Synthesis and optical properties of novel donor–acceptor poly(phenyleneethynylene)s containing quinoxaline

π-Conjugated polymers consisting of donor–acceptor repeating units often show a low band gap and hence have a good adsorbing efficiency of solar energy. Based on this fact, two novel π-conjugated polymers, PPE-1 and PPE-2, composed of electron-donating phenyl rings and electron-accepting quinoxaline units were prepared via Sonogashira polycondensation. The copolymers were characterised by NMR, FT-IR, GPC, TGA, UV and PL. These copolymers are thermostable and film forming. The PPE-1 and PPE-2 exhibited a decreased optical band gap (2.39 eV and 2.30 eV, respectively) compared to PPE homopolymer. And they showed red-shifted UV–vis absorption peak comparison with that of pure PPE. The absorption peak and PL emission peak of polymers are both red-shifted in solid state compared to polymers in solution due to strong inter-chain π–π interactions. Furthermore, the PL emission intensity of these copolymers is almost completely quenched when copolymers were blended with C60. The HOMO of two polymers estimated from CV is clearly lower in energy than MEH-PPV. This indicates that PPE-1 and PPE-2 are more oxidatively stable than MEH-PPV. The result shows that both PPE-1 and PPE-2 are useful for polymer solar cells.