Your microwave at home might be able to deliver a batch of popcorn in less than five minutes, but did you know that it’s also capable of cooking up a plate full of semiconductors?
Prashant Sarswat, a research associate at the University of Utah, co-authored this curious study with Michael Free, a professor of metallurgical engineering. Together, the duo discovered that when they melted the salts of metals in a standard kitchen microwave, an “ink” containing suspended CZTS (copper, zinc, tin, and sulfur) nanocrystals formed.
They applied this material to the active layer in a solar cell and found that they could convert solar energy into electricity.
Prototype solar cell that uses photovoltaic semiconductor material that metallurgists produced using an old kitchen microwave.
Major benefits
Sarswat says that compared with photovoltaic semiconductors, which use highly toxic materials cadmium and arsenic, ingredients for the photovoltaic material they cooked up in a kitchen microwave “are more environmentally friendly.” This includes the use of different “precursor” chemicals (acetate salts instead of chloride salts) and a different solvent (oleylamine instead of ethylene glycol).
What’s more, the use of a kitchen microwave to create this material will help expand the number of applications to which the material can be applied. “We hope in the next five years there will be some commercial products from this, and we are continuing to pursue applications and improvements,” says Free. “It’s a good market, but we don’t know exactly where the market will go.”
Cooking instructions
Specific to their process, salts were first dissolved in a solvent and then heated in a microwave.
After about 8 minutes, nanocrystals formed. Exciting, yes, but they were inconsistent in size. In order to produce the most uniformed crystals, Sarswat and Free found that the material needed to be microwaved for 18 minutes at a time. Doing this resulted in crystals ranging in size from 3 nanometers to 20 nanometers.
Transmission electron microscope image shows a single nanocrystal of the semiconductor CZTS dissolved in an organic solvent.
Optimum sizes being sought by researchers was between 7 nanometers and 12 nanometers.
Greater versatility
The duo’s microwave-ready CZTS material can be used in other applications, including the thermoelectric conversion of heat into electricity, biosensors, circuit components, and solar energy to break down water to produce hydrogen for fuel cells.
“The materials used for this are much lower cost and much more available than alternatives,” Free explains, referencing indium and gallium, both of which are used in semiconductors.
Whose idea was it to use the kitchen microwave?
While impressive, there is one pretty obvious question: why, when there’s a lab full of top-of-the-line equipment right next door, would you go and use a kitchen microwave?
The decision to do this rests with Sarswat, who decided to give at-home microwave production of CZTS a spin when the University of Utah’s Department of Metallurgical Engineering decided to get a new microwave oven for the kitchen.
“Our department secretary had a microwave to throw away,” Sarswat explains. So he took it to replace one that had recently burned up during other lab experiments.
Sarswat says many organic compounds are synthesized using microwaves, and Free notes microwaves sometimes are used in metallurgy to extract metal from ore for analysis.
They say that the use of microwaves for the purpose of processing materials is not only fast, it often suppresses unwanted chemical “side reactions.”
“The bottom line is you can use just a simple microwave oven to make the CZTS semiconductor,” Free says, adding, “Don’t do it at home. You have to be cautious when using these kinds of materials in a microwave.”
Look for the study
Free and Sarswat are publishing their study of the microwaved photovoltaic semiconductor in the June 1 issue of the Journal of Crystal Growth.
Story via: unews.utah.edu
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