Optical synaptic device based on molybdenum disulfide and chiral perovskite and preparation method thereof

Abstract

The invention discloses an optical synaptic device based on molybdenum disulfide and chiral perovskite and a preparation method of the optical synaptic device, and relates to the technical field of synaptic devices, the optical synaptic device comprises a substrate, a chiral perovskite layer, a MoS2 layer and a metal electrode which are arranged in sequence, the MoS2 layer completely covers the chiral perovskite layer, and the metal electrode covers the MoS2 layer. A non-contact region which is not in contact with the chiral perovskite layer is remained, and the metal electrode is positioned in the non-contact region of the MoS2 layer. According to the invention, the processing capability of the optical synapse device on the circularly polarized light signal is improved.

Description

Technical Field

[0001] The present application relates to the technical field of synaptic devices, and in particular to an optical synaptic device based on molybdenum disulfide and chiral perovskite and a preparation method thereof. Background Art

[0002] In neuromorphic vision systems, combining optical synaptic devices with optical learning and memory mechanisms can develop important research and application value. Among them, circularly polarized light (CPL), as a light signal with special physical properties, can effectively modulate and transmit information, providing a unique dimension for optical information processing and communication, and can become an ideal carrier for neuromorphic computing. However, conventional optical synaptic devices are weak in processing circularly polarized light signals, which restricts the application of optical synaptic devices. Summary of the invention

[0003] The main purpose of the present application is to provide an optical synapse device based on molybdenum disulfide and chiral perovskite and a preparation method thereof, thereby improving the processing capability of the optical synapse device for circularly polarized light signals.

[0004] To achieve the above-mentioned purpose, the embodiment of the present application provides an optical synaptic device based on molybdenum disulfide and chiral perovskite, comprising a substrate, a chiral perovskite layer, a MoS2 layer and a metal electrode arranged in sequence; The MoS2 layer completely covers the chiral perovskite layer; The metal electrode is located in a non-contact area of ​​the MoS2 layer, wherein the non-contact area is an area where the MoS2 layer is not in contact with the chiral perovskite layer.

[0005] In one embodiment, the material of the chiral perovskite layer includes: (R-NEA)PbI3 and / or (S-NEA)PbI3; And / or, the material of the metal electrode includes: Cr and / or Au.

[0006] In one embodiment, the thickness of the chiral perovskite layer is 98-102 nm; And / or, the thickness of the metal electrode is: 10-64 nm; And / or, the thickness of the MoS2 layer is: 0.7~1.6 nm.

[0007] In one embodiment, the metal electrode comprises a first metal layer and a second metal layer sequentially disposed in a non-contact region of the MoS2 layer; The material of the first metal layer includes: Cr, with a thickness of 10-12 nm; The material of the first metal layer includes: Au, with a thickness of 50-52 nm.

[0008] To achieve the above objectives, the present application provides a method for preparing an optical synapse device based on molybdenum disulfide and chiral perovskite, which is used to prepare the optical synapse device as described above, comprising the following steps: Provide chiral perovskite crystals and MoS2 crystals; The chiral perovskite crystals are released on one surface of the substrate by mechanical peeling to obtain a chiral perovskite layer; The MoS2 crystals are released on the PDMS film on the glass slide by mechanical peeling to obtain a MoS2 layer; Transferring the MoS2 layer to the surface of the chiral perovskite layer to obtain a heterojunction, wherein the MoS2 layer completely covers the chiral perovskite layer; A metal electrode is prepared on the surface of the heterojunction to obtain an optical synapse device, wherein the metal electrode is located in a non-contact area of ​​the MoS2 layer, and the non-contact area is an area where the MoS2 layer is not in contact with the chiral perovskite layer.

[0009] In one embodiment, the step of preparing a metal electrode on the surface of the heterojunction includes: Setting a mask on the surface of the heterojunction and preparing a metal layer; The mask and the metal layer on the upper surface thereof are peeled off to obtain the metal electrode.

[0010] In one embodiment, the step of preparing the metal layer comprises: The metal layer is prepared by thermal evaporation, wherein the evaporation rate is 0.1-0.5 Å / s.

[0011] In one embodiment, the step of transferring the MoS2 layer to the surface of the chiral perovskite layer to obtain a heterojunction comprises: The chiral perovskite layer is placed on a heating stage and heated at 65-85° C. for 1-2 min.

[0012] In one embodiment, the step of providing a chiral perovskite crystal comprises: dissolving a lead source in an iodine source solution to obtain a first solution; adding a chiral compound to the first solution and heating the solution to obtain a second solution; The second solution is cooled to obtain the chiral perovskite crystal.

[0013] In one embodiment, the lead source includes: at least one of lead oxide, lead hydroxide, lead carbonate and lead acetate; And / or, the iodine source comprises: hydrogen iodide; And / or, the chiral compound includes: R-NEA and / or S-NEA; And / or, the heating temperature of the first solution is 100-120°C.

[0014] The embodiment of the present application provides an optical synapse device based on molybdenum disulfide and chiral perovskite, comprising a substrate, a chiral perovskite layer, a MoS2 layer and a metal electrode arranged in sequence, wherein the MoS2 layer completely covers the chiral perovskite layer, and a non-contact area that is not in contact with the chiral perovskite layer remains, and the metal electrode is located in the non-contact area of ​​the MoS2 layer. Through the synergistic photoelectric effect of the heterojunction formed by the chiral perovskite and MoS2, the optical synapse device has a good polarization light resolution capability, can identify the handedness of circularly polarized light and respond to light stimulation, thereby effectively improving the processing capability of the optical synapse device for circularly polarized light signals. BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Figure 1 This is a schematic diagram of the structure of an optical synapse device involved in an embodiment of the present application; Figure 2 This is a flow chart of a method for preparing an optical synapse device according to an embodiment of the present application; Figure 3 The process flow of the optical synapse device preparation method involved in the embodiment of the present application is as follows: Figure 1 ; Figure 4 The process flow of the optical synapse device preparation method involved in the embodiment of the present application is as follows: Figure 2 ; Figure 5 The process flow of the optical synapse device preparation method involved in the embodiment of the present application is as follows: Figure 3 ; Figure 6 This is a schematic diagram of PL test results of Comparative Example 1, Example 1 and Example 2 of the present application; Figure 7 This is a schematic diagram of PL test results of Comparative Example 2, Example 3 and Example 4 of the present application; Figure 8 Output curves of Comparative Example 2, Example 5 and Example 6 of the present application under dark field and right-handed circular polarization and left-handed circular polarization illumination; Fig. 9 The light response curves of Examples 5 and 6 of the present application under CPL light illumination; Fig.10 The curves showing the g value changing with wavelength in Examples 5 and 6 of the present application; Fig.11 It is a schematic diagram of the transient EPSC results in response to a single Lcp and Rcp pulse in Examples 5 and 6 of the present application; Fig.12 This is a schematic diagram of the PPF behavior results of Example 5 and Example 6 of the present application triggered by two CPL pulses; Fig.13 Schematic diagram of the change of the PPF index with the excitatory stimulation interval in Examples 5 and 6 of the present application; Fig.14 Schematic diagram of the short-term plasticity and long-term plasticity results of Examples 5 and 6 of the present application; Fig.15 These are LTP and LTD diagrams of Examples 5 and 6 of the present application under different CPL states; Fig.16 A schematic diagram of a spike neural network according to an embodiment of the present application; Fig.17 A contour map of synaptic weight values ​​reshaped after iteration in an embodiment of the present application; Fig.18 This is a schematic diagram of the recognition accuracy results of letters under different CPL states in Example 5 and Example 6 of the present application.

[0016] Description of reference numerals: 110, substrate; 120, chiral perovskite layer; 130, MoS2 layer; 140. Metal electrode; 150. PDMS film; 160. Mask.

[0017] The realization of the purpose, functional features and advantages of this application will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0018] In order to make the purpose, technical scheme and advantages of the embodiments of the present application clearer, the technical scheme in the embodiments of the present application will be described clearly and completely below. If the specific conditions are not specified in the embodiments, they are carried out according to the conventional conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified for the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0019] Hereinafter, the embodiments of the optical synapse device based on molybdenum disulfide and chiral perovskite and the method for preparing the same are specifically disclosed with appropriate reference to the accompanying drawings. However, there may be cases where unnecessary detailed descriptions are omitted. For example, there are cases where detailed descriptions of well-known matters and repeated descriptions of actually the same structures are omitted. This is to avoid the following description from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the drawings and the following descriptions are provided for those skilled in the art to fully understand the present application and are not intended to limit the subject matter described in the claims.

[0020] The "range" disclosed in the present application is defined in the form of a lower limit and an upper limit, and a given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundaries of a particular range. The range defined in this way can be inclusive or exclusive of end values, and can be arbitrarily combined, that is, any lower limit can be combined with any upper limit to form a range. For example, if a range of 60 to 120 and 80 to 110 is listed for a particular parameter, it is understood that a range of 60 to 110 and 80 to 120 is also expected. In addition, if the minimum range values ​​1 and 2 are listed, and if the maximum range values ​​3, 4 and 5 are listed, the following ranges can all be expected: 1 to 3, 1 to 4, 1 to 5, 2 to 3, 2 to 4 and 2 to 5. In the present application, unless otherwise specified, the numerical range "a to b" represents an abbreviation of any real number combination between a and b, wherein a and b are both real numbers. For example, the numerical range "0-5" means that all real numbers between "0-5" are listed in this document, and "0-5" is just an abbreviation of these numerical combinations. In addition, when a parameter is expressed as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer of 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0021] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0022] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, a method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, a method may also include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0023] In order to make the above-mentioned purposes, features and advantages of the present application more obvious and understandable, the technical solution of the present application is further described below in conjunction with the accompanying drawings and embodiments. However, the present application is not limited to the listed embodiments, and should also include any other known changes within the scope of the rights claimed in the present application.

[0024] In order to better understand the technical solution of the present application, a detailed description will be given below in conjunction with the accompanying drawings and specific implementation methods.

[0025] In conventional technology, synaptic devices generally rely on complex manufacturing processes, which not only greatly prolongs the manufacturing cycle, but also significantly increases the economic cost, becoming one of the main bottlenecks restricting its large-scale application. The demand for these high-end materials and complex processes makes it difficult to popularize the research and development and production of synaptic devices, hindering the technology from moving from the laboratory to a wider range of practical application scenarios. At the same time, in the field of optical neural devices, although certain progress has been made, there are still many challenges in achieving efficient control and precise modulation of circularly polarized light. Conventional technologies often cannot meet the requirements of high resolution and high response current at the same time: some solutions can provide higher resolution, but are limited by lower response currents and are difficult to support efficient signal transmission; while others may have relatively high response currents, but the accuracy of data processing is affected by insufficient resolution. The existence of these problems makes it difficult for existing optical neural devices to meet the strict requirements for high performance, low energy consumption and fast response speed in practical applications.

[0026] The embodiment of the present application provides an optical synapse device, comprising a substrate, a chiral perovskite layer, a MoS2 layer and a metal electrode arranged in sequence, wherein the MoS2 layer completely covers the chiral perovskite layer, and a non-contact area that is not in contact with the chiral perovskite layer remains, and the metal electrode is located in the non-contact area of ​​the MoS2 layer. Through the synergistic photoelectric effect of the heterojunction formed by the chiral perovskite and MoS2, the optical synapse device has a good polarization light resolution capability, can identify the handedness of circularly polarized light and respond to light stimulation, thereby effectively improving the processing capability of the optical synapse device for circularly polarized light signals.

[0027] The first embodiment of the present application provides an optical synaptic device based on molybdenum disulfide and chiral perovskite, referring to Figure 1 , comprising a substrate 110, a chiral perovskite layer 120, a MoS2 layer 130 and a metal electrode 140 arranged in sequence; The MoS2 layer 130 completely covers the chiral perovskite layer 120; The metal electrode 140 is located in a non-contact region (not shown in the drawings) of the MoS 2 layer 130 , wherein the non-contact region is a region of the MoS 2 layer 130 that is not in contact with the chiral perovskite layer 120 .

[0028] In one embodiment, the MoS2 layer 130 is made of a two-dimensional material, molybdenum disulfide (MoS2), which has excellent photoelectric properties. Specifically, because a single layer or a few layers of MoS2 have direct band gap characteristics, it exhibits strong light absorption in the visible light region, and can also effectively convert optical signals into electrical signals, thus laying the foundation for achieving efficient photoelectric response. In addition, MoS2 also has a high carrier mobility, which helps to improve the operating speed and efficiency of the device. Furthermore, mechanical flexibility and processability also give MoS2 unique adaptability to meet different application requirements. Finally, MoS2 also has excellent stability and can operate stably under high temperature and strong light conditions, which significantly improves the overall durability and stability of the optical synapse device.

[0029] In one embodiment, the chiral perovskite layer 120 is made of a perovskite material with special chiral characteristics. Since the internal structure of the chiral perovskite contains specific chiral components or is designed as a chiral framework, this type of material can effectively distinguish circularly polarized light of different rotation directions. This characteristic enables the optical synapse device based on chiral perovskite to accurately identify and modulate circularly polarized light during information processing, thereby improving the efficiency and accuracy of data transmission. Secondly, since the perovskite material itself is known for its excellent photoelectric properties such as high absorption coefficient and long carrier diffusion length. When the chiral characteristics are introduced, these materials can not only maintain the original photoelectric conversion efficiency, but also further improve the response current by optimizing the chiral structure. Therefore, it helps to overcome the common problems of insufficient resolution or too low response current in existing optical synapse devices, ensuring efficient and stable signal transmission. Since the chiral perovskite can effectively distinguish circularly polarized light of different rotation directions, the optical synapse device based on chiral perovskite can accurately identify and modulate circularly polarized light during information processing. When combined with chiral perovskite and MoS2, due to the excellent photoelectric conversion efficiency and high carrier mobility of MoS2, the response speed and sensitivity of the entire heterojunction to circularly polarized light can be further enhanced, thereby improving the efficiency and accuracy of data transmission.

[0030] In one feasible embodiment, the material of the chiral perovskite layer 120 includes: (R-NEA)PbI3 and / or (S-NEA)PbI3. (R-NEA)PbI3 and (S-NEA)PbI3 are hybrid chiral perovskite materials based on chiral organic amine (1-(2-naphthyl)ethylamine, NEA) and inorganic lead iodine framework. Due to its internal chiral structure, it exhibits significant circular dichroism, that is, it has different absorption rates for left-handed and right-handed circularly polarized light. This property enables them to effectively distinguish circularly polarized light of different rotation directions. Compared with other chiral perovskite materials, such as (R-MBA)2PbI4, (S-MBA)2PbI4, etc., the highest resolution under 77 K test is 17.6%, while the chiral perovskite material used in the embodiment of the present application can reach a test resolution of nearly 25% at 78 K, which can make the optical synapse device based on it have better polarization light resolution.

[0031] In one feasible embodiment, the thickness of the chiral perovskite layer 120 is 98-102 nm; for example, the thickness of the chiral perovskite layer 120 is 98 nm, 98.5 nm, 99 nm, 99.5 nm, 100 nm, 100.5 nm, 101 nm, 101.5 nm, 102 nm, etc. The chiral perovskite layer 120 of different thicknesses has different polarization degrees for circularly polarized light; if the thickness of the chiral perovskite layer 120 is too large, it is not easy to transfer MoS2, and if it is too thin, it is difficult to process. At the same time, the embodiment of the present application found through experiments that the chiral perovskite layer 120 of 98-102 nm has a strong resolution for left and right polarized light, so it is determined to select the chiral perovskite layer 120 of 98-102 nm.

[0032] Exemplarily, when the material of the chiral perovskite layer 120 is selected from (R-NEA)PbI3 and the thickness is 98-102 nm, the optical synapse device has a discrimination capability of 24.29% for left and right polarized light.

[0033] Exemplarily, when the material of the chiral perovskite layer 120 is selected from (S-NEA)PbI3 and the thickness is 98-102 nm, the optical synapse device has a discrimination capability of 24.39% for left and right polarized light.

[0034] In one feasible implementation, the thickness of the MoS2 layer 130 is 0.7-1.6 nm. For example, the thickness of the MoS2 layer 130 is 0.7 nm, 0.8 nm, 0.9 nm, 1 nm, 1.1 nm, 1.2 nm, 1.3 nm, 1.4 nm, 1.5 nm, 1.6 nm, etc.

[0035] In one feasible implementation, the material of the metal electrode 140 includes: Cr and / or Au.

[0036] In one feasible implementation, the thickness of the metal electrode 140 is 10-64 nm. For example, the thickness of the metal electrode 140 is 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 61 nm, 62 nm, 63 nm, 64 nm, etc.

[0037] In one feasible embodiment, the metal electrode 140 includes a first metal layer and a second metal layer sequentially arranged in a non-contact area of ​​the MoS2 layer 130; the material of the first metal layer includes: Cr, with a thickness of 10~12 nm; the material of the first metal layer includes: Au, with a thickness of 50~52 nm.

[0038] Exemplarily, the thickness of the first metal layer is: 10 nm, 10.5 nm, 11 nm, 11.5 nm, 12 nm, 12 nm, etc.

[0039] Exemplarily, the thickness of the second metal layer is 50 nm, 50.5 nm, 51 nm, 51.5 nm, 52 nm, etc.

[0040] In this embodiment, the work function of MoS2 is 4.47 eV. Therefore, by using Cr (4.5 eV) which has a work function not much different from that of MoS2 as the metal electrode 140 evaporated on MoS2, electrons can be more easily conducted in the device, and a stable interface can be maintained, thereby enhancing the adhesion of the metal film. Furthermore, due to the high conductivity and good electrical properties of Au (5.1 eV), further combining with Au can further improve the device performance.

[0041] In this embodiment, through the synergistic photoelectric effect of the heterojunction formed by chiral perovskite and MoS2, the optical synapse device has good polarization light resolution capability, can identify the rotation direction of circularly polarized light and respond to light stimulation, thereby effectively improving the processing capability of the optical synapse device for circularly polarized light signals.

[0042] The second embodiment of the present application provides a method for preparing an optical synapse device based on molybdenum disulfide and chiral perovskite, referring to Figure 2 , including the following steps: Step S10, providing a chiral perovskite crystal and a MoS2 crystal; In a feasible embodiment, chiral perovskite crystals and MoS2 crystals are provided respectively. Commercial chiral perovskite crystals and MoS2 crystals can be directly selected or prepared by corresponding methods, which is not limited in this embodiment.

[0043] In one feasible implementation, step S10, the step of providing a chiral perovskite crystal includes: Step S11, dissolving a lead source in an iodine source solution to obtain a first solution; In a possible embodiment, the lead source is dissolved in an iodine source solution and subjected to ultrasonic treatment to obtain a light brown first solution.

[0044] Exemplarily, the lead source includes at least one of lead oxide, lead hydroxide, lead carbonate and lead acetate.

[0045] Exemplarily, the iodine source includes: hydrogen iodide.

[0046] For example, 100.1 mg of lead oxide was dissolved in 1.5 mL of 58 wt.% HI solution, and a light brown first solution was obtained after ultrasonic treatment.

[0047] Step S12, adding a chiral compound to the first solution and heating it to obtain a second solution; In one possible embodiment, the chiral compound is continuously and slowly added to the first solution and heated until a bright yellow second solution is formed.

[0048] Exemplarily, the chiral compound includes: R-NEA and / or S-NEA.

[0049] Exemplarily, 134.4 mg of the chiral compound and 1 mL of 1-butanol are continuously and slowly added dropwise to the first solution and heated in an oil bath at 100-120 °C until a bright yellow second solution is formed, wherein 1-butanol is used as a solvent to promote the dissolution of the chiral compound.

[0050] Step S13, cooling the second solution to obtain chiral perovskite crystals.

[0051] In a feasible embodiment, the container is placed at 100-120° C. for 4-8 hours, cooled to precipitate crystals, and dried to obtain chiral perovskite crystals.

[0052] For example, the container is placed at 100-120°C for 4-8 hours, or at 5°C for 1 hour. −1 The temperature was cooled to 70 °C at a rate of 2 °C h −1 The reaction mixture was cooled to 20°C at a rate of 0.05 to obtain yellow crystals, which were then dried under vacuum to obtain chiral perovskite crystals.

[0053] In this embodiment, a chiral perovskite material with high crystallinity is synthesized at low temperature by a solution method. The chiral direction and strength can be precisely controlled by adjusting the solution concentration, reaction temperature and chiral amine ratio, thereby avoiding the safety risks and high energy consumption of traditional high-temperature film-forming processes.

[0054] Step S20, releasing the chiral perovskite crystals on one side surface of the substrate by mechanical peeling to obtain a chiral perovskite layer; In one possible embodiment, referring to Figure 3 , providing a clean substrate 110 , releasing the chiral perovskite crystals on one side surface of the substrate 110 by mechanical stripping, and obtaining a chiral perovskite layer 120 located on one side surface of the substrate 110 .

[0055] Step S30, releasing the MoS2 crystals on the PDMS film on the glass slide by mechanical peeling to obtain a MoS2 layer; In one possible embodiment, referring to Figure 3 By mechanical peeling, the MoS2 crystals are released on the PDMS film 150 located on a glass slide (not shown in the drawings), thereby obtaining a MoS2 layer 130 located on the PDMS film 150.

[0056] Step S40, transferring the MoS2 layer to the surface of the chiral perovskite layer to obtain a heterojunction, wherein the MoS2 layer completely covers the chiral perovskite layer; In one possible embodiment, referring to Figure 4 In an inert gas glove box, the MoS2 layer 130 is transferred to the surface of the chiral perovskite layer 120 using a high-resolution two-dimensional material metallographic microscopic transfer system to obtain a heterojunction on the substrate 110, wherein the MoS2 layer 130 completely covers the chiral perovskite layer 120.

[0057] In one feasible implementation, step S40, transferring the MoS2 layer 130 to the surface of the chiral perovskite layer 120 to obtain a heterojunction comprises: Step S41, placing the chiral perovskite layer 120 on a heating platform and heating at 65-85° C. for 1-2 min.

[0058] In one feasible embodiment, the chiral perovskite layer 120 is placed on a heating stage and heated at 65-85° C. for 1-2 min to ensure that the MoS 2 layer 130 is successfully transferred to the perovskite layer to form a heterojunction.

[0059] Step S50, preparing a metal electrode on the surface of the heterojunction to obtain an optical synapse device, wherein the metal electrode is located in a non-contact area of ​​the MoS2 layer, and the non-contact area is an area where the MoS2 layer is not in contact with the chiral perovskite layer.

[0060] In one possible embodiment, referring to Figure 1 , a metal electrode 140 is prepared in the non-contact area of ​​the MoS2 layer 130 to obtain an optical synapse device.

[0061] In one feasible implementation, step S50, the step of preparing the metal electrode 140 on the surface of the heterojunction includes: Step S51, setting a mask 160 on the surface of the heterojunction and preparing a metal layer; In one possible embodiment, referring to Figure 5 , a mask 160 is set on the heterojunction surface, and a metal layer is deposited.

[0062] Exemplarily, the metal layer is prepared by thermal evaporation, wherein the evaporation rate is 0.1-0.5 Å / s. For example, the evaporation rate is 0.1 Å / s, 0.2 Å / s, 0.3 Å / s, 0.4 Å / s, 0.5 Å / s, etc.

[0063] Exemplarily, Cr is deposited on the heterojunction surface by thermal evaporation, with an evaporation rate of 0.1~0.2 Å / s and a deposition thickness of 10~12 nm; and Au is then evaporated at a evaporation rate of 0.4~0.5 Å / s and a deposition thickness of 50~52 nm.

[0064] Exemplarily, a copper mesh may be selected as the mask 160 .

[0065] Exemplarily, the tape is cut into a square smaller than the size of the PDMS film 150 and a window is cut in the middle, and then it is reversely fixed on the PDMS film 150 on the glass slide, the copper mesh is stably fixed on the window of the tape, and then the copper mesh is transferred to the heterojunction using a high-resolution two-dimensional material metallographic microscopy transfer system to form a 10 um wide channel.

[0066] Step S52 , peeling off the mask and the metal layer on its upper surface to obtain the metal electrode 140 .

[0067] In a feasible embodiment, the mask and the metal layer on the upper surface thereof are peeled off to obtain the metal electrode 140 .

[0068] In this embodiment, the deposited metal electrode 140 does not require electron beam etching to define the electrode, but uses a copper mesh as a mask 160, which not only saves costs, but also greatly reduces the manufacturing time of the device. At the same time, it also avoids contact with the organic solution in the photolithography to destroy the perovskite, thereby optimizing the process flow. In addition, the embodiment of the present application uses mechanical stripping instead of CVD to obtain two-dimensional materials, and combines the mask 160 technology to replace the photolithography process, without the need for complex equipment and high temperature environment, greatly reducing material costs and processing complexity, and realizing economical and environmentally friendly device manufacturing.

[0069] In order to enable the details and operations of the above embodiments of the present application to be clearly understood by those skilled in the art, and to significantly demonstrate the improved performance of the embodiments of the present application, the above technical solutions are illustrated by means of multiple embodiments below.

[0070] Example 1 (1) Dissolve 100.1 mg of lead oxide in 1.5 mL of 58 wt% HI solution and obtain a light brown first solution after ultrasonic treatment; (2) 134.4 mg of R-NEA and 1 mL of 1-butanol were continuously and slowly added dropwise to the first solution and heated at 110 °C until a bright yellow second solution was formed; (3) The second solution was placed at 110 °C for 6 h and the solution was heated at 5 °C for 1 h. −1 The temperature was cooled to 70 °C at a rate of 2 °C h −1 The reaction mixture was cooled to 20 °C at a rate of 0.1% to obtain yellow crystals. The crystals were filtered and then dried under vacuum to obtain (R-NEA)PbI3 crystals.

[0071] Example 2 The experimental steps are the same as those in Example 1, except that the chiral compound selected is S-NEA, and the obtained product is (S-NEA)PbI3 crystal.

[0072] Example 3 Based on Example 1, the (R-NEA) PbI3 crystal was stacked with a 0.8 nm MoS2 layer to form a heterojunction.

[0073] Example 4 Based on Example 2, the (S-NEA) PbI3 crystal was stacked with a 0.8 nm MoS2 layer to form a heterojunction.

[0074] Example 5 Based on the (R-NEA)PbI3 crystal obtained in Example 1, an optical synapse device was prepared, including a substrate (Si / SiO2), a 100 nm (R-NEA)PbI3 layer, a 0.8 nm MoS2 layer and a metal electrode arranged in sequence, and the metal electrode included 11 nm Cr and 51 nm Au arranged in sequence.

[0075] Example 6 Based on the (S-NEA)PbI3 crystal obtained in Example 2, an optical synapse device was prepared, including a substrate (Si / SiO2), a 100 nm (S-NEA)PbI3 layer, a 0.8 nm MoS2 layer and a metal electrode arranged in sequence, and the metal electrode included 11 nm Cr and 51 nm Au arranged in sequence.

[0076] Comparative Example 1 The experimental steps are the same as those in Example 1, except that the chiral compound selected is RAC-NEA, and the obtained product is (RAC-NEA)2PbI4 crystal.

[0077] Comparative Example 2 0.8 nm MoS2.

[0078] The circular polarization PL (Photoluminescence) degree test was performed on the above-mentioned Examples 1-4 and Comparative Examples 1-2 at 78 K. In order to quantify the degree of circular polarization PL, a parameter P was introduced, which is defined as:

[0079] Among them, P L and P R are the intensities of left and right circularly polarized PL, respectively. The results are as follows Figure 6 As shown, Figure 6 (a) is the PL test result of comparative example 1 (RAC-NEA)2PbI4, Figure 6 (b) is the PL test result of Example 1 (R-NEA) PbI3, Figure 6 (c) is the PL test result of Example 2 (S-NEA) PbI3. Figure 6 From (a) to (c), it can be seen that the main PL peak of (R-NEA)PbI3 is located at 702 nm, the main PL peak of (S-NEA)PbI3 is located at 707 nm, and the main PL peak of (RAC-NEA)2PbI4 is located at 650 nm. For chiral (S-NEA)PbI3 and (R-NEA)PbI3, under left-handed circularly polarized (Lcp) and right-handed circularly polarized (Rcp) irradiation, P is 24.29% and 24.39%, respectively, and obvious intensity differences are observed between circularly polarized PL. In contrast, the racemic (RAC-NEA)2PbI4 sample exhibits essentially the same PL intensity between left-handed and right-handed circularly polarized PL, indicating that the chiral perovskite materials used in Examples 1 and 2 of the present application have the ability to distinguish between left-handed and right-handed polarized light. For further reference, Figure 7 ,in, Figure 7 (a) is the PL test result of MoS2 in comparative example 2; Figure 7 (b) is the PL test result of MoS2 / (R-NEA)PbI3 heterojunction in Example 3; Figure 7 (c) is the PL test result of MoS2 / (S-NEA)PbI3 heterojunction in Example 4. Figure 7 From (a) to (c), it can be seen that the left-right polarized light PL intensity of MoS2 is almost the same (P=0.855%), and it does not have chirality. However, there is a significant difference in the left-right polarized light PL intensity between Example 3 and Example 4 (22.79% and 28.64%, respectively), indicating that even if a heterojunction is formed with MoS2, it will not interfere with the chirality of the chiral perovskite.

[0080] Furthermore, polarized light detection tests were performed on the above-mentioned Examples 5-6 and Comparative Example 2; the results are shown in Table 1. Figure 8 ,in, Figure 8 (a) is the output curve of MoS2 in comparative example 2 under dark field and right-handed circular polarization (Rcp) and left-handed circular polarization (Lcp) illumination; Figure 8 (b) is the output curve of the MoS2 / (R-NEA)PbI3 synaptic device of Example 5 under dark field and right-handed circular polarization (Rcp) and left-handed circular polarization (Lcp) illumination; Figure 8 (c) is the output curve of the MoS2 / (S-NEA)PbI3 synaptic device of Example 6 under dark field and right-handed circular polarization (Rcp) and left-handed circular polarization (Lcp) illumination. It can be seen that the current increases significantly under illumination, indicating that the synaptic device of the embodiment of the present application has a good photoresponse. Importantly, for the MoS2 / (R-NEA)PbI3 synaptic device of Example 5, the synaptic device exhibits a larger photocurrent under right-handed CPL illumination compared to left-handed CPL illumination, while the MoS2 / (S-NEA)PbI3 synaptic device of Example 6 is the opposite, which is consistent with the PL measurement results under circularly polarized illumination at 78K.

[0081] Further, refer to Fig. 9 ,in, Fig. 9 (a) is the light response curve of the MoS2 / (R-NEA)PbI3 synaptic device of Example 5 under CPL light illumination; Fig. 9 (b) is the light response curve of the MoS2 / (S-NEA)PbI3 synaptic device of Example 6 under CPL light illumination. It can be seen that the MoS2 / (R-NEA)PbI3 synaptic device of Example 5 and the MoS2 / (S-NEA)PbI3 synaptic device of Example 6 have time-dependent photocurrent response and time response, which also shows that the synaptic device has good repeatability and stability.

[0082] Furthermore, the anisotropy factor of the photocurrent can be defined as g Iph ,satisfy:

[0083] Among them, I R and I L are the photocurrents under Rcp and Lcp illumination respectively. Fig.10The g value of the MoS2 / (R-NEA)PbI3 synaptic device of Example 5 and the MoS2 / (S-NEA)PbI3 synaptic device of Example 6 is changed with the wavelength. It can be seen that the present application irradiates the MoS2 / (R-NEA)PbI3 synaptic device of Example 5 and the MoS2 / (S-NEA)PbI3 synaptic device of Example 6 with CPL light of different wavelengths, and calculates the g value of different wavelengths according to the obtained photocurrent. Among the light used in the present application, the incident light of 660nm has the highest g value, so the present application selects the CPL of 660nm.

[0084] Further, the above examples 5 to 6 were subjected to synaptic testing, and the results were shown in Table 1. Fig.11 ,in, Fig.11 (a) is the transient EPSC (Excitatory Postsynaptic Current) of the MoS2 / (R-NEA) PbI3 synaptic device in Example 5 in response to a single Lcp and Rcp pulse; Fig.11 (b) is the transient EPSC of the MoS2 / (S-NEA)PbI3 synaptic device in Example 6 in response to a single Lcp and Rcp; the conditions for Lcp and Rcp are: 660 nm, 0.5 Hz, 7 mW cm -2 .according to Fig.11 (a) and Fig.11 As shown in (b), EPSC is triggered by a single Rcp / Lcp, and the current difference between the peak EPSCs means that the synaptic device of the present application can respond differently to CPL stimulation with opposite circular polarization. The MoS2 / (R-NEA)PbI3 synaptic device in Example 5 exhibits an EPSC response of 1.21 times that of the Rcp pulse under Rcp pulse modulation, while the MoS2 / (S-NEA)PbI3 synaptic device in Example 6 exhibits an EPSC response of 1.16 times that of the Rcp pulse under Lcp pulse modulation, demonstrating synaptic behavior with CPL resolution capability.

[0085] In addition, the synaptic device also mimics the key feature of STP (Short-Term Plasticity) PPF (Paired-pulse Facilitation), and the results refer to Fig.12 ,in, Fig.12 (a) shows the PPF behavior of the MoS2 / (R-NEA)PbI3 synaptic device of Example 5 triggered by two CPL pulses; Fig.12 (b) shows the PPF behavior of the MoS2 / (S-NEA)PbI3 synaptic device of Example 6 triggered by two CPL pulses, where the CPL duration is 2 s and the intensity is 7 mWcm−2 , and the PPF index is described by A2 / A1; the increment of A2 usually depends on the time interval (Δt) between two spikes. A larger PPF value can lead to higher time resolution, thereby processing time information efficiently and accurately. Further, refer to Fig.13 ,in, Fig.13 (a) shows the change of the PPF index of the MoS2 / (R-NEA)PbI3 synaptic device in Example 5 with the excitatory stimulation interval; Fig.13 (b) shows the variation of the PPF index of the MoS2 / (S-NEA)PbI3 synaptic device with the excitatory stimulation interval in Example 6. It can be seen that the PPF index decays slowly with the increase of Δt. The PPF index induced by Lcp in the MoS2 / (S-NEA)PbI3 synaptic device in Example 6 is higher at 121%, while for the MoS2 / (R-NEA)PbI3 synaptic device in Example 5, the PPF induced by Rcp has a higher PPF index, up to 125%.

[0086] Furthermore, the synaptic device was stimulated with pulses of different pulse durations, and the results were compared with those of Fig.14 ,in, Fig.14 (a) is a schematic diagram of the STP (short-term plasticity) and LTP (long-term plasticity) results of the MoS2 / (R-NEA)PbI3 synaptic device in Example 5; Fig.14 (b) is a schematic diagram of the STP and LTP results of the MoS2 / (S-NEA)PbI3 synaptic device in Example 6. It can be seen that as the pulse duration increases, the EPSC gradually becomes higher, and after a period of time, the high EPSC can no longer drop back to the starting value, while the relatively low EPSC can drop to the starting value or close to the starting value, and memory and learning behavior are usually attributed to this characteristic, namely short-term plasticity (STP) and long-term plasticity (LTP).

[0087] At the same time, this application also studies the LTP / LTD (long-term inhibition) process of synaptic devices under photoelectric modulation. The results are as follows Fig.15 As shown, Fig.15 (a) is the LTP and LTD diagram of the MoS2 / (R-NEA)PbI3 synaptic device in Example 5 under different CPL states; Fig.15 (b) is the LTP and LTD diagram of the MoS2 / (S-NEA)PbI3 synaptic device in Example 6 under different CPL states. Fig.15 (a) and Fig.15 As shown in (b), after applying 100 consecutive light pulses (660 nm pulse duration 2 s, pulse width 0.5 s, intensity 7 mWcm −2), the conductance of the MoS2 / (R-NEA)PbI3 synaptic device in Example 5 reached nearly 7 pS under the irradiation of Rcp, while the conductance of the MoS2 / (S-NEA)PbI3 synaptic device in Example 6 reached nearly 4 pS under the irradiation of Rcp. Then 100 continuous electric pulses (-20V) were applied to reduce the conductance of the two synaptic devices to the initial level. This test was based on the LTP and LTD behaviors observed under the Rcp and Lcp conditions.

[0088] To further evaluate the potential of this application in large-scale image recognition tasks, we used optical synapse modeling as spiking neurons to simulate spiking neural networks (SNNs), referring to Fig.16 ; The SNN architecture consists of the following parts: 784 input neurons, 100 hidden neurons, and 26 output neurons. During the training process, the membrane potential of each output neuron is accumulated through input spikes and weights from other connected synapses. When the membrane potential value of an output neuron exceeds the threshold, the neuron excites and releases a spike to its next connection, and its membrane potential is reset. The excited neuron will also prevent other neurons from firing by perching laterally. For a period of time, the neuron remains in a refractory state and cannot be excited. In addition, the corresponding synapses that contribute to the discharge result will be strengthened, while the synapses that do not contribute to the excitation will be weakened. Further, Fig.17 A 28×28 outline image of the letters “S”, “Z”, and “U” depicting each region after a period of time. It can be seen that after a series of stimulations, the image gradually becomes clearer. This control is crucial for simulating the development of artificial optical synapses.

[0089] Fig.18 (a) shows the letter recognition accuracy of the MoS2 / (R-NEA)PbI3 synaptic device in Example 5 under different CPL states; Fig.18 (b) in the figure is the recognition accuracy of the letters of the MoS2 / (S-NEA)PbI3 synaptic device in Example 6 under different CPL states. It can be seen that with the increase of iterations, the recognition accuracy continues to improve. After 1400 iterations, the recognition accuracy of the Rcp and Lcp modulated SNN of the MoS2 / (R-NEA)PbI3 synaptic device in Example 5 is ~0.91 and ~0.78, respectively, while the recognition accuracy of the Rcp and Lcp modulated SNN of the MoS2 / (S-NEA)PbI3 synaptic device in Example 6 is ~0.90 and ~0.96, respectively, showing polarization-dependent learning efficiency.

[0090] The above are only preferred embodiments of the present application, and do not limit the scope of the present application. For those skilled in the art, the present application may have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present application shall be included in the scope of patent protection of the present application.

Claims

1. An optical synaptic device based on molybdenum disulfide and chiral perovskite, characterized in that: The optical synapse device comprises a substrate, a chiral perovskite layer, a MoS2 layer and a metal electrode arranged in sequence; The MoS2 layer completely covers the chiral perovskite layer; The metal electrode is located in a non-contact area of ​​the MoS2 layer, wherein the non-contact area is an area where the MoS2 layer is not in contact with the chiral perovskite layer.

2. The optical synaptic device based on molybdenum disulfide and chiral perovskite according to claim 1, characterized in that: The material of the chiral perovskite layer includes: (R-NEA)PbI3 and / or (S-NEA)PbI3; And / or, the material of the metal electrode includes: Cr and / or Au.

3. The optical synaptic device based on molybdenum disulfide and chiral perovskite according to claim 1, characterized in that: The thickness of the chiral perovskite layer is 98-102 nm; And / or, the thickness of the metal electrode is: 10-64 nm; And / or, the thickness of the MoS2 layer is: 0.7~1.6 nm.

4. The optical synaptic device based on molybdenum disulfide and chiral perovskite according to claim 1, characterized in that: The metal electrode comprises a first metal layer and a second metal layer sequentially disposed in a non-contact region of the MoS2 layer; The material of the first metal layer includes: Cr, with a thickness of 10-12 nm; The material of the first metal layer includes: Au, with a thickness of 50-52 nm.

5. A method for preparing an optical synapse device based on molybdenum disulfide and chiral perovskite, characterized in that: The method for preparing an optical synapse device based on molybdenum disulfide and chiral perovskite is used to prepare an optical synapse device based on molybdenum disulfide and chiral perovskite as claimed in any one of claims 1 to 4, comprising the following steps: Provide chiral perovskite crystals and MoS2 crystals; The chiral perovskite crystals are released on one surface of the substrate by mechanical peeling to obtain a chiral perovskite layer; The MoS2 crystals are released on the PDMS film on the glass slide by mechanical peeling to obtain a MoS2 layer; Transferring the MoS2 layer to the surface of the chiral perovskite layer to obtain a heterojunction, wherein the MoS2 layer completely covers the chiral perovskite layer; A metal electrode is prepared on the surface of the heterojunction to obtain an optical synapse device, wherein the metal electrode is located in a non-contact area of ​​the MoS2 layer, and the non-contact area is an area where the MoS2 layer is not in contact with the chiral perovskite layer.

6. The method for preparing an optical synapse device based on molybdenum disulfide and chiral perovskite according to claim 5, characterized in that: The step of preparing a metal electrode on the surface of the heterojunction comprises: Setting a mask on the surface of the heterojunction and preparing a metal layer; The mask and the metal layer on the upper surface thereof are peeled off to obtain the metal electrode.

7. The method for preparing an optical synapse device based on molybdenum disulfide and chiral perovskite according to claim 6, characterized in that: The step of preparing the metal layer comprises: The metal layer is prepared by thermal evaporation, wherein the evaporation rate is 0.1-0.5 Å / s.

8. The method for preparing an optical synapse device based on molybdenum disulfide and chiral perovskite according to claim 5, characterized in that: The step of transferring the MoS2 layer to the surface of the chiral perovskite layer to obtain a heterojunction comprises: The chiral perovskite layer is placed on a heating stage and heated at 65-85° C. for 1-2 min.

9. The method for preparing an optical synapse device based on molybdenum disulfide and chiral perovskite according to claim 5, characterized in that: The step of providing a chiral perovskite crystal comprises: dissolving a lead source in an iodine source solution to obtain a first solution; adding a chiral compound to the first solution and heating the solution to obtain a second solution; The second solution is cooled to obtain the chiral perovskite crystal.

10. The method for preparing an optical synapse device based on molybdenum disulfide and chiral perovskite according to claim 9, characterized in that: The lead source comprises: at least one of lead oxide, lead hydroxide, lead carbonate and lead acetate; And / or, the iodine source comprises: hydrogen iodide; And / or, the chiral compound comprises: R-NEA and / or S-NEA; And / or, the heating temperature of the first solution is 100-120°C.

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