Nanocrystal-in-glass Prussian blue thin films for quasi-solid-state electrochromic devices with long-term stability

The ever-growing development from electrochromic devices has increased the interest of Prussian blue (PB) materials as counter electrodes. Herein, we report an innovative method for synthesizing Prussian blue precursor ink composed of sub-100 nm PB nanoparticles uniformly dispersed in ethanol. The resulting nanocrystal-in-glass PB thin films with nanoporous structure fabricated by blade coating technique exhibit an impressive optical modulation of 82.48 % at 700 nm and a high coloration efficiency of 178.59 cm 2 C −1 . The significantly enhanced electrochromic performance is primarily attributed to the short diffusion path, abundant active sites and buffering effect in the amorphous matrix, which can facilitate the rapid transport of ions and reduce electrode volume change. Furthermore, such nanocrystal-in-glass PB thin films can improve the long-term stability of quasi-solid-state complementary PB-WO 3 electrochromic devices, cycling more than 10,000 cycles. This work offers a novel approach to produce nanocrystal-in-glass PB thin films used as counter electrode in electrochromic devices with extraordinary durability.