Novel Abrasives for Cheaper Solar Cells
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The fundamental building blocks of the solar cells we see on rooftops are silicon wafers, which are 200 micrometers thin, human hair is 50 to 100 micrometers in comparison. These wafers are cut by a sawing process where a brick of silicon goes down at very slow speed. Tiny abrasives attached to steel wires are running at high speed, on these two rollers. The relative motion between the silicon brick and the abrasives wire, slices the brick into very thin wafers. Material cost can be reduced by manufacturing thinner wafers, which would however make them more probable to breaking unless they have higher mechanical strength. Strength of wafers depends on micro-cracks created by the abrasive particles while cutting. We found that the shape of abrasive critically affects the length and number of micro-cracks created. Currently the diamond abrasives used are irregular in shape and size, hence micro-cracks are not well controlled. The key thing which is missing is engineering the abrasive shape which directly affects the micro-cracks. In our research, we designed rounder shaped tungsten carbide abrasive particles, which produced fewer and smaller cracks, in lab-scale experiments, which simulated the slicing process.