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Title: Electrochromic and colorimetric properties of nickel(II) oxide thin films prepared by aerosol-assisted chemical vapor deposition
Authors: Sialvi, Muhammad Z.
Mortimer, Roger J.
Wilcox, G.D.
Mat-Teridi, Mohd
Varley, Thomas S.
Wijayantha, K.G.U.
Kirk, Caroline A.
Keywords: AACVD
Nickel(II) oxide
CIE chromaticity coordinates
Issue Date: 2013
Publisher: © American Chemical Society
Citation: SIALVI, M.Z. ... et al., 2013. Electrochromic and colorimetric properties of nickel(II) oxide thin films prepared by aerosol-assisted chemical vapor deposition. ACS Applied Materials and Interfaces, 5 (12), pp. 5675-5682.
Abstract: Aerosol-assisted chemical vapor deposition (AACVD) was used for the first time in the preparation of thin-film electrochromic nickel(II) oxide (NiO). The asdeposited films were cubic NiO, with an octahedral-like grain structure, and an optical band gap that decreased from 3.61 to 3.48 eV on increase in film thickness (in the range 500−1000 nm). On oxidative voltammetric cycling in aqueous KOH (0.1 mol dm−3) electrolyte, the morphology gradually changed to an open porous NiO structure. The electrochromic properties of the films were investigated as a function of film thickness, following 50, 100, and 500 conditioning oxidative voltammetric cycles in aqueous KOH (0.1 mol dm−3). Light modulation of the films increased with the number of conditioning cycles. The maximum coloration efficiency (CE) for the NiO (transmissive light green, the “bleached” state) to NiOOH (deep brown, the colored state) electrochromic process was found to be 56.3 cm2 C−1 (at 450 nm) for films prepared by AACVD for 15 min followed by 100 “bleached”-to-colored conditioning oxidative voltammetric cycles. Electrochromic response times were <10 s and generally longer for the coloration than the bleaching process. The films showed good stability when tested for up to 10 000 color/bleach cycles. Using the CIE (Commission Internationale de l’Eclairage) system of colorimetry the color stimuli of the electrochromic NiO films and the changes that take place on reversibly oxidatively switching to the NiOOH form were calculated from in situ visible spectra recorded under electrochemical control. Reversible changes in the hue and saturation occur on oxidation of the NiO (transmissive light green) form to the NiOOH (deep brown) form, as shown by the track of the CIE 1931 xy chromaticity coordinates. As the NiO film is oxidized, a sharp decrease in luminance was observed. CIELAB L*a*b* coordinates were also used to quantify the electrochromic color states. A combination of a low L* and positive a* and b* values quantified the perceived deep brown colored state.
Description: This document is the Accepted Manuscript version of a Published Work that appeared in final form in ACS Applied Materials & Interfaces, copyright (c) ACS after peer review and technical editing by the publisher. To access the final edited and published work see: http://dx.doi.org/10.1021/am401025v.
Sponsor: [The authors] thank the Loughborough University Materials Research School for the provision of a research studentship to MZS. AMT acknowledges the funding received from the Government of Malaysia for his doctoral studies in the Department of Chemistry, Loughborough University, U.K.
Version: Accepted for publication
DOI: 10.1021/am401025v
URI: https://dspace.lboro.ac.uk/2134/15413
Publisher Link: http://dx.doi.org/10.1021/am401025v
ISSN: 1944-8244
Appears in Collections:Published Articles (Chemistry)

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