Inkable CF3-functionalized benzothiazole/benzimidazole-Ir(III) complexes for efficient bilayer-inkjet-printed OLEDs

Abstract

The inkjet-printed organic light-emitting diodes (OLEDs) are gradually gaining popularity due to their low cost, free vacuum environment, patterning, and large-area display capability, but inkable phosphors are yet less reported. In order to develop inkable phosphorescent luminescent material, the introduction of the strong electron-withdrawing CF3 in the C^N ligand of iridium(III) [Ir(III)] complexes is a wise choice. Herein, a serials of phosphorescent Ir(III) complexes consisting of 2-phenybenzothiazole/1,2-diphenylbenzimidazole with the introduction of CF3 group at ortho (o)/meta (m)/para (p) position of the phenyl ring abbreviated as (obt)2Ir(acac), (mbt)2Ir(acac), (pbt)2Ir(acac), (obm)2Ir(acac), (mbm)2Ir(acac), (pbm)2Ir(acac), respectively, were designed and synthesized. The substituent effect and position effect of CF3 group based on the Ir(III) complexes were investigated in all aspects. The bilayer-inkjet-printed OLEDs with those phosphors were studied and showed promising electroluminescent performances. Among them, the OLEDs with (obt)2Ir(acac)/(obm)2Ir(acac) emitter exhibited the maximum external quantum efficiency of 3.7%/3.3%. In addition, the vacuum-deposited OLEDs with those Ir(III) phosphors as emitters were further investigated and demonstrated outstanding device performance.