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Highly Enhanced EL Properties of PF Copolymers with Pyrazole Derivatives

피라졸 유도체를 함유한 폴리알킬플루오렌 공중합체의 향상된 EL 특성

  • Kang, In-Nam (Department of Chemistry, The Catholic University of Korea) ;
  • Lee, Ji-Hoon (Department of Polymer Science and Engineering, Chungju National University)
  • 강인남 (가톨릭대학교 화학과) ;
  • 이지훈 (충주대학교 나노고분자공학과)
  • Received : 2010.04.19
  • Accepted : 2010.06.09
  • Published : 2010.07.01

Abstract

We have synthesized new blue electroluminescent polyalkylfluorene-based copolymers [poly(F-co-Py)x:y, where x:y = 99:1 or 95:5 mole ratios] containing the hole-injecting pyrazole derivative [3,3'-(4,6-bis(octyloxy)-1,3-phenylene)bis(1,5-diphenyl-4,5-dihydro-1H-pyrazole] through Ni(0) mediated polymerization, and their electroluminescent properties were investigated. Electroluminescent (EL) devices were fabricated with ITO / PEDOT:PSS (110 nm) / copolymers or PF homopolymer (80 nm) / Ca (50 nm) / Al (200 nm) configuration. Each EL device constructed from the copolymer exhibited significantly enhanced brightness and efficiency compared with a device constructed from the PF homopolymer. The EL device constructed with poly(F-co-Py)99:1 exhibited the highest luminous efficiency and brightness (0.95 cd/A and $2,907\;cd/m^2$, respectively). The achieved luminous efficiency was an excellent result, providing almost a 4-fold improvement on the efficiency obtainable with the a PF homopolymer device. This enhanced efficiency of the copolymer devices results from their improved hole injection and more efficient charge carrier balance, which arises from the HOMO level (~5.83 eV) of the poly(F-co-Py)99:1 copolymer, which is higher than that of the PF homopolyme (~5.90 eV).

Acknowledgement

Supported by : 한국학술진흥재단

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