Controlling Thermal Transport in Hybrid, 2D, Thermoelectric Devices from the Bottom-Up

从下到上控制混合二维材料中的热输运开发能将废热直接转化为电能的高效热电材料已成为纳米级科学技术的终极目标之一。利用纳米结构材料的独特性质导致热电材料的进步取得了令人难以置信的进展。然而，尽管取得了这些进展，但仍然很难准确预测这些复杂系统的性质将如何随着尺寸的扩大而演变，或者修改组件材料将如何影响最终的系统性质。造成这种困难的主要原因之一是，提高系统的热电性能需要同时控制三个特性：电导率、热功率（塞贝克系数）和导热系数。该项目将使用混合的二维（2D）分子-纳米颗粒材料作为模型系统来探索纳米结构热电材料的热输运特性。这是一种独特的材料系统，其中单个组件的特性可以被测量、控制和表征，然后嵌入到混合材料中，以便随着系统规模的扩大或组件的修改，可以确定组件之间复杂的相互作用。通过研究分子组分的热学和力学性质，以及这些性质对杂化材料热输运的影响，本项目旨在建立一套控制分子-纳米颗粒杂化热电器件热输运性质的设计规则。然后，这些知识可以被用于对纳米结构材料中控制热传输的特性的更普遍的理解，这样就可以从原子水平上设计这些系统的热传输特性的控制。本项目将重点了解和控制杂化材料的热输运性质，通过：i)检查分子取代基态的振动密度对热输运性质的作用；Ii)研究分子刚度、纳米颗粒质量和组成对热传递的影响；Iii)研究阵列的热输运性质随系统尺寸的变化；iv)检查这些性质之间的相互作用，以使纳米结构系统的设计具有所需的性质。这项研究将提供前所未有的信息，了解组件材料的原子尺度热性能与集成杂化材料在一定尺寸范围内的性能之间的相互作用。利用单分子光谱技术（非弹性电子隧道光谱）和机电α ？光谱学)，纳米颗粒大小和组成的修改，以及特征尺寸的光刻控制将揭示分子和纳米颗粒的性质如何决定二维，混合，分子-纳米颗粒阵列的热输运性质。这些研究将提供关于这些性质中哪一个在纳米结构材料中主导热传递，它们之间的关系，以及这种相互作用如何随着器件尺寸的扩大而演变的关键信息。这一系列系统的实验将使人们对纳米结构材料中的热传输原理有一个新的理解，并将使热传输的被动控制不仅可以通过控制其组成，还可以通过控制组成材料之间的关系来设计成热电材料。

Controlling Thermal Transport in Hybrid, 2-Dimensional Materials from the Bottom-UpThe development of highly-efficient thermoelectric materials, which can directly convert wasted heat into electrical power, has emerged as one of the ultimate goals of nanoscale science and technology. Utilizing the unique properties of nanostructured materials has resulted in incredible progress in the advancement of thermoelectric materials. However, despite these advances, it is still difficult to accurately predict how the properties of these complex systems will evolve as the size scales, or how modifying the component materials will affect the final system properties. One of the primary reasons for this difficulty is that improving the thermoelectric properties of a system requires simultaneous control of three properties: the electrical conductivity, the thermopower (Seebeck coefficient), and the thermal conductivity. This project will use hybrid, 2-dimensional (2D), molecule-nanoparticle materials as a model system for exploring the thermal transport properties of nanostructured thermoelectric materials. This is a unique materials system where the properties of individual components can be measured, controlled, and characterized, and then embedded into the hybrid material so that the complex interplay between the components can be determined as the system scales-up or as the components are modified. By examining the thermal and mechanical properties of the molecular components, and the effects of these properties on thermal transport of the hybrid materials, this project aims to develop a set of design rules for controlling the thermal transport properties of hybrid molecule-nanoparticle thermoelectric devices. This knowledge can then be leveraged into a more general understanding of the properties that govern heat transport in nanostructured materials, so that control of the thermal transport properties of these systems can be designed in from the atomic-level up. This project will focus on understanding and controlling the thermal transport properties of the hybrid materials by: i) examining the role of the vibrational density of states of the molecular substituents on the thermal transport properties; ii) studying how molecular rigidity and nanoparticle mass and composition influence heat transport; iii) investigating the evolution of the thermal transport properties of the arrays as the system size scales; and iv) examining the interplay between these properties to enable the design of nanostructured systems with desired properties. This investigation will provide unprecedented information about the interplay between the atomic-scale thermal properties of component materials and the properties of integrated, hybrid materials across a range of size-scales. Using a combination of single-molecule spectroscopic techniques (Inelastic Electron Tunneling Spectroscopy, and electromechanical ?alpha? spectroscopy), modification of nanoparticle size and composition, and lithographic control of feature sizes will reveal how both the molecular and nanoparticle properties dictate the thermal transport properties of 2D, hybrid, molecule-nanoparticle arrays. These studies will provide crucial information about which of these properties dominate heat transport in nanostructured materials, the relationships between them, and how this interplay evolves as the device size scales. This systematic series of experiments will allow for a new understanding of the principles that dictate thermal transport in nanostructured materials, and will enable the passive control of thermal transport to be designed into thermoelectric materials by controlling not just their composition, but the relationships between the component materials.