Researchers at MIT have found a significant way to improve solar-cell efficiency, utilizing the aid of tiny genetically modified viruses to perform assembly work at the microscopic level.
It may sound like a bad sci-fi story, but these viral improvements have allowed the effective use of nanotubes in solar power technology.
Previous research involving nanotubes and solar efficiency ran into two problems. The first issue was that the making of carbon nanotubes generally produces a mix of two types, some of which act as semiconductors (sometimes allowing an electric current to flow, sometimes not) or metals (which act like wires, allowing current to flow easily).
The new research, for the first time, shows 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.
The second issue was that nanotubes tend to clump together – reducing their effectiveness.
And that’s where the strange solution of the virus comes in. Graduate students Xiangnan Dang and Hyunjung Yi — working with Angela Belcher, the W. M. Keck Professor of Energy, and several other researchers — found that a genetically engineered version of a virus called M13, which normally infects bacteria, can be used to control the arrangement of the nanotubes on a surface, keeping the tubes separate so they can’t short out the circuits, and keeping the tubes apart so they don’t clump.
The system the researchers tested used a type of solar cell known as dye-sensitized solar cells, a lightweight and inexpensive type where the active layer is composed of titanium dioxide, rather than the silicon used in conventional solar cells.
The same technique could be applied to other types as well, including quantum-dot and organic solar cells. In tests, adding the virus-built structures enhanced the power conversion efficiency to 10.6 percent from 8 percent — almost a one-third improvement.
This substantial improvement takes place even though the viruses and the nanotubes make up only 0.1 percent by weight of the finished cell.
This process adds only a single, simple step to standard solar-cell manufacturing processes, and should be ready to implement rapidly. Will a virus pave the way for solar-cell efficiency?
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