Raman Scattering Of Organic Charge Transfer Compounds
Public Deposited- Last Modified
- March 19, 2019
- Creator
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Vermeulen, Derek
- Affiliation: College of Arts and Sciences, Department of Physics and Astronomy
- Abstract
- Understanding the intrinsic nature of charge transport in organic semiconductors is very important in the design of and creation of new organic electronic technology. In particular, charge transfer (CT) compounds offer an interesting sub-species of organic semiconductor, in which one-dimensional transport, ambipolar transport, and the effect of chemical and structural modification can be studied so that one day an organic electronic device can be designed from the molecule up. Electron-phonon (eph) coupling and the degree of charge transfer (ρ) in CT compounds are essential parameters to consider in studying charge transport in OS. Substantial theoretical research has been completed to determine the influence of both non-local and local eph coupling on electronic properties such as charge carrier mobility. However, very few experimental investigations have been completed to test the assertions of theory concerning eph coupling, especially non-local coupling. The aim of this project is to experimentally investigate eph coupling and ρ in organic semiconducting binary CT compounds using Raman spectroscopy, and to compare the results with theoretical calculations where possible. The first part of this dissertation is focused on the PnT1 (Perylenen-Tetracyanoquinomethane; n=1,2,3) CT compound system consisting of three compounds of differing stoichiometric ratios of perylene to TCNQ. In this project I show that ρ increases as the number of perylenes in the unit cell increases, due to greater electronic coupling resulting from a closer spacing of perylene and TCNQ, which is confirmed by theoretical calculations and X-ray measurements. I also estimate the local eph coupling constants per phonon of PnT1 using resonance Raman spectroscopy and obtain polaron binding energies of perylene and TCNQ, which are consistent with theoretical calculations. The last part of this dissertation is focused on anthracene-PMDA (Pyromellitic Dianhydride). Using resonance Raman spectroscopy I apply to this crystalline CT compound a method usually constrained to the study of excited electronic states of molecules in solution. From this technique I am able to extract eph constants, both local and non-local, for inter- and intramolecular phonons and show that both are equally influential in affecting charge transport in organic semiconductors, as predicted by theory.
- Date of publication
- August 2015
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- Rights statement
- In Copyright
- Advisor
- Henning, Reyco
- Moran, Andrew
- McNeil, Laurie
- Lopez, Rene
- Brennaman, Kyle
- Degree
- Doctor of Philosophy
- Degree granting institution
- University of North Carolina at Chapel Hill Graduate School
- Graduation year
- 2015
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- Place of publication
- Chapel Hill, NC
- Access right
- There are no restrictions to this item.
- Date uploaded
- August 25, 2015
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