Scientists at McGill University have acquired stimulating new knowledge about the properties of perovskites, one of the world’s most sought after materials for developing a more efficient, stronger, and economical solar cell.
In a research work reported recently in Nature Communications, the scientists used a multi-dimensional electronic spectrometer (MDES)—an exclusive instrument hand-built at McGill University—to monitor the behavior of electrons in cesium lead iodide perovskite nanocrystals.
The MDES that enabled these observations has the ability to measure the behavior of electrons across extremely short time frames—down to 10 femtoseconds, or ten-millionths of a billionth of a second. Perovskites are apparently solid crystals that first gained attention in 2014 for their unique potential to be used in future solar cells that might be cheaper or more fault-tolerant.
A Most Exciting Discovery
“It’s the most exciting result that I have been a part of since starting in science in 1995,” stated senior author and McGill chemistry professor Patanjali Kambhampati, reporting about the discovery of a unique feature of perovskites—liquid-solid duality. “Instead of searching for perfection in defect-free silicon microelectronics, here we have a defective thing that’s defect-tolerant. And now we know a bit more about why that is.”
Solids Acting Like Liquids
With the close examination of the crystals using the MDES, the scientists observed something that challenged their traditional understanding of the difference between solids and liquids.
Since childhood, we have learned to discern solids from liquids based on intuition: we know solids have a fixed shape, whereas liquids take the shape of their container. But when we look at what the electrons in this material are actually doing in response to light, we see that they behave like they typically do in a liquid. Clearly, they are not in a liquid —they are in a crystal—but their response to light is really liquid-like.
Hélène Seiler, Study Lead Author, Department of Physical Chemistry, Fritz-Haber-Institut, Max-Planck Institute
Seiler continued, “The main difference between a solid and a liquid is that a liquid has atoms or molecules dancing about, whereas a solid has the atoms or molecules is more fixed in space as on a grid.”
Seiler was a former PhD student in the Department of Chemistry at McGill University.
The study received funding from Natural Sciences and Engineering Research Council of Canada (NSREC), Canada Foundation for Innovation (CFI), Swiss National Science Foundation, and Fonds de Recherche du Québec—Nature et technologies (FQRNT).