Liquid Solar Cells Could Be Painted on Surfaces

An inexpensively producible, stable solar cell made from small nanocrystals suspended in a liquid solution can be printed or painted onto clear surfaces. The new technology holds potential for flexible solar panels that can be shaped to fit anywhere.

The solar cells as a liquid ink. (Images: Dietmar Quistorf/USC)

Liquid nanocrystal solar cells are cheaper to manufacture than single-crystal silicon wafer solar cells, but they are not as efficient at converting sunlight to electricity. This is because the organic ligand molecules, attached to the nanocrystals to keep them stable and stop them from clumping, also insulate the crystals, reducing their electrical conductivity.

Now, chemists at the University of Southern California (USC) have discovered a ligand that not only helps stabilize the nanocrystals, but also builds tiny bridges between them to help transmit an electric current. This finding allowed them to create a stable liquid that also conducts electricity.

The new cadmium selenide surface coating uses a relatively low-temperature process, making it possible to print solar cells onto plastic instead of glass without worrying about the plastic melting. This could open the door to cheap, flexible solar panels that could be shaped to fit in any location.

The liquid solar cells applied to a glass slide.

Because of the toxicity of cadmium selenide, 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,” said Richard L. Brutchey, assistant professor of chemistry at the USC Dornsife College of Letters, Arts and Sciences.

The research, funded by the National Science Foundation and USC Dornsife, was featured as a “hot article” in the April issue of Dalton Transactions.

For more information, visit: www.usc.edu