Strain induced valley degeneracy: a route to the enhancement of thermoelectric properties of monolayer WS₂

Abstract

Two-dimensional transition metal dichalcogenides show great potential as promising thermoelectric materials due to their lower dimensionality, the unique density of states and

Low lattice thermal conductivity and its role in the remarkable thermoelectric performance of newly predicted SiS2 and SiSe2 monolayers

“…eV/atom respectively which is in good agreement with previous calculation 43 . Our calculated values are comparable with other 2D materials such as graphene (8.00 eV/atom) 52 , silicene (3.94 eV/atom) 53 , phosphorene (3.44 eV/atom) 54 , WS2 (2.87 eV/atom) 39 and Be2C monolayer (4.84 eV/atom) 55 which suggest very good structural stabilities of the considered structures.…”

“…The thermoelectric properties have been calculated using BTE as implemented in BoltzTrap 50 code considering constant scattering time approximation (CSTA), which enables temperature and doping dependent electronic and thermal transport properties calculations assuming scattering time is unchanged with the energy. The details of the thermoelectric properties calculation can be found in our previous work 39 . The linearized phonon Boltzmann equation was used to calculate the 𝑘 𝑝ℎ in Phono3py 51 interfaced to QE package 47 .…”

“…So, for both materials S and PF for p-type is much higher than that of n-type which suggest p-type doping is more effective than n-type to get optimum thermoelectric performance in these monolayers. In contrast, n-type doping is preferable for thermoelectric application in popular two-dimensional TMDCs thermometric materials such as MoS2 61 and WS2 39 . SiSe2 monolayers.…”

“…Theoretical and experimental investigation on well-known TMDCs MoS2 30 and WS2 31 monolayer suggest that in spite of high PF, the ZT is limited because of relatively high value of 𝑘 𝑝ℎ as compared to other TMDCS such as PtX2 32 , HfX2 33,34 , SnX2 [35][36][37] and ZrX2 38 (where x = S and Se), whereas ultralow values of 𝑘 𝑝ℎ in PtX2, HfX2, SnX2 and ZrX2 result very high ZT greater than unity. Various efforts such as strain engineering [39][40][41] and chemical doping 42 have been attempted for the enhancement of thermoelectric efficiency. Although these two-dimensional layered materials showed good thermoelectric behavior but there are still some shortcomings to achieve high efficiency in thermoelectric power generation.…”

Strain and electric field-modulated indirect-to-direct band transition of monolayer GaInS2

“…However, band modulation is required for various device applications, which can be done by applying strain or external electric eld on 2D materials. By strain engineering, enhancement of materials properties has been reported 25 .…”