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Acceptor Derivatization of the 4CzIPN TADF System: Color Tuning and Introduction of Functional Groups |
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| Authors: | Fabian Hundemer Lorenz Graf von Reventlow Céline Leonhardt Mika Polamo Martin Nieger Stefan M. Seifermann Alexander Colsmann Prof. Dr. Stefan Bräse |
| Affiliation: | 1. Institute of Organic Chemistry, Karlsruhe Institute of Technology (KIT), Fritz-Haber-Weg 6, 76131 Karlsruhe, Germany These authors contributed equally to this work.;2. Karlsruhe Institute of Technology (KIT), Light Technology Institute, Engesserstrasse 13, 76131 Karlsruhe, Germany Karlsruhe Institute of Technology (KIT), Material Research Center for Energy Systems, Strasse am Forum 7, 76131 Karlsruhe, Germany These authors contributed equally to this work.;3. Institute of Organic Chemistry, Karlsruhe Institute of Technology (KIT), Fritz-Haber-Weg 6, 76131 Karlsruhe, Germany;4. Department of Chemistry, University of Helsinki, P. O. Box 55, 00014 University of Helsinki, Finland;5. Karlsruhe Institute of Technology (KIT), Light Technology Institute, Engesserstrasse 13, 76131 Karlsruhe, Germany Karlsruhe Institute of Technology (KIT), Material Research Center for Energy Systems, Strasse am Forum 7, 76131 Karlsruhe, Germany |
| Abstract: | We demonstrate modular modifications of the widely employed emitter 2,4,5,6-tetra(9H-carbazol-9-yl)isophthalonitrile (4CzIPN) by replacing one or both nitrile acceptors with oxadiazole groups via a tetrazole intermediate. This allows the introduction of various functional groups including halides, alkynes, alkenes, nitriles, esters, ethers and a protected amino acid while preserving the thermally activated delayed fluorescence (TADF) properties. The substituents control the emission maximum of the corresponding emitters, ranging between 472–527 nm, and show high solid-state photoluminescence quantum yields up to 85 %. The TADF emission of two compounds, 4CzCNOXDtBu and 4CzdOXDtBu, a mono- and a bis-oxadiazole substituted 4CzIPN is characterized in detail by time- and temperature-dependent photoluminescence. Solution-processed OLEDs comprising 4CzCNOXDtBu and 4CzdOXDtBu show a significant blue-shift of the emission compared to the reference 4CzIPN, with external quantum efficiencies of 16 %, 5.9 % and 17 % at 100 cd m−2, respectively. |
| Keywords: | thermally activated delayed fluorescence organic light emitting diodes (OLED) oxadiazoles color-tuning functionalization |