Electrochromic Properties of PEG-modified Tungsten Oxide Thin Films

doi:10.15541/jim20160273

Abstract

Abstract:

To improve the electrochromic properties of WO₃ thin films, polyethylene glycol (PEG)-modified WO₃ films via Sol-Gel method were prepared on indium-tin oxide (ITO) glass using dipping-coating technique with post annealing treatment in air. Crystal structures and morphologies of the as-prepared films were investigated by means of X-ray diffraction (XRD) and scanning electron microscope (SEM). Optical properties and cyclic voltage-current characteristic of the films were experimentally studied. Compared with the corresponding neat WO₃ films, the PEG-modified WO₃ films exhibit superior electrochromic properties, which possesses longer lifetime after 5000 cycles without obvious degradation, as well as higher optical modulation up to 71% at the wavelength of 633 nm. The results suggest that PEG addition in conjunction with post annealing treatment may change the micro-structure of WO₃ films to increase the electrochromic properties, due to the enhancement of ion diffusion capacity in the electrochromic material, as evident from the formation of the porous structure with an average pore diameter of 9 nm. As cycling stability is very crucial for practical applications of electrochromic materials, particularly for smart windows, this research provides a promising low-cost wet-chemical route to high performance WO₃-based electrochromic devices.

Key words: WO3 thin film, electrochromism, Sol-Gel, PEG-modified

CLC Number:

TQ174

LU Shu-Juan, WANG Chang, ZHAO Bo-Wen, WANG Hao, LIU Jing-Bing, YAN Hui. Electrochromic Properties of PEG-modified Tungsten Oxide Thin Films[J]. Journal of Inorganic Materials, 2017, 32(2): 185-190.

Figures/Tables 8

Fig. 1 XRD patterns of ITO, W300, and WP300

Fig. 2 SEM images of W300 (a), different magnification SEM images of WP300 (b,c) and corresponding cross-sectional morphology (d)

Fig. 3 First cycle (a) and 1000th cycle (b) cyclic voltammograms of the WO3 films

Table 1 Electrochemical properties of W300 and WP300 films

Sample	Anodic peak current density, i_p/(mA•cm^-2)	Diffusion coefficient D/(cm²•s^-1)	Reversibility K/%
W300	0.54	0.8×10^-10	61.3
WP300	2.24	13.53×10^-10	71.1

Fig. 4 Cyclic voltammograms for the WP300 film

Fig. 5 Transmittances of W300 and WP300 films in their original, bleached and colored stages after first and 1000th cycles

Table 2 Transmittances of W300 and WP300 films

Sample	Original T/%	1th ΔT/%	1000th ΔT/%
W300	80.07	13	14.0
WP300	73.31	54	71.1

Fig. 6 ΔT of W300 and WP300 films under different cycle times

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