Unraveling the Spin Relaxation Mechanism in Hybrid Organic–Inorganic Perovskites

The hybrid organic–inorganic perovskite (HOIP) CH3NH3PbI3 exhibits a long spin coherence despite its strong spin–orbit coupling. Elucidation of the spin relaxation mechanism is a prerequisite to harness this spin coherence for spintronic applications. Here, we show that exciton spin relaxation behaviors can be quantitatively accounted for by the Rashba splitting in the exciton bands together with piezoelectric (PE) coupling, both arising from structural inversion asymmetry of HOIPs. A large exciton size and Debye screening influence piezoelectric scattering and result in the unusual temperature and photoexcitation dependences in spin relaxation. Our results suggest that the strong PE coupling helps retain spin coherence in HOIPs with strong spin–orbit coupling and Rashba splittings.