Breakthrough in Solar Nano Technology
A chemistry professor at UC Santa Cruz, working with teams from California, Mexico and China, has published a paper reporting a breakthrough which may improve the conversion efficiency of incoming light photons to electrical current by as much as three times.The material developed by Jin Zhang relies on two existing technologies from the field of nanotechnology. One is the use of nitrogen doped metal oxide nanoparticles. The other method uses nanosize crystals, "quantum dots", to increase solar energy conversion by injecting electrons into the metal oxide film.
Dr. Zhang combined the two concepts to produce a film both doped with nitrogen and electron-injected by quantum dots. Scientists measure the effectiveness of solar panels by the "incident photon to current conversion efficiency", IPCE for short. Using this measure, the new film is up to three times more effective at converting solar energy to electrical current. The trick is to make it easier for the current to flow by helping it hop around. It is a little bit like how it would be easier for you to walk upstairs if the stairs are built with many smaller risers as opposed to trying to walk up steps which are each several feet high. The ideal solar panel will be a one-story house: everything on the same level.
An interview with Dr. Zhang in CleanTech helps to put the scope of this new discovery into perspective. The films developed for this paper have an overall efficiency of only 1%. Currently, commercially available silicon solar panels have efficiencies topping out at 20 to 30%. But that is not the point declares Dr. Zhang.
The point is that these panels could become a cheaper alternative. So even if the new nanostructures only achieve 10 or 15% efficiency, they could beat out silicon on volume. Dr. Zhang also compares the toxicity of materials used in the manufacturing of the nano materials. The main film material is titanium oxide, which is substantially less toxic to work with than the silicon process. The new material also uses cadmium, a toxic heavy metal. Dr. Zhang points out that there is no solution which is free of chemicals. The trick is to use the chemicals without human or environmental exposures, thereby producing a material that is itself environmentally beneficial by breaking our reliance on fossil fuels. Breakthroughs like the work of Dr. Zhang, hairy solar panels, and 40% efficient solar pave the way to an alternate future.