Self-assisted nucleation and growth of [010]-oriented Sb2Se3 whiskers: the crystal structure and thermoelectric properties

Abstract

The layered-chalcogenide Sb₂Se₃ has potential for use in photovoltaic devices and thermoelectric coolers, but its practical applications are restricted as bulk Sb₂Se₃ exhibits high electrical resistivity (ρ). Herein, we synthesize n-type Te-doped Sb₂Se₃ whiskers with the average feature size of 1 cm length and 200 μm width via a self-assisted vapor–solid (VS) method. In particular, based on the crystallographic identification using techniques of powder X-ray diffraction and transmission electron microscopy, the Te-doped Sb₂Se₃ whisker grows along a preferred orientation of [010], which is rarely reported for an orthorhombic structure due to the fact that the bonding energy along the c-axis is much stronger. The [010]-oriented Sb₂Se₃ whisker shows enhanced electrical conductivity, especially compared with its bulk form, and exhibits a high Seebeck value (S) within 300–400 K, resulting in a peak power factor (S²/ρ) of ∼7.6 (μW m K⁻²) at 350 K. The peak PF value is 10⁴ higher than that of Sb₂Se₃ bulk and is comparable to that of Sb₂Se₃ nanotubes, respectively, giving rise to the possibility of utilizing Sb₂Se₃ in the application of thermoelectric coolers.