N-type SnSe compound has been synthesized through melting with spark plasma sintering. By doping BiCl3, the carrier concentration of SnSe is significantly increased, leading to a large enhancement of electrical conductivity. Meanwhile, the SnSe0.95-BiCl3 samples also exhibit higher Seebeck coefficient and lower lattice thermal conductivity, compared with polycrystalline SnSe. Consequently, a high power factor of ∼5 μW cm−1 K−2 and a ZT of 0.7 have been achieved at 793 K. The synergistic roles of BiCl3 doping in SnSe provide many opportunities in the optimization of n-type SnSe materials.
Mn alloying in SnTe increases the band gap and decreases the energy separation between the light and heavy hole valence bands, leading to a significant enhancement in the Seebeck coefficient. The maximum ZT of ~1.25 is found at 920 K for p-type SnMn0.07Te.
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 μ V K − 1 at 300 K is observed in Sn 0.915 Mn 0.11 In 0.005 Te. By carefully tuning the band structure of the solid solution, we achieve a high ZT max of 1.15 at 823 K and an overall enhanced ZT ave of 0.62. The improved thermoelectric performance in a large temperature range leads to a competitive conversion efficiency of 10.1% with T c = 300 K and T h = 850 K, suggesting Mn−In codoped SnTe is a promising candidate for medium-temperature thermoelectric applications.
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