A novel low band-gap conjugated polymer poly[3-octylthien-2,5-ylenediethynylene-co- benzo[c]-1',2',5'-thiadiazo-3,6-ylenedi(2,5-thienylene)] (PTE-DTBT) was prepared by a palladium-catalyzed coupling reaction of 3,6-bis(5-bromothien-2-yl)benzo[c]-1',2',5'-thiadiazole with 2,5-diethynyl-3-octylthiophene. UV-Vis absorption spectrum and cyclic voltammetry of PTE-DTBT film show that its optical band gap and electrochemical band gap are 1.71 and 1.88 eV, respectively. The photoluminescence emission at 678 nm of the PTE-DTBT film can be easily quenched by TiO₂. The low band-gap and the electron transition property of the polymer indicate that PTE-DTBT is a suitable candidate for the active materials in polymer solar cells.

Key words: poly[3-octylthien-2,5-ylenediethynylene-co-benzo[c]-1',2',5'-thiadiazo-3,6-ylenedi(2,5, low band-gap conjugated polymer, optical property, synthesis