Surface Chemistry Dictates the Enhancement of Luminescence and Stability of InP QDs upon c-ALD ZnO Hybrid Shell Growth

Abstract

Indium phosphide quantum dots (InP QDs) are a promising example of Restriction of Hazardous Substances directive (RoHS)-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 those of 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 route and the more recently developed aminophosphine-based one. We find that the ZnO shell increases the photoluminescence emission 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 moistureinduced displacement of the ligands 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 devices and bioimaging.

Colloidal Atomic Layer Deposition on Nanocrystals Using Ligand-Modified Precursors

“…Recently, a c-ALD methodology was introduced to grow thin metal oxide coatings through an initial half reaction with a highly reactive alkylmetal precursor followed by the introduction of water, O 2 , or isopropanol as the second half reaction. − This scheme resulted in the formation of hybrid shells, in which the organic ligands become integral components of the grown metal oxide. ,, This structure offers new opportunities in the design of multifunctional materials for applications in photocatalysis, incoherent photon conversion, and electrocatalysis . However, these hybrid oxide shells are not readily amenable to solid-state optoelectronic devices, where ligands are commonly removed to promote electronic transport in dense NC films .…”