Long Zhiwei, Yang Gaoling, Shao Ruiwen, Chen Zhuo, Liu Yang, Liu Ronghui, Zhong Haizheng
National Engineering Research Center for Rare Earth, GRIREM Advanced Materials Co. Ltd., General Research Institute for Nonferrous Metals, Beijing, 100088, China.
MIIT Key Laboratory for Low-dimensional Quantum Structure and Devices, School of Materials Science & Engineering, Beijing Institute of Technology, Beijing, 100081, China.
Small. 2024 Jan;20(4):e2306602. doi: 10.1002/smll.202306602. Epub 2023 Sep 13.
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.
对于显示应用中追求纯蓝光发射体而言，大尺寸ZnSe/ZnS纳米晶体的壳层生长至关重要，然而，它面临着光谱蓝移和光致发光量子产率降低的挑战。在这项工作中，研究了不同尺寸ZnSe核上ZnS壳层的生长情况。通过控制Zn和S前驱体的反应活性，ZnS壳层的生长可以从与缺陷相关的应变释放模式调整为无缺陷的应变模式，分别对应于所得纳米晶体的蓝移和红移。应变释放的ZnSe/ZnS纳米晶体在壳层生长过程中形状可保持近乎球形，而应变纳米晶体在达到临界厚度后形状从球形演变为岛状。此外，ZnSe核与ZnS壳之间的应变可将能带排列从I型转变为II型核壳结构，导致红移并提高量子产率。通过将应变效应与界面缺陷相关联，提出了一种应变释放壳层生长模型，以获得具有各向同性壳层形态的大尺寸ZnSe/ZnS纳米晶体。
