Band structure engineering via piezoelectric fields in strained anisotropic CdSe/CdS nanocrystals.
Band structure engineering via piezoelectric fields in strained anisotropic CdSe/CdS nanocrystals.
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DOI：
10.1038/ncomms8905
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发表时间：
2015-07-29
影响因子：
16.6
通讯作者：
Moreels I
中科院分区：
文献类型：
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作者：
Christodoulou S;Rajadell F;Casu A;Vaccaro G;Grim JQ;Genovese A;Manna L;Climente JI;Meinardi F;Rainò G;Stöferle T;Mahrt RF;Planelles J;Brovelli S;Moreels I
具有非中心对称晶格的胶体异质晶体中的应变为控制光电性质提供了一个独特的机会，并为现有的波函数工程和掺杂范例增加了一个新的自由度。我们合成了嵌入在一个厚厚的硫化镉外壳中的纤锌矿CdSe纳米棒，从而利用两个磁区之间的巨大晶格失配来产生CdSe核心的压缩应变和沿其c轴的强压电势。有效的电荷分离导致间接的基态转变，寿命为几微秒，几乎比其他任何CdSe/CDS纳米晶体长一个数量级。由于激发态轨道的日益重叠，较高激发态在纳秒时间范围内辐射重组。K̇p计算证实了各向异性形状和晶体结构在压电势增强中的重要性。因此，应变工程提供了一种由专门的核/壳纳米晶体设计驱动的高度可调的单激子和多激子相互作用的有效方法。量子点将电子限制在纳米尺度内，这就产生了许多量子效应。在这里，作者通过操纵粒子内压电场来直接控制纳米晶体量子点的激子结构。
Strain in colloidal heteronanocrystals with non-centrosymmetric lattices presents a unique opportunity for controlling optoelectronic properties and adds a new degree of freedom to existing wavefunction engineering and doping paradigms. We synthesized wurtzite CdSe nanorods embedded in a thick CdS shell, hereby exploiting the large lattice mismatch between the two domains to generate a compressive strain of the CdSe core and a strong piezoelectric potential along its c-axis. Efficient charge separation results in an indirect ground-state transition with a lifetime of several microseconds, almost one order of magnitude longer than any other CdSe/CdS nanocrystal. Higher excited states recombine radiatively in the nanosecond time range, due to increasingly overlapping excited-state orbitals. k̇p calculations confirm the importance of the anisotropic shape and crystal structure in the buildup of the piezoelectric potential. Strain engineering thus presents an efficient approach to highly tunable single- and multiexciton interactions, driven by a dedicated core/shell nanocrystal design. Quantum dots confine electrons to a nanometre length scale, and this gives rise to numerous quantum effects. Here, the authors directly control the excitonic structure of nanocrystal quantum dots by manipulating intra-particle piezoelectric fields.