Electrochromic Devices Based on Porous Tungsten Oxide Thin Films

Abstract

Recent developments in the synthesis of transition metal oxides in the form of porous thin films have opened up opportunities in the construction of electrochromic devices with enhanced properties. In this paper, synthesis, characterization and electrochromic applications of porous WO3thin films with different nanocrystalline phases, such as hexagonal, monoclinic, and orthorhombic, are presented. Asymmetric electrochromic devices have been constructed based on these porous WO3thin films. XRD measurements of the intercalation/deintercalation of Li+into/from the WO3layer of the device as a function of applied coloration/bleaching voltages show systematic changes in the lattice parameters associated with structural phase transitions in LixWO3. Micro-Raman studies show systematic crystalline phase changes in the spectra of WO3layers during Li+ion intercalation and deintercalation, which agree with the XRD data. These devices exhibit interesting optical modulation (up to ~70%) due to intercalation/deintercalation of Li ions into/from the WO3layer of the devices as a function of applied coloration/bleaching voltages. The obtained optical modulation of the electrochromic devices indicates that, they are suitable for applications in electrochromic smart windows.

Electrochromism in tungsten oxide thin films prepared by chemical bath deposition

“…It was observed [30] that during the coloration process, the XRD peaks change in the position and in the intensities indicating a structural transition associated with intercalation of ions. When the ions were deintercalated by applying reverse potential, the crystalline structure reverts to the initial lattice.…”

Epitaxial growth of high quality WO3 thin films

“…C Tungsten trioxide (WO 3 ) is a well-known electrochromic material which changes color under an applied electric field. [1][2][3][4][5] It is also very sensitive to NO x exposure, and hence it is used to fabricate gas sensors. [6][7][8][9][10] Both of these applications require WO 3 to be grown in a thin film form.…”

Chemical composition and crystal structure of tungsten oxide films

“…Vibrational spectra of molecules are studied exper imentally by the methods of Raman scattering [47][48][49][50][51][52][53][54] and Fourier transform infrared (FTIR) spectros copy [55][56][57][58][59][60][61][62][63][64][65][66][67][68].…”

“…The IR spectra of the WO x films in the range of wave numbers from 400 to 4000 cm -1 [54][55][56][57][58][59][60][61][62][63][64][65][66] can be approximately divided into the following four areas: The authors in [55] have studied the films synthe sized on silicon by the electron beam evaporation and sol gel methods. The IR spectra of the samples are shown in Fig.…”