Preparation of an Inorganic All-Solid-State Electrochromic Device with Excellent Open-Circuit Memory

Due to the spontaneous transport of small-sized cations and redox reactions under open circuit conditions, the currently reported coloring electrochromic devices (ECDs) may self-bleach easily. The resulting ECDs exhibit poor open-circuit memory, which limits their applications in static display advertisement. By constructing energy barriers to effectively control small-sized cation transport, the redox reaction could be suppressed, thereby inhibiting the self-bleaching of ECDs. In this study, phosphate glass is used as an electrolyte to construct high-energy barriers. Sodium ions in phosphate glass absorb external heat to cross energy barriers and become conductive charge carriers. In this case, the electrochromism of ECDs is allowed. On the contrary, after the absorbed heat energy is released, sodium ions are immediately trapped by oxygen ions in the PO4 unit, becoming frozen ions. At this point, the electrochromization of ECDs is prohibited. Based on the ionic conductive feature of phosphate glass, ECDs absorb heat and are colored by applying an electric field first. Then, ECDs release the thermal energy and the sodium ions transport in the electrolyte is blocked to cut off the self-bleaching pathway. The prepared inorganic all-solid-state ECDs maintained the colored state for several months using the method mentioned above, which solved the problem of the poor open-circuit memory of ECDs.