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

Abstract

AbstractThe 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.