Intramolecular Noncovalent Interaction-Driven Syn-/Anti-Conformational Regulation in Nonfused-Ring Electron Acceptors

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.