Enhanced Carrier Mobility and Diffusion Length in Formamidinium-Rich Hybrid Perovskites: Effects of Grain-Size and Electron-Phonon Coupling.

. These differences in mobility and diffusion length persist across different fluences, and are captured by a fluence-dependent rate model that accounts for both carrier generation and recombination at different material depths. From scanning electron microscopy and THz time-domain spectroscopy measurements, we attribute the increased mobility and diffusion length for the FA-rich perovskite mainly to a larger average grain size, after considering possible Fröhlich-type interactions between carriers and THz-active phonon modes. Our work establishes a mechanistic link between material microstructure and ultrafast carrier dynamics, informing crucial design principles for perovskite-based photovoltaic and optoelectronic applications.