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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    The @journal of organic chemistry 49 (1984), S. 3382-3384 
    ISSN: 1520-6904
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 72 (1992), S. 564-568 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report visible light emission from diodes made from poly(3-octylthiophene). Use of a soluble derivative of polythiophene allows fabrication of the light emitting diodes by casting the polymer film from solution with no subsequent processing or heat treatment required. The devices emit dim red-orange light with relatively low external quantum efficiencies, below 2.5×10−5 photons per electron at room temperature. Electrical characterization reveals diode behavior with rectification ratios greater than 102. The temperature dependence indicates that tunneling phenomena dominate the charge injection.
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5177-5180 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We report the effect of conversion conditions on the device characteristics of poly(p-phenylene vinylene) (PPV) light-emitting diodes. Both electroluminescence and photoluminescence intensities decrease with increasing degree of conversion. Partial conjugation enhances the electroluminescence intensity and gives an efficiency (with Ca as electron-injecting contact) as high as 0.75% photons per electron, about two orders of magnitude more efficient than from similar devices prepared from fully converted PPV. The results of constant current stress measurements suggest that the partially conjugated PPV diode is relatively stable at room temperature.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 2750-2758 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present the results of the Austin-Model 1 (AM1) geometry optimizations and valence effective Hamiltonian (VEH) band-structure calculations aimed at determining the evolution of the geometric structure and electronic properties (ionization potentials, electron affinities, band gaps) as a function of unit cell content in two sets of regular block copolymers. The first set consists of poly(p-phenylene vinylene)/poly(2,5-dimethoxy-1, 4-phenylene vinylene) copolymers, the second set of poly(p-phenylene)/polyacetylene copolymers. In the latter case, the band gap can be tuned over the whole visible range, depending on the extent of the block copolymer sequences. Special attention is paid to the possible occurrence of localization phenomena.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 6504-6509 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present the results of time-resolved luminescence studies of poly[2-methoxy, 5-(2'-ethyl-hexyloxy)-p-phenylene-vinylene] (MEH-PPV), as a pure film, in solution, in a gel formed by a network of ultrahigh molecular weight polyethylene (UHMW-PE), and in a blend with UHMW-PE. The luminescence has a characteristic lifetime of 200–300 ps at room temperature, increasing to 500–700 ps when the materials are cooled to 80 K; the decay time is approximately the same for all the physical forms of the material (solution, film, gel, blend). The relatively short lifetimes, compared to intrinsic values calculated from absorption and emission spectra, and the observed temperature dependence indicate that the luminescence decay is quenched by nonradiative processes. The time decay of the photoluminescence deviates from a single exponential for most forms of the MEH-PPV. Best fits to stretched exponential and double exponential expressions are presented. Steady state photoluminescence spectra and integrated luminescence vs pump intensity data are presented in order to establish which of the possible mechanisms are most important.
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  • 6
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 99 (1993), S. 590-596 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We report the results of initial measurements on two derivatives of poly(1,6-heptadiyne): a di-ketone (PHDK) and a di-ester (PHDE). Both polymers have the degenerate ground state of poly(1,6-heptadiyne); both are soluble in common organic solvents. Electron spin resonance (ESR) measurements on pristine samples place an upper limit of 10−4 spins per monomer for both polymers. At low doping levels, we observe a single doping-induced absorption band at an energy of approximately half the π−π* gap, Eg/2; the doping-induced spectral features were fully reversible. In situ ESR and absorption measurements during doping show that charge is stored predominantly in spinless charge carriers. Because of the inequivalent carbons on the conjugated backbone, the results are discussed in terms of the (A=B)n polymer. Both PHDK and PHDE are relatively stable in air; the strength of the π−π* absorption band is nearly constant over a period of a week in air, decreasing to 80% of the initial value.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 98 (1993), S. 2664-2669 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present near steady state photoinduced absorption spectra of two forms of polyaniline. Both the emeraldine base (nondegenerate ground state) and pernigraniline (degenerate ground state) exhibit long lived photoinduced nonlinear excitations with transient absorptions within the π→π* gap. In the case of the emeraldine base, two well-resolved photoinduced absorption bands are observed with maxima at 0.9 and 1.47 eV, accompanied by a bleaching of the 2 eV absorption edge. The different relaxation rates of the two bands indicate that they arise from two independent photoinduced nonlinear excitations. The results are discussed in terms of intrachain and interchain excitations. The possibility of deep traps on defect sites in pernigraniline is suggested.
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  • 8
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Review of Scientific Instruments 68 (1997), S. 1119-1121 
    ISSN: 1089-7623
    Source: AIP Digital Archive
    Topics: Physics , Electrical Engineering, Measurement and Control Technology
    Notes: A low cost, low power compact optical correlator is demonstrated. It operates interchangeably in the matched-filter or joint-transform configurations. The active medium is a high diffraction efficiency photorefractive host–guest polymer system. Successful image correlation has been achieved. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 78 (1995), S. 4510-4515 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The photosensitivity of semiconducting polymers can be enhanced by blending donor and acceptor polymers to optimize photoinduced charge separation. We describe a novel phase-separated polymer blend (composite) made with poly[2-methoxy-5-(2′-ethyl-hexyloxy)-1,4-phenylene vinylene], MEH-PPV, as donor and cyano-PPV, CN-PPV, as acceptor. The photoluminescence and electroluminescence of both component polymers are quenched in the blend, indicative of rapid and efficient separation of photogenerated electron-hole pairs with electrons on the acceptor and holes on the donor. Diodes made with such a composite semiconducting polymer as the photosensitive medium show promising photovoltaic characteristics with carrier collection efficiency of 5% electrons/photon and energy conversion efficiency of 0.9%, ∼20 times larger than in diodes made with pure MEH-PPV and ∼100 times larger than in diodes made with CN-PPV. The photosensitivity and the quantum yield increase with reverse bias voltage, to 0.3 A/W and 80% electrons/photon respectively at −10 V, comparable to results obtained from photodiodes made with inorganic semiconductors. © 1995 American Institute of Physics.
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  • 10
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 4755-4766 
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The polymer grid triode (PGT) is a novel semiconductor device constructed using a self-assembling porous conducting polyaniline (PANI) network placed between two semiconducting polymer layers, and sandwiched between metal electrodes. The structure behaves as a three-terminal device capable of current amplification, with the PANI network functioning as the control grid. An analysis of the generalized field-assisted carrier injection by tunneling, controlled by the grid voltage, is presented to model the charge injection and transport in the PGT. The results are in good agreement with the measured current–voltage characteristics. Further, an effective diode model for the PGT is introduced, and a simple, intuitive expression for charge transport in the presence of the grid network is obtained. In the effective diode regime, the current through the PGT is a function of (Vac−PVag); i.e., Iac≈I(Vac−PVag) where P is a geometric factor, as required for use in image processing applications. Other application possibilities for the PGT are surveyed, and the limitations of this device when placed in common circuit configurations are discussed. © 1996 American Institute of Physics.
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