Side Chain Elimination Enables Low‐Cost Fused‐Ring Acceptors and Reveals a Compact Tetrameric Structure for High‐Photocurrent Organic Solar Cells

ABSTRACT Developing low‐cost, high‐performance non‐fullerene acceptors is crucial for the commercialization of organic solar cells (OSCs). Here, we introduce a β‐side‐chain‐free molecular design strategy that enables the preparation of two new Y6 derivatives, JSM5 and JSM6, with substantially reduced synthetic complexity and cost. Single‐crystal X‐ray analysis reveals an unusual tetrameric packing, originating from the removal of the β‐alkyl chains in the structure. Importantly, this packing unlocks multiple S···N intermolecular interactions between the benzothiadiazole cores, driving γ‐shaped molecular conformations to establish efficient layer‐by‐layer 3D charge transport pathways and exhibit superior intermolecular connectivity. Consequently, remarkably high short‐circuit current densities ( J _SC s) of up to 28 mA cm ⁻² are obtained, among the highest reported for Y‐series acceptors. PM6:JSM5 and PM6:JSM6 OSCs achieve power conversion efficiencies of 17.3% and 18.0%, respectively, comparable to the state‐of‐the‐art acceptors Y6 and BTP‐eC9, while reducing acceptor material cost by approximately threefold. Cost–performance analysis further indicates that JSMs rank among the most cost‐effective fused‐ring acceptors within the evaluated set. This work not only introduces a new packing motif enabled by β‐side chain elimination but also establishes a promising molecular design framework for high‐ J _SC , cost‐effective fused‐ring acceptors, paving the path toward commercially realizable acceptor materials.