Novel quinoxaline-based poly(phenylenevinylene)s copolymers: synthesis and optical properties

A novel poly(phenylenevinylene) copolymer PPV-PQ containing alternating phenyl rings and quinoxaline units has been synthesized and characterized by NMR, FT-IR, TGA, GPC, TGA and elemental analysis. The UV-Vis absorption spectra and PL spectra in solution/films were characterized. The absorption peak and PL emission peak of PPV-PQ in the solid state, were shift to long wavelengths compared to their corresponding peaks in solution due to strong inter-chain interactions and increased coplanarity. The PPV-PQ exhibited a decreased optical band gap (1.92 eV) compared to PPV homopolymer. The HOMO and LUMO levels of PPV-PQ were determined from electrochemical measurements. There is a clear difference between LUMO (-3.16 eV) of polymer and that of PCBM, which makes an effective charge transfer possible between polymers and PCBM. The PL emission intensity of PPV-PQ is almost completely quenched when PPV-PQ is blended with C₁₁₇. The result shows that PPV-PQ is useful for polymer solar cells.