Highly efficient electroluminescent materials based on fluorinated organometallic iridium compounds

Abstract

We report a class of highly efficient electroluminescent materials based on fluorinated iridium compounds. Using aluminum as the cathode, a device, using fac-tris[5-fluoro-2(5-trifluoromethyl-2-pyridinyl)phenyl-C,N]iridium (Ir-2h) as the luminescent layer, displayed intense electroluminescence at 525 nm with an efficiency of 20 cd/A and a maximum radiance of 4800 cd/m2. Differing from the previously reported Ir(ppy)3, Ir-2h can be used in the undiluted form without the use of a charge-transporting host. This indicates that Ir-2h by itself has good enough charge-transporting properties. Photoluminescence studies at room temperature and 77 K revealed that electroluminescence originates from the metal-to-ligand charge transfer state with a quantum yield of 0.56 for Ir-2h and 0.5 for Ir(ppy)3 in toluene at room temperature. In the thin-film form, photoluminescence quantum yield of Ir-2h is a factor of 10 greater than that of Ir(ppy)3 due to the larger self-quenching effect of Ir(ppy)3.

Color Tunable Organic Light‐Emitting Diodes Using Pentafluorophenyl‐Substituted Iridium Complexes

“…We expected a bulky and fluorinated substituent, such as a pentafluorophenyl group, to reduce the intermolecular interaction of the complexes and to enhance the PL by preventing self-quenching. [10,14,16] In addition to that, we are interested in examining how the position of the substitution with the p-electron substituent such as the pentafluorophenyl group affects the PL of the complex from the viewpoint of color tuning the OLED. Figure 2 shows PL spectra for the complexes doped in a host material of 4,4¢-di(carbazole-9-yl)biphenyl (CBP) film.…”

“…Preparation of 1: The synthetic procedure of 1 followed a route reported in the literature [10]. 1-Chlorohexadecane (0.25 mol, 65.22 g) was mixed with 1-methylimidazole (0.25 mol, 20.53 g).…”

Encapsulated Cores: Host‐Free Organic Light‐Emitting Diodes Based on Solution‐Processible Electrophosphorescent Dendrimers

“…Some devices containing neat films of small molecule fluorinated iridium(III) complexes have had reasonable efficiencies. [10,18] Nevertheless, it is generally the case that, when working with small phosphorescent molecules, blended light-emitting films are much better for controlling intermolecular interactions and achieving efficient devices. [10] A more elegant, robust, and simple way of controlling intermolecular interactions is to modify the molecular structure so that a single material could be used as the light-emitting layer.…”

The Efficient Green Emitting Iridium(III) Complexes and Phosphorescent Organic Light Emitting Diode Characteristics

“…A promising phosphorescent metal complex should have a short lifetime in the excited state and high phosphorescent efficiency for the highly efficient OLEDs. Among the various phosphorescent emitters, iridium complexes remain the most effective material due to their ability to achieve maximum internal quantum efficiency, nearly 100%, and high external quantum efficiency in the devices (O'Brien et al 2003;Duan et al 2003;Xie et al 2001;Noh et al 2003;Wang et al 2001;Neve et al 2001). The most widely used homoleptic green emitting iridium(III) complex, fac-tris(2-phenylpyridine)iridium [Ir(ppy) 3 ], derivatives have shown a number of advantages such as ease of tuning emission energy by functionalizing the 'ppy' ligand with electron donating and electron withdrawing substituents and high phosphorescent quantum efficiency at room temperature Jung et al 2004;Lee et al 2009).…”