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  • 1
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Spectral, field, and temperature dependencies of steady-state photoconductivity were studied in thin films of pure phenyl substituted copolymeric polyphenylenevinylene (PhPPV) and PhPPV doped by trinitrofluorenone. The films were sandwiched between indium tin oxide (ITO) and aluminum as well as between two aluminum contacts. Typical surface extrinsic carrier photogeneration was observed in ITO/PhPPV/Al samples with positively biased ITO while the intrinsic photoconductivity dominated in Al/PhPPV/Al samples and ITO/PhPPV/Al sandwiches with negatively biased ITO. Charge carrier photogeneration in both doped and undoped PhPPV at higher photon excess energies was found to be in good agreement with predictions of the hot exciton dissociation model. At low excess photon energy of the inducing light, carrier photogeneration is ascribed to dissociation of optical excitations on charge transfer centers which are either dopant molecules in the doped samples or intrinsic defects in the pure material. © 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 74 (1999), S. 1815-1817 
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Trapped electrons and holes, and their dynamics, were visualized from spatially resolved capacitance–voltage (C–V) curves and dC/dV images using scanning capacitance microscopy. A trapped charge of 10−16–10−18 C, localized within 2 μm diam circular test structures, was imaged. The detrapping process of the trapped electrons can be explained with a quantum-mechanical tunneling model. © 1999 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 117 (2002), S. 1395-1402 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Steady state as well as time-resolved fluorescence of phenyl-substituted polyphenylenevinylene (PhPPV), both in solution and in form of spin-coated films has been measured. In solution the fluorescence decays exponentially with a 1/e decay time of ∼700 ps, whereas the 1/e decay in the film is ∼400 ps and the decay approaches a stretched exponential with an exponent of β=0.65. Doping the film with various amounts of trinitrofluorenone (TNF) shortens the decay time without changing the form of the Kohlrausch–Williams–Watts decay law. This is a signature of exciton dissociation in a random polymer matrix through electron transfer to TNF. The data analysis shows that "neat" PhPPV contains a concentration of ≤ 0.04 wt. % of unidentified electron scavengers. A hypsochromic shift of the cw fluorescence spectra in doped films is interpreted in terms of increasingly frustrated spectral relaxation of singlet excitations within the inhomogeneously broadened distribution of hopping states. © 2002 American Institute of Physics.
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  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 3802-3807 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Employing the time-of-flight (TOF) technique, the hole mobility in films of polyphenylenevinylene-ether has been measured as a function of electric field and temperature. Charge carriers were generated upon either photoexcitation into the S1←S0 transition of the polymer or via sensitized injection from a thin rhodamine 6G layer. The results will be interpreted in terms of the concept of hopping among polymer segments featuring a Gaussian distribution of energies, its variance being 91 meV. While TOF signals generated via sensitized injection are similar to those in molecularly doped polymers bearing out a transition from nondispersive to dispersive transport, intrinsically generated TOF signal features a cusp at higher temperature and almost no dispersion. The latter phenomenon turns out to be a consequence of charge generation at the tail of the density distribution of hopping states. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
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