Electrochromic properties of NiO-based thin films prepared by sol-gel and dip coating

A new method for chemical deposition of NiOxHy-based films was developed. The films obtained have electrochromic properties and good adhesion to the substrate. The precursor sol consists of an alcoholic solution of NiCl2 and Ti alcoxide. Films deposited on indium-tin-oxide substrates were prepared by dip coating. The electrochromic efficiency of thin films prepared under different conditions was determined. We report on the effects of (a) Ni concentration, (b) Ti content and (c) temperature of firing on the electrochromic efficiency. Electrochromic efficiencies measured at lambda= 632.8 nm of films with different thicknesses ( similar to 100-200 nm) range from 10 to 42 cm(2) C (- 1), with a variation in transmittance up to 30%. The colouring response time is strongly dependent on Ti content. For Ti-doped films this time is 5-80 times longer than for undoped ones. The variations in monochromatic transmittance during voltammetric cycles suggest that all the electric charge consumed by redox reactions is involved in the colouring process. (C) 2001 Elsevier Science Ltd. All rights reserved.