First-principles study of structural stability, optoelectronic and thermoelectric properties of Cu-based halide perovskites RbCu2X3 (X= Cl, Br, I)

This study employs first-principles calculations using the full potential linearized augmented plane wave (LAPW) approach as integrated in WIEN2k package on emerging copper-based halide perovskites RbCu 2 X 3 (X= Cl, Br, I). These are direct wide bandgap semiconducting materials showing potential applications through the analysis of various optical parameters, like dielectric constant (ε(ω)), optical absorption coefficient (α(ω)), reflectivity (R(ω)), and refractive index (n(ω)) spectra. The optical absorption coefficient was found to be on the order of 10 5 cm −1 and indicates strong photon absorption suitable for UV–visible optoelectronics. Thermal stability was examined using the Gibbs2 code, while their mechanical stability was confirmed through the computation of elastic constants and all compositions were found to be both thermally and mechanically stable. To explore the thermoelectric applications, the transport coefficients were calculated using the semi-classical Boltzmann transport approach implemented in the BoltzTraP package. Thermoelectric performance of these compounds was evaluated by analyzing their electrical conductivity (σ/τ), electronic thermal conductivity (κ e /τ), Seebeck coefficient (S). The high Seebeck coefficient values, combined with low electronic thermal conductivity, highlight their promising electronic transport characteristics for thermoelectric applications. All observed trends are consistent with the available experimental and theoretical observations.