Green fabrication of a complementary electrochromic device using water-based ink containing nanoparticles of WO 3 and Prussian blue.

We fabricated a complementary electrochromic device (ECD) by using water-dispersible nanoparticles (NP) of Prussian blue (PB) and WO 3 by using a wet process, which involved just coating. Although the ECD had a thick WO 3 film, it showed much higher contrast compared to other techniques. In addition, the ECD also showed fast optical switching speed and high durability over 100 cycles because of wettability control of NP inks.