Electrochromic Properties of Nickel Hexacyanoferrate Thin Films Prepared by a Simple Chemical Deposition Method

In this work a simple chemical bath deposition method was developed and employed for the preparation of Nickel Hexacyanoferrate (NiHCF) films. The films were deposited by successive immersion of the fluorine doped glass substrates (FTO) into acidic aqueous solution of NiCl2 and K4[Fe(CN)6]. X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Atomic force microscopy (AFM) confirmed that the obtained NiHCF films had crystalline structure. Cycling voltammetry was performed in order to investigate the electrochemical properties of the films. Visible spectra of NiHCF films were recorded in-situ in the both, bleached and colored state. From those spectra were estimated the optical band gaps. The response times of the bleaching and coloring was estimated to an abrupt potential change from -2 V to +2 V and reverse. The coloration efficiency was estimated from the dependence of the optical density on charge density

A Simple Chemical Method for Deposition of Electrochromic Cobalt Hexacyanoferrate Thin Films

In this work a simple chemical method for depositing cobalt hexacyanoferrate (CoHCF) films has been developed. The films have been prepared by successive immersion of the fluorine doped glass substrates (FTO) into an acidic aqueous solution of CoCl2 and K4[Fe(CN)6]. The characterization of the films with X-ray diffraction (XRD), Scanning electron microscopy (SEM) and Atomic force microscopy (AFM) showed that the films have crystalline structure. The electrochemical properties of the films were characterized by cyclic voltammetry. Obtained films exhibited electrochromism, changing colour reversibly between transparent and brown. Visible transmittance spectra of CoHCF films in their bleached and coloured states were recorded in-situ. Those spectra were used to estimate the optical band gaps. The dependence of the optical density on charge density was examined and used to calculate the colouration efficiency. The response times of the colouring and bleaching to an abrupt potential change from -2 V to +2 V and reverse were also examined. The maximum light intensity modulation ability of the films and saved energy, when the AM 1.5 spectrum is taken as an input, were calculated to be 55% and 243.56 Wm-2, respectively, which makes this films suitable for application in electrochromic devices