EXPERIMENTAL DEMONSTRATION OF LIGHT TRAPPING AND INTERNAL LIGHT SCATTERING IN SOLAR CELLS

Renewable energy technologies have long-term economic and environmental advantages over fossil fuels, and solar power is the most abundant renewable resource, supplying 120 PW over earth’s surface. In recent years the cost of photovoltaic modules has reached grid parity in many areas of the world, including much of the USA. A combination of economic and environmental factors has encouraged the adoption of solar technology and led to an annual growth rate in photovoltaic capacity of 76% in the US between 2010 and 2014. Despite the enormous growth of the solar energy industry, commercial unit efficiencies are still far below their theoretical limits. A push for thinner cells may reduce device cost and could potentially increase device performance. Fabricating thinner cells reduces bulk recombination, but at the cost of absorbing less light. This tradeoff generally benefits thinner devices due to reduced recombination. The effect continues up to a maximum efficiency where the benefit of reduced recombination is overwhelmed by the suppressed absorption. Light trapping allows the solar cell to circumvent this limitation and realize further performance gains (as well as continue cost reduction) from decreasing the device thickness. This thesis presents several advances in experimental characterization, theoretical modeling, and device applications for light trapping in thin-film solar cells. We begin by introducing light trapping strategies and discuss theoretical limits of light trapping in solar cells. This is followed by an overview of the equipment developed for light trapping characterization. Next we discuss our recent work measuring internal light scattering and a new model of scattering to predict the effects of dielectric nanoparticle back scatterers on thin-film device absorption. The new model is extended and generalized to arbitrary stacks of stratified media containing scattering structures. Finally, we investigate an application of these techniques using polymer dispersed liquid crystals to produce switchable solar windows. We show that these devices have the potential for self-powering.

Legacy Resource Management Program Archaeological Reconnaissance Survey, United States Naval Academy, Annapolis, MD.

The Archaeological Reconnaissance Survey of United States Naval Academy will provide the Navy with a rich understanding of the history of this property. A National Register of Historic Places District, such as the Academy, deserves a thorough analysis of its past, in order to preserve what exists and to plan for the future. The goal of this project is to investigate the history of the Academy through traditional historic research, innovative computer analysis of historic maps, oral history interviews, and tract histories. This information has been synthesized to provide the Navy with a planning tool for Public Works, a concise look at the cartographic history of the Academy, and reference manual of the vast amounts of information which have been gathered during the course of this project. This information can serve as a reference tool to help the Public Works department comply with Section 106 regulations of the Historic Sites Preservation Act, with regard to construction. It can also serve as a source of cartographic history for those interested in the Academy's physical development, and as a way of preserving the culture of residents in Annapolis. This program and archaeological survey will ultimately serve to add to the rich history of the United States Naval Academy while preserving an important part of our nation's heritage.