The metal-on-polymer interface in polymer light emitting diodes

Authors

  • Prof. William R. Salaneck,

    Corresponding author
    1. Department of Physics, IFM Linköping Université S-58183 Linköping (Sweden)
    • Department of Physics, IFM Linköping University S-58183 Linköping (Sweden)
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  • Prof. Jean-Luc Brédas

    1. Service de Chimie des Matèriaux Nouveaux Centre de Recherches en Electronique et Photonique Molèculaires University de Mons–Hainaut B-7000 Mons (Belgium)
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  • The work was supported by the Commission of the European Union, within the SCIENCE program (project 0661 POLYSURF), as well as Philips Research, NL (within Brite/EURAM PolyLED, 0592). Research on conjugated polymers in Linköping is supported in general by grants from the Swedish Natural Sciences Research Council (NFR), the Swedish Research Council for Engineering Sciences (TFR), the Swedish National Board for Industrial and Technical Development (NuTek), the Neste Corp., Finland; research in Mons is supported by the Prime Minister Office of Science Policy (SPPS) “Pôle d'Attraction Interuniversitaire en Chimie Supramoléculaire et Catalyse” and “Programme d'Impulsion en Technologie de'Information (contract SC/IT/22)”, by the Belgian National Fund for Scientific Research FNRS/FRFC, and an IBM Academic Joint Study. In addition to the SCIENCE program, the Linköping-Mons collaboration is supported by the European Commission through the ESPRIT program (project number 8013 LEDFOS), the ESPRIT network of excellence NEOME, as well as by a contract with Hoechst AG, FRG (in connection with the Brite/EuRam project PolyLED).

Abstract

The oxidation of calcium electrodes on polymer light emitting diodes (LEDs) can influence the lifetime of the LEDs by an order of magnitude. This finding illustrates how important the metal–polymer interface can be for LEDs. This aspect, which so far has usually been neglected, is investigated experimentally and interpreted in terms of quantum chemical modeling. It is shown that for all the metals considered (A1, K, Rb, Na, Ca) an interfacial region is formed between the metal and the polymer which behaves differently from the bulk.

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