Lead-free perovskite proves stable and safe in solar cells

A widespread transition to solar energy will depend heavily on reliable, safe and affordable technologies like batteries for energy storage and solar cells for energy conversion. At Rensselaer Polytechnic Institute, researchers are focused heavily on both parts of that equation.

In a paper in Advanced Functional Materials, a team of engineers, material scientists and physicists demonstrated how a new material – a lead-free chalcogenide perovskite – that hadn't previously been considered for use in solar cells could provide a safer and more effective option than more commonly considered perovskites.

Organic-inorganic halide perovskites, a type of crystalline mineral, have shown promise as a key component in solar cells, but they also present large challenges. Their unique properties make them highly effective at converting energy from the sun into power and they are less expensive than silicon, which has traditionally been used in this capacity. However, they are unstable when exposed to moisture and sunlight, decreasing in efficiency as they degrade, and they break down into lead and lead iodide – both of which are hazardous substances.

"These types of materials give you very good performance on day one, but inside three or four days, maximum a week, you find that their performance drops precipitously," said Nikhil Koratkar, a professor of mechanical, aerospace and nuclear engineering at Rensselaer, and corresponding author of the paper. "Besides, these materials are not environmentally friendly since they contain lead."

To overcome this challenge, Koratkar and a team of researchers, which included Tushar Gupta, a doctoral student in mechanical engineering, demonstrated how a thin film of a lead-free chalcogenide perovskite called barium zirconium sulfide (BaZrS₃) could potentially replace lead-containing perovskites, for a much safer and more stable application.

In order to test this material's ability to convert light into electrical current, the team used it to build a light sensor, finding that BaZrS₃ is intrinsically more stable and water-resistant than lead-containing perovskites. The researchers were able to demonstrate through theoretical calculations and computational modeling that BaZrS₃ is highly resistant to reacting or breaking down when exposed to moisture or intense sunlight. They also experimentally validated this finding through detailed device-aging studies conducted over a period of four weeks. On top of all of that, Koratkar said, this perovskite is actually less expensive to manufacture than high-quality silicon.

"The National Academy of Engineering has defined 14 grand challenges; one of those is to make harvesting energy from the sun cheaper and more widespread," Koratkar said. "That's the motivation of this work, to come up with new materials that could rival the efficiency of silicon, but bring down the cost of manufacturing solar cells, and that is the key to achieving this goal."

This story is adapted from material from Rensselaer Polytechnic Institute, with editorial changes made by Materials Today. The views expressed in this article do not necessarily represent those of Elsevier. Link to original source.