NREL’s solar furnace makes sure that unusable silicon wafers don’t become solar cells

Silicon wafer photovoltaic cells

According to estimates up to 10 percent of the solar cells are destined to fail when being manufactured, due to weak silicon wafers that end up on the assembly lines. Silicon wafers go through a lot before they can become solar cells and can take a bruising when going through assembly lines where they are being oxidized, purified or diffused. While the PV industry generated about $82 billion in global revenue, a 10 percent failure rate makes the loss reach billions of dollars. Now scientists at the U.S. Department of Energy’s National Renewable Energy Laboratory (NREL) have developed an instrument that tests silicon wafers for their strength before they actually end up on the assembly lines.

The device, dubbed Silicon Photovoltaic Wafer Screen System or SPWSS, is actually a cube-shaped furnace about 15-inches a side, which puts pressure on the wafers to find out which ones are too weak to make it through the manufacturing process. Here each wafer passes through a narrow, high-intensity illumination zone, where silicon wafers are exposed to thermal stress in the form of carefully calibrated high temperatures.

The micro-cracks or breaks in silicon wafers happen to weaken it and since the problem is diagnosed before expensive coatings and layers are added to it, the end result could be savings for solar panel manufacturers. The best part is that the system can be retrofitted into an assembly line and helps make savings that can make the difference between a U.S. manufacturer winning or losing.

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