If the team gets to commercial market, the projection is a pathway to cheap, stable solar cells made with a liquid ink that can be painted or printed onto clear surfaces.
Richard L. Brutchey, assistant professor of chemistry at the USC Dornsife College of Letters, Arts and Sciences and USC postdoctoral researcher David H. Webber developed the new surface coating for the nanocrystals, which are made of the semiconductor cadmium selenide.Their research was featured as a “hot article” this month in the international journal for inorganic chemistry Dalton Transactions.
Brutchey explains, 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, “like you print a newspaper, you can print solar cells.”
The first problem is 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. The second problem is conducting the electricity out.
Brutchey and Webber solved the second 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.
Brutchey and Webber discovered a synthetic ligand that not only works well at stabilizing nanocrystals, but also actually builds tiny bridges connecting the nanocrystals to help transmit the current.
With a conducting solution the poor efficiency can be addressed both by efficiency gains, but sheer area of application.
The team’s build process is a relatively low-temperature operation. The 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.
For the research future Brutchey said 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 said.
In fairness to others the idea of painting solar cells isn’t new. The news releases have been popping up for years. But the USC team has reached into the fundamental problem, getting the power out.
The USC team may think that years are involved, but the conduction solution could fine a market right away. Reading the paper is free with a registration.
Solar is still regarded by most people a very expensive, a perspective not far from the truth. But a “paint your own solar cell” available in a box or kit at a big box home improvement store would shift the view to a more positive outlook. Adopted in mass though will pose problems.
Wind and solar plus the private generators already out there pose frequency problems for the gird, but management is getting a grip on of the power factor problems.
So if you think you have a great solar cell material that just needs hooking up, get in touch with the USC team.