Liquid Solar Cells

Solar nanocrystals float in printable ink

USC (US) — Scientists have developed a potential pathway to cheap, stable solar cells made from nanocrystals so small they can be painted onto clear surfaces as liquid ink.

The solar nanocrystals are about four nanometers in size—meaning you could fit more than 250,000,000,000 on the head of a pin—and float them in a liquid solution, so “like you print a newspaper, you can print solar cells,” says Richard L. Brutchey, assistant professor of chemistry at University of Southern California.

The researchers solved one of the key problems of liquid solar cells: how to create a stable liquid that also conducts electricity. (Credit: Dietmar Quistorf/USC)

Brutchey and 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 as a “hot article”this month in Dalton Transactions, the international journal for inorganic chemistry.

Liquid nanocrystal 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 says.

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 says he plans to work on nanocrystals built from materials other than cadmium, which is restricted in commercial applications due to toxicity.

“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 says.

This research was funded by the National Science Foundation and USC Dornsife.

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