Novel electrochromic gel with high optical contrast in the visible and near-infrared

We present a new transparent electrochromic gel able to absorb simultaneously in the visible and in the near-infrared (NIR) region of the solar spectrum. The electrochromic mixture was prepared dissolving in a polymeric matrix a viologen as cathodic coloring material and a novel triarylamine derivative as anodic NIR active molecule. In connection with the reversible electrochemical behavior detected by cyclic voltammetry experiments, a reversible coloration was observed in the film. High optical contrast both in the visible and in the NIR was obtained adjusting the applied potential to moderate low values. Fast coloration times (around 5 s) to achieve 90% of the maximum optical contrast in the visible and NIR were measured, while the bleaching process occurred within 20 s.