Photochromic Properties of WO 3 Thin films

WO3 sol was prepared through the sol-gel process. Ethanol, acetone and SiO2 sol were added to the WO3 sol. The WO3 thin films on glass substrate were obtained with the hybrid sol by the dip-coating technique, and then were heat-treated at different temperatures for a certain time. X-ray diffractometer and scanning electron microscope were used to characterize the crystal structure and surface morphology of these coatings. Visible light transmittance changes of the thin films irradiated under UV light were measured with UV spectrometer. The experimental results demonstrated that photochromic effect, hardness and uniformity of thin films were improved when the thin films are obtained with the hybrid sol.