Search

One-dimensional (1D) ZnO nanostructures showing various shapes were synthesized on ZnO-deposited Si substrates using a thermal chemical vapor deposition technique and their morphological, crystallographic, and optical properties were investigated. Relative to ZnO nanostructures prepared at 700 °C, the nanostructures synthesized at 900 °C increased in grain size and were tapered, resulting in the tapering of the 1D ZnO nanostructures. However, the morphologies of two samples fabricated using different source materials are different from each other, which is probably related to the producer gas reactions due to a carbothermal reduction process. All samples showed hexagonal wurtzite structures with a preferred orientation of the (002) plane and revealed photoluminescence spectra with different optical trapping at surface defect states and oxygen vacancies. [ABSTRACT FROM AUTHOR]

For achieving the fine pitch chip-on-film (COF) in display devices, wet chemical spray etching behaviors of the copper (Cu) films in the etching solutions with different cupric chloride (CuCl2) and hydrochloric acid (HCl) contents have been investigated. It is found that the etching rates and etching factors of the Cu films are strongly dependent on the composition of etchant solution and spray pressure, resulting from the chemical dissolution reaction and the kinetic energy of droplet, respectively. As a result, using the mixture of the CuCl2 and HCl, Cu films are defined successfully by wet chemical spray etching method, suggesting sufficient possibility for the application to fine pitch COF in the display devices. [ABSTRACT FROM AUTHOR]

Effects of the sodium borate concentrations in NaOH-Na2SiO3-Na2B4O7 electrolytes on the surface and corrosion properties of plasma electrolytic oxidation (PEO) coatings on AZ31 Mg alloy were investigated. Characteristics of PEO coatings were examined by scanning electron microscopy, X-ray diffraction, potentiodynamic polarization and electrochemical impedance spectroscopy. It was found that the corrosion resistance of the Mg alloy was remarkably improved via PEO treatment with the 3 g/L of sodium borate content in the electrolyte, resulting from relatively less porous morphology of PEO coating. Thus, the incorporation of sodium borate in the electrolytes can be provided an effective barrier to enhance corrosion resistance of the PEO coating on AZ31 Mg alloy. [ABSTRACT FROM AUTHOR]

In this study, we synthesized a self-photocurable intermediate by Michael addition reaction and synthesized a polyurethane acrylate oligomer. Photo-curable coatings were prepared by mixing the synthesized oligomer and HDDA/TMPEOTA ratio with a reactive diluent. The films were coated onto glass plates and base treatment metal plates using bar coaters with thicknesses of 120 μm and 30 μm, respectively. The mechanical properties increased with increasing crosslink density. The pencil hardness test was the best when the TMPEOTA content was 6 or 8 wt%, and the adhesion and banding test showed excellent physical properties when the TMPEOTA content was less than 10 wt%. MEK rubbing was all excellent. [ABSTRACT FROM AUTHOR]

We have investigated the properties of InGaZn6O9 thin films fabricated by radio frequency (RF) magnetron sputtering for the application to the electrodes in transparent thin film transistor (TTFT). The InGaZn6O9 thin films have been prepared with varying working pressure and RF power. It has been found that the InGaZn6O9 films have an amorphous structure and show a very smooth and featureless surface regardless of the deposition conditions. At optimized deposition condition, the InGaZn6O9 film shows an average transmittance of about 83.54% in the visible region and the sheet resistance of about 91.6 Ω/sq. The top gate InGaZnO4 TTFT device embedded with InGaZn6O9 electrode operates in enhanced mode with a threshold voltage of 1.1 V, a mobility of 3.48 cm2/Vs, an on-off ratio of > 104, and a sub-threshold slope of 0.9 V/decade. In addition, the optical transmittance of the TTFT device is observed about 85% at 550 nm wavelength. [ABSTRACT FROM AUTHOR]

In order to develop ultraviolet (UV)-curable coatings applicable to pre-coated metal (PCM), organic-inorganic hybrid UV curable polyurethane (PU)-acrylates were prepared using cage type metacryl-polyhedral oligomeric silsesquioxane (POSS) as a reactive diluent. To investigate the effect of POSS content on the physical properties of organic-inorganic hybrid polyurethane-acrylate coatings for PCM in this study, prepolymer was prepared by using H12MDI in PCL and HPBD, and oligomers capped at the end of 2-HEMA were synthesized. This study investigated the viscosities of the synthesized oligomers and prepared coatings; the thermal properties, mechanical properties, and transmittance of the UV-cured films; and the surface energy, adhesive property, pencil hardness, and MEK rubbing of the UV-curable films coated on the metal plate. [ABSTRACT FROM AUTHOR]

We have investigated effects of the sodium metasilicate addition into phosphate-based electrolytes on the surface properties of plasma electrolytic oxidation (PEO)-coated layers on Ti-6Al-4V. The surface properties of the PEO-coated layers have been characterized by using field emission scanning electron microscopy, energy dispersive X-ray spectroscopy, atomic force microscopy, and contact angle measurements. The study shows that the addition of sodium metasilicate in the phosphate-based electrolytes leads to the roughening surface and the change in the surface composition the PEO-coated layers. In addition, the contact angle of distilled water on the surface of the PEO-coated layers with the sodium metasilicate additive in electrolytes is reduced, resulting in higher surface energy. [ABSTRACT FROM AUTHOR]

Organic dyes were adsorbed on a compact TiO2 thin film and nanoporous TiO2 film for use as a photosensitizer and their photoelectrochemical (PEC) water-splitting responses were compared under visible light illumination. The compact TiO2 thin film exhibited a much better PEC response than the nanoporous TiO2 film, even though the latter adsorbed a much higher amount of dye, due to its higher surface area. This can be attributed to the depletion layer formed in the compact film morphology, because its electric field suppresses the back transfer (or recombination rate) of the electrons photogenerated by the dye molecules. [ABSTRACT FROM AUTHOR]

ZnO thin film transistors (TFTs) were fabricated through annealing of ZnO thin films at temperatures ranging from 250 °C to 400 °C. ZnO nanoparticles (NPs) synthesized via a sol-gel method were used as an active layer for ZnO TFTs due to their high Hall mobility, and ZnO thin films were produced by spin-coating a precursor solution of ZnO NPs, followed by annealing at 250 °C to 400 °C. When the grain size increases with increasing annealing temperature, the Hall mobility of the ZnO thin films increases due to decrease of the grain boundary density. As the annealing temperature increased from 250 °C to 350 °C, field effect mobility (µFE) and on-to-off (Ion/Ioff) ratio increased while threshold voltage (Vth) and subthreshold swing (S-S) decreased. This is likely due to an increase in the conductivity of the ZnO thin film according to the increasing grain size. 350 °C-annealed ZnO TFT exhibited the best electrical properties with a Vth of 4.8 V, an Ion/Ioff ratio of 104, and a field-effect mobility (μFE) of 0.2 cm2V−1s−1. [ABSTRACT FROM AUTHOR]

In this study, for the use as a transparent electrode in flexible dye-sensitized solar cells (DSSCs), the indium zinc oxide (IZO) thin films on unheated poly(ethylene naphthalate) (PEN) substrate in pure argon ambient by radio frequency (RF) magnetron sputtering method have been prepared, and their characteristics with respect to RF power were investigated. It has been found that the IZO films on PEN show a dense amorphous structure and the surface microstructure of the films is hardly sensitive to the RF power. The electrical and optical properties of RF magnetron sputtered IZO thin films on PEN are strongly influenced by RF power. At a RF power of 60 W, it is obtained the IZO thin film with the sheet resistance of about 7.65 Ω/sq. and optical transmittance of about 80% at 550 nm wavelength, resulting in the highest value for figure of merit. The flexible DSSC device embedded with the transparent IZO electrode deposited at 60 W shows the high power conversion efficiency, which is the value of 4.7% under simulated air mass 1.5 irradiation. [ABSTRACT FROM AUTHOR]

In the present study, the effect of iodine concentration on the photovoltaic properties of dye sensitized solar cells (DSSCs) based on the quasi-solid state electrolyte has been investigated. The electron transport properties and interfacial recombination kinetics have been evaluated by electrochemical impedance spectroscopy (EIS). It is found that increasing the concentration of iodine decreases the open-circuit voltage (Voc) whereas short circuit current density (Jsc) and fill factor (FF) shows improvement. The increment in Jsc for 0.05 M I2concentration is ascribed to the decreased charge transfer resistance value obtained by EIS analysis. In addition increasing the concentration of I2decreases the Voc which is attributed to the increased recombination with tri-iodide ions (I3−) as verified from the EIS analysis under dark condition. [ABSTRACT FROM AUTHOR]

Well-aligned ZnO nanorod arrays were prepared at different deposition times to determine the correlation between the length of the photoelectrodes and the photovoltaic performance in dye-sensitized solar cells. The length of the ZnO photoelectrode was controlled to 1.2, 2.7 and 4.0 μm by the deposition time. The DSSCs composed of the longer ZnO nanorods showed much better photovoltaic performance due to the enhanced amount of dyes adsorbed and electron injection, as determined by the intrinsic photon-to-current efficiency and electrochemical impedance spectroscopy. The photon-to-current efficiency of the DSSC containing ZnO photoelectrode was considered with the aspect of the length of ZnO nanorods. [ABSTRACT FROM AUTHOR]

Effects of thermal annealing on the structural, electrical and optical properties of transparent semiconducting Zn2SnO4(ZTO) thin films have been investigated. The ZTO thin film with the thickness of about 100 nm is prepared by the RF-magnetron sputtering technique using powder target. The experimental results show that the ZTO films annealed at above 400 °C possess inverse cubic spinel structure with a preferred grain orientation in the (311) direction. The transmittances of the ZTO films are approximately 80% in visible region regardless annealing temperature. The increasing annealing temperature leads to the increase in Hall mobility and electron concentration, resulting in the decrease of resistivity. The optical band gap of the films increases with the increase of annealing temperature. [ABSTRACT FROM AUTHOR]

In this work, the specific influences of atmospheric pressure plasma (APP) treatment on the surface modifications of poly(ethylene terephthalate) (PET) polymeric film have been explored. The APP was generated using dielectric barrier discharge in the ambient of Ar and N2gas mixture. Experimental results of the surface properties are presented for the PET film before and after the APP treatment. The exposure of PET films to APP leads to the roughening surface. Also, the APP-induced modifications are associated with incorporation of polar oxygen and nitrogen containing groups on the PET surface. Due to the changes of chemical composition and topology on the surface by the APP treatment, the contact angle of distilled water on the surface becomes smaller, resulting in higher surface wettability. [ABSTRACT FROM AUTHOR]

We prepared the ionic dyes and investigated their electrochemical properties and photosensitizing performances in the quasi-solid state dye-sensitized solar cells (QS-DSSCs). The LUMO energy level of ionic dye with carbazole moiety is higher than that of the dyes with phenothiazine and triphenylamine chromophore, resulting in highest power conversion efficiency (PCE) in the QD-DSSC. Compared with Ru-complex sensitizer, the ionic dyes showed relatively low photovoltaic performance in the QS-DSSCs, originating in lower LUMO energy level. The effect of Li+ion in the quasi-solid state electrolyte on the photovoltaic characteristics of QS-DSSCs was investigated in order to confirm the correlation between the conduction band of TiO2electrode and LUMO energy level of photosensitizers. The conduction band of TiO2electrode could be reduced by adding the Li+ion in the electrolyte, attributing for the enlargement of PCE value in the QS-DSSC. [ABSTRACT FROM AUTHOR]

We report an experimental optimization of the cleaning process in the fabrication of flexible polymer solar cells using an indium tin oxide (ITO) coated poly(ethylene naphthalate) (PEN) substrate. The effects of the solubility parameters of the cleaning solvents on the occurrence of ITO cracks have been systematically investigated. The experimental results showed that the ITO cracks caused during the ultrasonic cleaning process were mainly affected by differences between the solubility parameters of the solvent and that of the PEN substrate, not by direct interaction between the solvent and the ITO layer. Our results provide a simple method for reducing ITO cracks during wet cleaning processes by selecting solvents with solubility parameters which differ significantly from those of the flexible substrates. [ABSTRACT FROM PUBLISHER]

We prepared novel organic photo-sensitizers based on a carbazole framework containing various acceptors with thiophene bridge units in the chromophore for the application to dye-sensitized solar cell (DSSC). Furthermore, organic dyes without bridge in the chromophore also synthesized to investigate the correlation between conjugation lengths and photon-to-current efficiency (PCE). Compared to non-bridged dyes, the DSSCs device containing multi-anchoring dyes with thiophene bridge exhibited much higher PCEs, resulting from efficient electron extraction pathways, higher molar extinction coefficients, and better light absorption in longer wavelengths. [ABSTRACT FROM PUBLISHER]

For improving the thermal conductivity of carbon nanotube-epoxy composite, we have performed the chemical surface pre-treatment of multi-walled carbon nanotube (MWCNT) and investigated its effects. In the experiments, the mixtures of nitric and sulfuric acid have been used as the surface modifier for MWCNT. The chemical surface pre-treatments by acid mixtures lead to the production of oxygen-containing functional groups on the surfaces of MWCNT. Also, the surface area and pore volume of acid-treated MWCNT (AT-MWCNT) become larger than those of pristine MWCNT. By actions of the chemical pre-treatment, AT-MWCNT is well dispersed and forms the heat flow network in epoxy matrix, resulting in higher thermal conductivity of carbon nanotube-epoxy composite. [ABSTRACT FROM PUBLISHER]

For an application to the channel layer in flexible transparent thin-film transistor (TFT), we have prepared the amorphous indium gallium zinc oxide (a-InGaZnO) thin films on unheated polyethylene naphthalate (PEN) substrate by facing target sputtering. Two types of a-InGaZnO TFT design, one top gate configuration and the other bottom gate, have been fabricated for comparison with each other. The experimental results reveal that the top gate a-InGaZnO TFT is shown to be superior TFT performances, compared with bottom-gate structure. As a result, the top gate a-InGaZnO TFTs operate in depletion mode with a threshold voltage of −0.5 V, a mobility of 6.0 cm2/Vs, an on-off ratio of >106, and a sub-threshold slope of 0.95 V/decade. In addition, the optical transmittance of about 74% at 550nm wavelength is represented for the top gate a-InGaZnO TFT on PEN. [ABSTRACT FROM PUBLISHER]

Since the molecular structures based on donor-π-acceptor dye shows good optical absorption and emission properties by push-pull chromophore system, donor-π-acceptor dyes have been intensively studied as functional key materials. In this study, the new donor-π acceptor dyes were designed, synthesized and characterized. The absorption and fluorescence emission spectra of these dyes, being related with chromic color changes, were determined with the several solvents of widely different polarities. The electron energy states of dyes were also characterized by theoretical calculations. [ABSTRACT FROM PUBLISHER]

We have investigated the effects of an inductively coupled plasma (ICP) treatment using Ar and N2 gas mixtures on the surfaces properties of poly(ethylene terephthalate) (PET) films. The Ar/N2 ICP-modified PET surfaces have been characterized by X-ray photoelectron spectroscopy, atomic force microscopy, and contact angle measurements. The experimental results reveal that ICP treatment with Ar/N2 mixture gas induces physical and chemical changes of PET surface, showing the increases of surface roughness and hydrophilic functional groups in the surface Also, the contact angle of distilled water on the surface becomes smaller with increasing RF power applied to ICP antenna, resulting in higher adhesion energy. [ABSTRACT FROM AUTHOR]

We developed organic dye containing the multi-chromophororic system in a molecule by connecting two individual chromophores with alkyl chain directly forusein DSSCs. Each of chromophore contains phenothiazine moiety as an electron donor and various electron acceptor/anchor to identify the effects of the number of electron acceptor and the kind of electron acceptor on the performance of DSSCs. The molecular structure having multi-chromophoric system containing cyanoacrylic acid moieties provided about 10% higher Jsc value than their counter parts of single-chromophore type. [ABSTRACT FROM AUTHOR]

For the application to transparent electrode in flexible dye-sensitized solar cells (DSSCs), Zn-doped In2O3 (In2O3:Zn) thin films have been fabricated on polyethylene naphthalate (PEN) substrate by the radio frequency facing target sputtering method, and their characteristics have been investigated as a function of deposition pressure. X-ray diffraction study reveal that the structure of In2O3:Zn thin films is amorphous nature. The film morphology is slightly sensitive to the deposition pressure. At the sputtering pressure of 0.40 Pa, In2O3:Zn thin film on PEN exhibits a sheet resistance of about 12.4 Ω/□ and average transmittance of about 85% at 550 nm wavelength, resulting in the highest value for figure of merit. The flexible DSSC device with the In2O3:Zn electrode shows the efficient solar-to-electrical power conversion efficiency (η), which is the maximum η value of 4.6% under simulated air mass 1.5 irradiation (100 mW/cm2). [ABSTRACT FROM AUTHOR]

In this work, we have designed and synthesized a particular colorimetric dye sensor for the detection of heavy metal ions. Dye sensor, namely 4-hydroxy-3-(fluoro-phenyl-thiourea-N'-nitrilo-methylidynyl)-azobenzene was synthesized using 5-phenyldiazenyl salicylaldehyde and 4-phenylthiosemi carbazide. The dye sensor has promising properties which are applicable to detect and recognize the presence of heavy metal ions with colorimetric changing functions. Electron rich part in dye sensor structure, which can be utilized as metal binding unit, such as NH, N, S and OH (atom/group) provides the functions to coordinate metal ions. This metal ion detection property was determined by using UV-Vis absorption, 1H-NMR peak shift and computational calculation method analysis. Furthermore, we estimated the electrochemical properties of dye sensor by using cyclicvoltammetry. In addition, the formation type of metal binding complex was determined by Job's plot measurements. [ABSTRACT FROM AUTHOR]

Dye-sensitized solar cells (DSSCs) were fabricated using graphene-coated Al2O3 (GCA)-TiO2 nanocomposite electrodes. The GCA-TiO2 pastes were prepared by simply blending the GCA particles with TiO2 particles without any complex treatments. The DSSC with 1 wt.% GCA-TiO2 exhibited much better overall energy conversion efficiency, when compared to the DSSCs with TiO2 alone and with carbon nanotube-TiO2. It can be attributed to efficient electron transport through the GCA-TiO2 to the transparent conducting oxide, resulting in significantly enhanced electron lifetime. [ABSTRACT FROM AUTHOR]

Graphene-coated Al2O3 (GCA)-TiO2 nanocomposite photoanodes were fabricated by dispersing the GCA (1, 3, and 5 wt.%) and TiO2 nanoparticles. Photoelectrochemical (PEC) responses under the white light illumination were significantly enhanced with the increase of the GCA content and all of the GCA-TiO2 films exhibited much better PEC responses than the electrode prepared from the TiO2 alone. The significantly improved PEC response of the GCA-TiO2 can be attributed to the enhanced electron transport. [ABSTRACT FROM AUTHOR]

We have fabricated the transparent semiconducting indium zinc tin oxide (IZTO) thin films on polymeric substrates at room temperature by RF-magnetron sputtering method, and investigated their wet chemical etching behavior in HCl solution. The study has revealed that the control of O2 flow rate during deposition attribute to the variation of resistivity for IZTO films, resulting in the conductor-semiconductor conductivity transition. The increasing etchant molarity and temperature of etching solution lead to the increase in etching rate of IZTO films according to the chemical dissolution reaction. As a result, the IZTO active channel is defined successfully, suggesting sufficient possibility for the application to flexible transparent thin film transistors. [ABSTRACT FROM AUTHOR]

In this study, the surfaces of poly(ethylene terephthalate) (PET) films have been modified by high density inductively coupled plasma (ICP) using the oxygen gas. The ICP-modified PET surfaces have been characterized by atomic force microscopy, X-ray photoelectron spectroscopy, and contact angle measurement as a function of RF power applied to ICP antenna. The experimental results reveal that the exposure of PET films to ICP leads to the roughening surface and the increase of oxygen containing-functional groups such as O-C=O and C-O at the surface. Also, the contact angle of distilled water on the surface decreases with increasing RF power, resulting in the increase in the adhesion energy. [ABSTRACT FROM AUTHOR]

Organic photo-sensitizers containing multi-acceptors in a chromophore have been synthesized and characterized for the application of dye-sensitized solar cell (DSSC). In this study, we have used intramolecular push-pull system containing triphenylamine as the electron donor with different number of cyanoacetic acid moieties as electron acceptor/anchoring groups in a chromophore. The experimental results have revealed that when the induced electron acceptor increases, the larger amounts of dyes are adsorbed on the TiO2 surface in DSSC, resulting in the increase of short circuit photocurrent density. Our results suggest that the organic dyes with multi-electron acceptors moieties are promising for getting higher solar-to-electricity conversion efficiencies in DSSC. [ABSTRACT FROM AUTHOR]

Atomic force microscope (AFM) lithography based on localized current injection was carried out for fabricating nanostructures of metal oxide on tantalum (Ta). Fabricated nanopatterns of tantalum oxide (Ta 2 O 5 ) were selectively etched by magnetically enhanced inductively coupled plasma (MEICP) etching system. Nanopatterns of Ta with feature size in the range of a few tens-hundreds nm were successfully fabricated. [ABSTRACT FROM AUTHOR]