The Strain Effects and Interfacial Defects of Large ZnSe/ZnS Core/Shell Nanocrystals

The shell growth of large ZnSe/ZnS nanocrystals( is of great importance in the pursuit of pure-blue emitters for display applications, however, suffers from the challenges of spectral blue-shifts and reduced photoluminescence quantum yields. In this work, the ZnS shell growth on different-sized ZnSe cores is investigated. By controlling the reactivity of Zn and S precursors, the ZnS shell growth can be tuned from defect-related strain-released to defect-free strained mode, corresponding to the blue- and red-shifts of resultant nanocrystals respectively. The shape of strain-released ZnSe/ZnS nanocrystals can be kept nearly spherical during the shell growth, while the shape of strained nanocrystals evolutes from spherical into island-like after the critical thickness. Furthermore, the strain between ZnSe core and ZnS shell can convert the band alignment from type-I into type-II core/shell structure, resulting in red-shifts and improved quantum yield. By correlating the strain effects with interfacial defects, a strain-released shell growth model is proposed to obtain large ZnSe/ZnS nanocrystals with isotropic shell morphology. The ZnS shell growth on ZnSe nanocrystals can be tuned from defect-related strain-released to defect-free strained mode, and isotropic morphology is achieved via the strain-release mechanism by introducing defects. The strain between ZnSe core and ZnS shell can convert the band alignment of ZnSe/ZnS nanocrystals from type-I into type-II core/shell structure, resulting in spectral red-shifts with improved quantum yield.image

Automated summary

The growth of ZnS shell on ZnSe cores of different sizes is investigated. By controlling the reactivity of Zn and S precursors, the ZnS shell growth can be tuned to defect-related strain-released or defect-free strained mode, resulting in blue and red-shifts of the nanocrystals. The shape of the nanocrystals evolves differently depending on the growth mode, and the strain between the core and shell affects the band alignment and quantum yield.