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Nanostructured thermoelectrics

机译：纳米结构热电

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Thermal to electrical energy conversion, through thermoelectric and thermionic materials, has been proposed to be much more efficient in lower dimensional materials at the nanoscale. In this paper, we review the underlying materials physics of nanostructured thermoelectrics which gives rise to such enhanced efficiency. We first study the basic phenomenology of the contributing terms to the power factor in the thermoelectric figure of merit, I.e., the Seebeck coefficient (S) and the electrical conductivity (a), which are analyzed through the Boltzmann transport formalism and then thoroughly compared to recent experiments in nanostructures. Additional factors, hitherto not given much consideration, such as carrier scattering time approximations vis-à-vis dimensionality and the density of states (DOS) are also studied. Through such a study, we postulate that it is the sheer magnitude and not the specific shape of the DOS that is important in enhancing the thermoelectric power factor. We then see that most of the understood increase in the figure of merit of nanostructured thermoelectrics has been accomplished through a drastic reduction of the lattice thermal conductivity (K_L)-by two orders of magnitude from the bulk values through the introduction of scattering at different length scales. Such a reduction has provided a large impetus for the use of nanostructures and will be reviewed. We next consider solid state implementations of thermionic structures, which seem to be converging towards thermoelectric devices and hence can be described by a similar figure of merit. Approaches for energy filtering and further increasing efficiencies are also described.
机译：已经提出了通过热电和热离子材料的热至电能的转换在纳米尺度的低维材料中更加有效。在本文中，我们回顾了引起热效率提高的纳米结构热电学的基本材料物理。我们首先研究热电性能因数中功率因数的贡献项的基本现象，即，塞贝克系数（S）和电导率（a），然后通过玻耳兹曼输运形式主义进行分析，然后与纳米结构的最新实验。到目前为止，还没有考虑其他因素，例如相对于维数和状态密度（DOS）的载流子散射时间近似值。通过这样的研究，我们推测对于提高热电功率因数而言，重要的是DOS的绝对大小而不是其特定形状。然后，我们看到，通过将晶格热导率（K_L）大幅降低，通过引入不同长度的散射，可以从体积值大幅度降低两个数量级，从而实现了纳米结构热电性能的大部分可理解的提高秤。这种减少为纳米结构的使用提供了很大的推动力，并将进行审查。接下来，我们考虑热电子结构的固态实现，该固态实现似乎正在向热电器件汇聚，因此可以通过类似的品质因数来描述。还描述了用于能量过滤和进一步提高效率的方法。

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