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Red Phosphorescent Iridium Complex Containing Carbazole‐Functionalized β‐Diketonate for Highly Efficient Nondoped Organic Light‐Emitting Diodes
Author(s) -
Liu Z. W.,
Guan M.,
Bian Z. Q.,
Nie D. B.,
Gong Z. L.,
Li Z. B.,
Huang C. H.
Publication year - 2006
Publication title -
advanced functional materials
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 6.069
H-Index - 322
eISSN - 1616-3028
pISSN - 1616-301X
DOI - 10.1002/adfm.200600099
Subject(s) - iridium , phosphorescence , materials science , oled , carbazole , indium tin oxide , photochemistry , fluorescence , nanotechnology , chemistry , thin film , layer (electronics) , organic chemistry , optics , catalysis , physics
A novel red phosphorescent iridium complex containing a carbazole‐functionalized β‐diketonate, Ir(DBQ) 2 (CBDK) (bis(dibenzo[f,h]quinoxalinato‐ N ,C 2 ) iridium (1‐(carbazol‐9‐yl)‐5,5‐dimethylhexane‐2,4‐diketonate)) is designed, synthesized, and characterized. The electrophosphorescence properties of a nondoped device using the title complex as an emitter with a device configuration of indium tin oxide (ITO)/ N , N ′‐diphenyl‐ N , N ′‐bis(1‐naphthyl)‐1,1′‐diphenyl‐4,4′‐diamine (NPB; 20 nm)/iridium complex (20 nm)/2,9‐dimethyl‐4,7‐diphenyl‐1,10‐phenanthroline (BCP; 5 nm)/tris(8‐hydroxyquinoline) (AlQ; 30 nm)/Mg 0.9 Ag 0.1 (200 nm)/Ag (80 nm) are examined. The results show that the nondoped device achieves a maximum lumen efficiency as high as 3.49 lm W –1 . To understand this excellent result observed, two reference complexes Ir(DBQ) 2 (acac), where acac is the acetyl acetonate anion, and Ir(DBQ) 2 (FBDK), [bis(dibenzo[f,h]quinoxalinato‐ N ,C 2 ) iridium (1‐(9‐methyl‐fluoren‐9‐yl)‐6,6‐dimethylheptane‐3,5‐diketonate)], have also been synthesized, and as emitters they were examined under the same device configuration. The maximum lumen efficiency of the former compound is found to be 0.26 lm W –1 while that for the latter is 0.37 lm W –1 , suggesting that the excellent performance of Ir(DBQ) 2 (CBDK) can be attributed mainly to an improved hole‐transporting property that benefits the exciton transport. In addition, a bulky diketonate group separates the emitter centers from each other, which is also important for organic light‐emitting diodes.