Strain Induced Enhancement of Thermoelectric Properties of Monolayer WS2 through Valley Degeneracy

TL;DR

This study demonstrates that applying uniaxial compressive strain significantly improves the thermoelectric performance of monolayer WS2 by increasing the power factor and ZT value, highlighting strain engineering as a promising approach.

Contribution

It provides a detailed theoretical analysis of how mechanical strain affects thermoelectric properties of monolayer WS2, revealing optimal strain conditions for enhancement.

Findings

77% increase in power factor for n-type WS2 under compressive strain

40% increase in ZT value with uniaxial compressive strain at higher temperatures

Uniaxial compressive strain is most effective for enhancing thermoelectric performance

Abstract

Two-dimensional transition metal dichalcogenides show great potential as promising thermoelectric materials due to their lower dimensionality, the unique density of states and quantum confinement of carriers. The effect of mechanical strain on the thermoelectric performances of monolayer WS 2 has been investigated using density functional theory associated with semiclassical Boltzmann transport theory. The variation of Seebeck coefficient and band gap with applied strain has followed the same type of trend. For n-type material the relaxation time scaled power factor(S 2 {\sigma}/{\tau}) increases by the application of compressive strain whereas for p- type material it increases with the application of tensile strain. A 77% increase in the power factor has been observed for the n-type material by the application of uniaxial compressive strain. A decrease in lattice thermal conductivity with the increase in temperature causes an almost 40% increase in ZT product under applied uniaxial compressive strain. From the study, it is observed that uniaxial compressive strain is more effective among all types of strain to enhance the thermoelectric performance of monolayer WS 2 . Such strain induced enhancement of thermoelectric properties in monolayer WS 2 could open a new window for the fabrication of high-quality thermoelectric devices.