Poly {3-[12-(p-methoxyphenoxy)dodecyl]thiophene} films with different thickness were potentiostatically deposited on optically transparent glass electrodes using different deposition charges. Their spectroelectrochemical properties were studied as a function of thickness, i.e., deposition charge. Films obtained with a deposition charge of ca. 65 mC cm(-2) presented more stability to a high number of redox cycles (>1000), chromatic contrast of 40% at 725 nm, coulombic efficiency of 80% and good optical memory in the reduced state (E = 0.0 V). The surface morphology of these films was also characterized by atomic force microscopy. Films obtained with a deposition charge less than or equal to65 mC cm(-2) are homogeneous, while above this value the film surface morphology presents roughness and irregularities. Correlation between deposition charge and film thickness was estimated using a rugosimeter and atomic force microscopy experiments. (C) 2004 Elsevier Ltd. All rights reserved.