Hydrazine-based solution-processing of copper chalcopyrite for thin-film photovoltaics

Owing to the processing complexity associated with the vacuum-based fabrication of photovoltaic cells, the viability of solar energy is constantly challenged by the more economically attractive alternatives from fossil fuels. Solution-processing can overcome these issues due to the inherent processing advantages over conventional vacuum-based processes. The focus of this study is to demonstrate a viable route of fabricating highly efficient thin-film solar cells by means of solution-processing. This dissertation is organized in the chronological order describing the challenges in solution-processing Cu-chalcopyrite materials, and the methods to improve the solar cell efficiency from ground zero to above 8%.;Two methods to solution-deposit Cu-chalcopyrite material were examined: nanocrystal suspension and hydrazine-based precursor. Chapter 2 focuses on the nanocrystal-route, and analyzes the formation of zincblende and wurtzite CuInSe2 in the nano-meter dimension. This method, however, presented great difficulties to achieve films with decent physical quality; thus, solar cell performance was not examined. Chapter 3 describes the hydrazine-precursor route to solution-deposit CuInSe2 material. The chalcopyrite structure and p-type semiconducting behavior were both verified from the converted material. This method offers superior processing capability over the nanocrystal-route, and for the first time in this study, a solar cell with significant efficiency (3.50%) was demonstrated. This cell was then used as a reference throughout the remaining studies in this work.;The following chapters describe the modifications that were performed on each component in the CuInSe2-based solar cell and the corresponding improvements on the solar cell performance. Chapter 4 focuses on the window layer of the solar cell with the objective of decreasing the sheet resistance of the transparent conducting oxide material. Chapter 5 revisits the CulnSe 2 layer with bandgap engineering of CuInSe2 by sulfur incorporation. Chapter 6 centers on the cadmium sulfide buffer layer, and examines the influence of deposition parameters on the resulting film quality. Lastly, a summary and perspectives on the limiting factors that arise from the processing issues of each component is presented in Chapter 7.