Scientists at the University
of Southern California (USC) have developed a potential pathway to cheap,
stable solar cells made from nanocrystals so small they can exist as a liquid
ink and be painted or printed onto clear surfaces.
The solar nanocrystals
are about 4 nm in size—meaning one could fit more than 250 billion on the head
of a pin— and float them in a liquid solution, so “like you print a newspaper,
you can print solar cells,” said Richard L. Brutchey, assistant professor of
chemistry at the USC Dornsife College of Letters, Arts and Sciences.
Brutchey and USC
postdoctoral researcher David H. Webber developed a new surface coating for the
nanocrystals, which are made of the semiconductor cadmium selenide. Their
research is featured in Dalton
solar cells are cheaper to fabricate than available single-crystal silicon
wafer solar cells but are not nearly as efficient at converting sunlight to
electricity. Brutchey and Webber solved one of the key problems of liquid solar
cells: how to create a stable liquid that also conducts electricity.
In the past,
organic ligand molecules were attached to the nanocrystals to keep them stable
and to prevent them from sticking together. These molecules also insulated the
crystals, making the whole thing terrible at conducting electricity.
“That has been a
real challenge in this field,” Brutchey said.
Webber discovered a synthetic ligand that not only works well at stabilizing
nanocrystals but actually builds tiny bridges connecting the nanocrystals to
help transmit current.
With a relatively
low-temperature process, the researchers’ method also allows for the
possibility that solar cells can be printed onto plastic instead of glass
without any issues with melting, resulting in a flexible solar panel that can
be shaped to fit anywhere.
As they continue
their research, Brutchey said he plans to work on nanocrystals built from
materials other than cadmium, which is restricted in commercial applications
due to toxicity.
the commercialization of this technology is still years away, we see a clear
path forward toward integrating this into the next generation of solar cell
technologies,” Brutchey said.