Inside-fused perylenediimide dimers with planar structures for high-performance fullerene-free organic solar cells

For perylenediimide derivatives it seems that twisted structures are essential to avoid excessive aggregation tendencies and realize high-performance fullerene-free solar cells. However, in this communication, we designed and synthesized two planar inside-fused perylenediimide dimers, TDI2 and BDT-TDI2. Theoretical calculations reveal that both TDI2 and BDT-TDI2 have a highly planar molecular conformation with small dihedral angles of 0.02 degrees and 11.4 degrees between two TDI segments, respectively. By using BDDT as the donor polymer, power conversion efficiencies (PCEs) of the photovoltaic cells reached 5.80% for TDI2 and 4.52% for BDT-TDI2, with high open-circuit voltages (V-OC) of similar to 1.0 V. These results indicate planar PDI-dimer derivatives are also possible electron acceptors to realize high-performance fullerene-free solar cells.