Rational Design of Cu Vacancies and Antisite Defects for Boosting the Thermoelectric Properties of CuGaTe 2 -Based Compounds.

CuGaTe 2 -based compounds show great promise in the application for high-temperature thermoelectric power generation; however, its wide bandgap feature poses a great challenge for enhancing thermoelectric performance via structural defects modulation and doping the system. Herein, it is discovered that the presence of Ga Cu antisite defects in the CuGaTe 2 compound promotes the formation of Cu vacancies, and vice versa, which tends to form the charge-neutral structure defects combination with one Ga Cu antisite defect and two Cu vacancies. The accumulation of Cu vacancies in the structure of the (Cu 2 Te) x (Ga 2 Te 3 ) 1- x compounds evolves into twins and stacking faults. This in conjunction with Ga Cu antisite defects intensify the point defects phonon scattering, yielding a dramatic reduction on lattice thermal conductivity from 6.95 W m -1 K -1 for the pristine CuGaTe 2 sample to 2.98 W m -1 K -1 for the (Cu 2 Te) 0.45 (Ga 2 Te 3 ) 0.55 sample at room temperature. Furthermore, the high concentration of charge-neutral defects combination narrows the band gap and increases the carrier concentration, leading to an improved power factor of 1.58 mW/mK 2 at 600 K for the (Cu 2 Te) 0.49 (Ga 2 Te 3 ) 0.51 sample, which is 41% higher than for the pristine CuGaTe 2 sample. Consequently, the highest ZT value of 0.82 is achieved at 915 K for Cu 0.015 (Cu 2 Te) 0.48 (Ga 2 Te 3 ) 0.52 , which represents an enhancement of about 22% over that of the pristine CuGaTe 2 compound.