SnSe has attracted much attention due to the excellent thermoelectric (TE) properties of both p-and n-type single crystals. However, the TE performance of polycrystalline SnSe is still low, especially in n-type materials, because SnSe is an intrinsic p-type semiconductor. In this work, a three-step doping process is employed on polycrystalline SnSe to make it n-type and enhance its TE properties. It is found that the Sn 0.97 Re 0.03 Se 0.93 Cl 0.02 sample achieves a peak ZT value of ≈1.5 at 798 K, which is the highest ZT reported, to date, in n-type polycrystalline SnSe. This is attributed to the synergistic effects of a series of point defects: × × V V , Cl , ,Re ,Re Se .. Se . Sn ,, Sn 0 . In those defects, the V Se .. compensates for the intrinsic Sn vacancies in SnSe, the Cl Se .acts as a donor, the V Sn ,, acts as an acceptor, all of which contribute to optimizing the carrier concentration. Rhenium (Re) doping surprisingly plays dual-roles, in that it both significantly enhances the electrical transport properties and largely reduces the thermal conductivity by introducing the point defects, × × Re , Re Sn 0 . The method paves the way for obtaining high-performance TE properties in SnSe crystals using multipoint-defect synergy via a step-by-step multielement doping methodology.
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