A solid-state electrochromic device was assembled using a polymer electrolyte and optically transparent electrodes modified with thin films of poly{3-[12-(p-methoxyphenoxy)dodecyl]thiophene} and poly(3,4-ethylenedioxythiophene) doped with poly(styrenesulfonate). Poly(epichlorohydrin-co-ethylene oxide) containing LiClO4 was used as the polymer electrolyte. After assembling, the device was studied by spectroelectrochemical techniques. The best performance of this device could be obtained by adjusting the relative thickness of the active polymer films and the potential range of operation of the device. The device shows color variation during ca. 500 charge/discharge cycles and can be constructed under atmospheric conditions. The results obtained suggest a multitude of perspectives in applications in electrochromic displays. (C) 2004 Elsevier B.V. All rights reserved.