Lattice Chirality Prolongs Exciton Spin Depolarization in 2D Perovskites by Enhanced Exciton‐Phonon Coupling

Abstract Hybrid organic‐inorganic perovskites are receiving increasing attention due to their great potential in optoelectronic and spintronic applications. Through ligand modification, spin relaxation time can be prolonged in perovskites, which is a key parameter for spintronic devices. The lattice of perovskite can be endowed with chirality by introducing chiral ligands. Although some studies have pointed out that chiral perovskites can achieve longer excitonic spin relaxation time compared to their racemic counterparts, the understanding of the underlying physical mechanisms is still lacking. Here, chiral perovskites (R/S‐MBA) 2 PbI 4 [MBA = α‐Methylbenzylamine] are synthesized. Then circularly polarized transient absorption spectroscopy, combined with pump fluence‐dependent and temperature‐dependent experiments, is used to investigate the mechanism of prolonged spin relaxation time in (R/S‐MBA) 2 PbI 4 compared to their racemic counterpart (Rac‐MBA) 2 PbI 4 . It is found that the extension of excitonic spin relaxation time in (R/S‐MBA) 2 PbI 4 is due to stronger exciton‐phonon coupling in chiral perovskite, resulting in stronger dynamic polaronic screening effect.