Enhancing the Performance of Organic Solar Cells by Hierarchically Supramolecular Self-Assembly of Fused-Ring Electron Acceptors

Three novel non-fullerene small molecular acceptors ITOIC, ITOIC-F, and ITOIC-2F were designed and synthesized with easy chemistry. The concept of supra-molecular chemistry was successfully used in the molecular design, which includes noncovalently conformational locking (via intrasupramolecular interaction) to enhance the planarity of backbone and electrostatic interaction (intersupramolecular interaction) to enhance the pi-pi stacking of terminal groups. Fluorination can further strengthen the intersupramolecular electrostatic interaction of terminal groups. As expected, the designed acceptors exhibited excellent device performance when blended with polymer donor PBDB-T. In comparison with the parent acceptor molecule DC-IDT2T reported in the literature with a power conversion efficiency (PCE) of 3.93%, ITOIC with a planar structure exhibited a PCE of 8.87% and ITOIC-2F with a planar structure and enhanced electrostatic interaction showed a quite impressive PCE of 12.17%. Our result demonstrates the importance of comprehensive design in the development of high-performance non-fullerene small molecular acceptors.