About 5–10% of silicon wafers used to make photovoltaic solar cells are damaged as they go through the industrial material production process. These wafers are expensive enough that what might sound like an acceptable amount of damage actually translates into billions of dollars lost each year by the solar industry.
National Renewable Energy Laboratory (NREL) researchers set about trying to create a detector to identify damaged wafers before they are installed in solar cells in order to stop the manufacturing of defective ones. What they came up with is called the Silicon Photovoltaic Wafer Screening System. It is actually a small furnace which can be integrated into a wafer assembly line and functions by exposing wafers to high temperatures. When they are subjected to this thermal stress test the weak or defective wafers can be identified and pulled from solar cell production.
Cutting production losses can make solar cells more cost-competitive and therefore more marketable. (Consumers typically cite cost as the main barrier to purchasing residential or commercial solar PV systems). NREL’s wafer stress tester could help manufacturers improve their quality control and consumers by reducing costs. Presumably reducing the number of defective solar cells would also decrease consumer frustration for obvious reasons.
Another benefit to using the NREL device is that as solar wafers become thinner, they will likely be more prone to breakage. So such a detector will become even more valuable.
A manual version of the NREL instrument costs $60,000 and can test about 1,200 wafers per hour. An automated version can also remove the defective wafers it detects and place them in a container for melting and re-cycling back into material for making effective wafers. The device is very energy-efficient and the testing of a single wafer only costs a fraction of one penny.
NREL is exclusively dedicated to developing new renewable energy and energy-efficient technologies. By its own estimate the grants it provides to start-ups and other companies generate tens of thousands of jobs.
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