Conjugated terpolymers synthesized by incorporating anthracene units into the backbones of the diketopyrrolopyrrole-based polymers as electron donors for photovoltaic cells

Three new conjugated D-A terpolymers PADPP1, PADPP2 and PADPP3, which contain diketopyrrolopyrrole (DPP) as electron acceptors and thiophene/anthracene as electron donors, are described. In comparison with PDPP3T which contains just DPP and thiophene units, the DPP moieties are partially replaced with anthracene units in PADPP1, PADPP2 and PADPP3. The HOMO/LUMO levels of PADPP1, PADPP2 and PADPP3 are slightly enhanced in comparison with those of PDPP3T. Moreover, the incorporation of the anthracene units into the backbones leads to the formation of nanofibrils with an appropriate width within the blending thin films of PADPP2 with PC71BM. The short circuit currents (J(SC)) of the photovoltaic cells with blends of PADPP1, PADPP2 and PADPP3 with PC71BM are higher than those with the PDPP3T/PC71BM blend. As a result, PADPP1, PADPP2 and PADPP3 display better photovoltaic performances than PDPP3T after blending each polymer with PC71BM under the same conditions. The PCE of the photovoltaic cell of the PADPP2/PC71BM blending thin film at a weight ratio of 1 : 2 as the active layer can reach 6.24%.