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Device Physics of White Polymer Light-Emitting Diodes

Authors

  • Herman T. Nicolai,

    1. Molecular Electronics, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, NL-9747 AG Groningen, the Netherlands
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  • André Hof,

    1. Molecular Electronics, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, NL-9747 AG Groningen, the Netherlands
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  • Paul W. M. Blom

    Corresponding author
    1. Molecular Electronics, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, NL-9747 AG Groningen, the Netherlands
    2. Holst Centre, High Tech Campus 31, NL-5605 KN Eindhoven, the Netherlands
    • Molecular Electronics, Zernike Institute for Advanced Materials, University of Groningen, Nijenborgh 4, NL-9747 AG Groningen, the Netherlands.
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Abstract

The charge transport and recombination in white-emitting polymer light- emitting diodes (PLEDs) are studied. The PLED investigated has a single emissive layer consisting of a copolymer in which a green and red dye are incorporated in a blue backbone. From single-carrier devices the effect of the green- and red-emitting dyes on the hole and electron transport is determined. The red dye acts as a deep electron trap thereby strongly reducing the electron transport. By incorporating trap-assisted recombination for the red emission and bimolecular Langevin recombination for the blue emission, the current and light output of the white PLED can be consistently described. The color shift of single-layer white-emitting PLEDs can be explained by the different voltage dependencies of trap-assisted and bimolecular recombination.

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