Improved thermoelectric properties in n-type polycrystalline SnSe0.95 by PbCl2 doping

Abstract

Polycrystalline tin selenide (SnSe) has attracted extensive attention because of the better mechanical performance and simpler preparation conditions than those of its single crystal. However, the low carrier concentration severely limits optimization of the thermoelectric performance, especially for n-type polycrystalline SnSe. In this work, we use the PbCl₂ compound as the electron dopant to prepare n-type SnSe_0.95-based materials through ball milling and hot-pressing processes. It is found that PbCl₂ effectively boosts the room-temperature carrier concentration from 2.6 × 10¹⁷ cm⁻³ to 5.3 × 10¹⁹ cm⁻³. The electronic transport measurements parallel to the pressure direction indicate an enhanced power factor that increases from 0.3 μW cm⁻¹ K⁻² in pristine SnSe_0.95 to 7.3 μW cm⁻¹ K⁻² in the 6% PbCl₂ doped sample. The TEM images demonstrate that a large number of dislocations and grain boundaries exist in the polycrystalline, which can strengthen the phonon scattering and suppress the lattice thermal conductivity. Consequently, a maximum ZT of 1.13 at 823 K is obtained in the n-type SnSe_0.95 + 6% PbCl₂ polycrystalline parallel to the hot-pressing direction.