General Competition (October 1997)

Ultrathin Silicon Ribbon for High-Efficiency Solar Cells

Sponsor: Evergreen Solar, Inc.

• Project Performance Period: 10/1/1997 - 9/30/2000
• Total project (est.): $3,058,186.00
• Requested ATP funds: $1,367,714.00

Photovoltaic (PV) technology for harnessing the sun's energy has improved steadily over the past three decades and now serves a $1 billion market. However, solar energy systems are still not cost-effective solutions for meeting mainstream power or rural electrification needs in the United States and the developing world because today's PV material, crystalline silicon, is too expensive. Evergreen proposes to develop a manufacturing process that will dramatically reduce the costs of the silicon photoelectronic material and overall PV manufacturing costs. The company proposes to explore an innovative new approach to manufacturing the silicon materials, which involves growing an ultrathin silicon sheet called "String Ribbon" on which the solar cells are made. If this process is to become economical for maintstream power, it is necessary to achieve very thin ribbons with greater widths and higher process speeds than can be done today, while simultaneously achieving high efficiencies. The technical challenges are great and involve such things as achieving extremely precise control of thermal gradients in the silicon as it is formed and cools. In addition, the company plans to develop novel methods for fabricating solar cells with 16 percent efficiency at high yields. The new material technology is expected to cost much less than thick crystalline silicon PV products while retaining the reliability and market acceptance of the traditional PV material. If successful, the project will be an important step toward enabling the U.S. solar industry's goal of $1-per-watt PV module manufacturing costs. The technology would provide, if successful, environmentally friendly, affordable electricity for rural regions and developing nations while helping to reduce global warming emissions. Low-cost, ultrathin silicon also could potentially be used in flat-panel displays in electronic applications.

For project information:

Mark Farber, (617) 890-7117
farberma@aol.com

ATP Project Manager

Purabi Mazumdar, (301) 975-4891
purabi.mazumdar@nist.gov