Researchers at Ludwig-Maximilians-Universität (LMU) have reported two complementary advances that address longstanding bottlenecks in perovskite quantum dots (pQDs): instability in polar environments and the lack of precise growth control. The studies introduce a ligand-engineering strategy for solvent stability and a kinetically controlled growth method enabling sub-unit-cell precision.
Perovskite quantum dots are highly efficient light emitters due to quantum confinement effects, which enable tunable absorption and emission. However, their soft ionic lattices make them particularly vulnerable to polar solvents such as alcohols, where rapid dissolution and degradation commonly occur. This instability has limited their processing, especially in scalable and environmentally friendly (“green”) solvent systems. To overcome this, the LMU team developed a new class of dicationic Gemini ligands terminated with hydroxyl groups. These ligands form a structured, ultrathin shell (~0.7 nm) around the quantum dots. The binding mechanism is asymmetric: ammonium groups anchor strongly to the pQD surface, alkyl chains create an apolar barrier, and hydroxyl termini form a polar external interface. Crucially, the hydroxyl groups do not bind to the surface, ensuring directional ligand attachment and preventing structural disruption.
This architecture enables stable dispersion of pQDs in polar solvents such as ethanol while preserving their optical properties. Unlike polymer-based encapsulation approaches, which typically introduce thick shells (10–100 nm) and hinder conductivity, or inorganic coatings requiring strict synthesis conditions, the Gemini ligand strategy maintains both colloidal stability and functional thinness. The resulting pQDs retain high photoluminescence quantum yields and remain stable over extended periods, opening pathways for solution processing in optoelectronic and photocatalytic applications.
In parallel, the second study focuses on achieving precise structural control during quantum dot growth. Conventional syntheses often suffer from uncontrolled nucleation, leading to broad size distributions and variability in optical properties. The LMU researchers addressed this by suppressing burst nucleation and promoting controlled overgrowth on existing seeds.
Using CsPbBr₃ quantum dots as a model system, they implemented a multi-stage (stepwise and quasi-continuous) precursor injection strategy. By carefully tuning ligand coordination strength, monomer availability, and thermal energy, they directed the system toward heterogeneous growth rather than the formation of new nuclei. Stronger ligand coordination plays a key role here, stabilizing intermediates and slowing reaction kinetics sufficiently to enable controlled deposition.
This approach achieves submonolayer - effectively sub-unit-cell - precision in growth, allowing fine control over nanocrystal dimensions and therefore emission properties. The resulting quantum dots exhibit narrow size distributions and highly stable optical characteristics, both critical for applications such as LEDs and quantum light sources.
“Together, the two studies provide new approaches for solving challenges relating to perovskite quantum dots,” says LMU's Dr. Quinten Akkerman. “While the new ligand chemistry improves their processing and stability, the precise control of their growth enables precise tuning of their optical properties.”
By combining ultrathin, polarity-compatible surface chemistry with kinetically controlled growth, the LMU work establishes a coherent framework for advancing pQDs toward scalable, high-performance optoelectronic and quantum photonic technologies.
