Dye-sensitized solar cells have become an affordable alternative to conventional photovoltaics. Their efficiencies have become competitive by continued optimization of the semiconductor, dye, redox shuttle, and counter electrode. This thesis will evaluate low-spin Co(II) redox shuttles' ability to minimize photovoltage losses due to dye regeneration and recombination to semiconductor electrons. Their synthesis and properties will be described along with a comparison to typical high-spin Co(II) redox shuttles. The kinetic properties will be evaluated in terms of Marcus Theory with a particular focus being made on reorganization energy and free energy of electron transfer events. Chapter 1 will describe the motivation for dye-sensitized solar cells along with a description of their development and operation. Chapter 2 and 3 will describe the two extremes of redox potential of the redox shuttle. Chapter 4 demonstrates a system with a tunable potential in between. Chapter 5 will report other redox shuttle candidates and future directions to surpass 15% power conversion efficiency with low-spin Co(II) redox shuttles.
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