Organic synapse transistor and its application in adaptive vision bionics

Abstract

The application discloses an organic synapse transistor and application thereof in adaptive visual bionics, and belongs to the technical field of bionic electronic information. The polymer thin film layer of the organic synapse transistor device has a porous micro-nano structure. The source-drain electrode layer and the organic photosensitive semiconductor layer are periodically grown in a porous micro-nano pattern by using the self-templating effect of the polymer thin film. The porous micro-nano structure at the interface of the photosensitive semiconductor is helpful to the capture and separation of photo-generated excitons, thereby improving the photosensitive performance of the device. Under the stimulation of a stepped light intensity pulse, the source-drain current in the channel increases with the increase of the light intensity, but the current gain gradually slows down, and the volatility gradually strengthens. The current response trend under the stepped stimulation is similar to the adaptive behavior of the human eye vision, and is helpful to the realization of the adaptive synapse function of the human eye.

Description

Technical Field

[0001] This invention belongs to the field of biomimetic electronic information technology, specifically relating to an organic synaptic transistor and its application in adaptive visual biomimetic. Background Technology

[0002] The initial bionic eye system used an external camera connected to a processor and transmitted data to an internal computer system via a wireless transmitter. The physical separation between light detection, storage, and processing functions resulted in problems such as high energy consumption and complex hardware operation.

[0003] Inspired by the human brain, photoelectric synaptic transistors can integrate sensing, storage, and computing, and perform image recognition and image preprocessing functions in parallel, representing a qualitative leap in size, power consumption, and speed.

[0004] The basic devices for realizing human eye bionics are mainly divided into two-terminal and three-terminal electronic components. Compared with the single-path transmission characteristics of two-terminal memristors, organic synaptic transistors, as three-terminal synaptic transistors, can use grating signals as input signals, source current as output signals, and the gate as a neural regulator to adjust synaptic weights. Therefore, information transmission and synaptic learning can be carried out in parallel, and they have the characteristics of good reversibility, low power consumption, and high linearity.

[0005] In the visual nervous system, a crucial function is visual adaptation. When external light signals enter the human eye, photoreceptors in the cone and rod cells of the retina generate appropriate electrical spikes based on the light signal conditions. This enables the visual system to adjust its behavior to adapt to different lighting environments, such as color contrast, light intensity, and spatial adaptation. Simultaneously, the human visual adaptation mechanism is also a self-protective mechanism to avoid damage to the eye from abnormal light conditions. Therefore, simulating the human eye's visual adaptive function is an important research direction in the field of bionic eyes.

[0006] In recent years, various novel materials, fabrication processes, and structures have received widespread attention in order to obtain synaptic bionic devices with visual adaptive functions. Currently, the main research strategies for achieving visual adaptive functions using organic synaptic transistors include: 1) Two-dimensional layered semiconductor materials can provide strong light-matter interactions, unique physical defects, and electrostatic modulation, allowing for quantitative and dynamic adjustment of device conductivity through charge capture and release; 2) Using heterojunction structures, the built-in electric field in the heterojunction separates photoexcitons, thereby modulating the photocurrent within the channel. Visual adaptation is a novel research field that has emerged in recent years. The core of visual adaptation research strategies revolves around the manipulation of photoexcitons at or between device interfaces. However, the proposed research strategies are still relatively singular, and the underlying mechanisms require further investigation.

[0007] Chinese patent CN 105810820 A discloses a porous organic field-effect transistor (OPTM) photosensitive memory and its fabrication method. The memory includes source / drain electrodes, an organic photosensitive semiconductor layer, a porous polymer thin film layer, and a gate insulating layer. The polymer thin film layer serves as a porous template layer, inducing the organic photosensitive semiconductor layer and the metal source / drain electrodes to form a periodic porous morphology. This is primarily intended to improve the memory's storage and photosensitive performance when applied to an OPTM memory. However, there are no reports of such transistor devices being used in the field of adaptive vision bionics. If such transistor devices could be used to effectively simulate the human eye's light intensity adaptation function, it would undoubtedly greatly contribute to further expanding its market application scope, fill the gaps in existing visual adaptation research strategies, and provide new ideas for visual adaptation research. Summary of the Invention

[0008] The purpose of this invention is to provide a porous organic synaptic transistor for simulating the adaptive bionic function of the human eye and to reveal its application prospects in adaptive visual bionics. This organic synaptic transistor can effectively improve the photosensitivity of synaptic devices and realize the simulation of the human eye's light intensity adaptive function.

[0009] This invention is achieved as follows: an application of an organic synaptic transistor in adaptive visual bionics. The organic synaptic transistor includes, from top to bottom, a source / drain electrode layer, an organic photosensitive semiconductor layer, a polymer thin film layer, a gate insulating layer, and a substrate. The polymer thin film layer has a porous micro / nano structure. Both the source / drain electrode layer and the organic photosensitive semiconductor layer exhibit periodically grown porous micro / nano morphologies due to the self-templating effect of the polymer thin film. Under stepped light intensity pulse stimulation, the source / drain current in the channel of the organic synaptic transistor increases with increasing light intensity, but the current gain gradually decreases, and the volatility gradually increases.

[0010] Furthermore, the material forming the polymer film layer is a low dielectric constant polymer material, selected from polyvinylcarbazole, polystyrene or polymethyl methacrylate, and the thickness of the polymer film layer is 10 to 100 nm.

[0011] Furthermore, the thickness of the gate insulating layer is 50–300 nm, and the material used for the gate insulating layer is selected from silicon dioxide, alumina, or zirconium oxide.

[0012] Furthermore, the thickness of the organic photosensitive semiconductor layer is 30-50 nm. The materials used in the organic photosensitive semiconductor layer are selected from small molecules, polymers, and two-dimensional materials such as pentane, 2,7-dioctyl[1]benzothiophene[3,2-b]benzothiophene (C8-BTBT), perovskite quantum dots, or 3-hexylthiophene (P3HT). The organic photosensitive semiconductor layer is formed by thermal vacuum evaporation.

[0013] Furthermore, the source and drain electrode layers are made of gold, platinum, or copper, and the thickness of the source and drain electrode layers is 60–100 nm. The source and drain electrodes are prepared by magnetron sputtering, inkjet printing, or vacuum evaporation.

[0014] Furthermore, the polymer thin film layer with porous micro / nano structure can be prepared by photolithography, template etching, breath mapping, or phase separation, with breath mapping being preferred.

[0015] The fabrication method of the above-mentioned organic synaptic transistor is as follows:

[0016] (1) Dissolve the low dielectric constant polymer material in a low boiling point solvent to prepare a solution, and stir and mix at room temperature;

[0017] (2) Select a suitable substrate material as the substrate, and form a gate electrode and a gate insulating layer on the substrate. Clean the substrate and then dry it.

[0018] (3) Treat the dried substrate with ultraviolet ozone for 5 to 10 minutes;

[0019] (4) Spin-coat the solution prepared in step (1) onto the substrate after step (3). The spin-coating process is carried out in an environment with humidity higher than 50%. The spin-coated sample is annealed in a vacuum drying oven to obtain a polymer film layer.

[0020] Experiments have shown that spin coating in an environment with humidity greater than 50% helps to stably form nanoporous structures, while an environment with humidity less than 30% will form a continuous and smooth film. Humidity in between will cause the film morphology to be unstable. Whether a regular pore morphology can be formed will have a key impact on the photosensitivity of the device. Therefore, this application chooses to perform spin coating in an environment with humidity greater than 50%.

[0021] (5) An organic photosensitive semiconductor layer and a source / drain electrode layer are vacuum-deposited onto the sample prepared in step (4).

[0022] Furthermore, the evaporation rate of the organic photosensitive semiconductor layer is Vacuum degree controlled at 5×10 -5 pa~5×10 -4 pa.

[0023] Furthermore, the evaporation rate of the source and drain electrode layers

[0024] Furthermore, the concentration of the low dielectric constant polymer material solution is 2–20 mg / mL.

[0025] Beneficial effects:

[0026] 1. Under stepped light intensity pulse stimulation, the source leakage current in the channel of the organic synaptic transistor prepared in this application increases with the increase of light intensity, but the current gain gradually slows down and the volatility gradually increases. This current response trend under stepped stimulation is similar to the adaptive behavior of human vision, which helps to realize the adaptive synaptic function of human vision.

[0027] 2. This application fabricates an adaptive organic synaptic device based on a porous micro / nano structure. The channel layer is a photosensitive semiconductor material, which, upon illumination, excitons are excited at the interface. The optical signal is used as the stimulation of the synaptic tip, the source leakage current within the channel serves as the postsynaptic current, and the electric gate acts as a synaptic weight to adjust the conductivity level within the channel. Unlike traditional electric gate modulation, this application employs a grating-based electric modulation testing method, which can effectively reduce operating energy consumption, enrich the functional types of neural synapses, and facilitate the application and integration of neuromorphic devices.

[0028] 3. The organic photosensitive semiconductor layer in the adaptive organic synaptic device with porous micro / nano structure prepared in this application has a porous structure. The "microcavity effect" of the porous structure can effectively improve the refraction path of incident light on the surface of the organic semiconductor and increase the capture sites of photogenerated excitons when illuminated, thereby improving the absorption rate and utilization rate of photogenerated excitons at the semiconductor interface, and effectively improving the photosensitivity of the device when simulating the synaptic function of the device. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the porous organic synaptic transistor prepared in Example 1, wherein 1-copper, 2-organic photosensitive semiconductor layer, 3-polymer thin film layer, 4-gate insulating layer, and 5-substrate;

[0030] Figure 2 AFM image of the polymer thin film layer with porous micro / nano structure prepared in Example 1;

[0031] Figure 3 The excitatory postsynaptic current (EPSC) of the porous organic synaptic transistor prepared in Example 1 under single-pulse stimulation in a simulated synapse test;

[0032] Figure 4 The excitatory postsynaptic current (EPSC) of the porous organic synaptic transistor prepared in Example 1 under stepped light intensity pulse stimulation. Detailed Implementation

[0033] The preferred embodiments of the present invention will now be described in detail so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0034] Example 1: Fabrication of porous organic synaptic transistors

[0035] The structure of the organic synaptic transistor to be prepared in this embodiment is as follows: Figure 1 As shown, from top to bottom, it includes a source / drain electrode layer, an organic photosensitive semiconductor layer, a polymer thin film layer, a gate insulating layer, and a substrate. Heavily doped silicon serves as the substrate and gate electrode. A 50–300 nm thick silicon dioxide layer serves as the gate insulating layer. A poly(9-ethylenecarbazole) thin film layer with a porous micro / nano structure serves as the polymer thin film layer. A 30–50 nm thick pentane benzene layer is deposited on top of the gate insulating layer to serve as the organic photosensitive semiconductor layer. Copper is deposited on both sides of the conductive channel to serve as the source / drain electrodes.

[0036] In this embodiment, the polymer film layer with a porous micro / nano structure is preferably prepared by the breath pattern method. This method utilizes the physical characteristic of solvent evaporation and cooling during spin coating to introduce water molecules from the air into the polymer solution. Finally, drying yields the polymer film with a porous structure. The process is simple, easy to operate, and low in cost.

[0037] The specific preparation process is as follows:

[0038] (1) Prepare a poly(9-ethylenecarbazole) solution with Mw = 1,100,000. The solvent used is chloroform, a low-boiling-point solvent with a concentration of 5 mg / mL. After adding a magnetic stir bar and stirring without heating, let it stand for 24 hours to obtain a uniformly dissolved solution.

[0039] (2) The heavily doped silicon with a silicon dioxide layer (thickness of 300nm) on the surface is ultrasonically cleaned with acetone, ethanol and deionized water for 5-10 minutes at an ultrasonic frequency of 100KHz. Then, the surface liquid is blown dry with high-purity nitrogen to ensure that the silicon wafer surface is clean. After that, it is placed in a 120℃ drying oven to dry.

[0040] (3) The silicon wafers dried in step (2) are placed in an ultraviolet ozone generator for 5 minutes;

[0041] (4) Place the silicon wafer treated in the previous step in an environment with a humidity higher than 50%, and spin-coat the polymer solution prepared in step (1) on one side of the gate insulating layer. The spin-coating speed is 1000 r / min, the spin-coating time is 30 s, and the film thickness is controlled at about 60 nm. After spin-coating, the sample is placed in an 80℃ vacuum drying oven for drying and annealing for 30 min to obtain a porous polymer film layer; the AFM image of the obtained polymer film layer is as follows. Figure 2 As shown;

[0042] (5) Vacuum-deposit a 50 nm thick organic semiconductor pentacene onto the surface of the thin film prepared in step (4), at a deposition rate of [missing information]. Vacuum degree controlled at 5×10 -4 pa~5×10 -5 The thickness of the photosensitive semiconductor layer (pa) is controlled to be 40–50 nm using a crystal oscillator. A mask is added to the surface of the organic photosensitive semiconductor layer for patterning, and copper is vacuum-deposited as the source and drain electrodes at a deposition rate of [missing information]. A porous source / drain electrode layer was fabricated with a thickness controlled between 60 and 100 nm.

[0043] Related performance tests

[0044] The electrical performance of the device was characterized using a semiconductor analyzer. A grating-modulated testing method was employed, where a grating was applied above the organic photosensitive semiconductor. Simultaneously changing the grating voltage pulse allowed for precise control of the channel current at the device's synapses; the resulting instantaneous channel current can be considered as the excitatory postsynaptic current (EPSC). By testing the source-drain current response under different light pulse stimuli, wavelength ranges, pulse durations, or pulse frequencies, the response characteristics of the synaptic device under various stimuli can be simulated.

[0045] like Figure 3 As shown, the channel read voltage between the source and drain is 0V, and the intensity of the light pulse applied by the xenon lamp source is 11.59mW / cm². 2 The device was stimulated with white light for 1 second, while a 40V electrical pulse was applied to the gate of the synaptic transistor. EPSC analysis of the organic synaptic transistor device revealed a peak current exceeding 600 nA, indicating that the porous micro / nano structure at the photosensitive semiconductor interface facilitates the capture and separation of photogenerated excitons, thereby improving the device's photosensitivity.

[0046] like Figure 4 As shown, multiple light pulses are applied above the organic photosensitive semiconductor, with light intensity ranging from 1.9 mW / cm². 2 Increased to 8.1 mW / cm 2 Simultaneously, changing the gate voltage pulse allows for precise control of the channel current at the device synapses. The channel readout voltage between the source and drain is 0V, each optical pulse lasts 1s, and the pulse interval is 4s. A 20V electrical pulse is applied to the gate. The source-drain current level within the channel gradually increases with increasing light intensity, but the current gain shows a gradually decreasing trend, and volatility gradually increases. This stepwise stimulation-induced current response trend is similar to the adaptive behavior of human vision.

[0047] The test results above show that the porous organic synaptic transistors prepared by the breathing diagram method have excellent device photosensitivity and can help realize the human eye's adaptive synaptic function.

[0048] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. An application of an organic synaptic transistor in adaptive visual bionics, the organic synaptic transistor comprising, from top to bottom, a source / drain electrode layer, an organic photosensitive semiconductor layer, a polymer thin film layer, a gate insulating layer, and a substrate, characterized in that, The polymer thin film layer has a porous micro-nano structure, and the source / drain electrode layer and the organic photosensitive semiconductor layer both exhibit a periodically grown porous micro-nano morphology by utilizing the self-templating effect of the polymer thin film layer. The polymer film layer was prepared by the breath pattern method. The material forming the polymer film layer was poly(9-ethylenecarbazole) with Mw = 1100000. The concentration of the poly(9-ethylenecarbazole) solution was 2~20 mg / mL. The spin coating process was carried out in an environment with humidity higher than 50%. The material of the gate insulating layer is silicon dioxide; The organic photosensitive semiconductor layer is made of pentacene; The source and drain electrode layers are made of copper. The substrate is heavily doped silicon; Under stepped light intensity pulse stimulation, the channel leakage current of this organic synaptic transistor increases with increasing light intensity, the current gain gradually decreases, and the volatility gradually increases.

2. The application of an organic synaptic transistor as described in claim 1 in adaptive visual bionics, characterized in that, The thickness of the polymer film layer is 10~100 nm.

3. The application of an organic synaptic transistor as described in claim 1 in adaptive visual bionics, characterized in that, The thickness of the gate insulating layer is 50~300 nm.

4. The application of an organic synaptic transistor as described in claim 1 in adaptive visual bionics, characterized in that, The thickness of the organic photosensitive semiconductor layer is 30~50 nm, and the organic photosensitive semiconductor layer is formed by thermal vacuum evaporation.

5. The application of an organic synaptic transistor as described in claim 1 in adaptive visual bionics, characterized in that, The thickness of the source and drain electrode layers is 60~100nm, and the source and drain electrode layers are prepared by magnetron sputtering, inkjet printing or vacuum evaporation.

6. The application of an organic synaptic transistor as described in claim 1 in adaptive visual bionics, characterized in that, The concentration of the poly(9-ethylenecarbazole) solution was 5 mg / mL.

7. The method for fabricating an organic synaptic transistor according to any one of claims 1-6, characterized in that, The preparation steps are as follows: (1) Dissolve poly(9-ethylenecarbazole) with Mw=1100000 in a low-boiling-point solvent to prepare a solution, stir and mix at room temperature, and the concentration of the prepared solution is 2~20 mg / mL. (2) Select heavily doped silicon material as substrate, and use silicon dioxide formed on it as gate insulating layer. Clean and dry it. (3) Treat the dried substrate with ultraviolet ozone for 5-10 min; (4) Spin-coat the solution prepared in step (1) onto the substrate after step (3). The spin-coating process is carried out in an environment with humidity higher than 50%. The spin-coated sample is annealed in a vacuum drying oven to obtain a porous micro-nano structured polymer film layer. (5) An organic photosensitive semiconductor layer and a source / drain electrode layer are vacuum-deposited on the sample prepared in step (4). Both the source / drain electrode layer and the organic photosensitive semiconductor layer exhibit a periodically grown porous micro / nano morphology by utilizing the self-templating effect of the polymer thin film layer.

8. The method for fabricating an organic synaptic transistor as described in claim 7, characterized in that, In step (5), the evaporation rate of the organic photosensitive semiconductor layer is 0.2 Å / s, and the vacuum level is controlled at 5 × 10⁻⁶. -5 pa~5×10 -4 pa.

9. The method for fabricating an organic synaptic transistor as described in claim 7, characterized in that, In step (5), the evaporation rate of the source and drain electrode layers is 0.5 Å / s.

10. The method for fabricating an organic synaptic transistor as described in claim 7, characterized in that, In step (1), the concentration of the prepared solution is 5 mg / mL.

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