Boosting Organic Solar Cells to Over 18 % Efficiency through Dipole‐Dipole Interactions in Fluorinated Nonfused Ring Electron Acceptors

Abstract This study successfully designed and synthesized two nonfused ring electron acceptors, 412‐6F and 412‐6Cl, modified with fluorine and chlorine substituents, respectively. Single‐crystal analysis revealed that 412‐6F possesses a planar molecular backbone and exhibits pronounced dipole‐dipole interactions between the fluorine atoms on the lateral phenyl groups and the carbonyl oxygen atoms on the end groups. This specific interaction promotes dense end‐group stacking, leading to a reduced interlayer spacing. Improved crystallinity and coherence length are observed in the D18 : 412‐6F blend film. Conversely, 412‐6Cl adopts a more distorted configuration and lacks these interactions. As a result, the organic solar cell (OSC) based on D18 : 412‐6F achieved a remarkable power conversion efficiency of 18.03 %, surpassing the performance of the D18 : 412‐6Cl OSC. This underscores the importance of designing novel acceptors with beneficial intermolecular interactions to enhance OSC efficiency, thus providing a new direction for organic photovoltaic advancement.