Two-dimensional boron monochalcogenide monolayer for thermoelectric material

Abstract

Monochalcogenide materials have outstanding potential for thermoelectric applications. In this paper, we have investigated the electronic structure, vibrational and transport properties of boron chalcogenide BX (X = S, Se, Te) materials. Electronic structure calculations show that each material has an indirect bandgap in the range of 2.92 eV to 1.53 eV. The presence of positive phonon frequencies shows the dynamic stability of the materials. We also calculated the mobility (m) and relaxation time (t) of all the materials. Additionally, as the 2D boron monochalcogenide BX (X = S, Se, Te) materials have superior carrier mobility, they have a small effective mass of electrons. The 1T and 2H phases of the BS monolayer have superior electron carrier mobilities of 11 903.07 and 11 651.61 cm² V⁻¹ s⁻¹. We also found that for the low and mid-temperature range (200–450 K), all the materials have a high electronic figure of merit ZT_e nearly equal to 1, with the exception of the BS 2H phase. The BSe 1T phase has high ZT_e = 1.022, which is the maximum across all the materials. These theoretical investigations suggest that boron monochalcogenide BX (X = S, Se, Te) materials have promise for applications in high-performance thermoelectrics.