First-principles Study On Thermoelectric Properties Of Two-dimensional MSSe

In telecommunication devices,the heat of the chip increases the power consumption.Two-dimensional thermoelectric materials can convert thermal energy directly into electrical energy.When a thermoelectric device acts on a chip,it can collect the heat generated during the use of the chip,so it is valuable and meaningful to explore the materials with high thermoelectric conversion efficiency.Based on Density Functional Theory(DFT),the electronic structure of the material is calculated,and then the thermoelectric properties of the material are analyzed to explore the potential thermoelectric value of two-dimensional transition metal-sulfur compounds with Janus structure.The main research works of this paper are as follows:1.The electronic structure and thermoelectric properties of singlelayer Janus MSSe,MS2,and MSe2(M=Mo,W)were investigated in this study.The structural models of the unit cells were constructed and their stable structures were obtained through relaxation.The band structures and electronic density of states of the materials were calculated,and the band gaps of single-layer Janus MSSe(M=Mo,W)were found to be between those of single-layer MS2 and single-layer MSe2,both of which are direct bandgap semiconductors.The thermoelectric properties of the material system were calculated at 300 K,including electrical conductivity,thermal conductivity,Seebeck coefficient,and ZT value,and the effects of each parameter on the thermoelectric performance were analyzed.The ZT values of single-layer Janus MoSSe and WSSe were found to be 0.68 and 0.81,respectively.The ZT values of single-layer Janus MSSe(M=Mo,W)were found to be between those of MS2 and MSe2,demonstrating that Janus MSSe(M=Mo,W)is a potential thermoelectric material with application value.2.The electronic structure and thermoelectric properties of MSSe(M=Ti,Zr,Hf,V,Nb,Ta,Re)were calculated.The band structures and electronic density of states show that single-layer TiSSe,ZrSSe,and HfSSe are all indirect bandgap semiconductors,while single-layer VSSe,TaSSe,and ReSSe have bandgaps,but the Fermi level intersects with the bands,showing some metallic properties.Single-layer NbSSe has no bandgap.The thermoelectric properties of single-layer Janus MSSe were calculated at 300K,and the Seebeck coefficients,electrical conductivities,and thermal conductivities were analyzed to explore their influence on thermoelectric properties.At 300K,NbSSe has a small Seebeck coefficient,a large thermal conductivity,and a ZT value of only about 0.1.The other materials calculated experimentally have good thermoelectric properties,with ZT values ranging from 0.9 to 2.5,making them potential thermoelectric materials.