Researchers at North Carolina State University have shown a novel method that uses light to adjust the optical characteristics of quantum dots, making the process quicker, more energy-efficient, and environmentally sustainable without sacrificing material quality, according to a study published in Advanced Materials.
This image outlines the process of light-induced bandgap tuning of perovskite quantum dots. Image Credit: Pragyan Jha, NC State University
The discovery of quantum dots earned the Nobel Prize in chemistry in 2023 because they are used in so many applications. We use them in LEDs, solar cells, displays, quantum technologies and so on. To tune their optical properties, you need to tune the bandgap of quantum dots – the minimum energy required to excite an electron from a bound state to a free-moving state – since this directly determines the color of light they emit.
Milad Abolhasani, Study Corresponding Author and ALCOA Professor, Chemical and Biomolecular Engineering, North Carolina State University
Abolhasani added, “Existing methods for bandgap tuning of perovskite quantum dots rely on chemical modifications or high-temperature reactions, both of which are energy-intensive and can introduce inconsistencies in the final material properties. Our new approach uses light to drive the reaction, which requires less energy and allows us to be incredibly precise.”
For this study, the researchers began with green-emitting perovskite quantum dots and immersed them in a solution containing chlorine or iodine. This solution is then passed via a microfluidic system, which includes a light source.
The microfluidic environment allows for precise response control by providing uniform light exposure over small solution volumes, typically 10 microliters per reaction droplet. This is significant because the tiny volume solution allows light to reach the entire sample, and the resultant photochemical reactions occur quickly across the sample.
When chlorine is present in the solvent, the light stimulates processes that cause the green-emitting perovskite quantum dots to travel closer to the blue end of the spectrum, while iodine causes them to move closer to the red end of the spectrum.
“We can control the bandgap by controlling the amount of energy we introduce into the sample, and we control the amount of energy by controlling the light. This allows us to tune the bandgap very precisely. And while we are processing small reaction volumes, the process itself happens very quickly, which means that you ultimately end up producing perovskite quantum dots with tuned bandgaps more efficiently than was possible with previous techniques,” Abolhasani stated.
He continued, “This is a sustainable way to produce high-quality perovskite quantum dots using light. We are now in the process of scaling up to create perovskite quantum dots for use in optoelectronic devices.”
The first author of the study is Pragyan Jha, a PhD student at NC State.
The study was co-authored by NC State Ph.D. students Nikolai Mukhin, Fernando Delgado-Licona, Emily Brown, and Austin Pyrch; postdoctoral researchers Arup Ghorai and Richard Canty; former master's student Hamed Morshedian; and Felix Castellano, NC State's Goodnight Innovation Distinguished Chair of Chemistry.
Under grant 2420490 from the National Science Foundation’s Centers for Chemical Innovation Program, NC State's Center for Accelerated Photocatalysis (CAPS) provided assistance for this study. The Integrative Sciences Initiative at NC State includes CAPS. Additional funding for the study came from the University of North Carolina Research Opportunities Initiative program and NSF grant 1940959.
Journal Reference:
Jha, P. et. al. (2025) Photo-Induced Bandgap Engineering of Metal Halide Perovskite Quantum Dots in Flow. Advanced Materials. doi.org/10.1002/adma.202419668