CONTROL OF LATERAL ELECTRON TRANSFER BETWEEN COMPOUNDS ANCHORED TO SEMICONDUCTOR INTERFACES Public Deposited

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Last Modified
  • March 20, 2019
Creator
  • Motley, Tyler
    • Affiliation: College of Arts and Sciences, Department of Chemistry
Abstract
  • The need for a clean and renewable energy source is paramount to long term global economic and energy security and is the motivation for this work. The sun is one of the largest sources of renewable energy available. Dye-sensitized solar and photoelectrochemical cells that capture solar energy and convert it to either electricity or solar fuels provide an opportunity to investigate the relevant, molecular, reaction chemistry in such devices. One electron transfer pathway in both devices is lateral electron transfer between compounds anchored to the interface of the metal oxide films. The focus of this dissertation is to understand how structural changes to these compounds influence lateral electron transfer rates. The basic operating principles of dye-sensitized technologies and the relevant background to lateral electron transfer kinetics are given in Chapter 1. Chapters 2-4 explore the effect of molecular structure on lateral electron transfer kinetics. In Chapters 2 and 3, the effect of 4 and 4′ substituents are examined using a series of compounds of the type [Ru(R2bpy)2(bpy’)]2+, where R2bpy was a 4,4′-substituted-2,2′-bipyridine and bpy’ was a 2,2′-bipyrdine with either carboxylic or phosphonic acid binding groups at the 4 and 4′ positions. These studies reveal that the steric bulk is the dominant factor controlling the measured self-exchange rate constants. In Chapter 4, four compounds with two redox active groups, a bis(tridentate) cyclometalated RuII metal center and a substituted- triphenylamine donor connected by a thiophene bridge, are anchored to the TiO2 interface and lateral intermolecular electron transfer is studied. This study shows that the intramolecular electronic coupling influences lateral charge transport rates. Other processes relevant to dye-sensitized technologies are also explored. Thermal, bimolecular electron transfer between CoII and RuIII polypyridyl compounds that follows Marcus-inverted behavior is observed in acetonitrile and is the focus of Chapter 5. In Chapter 6, the photophysical properties and excited-state decay pathways are explored for a series of tris(bidentate) cyclometalated RuII chromophores which have emerged as a promising new paradigm for chromophore design in dye-sensitized solar cells. Temperature-dependent photoluminescence studies indicate that the dissociative ligand field states are not accessible at temperature, and that these compounds are photostable.
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  • In Copyright
Advisor
  • Meek, Simon
  • Dempsey, Jillian
  • Meyer, Gerald
  • Atkin, Joanna
  • Meyer, Thomas
Degree
  • Doctor of Philosophy
Degree granting institution
  • University of North Carolina at Chapel Hill Graduate School
Graduation year
  • 2018
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