Layered lead-free perovskite memristors with ultrahigh on/off ratio

High-quality, single-crystalline lead-free Cs 3 Bi 2 Br 9 (CBB) microplates have been successfully synthesized, and an Au/Ag/CBB/FTO vertical memristor has been proposed to study the resistive switching properties of CBB in its unique 2D lattice. CBB devices are capable of exhibiting volatile unipolar or non-volatile bipolar switching behaviors, with low leakage current and an ultrahigh on/off ratio>10 9 . • 2D Cs 3 Bi 2 Br 9 (CBB) microplates were synthesized and a vertical memristor was proposed. • Extremely low leakage current (~10 -12 A) and high on/off ratio (~10 9 ) were recorded. • The formation and rupture of Ag filaments in layered lattice account for the RS behavior. • Due to all-inorganic composition and layered lattice, the CBB microplates have shown long-term stability of over 20 months. Layered organic–inorganic hybrid halide perovskites hold promises for memristive and synaptic devices with ultralow power consumption. However, the lead-based layered perovskites often contain organic cations which are subject to thermal and optical instability. Here we report lead-free resistive switching devices incorporating nanostructured all-inorganic perovskite Cs 3 Bi 2 Br 9 . Monocrystalline hexagonal microplates of Cs 3 Bi 2 Br 9 were synthesized via a solution method featuring layered structure and smooth morphology. Upon sandwiched by sliver and conductive glass, the microplate devices exhibit resistive switching behavior under forming-free bias below 0.2 V. Ultrahigh on/off ratio up to 10 9 was recorded in these devices, favoring multi-level data storage capabilities within single memory units. The high switching ratio is attributed to the suppressed inter-layer electrical conductance of the microplates. In addition, the memristive devices demonstrate excellent stability over 20 months in ambient condition. This work offers insights into utilizing layered inorganic perovskite architectures for resistive switching devices with decoupled ionic and electronic transport.