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Proceedings Paper

New class of light-emitting polymers/oligomers
Author(s): Oh-Kil Kim; Hanyoung Woo; Jai Kyeong Kim; Z. Huang
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Paper Abstract

Novel electro-/photoactive multifunctional dyes were synthesized based on dithienothiophene, DTT ((pi) -center), linked by an electron D/D -- or D/A pair segment; D-(pi) -D (dye 1) or D-(pi) -A (dye 2), to develop efficient bipolar light-emitting (LE) materials capable of balanced electron/hole capture in a single-layer LE device. A strong bipolarity manifested by electrochemical amphotericity was observed notably with dye 1, which cannot be accounted for without the involvement of the (pi) -center, leading to the low HOMO/LUMO energy-gap and a small difference in the energy-gap between dye 1 and dye 2. Single-layer LE devices were fabricated by making a blend based on the dye (0.5 wt%), PVK (70%) as matrix and PBD (30%) as electron-transporting/hole blocking material, and by sandwiching between ITO and Al electrodes. PL intensity of the dyes by excitation at 440 - 450 nm ((lambda) max) is much weaker compared to that at 340 nm (exciting mainly PVK), suggesting that the excitation of the dyes occur by energy-transfer from PVK. When compared PL intensities between the two dyes at a concentration less than 1%, dye 1 is slightly higher relative to dye 2. In contrast, the EL intensity shows an opposite trend in that dye 2 is much higher relative to dye 1 under the same condition. This implies that unlike the PL, the EL is not due to the transfer of the excited-energy from PVK but carrier trapping/exciton formation on the dye chromophore, and that dye 2 is strongly bipolar and thus more capable of balanced carrier capture.

Paper Details

Date Published: 17 March 2000
PDF: 7 pages
Proc. SPIE 3955, Liquid Crystal Materials, Devices, and Flat Panel Displays, (17 March 2000); doi: 10.1117/12.379973
Show Author Affiliations
Oh-Kil Kim, Naval Research Lab. (United States)
Hanyoung Woo, Naval Research Lab. (United States)
Jai Kyeong Kim, Korea Institute of Science and Technology (South Korea)
Z. Huang, Univ. of Connecticut and Naval Research Lab. (United States)

Published in SPIE Proceedings Vol. 3955:
Liquid Crystal Materials, Devices, and Flat Panel Displays
Ranganathan Shashidhar; Bruce Gnade, Editor(s)

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