Understanding the electronic and phonon transport properties of thermoelectric material BiCuSeO: a first-principles study

摘要

Using first-principles pseudopotential method and Boltzmann transport theory,we give a comprehensive understanding of the electronic and phonon transportproperties of thermoelectric material BiCuSeO. By choosing proper hybridfunctional for the exchange-correlation energy, we find that the system issemiconducting with a direct band gap of ~0.8 eV, which is quite different fromthose obtained previously using standard functionals. Detailed analysis of athree-dimensional energy band structure indicates that there is a valleydegeneracy of eight around the valence band maximum, which leads to a sharpdensity of states and is responsible for a large p-type Seebeck coefficient.Moreover, we find that the density of states effective masses are much largerand results in very low hole mobility of BiCuSeO. On the other hand, we findlarger atomic displacement parameters for the Cu atoms, which indicates thatthe stronger anharmonicity of BiCuSeO may originate from the rattling behaviorof Cu instead of previously believed Bi atoms.