Leaves inspire improved solar cells

U.S. scientists say microscopic folds on the surface of photovoltaic materials can significantly increase the power output of flexible, low-cost solar cells. Taking their cue from the surface texture of leaves, scientists writing in the journal Nature say adding the folds can provide a 47 percent increase in electricity generation. Finely calibrated folds on the surface of the panels can guide light waves and increase the photovoltaic materials' exposure to light, researchers said. "On a flat surface, the light either is absorbed or it bounces back," said Yueh-Lin Loo, a professor of chemical and biological engineering at Princeton University. "By adding these curves, we create a kind of wave guide. And that leads to a greater chance of the light's being absorbed." The research focused on photovoltaic systems made of relatively cheap plastic as opposed to current solar panels typically made of silicon, which is both more brittle and more expensive than plastics. So far, plastic panels have not been practical for widespread use because their energy production has been too low, but researchers said if they can increase the plastic panels' efficiency, the material could produce power from an array of surfaces from inserts in window panels to overlays on exterior walls or backpacks. "It is flexible, bendable, light weight and low cost," Loo said.