University of Delaware
Photovoltaic (PV) energy has potential applications in a variety of areas, from small niche type applications such as handheld electronic devices, to medium residential type systems for homes or small businesses, to large scale utility plants. Furthermore, this alternative energy source can provide for extraterrestrial demands. Gallium arsenide (GaAs) and silicon solar cells have been the most prominent types for powering space technologies, including satellites and many other forms of spacecraft. II-VI thin-film cells are another promising option. They are lightweight, cost-effective, and exhibit high conversion efficiencies, which align with some of the major criteria that NASA prioritizes in the development the next generation of cells. As a result, findings from this investigation are applicable to that of NASA’s Space Technology Roadmap for Space Power and Energy Storage, particularly in the area of Solar Power Generation (TABS 220.127.116.11).
This project proposes to address improving the specific power of II-VI thin-film cells by exploring the electrical properties of the constituent materials that absorbs the electromagnetic radiation; specifically, improving their transport properties. By addressing the electronic quality of absorbing material, the photovoltaic cell can convert solar radiation into electricity more efficiently. But, what about the deposition process impacts their electronic quality? Why are these properties so influential in governing the performance of the cell? The proposed project strives to answer some of these questions. It is a component of a larger investigation called Elemental Vapor Transport at Atmospheric Pressures (EVTAP) under the direction of Christos S. Ferekides at the University of South Florida. This initiative is exploring the impact of stoichiometric variations on the doping of II-VI compounds, such as Cadmium Telluride (CdTe), on the conversion efficiency of the respective thin-film photovoltaic cell. The main experimental tool of the study is a vapor deposition apparatus, which will be used to deposit II-VI compound films under various growth conditions, including changes to the stoichiometric ratio of the constituent elements and extrinsic dopants. The proposed project is the development of a simulation tool, initially using CHEMCAD® and COMSOL Multiphysics® software packages, to model the deposition process and predict film properties. The segment of the tool designed in CHEMCAD will focus on the kinetics of the synthesis reaction for each II-VI compound. Then, the portion of the simulation produced in COMSOL will verify the results of its counterpart and also give critical information on the mass transfer elements associated with the development of the thin-film layers. These include predictions on the achievement of laminar flow within the deposition region as well as the thickness and uniformity of the deposited layer. This is an interdisciplinary investigation, incorporating chemical engineering concepts towards improving the transport properties of thin-film photovoltaic cells utilizing II-VI semiconductors.