A lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor and its preparation method

Abstract

The present invention discloses a lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor and a preparation method thereof, belonging to the field of non-volatile memory technology. The present invention discloses a preparation method for a lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor, comprising selecting a substrate and depositing a conductive film thereon as a conductive bottom electrode of the memristor; forming a lead-free all-inorganic halide perovskite film on the conductive bottom electrode to serve as the storage layer of the memristor; and then depositing a metal conductive film on the Cs3Cu2Br5 film as a conductive top electrode. The memristor based on the lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film prepared by the method of the present invention has the advantages of simple construction process and structure, environmental friendliness, and high stability. In addition, the materials for synthesizing the Cs3Cu2Br5 thin film are widely available and low-cost, which can be used to scale up the device and has good application prospects.

Description

Technical Field

[0001] The present invention belongs to the technical field of non-volatile memory, and in particular relates to a lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor and a preparation method thereof. Background Art

[0002] Halide perovskite semiconductors have attracted significant attention due to their tunable band gaps, superior charge transfer capabilities, and high carrier mobility, and are currently having a significant impact in applications such as solar cells, light-emitting devices, and other electronic devices. However, the moisture sensitivity and thermal instability of the organic cations in the hybrid perovskite structure, as well as the potential environmental pollution caused by the toxicity of lead in the perovskite, have limited their large-scale commercial prospects. Therefore, the exploration of stable and non-toxic halide perovskites is imperative.

[0003] Resistive memory, with its high integration density and fast switching speed, has broken the traditional von Neumann bottleneck. Fortunately, halide perovskites possess excellent defect-assisted carrier transport properties, making them considered ideal storage layers for resistive switching memories. Halide perovskites are typical ionic conductors, conforming to the ion migration mechanism. Halide perovskites exhibit stable current-voltage hysteresis due to the migration of ions or defects, making them suitable for use in resistive switching devices.

[0004] It is well known that inorganic halide perovskites generally exhibit better stability than organic halide perovskites. In addition, in order to address the toxicity of lead, the divalent lead in the perovskite can be replaced by isovalent / heterovalent metal cations or a combination of two heterovalent metal cations. The mainstream mechanism of halide perovskite-based resistive switching devices is attributed to the aggregation and migration of halide ions. Therefore, the electronic properties of ions in halide perovskites play an important role in the switching behavior. At present, halide perovskites have excellent physical properties and are one of the ideal materials for constructing memristors. However, the instability caused by the presence of organic groups and the environmental pollution of lead have limited their application prospects. Summary of the Invention

[0005] In order to overcome the shortcomings of the above-mentioned prior art, the purpose of the present invention is to provide a lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor and its preparation method, so as to solve the technical problems such as the instability caused by the presence of organic groups in halide perovskite and the great pollution to the environment caused by the addition of lead.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] The present invention discloses a method for preparing a lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor, which is characterized by comprising the following steps:

[0008] First, a conductive film is deposited on a substrate as a conductive bottom electrode. Then, CuBr powder and CsBr powder are mixed and dissolved in a solvent. After ultrasonic treatment, a Cs3Cu2Br5 precursor solution is obtained. The Cs3Cu2Br5 precursor solution is coated on the conductive bottom electrode. After film formation, annealing treatment is performed to obtain a Cs3Cu2Br5 perovskite thin film storage layer. A conductive film is deposited on the Cs3Cu2Br5 perovskite thin film storage layer as a conductive top electrode to obtain a lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor.

[0009] Furthermore, the solvent is dimethyl sulfoxide and N,N-dimethylformamide; the molar ratio of dimethyl sulfoxide to N,N-dimethylformamide is (1-8):1.

[0010] Furthermore, the molar ratio of the CuBr powder to the CsBr powder is 3:2.

[0011] Furthermore, the ultrasonic treatment is water bath ultrasonic treatment; the time of the water bath ultrasonic treatment is 10 min to 60 min, and the temperature of the water bath ultrasonic treatment is 40° C. to 90° C.

[0012] Furthermore, the material of the substrate is conductive glass or SiO2 / Si; the material of the conductive film is ITO, FTO, Au, Pt, Al or Ag.

[0013] Furthermore, both the methods of depositing the conductive film on the substrate and the methods of depositing the conductive film on the Cs3Cu2Br5 perovskite film storage layer adopt physical deposition processes; and the Cs3Cu2Br5 precursor solution is coated on the conductive bottom electrode using a spin coating process.

[0014] Furthermore, the spin coating process is as follows: first, the precursor solution is spin-coated on the bottom electrode at a rotation speed of 500 rpm to 2000 rpm for 5 s to 20 s, and then the film is formed at 2000 rpm to 8000 rpm for 10 s to 50 s; and methyl acetate is added in the last 5 s to 15 s of the spin coating.

[0015] Furthermore, the annealing treatment is performed in an argon environment; the temperature of the annealing treatment is 100° C. to 300° C., and the time is 10 min to 90 min.

[0016] The present invention also discloses a lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor prepared by the above-mentioned preparation method. The lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor includes a substrate, the upper surface of which is provided with a conductive bottom electrode; the upper surface of the conductive bottom electrode is provided with a Cs3Cu2Br5 perovskite thin film storage layer, and the upper surface of the Cs3Cu2Br5 perovskite thin film storage layer is provided with a conductive top electrode.

[0017] Furthermore, the thickness of the conductive bottom electrode and the conductive top electrode are both 50 nm to 200 nm.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] The present invention discloses a preparation method of a lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor. The lead-free all-inorganic halide Cs3Cu2Br5 thin film is used as the storage layer of the memristor to construct the memristor, thereby obtaining a device with excellent resistive switching characteristics. Since inorganic groups are used as the replacement, the instability caused by the presence of organic groups is avoided. The absence of added lead reduces pollution to the environment. The preparation method is simple to operate, environmentally friendly, and is conducive to large-scale production.

[0020] Furthermore, when preparing the Cs3Cu2Br5 precursor solution, water bath ultrasonic treatment is used. By controlling the ultrasonic time and temperature, the raw material powders can be fully mixed. When the ultrasonic treatment reaches a certain time, a precursor solution with good uniformity can be achieved.

[0021] Furthermore, a spin coating process is used to coat the Cs3Cu2Br5 precursor solution to form a thin film. By adjusting the spin coating speed in two steps, high and low, a uniform film can be obtained. A too fast spin coating speed results in a film thickness that does not meet device requirements, while a too slow spin coating speed results in excessive surface roughness, affecting device performance. Furthermore, by adding methyl acetate in the last 5 to 15 seconds of the spin coating cycle, an anti-solvent is added to achieve rapid film formation, which is then neutralized with a strong solvent mixture to form a resistive switching thin film layer.

[0022] Furthermore, by controlling the atmosphere, temperature, and time of film annealing, a protective atmosphere helps obtain high-quality crystals; while too low an annealing temperature will reduce the crystallinity of the film, while too high an annealing temperature will cause the lead-free all-inorganic halide Cs3Cu2Br5 perovskite film to decompose.

[0023] The present invention also discloses a lead-free, all-inorganic halide Cs3Cu2Br5 perovskite thin-film memristor prepared using the above-mentioned preparation method. The device has the advantages of simple structure and ease of large-scale production, thus having good market application prospects. Furthermore, the raw materials for synthesizing Cs3Cu2Br5 are widely available, resulting in low cost and a simple preparation process.

[0024] Furthermore, the thickness of the conductive bottom electrode and the conductive top electrode are both 50nm to 200nm. According to the requirements of the resistive switching characteristics, the top electrode and the bottom electrode are deposited with a certain thickness. If the thickness of the electrode is too small, the device is easily broken down; if it is too thick, the switching voltage of the device is too large and the stability is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram of the structure of the lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor prepared in Example 1 of the present invention;

[0026] Figure 2 This is a scanning electron microscope image of the Cs3Cu2Br5 storage layer prepared in Example 1 of the present invention;

[0027] Figure 3 This is a voltage-current curve of the lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor prepared in Example 1 of the present invention;

[0028] Figure 4 This is a voltage-current curve diagram of the lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor prepared in Example 1 of the present invention under different limiting currents. DETAILED DESCRIPTION

[0029] To facilitate understanding of the features and effects of the present invention by those skilled in the art, the following provides a general description and definition of the terms and expressions used in the specification and claims. Unless otherwise indicated, all technical and scientific terms used herein have the ordinary meanings as understood by those skilled in the art regarding the present invention. In the event of conflict, the definitions in this specification shall prevail.

[0030] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0031] Herein, all features such as values, amounts, amounts, and concentrations defined in numerical ranges or percentage ranges are for brevity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to include and specifically disclose all possible subranges and individual values within the range (including integers and fractions).

[0032] In this document, unless otherwise specified, “include,” “including,” “contains,” “has” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0033] In this document, for the sake of brevity, not all possible combinations of the various technical features in each embodiment or example are described. Therefore, as long as there are no contradictions in the combination of these technical features, the various technical features in each embodiment or example can be combined in any way, and all possible combinations should be considered to be within the scope of this specification.

[0034] like Figure 1 As shown, a lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor of the present invention comprises, from bottom to top, a conductive bottom electrode, a Cs3Cu2Br5 storage layer and a conductive top electrode; the conductive bottom electrode and the conductive top electrode are fixedly connected through the Cs3Cu2Br5 storage layer, and the thickness of the conductive bottom electrode and the conductive top electrode is 50 to 200 nm.

[0035] The present invention provides a method for preparing a lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor, comprising the following steps:

[0036] S1: The substrate is selected as conductive glass or SiO2 or Si, and a conductive film with a thickness of 50 to 200 nm is deposited on the substrate using a physical deposition process as the conductive bottom electrode of the memristor;

[0037] Preferably, the physical deposition process is DC magnetron sputtering.

[0038] Preferably, the conductive bottom electrode is made of platinum with a thickness of 100 nm.

[0039] S2: Dimethyl sulfoxide and N,N-dimethylformamide are selected, and a solvent is prepared according to a molar ratio of (1 to 8): 1. CuBr powder and CsBr powder are mixed and dissolved in the prepared solvent, and then ultrasonicated in a water bath, the ultrasonic time is 10 to 60 minutes, and the temperature is 40°C to 90°C to obtain a Cs3Cu2Br5 precursor solution; the Cs3Cu2Br5 precursor solution is spin-coated on the conductive bottom electrode at a low speed of 500 to 2000 rpm, and the spin-coating time is 5 to 20 seconds, followed by continuing to form a film at a high speed of 2000 to 8000 rpm for 10 to 50 seconds, and methyl acetate is added as an anti-solvent in the last 5 to 15 seconds of spin coating; then annealing is performed in a high-purity argon environment, the annealing temperature is 100 to 300°C, and the time is 10 to 90 minutes. After natural cooling, a Cs3Cu2Br5 perovskite thin film storage layer is obtained.

[0040] Preferably, the molar ratio of dimethyl sulfoxide to N,N-dimethylformamide is 4:1 to prepare the solvent, and the molar ratio of CuBr powder to CsBr powder is maintained at 3:2.

[0041] Preferably, the time of water bath ultrasonic treatment is 30 min, and the temperature of the water bath is 60°C.

[0042] Preferably, the Cs3Cu2Br5 precursor solution is spin-coated on the conductive bottom electrode at a low rotation speed of 1000 rpm for 10 seconds, and then the film formation is continued at a high rotation speed of 4000 rpm for 20 seconds.

[0043] Preferably, methyl acetate is added as an antisolvent during the last 10 s of spin coating.

[0044] Preferably, the annealing treatment is performed in a high-purity argon environment, with a temperature of 200° C. and a time of 60 minutes.

[0045] S3; Using physical vapor deposition process, a conductive film with a thickness of 50 to 200min is deposited on the Cs3Cu2Br5 perovskite thin film storage layer as a conductive top electrode to prepare a lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor.

[0046] Preferably, the conductive top electrode is aluminum with a thickness of 100 nm prepared by a sputtering process.

[0047] Below in conjunction with specific embodiment, further set forth the present invention.Should be understood that these embodiments are only used to illustrate the present invention and are not used in limiting the scope of the present invention.In addition, should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall equally within the scope limited by the appended claims of the application.

[0048] The following examples were prepared using conventional instruments and equipment in the art. Experimental methods in the following examples, where specific conditions are not specified, were generally performed under conventional conditions or according to the conditions recommended by the manufacturer. The various raw materials used in the following examples, unless otherwise specified, were conventional commercially available products, with specifications conventional in the art. In the present specification and the following examples, unless otherwise specified, "%" indicates percentage by weight, "part" indicates parts by weight, and "ratio" indicates weight ratio.

[0049] Example 1

[0050] A method for preparing a lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor comprises the following steps:

[0051] S1: Select conductive glass as the substrate and use DC sputtering process to deposit a 100 nm thick conductive film on the substrate as the conductive bottom electrode of the device;

[0052] S2: dimethyl sulfoxide and N,N-dimethylformamide are selected and a solvent is prepared according to a molar ratio of 4:1. CuBr and CsBr powders are mixed according to a molar ratio of 3:2 and dissolved in the prepared solvent. The mixture is then ultrasonicated in a water bath for 30 minutes at a temperature of 60°C to obtain a Cs3Cu2Br5 precursor solution. The Cs3Cu2Br5 precursor solution is spin-coated on a conductive bottom electrode at a low speed of 1000 rpm for 10 seconds, followed by a high speed of 4000 rpm for 20 seconds to form a film. Methyl acetate is added as an anti-solvent in the last 10 seconds of spin coating. Annealing is performed in a high-purity argon environment at a temperature of 200°C for 60 minutes to obtain a Cs3Cu2Br5 perovskite thin film storage layer.

[0053] S3: Using a DC sputtering process, a metal aluminum film with a thickness of 100 nm is deposited on the Cs3Cu2Br5 perovskite film storage layer as a conductive top electrode to obtain a lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor.

[0054] Example 2

[0055] A method for preparing a lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor comprises the following steps:

[0056] S1: Select conductive glass as the substrate and use DC sputtering process to deposit a 100 nm thick conductive film on the substrate as the conductive bottom electrode of the device;

[0057] S2: dimethyl sulfoxide and N,N-dimethylformamide are selected and prepared as a solvent in a molar ratio of 8:1, CuBr and CsBr powders are mixed in a molar ratio of 3:2, dissolved in the prepared solvent, and then subjected to water bath ultrasonic treatment for 30 minutes at a temperature of 60°C to obtain a Cs3Cu2Br5 precursor solution; the Cs3Cu2Br5 precursor solution is spin-coated on the conductive bottom electrode at a low speed of 1000 rpm for 10 seconds, followed by continuous film formation at a high speed of 8000 rpm for 20 seconds, and methyl acetate is added as an anti-solvent in the last 10 seconds of spin coating; annealing is performed in a high-purity argon environment at a temperature of 200°C for 60 minutes to obtain a Cs3Cu2Br5 perovskite thin film storage layer;

[0058] S3: Using a DC sputtering process, a metal aluminum film with a thickness of 100 nm is deposited on the Cs3Cu2Br5 perovskite film storage layer as a conductive top electrode to obtain a lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor.

[0059] Compared with the mutation process of Example 1, the surface roughness of the resistive switching layer of the memristor prepared in Example 2 is too large, which affects the stability of the constructed device.

[0060] Example 3

[0061] A method for preparing a lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor comprises the following steps:

[0062] S1: Select conductive glass as the substrate and use DC sputtering process to deposit a 100 nm thick conductive film on the substrate as the conductive bottom electrode of the device;

[0063] S2: dimethyl sulfoxide and N,N-dimethylformamide are selected and prepared as a solvent in a molar ratio of 1:1, CuBr and CsBr powders are mixed in a molar ratio of 3:2, dissolved in the prepared solvent, and then subjected to water bath ultrasonic treatment for 30 minutes at a temperature of 60°C to obtain a Cs3Cu2Br5 precursor solution; the Cs3Cu2Br5 precursor solution is spin-coated on the conductive bottom electrode at a low speed of 1000 rpm for 10 seconds, followed by continuous film formation at a high speed of 8000 rpm for 20 seconds, and methyl acetate is added as an anti-solvent in the last 10 seconds of spin coating; annealing is performed in a high-purity argon environment at a temperature of 200°C for 60 minutes to obtain a Cs3Cu2Br5 perovskite thin film storage layer;

[0064] S3: Using a DC sputtering process, a metal aluminum film with a thickness of 100 nm is deposited on the Cs3Cu2Br5 perovskite film storage layer as a conductive top electrode to obtain a lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor.

[0065] Compared with the mutation process of Example 1, Example 3 is the same as Example 2. The surface roughness of the resistive switching layer of the prepared memristor is also too large, which affects the stability of the constructed device.

[0066] Example 4

[0067] A method for preparing a lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor comprises the following steps:

[0068] S1: Select a conductive SiO2 / Si substrate and use a DC sputtering process to deposit a 100 nm thick conductive film on the substrate as the conductive bottom electrode of the device;

[0069] S2: dimethyl sulfoxide and N,N-dimethylformamide are selected and a solvent is prepared according to a molar ratio of 4:1. CuBr and CsBr powders are mixed according to a molar ratio of 3:2 and dissolved in the prepared solvent. The mixture is then ultrasonicated in a water bath for 30 minutes at a temperature of 60°C to obtain a Cs3Cu2Br5 precursor solution. The Cs3Cu2Br5 precursor solution is spin-coated on a conductive bottom electrode at a low speed of 1000 rpm for 5 seconds, followed by continuous film formation at a high speed of 4000 rpm for 50 seconds. Methyl acetate is added as an anti-solvent in the last 10 seconds of spin coating. Annealing is performed in a high-purity argon environment at a temperature of 200°C for 60 minutes to obtain a Cs3Cu2Br5 perovskite thin film storage layer.

[0070] S3: Using a DC sputtering process, a metal aluminum film with a thickness of 100 nm is deposited on the Cs3Cu2Br5 perovskite film storage layer as a conductive top electrode to obtain a lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor.

[0071] Compared with the mutation process of Example 1, the memristor prepared in Example 4 adopts a process compatible with the CMOS process, but the switching ratio of the device needs to be further improved.

[0072] Example 5

[0073] A method for preparing a lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor comprises the following steps:

[0074] S1: Select conductive glass as the substrate and use DC sputtering process to deposit a 100 nm thick conductive film on the substrate as the conductive bottom electrode of the device;

[0075] S2: dimethyl sulfoxide and N,N-dimethylformamide are selected and prepared as a solvent in a molar ratio of 1:1, CuBr and CsBr powders are mixed in a molar ratio of 3:2, dissolved in the prepared solvent, and then subjected to water bath ultrasonic treatment for 30 minutes at a temperature of 60°C to obtain a Cs3Cu2Br5 precursor solution; the Cs3Cu2Br5 precursor solution is spin-coated on a conductive bottom electrode at a low speed of 1000 rpm for 10 seconds, followed by continuous film formation at a high speed of 8000 rpm for 20 seconds, and methyl acetate is added as an anti-solvent in the last 10 seconds of spin coating; annealing is performed in a high-purity argon environment at a temperature of 300°C for 10 minutes to obtain a Cs3Cu2Br5 perovskite thin film storage layer;

[0076] S3: Using a DC sputtering process, a metal aluminum film with a thickness of 100 nm is deposited on the Cs3Cu2Br5 perovskite film storage layer as a conductive top electrode to obtain a lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor.

[0077] Compared with Example 1, in Example 6, since the annealing time is too short, the crystallinity of the resistive switching layer is too low, which affects the stability of the device.

[0078] Example 6

[0079] A method for preparing a lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor comprises the following steps:

[0080] S1: Select conductive glass as the substrate and use DC sputtering process to deposit a 100 nm thick conductive film on the substrate as the conductive bottom electrode of the device;

[0081] S2: dimethyl sulfoxide and N,N-dimethylformamide are selected and prepared as a solvent in a molar ratio of 1:1, CuBr and CsBr powders are mixed in a molar ratio of 3:2, dissolved in the prepared solvent, and then subjected to water bath ultrasonic treatment for 30 minutes at a temperature of 60°C to obtain a Cs3Cu2Br5 precursor solution; the Cs3Cu2Br5 precursor solution is spin-coated on the conductive bottom electrode at a low speed of 1000 rpm for 10 seconds, followed by continuous film formation at a high speed of 8000 rpm for 20 seconds, and methyl acetate is added as an anti-solvent in the last 10 seconds of spin coating; annealing is performed in a high-purity argon environment at a temperature of 300°C for 90 minutes to obtain a Cs3Cu2Br5 perovskite thin film storage layer;

[0082] S3: Using a DC sputtering process, a 100nm thick Ag film is deposited on the Cs3Cu2Br5 perovskite thin film storage layer as a conductive top electrode to obtain a lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor.

[0083] Compared with Example 1, in Example 6, the annealing time is too long, resulting in too few defects in the resistive switching layer, which affects the stability of the device.

[0084] Example 7

[0085] A method for preparing a lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor comprises the following steps:

[0086] S1: Select conductive glass as the substrate and use DC sputtering process to deposit a 100 nm thick conductive film on the substrate as the conductive bottom electrode of the device;

[0087] S2: dimethyl sulfoxide and N,N-dimethylformamide are selected and a solvent is prepared according to a molar ratio of 4:1. CuBr and CsBr powders are mixed according to a molar ratio of 3:2 and dissolved in the prepared solvent. The mixture is then ultrasonicated in a water bath for 30 minutes at a temperature of 60°C to obtain a Cs3Cu2Br5 precursor solution. The Cs3Cu2Br5 precursor solution is spin-coated on a conductive bottom electrode at a low speed of 1000 rpm for 5 seconds, followed by continuous film formation at a high speed of 8000 rpm for 10 seconds. Methyl acetate is added as an anti-solvent in the last 10 seconds of spin coating. Annealing is performed in a high-purity argon environment at a temperature of 100°C for 60 minutes to obtain a Cs3Cu2Br5 perovskite thin film storage layer.

[0088] S3: Using a DC sputtering process, a metal aluminum film with a thickness of 100 nm is deposited on the Cs3Cu2Br5 perovskite film storage layer as a conductive top electrode to obtain a lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor.

[0089] The resistive switching layer of the memristor prepared in Example 7 was annealed at 100° C. in a high-purity argon environment. Due to the relatively low annealing temperature, the prepared thin film had many crystal defects, and the stability of the prepared device needed to be improved.

[0090] Example 8

[0091] A method for preparing a lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor comprises the following steps:

[0092] S1: Select conductive glass as the substrate and use DC sputtering process to deposit a 100 nm thick conductive film on the substrate as the conductive bottom electrode of the device;

[0093] S2: dimethyl sulfoxide and N,N-dimethylformamide are selected and a solvent is prepared according to a molar ratio of 4:1. CuBr and CsBr powders are mixed according to a molar ratio of 1:2 and dissolved in the prepared solvent. The mixture is then ultrasonicated in a water bath for 30 minutes at a temperature of 60°C to obtain a Cs3Cu2Br5 precursor solution. The Cs3Cu2Br5 precursor solution is spin-coated on a conductive bottom electrode at a low speed of 1000 rpm for 10 seconds, followed by a high speed of 4000 rpm for 20 seconds to form a film. Methyl acetate is added as an anti-solvent in the last 10 seconds of the spin coating. Annealing is performed in a high-purity argon environment at a temperature of 200°C for 60 minutes to obtain a Cs3Cu2Br5 perovskite thin film storage layer.

[0094] S3: Using a DC sputtering process, a 100nm thick ITO film is deposited on the Cs3Cu2Br5 perovskite film storage layer as a conductive top electrode to obtain a lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor.

[0095] Example 8: CuBr powder and CsBr powder were mixed in a molar ratio of 1:2 and dissolved in a prepared solvent to prepare a precursor solution. Although the prepared device also had good characteristics, its stability needed to be improved.

[0096] Example 9

[0097] A method for preparing a lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor comprises the following steps:

[0098] S1: Select conductive glass as the substrate and use DC sputtering process to deposit a 100 nm thick conductive film on the substrate as the conductive bottom electrode of the device;

[0099] S2: dimethyl sulfoxide and N,N-dimethylformamide are selected and a solvent is prepared according to a molar ratio of 4:1. CuBr and CsBr powders are mixed according to a molar ratio of 3:2 and dissolved in the prepared solvent. The mixture is then ultrasonicated in a water bath for 30 minutes at a temperature of 60°C to obtain a Cs3Cu2Br5 precursor solution. The Cs3Cu2Br5 precursor solution is spin-coated on a conductive bottom electrode at a low speed of 1000 rpm for 10 seconds, followed by a high speed of 4000 rpm for 20 seconds to form a film. Methyl acetate is added as an anti-solvent in the last 10 seconds of spin coating. Annealing is performed in a high-purity argon environment at a temperature of 200°C for 60 minutes to obtain a Cs3Cu2Br5 perovskite thin film storage layer.

[0100] S3: Using a DC sputtering process, a 100nm thick platinum film is deposited on the Cs3Cu2Br5 perovskite film storage layer as a conductive top electrode to obtain a lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor.

[0101] In Example 9, metal platinum is selected as the top electrode, and the memristor has a large set voltage and reset voltage. This is because the density of the conductive channel is too sparse.

[0102] Example 10

[0103] A method for preparing a lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor comprises the following steps:

[0104] S1: Select conductive glass as the substrate and use DC sputtering process to deposit a 100 nm thick conductive film on the substrate as the conductive bottom electrode of the device;

[0105] S2: dimethyl sulfoxide and N,N-dimethylformamide are selected and a solvent is prepared according to a molar ratio of 4:1. CuBr and CsBr powders are mixed according to a molar ratio of 3:2 and dissolved in the prepared solvent. The mixture is then ultrasonicated in a water bath for 30 minutes at a temperature of 60°C to obtain a Cs3Cu2Br5 precursor solution. The Cs3Cu2Br5 precursor solution is spin-coated on a conductive bottom electrode at a low speed of 1000 rpm for 10 seconds, followed by a high speed of 2000 rpm for 20 seconds to form a film. Methyl acetate is added as an anti-solvent in the last 5 seconds of the spin coating. Annealing is performed in a high-purity argon environment at a temperature of 200°C for 60 minutes to obtain a Cs3Cu2Br5 perovskite thin film storage layer.

[0106] S3: Using a DC sputtering process, a 100nm thick FTO film is deposited on the Cs3Cu2Br5 perovskite film storage layer as a conductive top electrode to obtain a lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor.

[0107] In Example 10, film formation was continued at a high rotation speed of 2000 rpm, and methyl acetate was added as an anti-solvent in the last 5 seconds of spin coating. The stability of the prepared memristor was not sufficient for application, which was due to insufficient film thickness.

[0108] Figure 2 Shown is a scanning electron microscope image of the lead-free all-inorganic halide Cs3Cu2Br5 perovskite film prepared in Example 1. It can be seen from the figure that the film has good flatness. Figure 3The figure shows the voltage-current curve of the lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor prepared in Example 1. It can be seen from the figure that the resistive switching device exhibits stable bipolar characteristics. Figure 4 Shown is a voltage-current curve of the lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor prepared in Example 1 under different limiting currents. It can be seen from the figure that multi-bit storage characteristics can be achieved by controlling different limiting currents.

[0109] In summary, the lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor disclosed in the present invention has the following characteristics:

[0110] 1) The present invention proposes a simple structured memristor based on a lead-free, all-inorganic halide Cs3Cu2Br5 perovskite thin film. The environmentally friendly and highly stable all-inorganic Cs3Cu2Br5 perovskite thin film is used as the storage layer, resulting in a stable resistive switching device.

[0111] 2) By controlling the process of preparing the all-inorganic Cs3Cu2Br5 perovskite film and selecting appropriate upper and lower electrodes, a lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor with excellent resistive switching properties is obtained.

[0112] 3) The present invention proposes a method for preparing a lead-free all-inorganic halide Cs3Cu2Br5 perovskite film, which has the advantages of a wide range of material sources, low cost, and simple preparation process, can be applied on a large scale, and has good market application prospects.

[0113] The above content is only for explaining the technical idea of the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor, characterized in that: The following steps are involved: First, a conductive film is deposited on a substrate as a conductive bottom electrode. Then, CuBr powder and CsBr powder are mixed and dissolved in a solvent. After ultrasonic treatment, a Cs3Cu2Br5 precursor solution is obtained. The Cs3Cu2Br5 precursor solution is applied to the conductive bottom electrode. After film formation, the film is annealed to obtain a Cs3Cu2Br5 perovskite thin film storage layer. A conductive film is deposited on the Cs3Cu2Br5 perovskite thin film storage layer as a conductive top electrode to obtain a lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor. The solvent is dimethyl sulfoxide and N,N-dimethylformamide; the molar ratio of dimethyl sulfoxide to N,N-dimethylformamide is (1-8):1; The conductive film is deposited on the substrate and on the Cs3Cu2Br5 perovskite film storage layer using a physical deposition process; a Cs3Cu2Br5 precursor solution is applied to the conductive bottom electrode using a spin coating process; The spin coating process comprises the following steps: firstly, the precursor solution is spin-coated on the bottom electrode at a rotation speed of 500 rpm to 2000 rpm for 5 seconds to 20 seconds, and then the film is formed at a rotation speed of 2000 rpm to 8000 rpm for 10 seconds to 50 seconds; and methyl acetate is added in the last 5 seconds to 15 seconds of the spin coating.

2. The method for preparing a lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor according to claim 1, characterized in that: The molar ratio of the CuBr powder to the CsBr powder is 3:

2.

3. The method for preparing a lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor according to claim 1, characterized in that: The ultrasonic treatment is water bath ultrasonic treatment; the time of the water bath ultrasonic treatment is 10 min to 60 min, and the temperature of the water bath ultrasonic treatment is 40° C. to 90° C.

4. The method for preparing a lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor according to claim 1, characterized in that: The material of the substrate is conductive glass or SiO2 / Si; the material of the conductive film is ITO, FTO, Au, Pt, Al or Ag.

5. The method for preparing a lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor according to claim 1, characterized in that: The annealing treatment is performed in an argon environment; the temperature of the annealing treatment is 100° C. to 300° C., and the time is 10 min to 90 min.

6. A lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor prepared by the method for preparing a lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor according to any one of claims 1 to 5, characterized in that: The lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor includes a substrate, the upper surface of which is provided with a conductive bottom electrode; the upper surface of the conductive bottom electrode is provided with a Cs3Cu2Br5 perovskite thin film storage layer, and the upper surface of the Cs3Cu2Br5 perovskite thin film storage layer is provided with a conductive top electrode.

7. The lead-free all-inorganic halide Cs3Cu2Br5 perovskite thin film memristor according to claim 6, characterized in that: The thickness of the conductive bottom electrode and the conductive top electrode are both 50nm-200nm.

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