Magneto-electroluminescence response in 2D and 3D hybrid organic-inorganic perovskite light emitting diodes

We have studied the magneto-electroluminescence (MEL) response in light emitting diodes based on 2D-(PEA)₂PbI₄ and 3D-MAPbI₃ hybrid organic-inorganic perovskites at cryogenic temperatures. We found that the MEL is negative, i.e., the EL decreases with the applied field strength, B. In addition, the MEL(B) response has a Lorentzian line shape whose width depends on the perovskite used. We interpret the MEL(B) response using the "Δg mechanism" in which the spin of the injected electron-hole (e-h) pairs oscillates between singlet and triplet configurations due to different precession frequencies of the electron and hole constituents that originate from the difference, Δg, in the electron and hole gyromagnetic constants, g. In this model, the MEL(B) linewidth is inversely proportional to the spin lifetime and Δg. The model used is validated by directly measuring the spin lifetime of photogenerated e-h pairs using the circularly polarized pump-probe transmission technique with 100 fs resolution.