Simple and High Efficiency Phosphorescence Organic Light-Emitting Diodes with Codeposited Copper(I) Emitter
journal contributionposted on 08.04.2014, 00:00 by Zhiwei Liu, Jacky Qiu, Feng Wei, Jianqiang Wang, Xiaochen Liu, Michael G. Helander, Sarah Rodney, Zhibin Wang, Zuqiang Bian, Zhenghong Lu, Mark E. Thompson, Chunhui Huang
Phosphorescent copper(I) complexes show great promise as emitters in organic light-emitting diodes (OLEDs). However, most copper(I) complexes are neither soluble nor stable toward sublimation and, hence, not amenable to the typical methods to fabricate OLEDs. In this work, a compound 3-(carbazol-9-yl)-5-((3-carbazol-9-yl)phenyl)pyridine (CPPyC) was designed as both a good ligand and host matrix. Codeposition of CPPyC and copper iodide (CuI) gives luminescent films with photoluminescent quantum yields (PLQY) as high as 100%. A dimeric copper(I) complex Cu2I2(CPPyC)4 is formed in the thin film, characterized by X-ray absorption spectroscopy. A series of simple, highly efficient green-emitting OLEDs were demonstrated by using the codeposited film as an emissive layer. A device comprised of only CPPyC and CuI gave an external quantum efficiency (EQE) of 12.6% (42.3 cd/A) at 100 cd/m2, while a device with tailored hole and electron transporting layers gave an efficiency of 15.7% (51.6 cd/A) at the same brightness.