Lattice Dynamics and Thermoelectric Properties of 2D LiAlTe2, LiGaTe2, and LiInTe2 Monolayers

The lattice dynamics and thermoelectric properties of monolayers of LiAlTe2, LiGaTe2, and LiInTe2 are comprehensively investigated by using density functional theory calculations combined with the solution of the Boltzmann transport equation. At 300 K, the intrinsic lattice thermal conductivity is determined to be 10.41, 6.02, and 5.77 W/(m center dot K) for LiAlTe2, LiGaTe2, and LiInTe2, respectively, when spin-orbit coupling effects are included in the harmonic force constants. These thermal conductivity values are attributed to the combination of low acoustic frequencies and enhanced anharmonic phonon scattering rates. Further analysis reveals that thermal transport in these monolayers is dominated by in-plane longitudinal acoustic modes. These monolayers are direct band gap semiconductors with high electrical conductivity and Seebeck coefficients. The synergistic effect leads to a notably high power factor, which is especially evident in LiInTe2 monolayers, ultimately resulting in a ZT value of 0.8 at 700 K.