Manipulating Band Convergence and Resonant State in Thermoelectric Material SnTe by Mn–In Codoping

We report an enhanced thermoelectric performance by manipulating band engineering in Mn–In codoped SnTe. It has been revealed that SnTe is a unique example achieving the synergy of band convergence and resonant state. According to band theory, band convergence favors heavy doping, while resonant state favors light doping. Following this idea, a series of Mn–In codoped SnTe samples are prepared by hot pressing. A significantly enhanced Seebeck coefficient of 116 μV K–1 at 300 K is observed in Sn0.915Mn0.11In0.005Te. By carefully tuning the band structure of the solid solution, we achieve a high ZTmax of 1.15 at 823 K and an overall enhanced ZTave of 0.62. The improved thermoelectric performance in a large temperature range leads to a competitive conversion efficiency of 10.1% with Tc = 300 K and Th = 850 K, suggesting Mn–In codoped SnTe is a promising candidate for medium-temperature thermoelectric applications.