A novel electrically conducting polymer, poly(2-dodecyl-4,7-di(selenophen-2-yl)benzotriazole) (PSBT), containing selenophene as the strong donor and benzotriazole as the strong acceptor groups was synthesized by electrochemical polymerization. Homopolymerization and copolymerization (in the presence of 3,4-ethylenedioxythiophene (EDOT)) were achieved in acetonitrile/dichloromethane(95/5 v/v) with 0.1 M tetrabutylammonium hexafluorophosphate (TBAPF(6)). The electrochemical and optical properties of homopolymer and copolymer were investigated by cyclic voltammetry, UV-Vis, near IR Spectroscopy. Cyclic voltammetry and spectroelectrochemistry studies demonstrated that homopolymer can be reversibly reduced and oxidized (both n- and p-doped) between -1.9V and +1.4V. at a scan rate of 100 mV/s. The homopolymer revealed a transmissive light blue color in the oxidized state, and a red-purple color in the neutral state. A transmissive light blue color was also observed in the reduced state. Homopolymer films could be fully switched between their reduced and oxidized forms in 2.4 s and 0.4 s with a percent transmittance of 32% and 56% at 511 and 1200 nm, respectively. Poly(SBT) exhibits a lambda(max) value of 511 nm and a band gap of 1.67 eV which is quite low among the selenophene-containing polymers reported so far except for poly(1,2-bis(2-seleninyl)ethane). (C) 2008 Elsevier B.V. All rights reserved.