Characterization of Porous WO3Electrochromic Device by Electrochemical Impedance Spectroscopy

Chien Chon Chen

doi:10.1155/2013/785023

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 WO3film 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 cm2EC 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.

Highlights

In recent years, the nanometer technological progress has led to the creation of many special new materials. erefore information photoelectricity, catalysis, and magnetism have broader application domains because of nanotechnology
According to a 2012 US department of energy (DOE) report, windows contribute to about 40 percent of overall building heating and cooling load with annual impact of about 4.4 quads, and there is a potential to reduce lighting impact by 1 quad through day lighting. e Environmental Protection Agency says an average household spends over 40 percent of its annual energy budget on heating and cooling costs
According to the National Renewable Energy Laboratory (NREL), by allowing control of daylighting and solar gain, electrochromic windows have the potential to reduce annual US energy consumption by several quadrillion (1015) Btus. e United States currently consumes a total of about 94 quads of energy per year [3,4,5]

Summary

Introduction

The nanometer technological progress has led to the creation of many special new materials. erefore information photoelectricity, catalysis, and magnetism have broader application domains because of nanotechnology. Advanced electrochromic (EC) technologies such as EC windows will darken in sunlight without the use of an external control circuit. Such windows would be ideal for applications such as car sunroofs. Large-scale development of electrochromic glass based on porous lms can potentially result in tremendous increase color/bleach rate, extended durability, insulated heat transfer, and energy savings. W by lm was used to form a porous anodization, and (c) the 144 cm electrochromic device includes a working electrode (ITO, WO3), ion conductor (electrolyte), and counter (Pt, NiO2, ITO). We report results from an EIS analysis that describes ohmic resistance, electron transfer resistance, diffusion resistance, charge-transfer resistance, contact capacitance, chemical capacitance, electrolysis capacitance, and double-layer capacitance in porous WO3 EC glass

Experimental Procedures

Results and Discussion

Conclusions