The quest for greater photovoltaic efficiency, seemingly playing out at every energy-inclined research center on the planet, is taking shape at Arizona State University with the oddly named “dispersive concentrator” at the heart of things.
Does it disperse or does it concentrate? Well, it does both. In their solar cell architecture, Professor Cun-Zheng Ning and Ph.D. candidate Derek Caselli (pictured below) use an inexpensive dispersive optic that first separates sunlight into the different components of the light spectrum. Next, the light is focused as it leaves the optic. These discrete photons then meet solar-cell materials specially arranged – laterally, rather than vertically – to allow each material to absorb the individual photons that it is most adept at converting to electricity.
In their tests, the Arizona State researchers have been able to match the efficiencies “obtained by the highest-performing cells,” Caselli said. For the sake of simplicity, those tests were run under conditions that might enhance output, but the pair is confident “there are a number of ways the cell design could be optimized to make them as efficient as the highest-performing cells at a lower cost,” Caselli said.
That assumes they find a way to make the absorbing materials in all the cells “in a one-step fabrication process on a single substrate – or platform.” This is what would eventually yield high-efficiency, low-cost solar power, and is a focus of their continuing work.
The ASU project, supported by the U.S. Army Research Office, is written up on the website of the International Society for Optics and Electronics.