Excited State Dynamics of Model Photovoltaic Materials
2021-01
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Excited State Dynamics of Model Photovoltaic Materials
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2021-01
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Investigation of new materials for potential use in organic photovoltaics and dye-sensitized solar cells found unique systems that maintained a relatively long-lived (ns and longer) charge separated state or energy transferred state. The molecules studied in this thesis show promise for use in organic photovoltaics or dye-sensitized solar cells. Further studies in the solid state of these molecules are required to determine their efficiency andtheir ability to function in a photovoltaic module. Chapter 1 gives an overview of the status of energy usage in the world and how photovoltaics fit into it. This chapter also explains the key scientific concepts used for interpretation of experiments. Chapter 2 goes through an in-depth description of the experimental techniques and processes used in this thesis. Chapter 3 examines a thiophene- and furan-based dye when in an equimolar mixture with varying sizes of ZnO nanoparticles. A long-lived charge-separated state is found when both dyes are coordinated to the ZnO nanoparticles, showing a spectral signature of electron transfer from the thiophene and furan-based dyes to the ZnO. The charge-separated state exists beyond the time delay for the experiment (3.5 ns), indicating promise for a dye-sensitized solar cell containing these molecules. Investigation into BODIPY molecules for use as an absorber in organic photovoltaics begins with Chapter 4. In Chapter 4, the electron transfer properties from the catechol group to multiple BODIPY derivatives are identified. It is found that rapid electron transfer from the catechol, linked at the boron hub of the BODIPY, to the BODIPY deactivated the excited state from further interaction with surrounding systems, a detail missed in other publications with the same catechol attached to the boron-hub of BODIPY. This conclusion was carried into Chapter 5 where use of the catechol to bridge the fullerene to the BODIPY leads to no interaction with fullerene. This is because the catechol rapidly transferred an electron to the BODIPY and deactivated further electron transfer. Ferrocene added to the BODIPY-fullerene molecule out-competed the catechol for electron transfer to the BODIPY derivative, making a ~200 ps lived electron transfer state. The catechol linker is not the only bridge studied between a BODIPY derivative and fullerene. A pyridone ring connected at the alpha and position of the BODIPY is also used to bridge to fullerene. In this study the fullerene functioned as a triplet sensitizer for the BODIPY, leading to a microsecond lived BODIPY triplet. Lastly, a zinc phthalocyanine is studied when coordinated to a BODIPY derivative and fullerene through a pyridine ring. Spectral and redox evidence shows electron transfer from the phthalocyanine occurred, soon followed by recombination. Energy transfer from the BODIPY to the phthalocyanine was also present, followed by electron transfer back to the BODIPY before decaying to the ground state.
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University of Minnesota Ph.D. dissertation. January 2021. Major: Chemistry. Advisor: David Blank. 1 computer file (PDF); xii, 309 pages.
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Swedin, Rachel. (2021). Excited State Dynamics of Model Photovoltaic Materials. Retrieved from the University Digital Conservancy, https://hdl.handle.net/11299/219335.
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