Today’s organic perovskite aterials such as methylammonium lead iodide (MAPbI3) can be used in thin films effectively but have issues with scalability and durability.
“Methylammonium lead iodide has a very simple organic component, yet is a very high-performing light absorber,” said David Mitzi, the Simon Family Professor of Mechanical Engineering and Materials Science at Duke. “If we can find a new manufacturing approach that can build more complex molecular combinations, it will open new realms of chemistry for multifunctional materials.”
Mitzi worked with Adrienne Stiff-Roberts, associate professor of electrical and computer engineering at Duke, on a new manufacturing technique called Resonant Infrared Matrix-Assisted Pulsed Laser Evaporation, or RIR-MAPLE for short. This has been adapted from a technology invented in 1999 called MAPLE and involves freezing a solution containing the molecular building blocks for the perovskite, then blasting the frozen block with a laser in a vacuum chamber.
When a laser vaporises a small piece of the frozen target, the gas coats the bottom surface of an object hanging overhead, such as a component in a solar cell. Once enough of the material builds up, the process is stopped and the product is heated to crystallise the molecules and set the thin film in place.
In Stiff-Roberts’s version of the technology, the laser’s frequency is specifically tuned to the molecular bonds of the frozen solvent. This causes the solvent to absorb most of the energy, leaving the delicate organics unscathed as they travel to the product surface.
This can open up the use of organic materials in manufacturing.
“The RIR-MAPLE technology is extremely gentle on the organic components of the material, much more so than other laser-based techniques,” said Stiff-Roberts. “That also makes it much more efficient, requiring only a small fraction of the organic materials to reach the same final product. While solution-based techniques can also be gentle on organics and can make some great hybrid photovoltaic materials, they can’t be used for more complex and poorly soluble organic molecules.”
“With this demonstration of the RIR-MAPLE technology, we hope to open a whole new world of materials to the solar cell industry,” said Mitzi. “We also think these materials could be useful for other applications, such as light-emitting diodes, photodetectors and X-ray detectors.”