Multi-Color States of High Contrast Nano Prussian Yellow Electrochromic Film

Aim: Construction of electrochromic device via Prussian yellow nanofilm on glass electrode. Background: Energy conservation is one of the primary research topics nowadays. Electrochromic devices with low power consumption and short stable switching periods are well suited to energyefficient applications, e.g., smart windows, car mirrors, displays, and electronic papers. Objective: Preparation of electrochromic Prussian yellow nanofilm on ITO glass by a simple chemical facile method and study of its electrochromic features. Methods: Prussian yellow nanofilm (iron (III) hexacyanoferrate (III)), was prepared by immersing the substrate in a solution of ferric nitrate and Potassium hexacyanoferrate. Prussian yellow nanofilm is characterized by ultraviolet-visible (Uv-Vis) spectroscopy, cyclic voltammetry and electrochemical impedance spectroscopy. Prussian yellow nanofilm shows an intense yellow color when it is in a pristine state. Results: Resultant Prussian yellow nanofilm underwent reversible redox reactions accompanied by color changes from Prussian yellow to Prussian green to further Prussian blue, then to Prussian white. The transmittance of Prussian yellow nanofilm varies from 21% for colored state at 450nm to 81 % (for fully bleached) at 0.9V. The contrast ratio and ratio of optical density to charge density were examined and the coloration efficiency was calculated to be 299.6 cm²C^-1. Conclusion: Prussian yellow can be very simply prepared and used as an efficient, fast switching electrochromic device with high color contrast.