Microfluidic device generates perovskite quantum dots in every color of rainbow

A new microfluidic synthesis system can quickly and efficiently generate a wide range of perovskite quantum dots in a rainbow of colors. And it provides a way to probe the products spectroscopically in real time as they are being formed, to study the chemistry and ensure quality control.

Quantum dots’ absorption and emission properties depend strongly on their chemical composition and size. Thanks to their tunability, researchers and manufacturers use these materials in electronic displays, solar cells, biosensors, and other applications. One recently discovered class of these materials, metal halide perovskite quantum dots (PQDs), have quickly grabbed attention. Compared with other types of quantum dots, they offer reduced energy consumption in optoelectronic devices.

Typically, researchers make and study PQDs via manual flask-based methods. But that approach consumes a lot of chemicals and is slow, costly, and subject to batch variations. At the American Chemical Society national meeting in Orlando on Wednesday, Milad Abolhasani of North Carolina State University reported that his group’s microfluidic system can bypass many of those shortcomings.

Speaking in a symposium organized by the Division of Colloid and Surface Chemistry, Abolhasani described a recent study in which his group used the automated microflow system to study the effects of numerous parameters on ion-exchange reactions that convert green-emitting cesium lead tribromide to the chloride and iodide analogs, which emit blue and red light, respectively (Adv. Funct. Mater. 2019, DOI: 10.1002/adfm.201900712).

Fine-tuning the properties of PQDs via so-called post-synthesis modification is a standard preparation technique. But the enormous number of reaction variables—for example, the composition of the solvent, the halide reagents, the organic ligands that cap the crystals, and the rate at which reagents are mixed—makes searching for optimum reaction conditions laborious.

Abolhasani noted that with the new flow device researchers can evaluate more than 10,000 experimental conditions per day. “We have submitted a patent for the system, and are working with industry collaborators to commercialize the technology,” he said.

Paul J. A. Kenis, a specialist in nanomaterials and microchemical systems at the University of Illinois at Urbana-Champaign, commented that the new flow reactor with in-line product monitoring is particularly well suited for studying the kinetics of quantum dot growth. “This work underscores the potential of flow reactors to accelerate the discovery of novel nanomaterials and to manufacture them on a large scale,” he said.