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Journal of Nanomaterials
Volume 2013 (2013), Article ID 785023, 14 pages
http://dx.doi.org/10.1155/2013/785023
Research Article

Characterization of Porous WO3 Electrochromic Device by Electrochemical Impedance Spectroscopy

Department of Energy Engineering, National United University, Miaoli 36003, Taiwan

Received 4 October 2012; Accepted 22 December 2012

Academic Editor: Wen Zeng

Copyright © 2013 Chien Chon Chen. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

This paper concerns the microstructure of the anodic tungsten oxide (WO3) and its use in an electrochromic (EC) glass device. When voltages between 100 V and 160 V were applied to tungsten film for 1 h under 0.4 wt. % NaF electrolyte, porous WO3 film was formed. The film, which had a large surface area, was used as electrochromic film for EC glass. The average transmittance in a visible region of the spectrum for a 144 cm2 EC device was above 75% in the bleached state and below 40% in the colored state, respectively. Repeatability using of the colored/bleached cycles was tested good by a cyclic voltammograms method. The internal impedance values under colored and bleached states were detected and simulated using an electrical impedance spectra (EIS) technique. The EC glass impedance characteristics were simulated using resistors, capacitors, and Warburg impedance. The ITO/WO3, WO3/electrolyte, electrolyte/NiO, and NiO/ITO interfaces can be simulated using a resistance capacitance (RC) parallel circuits, and bulk materials such as the indium tin oxide (ITO) and conducting wire can be simulated by using a series of resisters.