Enhanced Transmittance Modulation of SiO2-Doped Crystalline WO3 Films Prepared from a Polyethylene Oxide (PEO) Template

Abstract

Polyethylene oxide (PEO)-modified silicon dioxide (SiO2)-doped crystalline tungsten trioxide (WO3) films for use as electrochromic layers were prepared on indium tin oxide (ITO) glass by the sol–gel spin coating technique. The effects of the PEO template and SiO2 on the electrochromic transmittance modulation ability of crystalline WO3 films were investigated. Fourier transform infrared spectroscopy (FT-IR) spectra analysis indicated that PEO was decomposed after annealing at 500 °C for 3 h. X-ray diffraction (XRD) pattern analysis showed that both SiO2 and PEO helped reduce the crystalline grain size of the WO3 films. Atomic force microscope (AFM) images showed that the combined action of SiO2 and PEO was helpful for achieving high surface roughness and a macroporous structure. An electrochromic test indicated that PEO-modified SiO2-doped crystalline WO3 films intercalated more charges (0.0165 C/cm2) than pure WO3 crystalline films (0.0095 C/cm2). The above effects resulted in a good transmittance modulation ability (63.2% at 628 nm) of PEO-modified SiO2-doped crystalline WO3 films, which was higher than that of pure WO3 crystalline films (9.4% at 628 nm).