Chemical bonding, conductive network, and thermoelectric performance of the ternary semiconductors Cu2SnX3 (X = Se, S) from first principles
Chemical bonding, conductive network, and thermoelectric performance of the ternary semiconductors Cu2SnX3 (X = Se, S) from first principles
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DOI：
10.1103/physrevb.86.155201
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发表时间：
2012-10-01
影响因子：
3.7
通讯作者：
Singh, D. J.
中科院分区：
文献类型：
--
作者：
Xi, L.;Zhang, Y. B.;Singh, D. J.
实验上已知p型Cu 2SnX 3（X = Se，S）化合物是良好的热电材料，尽管金刚烷衍生的晶体结构中这种良好性能的原因还没有很好地理解。在这里，我们证明了一个三维（3D）孔导电网络的存在，在这些三元类金刚石Cu 2SnX 3（X = Se，S）半导体使用从头计算，并确定负责这种良好的性能的电子结构的功能。我们还提供了作为掺杂水平的函数的结果，以找到将实现最高性能的制度，并估计最大的品质因数ZT。结果表明，Cu 2SnX 3（X = Se，S）中Cu的3d轨道与Se或S的p轨道在上价带的强杂化导致了3D p型空穴输运通道，主要由Cu-X和X-X网络组成.所得到的Cu d-硫族元素p特性的重的但仍然导电的杂化带对于热电性能是高度有利的。这些p型材料的电输运性质主要由这些能带决定，并已通过玻尔兹曼输运方法进行了研究。Cu 2SnX 3的最佳掺杂水平估计为在700 K下每晶胞约0.1个空穴。预测了理论优值ZT。
The p-type Cu2SnX3 (X = Se, S) compounds are known experimentally to be good thermoelectric materials, although the reasons for this good performance in an adamantine-derived crystal structure are not well understood. Here, we demonstrate the existence of a three-dimensional (3D) hole conductive network in these ternary diamondlike Cu2SnX3 (X = Se, S) semiconductors using ab initio calculations, and identify the features of the electronic structure responsible for this good performance. We also provide results as a function of doping level to find the regime where the highest performance will be realized and estimate the maximum figure of merit, ZT. Our results clearly show that the strong hybridization between 3d orbitals from copper and p orbitals from selenium or sulfur at the upper valence band leads to the 3D p-type hole transport channel, mainly consisting of Cu-X and X-X networks in Cu2SnX3 (X = Se, S). The resulting heavy, but still conductive, hybridized bands of Cu d-chalcogen p character are highly favorable for thermoelectric performance. The electrical transport properties of these p-type materials are mainly determined by these bands and have been investigated by Boltzmann transport methods. The optimal doping levels of Cu2SnX3 are estimated to be around 0.1 holes per unit cell at 700 K. The theoretical figure of merit ZT has been predicted.