Sixuan Wang, Siying Wang, Rui Zeng, Yuqi Hou, Xiaobin Gu, Ziyang Han, Jikai Lv, Na Yu, Jiawei Qiao, Zheng Tang, Xiaotao Hao, Qian Peng, Feng Liu, Yunhao Cai, Xin Zhang, Hui Huang
Molecular conformation is a critical structural attribute of organic molecules and polymers in addition to their constitution and configuration, thereby forming the foundation for understanding macroscopic material properties and device functionality. For nonfused-ring electron acceptors (NFREAs) featuring multiple σ-bonds with high rotational degrees of freedom, significant challenges remain in precisely regulating molecular conformation, particularly in modulating the syn- and anti-conformation preferences. Here, we demonstrate precise engineering of NFREAs through conformation-directed molecular design, achieving a syn-to-anti-conformational transition via utilizing intramolecular noncovalent S···F interactions. This conformational regulation strategy enables a systematic investigation of how syn-/anti-conformational preferences influence molecular planarity and rigidity, self-assembly behavior, charge transport properties, and device performance. Our results reveal that the anti-conformation endows anti-TT-F with enhanced crystallinity, reduced reorganization energy, and improved charge carrier mobility compared to its syn-conformational counterpart. Consequently, binary and ternary devices based on anti-TT-F achieve remarkable power conversion efficiencies of 15.08% and 19.88%, respectively. This conformational engineering strategy unveils a previously overlooked dimension in molecular design, providing fundamental guidelines for developing high-performance organic solar cells through the rational manipulation of conformational landscapes.