First-principles study of optoelectronic and thermoelectronic properties of the ScAgC half-Heusler compound

Abstract

In this paper, we have presented a theoretical study in the context of photovoltaic (PV) and thermoelectric (TE) applications of ScAgC. The electronic, optical, and thermoelectric properties have been investigated systematically using DFT and semi-classical Boltzmann transport theory. DFT calculates a direct band-gap of ∼0.47 eV, whereas the G 0 W 0 method estimates a band-gap of ∼1.01 eV. We used parabola fitting to estimate the effective mass (m *) values for bands B1-B4 at Γ-point, which are ∼−0.087 (−0.075), ∼−0.17 (−0.27), ∼−0.17 (−0.27), and ∼0.049 (0.058) along the Γ-X (Γ-L) direction, respectively. We have investigated phonon dispersion and thermal properties. Furthermore, the properties of optoelectronics are calculated and analysed over a range of photon energies from 0 to 10 eV. The optical conductivity σ(ω), refractive index , and dielectric function ϵ(ω) show strong optical transitions in the visible region. The lowest calculated value of reflectivity r(ω) is ∼0.24 at ∼4.7 eV, and the highest calculated value of absorption coefficient α(ω) is ∼1.7 × 106 cm−1 at ∼8.5 eV. At 300 K, we have expected a maximum solar efficiency (SLME) of ∼33% at ∼1 μm of thickness. The lattice part of thermal conductivity κ ph shows a maximum value of ∼3.8 Wm −1 K −1 at 1200 K. At 1200 K, for electron doping of ∼3.9 × 1021cm−3, the maximum value of S 2 σ/τ is ∼145 × 1014 μ WK−2 cm−1 s−1, while for hole doping of ∼1.5 × 1021cm−3, it is ∼123 × 1014 μ WK−2 cm−1 s−1. The highest ZT at 1200 K is expected to be ∼0.53, whereas the optimal %efficiency is predicted to be ∼8.5% for cold and hot temperatures of 300 K and 1200 K, respectively. The collected results suggest that the ScAgC compound would be a potential candidate for renewable energy sources such as solar cell and TE applications.