Promising defect thermoelectric semiconductors Cu1−xGaSbxTe2 (x = 0–0.1) with the chalcopyrite structure†
Through calculating the band structures of the defect chalcopyrite semiconductor Cu1−xGaSbxTe2 with the proper addition of Sb to CuGaTe2, we have demonstrated that Sb actually mostly occupies the Te rather than Cu lattice sites. Such a dominant occupation increases the density of states (DOS) at the Fermi level and the effective mass of the valence band, and thereby results in an increase in the Seebeck coefficient. The electrical conductivity (σ) is hardly related to Sb content when x < 0.1, due to the subtle change in the concentration n and mobility μ at the degenerate state of holes. The attempted addition of Sb causes a decrease in the lattice thermal conductivity (κL), but as the Sb content increases there is a limited enhancement of κL. We have thus determined the mechanism, proposing that the dual effect on the κL resulted from the extra lattice mismatch and crystal structure distortion. By considering all the effects mentioned above on the transport properties, we have attained the highest thermoelectric ZT value (1.07 ± 0.1) of the sample Cu1−xGaSbxTe2 (x = 0.02) at 721 K, which shows promise for application in the intermediate temperatures.