Phase-Dependent Shell Growth and Optical Properties of ZnSe/ZnS Core/Shell Nanorods

Research output: Journal Publications and Reviews (RGC: 21, 22, 62)21_Publication in refereed journalpeer-review

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Original languageEnglish
Pages (from-to)3413-3427
Journal / PublicationChemistry of Materials
Volume33
Issue number9
Online published29 Apr 2021
Publication statusPublished - 11 May 2021

Abstract

Shell growth around nanocrystal cores is the most efficient way to passivate their surface in order to improve their stability and optical properties. Due to the different atomic arrangements and curvatures of the tips and sides in one-dimensional nanorods (NRs), the epitaxial shell growth on those is still limited. Here, we offer a method to grow a ZnS shell on ZnSe NRs with either hexagonal wurtzite (WZ) or cubic zinc-blende (ZB) crystal structures and show how the phase difference in these ZnSe NRs induces different growth modes of the ZnS shell. A uniform shell of two ZnS monolayers can first be deposited on the WZ-ZnSe NRs, while thereafter, an island-like growth is observed when more zinc precursor was used. The highest photoluminescence quantum yield (PLQY) of 40% has been achieved for WZ-ZnSe/ZnS core/shell NRs with the uniform ZnS shell, while the PLQY decreased to 29% upon further island-like ZnS growth. For ZB-ZnSe NRs, the deposition rate of ZnS on the sides of the rods was found to be faster than that on the tips, which is related to higher surface energy of the former. For these NRs, peanut or dot-shaped ZB-ZnSe/ZnS core/shell nanocrystals were finally obtained. The PLQY of the ZB-ZnSe core/shell NRs reached a maximum of 40% upon increasing the thickness of the ZnS shell. As compared with WZ-ZnSe/ZnS core/shell NRs, ZB-ZnSe/ZnS core/shell NRs showed a much shorter PL lifetime, which is beneficial for light-emitting devices. Both types of the ZnSe/ZnS core/shell NRs (WZ and ZB) showed anisotropic emission, and the highest anisotropy value reached 0.18 in ZB-ZnSe/ZnS core/shell NRs, despite their lower aspect ratio.