| This thesis reports on fundamental studies designed to increase the general understanding of mechanistic processes involving the I-/I 3- redox mediator in dye sensitized solar cells. Chapter 1 introduces the dye-sensitized solar cell, and provides a review of literature reports detailing the spectroscopic and redox properties of the relevant iodine species present in the I-/I3- redox mediator. Chapter 2 discusses ion-pairing interactions between iodide, I -, and ruthenium polypyridyl sensitizers in dichloromethane. The metal-to-ligand charge transfer (MLCT) excited states of the sensitizers were found to be efficiently quenched by iodide at room temperature. In Chapter 3, we report efficient quenching of ruthenium polypyridyl excited states by triiodide, I3-, in dichloromethane and acetonitrile. In dichloromethane, triiodide was found to quench the excited states by static and dynamic mechanisms. Comparative studies with sensitizers anchored to mesoporous nanocrystalline TiO2 thin films also show efficient excited state quenching in acetonitrile and dichloromethane. Chapter 4 describes efficient iodine, I 2, quenching of ruthenium excited states on metal-oxide surfaces. Stern-Volmer analysis indicated the presence of static quenching on surface. Dynamic quenching rate constants were determined to be above the diffusion limit for electron transfer. Chapter 5 reports on a general strategy for improving dye-sensitized solar cell performance by increasing the distance between ruthenium metal centers and TiO2 surfaces. An increase in the open-circuit voltage is reported as a function of increasing distance. |
