Thermoelectric properties of monolayer and bilayer di boron nitride (di BN)

Abstract

Motivated by the diverse uses of 2D materials in the modern technologies, we explore the temperature dependent thermoelectric properties of monolayer and bilayer di boron nitride. These materials are not still synthesized therefore the formation energy for monolayer and binding energy for bilayer is computed indicating the thermodynamical stability of both systems. The monolayer has a moderate direct band gap of 1.71 eV, while the bilayer possesses a band gap of 0.99 eV. The Seebeck coefficient has no substantial thickness and directional dependency. The Seebeck coefficient for bilayer decreases more as compare to monolayer with increasing temperature and at 600 K it decreases more than 1.7 times as compared to monolayer. However, the bilayer system has a longer carrier relaxation time than the monolayer system. Besides, the p-type relaxation in the ZZ-direction is longer than the n-type for both monolayer and bilayer systems. Consequently, the electrical and electronic thermal conductivities are two times larger in bilayer system. Here, p-type doping system have higher magnitude of electrical and electronic thermal conductivities than n-type doping system. The bilayer system has a greater lattice thermal conductivity than the monolayer. As results, we obtain that the maximum ZT of 0.8 in the bilayer system while the monolayer has a maximum ZT of 0.36 at 600 K with hole doping.