The Br- ions in the perovskite had a relatively low activation energy for migration (∼0.2 eV) compared to that of CH3NH3 + ions (∼0.8 eV). This difference indicated that Br- could migrate more easily than CH3NH3 + ions; therefore, the migration of Br- ions may contribute more to synaptic behavior than the migration of CH3NH3 +.
Source
Metal Halide Perovskite-Based Memristors for Emerging Memory Applications