A Unified Description of Electron-Phonon Coupling and Ion Migration in Metal Halide Perovskites
The remarkable optoelectronic properties of metal halide perovskites are closely linked to their unusually soft and polar chemical bonds that enable both strong electron-phonon interactions and ion migration. Yet these two defining characteristics have largely been treated as independent consequences of the same underlying chemical bonding. Here we show that they originate from a common electronic-structure framework by developing a general description linking lattice dynamics, electron-phonon coupling, and halide ion migration across representative Pb-based, Sn-based, and double perovskites. Spectrally resolved phonon-mode contributions demonstrate that the low-frequency shearing modes dominate halide migration, whereas high-frequency stretching modes govern carrier scattering through the Fr\"ohlich interaction in all three compositions. We introduce an orbital hybridization descriptor to unify these findings, which connects metal-halide bonding characteristics with the migration barrier energies and Fr\"ohlich coupling strengths, indicating a cooperative evolution of these two properties. These findings provide a generalized microscopic mechanism for simultaneously optimizing charge and ionic transport in soft semiconductors.