Synthesis and characterization of green-emitting Ir(iii) complexes based on a functionalized benzimidazole ligand

Abstract

Two new green-emitting Ir(III) complexes containing a hole transporting group-functionalized benzimidazole ligand (L) as the cyclometalated ligand, and acetylacetonate and picolinate as the ancillary ligands, Ir(L)₂(acac) and Ir(L)₂(pic), where L = 1-(4-(9H-carbazole-9-yl)phenyl)methyl-2-(4-(9H-carbazol-9-yl)phenyl)-1H-benzimidazole, were successfully synthesized for use as green phosphorescent organic light-emitting diodes. The photophysical and electrochemical properties and thermal stabilities of the Ir(III) complexes were systematically investigated. The results showed that the Ir(III) complexes had high thermal stabilities and strong green emissions, and the ancillary ligand pic induced a blue shift of 10 nm in comparison with the Ir(L)₂(acac) complex (517 nm). Solution processed light-emitting devices based on the Ir(L)₂(acac) complex exhibit a maximum efficiency of 12.57 cd A⁻¹ and a maximum brightness of 4914 cd m⁻², while devices based on Ir(L)₂(pic) display a maximum efficiency of 6.73 cd A⁻¹ and a maximum brightness of 3690 cd m⁻².