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

In complementary electrochromic devices (ECDs), nickel oxide (NiO) is generally used as a counter electrode material for enhancing the coloration efficiency. However, an NiO film as a counter electrode in ECDs is susceptible to degradation upon prolonged electrochemical cycling, which leads to an insufficient device lifetime. In this study, a type of counter electrode iridium oxide (IrO2) layer was fabricated using vacuum cathodic arc plasma (CAP). We focused on the comparison of IrO2 and NiO deposited on a 5 × 5 cm2 indium tin oxide (ITO) glass substrate with various Ar/O2 gas-flow ratios (1/2, 1/2.5, and 1/3) in series. The optical performance of IrO2-ECD (glass/ITO/WO3/liquid electrolyte/IrO2/ITO/glass) was determined by optical transmittance modulation; ∆T = 50% (from Tbleaching (75%) to Tcoloring (25%)) at 633 nm was higher than that of NiO-ECD (ITO/NiO/liquid electrolyte/WO3/ITO) (∆T = 32%). Apart from this, the ECD device demonstrated a fast coloring time of 4.8 s, a bleaching time of 1.5 s, and good cycling durability, which remained at 50% transmittance modulation even after 1000 cycles. The fast time was associated with the IrO2 electrode and provided higher diffusion coefficients and a filamentary shape as an interface that facilitated the transfer of the Li ions into/out of the interface electrodes and the electrolyte. In our result of IrO2-ECD analyses, the higher optical transmittance modulation was useful for promoting electrochromic application to a cycle durability test as an alternative to NiO-ECD.

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

Nanoporous structures have proven as an effective way for enhanced electrochromic performance by providing a large surface area can get fast ion/electron transfer path, leading to larger optical modulation and fast response time. Herein, for the first time, application of vacuum cathodic arc plasma (CAP) deposition technology to the synthesis of WO3/NiO electrode films on ITO glass for use in fabricating complementary electrochromic devices (ECDs) with a ITO/WO3/LiClO4-Perchlorate solution/NiO/ITO structure. Our objective was to optimize electrochromic performance through the creation of electrodes with a nanoporous structure. We also examined the influence of WO3 film thickness on the electrochemical and optical characteristics in terms of surface charge capacity and diffusion coefficients. The resulting 200-nm-thick WO3 films achieved ion diffusion coefficients of (7.35 × 10-10 (oxidation) and 4.92 × 10-10 cm2/s (reduction)). The complementary charge capacity ratio of WO3 (200 nm thickness)/NiO (60 nm thickness) has impressive reversibility of 98%. A demonstration ECD device (3 × 4 cm2) achieved optical modulation (ΔT) of 46% and switching times of 3.1 sec (coloration) and 4.6 sec (bleaching) at a wavelength of 633 nm. In terms of durability, the proposed ECD achieved ΔT of 43% after 2500 cycles; i.e., 93% of the initial device.

Indium-Zinc-Tin-Oxide Film Prepared by Reactive Magnetron Sputtering for Electrochromic Applications.

This paper reports on the fabrication of indium-zinc-tin-oxide (IZTO) transparent conductive film deposited by direct current (DC) reactive magnetron sputtering. The electrical, structural, and optical properties of IZTO film were investigated by Hall measurement, X-ray diffraction (XRD), and optical transmission spectroscopy with various sputtering powers. The IZTO film prepared used power at 100 W showed the lowest resistivity of 5.2 × 10-4 Ω cm. To accomplish rapid switching and high optical modulation, we have fabricated an electrochromic device (ECD) consisting of an working electrode (WO3 electrode film deposited on IZTO/ITO/glass) and a counter-electrode (Pt mesh) in 0.2 M LiClO4/PC liquid solution. The device demonstrated an optical contrast of 44% and switching times of 4.6 s and 8.1 s for the coloring and bleaching state, respectively, at the wavelength of 550 nm.

Infrared absorption spectra of t-HNOH radicals generated on VUV irradiation of NO in solid hydrogen.

Photoproduct signature: Irradiation of solid hydrogen near 3 K containing NO with vacuum-UV light from synchrotron radiation yields new infrared absorption lines at 1241.7, 1063.6 and 726.2 cm(-1) (see figure). These new lines are assigned to vibrational modes of t-HNOH. This photoproduct is formed from electronically excited NO reacting with neighboring hydrogen in the solid sample.Irradiation of solid H(2) near 3 K containing NO with vacuum-ultraviolet light from a synchrotron yields new infrared absorption lines at 1241.7, 1063.6 and 726.2 cm(-1). The structures of four possible structural isomers: H(2)NO, t-HNOH, c-HNOH and NOH(2), their vibrational wavenumbers, IR intensities and D-isotopic shifts are calculated with density-functional theory according to B3LYP and PW91PW91/aug-cc-pVTZ methods. Based on the results of those calculations and of experiments with deuterium labeling, we assign the new lines to nu(4) (cis bending), nu(5) (N==O stretching) and nu(6) (out-of-plane deformation) modes, respectively, of t-HNOH. This photoproduct is formed through reaction of electronically excited NO with neighboring H(2) in the solid sample.