Spin Preserved Exciton Funneling through a Polaronic Intermediate State in Layered Perovskite Single Crystals

The spintronic device is another application of perovskite beyond solar cells, light emitting diodes, and photodetectors. Spin relaxation with a lifetime of several ps has been observed in both 3D and 2D perovskite. In this study, Ruddlesden-Popper (RP) perovskite single crystals with mixed n and n + 1 phase are synthesized. It is found that the spin-polarized exciton can funnel from n phase to n + 1 phase with spin information retained effectively. Interestingly, the spin lifetime of the funneled exciton in n + 1 phase is much longer than that in the pristine n phase. This is attributed to the fact that the funneling is realized through a polaronic intermediate state, in which the spin relaxation is much slower. The polaronic intermediate states originate from the interaction between photogenerated excitons and the lattice distortion. The formation of the polaronic states can reduce overlap of electron-hole wave function and modified lattice symmetry; these two changes contribute to retain the exciton spin information in such polaronic states. The findings deepen the understanding of spin-polarized exciton transportation and relaxation dynamics and provide a potentially novel approach to enhance the spin relaxation lifetime of perovskite single crystals.