Showing papers on "Indium tin oxide published in 2003"

Efficient Methano[70]fullerene/MDMO‐PPV Bulk Heterojunction Photovoltaic Cells

Abstract: The authors report on a bulk heterojunction photovoltaic cell in which an isomeric mixt. of C70 derivs. is used as an electron acceptor in combination with poly[2-methoxy-5-(3',7'-dimethyloctyloxy)-p-phenylenevinylene] (MDMO-PPV). [70]PCBM, in this case a mixt. of isomeric [6,6]-phenyl- C71- butyric acid Me esters, is the higher fullerene analog of [60]PCBM, and displays improved light absorption in the visible region. Consequently, when this material is used in a photovoltaic cell instead of [60]PCBM, 50 % higher current densities are obtained. The synthesis of [70]PCBM was performed and the monoadduct fraction was isolated from the higher adducts and unreacted C70 by column chromatog. 1H and 13C NMR were performed on the [70]PCBM, as was UV/VIS absorption in toluene soln. Spin-coated composite films were made with MDMO-PPV, and photoinduced absorption measurements give direct spectral evidence for photoinduced charge sepn., not only upon excitation of the polymer, but also after selective excitation of [70]PCBM at 630 nm. Time-resolved photoluminescence measurements ater excitation at 488 mn, obsd. at 570 nm indicate near quant. charge generation upon polymer excitation, but at 720 nm this quenching depends on the processing solvent, chlorobenzene, o-dichlorobenzene, vs. o-xylene. At. force microscopy reveals a difference in film roughness dependent upon spinning solvent. Photovoltaic cells were made by sandwiching the photoactive mixt., consisting of [70]PCBM and MDMO-PPV in a 4.6:1 (wt./wt.) ratio, between charge-selective electrodes of ITO/PEDOT:PSS (ITO: indium tin oxide; PEDOT: poly(3,4-ethylenedioxythiophene); PSS: poly(styrenesulfonate)) and LiF/Al. The external quantum efficiency (EQE) from a 12V, 50 W halogen lamp varied from a max. of 0.2 for chlorobenzene- processed films, to 0.68 for the o-dichlorobenzene- processed films, compared to 0.5 for equiv. films made with [60]PCBM. Photovoltage-photocurrent behavior were also measured. Overall power conversion efficiency was about 3.0%. [on SciFinder (R)]

Nanostructured Electrochemical Sensor Based on Dense Gold Nanoparticle Films

Abstract: Polyelectrolyte (PE)/gold nanoparticle hybrid films that can be utilized as efficient electrochemical sensors were prepared by infiltrating 4-(dimethylamino)pyridine-stabilized gold nanoparticles (DMAP−AuNP) into PE multilayers preassembled on indium tin oxide (ITO) electrodes. Quartz crystal microgravimetry (QCM) and UV−vis spectroscopy showed that via this infiltration method, composite films with densely packed DMAP−AuNP were obtained. Electrochemical experiments revealed that the presence of gold nanoparticles in the PE multilayers could significantly improve the electron-transfer characteristics of the films, which showed high electrocatalytic activity to the oxidation of nitric oxide (NO). The sensitivity of the composite films for measuring NO could be further tailored by controlling the gold nanoparticle loading in the film.

Fabrication and photoresponse of a pn-heterojunction diode composed of transparent oxide semiconductors, p-NiO and n-ZnO

Abstract: Transparent trilayered oxide films of ZnO/NiO/indium tin oxide were heteroepitaxially grown on a YSZ (111) substrate by pulsed-laser deposition combined with a solid-phase-epitaxy technique, and were processed to fabricate a p-NiO/n-ZnO diode. The diode exhibited a clear rectifying I–V characteristic with an ideality factor of ∼2 and a forward threshold voltage of ∼1 V. Although the photoresponsivity was fairly weak at the zero-bias voltage, it was enhanced up to ∼0.3 A W−1 through the application of a reverse bias of −6 V under the irradiation of 360 nm light, a value comparable to that of commercial devices.

Indium tin oxide (ITO) thin film gas sensor for detection of methanol at room temperature

Abstract: Thin films of indium tin oxide (In2O3+SnO2) (ITO) were grown on alumina substrate using the direct evaporation method. The sensing characteristics of these films to methanol vapors were studied at room temperature. The effects of different concentrations of tin oxide in indium oxide and film thickness on sensitivity were studied. The effects of thin layers of noble metals—Au, Ag, Pt and Cu on top of ITO films were studied. A novel approach of stimulated recrystallization of ITO film by depositing ITO film over ultra thin layer of Cu stimulator was used to improve the sensitivity, selectivity and minimum detection limit of methanol sensors operating at room temperature.

Fully depleted, back-illuminated charge-coupled devices fabricated on high-resistivity silicon

Abstract: Charge-coupled devices (CCDs) have been fabricated on high-resistivity, n-type silicon. The resistivity, on the order of 10 000 /spl Omega//spl middot/cm, allows for depletion depths of several hundred micrometers. Fully depleted, back-illuminated operation is achieved by the application of a bias voltage to an ohmic contact on the wafer back side consisting of a thin in situ doped polycrystalline silicon layer capped by indium tin oxide and silicon dioxide. This thin contact allows for a good short-wavelength response, while the relatively large depleted thickness results in a good near-infrared response.

High efficiency transparent organic light emitting devices

Abstract: A highly transparent non-metallic cathode is disclosed that comprises a metal-doped organic electron injection layer that is in direct contact with a transparent non-metallic electron injecting cathode layer, such as indium tin oxide (ITO), wherein the metal-doped organic electron injection layer also functions as an exciton blocking or hole blocking layer. The metal-doped organic electron injection layer is created by diffusing an ultra-thin layer of about 5-10 Å of a highly electropositive metal such as Li throughout the layer. A representative embodiment of the highly transparent non-metallic cathode comprises a layer of ITO, a layer of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP), which acts as an electron injection, exciton blocking, and hole blocking layer, and an ultra-thin layer of lithium, which degenerately dopes the layer of BCP, improving the electron injecting properties of the BCP layer. This cathode is demonstrated for use in an OLED having a transparency of about 90% or higher combined with a device external quantum efficiency of about 1% or higher.

Top-emitting organic light-emitting devices using surface-modified Ag anode

Abstract: A high-reflectivity bottom anode is essential for high-performance top-emitting organic light-emitting devices (OLEDs). Ag has the highest reflectivity for visible light among all metals, yet its electronic properties are not ideal for anodes of OLEDs. In this letter, we report that by inducing a thin silver oxide at the surface of Ag, hole injection from Ag anodes into OLEDs is largely enhanced yet with rather high reflectivity retained. Top-emitting devices using such surface-modified Ag anode show device characteristics competitive with those of a bottom-emitting device using the indium tin oxide anode.

Switching effect in Cu:TCNQ charge transfer-complex thin films by vacuum codeposition

Abstract: We demonstrate the operation of an organic switching device using a uniform poly-crystalline Cu:7, 7, 8, 8-Tetracyanoquinodimethane (TCNQ) charge transfer (CT)-complex thin film that is prepared by vacuum vapor codeposition. Characteristic CT-absorption at λ=600–1200 nm was observed in the complex film in the UV-visible spectrum and the cyano stretching peak in the IR spectrum shifted to a higher (more than 29 cm−1) wave number than that of a pristine TCNQ film, suggesting the formation of a CT-complex in the evaporated thin film. Reproducible electrical switching characteristics were observed in the indium tin oxide/Al/(Al2O3)/Cu:TCNQ/Al structure. The device exhibited a clear threshold from low impedance to high impedance at an applied voltage of 10.0±2.0 V and a reverse phenomenon at a negative bias of −9.5±2.0 V. In this study, we demonstrate that a thin Al2O3 layer between the aluminum (Al) anode and Cu:TCNQ layers creates reproducible switching.

Photoluminescent and electroluminescent properties of Mn-doped ZnS nanocrystals

Abstract: ZnS:Mn nanocrystals with sizes between 3 and 4 nm were synthesized via a competitive reaction chemistry method, where the surface capping organic species (p-thiocresol) is used as an inhibitor of the crystal growth The x-ray diffraction and photoluminescent (PL) properties of ZnS:Mn bulk and nanocrystals were compared A direct current electroluminescent (EL) device having a hybrid organic/inorganic multilayer structure, indium tin oxide/poly(3,4-ethylenedioxythiophene)/poly(styrenesulfonate) (PEDOT-PSS)/PVK/ZnS:Mn NC/Al, was tested In this multilayer EL device structure, the PEDOT-PSS leads to enhanced hole injection, while the poly(N-vinylcarbazole) (PVK) serves as a passivation layer between the PEDOT-PSS and nanocrystal layers Electron–hole recombination was not confined to the ZnS:Mn nanocrystal layer, but also occurred in the PVK layer The result was emission from both the blue-emitting PVK and yellow-emitting ZnS:Mn nanocrystals The EL emission spectrum was dependent upon the voltage, showing an increasing ratio of PVK emission to nanocrystal emission with increased voltage The dependence of PL and EL emissions on Mn concentration (040 to 214 mol %) is also reported

Y 3Al5 O 12 : Ce0.05 Phosphor Coatings on Gallium Nitride for White Light Emitting Diodes

Abstract: White light was obtained by mixing blue light from the emission of a gallium nitride (GaN) chip and yellow light from the fluorescence of a Y 3 Al 5 O 12 :Ce 0.05 yellow phosphor. A uniform coating and an optimized thickness of yellow phosphor layer on a GaN chip were necessary for achieving an efficient white light emitting diode. The phosphor particles were coated on a GaN chip or indium tin oxide by several methods including the slurry method, the settling method, and electrophoretic deposition (EPD). The properties of the phosphor layers prepared by these methods were examined using scanning electron microscope and photoluminescence. The chromaticity of white light was dependent upon the thickness of the phosphor layer. The properties of the phosphor layer prepared by EPD such as packing density, thickness, and uniformity could be more easily controlled than those by the slurry and settling methods. Further high packing density of the EPD could compensate for the typical thick phosphor layer, allowing the thin layer to be fabricated. To overcome the weak adhesion strength of phosphor particles by the EPD, an aqueous solution including poly(vinyl alcohol) + ammonium dichromate was coated on the phosphor layer and cured by exposure to ultraviolet light.

Interstitial pneumonia developed in a worker dealing with particles containing indium-tin oxide

Abstract: The use of indium compounds in the electronics and semiconductor industry has risen sharply from the 1990s, and indium demand increased to a record 335 tons in 2000 in Japan, which was about 5 times that in 1990 . Indium-tin oxide (ITO) is a sintered alloy containing a large portion of indium oxide and a small portion of tin oxide, and is used in the making of thin-film transistor liquid crystal displays (LCDs) for television screens, portable computer screens, cell phone displays and video monitors. Japan was the world’s largest consumer of indium, with three-fourths of it going for ITO coatings in 2000. More than one-half of the world’s indium consumption is for ITO coatings . Due to the increasingly frequent industrial use of ITO, the potential occupational exposure to this material has attracted much attention. Although there are no available data about the potential of ITO to induce lung damage in humans, pulmonary and testicular toxicity was reported recently when ITO was given to hamsters in intermittent intratracheal instillations . This is the first case history to our knowledge describing a man with interstitial pneumonia consistent with the inhalation of ITO particles.

Epitaxial Directional Growth of Indium-Doped Tin Oxide Nanowire Arrays

Abstract: In this report, we show controlled in-situ doping of a single crystalline metal oxide nanowire, using indium-doped tin oxide (In−SnO2) as an example, during a heteroepitaxial growth process. Highly regular and high-density arrays of In−SnO2 nanowires, which demonstrate three- and four-fold growth symmetry, are obtained directly on optical sapphire substrates. Similar synthesis strategies, involving careful selection of desired growth conditions and smart manipulation of favorable thermodynamic properties, could be extended to production of various doped metal oxide nanowires.

Highly reliable nitride-based LEDs with SPS+ITO upper contacts

Abstract: Nitride-based blue light emitting diodes (LEDs) with an n/sup +/-short period superlattice (SPS) tunnel contact layer and an indium tin oxide (ITO) transparent contact were fabricated. Compared with conventional nitride-based LEDs with Ni/Au upper contacts, it was found that we could achieve a 60% increase in electroluminescence (EL) intensity by using ITO upper contacts. However, it was also found that the lifetime of ITO LEDs were much shorter. Furthermore, it was found that we could achieve a longer lifetime and a smaller reverse leakage current (I/sub R/) by the deposition of a SiO/sub 2/ layer on top of the ITO LEDs.

High‐Tg Carbazole Derivatives as Blue‐Emitting Hole‐Transporting Materials for Electroluminescent Devices

Abstract: A series of dicarbazolyl derivatives bridged by various aromatic spacers and decorated with peripheral diarylamines were synthesized using Ullmann and Pd-catalyzed C–N coupling procedures. These derivatives emit blue light in solution. In general, they possess high glass-transition temperatures (Tg > 125 °C) which vary with the bridging segment and methyl substitution on the peripheral amine. Double-layer organic light-emitting devices were successfully fabricated using these molecules as hole-transporting and emitting materials. Devices of the configuration ITO/HTL/TPBI/Mg:Ag (ITO: indium tin oxide; HTL: hole-transporting layer; TPBI: 1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene) display blue emission from the HTL layer. The EL spectra of these devices appear slightly distorted due to the exciplex formation at the interfaces. However, for the devices of the configuration ITO/HTL/Alq3/Mg:Ag (Alq3 = tris(8-hydroxyquinoline)aluminum) a bright green light from the Alq3 layer was observed. This clearly demonstrates the facile hole-transporting property of the materials described here.

Inverted top-emitting organic light-emitting diodes using sputter-deposited anodes

Abstract: We demonstrate vacuum-sublimed topside-emitting inverted organic light-emitting diodes (IOLEDs) employing low-power radio-frequency magnetron sputter-deposited indium tin oxide (ITO) anodes. The device introduces a two-step sputtering sequence to reduce damage incurred by the sputtering process, paired with a buffer- and hole-transporting material Pentacene. Systematic optimization of the organic growth sequence focused on device performance characterized by current and luminous efficiencies, suggest the incorporation of rather thick Pentacene layers. The optimized thickness is obtained as a trade-off between light absorption and protective properties of Pentacene. The optically and electrically undoped organic multilayer devices capped with 90-nm ITO exhibit high current efficiencies of 3.9 cd/A at a raised luminance level of 1.500 cd/m2, combined with luminous efficiencies of 0.7 lm/W. The inverted configuration allows for integration of organic light-emitting diodes (OLEDs) with preferentially used n-c...

Mechanical Stability of Externally Deformed Indium–Tin–Oxide Films on Polymer Substrates

Abstract: In this study, we investigated the basic mechanical properties of indium–tin–oxide (ITO) films on polymer substrates which are exposed to externally inducing bending force. By using the Storney formula including the triple layer structure and bulge tests for measuring the conductive changes of patterned ITO islands as a function of bending curvature, the mechanical stability of ITO films on polymer substrates was intensively investigated. Numerical analyses and experimental results show that externally induced mechanical stress in the films depends on substrate material and its thickness, respectively. Therefore, an organic buffer layer was employed to improve the mechanical stability of ITO films, and then, the effects of the buffer layer were quantified in terms of conductivity–strain variations. As a result, it is found that a buffer layer is also a critical factor for determining the magnitude of mechanical stress and that the layer with Young's modulus lower than the specified value can contribute to relieving the mechanical stress of the films.

Microchip capillary electrophoresis with an integrated indium tin oxide electrode-based electrochemiluminescence detector.

Abstract: This paper describes an indium tin oxide (ITO) electrode-based Ru(bpy)32+ electrochemiluminecence (ECL) detector for a microchip capillary electrophoresis (CE). The microchip CE-ECL system described in this article consists of a poly(dimethylsiloxane) (PDMS) layer containing separation and injection channels and an electrode plate with an ITO electrode fabricated by a photolithographic method. The PDMS layer was reversibly bound to the ITO electrode plate, which greatly simplified the alignment of the separation channel with the working electrode and enhanced the photon-capturing efficiency. In our study, the high separation electric field had no significant influence on the ECL detector, and decouplers for isolating the separation electric field were not needed in the microchip CE-ECL system. The ITO electrodes employed in the experiments displayed good durability and stability in the analytical procedures. Proline was selected to perform the microchip device with a limit of detection of 1.2 μM (S/N = 3)...

Electrochemical and Laser Deposition of Silver for Use in Metal-Enhanced Fluorescence.

Abstract: We describe two reagentless methods of silver deposition for metal-enhanced fluorescence. Silver was deposited on glass positioned between two silver electrodes with a constant current in pure water. Illumination of the glass between the electrodes resulted in localized silver deposition. Alternatively, silver was deposited on an Indium Tin Oxide cathode, with a silver electrode as the anode. Both types of deposited silver produced a 5-18-fold increase in the fluorescence intensity of a nearby fluorophore, indocyanine green (ICG). Additionally, the photostability of ICG was dramatically increased by proximity to the deposited silver. These results suggest the use of silver deposited from pure water for surface-enhanced fluorescence, with potential applications in surface assays and lab-on-a-chip-based technologies, which ideally require highly fluorescent photostable systems.

InGaN/GaN light emitting diodes with Ni/Au, Ni/ITO and ITO p-type contacts

Abstract: The optical and electrical properties of indium tin oxide (ITO)(60 nm), Ni(3.5 nm)/ITO(60 nm) and Ni(5 nm)/Au(5 nm) films were studied. It was found that the normalized transmittance of ITO and Ni/ITO films could reach 98.2% and 86.6% at 470 nm, which was much larger than that of the Ni/Au film. It was also found that both Ni/ITO and Ni/Au could form good ohmic contact on top of p-GaN. In contrast, ITO on p-GaN was electrically poor and non-ohmic. Nitride-based light-emitting diodes (LEDs) with these three p-contact layers were also fabricated. It was found that the LED forward voltage was 3.65, 3.26 and 3.24 V for the LEDs with ITO, Ni/ITO and Ni/Au p-contact layer, respectively. With a 20 mA current injection, it was also found that measured output power was 7.50, 6.59 and 5.26 mW for the LEDs with ITO, Ni/ITO and Ni/Au p-contact layer, respectively. Although the LED with ITO p-contact could provide the largest output intensity, its lifetime was the shortest due to severe heating effect.

Performance of flexible polymeric light-emitting diodes under bending conditions

Abstract: Organic light-emitting diodes were fabricated on a 125-μm-thick polyethylene terephthalate substrate covered with 100 nm indium tin oxide. The luminance–current–voltage performance and the emission spectrum of the devices are investigated in the bent state under mechanical stress at different bending radii. Down to a curvature of 15 mm, no significant decrease in the device performance is found compared to the relaxed state, as well as to conventional devices on glass substrates.