Vacancy scattering for enhancing the thermoelectric performance of CuGaTe2 solid solutions
Enhancing the thermoelectric performance through an effective phonon scattering by point defects has long been proven to be successful in many materials. This type of phonon scattering relies on the mass and strain fluctuations between the host and guest atoms, both of which can be maximized when the dominant point defects are vacancies. Besides the intrinsic vacancies in some compounds by nature, the formation of solid solutions with a solvent having a smaller cation-to-anion ratio as compared to the matrix is expected to create vacancies because the crystal structure needs to be stabilized in that of the matrix compound. In this work, In2Te3 and Ga2Te3i, compounds with a smaller cation-to-anion ratio as compared to the CuGaTe2 matrix, are chosen as molecular solvents to form solid solutions. The resulting high concentration vacancies on the cation sites, which can act as the phonon scattering centers, significantly reduce the lattice thermal conductivity and therefore enhance the thermoelectric performance by up to ∼75% in the entire temperature range. This work demonstrates a useful strategy for enhancing thermoelectric performance by vacancy creation in solid solutions.