中国物理B ›› 2010, Vol. 19 ›› Issue (3): 37105-037105.doi: 10.1088/1674-1056/19/3/037105

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Dependence of charge trapping of fluorescent and phosphorescent dopants in organic light-emitting diodes on the dye species and current density

魏斌, 廖英杰, 刘纪忠, 路林, 曹进, 王军, 张建华   

  1. Key Laboratory of Advanced Display and System Applications, Ministry of Education, Shanghai University, Shanghai 200072, China
  • 收稿日期:2009-06-14 修回日期:2009-07-15 出版日期:2010-03-15 发布日期:2010-03-15
  • 基金资助:
    Project supported by the Key Project of Shanghai Education Committee (Grant No.~08ZZ42), and Science and Technology Commission of Shanghai Municipal (Grant Nos.~08PJ14053, 08DZ1140702 and 08520511200).

Dependence of charge trapping of fluorescent and phosphorescent dopants in organic light-emitting diodes on the dye species and current density

Wei Bin(魏斌)†, Liao Ying-Jie (廖英杰), Liu Ji-Zhong (刘纪忠), Lu Lin(路林), Cao Jin(曹进), Wang Jun (王军), and Zhang Jian-Hua (张建华)   

  1. Key Laboratory of Advanced Display and System Applications, Ministry of Education, Shanghai University, Shanghai 200072, China
  • Received:2009-06-14 Revised:2009-07-15 Online:2010-03-15 Published:2010-03-15
  • Supported by:
    Project supported by the Key Project of Shanghai Education Committee (Grant No.~08ZZ42), and Science and Technology Commission of Shanghai Municipal (Grant Nos.~08PJ14053, 08DZ1140702 and 08520511200).

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摘要： This paper utilizes multilayer organic light-emitting diodes with a thin layer of dye molecules to study the mechanism of charge trapping under different electric regimes. It demonstrates that the carrier trapping was independent of the current density in devices using fluorescent material as the emitting molecule while this process was exactly opposite when phosphorescent material was used. The triplet--triplet annihilation and dissociation of excitons into free charge carriers was considered to contribute to the decrease in phosphorescent emission under high electric fields. Moreover, the fluorescent dye molecule with a lower energy gap and ionized potential than the host emitter was observed to facilitate the carrier trapping mechanism, and it would produce photon emission.

Abstract: This paper utilizes multilayer organic light-emitting diodes with a thin layer of dye molecules to study the mechanism of charge trapping under different electric regimes. It demonstrates that the carrier trapping was independent of the current density in devices using fluorescent material as the emitting molecule while this process was exactly opposite when phosphorescent material was used. The triplet--triplet annihilation and dissociation of excitons into free charge carriers was considered to contribute to the decrease in phosphorescent emission under high electric fields. Moreover, the fluorescent dye molecule with a lower energy gap and ionized potential than the host emitter was observed to facilitate the carrier trapping mechanism, and it would produce photon emission.

Key words: organic light-emitting diodes, excitation mechanism, charge trapping, current density

中图分类号:  (Light-emitting devices)

  • 85.60.Jb
73.50.Gr (Charge carriers: generation, recombination, lifetime, trapping, mean free paths) 78.60.Fi (Electroluminescence) 73.61.Ph (Polymers; organic compounds) 71.35.-y (Excitons and related phenomena) 71.20.Rv (Polymers and organic compounds)