Achieving high thermoelectric performance with Pb and Zn codoped polycrystalline SnSe via phase separation and nanostructuring strategies. (November 2018) - Liu, Jiang
Abstract: Thermoelectric technology, enables direct conversion between heat and electricity and may have a significant impact on heat pumps and power generators. SnSe emerges as a promising thermoelectric material since the recent discovery of an ultrahigh thermoelectric figure of merit in its single crystals. It is still challenging to achieve thermoelectric performance comparable to those of the SnSe single crystals in polycrystalline SnSe. Here, we propose a new concept that extremely low thermal conductivity and high thermoelectric performance in polycrystalline SnSe can be achieved via phase separation and nanostructuring strategies. We demonstrate that Pb and Zn codoping and introduction of PbSe secondary phase contribute to remarkable enhancement of electrical conductivity and power factor. The peak power factor reaches to 5.43 μW cm −1 K −2 in Sn0.98 Pb0.01 Zn0.01 Se. Phase-separation and nanostructuring strategies construct all-hierarchical architectures to scattering phonons. The lattice thermal conductivity is significantly reduced to 0.13 W m −1 K −1 through constructing all-hierarchical architectures and dual-atom point-defect scattering. A record high thermoelectric performance ZT = 2.2 was achieved in polycrystalline SnSe through enhancing electrical transport properties while keeping ultralow thermal conductivity. This work offers new strategies to realize high value of ZT in polycrystalline SnSe. Graphical abstract: fx1 Highlights: We propose a new concept that extremely low thermal conductivity and high thermoelectric performance in polycrystalline SnSe can be achieved via phase separation and nanostructuring strategies. This work provides a new strategy for realizing high performance in nanostructured polycrystalline SnSe through enhancing electrical transport properties while keeping low thermal conductivity. We fabricate nanostructured polycrystalline SnSe and artificially introduce secondary phase into them. T-EBSD and HAADF-STEM analysis demonstrate that the obtained materials are phase separated nanostructured polycrystalline SnSe. It indicates that nanostructuring approach is a fascinating strategy to realize high thermoelectric performance of polycrystalline SnSe due to substantial reduction in lattice thermal conductivity. A remarkably high thermoelectric performance ZT = 2.2 was achieved in phase separated nanostructured polycrystalline SnSe, which is a record high ZT reported so far for SnSe polycrystals and is competitive high value compared to those of most state-of-the-art thermoelectric materials. This work indicates that high performance could be achieved in low-cost, earth-abundant and environmentally-friendly polycrystalline SnSe.