Ultralong spin coherence in MAPbI₃ single crystals revealed by ultrafast optics

Hybrid organic-inorganic perovskites (HOIPs) have demonstrated remarkable optoelectronic properties with their unprecedented rate of increase in solar cell efficiency, and their applications have been quickly extended to many areas, including light emitting diodes, lasing, and photo detection. Recent studies have also revealed their great potential in spintronics because of spin-dependent optical transitions, long spin lifetimes, and predicted large spin-orbit coupling effects for potential spin manipulation. Our previous study revealed long spin lifetimes (T₂^*) exceeding 1 ns at 4 K on MAPbI₃ polycrystalline films despite the presence of large spin-orbit coupling. Here, in order to exclude the influence of the polycrystalline structure and obtain intrinsic spin dynamics, we investigate spin dynamics on high quality MAPbI₃ single crystals by time-resolved Faraday rotation (TRFR). The spin lifetime improved by an order of magnitude when compared to polycrystalline films, which suggests the long spin lifetime is an intrinsic property of MAPbI₃. Combining the TRFR measurements with circularly-polarized photoluminescence, we analyze the interplay between carrier dynamics and spin dynamics upon optical excitation of spin-polarized carriers in this HOIP.