Design of Nanophotonic Antireflection Coatings for III-V Thin-Film Photovoltaics

Thin-film photovoltaics have provided a critical design avenue to help decrease the overall cost of solar power. However, a major drawback of thin-film solar cell technology is decreased optical absorption, making compact, high-quality antireflection coatings of critical importance to ensure that all available light enters the cell. In this thesis, we describe high efficiency thin-film InP and GaAs solar cells that utilize a periodic array of nanocylinders as antireflection coatings. We use coupled optical and electrical simulations to find that these nanophotonic structures reduce the solar-weighted average reflectivity of InP and GaAs solar cells to around 1.3 %, outperforming the best double-layer antireflection coatings. The coupling between Mie scattering resonances and thin-film interference effects accurately describes the optical enhancement provided by the nanocylinders. The spectrally resolved reflectivity and J-V characteristics of the devices under AM1.5G solar illumination are determined via the coupled optical and electrical simulations, resulting in predicted power conversion efficiencies > 23 %. We conclude that the nanostructured coatings reduce reflection without negatively affecting the electronic properties of the InP and GaAs solar cells by separating the nanostructured optical components from the active layer of the device.

Final Report of the Phase III Archaeological Investigations at the Dr. Upton Scott House (18AP18), Annapolis, Anne Arundel County, Maryland, 1998-1999

In the summers of 1998 and 1999, the Archaeology in Annapolis project carried out archaeological investigation at the eighteenth century Dr. Upton Scott House site (18AP18)located at 4 Shipwright Street in the historic district of Annapolis, Anne Arundel County, Maryland. The Upton Scott House is significant as one of only a few Georgian houses with remnants of its original plantation-inspired landscape still visible (Graham 1998:147). Investigation was completed in agreement with the owners of the historic property, Mr. and Mrs. Paul Christian, who were interested in determining the condition and arrangement of Dr. Upton Scott’s well-documented pleasure gardens. Betty Cosans’ 1972 Archaeological Feasibility Report, the first real archaeological study of the Upton Scott House site, guided the research design and recovery efforts. Cosans determined that testing and survey in the back and side yards of the Scott property would yield important information on the use and history of the property, including that of Scott’s famous gardens. Excavation units and trenches were placed within three separate areas of backyard activity on the site which included Area One: extant brick stables in the southwest of the property; Area Two: the brick foundations of a small outbuilding located in the northwest area of the site; and Area Three: the area of Scott’s formal gardens. The research design included an interest in recovering evidence of African-American spiritual practice and domestic life at the site. Also of significant importance was an analysis of Scott’s garden beds, concerning the order and layout. Also sought was an understanding of the change in perception and use of the backyard by the various owners of the property.