II型ZnTe / CdSe纳米晶体的可预测光谱性质和电子/空穴猝灭。,Physical Chemistry Chemical Physics

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II型ZnTe / CdSe纳米晶体的可预测光谱性质和电子/空穴猝灭。
Physical Chemistry Chemical Physics ( IF 2.9 ) Pub Date : 2019-03-06 , DOI: 10.1039/c9cp00026g
Tongqing Long ₁ , Jun Cao , Zhong-Jie Jiang

Affiliation

核/壳结构的ZnTe / CdSe纳米晶体（NCs）的光谱性质已得到系统地研究。通过改变ZnTe核的直径和CdSe壳的厚度，可以很容易地在很宽的范围内调节ZnTe / CdSe NCs的吸收起始点和光致发光峰位置。基于有效质量近似的理论模型表明，ZnTe / CdSe NCs具有II型载流子定位，其中光激发电子和空穴分别在空间上分离并限制在壳和核中。准确预测了ZnTe / CdSe NCs的导带和价带以及带隙的能量。光致发光实验表明，在其还原电势与ZnTe / CdSe纳米晶体的最低导带边缘之间具有较大能量差的电子猝灭剂可以完全猝灭发光。具有仅略低于导带边缘的还原电位的电子受体部分地淬灭了纳米晶体的光致发光。在这种情况下，淬火的程度取决于壳的厚度和能量差。尽管将光激发的空穴限制在芯中，但是光致发光仍可以通过吸附的空穴猝灭剂来猝灭。空穴淬灭的程度取决于核的大小，壳的厚度和淬灭剂的氧化电势。基本上，核尺寸和壳厚度的增加可能导致空穴淬火程度的降低。此处介绍的工作引起了极大的兴趣，因为它可以扩展为了解其他核/壳半导体NC的光谱性质和光致发光猝灭行为。

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Predictable spectroscopic properties of type-II ZnTe/CdSe nanocrystals and electron/hole quenching.

The spectroscopic properties of core/shell structured ZnTe/CdSe nanocrystals (NCs) have been systematically studied. By varying the ZnTe core diameter and the CdSe shell thickness, the absorption onset and the photoluminescence peak position of the ZnTe/CdSe NCs can be readily tuned over a wide range. The theoretical model based on an effective mass approximation demonstrates that the ZnTe/CdSe NCs have type II carrier localization in which the photoexcited electrons and holes are spatially separated and confined in the shell and core, respectively. The energetics of the conduction and valence bands and the bandgaps of the ZnTe/CdSe NCs are accurately predicted. The photoluminescent experiments show that electron quenchers having a large energy difference between their reduction potential and the lowest conduction band edge of the ZnTe/CdSe nanocrystals can completely quench the luminescence. Electron acceptors having a reduction potential only slightly below the conduction band edge partially quench the photoluminescence of the nanocrystals. In this case, the extent of quenching depends upon the thickness of the shell and the energy difference. Despite the confinement of photoexcited holes in the core, the photoluminescence could be still quenched by adsorbed hole quenchers. The extent of hole quenching depends upon the core size, the shell thickness and the oxidation potential of the quenchers. Basically, an increase in the core size and the shell thickness may lead to a decrease in the extent of hole quenching. The work presented here is of great interest since it can be extended to understand the spectroscopic properties and photoluminescence quenching behaviors of other core/shell semiconductor NCs.

更新日期：2019-02-15

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