First-principles study of structural, electronic, optical, and thermoelectric properties of BaTmSe2 (TM = Fe, Co, and Ni) for optoelectronic devices

In this study, the structural, electrical, optical, and thermoelectric properties of BaTMSe2 (TM = Fe, Co, Ni) are investigated using DFT within the Wien2k software. For electronic band structure and thermal characteristics, the PBE + GGA approximation method is employed, while the density of state analysis is used to ascertain the contributions and polarization of electronic states. The compounds exhibit unsymmetrical behavior of majority charge carriers in spin up and down, and Fe, Co, and Ni atoms contribute most to TDOS and PDOS via hybridization with Se and Ba atoms. The materials show semiconductor characteristics, with BaFeSe2 having the largest peak on the optical properties graph. BaXSe2 has a refractive index higher than, and BaFeSe2 and BaCoSe2 have separate peaks in their extinction coefficients within the visible spectrum. The optical properties graph shows that BaFeSe2 has the highest peak at 1eV and that all compounds exhibit a comparable pattern as they move towards greater energies. The negative value in the real part expresses that the electromagnetic radiation is partially reflected from the surface of the material and shows semiconductor behaviour. The extinction coefficient of BaFeSe2 and BaCoSe2 have sharp peaks in the visible energy range. The refractive index of BaXSe2 (X = Fe, Co, Ni) is higher than 1 due to the interplay of electrons with the substance slowing down photons. The highest peak of the refractive index is at 0.1 eV, 0.2 eV, and 0.3 eV for BaFeSe2, BaCoSe2, and BaNiSe2, respectively. The trend gradually declines in higher energies before becoming constant after 4 eV. Additionally in this article, thermal properties of BaTMSe2 (TM=Fe, Co, Ni) like the Seebeck coefficient, thermal conductivity, magnetic susceptivity, figure of merit, and specific heat capacity are investigated, and it significantly enhances the properties of compounds having a rapid response to charge mobility.