Making solar cells with a kitchen microwave
May 8, 2013
For most people, experiments involving a home microwave typically don't go much further than inflating a marshmallow like a balloon or reheating leftovers in plasticware – both with messy results. For metallurgists though, microwaves are sometimes employed to efficiently process metals, which is how researchers at the University of Utah found themselves using a secondhand kitchen appliance in their lab. Their resourcefulness paid off recently, when the team discovered a method for creating solar cell material with just a few basic ingredients and an old microwave.
The material is called CZTS after its components, copper, zinc, tin, and sulfur, and is known to act as a photovoltaic semiconductor, converting the sun's rays into usable electricity. Scientists have only recently begun turning to it for use in commercial-grade solar cells, since its low-cost, environmentally friendly ingredients make it a perfect fit with green energy sources. Unfortunately, CZTS has been difficult to create properly in the past and usually requires more complicated methods involving chemical suspensions.
Pierce film with fork or similar
Prashant Sarswat and Michael Free, two metallurgical engineers at the University of Utah, devised a cheaper, faster method using a microwave rescued from a student kitchen. The pair dissolved acetate salts from each metal in a solvent of oleylamine and sent that concoction straight into the microwave (presumably after wiping away the splatter from months-old spaghetti sauce). After just 8 minutes, the nanocrystals needed to form CZTS began to take shape and reached equivalent sizes after 18 minutes, which isn't bad compared to previous methods that required 45 to 90 minutes to prepare.
The resulting CZTS is suspended in an ink-like substance, which can be painted onto most surfaces or combined with other substances to build a functional solar cell. Sarswat and Free even built a small photovoltaic cell to prove their microwave-made CZTS would work. Leaving the CZTS in the microwave for specific times will also form different sizes of nanocrystals, giving the material different properties. Larger crystals absorb heat and convert it to electricity, while smaller crystals can be made to emit light at certain energy levels. The two researchers believe this could lead to LEDs that require less power.
Don't try this at home. Obviously
With cheaper, less toxic ingredients than most semiconductors combined with an easier manufacturing process, CZTS is poised to become a widespread material in a number of industries. However, the research team has warned that most people should not try to concoct CZTS in their own microwave at home since, as your mother no doubt warned you, putting metal into a microwave can be dangerous.
Sarswat and Free also learned during the course of their study that a research team at Oregon State University was developing a similar microwaving method, though their process uses different chemicals. The pair of metallurgists are now performing further experiments to improve their process and find more applications for CZTS. Besides solar cells, they've also looked at possibly incorporating the material into biological sensors, hydrogen fuel cells, and electronic circuitry, though it's still too soon to tell when or if any of these ideas will lead to a commercial product.
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