Janus 2d B2p6: A Promising Anisotropic Thermoelectric Material with High Power Factor

Abstract

A two-dimensional (2D) material with high thermoelectric (TE) performance is of great interest for the energy conversion device. In this study, by using the first-principles calculations, we show that the Janus 2D B2P6 has an extremely high TE power factor of 0.10 and 0.17 W/mK2 for p-type and n-type at room temperature, respectively, which are higher than that of conventional 2D TE materials. The origin of the high TE power factor of the n-type comes from both convergence of the conduction bands and high carrier mobility up to 1386 cm2V-1s-1 in the zigzag direction. We also investigate lattice thermal conductivity, κph, of B2P6 by using the Boltzmann transport theory with phonon-phonon interaction. With κph of 41.45 and 133.3 W/mK for the armchair and zigzag directions, respectively, the optimized values of the TE figure of merit are up to 0.7 at 900 K. Moreover, the Janus 2D B2P6 exhibits anisotropic mechanical properties, in which the ideal strength of B2P6 is 10.7 and 18.63 N/m for the armchair and zigzag directions, respectively. Thus, our results suggest that the Janus 2D B2P6 is the potentially promising flexible anisotropic TE material.

Keywords: 2D Janus materials, density functional theory, the Boltzmann transport theory, thermoelectricity, ideal strength.