Excellent thermoelectric transport performance in semiconducting hhk-silicene

Abstract

Unlike graphene-like silicene, a recently reported hybrid honeycomb-kagome (hhk) silicene is a semiconductor instead of a gapless Dirac-cone, which has great potential applications in semiconducting devices. Here, using first-principles calculations combined with Boltzmann transport equation, we find that hhk-silicene has high Seebeck coefficient and power factor as arising from the moderate band-gap and low effective mass. Meanwhile, compared to graphene-like silicene, the soften acoustic branches and enhanced anharmonicity lead to the extremely low lattice thermal conductivity, i.e., 0.68 W mK−1 at 300 K. Calculated thermoelectric figure of merit reaches 1.98 at 300 K, which is a recorded value among two-dimensional materials, indicating the potential of hhk-silicene as a thermoelectric material.