Hydrothermally synthesized WO3 nanowire arrays with highly improved electrochromic performance

Abstract

A hexagonal WO 3 nanowire array film is obtained using a template-free hydrothermal method by adding ammonium sulfate as a capping agent. The WO 3 nanowires grown vertically on a FTO-coated glass substrate are woven together at the surface of the film, forming well-aligned arrays at the bottom part and a porous surface morphology. Transmission electron microscopy (TEM) and X-ray diffraction (XRD) reveal that each nanowire is a hexagonal single crystal and their long axes are oriented toward the [0001] direction. Due to the highly porous surface, good contact with the conductive substrate and large tunnels of the hexagonal-structured WO 3 , a fast switching speed of 7.6 and 4.2 s for coloration and bleaching, respectively, and a high coloration efficiency of 102.8 cm 2 C À1 are achieved for the WO 3 nanowire array film.

Electrochromic properties of nanostructured tungsten trioxide (hydrate) films and their applications in a complementary electrochromic device

“…However, previous reports of directly grown WO 3 thin films on substrate using a template-free hydrothermal process and their corresponding electrochromic characteristics have been quite limited. For example, Tu's group reports a hydrothermally grown WO 3 nanowire arrays film recently [27]. A high coloration efficiency of 102.8 cm 2 /C and fast switching response of 4.2 s for coloration and 7.6 s for bleaching is achieved for this film.…”

Fabrication and capacitive characteristics of conjugated polymer composite p-polyaniline/n-WO3 heterojunction

“…Transparent conducting oxide (TCO), WO 3 , has been successfully utilized in photoelectrocatalytic processes, electrochromic devices, dye-synthesized solar cells (DSSCs), gas sensors and electrocatalysis [25]. Different structures of WO 3 have been prepared by different deposition techniques including hydrothermal process [26], solgel-derived spin or dip coating methods [27], electrodeposition [28] and sputtering [29]. However, the sol-gel method has been suggested as preference for preparation of amorphous electrochromic WO 3 films, which offers possibility for obtaining homogenous finely grained ceramics and control of chemical purity and crystallinity [30].…”

Controllability of assemblage from WO3·H2O nanoplates to nanoflowers with the assistance of oxalic acid

“…Due to some extraordinary chemical and physical properties, WO 3 has been comprehensively applied and developed in many researches and industries, such as gas sensor [1][2][3], electrochromic [4][5][6], photochromic [7,8], solar energy devices [9,10], photocatalysts [11][12][13][14][15][16] and so on. Since many fundamental properties of semiconductor materials rely not only on the composition but also on the structure, shape and morphology, synthesis of WO 3 with a tunable shape or morphologies has been the subject of insensitive research, such as one-dimensional (1D) like nanorods [17][18][19], nanowires [20,21], and 2D like nanoplates [22], nanofilms [23][24][25], and 3D like nanoflowers [26], nanotrees [27].…”