Tungsten Oxide-Modified ITO Electrode for Electrochromic Window Based on Reversible Metal Electrodeposition

Abstract

Abstract: Reversible metal electrodeposition (RME) windows are a promising material for electrochromic windows and electronic display applications. However, the lifetime of RME devices is a major drawback in the preparation of commercial and practical devices. In this study, we propose a new strategy to prolong the stability and improve the efficiency of RME devices. By using tungsten oxide, a well-known electrochromic material, to modify the surface of a transparent conductive electrode, superior, stable, and highly effective devices were prepared successfully. By applying a low potential of − 0.8 V to 0.5 V, the RME device can quickly switch between a bleached state and colored state with different colors changing from transparent to black and deep blue. The performance improvement of the RME device can be explained by the simultaneous reduction of tungsten oxide and metal ion deposition in the conductive substrate under an applied potential. Furthermore, the lifetime of the device increased significantly (over 1500 cycles) owing to the shielding role of tungsten oxide film in the acid medium, which is an indispensable component of reversible electrochromic devices. Graphic Abstract: [Figure not available: see fulltext.]Recently, reversible metal electrochromic (RME) windows are promising electrochromic device (ECD) due to simple process, low cost, and fast response. However, the main drawback of RME devices is their instability caused by the erosion of conductive electrode in an electrolyte-acidic medium. Therefore, developing stable, effective, and noble-metal-free RME devices is a tough challenge in the development of ECDs. In this study, a well-known electrochromic material, tungsten oxide (WO3), was successfully employed to modify the surface of a transparent conductive electrode (TCE)-the indispensable part for ECDs, which plays an important role as a shield of TCE electrode. ECD fabricated using WO3 modified TCE had an extremely prolonged lifetime (over 1500 cycles) compared with ECD prepared by using bare TCE. The efficiency of ECD also increased significantly owing to the electrochromic performance of WO3 that took place simultaneously with reversible metal deposition in the redox process. Therefore, WO3 modified conductive electrodes are a great candidate for enhancing the performance of ECD. © 2021, The Korean Institute of Metals and Materials.