Researchers overcome technical hurdles in quest for inexpensive, durable electronics and solar cells

Jul 30, 2013
Light is emitted from excited argon gas atoms flowing through the glass tube of a plasma reactor. The plasma is a reactive environment used to produce silicon nanocrystals that can be applied to inexpensive, next-generation electronics. Credit: University of Minnesota

Electronic touch pads that cost just a few dollars and solar cells that cost the same as roof shingles are one step closer to reality today.

Researchers in the University of Minnesota's College of Science and Engineering and the National Renewable Energy Laboratory in Golden, Colo., have overcome technical hurdles in the quest for inexpensive, durable electronics and made with non-toxic chemicals. The research was published in the most recent issue of Nature Communications, an international online research journal.

"Imagine a world where every child in a could learn reading and math from a touch pad that costs less than $10 or home solar cells that finally cost less than fossil fuels," said Uwe Kortshagen, a University of Minnesota mechanical engineering professor and one of the co-authors of the paper.

The research team discovered a to produce a specialized type of ink from non-toxic nanometer-sized crystals of silicon, often called "." This "electronic ink" could produce inexpensive electronic devices with techniques that essentially print it onto inexpensive sheets of plastic.

"This process for producing electronics is almost like screen printing a number on a softball jersey," said Lance Wheeler, a University of Minnesota mechanical engineering Ph.D. student and lead author of the research.

But it's not quite that easy. Wheeler, Kortshagen and the rest of the research team developed a method to solve fundamental problems of silicon electronic inks.

First, there is the ubiquitous need of organic "soap-like" molecules, called , that are needed to produce inks with a good shelf life, but these molecules cause detrimental residues in the films after printing. This leads to films with too poor for electronic devices. Second, are often deliberately implanted with impurities, a process called "doping," to enhance their electrical properties.

In this new paper, researchers explain a new method to use an ionized gas, called nonthermal plasma, to not only produce silicon nanocrystals, but also to cover their surfaces with a layer of chlorine atoms. This surface layer of chlorine induces an interaction with many widely used solvents that allows production of stable silicon inks with excellent shelf life without the need for organic ligand molecules. In addition, the researchers discovered that these solvents lead to doping of films printed from their silicon inks, which gave them an electrical conductivity 1,000 times larger than un-doped silicon nanoparticle films. The researchers have a provisional patent on their findings.

"What this research means is that we are one step closer to producing more pure and more stable electronic ink with non-," Kortshagen said. "The bigger goal here is to find a way that this research can benefit everyone and make a real difference."

Explore further: Demystifying nanocrystal solar cells

More information: "Hypervalent Surface Interactions for Colloidal Stability and Doping of Silicon Nanocrystals," Nature Communications,… full/ncomms3197.html

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5 / 5 (4) Jul 30, 2013
"Imagine a world where every child in a developing country could learn reading and math from a touch pad that costs less than $10

Yes. It's called a book.

What the computer revolutionaires, the OLPC project etc. fail to understand is that throwing computers at the problem doesn't work - the children need schools and teachers first, and expensive ($10 for someone who subsists on less than a dollar per day!) gizmos are useless in that perspective.

Give me a competent teacher and a single math book, and even clay tablets can serve as perfectly functional learning tools.
not rated yet Jul 31, 2013
Yes. It's called a book.

I think you can get a bit more information from the internet than from a book for 10$.

And there are teachers on the internet (downloadable lectures). While this is nowhere as good as live schools or teachers it is certainly better than just handing a child a book.

(and you'd be hard pressed to provide a child with a competent teacher for 10$ in addition to the book)

You have to start thinking about the limitations some people face. We don't live in an ideal world where we can just willi-nilly decide to have competent teachers in every remote village. But we DO live in a world where every remote village can have internet access with very little effort/expenditure.
1.5 / 5 (8) Jul 31, 2013
I've got an 11 and 12yr old. It's distressing watching them lug backpacks loaded with books. It may be expensive, but I think tablets are the future. It may actually be cheaper in the long run. School books are only getting more expensive, while tablet prices continue to fall.
not rated yet Jul 31, 2013
I am not actually comment on this post -- i am testing quoting techniques

I've got an 11 and 12yr old.

[cite] I've got an 11 and 12yr old.[/cite]

not rated yet Jul 31, 2013
only [ q ] works it seems

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