First-principles investigation of CuBiSeCl2: a quaternary halide chalcogenide material for advanced optoelectronic and thermoelectric energy harvesting and conversion technologies

Abstract

In response to the growing interest in multifunctional materials for energy conversion devices, CuBiSeCl₂ is systematically investigated as a quaternary halide chalcogenide with significant potential for both optoelectronic and thermoelectric applications. Utilizing density functional theory (DFT) and the semiclassical Boltzmann transport theory-based full-potential linearized augmented plane wave (FP-LAPW) technique, this study investigates the electronic, thermoelectric, optical and mechanical properties of CuBiSeCl₂. Structural optimization shows that the material crystallizes in an orthorhombic phase and the calculated elastic constants meet the Born stability criterion. Electronic calculations show that there is a direct band gap of about 0.737 eV at the high-symmetry Γ point. In contrast, anisotropy in the optical response shows that the crystal has a layered structure. The optical response also demonstrates strong absorption in the visible and UV range with a high refractive index, and a dielectric response, where the absorption spectrum is initiated near ∼0.8 eV and exceeds 1.5 × 10⁵ cm⁻¹ above 2 eV, highlighting its potential as an efficient light-harvesting material. Thermoelectric investigations indicate that CuBiSeCl₂ exhibits promising performance, where the Seebeck coefficient and electrical conductivity go up from 300 K to 600 K, which brings zT up to about 0.52. In contrast, zT reaches around 0.88 for temperatures ranging from 600 K to 900 K. However, calculated mechanical properties, such as bulk and shear moduli, show that CuBiSeCl₂is moderately stiff, while the Poisson ratio (0.304) and Pugh ratio (2.215) indicate its mechanical stability with moderate ductility. The average speed of sound is 2449.28 m s⁻¹, and the elastic Debye temperature is ∼257 K. Overall, these results show that CuBiSeCl₂ is a material with high potential for sustainable energy harvesting and conversion technologies.