Novel microwave assisted sol–gel synthesis (MW-SGS) and electrochromic performance of petal like h-WO3 thin films

Use of domestic microwave oven is first time employed for chemical deposition of nanocrystalline hexagonal WO3 (h-WO3) thin films. Low cost precursors like sodium tungstate, hydrochloric acid, oxalic acid and potassium sulfate signifies cost effectiveness of this thin film fabrication route. Scanning electron microscopy images reveal formation of petal like nanodisks. A number of analytical techniques were used to characterize the WO3 petal like nanodisks, including X-ray diffraction (XRD), energy dispersive X-ray spectroscopy (EDX), X-ray photoelectron spectroscopy, FT-IR spectroscopy, Raman scattering spectroscopy, UV–visible spectrophotometry and cyclic voltammetry (CV). The X-ray photoelectron spectroscopic studies revealed 2.89 O/W atomic ratio. The electrical transport studies on WO3 thin films show semiconducting behavior with n-type semiconductivity. The value of determined coloration efficiency is 57.90 cm2/C. The mechanism of Li+ intercalation and deinercalation in h-WO3 matrix is proposed for enhanced electrochromism.

Graphical abstractElectrochromic intercalation and deintercalation of Li+ ions and electrons is facilitated by providing hexagonal tunnel, trigonal cavity and square window which allows easy and fast insertion and extraction of ions.Figure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Novel two step MW-SGS is first time employed to prepare WO3 thin films. ► MW-SGS is simple and cost effective technique for preparation of nanostructures. ► Petal-like hexagonal WO3 nanodisks were successfully deposited. ► O/W ratio calculated by XPS studies is 2.89. ► Good electrochromic performance suggests practical usability of proposed technique.