Resistive Switching Behavior in Organic-Inorganic Hybrid CH3 NH3 PbI3-x Clx Perovskite for Resistive Random Access Memory Devices

Effect of halide-mixing on the switching behaviors of organic-inorganic hybrid perovskite memory

Mixed halide perovskite materials are actively researched for solar cells with high efficiency. Their hysteresis which originates from the movement of defects make perovskite a candidate for resistive switching memory devices. We demonstrate the resistive switching device based on mixed-halide organic-inorganic hybrid perovskite CH3NH3PbI3-xBrx (x = 0, 1, 2, 3). Solvent engineering is used to deposit the homogeneous CH3NH3PbI3-xBrx layer on the indium-tin oxide-coated glass substrates. The memory device based on CH3NH3PbI3-xBrx exhibits write endurance and long retention, which indicate reproducible and reliable memory properties. According to the increase in Br contents in CH3NH3PbI3-xBrx the set electric field required to make the device from low resistance state to high resistance state decreases. This result is in accord with the theoretical calculation of migration barriers, that is the barrier to ionic migration in perovskites is found to be lower for Br- (0.23 eV) than for I- (0.29-0.30 eV). The resistive switching may be the result of halide vacancy defects and formation of conductive filaments under electric field in the mixed perovskite layer. It is observed that enhancement in operating voltage can be achieved by controlling the halide contents in the film.

Flexible All-Inorganic Perovskite CsPbBr3 Nonvolatile Memory Device

All-inorganic perovskite CsPbX₃ (X = Cl, Br, or I) is widely used in a variety of photoelectric devices such as solar cells, light-emitting diodes, lasers, and photodetectors. However, studies to understand the flexible CsPbX₃ electrical application are relatively scarce, mainly due to the limitations of the low-temperature fabricating process. In this study, all-inorganic perovskite CsPbBr₃ films were successfully fabricated at 75 °C through a two-step method. The highly crystallized films were first employed as a resistive switching layer in the Al/CsPbBr₃/PEDOT:PSS/ITO/PET structure for flexible nonvolatile memory application. The resistive switching operations and endurance performance demonstrated the as-prepared flexible resistive random access memory devices possess reproducible and reliable memory characteristics. Electrical reliability and mechanical stability of the nonvolatile device were further tested by the robust current-voltage curves under different bending angles and consecutive flexing cycles. Moreover, a model of the formation and rupture of filaments through the CsPbBr₃ layer was proposed to explain the resistive switching effect. It is believed that this study will offer a new setting to understand and design all-inorganic perovskite materials for future stable flexible electronic devices.

Status and Prospects of ZnO-Based Resistive Switching Memory Devices

In the advancement of the semiconductor device technology, ZnO could be a prospective alternative than the other metal oxides for its versatility and huge applications in different aspects. In this review, a thorough overview on ZnO for the application of resistive switching memory (RRAM) devices has been conducted. Various efforts that have been made to investigate and modulate the switching characteristics of ZnO-based switching memory devices are discussed. The use of ZnO layer in different structure, the different types of filament formation, and the different types of switching including complementary switching are reported. By considering the huge interest of transparent devices, this review gives the concrete overview of the present status and prospects of transparent RRAM devices based on ZnO. ZnO-based RRAM can be used for flexible memory devices, which is also covered here. Another challenge in ZnO-based RRAM is that the realization of ultra-thin and low power devices. Nevertheless, ZnO not only offers decent memory properties but also has a unique potential to be used as multifunctional nonvolatile memory devices. The impact of electrode materials, metal doping, stack structures, transparency, and flexibility on resistive switching properties and switching parameters of ZnO-based resistive switching memory devices are briefly compared. This review also covers the different nanostructured-based emerging resistive switching memory devices for low power scalable devices. It may give a valuable insight on developing ZnO-based RRAM and also should encourage researchers to overcome the challenges.

Solvent-Assisted Gel Printing for Micropatterning Thin Organic-Inorganic Hybrid Perovskite Films

While tremendous efforts have been made for developing thin perovskite films suitable for a variety of potential photoelectric applications such as solar cells, field-effect transistors, and photodetectors, only a few works focus on the micropatterning of a perovskite film which is one of the most critical issues for large area and uniform microarrays of perovskite-based devices. Here we demonstrate a simple but robust method of micropatterning a thin perovskite film with controlled crystalline structure which guarantees to preserve its intrinsic photoelectric properties. A variety of micropatterns of a perovskite film are fabricated by either microimprinting or transfer-printing a thin spin-coated precursor film in soft-gel state with a topographically prepatterned elastomeric poly(dimethylsiloxane) (PDMS) mold, followed by thermal treatment for complete conversion of the precursor film to a perovskite one. The key materials development of our solvent-assisted gel printing is to prepare a thin precursor film with a high-boiling temperature solvent, dimethyl sulfoxide. The residual solvent in the precursor gel film makes the film moldable upon microprinting with a patterned PDMS mold, leading to various perovskite micropatterns in resolution of a few micrometers over a large area. Our nondestructive micropatterning process does not harm the intrinsic photoelectric properties of a perovskite film, which allows for realizing arrays of parallel-type photodetectors containing micropatterns of a perovskite film with reliable photoconduction performance. The facile transfer of a micropatterned soft-gel precursor film on other substrates including mechanically flexible plastics can further broaden its applications to flexible photoelectric systems.

Organolead Halide Perovskites for Low Operating Voltage Multilevel Resistive Switching

Organolead halide perovskites are used for low-operating-voltage multilevel resistive switching. Ag/CH3 NH3 PbI3 /Pt cells exhibit electroforming-free resistive switching at an electric field of 3.25 × 10(3) V cm(-1) for four distinguishable ON-state resistance levels. The migration of iodine interstitials and vacancies with low activation energies is responsible for the low-electric-field resistive switching via filament formation and annihilation.

Flexible Hybrid Organic-Inorganic Perovskite Memory

Active research has been done on hybrid organic-inorganic perovskite materials for application to solar cells with high power conversion efficiency. However, this material often shows hysteresis, which is undesirable, shift in the current-voltage curve. The hysteresis may come from formation of defects and their movement in perovskite materials. Here, we utilize the defects in perovskite materials to be used in memory operations. We demonstrate flexible nonvolatile memory devices based on hybrid organic-inorganic perovskite as the resistive switching layer on a plastic substrate. A uniform perovskite layer is formed on a transparent electrode-coated plastic substrate by solvent engineering. Flexible nonvolatile memory based on the perovskite layer shows reproducible and reliable memory characteristics in terms of program/erase operations, data retention, and endurance properties. The memory devices also show good mechanical flexibility. It is suggested that resistive switching is done by migration of vacancy defects and formation of conducting filaments under the electric field in the perovskite layer. It is believed that organic-inorganic perovskite materials have great potential to be used in high-performance, flexible memory devices.

Compact Layers of Hybrid Halide Perovskites Fabricated via the Aerosol Deposition Process-Uncoupling Material Synthesis and Layer Formation

We present the successful fabrication of CH₃NH₃PbI₃ perovskite layers by the aerosol deposition method (ADM). The layers show high structural purity and compactness, thus making them suitable for application in perovskite-based optoelectronic devices. By using the aerosol deposition method we are able to decouple material synthesis from layer processing. Our results therefore allow for enhanced and easy control over the fabrication of perovskite-based devices, further paving the way for their commercialization.

Abnormal Current-Voltage Hysteresis Induced by Reverse Bias in Organic-Inorganic Hybrid Perovskite Photovoltaics

In this study, reverse bias (RB)-induced abnormal hysteresis is investigated in perovskite solar cells (PVSCs) with nickel oxide (NiOx)/methylammonium lead iodide (CH3NH3PbI3) interfaces. Through comprehensive current-voltage (I-V) characterization and bias-dependent external quantum efficiency (EQE) measurements, we demonstrate that this phenomenon is caused by the interfacial ion accumulation intrinsic to CH3NH3PbI3. Subsequently, via systematic analysis we discover that the abnormal I-V behavior is remarkably similar to tunnel diode I-V characteristics and is due to the formation of a transient tunnel junction at NiOx/CH3NH3PbI3 interfaces under RB. The detailed analysis navigating the complexities of I-V behavior in CH3NH3PbI3-based solar cells provided here ultimately illuminates possibilities in modulating ion motion and hysteresis via interfacial engineering in PVSCs. Furthermore, this work shows that RB can alter how CH3NH3PbI3 contributes to the functional nature of devices and provides the first steps toward approaching functional perovskite interfaces in new ways for metrology and analysis of complex transient processes.

Nonvolatile memory devices based on poly(vinyl alcohol) + graphene oxide hybrid composites

The performance of the ITO/PVA + GO/Al device was effectively enhanced by the introduction of GO into the PVA matrix.

Two in one: switchable ion conductivity and white light emission integrated in an iodoplumbate-based twin chain hybrid crystal

A [Pb₂I₆]_∝ twin chain hybrid crystal shows novel switchable ion conductivity arising from the structural phase transition and color-tunable photoluminescence attributed to the broadband semiconductor emission of twin chain.

High-efficiency bulk heterojunction memory devices fabricated using organometallic halide perovskite:poly(N-vinylcarbazole) blend active layers

The as-fabricated ITO/CH₃NH₃PbI₃:PVK/Al bulk heterojunction device exhibited a nonvolatile write-once read-many-times memory effect, with a maximum ON/OFF current ratio exceeding 10³and a turn-on voltage of −1.57 V.

Highly stabilized perovskite solar cell prepared using vacuum deposition

With proper optimization, high efficiency solar cells are fabricated with the perovskite layers prepared using a one-step solution process and vacuum deposition methods and the devices prepared by vacuum deposition show significantly better ambient and thermal stability.