Highly efficient yellow-emitting iridium complexes: Syntheses, structures, luminescence, and electroluminescence

Document Type

Conference Proceeding

Publication Date

12-1-2007

Abstract

The synthesis, structural, photophysical, and electroluminescent (EL) properties of three new luminescent cyclometalated iridium (III) complexes are reported. The cyclometalated ligand used here is 2-(2-fluorphenyl)-benzothiazole (F-BT). The auxiliary ligands are acetylacetone (acac), 1,1,1- trifluoracetylaceton (3F-acac), 1,1,1,5,5,5-hexafluoroacetylacetone (6F-acac), respectively. The crystal structures of the complexes, (F-BT) 2Ir(acac) (1) and (F-BT)2Ir(6F-acac) (3), show that the iridium (III) ion resides in an distorted octahedral environment. All complexes exhibit bright photoluminescence at room temperature. Organic light emitting devices (OLEDs) are fabricated by doping the iridium (III) complexes in 4,4′-N,N′-dicarbazole-biphenyl (CBP), and the device characteristics are investigated. Among these devices, the performances of the optimized devices based on 1 at high current density are among the best reported for devices with iridium (III) complexes as emitters. EL efficiencies show weak dependence on doping concentration and current density. The optimized device exhibits a peak current efficiency of 28.5 cd/A and power efficiency of 11.2 lm/W, respectively, at 20 mA/cm2, an efficiency of 22.7 cd/A at 100 mA/cm2, 80% of the maximum, can be achieved. Short triplet decay time of 1 measured in solid films is supposed to be responsible for the minor lose in EL efficiency, which suggests depressed triplet-triplet annihilation and site saturation of the phosphor.

Publication Source (Journal or Book title)

Society for Information Display - 10th Asian Symposium on Information Display 2007, ASID'07

First Page

344

Last Page

366

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