Electrochromic properties of spin-coated nickel oxide films

Nickel 2-ethylhexanoate was spin-coated from organic solution, followed by pyrolysis in air at 380 degrees C. The scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis showed that the spin-coated films consisted of fine particles of NiO crystallites, 10-20 nm in diameter. The optical response and circling ability of the films were measured by applying a rectangular potential pulse between 0.0 and 0.5 V vs. SCE in a 1 M KOH electrolyte. The influence of the processing temperature on the electrochromic properties of the films was studied. Although the films pyrolyzed in air at 380 degrees C showed the response time of 1-2 s for coloration/bleaching, the degradation was observed within a few thousands to 10(4) cycles. The cycling ability could be much improved by post heat-treatment at 500 degrees C for 20 min in air without sacrificing the response speed. (C) 1998 Elsevier Science B.V. All rights reserved.