Electronic structure, elastic and optical properties of Bi2Te3/Sb(2)Te3 thermoelectric composites in the periodic-superlattice thin films

The outstanding p-type Sb2Te3-based materials such as the Bi2Te3/Sb2Te3 thermoelectric thin films with consideration of anisotropy and synergetic optimization of thermoelectric performance are promising used in practical applications through improving the power factor and reducing the thermal conductivity. Electronic structure, heat capacity and homogenized elastic properties of anisotropic Bi2Te3 and Sb2Te3 crystals are investigated, and then modeled to calculate elastic properties of the composite Bi2Te3/Sb2Te3 thin films. Debye temperature, thermal conductivity and ZT value are especially analysed and found that the Sb-5p/Bi-6p and Te5p at Debye temperatures of 179.29 K and 178.20 K, with the energy gap of 0.207 eV and 0.256 eV in Bi2Te3 and Sb2Te3, which contribute a multiscale modeling scheme from periodic single crystal film to multilayer composite Bi2Te3/Sb2Te3 thin films with higher ZT value, resulting in the significant reduction of band gap and the thermal conductivity due to its superlattice multi-layer structure.