CsPbX 3 (X = halide, Cl, Br, or I) all-inorganic halide perovskites (IHPs) are regarded as promising functional materials because of their tunable optoelectronic characteristics and superior stability to organic-inorganic hybrid halide perovskites. Herein, nonvolatile resistive switching (RS) memory devices based on all-inorganic CsPbI 3 perovskite are reported. An air-stable CsPbI 3 perovskite film with a thickness of only 200 nm is successfully synthesized on a platinum-coated silicon substrate using low temperature all-solution process. The RS memory devices of Ag/polymethylmethacrylate (PMMA)/ CsPbI 3 /Pt/Ti/SiO 2 /Si structure exhibit reproducible and reliable bipolar switching characteristics with an ultralow operating voltage (<+0.2 V), high on/off ratio (>10 6 ), reversible RS by pulse voltage operation (pulse duration < 1 ms), and multilevel data storage. The mechanical flexibility of the CsPbI 3 perovskite RS memory device on a flexible substrate is also successfully confirmed. With analyzing the influence of phase transition in CsPbI 3 on RS characteristics, a mechanism involving conducting filaments formed by metal cation migration is proposed to explain the RS behavior of the memory device. This study will contribute to the understanding of the intrinsic characteristics of IHPs for low-voltage resistive switching and demonstrate the huge potential of them for use in low-power consumption nonvolatile memory devices on next-generation computing systems.

Recently, organometallic and all-inorganic halide perovskites (HPs) have become promising materials for resistive switching (RS) nonvolatile memory devices with low power consumption because they show current–voltage hysteresis caused by fast ion migration. However, the toxicity and environmental pollution potential of lead, a common constituent of HPs, has limited the commercial applications of HP-based devices. Here, RS memory devices based on lead-free all-inorganic cesium tin iodide (CsSnI3) perovskites with temperature tolerance are successfully fabricated. The devices exhibit reproducible and reliable bipolar RS characteristics in both Ag and Au top electrodes (TEs) with different switching mechanisms. The Ag TE devices show filamentary RS behavior with ultralow operating voltages (<0.15 V). In contrast, the Au TE devices have interface-type RS behavior with gradual resistance changes. This suggests that the RS characteristics are attributed to either the formation of metal filaments or the ion migration of defects in HPs under applied electric fields. These distinct mechanisms may permit the opportunity to design devices for specific purposes. This work will pave the way for lead-free all-inorganic HP-based nonvolatile memory for commercial application in HP-based devices.

Fascinating characteristics of halide perovskites (HPs), which cannot be seen in conventional semiconductors and metal oxides, have boosted the application of HPs in electronic devices beyond optoelectronics such as solar cells, photodetectors, and light-emitting diodes. Here, recent advances in HP-based memory and logic devices such as resistive-switching memories (i.e., resistive random access memory (RRAM) or memristors), transistors, and artificial synapses are reviewed, focusing on inherently exotic properties of HPs: i) tunable bandgap, ii) facile majority carrier control, iii) fast ion migration, and iv) superflexibility. Various fabrication techniques of HP thin films from solution-based methods to vacuum processes are introduced. Up-to-date work in the field, emphasizing the compositional flexibility of HPs, suggest that HPs are promising candidates for next-generation electronic devices. Taking advantages of their unique electrical properties, low-cost and low-temperature synthesis, and compositional and mechanical flexibility, HPs have enormous potential to provide a new platform for future electronic devices and explosively intensive studies will pave the way in finding new HP materials beyond conventional silicon-based semiconductors to keep up with "More-than-Moore" times.

Recently, organic-inorganic halide perovskite (OHP) has been suggested as an alternative to oxides or chalcogenides in resistive switching memory devices due to low operating voltage, high ON/OFF ratio, and flexibility. The most studied OHP is 3-dimensional (3D) MAPbI. However, MAPbI often exhibits less reliable switching behavior probably due to the uncontrollable random formation of conducting filaments. Here, we report the resistive switching property of 2-dimensional (2D) OHP and compare switching characteristics depending on structural dimensionality. The dimensionality is controlled by changing the composition of BAMAPbI (BA = butylammonium, MA = methylammonium), where 2D is formed from n = 1, and 3D is formed from n = ∞. Quasi 2D compositions with n = 2 and 3 are also compared. Transition from a high resistance state (HRS) to a low resistance state (LRS) occurs at 0.25 × 10 V m for 2D BAPbI film, which is lower than those for quasi 2D and 3D. Upon reducing the dimensionality from 3D to 2D, the ON/OFF ratio significantly increases from 10 to 10, which is mainly due to the decreased HRS current. A higher Schottky barrier and thermal activation energy are responsible for the low HRS current. We demonstrate for the first time reliable resistive switching from 4 inch wafer-scale BAPbI thin film working at both room temperature and a high temperature of 87 °C, which strongly suggests that 2D OHP is a promising candidate for resistive switching memory.

It was demonstrated that organolead halide perovskites (OHPs) show a resistive switching behavior with an ultralow electric field of a few kilovolts per centimeter. However, a slow switching time and relatively short endurance remain major obstacles for the realization of the next-generation memory. Here, we report a performance-enhanced OHP resistive switching device. To fabricate topologically and electronically improved OHP thin films, we added hydroiodic acid solution (for an additive) in the precursor solution of the OHP. With drastically improved morphology such as small grain size, low peak-to-valley depth, and precise thickness, the OHP thin films showed an excellent performance as insulating layers in Ag/CHNHPbI/Pt cells, with an endurance of over 10 cycles, a high on/off ratio of 10, and an operation speed of 640 μs and without electroforming. We suggest plausible resistive switching and conduction mechanisms with current-voltage characteristics measured at various temperatures and with different top electrodes and device structures. Beyond the extended endurance, highly flexible resistive switching devices with a minimum bending radius of 5 mm create opportunities for use in flexible and wearable electronic devices.

required. Several types of emerging mem ories have been researched in the past few decades such as magnetic memory, phase change memory, ferroelectric tunnel junc tions, and resistive switching memory. Among these emerging devices, resistive switching memory called memristors, introduced by Chua in 1971, [1] have strong points of small cell size, nonvolatile and random data access possibility, easy fabri cation process, and simple structure. [2,3] Because of these advantages, various mate rials are examined for achieving memris tive properties.In addition, different from the past sev eral decades, information is being made depending on experiences or repeated stimuli similar to that in the human brain. The human brain contains ≈10 11 neurons and 10 15 synapses, occupies a small space, and consumes less than 20 W, which is lower than the power required to run a household light bulb. [4][5][6] Moreover, the human brain is currently considered as the most intelligent and fastest operation system. Therefore, neuromorphic computing, which emu lates the human brain, has been regarded as a promising nextgeneration computing system. Studies on neuromorphic computing have been rapidly growing and highlighted for various applications such as artificial intelligence, sensors, robotic devices, and memory devices.Existing neural networks are implemented by the combination of machine learning as software and the von Neumann archi tecture as hardware based on the complementary metaloxide semiconductor (CMOS) technology. However, CMOSbased cir cuits require 6-12 transistors and the design is not flexible. [7] The present computing system with the von Neumann architecture is implemented by a serial operation through a central processing unit (CPU). Because of the von Neumann bottleneck, memory devices have limitations in data processing speed between memory and CPU and require high power and large space. [8][9][10] Therefore, a new neuromorphic computing system that is exe cuted by parallel operation with a high operation speed, low energy consumption, and small volume is critically required.To achieve such requirement, memristive materials have been actively examined as emulating several functions of human brain. A memristor could act as a single unit of synapse without software programming supports. Memristorbased neu romorphic architecture is implemented by parallel operation with efficient power, small volume, and high data processing Neuromorphic architectures are in the spotlight as promising candidates for substituting current computing systems owing to their high operation speed, scale-down ability, and, especially, low energy consumption. Among candidate materials, memristors have shown excellent synaptic behaviors such as spike time-dependent plasticity and spike rate-dependent plasticity by gradually changing their resistance state according to electrical input stimuli. Memristor can work as a single synapse without programming support, which remarkably satisfies the requirements of neuromorphic computing. Here, the mo...

Resistive random-access memory (ReRAM) devices based on halide perovskites have recently emerged as a new class of data storage devices, where the switching materials used in these devices have attracted extensive attention in recent years. Thus far, three-dimensional (3D) halide perovskites have been the most investigated materials for resistive switching memory devices. However, 3D-based memory devices display ON/OFF ratios comparable to those of oxide or chalcogenide ReRAM devices. In addition, perovskite materials are susceptible to exposure to air. Herein, we compare the resistive switching characteristics of ReRAM devices based on a quasi-two-dimensional (2D) halide perovskite, (PEA) 2 Cs 3 Pb 4 I 13 , to those based on 3D CsPbI 3. Astonishingly, the ON/OFF ratio of the (PEA) 2 Cs 3 Pb 4 I 13-based memory devices (10 9) is three orders of magnitude higher than that of the CsPbI 3 device, which is attributed to a decrease in the high-resistance state (HRS) current of the former. This device also retained a high ON/OFF current ratio for 2 weeks under ambient conditions, whereas the CsPbI 3 device degraded rapidly and showed unreliable memory properties after 5 days. These results strongly suggest that quasi-2D halide perovskites have potential in resistive switching memory based on their desirable ON/OFF ratio and long-term stability.

Halide-perovskites-based resistive random-access memory (ReRAM) devices are emerging as a new class of revolutionary data storage devices because the switching material—halide perovskite—has received considerable attention in recent years owing to its unique and exotic electrical, optical, and structural properties.