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Increasing the operating lifetime of green phosphorescent organic light emitting diodes by reducing charge
Yibing Wu1, Jianhui Luo1, Chengwei Lin1
1Institute of Polymer Optoelectronic Materials and Devices, Guangdong Provincial Key Laboratory of Luminescence from Molecular Aggregates, State Key Laboratory of Luminescent Materials and Devices, South China University of Technology, Guangzhou 510640, People's Republic of China. msdgma@scut.edu.cn.
Abstract:
The stability and degradation mechanism of phosphorescent organic light emitting diodes (OLEDs) has been an unresolved problem in the past decades. Here, we found that electron accumulation at the interface between the electron blocking layer and the emitting layer is one of the reasons for device degradation. By inserting a thin layer with a shallower LUMO level than that of the electron transporting layer between the emitting layer and the electron transporting layer, we successfully reduced the density of electrons at the interface and greatly improved the lifetime of the resulting green phosphorescent OLEDs. The half decay lifetime LT50 at the initial luminance of 1000 cd m-2 reached as high as 399 h, which is 1.7 times longer than that of the compared device without a thin layer.
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