Sol-gel derived tungsten oxide based electrochromic coatings

Download

index.pdf

Date

2008

Author

Işık, Dilek

Metadata

Show full item record

Item Usage Stats

350
views

215
downloads

The microstructural, electrochemical and optical properties of sol-gel derived tungsten oxide electrochromic coatings have been investigated. Coatings were formed by spinning of tungsten metal based aqueous sol on glass with native ITO layer. Three sol formulations; acetylated peroxotungstic acid (APTA), peroxotungstic acid (PTA) and titanium-doped peroxotungstic acid (Ti-PTA) were employed to obtain 200-300 nm thick multi-layered coatings. Material and electrochromic characterization of the coatings have been performed by DSC, XRD, SEM, cyclic voltammetry and UV-Vis spectroscopy. The electrochromic performance of the WO3 coatings was influenced by calcination temperature, by sol chemistry and by the adsorbed water content. For all sol formulations the coatings calcined at 250 °C were amorphous and have shown better performance compared to crystalline counterparts calcined at 400 °C. High calcination temperature also leads to formation of WO3 nanocrystals for APTA and PTA derived coatings, titanium doping retards crystallization. Presence of acetic acid as in APTA sol improved the electrochromic and electrochemical performance. This was related to removal of organics- acetic acid and peroxo ligands- during calcination, which results in an open W-O network providing more ion insertion sites. The water adsorption affected the electrochromic performance in different ways for the coatings calcined at 250 °C and 400 ºC. The amorphous coatings with limited structural water removal and excessive hydroxyl groups tend to crystallize by condensation of W-OH groups upon storage in open atmosphere, therefore exhibiting degrading electrochromic activity with aging. Conversely, hydroxyl groups enhanced Li+ ion insertion for the stable crystalline coatings calcined at 400 °C.

Subject Keywords

Metallurgy., Electrochromic devices.

URI

http://etd.lib.metu.edu.tr/upload/2/12609686/index.pdf
https://hdl.handle.net/11511/17682

Collections

Graduate School of Natural and Applied Sciences, Thesis

Suggestions

OpenMETU
Core

Zinc Oxide Nanowire Photodetectors with Single-Walled Carbon Nanotube Thin-Film Electrodes Ates, Elif Selen; Kucukyildiz, Seyda; Ünalan, Hüsnü Emrah (2012-10-01) In this study, transparent and flexible zinc oxide (ZnO) nanowire ultraviolet (UV) photodetectors prepared via a solution-based method in which single-walled carbon nanotube (SWNT) thin films were used as transparent electrodes are reported. The photoresponse current was found to be in proportion with the ZnO nanowire density, and the nanowire density could be tuned to increase the photocurrent by a factor of 300. The decay time for the fabricated photodetectors was found to be as low as 16 s. This study su...
Electrical transport, optical and thermal properties of polyaniline-pumice composites YILMAZ, KORAY; Akgoz, A.; Cabuk, M.; Karaagac, H.; KARABULUT, ORHAN; YAVUZ, Mustafa (2011-11-01) In this study, electrical conductivity, photoconductivity, absorbance and thermal properties of polyaniline (PANI) and polyaniline-pumice composites were investigated. Temperature dependent conductivity and photoconductivity measurements were carried out in the temperature range of 80-400K. The measurements revealed that the dominant conduction mechanisms in polyaniline and 15% pumice doped composite were hopping conduction. The low activation energies calculated for 36% pumice doped composite indicated tha...
Temperature-Induced Activation of Graphite Co-intercalation Reactions for Glymes and Crown Ethers in Sodium-Ion Batteries Goktas, Mustafa; Akduman, Baris; Huang, Peihua; Balducci, Andrea; Adelhelm, Philipp (American Chemical Society (ACS), 2018-11-29) The intercalation of solvated ions into graphite leads to ternary graphite intercalation compounds (t-GICs). Here, we study the impact of temperature on the electro-chemical activity of graphite electrodes for co-intercalation reactions between 20 and 80 degrees C in sodium cells. For this, a range of linear ethers (mono-, di-, tri-, and tetraglyme) are studied. For the first time, pentaglyme and several crown ethers are also investigated. We find that several solvents that appear as unsuitable for the co-i...
Long wavelength mercury cadmium telluride photodiodes and focal plane arrays Aşıcı, Burak; Beşikci, Cengiz; Department of Electrical and Electronics Engineering (2005) This thesis reports the fabrication and characterization of long wavelength infrared mercury cadmium telluride (Hg1-xCdxTe) photodiodes and 128x128 focal plane arrays grown on lattice matched cadmium zinc telluride (Cd1-yZnyTe) substrates by metal organic vapor phase epitaxy (MOVPE). The dark current modeling of 33x33 mm2 Hg1-xCdxTe photodiodes has shown the dark current is dominated by trap assisted tunneling under small reverse bias voltages typically used to bias these detectors. The dominant dark curren...
Energy transfer and stimulated emission dynamics at 1.1 mu m in Nd-doped SiNx Li, Rui; Yerci, Selçuk; Kucheyev, Sergei O.; van Buuren, Tony; Dal Negro, Luca (2011-03-14) Neodymium (Nd) doped amorphous silicon nitride films with various Si concentrations (Nd:SiNx) were fabricated by reactive magnetron co-sputtering followed by thermal annealing. The time dynamics of the energy transfer in Nd:SiNx was investigated, a systematic optimization of its 1.1 mu m emission was performed, and the Nd excitation cross section in SiNx was measured. An active Nd:SiNx micro-disk resonator was fabricated and enhanced radiation rate at 1.1 mu m was demonstrated due to stimulated emission at ...

Citation Formats

D. Işık, “Sol-gel derived tungsten oxide based electrochromic coatings,” M.S. - Master of Science, Middle East Technical University, 2008.