Correlations in Cu-based chalcogenides for optical and transport performance in sustainable technologies: First-principles calculation

Abstract

Researchers have taken an interest in semiconductor chalcogenide compounds because of the wide variety of physical properties that these compounds exhibit. The study of the elastic, optical, and thermoelectric properties of Cu-based AlCu₃PbX₄ (X = S, Se, Te) chalcogenides has been conducted using the PBEsol-mBJ scheme within the framework of Density Functional Theory (DFT). The calculated band structure shows that both direct band gaps are semiconducting (1.0 eV–1.8 eV) as the valence band maximum (VBM) is primarily formed of Cu-d states. The conduction band minima (CBM) is primarily Al/Pb-s, p states. The optical and thermoelectric properties of AlCu₃PbX₄ (X = S, Se, Te) have been thoroughly examined using first-principles calculations. The dielectric function analysis reveals a static dielectric constant of 5.5–8.6, with significant peaks in the visible and ultraviolet regions. The refractive index varies between 2.0 and 2.8, while the absorption coefficient reaches a maximum of 180 cm⁻¹ in the UV range, indicating strong optical absorption. These materials exhibit high reflectivity (>40 %) at photon energies exceeding 4 eV and a plasmon energy loss peak near 13 eV. Zener anisotropy factor deviating from 1, indicates anisotropic elastic behavior, while Pugh’s ratio (B/G), which is less than 1.75 for these materials, further classifies them as brittle in nature. Thermoelectric investigations using Boltztrap show high Seebeck coefficients of 250–400 µV/K, power factors of 2.0 × 10¹⁰ to 8.0 × 10¹⁰ W/mK²s, and impressive dimensionless figure-of-merit (ZT) values of 0.1–1.1 at temperatures (∼800 K), demonstrating their potential for high-efficiency thermoelectric applications. These findings suggest that AlCu₃PbX₄ compounds are promising candidates for energy-efficient thermoelectric and optoelectronic devices.