Improved electrochromic response time of nickel hydroxide thin film by ultra-thin nickel metal layer

Improvements in the optical switching properties of electrochromic nickel hydroxide/nickel/glass thin film are reported. Nickel metal film was deposited on glass by e-beam evaporation prior to following electrochemical redox cycling to form nickel hydroxide for electrochromic activation. In the absence of the indium tin oxide (ITO) layer as an electrical conductor, this electrode showed a more rapid coloration rate than a nickel hydroxide film on ITO substrate in terms of change in electric voltage and optical transmittance. X-ray photoelectron spectroscopy analysis confirmed the existence of ultra-thin nickel metal layer between the electrochemically grown nickel hydroxide and the glass substrate. We conclude that the nickel metal nanolayer can be attributed to the conduction layer and the enhanced response time.