Surface chemistry dictates the enhancement of luminescence and stability of InP QDs upon c-ALD ZnO hybrid shell growth

Indium phosphide quantum dots (InP QDs) are a promising example of RoHS (Restriction of Hazardous Substances) compliant light-emitting materials. However, they suffer from low quantum yield and instability upon processing under ambient conditions. Colloidal atomic layer deposition (c-ALD) has been recently proposed as a methodology to grow hybrid materials including QDs and organic/inorganic oxide shells, which possess new functions compared to the as-synthesized QDs. Here, we demonstrate that ZnO shells can be grown on InP QDs obtained via two synthetic routes, which are the classical sylilphosphine-based and the more recently developed aminophosphine-based one. We find that the ZnO shell increases the photoluminescence emission significantly only in the case of aminophosphine-based InP QDs. We rationalize this result with the different chemistry involved in the nucleation step of the shell and the resulting surface defect passivation. Furthermore, we demonstrate that the ZnO shell prevents degradation of the InP QD suspension under ambient conditions by avoiding moisture induced ligand displacement from their surface. Overall, this study proposes c-ALD as a methodology for the synthesis of alternative InP-based core@shell QDs and provides insight into the surface chemistry that results in both enhanced photoluminescence and stability required for application in optoelectronic devise and bio-imaging.