Band-Emission Evolutions from Magic-sized Clusters to Nanosized Quantum Dots of Cd3As2 in the Hot-Bubbling Synthesis

Abstract

In this work, the band-emissions of both the magic-sized clusters (MSCs) and nanosized quantum dots (QDs) of cadmium arsenide (Cd3As2) are studied versus time during the hot-bubbling synthesis. The syntheses are performed by introducing the ex-situ produced H3As into the hot-surfactant solutions dissolved with cadmium oleate and ligand molecules. It is found that the MSCs are produced within 4.0 min because of the color change of the solution. However, these clusters are not stable, and the peak of the photoabsorption shifts from 528 to 540 nm with the growth time. Across a shallow energy barrier, the MSCs grow into nanosized quantum dots whose photoluminescence wavelengths are found to extend into the NIR region (λ > 1480 nm) after a growth period of ∼45.0 min. The quantum yield of the band emissions ranges 2.5–8.0% during the growth of Cd3As2 QDs. Analyses from the time-resolved fluorescence decay profiles suggest that the ultrafast exciton radiative decays are the dominant recombination in the Cd3As2 MSCs, and the lifetime is about 0.69 ns. Longer lifetime emissions (200–300 ns) are found in the nanosized QDs, which is ascribed to the delocalized excitons in the lowest QD state after thermalization. This research highlights the origin and evolution of band-emissions in Cd3As2 QDs, which gives an in-depth understanding of the electronic structures of Cd3As2 QDs, and thus lending them wider potential applicability.