Synthesis, characterization and photovoltaic properties of poly{[1′,4′-bis-(thienyl-vinyl)]-2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylene-vinylene}

A new conjugated polymer, poly{[1′,4′-bis-(thienyl-vinyl)]-2-methoxy-5-(2′-ethylhexyloxy)-1,4-phenylene-vinylene} (PTVMEH-PPV) was synthesized via Grim polymerization. The polymer is soluble in common organic solvents such as chloroform and tetrahydrofuran, and possesses adequate thermal stability (Td > 246 °C). The absorption spectrum of PTVMEH-PPV film shows a broader absorption peak covering the wavelength range from 380 nm to 620 nm, which is red-shifted and broadened in comparison with that of MEH-PPV. The onset oxidation potential of the polymer is 0.12 V versus Ag/Ag+, ca. 0.2 V lower than that of MEH-PPV. The band gap of the polymer measured by cyclic voltammetry is 1.82 eV, which basically agrees with that obtained from the onset wavelength of the absorption spectra. Polymer solar cell was fabricated based on the blend of PTVMEH-PPV and PCBM with a weight ratio of 1:1. The device shows the maximum external quantum efficiency of 14% at ca. 520 nm, an open circuit voltage of 0.67 V and a power conversion efficiency of 0.32% under the illumination of AM1.5, 80 mW/cm2.