The power of attraction

Yale engineers hope to make solar energy more attractive (to consumers) by using magnetic attraction.

One of the newest generations of solar cells has proved cheaper to produce than traditional silicon panels. But a major reason they aren't used more widely is their relative inefficiency. Because the compounds used in the cells are randomly mixed, electrons flow through them in a meandering path, as if they were wandering around a dense forest. Therefore, only a small portion of sunlight gets converted into energy.

A team led by engineering professor Chinedum Osuji has devised a way to straighten the path. It used polymer-coated nanowires inside the cells—nanowires aligned with a powerful superconducting magnet. Lined up and arrayed in the same direction, the tiny wires provide straighter paths for electrons.

Silicon panels in use today convert roughly between 15 and 20 percent of sunlight into electricity. The new cells get between 4 and 7 percent efficiency. Osuji's goal is to increase that to more than 10 percent. He concedes that silicon panels will be more efficient for the foreseeable future, but says improved durability, higher efficiency, and lower cost could make the new cells an option down the road.

"In the end it'll be the efficiency-cost ratio that determines which technology wins out," Osuji says. "Hybrids needn't be as efficient as silicon as long as they are a lot cheaper."