Photovoltaic Breakthroughs Brighten Outlook for Cheap Solar Power

Enough sunlight bathes Earth’s daytime half in an hour to meet all human energy needs for a year.

Sadly, there are several problems with meeting human energy demands by tapping such abundant, free solar power—not least of which is the cost of making semiconducting material that can cheaply harvest the power in sunlight. But material improvements from the California Institute of Technology and IBM might just lower the cost of solar power.

Graduate student Michael Kelzenberg and other materials scientists at Caltech employed vertical crystals of silicon—microwires, like “blades of grass,” Kelzenberg says—to capture as much as 85 percent of the full spectrum of incoming sunlight, the researchers report in the February 14 Nature Materials. (Scientific American is part of Nature Publishing Group.) Their efficiency is almost as good as that of traditional silicon wafers, yet they require just one percent of the silicon in such wafers.

“With one one-hundredth of the material, we’ve gotten it to absorb 96 percent of the peak visible light,” Kelzenberg says. “There’s lots of reasons to believe this could be scaled to make thin-film solar cells.”