Organic multiviologen electrochromic cells for a color electronic display application

ABSTRACT The electrochromic (EC) and optical properties of three new viologen compounds containing 1,1′‐di‐n‐heptyl‐4,4′‐bipyridinum dibromide (DHBPDB; C24H38Br2N2), 1‐heptyl‐4‐(4‐pyridyl)pyridinium bromide (HPPB; C17H23BrN2), and 1,1′‐dis(p‐cyanophenyl)‐4,4′‐bipyridinium chloride (DCBPC; C12H8N2OBr2) for potential use in electrochromism applications were investigated. The repetitive stability of all of the EC cells could be improved through the addition of ferrocene as an electron donor (a counter redox material) to the electrolyte solution under several redox cycles. The experimental results demonstrate that the EC cell showed a reversible color change from clear (tintless) to three different colors with the application of electrochemical stimuli at specific potentials. The color of the EC cells turned red, green, or blue upon electrochemical reduction for DHBPDB, HPPB, and DCBPC in indium tin oxide sandwich‐type cells. Because of the different viologen molecules competing to capture electrons and affecting the EC efficiency and life of the multiviologen cells, they could be improved by the optimization of the working voltage in the multiviologen cells from the modification of an operative potential based on the cyclic voltammetry measurements. In this article, we propose a prototype device of multicolor electrochromic display, which provides potential application for multicolor electronic displays or EC paper. © 2014 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2014, 131, 40485.