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Indexed by:期刊论文

Date of Publication:2013-12-01

Journal:DISPLAYS

Included Journals:SCIE、EI

Volume:34

Issue:5

Page Number:413-417

ISSN No.:0141-9382

Key Words:Iridium complex; OLEDs; Carbazole unit; Vacuum-deposited; Solution-processing

Abstract:Iridium(III)bis(4,6-(difluorophenyl)pyridinato-N,C-2')picolinate (Firpic) is one typical bluish-green phosphor widely used in phosphorescent organic light-emitting diodes (PhOLEDs). In order to optimize its electroluminescent performance, 3,6-(di-tert-butyl)carbazolyl was introduced into the pyridine ring of the 2,4-difluorophenyl-pyridine ligand via a non-conjugated CH2 linkage. The generated 3,6-ditert-butyl-9-((6-(2,4-difluorophenyl)pridine-3-yl)methyl)-9H-carbazole (Cz-CH2-dfppy) was used as cyclometalating ligand to prepare iridium complex 1, (Cz-CH2-dfppy)(2)Ir(pic). In comparison with the case to attach carbazole directly on pyridine, this non-conjugated CH2 linking strategy avoids the unwanted bathochromic shift of the phosphorescence and improves the solubility of the iridium complex. (Cz-CH2-dfPPY)(2)Ir(pic) (1) was used as doped emitter to fabricate OLEDs by both spin-coating and vacuum evaporation methods. Efficient bluish-green electrophosphorescence was obtained with maximum luminance efficiency of 22 cd/A (14 lm/W, 8.7%) and 26 cd/A (12 lm/W, 9.5%) for the solution-processed and vacuum-deposited devices, respectively, which far exceed those of the parent Firpic based device. The improved performance for (Cz-CH2-dfPPY)(2)Ir(pic) was interpreted in terms of improved charge balance brought by the presence of the carbazole groups in the ligands. (C) 2013 Elsevier B.V. All rights reserved.