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Green and Yellow Electroluminescent Dipolar Carbazole Derivatives: Features and Benefits of Electron-Withdrawing Segments
New multiply substituted carbazole derivatives containing fluorene or phenylene conjugated oxadiazole segments and quinoxaline units were obtained by palladium-catalyzed C−N coupling reactions. They are amorphous with the glass transition temperature (T g) in the range 104−176 °C. The emission color...
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Published in: | Chemistry of materials 2002-09, Vol.14 (9), p.3852-3859 |
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Main Authors: | , , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | New multiply substituted carbazole derivatives containing fluorene or phenylene conjugated oxadiazole segments and quinoxaline units were obtained by palladium-catalyzed C−N coupling reactions. They are amorphous with the glass transition temperature (T g) in the range 104−176 °C. The emission color of the materials varies from blue to yellow and is dependent on the nature of the electron-withdrawing segments and solvents. Two reversible one-electron oxidations were observed for these molecules in cyclic voltammograms, which originate from the peripheral 3,6-diarylamino units in the 3,6,9-trisubstituted derivatives and diarylamine and carbazole segments in the 3,9-disubstituted compounds. Reductions originating from quinoxaline segments were also located for the molecules incorporating quinoxaline moieties. The double-layer organic light-emitting diodes fabricated using these compounds as hole-transporting/emitting layers and TPBI or Alq3 as an electron-transporting layer emit bluish green to yellow colors. The recombination zone is restricted in the HTL layer for the quinoxaline-containing molecules irrespective of the electron-transporting layer used and emission occurs from them. However, for the oxadiazole derivatives emission in the Alq3-based devices is either red-shifted or resembles that of Alq3. Cyclic voltammetric and spectroscopic data support more pronounced electron affinity for the quinoxaline-incorporated carbazole derivatives than for the oxadiazole-tethered carbazole materials. |
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ISSN: | 0897-4756 1520-5002 |
DOI: | 10.1021/cm0202512 |