Potentiodynamical polymerization and redox process of PPy films were examined in situ by both electrochemical quartz crystal microbalance (EQCM) and photothermal (PT) techniques. It was observed that the polymerization was favorable on the An electrode covered by a thin as-grown polypyrrole (PPy) film rather than that on the bare Au electrode. It was confirmed that the PPy film was not fully oxidized during polymerization. The correlation of the doping/dedoping and the electrochromic properties of the PPy film was studied by combining in situ EQCM and PT techniques, and it is found that only the ion exchange in the potential of -0.33 to 0.17 V (versus Ag/AgCl) for anodic scan and in the potential range of -0.44 to -0.7 V (versus Ag/AgCl) for cathodic scan was contributed to electrochromic behavior. (C) 2004 Elsevier B.V. All rights reserved.