Shell-dependent blinking behavior and fluorescence dynamics of single ZnSe/CdS core/shell quantum dots.
Shell-dependent blinking behavior and fluorescence dynamics of single ZnSe/CdS core/shell quantum dots.
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DOI：
10.1039/c8nr06749j
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发表时间：
2018-10
期刊：
影响因子：
6.7
通讯作者：
Xing Guo;Yanmin Kuang;Sheng Wang;Zhaohan Li;Huaibin Shen;Lijun Guo
中科院分区：
文献类型：
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作者：
Xing Guo;Yanmin Kuang;Sheng Wang;Zhaohan Li;Huaibin Shen;Lijun Guo
理解闪烁行为和光动力学对于改善量子点的光学性质是至关重要的。在这里，我们报告的发光闪烁行为和动力学机制的单个ZnSe/CdS核/壳量子点的壳层厚度从1到6单层变化。我们发现，通过调节壳层厚度，可以有效地抑制ZnSe/CdS量子点在单激子区的发光闪烁行为，并优化量子点的光致发光（PL）量子产率（QY）和相应的亮度分数。具体地，当壳层厚度为4个单层时，PL QY达到最大值93%。单量子点的强度分辨和时间分辨荧光动力学研究表明，ZnSe/CdS量子点的闪烁行为主要由激子发射、带边发射和浅表面陷阱态发射三条途径引起.这三种衰变组分的竞争贡献比是导致不同壳层厚度的ZnSe/CdS量子点的发射性质存在显著差异的原因。我们的研究结果表明，提高量子产率和分数亮度的核/壳量子点的有效途径是提高带边发射，同时抑制三振子发射和表面陷阱态发射。
An understanding of blinking behavior and photodynamics is crucial for improving the optical properties of quantum dots (QDs). Here we report the emission blinking behavior and dynamical mechanisms of single ZnSe/CdS core/shell QDs with the shell thickness varying from 1 to 6 monolayers. We find that the emission blinking behavior can be efficiently suppressed in the single-exciton regime and that the photoluminescence (PL) quantum yields (QY) and the corresponding fraction-bright of ZnSe/CdS QDs can be optimized by regulating the shell thickness. Specifically, the PL QY reaches a maximum of 93% when the shell thickness is 4 monolayers. The intensity-resolved and time-resolved fluorescence dynamics of single QDs indicate that three exciton decay pathways via trion emission, band-edge emission and shallow surface trap-state emission contribute to the blinking behavior of ZnSe/CdS QDs. The competitive contribution ratios of these three decay components are responsible for the significant difference in emission properties of ZnSe/CdS QDs with different shell thicknesses. Our findings in this work demonstrate that an effective way to improve the quantum yields and fraction-bright of core/shell QDs is to enhance the band-edge emission while suppressing the trion emission and surface trap-state emission.