Mixed Nanostructured Ti-W Oxides Films for Efficient Electrochromic Windows

Nguyen Nang Dinh,Truong Vo-Van,Dang Hai Ninh,Tran Thi Thao

doi:10.1155/2012/781236

Nguyen Nang Dinh, Truong Vo-Van + Show 2 more

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https://doi.org/10.1155/2012/781236

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Abstract

With the aim to enhance the electrochromic (EC) efficiency and electrochemical stability of electrochromic devices (ECD), mixed nanostructured TiO2/WO3films were prepared by an electrochemical deposition method with the purpose of adding WO3nanoparticles to porous nanocrystalline doctor-blade TiO2(nc-TiO2) films. The results of the characterization of electrochromic properties in 1 M LiClO4+ propylene carbonate (LiClO4+ PC) of both the nc-TiO2/F-doped tin oxide (FTO) and WO3/TiO2/FTO configurations showed the reversible coloration and bleaching of the ECDs. The response time of the ECD coloration of WO3/TiO2/FTO was found to be as small as 2 sec, and its coloration efficiency (CE) as high as 35.7 cm2× C−1. By inserting WO3nanoparticles into the porous TiO2structures, WO3/TiO2heterojunctions were formed in the films, consequently enabling both the CE and electrochemical stability of the working electrodes to be considerably enhanced. Since a large-area WO3/TiO2can be prepared by the doctor-blade technique followed by the electrochemical deposition process, mixed nanostructured Ti-W oxides electrodes constitute a good candidate for smart window applications, taking advantage of the excellent coloration and stability properties as well as the simple and economical fabrication process involved.

Highlights

Electrochromism is a topic that has attracted a great deal of interest from researchers because of its potential application in various areas
Electrochromic (EC) properties can be found in almost all the transition-metal oxides, and their properties have been investigated extensively in the last decades [1]. These oxide films can be coloured anodically (Ir, Ni) or cathodically (W, Mo); WO3 is clearly the preferred material for applications. This is principally due to the fact that WO3based electrochromic devices (ECDs) have normally a faster response time to a change in voltage and a larger coloration efficiency (CE) as compared to devices based on other electrochromic materials
[8], we have shown that by using the so-called “doctor-blade” method, nanoporous TiO2 anatase films on F-doped tin oxide (FTO) substrates were prepared for the ECDs with much improved electrochromic response time and coloration efficiency (CE)

Summary

Introduction

Electrochromism is a topic that has attracted a great deal of interest from researchers because of its potential application in various areas (photonics, optics, electronics, architecture, etc.). The nanocrystalline TiO2 anatase thin films on ITO, prepared by sol-gel dipping method, exhibited a good reversible coloration and bleaching process [7], but the response time was slow and the electrochromic efficiency was not large. [8], we have shown that by using the so-called “doctor-blade” method, nanoporous TiO2 anatase films on F-doped tin oxide (FTO) substrates (nc-TiO2/FTO) were prepared for the ECDs with much improved electrochromic response time and coloration efficiency (CE). With such porous films, for a long exposed performance time, the durability of the devices was limited, making the resulting ECD less satisfying for smart windows applications. With the aim to enhance the stability of the EC devices on one hand by making more tightly knitted films, and on the other hand, to improve the CE of the ECD performance with the help of nanostructured heterojunctions of TiO2/WO3, we combined a doctor-blade technique for preparing large-area films with an electrochemical process for depositing WO3 films into the nanoporous TiO2 structures

Experimental

Results and Discussion

Conclusion