High-Tg Carbazole Derivatives as Blue-Emitting Hole-Transporting Materials for Electroluminescent Devices

A series of dicarbazolyl derivatives bridged by various aromatic spacers and decorated with peripheral diarylamines were synthesized using Ullmann and Pd‐catalyzed C–N coupling procedures. These derivatives emit blue light in solution. In general, they possess high glass‐transition temperatures (Tg ...

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Bibliographic Details
Published in:Advanced functional materials 2003-06, Vol.13 (6), p.445-452
Main Authors: Kundu, P., Justin Thomas, K.R., Lin, J.T., Tao, Y.-T., Chien, C.-H.
Format: Article
Language:English
Subjects:
Blue-emitting materials
Carbazoles
Electroluminescence
Hole transport
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Summary:A series of dicarbazolyl derivatives bridged by various aromatic spacers and decorated with peripheral diarylamines were synthesized using Ullmann and Pd‐catalyzed C–N coupling procedures. These derivatives emit blue light in solution. In general, they possess high glass‐transition temperatures (Tg > 125 °C) which vary with the bridging segment and methyl substitution on the peripheral amine. Double‐layer organic light‐emitting devices were successfully fabricated using these molecules as hole‐transporting and emitting materials. Devices of the configuration ITO/HTL/TPBI/Mg:Ag (ITO: indium tin oxide; HTL: hole‐transporting layer; TPBI: 1,3,5‐tris(N‐phenylbenzimidazol‐2‐yl)benzene) display blue emission from the HTL layer. The EL spectra of these devices appear slightly distorted due to the exciplex formation at the interfaces. However, for the devices of the configuration ITO/HTL/Alq3/Mg:Ag (Alq3 = tris(8‐hydroxyquinoline)aluminum) a bright green light from the Alq3 layer was observed. This clearly demonstrates the facile hole‐transporting property of the materials described here. Aromatic bridged biscarbazolyl derivatives containing peripheral diarylamine segments (see Figure) have been synthesized and successfully fabricated into organic LEDs as emitting hole‐transporting materials. Their Tg is dependent on the bridging aromatic unit and the peripheral diarylamine segments. The molecules’ effective hole‐transporting properties are attributed to the multiple hopping pathways provided by the peripheral diarylamine moieties.
ISSN:1616-301X
1616-3028
DOI:10.1002/adfm.200304308