Oxygen-Content-Regulated Nanocrystalline InON Thin Films with Ultrafast Electrochromic Response and Excellent Stability

Despite significant advancements in electrochromic (EC) technology, traditional materials like WO₃ and NiO continue to struggle with slow EC response times and poor stability. In this study, nanocrystalline InON thin films with adjustable oxygen content were prepared using direct current magnetron sputtering. The films were thoroughly characterized using a powder X-ray diffractometer (XRD), a field-emission transmission electron microscope (TEM), an X-ray photoelectron spectroscope (XPS), a field-emission scanning electron microscope (SEM), an ultraviolet–visible spectrophotometer, and an electrochemical workstation. XRD and TEM analysis confirmed the nanocrystalline structure of the InON films, while XPS, combined with optical and electrical studies, revealed that the oxygen content in the films could be adjusted by varying the base vacuum pressure during deposition, thus optimizing their optical bandgap and conductivity. Chronoamperometry (CA) tests showed that the InON films exhibited ultrafast EC response across the full visible spectrum, with bleaching time as short as 0.19 s and coloring time as short as 0.40 s. Stability tests, including cyclic voltammetry (CV), demonstrated the excellent electrochemical cycling stability and environmental tolerance of the InON films. Furthermore, this study validated the crucial impact of electrolyte pH on the EC process of InON films and proposed a specific EC mechanism for oxygen-regulated nanocrystalline InON films.