Designing Head‐to‐Tail Topological Vinylene‐Bridged Dimer Acceptor for Efficient and Stable Organic Solar Cells

Abstract Dimerized small‐molecule acceptors are promising materials for high‐performance organic solar cells (OSCs), yet the diversity of their topological configurations remains underexplored. In this study, two dimer acceptors are designed and investigated, QD‐2 and QD‐3, constructed via an unconventional “head‐to‐tail” linkage of Y‐series building blocks, bridged by vinylene and ethynylene units, respectively. Comprehensive characterization reveals that QD‐2 simultaneously suppresses energy disorder and electron–phonon coupling while facilitating favorable molecular stacking. These features yield a fibrous film morphology with improved exciton and charge dynamics. As a result, QD‐2‐based OSCs achieve outstanding power conversion efficiencies (PCEs) of 19.39% in binary and 20.04% in ternary devices, surpassing the QD‐3‐based binary counterpart (18.05%). Moreover, both QD‐2 and QD‐3 exhibit high glass transition temperatures (Tg), conferring excellent thermal stability to their devices. This work highlights the critical role of linker chemistry and molecular topology in advancing dimer acceptor design and offers a guiding framework for next‐generation OSC materials.