Spacing Controlled Quantum Resonance in Colloidal CdSe Quantum Dot Superlattices

Understanding the correlation between interdot spacing and their interactions is crucial for controlling the properties of quantum dot superlattices. In this study, the interdot spacing of the colloidal quantum dot superlattice is tuned from 1.4 to 0.5 nm by varying the self-assembly solvents and the subsequent surface ligand engineering. Reducing the spacing to 1.0 nm or below induces a secondary narrow PL peak located ∼130 meV below the conventional emission peak. The new peak is attributed to quantum resonance, evidenced by the loss of size selectivity at different excitation wavelengths and a significant red-shift at room temperature. The photoluminescence associated with the quantum resonance remains stable in oxygen-free conditions and exhibits a lifetime that is six times longer than that of the weakly coupled state. The spacing control strategy for achieving quantum resonance can be applied to develop narrow-line-width emission devices based on nanocrystal superlattices.