Enhanced transmittance modulation of ITO/NiO _x/ZrO₂:H/WO₃/ITO electrochromic devices

ZrO₂:H thin films were deposited by DC magnetron sputtering at room temperature. The effects of thickness on structure and morphologies of ZrO₂:H thin films were lucubrated. The X-ray photoelectron spectroscopy analysis reveals that the fully oxidized value of Zr (Zr⁴⁺) exists in both ZrO₂ and ZrO₂:H films. X-ray diffraction data show the crystallinity of ZrO₂:H thin films tends to be weak and the microstructure changes slightly. Atomic force microscopy analysis presents that both the grain size and surface roughness increase as the thickness increases. Correspondingly, all-thin-film ITO/NiO_x/ZrO₂:H/WO₃/ITO electrochromic devices (ECDs) were monolithically fabricated, among which the thickness of ZrO₂:H film was adjusted. The ECD assembled with 50 nm ZrO₂:H film has the best electrochromic property with transmittance modulation (ΔT) of 65.2 % at 550 nm. The effects of operation potential on ECDs were also elaborated studied. ECDs can get colored in saturated states at relatively high potential as no more unoccupied sites exist in WO₃ to accommodate the continuously injected H⁺ ions.