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Coating Processes Boost Performance of Solar Cells

NASA Technology

NASA currently has spacecraft orbiting Mercury (MESSENGER), imaging the asteroid Vesta (Dawn), roaming the red plains of Mars (the Opportunity rover), and providing a laboratory for humans to advance scientific research in space (the International Space Station, or ISS). The heart of the technology that powers those missions and many others can be held in the palm of your hand—the solar cell.

altSolar, or photovoltaic (PV), cells are what make up the panels and arrays that draw on the Sun’s light to generate electricity for everything from the Hubble Space Telescope’s imaging equipment to the life support systems for the ISS. To enable NASA spacecraft to utilize the Sun’s energy for exploring destinations as distant as Jupiter, the Agency has invested significant research into improving solar cell design and efficiency.

Glenn Research Center has been a national leader in advancing PV technology. The Center’s Photovoltaic and Power Technologies Branch has conducted numerous experiments aimed at developing lighter, more efficient solar cells that are less expensive to manufacture. Initiatives like the Forward Technology Solar Cell Experiments I and II—in which PV cells developed by NASA and private industry were mounted outside the ISS—have tested how various solar technologies perform in the harsh conditions of space. While NASA seeks to improve solar cells for space applications, the results are returning to Earth to benefit the solar energy industry.

Partnership

Throughout the 1980s and 1990s, Maria Faur, while conducting research for NASA Glenn (then Lewis Reseach Center), developed new techniques for enhancing solar cell manufacturing and design. In 1995, Faur founded Special Materials Research and Technology Inc. (SPECMAT) to expand these efforts. The following year, the company entered into a Space Act Agreement with Glenn, and in 1999, became one of the first tenants of the NASA Lewis Incubator for Technology. Both partnerships helped to provide SPECMAT with the means to advance a proprietary method Faur had developed while working for NASA to enhance solar cells in a way not previously achievable.

SPECMAT’s room-temperature wet chemical growth (RTWCG) silicon oxide process provides a unique method to fabricate high-efficiency silicon solar cells at significantly reduced cost. Solar cells require an antireflective coating to help the cells capture the light particles, called photons, needed to generate electricity. Traditional crystalline silicon cells typically use a silicon nitride coating, sometimes in conjunction with a textured surface, to produce the necessary antireflective characteristics. But the current processes for adding antireflective coatings employ expensive machines that operate at high temperatures and require use of toxic gasses. SPECMAT’s RTWCG process involves bathing the PV cell in a room-temperature chemical solution for less than a minute, growing an antireflective layer of silicon oxide on the cell’s surface and providing the cell with a range of enhanced qualities.

“The ability to grow oxide at room temperature is unique in the industry,” says Faur, president and CEO of SPECMAT. The company patented the RTWCG process, and now, says Faur, the NASA-derived innovation stands poised to become a powerful technology for use in the fabrication of solar cells, microelectronics, and photonic devices.

Benefits

altSPECMAT has licensed the patented RTWCG process to Equity Solar Inc. and Equity Microelectronics Inc. of San Anselmo, California, to bring the technology to the commercial solar energy and microelectronics markets.