Optimized ZT of Bi2Te3-GeTe compounds from first principles guided by homogeneous data

Abstract

We predict the thermoelectric properties of layered [GeTe](m)[Bi2Te3](n) (GBT) compounds ( 1 <= m <= 8, 1 <= n <= 3), using first-principles-Boltzmann transport calculations of the homogeneous (Bi2Te3 and GeTe) data. The lattice strain and the quantum-confinement effects of compounds evolve the band-gap structures, resulting in asymmetric and large Seebeck coefficient, at high GeTe content. Using semiempirical calculations of electron scattering rate 1/tau(e), dominated by electron-acoustic phonon scattering, we reproduce reported TE properties of GBT compounds. We predict that, due to small Seebeck coefficient, the GBT compounds with high n- and p-type doping (similar to 10(20) cm(-3)), do not have high ZT near room temperature. However, we predict that the moderately doped (similar to 10(19) cm(-3)), p-type GBT compounds have enhanced ZT approximate to 1.4 near room temperature.