The anodized crystalline WO3 nanoporous network with enhanced electrochromic properties

Abstract

We demonstrate that a three dimensional (3D) crystalline tungsten trioxide (WO(3)) nanoporous network, directly grown on a transparent conductive oxide (TCO) substrate, is a suitable working electrode material for high performance electrochromic devices. This nanostructure, with achievable thicknesses of up to 2 μm, is prepared at room temperature by the electrochemical anodization of a RF-sputtered tungsten film deposited on a fluoride doped tin oxide (FTO) conductive glass, under low applied anodic voltages and mild chemical dissolution conditions. For the crystalline nanoporous network with thicknesses ranging from 0.6 to 1 μm, impressive coloration efficiencies of up to 141.5 cm(2) C(-1) are achieved by applying a low coloration voltage of -0.25 V. It is also observed that there is no significant degradation of the electrochromic properties of the porous film after 2000 continuous coloration-bleaching cycles. The remarkable electrochromic characteristics of this crystalline and nanoporous WO(3) are mainly ascribed to the combination of a large surface area, facilitating increased intercalation of protons, as well as excellent continuous and directional paths for charge transfer and proton migration in the highly crystalline material.

Enhanced black state induced by spatial silver nanoparticles in an electrochromic device

“…ECDs offer many advantages over conventional displays, including a low operating voltage (V OP ), memory effects, color variations and visibility in sunlight. [3][4][5][6][7] Therefore, ECDs are expected to achieve applications in information displays or in light-modulating devices such as smart windows, switchable mirrors, electronic papers and chemical sensors. [8][9][10][11][12] Conventional ECDs are composed of a non-metal (NM) EC material (for example, poly(ethylene oxide), poly(methyl methacrylate), polyvinylidene difluoride, WO 3 , MoO 3 , Ir(OH) 3 , NiO).…”

“…[3][4][5][6][7] Therefore, ECDs are expected to achieve applications in information displays or in light-modulating devices such as smart windows, switchable mirrors, electronic papers and chemical sensors. [8][9][10][11][12] Conventional ECDs are composed of a non-metal (NM) EC material (for example, poly(ethylene oxide), poly(methyl methacrylate), polyvinylidene difluoride, WO 3 , MoO 3 , Ir(OH) 3 , NiO). [13][14][15][16][17] In particular, WO 3 , which is the most widely known EC material, has attracted considerable attention because of its broad applications such as in ECDs, photocatalysis and sensing devices.…”

“…[13][14][15][16][17] In particular, WO 3 , which is the most widely known EC material, has attracted considerable attention because of its broad applications such as in ECDs, photocatalysis and sensing devices. 3 However, the use of NM-ECD encounters two drawbacks. (1) It has low optical transmittance when in the transparent state because of the inherent color and high extinction coefficient (k) of the NM materials compared with the metal ions in the electrolyte of the transparent state.…”

“…[8][9][10][11][12] Conventional ECDs are composed of a non-metal (NM) EC material (for example, poly(ethylene oxide), poly(methyl methacrylate), polyvinylidene difluoride, WO 3 , MoO 3 , Ir(OH) 3 , NiO). [13][14][15][16][17] In particular, WO 3 , which is the most widely known EC material, has attracted considerable attention because of its broad applications such as in ECDs, photocatalysis and sensing devices. 3 However, the use of NM-ECD encounters two drawbacks.…”

A WO3Nanoporous-Nanorod Film Formed by Hydrothermal Growth of Nanorods on Anodized Nanoporous Substrate

“…Several anodization works showed good electrochromic properties (short coloring and bleaching times of 2.5-9.8 s and 3.5-16.6 s, respectively) on the nanoporous WO 3 formed on tungsten (W) foil 5 and conductive glass substrates. [6][7][8][9] WO 3 nanorods can be produced in powder form or directly grown on a substrate. The nanorods in powder form are synthesized by typical hydrothermal, 10 solvothermal, 11 and colloidal approaches, 12 followed by spin coating or dip coating onto a substrate for application.…”