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Rheological and Drying Considerations for Uniformly Gravure-Printed Layers: Towards Large-Area Flexible Organic Light-Emitting Diodes

Authors

  • Gerardo Hernandez-Sosa,

    Corresponding author
    1. Light Technology Institute, Karlsruhe Institute of Technology, Engesserstr. 13, 76131 Karlsruhe, Germany
    2. InnovationLab GmbH, Speyerer Strasse 4, 69115 Heidelberg, Germany
    • Light Technology Institute, Karlsruhe Institute of Technology, Engesserstr. 13, 76131 Karlsruhe, Germany.
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  • Nils Bornemann,

    1. Institute for Printing Science and Technology, Technical University Darmstadt, Magdalenenstr. 2, 64289 Darmstadt, Germany
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  • Ingo Ringle,

    1. Heidelberger Druckmaschinen AG, Kurfürstenanlage 52-60, 69115 Heidelberg, Germany
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  • Michaela Agari,

    1. Heidelberger Druckmaschinen AG, Kurfürstenanlage 52-60, 69115 Heidelberg, Germany
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  • Edgar Dörsam,

    1. Institute for Printing Science and Technology, Technical University Darmstadt, Magdalenenstr. 2, 64289 Darmstadt, Germany
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  • Norman Mechau,

    Corresponding author
    1. Light Technology Institute, Karlsruhe Institute of Technology, Engesserstr. 13, 76131 Karlsruhe, Germany
    2. InnovationLab GmbH, Speyerer Strasse 4, 69115 Heidelberg, Germany
    • Light Technology Institute, Karlsruhe Institute of Technology, Engesserstr. 13, 76131 Karlsruhe, Germany.
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  • Uli Lemmer

    1. Light Technology Institute, Karlsruhe Institute of Technology, Engesserstr. 13, 76131 Karlsruhe, Germany
    2. InnovationLab GmbH, Speyerer Strasse 4, 69115 Heidelberg, Germany
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Abstract

Printing organic semiconductor inks by means of roll-to-roll compatible techniques will allow a continuous, high-volume fabrication of large-area flexible optoelectronic devices. The gravure printing technique is set to become a widespread process for the high throughput fabrication of functional layers. The gravure printing process of a poly-phenylvinylene derivative light-emitting polymer dissolved in a two solvent mixture on poly(3,4-ethylenedioxythiophene):poly(styrene sulfonate) (PEDOT:PSS) is studied. The surface tensions, contact angles, viscosities, and drying times of the formulations are investigated as a function of the solvent volume fraction and polymer concentration. The properties of the ink grant a homogeneous printed layer, suitable for device fabrication, when the calculated film leveling time is shorter than a critical time, at which the film has been frozen due to loss of solvent via evaporation. The knowledge obtained from the printing process is applied to fabricate organic light-emitting diodes (OLEDs) on flexible substrates, yielding a luminance of ≈5000 cd m−2.

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