Intrinsic spin dynamics in MAPbI3 single crystals with low defects*

Hybrid organic-inorganic perovskites (HOIPs) are a new class of solution-processed semiconductors with remarkable performance in photovoltaics. Beyond the broad optoelectronic applications, they are great candidates for spintronics because of the long spin lifetime and predicted large spin-orbit coupling (SOC) effects for potential spin manipulation. Our previous study has revealed long spin lifetime (T₂^*) exceeding 1 ns at 4 K on MAPbI₃ polycrystalline films, which is unusual given the large SOC of Pb and I. A critical question is whether the long spin lifetime is an intrinsic property of MAPbI₃ or related to extrinsic factors, such as high defect concentrations or grain boundaries. Recently we have made significant progress in single crystal growth and surface treatment, resulting in a reduction in defect densities of several orders of magnitude. We measured time-resolved Kerr rotation (TRKR) on these high quality MAPbI3 single crystals, and showed that the spin lifetime improves by an order of magnitude, which suggests the intrinsic origin of this property. Combined with results from complementary optical measurements, we will also discuss the interplay between carrier dynamics and spin dynamics upon optical excitation of spin-polarized carriers.