Fused Perylene Diimide-Based Polymeric Acceptors for Efficient All-Polymer Solar Cells

Two polymeric electron acceptors (PFPDI-2T and PFPDI-2FT) based on the fused perylene diimide (PDI) and bithiophene or difluorobithiophene units were synthesized via the Stille polymerization. Both polymers exhibit the strong absorption between 350 and 650 nm, which have the good absorption compensation with the low band gap conjugated polymer in polymer solar cells (PSCs). PFPDI-2T and PFPDI-2FT have the LUMO energy levels of around -4.12 to -4.15 eV, which are comparable with other PDI-based polymers and fullerene derivatives. All:polymer solar cells (all-PSCs) based on PFPDI-2T or PFPDI-2FT as the polymeric electron acceptor were fabricated with PTB7-Th as the polymeric electron donor. Power conversion efficiency of as high as 6.39% based on PFPDI-2T/PTB7-Th was achieved under the standard illumination of simulated sunlight (AM 1.5, 100 mW cm(-2)), which is significant higher than that of the all-PSC based on the nonfused PDI counterpart. The results demonstrate that the direct fusion of PDI unit is an effective design strategy to enhance the photovoltaic performances of all-PSCs.