Influences of Device Architectures on Characteristics of Organic Light-Emitting Devices Incorporating Ambipolar Blue-Emitting Ter(9,9-diarylfluorenes)

Authors

  • Chung-Chih Wu Dept. of Elec. Eng., Graduate Institute of Electro-optical Eng., and Graduate Institute of Electronics Eng., National Taiwan University, Taipei, Taiwan 10617, Republic of China
  • K.-T. Wong Dept. of Chemistry, National Taiwan University, Taipei, Taiwan 10617, Republic of China
  • L.-Y Chen Dept. of Elec. Eng., Graduate Institute of Electro-optical Eng., and Graduate Institute of Electronics Eng., National Taiwan University, Taipei, Taiwan 10617, Republic of China
  • R.-T. Chen Dept. of Chemistry, National Taiwan University, Taipei, Taiwan 10617, Republic of China
  • Y.-T. Lin Dept. of Elec. Eng., Graduate Institute of Electro-optical Eng., and Graduate Institute of Electronics Eng., National Taiwan University, Taipei, Taiwan 10617, Republic of China
  • Y.-Y. Chien Dept. of Chemistry, National Taiwan University, Taipei, Taiwan 10617, Republic of China
Abstract:

In this article, we report the studies of various device architectures of organic lightemitting devices (OLEDs) incorporating highly efficient blue-emitting and ambipolar carriertransport ter(9,9-diarylfluorene)s, and their influences on device characteristics. The device structures investigated include single-layer devices and multilayer heterostructure devices employing the terfluorene as one functional layer. It is found that, although these terfluorenes are capable of bipolar carrier transport, rather poor device performance of single-layer devices in comparison with multilayer devices indicates that the heterostructure is still essential for balancing hole/electron injection and currents, for achieving high emission efficiencies, and for full utilization of high luminescence efficiency of these terfluorenes. With the heterostructure of hole-transport layer/terfluorene/electrontransport layer and careful choice of carriertransport materials, effective hole and electron injection, confinement of carriers, and confinement of excitons in terfluorenes are achieved. As a consequence, a highly efficient (4.1% quantum efficiency), low-voltage (~2.5 V turn-on voltage), and color-saturated nondoped blue-emitting device is demonstrated. Such high electroluminescent efficiency is consistent with high photoluminescent quantum yields of these terfluorenes and is competitive with those of efficient doped blue OLEDs.

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Journal title

volume 2  issue None

pages  45- 58

publication date 2008-02

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