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Voltage-Induced Formation of Accumulation Layers at Electrode Interfaces in Organic Solar Cells

Authors

  • Felix F. Stelzl,

    1. Freiburg Material Research Center (FMF), University of Freiburg, Stefan-Meier-Str. 21, 79104 Freiburg, Germany
    2. Fraunhofer Institute for Solar Energy Systems (ISE), Heidenhofstr. 2, 79110 Freiburg, Germany
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  • Jan Schulz-Gericke,

    1. Fraunhofer Institute for Solar Energy Systems (ISE), Heidenhofstr. 2, 79110 Freiburg, Germany
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  • Ed Crossland,

    1. Freiburg Institute of Advanced Studies (FRIAS), University of Freiburg, Albertstr.19, 79104 Freiburg, Germany
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  • Sabine Ludwigs,

    1. Freiburg Institute of Advanced Studies (FRIAS), University of Freiburg, Albertstr.19, 79104 Freiburg, Germany
    2. Institute of Polymer Chemistry, University of Stuttgart, Paffenwaldring 55, 70569 Stuttgart, Germany
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  • Uli Würfel

    Corresponding author
    1. Freiburg Material Research Center (FMF), University of Freiburg, Stefan-Meier-Str. 21, 79104 Freiburg, Germany
    2. Fraunhofer Institute for Solar Energy Systems (ISE), Heidenhofstr. 2, 79110 Freiburg, Germany
    • Freiburg Material Research Center (FMF), University of Freiburg, Stefan-Meier-Str. 21, 79104 Freiburg, Germany.
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Abstract

This work reports on organic bulk heterojunction solar cells based on poly(3-hexylthiophene) (P3HT) blended with [6,6]-phenyl-C61 butyric acid methyl ester (PCBM) in a configuration with so-called interdigital nanoelectrodes, i.e., vertical electrodes on substrates structured in the submicrometer range. In this setup, both electrodes are in place prior to the deposition of the photoactive blend solution and therefore allow for the application of a voltage during drying of the blend. A strong correlation is observed between the photovoltaic performance of these devices and the voltage that is applied during film formation. Even the polarity of the solar cells can be controlled with this method. It is suggested that this is a consequence of a strong segregation of donor and acceptor phases at the electrode interfaces induced by the applied voltage. Further experiments on planar solar cell geometries, including a solvent-vapor treatment and the introduction of an additional layer of pure P3HT, as well as numerical simulations, are presented. All results obtained are consistent with the suggested hypothesis.

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