Jpn. J. Appl. Phys. 46 (2007) pp. 5164-5167  |Previous Article| |Next Article|  |Table of Contents|
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Undoped White Organic Light-Emitting Diodes Utilizing Two Sources of Excitons

Yoga Divayana^1,2, Xiao Wei Sun^1,2, Baijun Chen¹, Guo Qiang Lo², Changyun Jiang², Dim Lee Kwong², and Kalluri R. Sarma³

(Received March 20, 2007; accepted May 25, 2007; published online August 6, 2007)

We report two undoped white organic light-emitting diodes with the structures of ITO/m-MTDATA/Alq₃/NPB/BCP/Alq₃/Mg:Ag (device A), and ITO/NPB/DCM/NPB/Alq₃/NPB/BCP/Alq₃/Mg:Ag (device B), where ITO is indium tin oxide, m-MTDATA is 4,4',4''-tris{N,(3-methylphenyl)-N-phenylamino}-triphenylamine, Alq₃ is tris(8-hydroxyquinoline) aluminum, NPB is N,N'-di(naphth-2-yl)-N,N'-diphenyl-benzidine, BCP is 2,9-dimethyl-4,7-diphenylphenanthroline, and DCM is 4-(dicyanomethylene)-2-methyl-6-(p-dimethyl aminostyryl)-4H-pyran. Red emission was harvested from the exciplex at the m-MTDATA/Alq₃ interface and DCM (0.5 nm) for devices A and B, respectively, while green and blue emissions were from Alq₃ and NPB respectively, for both devices. A maximum brightness of 1100 and 4500 cd/m² was achieved at a current density of 270 mA/cm² (12 V) for devices A and B, respectively. Device B showed a maximum external quantum efficiency of 0.89% photon/electron (2 cd/A), which is about four times of that of device A.

URL: http://jjap.jsap.jp/link?JJAP/46/5164/
DOI: 10.1143/JJAP.46.5164
KEYWORDS:excitons, white, OLED, undoped, exciplex, fluorescent, organic light-emitting diodes

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