High thermoelectric performance in polycrystalline SnSe via dual‐doping with Ag/Na and nanostructuring with Ag8SnSe6

• Main Authors: Luo, Yubo, Cai, Songting, Hua, Xia, Chen, Haijie, Liang, Qinghua, Du, Chengfeng, Zheng, Yun, Shen, Junhua, Xu, Jianwei, Wolverton, Chris, Dravid, Vinayak P., Yan, Qingyu, Kanatzidis, Mercouri G.
• Other Authors: School of Materials Science & Engineering
• Format: Article
• Language: English
• Published: 2020
• Subjects: Engineering::Materials; Ag8SnSe6; Dual-doping
• Online Access: https://hdl.handle.net/10356/139256
• Institution: Nanyang Technological University

Single crystalline SnSe is one of the most intriguing new thermoelectric materials but the thermoelectric performance of polycrystalline SnSe seems to lag significantly compared to that of a single crystal. Here an effective strategy for enhancing the thermoelectric performance of p‐type polycrystalline SnSe by Ag/Na dual‐doping and Ag8SnSe6 (STSe) nanoprecipitates is reported. The Ag/Na dual‐doping leads to a two orders of magnitude increase in carrier concentration and a convergence of valence bands (VBM1 and VBM5), which in turn results in sharp enhancement of electrical conductivities and high Seebeck coefficients in the Ag/Na dual‐doped samples. Additionally, the SnSe matrix becomes nanostructured with dispersed nanoprecipitates of the compound Ag8SnSe6, which further strengthens the scattering of phonons. Specifically, ≈20% reduction in the already ultralow lattice thermal conductivity is realized for the Sn0.99Na0.01Se–STSe sample at 773 K compared to the thermal conductivity of pure SnSe. Consequently, a peak thermoelectric figure of merit ZT of 1.33 at 773 K with a high average ZT (ZTave) value of 0.91 (423–823 K) is achieved for the Sn0.99Na0.01Se–STSe sample.