Recent Advances with Terpyridine-Based Monolayer Electrochromic Materials

Abstract

Electrochromic (EC) materials are a class of “smart” materials that change their optical properties in response to an applied potential. This optical change can be the development, loss, or variation in the color of the material. EC materials have recently become a research focus because of their high commercial applicability in “smart” windows, antiglare mirrors, and low-power displays. Most current EC materials are based on thick layers of EC molecules or EC molecules/ conductive polymer blends on the electrodes. The device properties depends strongly on the overall composition and distribution of the EC species in the polymer structure. We have developed an EC systems that contain as little as a monolayer of the EC molecules deposited onto a surface-enhanced conductive support [1]. The process involves the covalent attachment of various terpyridine-based ligand to the surface of a nanostructured conductive indium − tin oxide (ITO) screen-printed support by a simple submerging of the support into an aqueous solution of L. Subsequent reaction of with metal ions (e.g. Fe, Ru) leads to the formation the monolayer of the redox-active metal complex covalently bound to the ITO support. In addition, isolated and well-defined terpyridine- based metal complexes (Fe, Os,Co) were simply deposited on ITO screen-printed surface via conventional chlorobenzylsiloxane-based template. Our fabrication approach utilizes the inter-particle porosity of the support and requires as low as a monolayer of EC active molecule, giving significant molecular economy when compared with traditional polymer-based EC devices. This presentation will feature an overview of our synthetic methods, including how we can alter the color of the films by changing either the metal center of the ligand itself [2]. Spectro-electrochemical studies enabled us to correlation optical density with redox site density. Furthermore, detailed electrochemical studies enabled the determination of the kinetic rate constants for electron transfer for these films [3], which were considerably higher than other approaches in the literature. These novel light-reflective EC materials demonstrate a high color difference, significant durability, fast switching speed, excellent stability and high EC reversibility.