Application of heteroleptic iridium complexes with fluorenyl-modified 1-phenylisoquinoline ligand for high-efficiency red polymer light-emitting devices

A series of new heteroleptic iridium complexes bearing fluorenyl-modified 1-phenylisoquinoline as the first ligand and different ancillary ligands has been prepared and characterized. These complexes bis(1-(3-(9,9-dimethyl-fluoren-2-yl)phenyl)isoquinoline-C2,N′)iridium(III)acetylacetonate(Ir(DMFPQ)2acac)), bis(1-(3-(9,9-dimethyl-fluoren-2-yl)phenyl)isoquinoline-C2,N′)iridium(III)(3-(pyridin-2-yl)-1,2,4-triazolate)(Ir(DMFPQ)2pt) and bis(1-(3-(9,9-dimethyl-fluoren-2-yl)phenyl)isoquinoline-C2,N′)iridium(III)(2-(2-pyridyl)benzimidazolate)(Ir(DMFPQ)2pbi) showed red phosphorescent emissions of 615–630 nm in dichloromethane solution. The device fabricated with these complexes doped into a host polyfluorene (PFO) blend with 30% of an electron transport material 2-(4-biphenyl)-5-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD) showed high device efficiencies. Ir(DMFPQ)2acac exhibited red emission with an external quantum efficiency(ηext) of 14.3% and luminous efficiency(ηc) of 7.8 cd/A at 1.2 mA/cm2 and the maximum brightness reached 10 006 cd/m2 (Commission Internationale de I’Eclairage(CIE) chromaticity coordinates: (0.67, 0.32)) at 412 mA/cm2. Ir(DMFPQ)2pt showed a ηext of 13.0% and ηc of 9.2 cd/A at 17 mA/cm2, 1532 cd/m2, and the maximum brightness reached 15085 cd/m2 (CIE: 0.64, 0.34) at 360 mA/cm2.