Red Electrophosphorescent Devices Based on Heteroleptic Tris-cyclometalated Iridium Complexes with Fluorinated 2,4-diphenylquinoline Ligands

Abstract

New heteroleptic tris-cyclometalated iridium complex having two different (C^∧N) ligands, [Ir(dpq)₂(dpq-3F)] (dpq = 2,4-diphenylquinoline, dpq-3F = 2-(3′-fluorophenyl)-4-phenylquinoline), have been synthesized and characterized for an efficient red organic light-emitting diodes (OLEDs). The iridium phosphors emit bright red light with its maximum at 608 nm. The heteroleptic tris-cyclometalated iridium complex [Ir(dpq)₂(dpq-3F)] is shown to be a more efficient electrophosphor than the homoleptic tris-cyclometalated iridium complex [Ir(dpq-3F)₃] to avoid the T-T annihilation by decreasing the number of the luminescent ligand. A maximum luminous efficiency was 10.9 cd/A at a current density of J = 0.6 mA/cm². At a higher current density of J = 100 mA/cm², the luminous efficiency maintained 54% of its maximum value as 5.9 cd/A.

Keywords:

• heteroleptic ligands
• organic light-emitting diodes
• red phosphorescent material
• triplet-triplet annihilation

Acknowledgments

This work was supported by Seoul R&BD Program (10555).