Abstract
In this work, we have studied thermoelectric properties of monolayer and fewlayer MoS2 in both armchair and zigzag orientations. Density functional theory (DFT) using non-equilibrium Green’s function (NEGF) method has been implemented to calculate the transmission spectra of mono- and fewlayer MoS2 in armchair and zigzag directions. Phonon transmission spectra are calculated based on parameterization of Stillinger-Weber potential. Thermoelectric figure of merit, ZT, is calculated using these electronic and phonon transmission spectra. In general, a thermoelectric generator is composed of thermocouples made of both n-type and p-type legs. Based on our calculations, monolayer MoS2 in armchair orientation is found to have the highest ZT value for both p-type and n-type legs compared to all other armchair and zigzag structures. We have proposed a thermoelectric generator based on monolayer MoS2 in armchair orientation. Moreover, we have studied the effect of various dopant species on thermoelectric current of our proposed generator. Further, we have compared output current of our proposed generator with those of Silicon thin films. Results indicate that thermoelectric current of MoS2 armchair monolayer is several orders of magnitude higher than that of Silicon thin films.
Highlights
Compared to the research progress in its electronic and mechanical characteristics[22,23,24], thermoelectric (TE) properties of MoS2 have not been widely studied
It has been reported that MoS2 has anisotropic thermal properties[32], which provides another degree of freedom to optimize TE conversion performance
The computational model used in this paper is based on self-consistent density functional theory (DFT) using non-equilibrium Green’s function (NEGF) method[39,40] implemented in QuantumWise ATK software package
Summary
Compared to the research progress in its electronic and mechanical characteristics[22,23,24], thermoelectric (TE) properties of MoS2 have not been widely studied. Bi2Te3 and the similar alloys have played a main role in the application of thermoelectric devices It is well-known that efficiency of thermoelectric conversion can be evaluated by a dimensionless figure of merit ZT = GS 2T/(κe + κ ph), in which G, S, ke, kph and T are electrical conductance, Seebeck’s coefficient, electronic contribution to thermal conductance, phonon contribution to thermal conductance and absolute temperature, respectively[26]. In order to have a high ZT, it is desirable to have a high electrical conductance and large Seebeck’s coefficient and low thermal conductance These parameters mainly depend on the intrinsic properties of materials and they are generally coupled with each other. Transmission coefficient and phonon thermal conductance of zigzag orientation is higher than those of armchair with the same number of layers Their effect on ZT has been studied in this work. The comparison indicates that proposed MoS2 generator exhibits superior TE conversion efficiency
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