The Dynamic Rashba Effect Does Not Account for the Prolonged Charge Carrier Lifetime in Metal Halide Perovskites
Haoran Lu, Run Long
Abstract
Rashba spin–orbit splitting in metal halide perovskites has been widely associated with a direct-to-indirect bandgap transition, a mechanism often proposed to suppress nonradiative recombination and extend carrier lifetimes. To critically assess this hypothesis, we developed a nonadiabatic molecular dynamics framework in momentum space that explicitly incorporates spin–orbit coupling and goes beyond harmonic approximation. Using this approach, we investigated electron–hole recombination dynamics in the racemic ( rac ), S, and R configurations of the chiral 3BrMBA 2 PbI 4 perovskites. The rac structure, which preserves inversion symmetry, exhibits weak Rashba splitting and retains a direct-like bandgap under thermal fluctuations, yielding ∼1 ns recombination times. In contrast, the chiral S and R configurations break inversion symmetry, display pronounced Rashba splitting, and exhibit an indirect bandgap but show only ∼20% slower recombination. These findings indicate that dynamic Rashba spin–orbit splitting alone does not significantly enhance carrier lifetimes, underscoring the importance of atomistic-level understanding of recombination processes in perovskites.