Electronic, phonon transport and thermoelectric properties of Cs2InAgCl6 from first-principles study

Abstract We have studied electronic, phonon transport and thermoelectric properties of Cs 2 InAgCl 6 using first-principles calculations. The PBE functional severely underestimates the bandgap and calculated value for fully relaxed Cs 2 InAgCl 6 is 1.01 eV. Our calculated direct bandgap using TB-mBJ potential of partially relaxed Cs 2 InAgCl 6 is 3.3 eV which agree with the measured value 3.3 eV whereas it is 2.53 eV for fully relaxed Cs 2 InAgCl 6 and underestimates the experimental value by 23.3%. The In-5s and Ag-4d mainly formulate the direct bandgap. We have found that the lattice thermal conductivity (κ l ) is quite low (0.2 Wm −1 K −1 ) in Cs 2 InAgCl 6 . The quite low phonon group velocity in the large weighted phase space and high anharmonicity (large phonon scattering) are responsible for low κ l value. This halide possesses high Seebeck coefficient (∼900 μV/K at 700 K) because of its large bandgap. The maximum ZT value obtained at 700 K is ∼0.94. Therefore, we predict that Cs 2 InAgCl 6 is a promising material for thermoelectric device applications.