Noncovalently Fused-Ring Electron Acceptors with C2v Symmetry for Regulating the Morphology of Organic Solar Cells

Four noncovalently fused-ring electron acceptors p -DOC6-2F, o -DOC6-2F, o -DOC8-2F, and o -DOC2C6-2F have been designed and synthesized. p -DOC6-2F and o -DOC6-2F have the same molecular backbone but different molecular shapes and symmetries. p -DOC6-2F has an S-shaped molecular backbone and C 2 h symmetry, whereas o -DOC6-2F possesses a U-shaped molecular backbone and C 2 v symmetry. The molecular shape and symmetry can influence the dipole moment, solubility, optical absorption, energy level, molecular packing, and film morphology. Compared with the corresponding p -DOC6-2F, o -DOC6-2F exhibits better solubility, a wider band gap, and a larger dipole moment. When blended with the donor polymer PBDB-T, the C 2 v symmetric o -DOC6-2F can form an appropriate active layer morphology, whereas the C 2 h symmetric p -DOC6-2F forms oversized domains. Organic solar cells (OSCs) based on p -DOC6-2F, o -DOC6-2F, o -DOC8-2F, and o -DOC2C6-2F obtained power conversion efficiencies of 9.23, 11.87, 11.23, and 10.80%, respectively. The result reveals that the molecular symmetry can facilely regulate the performance of OSCs.