Fast response of complementary electrochromic device based on WO₃/NiO electrodes.

Area of Science:

• Materials Science
• Electrochemistry
• Nanotechnology

Background:

• Nanoporous structures enhance electrochromic performance by increasing surface area and facilitating ion/electron transfer.
• Tungsten oxide (WO3) and nickel oxide (NiO) are key materials for electrochromic devices (ECDs).

Purpose of the Study:

• To synthesize nanoporous WO3/NiO electrode films using vacuum cathodic arc plasma (CAP) deposition for complementary electrochromic devices (ECDs).
• To optimize electrochromic performance by controlling electrode structure and WO3 film thickness.
• To investigate the influence of WO3 film thickness on electrochemical and optical properties.

Main Methods:

• Fabrication of WO3/NiO electrode films on ITO glass using vacuum cathodic arc plasma (CAP) deposition.
• Construction of complementary electrochromic devices (ECDs) with the structure ITO/WO3/LiClO4-Perchlorate solution/NiO/ITO.
• Characterization of electrochemical properties (ion diffusion coefficients, charge capacity) and optical characteristics (optical modulation, switching times).

Main Results:

• Optimized 200-nm-thick WO3 films exhibited ion diffusion coefficients of 7.35 × 10^-10 cm²/s (oxidation) and 4.92 × 10^-10 cm²/s (reduction).
• The WO3 (200 nm)/NiO (60 nm) complementary electrode system showed 98% reversibility.
• A demonstration ECD achieved 46% optical modulation (ΔT) with switching times of 3.1 s (coloration) and 4.6 s (bleaching) at 633 nm.
• The ECD maintained 93% of its initial performance (43% ΔT) after 2500 cycles, indicating excellent durability.

Conclusions:

• Vacuum cathodic arc plasma (CAP) deposition is effective for synthesizing nanoporous WO3/NiO films for high-performance ECDs.
• WO3 film thickness significantly impacts electrochemical and optical properties, with 200 nm proving optimal in this study.
• The developed ECDs offer promising optical modulation, fast switching speeds, and exceptional long-term stability for applications like smart windows.