Optical Synaptic Device Based on Molybdenum Disulfide and Chiral Perovskite and Preparation Method Thereof

Abstract

The present application discloses an optical synaptic device based on molybdenum disulfide and chiral perovskite and a preparation method thereof, relating to the technical field of synaptic devices. The optical synaptic device is disclosed, which includes a substrate, a chiral perovskite layer, a MoS2 layer, and a metal electrode arranged in sequence. Among them, the MoS2 layer completely covers the chiral perovskite layer and leaves a non-contact area that does not contact the chiral perovskite layer, and the metal electrode is located in the non-contact area of the MoS2 layer. The present application improves the processing ability of the optical synaptic device for circularly polarized light signals.

Description

Technical Field

[0001] This application relates to the technical field of synaptic devices, and particularly 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 values. Among them, circularly polarized light (CPL) is a light signal with special physical properties, which 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, the ability of conventional optical synaptic devices to process circularly polarized light signals is weak, thus restricting the application of optical synaptic devices. Summary of the Invention

[0003] The main purpose of this application is to provide an optical synaptic device based on molybdenum disulfide and chiral perovskite and a preparation method thereof, which improves the processing ability of the optical synaptic device for circularly polarized light signals.

[0004] To achieve the above purpose, an embodiment of this application provides an optical synaptic device based on molybdenum disulfide and chiral perovskite, including a substrate, a chiral perovskite layer, a MoS2 layer, and a metal electrode arranged in sequence;

[0005] The MoS2 layer completely covers the chiral perovskite layer;

[0006] The metal electrode is located in the non-contact area of the MoS2 layer, where the non-contact area is the area where the MoS2 layer does not contact the chiral perovskite layer.

[0007] In one embodiment, the material of the chiral perovskite layer includes: (R-NEA)PbI3 and / or (S-NEA)PbI3;

[0008] And / or, the material of the metal electrode includes: Cr and / or Au.

[0009] In one embodiment, the thickness of the chiral perovskite layer is 98 - 102 nm;

[0010] And / or, the thickness of the metal electrode is: 10 - 64 nm;

[0011] And / or, the thickness of the MoS2 layer is: 0.7 - 1.6 nm.

[0012] In one embodiment, the metal electrode includes a first metal layer and a second metal layer arranged in sequence in the non-contact area of the MoS2 layer;

[0013] The material of the first metal layer includes: Cr with a thickness of 10 - 12 nm;

[0014] The material of the second metal layer includes: Au with a thickness of 50 - 52 nm.

[0015] To achieve the above object, an embodiment of the present application provides a method for preparing an optical synaptic device based on molybdenum disulfide and chiral perovskite, which is used to prepare the optical synaptic device as described above, and includes the following steps:

[0016] Provide chiral perovskite crystals and MoS2 crystals;

[0017] By mechanical exfoliation, release the chiral perovskite crystals on one side surface of the substrate to obtain a chiral perovskite layer;

[0018] By mechanical exfoliation, release the MoS2 crystals on a PDMS film located on a glass slide to obtain a MoS2 layer;

[0019] Transfer 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;

[0020] Prepare metal electrodes on the surface of the heterojunction to obtain an optical synaptic device, wherein the metal electrodes are located in the non-contact area of the MoS2 layer, and the non-contact area is the area where the MoS2 layer does not contact the chiral perovskite layer.

[0021] In one embodiment, the step of preparing metal electrodes on the surface of the heterojunction includes:

[0022] Set a mask on the surface of the heterojunction and prepare a metal layer;

[0023] Strip the mask and the metal layer on its upper surface to obtain the metal electrodes.

[0024] In one embodiment, the step of preparing the metal layer includes:

[0025] Prepare the metal layer by thermal evaporation, wherein the evaporation rate is 0.1 - 0.5 Å / s.

[0026] In one embodiment, the step of transferring the MoS2 layer to the surface of the chiral perovskite layer to obtain a heterojunction includes:

[0027] Place the chiral perovskite layer on a heating stage and heat it at 65 - 85 °C for 1 - 2 min.

[0028] In one embodiment, the step of providing chiral perovskite crystals includes:

[0029] Dissolve a lead source in an iodine source solution to obtain a first solution;

[0030] Add a chiral compound to the first solution and heat it to obtain a second solution;

[0031] Cool the second solution to obtain the chiral perovskite crystal.

[0032] In one embodiment, the lead source includes at least one of lead oxide, lead hydroxide, lead carbonate, and lead acetate;

[0033] And / or, the iodine source includes: hydrogen iodide;

[0034] And / or, the chiral compound includes: R-NEA and / or S-NEA;

[0035] And / or, the heating temperature of the first solution is 100-120 °C.

[0036] The embodiment of the present application provides an optical synaptic device based on molybdenum disulfide and chiral perovskite, including a substrate, a chiral perovskite layer, a MoS2 layer, and a metal electrode arranged in sequence. Among them, the MoS2 layer completely covers the chiral perovskite layer and leaves a non-contact area that does not contact the chiral perovskite layer, while the metal electrode is located in the non-contact area of the MoS2 layer. Through the synergistic optoelectronic effect of the heterojunction formed by chiral perovskite and MoS2, the optical synaptic device has good polarized light resolution ability, can identify the circular polarization direction of circularly polarized light and respond to light stimuli, thereby effectively improving the processing ability of the optical synaptic device for circularly polarized light signals. Description of the Drawings

[0037] Figure 1 It is a schematic structural diagram of the optical synaptic device related to the solution of the embodiment of the present application;

[0038] Figure 2 It is a flowchart of the preparation method of the optical synaptic device related to the solution of the embodiment of the present application;

[0039] Figure 3 It is the process flow of the preparation method of the optical synaptic device related to the solution of the embodiment of the present application Figure 1 ;

[0040] Figure 4 It is the process flow of the preparation method of the optical synaptic device related to the solution of the embodiment of the present application Figure 2 ;

[0041] Figure 5 It is the process flow of the preparation method of the optical synaptic device related to the solution of the embodiment of the present application Figure 3 ;

[0042] Figure 6Schematic diagram of the PL test results of Comparative Example 1, Example 1 and Example 2 of the present application;

[0043] Figure 7 Schematic diagram of the PL test results of Comparative Example 2, Example 3 and Example 4 of the present application;

[0044] 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;

[0045] Figure 9 Optical response curves of Example 5 and Example 6 of the present application under CPL light illumination;

[0046] Figure 10 Curve of the change of the g value of Example 5 and Example 6 of the present application with wavelength;

[0047] Figure 11 Schematic diagram of the transient EPSC results of Example 5 and Example 6 of the present application in response to a single Lcp and Rcp pulse;

[0048] Figure 12 Schematic diagram of the PPF behavior results of Example 5 and Example 6 of the present application triggered by two CPL pulses;

[0049] Figure 13 Schematic diagram of the change of the PPF index of Example 5 and Example 6 of the present application with the excitatory stimulus interval;

[0050] Figure 14 Schematic diagram of the short-term plasticity and long-term plasticity results of Example 5 and Example 6 of the present application;

[0051] Figure 15 LTP and LTD diagrams of Example 5 and Example 6 of the present application in different CPL states;

[0052] Figure 16 Schematic diagram of the spiking neural network of the example of the present application;

[0053] Figure 17 Contour plot of the synaptic weight values reshaped after iteration of the example of the present application;

[0054] Figure 18 Schematic diagram of the letter recognition accuracy results of Example 5 and Example 6 of the present application in different CPL states.

[0055] Explanation of reference numerals:

[0056] 110, substrate; 120, chiral perovskite layer; 130, MoS2 layer;

[0057] 140. Metal electrode; 150. PDMS film; 160. Mask.

[0058] The realization of the purpose, functional features and advantages of this application will be further described in conjunction with the embodiments with reference to the accompanying drawings. Detailed implementation manners

[0059] To make the purpose, technical solutions and advantages of the embodiments of this application clearer, the technical solutions in the embodiments of this application will be clearly and completely described below. Those not specified in the embodiments are carried out according to conventional conditions or conditions recommended by the manufacturer. Those reagents or instruments not specified by the manufacturer can be obtained as conventional products through commercial purchase.

[0060] Hereinafter, the embodiments of the optical synaptic device based on molybdenum disulfide and chiral perovskite and its preparation method disclosed in this application will be specifically described in detail with reference to the accompanying drawings as appropriate. However, there will be cases where unnecessary detailed descriptions are omitted. For example, there are cases where the detailed descriptions of well-known matters and the repeated descriptions of actually identical structures are omitted. This is to avoid the following descriptions from becoming unnecessarily lengthy and to facilitate the understanding of those skilled in the art. In addition, the accompanying drawings and the following descriptions are provided for those skilled in the art to fully understand this application, and are not intended to limit the subject matter recited in the claims.

[0061] The "range" disclosed in this application is defined in the form of a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, and the selected lower limit and upper limit define the boundary of a specific range. The ranges defined in this way can include or not include the end values, and can be combined arbitrarily, that is, any lower limit can be combined with any upper limit to form a range. For example, if ranges of 60-120 and 80-110 are listed for a specific parameter, ranges of 60-110 and 80-120 are also contemplated. In addition, if the minimum range values 1 and 2 are listed, and if the maximum range values 3, 4 and 5 are listed, then the following ranges are all contemplated: 1-3, 1-4, 1-5, 2-3, 2-4 and 2-5. In this application, unless otherwise specified, the numerical range "a~b" represents the abbreviated representation of any real number combination between a and b, where a and b are both real numbers. For example, the numerical range "0~5" means that all real numbers between "0~5" have been fully listed herein, and "0~5" is only the abbreviated representation of these numerical combinations. In addition, when it is stated that a certain parameter is an integer ≥2, it is equivalent to disclosing that the parameter is, for example, the integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc.

[0062] If there is no special description, all the embodiments and optional embodiments of this application can be combined with each other to form a new technical solution.

[0063] Unless otherwise specified, all steps of this application can be carried out in sequence or randomly, preferably in sequence. For example, if the method includes steps (a) and (b), it means that the method can include steps (a) and (b) carried out in sequence, or steps (b) and (a) carried out in sequence. For example, if it is mentioned that the method may further include step (c), it means that step (c) can be added to the method in any order. For example, the method can include steps (a), (b), and (c), or steps (a), (c), and (b), or steps (c), (a), and (b), etc.

[0064] To make the above objects, features, and advantages of this application more obvious and understandable, the technical solutions of this application will be further described below in conjunction with the accompanying drawings and embodiments. However, this application is not limited to the listed embodiments and should also include any other well-known changes within the scope of the rights required by this application.

[0065] To better understand the technical solutions of this application, the following will be described in detail in conjunction with the drawings of the specification and specific implementation manners.

[0066] In conventional technologies, synaptic devices generally rely on complex manufacturing processes, which not only greatly extend the manufacturing cycle but also significantly increase the economic cost, becoming one of the main bottlenecks restricting their large-scale application. The requirements for these high-end materials and complex processes make the research and development and production of synaptic devices difficult to popularize, hindering the technology from moving from the laboratory to more extensive 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 simultaneously: some solutions can provide relatively high resolution but are limited by low response current and are difficult to support efficient signal transmission; while others may have relatively high response current but affect the accuracy of data processing due to insufficient resolution. The existence of these problems makes the existing optical neural devices difficult to meet the strict requirements for high performance, low energy consumption, and fast response speed in practical applications.

[0067] The embodiment of this application provides an optical synaptic device, including a substrate, a chiral perovskite layer, a MoS2 layer, and a metal electrode arranged in sequence. Among them, the MoS2 layer completely covers the chiral perovskite layer and leaves a non-contact area that does not contact the chiral perovskite layer, and the metal electrode is located in the non-contact area of the MoS2 layer. Through the synergistic optoelectronic effect of the heterojunction formed by the chiral perovskite and MoS2, the optical synaptic device has good circularly polarized light resolution ability, can identify the handedness of circularly polarized light and respond to light stimuli, thereby effectively improving the processing ability of the optical synaptic device for circularly polarized light signals.

[0068] The first embodiment of the present application provides an optical synaptic device based on molybdenum disulfide and chiral perovskite. Referring to Figure 1 , it includes a substrate 110, a chiral perovskite layer 120, a MoS2 layer 130, and a metal electrode 140 arranged in sequence;

[0069] The MoS2 layer 130 completely covers the chiral perovskite layer 120;

[0070] The metal electrode 140 is located in the non-contact area of the MoS2 layer 130 (not shown in the drawings), where the non-contact area is the area where the MoS2 layer 130 does not contact the chiral perovskite layer 120.

[0071] In one embodiment, the MoS2 layer 130 is made of the two-dimensional material molybdenum disulfide (MoS2), which has excellent optoelectronic properties. Specifically, since monolayer or few-layer MoS2 has direct bandgap characteristics, it shows strong light absorption ability in the visible light region and can effectively convert optical signals into electrical signals, thus laying a foundation for achieving efficient optoelectronic response. In addition, MoS2 also has a high carrier mobility, which helps to improve the operation speed and efficiency of the device. Moreover, mechanical flexibility and processability also endow MoS2 with unique adaptability to meet different application requirements. Finally, MoS2 also has excellent stability and can operate stably under high temperature and strong light conditions, significantly improving the durability and stability of the overall optical synaptic device.

[0072] In one embodiment, the chiral perovskite layer 120 is made of a perovskite material with special chiral characteristics. Due to the specific chiral components or chiral frameworks included in the internal structure of chiral perovskite, such materials can effectively distinguish circularly polarized light with different rotation directions. This property enables the optical synaptic device based on chiral perovskite to achieve precise recognition and modulation of circularly polarized light during information processing, thereby improving the efficiency and accuracy of data transmission. Secondly, perovskite materials are famous for their excellent optoelectronic properties such as high absorption coefficient and long carrier diffusion length. When the chiral feature is introduced, these materials can not only maintain the original optoelectronic conversion efficiency but also further enhance 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 synaptic devices and ensures efficient and stable signal transmission. Since chiral perovskite can effectively distinguish circularly polarized light with different rotation directions, the optical synaptic device based on chiral perovskite can achieve precise recognition and modulation of circularly polarized light during information processing. When chiral perovskite is combined with MoS2, due to the excellent optoelectronic 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.

[0073] In a 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 composed of a chiral organic amine (1-(2-naphthyl)ethylamine, NEA) and an inorganic lead iodide framework. Due to their internal chiral structure, they exhibit significant circular dichroism, that is, different absorption rates for left-handed and right-handed circularly polarized light. This property enables them to effectively distinguish circularly polarized light with different polarizations. Compared with other chiral perovskite materials, for example, (R-MBA)2PbI4, (S-MBA)2PbI4, etc., the highest resolution under 77 K test is 17.6%, while the test resolution of the chiral perovskite material used in the embodiments of this application can reach nearly 25% at 78 K, which can further enable the optical synaptic device prepared based on this to have better polarized light resolution ability.

[0074] In a 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. Chiral perovskite layers 120 with different thicknesses have 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, the processing difficulty is great. At the same time, through experiments, the embodiments of this application found that the chiral perovskite layer 120 with a thickness of 98 - 102 nm has strong resolution ability for left and right polarized light. Therefore, it is determined to select the chiral perovskite layer 120 with a thickness of 98 - 102 nm.

[0075] Exemplarily, when the material of the chiral perovskite layer 120 is selected from (R-NEA)PbI3 and the thickness is 98 - 102 nm, the discrimination ability of the optical synaptic device for left and right polarized light is 24.29%.

[0076] Exemplarily, when the material of the chiral perovskite layer 120 is selected from (S-NEA)PbI3 and the thickness is 98 - 102 nm, the discrimination ability of the optical synaptic device for left and right polarized light is 24.39%.

[0077] In a feasible embodiment, 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.

[0078] In a feasible embodiment, the material of the metal electrode 140 includes: Cr and / or Au.

[0079] In a feasible embodiment, 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.

[0080] In a feasible embodiment, the metal electrode 140 includes a first metal layer and a second metal layer sequentially arranged in the non - contact area of the MoS2 layer 130; the material of the first metal layer includes: Cr, and the thickness is 10 - 12 nm; the material of the second metal layer includes: Au, and the thickness is 50 - 52 nm.

[0081] Exemplarily, the thickness of the first metal layer is: 10 nm, 10.5 nm, 11 nm, 11.5 nm, 12 nm, etc.

[0082] Exemplarily, the thickness of the second metal layer is: 50 nm, 50.5 nm, 51 nm, 51.5 nm, 52 nm, etc.

[0083] In this embodiment, the work function of MoS2 is 4.47 eV. Therefore, by using Cr (4.5 eV), whose work function is 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, enhancing the adhesion of the metal film; and because of the high conductivity and good electrical properties of Au (5.1 eV), further combining Au can further improve the device performance.

[0084] In this embodiment, through the synergistic optoelectronic effect of the heterojunction formed by chiral perovskite and MoS2, the optical synaptic device has good polarized light resolution ability, can identify the circular polarization direction of circularly polarized light and respond to light stimuli, thus effectively improving the processing ability of the optical synaptic device for circularly polarized light signals.

[0085] The second embodiment of the present application provides a preparation method of an optical synaptic device based on molybdenum disulfide and chiral perovskite, referring to Figure 2 , including the following steps:

[0086] Step S10, providing chiral perovskite crystals and MoS2 crystals;

[0087] In a feasible embodiment, when providing chiral perovskite crystals and MoS2 crystals respectively, commercially available chiral perovskite crystals and MoS2 crystals can be directly selected, or they can be prepared by corresponding methods, and this embodiment does not limit this.

[0088] In a feasible embodiment, step S10, the step of providing the chiral perovskite crystal includes:

[0089] Step S11, dissolving a lead source in an iodine source solution to obtain a first solution;

[0090] In a feasible example, the lead source is dissolved in the iodine source solution and ultrasonic treatment is performed to obtain a light brown first solution.

[0091] Exemplarily, the lead source includes at least one of lead oxide, lead hydroxide, lead carbonate, and lead acetate.

[0092] Exemplarily, the iodine source includes hydrogen iodide.

[0093] Exemplarily, 100.1 mg of lead oxide is dissolved in 1.5 mL of 58 wt.% HI solution, and a light brown first solution is obtained after ultrasonic treatment.

[0094] Step S12, adding a chiral compound to the first solution and heating to obtain a second solution;

[0095] In a feasible example, the chiral compound is continuously and slowly added to the first solution and heated until a bright yellow second solution is formed.

[0096] Exemplarily, the chiral compound includes R-NEA and / or S-NEA.

[0097] Exemplarily, 134.4 mg of the chiral compound and 1 mL of 1-butanol are continuously and slowly dropped into the first solution and heated in an oil bath at 100~120 °C until a bright yellow second solution is formed, where 1-butanol is used as a solvent to promote the dissolution of the chiral compound.

[0098] Step S13, cooling the second solution to obtain chiral perovskite crystals.

[0099] In a feasible example, the container is left standing at 100~120 °C for 4~8 h, and the crystals are precipitated by cooling. After drying, chiral perovskite crystals are obtained.

[0100] Exemplarily, the container is left standing at 100~120 °C for 4~8 h and cooled to 70 °C at a rate of 5 °C / h −1 and then cooled to 20 °C at a rate of 2 °C / h −1 to obtain yellow crystals, which are dried under vacuum to obtain chiral perovskite crystals.

[0101] In this embodiment, a chiral perovskite material with high crystallinity is synthesized at low temperature by a solution method. By adjusting the solution concentration, reaction temperature, chiral amine ratio, etc., precise control of the chiral direction and intensity can be achieved, avoiding the safety risks and high energy consumption of traditional high-temperature film-forming processes.

[0102] Step S20: Release the chiral perovskite crystal on one surface of the substrate by mechanical exfoliation to obtain a chiral perovskite layer.

[0103] In a feasible embodiment, refer to Figure 3 , provide a clean substrate 110, and release the chiral perovskite crystal on one surface of the substrate 110 by mechanical exfoliation to obtain a chiral perovskite layer 120 located on one surface of the substrate 110.

[0104] Step S30: Release the MoS2 crystal on the PDMS film located on the glass slide by mechanical exfoliation to obtain a MoS2 layer.

[0105] In a feasible embodiment, refer to Figure 3 , release the MoS2 crystal on the PDMS film 150 located on a glass slide (not shown in the drawing) by mechanical exfoliation to obtain a MoS2 layer 130 located on the PDMS film 150.

[0106] Step S40: Transfer the MoS2 layer to the surface of the chiral perovskite layer to obtain a heterojunction, where the MoS2 layer completely covers the chiral perovskite layer.

[0107] In a feasible embodiment, refer to Figure 4 , in an inert gas glove box, use a high-resolution two-dimensional material metallographic micro-transfer system to transfer the MoS2 layer 130 to the surface of the chiral perovskite layer 120 to obtain a heterojunction located on the substrate 110, where the MoS2 layer 130 completely covers the chiral perovskite layer 120.

[0108] In a feasible implementation manner, in step S40, the step of transferring the MoS2 layer 130 to the surface of the chiral perovskite layer 120 to obtain a heterojunction includes:

[0109] Step S41: Place the chiral perovskite layer 120 on a heating stage and heat it at 65 - 85 °C for 1 - 2 min.

[0110] In a feasible embodiment, place the chiral perovskite layer 120 on a heating stage and heat it at 65 - 85 °C for 1 - 2 min to ensure that the MoS2 layer 130 is successfully transferred onto the perovskite layer to form a heterojunction.

[0111] Step S50: Prepare a metal electrode on the surface of the heterojunction to obtain an optical synaptic device, where the metal electrode is located in the non-contact area of the MoS2 layer, and the non-contact area is the area where the MoS2 layer does not contact the chiral perovskite layer.

[0112] In a feasible embodiment, referring to Figure 1 , prepare a metal electrode 140 in the non-contact area of the MoS2 layer 130 to obtain an optical synaptic device.

[0113] In a feasible implementation manner, step S50, the step of preparing the metal electrode 140 on the surface of the heterojunction includes:

[0114] Step S51: Set a mask 160 on the surface of the heterojunction and prepare a metal layer;

[0115] In a feasible embodiment, referring to Figure 5 , set a mask 160 on the surface of the heterojunction and deposit a metal layer.

[0116] Exemplarily, the metal layer is prepared by thermal evaporation, where the evaporation rate is 0.1 - 0.5 Å / s. For example, the evaporation rates are 0.1 Å / s, 0.2 Å / s, 0.3 Å / s, 0.4 Å / s, 0.5 Å / s, etc.

[0117] Exemplarily, by thermal evaporation, deposit Cr on the surface of the heterojunction, the evaporation rate is 0.1 - 0.2 Å / s, and the deposition thickness is 10 - 12 nm; then deposit Au, the evaporation rate is 0.4 - 0.5 Å / s, and the deposition thickness is 50 - 52 nm.

[0118] Exemplarily, a copper mesh can be selected as the mask 160.

[0119] Exemplarily, cut the tape into a square smaller than the size of the PDMS film 150 and cut a window in the middle, then fix it reversely on the PDMS film 150 located on the glass slide, fix the copper mesh steadily on the window of the tape, and then use a high-resolution two-dimensional material metallographic micro-transfer system to transfer the copper mesh onto the heterojunction to form a 10 um wide channel.

[0120] Step S52: Strip the mask and the metal layer on its upper surface to obtain the metal electrode 140.

[0121] In a feasible embodiment, strip the mask and the metal layer on its upper surface to obtain the metal electrode 140.

[0122] In this embodiment, the deposition of the metal electrode 140 does not require electron beam etching to define the electrode. Instead, a copper mesh is used as the mask 160, which not only saves costs but also significantly reduces the manufacturing time of the device. At the same time, it also avoids contact with the organic solution in photolithography, preventing the perovskite from being damaged and optimizing the process flow. In addition, the embodiment of the present application uses mechanical exfoliation to replace the CVD method to obtain two-dimensional materials, combines the mask 160 technology to replace the photolithography process, does not require complex equipment and high-temperature environment, greatly reduces the material cost and processing complexity, and realizes the manufacturing of economical and environmentally friendly devices.

[0123] To enable those skilled in the art to clearly understand the details and operations of the above embodiments of the present application, and to significantly reflect the advanced performance of the embodiments of the present application, the following uses multiple embodiments to illustrate the above technical solutions.

[0124] Example 1

[0125] (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;

[0126] (2) Continuously and slowly add 134.4 mg of R-NEA and 1 mL of 1-butanol to the first solution, and heat at a temperature of 110 °C until a bright yellow second solution is formed;

[0127] (3) Let the second solution stand at 110 °C for 6 h, and cool the solution at a rate of 5 °C / h −1 to 70 °C, and then cool it at a rate of 2 °C / h −1 to 20 °C to obtain yellow crystals; filter the crystals and then dry them under vacuum to obtain (R-NEA)PbI3 crystals.

[0128] Example 2

[0129] 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 crystals.

[0130] Example 3

[0131] Based on the (R-NEA)PbI3 crystals obtained in Example 1, a heterojunction is formed by stacking with a 0.8 nm MoS2 layer.

[0132] Example 4

[0133] Based on the (S-NEA)PbI3 crystals obtained in Example 2, a heterojunction is formed by stacking with a 0.8 nm MoS2 layer.

[0134] Example 5

[0135] (R-NEA)PbI3 crystals were obtained based on Example 1, and an optical synaptic device was fabricated, including a substrate (Si / SiO2), a 100 nm (R-NEA)PbI3 layer, a 0.8 nm MoS2 layer, and metal electrodes arranged in sequence. The metal electrodes include 11 nm Cr and 51 nm Au arranged in sequence.

[0136] Example 6

[0137] (S-NEA)PbI3 crystals were obtained based on Example 2, and an optical synaptic device was fabricated, including a substrate (Si / SiO2), a 100 nm (S-NEA)PbI3 layer, a 0.8 nm MoS2 layer, and metal electrodes arranged in sequence. The metal electrodes include 11 nm Cr and 51 nm Au arranged in sequence.

[0138] Comparative Example 1

[0139] The experimental procedure was the same as that of Example 1, except that the chiral compound used was RAC-NEA, and the resulting product was (RAC-NEA)2PbI4 crystals.

[0140] Comparative Example 2

[0141] 0.8 nm of MoS2.

[0142] The above Examples 1-4 and Comparative Examples 1-2 were tested for the degree of circularly polarized PL (Photoluminescence) at 78 K. To quantify the degree of circularly polarized PL, a parameter P was introduced and defined as:

[0143]

[0144] where P L and P R are the intensities of left and right circularly polarized PL, respectively. The results are as Figure 6 shown, where Figure 6 (a) in is the PL test result of (RAC-NEA)2PbI4 in Comparative Example 1, Figure 6 (b) in is the PL test result of (R-NEA)PbI3 in Example 1, Figure 6 (c) in is the PL test result of (S-NEA)PbI3 in Example 2. According to Figure 6As can be seen from (a) to (c) therein, the main peak of the PL of (R-NEA)PbI3 is located at 702 nm, the main peak of the PL of (S-NEA)PbI3 is located at 707 nm, and the main peak of the PL of (RAC-NEA)2PbI4 is located at 650 nm. For the chiral (S-NEA)PbI3 and (R-NEA)PbI3, under the irradiation of left-handed circular polarization (Lcp) and right-handed circular polarization (Rcp), P is 24.29% and 24.39% respectively, and an obvious intensity difference is observed between the circularly polarized PLs. In contrast, the racemic (RAC-NEA)2PbI4 sample shows basically the same PL intensity between the left-handed and right-handed circularly polarized PLs, indicating that the chiral perovskite materials used in Examples 1 and 2 of this application have the ability to distinguish left and right polarized light. Further referring to Figure 7 , wherein, Figure 7 in (a) is the PL test result of Comparative Example 2 MoS2; Figure 7 in (b) is the PL test result of Example 3 MoS2 / (R-NEA)PbI3 heterojunction; Figure 7 in (c) is the PL test result of Example 4 MoS2 / (S-NEA)PbI3 heterojunction. According to Figure 7 from (a) to (c) therein, there is almost no difference in the PL intensities of the left and right polarized lights of MoS2 (P = 0.855%), and it does not have chirality. However, there are obvious differences in the differences between the PL intensities of the left and right polarized lights in Examples 3 and 4 (22.79% and 28.64% respectively), indicating that even when forming a heterojunction with MoS2, it will not interfere with the chirality of the chiral perovskite.

[0145] Furthermore, polarization light detection tests were carried out on the above Examples 5 to 6 and Comparative Example 2; the results are referred to Figure 8 , wherein, Figure 8 in (a) is the output curve of Comparative Example 2 MoS2 under dark field and right-handed circular polarization (Rcp) and left-handed circular polarization (Lcp) illumination; Figure 8 in (b) is the output curve of Example 5 MoS2 / (R-NEA)PbI3 synaptic device under dark field and right-handed circular polarization (Rcp) and left-handed circular polarization (Lcp) illumination; Figure 8Among them, (c) in [description] is the output curve of the synaptic device of Example 6 MoS2 / (S-NEA)PbI3 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 good light response. Importantly, for the synaptic device of Example 5 MoS2 / (R-NEA)PbI3, compared with left-handed CPL illumination, the synaptic device shows a larger photocurrent under right-handed CPL illumination, while the synaptic device of Example 6 MoS2 / (S-NEA)PbI3 is the opposite, which is consistent with the PL measurement results under circular polarization illumination at 78K.

[0146] Further, referring to Figure 9 , where Figure 9 in (a) is the light response curve of the synaptic device of Example 5 MoS2 / (R-NEA)PbI3 under CPL light illumination; Figure 9 in (b) is the light response curve of the synaptic device of Example 6 MoS2 / (S-NEA)PbI3 under CPL light illumination. It can be seen that the synaptic devices of Example 5 MoS2 / (R-NEA)PbI3 and Example 6 MoS2 / (S-NEA)PbI3 have time-dependent photocurrent response and time response, and at the same time, it also indicates that the synaptic device has good repeatability and stability.

[0147] Further, the anisotropy factor of the photocurrent can be defined as g Iph , satisfying:

[0148]

[0149] where I R and I L are the photocurrents under Rcp and Lcp illumination respectively. Referring to Figure 10 is the curve of the g value of the synaptic devices of Example 5 MoS2 / (R-NEA)PbI3 and Example 6 MoS2 / (S-NEA)PbI3 varying with wavelength. It can be known that in the present application, CPL light of different wavelengths is respectively irradiated on the synaptic devices of Example 5 MoS2 / (R-NEA)PbI3 and Example 6 MoS2 / (S-NEA)PbI3, and the g values of different wavelengths are calculated according to the obtained photocurrents. Among the lights used in the present application, the incident light of 660 nm has the highest g value. Therefore, 660 nm CPL is selected in the present application.

[0150] Further, synaptic tests are carried out on the above Examples 5-6, and the results are referred to Figure 11 , where Figure 11In (a), 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; Figure 11 In (b), the transient EPSC of the MoS2 / (S-NEA)PbI3 synaptic device in Example 6 in response to a single Lcp and Rcp; the conditions of Lcp and Rcp are both: 660 nm, 0.5 Hz, 7 mW cm -2 According to Figure 11 in (a) and Figure 11 in (b), it can be seen that the EPSC is triggered by a single Rcp / Lcp, and the current difference between the peak EPSCs means that the synaptic device of this application can respond differently to CPL stimuli with opposite circular polarizations. The MoS2 / (R-NEA)PbI3 synaptic device in Example 5 shows a 1.21-fold EPSC response compared to the Rcp pulse under Rcp pulse modulation, while the MoS2 / (S-NEA)PbI3 synaptic device in Example 6 shows a 1.16-fold EPSC response compared to the Rcp pulse under Lcp pulse modulation, demonstrating synaptic behavior with CPL resolution ability.

[0151] In addition, the synaptic device also mimics the key property PPF (Paired-pulse Facilitation) of STP (Short-Term Plasticity), and the results are shown in Figure 12 , where Figure 12 in (a) is the PPF behavior of the MoS2 / (R-NEA)PbI3 synaptic device in Example 5 triggered by two CPL pulses; Figure 12 in (b) is the PPF behavior of the MoS2 / (S-NEA)PbI3 synaptic device in Example 6 triggered by two CPL pulses, where the CPL duration is 2 seconds and the intensity is 7 mW cm −2 , and the PPF index is described by A2 / A1; the increment of A2 usually depends on the time interval (Δt) between two spikes, and a larger PPF value can lead to higher time resolution, thus efficiently and accurately processing time information. Further, referring to Figure 13 , where Figure 13 in (a) is the variation of the PPF index of the MoS2 / (R-NEA)PbI3 synaptic device in Example 5 with the excitatory stimulus interval; Figure 13In (b) of [reference], the change of the PPF index of the MoS2 / (S-NEA)PbI3 synaptic device in Example 6 with the excitatory stimulus interval is shown. It can be seen that the PPF index slowly decays with the increase of Δt. The PPF index induced by Lcp of the MoS2 / (S-NEA)PbI3 synaptic device in Example 6 is higher, reaching 121%. For the MoS2 / (R-NEA)PbI3 synaptic device in Example 5, the PPF induced by Rcp has a higher PPF index, up to 125% at most.

[0152] Furthermore, pulse stimulation with different pulse durations was performed on the synaptic device, and the results are referred to Figure 14 , where Figure 14 In (a) of [reference], the schematic diagrams of STP (short-term plasticity) and LTP (long-term plasticity) of the MoS2 / (R-NEA)PbI3 synaptic device in Example 5 are shown; Figure 14 In (b) of [reference], the schematic diagrams of STP and LTP of the MoS2 / (S-NEA)PbI3 synaptic device in Example 6 are shown. It can be seen that as the pulse duration increases, the EPSC gradually becomes higher, and after a period of time, the high EPSC cannot drop back to the starting value, while the relatively low EPSC can drop to or close to the starting value. Memory and learning behaviors are usually attributed to this characteristic, namely short-term plasticity (STP) and long-term plasticity (LTP).

[0153] Meanwhile, the present application also studied the LTP / LTD (long-term depression) process of the synaptic device under optoelectronic modulation, and the results are as shown in Figure 15 , where Figure 15 In (a) of [reference], the LTP and LTD diagrams of the MoS2 / (R-NEA)PbI3 synaptic device in Example 5 under different CPL states are shown; Figure 15 In (b) of [reference], the LTP and LTD diagrams of the MoS2 / (S-NEA)PbI3 synaptic device in Example 6 under different CPL states are shown. According to Figure 15 In (a) of [reference] and Figure 15 In (b) of [reference], it can be known that after applying 100 consecutive light pulses (660 nm, pulse duration of 2 s, pulse width of 0.5 s, intensity of 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 consecutive electrical pulses (-20V) were applied to reduce the conductance of both synaptic devices to the initial level, and this test was based on the LTP and LTD behaviors observed under the conditions of Rcp and Lcp.

[0154] To further evaluate the potential of this application in large-scale image recognition tasks, optical synapse modeling is used as spiking neurons to simulate a spiking neural network (SNN), referring to Figure 16 ; The SNN architecture consists of the following parts: 784 input neurons, 100 hidden neurons, and 26 output neurons. During training, the membrane potential of each output neuron accumulates input spikes and weights from other connected synapses. When the membrane potential value of an output neuron exceeds the threshold, the neuron fires and releases a spike to its next connection, and its membrane potential is reset. The fired neuron will also prevent the firing of other neurons through lateral inhibition. For a period of time, the neuron remains refractory and cannot be fired. In addition, the corresponding synapses that contribute to the firing result will be strengthened, while the synapses that do not contribute to the firing will be weakened. Further, Figure 17 describes the 28×28 contour images of the letters "S", "Z", and "U" after one epoch for each region. It can be seen that after a series of stimuli, the images gradually become clear, and this control is crucial for simulating the development of artificial optical synapses.

[0155] Figure 18 In (a) of Figure 18 is the recognition accuracy of the MoS2 / (R-NEA)PbI3 synaptic device in Example 5 for letters in different CPL states;

[0156] The above are only the preferred embodiments of this application, and do not limit the patent scope of this application. For those skilled in the art, this application can have various changes and modifications. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of this application shall be included in the patent protection scope of this 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, and the material of the chiral perovskite layer includes (R-NEA)PbI3 and / or (S-NEA)PbI3; 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, and the metal electrode includes a first metal layer and a second metal layer sequentially arranged in the non-contact area of ​​the MoS2 layer, the material of the first metal layer includes Cr, and the material of the second metal layer includes Au.

2. 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.

3. The optical synaptic device based on molybdenum disulfide and chiral perovskite according to claim 1, characterized in that: The thickness of the first metal layer is: 10-12 nm; The thickness of the second metal layer is 50-52 nm.

4. 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 3, 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, and the material of the chiral perovskite layer includes (R-NEA)PbI3 and / or (S-NEA)PbI3; 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, the non-contact area is an area where the MoS2 layer is not in contact with the chiral perovskite layer, and the metal electrode includes a first metal layer and a second metal layer sequentially arranged in the non-contact area of ​​the MoS2 layer, the material of the first metal layer includes Cr, and the material of the second metal layer includes Au.

5. The method for preparing an optical synapse device based on molybdenum disulfide and chiral perovskite according to claim 4, 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.

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 the metal layer comprises: The metal layer is prepared by thermal evaporation, wherein the evaporation rate is 0.1-0.5 Å / s.

7. The method for preparing an optical synapse device based on molybdenum disulfide and chiral perovskite according to claim 4, 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.

8. The method for preparing an optical synapse device based on molybdenum disulfide and chiral perovskite according to claim 4, 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.

9. The method for preparing an optical synapse device based on molybdenum disulfide and chiral perovskite according to claim 8, 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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