Efficient near-infrared organic light-emitting diodes based on multimetallic assemblies of lanthanides and iridium complexes

Two structurally simple Iridium(III) complexes with pyrimidin-imidazole derivatives as the ancillary ligands (Ir1 and Ir2) were synthesized. Photophysical studies showed that the iridium complexes have suitable triplet energy levels for sensitizing Nd-III. The efficient energy transfer from Ir-III moiety to Nd-III is observed in both solutions and films. Utilizing co-deposition film of Ir-Nd assemblies as the emitting layer, nondoped OLEDs were fabricated. EL devices with a structure of NPB (1,4-bis((1-naphthylphenyl) amino) biphenyl, 30 nm)/Ir1-Nd(PMIP)(3) (1-phenyl-3-methyl-4-isobutyryl-5-pyrazolone, 1:1, 40 nm)/BCP (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline, 10 nm)/Alq(3) (tris(8-hydroxyquinoline), 30 nm) exhibited a NIR emission from Nd-III ions. The highest EQE achieved is 0.3%, with a maximum radiance of 6.1 mu W cm(-2) at the main emission wavelength of 1060 nm. This result provides a useful guidance for the future work of lanthanide complexes based NIR OLEDs. (C) 2009 Elsevier B.V. All rights reserved.