REFINE2LASE · Monodisperse Nanocrystals: Thermal Refinement for High-Performance Microlasers

Materials discovery is a central theme in science. The right material may solve grand challenges such as the energy problem or the colonization of other planets. Often this discovery of a new material occurs when scientists find conditions to stabilize new structural arrangements at the nano- or mesoscale. One versatile approach relies on artificial building blocks known as nanocrystals (NCs). NCs are nanometer-scale atomic crystals with size-tunable physical properties. Their hierarchical assembly into crystalline lattices, superlattices, has the potential to integrate orthogonal physical properties, such as photoluminescence and magnetism, unlocking a vast and unexplored design space for multifunctional materials.So far, significant advances in this direction have been hindered by the inherent distribution in size and shape of NCs, polydispersity. The polydispersity of as-synthesized NCs frustrates superlattice formation and affects the performance of the resulting optoelectronic devices, such as lasers. All previous efforts to optimize synthetic protocols have been unable to eliminate NC polydispersity. As a result, modern NC ensembles still show restrictive levels of polydispersity exceeding 10%: A radically different strategy is needed to obtain monodisperse NCs. Here, I propose to develop a universal thermal refinement strategy to reduce the polydispersity of NC ensembles, resulting in the separation and exploitation of monodisperse NCs.The proposed NC refinement strategy relies on a crystallization process engineered to isolate a single NC size from a polydisperse ensemble. My experience in nanoscience will allow me to reach a profound understanding of NC refinement by establishing a robust link between experiments and simulations. I will exploit the superior optical properties of refined NCs to build a new device concept based on the reinforcing optical feedback between colloidal microlasers with sub-mJ lasing thresholds and single-mode operation