Unveiling the potential of rare-earth XCuSeO (X = Dy, Sm) oxychalcogenides for high-performance UV shielding and photovoltaics

Abstract

With the density functional theory and the Tran-Blaha modified Becke-Johnson potential, the work explores the structural, electronic, optical, and thermoelectric features of DyCuSeO and SmCuSeO compounds. The thermodynamic stability of both compounds is demonstrated by formation energy predictions, with SmCuSeO displaying slightly stronger internal bonding because of its lower cohesive energy (−4.32 eV/atom compared to −4.12 eV/atom for DyCuSeO). Electronic band structure studies have identified direct band gaps; DyCuSeO has a greater band gap of 2.38 eV than SmCuSeO (0.41 eV). The valence band is significantly impacted by Cu-d, Se-p, and O-p orbitals, according to the density of states (DOS) study, but the conduction band is also affected by Dy/Sm-f states. Band separation is increased by DyCuSeO's larger spin-orbit coupling effects. DyCuSeO (ε₁(0) = 6.0, n(0) = 5.5), optical study shows that SmCuSeO has a greater static dielectric constant (ε₁(0) = 9.0) and refractive index (n(0) = 3.0), implying stronger electronic polarization. With bulk plasmon resonance energies at 17.5 eV (DyCuSeO) and 17.0 eV (SmCuSeO), both materials exhibit important absorption in the visible and near-infrared spectrum. Based on thermoelectric calculations, electronic thermal conductivity rises with temperatures, reaching 1.35 × 10¹⁴ W/mK for DyCuSeO and 1.18 × 10¹⁴ W/mK for SmCuSeO at 600 K. They are interesting candidates for thermoelectric applications as their figure of merit increases along the temperature, approaching 0.133 in DyCuSeO and 0.129 in SmCuSeO at 600 K. DyCuSeO and SmCuSeO have good electronic, optical, and thermoelectric characteristics that make them appropriate for energy-harvesting and optoelectronic applications.