Electrochromic Devices Transmission Mode

The electrochromic electrode of these devices, which can work either in the reflective or transmissive mode, is constituted by a conductive, transparent glass coated with electrochromic material. The counterelectrode can be of any material that provides a reversible electrochemical reaction in devices operating in the reflective mode (like electrochromic displays) by contrast, in variable light transmission electrochromic devices (like electrochromic windows) it has to be either colourless in both oxidized and reduced states or electrochromic in a complementary mode to the... 

Polymer-based, variable light transmission electrochromic devices have been fabricated with counter-electrodes that are either optically passive or electrochromic in the complementary mode. Two devices with pMeT, electrochemically grown by monomer oxidation on ITO-coated glass as the electrochromic electrode, having colourless counter-electrodes in both oxidized and reduced states, and operating in liquid electrolyte, such as PC-LiC104, have been developed [29, 30]. 

Several variable-light transmission electrochromic devices based on pANI with a counter-electrode that is electrochromic in the complementary mode have been developed. The device tested at Toyota Central R D Labs [27]... 

Preliminary results of a light-variable transmission electrochromic device in acid aqueous solution which uses Prussian blue as the electrochromic material to operate in a mode complementary to pANI have been reported by Duek et al [32]. Prussian blue exhibits interesting bicolour electroch-romism as shown below (Fe"Fe" is the mixed valence Prussian blue (PB) compound, its reduced form Fe Fe is Everitt salt (ES) and its oxidized form Fe Fe is Berlin green (BG)) ... 

Electrochromism can be monitored via standard transmission spectroscopy (transmission-mode electrochromism), applicable to thin films, and to solutions in the very limited cases in which a CP can be prepared at different doping levels in solution. It can also be monitored by reflection spectroscopy (r ectance-mode electrochromism), useful e.g. for IR measurements, or if die final application envisioned is a display device. 

Fig. 20-1 Schematic of typical transmission-mode electrochromic device.

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