Applied IrO₂ Buffer Layer as a Great Promoter on Ti-Doping V₂O₅ Electrode to Enhance Electrochromic Device Properties

Electrochromic devices (ECDs) are a promising material for smart windows that are capable of transmittance variation. However, ECDs are still too expensive to achieve a wide market reach. Reducing fabrication cost remains a challenge. In this study, we inserted an IrO₂ buffer layer on Ti-doped V₂O₅ (Ti:V₂O₅) as a counter electrode using various Ar/O₂ gas flow ratios (1/2, 1/2.5, 1/3 and 1/3.5) in the fabrication process. The buffered-ECD resulted in a larger cyclic voltammetry (CV) area and the best surface average roughness (Ra = 3.91 nm) to promote electrochromic performance. It was fabricated using the low-cost, fast deposition process of vacuum cathodic arc plasma (CAP). This study investigates the influence of the IrO₂ buffer/Ti:V₂O₅ electrode on ECD electrochemical and optical properties, in terms of color efficiency (CE) and cycle durability. The buffered ECD (glass/ITO/WO₃/liquid electrolyte/IrO₂ buffer/Ti:V₂O₅/ITO/glass) demonstrated excellent optical transmittance modulation; ∆T = 57% (from T_bleaching (67%) to T_coloring (10%)) at 633 nm, which was higher than without the buffer (ITO/WO₃/liquid electrolyte/Ti:V₂O₅/ITO) (∆T = 36%). In addition, by means of an IrO₂ buffer, the ECD exhibited high coloration efficiency of 96.1 cm²/mC and good durability, which decayed by only 2% after 1000 cycles.