Refined band structure plus enhanced phonon scattering realizes thermoelectric performance optimization in CuI-Mn codoped SnTe

With the same crystal structure and a similar band structure, SnTe is regarded as an eco-friendly alternative to PbTe for the mid-temperature power generation application, but its thermoelectric performance suffers from a relatively low power factor and high thermal conductivity. In this work, we report the synergistic effects of CuI-Mn codoping in SnTe to improve the ZT value. It is found that tiny CuI alloying obviously decreases the carrier mobility and thus reduced the electrical conductivity and electronic thermal conductivity, while Mn doping promotes the valence band convergence and greatly increases the Seebeck coefficient. Moreover, Mn doping introduces many phonon scattering centers including nanoprecipitations, dislocations and point defects, which suppress the lattice thermal conductivity to 0.61 W m(-1) K-1 at 800 K. Consequently, the Sn0.89Mn0.11Te0.99(CuI)(0.01) sample exhibits a peak ZT value of 1.42 at 800 K and an average ZT of 0.68 between 300 and 830 K