Thermoelectric performance enhancement of Cu2S by Se doping leading to a simultaneous power factor increase and thermal conductivity reduction
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 Cu2S1−xSex 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 Cu2S0.9Se0.1 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.