2000 Fiscal Year Final Research Report Summary
Excitonic nonlinearity of regioregular π-conjugated polymer
| Project/Area Number |
11440099
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| Research Category |
Grant-in-Aid for Scientific Research (B).
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
固体物性Ⅰ(光物性・半導体・誘電体)
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| Research Institution | Sophia University |
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Principal Investigator |
EMA Kazuhiro Sophia University, Department of Physics, Professor, 理工学部, 教授 (40194021)
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| Co-Investigator(Kenkyū-buntansha) |
KUNUGITA Hideyuki Sophia University, Department of Physics, Research Associate, 理工学部, 助手 (50296886)
RIKUKAWA Masahiro Sophia University, Department of Chemistry, Associate Proffesor, 理工学部, 助教授 (10245798)
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| Project Period (FY) |
1999 – 2000
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| Keywords | polymer / exciton / nonlinear optics / polythiophene / Langmuir-Blodgett (LB) films / low-dimensional material / conjugation length / relaxation mechanism |
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| Research Abstract |
We investigated excitonic nonlinearity of polythiophene derivative poly(3-[2-((S)-2-methylbutoxy)ethyl]thiophene), which has good regularity in structure. Our study focused two points ; 1) the dependence of excitonic nonlinearity on the effective conjugation length, 2) the relaxation mechnism of exciton. Our research results are following ;
1) Third-order optical nonlinearity around excitonic resonance in spincoated films and Langmuir-Blodgett (LB) films of polythiophene derivative, poly(3-[2-((S)-2-methylbutoxy)ethyl]thiophene), is measured using degenerate four wave mixing method. The largest χ^<(3)> value (〜10^<-7> esu) in conjugated polymers is obtained. By a fitting procedure on absorption spectrum and χ^<(3)> spectrum, the average effective conjugation lengths of the spincoated film and the LB film are estimated to be approximately 20 and 36 thiophene rings, respectively.
2) The time-resolved photoluminescence spectrum of a polythiophene derivative has been analyzed from the viewpoint of the vibronic structure and its dynamics. We found that the photoluminescence (PL) originates from two mixed states that consist of the odd-parity 1Bu component and the even-parity 2Ag component. Since the fluorescence from the two states have different time constants and different vibronic structure, the PL shows a biexponential decay and a spectral change. This model also explains the PL spectrum and its dynamics of many other π conjugated polymers quite well.
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