Thiophene-based pi-conjugated polymers have been widely used in p-channel OTFTs due to their high charge carrier mobility. SPQT-12 which has dodecylsulfanyl side-chain was synthesized by Stille polymerization. The polymer was characterized by (1)H NMR, GPC, UV-Vis spectroscopy, and cyclic voltammetry. Molecular weight (Mn) of SPQT-12 was 10,000 (PDI = 1.7), and SPQT-12 were readily soluble in common organic solvents. In the film state, SPQT-12 showed absorption with lambda(max) at 553 nm and optical band gap of 1.87 eV. A mobility of 1.0 x 10(-3) cm(2)/Vs, an on/off ratio of 5.8 x 10(3) and threshold voltage of -11V have been obtained with OTFTs using SPQT-12.