Theoretical Investigation Of Optimizing Thermoelectric Performance Of Bi₂Te₃ Nanowires

Thermoelectric materials are a kind of function materials, which can realize the direct transformation between heat and electricity through the carrier movement of solids. They are manufactured into tiny semiconductor devices with light weight and small volume, for the advantages of non-toxic, non-pollution, long efficient work circle etc. Thermoelectric materials have good application prospects in many fields, like computer technology, space technology, superconducting technology and microelectronic technology.The Bi2Ti3 materials have relatively good thermal performance and highly anisotropic band structure near the normal temperature. Hence, they are considered as a hot topic of low dimensional thermoelectric materials, and their theoretical research is also in constant development and improvement. Based on the existing theoretical study of Bi2Te3 nanowires, this paper establishes the relationships among the band structure, relaxation time and ZT values by solving the Boltzmann equation. Then, comprehensive analysis is made to figure out how these factors have influence on ZT values of Bi2Te3 thermoelectric materials, including the size of rectangular nanowires, doping concentration and temperature. The results show that level discretization occurs because of the quantum size effect, when the relationships between the relaxation time and ZT values have been built. Therefore, ZT values of Bi2Te3 nanowires have step oscillation changes with the change of the side length, doping concentration and temperature. Among four types of Bi2Te3 rectangular nanowires researched in this paper, the thermoelectric performance of the p-type nanowires with [110] direction is best for the ZT value reaching 65.3, when the side length ax = 6.5nm, az = 5.3nm, doping concentration n = 4.4×1018cm-3 and temperature T = 300 K.In order to further verify the calculation and analysis above, this paper uses the software Atomistix Toolkit(ATK) for the simulation and design of doped Bi2Te3 nanowires to expand the theory research direction of Bi2Te3 nanowires on thermoelectric performance. The research is carried out to analyze the structures, electronic properties and thermoelectric performance of the doping nanowires, through the calculation of First Principals, one-dimensional Boltzmann Transport Theory(BTE) and molecular dynamic simulation.