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Single molecule quantum-confined Stark effect measurements of semiconductor nanoparticles at room temperature

机译:室温下半导体纳米粒子的单分子量子受限斯塔克效应测量

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We investigate the quantum confined Stark effect (QCSE) of various nanoparticles (NPs) on the single molecule level at room temperature. We tested 8 different NPs with different geometry, material composition and electronic structure, and measured their QCSE by single molecule spectroscopy. This study reveals that suppressing the Coulomb interaction force between electron and hole by asymmetric type-Ⅱ interface is critical for an enhanced QCSE. For example, ZnSe-CdS and CdSe(Te)-CdS-CdZnSe asymmetric nanorods (type-Ⅱ) display respectively twice and more than three times larger QCSE than that of simple type-Ⅰ nanorods (CdSe). In addition, wavelength blue-shift of QCSE and roughly linear Δλ-F (emission wavelength shift vs. the applied electric field) relation are observed for the type-Ⅱ nanorods. Experimental results (Δλ-F or ΔE-F) are successfully reproduced by self-consistent quantum mechanical calculation. Intensity reduction in blue-shifted spectrum is also accounted for. Both calculations and experiments suggest that the magnitude of the QCSE is predominantly determined by the degree of initial charge separation in these structures.
机译:我们研究在室温下单个分子水平上的各种纳米粒子(NP)的量子限制斯塔克效应(QCSE)。我们测试了8种具有不同几何形状,材料成分和电子结构的NP,并通过单分子光谱法测量了它们的QCSE。这项研究表明,通过不对称的Ⅱ型界面抑制电子与空穴之间的库仑相互作用力对于提高QCSE至关重要。例如,ZnSe-CdS和CdSe(Te)-CdS-CdZnSe不对称纳米棒(Ⅱ型)的QCSE分别是简单Ⅰ型纳米棒(CdSe)的两倍和三倍以上。另外,对于Ⅱ型纳米棒,观察到了QCSE的波长蓝移和大致线性的Δλ-F(发射波长移与施加的电场)的关系。通过自洽量子力学计算成功地再现了实验结果(Δλ-F或ΔE-F)。还考虑了蓝移光谱的强度降低。计算和实验均表明,QCSE的大小主要取决于这些结构中初始电荷分离的程度。

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