Scientists develop laser evaporation process for thin film deposition

Duke University scientists working with perovskite materials have developed a process, which they say could open a “whole new world” of materials to the solar cell industry, as well as useful materials for light emitting diodes, photo detectors and X-ray detectors.

The research, published in the journal ACS Energy Letters, details a method whereby a solution containing the materials to create a thin film, is frozen, and then placed insided a vacuum chamber and blasted with a laser. In this case the researchers worked with methylammonium lead iodide, a common material in perovskite PV research.

The laser vaporizes the frozen material, which then travels upwards in a plume, which coats the bottom of any surface hanging above. Once the material builds up sufficiently, the product is heated to crystallize the molecules and set the thin-film in place.

The process, named Resonant Infrared Matrix-Assisted Pulsed Laser Evaporation (RIR-MAPLE), uses a laser specifically tuned to the bonds of the frozen solution, which absorbs most of the energy leaving the delicate organic molecules unscathed. The researchers say that the process could be used to create complex thin-film materials which would be too fragile for the more common solvent based processes.

“The RIR-MAPLE technology is extremely gentle on the organic components of the material, much more so than other laser-based techniques,” says Associate Professor of Electrical and Computer Engineering at Duke, Adrienne Stiff-Roberts. “That also makes it much more efficient, requiring only a small fraction of the organic materials to reach the same final product.”

Although the solar cells produced in this study did not reach efficiencies comparable to those seen with methylammonium lead iodide produced using solvent based processes, the researchers argue that their new process could be suitable for a whole range of other materials that were previously too complex to create.

“While solution based techniques can also be gentle on organics and can make some great hybrid PV materials,” continued Stiff Roberts, “they can’t be used for more complex and poorly soluble materials.