(July 20, 2015) The
same quality that buffers a raincoat against downpours or a pan against sticky
foods can also boost the performance of solar cells, according to a new study
from UNL engineers.
Published July 20 in the journal Nature Communications, the
study showed that constructing a type of organic solar cell on a
"non-wetting" plastic surface made it 1.5 times more efficient at
converting sunlight to electricity.
The researchers used the technique to grow polycrystalline
cells, which are less expensive, faster and easier to produce than those made
from only a single crystal. Yet single-crystal cells have traditionally boasted
better efficiency, partly because they feature far fewer grains -- fragments
akin to microscopic puzzle pieces.
The barriers between these grains reduce cell efficiency by
trapping and recombining negatively charged electrons with their positively
charged "holes," which ideally produce electric current by migrating
in opposite directions following their separation by photon-carrying sunlight.
Lead author Jinsong Huang and his team sought to reduce the
number of these efficiency-draining barriers by increasing the size of the
grains themselves. Though grain size is typically limited to the thickness of a
solar cell, Huang's team found that a non-wetting surface allowed it to
fabricate grains up to eight times larger than the cell is thick.