Color tuning of OLEDs using the Ir complexes of white emission by adjusting the band gap of host materials

Abstract

We report on white organic light-emitting diodes (WOLEDs) based on single white dopants, Ir(pq)2(F2-ppy) and Ir(F2-ppy)2(pq), where F2-ppy and pq are 2-(2,4-difluorophenyl) pyridine and 2-phenylquinoline, respectively. The similar phosphorescent lifetime of two ligands lead to luminescence emission in two ligands simultaneously. However, the emission color of the devices was reddish, because the energy was not transferred efficiently from the 4,4, N, N‘-dicarbazolebiphenyl (CBP) to the F2−ppy ligand, due to the small band gap of the CBP. Accordingly, we used 1,4-phenylenesis(triphenylsilane) (UGH2) with a large band gap, instead of CBP as the host material. As a result, it was possible to adjust the emission color by the host material. The luminous efficiency of the device with Ir(F2-ppy)2(pq) doped in UGH2 was about 11 cd/A at 0.06 cd/m2. © 2008 Taylor & Francis Group, LLC.