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Title: Theory of charge transfer in solar energy materials
Author: Gillespie, Peter N. O.
ISNI:       0000 0004 7655 3365
Awarding Body: University of Sheffield
Current Institution: University of Sheffield
Date of Award: 2018
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Developing materials for applications in renewable energy is one of the greatest challenges of the 21st century. The work in this thesis explores the electronic structure of several materials for use in solar energy conversion, utilising computational chemical techniques to better understand the mechanisms responsible for these materials' properties. First the graphene/titanium dioxide (TiO2) photocatalytic composite is studied. This material is known from experimental studies to be much more effective for UV and visible-light photocatalysis than TiO2 alone, but the mechanism of its photocatalytic activity enhancement is under debate. Out hybrid HF/DFT calculations show that there is groundstate charge transfer from graphene to TiO2, which provides a rationale for the observed increases in both UV and visible-light photocatalytic rates and rapid charge transfer within the system. In experimental examples of this composite, the graphene is typically derived from graphene oxide (GO) and contains oxygen functional groups in addition to the graphene structure. We therefore develop the model of graphene/TiO2 further by studying the role of oxygen functional groups in the electronic structure of the composite, which leads to a model for composites of GO and reduced graphene oxide (RGO) with TiO2 . It is found that the interaction of these oxygen functional groups with TiO2 produces electronic states that can act as electron traps which inhibit undesirable electron-hole recombination. This is proposed to be the reason for the experimentally observed improvements in photocatalytic performance of the composite compared to TiO2 . Finally, a series of dye-sensitised solar cells (DSSCs) based on TiO2 are studied to understand the source of their unexpectedly low light-harvesting performances seen in experiment. Here variations in the design of the dyes' ligands are presented as a means to improve the performance of these dyes.
Supervisor: Martsinovich, Natalia Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available