掺杂SnSe晶格和电子热导率的第一性原理研究
The lattice and electronic thermal conductivity of doped SnSe: a first-principles study
摘要：
近年来，人们发现硒化锡（SnSe）晶体具有极低的热导率和适中的电子输运性能，是一种极具潜力的热电材料。由于热电应用通常需要掺杂材料，因此载流子在掺杂SnSe的热输运中起作用，但这种作用在以前的理论和实验研究中没有得到明确的阐明。在这里，我们进行了一个完全的第一性原理研究的影响，电子的热输运在掺杂SnSe。采用模式特异性计算方法，考虑了声子和载流子的电子-声子耦合效应。结果发现，对于声子，EPC是弱的相比，即使在高载流子浓度的固有的声子-声子散射，从而对晶格热导率的影响可以忽略不计。当载流子浓度高于$10^{19} cm^{-3}$时，电子热导率不可忽略，在300 K时，$10^{20} cm^{-3}$电子浓度在a、b和c轴上的数值分别高达1.55、1.45和1.77 $Wm^{-1}K^{-1}$。还计算了SnSe的洛伦兹数，它取决于晶体取向、载流子浓度和载流子类型。用Wiedemann-Franz定律简单估算掺杂SnSe的电子热导率会产生很大的不确定性。
英文摘要：
Recently, it has been found that crystalline tin selenide (SnSe) holds great potential as a thermoelectric material due to its ultralow thermal conductivity and moderate electronic transport performance. As thermoelectric application usually requires doped material, charge carriers can play a role in the thermal transport in doped SnSe, but such an effect has not been clearly elucidated in previous theoretical and experimental studies. Here we performed a fully first-principles study on the effects of electrons to the thermal transport in doped SnSe. The electron-phonon coupling (EPC) effects on both phonons and charge carriers were considered using the mode specific calculation in our work. It is found that for phonons, EPC are weak compared to the intrinsic phonon-phonon scattering even at high carrier concentrations and thus have negligible effects on the lattice thermal conductivity. The electronic thermal conductivity is not negligible when the carrier concentration is higher than $10^{19} cm^{-3}$ and the values can be as high as 1.55, 1.45 and 1.77 $Wm^{-1}K^{-1}$ on a, b and c axes, respectively, for $10^{20} cm^{-3}$ electron concentration at 300K. The Lorenz number of SnSe is also calculated and it is dependent on crystal orientations, carrier concentrations, and carrier types. The simple estimation of electronic thermal conductivity using Wiedemann-Franz law can cause large uncertainties for doped SnSe.
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