Applications of reversible electrodeposition electrochromic devices

Abstract

Electrochromic devices based upon the reversible electrodeposition of Bi are described. The electrochemistry, interface chemistry and spectroelectrochemistry of the system relevant to information display and smart windows applications are briefly reviewed. The detailed nucleation and growth behavior of the system are described to help explain electrochromic device performance. Electrochromic displays have been formulated to produce full RGB color, and switching speeds as high as 33 Hz have been achieved. Black and white contrast ratio is found to be 25:1, and lifetime greater than 5 × 10 7 cycles has been reported. For smart windows the transmittance of the system is continuously variable from nearly 100% to 0% relative to the ITO or FTO coated substrate. Coloration efficiency values are greater than 70 cm 2/C, and are relatively flat throughtout the visible spectral region. The feasibility of using the system as the cathodically coloring material in tandem with anodically coloring Prussian Blue has been established. Electrolyte systems have been developed that allow both electrochromic systems to be used together. Coloration efficiencies have been determined for tandem devices and a maximum of 120 cm 2/C at 700 nm (60 cm 2/C at 550 nm) has been measured.