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Abstract
In this paper, we demonstrate development of red phosphorescent Organic Light-Emitting Diodes (OLEDs) as the doping concentrations are varied with lithium-quinolate (Liq) doped electron transport layer (ETL). The experimental device has both mixed electron transport layer and electron injection layer. The device configuration was ITO/NPB (50 nm)/4,4′-N-N′-dicarbazole-biphenyl (CBP) doped with 8% bis(2-phenylquinoline)iridium(III) (acetylacetonate) [Ir(pq)2(acac)] (30 nm)/Bphen doped with X% Liq (30 nm)/Liq (2 nm)/Al (100 nm), where the doping concentration of Liq in ETL was varied as 5%∼65%. When the Liq was mixed in the ETL, the efficiency and operating voltage of the experimental devices were improved in comparison with the reference device due to greater electron transport efficiency and an improved hole-electron balance.
Acknowledgment
This work was supported by Energy Resources Technology Development program (2007-E-CM11-P-07) of the Korea Institute of Energy Technology Evaluation and Planning (KETEP) grant funded by the Korea government Ministry of Knowledge Economy and Strategy Technology Development program (No. 10030834) from Ministry of Knowledge Economy (MKE). Moreover, this research was also supported by the ERC program of the Korea Science and Engineering Foundation (KOSEF) grant funded by the Korea Ministry of Education, Science and Technology (MEST) (No. R11-2007-045-03001-0).