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Bipolar Host Material for Phosphorescent OLEDs Based on 2,7‐Diazacarbazole as a New Electron‐transporting Unit
Author(s) -
Cha JaeRyung,
Lee Chil Won,
Gong MyoungSeon
Publication year - 2017
Publication title -
bulletin of the korean chemical society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.237
H-Index - 59
ISSN - 1229-5949
DOI - 10.1002/bkcs.11209
Subject(s) - phosphorescence , carbazole , moiety , oled , materials science , diode , molecule , photochemistry , optoelectronics , chemistry , nanotechnology , stereochemistry , physics , optics , organic chemistry , fluorescence , layer (electronics)
The novel electron‐transporting moiety of 2,7‐diazacarbazole was used to construct a bipolar host molecule for phosphorescent organic light‐emitting diodes ( PHOLEDs ). This moiety was incorporated with typical hole‐transporting carbazole moieties to synthesize a 2,7‐diazacarbazole/carbazole hybrid called 9‐(3,5‐bis(carbazol‐9‐yl)phenyl)–2,7‐diazacarbazole. The hybrid exhibits a high triplet energy above 2.88 eV and very high glass transition temperature of T g = 148°C. It shows good thermal stability owing to the rigid nature of its symmetrical bipolar structure. The 2,7‐diazacarbazole‐based host material turns on at 3.6 and 3.7 V and approaches external quantum efficiencies above 16.0 and 22.6% in blue and green PHOLEDs , respectively. These results demonstrate that 2,7‐diazacarbazole should be an excellent electron‐transporting unit for bipolar phosphorescent hosts.