Novel Materials and Devices for Solar Energy Conversion

Grant # 07-05
Principal Investigator: Vikram L. Dalal
Organization: Iowa State University
Technical Area: Renewable Energy

Abstract
Conversion of solar energy into electricity using solar cells (photovoltaics) is becoming very important technology for assuring the nation’s energy independence. President Bush has made this specific technology one of the cornerstones of the strategy for reducing our dependence on imported oil. The technology is also very important for reducing global warming, and can serve as an important technology for providing the hydrogen needed for both a hydrogen based economy and for converting biological materials into fuels.

Currently, the market for photovoltaic products is about $10 billion and has grown at a ~35-40% rate per year over the past few years. The annual worldwide production of solar cells in this year is expected to be 1.7 Gigawatts, based mostly on crystalline Si technology.

While the costs of producing solar power have reduced dramatically over the last few years, they seem to have plateaued because of the high cost of Si wafers, which are increasing because the worldwide demand outstrips the supply of Si wafers. Further reductions in cost will have to come from thin film Si-based technologies which can produce an equivalent amount of power but by using much less material. One such material is nano-crystalline Si, which in thin film form (~ 2 micrometer) has been shown to produce conversion efficiencies approaching ~9-10%. The current nano-crystalline Si material is limited in its efficiency because of the inherent defects in the materials.

Objectives
It is the objective of this proposal to develop a more ordered nano-crystalline Si so as to increase the efficiency of thin film Si based solar cells and also to improve its stability. The ordered nano-crystalline Si films will be grown using a novel plasma-deposition growth technique which can be easily scaled up to manufacturing scale. The program includes a systematic exploration of growth of films, characterization of their most important structural, optical and electronic properties and fabrication of proof-of-concept solar cell devices. Both single junction and tandem junction devices will be fabricated so as to improve the conversion efficiency of the solar cells.

The project includes significant graduate and undergraduate student education. Two graduate students will participate in the research program. There will also be a significant involvement of undergraduates in the program as REU students. The materials developed will be integrated into appropriate graduate and undergraduate courses at Iowa State.

An excellent infrastructure exists at Iowa State to undertake this work, backed by many years of experience in the field. Public dissemination of the results will be undertaken through participation in annual meetings of Iowa Science Academy, through public talks at events sponsored by Renewable Energy organizations throughout Iowa and organizations such as local chapters of IEEE and student organizations such as Etta-Kappa-Nu, and through publications and presentations at international conferences.

A significant cost share is included in the project. We expect appropriate IP to be developed as a result of this project.

The importance of this project to Iowa lies not only in developing new technology for cost-effective solar conversion but also in providing trained manpower and new technology to Iowa companies working in this field.