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Title: Origin of the blue emission from poly(1-phenyl-2-alkynes) and poly(phenylacetylenes)
Authors: Ge, Wei-Kun
Huang, Yuan Ming
Lam, Wing Yip
Tang, Ben-Zhong
Keywords: Substituted polyacetylene
Density of states
Electronic structure
Localized states
Extended states
Issue Date: Jul-2000
Citation: Optoelectronic Materials and Devices II, Yan-Kuin Su, Pallab Bhattacharya, Editors, Proceedings of SPIE Vol. 4078, p. 279-288 (2000)
Abstract: We have studied the electronic structure, absorption, and photoluminescence of poly(1-phenyl-2-alkynes) - [(C6H5)C=C(CmH2m+1))]n-(m=1,2), poly(phenylacetylenes)-[HC=C(C6H5)]n-and its derivatives-[HC=C(C6H4-p-R]n-with various non-liquid crystal ring substitutents. For poly(1-phenyl-2-alkynes), the PL efficiency is very sensitive to the molecular structure of the alkyl pendant and can be enhanced up to 50 times as the alkyl side-chain increases in length. But for poly(phenylacetylenes), their luminescent efficiency can be improved several times only as the tail becomes bulky. Regardless of the types of the pendants, the emission color of the polymers is pinned at ~450 nm (2.7 eV). The band structure of the polymers, which has been calculated using extended Hückel tight-binding method, is essentially an ensemble of the backbone (extended states) and the pendants (localized states), and the processes of optical absorption and blue emission are confined in the directly attached aromatic ring. The interaction between the phenyl chromophore and its nearest neighbors is of vital importance in improving the emission efficiency. Although the band gap of the backbone can be enlarged by the pendant, its π-π*/ interband transition is insignificant for the blue emission.
Rights: Copyright 2000 Society of Photo-Optical Instrumentation Engineers. This paper was published in Optoelectronic Materials and Devices II, Yan-Kuin Su, Pallab Bhattacharya, Editors, Proceedings of SPIE Vol. 4078, p. 279-288 (2000) and is made available as an electronic reprint with permission of SPIE. One print or electronic copy may be made for personal use only. Systematic or multiple reproduction, distribution to multiple locations via electronic or other means, duplication of any material in this paper for a fee or for commercial purposes, or modification of the content of the paper are prohibited.
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