An artificial synapse based on PIN heterojunction at both ends and its preparation method

Abstract

The present invention relates to an artificial synapse based on a two-terminal PIN heterojunction and a method for preparing the same. The structure of the artificial synapse comprises: an electron transport layer distributed partially on a substrate, a light absorption layer and a hole transport layer disposed sequentially above the electron transport layer; a metal layer covering the non-electron transport layer portion of the substrate and a portion of the surface above the hole transport layer; and the hole transport layer is a thiophene polymer. When illuminated, the artificial synapse of the present invention generates currents in the same and opposite directions as the photogenerated current by applying positive and negative voltage stimulation to the right top electrode. The combined effect of the two can enhance and suppress two different light responses, respectively.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductor devices, and in particular relates to a two-terminal artificial synapse electronic device. Background Art

[0002] The biological visual system is a complex and extensive neural network composed of multiple neurons, receptors, and effectors. Over 80% of the information received by the brain is collected through the visual system. The fundamental unit of this complex and sophisticated system is the individual nerve cell, each of which is connected by thousands of synapses, which serve as bridges for information exchange. A complete biological synapse consists of three main parts: the presynaptic membrane, the postsynaptic membrane, and the synaptic cleft. Cells exchange information by regulating the strength of the connections between synapses. This property is called synaptic plasticity, which includes both short-range and long-range plasticity. Synaptic plasticity also serves as the molecular basis for learning and memory. Research on optoelectronic synapses is of great significance for the development of artificial visual systems.

[0003] Artificial synapses based on perovskite materials are mostly photoexcitable devices, but some complex physiological activities require the synergistic action of both inhibitory and excitatory synapses. To address this issue, the present invention proposes an artificial synapse based on a PIN heterojunction at both ends and a method for its fabrication. The fabricated artificial synapse exhibits a pronounced photoresponse to visible light and can simultaneously achieve both photoenhancement and photoinhibition in a single device, addressing the shortcomings of current optoelectronic artificial synapses. Summary of the Invention

[0004] The present invention aims to address the problem that single-layer perovskite-based two-terminal artificial synapses only have a single response to light pulse stimulation. It provides a two-terminal artificial synapse based on a PIN heterojunction and a method for preparing the same. The present invention adds a tin dioxide electron transport layer and a poly(3-hexylthiophene) hole transport layer to the traditional two-terminal artificial synapse structure based on a single perovskite layer, forming a two-terminal artificial synapse device with a tin dioxide / perovskite / poly(3-hexylthiophene) heterojunction structure. When illuminated, positive and negative voltages are applied to the electrodes above the right hole transport layer to generate currents in the same and opposite directions as the photogenerated current. The combined effect of these two currents can enhance and suppress two different light responses, respectively.

[0005] The technical solutions of the present invention are as follows:

[0006] An artificial synapse based on two ends of a PIN heterojunction, the structure of the artificial synapse comprising: an electron transport layer distributed partially on a substrate, a light absorption layer and a hole transport layer arranged on the electron transport layer in sequence; a metal layer covering a portion of the substrate not containing the electron transport layer and a portion of the surface above the hole transport layer;

[0007] The substrate is made of glass with a thickness of 1-2 microns;

[0008] The electron transport layer is a binary metal oxide with a thickness of 30-60 nanometers;

[0009] The light absorption layer is made of perovskite material and has a thickness of 0.5-1 micron;

[0010] The hole transport layer is a thiophene polymer with a thickness of 30-100 nanometers;

[0011] The metal layer is divided into a left metal electrode and a right metal electrode, both of which are made of gold. The left electrode is the substrate surface electrode, and the right electrode is the hole transport layer surface electrode.

[0012] The area of the electron transport layer is 20-50% of the area of the substrate.

[0013] The horizontal distance between the left and right electrodes is 100-150 microns, and the thickness is 80-100 nanometers.

[0014] The substrate is a quartz glass silicon wafer or an indium tin oxide conductive glass.

[0015] The electron transport layer is a binary metal oxide, including but not limited to any one of tin oxide, zinc oxide, and titanium oxide.

[0016] The light absorbing layer is a perovskite material having the general formula ABX3, wherein A includes but is not limited to any one of cesium, methylamine, and formamidine; B includes but is not limited to any one of lead, tin, zinc, and potassium; and X includes but is not limited to any one of chlorine, bromine, and iodine.

[0017] The hole transport layer includes but is not limited to any one of polythiophene, poly (3-hexylthiophene), and poly (3-bromohexylthiophene).

[0018] The artificial synapse based on the two ends of the PIN heterojunction is characterized in that the method comprises the following steps:

[0019] (1) The substrate was ultrasonically cleaned with deionized water, acetone, and isopropyl alcohol in sequence, and then the substrate surface was blown dry with nitrogen and placed in a UV cleaning machine for 15-20 minutes;

[0020] (2) In an air environment, a tin dioxide ammonia solution is added dropwise to the substrate of step (1), and then spin-coated at a speed of 3000-5000 revolutions per minute using a spin coater for 20-40 seconds, and then the substrate is placed on a hot plate and heated at 130-180° C. for 20-40 minutes to obtain an electron transport layer;

[0021] The tin dioxide ammonia solution is prepared by mixing a 15%-20% by mass tin dioxide aqueous colloidal dispersion and a 10%-35% ammonia aqueous solution in a volume ratio of 1 to 2-4; 80-100 microliters of the tin dioxide ammonia solution is added dropwise per 2-4 square centimeters of the substrate;

[0022] (3) In a glove box, the MAPbI3 precursor solution is added dropwise to the electron transport layer obtained in step (2), and spin-coated at a speed of 3000-5000 rpm for 50-80 seconds using a spin coater to directly obtain a perovskite film;

[0023] The MAPbI3 precursor solution is prepared by adding methylammonium iodide (MAI) and lead iodide (PbI2) to a mixed solution at a molar ratio of 1 to 1-1.5, and stirring to obtain a MAPbI3 precursor solution with a concentration of 1-1.2 mol / ml. The mixed solution is prepared by mixing methylamine ethanol and acetonitrile at a volume ratio of 1:0.5-1. 80-100 microliters of the MAPbI3 precursor solution is added dropwise per 2-4 square centimeters of the electron transport layer.

[0024] (4) adding the P3HT precursor solution dropwise onto the perovskite film of step (3), spin coating the film at a speed of 2000-3000 rpm for 20-40 seconds using a spin coater, and then placing the substrate on a hot plate and heating it at 50-100° C. for 5-20 minutes to obtain a hole transport layer;

[0025] The P3HT precursor solution is prepared by adding chlorobenzene solvent to poly (3-hexylthiophene) (P3HT) and stirring, with a concentration of 5-10 mg / ml. 60-100 μl of the P3HT precursor solution is added dropwise to each 2-4 square centimeters of the perovskite film.

[0026] (5) The semiconductor layer covering part of the upper surface of the substrate is removed to expose part of the substrate; then, through thermal evaporation technology, a left electrode is obtained on the surface of the substrate, and a right electrode is obtained on the surface of the hole transport layer, and finally an artificial synapse based on the two ends of the PIN heterojunction is obtained.

[0027] Among them, the thermal evaporation parameters are temperature controlled at 40-50 degrees, vacuum degree 10 -3 -10 -4 Pa, deposition rate 0.8-1 angstrom / second, evaporation time 30-40 minutes.

[0028] The essential features of the present invention are:

[0029] Traditional artificial synapses at both ends of a perovskite typically use a single layer of perovskite material as the semiconductor functional layer. This invention builds on this by adding a tin dioxide electron transport layer and a poly(3-hexylthiophene) hole transport layer, thereby forming a tin dioxide / perovskite / poly(3-hexylthiophene) heterojunction with the perovskite light-absorbing layer.

[0030] Wherein, the hole transport layer generally used Spiro-OMeTAD before; the present invention uses poly (3-hexylthiophene) hole transport layer.

[0031] The beneficial effects of the present invention are:

[0032] The most significant feature of the optoelectronic synaptic device provided by the present invention is that it can achieve two different responses, enhancement and inhibition, to light pulse stimulation.

[0033] Traditional artificial synapses at both ends of perovskites mostly use a single layer of perovskite material as the semiconductor functional layer, which can only produce a single enhanced response to light pulse stimulation. On this basis, the present invention adds a tin dioxide electron transport layer and a poly (3-hexylthiophene) hole transport layer, thereby forming a tin dioxide / perovskite / poly (3-hexylthiophene) heterojunction between the perovskite light absorption layer. The tin dioxide electron transport layer and the poly (3-hexylthiophene) hole transport layer are used to separate the holes and electrons generated by light in the perovskite layer, forming a photogenerated current; by applying positive and negative polarity voltage stimulation to the right top electrode, a current in the same direction and opposite direction as the photogenerated current is generated. By utilizing the superposition of the two, without changing the wavelength, light intensity, duration, etc. of the incident light, two different responses, enhancement and suppression, can be achieved simultaneously.

[0034] As shown in the attached figure, the conventional artificial synapses at both ends of perovskite can only produce similar adhesion under the stimulation of continuous light pulses. Figure 2 In the artificial synaptic device based on the PIN heterojunction at both ends provided by the present invention, by changing the voltage polarity applied to the right top electrode, the attachment can be simultaneously achieved under the stimulation of continuous light pulses. Figure 2 and attached Figure 3 Two different responses are shown: enhancement and inhibition. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 This is a schematic diagram of the structure of an artificial synapse based on the two ends of a PIN heterojunction;

[0036] Figure 2 This is a graph showing the excitatory postsynaptic currents generated by the artificial synapses at both ends of the PIN heterojunction obtained in Example 1 under stimulation by 1, 5, 10, 20, 30, and 50 consecutive light pulses. The voltage applied to the top electrode on the right side is -0.1V.

[0037] Figure 3Curves of inhibitory postsynaptic currents generated by the artificial synapse at both ends of the PIN heterojunction obtained in Example 1 under stimulation by 1, 5, 10, 20, 30, and 50 consecutive light pulses. The voltage applied to the top electrode on the right side was 0.3V. DETAILED DESCRIPTION

[0038] The present invention will be described in detail below with reference to specific examples. The following examples are helpful for relevant persons to study and think about the present invention, but will not have any limiting effect on the present invention.

[0039] Example 1:

[0040] A method for preparing an artificial synaptic electronic device based on a PIN heterojunction at both ends is as follows:

[0041] (1) A 2×2 cm, 2 μm thick conductive glass substrate was ultrasonically cleaned with deionized water, acetone, and isopropyl alcohol, followed by drying the substrate surface with nitrogen and placing it in a UV cleaning machine for 15 minutes.

[0042] (2) A 20% by mass tin dioxide aqueous colloidal dispersion and a 20% by weight ammonia water were mixed in a volume ratio of 1 to 2 and stirred to obtain a transparent and clear tin dioxide ammonia water solution.

[0043] (3) Methylammonium iodide (MAI) and lead iodide (PbI2) were mixed in a molar ratio of 1:1, and a mixed solution of methylamine ethanol and acetonitrile in a volume ratio of 3:2 was added, and then stirred evenly to obtain a MAPbI3 precursor solution with a concentration of 1.1 mol / ml.

[0044] (4) Chlorobenzene solvent is added to poly (3-hexylthiophene) (P3HT), and then stirred evenly to obtain a P3HT precursor solution with a concentration of 5 mg P3HT / ml chlorobenzene.

[0045] (5) In an air environment, 100 μL of the tin dioxide ammonia solution in step (2) was added dropwise to a 4 cm2 substrate in step (1), and then spin-coated at 4000 rpm for 30 seconds using a slurry coater. The substrate was then placed on a hot plate and heated at 150°C for 30 minutes to obtain a 40 nm thick high-quality electron transport layer.

[0046] (6) In a glove box, 100 μL of the MAPbI3 precursor solution obtained in step (3) was added dropwise to the tin dioxide film obtained in step (5). The film was spin-coated at 4000 rpm for 60 seconds using a spin coater. After the spin-coating, a high-quality perovskite film with a thickness of 0.6 μm was directly obtained.

[0047] (7) 70 μL of the P3HT precursor solution obtained in step (4) was added dropwise to the perovskite film in step (6), and spin-coated at 2500 rpm for 30 seconds using a spin coater. The substrate was then placed on a hot plate and heated at 70°C for 10 minutes to obtain a 50 nm thick high-quality hole transport layer.

[0048] (8) Using a blade to remove the semiconductor layer in a part of the upper surface of the substrate, the removed area is a rectangle of 1×1 cm, located at the lower left corner of the upper surface of the substrate; a mask (the area of the left and right grooves of the mask are both 1.5 mm*1 mm, the total area of the mask is 5*5 mm, and the distance between the two grooves is 100 μm) is covered on the surface of the hole transport layer obtained in step (7), and the hole transport layer is formed by thermal evaporation technology (the chamber temperature is controlled at 40-50 degrees, the vacuum degree is 4*10 -4 -5*10 -4 Pa, deposition rate 1 angstrom / s, evaporation time 30 minutes, deposition thickness 80 nanometers), and deposited gold electrodes with a thickness of 80 nanometers and a left-right spacing of 100 microns on the surface of the film in the groove part, thereby obtaining a complete artificial synaptic electronic device based on the two ends of the PIN heterojunction.

[0049] Performance testing and experimental results analysis:

[0050] The electrical performance of the artificial synapses at both ends of (8) was tested and analyzed using a semiconductor analyzer Keithley 4200A-SCS, and the following important results were obtained (the test environment was in a nitrogen-enclosed glove box with a nitrogen purity greater than 99% and an ambient temperature of 20-25 degrees Celsius):

[0051] The artificial synaptic device based on the PIN heterojunction at both ends in Example 1 has good light enhancement and suppression effects. Figure 2 As shown in the figure, under the condition of a voltage of -0.1V applied to the right top electrode, different numbers of light pulses stimulated a significant current enhancement effect. When the number of light pulses increased from 1 to 50, the postsynaptic current increased rapidly from -0.18 nanoamperes to -0.4 nanoamperes, and the time it took for the current to decay to baseline was also significantly improved. This shows that short-term facilitation and long-term potentiation can be achieved in artificial synaptic devices based on PIN heterojunctions.

[0052] At the same time, under the condition of applying a voltage of -0.1V to the right top electrode, different numbers of light pulse stimulations will produce a significant current inhibition effect. Figure 3 As shown, the postsynaptic current significantly decreased from 0.4 nanoamperes to 0 under stimulation with varying numbers of light pulses, ranging from 1 to 50. Furthermore, the greater the number of light pulses, the longer it took for the current to return to its initial value. This demonstrates that both short-term and long-term synaptic behaviors can be achieved. This holds important implications for modeling complex synaptic behaviors and physiological processes.

[0053] Example 2:

[0054] A method for preparing an artificial synaptic electronic device based on a PIN heterojunction at both ends is as follows:

[0055] (1) A 2×2 cm, 2 μm thick conductive glass substrate was ultrasonically cleaned with deionized water, acetone, and isopropyl alcohol, followed by drying the substrate surface with nitrogen and placing it in a UV cleaning machine for 20 minutes.

[0056] (2) A 15% by mass tin dioxide aqueous colloidal dispersion and a 35% by weight ammonia solution were mixed in a volume ratio of 1 to 3 and stirred to obtain a transparent and clear tin dioxide ammonia solution.

[0057] (3) Methylammonium iodide (MAI) and lead iodide (PbI2) were mixed in a molar ratio of 1 to 1.5, and a mixed solution of methylamine ethanol and acetonitrile in a volume ratio of 1 to 1 was added, and then stirred evenly to obtain a MAPbI3 precursor solution with a concentration of 1.2 mol / ml.

[0058] (4) Chlorobenzene solvent was added to poly (3-hexylthiophene) (P3HT), and then stirred to obtain a 10 mg / ml P3HT precursor solution.

[0059] (5) In an air environment, 120 μL of the tin dioxide ammonia solution in step (2) was added dropwise to the substrate in step (1), and then spin-coated at 5000 rpm for 40 seconds using a slurry coater. The substrate was then placed on a hot plate and heated at 180°C for 20 minutes to obtain a 30 nm thick high-quality electron transport layer.

[0060] (6) In a glove box, 80 μL of the MAPbI3 precursor solution obtained in step (3) was added dropwise to the tin dioxide film obtained in step (5). The film was spin-coated at 3000 rpm for 50 seconds using a spin coater. After the spin-coating, a high-quality perovskite film with a thickness of 1 μm was directly obtained.

[0061] (7) 100 μL of the P3HT precursor solution obtained in step (4) was added dropwise to the perovskite film in step (6), and spin-coated at 3000 rpm for 40 seconds using a spin coater. The substrate was then placed on a hot plate and heated at 100°C for 5 minutes to obtain a 40 nm thick high-quality hole transport layer.

[0062] (8) Using a blade to remove the semiconductor layer in a part of the upper surface of the substrate, the removed area is a rectangle of 1×1 cm, located at the lower left corner of the upper surface of the substrate; a mask (the area of the left and right grooves of the mask are both 1.5 mm*1 mm, the total area of the mask is 5*5 mm, and the distance between the two grooves is 150 μm) is covered on the surface of the hole transport layer obtained in step (7), and the hole transport layer is formed by thermal evaporation technology (the chamber temperature is controlled at 40-50 degrees, the vacuum degree is 4*10 -4 -5*10 -4 Pa, deposition rate 1 angstrom / second, evaporation time 40 minutes), a gold electrode with a thickness of 100 nm and a left-right spacing of 150 μm was obtained on the surface of the film in step (7), and an artificial synapse based on the two ends of the PIN heterojunction was obtained.

[0063] The above implementation cases and test results are intended to provide a certain research basis for researchers in related fields. Any other non-substantive research changes, including modification, simplification, replacement and other simple changes in experimental conditions, should be within the scope of protection of this invention.

[0064] Matters not covered by the present invention are known technologies.

Claims

1. An artificial synapse based on a PIN heterojunction at both ends, characterized by The structure of the artificial synapse includes: an electron transport layer distributed on a portion of the substrate, a light absorption layer and a hole transport layer on the electron transport layer in sequence; a metal layer also covering a portion of the substrate not on the electron transport layer and a portion of the surface on the hole transport layer; The substrate is made of glass; the electron transport layer is a binary metal oxide; the light absorption layer is a perovskite material; the hole transport layer is a thiophene polymer; the metal layer is divided into a left metal electrode and a right metal electrode, both made of gold, the left electrode is the substrate surface electrode, and the right electrode is the hole transport layer surface electrode; The substrate is a quartz glass silicon wafer or an indium tin oxide conductive glass; The electron transport layer is a binary metal oxide, including but not limited to any one of tin oxide, zinc oxide, and titanium oxide; The light absorbing layer is a perovskite material having the general formula ABX3, wherein A includes but is not limited to any one of cesium, methylamine, and formamidine; B includes but is not limited to any one of lead, tin, zinc, and potassium; and X includes but is not limited to any one of chlorine, bromine, and iodine; The hole transport layer is not limited to any one of polythiophene, poly (3-hexylthiophene), and poly (3-bromohexylthiophene); The method for preparing artificial synapses at both ends of a PIN heterojunction comprises the following steps: (1) The substrate was ultrasonically cleaned with deionized water, acetone, and isopropyl alcohol in sequence, and then the substrate surface was blown dry with nitrogen and placed in a UV cleaning machine for 15-20 minutes; (2) In an air environment, a tin dioxide ammonia solution is added dropwise to the substrate of step (1), and then spin-coated at a speed of 3000-5000 revolutions per minute using a spin coater for 20-40 seconds, and then the substrate is placed on a hot plate and heated at 130-180° C. for 20-40 minutes to obtain an electron transport layer; The tin dioxide ammonia solution is prepared by mixing a 15%-20% by mass tin dioxide aqueous colloidal dispersion and a 10%-35% ammonia aqueous solution in a volume ratio of 1 to 2-4; 80-100 microliters of the tin dioxide ammonia solution is added dropwise per 2-4 square centimeters of the substrate; (3) In a glove box, the MAPbI3 precursor solution is added dropwise to the electron transport layer obtained in step (2), and spin-coated at a speed of 3000-5000 rpm for 50-80 seconds using a spin coater to directly obtain a perovskite film; The MAPbI3 precursor solution is prepared by adding methylammonium iodide (MAI) and lead iodide (PbI2) to a mixed solution at a molar ratio of 1 to 1-1.5, and stirring to obtain a MAPbI3 precursor solution with a concentration of 1-1.2 mol / ml. The mixed solution is prepared by mixing methylamine ethanol and acetonitrile at a volume ratio of 1:0.5-1. 80-100 microliters of the MAPbI3 precursor solution is added dropwise per 2-4 square centimeters of the electron transport layer. (4) adding the P3HT precursor solution dropwise onto the perovskite film of step (3), spin coating the film at a speed of 2000-3000 rpm for 20-40 seconds using a spin coater, and then placing the substrate on a hot plate and heating it at 500-100° C. for 5-20 minutes to obtain a hole transport layer; The P3HT precursor solution is prepared by adding chlorobenzene solvent to poly (3-hexylthiophene) (P3HT) and stirring, with a concentration of 5-10 mg / ml. 60-100 μl of the P3HT precursor solution is added dropwise to each 2-4 square centimeters of the perovskite film. (5) removing the semiconductor layer covering part of the upper surface of the substrate to expose part of the substrate; then, using thermal evaporation technology, obtaining a left electrode on the substrate surface and a right electrode on the hole transport layer surface, ultimately obtaining an artificial synapse based on the two ends of the PIN heterojunction; Among them, the thermal evaporation parameters are temperature controlled at 40-50 degrees, vacuum degree 10 -3 -10 -4 Pa, deposition rate 0.8-1 angstrom / second, evaporation time 30-40 minutes.

2. The artificial synapse based on a PIN heterojunction as claimed in claim 1, wherein the horizontal distance between the left and right electrodes is 100-150 microns and the thickness is 80-100 nanometers; The thickness of the substrate is 1-2 microns; The thickness of the electron transport layer is 30-60 nanometers; The thickness of the light absorbing layer is 0.5-1 micron; The hole transport layer has a thickness of 30-100 nanometers.

3. The artificial synapse based on the PIN heterojunction at both ends according to claim 1, characterized in that The area of the electron transport layer is 20-50% of the area of the substrate.

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