Ta2O5 layers were deposited on NiO/indium tin oxide (ITO) and Ni(OH)(2)/ITO, respectively, by means of an RF magnetron sputtering system, and their electrochromic properties were then compared by means of in situ transmittance measurements during continuous potential cycling and pulse potential cycling. The electrochromic response speed of the Ta2O5/Ni(OH)(2)/ITO was much more rapid than that of the Ta2O5/NiO/ITO. This can be attributed to the interfacial property between the TA(2)O(5) and the electrochromic layer. The NiO layer of Ta2O5/NiO/ITO was irreversibly transformed into an electrochromic active form, Ni(OH)(2), during the first potential cycling, leading to an increase in the interfacial reaction resistance and, as a result, a slow response speed. (C) 2003 Elsevier B.V. All rights reserved.