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  • 1
    Electronic Resource
    Electronic Resource
    Photocarrier generation and injection at the interface in double-layered organic photoconductors (1989)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 54 (1989), S. 872-874 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photocarrier generation and injection processes in double-layered organic photoconductors consisting of carrier generation layer (CGL) and carrier transport layer (CTL) were studied by means of photoacoustic and xerographic time-of-flight methods. In the photoacoustic method, the photocarrier generation efficiency in the CGL was derived by measuring the decrease in photoacoustic signal due to carrier recombination in the CGL. On the other hand, in the xerographic method, the ratio of the number of holes emitted into the CTL to that of absorbed photons in the CGL was obtained from the temporal change in surface voltage under light pulse irradiation. From comparing two experimental results, we evaluated the injection efficiency of holes at the CGL/CTL interface. The injection efficiency is determined by the trapping of holes at the CGL/CTL interface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.100794
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  • 2
    Electronic Resource
    Electronic Resource
    Photocarrier generation, injection, and trapping at the interface in a layered organic photoconductor: Metal-free phthalocyanine/molecularly doped polymer (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 3728-3736 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied photocarrier generation and injection at the interface in a double-layered organic photoconductor consisting of a charge generation layer (CGL) of vacuum-deposited phthalocyanine film and a charge transport layer (CTL) of p-diethylaminobenzaldehyde-1,1-diphenyl hydrazone doped polymer film. The photocarrier generation efficiency in the CGL was measured by the photoacoustic method. The transport and trapping of holes in the CTL and at the CGL/CTL interface were studied by xerographic discharge measurements and time-of-flight photoconductivity measurements. The photogeneration efficiency in the CGL is affected by the hydrazone concentration in the CTL. At high hydrazone concentrations, the photogeneration efficiency means the quantum efficiency of photocarrier generations controlled by geminate and nongeminate recombination in the CGL. At low hydrazone concentrations, the photogeneration efficiency is affected by the injection and trapping of holes at the CGL/CTL interface. Xerographic and time-of-flight photoconductivity measurements show that the lifetime of holes at the CGL/CTL interface is short compared with that in the CTL and no trapping of holes occurs in the CTL. The lifetime of holes at the CGL/CTL interface decreases with increasing hydrazone concentration in the CTL. The injection efficiency of holes is determined by the competition between the trapping of holes at the CGL/CTL interface and the hopping transport of holes across the CGL/CTL interface. We discuss the influence of the hydrazone concentration in the CTL on the photocarrier generation in the CGL and the injection of holes at the CGL/CTL interface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.345014
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  • 3
    Electronic Resource
    Electronic Resource
    Charge trapping in a layered organic photoconductor studied by photoacoustic and xerographic discharge measurements (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 997-999 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The influence of charge trapping on photocarrier generation in a layered organic photoconductor consisting of a charge generation layer (CGL) and a charge transport layer was studied by means of photoacoustic and xerographic discharge techniques. The photocarrier generation efficiency in the CGL was derived by measuring the decrease in the photoacoustic (PA) signal when an electric field was applied to the sample. Prolonged light exposure under a high applied field increased the photocarrier generation efficiency and the negative xerographic residual potential. After the termination of the applied field, the PA signal reverted to the initial value very slowly. The recovery time of the PA signal after the termination of the applied field agreed well with the decay time of the xerographic residual potential. The increase in the photocarrier generation efficiency and the negative residual potential are due to the trapping of electrons in the CGL.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343485
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  • 4
    Electronic Resource
    Electronic Resource
    Xerographic studies of charge trapping in layered organic photoconductors (1990)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 67 (1990), S. 4152-4158 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Charge trapping in layered organic photoconductors consisting of a charge generation layer (CGL) and a charge transport layer (CTL) was studied by xerographic residual potential measurements. The residual potential builds up during repeated corona charging and light exposure cycles of photoconductors. The negative residual potential is proportional to the square of the CGL thickness and is linearly proportional to the CTL thickness. The square dependence is caused by the bulk trapping of electrons in the CGL, and the linear dependence is due to the negative charges on the CTL surface. From experimental results, it is concluded that the electron trapping in the CGL enhances the trapping of holes at the CGL/CTL interface, and consequently a fraction of negative corona charges remains on the CTL surface even after light exposure. The buildup of the residual potential during xerographic cycling is initiated by the electron trapping in the CGL. On the other hand, the decay rate of the residual potential after xerographic cycling depends on hole transport properties in the CTL. The activation energy for the decay of the residual potential is in good agreement with that for the drifting of holes through the CTL obtained from thermally stimulated current measurements. The decay rate of the residual potential is controlled by the surface charge neutralization process which involves the release of holes trapped at the CGL/CTL interface and the subsequent drifting of holes to the surface.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.344977
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of polymer matrix on a reversible light-induced change in charge acceptance and retention of molecularly doped polymers (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 66 (1989), S. 4526-4528 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied the effects of a polymer matrix on charge acceptance and retention of polymers doped with hole-transport molecules in order to understand the nature of traps in molecularly doped polymers (MDPs). Prolonged illumination decreases charge acceptance and retention of MDPs. A light-induced change in charge acceptance depends on the kind of polymer binder. A remarkable change is observed in acidic polymer binders or basic polymer binders exhibiting broad absorption spectra. In MDPs manifesting a remarkable light-induced change, the transient photocurrent pulse shape becomes dispersive after prolonged light exposure. The experimental results show that the shallow charge emission centers increase during light exposure. These shallow charge emission centers are metastable states formed by charge transfer between the transport molecule and the polymer matrix during light exposure.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343919
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  • 6
    Electronic Resource
    Electronic Resource
    Hopping charge transport in molecularly doped polymers: Polymer matrix dependence of the hole drift mobility (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 3033-3035 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Effects of the polymer matrix on the drift mobility of holes in polymers doped with 2-(p-dipropylaminophenyl)-4-(p-dimethylaminophenyl)-5-(o-chlorophenyl)-1, 3-oxazole were studied by means of time-of-flight photoconductivity measurements. The drift mobility at zero field, the activation energy for hopping, and the electric field dependence of the mobility strongly depend on the polymer composition. These polymer matrix dependence of the drift mobility are largely related to energetic disorder of hopping sites in binary solid solution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350987
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  • 7
    Electronic Resource
    Electronic Resource
    Photocarrier generation in metal-free phthalocyanines: Effect of the stacking habit of molecules on the photogeneration efficiency (1991)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 69 (1991), S. 7333-7335 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The photocarrier generation mechanism in metal-free phthalocyanines (H2Pc) was studied by time-of-flight photoconductivity measurements. The quantum efficiencies of photogeneration of holes depend on the crystal structure of H2Pc. The photogeneration efficiencies in X- and τ-H2Pc are high compared with those of α- and β-H2Pc. The lifetimes of the precursor state of free carriers in X- and τ-H2Pc are between those of α-H2Pc and β-H2Pc. Moreover, infrared absorption and Raman spectra show that X- and τ-H2Pc are intermediate states between α-H2Pc and β-H2Pc. It is pointed out that the photogeneration dynamics of H2Pc is controlled by the intermolecular overlap of the π-electron wavefunctions and the stacking habit of molecules.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.347587
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  • 8
    Electronic Resource
    Electronic Resource
    A near-infrared photoluminescence study of GaAs nanocrystals in SiO2 films formed by sequential ion implantation (1999)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 86 (1999), S. 1762-1764 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have studied photoluminescence (PL) properties of Ga+ and As+ implanted SiO2 films on Si substrate. After thermal annealing, zinc blende GaAs nanocrystals are formed in SiO2 films and several PL bands appear in the red and near-infrared spectral region. Defects and impurities in GaAs nanocrystals and SiO2 cause weak luminescence in the near-infrared spectral region at low temperatures. After low-energy deuterium implantation, the defect PL intensity decreases and the red PL from GaAs nanocrystals is clearly observed. It is demonstrated that GaAs/SiO2 nanocompostites with low defect density are fabricated by sequential ion implantation followed by thermal annealing and hydrogen passivation. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.370960
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  • 9
    Electronic Resource
    Electronic Resource
    A photoacoustic study of photoinjection processes in double-layered organic photoconductors (1988)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 63 (1988), S. 239-241 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Photoinjection efficiencies of holes from the carrier generation layer (CGL) into the carrier transport layer (CTL) in double-layered organic photoconductors were measured by using a photoacoustic technique. The photoinjection efficiency depends on the concentration of transporting molecules doped in the polymer of the CTL. At low molecular concentrations, the injection efficiency is mainly limited by the low ability to transport carriers in the CTL. The concentration dependence of the photoinjection efficiency is found to be similar to that of hopping transport processes in the CTL. At high molecular concentrations, the photoinjection efficiency is limited by the free-carrier generation process in the CGL.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.340505
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  • 10
    Electronic Resource
    Electronic Resource
    Electric-field dependence of the hole drift mobility in molecularly doped polymers: Importance of the disorder of hopping sites (1992)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 71 (1992), S. 300-303 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electric-field dependence of the drift mobility of holes in a polymer matrix doped with various different molecules was studied by means of time-of-flight (TOF) photoconductivity measurements. It was first found that the degree of the positive field dependence of the drift mobility increases with decreasing magnitude of the drift mobility at zero field. The tail of the Gaussian TOF current signal becomes broad in molecularly doped polymers having a large disorder of hopping site energies. It was pointed out that the field dependence of the mobility and the energy barrier for charge transport are largely related to energetic disorder of hopping sites.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.350705
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