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Proceedings Paper

Improved electroluminescence efficiency of organic light-emitting diodes by using molecularly doped hole-transport layer
Author(s): C. H. Lee; Y. C. Shin; D. S. Kwon; H. K. Lee
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Paper Abstract

We studied the hole mobility of molecularly doped hole transport layer (HTL), 4,4'-bis[N-(1-napthyl)-N-phenyl-amino]-biphenyl (α-NPD), as a function of the doping concentration of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) by employing the time-of-flight photoconductivity (TOF-PC) technique. The hole transport is non-dispersive for α-NPD and the hole mobility of pristine α-NPD is about 10-3 cm2/Vs at room temperature. However, the hole mobility decreases with the BCP doping concentration in α-NPD. We characterized the current-voltage-luminance dependence, the EL quantum efficiency, and transient EL response for the devices of ITO/doped α-NPD/Alq3/LiF/Al. The devices with the BCP doped α-NPD show higher EL efficiency compared with the device with pristine α-NPD. The reduced hole mobility in the BCP doped α-NPD enhances the electron-hole balance, resulting in an increased EL efficiency.

Paper Details

Date Published: 9 October 2005
PDF: 8 pages
Proc. SPIE 5937, Organic Light-Emitting Materials and Devices IX, 593719 (9 October 2005); doi: 10.1117/12.627072
Show Author Affiliations
C. H. Lee, Seoul National Univ. (South Korea)
Y. C. Shin, Seoul National Univ. (South Korea)
D. S. Kwon, Seoul National Univ. (South Korea)
H. K. Lee, Seoul National Univ. (South Korea)


Published in SPIE Proceedings Vol. 5937:
Organic Light-Emitting Materials and Devices IX
Zakya H. Kafafi; Paul A. Lane, Editor(s)

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