Transactions on Electrical and Electronic Materials

The Korean Institute of Electrical and Electronic Material Engineers (한국전기전자재료학회)
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Stability of ITO/Buffer Layer/TPD/Alq3/Cathode Organic Light-emitting Diode

  • Chung, Dong-Hoe (Department of Electrical Engineering, Kwangwoon University) ;
  • Ahn, Joon-Ho (Department of Electrical Engineering, Kwangwoon University) ;
  • Oh, Hyun-Seok (Department of Electrical Engineering, Kwangwoon University) ;
  • Park, Jung-Kyu (Department of Electrical Engineering, Kwangwoon University) ;
  • Lee, Won-Jae (Department of Electronic Engineering, Kyungwon University) ;
  • Choi, Sung-Jai (Department of Electronic Engineering, Kyungwon University) ;
  • Jang, Kyung-Uk (Department of Electrical Engineering, Kyungwon University) ;
  • Shin, Eun-Chul (Department of Information Display, Hongik University) ;
  • Kim, Tae-Wan (Department of Information Display, Hongik University)
  • Published : 2007.12.31
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Abstract

We have studied stability in organic light-emitting diode depending on buffer layer and cathode. A transparent electrode of indium-tin-oxide(ITO) was used as an anode. An electron injection energy barrier into organic material is different depending on a work function of cathodes. Theoretically, the energy barriers for the electron injection are 1.2 eV, -0.1 eV, and 0.0 eV for Al, LiAl, and LiF/Al at 300 K, respectively. We considered the cases that holes are injected to organic light-emitting diode. The hole injection energy barrier is about 0.7 eV between ITO and TPD without buffer layer. For hole-injection buffer layers of CuPc and PEDOT:PSS, the hole injection energy barriers are 0.4 eV and 0.5 eV, respectively. When the buffer layer of CuPc and PEDOT:PSS is existed, we observed the effects of hole injection energy barrier, and a reduction of operating-voltage. However, in case of PVK buffer layer, the hole injection energy barrier becomes high(1.0 eV). Even though the operating voltage becomes high, the efficiency is improved. A device structure for optimal lifetime condition is ITO/PEDOT:PSS/TPD/$Alq_3$/LiAl at an initial luminance of $300cd/m^2$.

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References

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