Current Applied Physics

Korean Physical Society (한국물리학회)
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Organic electrophosphorescent devices with mixed hole transport material as emission layer

Matsushima, Hidenobu;Naka, Shigeki;Okada, Hiroyuki;Onnagawa, Hiroyoshi

  • Published : 20050500
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Abstract

We report on the reduction of driving voltage in organic electrophosphorescent devices with mixed hole transport material as emission layer. The emission layer was mixed with N,N’-diphenyl-N,N’-(3-methylphenyl) -[1,1’-biphenyl]-4,4’-diamine (TPD) as a hole-transport material, 4,4’-bis(9-carbazolyl)-biphenyl (CBP) as a host material for a phosphorescent material, tris(2-phenylpyridine) iridium ($Ir(ppy)_3$) as a phosphorescent material and 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (bathocuproine: BCP) as an electron-transport material. The emission occurred from $Ir(ppy)_3$ and was independent on the ratio of TPD and CBP. For triplelayered device with the TPD:CBP mixing ratio of 10:90, maximum luminance obtained was 104,000 cd/$m^2$ at V = 12 V, J = 490 mA/$cm^2$. Maximum efficiency was 20lm/W at 3.1 mA/$cm^2$.

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