GeTe-based materials usually possess brilliant thermoelectric performance through band degeneracy and optimized carrier concentration. In this study, Ti doping is effective for the realization of band degeneracy. However, the high carrier concentration after Ti doping limited the enhanced thermoelectric performance. Accordingly, Sb was used to optimize hole carrier concentration. Combined with the decreased thermal conductivity, the enhanced power factors, due to band degeneracy and carrier concentration optimization, result in a high zT of 1.60 in Ge0.92Ti0.01Sb0.07Te. The achieved high zT demonstrates that the p-type Ti/Sb co-doped GeTe compounds are promising as mid-temperature thermoelectric materials.

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Recent years have witnessed the chalcopyrite compound CuGaTe2 receiving widespread attention as a promising thermoelectric material. In the work, we calculated the band structure of Zn substitution at the Ga site and found that the Zn element can effectively adjust the band degeneracy and tetragonal distortion parameters of CuGaTe2. By doping CuGaTe2 with different contents of ZnTe, it is discovered that the ZnGa – point defects formed by CuGaTe2–ZnTe concrete solutions can increase the carrier concentration of CuGaTe2 material significantly. Meanwhile, it strongly scatters the short-wavelength phonons and reduces the lattice thermal conductivity. Therefore, the electrical and thermal properties of the material are effectively improved. The ZT value of (CuGaTe2)0.9975(2ZnTe)0.0025 reaches 0.74 at 810 K, which is nearly 28% higher than the 0.58 of the undoped CuGaTe2 sample.

A high TE performance GeMnTe2-based material with improved thermoelectric and mechanical properties is obtained by Sb doping. Excellent power factors could be achieved in the tested temperature range.

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