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UBC Theses and Dissertations
Two-photon photoelectron emission studies of metal/conjugated polymer interfaces Sohn, Youngku
Abstract
Two photon photoelectron spectroscopy (2PPE) has been used in the investigation of the electronic structure of interfaces between metals and conjugated polymers. This technique probes excited intermediate states in the polymers. The systems studied in this thesis are regioregular poly(3-hexlythiophene-2,5-diyl) (P3HT) and MEH-PPV polymers on a Au(lll) substrate. Electron kinetic energy distributions and quantum yields were recorded with varying polymer thicknesses to investigate the influence of the metal substrate. Spectra and yields were also measured as a function of various photon energies and incident laser power. The kinetic energy distribution increases in width by an amount equal to the increment in photon energy, characteristic of the 2PPE process with photoexcitation from a fixed intermediate state. Kinetic modeling of the emission yield as a function of incident laser power and photon energy suggests that the intermediate state accessed during the 20 ns laser pulse is the negatively charged polaron. The binding energy of the intermediate state decreases for films thinner than 4 nm. This behavior can be understood by polarization at the interface, or alternatively by charge transfer. Also, thickness has a very large effect on quantum yield. Intermediate state pumping efficiency is lowered more than -1000-fold for thin films compared to films more than 4 nm thick. Change in lifetime quenching with polymer film thickness maybe a consequence of diffusion and dipole coupling to the metal.
Item Metadata
Title |
Two-photon photoelectron emission studies of metal/conjugated polymer interfaces
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Creator | |
Publisher |
University of British Columbia
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Date Issued |
2004
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Description |
Two photon photoelectron spectroscopy (2PPE) has been used in the investigation of the
electronic structure of interfaces between metals and conjugated polymers. This
technique probes excited intermediate states in the polymers. The systems studied in this
thesis are regioregular poly(3-hexlythiophene-2,5-diyl) (P3HT) and MEH-PPV polymers
on a Au(lll) substrate. Electron kinetic energy distributions and quantum yields were
recorded with varying polymer thicknesses to investigate the influence of the metal
substrate. Spectra and yields were also measured as a function of various photon energies
and incident laser power. The kinetic energy distribution increases in width by an amount
equal to the increment in photon energy, characteristic of the 2PPE process with
photoexcitation from a fixed intermediate state. Kinetic modeling of the emission yield
as a function of incident laser power and photon energy suggests that the intermediate
state accessed during the 20 ns laser pulse is the negatively charged polaron. The binding
energy of the intermediate state decreases for films thinner than 4 nm. This behavior can
be understood by polarization at the interface, or alternatively by charge transfer. Also,
thickness has a very large effect on quantum yield. Intermediate state pumping efficiency
is lowered more than -1000-fold for thin films compared to films more than 4 nm thick.
Change in lifetime quenching with polymer film thickness maybe a consequence of
diffusion and dipole coupling to the metal.
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Extent |
16207402 bytes
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Genre | |
Type | |
File Format |
application/pdf
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Language |
eng
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Date Available |
2009-11-27
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Provider |
Vancouver : University of British Columbia Library
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Rights |
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.
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DOI |
10.14288/1.0061205
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URI | |
Degree | |
Program | |
Affiliation | |
Degree Grantor |
University of British Columbia
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Graduation Date |
2004-11
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Campus | |
Scholarly Level |
Graduate
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Aggregated Source Repository |
DSpace
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Item Media
Item Citations and Data
Rights
For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use.