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

Four noncovalently fused-ring electron acceptors -DOC6-2F, -DOC6-2F, -DOC8-2F, and -DOC2C6-2F have been designed and synthesized. -DOC6-2F and -DOC6-2F have the same molecular backbone but different molecular shapes and symmetries. -DOC6-2F has an S-shaped molecular backbone and symmetry, whereas -DOC6-2F possesses a U-shaped molecular backbone and 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 -DOC6-2F, -DOC6-2F exhibits better solubility, a wider band gap, and a larger dipole moment. When blended with the donor polymer PBDB-T, the symmetric -DOC6-2F can form an appropriate active layer morphology, whereas the symmetric -DOC6-2F forms oversized domains. Organic solar cells (OSCs) based on -DOC6-2F, -DOC6-2F, -DOC8-2F, and -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.