Iodine contaminates perovskite film evaporation equipment by staying semi-volatile
Iodine contaminates perovskite film evaporation equipment by staying semi-volatile lead image
Thermal evaporation carries several potential advantages for creating uniform perovskite films. It offers precise control of film thickness and compositional uniformity, and it’s easy to deposit high-quality films over large areas without requiring hazardous solvents. Currently, however, evaporation equipment is often shared between materials systems, which can lead to contamination that substantially effects device performance.
Burlingame et al. identified iodine contamination from the evaporation of perovskite precursors like lead and cesium iodide as the culprit. The group found that these halides are resistant to standard decontamination practices.
“When this iodine incorporates itself into films and devices grown later in the chamber, it can be devastating to device performance,” said author Quinn Burlingame. “In our case, the organic solar cells we fabricated right after using the chamber for perovskites lost more than 90 percent of their performance compared to those grown before perovskites were deposited in the chamber.”
The paper notes that solvent cleaning, chamber bakeout, and foil replacement all fail to fully remove iodine from evaporators
“What seems to happen in the case of iodine is that it stays semi-volatile in the evaporator, so rather than sticking to the foil and staying where it was originally evaporated, it will jump around and coat every surface,” Burlingame said.
They found that a total resurfacing/replacement of all interior evaporator surfaces was required to remove the contamination and restore the performance of other optoelectronic devices.
The group hopes their findings will help push for wider adoption of thermal evaporation in a way that is safe for equipment and other materials.
Source: “Persistent iodine contamination resulting from thermal evaporation of inorganic perovskites,” by Quinn C. Burlingame, Alan Kaplan, Tianran Liu, and Yueh-Lin Loo, JVST: B (2022). The article can be accessed at https://doi.org/10.1116/6.0002174 .
