Efficient green phosphorescent Ir(iii) complexes with β-diketonate ancillary ligands

Abstract

Three new iridium complexes containing 3-(pyridine-2-yl)coumarin as the cyclometalated ligand (L) and 1-(3,5-bis(trifluoromethyl)phenyl)-3-(4-methoxyphenyl)propane-1,3-dione (¹L), 1-(furan-2-yl)-4,4-dimethylpentane-1,3-dione (²L) and 1-(3,4-dimethoxyphenyl)-4,4-dimethylpentane-1,3-dione (³L) as the ancillary ligands, respectively, were synthesized as emissive materials for organic light-emitting devices. Among them, the crystal structure of the Ir(III) complex based on the ancillary ligand ¹L was characterized by single crystal X-ray diffraction. The photophysical and electrochemical properties and thermal stabilities of the Ir(III) complexes were systematically investigated. The results showed that all the Ir(III) complexes not only exhibit excellent thermal stabilities but also emit strong green emissions. Furthermore, based on these Ir(III) complexes, solution-processed green organic light-emitting devices with a configuration of ITO/PEDOT:PSS/PVK:PBD (7 : 3, wt%):Ir(III) complex (x wt%, 30 nm)/TPBi (50 nm)/Liq (2 nm)/Al (150 nm) have been successfully fabricated, in which the devices fabricated from the Ir(III) complex based on the ancillary ligand ³L exhibited the best electroluminescence performance with a maximum brightness of 9275 cd m⁻² and a maximum luminous efficiency of 19.38 cd A⁻¹ and a maximum external quantum efficiency (EQE) of 5.37%.