Large Polaron Self-trapped States in 3D Metal-Halide Perovskites

In recent years, metal halide perovskites have generated tremendous interest for optoelectronic applications and their underlying fundamental properties. Because of the large electron-phonon coupling characteristic of soft lattices, self-trapping phenomena are expected to dominate hybrid perovskite photoexcitation dynamics. Yet, while the photogeneration of small polarons was proven in low-dimensional perovskites, the nature of polaron excitations in technologically relevant 3D perovskites, and their influence on charge carrier transport, remain elusive. In this study, we used a combination of first principle calculations and advanced spectroscopy techniques spanning the entire optical frequency range to pin down polaron features in three-dimensional metal halide perovskites. Mid-infrared photoinduced absorption shows the photogeneration of states associated with low energy intragap electronic transitions with lifetime up to the millisecond time scale, and vibrational mode renormalization in both frequenc...