Highly transparent electrochromic plastic device that changes to purple and to blue by increasing the potential

We report the assembly and characterization of a highly transparent electrochromic device showing dual-coloration (purple and blue color change) using an innovative electrochromic formulation recently patented. This electrochromic formulation is composed of the three electroactive materials needed in a traditional electrochromic device (electrolyte, electrochromic and ion storage material) embedded in a polymeric matrix to reduce the chance of device malfunction by leaking and evaporation of the solvent. Two materials based on viologen, which show different electrochromic behaviors at 1.5 and 2.5 V, have been incorporated into the electrochromic formulation. Therefore, the electrochromic device was transparent in the bleach state but depending on the potential applied the final coloration was pink at 1.5 V and blue at 2.5 V. The maximum transparency of the device was 80% in the bleach state, 25.21% at 1.5 V when showing purple coloration and 3% at 2.5 V when showing blue coloration. The device presented a coloration efficiency (CE) of 136.6 cm2/C and a coloring time of 6.5 s to achieve 90% of the maximum change in absorbance. The device exhibited a memory effect of 8 min estimated as the time needed to obtain the initial transparency.