Preparing Smaller InP Quantum Dots by Suppressing Over-Etch Using Core Protective Layer and Ammonium Fluoride as Alternative Etchant.

Indium phosphide (InP) is emerging as a viable and environmentally friendly alternative to toxic cadmium-based quantum dots (QDs), especially in the fields of lighting and display. This is owing to similar material properties of InP to those of commercial Cd-based QDs. Nonetheless, the surface quality of InP needs enhancement through a post-treatment process to eliminate surface oxides, typically with hydrofluoric acid (HF). The challenge arises with smaller, such as green InP QDs, as HF easily over-etch the InP cores, thus leading to an unpredictable size distribution and reduced production consistency. This research introduces a refined synthetic strategy that circumvents this over-etching phenomenon and offers a more precise control over the etching process of smaller InP QDs. By applying an additional protective layer to the InP cores prior to etching and employing ammonium fluoride (NH₄F) as an alternative to the conventional HF, the over-etching incidence can be markedly mitigated. The results reveal that smaller InP/ZnSeS QDs with photoluminescence quantum yield (QY) >90% can be consistently produced, thereby proposing a more efficient and safer method for the fabrication of smaller InP QDs.