AsianScientist (May 9, 2019) – An international team of scientists has discovered that caffeine could be used to enhance the efficiency of perovskite solar cells. They published their findings in Joule.
Caffeine in coffee is an alkaloid compound containing molecular structures that could interact with the precursors of perovskite materials—compounds with a particular crystal structure that form the light-harvesting layer in a particular class of solar cells. Previous attempts to improve the thermal stability of these solar cells have included introducing compounds such as dimethyl sulfoxide to the perovskite layer, albeit with limited success. No one had tried adding caffeine to the mix.
In this study, researchers led by Professor Yang Yang at the University of California, Los Angeles (UCLA), US, in collaboration with colleagues at Solargiga Energy in China, added caffeine to the perovskite layer of forty solar cells and used infrared spectroscopy to determine that the caffeine had successfully bonded with the material.
Conducting further tests, they observed that a chemical group in caffeine, containing a carbon atom double bonded to an oxygen, interacted with lead ions in the layer to create a molecular lock. This interaction increased the minimum amount of energy required for the perovskite film to react, boosting the solar cell efficiency from 17 percent to over 20 percent. The molecular lock persisted when the material was heated.
Although caffeine appears to significantly improve the performance of cells that utilize perovskite to absorb sunlight, the researchers do not think it will be useful for other types of solar cells. The unique molecular structure of caffeine only allows it to interact with perovskite precursors, which may give this solar cell variety an edge on the market.
Perovskite solar cells already have the advantage of being cheaper and more flexible than their silicon counterparts. They are also easier to manufacture as they can be fabricated from solution-based precursors as opposed to solid crystal ingots. With further research, the researchers believe caffeine may facilitate large-scale production of perovskite solar cells.
“Caffeine can help the perovskite achieve high crystallinity, low defects and good stability,” said the authors. “This means it can potentially play a role in the scalable production of perovskite solar cells.”
The team plans on further investigating the chemical structure of the caffeine-incorporated perovskite material and to identify the best protective materials for perovskites.
The article can be found at: Wang et al. (2019) Caffeine Improves the Performance and Thermal Stability of Perovskite Solar Cells.
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Source: Cell Press; Photo: Wang Rui, UCLA.
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