Scientists at the University of Southern California (USC) have developed technology to cheaply produce stable liquid solar cells that can be painted or printed onto clear surfaces. The technology relies on solar nanocrystals that are around four nanometers in size - meaning you could fit more than 250 billion on the head of a pin. Their size allows them to be suspended in a liquid solution so they could be printed like a newspaper.
While liquid nanocrystal solar cells are cheaper to manufacture than single-crystal silicon wafer solar cells, they are nowhere near as efficient at converting solar energy into electricity. This is partly due to the fact that the organic ligand molecules that are attached to the nanocrystals to keep them stable and stop them from clumping together, also insulate the crystals, reducing their electrical conductivity.
Richard L. Brutchey, assistant professor of chemistry at the USC Dornsife College of Letters, Arts and Sciences, and USC postdoctoral researcher David H. Webber, discovered a synthetic ligand that not only helps stabilize the nanocrystals, but also builds ting bridges between them to help transmit an electric current. This allowed them to create a stable liquid that also conducts electricity.
As the new surface coating uses a relatively low-temperature process, the researchers say there it’s the potential to print solar cells onto plastic instead of glass without worrying about the plastic melting. This could enable cheap, flexible solar planels that can be shaped to fit just about anywhere.
Because the new surface coating for the nanocrystals is made of the semiconductor cadmium selenide, which faces commercial application restrictions due to toxicity, the researchers plan to work on nanocrystals built from other materials.
“While 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.
The researchers’ work is featured in the international journal for inorganic chemistry, Dalton Transactions.