Fine-Tuning of Yellow or Red Photo- and Electroluminescence of Functional Difluoro-boradiazaindacene Films

Authors

  • Laure Bonardi,

    1. Laboratoire de Chimie Moléculaire Ecole Chimie, Polymères, Matériaux (ECPM), ULP-CNRS 25 rue Becquerel, 67008 Strasbourg Cedex (France)
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  • Hani Kanaan,

    1. Laboratoire Plasma et Conversion d'Energie (LAPLACE) Université Paul Sabatier, Bât 3R3 31062 Toulouse Cedex 09 (France)
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  • Franck Camerel,

    1. Laboratoire de Chimie Moléculaire Ecole Chimie, Polymères, Matériaux (ECPM), ULP-CNRS 25 rue Becquerel, 67008 Strasbourg Cedex (France)
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  • Pascale Jolinat,

    1. Laboratoire Plasma et Conversion d'Energie (LAPLACE) Université Paul Sabatier, Bât 3R3 31062 Toulouse Cedex 09 (France)
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  • Pascal Retailleau,

    1. Laboratoire de Cristallochimie, ICSN – CNRS, Bât 27 1 avenue de la Terrasse, 91198 Gif-sur-Yvette (France)
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  • Raymond Ziessel

    Corresponding author
    1. Laboratoire de Chimie Moléculaire Ecole Chimie, Polymères, Matériaux (ECPM), ULP-CNRS 25 rue Becquerel, 67008 Strasbourg Cedex (France)
    • Laboratoire de Chimie Moléculaire Ecole Chimie, Polymères, Matériaux (ECPM), ULP-CNRS 25 rue Becquerel, 67008 Strasbourg Cedex (France).
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  • This work was jointly supported by the Louis Pasteur University through the European School of Polymer and Materials Chemistry (ECPM), by the Centre National de la Recherche Scientifique (CNRS) of France, and ANR Contract ANR-05-BLAN-0004-01, FCP-OLEDs. We warmly thank Dr Bertrand Donnio from the IPCMS in Strasbourg for performing low- and wide-angle X-ray diffraction experiments on these novel compounds. We are also indebted to Professor Jack Harrowfield (ISIS Strasbourg) for careful reading and commenting this manuscript prior to journal submission. Supporting information is available online from Wiley InterScience or from the author.

Abstract

The present work describes the synthesis of difluoro-boradiazaindacenes (Bodipy) functionalized at the central 8-position by phenylamino moieties easily transformable into phenyl amide scaffoldings. Molecules carrying three linear or branched chains were prepared and characterized. An X-ray crystal structure for the pivotal trimethoxyphenyl-Bodipy derivative was determined, and the packing is discussed in terms of molecular interactions; a key feature for the formation of thin films. All of the dyes are thermally stable up to 170 °C but no liquid-crystalline phases are observed. Reversible reduction and oxidation processes occur around +0.97 and −1.34 V, respectively, versus saturated calomel electrode in solution and the electroactivity and photoluminescence are maintained in thin films produced by vacuum evaporation. Interestingly, two distinct emissions are observed at 550 and 635 nm by electroluminescence of the trimethoxyphenyl-Bodipy derivative, corresponding to the luminescence of isolated molecules and dimers, respectively. Doping Alq3 films with this Bodipy molecule by vacuum evaporation produces organic light-emitting diodes (OLEDs) in which very efficient energy transfer from the Alq3 matrix to the Bodipy occurs by a resonance mechanism involving the first Bodipy excited state. Yellow light (550 nm, 344 cd m−2 at 15 V) is emitted at low doping concentration (7 mol %), whereas red light (635 nm, 125 cd m−2 at 15 V) is emitted at higher concentration (19 mol %). Dispersion of the Bodipy into a fluorescent poly(N-vinylcarbazole) polymer (PVK) (≈3 mol % per repeating unit of PVK) by solution processing exclusively produces yellow emission owing to the isolated Bodipyfluorophore (550 nm, 213 cd m−2 at 15 V). The second excited state of the Bodipy dye is likely involved during energy transfer from the PVK matrix.

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