Optimizing the thermoelectric performance of In–Cd codoped SnTe by introducing Sn vacancies

SnTe has been known as a unique thermoelectric material to achieve the synergy of a resonant level and band convergence, originating from its characteristic band structure. In this work, we report an optimization of the two kinds of band engineering in In–Cd codoped SnTe. Owing to the complementary and competitive effects of the resonant level and band convergence, the location of the Fermi level is critical to the optimization. We show that the highest power factor and thermoelectric figure of merit ZT are reached by introducing Sn vacancies, rather than reducing Sn vacancies as normally done in SnTe. The peak ZT ∼ 1.1 appears at 850 K, while an overall enhanced ZTave of 0.54 between 300 and 850 K and an estimated conversion efficiency of 9% are obtained. This study discloses the non-trivial interplay between the resonant level and band convergence.

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