FABRICATION AND CHARACTERIZATION OF TUNGSTEN TRIOXIDE ELECTROCHROMIC FILMS FOR EMISSIVITY MODULATION PURPOSES
Amorphous and crystalline tungsten trioxide (WO3) electrochromic films of 240 to 400 nm thick were grown on single crystal silicon wafer and ITO-coated glass substrates by reactive sputtering from a tungsten target. The electrochemical properties of the films were characterized by cyclic voltammetry between −1.0 ~ +1.0 V in 1M LiClO4/PC solutions. The Cary 500 measurements of the films indicated remarkable changes in the transmission and reflection in visible and infrared regions due to Li+ ions injection/extraction. The emissivity of the WO3 films on the Au substrates was modulated in the range from 0.042 to 0.450. The results showed that the crystalline WO3, films obtained here have excellent thermal emissivity modulation, enabling fabrication of electrochromic devices that can freely change their optical properties under a slight voltage pulse.
