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  • 1
    Electronic Resource
    Electronic Resource
    Poling and orientational relaxation: Comparison of nonlinear optical main-chain and side-chain polymers (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 80 (1996), S. 3162-3166 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We investigated both time and temperature dependence of chromophore movements by means of in situ second-harmonic generation (SHG) measurements. Using real-time detection of the SHG intensities during and after poling of various nonlinear-optical polymer films we observed differences between main-chain and side-chain polymers regarding the nonlinear coefficients d33 and the glass transition dynamics. We present experimental data on new main-chain polymers with polar stilbene chromophores attached in the most common transverse position to the backbones (MC-T) or incorporated in a linear fashion where they are a part of the main-chain (MC-L). The side-chain polymer (SC) presented here has been developed for photorefractive applications and is a copolymer containing Disperse Red 1 and a photoconducting carbazole unit in the side chain. The influence of the macromolecular structure on the chromophore dynamics is striking. This is verified by means of in situ corona poling experiments and thermal experiments based on temperature ramps on poled polymers. MC-T and especially MC-L polymers show a better thermal stability of the chromophore orientation relative to the glass transition temperature than SC polymers; however, chromophores of main-chain polymers are, as can be expected, less mobile during the poling process. We obtained resonance enhanced nonlinear optical coefficients d33 of 100 pm/V in a SC polymer, 90 pm/V in a MC-T polymer, and 30 pm/V in a MC-L polymer. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.363254
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  • 2
    Electronic Resource
    Electronic Resource
    Electron transport in a starburst oxadiazole (1997)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 82 (1997), S. 4957-4961 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this article we report on the electron mobility of a starburst oxadiazole, 1,3,5 -[(4-tert.-butylphenyl)-2-oxadiazolyl] benzene. For direct evidence of the electron transport capability the charge drift mobility and its field dependence have been measured by the time-of-flight technique. The electron mobility showed a square root dependence of the electric field and was somewhat larger than that for PBD. In addition, the oxadiazole compound has been used as the electron transport layer (ETL) in light-emitting diodes (LEDs) together with poly(1,4-phenylene vinylene). The characteristics of these devices are compared to analogous LEDs with Alq3 as the ETL. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.366396
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  • 3
    Electronic Resource
    Electronic Resource
    Holographic and photoelectric characterization of a novel photorefractive organic glass (1999)
    Springer
    Applied physics 68 (1999), S. 899-906 
    Details
    ISSN: 1432-0649
    Keywords: PACS: 42.65.Hq; 42.70.Nq
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract. We present a detailed study of the photoelectric as well as the holographic properties of a novel organic photorefractive glass based on triphenylamine. We studied the quantum efficiency Φ of the photogeneration of charges by means of photoinduced discharge measurements. The photoconductivity σ and the charge carrier mobility μ were obtained via dc photoconduction and pulsed time-of-flight experiments, respectively. The holographic characterization was performed by two-wave and degenerate four-wave mixing experiments allowing for the determination of properties such as diffraction efficiency η, modulation of the refractive index Δn, gain coefficient Γ, and phase-shift φp of the investigated system. The experimental data for Φ could be successfully described by the Onsager formalism with a thermalization radius of r0=24 Å and a primary quantum yield of Φ0=40%. We evaluated the E field and temperature-dependent measurements of μ using the Bässler formalism yielding a width of the density of states of σ=0.13 eV and a disorder parameter Σ=3.6. On this basis the lifetime and the average drift length of the charge carriers could be estimated from the dc photoconduction experiments. From the photoelectric measurements we also calculated the holographic response time that matched very well to the measured response time and described the E-field dependence satisfactorily. The presented photorefractive system shows outstanding optical properties and stability with respect to degradation. We measured a gain coefficient of Γ=90 cm-1, and a diffraction efficiency of η=27% at a response time of 30 ms for only 40-μm-thick samples. Orientational enhancement was observed and evaluated quantitatively. To our knowledge, this work presents the first determination of each of the above quantities all in one single organic photorefractive material.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s003400050721
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  • 4
    Electronic Resource
    Electronic Resource
    A polysiloxane-based photorefractive polymer with high optical gain and diffraction efficiency*This work was supported by the Fonds der Chemischen Industrie and by FOROPTO. (1995)
    Weinheim : Wiley-Blackwell
    Advanced Materials 7 (1995), S. 911-914 
    Details
    ISSN: 0935-9648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/adma.19950071108
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  • 5
    Electronic Resource
    Electronic Resource
    Synthesis, electrical conductivity and electroluminescence of poly(p-phenylene vinylene) prepared by the precursor route (1993)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 44 (1993), S. 201-205 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We present a detailed experimental procedure for the synthesis of poly(p-phenylene vinylene) by the precursor route. Special emphasis is given to the conditions of the thermal elimination reaction that leads from the processable precursor polymer 4 to PPV. We found that a temperature of 320°C is necessary to remove sulphur and chlorine containing defect structures which are probably formed by nucleophilic substitutions during thermal elimination. PPV prepared by our procedure contains 0.12% of chlorine and 0.15% of sulphur. With this material we are able to prepare large area light emitting diodes (LED) which work at driving voltages as low as 2 Volts in an ITO/PPV/Al configuration. The low threshold results in an improved device performance: So a LED continuously driven with a current density of 20 mA/cm2 emits light for one week at ambient conditions and for more than four weeks if operated in a glove box at room temperature.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1993.010440405
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  • 6
    Electronic Resource
    Electronic Resource
    In-situ absorption studies of nonlinear optically active side-chain polymers during corona poling (1993)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 44 (1993), S. 302-306 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Absorption measurements in the wavelength range from 300 to 700 nm are used to study the orientation of nonlinear optical side groups in an acrylic polymer oriented by corona poling inside a spectrophotometer. The poling and relaxation behavior of these films are measured. The in-situ poling process produces efficient orientational order in acrylic side-chain polymers, which can be described by an order parameter.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1993.010440607
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