Believe it or not, it is true. Just as coffee energizes us humans, so does it to perovskite solar cells. Caffeine is the active element in coffee which helps perovskites improve their efficiency significantly. While we humans need to drink coffee again and again, perovskite solar cells will not. Just one treatment in the development stage will do it , and the efficiency is boosted high enough to rival that of the reigning champions, the silicon solar cells.
This is one example of where a casual, joking remark led to a scientific breakthrough. It is nothing new. Have you not read of dreams giving clues to scientific breakthroughs of unparalleled significance? Scientists were confused over the layout of atoms within the benzene molecule. Observations clashed with each other, and no structure of the benzene atom proposed by chemists could explain the observations. Then Scientist Kekule, had a dream. He saw a snake with its tail in the mouth. That was the clue to benzene structure, a ring form. It was never thought of before.
Perovskite Cells and Coffee
The caffeine story also started as a casual joking remark. Researchers were having morning coffee together. It is usual for researchers to discuss their research issues rather than girls even at such occasions. If coffee could boost human energy, would it also boost the perovskites? This thought must have come from a tired researcher at the University of California, Los Angeles (UCLA) feeling better after drinking coffee with other colleagues. But the idea did hit. They recalled that caffeine being an alkaloid could interact with structures in the perovskites. The idea was pursued by the scientists at UCLA who worked in collaboration with Solargiga Energy in China. The answer to this casual question was a very pleasant “yes”.
Caffeine was added to the perovskite layer in forty solar panels. It was confirmed via spectroscopy that a carbonyl group in caffeine interacted with the lead in the perovskite to create what they called a “molecular Lock”.The result was a major boot in the energy efficiency of the panels. 20% efficiency was recorded compared to 17 % for other perovskite solar panels that were not offered coffee. 20% efficiency is major advance in perovskites which are already threatening silicon solar panels due to the former being open to much simpler and cheaper production.
The Achille’s Heel of perovskites has been their stability.Caffeine not only increased the efficiency, it is reported to have improved perovskite thermal stability also.
When will perovskite panels knock out silicon panels, the day is not very far.
Rui Wang, Jingjing Xue, Lei Meng, Jin-Wook Lee, Zipeng Zhao, Pengyu Sun, Le Cai, Tianyi Huang, Zhengxu Wang, Zhao-Kui Wang, Yu Duan, Jonathan Lee Yang, Shaun Tan, Yonghai Yuan, Yu Huang, Yang Yang. Caffeine Improves the Performance and Thermal Stability of Perovskite Solar Cells. Joule, 2019; DOI: 10.1016/j.joule.2019.04.005