A simple unilateral homogenous PhOLEDs with enhanced efficiency and reduced efficiency roll-off

Abstract

In this paper, highly efficient phosphorescent organic lighting emitting diodes (PhOELDs) with low efficiency roll-off are demonstrated by using a unilateral homogenous device structure with wide band-gap material 4, 4', 4″-tri(N-carbazolyl)-triphenylamine (TCTA) as hole transporting layer and emitting layer (EML). The optimized blue device exhibits a high power efficiency of 40 lm/W, external quantum efficiency of 19.2% and current efficiency of 37.7 cd/A. More importantly, the device exhibits a low efficiency roll-off at 1000 cd/m². In addition, the white homogenous PhOLEDs only exhibits the efficiency roll-off 5.6% and 17.5%, corresponding to the brightness of 1000 and 5000 cd/m² respectively. These interesting results demonstrate that the simple unilateral homogenous device structure is a promising way to enhance the device efficiency and reduce the efficiency roll-off.

Keywords

enhance efficiency / efficiency roll-off / unilateral homogenous structures

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Acknowledgements

This research work was supported by the National Natural Science Foundation of China (Grant Nos. 21161160442 and 51203056), the National Basic Research Program of China (973 Program) (No. 2013CB922104), Wuhan Science and Technology Bureau (NO. 01010621227) and the Open Research Fund of State Key Laboratory of Polymer Physics and Chemistry.

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2014 Higher Education Press and Springer-Verlag Berlin Heidelberg