Study of sol–gel prepared nanostructured WO 3 thin films and composites for electrochromic applications

Abstract

Nanostructured tungsten oxide (WO 3) thin films have been prepared by the sol–gel method following the inorganic route in which alcoholic solutions containing tungsten salts have been used as precursors. The WO 3 films were deposited by dipcoating on glass substrates. In order to create nanoporosity in some of these films, the films were deposited on glass substrates coated with a layer of polystyrene (PS) microspheres. This polymer was then removed either by thermal treatment or by solvent extraction, generating a high density of pores within the tungsten framework. The characterization of these films has been carried out by atomic force microscopy (AFM), optical studies and ATR–FTIR spectroscopy. The lithium intercalation of these WO 3 films has been carried out using a dry (in vacuo) technique. Results on the comparative study of the optical and electrochromic properties of these different types of WO 3 are presented here.