论文标题
3D和2D热电半导体中热电效率的非全额度尺度
Non-universal Scaling of Thermoelectric Efficiency in 3D and 2D Thermoelectric Semiconductors
论文作者
论文摘要
We performed the first-principles calculation on common thermoelectric semiconductors $\rm Bi_2Te_3$, $\rm Bi_2Se_3$, $\rm SiGe$, and $\rm PbTe$ in bulk three-dimension (3D) and two-dimension (2D).我们发现，根据Hicks和Dresselhaus（HD）理论，材料的微型化通常不会增加功绩的热电图（$ ZT $）。例如，$ ZT $值为2D $ \ RM PBTE $（0.32）和2D $ \ RM SIGE $（0.04）小于其3D对应物（分别为0.49和0.09）。同时，$ zt $值为2D $ \ rm bi_2te_3 $（0.57）和2d $ \ rm bi_2se_3 $（0.43）大于散装（分别为0.54和0.18），这与HD理论一致。高清理论的崩溃之所以发生，是因为材料的带隙和带状平面度在尺寸还原时发生了变化。我们发现，平面带具有3D材料的较大电导率（$σ$）和电子导热率（$κ_{EL} $），而2D材料中的值则较小。在所有情况下，最大$ zt $值值与频带差距成比例地增加，并且对频段间隙的饱和量高于$ 10 \ k_bt $。 2d $ bi_2te_3 $和$ bi_2se_3 $由于平坦的瓦楞纸带和DOS中的狭窄峰值而获得更高的$ ZT $。同时，第二个PBTE违反了由于表现出的扁平带，而2d Sige拥有一个小的Gap Dirac-cone频段。
We performed the first-principles calculation on common thermoelectric semiconductors $\rm Bi_2Te_3$, $\rm Bi_2Se_3$, $\rm SiGe$, and $\rm PbTe$ in bulk three-dimension (3D) and two-dimension (2D). We found that miniaturization of materials does not generally increase the thermoelectric figure of merit ($ZT$) according to the Hicks and Dresselhaus (HD) theory. For example, $ZT$ values of 2D $ \rm PbTe$ (0.32) and 2D $ \rm SiGe$ (0.04) are smaller than their 3D counterparts (0.49 and 0.09, respectively). Meanwhile, the $ZT$ values of 2D $\rm Bi_2Te_3$ (0.57) and 2D $\rm Bi_2Se_3$ (0.43) are larger than the bulks (0.54 and 0.18, respectively), which agree with HD theory. The HD theory breakdown occurs because the band gap and band flatness of the materials change upon dimensional reduction. We found that flat bands give a larger electrical conductivity ($σ$) and electronic thermal conductivity ($κ_{el}$) in 3D materials, and smaller values in 2D materials. In all cases, maximum $ZT$ values increase proportionally with the band gap and saturate for the band gap above $10\ k_BT$. The 2D $Bi_2Te_3$ and $Bi_2Se_3$ obtain a higher $ZT$ due to the flat corrugated bands and narrow peaks in their DOS. Meanwhile, the 2D PbTe violates HD theory due to the flatter bands it exhibits, while 2D SiGe possesses a small gap Dirac-cone band.
