Multicolor Electrochromics: Rainbow-like Devices.

Stimuli-responsive reversible coloration-change materials represent a highly demanded type of smart systems useful for a wide variety of applications, with a significant growing interest on multi-color abilities. In particular, electrochromic materials have received a great deal of attention due to their versatility and broad range of industrial uses. However, most of the existing electrochromic technologies provide a single coloration, while achieving multiple colors based on simple approaches remains a challenge. The present article reports on PVA gel-based electrochromic devices, containing a single viologen, providing a colorless and two different well-defined colored states. The successful fabrica-tion of a device, based on two viologens (multi-EC gel) with a simple architecture (glass/TCO/multi-EC gel/TCO/glass), with five different multi-switchable colors based on four-zoned electrodes (rainbow-like ECD) is also demonstrated. This novel easy-to-make multi-chromic system represents a significant breakthrough towards the generation of full-color devices, expanding the potential of the electrochromic technology.