U of S researchers develop simple, high-efficiency flexible solar cells

University of Saskatchewan researcher Tim Kelly and his team have developed a simple process that allows production of highly efficient, flexible solar cells.

Kelly, an assistant professor of chemistry and Canada Research Chair in Photovoltaics, explained the key is swapping out titanium dioxide with zinc oxide nanoparticles in one layer of his solar cells. This eliminates the need for sintering - or baking - which means the cells can be created using plastics or other flexible materials.

"It comes down to fabrication," Kelly said. "These cells are very easy to produce. We coat conductive substrates with solutions of simple chemicals - there are no air-sensitive or high-temperature processing steps. You're basically taking a piece of glass or plastic and dipping it in a beaker."

The process, described in the December 22, 2013 issue of Nature Photonics, means that inexpensive and highly scalable processing techniques could potentially be used to fabricate solar cells in a manner similar to printing newspapers. The U of S Industry Liaison Office has filed a provisional patent on the process.

Kelly's cells are based on a type of perovskite, a class of compounds whose crystal structure allows them to act as semiconductors. He explained that initially, solar cells based on perovskites yielded three to four per cent efficiency. Breakthroughs in the field in mid-2012 pushed this up to 10 per cent. By 2013, researchers had produced cells that were 15 per cent efficient; Kelly's team has achieved nearly 16 per cent.

"Output has shot up from 10 per cent to almost 16," Kelly said, explaining that it is an extremely competitive field of study with new papers coming out nearly every week. "It's almost exponential growth - things are moving really quickly out there."

Part of the success of Kelly's technology stems from its ability to absorb a fairly wide range of light.

"If you look at a film of this material, it looks black or very dark brown because it absorbs so much of the visible spectrum," he said, adding that they hope to continue to push cell efficiencies closer to the 20 per cent mark that some researchers suggest is attainable.

As for possible consumer applications, Kelly cited lower-cost rooftop solar power arrays or new products made possible by the flexible nature of the solar cells.

Kelly stressed that more work needs to be done to resolve some important challenges. Perovskite-based solar cells are susceptible to damage from air and moisture, and Kelly's are no exception. This means hermetically sealing the cells, coming up with some stabilizing chemistry, or both. The team will also be looking at alternative light-absorbing materials that do not require the use of lead.


For more information, contact:


Jennifer Thoma

Media Relations

University of Saskatchewan


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