Synthesis and Photovoltaic Properties of New Narrow Gap Polymer with A DPP Core

New narrow gap D-A type copolymer 3,7-di(4-vinylphenyl)-benzo［1,2-b:4,5-b'］difuran ketone/2,5-dimethyl-3,6-di(5-bromothiophene)-pyrrolo［3,4-c］pyrrole ketone(PDBFP) and graphene quantum dots(GQDs) were prepared by means of Heck coupling and hydrothermal process, respectively. The synthesized PDBFP and GQDs were characterized by 1H-NMR and FT-IR. The morphology and size of GQDs were characterized by DLS, HR-TEM and AFM. Results showed that the absorption peaks and the emission peak under optimal excitation peak(320 nm) of GQDs were at 307 nm and 424 nm. The red shift and higher PL intensity of PDBFP-GQDs active layer material compared with the emission peak(712 nm) of PDBFP suggested that the introduction of GQDs had coordination optimization effect. The highest occupied molecular orbital energy levels(HOMO), lowest unoccupied molecular orbital energy levels(LUMO) and band gap(Eg) of PDBFP and GQDs were -5.32、-3.39、1.93 eV and -4.11、-3.87、0.24 eV, respectively. The photovoltaic devices with an ITO/PEDOT∶PSS/PDBFP∶GQDs(8∶1)/Ag showed the best performance with a power conversion efficiency of 1.04%.