Resistive switching and artificial synaptic performances of memristor based on low-dimensional bismuth halide perovskites

Zero-dimensional (0D)-Cs3Bi2I9, two-dimensional (2D)-Cs3Bi2Br9, and one-dimensional (1D)-Cs3Bi2Cl9 perovskite films have been successfully grown on indium tin oxide (ITO) glass substrates, which were used to fabricate memristors with the structure of Al/Cs3Bi2X9 (X = I, Br, and Cl)/ITO glass. The current three types of memristors exhibited bipolar resistive switching behaviors. Both the endurance and retention time tests clearly demonstrated the excellent stability of present devices. Especially, the ON/OFF ratio of the 0D-Cs3Bi2I9 device is close to 104 at the reading voltage of 0.1 V, which is nearly 100 and 1000 times larger than those of the 1D-Cs3Bi2Cl9 device and the 2D-Cs3Bi2Br9 device, respectively. The activation energy of halide vacancies in the Cs3Bi2X9 (X = I, Br, and Cl) films was calculated using the density functional theory by considering a minimum migration path, demonstrating the dimensionality of the Cs3Bi2X9 (X = I, Br, and Cl) film affected the formation and rupture of conductive filaments. Moreover, the short-term plasticity and long-term plasticity of biological synapse were simulated by evaluating the conductance responses of Al/Cs3Bi2X9 (X = I, Br, and Cl)/ITO devices under various voltage pulses in detail. The duration time of long-term plasticity in all the present devices can last for up to 250 s. The 0D-Cs3Bi2I9 device showed both the highest spike-duration-dependent plasticity and paired-pulse facilitation indexes compared to the other two devices. Additionally, the 0D-Cs3Bi2I9 device successfully established the associative learning behavior by simulating the Pavlov's dog experiment.