Silicon Wafers

Silicon Wafers Developed by the Mississippi Start-up Aims to Cut the Cost of Solar Cells in Half

Regularly, the crystalline silicon wafers are cut out of silicon ingots into wafers about 200 micrometers thick, wasting good half of an ingot. Grinding-honing causes further loss of silicon. Today industry utilizes 200 micrometer thick wafers because anything thinner than that becomes brittle and does not survive the manufacturing line. Researchers, however, knew that thinner silicon wafers could lead to even more efficient conversion of sunlight into electric current.Twin Creeks Technologies - that has not been drawing much attention until now - has announced the new technology it developed that could slice the cost of making silicon solar panels in half. A small start-up from Mississippi has conducted first tests in its factory built in Senatobia. Though the best deal on silicon panel market today is roughly 80 cents per Watt, the CEO of Twin Creeks Siva Sivaram claims they can produce them for about 40 cents per Watt. The promising technology has helped the company to raise almost $100 Million in venture capital this year; local state and private loans were used to build its factory. Siva says that new technology significantly reduces the cost of the equipment needed to manufacture wafers as well as the amount of silicon used to produce wafers.

Current manufacturing process involves intense use of wire saws which produce lots of waste. Twin Creeks reduced the use of wire saws and the equipment accommodating cutting process substantially by implementing self-made Hyperion 3 Ion Accelerator that reduces the thickness of a wafer by bombarding it with hydrogen atoms. The company has figured out how to reinforce a silicon wafer with a thin layer of metal enough to survive conventional honing machinery after the wafer is made. Siva claims that company is able to reduce the amount of silicon ingots needed for cutting by almost half, significantly reducing rough material costs. Since the wafers can be finished by conventional honing equipment after they are formed, the technology can be merged with existing silicon wafer production lines. As a matter of fact Twin Creeks intend to manufacture and sell manufacturing equipment rather than solar cells. The company expects up to a dozen production lines open within a year.

How does it work?

The rough 3 millimeter thick silicon wafers are fixed on the surface of the spinning drum inside vacuum chamber - vacuum is necessary in order to minimize the undesired particle interference. When the drum spins wafers get blasted by the hydrogen ions which penetrate wafers down to precise 20 micrometers and no deeper, thanks to precisely controlled voltage beam. Next, silicon wafers are placed inside a furnace to flake off the layer soaked with hydrogen because it expands and bubbles up under heat. The metal backing helps wafers to maintain strength through this process. After that stage wafers can be finished by conventional equipment which is the greatest advantage of this new technology.

SILICON WAFERS

Since the silicon wafers come out of “vacuum ion blaster” being 'thickness compatible' and 'integrity compatible' with conventional solar-cell production machinery, the company considers adopting this process to work with other crystalline materials such as gallium arsenide, also a semiconductor used in the industry, famous for high efficiency solar cells. This is not the first time someone considered using ion beam to shave down crystalline silicone, but until today it was considered economically impractical because ion accelerators are famous for their high cost. Twin Creeks, however, managed to develop their own accelerator that is 10 times more powerful than anything commercially available today. While compatibility with existing silicon panel production lines is a plus there is still a need for one more improvement. All solar silicon panels require rough texture to be created on the surface in order to minimize sun light reflection - more light it absorbs, more energy it produces. Conventionally the grain texture is created, sort of like pyramids, but the thickness of new wafers is not sufficient to engrave anything that deep into their surface. Twin Creeks, however, is ready to implement yet another anti-reflection innovation that promises to perform just as good as grain structure used by the conventional process.

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