Employing polyaniline/viologen complementarity to enhance coloration and charge dissipation in multicolor...

Multicolor electrochromic devices have gained attention widely. To support the development of multicolor electrochromic devices, we studied complementary combinations of a multicolor switchable polyaniline (PANI) electrode and 1-methyl-4,4'-bipyridyl iodide (MBI). In particular, MBI acting as an electrolyte and cathodic electrochromic layer can not only simplify the architecture of a device, but also support the color richness of the device simultaneously. Wide band optical modulation in visible light (58.1% at 550 nm) and near-infrared light (35% at 800 nm) confirms the advantageous optical properties of the combination, possessing a wide color gamut range over a range of working voltages adjustable for red, yellow, green, blue, and purple, each having a high color contrast of up to 73.8. This is accompanied by the excellent electrochemical performances of the mentioned combination, such as a fast response time of 1 s/1.9 s (modulating 77%-colored/bleached) with good cycle stability, and high coloration efficiency of 140.63 cm²/C. In addition, utilizing a screen-printed polyvinyl alcohol (PVA) as a masking barrier layer, it is possible to display patterned anti-counterfeit information within the application. Given these electrochromic performance properties, it is considered a readily feasible strategy to utilize PANI and MBI combination to develop novel electrochromic devices, which can be used widely in the areas of smart packaging, smart labels, and flexible smart windows associated with specific application scenarios.