Etchings on silicon improve light absorption – M.I.T.

Researchers at the Massachusetts Institute of Technology have devised a method to increase silicon’s ability to absorb sunlight, which could lead to a reduction in the the amount of silicon needed in a solar device, and reducing costs in the process.

By etching a pattern of tiny inverted pyramids on the surface of a thin sheet of silicon, the MIT scientists found they could use 90 percent less silicon while still maintaining a high efficiency. A solar cell with the technology only around 10 micrometers thick can absorb the same amount of sunlight a conventional solar panel can, which is 30 times larger.

The etchings create indentations less than a millionth of a meter across that greatly increases the thin silicon’s light absorption capacity, allowing it to trap rays of light as effectively as conventional solid silicon surfaces.

Silicon solar cells are the most common type of photovoltaic device with the best conversion efficiencies – ranging between 11 to 19 percent on average– on the market to date.

However, silicon is an expensive material, representing up to 40 percent of the overall costs of conventional solar arrays.

Using the etched thin silicon devised from MIT could reduce the amount of expensive silicon needed for solar cells. It would also have the added benefit of making the solar cells lighter, which would in turn reduce the materials needed for frames and supports.

They believe that they can achieve conversion efficiencies of about 20 percent, compared to 24 percent for the best current commercial silicon solar cells.

The team has tested the etching process, using equipment and materials that are standard parts of silicon-chip processing, and demonstrated its improvement in trapping light. The next step would be to add components to produce a photovoltaic cell using the material that is comparable to conventional solar cells. EcoSeed Staff 

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