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Chili Pepper Compound Increases Solar Cell Efficiency

Adding capsaicin, the chemical responsible for making chili peppers spicy, improved the efficiency of solar cells in experiments

A group of perovskite solar cells that have been treated with capsaicin. (Jin Yang)
smithsonianmag.com

New research suggests spicy solar cells might work more efficiently. That’s right, scientists treated solar cells with capsaicin, the compound responsible for the mouth-burning heat of chili peppers, and found those cells became more efficient at turning solar energy into electricity, reports Karina Shah for New Scientist.

The findings, published last month in the journal Joule, apply to an up-and-coming type of solar cell utilizing materials called perovskites that often contain lead-based materials. Silicon has dominated solar panel construction for decades now, but perovskite solar cells have shown promise working in tandem with silicon solar cells to harvest even more energy, as well as on their own where they can be made thin and flexible, reported Andy Extance for Nature in 2019.

However, while perovskite solar cells beat silicon’s efficiency at absorbing sunlight, the technology has had issues turning that sunlight into electricity—instead losing it as heat, per New Scientist.

Qinye Bao, the study’s senior author and an electrical engineer at East China Normal University, were looking for some cheap, easy-to-find additive that could help alleviate this issue with perovskite solar cells. "Considering the electric, chemical, optical, and stable properties of capsaicin, we preliminarily found that it would be a promising candidate," says Bao in a statement.

When the researchers behind the new study added capsaicin to thin perovskite solar cells in the lab, the spicy chemical compound increased the solar cells’ efficiency. The untreated cells’ power conversion was 19.1 percent, but the capsaicin-treated cells converted 21.88 percent of the available solar energy, according to the study. Per the statement, the treated solar cells were also more stable, retaining more than 90 percent of their efficiency after 800 hours.

As Jon Major, a renewables researcher at the University of Liverpool, writes in the Conversation:

“Adding capsaicin expands the grains which make up the active material of the solar cell, allowing it to more effectively transport electricity. More importantly, the material goes from having a deficit of electrons to having an excess, changing how the cell operates and allowing more sunlight to be converted to electricity.”

Subsequent analysis using spectroscopy confirmed that the capsaicin somehow led to an increased number of free electrons on the solar cells’ surface and reduced heat loss, according to New Scientist. However, the researchers aren’t exactly sure how capsaicin did all that. Bao tells New Scientist that his team thinks the capsaicin molecules may react with lead ions inside the perovskite solar cells, freeing up electrons which are then available to carry a charge.

Perovskite cells can be cheaper and easier to make than silicon solar cells, according to Nature, and tricks like adding a bit of spice could make them into an even more promising part of a future that is less reliant on planet-warming fossil fuels.

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