You’re a graduate engineer. You’ve been working on perovskite solar panels. Perovskite describes a class of crystalline compounds which are easy and cheap to make, and as a result they are promising candidate materials to form light-harvesting layers on solar panels.
However, if the crystals are exposed to atmospheric humidity and oxygen, they degrade rapidly. This instability is your everyday challenge in the lab: you try introducing different compounds to protect the perovskite structure, but so far, all you get is sleepless nights.
Sleepless nights lead to sleepy mornings, and in an attempt to boost your energy levels, you drag your office-mate to the University canteen for a cup of coffee. “If only caffeine could boost your perovskite cells as much as it can wake up your brain cells”, your colleague comments to tease you, and suddenly you freeze looking at each other. You realize that, actually, this might well be possible!
In a recent publication, Rui Wang and Jingjing Xue of the University of California, Los Angeles describe what happened when they used caffeine to improve the stability and performance of perovskite solar cells. It appears that perovskite structures are quite caffeine-friendly: not only do they become more thermally stable with the use of caffeine, but they also become more efficient.
As the authors explain, caffeine interacts with lead ions to create a protective molecular lock that increases activation energy and leads to the formation of a perovskite film with preferred orientation and improved electronic properties. Their stabilized cells reached a conversion efficiency of 19.8%, the majority of which was retained despite prolonged exposure to heat.
Along with cell performance, these results have boosted research in the field of solar cells without requiring direct consumption of coffee by the researchers. And the technique may be applicable to other types of perovskite-based solar cells, like tandem cells, or even lead to the design of more stabilizing molecules.