Understanding the dopability of p-type Mg2(Si,Sn) by relating hybrid-density functional calculation results to experimental data
Year: 2022
Type: article
Abstract: It is crucial to reach a sufficiently high carrier concentration in order to optimize the thermoelectric (TE) material in the development of Mg2X(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-xSnxhas 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.
Source: Journal of Physics Energy
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $2,405
Funders: Deutscher Akademischer Austauschdienst, Deutsche Forschungsgemeinschaft, Ministry of Trade, Industry and Energy, Korea Electrotechnology Research Institute, National Research Council of Science and Technology, Ministry of Science and ICT, South Korea, Korea Institute of Energy Technology Evaluation and Planning
OpenAlex ID: W4224293350