Journal of the Korean institute of surface engineering (한국표면공학회지)

The Korean Institute of Surface Engineering (한국표면공학회)
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Emission Characteristics of Dual Emission Tandem OLED with Charge Generation Layer MoOx and Cathode Al Thickness

전하생성층 MoOx와 음극 Al의 두께에 따른 양면발광 적층 OLED의 발광 특성

  • Kim, Ji-Hyun (Department of Advanced Materials Science & Engineering, Daejin University) ;
  • Ju, Sung-Hoo (Department of Advanced Materials Science & Engineering, Daejin University)
  • 김지현 (대진대학교 신소재공학과) ;
  • 주성후 (대진대학교 신소재공학과)
  • Received : 2016.05.24
  • Accepted : 2016.06.28
  • Published : 2016.06.30
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Abstract

To study emission characteristics for dual-emission tandem organic light emitting display (OLED), we fabricated blue fluorescent OLED according to thickness variation of $MoO_x$ as charge generation layer and Al as cathode. The bottom emission characteristics of OLED with $MoO_x$ 2, 3, 5 nm thickness showed threshold voltage of 9, 7, 9 V, maximum current emission efficiency of 19.32, 23.18, 15.44 cd/A and luminance of $1,000cd/m^2$ at applied voltage of 17.6, 13.2, 16.5 V, respectively. The top emission characteristics of OLED with $MoO_x$ 2, 3, 5 nm thickness indicated threshold voltage of 13, 10, 13 V, maximum current emission efficiency of 0.17, 0.23, 0.16 cd/A and luminance of $50cd/m^2$ at applied voltage of 22.6, 16.5, 20.1 V, respectively. In case of thicker or thinner than $MoO_x$ of 3 nm, the emission characteristics were decreased because of mismatching of electron and hole in emission layer. The bottom emission characteristics of OLED with Al 15, 20, 25 nm thickness showed threshold voltage of 8, 8, 7 V, maximum current emission efficiency of 18.42, 22.98, 23.18 cd/A and luminance of $1000cd/m^2$ at applied voltage of 16.2, 13.9, 13.2 V, respectively. The reduction of threshold voltage and increase of maximum current emission efficiency are caused by the increase of current injection according to increase of Al cathode thickness. The top emission characteristics of OLED with Al 15, 20, 25 nm thickness indicated threshold voltage of 7, 7, 8 V, maximum emission luminance of 371, 211, $170cd/m^2$, respectively. The top emission OLED of Al cathode with 15 nm thickness showed maximum luminance and it decreased at thickness of 20 nm. These phenomena are caused by the decrease of intensity of emitted light by reduction of optical transmittance according to increase of Al cathode thickness.

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References

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