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 (7.35x10(-10) (oxidation) and 4.92x10(-10)cm(2)/s (reduction)). The complementary charge capacity ratio of WO3 (200nm thickness)/NiO (60nm thickness) has impressive reversibility of 98%. A demonstration ECD device (3x4cm(2)) achieved optical modulation (Delta T) of 46% and switching times of 3.1sec (coloration) and 4.6sec (bleaching) at a wavelength of 633nm. In terms of durability, the proposed ECD achieved Delta T of 43% after 2500 cycles; i.e., 93% of the initial device.