Spice up your solar

Chilli is known to have a range of health benefits, from reducing infections to improving digestive performance. But here’s one you probably didn’t know: it appears a pinch of capsaicin – the chemical compound that gives chillies their spice – may also improve perovskite solar cells.

Perovskites are a class of human-made compounds with the same type of crystal structure as the mineral calcium titanium oxide, the first perovskite crystal known. They make highly efficient solar cells that could potentially replace traditional silicon solar panels.

A team of scientists from China and Sweden found that by sprinkling some spice, capsaicin, into ultra-thin perovskite solar cells they could improve the cells’ efficiency at storing solar energy.

“Considering the electric, chemical, optical and stable properties of capsaicin, we preliminarily found that it would be a promising candidate,” says Qinye Bao, senior author of the study from East China Normal University.

While solar cells made with lead-based materials show promise in solar cell technologies, they are plagued by an “undesirable” electron level process called nonradiative recombination, which reduces efficiency and exacerbates heat losses.

“In the future, green and sustainable forest-based biomaterial additive technology will be a clear trend in non-toxic, lead-free perovskite materials,” Bao explains.

“We hope this will eventually yield a fully green perovskite solar cell for a clean energy source.” 

The team report in their paper – published in the journal Joule – that the capsaicin made the solar cells more efficient with a power conversion of 21.88%, compared to 19.1% without capsaicin.

The capsaicin also addressed other defects. Capsaicin-spiced cells were found to maintain more than 90% of their initial efficiency after 800 hours of storage in ambient air. The chilli-free control device lost more than 60% of its initial efficiency over the same period.

Capsaicin also appeared to reduce the perovskite film’s defect density, increasing electron density and boosting charge transport. The researchers also observed a smaller leakage current in the capsaicin cells.

While capsaicin-spiced cells may provide a low-cost, widely available additive for the development of solar cells, the authors say future research is needed to investigate the compounds effect on non-toxic, lead-free perovskites.

“We will further focus on the relationship between chemical structures of natural forest-based biomaterial additives, their interaction with photoactive materials, and the corresponding photovoltaic performance,” says Bao.

“We hope to generate new knowledge of great value to further increase the power conversion efficiency and stability of perovskite solar cells.”

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