The Electronic Structure And Thermoelectric Properties Of Doped Bi₂Te₃

With increasing prominent issues of energy and environment problems, we need for an efficient, non-polluting energy conversion and utilization method to use energy effectively again. Thermoelectric materials can realize the direct transfer between thermal energy and electric energy, and its usage provides a good idea to solve the problem of energy shortage and environmental pollution. Currently, the key question is how to improve the conversion efficiency of thermoelectric materials.In my paper, the electronic structure and thermoelectric properties of doped Bi2Te3are investigated based on Density functional theory (DFT) and semiclassical Boltzmann theory. The main contents of this thesis are as follows:The electronic structure of Sb-doped Bi2Te3materials has been studied. A larger1x1x3supercell is proposed based on full electronic potential. Spin-orbit coupling has been introduced for the calculation of electronic structure. Band modulation and its influence on the thermoelectric properties because of doping have been investigated. The relationship between the band structure and its Seebeck coefficient has also been studied in detail.We investigated the thermoelectric properties at full range of Sb compositions from x=0to x=1. By using Boltzmann theory the assumption of the constant relaxation time approximation, we calculated Seebeck coefficient, electrical conductivities relative to relaxation time, and power factor. Finally, we list all of the peak values of transport coefficients of (Bi1-xSbx)2Te3alloy around the vicinity of Fermi level. Then, the ZT values of different concentration were calculated. The theoretical values are in good agreement with experimental results. Due to the potential applications in thermoelectric field of nano clusters, the structural stability and electronic properties of X-doped Al13cluster have been investigated. Besides, we have studied structural, electronic, and magnetic properties of Ga12N12clusters doped with Mn atoms in the framework of first-principles.