Effect of CuS:WO3 ratio on the Photochromic properties of CuS-WO3 film

Abstract

Abstract Controlling light and heat penetration through building is of considerable interest. Photochromic smart window is a promising device to control them. The smart window is generally composed of metal oxide, i.e. WO3, which is widely used as photochromic materials because of adjustable transmittance under UV light, CuS which exhibits low reflectance in visible light, in contrast to high absorbed in the near-infrared light. The optical properties of CuS-WO3 films fabricated at different conditions were investigated. The optical properties of the films were characterized by spectrophotometer for color. The difference of color in CIE scale before and after irradiations was determined by maximum color contrast (ΔC) and initial coloration rate (ΔC/min). The prepared films were characterized by a Scanning Electron Microscope/Energy Dispersive using X-ray analysis (SEM/EDX), the crystalline structure was investigated by X-ray diffraction (XRD) and the photoelectrochemical measurement was also conducted. Under UV irradiating intensity of 5 mW/cm2, transparent WO3 film changed to dark blue color. The controlling oxygen concentration in drying chamber could enhance the coloration of film. The molar ratios of CuS: WO3 in films were varied from 1:0.1 to 1:0.4. The maximum color contrasts of WO3 films was increased relatively with amount of WO3. The CuS-WO3 film at molar ratio of 1:0.4 in oxygen- free atmosphere exhibited the excellent coloration which are 1.2 times of maximum color contrast and 1.1 times of initial coloration rate of WO3 film.