한국정보디스플레이학회:학술대회논문집

The Korean Infomation Display Society (한국정보디스플레이학회)
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Characteristic Improvements of Organic Light Emitting Diodes By Using Co-Evaporated Cathodes

  • Kwak, Y.H. (Dept. of Electrical and Control Engineering, Hongik Univ.) ;
  • Lee, Y.S. (Dept. of Electrical and Control Engineering, Hongik Univ.) ;
  • Park, J.H. (Dept. of Electrical and Control Engineering, Hongik Univ.) ;
  • Choi, Jong-Sun (Dept. of Electrical and Control Engineering, Hongik Univ.)
  • Published : 2002.08.21
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Abstract

In order to improve the power efficiency of multi-layer organic light emitting diodes (OLEDs), electron injection into ETL(electron transport layer) from cathode at the interface between ETL and cathode was enhanced by interposing a proper electron injection layer at the interface. The HTL(hole transport layer) and ETL materials used were N, N'diphenyl- N, N' - bis(3-methylphenyl-1, 1'- biphenyl - 4, 4 'diamine (TPD) and tris (8-hydroxyquinoline) aluminum ($Alq_3$) respectively. Cathodes using co-evaporated Al-CsF, Al-KF, and Al-NaF composites are adopted to enhance the electrical and optical properties of OLEDs. OLEDs with alkaline metal-doped cathode show a luminance of as high as 35,000 cd/$m^2$, and external quantum efficiency about 1.35 %. In addition, they show higher power efficiency at all bias conditions and good reproducibility.

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