Synthesis and charge carrier mobility of a solution-processable conjugated copolymer based on cyclopenta[c]thiophene

A new polymer comprising alternate thiophene and didodecyloxymethyl substituted cyclopenta[c]thiophene unit, PDCPTT, was synthesized by the Stille coupling reaction and characterized by 1H NMR, GPC, TGA, DSC, XRD, UV–vis absorption spectroscopy, photoluminescence spectroscopy and cyclic voltammetry. The copolymer is readily soluble in tetrahydrofuran, chloroform and toluene at ambient conditions and exhibits good thermal stability as it does not exhibit noteworthy weight loss until ∼300 °C under nitrogen. This polymer possesses a broad absorption band ranging at 400–650 nm (with an optical band gap of 1.90 eV). The DFT calculation predicts the polymer to be planar and the calculated band gap is only 0.17 eV higher than the experimentally determined band gap. Didodecyloxymethyl-3,4-cyclopentane substitution on alternate thiophene in a polythiophene, hitherto unexplored, showed an effective polymer based field effect transport characteristics; exhibiting hole mobility ≈1.4 × 10−2 cm2 V−1 s−1.