The National Photovoltaics Program managed by the United States Department of Energy has the goal of establishing solar photovoltaic energy as a significant energy source for the United States. Some of the means for reaching this goal include advanced and applied research in photovoltaic cells to advance the state of technology, and support of education programs for training of future professionals in solar photovoltaic energy.
Sandia National Laboratories has responsibility for development of crystalline silicon cell technology within the National Photovoltaics Program. As part of this program, Sandia National Laboratories is supporting the University Center of Excellence for Photovoltaics Research and Education in Crystalline Silicon Solar Cells at the Georgia Institute of Technology. The purpose of the Center is to advance the state of technology in crystalline-silicon solar cells through research, to investigate industrially relevant processes that may result in lower-cost processing techniques, to collaborate with U.S. manufacturers of crystalline silicon cells to improve their performance and reduce their cost, and to provide educational assistance to university students through the operation of a silicon solar cell fabrication laboratory. Hence, the Center will help train undergraduate and graduate students in the field of crystalline-silicon solar cells, both at Georgia Tech and at other Universities through joint research efforts.
The goal is to determine which processing techniques work best for each of the many types of solar-grade silicon which is commercially in use. In this way, different variations of processing techniques or entirely different processes can be developed to optimize fabrication of high-efficiency cells on PV-industry Cz silicon and multicrystalline silicon, and to optimize techniques for light trapping in multicrystalline silicon.
The goal is to develop processing techniques that combine the functions of several distinct conventional furnace processes into fewer rapid thermal processes which can be performed in a much shorter interval of time. The cells so produced should perform as well as or better than cells conventionally produced. The rapid processing techniques should be limited to those which can be scaled up to mass production.
The purpose is to take advantage of some recent innovative solar cell design concepts that would allow the fabrication of moderate-efficiency large-area cells on relatively low-quality thin crystalline-silicon layers. This could reduce the cost of silicon solar cells considerably since presently the largest component of cell cost is due to the growth of ingots and their cutting into silicon wafers.
Because of the high degree of difficulty involved in accomplishing this, we are joined in partnership with members of the U.S. PV industry or other Universities who are pursuing similar approaches.
1. Develop titanium boride (TiB2) coated graphite substrates for thin silicon cells and grow thin CVD Silicon layers on these substrates.
2. Fabricate thin silicon cells on foreign substrates by conventional and RTP/PECVD/SPC techniques.
The goal is to implement novel approaches to solar cell manufacturing that will not
require the purchase of new capital equipment, and will significantly enhance the
performance of existing cell designs. Such techniques should be capable of batch
processing, resulting in high throughput for all stages of cell fabrication. In addition,
the number of thermal cycles required for junction formation, oxidation and gettering
should be sharply reduced to further increase throughput.
The purpose is to collaborate with U.S. manufacturers of crystalline-silicon cells to help them understand how to improve their device designs or material quality to improve cell performance and reduce cost. This relationship will characterize and improve their material quality, develop and transfer appropriate gettering and passivation techniques which would improve cell performance, design and fabricate high-efficiency cells on industry materials, provide guidelines to industry for reducing cost and improving cell performance, and publish joint technical papers.
This is a university-level educational program in solar cells,operated through a silicon solar cell fabrication laboratory. The laboratory fabricates silicon solar cells according to runsheets and materials submitted by students in solar cell cources. Any university that meets the ESP prerequisites is eligible to participate in this program (University Participant). The prerequisites are that the university offer a course on solar cells or on semiconductor device fabrication at a senior/graduate level, and that this course have a prerequisite of a course on semiconductor device physics. The right is reserved to limit the number of University Participants based on the capacity and the capabilities of the laboratory. The management of the ESP ensures that information on the program is disseminated to prospective universities. The ESP offers at least one classroom course on solar cells. It provides hands-on training to undergraduate and graduate students in fabricating high efficiency cells and supports other uiversity PV programs in the U.S. through collaborations and technical assistance. There is a process line that routinely produces high efficient celss on single crystal float zone silicon in order to provide prompt inter-university research support.