Lattice thermal conductivity of CsSnBr3/Cs2SnBr6 interface from ab initio based neuroevolution potential simulations.

Engineering of interface phonons is of vital importance to achieve extremely low thermal conducting candidates, which are crucial for energy conversion devices. Here, we reported an ultralow lattice thermal conductivity (0.173 W m-1 K-1) across the all-inorganic halide perovskite CsSnBr3/Cs2SnBr6 interface based on large-scale atomic molecular dynamics simulations. Accurate neuroevolution potential derived from ab initio density functional theory was employed to reveal the enhanced anharmonicity and phonon scattering/localization that contribute to the low lattice thermal transport capability. A strong mixed phonon liquid character and nonlinear interface density dependent thermal conductivity have been observed for the CsSnBr3/Cs2SnBr6 interface. The insights obtained from our findings might provide an efficient way to design crystalline anisotropic thermoelectric materials.