2003 Fiscal Year Final Research Report Summary
RESEARCH ON THE PRIMARY PROCESSES OF PHOTO-CONDUCTION IN AROMATIC VINYL POLYMERS BY MEANS OF FEMTOSECOND DICHROISM MEASUREMENT AND NEAR LASER SPECTROSCOPY.
| Project/Area Number |
14340183
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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 |
Physical chemistry
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| Research Institution | Osaka University |
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Principal Investigator |
MIYASAKA Hiroshi Osaka University, 大学院・基礎工学研究科, 教授 (40182000)
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| Project Period (FY) |
2002 – 2003
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| Keywords | PICOSECOND LASER SPECTROSCOPY / FEMTSECOND LASER SPECTROSCOPY / ELECTRON TRANSFER / PHOTOCONDUCTIVE POLYMER / CARRIER GENERATION / CARRIER TRANSPORT |
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| Research Abstract |
The transport of electrons initiated by photoexcitation is ubiquitous in nature as well as in artificial systems. Photoconductivity in aromatic vinyl polymers is one of the typical phenomena closely related to these fundamental processes. Since the band structures in the electronic states are not plausible because of rather small interaction among the pendant aromatic groups, hopping model has been proposed for this carrier transport processes. Still unclear are the factors regulating the charge shift reaction between two neighboring aromatic groups in a molecular level. To obtain deeper insights into this efficient electron transfer reaction, photoinduced electron transfer dynamics (charge separation, charge recombination and hole transfer reactions) in poly (N-vinylcarbazole) (PVCz) and solvent effects on the reaction profiles were studied by means of picosecond and femtosecond transient absorption spectroscopy and transient dichroism measurements.
Electron transfer dynamics in PVCz in rather polar solutions was well described by the simple scheme that the cation state of carbazolyl (Cz+) moiety continuously migrates along pendant Cz moieties in the polymer chain with the charge recombination at the initial position of the charge separation. The dichroism measurement in femtosecond -a few picosecond time region revealed that the delocalization of the cationic state over Cz units takes an important role for the subsequent hole transfer. That is, the delocalization leads to the decrease in the effective inter-ionic distance to reduce the Coulombic attractive energy in the initial pair and also the decrease in the reorganization energy in the electron transfer reaction accelerates the hole transfer process.
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