Electropolymerization of poly(3,4-ethylenedioxythiophene) (PEDOT) films on indium tin oxide (ITO), using a very thin PEDOT:poly(styrene sulfonate) (PEDOT:PSS) film as a base coating, was carried out in a non-aqueous solution containing the monomer, an electrolyte and propylene carbonate by a two-electrode system. For comparison, PEDOT film electrodeposited on bare ITO substrate under the same condition was also presented. The PEDOT films deposited on these two substrates were characterized by scanning electron microscopy, energy disperse X-ray spectroscopy and Raman spectroscopy. The results indicate that the PEDOT film electrodeposited on bare ITO was not uniform, while the PEDOT film electrodeposited on PEDOT:PSS/ITO has better uniformity. The compositions of the different regions of PEDOT film electrodeposited on bare ITO and PEDOT:PSS/ITO were studied and discussed. Electrochromic devices (ECDs) based on PEDOT films electrodeposited on bare ITO and PEDOT:PSS/ITO were fabricated and characterized by UV-Vis-NIR spectrophotometric study. The results show that the display contrast of the ECD based on PEDOT film electrodeposited on PEDOT:PSS/ITO was improved over that on a bare ITO substrate. (c) 2006 Elsevier B.V. All rights reserved.