Published on April 26, 2019 |
by Steve Hanley
26. April 2019 by Steve Hanley
Many important discoveries are the result of accidents. Researchers who wanted to make extremely strong adhesives to bond parts of airplanes together formed one of the least sticky substances known to science. It has been re-created for post-it notes, those little notes that can hardly stick to a refrigerator. WD-40 was intended as a spraying substance that would displace water from metal surfaces. The WD part stands for "water displacement". The "40" part represents the other 39 attempts that did not work.
People who mocked Thomas Edison as he tried hundreds of filament filament materials. All have failed. "It just means that I'm so much closer to finding something that works," he allegedly told his critics. Then he tried tungsten wire, and the rest, they say, are history.
Theoretically, perovskites should produce solar cells that are cheaper because they use elements that are abundant in nature. The original perovskite solar cells had an efficiency of about 1%. Non-tandem perovskite solar cells today can achieve up to 24.2% efficiency, but still have some drawbacks. They do not last long and disintegrate in the presence of water and other impurities. There is no way that a solar panel that uses perovskite cells can function as reliably in the open air for 20 years or more as conventional solar panels.
University of California researchers at Los Angeles believe they may have found a way to improve perovskite performance. They sat with coffee in the cafeteria one day, looking for a boost of energy when one of them suggested trying caffeine to improve the performance of the perovskites they worked in the lab. They did.
It was a moment of "pure happiness," says UCLA engineer Yang Yang, the faculty advisor to the students. "We needed a kind of molecule with single-electron pairs," he tells Scientific American . As it turns out, caffeine is exactly the molecule you were looking for. The research was published this month in the journal Joule.
Caffeine causes perovskite crystals to emerge without as much "cluttering" as those growing without it, says Joseph Berry, a physicist at the National Renewable Energy Lab, who was not involved in the research. "In general, the perspective is:" If you make the material more perfect, you get one that is better. "The caffeine at the local level ensures that you get a material that is a bit more structured," he says. "The result is a more stable device."
"Basically, these perovskite materials provide functionality that can not be matched. We're just starting to understand it well enough to start development, "he adds. "That's why these results from Yang are so convincing." Findings from the new research could help scientists discover or develop new molecules that stabilize perovskite solar cells even better than caffeine.
Jinsong Huang, physicist at the University of North Carolina Chapel Hill believes this new discovery could help bring perovskite solar cells closer to commercial sales. "Stability is the last hurdle we need to overcome [for perovskite cells] to get to market. They can make solar cells more efficient and stable in other ways. However, this is a very good result, and it opens our heads to various materials you would not expect to work.
The caffeine-infused perovskite cells proved to be more durable than conventional perovskites and increased efficiency from 16% (the start effect) / standard cells) to 20%. (Note: This is still less than the record number of non-tandem cells with an efficiency of 24.2%.)
Tandmospheric kites have achieved an efficiency of nearly 30% in the laboratory. Imagine what they could achieve by using caffeine-based cells. "Tandem solar cells are like a double-decker bus," says Yang. "Anything that helps the single-layer bus can help the biplane."
Building perovskites is easy, says Yang. "We just buy chemicals and mix them in a beaker in our lab. It's like cooking. Then we add a little caffeine to the liquid and mix everything evenly. "Finally, the mixture is poured over glass to produce pervoskite crystals. "A high school kid could make a good perovskite solar cell in our lab," says Yang.
Some may doubt that perovskites are far from leaving the lab and entering commercial production. That's right, but it was not that long ago that the light from LEDs was so weak. People wondered if they would ever have a useful purpose. Never say never, in other words. Inexpensive solar cells made from readily available materials may be closer than we think.