1D Hexagonal HC(NH₂)₂PbI₃ for Multilevel Resistive Switching Nonvolatile Memory

Organic–inorganic halide perovskite is regarded as one of the potential candidates for next generation resistive switching memory (memristor) material because of fast, millivolt-scale switching, multilevel capability, and high On/Off ratio. Here, resistive switching property of HC(NH₂)₂PbI₃ (FAPbI₃) depending on structural phase is reported. It is found that 1D hexagonal FAPbI₃ (δ-FAPbI₃), formed at relatively low temperature, is active in memristor, while 3D trigonal FAPbI3 (α-FAPbI₃), formed at temperature higher than 150 °C, is inactive. Failure of switching from low resistance state to high resistance state is found for α-FAPbI₃, while δ-FAPbI₃ shows stable switching behavior. Density functional calculation reveals that iodine cluster in isotropic 3D α-FAPbI₃ is so stable after forming filament that the filament is hard to be ruptured at off state. However, for anisotropic δ-FAPbI₃, iodine cluster is not stable and migration barrier is much lower for c-axis (0.48 eV) than for ab-plane (0.9 eV), which is beneficial for switching. The memristor devices based on δ-FAPbI₃ demonstrate endurance up to 1200 cycles with On/Off ratio (>10⁵), retention time up to 3000 s, multilevel storage capacity, and working even at 80 °C.