Enhanced electrochromic coloration in Ag nanoparticle decorated WO3 thin films

• Electrochromic WO3/Ag nanocomposites prepared by hybrid physico-chemical route.
• XRD and XPS results confirm formation of Ag8W4O16 phase.
• WO3/Ag thin films showed good optical transmittance change and coloration efficiency.
• SPR enhanced coloration and bleaching mechanism is well explained for electrochromism.
• Color stimuli are quantified using CIE chromaticity principles.

WO3/Ag composite thin films were prepared by microwave assisted sol–gel synthesis (MW-SGS) of WO3 followed by vacuum evaporation of Ag nanoparticles and their enhanced electrochromic coloration was investigated. The composition and morphology of WO3 thin films with different thickness of Ag layer obtained by vacuum evaporation were investigated. Distinct plasmon absorption bands of Ag nanoparticle thin films were obtained. The optical band gap energy of WO3/Ag films decreased with increasing the Ag layer thickness. The surface of these films has been examined using X-ray photoelectron spectroscopy (XPS) to gain information about the chemical states of species present at surfaces. Experimental results indicated that the conductivity of the films increased after surface modification by Ag layer. To investigate the origin of enhanced electrochromic absorption in optical properties, working electrode consisting of WO3/Ag thin film was used and observed the optical properties during electrochemical reaction. It was found that composite electrode shows enhancement in electrochromic properties in terms of optical modulation (ΔOD) and coloration efficiency (η).

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