Layer-Dependent Rashba Band Splitting in 2D Hybrid Perovskites

The strong spin–orbit coupling (SOC) in perovskite materials due to the presence of heavy atoms induces interesting electronic characteristics, such as Rashba band splitting. In spite of several recent reports on Rashba effects in 2D perovskites, the impacts of the nature of surface termination and of the number of inorganic layers on the extent of Rashba band splitting still remain to be determined. Here, using a combination of density functional theory (DFT) calculations and time-resolved laser spectroscopy, we provide a comprehensive understanding of the Rashba band splitting of the prototype 3D MAPbI₃ and of 2D Ruddlesden–Popper (RP) hybrid perovskites. We demonstrate that significant structural distortions associated with different surface terminations are responsible for the observed Rashba effect in 2D perovskites. Interestingly, our theoretical and experimental data clearly indicate that the intrinsic Rashba splitting occurs in the perovskite crystals with an even number of inorganic layers (n = 2), but not for the ones with an odd number of layers (n = 1 and n = 3). These findings not only provide a possible explanation for the elongated electron–hole recombination in perovskites but also elucidate the significant impact of the number of inorganic layers on the electronic properties of 2D perovskites.