Unraveling the Effect of Metal Halide Complex on the Surface Chemistry of InP Quantum Dots

Abstract

Metal halide–ligand complexes are widely employed to enhance the photoluminescence (PL) of colloidal quantum dots (QDs). In III–V materials such as indium phosphide (InP) QDs, these complexes are particularly effective at eliminating surface oxidative defects, yet the underlying mechanism and their interactions with metal carboxylates remain unclear. Here, we investigate how zinc oleate (Zn(OA)2), in combination with ZnX2–TOP complexes (ZXT; X = halides), promotes the removal of the surface oxide layer compared to ZXT-only treatment, with the extent of this promotion depending on the halide identity. The results suggest that ZXT can participate in TOP-mediated reactions with surface oxide species, but its effect on defect removal remains limited without Zn(OA)2. The presence of Zn(OA)2 appears to modify the original ZXT coordination state toward a less sterically hindered mixed-ligand Zn coordination environment. This modification facilitates more effective oxide removal and passivation of the oxide-removed surface, thereby suppressing reoxidation and trap formation, which, in turn, enhances the PL quantum yield (PLQY). Among the ZXT, ZnCl2–TOP enables the most efficient oxide removal at lower molar equivalents than ZnBr2–TOP and ZnI2–TOP. This synergistic pathway alleviates strain accumulation during metal chalcogenide shell growth, leading to more uniform shell formation and high-quality InP/ZnSe/ZnS core/shell QDs with a PLQY of 88.2%. This study provides insight into how ligand interactions influence oxidative defect removal and passivation, thereby offering a useful basis for the rational design of surface treatments for InP QDs.