Electronic and thermoelectric properties of group IV-VI van der Waals heterostructures

Stacking of two-dimensional materials, in the form of heterostructures, is recently considered as a promising candidate for thermoelectric devices application because it can combine the advantages of the individual 2D materials. The structural, electronic, and thermoelectric properties of group IV-VI [AB/XY (A = Ge, B = O, S, Se, Te, X = C, Sn, Si, Sn, and Y = Se, S)] van der Waals heterostructures are investigated by using first principles calculations. Binding energies and thermal stability showed that all heterobilayers are energetically and thermally stable. Calculated electronic band structure confirmed that IV-VI [AB/XY (A = Ge, B = O, S, Se, Te, X = C, Sn, Si, Sn, and Y = Se, S)] van der Waals heterostructures have indirect with type-II band alignment, which is crucial for separation of photogenerated carriers in solar cell device applications. Transport coefficients including Seebeck coefficient, electrical conductivity and power factor versus chemical potential are calculated by using Boltzmann transport theory which is implemented in BoltzTrap code. Among these heterobilayers, GeO/CSe has considerably large power factor at 800 K, making it more promising for good thermoelectric purposes. These findings pave the way for designing future electronic and thermoelectric devices.