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http://dx.doi.org/10.4313/JKEM.2009.22.9.781

Effects of BCP Thickness on the Electrical and Optical Characteristics of Blue Phosphorescent Organic Light Emitting Diodes  

Seo, Yu-Seok (순천향대학교 디스플레이신소재공학과)
Moon, Dae-Gyu (순천향대학교 디스플레이신소재공학과)
Publication Information
Journal of the Korean Institute of Electrical and Electronic Material Engineers / v.22, no.9, 2009 , pp. 781-785 More about this Journal
Abstract
We have fabricated simple triple-layer blue-emitting phosphorescent organic light emitting diodes (OLEDs) using different thicknesses (25 and 55 nm) of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) electron transport layers. 1,1-bis[4-bis (4-methylphenyl)- aminophenyllcyclohexane (TAPC), bis[(4,6-di-fluorophenyl)-pyridinate-$N,C^{2]picolinate (FIrpic) and N,N' -dicarbazolyl-3,5-benzene (mCP) were used as hole transport, blue guest and host materials, respectively. The driving voltage, electroluminescence (EL) efficiency and emission characteristics of devices were investigated. The maximum EL efficiency was 20 cd/A in the device with 55 nm BCP layer, which efficiency was about 33% higher than the device with 25 nm BCP layer. The higher efficiency in the 55 nm BCP device resulted from the enhanced electron-hole balance. In the EL spectrum of blue phosphorescent OLED with BCP layer, the relative intensity between 470 and 500 nm peaks was related to the location of emission zone.
Keywords
OLED; Blue; Phosphorescence; Electron transport layer; BCP;
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