Hole doping in Al-containing nickel oxide materials to improve electrochromic performance

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Electrochromic materials offer tunable optical properties for applications like smart windows and displays.
• Nickel oxide-based materials are promising electrochromic candidates, with performance influenced by composition and nanostructure.
• Post-treatment methods present cost-effective strategies for enhancing electrochromic device performance.

Purpose of the Study:

• To investigate the impact of a post-processing ozone technique on the electrochromic performance of aluminum-containing nickel oxide.
• To elucidate the structural and chemical changes induced by ozone exposure.
• To compare the performance of ozone-treated films with untreated and lithium-doped counterparts.

Main Methods:

• X-ray diffraction (XRD) for crystallinity analysis.
• Scanning electron microscopy (SEM) for morphological characterization.
• X-ray photoelectron spectroscopy (XPS) and X-ray absorption spectroscopy (XAS) for chemical state analysis.
• UV-vis-NIR spectroscopy for optical property evaluation.
• Electrochemical testing to assess switching kinetics and optical modulation.

Main Results:

• Ozone exposure increased the nickel (Ni) oxidation state by introducing hole states in the NiO(6) octahedral unit.
• Ozone treatment led to decreased crystallinity and an increased Ni oxidation state in aluminum-containing nickel oxide films.
• The treated films exhibited improved switching kinetics, enhanced bleached-state transparency, and superior optical modulation compared to control samples.

Conclusions:

• Post-processing with ozone is an effective method for enhancing the electrochromic performance of aluminum-containing nickel oxide.
• The improved performance is linked to increased nickel oxidation state and reduced film crystallinity.
• This study offers a novel and efficient route for optimizing nickel oxide-based electrochromic materials.