Wafer thin nano-films make a solar power play

The Californian creators of new ultra-thin nanocrystal solar cells are heralding their invention as the leading contender in the race for future dominance of the solar market, arguing they have several advantages over the betting man's current favourite, organic cells.

Researchers at the University of California’s Berkeley have developed the first ultra-thin solar cells made entirely of inorganic materials which they claim gives the technology the cutting edge over its competitiors.

Such cells have been a theoretic possibility for some time but the American team’s prototypes are the first to have been produced.

Ilan Gur, principal author of a paper on the research published in journal Science, said the cadmium-based cells would be as cheap to produce as organic equivalents but would be more durable.

“Our colloidal inorganic nanocrystals share all of the primary advantages of organics – scalable and controlled synthesis, an ability to be processed in solution, and a decreased sensitivity to substitutional doping – while retaining the broadband absorption and superior transport properties of traditional photovoltaic semiconductors,” said the Berkeley boffin.

The problem with the tiny cells, each 1,000 times thinner than a human hair, is their efficiency.

Currently their efficiency at converting the light from the sun into electricity is just 3%, similar to that of the best organic cells but still well behind that of existing silicon-based technologies.

Silicon cells, however, are expensive to produce and the researchers hope their discoveries will pave the way to cheap, efficient solar power that will make PV a more competitive player in energy markets.

They have described a utopian future whereby roofs can be laminated with an inexpensive film of the nanocrystal cells that will meet virtually all energy needs of the building it covers.

“We obviously still have a long way to go in terms of energy conversion efficiency,” said Mr Gur.

“But our dual nanocrystal solar cells are ultra-thin and solution-processed, which means they retain the cost-reduction potential that has made organic cells so attractive vis-a-vis their conventional semiconductor counterparts.”

“The next step is for us to better characterize and further develop our prototypical system, as there is still a great deal we don’t fully understand.

“After that, we have a lot of directions that we’d like to pursue, such as introducing variations in the system architecture and our choice of semiconductor materials.”

By Sam Bond

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