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 NdIII. The efficient energy transfer from IrIII moiety to NdIII 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)/Alq3 (tris(8-hydroxyquinoline), 30 nm) exhibited a NIR emission from NdIII ions. The highest EQE achieved is 0.3%, with a maximum radiance of 6.1 μW 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.