Impacts of Crystalline Phases on Rashba Splitting in Lead Halide Perovskites from Bulk to Surfaces

The Rashba effect induced by the presence of spin–orbit coupling and the breaking of inversion symmetry has been proposed as a plausible cause for reduced radiative recombination rates in lead halide perovskites (LHPs). However, it is unclear how the crystalline phases impact the Rashba effect which has been experimentally observed with the difficulty on differentiating the factors from the bulk and surfaces. Here, we investigate the Rashba effect from the bulk and surfaces of MAPbX 3 (MA = CH 3 NH 3 and X = I and Br) in different phases by using the density functional theory approach. Our simulations disclose that the Rashba effect extracted from the bulk and surfaces with the ordered arrangement of oriented MA cations is progressively quenched in MAPbX 3 from high-temperature to low-temperature phases largely due to the diminished distortion of inorganic octahedrons. More importantly, the angle-resolved Rashba splitting is not significantly affected when going from the bulk to surfaces of MAPbI 3 in the room-temperature phase. This is highly different from the case of MAPbBr 3 in the room-temperature phase where the Rashba splitting exhibiting a three-dimensional feature in the bulk collapses into anisotropic Rashba splitting at the surfaces. These findings would provide insights for manipulating spin-polarized carrier dynamics in photovoltaic devices and spintronic devices with LHPs in the presence of ferroelectricity arising from the order of the MA species.