Low-dimensional materials have an excellent prospect in thermoelectric applications. We have investigated the geometric structure, band structure, and electron transport properties of hydrogenated and pure multilayer silicene using first-principle calculation within density functional theory. The Boltzmann theory for electrons under relaxation time approximation was employed to obtain the Seebeck coefficient and electrical conductivity. The calculations of electron relaxation time were based on the deformation potential theory. Hydrogenation can effectively change the band structure of multilayer silicene. The simulation results reveal a big difference in the relaxation times between pure and hydrogenated structures. And, this difference decreases as the layer number $n$ increases. The anisotropy of hydrogenated structures leads to a high thermoelectric performance along the armchair direction. When the layer number $n$ is larger than 2, hydrogenation can greatly improve the electronic figure of merit $Z{T}_{\mathrm{e}}$ of multilayer silicene. The band structure can also be engineered by adjusting the hydrogenation ratio. A band of 0.33 eV can be achieved when the hydrogenation ratio is 66.7%. By combining the adjustment of the hydrogenation ratio with the method of changing the geometric structure, a high thermoelectric performance can be achieved in multilayer silicene. The results provide a viable strategy for thermoelectric optimization in multilayer silicene, and can be potentially extended to the thermoelectric optimization of other two-dimensional materials.

• Received 8 February 2019
• Revised 11 May 2019

DOI:https://doi.org/10.1103/PhysRevB.99.235428