Precision engineering of copper vacancies in CuInTe2 for synergistically enhanced thermoelectric performance†

Complex defects play a pivotal role in determining the thermoelectric performance of narrow gap semiconductors. In this study, we employed a meticulous approach to regulate Cu vacancies by fine-tuning the Cu content in CuInTe₂. A slight Cu deficiency triggered triple valence band degeneracy at the Γ point, effectively augmenting the density-of-states effective mass and enhancing the weighted carrier mobility. Additionally, we discovered that the defect formation energy of Cu vacancies exhibited a negative correlation with temperature; higher temperatures lowered energy barriers, increasing carrier concentration and optimizing the electrical conductivity. Consequently, the Cu_0.992InTe₂ sample achieved a peak ZT value of ∼0.9 at 873 K. Compared with the pristine sample, this variant exhibited a 75% increase in the average power factor and an 11% rise in the average ZT. This research conclusively demonstrates that precise Cu vacancy regulation represents an efficient strategy for optimizing electrical transport properties and enhancing the thermoelectric performance of CuInTe₂, offering valuable insights for the development of advanced chalcopyrite thermoelectric materials.