Realizing high thermoelectric performance of n-type SnTe through optimizing carrier and resonance level

The environmentally friendly thermoelectric material SnTe has attracted significant attention. For practical applications, thermoelectric devices require integrating p-type and n-type thermoelectric materials within the same system to avoid potential mismatches and enhance reliability. The inherent abundance of Sn vacancies in SnTe imparts strong p-type characteristics. Despite the significant challenge of realizing n-type SnTe, recent experimental results on n-type SnTe transport have sparked widespread interest in this simple binary compound. In this study, we successfully synthesized n-type SnTe through the alloying of SnTe with Pb and subsequent doping with cost-effective compound PbI2. Significantly, through the doping of Sb into this n-type SnTe, we achieved a decoupling of conductivity and Seebeck coefficient, resulting in an exceptionally high power factor to 19.66 mu W/cmK(2) for Sn0.594Pb0.4Sb0.06Te0.98I0.02 at 373 K. Meanwhile, extensive point defects and dislocations led to significant phonon scattering, contributing to a low lattice thermal conductivity to 0.99 Wm(-1)K(-1) for Sn0.594Pb0.4Sb0.06Te0.98I0.02 at 573 K. Consequently, the sample Sn0.594Pb0.4Sb0.06Te0.98I0.02 achieved a maximum zT value of 0.69 at 473 K and achieved a record-high average zT value of 0.54 for polycrystalline SnTe over the temperature range from 300 K to 823 K. Furthermore, when the cold end is at 300 K and the hot end at 773 K, the conversion efficiency calculated based on the Snyder's model is 8.42 %. This work is of great significance for the promotion of n-type SnTe and SnTe-based thermoelectric devices.