Understanding the dopability of p-type Mg2(Si,Sn) by relating hybrid-density functional calculation results to experimental data
Understanding the dopability of p-type Mg2(Si,Sn) by relating hybrid-density functional calculation results to experimental data
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DOI：
10.1088/2515-7655/ac689d
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发表时间：
2022-04
期刊：
影响因子：
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通讯作者：
H. Kamila;B. Ryu;S. Ayachi;Aryan Sankhla;E. Mueller;J. de Boor
中科院分区：
文献类型：
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作者：
H. Kamila;B. Ryu;S. Ayachi;Aryan Sankhla;E. Mueller;J. de Boor
在开发基于Mg 2 X（X= Si、Ge和Sn）的热电（TE）发电机时，达到足够高的载流子浓度以优化热电（TE）材料是至关重要的。虽然n型Mg 2（Si，Sn）具有优异的TE性能，但是p型显示出次优的TE性能，因为载流子浓度不足，特别是对于Mg 2Si和富Si的Mg 2（Si，Sn）。Li掺杂的Mg 2Si 1-xSnx的系统研究已经进行，因为Li与其他典型的掺杂剂相比，在材料系统中具有高溶解度，并且已经显示出产生最高的报道的载流子浓度。我们观察到载流子浓度随Li含量的增加而增加，但掺杂效率降低。相对于Si：Sn比，我们发现随着Sn含量的增加，最大可实现的载流子浓度和掺杂剂效率明显增加。可以理解的趋势，通过采用内的混合密度泛函理论（DFT）的二进制得到的缺陷形成能。此外，我们使用的混合DFT结果从二元到三元Mg 2（Si，Sn）的组合物和一个简单的单抛物线带模型的线性插值预测的最大可实现的载体浓度的固溶体，提供了一个简单的指导实验工作。最后，我们表明，该方法是可转移到其他材料类。这项工作强调，除了掺杂剂溶解度之外，本征和非本征缺陷之间的相互作用决定了可实现的载流子浓度。
It is crucial to reach a sufficiently high carrier concentration in order to optimize the thermoelectric (TE) material in the development of Mg2 X (X= Si, Ge, and Sn)-based TE generators. While n-type Mg2(Si,Sn) has excellent TE properties, p-type shows suboptimal TE performance because of insufficient carrier concentration, in particular for Mg2Si and Si-rich Mg2(Si,Sn). A systematic investigation of Li-doped Mg2Si1-x Sn x has been performed as Li, in contrast to other typical dopants, has a high solubility in the material system and has been shown to yield the highest reported carrier concentrations. We observe that the carrier concentration increases with Li content, but the dopant efficiency decreases. With respect to the Si:Sn ratio, we find a clear increase in maximum achievable carrier concentration and dopant efficiency with increasing Sn content. The trends can be understood by employing defect formation energies obtained within the hybrid-density functional theory (DFT) for the binaries. Further, we use a linear interpolation of the hybrid-DFT results from the binaries to the ternary Mg2(Si,Sn) compositions and a simple single parabolic band model to predict the maximal achievable carrier concentration for the solid solutions, providing a simple guideline for experimental work. Finally, we show that the approach is transferable to other material classes. This work highlights that, besides dopant solubility, the interplay between intrinsic and extrinsic defects determines the achievable carrier concentration.