If you had to pick the best color for solar cell efficiency off the top of your head, yellow – as in sunlight – would probably get the nod. However, there is a lot of efficiency to be mined in the blue end of the spectrum. The problem is, blue light has excess energy that conventional solar cell materials can’t capture efficiently, and away it goes in the form of heat.
That makes finding a cheap, blue light-friendly solar cell material one of the keys to kicking solar cell efficiency up to the next level while keeping costs down, and researchers over at Argonne National Laboratory and the University of Texas at Austin believe they have found just such a one.
Blue light by bigpresh.
Harvesting Blue Light For Solar Cell Efficiency
The material in question is copper indium selenide (CIS), which is a close cousin of CIGS (a combination of copper, indium, gallium, and selenium) the go-to material for thin film solar cells.
The thin film angle is important to solar cell affordability because, although thin film is not as efficient as the gold standard (that would be silicon), it is far more inexpensive to manufacture and it has a greater range of applications.
The new Argonne solar cell research pivots on the manufacturing process to harvest more light from the blue end of the spectrum.
To deposit thin films of CIS, the researchers used a fabrication method called phonic curing. In photonic curing, you heat and cool the top layer of a material in less than a second. Aside from binding the materials, photonic curing also vaporizes organic molecules.
Once the organic molecules are out of the way, that leaves the field clear for multiple exciton generation, and thus greater efficiency in blue light conversion (in other words, one high-energy photon is stimulating multiple excitons, instead of just one exciton per photon).
Before you get too excited about all those excitons bouncing around, researcher Brian Korgel of the University of Texas cautions that the labwork looks promising, but it’s the relationship between manufacturing and multiple exciton generation that will make the technology competitive in the marketplace:
The holy grail of our research is not necessarily to boost efficiencies as high as they can theoretically go, but rather to combine increases in efficiency to the kind of large-scale roll-to-roll printing or processing technologies that will help us drive down costs.
The cost of solar power is already sinking like a stone and apparently it hasn’t nearly hit bottom yet.
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About the Author
Tina Casey Tina Casey specializes in military and corporate sustainability, advanced technology, emerging materials, biofuels, and water and wastewater issues. Tina’s articles are reposted frequently on Reuters, Scientific American, and many other sites. You can also follow her on Twitter @TinaMCaseyand Google+.
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