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Efficient Organic Light-emitting Diodes using Hole-injection Buffer Layer

  • Chung, Dong-Hoe (Department of Electrical Engineering, Kwangwoon University) ;
  • Kim, Sang-Keol (Department of Electrical Engineering, Kwangwoon University) ;
  • Lee, Joon-Yng (Department of Electrical Engineering, Kwangwoon University) ;
  • Hong, Jin-Woong (Department of Electrical Engineering, Kwangwoon University) ;
  • Cho, Hyun-Nam (Electronic Materials and Devices Research Center, KIST) ;
  • Kim, Young-Sik (Electronic Materials and Devices Research Center, KIST) ;
  • Kim, Tae-Wan (Electronic Materials and Devices Research Center, KIST)
  • Published : 2003.03.24
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Abstract

We have investigated the effects of hole-injection buffer layer in organic light-emitting diodes using copper phthalocyanine (CuPc), poly(vinylcarbazole)(PVK), and Poly(3,4-ethylene dioxythiophene):poly(styrenesulfonate) (PEDOT: PSS) in a device structure of $ITO/bufferr/TPD/Alq_3/Al$. Polymer PVK and PEDOT:PSS buffer layer were produced using the spin casting method where as the CuPc layer was produced using thermal evaporation. Current-voltage characteristics, luminance-voltage characteristics and efficiency of device were measured at room temperature at various a thickness of the buffer layer. We observed an improvement in the external quantum efficiency by a factor of two, four, and two and half when the CuPc, PVK, and PEDOT:PSS buffer layer were used, respectively. The enhancement of the efficiency is assumed to be attributed to the improved balance of holes and elelctrons resulting from the use of hole-injection buffer layer. The CuPc and PEDOT:PSS layer function as a hole-injection supporter and the PVK layer as a hole-blocking one.

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References

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