Realizing high thermoelectric performance and thermal stability in CuInTe2 through heavy dose Mg doping

Cu based ternary compounds have received intensive attentions as thermoelectric materials but their carrier mobility and thermal stability are subject to native Cu vacancy. In this work, the synergistic improvement in thermoelectric performance and stability in CuInTe2 is presented, facilitated by local chemical bond enhancement. Heavy dose Mg doping on In site can successfully suppress the formation of Cu vacancy in CuInTe2 and its thermal stability is significantly improved. As a result, In comparison to alternative dopants, Mg doping demonstrates a notable capacity for reinforcing the lattice structure through the inhibition of copper vacancies, thereby yielding a considerable enhancement in mobility by 20 %∼50 %, and the zT value of CuIn0.94Mg0.06Te2 exceeds 1.2 at 873 K. By further alloying with Ga on In site, the thermal conductivity is greatly reduced and more surprisingly the thermal stability is continuously enhanced. Notably, in Cu(In0.4Ga0.6)0.94Mg0.06Te2, a peak zT value of 1.72 at 973 K is achieved, while in Cu(In0.6Ga0.4)0.94Mg0.06Te2, an average zT value of 0.82 is attained. This study offers valuable insights into optimizing the thermoelectric performance and thermal stability of Cu-based ternary compounds through effective doping and defect regulation, providing guidance for future research in this field.