Showing papers on "Indium tin oxide published in 2004"

Transparent, Conductive Carbon Nanotube Films

Abstract: We describe a simple process for the fabrication of ultrathin, transparent, optically homogeneous, electrically conducting films of pure single-walled carbon nanotubes and the transfer of those films to various substrates. For equivalent sheet resistance, the films exhibit optical transmittance comparable to that of commercial indium tin oxide in the visible spectrum, but far superior transmittance in the technologically relevant 2- to 5-micrometer infrared spectral band. These characteristics indicate broad applicability of the films for electrical coupling in photonic devices. In an example application, the films are used to construct an electric field-activated optical modulator, which constitutes an optical analog to the nanotube-based field effect transistor.

Effect of Temperature and Illumination on the Electrical Characteristics of Polymer-Fullerene Bulk-Heterojunction Solar Cells

Abstract: The current-voltage characteristics of ITO/PEDOT:PSS/OC1C10-PPV:PCBM/Al solar cells were measured in the temperature range 125-320 K under variable illumination, between 0.03 and 100 mW cm(-2) (white light), with the aim of determining the efficiency-limiting mechanism(s) in these devices, and the temperature and/or illumination range(s) in which these devices demonstrate optimal performance. (ITO: indium tin oxide; PEDOT:PSS: poly(styrene sulfonate)-doped poly(ethylene dioxythiophene); OC1C10-PPV: poly[2-methoxy-5-(3,7-dimethyl octyloxy)-1,4-phenylene vinylene]; PCBM: phenyl-C-61 butyric acid methyl ester.) The short-circuit current density and the fill factor grow monotonically with temperature until 320 K. This is indicative of a thermally activated transport of photogenerated charge carriers, influenced by recombination with shallow traps. A gradual increase of the open-circuit voltage to 0.91 V was observed upon cooling the devices down to 125 K. This fits the picture in which the open-circuit voltage is not limited by the work-function difference of electrode materials used. The overall effect of temperature on solar-cell parameters results in a positive temperature coefficient of the power conversion efficiency, which is 1.9% at T = 320 K and 100 mW cm(-2) (2.5% at 0.7 mW cm(-2)). The almost-linear variation of the short-circuit current density with light intensity confirms that the internal recombination losses are predominantly of monomolecular type under short-circuit conditions. We present evidence that the efficiency of this type of solar cell is limited by a light-dependent shunt resistance. Furthermore, the electronic transport properties of the absorber materials, e.g., low effective charge-carrier mobility with a strong temperature dependence, limit the photogenerated current due to a high series resistance, therefore the active layer thickness must be kept low, which results in low absorption for this particular composite absorber.

Template Synthesis and Photocatalytic Properties of Porous Metal Oxide Spheres Formed by Nanoparticle Infiltration

Abstract: Porous polymeric beads have been used as templates for the fabrication of porous metal oxide spheres. The beads were soaked in sols of titanium dioxide, zirconium dioxide, iron oxide, aluminum oxide, indium oxide, tin oxide, and cerium oxide. Successful infiltration and templating was obtained for titania, zirconia, tin oxide, and ceria giving monodisperse, nonaggregated spheres with a porous surface and inner structure. The use of iron and aluminum oxide sols resulted in cracked spheres with excess oxide material on the sphere surfaces, and in the case of indium oxide, broken, hollow, shell-like structures were produced. Combining the iron, aluminum, or indium oxide sols with the titania sol, at a 1:1 weight ratio, and impregnating the template produced inorganic spheres containing the two metal oxides. The photocatalytic properties of the titania and mixed titania/indium oxide spheres were studied by monitoring the decomposition of 2-chlorophenol as a function of time and solution pH. Both the porous ti...

Organic small molecule solar cells with a homogeneously mixed copper phthalocyanine: C60 active layer

Abstract: An efficient organic solar cell with a vacuum codeposited donor–acceptor copper phthalocyanine (CuPc):C60 mixed layer is described. A device with a structure of indium tin oxide/330 A CuPc:C60(1:1)/100 A C60/75 A 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline/Ag has a series resistance of only RS=0.25 Ω cm2, resulting in a current density of ∼1 A/cm2 at a forward bias of +1 V, and a rectification ratio of 106 at ±1 V. Under simulated solar illumination, the short circuit current density increases linearly with light intensity up to 2.4 suns. The maximum power conversion efficiency is ηP=(3.6±0.2)% at 0.3 suns (AM1.5G simulated solar spectrum) and ηP=(3.5±0.2)% at 1 sun. Although the fill factor decreases with increasing intensity, a power efficiency as high as ηP=(3.3±0.2)% is observed at 2.4 suns intensity.

Photoelectrochemical Behavior of Electrodeposited CuO and Cu2 O Thin Films on Conducting Substrates

Abstract: Cuprous oxide has been prepared by the photoelectrochemical reduction of a CuO film formed on a conducting substrate by the anodic deposition from an alkaline solution of a Cu(II)-amino acid complex Both copper oxide films thus prepared are found to be typical p-type semiconductors The onset of the cathodic photocurrent due to the reduction of O 2 on CuO/ITO (ITO, indium tin oxide) and Cu 2 O/ITO electrodes give positive shifts of about 02 and 003 V, respectively, from the dark current rises Optical bandgap energies of CuO films depend on the amino acids used, 156 (glycine), 140 (alanine), 138 (isoleucine), 138 eV (valine), and the value of Eg for the Cu 2 O film is 217 eV The relationship between the flatband potential (V FB ) and the pH for CuO and Cu 2 O films are both linear with the slope of about -60 mV/pH in agreement with the Nernstian expression for the V FB of a semiconductor

Optical-interference type display panel and method for making the same

Abstract: An optical-interference type display panel and a method for making the same are disclosed, wherein the display panel has a substrate on which multiple first conductive optical film stacks, supporting layers and multiple second conductive optical film stacks are formed. The substrate further has a plurality of connecting pads consisting of a transparent conductive film of the first conductive optical film stacks. Since the transparent conductive film is made of indium tin oxide, these connecting pads have the excellent anti-oxidation ability at their surface.

Hybrid nanocrystalline TiO2 solar cells with a fluorene–thiophene copolymer as a sensitizer and hole conductor

Abstract: We report the effects of layer thickness, interface morphology, top contact, and polymer–metal combination on the performance of photovoltaic devices consisting of a fluorene–bithiophene copolymer and nanocrystalline TiO2. Efficient photoinduced charge transfer is observed in this system, while charge recombination is relatively slow (∼100 μs–10 ms). External quantum efficiencies of 13% and monochromatic power conversion efficiencies of 1.4% at a wavelength of 440 nm are achieved in the best device reported here. The device produced an open-circuit voltage of 0.92 V, short-circuit current density of about 400 μA cm−2, and a fill factor of 0.44 under simulated air mass 1.5 illumination. We find that the short-circuit current density and the fill factor increase with decreasing polymer thickness. We propose that the performance of the indium tin oxide/TiO2/polymer/metal devices is limited by the energy step at the polymer/metal interface and we investigate this situation using an alternative fluorene-based ...

Defect structure studies of bulk and nano-indium-tin oxide

Abstract: The defect structure of bulk and nano-indium-tin oxide was investigated by a combination of experimental techniques, including high-resolution synchrotron x-ray diffraction, extended x-ray absorption fine structure, and time-of-flight neutron diffraction on powder specimens. The structural results include atomic positions, cation distributions, and oxygen interstitial populations for oxidized and reduced materials. These structural parameters were correlated with theoretical calculations and in situ electrical conductivity and thermopower measurements as well as existing defect models, with special reference to the model of Frank and Kostlin [G. Frank and H. Kostlin, Appl. Phys. A 27, 197 (1982)].

White electroluminescence from polyfluorene chemically doped with 1,8-napthalimide moieties

Abstract: An efficient white light-emitting polymer was developed with blue polyfluorene (PFO) chemically doped with orange fluorescent 1, 8-naphthalimide moieties. The emission spectrum can be easily tuned by varying the content of 1, 8-naphthalimide moieties. A white polymeric light-emitting diode (WPLED) with a structure of indium tin oxide (ITO)/the complex of (3,4-ethylenedioxythiophene) and polystyrene sulfonic acid (PEDOT)/polymer∕Ca∕Al showed a current efficiency of 5.3cd∕A and a power efficiency of 2.8Lm∕W at 6V with the Commission Internationale de L'Eclairage (CIE) coordinates at (0.25,0.35). Moreover, the WPLED from the copolymer showed a very stable white light emission at different driving voltage and brightness. The CIE coordinates of the WPLED were (0.25, 0.35), (0.26, O.36), and (0.26, 0.36) under driving voltages of 6, 8, and 10V, corresponding to the brightness of 82, 3555, and 7530cd∕m2, respectively. This approach for realization of white light emission is promising over the polymer blending sy...

FTO/ITO double-layered transparent conductive oxide for dye-sensitized solar cells

Abstract: New transparent conductive oxide (TCO) films, fluorine-doped tin oxide (FTO) films coated on indium–tin oxide (ITO) films, were developed for dye-sensitized solar cells (DSC). These transparent conductive films were prepared by a spray pyrolysis deposition (SPD) method at a substrate temperature of 350 °C in ITO and 400 °C in FTO. For ITO deposition, an ethanol solution of indium(III) chloride, InCl 3 ·4H 2 O, and tin(II) chloride, SnCl 2 ·2H 2 O (Sn/(In+Sn), 5 at.%) was sprayed on a TEMPAX #8330 glass substrate (100×100×1.1 mm 3 ). After the deposition of ITO, FTO films were consecutively deposited for protecting oxidation of ITO films. FTO deposition was carried out by an ethanol solution of tin(IV) chloride, SnCl 4 ·5H 2 O within the saturated water solution of NH 4 F. These films achieved the lowest resistivity of 1.4×10 −4 Ω cm and the optical transmittance of more than 80% in the visible range of the spectrum. The electrical resistance of these films increased by less than 10% even though exposed to high temperatures of 300–600 °C for 1 h in the air. The DSC composed of the films were fabricated to confirm their availability. The films were of large size, 100×100 mm 2 . The DSC were made by conventional method. As a result, energy conversion efficiency of η =3.7% was obtained.

Effect of ultraviolet-ozone treatment of indium-tin-oxide on electrical properties of organic light emitting diodes

Abstract: We report the change of surface electronic structure of indium–tin–oxide (ITO) as a function of ultraviolet (UV)–ozone treatment time. The voltage of organic light emitting diodes at a current density of 100 mA/cm2 was reduced as the surface treatment time using UV–ozone was lengthened. X-ray photoelectron spectroscopy results showed that the relative concentration of carbon atoms decreased, but oxygen concentration increased relatively with UV–ozone treatment. This led to the increase in the ITO work function via the reduction of operation voltage.

Conjugated Polymers Based on Phenothiazine and Fluorene in Light-Emitting Diodes and Field Effect Transistors

Abstract: Poly[10-(2‘-ethylhexyl)-phenothiazine-3,7-diyl] (PPTZ), poly[9,9-bis(2‘-ethylhexyl)fluorene-2,7-diyl] (PBEHF), and their random copolymers, poly(BEHF-co-PTZ), were synthesized through Ni(0)-mediated polymerization. Light-emitting devices were fabricated using these polymers in an ITO (indium tin oxide)/PEDOT:PSS/polymer/Ca/Al configuration. Each EL device constructed with a poly(BEHF-co-PTZ) copolymer exhibited significantly enhanced efficiency and brightness compared to devices constructed from the PPTZ and PBEHF homopolymers. The EL device constructed with poly(88BEHF-co-12PTZ) exhibited the highest power efficiency and brightness (4200 cd/m2 and 2.08 cd/A respectively). This enhanced efficiency of the copolymer devices results from their improved hole injection and more efficient charge carrier balance, which arise due to the HOMO levels (∼5.4 eV) of the poly(BEHF-co-PTZ) copolymers, which are lower than that of the PBEHF homopolymer (∼5.8 eV). An organic field effect transistor was also fabricated usi...

Mechanism for the increase of indium-tin-oxide work function by O2 inductively coupled plasma treatment

Abstract: The effects of O2 inductively coupled plasma (ICP) treatment on the chemical composition and work function of indium-tin-oxide (ITO) surface were investigated. Synchrotron radiation photoemission spectroscopy showed that the O2 ICP treatment resulted in the increase of the ITO work function by 0.8 eV. Incorporation of oxygen atoms near the ITO surface during the ICP treatment induced a peroxidic ITO surface, increasing the work function. The enhanced oxidation of a thin Ni overlayer on the O2-ICP-treated sample suggests that preventing the migration of oxygen atoms into the active region of organic light-emitting diodes is important for improving device lifetime.

High-temperature ferromagnetism in manganese-doped indium–tin oxide films

Abstract: High-temperature ferromagnetism is demonstrated in Mn-doped indium–tin oxide (ITO) films deposited using reactive thermal evaporation. These films were grown on sapphire (0001), Si∕SiO2 as well as Si (100) substrates with the highest magnetic moment observed around 0.8μB∕Mn in 5% Mn-doped ITO films. The electrical conduction is n type and the carrier concentration is ∼2.5×1019cm−3 for 5% Mn doping. An anomalous Hall effect is observed in magnetotransport measurements, showing that the charge carriers are spin polarized, revealing the magnetic interaction between itinerant electrons and localized Mn spins. The carrier concentration can be varied independent of the Mn concentration in this transparent ferromagnetic semiconductor for its easy integration into magneto-optoelectronic devices.

Aqueous latex/ceramic nanoparticle dispersions: colloidal stability and coating properties.

Abstract: The effect of pH on the colloidal stability of aqueous dispersions containing antimony-doped tin oxide (ATO) or indium tin oxide (ITO) nanoparticles and poly(vinyl acetate-acrylic) copolymer (PVAc-co-acrylic) latex particles was investigated using experimental observations and Derjiaguin, Landau, Verwey and Overbeek (DLVO) theory. The microstructure, electrical properties and optical properties of composite coatings prepared from various dispersions were also studied. Zeta potential measurements revealed that the isoelectric point (IEP) of ATO nanoparticles was below pH 2.0, that of ITO nanoparticles was at pH ∼ 6.0 and that of PVAc-co-acrylic latex was at pH ∼ 2.0. ATO/PVAc-co-acrylic dispersions prepared at pH 3 were stable, but those prepared at pH 1.5 formed aggregates, which settled quickly with time. DLVO theory predictions are in accord with these results. Stable ITO/PVAc-co-acrylic dispersions are obtained at a pH of 3.0 and 11.0, but dispersions are not stable at a pH of 6.0, the IEP of ITO. At a pH of 3.0, DLVO results predict attraction between ITO particles and latex particles. Dispersion pH affected the microstructures and properties of ATO (or ITO)/PVAc-co-acrylic coatings. Suspensions that formed aggregates produced coatings with lower percolation thresholds and lower transparencies than those produced from stable suspensions.

High-mobility, sputtered films of indium oxide doped with molybdenum

Abstract: Thin films of molybdenum-doped indium oxide, an n-type transparent conducting oxide, were deposited on glass substrates by a large-area deposition technique, radio-frequency magnetron sputtering, and their electrical properties were examined. Molybdenum content was varied from 1 to 4 wt%, and the highest mobility achieved was 83 cm2 V−1 s−1 at a carrier concentration of 3.0×1020 cm−3 without any postdeposition treatment for one of the films made from the target with 2 wt% Mo. Temperature-dependent Hall analysis indicated that this high mobility is limited by phonon scattering, whereas the method of four coefficients analysis showed that the conduction band is parabolic.

Organic el element

Abstract: PROBLEM TO BE SOLVED: To eliminate the inconvenience caused by formation of a transparent electrode of metal oxide by eliminating the necessity to form the transparent electrode of the metal oxide of ITO or the like requiring a high temperature annealing to give a harmful effect on an organic layer at a negative electrode in an organic EL element of a top emission type. SOLUTION: As for the organic EL element 10, a positive electrode 12, the organic layer 13 including the light-emitting layer 17, and the negative electrode 14 are consecutively laminated on the substrate 11, and light emission of the light-emitting layer 17 is taken out from the opposite side of the substrate 11. The negative electrode 14 is constituted of an electron injection layer 18 transparently formed by calcium of alkaline earth metal, and a covered layer 19 which covers the other side face of a face opposed to the organic layer 13 of the electron injection layer 18, and which is transparently formed by the metal (silver) to play a role to protect the electron injection layer 18. Then, this is formed so that resistance value of the negative electrode 14 becomes the resistance value or less of the transparent electrode made of the ITO (indium tin oxide) which is formed in the same shape as the negative electrode 14 and at the same position. COPYRIGHT: (C)2004,JPO&NCIPI

CdTe solar cell in a novel configuration

Abstract: Polycrystalline thin-film CdTe/CdS solar cells have been developed in a configuration in which a transparent conducting layer of indium tin oxide (ITO) has been used for the first time as a back electrical contact on p-CdTe. Solar cells of 7·9% efficiency were developed on SnOx:F-coated glass substrates with a low-temperature (<450°C) high-vacuum evaporation method. After the CdCl2 annealing treatment of the CdTe/CdS stack, a bromine methanol solution was used for etching the CdTe surface prior to the ITO deposition. The unique features of this solar cell with both front and back contacts being transparent and conducting are that the cell can be illuminated from either or both sides simultaneously like a ‘bi-facial’ cell, and it can be used in tandem solar cells. The solar cells with transparent conducting oxide back contact show long-term stable performance under accelerated test conditions. Copyright © 2004 John Wiley & Sons, Ltd.

Chemical and thermal treatment of PEDOT:PSS thin films for use in organic light emitting diodes

Abstract: We have investigated the effects of thermal and chemical treatments on the optical and electrical properties of poly(3,4-ethylenedioxythiophene)/poly(4-styrenesulfonate) (PEDOT:PSS), a doped polymer widely used as a buffer layer to increase the stability and the charge injection in organic light emitting diodes (OLEDs). Thermal treatments carried out on thin films in the temperature range of 120–250 °C did not strongly modify the structure of the polymer as proved by Raman and infrared measurements while their resistivity increased with increasing temperature. Chemical treatment of different durations by 10% hydrochloric acid showed a strong increase in the conductivity but the structure of the polymer was generally preserved. X-Ray photoelectron spectroscopic analysis of the treated films indicated a partial change of their composition, which favoured the electronic conduction upon acid treatments. When using PEDOT:PSS as a buffer layer on indium tin oxide substrates, a diffusion of indium was observed in the as-deposited polymer films. A thermal treatment most probably increased the diffusion and an acid treatment removed the diffused metal. A combination of these treatments appears to be the best way to improve the quality of the films for their use in OLEDs.

Influence of the hole injection layer on the luminescent performanceof organic light-emitting diodes

Abstract: We investigate the influence of the hole injection layer (HIL) on the performance of vapor-deposited tris-(8-hydroxyquinoline) aluminum-based organic light-emitting diodes. Four different HIL materials were used: 4,4′, 4″-tris{N,(3-methylphenyl)-N-phenylamino}-triphenylamine) (m-MTDATA), 4,4′, 4″-tris{N,-(2-naphthyl)-N-phenylamino}-triphenylamine, copper phthalocyanine, and oxotitanium phthalocyanine. In all cases, Alq3 acts as the emitting layer as well as electron-transporting layers. Evidence showed that m-MTDATA exhibits a dense film structure and fine surface morphology, leading to easier hole migration at the indium tin oxide/m-MTDATA and m-MTDATA/hole-transport layer junctions. It also possesses a shallow bulk trap level, providing more detrapping holes from the bulk trap states to highest occupied molecular orbital states for transporting in m-MTDATA. We suggest that these are the main contributing factors to the superior current density–voltage and luminance-voltage performance of this device.