Goals For The Inexpensive Solar Cells

The world is facing severe energy crisis and the situation is going to be worst in coming decades. So, Multi-National corporations are trying their level best to devise ways to alleviate the situation. Twin Creeks Technologies, a company that has been operating undisclosed until today, has developed a system that creates thin wafers of crystalline silicon with an aim that it could cut the price of manufacturing silicon based solar cells in half. They have also revealed their technology on a very small scale, 25-MW per Annum generation facility in Senatobia, Mississippi, using solar cells that are built on tiny silicon wafers.

The chief executive officer of Twin Creeks says the enterprise’s technology reduced the quantity of silicon that is needed to manufacture the solar cells. And on the other hand it also cuts the cost of production line machinery. He also says that the company is capable of producing cells that can provide power at 40 cents per Watt. The company has raises roughly $93 million in venture capital. Moreover, Twin Creeks has also acquired loans from the state of Mississippi and some other sources to develop its infrastructure to build these cells.

Up till now, the most predominant material that is used for the manufacturing of these cells is crystalline Silicon also known as the “solar grade Silicon”. Furthermore, this silicon is divided into many categories depending upon their crystal size and other properties in the subsequent ingot, ribbon or wafer, etc.

• Mono-Crystalline Silicon (c-Si): often prepared using Czochralski process. Single-crystal is expensive and because they are cut from cylindrical ingots, do not fully shield a rectangular solar cell panel without considerable wastage of refined Silicon. That’s why c-Si solar panels have exposed gaps at four corners of the cells. 

• Poly-Crystalline Silicon, also known as Multi-Crystalline Silicon (mc-Si), is made from cast square lumps or ingots of molten Silicon that are carefully cooled and solidified. They are easier to manufacture but are less efficient than the Mono-crystalline ones. According to data collected by United state Dept Of Energy, there was higher number of Polycrystalline cells sales than the c-Si panels. 

On the other Hand, Twin Creeks’ process makes 20-micrometer thick wafers without wastage of refined silicon. This procedure involves the application of thin layer of metal that increases the durability of these wafers to endure solar-cell manufacturing machinery. Sivaram, the CEO of the company also says that his company while reducing the usage of wire saws and other associated equipment and producing thinner wafers that cuts the end user cost. It also reduces the amount of Silicon used during the manufacturing by almost 90% which is certainly a substantial extent. He also adds to his statement that thus new technology can be used with the existing production lines. 

The fundamental principal of the process is explained here: It all begins with placement of 3mm thick slabs of crystalline Silicon in a vacuum chamber. Then these slabs are bombarded with a beam of hydrogen ions. These ions are accumulated by the slab at a very precise depth if 20um, which is controlled by the potential of the striking beam. Once required quantity of ions are stored by the slabs of crystalline Silicon, a mechanical arm (Robotic Arm) takes these Silicon wafers out of the vacuum chamber and places it inside a furnace, where the ions in the Silicon form microscopic bubbles of Hydrogen gas that expand, making little fractures or breaks within the silicon wafer which causes a 20um thick layer of Silicon to peel off. Then a metal support is provided to thin Silicon for supporting it. Their wafers are in compatibility with the orthodox solar-cell assembly line machinery and the method that fabricate advanced solar-cell layouts like hetero-junction solar cells. 

Sivaram also claims that that this process is also equally good for other single-crystal materials including Gallium Arsenide, a semiconductor that is known for record holding efficient performance as far as solar cells are concerned.If we see the history of ion bombardment technique then we come to know that it was available in theoretical work but due to unavailability of large ion accelerators, it was a bit impractical, considering the expense on it. To make this process feasible, Twin Creeks has made an ion accelerator that is 10 times more powerful than any commercially available particle accelerator, providing high values of current and very high energy too. 

One factor that the company should work on is the surface texture of the wafers. Usually, the surface is rough so that it can absorb light rather than reflecting it. This is typically accomplished by making texture as pyramidal shaped (about as tall as Twin Creeks wafer thickness). So this cannot be done with existing wafer technology of the company. We look forward to the technical improvements in their design making possible cheap and efficient Solar cells available to people and getting most out from the nature.

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