Very high thermoelectric figure of merit 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 MX 2 (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 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 MoS 2 /MoSe 2 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.

Thermoelectric properties of finite two dimensional triangular lattices coupled to electrodes

“…Although (ZT ) max shows a significant value when µ is far away from the LBE, its P F becomes vanishingly small. When compared with the band structures of TMDC and TMO materials calculated by the first-principle method, [19][20][21][22][23] we estimate Γ 0 to be between 5 meV and 15 meV . In this work, we adopte Γ 0 = 10 meV .…”

“…In addition, the thermal conductivity of ITDMs is much smaller than that of their corresponding bulk materials [16][17][18]. Although the thermoelectric properties of ITDMs have been theoretically studied using the first-principle method [19][20][21][22][23], the contact and size effects on the electron transport of their heterostruc-tures are still unclear [24]. Because the unusual transport and optical properties of ITDMs originate mainly from the triangular (hexagonal) lattices (TLs) [25][26][27][28], their potential application to micro power generators and refrigerators calls for an investigation of the thermoelectric properties of finite 2D TLs coupled to electrodes as shown in Fig.…”

Nanostructured and Heterostructured 2D Materials for Thermoelectrics

“…Different kinds of nanoribbon structures have been studied for thermoelectric properties, including graphene nanoribbons (GNRs) of various shapes, [118 sp3-bonded graphane nanoribbons, [136] silicene and germanene nanoribbons, [137]- [139] TMDC nanoribbons, [140 [142] phosphorene nanoribbons [143], and hybrid superlattice nanoribbons. [144 [150], [137] Table 1 lists the reported ZT values of nanoribbons in the existing theoretical studies, which range from 0.1 to ~6 at RT.…”

“…[128], [129] In the superlattice nanoribbons consisting of hybrid 2D crystals ( Fig. 3 (b),(c), and(f), [144] [150] ), the mechanisms of thermal conductivity reduction include the phonon-interface scattering and interference effects.…”

Thermal and Photo Sensing Capabilities of Mono- and Few-Layer Thick Transition Metal Dichalcogenides

“…Layer mixing has shown to both improve power factor of 2D TMD-based thermoelectric devices and reduce the thermal conductance of the device [ 99 ]. Ouyang et al [ 100 ] showed via first principles calculations that hybrid interfaces drastically reduced thermal efficiency in armchair nanoribbons, resulting in extremely high ZT. Through their calculations, they found a MoS 2 /MoSe 2 armchair structure with an optimized ZT value of 7.4, higher than any other thermoelectric material previously calculated or fabricated.…”