High-Performance Complementary Electrochromic Device Based on Iridium Oxide as a Counter Electrode.

Area of Science:

• Materials Science
• Electrochemistry
• Optoelectronics

Background:

• Complementary electrochromic devices (ECDs) commonly use nickel oxide (NiO) as a counter electrode for enhanced coloration efficiency.
• NiO counter electrodes in ECDs suffer from degradation during electrochemical cycling, limiting device lifespan.
• Developing durable and efficient counter electrode materials is crucial for advancing ECD technology.

Purpose of the Study:

• To fabricate and evaluate iridium oxide (IrO2) as a counter electrode material for ECDs.
• To compare the performance of IrO2-based ECDs against traditional NiO-based ECDs.
• To investigate the effect of Ar/O2 gas-flow ratios on IrO2 film properties and device performance.

Main Methods:

• Fabrication of IrO2 thin films using vacuum cathodic arc plasma (CAP).
• Deposition of IrO2 and NiO on indium tin oxide (ITO) glass substrates.
• Characterization of ECDs including optical transmittance modulation, coloring/bleaching times, and cycling durability.
• Analysis of electrode morphology and ion diffusion properties.

Main Results:

• IrO2-ECDs exhibited a higher optical transmittance modulation (ΔT = 50%) compared to NiO-ECDs (ΔT = 32%).
• IrO2-ECDs demonstrated fast response times (4.8 s coloring, 1.5 s bleaching) and excellent cycling durability (maintained 50% ΔT after 1000 cycles).
• The filamentary shape and higher diffusion coefficients at the IrO2 interface facilitated efficient Li-ion transfer.

Conclusions:

• Iridium oxide (IrO2) is a promising alternative counter electrode material for electrochromic devices, outperforming nickel oxide (NiO).
• IrO2-based ECDs offer superior optical modulation, faster switching speeds, and enhanced cycle durability.
• The findings support the use of IrO2 as a viable material for next-generation electrochromic applications requiring long-term stability.