Etching Silicon Could Maximize Its Power Output

Researchers from the Cambridge-based Massachusetts Institute of Technology (MIT) announce the development of a technique for maximizing the power output of conventional solar cell arrays, while at the same time reducing the costs associated with manufacturing these high-tech products.

Their focus was the highly purified silicon that is required in order to construct these arrays. The material accounts for more than 40 percent of the overall costs, so it seemed like a good place to start.

What the MIT did was develop a method of reducing the thickness of the required silicon substrate, while at the same time boosting the power output the material is capable of. This was made possible through the use of nanoscale etching technologies.

Scientists are now able to pattern tiny inverted pyramids on the surface of silicon, indentations less than a millionth of a meter across. The structures are able to trap photons just as efficiently as solid silicon surfaces up to 30 times thicker.

Details of the new research were published in the latest issue of the esteemed journal Nano Letters. The work was authored by MIT postdoctoral researcher Anastassios Mavrokefalos and MIT Department of Mechanical Engineering professor Gang Chen, among others.

“We see our method as enhancing the performance of thin-film solar cells. It would enhance the efficiency, no matter what the thickness,” Mavrokefalos reveals.

“If you can dramatically cut the amount of silicon [in a solar cell] you can potentially make a big difference in the cost of production. The problem is, when you make it very thin, it doesn’t absorb light as well,” adds graduate student and paper coauthor, Matthew Branham.

Investigators synthesized a crystalline silicon sheet as part of the experiments. At just 10 micrometers thick, it displayed the same efficiency in harvesting light as a conventional silicon substrate 30 times thicker. The sheet featured the new nanoscale inverted pyramids.

Funds for this study came from the US Department of Energy’s (DOE) Sunshot Program and the National Science Foundation (NSF). The MIT group hopes to have the new technology available for marketing in the very near future.