Abstract:
The greatest alternative to conventional windows and curtains is an electrochromic
smart device with adjustable optical properties. Transition metal oxide plays a major
role in electrochromic devices (ECDs). A simple hydrothermal method was developed to
fabricate WO3 thin films on Fluorine-doped Tin Oxide (FTO) glass substrates. Sodium
Tungstate Dihydrate (Na2WO4.2H2O) and Sodium Nitrate (NaNO3) were used as the
starting materials for the preparation of WO3 thin films under different hydrothermal
reaction time. The structural, chemical and morphological characterization of the thin
films were conducted using different techniques including X-Ray Diffraction (XRD), UVVis
absorption, Electrochemical Impedance Spectroscopy (EIS) and Scanning Electron
Microscopy (SEM). According to the results, the particle size of the thin films was
ranging from a few microns to hundreds of nanometers. XRD results showed that the
WO3 was in monoclinic phase and the average crystallite size was 56.55 nm. The band
gap value of the prepared WO3 was measured and it was 2.9 eV. The electrochromic
performance of the WO3 thin films was characterized by LiCl in Propylene Carbonate
(PC) and Ethylene Carbonate (EC) as the electrolyte. ECD with the configuration of
WO3/Gel electrolyte (LiCl in PC+EC+ poly ethylene oxide (PEO))/FTO was prepared
and a color change between dark blue and colorless was observed when an electric field
of 3.5 V was applied across the device. A relatively high optical modulation of 12.2% at
675 nm was observed.
