Exploring electrochromic performance via layered deposition of tungsten oxide on niobium oxide composite electrode

Abstract

Previous studies examined the incorporation of several transition metal oxides into niobium oxide (Nb2O5) to enhance the electrochromic (EC) performance. The objective was to improve the durability, color neutrality, coloring efficiency, and optical characteristics because individual metal oxides often exhibit limits that might affect overall functioning. Therefore, an innovative approach, integrating mixed metal oxides, emerges. This novel approach addresses these challenges and unlocks new possibilities to enhance EC efficiency. This paper introduces a new method for synthesizing niobium oxide/tungsten oxide (Nb2O5/WO3) bilayer composite materials using a combination of facile hydrothermal synthesis with electrodeposition. The electrochromic, structural, morphological, and optical characteristics of Nb2O5 thin films were enhanced by conducting thorough investigations into different electrodeposition cycles of WO3. X-ray diffraction confirmed the amorphous nature of WO3 in combination with the crystalline orthorhombic Nb2O5 structure. Raman spectroscopy examined the vibrational modes and structural attributes in the Nb2O5/WO3 bilayer composite thin films. X-ray photoelectron spectroscopy was conducted to examine the chemical composition, elemental state, and surface characteristics. Field emission scanning electron microscopy was used to examine the impact of different WO3 electrodeposition cycles on the morphology of Nb2O5 thin films, revealing the formation of porous, clumped, and dense nanogranules on the film surface. EC investigations highlight the superior performance of the NW-20 thin film, showing efficient Li+ accommodation. The optimized NW-20 sample exhibits excellent EC performance, including high optical modulation (81.48 %), good reversibility (98.11 %), and high coloration efficiency (115.09 cm2/C) with long-term cycling stability. The NW-20 electrode incorporated into a device form exhibited functionality on a real-world scale, delivering remarkable EC performance with substantial optical modulation (78.1 %) and excellent cycling stability. These findings expand the potential applications of Nb2O5/WO3 bilayer composite materials for EC performance. © 2024 Elsevier B.V.