Thermoelectric and optical properties of half-Heusler compound TaCoSn: A first-principle study

Based on first-principles simulation and semi-classical Boltzmann transport theory, we investigated the electronic structures and optical and thermoelectric properties of ternary half-Heusler compound TaCoSn. Results indicated that TaCoSn is a narrow-gap semiconductor. The accidental degeneracy of the valence-band maximum resulted in higher p-type Seebeck coefficients than n-type doping, in which the highest value reached 660 μV/K at 900 K. The optimum carrier concentration is approximately 1019 cm−3. In comparison to the experimental results of TaCoSn, we obtained the electrical conductivity and power factor of TaCoSn as a function of temperature and carrier concentrations, respectively. TaCoSn exhibits a large power factor of 10.93 μW cm−1K−2 at 820 K. The calculated electrical conductivity and optical absorption coefficient agree well with the reported experimental data. ZTe shows a relatively high value for carrier concentrations at approximately 1019 cm−3, and the p-type is superior to the n-type. These results indicate that TaCoSn can be used as an important photoelectric and thermoelectric material in the future.