Optical Properties of VO2 Thin Film Deposited on F:SnO2 Substrate for Smart Window Application

Abstract

Vanadium dioxide (VO 2) is an attractive material for smart window applications where the transmittance of light can be automatically modulated from a transparent state to an opaque state at the critical temperature of ~68 o C. Meanwhile, F : SnO 2 (F-doped SnO 2 , FTO) glass is a transparent conductive oxide material that is widely used in solar-energy-related applications because of its excellent optical and electrical properties. Relatively high transmittance and low emissivity have been obtained for FTO-coated glasses. Tunable transmittance corresponding to ambient temperature and low emissivity can be expected from VO 2 films deposited onto FTO glasses. In this study, FTO glasses were applied for the deposition of VO 2 thin films by pulsed DC magnetron sputtering. VO 2 thin films were also deposited on a Pyrex substrate for comparison. To decrease the phase transition temperature of VO 2 , tungsten-doped VO 2 films were also deposited onto FTO glasses. The visible transmittance of VO 2 /FTO was higher than that of VO 2 /pyrex due to the increased crystallinity of the VO 2 thin film deposited on FTO and decreased interface reflection. Although the solar transmittance modulation of VO 2 /FTO was lower than that of VO 2 /pyrex, room temperature solar transmittance of VO 2 /FTO was lower than that of VO 2 /pyrex, which is advantageous for reflecting solar heat energy in summer.