First-principles calculations of thermoelectric transport properties in WSe2/SnS2 bilayer heterostructure

Recently, the experimentally fabricated van der Waals bilayer heterostructure of WSe2/SnS2 was found to possess excellent electronic and optoelectronic applications in p-n diode, photodetector and transistor (Yang et al., Nat. Commun., 2017, 8, 1906; Zhou et al., Adv. Mater., 2018, 30, 1703286). However, the thermoelectric properties have not been studied. Here, using the first-principles calculations and Boltzmann transport theory, we present a study on the thermoelectric transport properties for the WSe2/SnS2 bilayer heterostructure. The results show that the n-type power factor of WSe2/SnS2 bilayer heterostructure is greatly improved compared to that of WSe2 monolayer. The calculated phonon relaxation time and three-phonon scattering phase space indicate that the low-frequency optical branches overlapping with the acoustic modes in WSe2/SnS2 bilayer heterostructure provides more scattering channels, resulting in a lower lattice thermal conductivity, 22.69 W m- 1 K-1 at room temperature, which is smaller than that of monolayer WSe2. The optimized n-type thermoelectric ZT value at 800 K for WSe2/SnS2 can reach 1.16, which indicate the bilayer heterostructure WSe2/SnS2 is predicted to be promising for thermoelectric applications.