| The contents herein this thesis report on mechanistic processes important for the dye-sensitized solar cell (DSSC) with a focus on the influential nature of small cations at the interface. Chapter 1 introduces the reader to the DSSC by describing the accepted mechanism of a functioning cell and detailing its working components. Chapter 2 reports on a novel strategy aimed to improve device efficiencies and exceed the Shockley-Queisser limit, a well-known theoretical solar-to-electrical energy conversion efficiency standard. This strategy uses the ultrafast electron injection properties of the TiO2 to produce products from sunlight that are uphill in fluid solution. In Chapter 3, the mechanism of recombination of this charge-separated state is studied using chronoabsorption measurements. It is proposed that while the hole transport is limited through self-exchange reactions, the conduction band states of TiO2 mediate electron transport. Potential determining cations were introduced to "tune" the electron diffusion rates. Chapter 4 reports on a high-extinction ruthenium compound for its use as a sensitizer. Interestingly, after photo-oxidation of this compound on TiO2, the hole transferred out to a remote ligand, increasing the charge separation distance. Cation motion was studied in Chapter 5 using a novel ruthenium(II) compound that underwent large spectroscopic changes when exposed to lithium cations. These absorption changes allowed the determination of its transport mechanism at the interface during electron injection and charge recombination. |
