Thermoelectric performance of MX2 (M = Mo,W; X = S,Se) monolayers

Abstract

Using ab-initio method and ballistic transport model, we study electron and phonon energy dispersion relations of monolayer transition-metal dichalcogenides: MoS2, MoSe2, WS2, and WSe2. Their electron and heat transports as well as their thermoelectric properties are also studied under linear response regime with different doping types, crystal orientations, and temperatures. Our results show that electron and phonon transports are not very sensitive to crystal orientations because the differences between group velocity and transmission of these carriers along different transport directions are not significant. Furthermore, as temperature increases, first peak values of thermoelectric figure of merit (ZT1st peak) increase linearly except for monolayer n-type WSe2/MoSe2 and p-type WS2, which have higher increasing rates when temperature is high due to the electron transport contribution from an additional valley. Among these various conditions, the results show that all monolayers have similar ZT1st peak at low temperatures below 100 K, and p-type monolayer MoS2 has the largest ZT1st peak at room temperature while n-type WSe2 has the largest ZT1st peak at high temperatures.

Electronic and thermoelectric properties of few-layer transition metal dichalcogenides

“…55 Without the inclusion of spin-orbit interaction our values of the ballistic ZT for the monolayer TMDC materials are consistent with a prior report on the monolayer thermoelectric properties of these TMDC materials. 23 Our calculations show that without the inclusion of spin-orbit interaction the peak n-type ZT values for all materials continue to occur at thicknesses above a single monolayer. The peak n-type ZT values (and corresponding layer thicknesses) without spin-orbit interaction for MoS 2 , MoSe 2 , WS 2 and WSe 2 are 1.38 (t=3L), 1.52 (t=2L), 1.13 (t=4L) and 1.28 (t=2L).…”

“…16,17,23 In the linear response regime, the electronic conductivity (σ), the electronic thermal conductivity (κ e ), and the Seebeck coefficient (S) are expressed as 32,33…”

Graphene versus MoS2: A short review

“…Although there are currently no measurements on the thermal conductivity of SLMoS 2 , this topic has attracted increasing interest in the theoretical community [151][152][153]. In 2010, Varshney et al performed force-field-based MD simulations to study the thermal transport in SLMoS 2 [151].…”

“…In 2010, Varshney et al performed force-field-based MD simulations to study the thermal transport in SLMoS 2 [151]. In 2013, two first-principles calculations were performed to investigate the thermal transport in SLMoS 2 in the ballistic transport regime [152,153]. The predicted roomtemperature thermal conductivity in the ballistic regime was below 800 W·m −1 ·K −1 for a 1.0 µm long SLMoS 2 sample [153].…”

Potential 2D thermoelectric materialATeI (A= Sb and Bi) monolayers from a first-principles study

“…To design high-performance ther- moelectric devices, the thermoelectric properties related with these 2D materials have also been investigated. Based on ab-initio method and ballistic transport model,the thermoelectric properties of MX 2 (M=Mo, W; X=S, Se) monolayers have been studied 13 , and a maximum ZT of monolayer MoS 2 is up to 0.5 at room temperature. For monolayer MoS 2 , a value of S as 30 mV/K has been reported experimentlly 14 .…”