22 September 2015 Highly enhanced phosphorescent organic light-emitting diodes with cesium fluoride doped electron injection layer
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Abstract
We systematically investigate doping effect of cesium fluoride (CsF) on the device performance of organic light-emitting diodes (OLEDs). CsF can be used as a stable n-type dopant due to its low chemical reactivity and simple deposition process. We have observed that CsF could be employed as an effective n-type dopant in thin films of 3,3'-[5'- [3-(3-Pyridinyl)phenyl][1,1':3',1''-terphenyl]-3,3''-diyl]bispyridine (TmPyPB) through experimental studies of optical absorption spectroscopy, and X-ray photoelectron spectroscopy (XPS) with different doping concentration. In addition, we measured bulk resistance using impedance spectroscopy in an electron-only devices (EODs) with CsF-doped TmPyPB. As the doping ratio of the CsF increases, the current densities of EOD increase and the bulk resistances of the CsF-doped layer decrease. Owing to high electrical property of CsF-doped TmPyPB in EIL, green phosphorescent OLEDs showed significantly lower voltage and considerably enhanced efficiency. The device with 30 vol% CsF-doped TmPyPB showed power efficiency of 28.1 lm/W at 1000 cd/m2, whereas the device with pristine TmPyPB exhibited 13.8 lm/W. From these results, CsF-doped TmPyPB as EIL can reduce bulk resistance of EIL and improve the electron-injection and transport properties of electron-transport layer. Therefore, we can utilize CsF as an efficient n-type dopant in EIL of OLEDs.
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Jongseok Han, Jongseok Han, Yongwon Kwon, Yongwon Kwon, Jiho Sohn, Jiho Sohn, Changhee Lee, Changhee Lee, } "Highly enhanced phosphorescent organic light-emitting diodes with cesium fluoride doped electron injection layer", Proc. SPIE 9566, Organic Light Emitting Materials and Devices XIX, 95662E (22 September 2015); doi: 10.1117/12.2187588; https://doi.org/10.1117/12.2187588
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