Abstract
In this letter, we used space charge limited current measurements to evaluate the hole mobilities of candidate host materials with or without doped phosphorescent guests through a study of “hole only” devices. We found different impacts to hole mobility in each material when the dopant concentration changes. We postulated that the guest/host energy level matching in the light emissive layer plays an important role in the performance of organic light emitting devices. A number of white organic light emitting devices were designed to prove the supposition. Using guest/host energy level matching a device was fabricated which demonstrated higher efficiency, lower efficiency roll-off and lower driving voltage compared to a non-level-matched device.
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Acknowledgments
This work was supported by Program of international science and technology cooperation (2014DFG12390), National High Technology Research and Development Program of China (Grant No. 2011AA03A110), Ministry of Science and Technology of China (Grant No. 2010CB327701, 2013CB834802), the National Natural Science Foundation of China (Grant Nos. 61275024, 61274002, 61275033, 6137706 and 41001302), Scientific and Technological Developing Scheme of Jilin Province (Grant No. 20140101204JC, 20140520071JH), Scientific and Technological Developing Scheme of Changchun (Grant No.13GH02), the Opened Fund of the State Key Laboratory on Integrated Optoelectronics No. IOSKL2012KF01.
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Luo, Y., Duan, Y., Chen, P. et al. Effect of hole mobilities through the emissive layer on space charge limited currents of phosphorescent organic light-emitting diodes. Opt Quant Electron 47, 375–385 (2015). https://doi.org/10.1007/s11082-014-9919-x
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DOI: https://doi.org/10.1007/s11082-014-9919-x