Fabrication of Highly Transparent Electrochromic Mirror Device with Nanoporous Counter Electrode

A new inorganic-organic hybrid electrochromic mirror device was fabricated, which is very transparent; its transparency and optical and electrical properties are highly influenced by the structure of the counter electrode (CE). The working electrode (WE) was fabricated via vacuum deposition of Ag, ITO, and WO3 films on glass, in sequence. Ag, ITO, and WO3 served as mirror and low resistance electrode, Ag protective layer, and inorganic reduction electrochromic layer, respectively. This study used a flat CE and nanoporous structured CE that had greatly increased surface to volume ratio. Flat CE did not reduce portion of oxidized phenothiazine (PH). In decoloration state, mirror device still had reddish color; this was a factor that decreased the decoloration reflectance. On the other hand, the use of nanoporous structured CE reduced the entire amount of oxidized PH, completely eliminated the reddish color, and enabled the fabrication of highly reflective mirror devices. Moreover, the use of nanoporous structured CE improved the electrochromic optical and electrical properties, leading to high reflectance variation, low consumed charge, low coloration static current, and fast response time compared to those characteristics of flat CE.