Thickness Dependence of WO_3-xThin Films for Electrochromic Device Application

Abstract

The phenomenon of color change in a particular material caused by an electrochemical reaction is called "electrochromism." Since the discovery of the electrochromic phenomenon in tungsten oxide, amorphous WO 3 is the most widely studied electrochromic material. Until now, WO 3 remains the most promising candidate for electrochromic devices. Electrochromic devices can switch between two optical states (colored/bleached) by injection/extraction of ions and electrons, based on the modification of transmittance and reflectance that are induced by an applied external voltage. In this study, tungsten oxide (WO 3-x ) thin films were deposited onto an ITO-coated glass substrate by reactive facing-target sputtering, and their electrochromic properties studied as a function of film thickness. The X-ray diffraction patterns reveal the amorphous properties of all the WO 3-x thin films prepared in this study. Of all the different samples prepared in this study, WO 3-x thin film of thickness 500 nm exhibited the maximum coloration efficiency of 37.3 cm 2 /C.

Reactive Sputter Deposition of WO3/Ag/WO3 Film for Indium Tin Oxide (ITO)-Free Electrochromic Devices

“…The coloration efficiency can be defined as the change in optical density (ΔOD) at a given wavelength (here, we use the transmittance at 650 nm) for the charge consumed per unit of electrode area, which can be calculated using the following formula: where Q is the injected charge density, corresponding to the ratio of the inserted charge over the device area. The calculated η values after the 1st and 2000th scan cycles are 28.3 and 32.8 cm 2 C –1 , respectively, which is comparable to the direct-sputtered WO 3 film on an ITO substrate with a thickness of 500 nm. , In addition, the cyclic CA and the corresponding transmittance measurements were employed to study the switching characteristics of the sputtered WAW film. The cycling of CA stepping from −1.2 to 1.2 V with a 40 s interval.…”

“…The calculated η values after the 1st and 2000th scan cycles are 28.3 and 32.8 cm 2 C −1 , respectively, which is comparable to the directsputtered WO 3 film on an ITO substrate with a thickness of 500 nm. 32,33 In addition, the cyclic CA and the corresponding transmittance measurements were employed to study the switching characteristics of the sputtered WAW film. The cycling of CA stepping from −1.2 to 1.2 V with a 40 s interval.…”

Reactive Oxygen Species Sequestration Induced Synthesis of β-PbO and Its Polymorphic Transformation to α-PbO at Atomically Thin Regimes

“…Focused studies on the change in the crystal structure during exfoliation can make a substantial addition to the well-established effects of 2D crystal thickness on their optical, electronic, chemical, and biological proper- ties. 21,38,40,41,43 Further, such studies will aid in the increasingly important aspects of the discovery, stabilization, engineering, and functionality control of 2D polymorphs, as nicely summarized in a review by Hersam et al 44 Lead monoxide (PbO) is an ideal model system to study this aspect, as it harbors a mixture of red tetragonal P4/nmm litharge (α-PbO) and yellow orthorhombic Pbcm (β-PbO) massicot phases in natural bulk crystals. 42 Both of these polymorphs form lamellar morphologies with open-packed distorted rock salt-like structures.…”

Near infrared light‐induced photocurrent in NaYF4:Yb3+, Er3+/WO2.72 composite film

“…The tungsten oxide is an n‐type semiconductor, which has important potential applications in the various fields of gas sensors, photochromic devices, electrochromic windows, and photocatalysts . The bandgap of tungsten oxide is about 2.4‐3.25 eV, which is responsive to the blue and UV light of solar spectrum .…”

“…The tungsten oxide is an n-type semiconductor, which has important potential applications in the various fields of gas sensors, photochromic devices, electrochromic windows, and photocatalysts. [22][23][24][25] The bandgap of tungsten oxide is about 2.4-3.25 eV, which is responsive to the blue and UV light of solar spectrum. 26,27 In view of UCL spectral converted solar cells, the tungsten oxide (WO 3 ) cannot harvest the green or red UCL of NaYF 4 :Yb 3+ , Er 3+ nanoparticles.…”