Electronic structure and thermoelectric properties of n- and p-type SnSe from first-principles calculations
Electronic structure and thermoelectric properties of n- and p-type SnSe from first-principles calculations
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DOI：
10.1103/physrevb.91.205201
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发表时间：
2015-05-07
影响因子：
3.7
通讯作者：
Tobola, J.
中科院分区：
文献类型：
--
作者：
Kutorasinski, K.;Wiendlocha, B.;Tobola, J.
利用Korringa-Kohn-Rostoker方法和Boltzmann输运方法，我们给出了正交n型和p型SnSe中电子能带结构、费米表面和电子输运性质的计算结果。该分析考虑了温度对Pnma结构的晶体学参数的影响，以及在类似于807 K的温度下向CmCm结构的相变。在T-c之前，随着结构内部晶体学参数的变化，导价带发生了显著的变化，而相变主要导致带隙值的跳变。在较宽的温度（15-900 K）和空穴（p型）和电子（n型）浓度(10(17)-10（21)cm(-3)）范围内，计算了动力学参数张量（速度、有效质量）和由此产生的输运量张量[电导率sigma、热功率S和功率因数（PF）]的对角线分量。SnSe在两种类型的电荷电导率下都具有很强的电子传输性质的各向异性，正如层状结构所期望的那样，与n型相比，p型有效质量通常更重。有趣的是，p型SnSe具有强烈的非抛物色散关系，其最高价带呈“布丁霉菌”状。对sigma、S和PF张量的分析表明，层间电子传递有利于n型SnSe的热电性能，而在p型SnSe中，这一方向被阻挡，p型SnSe更倾向于平面内传输。我们的结果预测，n型SnSe可能是比p型SnSe更好的热电材料。将理论结果与单晶p-SnSe测量结果进行了比较，在600 K以下得到了很好的一致性。在较高温度下出现的计算数据与实验数据之间的差异可以解释为假设空穴浓度随T的增加，这与实验霍尔数据相关。
We present results of the electronic band structure, Fermi surface, and electron transport property calculations in the orthorhombic n- and p-type SnSe, applying the Korringa-Kohn-Rostoker method and the Boltzmann transport approach. The analysis accounted for the temperature effect on crystallographic parameters in Pnma structure as well as the phase transition to CmCm structure at T-c similar to 807 K. Remarkable modifications of the conduction and valence bands were noticed upon varying crystallographic parameters within the structure before T-c, while the phase transition mostly leads to the jump in the band-gap value. The diagonal components of the kinetic parameter tensors (velocity, effective mass) and resulting transport quantity tensors [electrical conductivity sigma, thermopower S, and power factor (PF)] were computed for a wide range of temperature (15-900 K) and hole (p-type) and electron (n-type) concentrations (10(17)-10(21) cm(-3)). SnSe is shown to have a strong anisotropy of the electron transport properties for both types of charge conductivity, as expected for the layered structure, with the generally heavier p-type effective masses compared to n-type ones. Interestingly, p-type SnSe has strongly nonparabolic dispersion relations, with the "pudding-mold-like" shape of the highest valence band. The analysis of sigma, S, and PF tensors indicates that the interlayer electron transport is beneficial for thermoelectric performance in n-type SnSe, while this direction is blocked in p-type SnSe, where in-plane transport is preferred. Our results predict that n-type SnSe is potentially even better thermoelectric material than p-type SnSe. Theoretical results are compared with the single-crystal p-SnSe measurements, and good agreement is found below 600 K. The discrepancy between the computational and experimental data, appearing at higher temperatures, can be explained assuming an increase of the hole concentration versus T, which is correlated with the experimental Hall data.