Extremely low thermal conductivity and enhanced thermoelectric performance of polycrystalline SnSe by Cu doping

Here, we systematically investigated the effect of Cu doping on the thermoelectric properties of SnSe prepared by hydrothermal synthesis. Low Cu doped content (x = 0.01) lead to enhanced electrical conductivity and power factor compared with reported polycrystalline SnSe. Nanoscale precipitates and mesoscale grains define all-scale hierarchical architectures to scattering phonons. Furthermore, Cu atomic point-defect scattering play an important role in reducing the lattice thermal conductivity. These two favorable factors lead to low lattice thermal conductivity as low as 0.2 Wm^{− 1} K^{− 1} at 873 K. This ultralow thermal conductivity results in a ZT of ~ 1.2 at 873 K in Cu_0.01Sn_0.99Se.