Solar power goes viral for peak efficiency

The new MIT research is based on findings that carbon nanotubes -- microscopic, hollow cylinders of pure carbon -- can boost the efficiency of electron collection from a solar cell's surface, the journal Nature Nanotechnology reports.

Previous attempts to use the nanotubes, however, had been stymied by two problems. First, the making of carbon nanotubes generally produces a mix of two types, some of which sometimes act as semiconductors or metals (allowing current to flow easily), according to an MIT statement.

The new research, for the first time, showed that the effects of these two types tend to be different, because the semiconducting nanotubes can enhance the performance of solar cells, but the metallic ones have the opposite effect.

Second, nanotubes tend to clump together, which reduces their effectiveness. And that's where viruses come to the rescue.  Graduate students Xiangnan Dang and Hyunjung Yi, working with Angela Belcher, who is professor of energy at The Massachusetts Institute of Technology (MIT), found that a GM version of a virus called M13, which normally infects bugs, can be used to keep the tubes separate so that they can't shortcircuit or clump.

In their tests, adding the virus-built structures enhanced the power conversion efficiency to 10.6 percent from eight percent, almost a one-third improvement. This dramatic improvement takes place even though the viruses and the nanotubes make up only 0.1 percent by weight of the finished cell.

“A little biology goes a long way,” Belcher says. With further work, the researchers think they can ramp up the efficiency even further.