ChemInform Abstract: H Insertion and Electrochromism in NiOx Thin Films.

Scarmínio, Jair; Estrada, Walter; Andersson, A.; Gorenstein, A.; Decker, F.

doi:10.1002/chin.199229012

Cited by 1 publication

(1 citation statement)

References 1 publication

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The observed shift toward larger diffraction angles upon coloration may be associated with stress, which is known to develop in conjunction with ion intercalation. 30 The data give clear evidence for the presence of the hydroxide phases. The stabilized oxyhydroxide phase is produced solely via hydrogen transport, as shown before.…”

Section: Sample Characterizationmentioning

confidence: 87%

Coloration Mechanism in Proton-Intercalated Electrochromic Hydrated NiO[sub y] and Ni[sub 1−x]V[sub x]O[sub y] Thin Films

Avendaño¹,

Rensmo

Azens

et al. 2009

J. Electrochem. Soc.

View full text Add to dashboard Cite

Electrochromic ͑EC͒ films of nickel oxide, with and without vanadium, were prepared by reactive dc magnetron sputtering. They were characterized by electrochemical and optical measurements and studied by X-ray photoelectron spectroscopy ͑PES͒ using synchrotron radiation. The films were analyzed under as-deposited conditions and after bleaching/coloration by insertion/ extraction of protons from a basic solution and ensuing charge stabilization. Optical measurements were consistent with a coloration process due to charge-transfer transitions from Ni 2+ to Ni 3+ states. The PES measurements showed a higher concentration of Ni 3+ in the colored films. Moreover, two peaks were present in the O 1s spectra of the bleached film and pointed to contributions of Ni͑OH͒ 2 and NiO. The changes in the O 1s spectra upon coloration treatment indicate the presence of Ni 2 O 3 in the colored film and necessitated an extension of the conventional model for the mechanism of EC coloration. The model involves not only proton extraction from nickel hydroxide to form nickel oxyhydroxide but also participation of NiO in the coloration process to form Electrochromic ͑EC͒ materials are able to change their optical properties reversibly and persistently upon charge insertion/ extraction under the application of an external voltage.1 Materials that color upon charge insertion/extraction are called cathodic/ anodic. These materials can be implemented in energy-saving and comfort-enhancing architectural "smart windows," and other application areas include mirrors with variable specular reflectance, nonemissive information displays, surfaces with variable thermal emittance, eyewear, etc.1-4 EC technology has been used for some niche applications for several years. However, the situation is now changing and electrochromism will reach wider applications. 5Thin films of Ni oxide possess anodic electrochromism, as discovered in the mid-1980s 6-9 and subsequently studied in a large number of investigations. [1][2][3][4] The visual appearance goes between transparent and brown upon extraction and insertion of charge. In EC devices incorporating cathodically coloring W oxide films, the brown color of Ni oxide is complementary to the blue color of W oxide, both together yielding a neutral ͑gray͒ color in transmittance for dark films. Ni oxide films produced for EC applications exhibit a cubic polycrystalline structure 1,9-14 and a density between 3 and 6.5 g/cm 3 depending on deposition conditions. 1,14,15 The low density is indicative of porosity. 10,14,16 The grain size depends strongly on film deposition conditions and can range from 3 to 300 nm. 9,10,12,14,15,17 The porosity and small grain size, leading to a large surface-to-bulk ratio, increase the EC activity of the films, 12,18,19 and the reaction that produces the color takes place in the outermost parts of the grains. 12Several varieties of reactively sputter-deposited EC hydrated nickel-based oxide thin films have been reported. [1][2][3][4]20 Optimized Ni 1−x V x O y films made by sputter...

show abstract

Section: Sample Characterizationmentioning

confidence: 87%