Ionic Iridium(III) Complexes with Bulky Side Groups for Use in Light Emitting Cells: Reduction of Concentration Quenching
作者：Carsten Rothe, Chien-Jung Chiang, Vygintas Jankus, Khalid Abdullah, Xianshun Zeng, Rukkiat Jitchati
關(guān)鍵字：light emitting cells, Ionic Iridium(III) Complexes
論文來源：期刊
具體來源：Adv. Funct. Mater. 2009, 19, 2038–2044
發(fā)表時間：2009年
Here, the photophysics and performance of single-layer light emitting cells (LECs) based on a series of ionic cyclometalated Ir(III) complexes of formulae [Ir(ppy)2( bpy)]+ PF6- and [Ir(ppy)2(phen)]+ PF6- where ppy, bpy, and phen are 2-phenylpyridine, substituted bipyridine and substituted phenanthroline ligands, respectively, are reported. Substitution at the N^N ligand has little effect on the emitting metal-ligand to ligand charge-transfer (MLLCT) states and functionalization at this site of the complex leads to only modest changes in emission color. For the more bulky complexes the increase in intermolecular separation leads to reduced exciton migration, which in turn, by suppressing concentration quenching, significantly increases the lifetime of the excited state. On the other hand, the larger intermolecular separation induced by bulky ligands reduces the charge carrier mobility of the materials, which means that higher bias fields are needed to drive the diodes. A brightness of ca. 1000 cdm-2 at 3 V is obtained for complex 5, which demonstrates a beneficial effect of bulky substituents.