About Carrier's Self‐Trapping and Dynamical Rashba Splitting in the 2D Hybrid Perovskite (BA) 2 (MA) 2 Pb 3 l 10

ABSTRACT Time‐ and Angle‐Resolved Photoelectron Spectroscopy (tr‐ARPES) is employed to monitor photoexcited electrons in the 2D hybrid perovskite (BA)(MA). Photoelectron intensity maps are in good agreement with ab‐initio calculations of the band structure. The effective mass is and for holes and electrons, respectively. In the photoexcited state, spin‐orbit splitting of the conduction band cannot be resolved. This sets the upper bound of photoinduced Rashba coupling to eVÅ. The correlated electron‐hole plasma evolves in Wannier excitons with Bohr radius of 2.8 nm, while no sign of self‐trapping in small polarons is found within the investigated time window of up to 120 ps following photoexcitation.