Electronic structures and thermoelectric properties of layered BiCuOCh oxychalcogenides (Ch = S, Se and Te): first-principles calculations

The p-type BiCuOCh (Ch = S, Se and Te) compounds exhibit very low lattice thermal conductivities and moderate power factors in the medium temperature range, resulting in high thermoelectric figures of merit. In this paper, we investigated their electronic structures using density functional theory, and discovered that a mixture of heavy and light bands near the valence band maximum is beneficial for good thermoelectric performance, and the Cu 3d-Ch np antibonding state near the valence band edge determines the transport properties of BiCuOCh. Semi-classic Boltzmann transport theory was then used to calculate the Seebeck coefficients, electrical conductivities and power factors of BiCuOCh, and the optimal doping concentrations were estimated based on the predicted maximum power factors. The temperature dependence of the thermoelectric transport properties of BiCuOSe were also estimated and compared with experimental data, with good agreement observed.