Mechanical, optoelectronic and thermoelectric properties of MoSI: A DFT insights

Abstract

The structural, mechanical, electrical, optical, and thermoelectric properties of MoSI are investigated using DFT and Boltzmann transport theory to evaluate its stability and potential as an environmentally safe energy harvesting material. The calculated lattice parameters are consistent with experimental data, and stability is confirmed using elastic, thermodynamic and phonon calculations. Mechanical analysis revealed that MoSI is ductile at 0 GPa making it suitable for industrial applications. The electronic band structure indicates an indirect band gap with semiconducting nature. At 0 GPa and 10 GPa, the maximum absorption coefficient in the visible region of light spectra are estimated to be 44.61 × 10⁴ cm⁻¹ and 46.13 × 10⁴ cm⁻¹, respectively and the corresponding optical conductivity are 3.85 × 10³ (1/Ωcm) and 4.25 × 10³ (1/Ωcm). The predicted absorption is suggesting that the material is a good absorber and suitable for photovoltaic applications. The effective mass of holes decreases with pressure and hence increases hole mobility and conductivity. The study of pressure effect is not beneficial for thermoelectric transport in MoSI and it is found that power factors decrease with the increase of temperature and pressure. At 0 GPa, the predicted maximum power factor in n–type MoSI at 300 and 900 K are found to be 10.2 and 5.88 mW/mK², respectively. At 0 GPa, the predicted ZT values for n–type MoSI at 300K and 900 K are 0.45 and 0.75, respectively and the corresponding thermal conductivities are 7.25 and 5.38 W/mK. The calculated thermal conductivity is much higher than conventional thermoelectric materials. ZT value is lower due to this higher thermal conductivity, and it can be further improved through the reduction of thermal conductivity by applying suitable strategies such as doping, alloying, or nano-structuring. The predicted interesting results will be able to draw the attention of the scientific community for experimental verification and make lead free MoSI as potential in efficient energy harvesting devices.