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  • 1
    Electronic Resource
    Electronic Resource
    Transient and steady-state behavior of space charges in multilayer organic light-emitting diodes (2001)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 89 (2001), S. 4575-4586 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A numerical study of space charge effects in multilayer organic light-emitting diodes (OLEDs) is presented. The method of solving the coupled Poisson and continuity equations, previously established for single-layer polymer LEDs, has been extended to treat internal organic interfaces. In addition, we consider the transient current and electroluminescence response. We discuss the accumulation of charges at internal interfaces and their signature in the transient response as well as the electric field distribution. Comparison to experimental transient data of a typical bilayer LED based on tris(8-hydroxyquinolinato)aluminum (Alq3) is provided and good agreement is found. Our results are consistent with commonly assumed operating principles of bilayer LEDs. In particular, the assumptions that the electric field is predominantly dropped across the Alq3 layer and that the electroluminescence delay time is determined by electrons passing through Alq3 to the internal interface are self-consistently supported by the results of the simulation. Moreover, the creation of emissive singlet excitons is found to be strongly confined to the Alq3 side of the internal interface and the emission zone width is dictated by the exciton diffusion length. Design principles for trilayer LEDs with improved power efficiency are also discussed. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1352027
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  • 2
    Electronic Resource
    Electronic Resource
    High sensitivity sensor for moderate pressures (1996)
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 67 (1996), S. 617-618 
    Details
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: The metal–insulator transition of (V0.99Ti0.01)2O3 is marked by dramatic changes in the electrical resistivity and the magnetic susceptibility, with a linear pressure variation of −6.06 K/kbar for P≤15 kbar. We propose its use as the sensing element of a manometer in applications where the superconducting transition of soft metals has been traditional. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1146619
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  • 3
    Electronic Resource
    Electronic Resource
    Enhanced luminance in polymer composite light emitting devices (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 71 (1997), S. 1145-1147 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We demonstrate that mixing insulating oxide nanoparticles into electroluminescent polymer materials results in increased current densities, radiances, and power efficiencies in polymer light emitting diode devices. For low driving voltages, an order of magnitude increase in current density and light output is achieved with minimal loss in device lifetime. At 5 V, we achieve radiances of 10 000 cd/m2 with external quantum efficiencies ∼1% for nanoparticle/MEH–PPV composite films. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.119848
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  • 4
    Electronic Resource
    Electronic Resource
    Transparent conducting thin films of GaInO3 (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 65 (1994), S. 115-117 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: GaInO3 is recently identified transparent conducting material which is structurally and chemically distinct from indium tin oxide [R. J. Cava, J. M. Phillips, J. Kwo, G. A. Thomas, R. B. van Dover, S. A. Carter, J. J. Krajewski, W. F. Peck, Jr., J. H. Marshall, and D. H. Rapkine, Appl. Phys. Lett. 64, 2071 (1994)]. We have used both dc reactive sputtering in the on- and off-axis geometries and pulsed laser deposition to grow films of this material. Layers of pure GaInO3 as well as those partially substituted with Ge for Ga or Sn for In have been studied. Both growth techniques are capable of producing films with conductivity ∼400 (Ω cm)−1 and transmission as high as 90% throughout the visible spectrum for ∼1-μm-thick films. The growth techniques differ in the morphology of the films produced as well as in the degree of dopant incorporation that can be achieved. A post-growth anneal in H2 can help produce an optimized oxygen content and a reduction of resistivity. Hall measurements indicate a carrier concentration up to 4×1020 cm−3 for all films and a Hall mobility up to 10 cm2/(V s). Doping appears to be due both to oxygen vacancies and aliovalent ion substitution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.113052
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  • 5
    Electronic Resource
    Electronic Resource
    Zinc-indium-oxide: A high conductivity transparent conducting oxide (1995)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 67 (1995), S. 2246-2248 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the fabrication and characterization of zinc-indium-oxide films with similar electrical conductivity and better transparency in both the visible and infrared compared with indium–tin–oxide, a widely used transparent conductor in many technological applications. Dramatically superior transmission properties in the 1–1.5 μm range in particular make zinc–indium–oxide attractive for use in infrared devices, where transparent electrodes are required. Resisitivities as low as 400 μΩ cm result from doping with small quantities of Sn; Al, Ga, and Ge are also effective dopants. Deposition on glass and quartz substrates as amorphous films by pulsed laser deposition and dc reactive sputtering is described. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.115118
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  • 6
    Electronic Resource
    Electronic Resource
    GaInO3: A new transparent conducting oxide (1994)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 64 (1994), S. 2071-2072 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: GaInO3, a layered material with the β Ga2O3 crystal structure, can be doped with electrons through the introduction of oxygen deficiency, Sn doping for In, or Ge doping for Ga. At atomic doping levels of 10% or less, resistivities as low as 3 mΩ cm are obtained. In contrast to polycrystalline indium tin oxide (ITO), which is distinctly green, conductive gallium indium oxide is light grey with no visible coloration. Thin films of doped GaInO3 display good transparency over the whole optical window, superior to that of ITO in the green-blue region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.111686
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  • 7
    Electronic Resource
    Electronic Resource
    Polymeric anodes for improved polymer light-emitting diode performance (1997)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 70 (1997), S. 2067-2069 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied polyaniline and polyethylenedioxythiophene transparent electrodes for use as hole-injecting anodes in polymer light emitting diodes. The anodes were doped with a variety of polymer and monomer-based acids and cast from either water or organic solvents to determine the effect of the dopant and solvent on the hole-injection properties. We find that the anodes with polymeric dopants have improved device quantum efficiency and brightness relative to those with small molecule dopants, independent of conductivity, solvent, or type of conducting polymer. For the most conducting polymer anodes [σ〉2(Ωcm)−1], diodes could be made without an indium tin oxide underlayer. These diodes show substantially slower degradation. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.118953
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  • 8
    Electronic Resource
    Electronic Resource
    Temperature- and field-dependent electron and hole mobilities in polymer light-emitting diodes (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 1132-1134 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied the transport properties of electron- and hole-dominated MEH-PPV, poly(2-methoxy,5-(2′-ethyl-hexoxy)-p-phenylene vinylene), devices in the trap-free limit and have derived the temperature-dependent electron and hole mobilities (μ=μ0eγ(square root of)E) from the space-charge-limited behavior at high electric fields. Both the zero-field mobility μ0 and electric-field coefficient γ are temperature dependent with an activation energy of the hole and electron mobility of 0.38±0.02 and 0.34±0.02 eV, respectively. At 300 K, we find a zero-field mobility μ0 on the order of 1±0.5×10−7 cm2/V s and an electric-field coefficient γ of 4.8±0.3×10−4 (m/V)1/2 for holes. For electrons, we find a μ0 an order of magnitude below that for holes but a larger γ of 7.8±0.5×10−4 (m/V)1/2. Due to the stronger field dependence of the electron mobility, the electron and hole mobilities are comparable at working voltages in the trap-free limit, applicable to thin films of MEH-PPV. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.123959
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  • 9
    Electronic Resource
    Electronic Resource
    Charge transfer in photovoltaics consisting of interpenetrating networks of conjugated polymer and TiO2 nanoparticles (1999)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 1698-1700 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We study the effect of blended and layered titanium dioxide (TiO2) nanoparticles on charge transfer processes in conjugated polymer photovoltaics. A two order of magnitude increase in photoconductivity and sharp saturation is observed for layered versus blended structures, independent of the cathode work function. Using electrodes with similar work functions, we observe low dark currents and open circuit voltages of 0.7 V when a TiO2 nanoparticle layer is self-assembled onto the indium–tin–oxide electrode. Our results for the layered morphologies are consistent with charge collection by exciton diffusion and dissociation at the TiO2 interface. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.123659
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  • 10
    Electronic Resource
    Electronic Resource
    Temperature-dependent recombination in polymer composite light-emitting diodes (1998)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 73 (1998), S. 3911-3913 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We study the temperature dependence of the current–voltage and radiance–voltage curves in double-carrier injected polymer light-emitting devices comprised of poly(2-methoxy,5-(2′-ethyl-hexoxy)–p-phenylene vinylene) (MEH–PPV) and MEH–PPV/SiO2 as the active layer. The quantum efficiency increases significantly as the temperature is decreased in agreement with an increase in the recombination efficiency with decreasing temperature. Moreover, the bimolecular recombination efficiency saturates at low temperatures and high currents to a very high value for both the composite and plain MEH–PPV devices with the nanoparticles serving as charge traps only at moderately low current densities. Finally, we find that the order of magnitude improvement in radiance observed in some polymer/nanoparticle composites is due to an increase in the effective electric field across the device. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.122933
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