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

Abstract 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 (NH 4 F) 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.