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.

Influences of fluorination on homoleptic iridium complexes with C∧N=N type ligand to material properties, ligand orientation and OLED performances

“…E ox refers to oxidation potential of molecules relative to the reference electrode used in measurement [35,36]. LUMO values can be deduced using HOMO and the [27,37,38] obtained from the absorption spectra shown in Figure 1(a). All the photophysics and electrochemical data are summarized in Table 1.…”

Non-interlayer and color stable WOLEDs with mixed host and incorporating a new orange phosphorescent iridium complex

“…1b. The HOMO energy level was calculated from the oxidation potential (E ox ), while the LUMO energy level was derived by combining the HOMO level with the optical bandgap obtained from the absorption edge [24,25]. To determine the oxidation potentials, the reference electrode was calibrated using a ferrocene/ferrocenium salt couple, which is assumed to have a redox potential with an absolute energy level of À4.80 eV in vacuum.…”

Recent progress in the use of fluorescent and phosphorescent organic compounds for organic light-emitting diode lighting

“…Nonetheless, the device that used emitter 71 had a CIE of (0.19, 0.44), which is more greenish blue compared to the (0.16, 0.36) CIE of the device that used emitter 70. Lee et al 69 developed emitters 72 and 73 as perfluoro carbonyl-substituted iridium complexes for the development of phosphorescent blue dopants with high efficiency and emission of deep-blue light (see Fig. 11).…”