Optimized thermoelectric performance of Bi2Te3 nanowires

Abstract

The structural and electronic properties of a series of stoichiometric Bi2Te3 nanowires with two growth orientations [110] and [210] are studied by using density functional calculations. Our results indicate that the nanowires with [110] orientation are energetically more favorable than those with [210] orientation. All the investigated Bi2Te3 nanowires are found to be semiconducting and the band gaps of [110] nanowires monotonically increase with the decreasing cross-sectional width. For the [210] orientation, however, the band gaps exhibit an interesting width-dependent even–odd oscillation behavior. The electronic transport properties of these nanowires are then evaluated by using the semi-classical Boltzmann theory with the relaxation time approximation. For the phonon transport, the lattice thermal conductivity is predicted by using the non-equilibrium molecule dynamics simulations. Our theoretical calculations suggest that the thermoelectric performance of Bi2Te3 nanowires can be optimized at appropriate carrier concentration with particular orientation and cross-sectional size. The figure of merit (ZT value) can reach as high as 2.3 at 300 K and 2.5 at 350 K for the [210] nanowire with the width N = 5.