Enhanced Thermoelectric Performance of p-type AgSbTe₂ via Cu Doping

Recently, the p-type semiconductor AgSbTe₂ has received a great deal of attention due to its promising thermoelectric performance in intermediate temperatures (300-700 K). However, its performance is limited by the suboptimal carrier concentration and the presence of Ag₂Te impurities. Herein, we synthesized AgSb_1-CuTe₂ (x = 0, 0.02, 0.04, and 0.06) and investigated the effect of Cu doping on the thermoelectric properties of AgSbTe₂. Our results indicate that Cu doping suppresses the Ag₂Te impurities, raises the carrier concentration, and results in an improved power factor (PF). The calculation reveals that Cu doping downshifts the Fermi energy level, reduces the energy band gap and the difference among several valence band maximums, and thereby explains the improvement of PF. In addition, Cu doping reduces the thermal conductivity, possibly attributed to the inhibition of Ag₂Te impurities and the phonon softening of the AgSb_1-CuTe₂. Overall, Cu doping improves the ZT of AgSb_1-CuTe₂. Among all samples, AgSb_0.96Cu_0.04Te₂ has a maximum ZT of ∼1.45 at 498 K and an average ZT of ∼1.11 from 298 to 573 K.