Want More Efficient Solar Cells? Just Add Coffee!

Two UCLA graduate students added coffee to solar cells on a whim and even experts could not believe the results.


If the we consume in our and our tea every day makes us more efficient in our work, is it possible that caffeine might make cells more efficient, too? This seemingly ridiculous question came to mind during a mid-day study break between two engineering students on the University of California, Los Angeles campus not too long ago. The graduate students, Rui Wang and Jingjing Xue, could have shrugged off the half-hearted suggestion given by Wang as an improbable idea. Instead, it dawned on them that, perhaps, there might just be something positive to be found in combining caffeine with solar cells. 

It turned out that Wang was right. Adding caffeine to solar cells actually does make them more efficient. With the help of their U.C.L.A. engineering graduate advisor, Yang Yang, Wang and Xue set out to put their theory into practice and energize a particular solar cell known as a cell. 

What is a Solar Cell? 

Traditional solar cells are made of silicon and produce solar through the use of two silicon layers that work in conjunction with one another. Solar cells can only reach an efficiency level that is so high, so engineers and solar panel developers are always trying to find ways to improve solar cell efficiency. 

Perovskite solar cells are a type of solar cell that is quickly becoming a top competitor to traditional solar cells. These particular solar cells work similarly to traditional cells, except they are infused with man-made materials known as perovskites. Perovskite solar cells have a crystallographic structure that makes them more efficient at converting sunlight into usable energy. Many researchers are looking at perovskite solar cells to replace traditional solar cells in the near future, due to their low production costs and high-efficiency rates.  

While show a lot of promise, they are not as stable as researchers would like them to be. Perovskite solar cells are unreliable due to the connective elements that hold them in place. According to Yang Yang, the boundaries that border the perovskite solar cells, known as the grain boundaries, can easily become damaged from air, water, or moisture. Thus, the cell itself can erode in as little as one day. This is the very problem Wang and Xue hoped caffeine might help solve. 

Adding Caffeine to Perovskite Solar Cells 

Caffeine has a molecular structure consisting of two carbon-oxygen groups that carry lone electron pairs. When paired with a perovskite solar cell, the caffeine helps to lock the perovskite grain boundary in place and stabilizes the solar cell entirely. The caffeine essentially locks into the lead atoms in the perovskite solar cell and locks the boundary in place.  

To test their hypothesis, Yang and Xue ran several tests on solar cells infused with caffeine against a control group infused, of course, with decaf. Their results showed that the caffeine helped to increase the efficiency of the perovskite solar cells from 16 to 20 percent. Additionally, other tests run on hybrid solar cells containing different types of perovskite solar cells were able to reach efficiency levels of nearly 30 percent. 

Experts Weigh in on the Results 

Joseph Berry, a physicist at the National Renewable Energy Lab in Colorado, relayed his impressions of the study to Scientific America. He believes that the findings can help researchers continue to improve perovskite solar cells. According to Berry, the caffeine seems to allow the perovskite crystals to form without the same disorder and chaos seen when caffeine is not present.  

Jinsong Huang, a physicist from the University of North Carolina who was not involved in the work, also weighed in and stated that stability has been a major hurdle for researchers to overcome when working with perovskite solar cells. The idea of introducing caffeine into the perovskite solar cells might just allow these solar cells to soon enter into the commercial market. Additionally, these results from the caffeine perovskite solar cell experiment may just influence how scientists both research and design perovskite solar cells in the future.  

Undoubtedly, experts can agree that the innovative and clever use of our nation’s most popular psychoactive on perovskite solar cells has opened up our minds to solutions that may be brewing right in front of us every day. 





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