Thermoelectric performance enhancement of Cu2S by Se doping leading to a simultaneous power factor increase and thermal conductivity reduction

Abstract

Copper sulfide is a promising thermoelectric (TE) material consisting of earth-abundant, low cost, and non-toxic elements, which recently has attracted increasing attention. In this work, a series of single-phased Cu₂S_1−xSe_x bulks were prepared by using mechanical alloying (MA) combined with spark plasma sintering (SPS). We found that Se doping could not only enhance the power factor (PF) of Cu₂S by modifying the band structure, but also reduce the thermal conductivity (κ) by generating point defects to intensify the phonon scattering. A peak ZT value of 0.74 was achieved at 723 K for the Cu₂S_0.9Se_0.1 composition, resulting from a high PF = 260.5 μW m⁻¹ K⁻² and a low κ = 0.25 W m⁻¹ K⁻¹, which is 131% higher than that (0.32) of the pristine Cu₂S. Our results suggest that the TE properties of Cu₂S can be greatly enhanced by simultaneously increasing PF and decreasing κ via doping a sole Se element.