Showing papers on "Indium tin oxide published in 1993"

Efficient light-emitting diodes based on polymers with high electron affinities

Abstract: CONJUGATED polymers have been incorporated as active materials into several kinds of electronic device, such as diodes, transistors1 and light-emitting diodes2. The first polymer light-emitting diodes were based on poly(p-phenylene vinylene) (PPV), which is robust and has a readily processible precursor polymer. Electroluminescence in this material is achieved by injection of electrons into the conduction band and holes into the valence band, which capture one another with emission of visible radiation. Efficient injection of electrons has previously required the use of metal electrodes with low work functions, primarily calcium; but this reactive metal presents problems for device stability. Here we report the fabrication of electroluminescent devices using a new family of processible poly(cyanoterephthalylidene)s. As the lowest unoccupied orbitals of these polymers (from which the conduction band is formed) lie at lower energies than those of PPV, electrodes made from stable metals such as aluminium can be used for electron injection. For hole injection, we use indium tin oxide coated with a PPV layer; this helps to localize charge at the interface between the PPV and the new polymer, increasing the efficiency of recombination. In this way, we are able to achieve high internal efficiencies (photons emitted per electrons injected) of up to 4% in these devices.

Structures and properties of electron-beam-evaporated indium tin oxide films as studied by x-ray photoelectron spectroscopy and work-function measurements

Abstract: Indium tin oxide (ITO) films deposited on single‐crystal Si wafers by the electron‐beam‐(EB) evaporation method have been investigated by x‐ray photoelectron spectroscopy (XPS) together with work‐function and resistivity measurements. The XPS studies suggest that all the ITO films consist of crystalline and amorphous phases. The amount of the crystalline phase with respect to the amorphous phase for the ITO films, deposited with the incident angle of the ITO vapor to the Si substrate θi at 0°, is smaller than that for the ITO films deposited at θi=45°. The amount of the crystalline phase hardly depends on the conditions of postdeposition heat treatments, while that of the amorphous phase increases by raising the temperature of the heat treatments. Metal indium present in the films deposited at θi=0° is transformed into amorphous indium oxide by heating at 450 °C in air. Metal tin is also present near the ITO/Si interface for the ITO films deposited at θi=0°. The work function of the ITO films deposited at...

Low resistivity indium tin oxide films by pulsed laser deposition

Abstract: Indium tin oxide films were grown by pulsed laser deposition on glass substrates. The electrical and optical properties of these films were studied. At optimized oxygen pressures, films with resistivity values of 1.4×10−4 and 5.6×10−4 Ω cm were deposited at substrate temperatures of 310 and 20 °C, respectively. Films with a thickness of 180 nm had a transmission of nearly 100% for the wavelength range of 600–800 nm.

New oxide phase with wide band gap and high electroconductivity CdGa2O4 spinel

Abstract: CdGa2O4 spinel was found to be a promising material as a transparent electronic conductor. By measurements of diffuse reflectance spectra, CdGa2O4 was found to have a wider band gap (∼3.5 eV) than indium tin oxide. The electrical conductivity of the sintered sample of CdGa2O4 was over 102 S cm−1 with no intentional doping.

Electrochromic and gas adsorption properties of Langmuir-Blodgett films of lutetium bisphthalocyanine complexes

Abstract: The electrochromic behaviour, spectroscopic properties and gas chemisorption of ultra thin films of lutetium octa-4-phenyldiphthalocyanine (LuPc[sub 2][sup Ph]), and the lutetium octa-3-bromo-octa-5-tert-butylphthalocyanine (LuPc[sub 2][sup tBr]) are reported. Electrochromism was observed for Langmuir-Blodgett (LB) and films cast onto indium tin oxide (ITO) coated glass electrodes in aqueous KClO[sub 4] solution. Mixed LB films supported on ITO glass electrodes were more stable to repetitive cycling than cast films. Films of LuPc[sub 2][sup Ph] and LuPc[sub 2][sup tBr] were sensitive to electron-acceptor gases as observed by the changes in the electronic absorption spectra and the surface-enhanced resonance Raman scattering (SERRS) spectra. The presence of electron-withdrawing bromine atoms in the phthalocyanine ring increased the rate of desorption for chemisorbed electron-acceptor molecules. 10 refs., 8 figs., 3 tabs.

Micrograin structure influence on electrical characteristics of sputtered indium tin oxide films

Abstract: The relationship between micrograin structures and electrical characteristics of sputtered indium tin oxide (ITO) films was investigated. Micrograin structures were observed by a high resolution scanning electron microscope. Electrical characteristics were evaluated by four point probe resistance measurement and Hall effect measurement. Low resistivity ITO films had domain structures. One domain consisted of many sputter grains having the same orientation. The resistivity decreased with increasing domain size. The domain boundary might cause scattering for conduction electrons. Therefore, larger domain ITO films had a higher Hall mobility. The minimum resistivity was 1.8×10−4 Ω cm, deposited at a sputtering voltage of −250 V and a 250 °C deposition temperature. The electron conduction mechanism in domain structured ITO films was taken into consideration.

Transparent strain sensitive devices and method

Abstract: A transparent strain sensitive surface is disclosed which is suitable for strain gages, video terminal touch panels, security panels (windows, display cases, etc.). The strain gage includes a transparent, strain sensitive conductor of indium tin oxide (ITO) or indium oxide (IO) on a transparent substrate. The strain sensitive panels include a crossed xy matrix of transparent IO or ITO strain sensitive conductors formed on the same side or on opposite sides of a transparent substrate.

Microstructure and Electrical Characteristics of Sputtered Indium Tin Oxide Films

Abstract: The relationship between microstructure and electron characteristics of indium tim oxide (ITO) films was investigated. The microstructure and resistivity were found to be dependent on the oxygen partial pressure in the sputtering ambient. Lower resistivity ITO films had a domain structure and a small amount of surface roughness. The small roughness and the large size domain structure caused a decrease in electron scattering, and hence an increase in mobility. Crystallinity was also affected by the oxygen partial pressure. For ITO films with a domain structure, the relative X-ray diffraction intensity of the (440) crystal plane increased.

Increases in photovoltage of ‘‘indium tin oxide/silicon oxide/mat‐textured n‐silicon’’ junction solar cells by silicon preoxidation and annealing processes

Abstract: Indium‐tin‐oxide (ITO)/silicon oxide/mat‐textured n‐Si junction solar cells having an energy conversion efficiency of 15% are fabricated by the spray pyrolysis method. Their characteristics and the junction properties are compared with the same junction solar cells having a flat Si surface. In cases where the ITO film is deposited on a hydrofluoric acid‐etched mat‐textured Si surface, the open circuit photovoltage (Voc) is low (405 mV). Scanning electron microscopy observation shows that high‐density dislocations are formed near the Si surface, and the temperature dependence of the current‐voltage characteristics suggests that the trap‐assisted multistep tunneling through the Si depletion layer is a dominant current flow mechanism. In cases where the ITO film is deposited on a thermal silicon oxide‐covered mat‐textured Si surface, the formation of the dislocations is suppressed, and consequently Voc is increased to 485 mV. For this solar cell, a surface recombination current takes the dominant part of the dark current in the bias region below ∼250 mV, and a thermionic‐assisted tunneling current is dominant in the higher bias region. For a cell where the thermal silicon oxide‐covered mat‐textured Si surface is annealed at 800 °C under nitrogen before the deposition of the ITO film, Voc is further increased to 540 mV, and the energy conversion efficiency of 15% is achieved. In this case, the thermionic‐assisted tunneling current density is decreased by an increase in the barrier height due probably to a reduction in the density of the positive charge in the silicon oxide layer. The surface recombination current density is also reduced by the removal of interface states, leading to the improvement of the fill factor.

Preparation and properties of electrodeposited indium tin oxide/SnO2/CdTe and indium tin oxide/SnO2/CdS/CdTe solar cells

Abstract: Cadmium telluride‐based solar cells have been prepared as indium tin oxide (ITO)/SnO2/CdTe and indium tin oxide/SnO2/CdS/CdTe structures where CdS and CdTe were prepared by an electrodeposition technique. Both open circuit voltage and short circuit current of ITO/SnO2/CdTe cells were higher than that of ITO/SnO2/CdS/CdTe cells. The spectral response measurement showed that the current collection was higher in the ITO/SnO2/CdTe cell relative to the ITO/SnO2/CdS/CdTe cell. Current‐voltage temperature measurements indicated that the junction transport could be controlled by recombination or thermally assisted tunneling in the ITO/SnO2/CdTe cell, whereas tunneling could be the dominant junction transport mechanism in the ITO/SnO2/CdS/CdTe cell. Activation energies of ITO/SnO2/CdTe and ITO/SnO2/CdS/CdTe cells were 0.60 and 0.76 eV, respectively. The values of the built‐in potential, Vbi calculated from the measurement of open circuit voltage with temperature were 1.41 and 1.5 eV for ITO/SnO2/CdTe and ITO/SnO2/...

Transient electroluminescence from hole transporting emitting layer in nanosecond region

Abstract: Transient electroluminescence (EL) for an organic thin film cell with a hole transporting emitting layer was observed by short voltage pulse measurements. For the cell with indium tin oxide/hole transporting emitting layer/Mg:Ag structure, we realized very fast response at a time about 20 ns. This response time has been the fastest in organic EL ever reported. In these measurements, we could observe carrier transit time. We found that this carrier transit time was attributed to that of holes in the emitting layer. The hole mobility in 120‐nm‐thick emitting layer was obtained to be 1±0.3×10−3 cm2/V s in the electric field region from 1 to 3 MV/cm. Furthermore, we could observe the fast EL decay component with a time constant of 3.0±1.5 ns, which was essentially attributed to the decay of singlet excited states.

Liquid crystal light valve with minimized double reflection

Abstract: A reflective liquid crystal light valve includes transparent conductive layers of indium tin oxide (30a) employed as an electrode to electrically modulate orientation of molecules of a liquid crystal material (22a) that receives a high intensity reading light applied through the transparent electrode (30a). Unwanted double reflection from interfaces between the indium tin oxide electrode (30a) and adjacent layers (22a, 32a) are minimized by application of broad band anti-reflective coatings (70, 72, 74, 76) formed by one or more pairs of thin layers having alternately high and low indices of refraction.

Molecularly Engineered Polymer Leds

Abstract: Polymeric light emitting devices may be fabricated from a simple structure consisting of a low work function cathode (typically calcium or magnesium), a conjugated semiconducting polymer and a transparent anode (typically indium-tin oxide). Optimum device efficiencies require the balanced injection of electrons and holes. This paper describes the application of molecular engineering in the design of a family of poly(cyanoterephthalylidenene)s which show increased electron affinity over the unsubstituted analogue [poly(p-phenylenevinylene) PPV]. In particular these polymers as the emissive layer in a bilayer device with indium tin oxide (ITO, positive transparent contact) and aluminum (stable negative contact) and PPV as a hole transporting layer exhibit internal efficiencies up to 4%.

Indium-tin oxide thin films by metal-organic decomposition

Abstract: In2O3–SnO2 films were produced by thermal decomposition of a deposit which was dip coated on borosilicate glass substrates from an acetylacetone solution of indium and tin acetoacetonate. Thermal analysis showed complete pyrolysis of the organics by 400 °C. The thermal decomposition reaction generated acetylacetone gas and was found to be first order with an activation energy of 13.6 Kcal/mole. Differences in thermal decomposition between the film and bulk materials were noted. As measured by differential scanning calorimetry using a 40 °C/min temperature ramp, the glass transition temperature of the deposited oxide film was found to be ∼462 °C, and the film crystallization temperature was found to be ∼518 °C. For film fabrication, thermal decomposition of the films was performed at 500 °C in air for 1 h followed by reduction for various times at 500 °C in a reducing atmosphere. Crystalline films resulted for these conditions. A resistivity of ∼1.01 × 10−3 Ω · cm, at 8 wt. % tin oxide with a transparency of ∼95% at 400 nm, has been achieved for a 273 nm thick film.

Fabrication of poly(p-phenyleneacetylene) light-emitting diodes

Abstract: Acetylene containing poly(p-phenyleneacetylene) (PPA) - based light-emitting diodes (LEDs) are provided. The LEDs are fabricated by coating a hole-injecting electrode, preferably an indium tin oxide (ITO) coated glass substrate, with a PPA polymer, such as a 2,5-dibutoxy or a 2,5-dihexoxy derivative of PPA, dissolved in an organic solvent. This is then followed by evaporating a layer of material capable of injecting electrons, such as A1 or A1/Ca, onto the polymer to form a base electrode. This composition is then annealed to form efficient EL diodes.

Transparent film radiant heat source for use with incubators

Abstract: A radiant heater is provided, which can be in the form of an overlay on an existing incubator hood or integrated in an incubator hood. The heater has an optically transparent, radiotransparent and phototherapy transparent electrically conductive coating, preferably indium tin oxide.

Concrete solar cell

Abstract: An inexpensive, robust concrete solar cell (10) comprises a photovoltaic material embedded in and extending beyond the major surfaces (16 and 18) of a matrix layer (14). The matrix layer typically comprises a high strength, cementitious material, such as a macrodefect free cement. The photovoltaic material comprises particles (12) of high-resistivity single crystal silicon, typically ball milled from ingot sections unsuitable for slicing into silicon wafers. The ingot sections include unprecipitated dissolved oxygen that is electrically activated by a low temperature annealing process to produce n-type silicon, even in silicon crystals that include a p-type dopant. An aluminum sheet (28), positioned on the backside of the matrix layer, is briefly melted together with the silicon particles to produce a p-type aluminum-doped silicon region (22) that forms a pn junction with the n-type region (24) of the particle. The aluminum sheet also provides the electrical contact to the p-type regions. The front surface of the matrix layer, from which the n-portion of the silicon particle protrudes, is covered with a translucent indium tin oxide conductive layer (30) that provides electrical contacts to the n-portion of the pn junction and digitated electrode (32) for conducting current off the cell. A voltage is generated between the two conductive layers when light incident on the photovoltaic particle through the indium tin oxide conductive layer creates charge carriers.

Electronic and optical properties of room temperature sputter deposited indium tin oxide

Abstract: The purpose of this article is to demonstrate a simple technique for magnetron sputter deposition of thin ITO films at room temperature without postdeposition annealing. Using a gas mixture of 0.7% O2 balanced with Ar and 50 W rf power, thin films with resistivity as low as 8.2×10−4 Ω cm have been fabricated. The sputter deposited films have optical transmittance of over 80% in the visible range. The absorption edge located in the mid‐infrared (4000–400 cm−1) has been observed to shift toward increasing wave number (decreasing wavelength) with increasing resistivity of the thin ITO films. At 0.7% O2 concentration it has been found that the resistivity is insensitive to the total pressure of the sputtering chamber over the range of 1.4–8.0 mTorr.