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http://dx.doi.org/10.12925/jkocs.2015.32.1.1

Effect of Stepwise Doping on Performance of Green Phosphorescent Organic Light-Emitting Diodes  

Hwang, Kyo-Min (Dept. of Information Display, Hongik University)
Lee, Song-Eun (Dept. of Information Display, Hongik University)
Lee, Seul-Bee (Dept. of Information Display, Hongik University)
Yoon, Seung-Soo (Dept. of Chemistry, Sungkyunkwan University)
Kim, Young-Kwan (Dept. of Information Display, Hongik University)
Publication Information
Journal of the Korean Applied Science and Technology / v.32, no.1, 2015 , pp. 1-6 More about this Journal
Abstract
We investigated green phosphorescent organic light-emitting diodes with stepwise doping to improve efficiency roll-off and operational lifetime by efficient distribution of triplet excitons. The host material which was 4,4,N,N'-dicarbazolebiphenyl (CBP) of bipolar characteristic that can control the carrier in emitting layer (EML). When the EML devided into four parts with different doping concentration, each devices shows various efficiency roll-off and lifetime enhancement. The distribution of the carrier and excitons in the EML can be confirmed by using stepwise doping structure. The properties of device C exhibited luminous efficiency of 51.10 cd/A, external quantum efficiency of 14.88%, respectively. Lifetime has increased 73.70% compared to the reference device.
Keywords
green phosphorescent organic light-emitting diodes; recombination zone; stepwise doping; lifetime; charge balance;
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