New record of high ZT found in hybrid transition-metal-dichalcogenides

Abstract

The search for thermoelectrics with higher figures of merit (ZT) will never stop due to the demand of heat harvesting. Single layer transition metal dichalcogenides (TMD), namely MX2 (where M is a transition metal and X is a chalcogen) that have electronic band gaps are among the new materials that have been the focus of such research. Here, we investigate the thermoelectric transport properties of hybrid armchair-edged TMDs nanoribbons, by using the nonequilibrium Green's function technique combined with the first principles and molecular dynamics methods. We find a ZT as high as 7.4 in hybrid MoS2/MoSe2 nanoribbons at 800K, creating a new record for ZT. Moreover, the hybrid interfaces by substituting X atoms are more efficient than those by substituting M atoms to tune the ZT. The origin of such a high ZT of hybrid nanoribbons is the high density of the grain boundaries: the hybrid interfaces decrease thermal conductance drastically without a large penalty to electronic conductance.