Enhancing optical properties through zinc halide precursor selection: interfacial optimization of InZnP quantum dots

Zinc is frequently employed in the synthesis of InP quantum dots (QDs) to enhance the photoluminescence efficiency of the resulting InZnP alloy nanostructures. The precise function of Zn within the structure and the mechanism by which it enhances the optoelectronic properties of QDs remain the subject of ongoing research. The addition of zinc promotes the formation of InZnP alloy nanocrystals, which exhibit a wider bandgap energy compared to InP. By using X-ray absorption spectroscopy, we demonstrate that this alloy displays a notable zinc-rich surface layer, enabling a smoother lattice parameter transition at the interface between the InZnP core and the ZnS shell. This transition facilitates the growth of the ZnS shell. Compared to InP cores, the InZnP alloy structure mitigates the presence of InP defect states, resulting in a substantial enhancement in the quantum yield (QY) of InZnP/ZnS QDs. Additionally, our investigation highlights the substantial impact of various zinc halide precursors on the optical properties of the QDs. Specifically, QDs with a core structure synthesized using highly reactive zinc chloride, exhibited increased Zn-O bonds, effectively reducing the inherent surface defects in InP QDs. This enhancement in optical characteristics, observed after the subsequent shell coating, highlights the essential role of precursor selection in determining the optical characteristics of QDs. Overall, these findings emphasize the crucial role of zinc and the selection of precursors in the synthesis process, opening up new avenues for more refined and efficient approaches in the production and application of InP-based QDs.