魏百駿

Abstract:

This presentation highlights the complex phonon dynamics in organic-inorganic hybrid perovskites stemming from the interplay between rotationally active organic cations and dynamically disordered inorganic octahedra mediated by hydrogen bonding. To elucidate these interactions, the study investigates representative compounds from the hybrid perovskite family, including three-dimensional (3D) MAPbCl₃^[1] and MAPbBr₃^[2], as well as two-dimensional (2D) EA₂PbI₄^[3], with an emphasis on phonon scattering mechanisms and thermal transport behavior. Our results show that the thermal conductivity of these single-crystalline perovskites approaches the theoretical amorphous limit over a broad temperature range. In 3D perovskites, phonon velocities are found to be extremely low, and a notable shift from crystalline-like to liquid-like thermal transport behavior[2,4] is observed during the structural transition from the orthorhombic to the cubic phase. This transformation signifies a shift in the dominant phonon scattering mechanism: at low temperatures, immobilized cations result in a crystal-like lattice with prominent Umklapp scattering, whereas at elevated temperatures, the activation of rotational hopping of methylammonium (MA⁺) ions induces dynamic lattice distortions that give rise to more liquid-like thermal transport behavior. In contrast, for EA₂PbI₄, the average phonon mean free path approaches the covalent bond length of the PbI₆ octahedron, which contributes to the highly resistive thermal transport characteristic of this two-dimensional organic-inorganic hybrid structure.

Keywords – organic-inorganic hybrid perovskites, inelastic neutron scattering, phonon transport behavior.

 Back