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Proceedings Paper

Energy alignment and trap states in dye-doped tris-8-(hydroxyquinoline) aluminum light-emitting devices
Author(s): Eric W. Forsythe; David C. Morton; Quoc Toan Le; Li Yan; F. Nuesch; Ching W. Tang; Yongli Gao
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Paper Abstract

Thermally stimulated luminescence has used to directly measure the trap states in intrinsic Alq3 and Alq3 doped with coumarin 6. For Alq3 doped with coumarin 6, we observe an increase in the trap energy from 0.25eV for undoped Alq3 to 0.32eV for doping concentrations as high as 2 percent. The origin of these trap states may be related to the relative energy level alignment between the Alq3 host and coumarin dopant. Using UV photoemission spectroscopy, we have measured the solid state energy alignment of the highest occupied molecular orbitals between Alq3 and coumarin 6. Finally, we report I-V curves for single layer devices as a function of doping with Al/LiF top and bottom contacts. The charge transport shows the trap states induced in the Alq3 films due to the presence of the coumarin 6 molecules decrease the carrier mobility and increase the energetic disorder. These results can be directly observed from the measured I-V curves.

Paper Details

Date Published: 18 May 1999
PDF: 7 pages
Proc. SPIE 3623, Organic Photonic Materials and Devices, (18 May 1999); doi: 10.1117/12.348397
Show Author Affiliations
Eric W. Forsythe, Univ. of Rochester (United States)
David C. Morton, Army Research Lab. (United States)
Quoc Toan Le, Univ. of Rochester (United States)
Li Yan, Univ. of Rochester (United States)
F. Nuesch, Univ. of Rochester (United States)
Ching W. Tang, Eastman Kodak Co. (United States)
Yongli Gao, Univ. of Rochester (United States)

Published in SPIE Proceedings Vol. 3623:
Organic Photonic Materials and Devices
Bernard Kippelen, Editor(s)

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