Synthesis of Nb2O5 thin films for electrochromic devices

Abstract

A large number of metal oxides such as TiO2, CeO2, WO3, V205 and Nb205 have been investigated for their use in various solid state electrochemical devices, including batteries, and electrodes for photoelectrochemical and electrochromic devices [1, 2]. One fundamental characteristic of these oxide films is their rapid and reversible coloration when small ions such as H + and Li + are inserted in the layer lattice, which typically changes their optical transmission from a quasi-transparent state (TE 85%) to less than T = 20% in the ultraviolet (UV), visible or near infrared (IR) range. The electro-optical performance of electrochromic coatings is strongly dependent on their structural morphology. Outstanding performance has been obtained recently using materials constituted of aggregates of nano-sized particles with CeO2-TiO2 [3-6], TiO2 [7] and Nb205 [8, 9]. The sol-gel process is a particularly well-adapted method for achieving such morphology. Moreover, the dip coating technique, a common method of deposition in this field, allows the deposit of large-area coatings at a low cost and offers advantages in controlling the microstructure of the film. Very few studies have been reported on the