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Simple and High Efficiency Phosphorescence Organic Light-Emitting Diodes with Codeposited Copper(I) Emitter

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journal contribution
posted 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.