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  • 1
    Electronic Resource
    Electronic Resource
    Effect of LiF/metal electrodes on the performance of plastic solar cells (2002)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 80 (2002), S. 1288-1290 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The insertion of thin interlayers of LiF under the negative metal electrode (Al and Au) of bulk heterojunction solar cells significantly enhances the fill factor and stabilizes high open circuit voltages. Compared to devices without the LiF interfacial layer, the white light efficiencies increase by over 20% up to ηeff∼3.3%. Substitution of the LiF by another insulating interlayer SiOx results in lower overall efficiencies. In the case of a LiF/Au electrode, substantial efficiency enhancement is observed compared to a pristine Au electrode and white light efficiencies up to ηeff∼2.3% are reported.© 2002 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1446988
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  • 2
    Electronic Resource
    Electronic Resource
    2.5% efficient organic plastic solar cells (2001)
    Woodbury, NY : American Institute of Physics (AIP)
    Applied Physics Letters 78 (2001), S. 841-843 
    Details
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We show that the power conversion efficiency of organic photovoltaic devices based on a conjugated polymer/methanofullerene blend is dramatically affected by molecular morphology. By structuring the blend to be a more intimate mixture that contains less phase segregation of methanofullerenes, and simultaneously increasing the degree of interactions between conjugated polymer chains, we have fabricated a device with a power conversion efficiency of 2.5% under AM1.5 illumination. This is a nearly threefold enhancement over previously reported values for such a device, and it approaches what is needed for the practical use of these devices for harvesting energy from sunlight. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1345834
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  • 3
    Electronic Resource
    Electronic Resource
    Influence of disorder on the photoinduced excitations in phenyl substituted polythiophenes (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 7235-7244 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Regioregular poly(3-(4′-(1″,4″,7″-trioxaoctyl)phenyl)thiophenes) (PEOPTs) exhibit interesting properties for the use in polymer electronics. Exposing thin films of the amorphous, disordered phase (orange phase) of the "as prepared" polymer to chloroform vapor or annealing them by heat treatment results in a redshift of the absorption maximum due to the formation of nanocrystals in an ordered phase (blue phase). As such, PEOPT thus is a very interesting conjugated polymeric material, which exhibits two different phases with well-defined order/disorder characters on one-and-the-same material. This property opens up the unique possibility to investigate the role of order/disorder on the photoexcited pattern without being obscured by the differences in chemical structure by using different materials with different crystallinity. The fact, that blue phase PEOPT exhibits absorption edges at relatively low energies around 1.8 eV, thereby demonstrating an enhanced spectral absorption range as compared to the orange phase, makes them attractive for use in photodiodes and solar cells as well. The photoinduced charge generation efficiency in both phases of PEOPT is significantly enhanced by the addition of a strong electron acceptor such as fullerene C60, as observed by quenching of the luminescence and by photoinduced absorption measurements in the infrared and uv–visible regime. The average number and the lifetime of photoinduced carriers in composites of PEOPT with a methanofullerene [6,6]-phenyl C61–butyric acid methyl ester (PCBM) are found to depend on the crystallinity of PEOPT in thin films, which gives rise to charged photoexcitations delocalized between polymer chains. Stronger bimolecular recombination in composites of the blue phase PEOPT with PCBM is observed as compared to the orange phase PEOPT/PCBM films. The origin of this enhanced recombination is found to be related to the hole mobility of the polymer. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1404984
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  • 4
    Electronic Resource
    Electronic Resource
    Investigation of the linear flow regime of commercial polymers by numerical conversion of MVM creep measurements (1997)
    Springer
    Rheologica acta 36 (1997), S. 657-666 
    Details
    ISSN: 1435-1528
    Keywords: Key words Retardation time ; spectra ; creep measurements ; compliance ; MVM ; regularization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract A new experimental and numerical method has been developed to characterize the terminal flow behavior of polydisperse, commercial grade polymer melts over a wide dynamic range of time/frequency scales. Experimentally, an MVM rheometer specifically designed for long time scale (t∼104s) creep measurements is used to measure the creep compliance of three commercial polymers: two high density polyethylenes and one polystyrene. The long time scale MVM creep data are complemented in the short time scale regime by creep data from an industrial plate-plate rheometer. The time-dependent creep data is combined and converted to a discrete retardation spectra using a nonlinear regularization algorithm to address the ill-posed nature of the interconversion. The retardation spectrum is analytically converted to dynamic moduli and compared with independently measured dynamic moduli. In the overlapping frequency region, calculations and measurements show excellent agreement and the combined data span a much larger dynamic range than either independent data set. The calculated and measured dynamic moduli data are combined and a retardation spectrum with a vastly expanded dynamic range is generated. Combining long time scale MVM creep compliance data and dynamic moduli data exploits the intrinsic sensitivities of controlled strain and controlled stress rheological experiments and is a powerful means to greatly expand the experimentally accessible dynamic range of time/frequency. This approach is particularly useful for commercial polymers with broad molecular weight distributions and commensurately large distributions of relaxation times.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00367362
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  • 5
    Electronic Resource
    Electronic Resource
    Investigation of relaxation properties of polymer melts by comparison of relaxation time spectra calculated with different algorithms (1997)
    Springer
    Rheologica acta 36 (1997), S. 667-676 
    Details
    ISSN: 1435-1528
    Keywords: Key words Relaxation time ; spectra ; relaxation phenomena ; iterative filtering method ; regularization ; dynamic moduli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract In this paper a recently introduced algorithm (Brabec and Schausberger, 1995) for the calculation of relaxation time spectra is compared with two standard methods, i.e., Weese’s regularization, and Baumgaertel’s and Winter’s regression algorithm. A reasonable agreement between those three algorithms is found for the relaxation properties of mono-, polydisperse, bi-, and multimodal polystyrene samples. All three numerical methods reproduce the relaxation properties for long and medium times correctly, but they show some disagreement at short times because of sparse experimental data. The high numerical accuracy opens the possibility to test and improve the physical models which underlie the calculations. The good agreement of the different algorithms suggests that small inconsistencies to physical models are not due to a failure of the numerical methods, but due to an insufficiency of the generalized Maxwell model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00367363
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  • 6
    Electronic Resource
    Electronic Resource
    An improved algorithm for calculating relaxation time spectra from material functions of polymers with monodisperse and bimodal molar mass distributions (1995)
    Springer
    Rheologica acta 34 (1995), S. 397-405 
    Details
    ISSN: 1435-1528
    Keywords: Relaxation time spectra ; molar mass distribution ; dynamic moduli ; iterative filtering method
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract Using the basic concept of Emri and Tschoegl, the algorithm for calculating relaxation time spectra has been improved such that excellent results are provided in the difficult case of polymers with narrow molar mass distributions. These spectra can be compared with those calculated by nonlinear regularization (Weese 1992), which we regard as a very exact method, and show equally good results with even less mathematical effort. Examples of dense relaxation time spectra (up to eight points per decade) are given for nearly monodisperse polystyrene melts and for mixtures of these up to four components. The relaxation time spectra describe the dynamic mechanical experimental data in each case with an overall error of less than 3%. The filtering method used to avoid physically senseless oscillations has been proven to resolve the characteristic peaks contributed by monodisperse polymers accurately.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00367154
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  • 7
    Electronic Resource
    Electronic Resource
    Investigation of relaxation properties of polymer melts by comparison of relaxation time spectra calculated with different algorithms (1997)
    Springer
    Rheologica acta 36 (1997), S. 667-676 
    Details
    ISSN: 1435-1528
    Keywords: Relaxation time spectra ; relaxation phenomena ; iterative filtering method ; regularization ; dynamic moduli
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract In this paper a recently introduced algorithm (Brabec and Schausberger, 1995) for the calculation of relaxation time spectra is compared with two standard methods, i.e., Weese's regularization, and Baumgaertel's and Winter's regression algorithm. A reasonable agreement between those three algorithms is found for the relaxation properties of mono-, polydisperse, bi-, and multimodal polystyrene samples. All three numerical methods reproduce the relaxation properties for long and medium times correctly, but they show some disagreement at short times because of sparse experimental data. The high numerical accuracy opens the possibility to test and improve the physical models which underlie the calculations. The good agreement of the different algorithms suggests that small inconsistencies to physical models are not due to a failure of the numerical methods, but due to an insufficiency of the generalized Maxwell model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00367363
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  • 8
    Electronic Resource
    Electronic Resource
    Investigation of the linear flow regime of commercial polymers by numerical conversion of MVM creep measurements (1997)
    Springer
    Rheologica acta 36 (1997), S. 657-666 
    Details
    ISSN: 1435-1528
    Keywords: Retardation time spectra ; creep measurements ; compliance ; MVM ; regularization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract A new experimental and numerical method has been developed to characterize the terminal flow behavior of polydisperse, commercial grade polymer melts over a wide dynamic range of time/frequency scales. Experimentally, an MVM rheometer specifically designed for long time scale (t ∼ 104 s) creep measurements is used to measure the creep compliance of three commercial polymers: two high density polyethylenes and one polystyrene. The long time scale MVM creep data are complemented in the short time scale regime by creep data from an industrial plate-plate rheometer. The time-dependent creep data is combined and converted to a discrete retardation spectra using a nonlinear regularization algorithm to address the ill-posed nature of the interconversion. The retardation spectrum is analytically converted to dynamic moduli and compared with independently measured dynamic moduli. In the overlapping frequency region, calculations and measurements show excellent agreement and the combined data span a much larger dynamic range than either independent data set. The calculated and measured dynamic moduli data are combined and a retardation spectrum with a vastly expanded dynamic range is generated. Combining long time scale MVM creep compliance data and dynamic moduli data exploits the intrinsic sensitivities of controlled strain and controlled stress rheological experiments and is a powerful means to greatly expand the experimentally accessible dynamic range of time/frequency. This approach is particularly useful for commercial polymers with broad molecular weight distributions and commensurately large distributions of relaxation times.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00367362
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  • 9
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    Angle dependence of external and internal quantum efficiencies in bulk-heterojunction organic solar cells (2007)
    American Institute of Physics
    Details
    Publication Date: 2007-09-01
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
    Published by American Institute of Physics
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  • 10
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    Design of efficient organic tandem cells: On the interplay between molecular absorption and layer sequence (2007)
    American Institute of Physics
    Details
    Publication Date: 2007-12-15
    Print ISSN: 0021-8979
    Electronic ISSN: 1089-7550
    Topics: Physics
    Published by American Institute of Physics
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