Fully spray-coated electrochromic devices containing octa-viologen substituted polyhedral oligomeric silsesquioxane

Abstract

Here we present the fully spray-coated electrochromic devices (ECDs) containing octa-viologen substituted polyhedral oligomeric silsesquioxane (OHV-POSS). By adopting various compositions and layer configurations, transmissive and reflective ECDs were fabricated by spray-coating on polyester and polycarbonate, respectively, substrates. As an electrode, the mixture of silver nanowires and poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) was used in the presence of divinyl sulfone. The electrical conductivity and figure-of-merit values of the electrodes were estimated depending on the compositions. The ion gel containing OHV-POSS with ionic liquid was prepared for an electrochromic layer. An electrolyte layer containing lithium salt and a curable polymer matrix was inserted between the electrochromic and electrode layers to minimize solvent infiltration. The spray-coated plastic ECDs exhibited a low redox potential of -1.5 V and reversible color changes. The devices maintained the switching times are less than 10 s and the cyclic stability for up to 90,000 s. Using all spray-coating methods, we demonstrate a proof-of-concept for electrochromic paint. With the current achievements, it would be possible to avoid the restriction imposed on the substrate and the resulting device structure. Various device structures can be constructed as the current approach does not require an upper substrate, which is further extended to diverse solid surfaces that exhibit on-demand color-changing capabilities.