A faster, cheaper way to manufacture silicon solar cells, partially funded by the Energy Department and fine-tuned at its National Renewable Energy Laboratory (NREL), has won a coveted R&D 100 award as one of the top technology innovations of 2013.
Crystal Solar's approach to growing high-quality, high-efficiency silicon wafers at 100 times the usual throughput and half the cost could be a game-changer, creating American jobs and stemming the flow of solar cell manufacturing overseas, says T.S. Ravi, chief executive officer of the Santa Clara, California-based company.
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Even before he founded Crystal Solar, Ravi set a goal to speed up the manufacturing process. In 2011, his nascent company applied for the Energy Department's SunShot Initiative's Photovoltaic (PV) Incubator Program, which at that time was run out of NREL. The PV Incubator Program has a very competitive selection process, searching for ideas that are truly disruptive in terms of lowering costs.
"We applied for the program and were selected in late 2011," Ravi said, recalling a conversation he had several years ago with NREL's Harin Ullal. "I knew that if I could bunch a lot of wafers together, and find a way to remove the epitaxial wafer with a simple mechanical process, it could actually change the game in the solar industry."
Crystal Solar's direct gas-to-wafer method is epitaxial, which means it grows a layer of material on top of another material that has the same crystal structure. In the direct gas-to-wafer method—the official name is Direct Monocrystalline Silicon Wafer Growth by High-Throughput Epitaxy—gaseous layers of semiconducting silicon material are grown directly on reusable silicon substrates. The method has several advantages, including eliminating the waste incurred in the traditional approach, which involves sawing thin slices from a large ingot or block of silicon. In the new approach, wafers can be made thinner without compromising their quality or efficiency.
However, semiconductor material using the epitaxial approach typically grows very slowly—about two wafers an hour for the thickness needed for solar wafers. That's much too slow—and therefore costly—for solar cells. The Energy Department's SunShot Initiative has set a goal for solar energy of less than $1 per watt system price by 2020, as a way of making it cost competitive with fossil-fuel-based electricity.
Fore more NREL success stories visit http://www.nrel.gov/technologytransfer/success_stories.html