Thin Cells Offer Path To Efficient Solar

It wasn’t considered an immutable law, but for a long time engineers worked within a limit to how long light could be trapped inside a solar cell. Busting through that limit has been a goal — if not the holy grail — of solar research, since longer confinement could mean greater energy extraction.

Now it appears researchers at Stanford might have succeeded, finding a way to absorb perhaps 10 times more energy than conventional theory predicted and, in the process, raising hopes of designing more efficient solar cells.

image via Stanford University

The key to the breakthrough, according to a Stanford press release, was moving beyond approaching light at the macroscale common with conventional solar cells. Instead, they worked with organic polymer films at a nanoscale — thinner than waves of light. Those ultra-thin layers were sandwiched between cladding layers. And those outside layers were roughed up, causing entering light to go off in different directions.

The result was a big increase in light absorption — up to 12 times the macroscale limit.

“The amount of benefit of nanoscale confinement we have shown here really is surprising,” said one of the researchers, post doctoral fellow Zongfu Yu. “Overcoming the conventional limit opens a new door to designing highly efficient solar cells.”

The Stanford research bolsters the cause of organic cells as an emerging solar-power technology. Rochester Institute of Technology recently reported that organic cells have a big life-cycle energy advantage over traditional silicon based cells. “Most of the research these days is looking into many different kinds of materials for solar cells,” said Shanhui Fan, who led the Stanford study. “Where this will have a larger impact is in some of the emerging technologies; for example, in organic cells.”

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Pete Danko is a writer and editor based in Portland, Oregon. His work has appeared in Breaking Energy, National Geographic's Energy Blog, The New York Times, San Francisco Chronicle and elsewhere.