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Efficient Directed Energy Transfer through Size-Gradient Nanocrystal Layers into Silicon Substrates

机译：通过尺寸梯度纳米晶体层到硅基板的有效定向能量转移

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摘要

Spectroscopic evidence of directed excitonic energy transfer (ET) is presented through size-gradient CdSe/ZnS nanocrystal quantum dot (NQD) layers into an underlying Si substrate. NQD monolayers are chemically grafted on hydrogen-terminated Si surfaces via a self-assembled monolayer of amine modified carboxy-alkyl chains. Subsequent NQD monolayers are linked with short alkyldiamines. The linking approach enables accurate positioning and enhanced passivation of the layers. Two different sizes of NQDs (energy donors emitting at 545 nm, and energy acceptors emitting at 585 nm) are used in comparing different monolayer and bilayer samples grafted on SiO_2 and oxide-free Si surfaces via time-resolved photoluminescence measurements. The overall efficiency of ET from the top-layer donor NQDs into Si is estimated to approach ≈90% through a combination of different energy relaxation pathways. These include sequential ET through the intermediate acceptor layer realized mainly via the non-radiative mechanism and direct ET into the Si substrate realized by means of the radiative coupling. The experimental observations are quantitatively rationalized by the theoretical modeling without introducing any extraneous energy scavenging processes. This indicates that the linker-assisted fabrication enables the construction of defect-free, bandgap-gradient multilayer NQD/Si hybrid structures suitable for thin-film photovoltaic applications.
机译：通过尺寸梯度CdSe / ZnS纳米晶体量子点（NQD）层到下面的Si衬底中，表明了定向激子能量转移（ET）的光谱证据。 NQD单层通过胺修饰的羧基烷基链的自组装单层化学接枝在氢封端的Si表面上。随后的NQD单层与短烷基二胺连接。链接方法可实现层的精确定位和增强的钝化。通过时间分辨光致发光测量，使用两种不同大小的NQD（在545 nm处发射的能量供体，在585 nm处发射的能量受体）比较接枝到SiO_2和无氧化物Si表面上的不同单层和双层样品。通过结合不同的能量弛豫途径，从顶层供体NQD到Si的ET的整体效率估计接近90％。这些包括通过主要通过非辐射机制实现的穿过中间受体层的顺序ET，以及将ET引入通过辐射耦合实现的Si衬底中。通过理论建模对实验观察进行定量合理化，而无需引入任何多余的能量清除过程。这表明链接器辅助的制造能够构建适用于薄膜光伏应用的无缺陷，带隙梯度多层NQD / Si杂化结构。

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  • 来源
    《Advanced Functional Materials》 |2014年第31期|5002-5010|共9页
  • 作者

    William J. I. De Benedetti; Michael T. Nimmo; Sara M. Rupich; Louis M. Caillard; Yuri N. Gartstein; Yves J. Chabal; Anton V. Malko;

  • 作者单位

    Department of Materials Science and Engineering The University of Texas at Dallas Richardson, Texas 75080, USA;

    Department of Physics The University of Texas at Dallas, EC36 Richardson, Texas 75080, USA;

    Department of Materials Science and Engineering The University of Texas at Dallas Richardson, Texas 75080, USA;

    Department of Materials Science and Engineering The University of Texas at Dallas Richardson, Texas 75080, USA;

    Department of Physics The University of Texas at Dallas, EC36 Richardson, Texas 75080, USA;

    Department of Materials Science and Engineering The University of Texas at Dallas Richardson, Texas 75080, USA;

    Department of Physics The University of Texas at Dallas, EC36 Richardson, Texas 75080, USA;

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