New Fraunhofer technique lowers cost of solar cells

Scientists at German research organisation Fraunhofer ISE have found a way to dramatically lower the amount of wasted silicon and energy when manufacturing solar wafers.

Currently, producing solar wafers is expensive. Impure silicon is liquefied and purified by adding chlorine, which is then broken into chunks and reformed again into blocks of its crystalline form for sawing into the wafers needed for the cells.

The final shaping process results in 50 per cent of the pure silicon being machined into dust which cannot be used. The current price for polysilicon is around £11 per kilogram, which means that approximately £6 of the substance is wasted for every kilogram.

The researchers have developed a technique which grows the silicon into the right shape at an atomic level without the need for the final sawing process. This prevents the loss of silicon from the traditional manufacturing process and reduces energy usage by up to 80 per cent.

“With our method, we can avoid almost all of the losses that occur during the conventional production process and the wafers are of the same quality as those produced using conventional methods,” says researcher Dr. Stefan Janz at the ISE.

Another advantage of the new technique is that it allows the wafers to be made as thin as desired.

With the conventional process, the silicon wafers must be at least 150 to 200 micrometers thick to minimise losses from the cutting process even though solar cells are capable of producing energy with far thinner wafers. The thinner wafers will also result in a cheaper solar cell.

The researchers say that by the end of the manufacturing process, the gains become really significant because cutting the cost of the wafer in half brings down the cost of the entire solar module by 20 per cent.

The researchers are working with a company called NexWafe to bring the new wafer production technique to market.

“In the pilot phase of this technology we’re working in close cooperation with our colleagues at Fraunhofer ISE,” says Dr. Stefan Reber, NexWafe CEO.

The completion of the factory and the start of mass production for the lower-cost wafers are both slated for late 2017.

More specifics on the details of the new process can be accessed on the Fraunhofer website.

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