Mr. Shai Levy - Ph.D. Candidate
04/06/2026
אודיטוריום ע"ש דויד וואנג, בניין מידן, קומה 3
13:30
Quantum dots (QDs) are semiconducting nanocrystals whose electronic and optical properties are highly dependent on their composition, size, and morphology. Lead halide perovskite (APbX3, X=Cl,Br,I) QDs have recently emerged as exceptional light emitting materials due to their remarkable defect tolerance, high emission yield, and fast radiative rates. Formation of halide solid solutions is a common method to tune their properties, although Cl:I fundamental incompatibility restricts many possible compositions throughout the ternary halide Cl:Br:I range. However, solubility is usually extended in nanocrystals accommodating a wider range of ions within their lattice. To study these limits, a robotic high-throughput platform was employed to perform anion exchange and optical spectroscopy across thousands of samples. These results determined the halide solubility boundaries of perovskite nanocrystals and showed an extended size-dependent miscibility.
Ordered assemblies of perovskite QDs enable interactions and collective superfluorescent synchronized light emission. Superfluorescence is highly influenced by dipole-dipole interactions between the excited QDs. Modifying the QD size and composition showed how quantum confinement governs the nature of coupling between emitters, switching between two distinct regimes. Weakly confined QDs showed red-shifted collective superfluorescent emission, while strongly quantum-confined QDs showed blue-shifted subfluorescent emission. To resolve these interactions at nanometric scale, ultrafast scanning electron microscopy was used to probe the local emission and induce free electron driven superfluorescence. Electron probes enable us to locally excite and observe correlations between the QDs and measuring collective emission dynamics with picosecond temporal resolution. These observations provide better understanding of exciton interactions and collective light emission at the solid state.