analogs Enabling Efficient Ambient‐Air‐Processed Organic Solar Cells

ABSTRACT Achieving high efficiency and long‐term stability under ambient processing conditions remains a critical hurdle for the commercialization of organic solar cells (OSCs). Here, we report two new Y6‐analogs—BT(BO)‐ v ‐T(C12)‐4F (4F) and BT(BO)‐ v ‐T(C12)‐4Cl (4Cl)—featuring vinylene ( v )‐bridged DA′D cores, designed to improve the material's scalability while maintaining the structural advantages of Y6‐type acceptors. Morphological and device‐level investigations reveal that these M‐Y6 derivatives facilitate thermodynamically stable molecular packing and favorable crystalline orientation, even when fully processed in air. Incorporation of 4F into a layer‐by‐layer ternary architecture with D18/L8‐BO via a reproducible air‐processing protocol results in a certified power conversion efficiency (PCE) of 19%, among the highest reported for conventional OSCs fabricated under ambient conditions. Moreover, 4F‐based devices demonstrate exceptional thermal and photostability, retaining over 80% of their initial PCE after extended aging under the ISOS‐L‐1 protocol without encapsulation. These improvements are attributed to the enhanced crystallinity, vertical molecular alignment, and morphological robustness imparted by the 4F acceptor. This study identifies BT(BO)‐ v ‐T(C12)‐4F as a promising air‐processable acceptor for scalable OSCs that combine high efficiency with long‐term operational durability.