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Open AccessArticle

Effect of the Ammonium Tungsten Precursor Solution with the Modification of Glycerol on Wide Band Gap WO3 Thin Film and Its Electrochromic Properties

1
Institute of Polymer Optoelectronic Materials and Devices, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, China
2
School of Medical Instrument & Food Engineering, University of Shanghai for Science and Technology, No.516 Jungong Road, Shanghai 200093, China
3
Department of Intelligent Manufacturing, Wuyi University, Jiangmen 529000, China
4
Guangdong Province Key Lab of Display Material and Technoloy, Sun Yat-sen University, Guangzhou 510275, China
*
Authors to whom correspondence should be addressed.
Micromachines 2020, 11(3), 311; https://doi.org/10.3390/mi11030311
Received: 11 February 2020 / Revised: 11 March 2020 / Accepted: 14 March 2020 / Published: 16 March 2020
(This article belongs to the Special Issue Wide Bandgap Based Devices: Design, Fabrication and Applications)
Tungsten trioxide (WO3) is a wide band gap semiconductor material, which is commonly not only used, but also investigated as a significant electrochromic layer in electrochromic devices. WO3 films have been prepared by inorganic and sol-gel free ammonium tungstate ((NH4)2WO4), with the modification of glycerol using the spin coating technique. The surface tension, the contact angle and the dynamic viscosity of the precursor solutions demonstrated that the sample solution with a 25% volume fraction of glycerol was optimal, which was equipped to facilitate the growth of WO3 films. The thermal gravimetric and differential scanning calorimetry (TG-DSC) analysis represented that the optimal sample solution transformed into the WO3 range from 220 °C to 300 °C, and the transformation of the phase structure of WO3 was taken above 300 °C. Fourier transform infrared spectroscopy (FT-IR) spectra analysis indicated that the composition within the film was WO3 above the 300 °C annealing temperature, and the component content of WO3 was increased with the increase in the annealing temperature. The X-ray diffraction (XRD) pattern revealed that WO3 films were available for the formation of the cubic and monoclinic crystal structure at 400 °C, and were preferential for growing monoclinic WO3 when annealed at 500 °C. Atomic force microscope (AFM) images showed that WO3 films prepared using ammonium tungstate with modification of the glycerol possessed less rough surface roughness in comparison with the sol-gel-prepared films. An ultraviolet spectrophotometer (UV) demonstrated that the sample solution which had been annealed at 400 °C obtained a high electrochromic modulation ability roughly 40% at 700 nm wavelength, as well as the optical band gap (Eg) of the WO3 films ranged from 3.48 eV to 3.37 eV with the annealing temperature increasing. View Full-Text
Keywords: tungsten trioxide film; spin coating; optical band gap; morphology; electrochromism tungsten trioxide film; spin coating; optical band gap; morphology; electrochromism
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Liu, J.; Zhang, G.; Guo, K.; Guo, D.; Shi, M.; Ning, H.; Qiu, T.; Chen, J.; Fu, X.; Yao, R.; Peng, J. Effect of the Ammonium Tungsten Precursor Solution with the Modification of Glycerol on Wide Band Gap WO3 Thin Film and Its Electrochromic Properties. Micromachines 2020, 11, 311.

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