Synthesis of SnSe nanobelts and the enhanced thermoelectric performance in its hot-pressed bulk composite

Layer-structured SnSe is a promising thermoelectric material with a record high dimensionless figure of merit zT in its single-crystalline form along its b axis. However, the thermoelectric performance of polycrystalline SnSe significantly degrades due to the degenerated isotropic electrical and thermal conductivity. In this work, we successfully synthesized high-quality SnSe single crystalline nanobelts with growth direction along the b axis through solvothermal technique. The pure phase and homogeneous composition distribution were observed in the SnSe nanobelts. The lower thermal conductivity compared to its single crystals in the SnSe nanobelt bulk material was observed with the decreased electrical conductivity as can be expected. The anisotropic thermoelectric transports in the bulk SnSe material composed by hot pressed nanobelts were investigated and a high zT value of ~0.83 along the in-plane direction at 803 K were obtained, which is 60% increase compared with that for the previous SnSe polycrystalline samples. The present results demonstrate the great potential to obtain higher zT value in SnSe polycrystalline materials through a synergic nanostructuring and boundary engineering strategy.