Optoelectronic properties of new functionalized heteroleptic iridium complex

Abstract

A new functionalized heteroleptic iridium complex coordinated with 1-phenylisoquinoline (1-piq) and a functionalized β-diketone (G1), Ir(1-piq)₂G1, was synthesized and characterized by ¹H-NMR, mass spectrometry and elemental analysis. The larger conjugation of the replacement of acetylacetone (acac) by a functionalized β-diketonate ligand led to a significant decrease in the HOMO level toward vacuum level, while Ir(1-piq)₂G1 and Ir(1-piq)₂(acac) showed red phosphorescent emissions of about 620 nm in dichloromethane solution. The phosphorescent polymer light-emitting devices were achieved, with the complexes incorporated with polyfluorene (PFO) as a host polymer doped with 30% of 5-(4-biphenylyl)-2-(4-tert-butylphenyl)-1,3,4-oxadiazole (PBD) as electron transport material. The energy transfer mechanism of the devices was also discussed. The lower EL performance of Ir(1-piq)₂G1 is ascribed to the inter-ligand energy transfer, indicating that it is important to control the energy level of the cyclometalated and ancillary ligands.

Keywords

iridium complex / phosphorescence / energy transfer / ancillary ligands