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Interviewee: John Rogers, University of Illinois Urbana-Champaign
John Rogers is also working on artificial, bionic-like eyes, similar to the ones in the iconic image of “The Terminator.” Check out that news video here. The trick was in order to make a tiny video camera work like an eye, it must be shaped like an eye.
Thin Is In
By Heather Mayer
Up until now solar panels have had their fair share of limitations, being heavy, rigid and fragile. But John Rogers, a professor at the University of Illinois Urbana-Champaign, and his team of researchers have created a method to produce extremely thin solar cells that can also be transparent and flexible.
“If you look at a conventional solar panel, it’s relatively heavy, mechanically rigid, it’s fragile, you can’t bend it, it’s opaque, you can’t see through it,” Rogers explains. “Our work here is to address those limitations.”
No one has found a more desirable material than silicon for generating solar power, but Rogers and his team invented a way to use extremely thin slices of the material.
"The way solar cells are currently manufactured with silicon demand that thickness to achieve sufficient resistance to fracture so that they can make the solar cells at high yields," Rogers explains.
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He and his team showed that thickness is not necessary to make silicon solar cells efficient at producing power from the sun. They figured out how to create silicon solar cells that are 100 times thinner than conventional solar cells. To
achieve the best possible performance, Rogers’ team uses a monocrystalline variety of silicon. And they invented a process for using the ultra-thin cells to design solar modules without damaging them. The process is similar to a print process, which transfers the slices onto lightweight plastic or fabric.
This method allows photovoltaic cells, the building blocks of solar panels, to be more efficient and potentially less costly.
“So we have thin, lightweight, mechanically bendable and even partially transparent module designs that we think could potentially open up new areas of application for silicon-based solar technology," Rogers says.
Recycle, Reduce, Reuse
Because the new, thin modules use much less material, the researchers can create more solar cells from the same silicon “wafer.”
“We work our way through the entire thickness of the wafer, thereby making very efficient use of the silicon material in the solar cell technology that we developed,” Rogers says.
But this extreme thinness requires a support system to prevent breakage.
“These are extremely thin solar cells — about one tenth the thickness of a human hair — so without that support structure they can be easily broken,” he explains. “The purpose of the plastic substrate is just to form a mechanism support so that your solar cell is robust and not prone to fracture or failure.”
A Bright Future
According to Rogers and his researchers’ report in the journal, “Nature Materials,” their tests showed that the ultra-thin cells are just as efficient as the conventional cells, while using much less material. Rogers says their flexibility and transparency will open the doors to more solar power possibilities.
“You could roll them up, throw them in the back of a truck like a carpet, and then unfurl them when you’re installing them in their final location,” Rogers says. "Those kinds of things are very difficult to do when your solar cell technology is rigid and bulky and heavy."
And by adjusting the density of the cells on the module designs, the researchers can give them different degrees of transparency or opacity. They could be used as lamination on the outside of a building, on power-generating windows, or on the tinted sunroof of a car, Rogers explains.
“You can imagine putting solar cells in all kinds of places that previously were extremely difficult to do,” he says. "You can imagine integrating these things with clothing, or the surfaces of tents or backpacks."
Those applications "could be possible with other kinds of flexible solar cells, but they have their own disadvantages in terms of performance and reliability. So it’s really bringing the well-developed silicon technology to this world of flexible solar cells to enable these new possibilities,” he says.
Indeed, some of those applications are now available using other materials, but Rogers writes that there’s good reason why silicon "is used in more than 90% of all installed photovoltaic capacity… "If one considers a metric that integrates, cost, materials abundancy, efficiency and lifetime, by this measure, silicon is the best."
Rogers has confidence that this new method of creating solar panels will not only be efficient and attractive, but there’s a good chance it will reduce the cost of solar energy, making it a more affordable energy option for the future.
The University of Illinois has filed patents on the new inventions, and a North Carolina company called Semprius has licensed the technology.
“We’re pretty optimistic that the kinds of approaches we’re developing now could have real commercial potential and could be valuable as an alternative way to generate industry,” Rogers says.
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