Control over ultrafast Rashba splitting dynamics in quasi-2D arrays of 3D hybrid perovskite nanocrystals by the interfacial electric field

Snapshot spectral imaging has been performed with 100 fs steps in delay-times for fully encapsulated quasi-2D arrays of 3D hybrid perovskite MAPbBr₃ nanocrystals (~20 nm in size) spin-coated to either the clean sapphire plate or to that initially ALD-coated by a ~30 or ~100 nm thick ZnO layer. The absorption bleaching band for the bare MAPbBr₃ nanocrystal arrays reveals a ~200 meV splitting appearing within ~1 ns, which has been assigned to the Rashba splitting effect. However, the splitting unexpectedly disappears for the MAPbBr₃/ZnO samples at delay-times longer than ~500-600 fs when the interfacial electric field at the MAPbBr₃/ZnO heterointerface develops due to charge separation. The effect has been treated theoretically in the frame of the model taking into account the interfacial-field-induced structural phase transition in MAPbBr₃ nanocrystals.