Novel heteroleptic iridium(III) complexes with a 2-(1H-pyrazol-5-yl)pyridine derivative containing a carbazole group as ancillary ligand: Synthesis and application for polymer light-emitting diodes

A novel organic compound 9-(2-ethylhexyl)-3-(5-(pyridin-2-yl)-1H-pyrazol-3-yl)-9H-carbazole (PPC) was synthesized and used as ancillary ligand in heteroleptic iridium(III) complexes (npy)(2)Ir(PPC), (PPY)(2)Ir(PPC) and (dfPPY)(2)Ir(PPC) (npy: 2-(napfitnalen-1-yl)pyridine; ppy: 2-phenylpyridine; dfppy: 2-(2,4-difluorophenyl)pyridine). All of the iridium(III) complexes are amorphous and have high thermal stability. Their glass-transition temperatures are 171 degrees C, 172 degrees C and 165 C, and 5% weight-reduction temperatures are 411 C, 406 degrees C and 433 degrees C, respectively. The polymer light-emitting diodes using the iridium(III) complexes as phosphorescent dopants exhibited good EL performance, the maximum luminances of (npy)(2)Ir(PPC), (ppy)(2)Ir(PPC) and (dfppy)(2)Ir(PPC) are 4948 cd m(-2), 11215 cd m(-2) and 4696 cd m(-2), and the maximum current efficiencies are 11.6 cd A(-1), 25.2 cd A(-1) and 16.4 cd A(-1), respectively. The CIEs of their devices are around (0.59, 0.40), (0.31, 0.57) and (0.32, 0.54), respectively. (C) 2013 Elsevier B.V. All rights reserved.