Three kinds of oxidant are synthesized, ferric benzenesulfonate (Fe(OBs)(3)), ferric 4-methylbenzenesulfonate (Fe(OMBs)(3)), and ferric 4-ethylbenzenesulfonate (Fe(OEBs)(3)). Then, 3,4-ethylenedioxythiophene (EDOT) is polymerized with these oxidants to obtain benzenesulfonate-doped poly(3,4- ethylenedioxythiophene) (PEDOT-OBs), 4-methyl-benzenesulfonate-doped poly(3,4- ethylenedioxythiophene) (PEDOT-OMBs) and 4-ethyl-benzenesulfonate-doped poly(3,4- ethylenedioxythiophene) (PEDOT-OEBs), respectively. PEDOT-OBs had the highest surface conductivity among the fabricated materials, because PEDOT-OBs had a better defined crystalline structure than the other polymers and the doping concentration of PEDOT-OBs is much higher than that of PEDOT-OMBs and PEDOT-OEBs. The capacitance of PEDOT-OBs is higher than those of PEDOT-OMBs and PEDOT-OEBs while the equivalent series resistance (ESR) and leakage current values of PEDOT-OMBs is lower than those of PEDOT-OMBs and PEDOT-OEBs because of the high electrical conductivity and low amount of undoped oxidant in PEDOT-OBs. Thermal degradation of all polymerized materials occur in the range of 300-330 degrees C, indicating that all of the polymerized materials had excellent thermal stability. (C) 2012 Elsevier B.V. All rights reserved.