Transport and thermoelectric properties of penta-Sb2X monolayers

Abstract

Thermoelectrics enable direct conversion between heat and electricity, with broad implications for energy and nano-technologies. A key challenge is improving the efficiency of devices, which depends on improved thermoelectric materials. Here we investigate the novel penta-Sb₂X (X = Si, Ge, Sn) 2D materials as potential thermoelectrics, using first-principles methods and Boltzmann transport theory. All the three monolayer structures are semiconducting. Sb₂Si is found to have excellent electric conductivity with high electron mobility of 4010 cm² V⁻¹ s⁻¹. Sb₂Ge and Sb₂Sn have very low lattice thermal conductivity of 2.34 and 0.94 W m⁻¹ K⁻¹. Optimization of the carrier concentration leads to high estimated values of the figure of merit, ZT. We predict the ZT of n-type Sb₂Si to be as high as 4.38, while the ZT values of p-type Sb₂Ge and Sb₂Sn at 700 K are up to 7.37 and 8.0. These results suggest experimental investigation of the semiconducting and thermoelectric properties of these monolayers.