title: Deep-blue phosphorescence from perfluoro carbonyl-substituted iridium complexes.
abstract: The new deep-blue iridium(III) complexes, (TF)2Ir(pic), (TF)2Ir(fptz), (HF)2Ir(pic), and (HF)2Ir(fptz), consisting of 2',4″-difluororphenyl-3-methylpyridine with trifluoromethyl carbonyl or heptafluoropropyl carbonyl at the 3' position as the main ligand and a picolinate or a trifluoromethylated-triazole as the ancillary ligand, were synthesized and characterized for applications in organic light-emitting diodes (OLEDs). Density function theory (DFT) calculations showed that these iridium complexes had a wide band gap, owing to the introduction of the strong electron withdrawing perfluoro carbonyl group. Time-dependent DFT (TD-DFT) calculations suggested that their lowest triplet excited state was dominated by a HOMO → LUMO transition and that the contribution of the metal-to-ligand charge transfer (MLCT) was higher than 34% for all four complexes, indicating that strong spin-orbit coupling exists in the complexes. The 10 wt % (TF)2Ir(pic) doped 9-(3-(9H-carbazole-9-yl)phenyl)-3-(dibromophenylphosphoryl)-9H-carbazole (mCPPO1) film exhibited the highest photoluminescence quantum yield of 74 ± 3% among the films based on the four complexes. Phosphorescent OLEDs based on (TF)2Ir(pic) and (TF)2Ir(fptz) exhibited maximum external quantum efficiencies of 17.1% and 8.4% and Commission Internationale de l'Eclairage (CIE) coordinates of (0.141, 0.158) and (0.147, 0.116), respectively. These CIE coordinates represent some of the deepest blue emissions ever achieved from phosphorescent OLEDs with considerably high EQEs.
authors.affiliation: WCU Hybrid Materials Program, Department of Materials Science and Engineering and the Center for Organic Light Emitting Diode, Seoul National University , Seoul 151-744, South Korea.
authors.forename: Sunghun
authors.initials: S
authors.lastname: Lee
authors.forename: Seul-Ong
authors.initials: SO
authors.lastname: Kim
authors.forename: Hyun
authors.initials: H
authors.lastname: Shin
authors.forename: Hui-Jun
authors.initials: HJ
authors.lastname: Yun
authors.forename: Kiyull
authors.initials: K
authors.lastname: Yang
authors.forename: Soon-Ki
authors.initials: SK
authors.lastname: Kwon
authors.forename: Jang-Joo
authors.initials: JJ
authors.lastname: Kim
authors.forename: Yun-Hi
authors.initials: YH
authors.lastname: Kim