Thermoelectric and optical properties of 2D hexagonal Dirac material Be3X2 (X = C, Si, Ge, Sn): A density functional theory study

Abstract

The thermoelectric and optical properties of the 2D hexagonal Dirac material Be3X2 (X=C, Si, Ge, Sn) have been investigated by the first-principles method. These structures have thermoelectric properties superior to graphene. The pristine Be3C2, Be3Si2, Be3Ge2 structures show an extraordinary large Seebeck coefficient, power factor, and ZT∼1 at a low temperature. The maximum thermoelectric efficiency is observed at T∼100–400 K and chemical potential in the range of −0.2 to 0.2 eV. The system performs better when they are n-doped. The optical properties indicate a contribution from both interband and intraband transitions. At a low frequency, the system shows optically metallic and semiconducting characteristics for parallel and perpendicular polarization of incident light, respectively. The materials behave as optically transparent for visible light. A σ–σ∗ interband transition is observed in the UV region of the electromagnetic spectrum. Both π and π+σ plasmon peaks are identified in the infrared and UV regions, respectively. All these intriguing properties of the Be3X2 monolayer may motivate fabricating this material and its application in smart thermoelectric and opto-electronic devices.