Results on the electrochromic and photocatalytic properties of vanadium doped tungsten oxide thin films prepared by reactive dc magnetron sputtering technique

In this investigation, vanadium doped tungsten oxide (V : WO3) thin films are prepared at room temperature by reactive dc magnetron sputtering employing a tungsten-vanadium 'inlay' target. In comparison with pure sputtered tungsten oxide thin films, 11% vanadium doping is observed to decrease the optical band gap, enhance the colour neutral property, decrease the coloration efficiency (from 121 to 13 cm(2) C-1), increase the surface work function (4.68-4.83 eV) and significantly enhance the photocatalytic efficiency in WO3 thin films. These observations suggest that (i) vanadium creates defect levels that are responsible for optical band gap reduction, (ii) multivalent vanadium bonding with terminal oxygen in the WO3 lattice gives rise to localized covalent bonds and thus results in an increase in the work function, and (iii) a suitable work function of V: WO3 with ITO results in an enhancement of the photocatalytic activity. These results on electrochromic and photocatalytic properties of V: WO3 thin films show good promise in the low maintenance window application.