An Asymmetric Perylene Diimide Dimer Acceptor for High Performance Organic Solar Cells.

The vinylene-bridged helical perylene diimide (PDI) dimer (PDI2) with a build-in twisted configuration is an alternative building block to the parent PDI for the construction of efficient non-fullerene acceptor (NFAs). Moreover, it has been proved asymmetric strategy plays a vital role in the development of NFAs. Herein, we designed and synthesized a pair of acceptor-donor-acceptor (A-D-A) type PDI2 derivatives, namely IDTIC-PDI and IDT-diPDI2, which contain asymmetric and symmetric end-cap units, respectively. To determine the structure-performance relationships of asymmetric strategy, the organic solar cells (OSCs) based on these two molecules were fabricated and measured. The asymmetric IDTIC-PDI based device exhibits a much higher PCE of 8.23 % than that of symmetric IDT-diPDI2 (5.21 %). These results reveal that symmetry breaking provides an effective way to optimize the photovoltaic performances of PDI2 based OSCs.