Tailoring tungsten trioxide (WO3): pH-dependent synthesis, structural insights, and exceptional electrochromic performance

Abstract

In the current investigation, WO₃ thin films are prepared via simple hydrothermal method at different pH values (1, 7 and 11). In this study, XRD, SEM, FTIR, UV–visible, and electrochemical techniques were used to study pH effects on the preparation of WO₃ and their structural, morphological, and electrochromic variations. The XRD analysis revealed that the pH of the precursor solution significantly influences crystallinity, with acidic conditions favouring high crystallinity and efficient electrochromic (EC) performance, while more alkaline conditions result in reduced crystallinity and amorphous film formation. The SEM analysis demonstrates that pH significantly influences the morphology of WO₃ films. FTIR spectroscopy exhibited characteristic peaks associated with WO₃, affirming the successful synthesis of WO₃ thin films. The electrochemical investigations demonstrated that WO₃ films prepared at a pH of 1 exhibited exceptional EC activity, characterized by the highest optical modulation density of 0.3 and a colouration efficiency (CE) of approximately 122.2 cm²/C at 633 nm. These findings underscore the promising potential of pH-controlled hydrothermal method for tailoring the electrochromic behavior of WO₃ thin films, with implications in energy efficient smart windows.