Dynamical Origin of the Rashba Effect in Organohalide Lead Perovskites: A Key to Suppressed Carrier Recombination in Perovskite Solar Cells?

The presence of a Rashba band-splitting mechanism mediated by spin orbit coupling and breaking of inversion symmetry has been suggested as a possible cause for the reduced recombination rates observed in organohalide perovskites. Here, we investigate the interplay of electronic and nuclear degrees of freedom in defining the Rashba splitting in realistic MAPbI(3) models. Our simulations disclose a "dynamical Rashba effect", allowing for a quantification of its magnitude under thermal conditions. We find that even in globally centrosymmetric structures the dynamics of the coupled inorganic-organic degrees of freedom give rise to a spatially local Rashba effect which fluctuates on the subpico-second time scale typical of the methylammonium cation dynamics. This effect is progressively quenched in globally centrosymmetric structures, likely representing the MAPbl(3) perovskite at room temperature, on increasing the probed spatial scale up to 32 MAPbl(3) units (similar to 3 nm size) because of the incoherent nuclear thermal motion mediated by the disorder of the organic cations.