Computationally Guided Synthesis of High Performance Thermoelectric Materials: Defect Engineering in AgGaTe2

Abstract

AbstractThe rational synthesis of high‐performance thermoelectric (TE) materials guided by theoretical design is still in its infancy. Here by computationally exploiting the possibilities of materials’ dopability and hence the electron–phonon transport/scattering, a new defective compound, AgGaTe2, with simultaneous Ag deficiency and isoelectronic substitution of In on Ga‐site (InGa) is predicted, and its high performance is then confirmed via experiments. Using density functional theory and density functional perturbation theory calculations, it is identified that controlled defects viz. Ag vacancy and In substitution in AgGaTe2 system can lead to extremely low lattice thermal conductivity (κL) of around 0.13 WK−1 m−1 at 850 K. This ultralow κL results from both the Ag vacancy that serves as a better rattler and the extra phonon scattering due to the defect induced internal lattice distortion (ψ). The synthesized compounds Ag0.85Ga1−xInxTe2 (x = 0–0.3) indeed achieve the extremely low κL (0.08 WK−1 m−1 for x = 0.15). As a result, the highest TE figure of merit (ZT) of 1.44 is obtained, which is the highest recorded value for silver‐based ternary chalcopyrite semiconductors to date.