Insight into the optoelectronic and thermoelectric properties of novel LaSeM (M = Cl, F) chalcohalide semiconductors: ab-initio study

Abstract Chalcohalide materials demonstrate extraordinary thermal capacity and adjustable optoelectronic properties. Here we used the density functional theory and studied the structural, electronic, optical, and thermoelectric properties of novel LaSeM (M = Cl, F) ternary chalcohalides. The formation energies of LaSeCl and LaSeF were determined to be −2.21 (eV/f. u) and −2.32 (eV/f. u), respectively. The cohesive and formation energies well impacted the stable nature and phase transition features of these materials. The studeid materials were predicted to have a direct band gap nature as observed from the band structure investigation. For LaSeCl material, the projected band gaps as determined by the PBE-GGA and TB-mBJ potentials are 1.41 eV and 1.95 eV, whereas for the LaSeF the values are 1.72 eV and 2.36 eV, respectively. The complex dielectric function along with the other noteworthy optical parameters are computed for their potential applications in optoelectronics devices. The spectral region with a negative value of ε 1 ( ω ), suggests these materials to have a metallic behavior. The predicted negative Seebeck coefficient values throughout the temperature range for LaSeCl and LaSeF materials display n-type conduction behavior. LaSeF exhibits more noticeable temperature-dependent improvements in electrical conductivity compared to LaSeCl.