Exploring the electronic, optical, and thermoelectric features of BaXCu₃Se₄ (X = In, Tl) quaternary chalcogenides: first-principles study

Abstract

The tunable optical characteristics and superior thermal stability of Indium and Thallium-based quaternary chalcogenides are significant. We studied the intricate relationship between the optoelectronic, and thermoelectric features of notable BaXCu3Se4 (X = In, Tl) quaternary chalcogenides. Both the maximum of the valence band and conduction band coincide at the Γ-point, confirming these materials as direct band gap materials. By substituting Indium for thallium, the calculated band gap decreases from 0.71 eV to 0.53 eV. These anions have a considerable impact and contribute to a decrease in the energy gap via valence electrons. Partially filled d orbitals of copper play an important role in electronic states at the Fermi level. The components of the complex dielectric function, as well as other important optical parameters, are examined and analyzed to identify their potential use in optoelectronic applications. The ε1(ω) becomes negative at 6.32 eV, suggesting that the medium is reflecting all of the incident light. Thallium affects the absorption spectrum because it changes the density of states and electronic transitions. The absorption spectra indicated that the material absorbs in the visible and near-UV parts of the spectrum, which is fascinating and might have applications in optoelectronics. The investigated materials are suitable for thermoelectric devices as evidenced by significant and notable thermoelectric properties. Because the Seebeck coefficient is negative, most charge carriers, typically electrons, flow from the higher temperature area to the lower temperature region. At both low and high temperatures, thallium is accountable for BaTlCu3Se4's higher thermal conductivity than BaInCu3Se4 material.