Synchrotron radiation photoelectron spectroscopy study of oxygen doping effect by oxygen plasma treatment to inverted top emitting organic light emitting diodes

  • Hong, Ki-Hyon (Division of Advanced Materials Science and Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH)) ;
  • Kim, Ki-Soo (Division of Advanced Materials Science and Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH)) ;
  • Kim, Sung-Jun (Division of Advanced Materials Science and Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH)) ;
  • Choi, Ho-Won (LG Electronics Inc.) ;
  • Tak, Yoon-Heung (LG Electronics Inc.) ;
  • Lee, Jong-Lam (Division of Advanced Materials Science and Department of Materials Science and Engineering, Pohang University of Science and Technology (POSTECH))
  • Published : 2009.10.12

Abstract

We reported that the evidence of oxygen doping to copper-phthalocyanine (CuPc) by $O_2$-plasma treatment to Au electrode of inverted top emitting organic light emitting diodes (ITOLEDs). The operation voltage of OLEDs at 150 mA/$cm^2$ decreased from 16.1 to 10.3 V as oxygen atoms indiffued to CuPc layer using $O_2$-plasma. Synchrotron radiation photoelectron spectroscopy results showed that a new bond of Cu-O appeared and the energy difference between the highest occupied molecular orbital and $E_F$ is lowered by 0.20 eV after plasma treatment. Thus the hole injection barrier was lowered, reducing the turn-on voltage and increasing the quantum efficiency of OLEDs.

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