Understanding the performance determining processes in dye sensitized solar cells

The work presented in this thesis is aimed at optimizing the performance of the dye-sensitized solar cell (DSSC). Chapter 1 presents a brief overview of the history of solar cells and introduces the reader to the components, mechanisms and characterization techniques relevant to the DSSC. Chapter 2 describes the effect pH has on electron injection and collection processes in DSSC's. Charge collection efficiency, and not the electron injection yield, was related to the TiO2 surface protonation-deprotonation equilibria. In Chapter 3 we examine alternate redox mediators to optimize the regeneration of the oxidized sensitizer while maximizing open circuit voltage (VOC ). Bipyrazine based ruthenium sensitizers anchored to SnO2 had higher photocurrent efficiencies and cell voltages with the alternative redox mediator (SeCN)2/SeCN- than with the commonly used I3-/I-. In Chapter 4 the interaction of iodide with a ruthenium polypyridyl sensitizer was studied to elucidate the workings of the iodide/tri-iodide redox mediator. The interaction between the sensitizer and iodide in solid phase and in dichloromethane solution was shown to potentially improve solar cell performance. A more specific interaction between iodide and a zinc tetraphenylporphyrin sensitizer was shown to improve the light harvesting efficiency of the DSSC in Chapter 5.