Low cost, highly efficient TiO2 based Electrochromic device for architectural application

Abstract

Nowadays global warming has become a copiously discussed issue, the need of energy efficient solutions increasingly attracts attention of architectural windows. The reduction of heating and cooling energy consumption in the building construction sector for instance is of an economic and environmental concern. Electrochromic devices are opto-electrochemical systems that change their optical properties, mainly their transmittance, when a voltage is applied to them. This interesting behavior leads to many applications, such as windows, sunroofs, architectural windows, displays and other electro-optical devices. Therefore, in this study we have explored the possibility of replacing expensive WO3 and CeO2 using low cost transparent nano-crystalline titanium dioxide (TiO2) as the electrochromic material and a FTO glass substrate as the counter electrode in electrochromic devices (ECD). Electrochromic TiO2anatase thin films (film thickness ~ 6.49μm) on F-doped tin oxide (FTO) substrates were prepared by doctorblade method using a colloidal solution of titanium dioxide with particles of 15 nm in size. EC devices with the configuration FTO glass/TiO2/Poly ethylene oxide-LiCl electrolyte /FTO glass were fabricated and tested their electrochromic properties. A reversible colour change between dark blue and colourless state was observed when an appropriate potential was applied repeatedly to the device. The device changes its transmission between 64% (bleached state) and 0.08% (colored state) at the wavelength of 600 nm. The optical density of the device was 2.89 andthe response time of the EC device for coloration process was 30 s for a 1.5 x 2.1 cm2 sample.