Three branched poly(thienylene vinylene)s, i.e., poly( thienylene vinylene) derivatives with bi-(thienylene vinylene) side chains (biTV-PTVs), biTV-PTV1-3, were synthesized for obtaining the conjugated polymers with broad and strong visible absorption spectra. The polymers were characterized by thermogravimetric analysis (TGA), absorption spectroscopy, cyclic voltammetry, in situ spectroelectrochemical and photovoltaic measurements, and compared with poly(3-hexyl-thienylene vinylene) (P3HTV). The absorption peaks of the conjugated side chains and main chains of the biTV-PTVs both red-shifted in comparison with those of the monomer and P3HTV, indicating that the conjugation degree of both the side chains and the main chains is extended in the biTV-PTVs. In particular, the biTV-PTV3 film shows a strong and broad absorption band covering the whole visible region from 380 to 780 nm. Cyclic voltammograms of the polymers revealed that the LUMO of the biTV-PTVs decreased and their HOMO increased a little so that the E-g values of the biTV-PTVs were reduced in comparison with P3HTV. In situ absorption spectra of biTV-PTV3 at different potentials indicate that the oxidation of the polymer is accompanied by the p-doping of the conjugated main chains and the polymer can be used as an electrochromic material. Photovoltaic properties of biTV-PTV3 were investigated with the polymer solar cell (PSC) based on the blend of the polymer and PCBM (1:1, w/w) under the illumination of AM 1.5, 100 mW/cm(2). The power conversion efficiency of the PSC reached 0.32%, which is 52% increased in comparison with that of the device based on P3HTV under the same experimental conditions.