The Preparation Of Nickel Oxide Film And Effect Of Preparation Conditions On The Electrochromic Property

Electrochromism (EC) is characterized as a stable and reversible transformation in the optical properties of materials, including transmittance, reflection and absorption, caused by inducing an electric field or a electrical change. This reversible transformation in appearance is observed as the variable color and transparency. Electrochromic materials are widely used in smart glass, auto-dimming rearview mirrors and electrochromic display devices, etc., and having an attractive prospects for applying in saving energy and environmental protection. Nickel oxide films are now considered to have excellent electrochromic performance, which can be used as electrochromic films and also as the ion storage electrode in electrochromic devices.In this article, NiOx films were prepared by the RF magnetron sputtering and sol-gel methods under different processes and conditions, and theire stuctures, qualities and electrochromic performances were carefully estimated. The electrochromic mechanism and process of NiOx films were studied after the RF magnetron sputtering. In Sol-Gel process, the preparing conditions were controled according to the electrochromic mechanism of NiOx films to abtain the good electrochromic performance. The best condition to prepare NiOx films with the existing equipment is summarized.XPS studies on nickel oxide thin films, prepared by RF sputtering, have shown that the main component are Ni and O. XRD analysis show that the prepared films are of polycrystalline structure and the sputtering oxygen partial pressure affect the prior growth direction of NiOx films. There is a large number of Ni vacancies, and this leads to the mixed valence of Ni.In the sol-gel process, NiOx films were prepared by changing the sol composition, aging time, coating layer number, drying temperature, heat treatment temperature and time. The relatively better condition to prepare NiOx films of the 'nickel acetate by four water-anhydrous alcohol-polyethylene glycol (PEG6000)' system were summerized after testing cyclic voltammetry and electrochromic properties with electrochemical corrosion system and UV-visible spectrometer. That is, the sol system of nickel acetate and ethylene glycol (2:5), aging 15 days and spin-coating three times in this period, annealed for 2h at 250℃. After that, the tuning range is up to 54% whenλ= 560 nm, and 62% whenλ=391nm.