The Quest for Inexpensive Silicon Solar Cells
It's not unusual to combine one invention with another to create a successful new product or technology. As Henry Ford said, "I simply combined the inventions of others into a car." Working with NREL and Oak Ridge National Laboratory (ORNL), the Ampulse Corporation may have discovered such a success—one that combines inventions and expertise from both labs for creating a less expensive alternative to wafer crystalline silicon solar cells.
Most of today's solar cells are made out of wafer crystalline silicon. "It's a wonderful material," said NREL Senior Principal Scientist Howard Branz. "It has supported the growth of a $10 billion solar industry, but it's really a relic leftover from the computer chip industry. So our goal here is to get crystalline silicon photovoltaics on this inexpensive foil developed by ORNL."
Promising New Solar Application Discovered
ORNL developed this metal foil—called RABiTS (rolling assisted biaxially textured substrates)—in the mid-1990s. It's often used for growing layers of superconducting material, providing the capability to create affordable, high-temperature superconducting wires. More than a decade later, Glenn Kline, with Innovation Valley Partners, a co-investor in Ampulse, wondered if it also held promise for solar applications. "I saw how the solar market was developing films that could be provided in roll-to-roll applications," Kline said. "I wondered if you could use it as a solar substrate."
For growing crystalline silicon on wafers and films, Kline discovered that NREL had developed a process called hot-wire chemical vapor deposition. Using this process, Branz and NREL Senior Scientist Chaz Teplin had already been pursuing the growth of silicon on alternative materials to reduce costs. The two NREL researchers and Kline decided it had potential to also grow silicon on RABiTS.
"The trick is to get as good material quality as you have in a wafer," Teplin said. "We're using our existing knowledge of how to grow silicon directly from a gas phase onto these metal foils."
U.S. Department of Energy Fund Advances Research
To ultimately see if the combination of technologies could be applied to solar, Kline joined forces with Kef Kasdin at Battelle Ventures, the affiliate fund manager of Innovation Valley Partners, to invest in and set up Ampulse. Ampulse then established a cooperative research and development agreement (CRADA) with NREL. In support of the CRADA, the project has received $620,000 from the U.S. Department of Energy's Technology Commercialization & Deployment Fund (TCDF). As part of a pilot program, NREL received $4 million from the TCDF to invest in commercializing promising new technologies through company partnerships.
"Our initial technology successes from those funds gave Ampulse the chance to raise $8 million in investments," Branz said.
While the available funds have accelerated the research, the silicon film solar cell technology is still very immature. It faces many technological challenges. But so far the collaboration between NREL and ORNL has proved to be a good combination of expertise and creative synergy. "With this new technology, we really want to help Ampulse change the face of solar electric energy and photovoltaics," Branz said.
To learn more about NREL's silicon solar cell research, visit the Silicon Materials and Devices Web site.