The Transactions of the Korean Institute of Electrical Engineers C (대한전기학회논문지:전기물성ㆍ응용부문C)

The Korean Institute of Electrical Engineers (대한전기학회)
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Studies on the Optical and the Electrical Characterization of Organic Electroluminescence Devices of Europium Complex Fabricated with PVD(Physical Vopor Deposition) Technique

진공 증착법에 의하여 제작한 Europium complex 유기 박막 전기발광소자의 광학적.전기적 특성에 관한 연구.

  • Lee, Myeong-Ho (Dept. of Electronic and Electrical Engineering, Hongik University) ;
  • Lee, Han-Seong (Dept. of Electronic and Electrical Engineering, Hongik University) ;
  • Kim, Yeong-Gwan (Dept. of Electronic and Electrical Engineering, Hongik University) ;
  • Kim, Jeong-Su (Dept. of Electronic and Electrical Engineering, Hongik University)
  • 이명호 (홍익대 대학원 전기제어공학과) ;
  • 이한성 (홍익대 대학원 전기제어공학과) ;
  • 김영관 (홍익대 공대 화학공학과) ;
  • 김정수 (홍익대 공대 전기제어공학과)
  • Published : 1999.05.01
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Abstract

Electroluminescent(EL) devices based on organic materials have been of great interest due to their possible applications for large-area flat-panel displays. They are attractive because of their capability of multi-color emission, and low operation voltage. An approach to realize such device characteristics is to use active layers of lanthanide complexes with their inherent extremely sharp emission bands in stead of commonly known organic dyes. In general, organic molecular compounds show emission due to their $\pi$-$\pi*$ transitions resulting in luminescence bandwidths of about 80 to 100nm. Spin statistic estimations lead to an internal quantum efficiency of dye-based EL devices limited to 25%. On the contrary, the fluorescence of lanthanide complexes is based on an intramolecular energy transfer from the triplet of the organic ligand to the 4f energy states of the ion. Therefore, theoretical internal quantum efficiency is principally not limited. In this study, Powders of TPD, $Eu(TTA)_3(phen) and AlQ_3$ in a boat were subsequently heated to their sublimation temperatures to obtain the growth rates of 0.2~0.3nm/s. Organic electrolumnescent devices(OELD) with a structure of $glass substrate/ITO/Eu(TTA)_3(phen)/AI, glass substrate/ITO/TPD/Eu(TTA)_3(phen)/AI and glass substrate/ITO/TPD/Eu(TTA)_3(phen)/AIQ_3AI$ structures were fabricated by vacuum evaporation method, where aromatic diamine(TPD) was used as a hole transporting material, $Eu(TTA)_3(phen)$ as an emitting material, and Tris(8-hydroxyquinoline)Aluminum$(AlQ_3)$ as an electron transporting layer. Electroluminescent(EL) and current density-voltage(J-V) characteristics of these OELDs with various thickness of $Eu(TTA)_3(phen)$ layer were investigated. The triple-layer structure devices show the red EL spectrum at the wavelength of 613nm, which is almost the same as the photoluminescent(PL) spectrum of $Eu(TTA)_3(phen)$.It was found from the J-V characteristics of these devices that the current density is not dependent on the applied field, but on the electric field.

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References

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