P-type doping of transition metal elements to optimize the thermoelectric properties of CuGaTe2

Abstract CuGaTe2 has received extensive attention due to the potential for high thermoelectric performance. In this work, we report the electronic structures and thermoelectric properties of CuGa1-xMxTe2 (M = Ni, Mn, Fe, x  = 0.01–0,03). It is found that the doping of the above elements can increase the band degeneracy and the electron density of states near the Fermi level, and introduce acceptor-type defects into the matrix to achieve p-type doping to increase the carrier concentration. Among them, Ni doping can synergistically improve the electrical and thermal properties of CuGaTe2, and the ZTmax of CuGa0.99Ni0.01Te2 is increased by nearly 38.2% compared with the pristine CuGaTe2. Mn doping can significantly improve the carrier concentration and the m d ∗ of the material, thereby obtaining high conductivity while retaining a high Seebeck coefficient, making the maximum PFave of CuGa0.97Mn0.03Te2 59% higher than the pristine CuGaTe2. Fe elements exist in different valence states and have low solubility in CuGaTe2, when the doping amount is 0.02, the second phase of FeTe2 is precipitated in the grain boundary, which cooperates with point defects to scatter low- and medium-frequency phonons, thereby greatly reducing the lattice thermal conductivity at low and medium temperature. At 325 K, the thermal conductivity is reduced from 5.77 Wm-1K−1 to 3.8 Wm-1K−1. This result suggested that Ni, Mn, and Fe elements can effectively improve the thermoelectric properties of CuGaTe2, and provides theoretical guidance and new ideas for subsequent research.