Thermoelectric Performance Of Two Materials From The First-principles Study

Energy is the basis for people of survival and developments,and the world`s demand for energy supply is causing a dramatic escalation of social and political unrest. The environmental issues is becoming increasingly alarming due to the combustion of fossil fuel. These problems compel us to search for sustainable energy with not only high efficiency but also environmental friendship. Thermoelectric materials are a kind of new energy material that can convert energy between thermal energy and electrical energy directly. And the merits of thermoelectric material lie in the gas-free emissions, the maintenance-free operation without any moving parts, the solid-state operation, no damage to the environment and a long life-span of reliable operation.We calculated the electronics?phonon and thermoelectric properties of Co Nb Sn and single-layered Ge Se sheet by using first-principles calculation and semiclassical Boltzmann transport equation:By analyzing the properties of Co Nb Sn alloy, we find that the maximum value of the seebeck coefficient is 1652 ?KV, and the transport properties of P-type Co Nb Sn are better than those of N-type one in the temperature range of 300 K to 900 K, which is mainly reflected in the higher power factor. The power factor for Co Nb Sn can reach2.23×1012WK-1m-1s-1 for P-type doping at 900 K, corresponding to the chemical potential-0.59 e V, and the power factor for Co Nb Sn can reach 1.35×1012WK-1m-1s-1 for N-type doping at 900 K, corresponding to the chemical potential 0.62 e V.By analyzing the properties of single-layered Ge Se sheet and using the Sheng BTE software, we obtain the lattice thermal conductivity of single-layered Ge Se sheet, which is6.36 KW m along the y-axis direction and 5.49 KW m along the x-axis direction at room temperature. We also find that the best transport direction is the x-axis direction, and the ZT of single-layered Ge Se sheet could reach 1.51 at 700 K along this direction,corresponding to the carrier concentration 1.04×1020cm-3, which is N-type doping. The maximum ZT for p-type doping is 0.98. This shows that the thermoelectric transport properties of N-type single-layered Ge Se sheet are better than those of P-type one. The ZT values calculated in this work approach commercial demands, indicating great potential of the single-layered Ge Se sheet as a 2D high performance thermoelectric material.