Fabrication and electrochromic performance of PB nanoparticle-based flexible electrochromic devices

Flexible device integration has become crucial for expanding the application scope of electrochromic systems. Nanoparticle films not only preserve the exceptional chemical stability inherent to inorganic electrochromic materials but also alleviate mechanical stress during deformation. Soluble Prussian blue (PB) nanoparticles (NPs) were successfully synthesized through surface modification in this study. And it was deposited on the ITO/PET substrate, achieving a breakthrough in the application of PB family electrochromic materials in flexible devices. The optimized system exhibited a high optical modulation range (48.6%) at specific wavelengths, rapid switching speed (tc/tb=5.9/4 s), and superior coloration efficiency (90.4 cm²/C). Charge transfer analysis reveals partial immobilization of lithium ions (Li⁺) within the film matrix during intercalation, which effectively enhances the optical memory effect. Compared to dense PB films fabricated via hydrothermal or electrodeposition methods, PB nanoparticle films demonstrate highly reversible chromatic transitions between the yellow and other colored states. Nanoparticle films offer a novel methodology for the application of PB in flexible electrochromic devices.