Efficient blue-green organic light-emitting diodes based on heteroleptic tris-cyclometalated iridium(III) complexes

초록

The blue-green organic light-emitting diodes based on heteroleptic tris-cyclometalated iridium(III) complexes containing the F-2-ppy (2,4-difluorophenylpyridine) and ppy (2-phenylpyridine) ligands were fabricated. Ir(ppy)(3) has been known to have a high phosphorescence efficiency in electroluminescence owing to its strong metal-to-ligand-charge transfer (MLCT) excited state, whereas the luminous efficiency of Ir(F(2-)ppy)(3) was found to be low due to weak MLCT. Herein, we report two heteroleptic phosphorescent blue-green emitters, Ir(ppy)(2)(F-2-ppy) and Ir(ppy)(F-2-ppy)(2), that exhibit emission peaks at 502 nm and 495 nm, respectively. The maximum luminous efficiencies of the devices with Ir(ppy)(2)(F-2-ppy) and Ir(ppy)(F-2-ppy)(2) were 8.93 cd/A and 13.80 cd/A, respectively. The quantum efficiency of the device containing Ir(ppy)(F-2-ppy)(2) was 3.63% at J = 10 mA/cm(2). (C) 2008 Elsevier B.V. All rights reserved.

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