US team demonstrates promising solar cell compound
Lead-free peroviskite Barium zirconium sulphide is highly resistant to reacting or breaking down when exposed to moisture or intense sunlight
A widespread transition to solar energy will depend on reliable, safe, and affordable technology 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 new research published in Advanced Functional Materials, a team of engineers, material scientists, and physicists from the institute demonstrated how 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 others that are commonly considered.
Organic-inorganic halide perovskites have shown promise in solar cells but they have also posed challenges. They efficiently convert energy from the sun into power and are cheaper than silicon. However, they are unstable when exposed to moisture and sunlight. That means they decrease in efficiency and they break down into hazardous lead and lead iodide.
"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, an endowed professor of mechanical, aerospace, and nuclear engineering at Rensselaer, and the corresponding author on this paper. "Besides, these materials are not environmentally friendly since they contain lead."
To overcome that 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, specifically barium zirconium sulphide (BaZrS3), could potentially replace lead-containing perovskites for a much safer, and more stable application.
To test this compound's ability to convert light into electrical current, the team used it to build a light sensor. The researchers' work in the lab revealed that BaZrS3 is intrinsically more stable and water-resistant.
They were able to demonstrate through theoretical calculations and computational modelling that BaZrS3 is highly resistant to reacting or breaking down when exposed to moisture or intense sunlight. This was also experimentally validated through detailed device-ageing studies that were conducted over a period of four weeks. On top of all of that, Koratkar said, manufacturing this compound is actually less expensive 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."
Koratkar has secured funding from the US National Science Foundation (NSF) to further develop and optimise these materials and deploy them in solar cell devices.
