Improved thermoelectric performance of CuGaTe2 with convergence of band valleys: a first-principles study
Improved thermoelectric performance of CuGaTe2 with convergence of band valleys: a first-principles study
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通过带谷收敛改善 CuGaTe2 的热电性能：第一性原理研究
DOI：
10.1039/c4ra02595d
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发表时间：
2014-01-01
期刊：
影响因子：
3.9
通讯作者：
Yang, Gui
中科院分区：
文献类型：
--
作者：
Yang, Jueming;Yan, Yuli;Yang, Gui
T. Plirdpring等人通过实验发现了CuGaTe2的高品质系数（ZT） （1.4） [Adv. Mater. 24, 3622(2012)]。为了进一步提高其热电性能，我们采用第一性原理研究了其电子结构和热电性能。较大的带谷数和底部导带的高收敛性使得n型CuGaTe2具有较大的塞贝克系数和较高的电导率。因此，对于n型CuGaTe2，通过适当的载流子浓度调整，可以在950 K时找到ZT值的最大值2.1，使ZT值比p型CuGaTe2增加25%。带分解电荷密度计算表明，输运性质主要由价带最大值处的Cu和Te原子决定，而电导带最小值处的三种原子同时影响输运性质。在高温下，从头算分子动力学计算表明，Cu原子从晶体基体中析出导致热功率降低。沿高对称点M，所有原子的电荷密度都是中心对称的。也许这种中心对称的电子结构导致了导带谷在M点的收敛。
A high value (1.4) of figure of merit (ZT) of CuGaTe2 has been experimentally discovered by T. Plirdpring et al. [Adv. Mater. 24, 3622 (2012)]. In order to further enhance its thermoelectric properties, we investigated its electronic structure and thermoelectric properties by first-principles study. Large band-valley number and high convergence of the bottom conduction bands induced a large Seebeck coefficient and a high electrical conductivity of n-type CuGaTe2. So, for n-type CuGaTe2, the maximum ZT values 2.1 may be found at 950 K by suitable carrier concentration tuning, which results in a 25% increment in the ZT value compared with p-type CuGaTe2. Band decomposed charge density calculations indicate that the transport properties are mainly determined by the Cu and Te atoms at the valence-band maximum, in contrast, transport properties are simultaneously affected by the three kind of atoms at the conduction-band minimum. At high temperature, ab initio molecular dynamics calculations demonstrate that Cu atoms precipitated from their crystal matrices lead to a decrease in thermopower. Along the high symmetry point M, the charge density of all atoms is centrosymmetric. Maybe this centrosymmetric electronic structure leads to the conduction band valley convergence at the M point.