All-solid-state electrochromic device using polymer electrolytes with a wet-coated electrochromic layer

Next-generation automobiles will feature smart windows that can vary their optical properties dynamically. We previously fabricated electrochromic devices (ECDs) for such applications by wet-coating gel-electrolyte materials with nanoparticle-water-dispersive inks containing tungsten oxide and Prussian blue. However, the gel electrolyte must be carefully sealed to avoid leakage, and air must be prevented from entering the device. To avoid such practical difficulties, we develop an all-solid-state ECD using a polymer electrolyte prepared with hydroxypropyl methylcellulose (HPMC) that has an affinity for K+ ions. It has excellent color efficiency at 633 nm (139 cm2/C); although it has a longer response time than the gel electrolyte ECD, it is more easily assembled at room temperature under atmospheric pressure. We anticipate that ECDs of this design will be easier to implement in practical industrial settings.