Charge Dynamics in New Architectures for Dye-Sensitized Solar CellsPublic Deposited
The promise of a clean, renewable, and abundant energy supply make the efficient conversion of solar energy to electricity a compelling scientific and societal goal. In the following chapters, I will describe my efforts to advance one class of photovoltaic technology, dye-sensitized solar cells, by demonstration and characterization of unexplored device architectures. Chapter 1 provides an introduction to the origin of solar energy conversion and the fundamentals of dye-sensitized solar cells. An understanding of device operation through charge dynamics facilitates a survey of the state of the art in addition to predictions for promising future directions. Chapter 2 elucidates the electron transport and interception dynamics in ZnO nanorod array based dye-sensitized solar cells. The data presented suggest that the study of alternative photoanode architectures is a viable means of improving device performance and understanding. Chapter 3 introduces a new photoanode design in which anodic aluminum oxide and atomic layer deposition are utilized to fabricate oriented arrays of electrically interconnected semiconductor nanotubes. The viability of these structures as dye-sensitized electrodes is demonstrated by characterization of their morphology, light harvesting efficiency, and photovoltaic performance. Chapter 4 builds upon the successful implementation of nanotube based dye-sensitized solar cells by quantifying charge dynamics through electrochemical impedance spectroscopy. Fitting the impedance data to an appropriate equivalent circuit establishes ZnO nanotubes as the most effective architecture for rapid electron collection to date. Chapter 5 expands the synthetic palette of atomic layer deposition to include transparent conducting oxides that may be grown on high aspect ratio templates. Understanding and optimizing the growth mechanism of two versatile systems enables the structures to be presented in the final chapter. Chapter 6 concludes with a presentation of a unique dye-sensitized solar cell architecture in which electrons are collected radially through adjacent, concentric transparent conducting oxide nanotubes. The exceedingly fast electron collection exhibited suggests the design strategy has potential to revitalize the field by overcoming its most prominent obstacle, iodide-based electrolytes.