Effects of stresses on the thermoelectric properties of In4Se3

Thermoelectric research has made great progress in recent years, but large-scale applications of thermoelectric materials are still far from realisation. Finding ways to improve their thermoelectric performance remains an important challenge. In4Se3 stands out as a material with exceptional thermoelectric performance and notably low thermal conductivity. However, its ZT value is constrained by the power factor. We employed first principles calculations to assess the impact of stresses on the structural and electronic properties of In4Se3. Independent elastic constants, bulk modulus B, shear modulus G, and Young's modulus E all exhibit an increase with increasing stresses. The B/G value of In4Se3 increased from 1.75 at 0 GPa to 2.12 at 5 GPa, indicating that the toughness of the material gradually increased. The calculated phonon curves show that In4Se3 demonstrates mechanical stability under both tensile stress (-1 GPa) and compressive stress (1-5 GPa) conditions. The calculated electronic structure reveals that, with increasing compressive stresses, the band gap in the PBE potential decreases from 0.15 eV at 0 GPa to 0.01 eV at 5 GPa. Similarly, in the HSE06 potential, the band gap decreases from 1.00 eV at 0 GPa to 0.73 eV at 5 GPa. Thermoelectric transport parameters of the material are calculated by solving the semi classical Boltzmann transport equation. Increasing the compressive stresses can increase both the Seebeck coefficient and the conductivity. Consequently, the power factor of In4Se3 has been greatly improved. At 700 K, the power factor can be increased by 19% in the optimal carrier range. Therefore, this study offers a theoretically viable approach to enhance the thermoelectric performance of In4Se3.