Enhanced optical bistability of energy saving viologen-based electrochromic display with a commercial phenol-based epoxy resin

A highly bistable viologen-based electrochromic display was successfully developed by using a simple strategy with cheap commercial phenol-based epoxy. By adding epoxy, phenol species can contribute a dual effect, in which they can play as electron shuttles to facilitate fast coloration of ECDs and stabilize the long bistability of ECDs through the proton-coupled electron transfer (PCET) mechanism during coloration state. With the use of epoxy, CPHEV 2+ /E exhibits an improvement of maximum ΔT, which is 78.6 % at 596 nm compared to 53 % for that of ECD without epoxy. The ECD with added epoxy can hold the colored state up to 50 h after applying a voltage of −2.5 V for 15 s compared with ECD without epoxy which is 22 min. Notably, the color state undergoes decomposition to 10 % of its initial value after 3.5 h without any extra power supply. The 3D-printed rose flower ECD was successfully demonstrated using digital light processing (DLP) with good dimensional accuracy and resolution.