Journal of the Semiconductor & Display Technology (반도체디스플레이기술학회지)

The Korean Society Of Semiconductor & Display Technology (한국반도체디스플레이기술학회)
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Effect of the Surface Roughness of ITO Thin Films on the Characteristics of OLED Device

ITO 박막의 표면 거칠기에 따른 OLED 소자의 특성

  • Lee, Bong-Kun (Dept. of Materials Engineering, Korea University of Technology and Education) ;
  • Lee, Kyu-Mann (Dept. of Materials Engineering, Korea University of Technology and Education)
  • 이봉근 (한국기술교육대학교 신소재공학과) ;
  • 이규만 (한국기술교육대학교 신소재공학과)
  • Published : 2009.12.31
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Abstract

We have investigated the effect of the surface roughness of TCO substrate on the characteristics of OLED (organic light emitting diodes) devices. In order to control the surface roughness of ITO thin films, we have processed photolithography and reactive ion etching. The micro-size patterned mask was used, and the etching depth was controlled by changing etching time. The surface morphology of the ITO thin film was observed by FESEM and atomic force microscopy (AFM). And then, organic materials and cathode electrode were sequentially deposited on the ITO thin films. Device structure was ITO/$\alpha$-NPD/DPVB/Alq3/LiF/Al. The DPVB was used as a blue emitting material. The electrical characteristics such as current density vs. voltage and luminescence vs. voltage of OLED devices were measured by using spectrometer (minolta CS-1000A). The current vs. voltage and luminance vs. voltage characteristics were systematically degraded with increasing surface roughness. Furthermore, the retention test clearly presented that the reliability of OLED devices was directly influenced with the surface roughness, which could be interpreted in terms of the concentration of the electric field on the weak and thin organic layers caused by the poor step coverage.

Keywords

References

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