Electronic and thermoelectric properties of chalcopyrite compounds Cu2(XY)S4 (X = Zn, Cd and Y = Sn, Pb): first-principles study

Abstract

In this work, we have presented a correlation between the bond length and electronic properties of Cu2XYS4 (X = Zn, Cd and Y = Sn, Pb) from the first-principles calculation. Lattice parameters, bond length, electronic structure and partial density of state are determined by using density functional theory based on generalized gradient approximation. Further, we have calculated the thermoelectric properties in relation to electronic band energy from the Boltzmann transport theory. The room temperature (300 K) optimum value of electrical conductivity is found to be 5 × 105 S m for Cu2CdPbS4, Seebeck coefficient is 320 µV/K for Cu2ZnSnS4, thermal conductivity is 0.12 W/m K for Cu2ZnSnS4, and the optimal figure of merit is 0.68 for Cu2ZnSnS4. This study shows that the stronger interaction between (Zn, Sn) and S atoms leads to the combination of heavy and light bands in the valence region which improves the thermoelectric performance. It is concluded that the Cu2ZnSnS4 and Cu2CdSnS4 compounds can be considered as potential materials for thermoelectric applications due to their strong bonding interactions.