University of Arizona scientists have developed a new printing process called Restricted Area Printing by Ink Drawing, or RAPID, and received a three-year, $700,000 grant from the Department of Energy Solar Energy Technologies Office (SETO) to advance the method.
Adam Printz, an assistant professor of chemical and environmental engineering at the University of Arizona, along with his team, started developing the perovskite printing process in late 2019, and they’ve been able to demonstrate on a small scale with 3D-printed parts how it works – using “whatever they had lying around in the lab.” This funding enables them to create a more reproducible and scalable version.
Perovskite materials are made by spreading a thin layer of specialized ink over a surface, then heating the ink to cause the formation of the perovskite crystalline structure. This printed film consists of many tiny grains separated by boundary areas. Under a high-powered microscope, it looks like dry, cracked mud. It’s in these boundary areas – which are more chemically reactive than the grains themselves – where things can get tricky.
“These boundary areas can actually interact with moisture in the air and cause the perovskite to convert into a completely different material that does not absorb light – which makes for a terrible solar cell,” Printz said. “We want to minimize grain boundary surface area so that those reactions don’t happen, and the perovskite is more likely to stay perovskite.”
Thus, the aim of RAPID is to produce as few boundary areas as possible. It does this by using a confined printing area so large grains can form without the solvent evaporating too quickly in the heat. Bigger grains mean reduced boundary area between grains, and reduced boundary area equates to more stability and efficiency.
Over the course of this three-year project, Printz and his team aim to reduce the grain boundaries by 90%. They also hope to improve the perovskite solar cells’ efficiency stability, or their ability to maintain efficiency over time, by 50%.
“When we get RAPID working at scale, we are hopeful that it will have profound impacts on the production of perovskites, significantly improving the stability of these low-cost and high efficiency devices,” Printz said.