Improved thermoelectric properties of n-type polycrystalline SnSe via carrier concentration optimization

Polycrystalline SnSe thermoelectric materials have received extensive interests owing to the low thermal con-ductivity and available mechanical properties. However, the low electrical conductivity seriously hinders its application. In this work, stemming from the introducing of Hf and Cl substitution, they released more electrons. Owing to the improved carrier concentration, a high electrical conductivity of 33 S cm-1 for the SnSe0.95+1 wt% HfCl4 sample was obtained at 773 K, about 5 times as much as that of the SnSe0.95 sample. Thus, a peak power factor of 553.8 mu Wm- 1 K-2 of SnSe0.95+3 wt%HfCl4 sample at 773 K was obtained. Meanwhile, the phonon scattering was enhanced due to the decrease of grain size, the lattice thermal conductivity was suppressed. The pretty low xl of 0.33 W m-1 K-1 was obtained at 773 K for the SnSe0.95+4 wt%HfCl4 sample. Consequently, the peak ZT value of-1.1 was achieved for SnSe0.95+3 wt%HfCl4 sample at 773 K.