Investigation of electrochromic properties of nanocrystalline tungsten oxide thin film

Thin films of tungsten oxide were grown by organometallic chemical vapor deposition (OMCVD) using tetra(allyl)tungsten, W(eta(3)-C3H5)(4). X-Ray diffraction (XRD) analyses showed amorphous films at substrate temperatures (T-s) <350degreesC and polycrystalline films at T-s>350degreesC. Atomic force microscopy (AFM) and scanning electron microscopy (SEM) revealed grain sizes in the range 20-40 nm. In situ electrochemical reduction of WO3,2/ITO (2.0 M HCl) produced a faint blue color in less than 1 s. The maximum coloration efficiency (CE) was found to be 22 cm(2)/mC at 630 nm. The density of the films decreases from 4.53 to 4.29 g/cm(3) after annealing. An optical bandgap (E-g) of similar to3.2 eV was estimated for both as-deposited and annealed films. (C) 2002 Elsevier Science B.V. All rights reserved.