Journal of the Semiconductor & Display Technology (반도체디스플레이기술학회지)

The Korean Society Of Semiconductor & Display Technology (한국반도체디스플레이기술학회)
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Recrystallization-Free Coating of Small Molecules for OLEDs

OLED를 위한 저분자 재결정 방지 코팅 기술

  • Hong, Gi-Young (School of Electrical & Electronic & Communication Engineering, Korea University of Technology and Education) ;
  • Lee, Jin-Young (School of Electrical & Electronic & Communication Engineering, Korea University of Technology and Education) ;
  • Shin, Dong-Kyun (School of Electrical & Electronic & Communication Engineering, Korea University of Technology and Education) ;
  • Park, Jong-Woon (School of Electrical & Electronic & Communication Engineering, Korea University of Technology and Education) ;
  • Seo, Hwa-Il (School of Electrical & Electronic & Communication Engineering, Korea University of Technology and Education)
  • 홍기영 (한국기술교육대학교 전기.전자.통신공학부) ;
  • 이진영 (한국기술교육대학교 전기.전자.통신공학부) ;
  • 신동균 (한국기술교육대학교 전기.전자.통신공학부) ;
  • 박종운 (한국기술교육대학교 전기.전자.통신공학부) ;
  • 서화일 (한국기술교육대학교 전기.전자.통신공학부)
  • Received : 2016.05.27
  • Accepted : 2016.06.22
  • Published : 2016.06.30
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Abstract

We investigate the solution coating process of organic small molecules that are easily recrystallized in a solvent. The spin-coated films of small molecule N,N'-diphenly-N,N'-bis(1,1'-biphenyl)-4,4'-diamine (NPB) exhibit many aggregations on the surface and thus poor surface morphology. To tackle it, we have added a chain-entangled polymer poly(N-vinylcarbazole) (PVK) into the NPB solution. It is found that a small amount of PVK indeed prohibits the recrystallization of NPB in a solvent. By the addition of PVK (30 wt%), the peak-to-peak roughness of the films is reduced from 262 nm down to 2.7 nm, which is even lower than that (~5.1 nm) of the polymer film. It is also demonstrated that OLED with the PVK-mixed NPB film shows higher current and power efficiencies, compared to OLED with the NPB or PVK film. It is attributed that the addition of PVK into NPB suppresses the occurrence of leaky channels induced by the recrystallization phenomenon.

Keywords

References

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