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Proceedings Paper

Performance optimization of organic electroluminescent devices
Author(s): Shuit-Tong Lee; C. S. Lee; Zhi Qiang Gao; B. J. Chen; W. Y. Lai; Tsz Cheung Wong
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Paper Abstract

Performance of organic electroluminescent (EL) devices has been found to depend critically on various processing parameters including the purity and deposition rate of organic materials and substrate temperature. The effects of these processing parameters were systematically investigated by using the time-of-flight measurement of carrier mobility, photoluminescence, Raman as well as photoemission spectroscopies. It was observed that carrier mobility in organic EL materials could be improved substantially by either increasing the material purity or decreasing the deposition rate. Concomitantly, the increase in carrier mobility also led to considerable enhancement in the efficiency of EL devices. By depositing organic EL materials at elevated substrate temperatures, significant improvement in EL efficiency was also obtained. The EL devices thus fabricated consisted of a crystalline hole-transporting layer (HTL). Such devices not only showed improved efficiency but also enhanced stability. The improvement in stability is attributed to the fact that the HTL was already crystalline in the fabricated device so that subsequent operation and storage of the device would not lead to further crystallization. Thus, the widely accepted degradation mechanism via operation-induced crystallization and interfacial diffusion appears not important in the devices fabricated with a crystalline HTL.

Paper Details

Date Published: 17 December 1999
PDF: 19 pages
Proc. SPIE 3797, Organic Light-Emitting Materials and Devices III, (17 December 1999); doi: 10.1117/12.372704
Show Author Affiliations
Shuit-Tong Lee, City Univ. of Hong Kong (Hong Kong)
C. S. Lee, City Univ. of Hong Kong (Hong Kong)
Zhi Qiang Gao, City Univ. of Hong Kong (Hong Kong)
B. J. Chen, City Univ. of Hong Kong (Hong Kong)
W. Y. Lai, City Univ. of Hong Kong (Hong Kong)
Tsz Cheung Wong, City Univ. of Hong Kong (Hong Kong)

Published in SPIE Proceedings Vol. 3797:
Organic Light-Emitting Materials and Devices III
Zakya H. Kafafi, Editor(s)

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