LAUSR

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 Sn0.98Pb0.01Zn0.01Se. 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.