Electrical and optical properties of W-doped V2O5/FTO composite films fabricated by sol–gel method

Abstract V2O5/FTO composite films with different tungsten doping molar ratios were fabricated on soda-lime glass substrates by sol–gel spin coating method followed with annealing process. The analysis on crystallinity and surface morphology shows that W doping would induce V2O5 lattice distortion and make the film surface rougher. The resistance and transmittance during the phase transition process were measured to explore the electrical and optical properties of W-doped V2O5/FTO films. The results show that 3% W doping molar ratio is the most effective in improving the properties of V2O5/FTO films. The resistance of the prepared films is reduced by about three orders of magnitude from room temperature to 320℃. Compared to the undoped films, the 1%, 3% and 5% W-doped V2O5/FTO films possess higher conductivity and the width of the thermal hysteresis loop is narrowed from 14℃ to 13℃, 10℃ and 8℃, respectively. For undoped, 1%, 3% and 5% W-doped V2O5/FTO films, the phase transition temperature is 245℃, 238℃, 222℃ and 223℃, and the average transmittance decreased 7.7%, 7.8%, 11.7% and 5.7% in the range of 900–1400 nm before and after the phase transition, respectively.