Electrochromic Properties of Prussian Blue Thin Films Prepared by Chemical Deposition Method

The manifestation of electrochromic phenomena makes Prussian blue (PB) thin films very attractive, especially because they exhibit four-color polyelectrochromicity. In this work PB thin films were prepared by simple and low cost shemical deposition method. The films were deposited onto fluorine doped tin oxide (FTO) coated glass substrates. An electrochromic test device (ECTD) was constructed by using these films as working electrodes, and FTO coated glass as an opposite electrode in aqueous solution of 1 mol/dm3 KCl as supporting electrolyte. The electrochemical properties of the films were characterized by cyclic voltammetry. The obtained films exhibited electrochromism, changing color from deep blue in as deposited state into green, and back to blue and colorless. Visible transmittance spectra of PB films were studied in-situ in as deposited, colored and bleached states. From those spectra, contrast ratio (CR) and the optical band gaps Eg were evaluated. The dependence of the optical density (OD) on charge density was examined and the coloration efficiency (CE) was calculated to be 149.8 cm2C-1. The time response during the film switching between transparent and blue states was also examined