An organic photoelectrochemical transistor neuromorphic vision sensor based on n-type semiconductor material and a preparation method thereof

Abstract

This invention discloses an organic photoelectrochemical transistor neuromorphic visual sensor based on n-type semiconductor materials and its fabrication method. The sensor includes a substrate; a source electrode and a drain electrode disposed on the substrate surface, with a channel formed between the source electrode and the drain electrode; an n-type semiconductor thin film layer covering the source electrode, the drain electrode, and part of the channel; a photosensitive gate electrode coupled to the n-type semiconductor thin film layer via electrolytic ion coupling; a photosensitive thin film disposed on the working surface of the photosensitive gate electrode, the photosensitive thin film being a metal-doped porphyrin-based metal-organic framework material; and an electrolytic cell containing the electrolyte. The sensor provided by this invention exhibits high sensitivity, excellent biocompatibility, and stability, and can simulate various synaptic behaviors such as short-term / long-term plasticity, pairing pulse promotion, and pulse number dependence, showing broad application prospects in neuromorphic visual systems, high-sensitivity photosensing, and other fields.

Description

Technical Field

[0001] This invention relates to the field of organic photochemical transistor technology, and in particular to an organic photochemical transistor neuromorphic visual sensor based on n-type semiconductor materials and its fabrication method. Background Technology

[0002] Vision is one of the most important ways humans perceive the external environment. The photoreceptor cells, bipolar cells, and ganglion cells in the human retina form a sophisticated signal processing network that efficiently converts incident light signals into neural electrical signals, and performs preliminary processing and encoding. Developing artificial vision systems that can simulate the structure and working principles of the human eye is not only crucial for understanding the information processing mechanisms of biological vision systems, but also has a profound impact on promoting the development of next-generation intelligent sensing technologies, bionic robots, and medical rehabilitation devices such as retinal implants.

[0003] Existing artificial visual perception technologies mainly include photomemristors, traditional photoelectrochemical sensors, and optoelectronic fibers. However, these technologies still face many challenges in practical applications. First, inconsistent operating modes are a prominent issue: most solid-state devices (such as photomemristors) operate in dry solid environments, making it difficult to simulate the ion-mediated signal transmission process of biological visual systems in aqueous environments, resulting in poor compatibility with biological systems. Second, while traditional photoelectrochemical (PEC) detection methods can operate in the liquid phase, their signal amplification capability is relatively insufficient, making them susceptible to background interference. Furthermore, their function is singular, primarily focusing on photocurrent generation, making it difficult to achieve complex optical information processing and neuromorphic function simulation. Third, optoelectronic fiber technology typically relies on heterojunctions of different materials, resulting in complex structures, limited absorption spectral ranges, and single functional modes, making it difficult to achieve deep integration of optical sensing and information processing. In summary, existing technologies generally suffer from problems such as separation of optical sensing and information processing functions, single functional modality, insufficient biocompatibility, and weak adaptability in complex lighting environments, making it difficult to realistically and efficiently simulate the entire chain of processes from light perception to neural signal processing in biological visual systems.

[0004] Neuromorphic devices based on organic photochemical transistors (OPECTs) represent a cutting-edge research direction in the field of neuromorphic vision. OPECTs combine photochemistry with organic hybrid ion-electron conductors, transmitting signals in an aqueous environment through photoinduced ion migration and chemical reactions. This is highly similar to the signal transmission mechanisms of ions and neurotransmitters in biological nervous systems, providing a unique advantage for constructing biomimetic visual systems. Furthermore, by modifying the interface material of the working electrodes in OPECTs, signal amplification characteristics can be achieved, and these characteristics can be controllably adjusted according to actual visual effect requirements.

[0005] In the field of organic semiconductor materials, the n-type semiconductor material polybenzimidazole benzophenanthreneroline (BBL) is renowned for its excellent electron transport properties and good environmental stability. However, BBL is traditionally used to construct high-performance n-type transistors, and its potential as a channel material in OPECT devices, particularly for simulating the neuromorphic function of the visual system, has not been fully explored. On the other hand, porphyrin-based metal-organic framework (MOF) materials, such as indium-tetra(4-carboxyphenyl)porphyrin (In-TCPP), have attracted much attention in photocatalysis, sensing, and energy conversion due to their advantages such as broad spectral absorption, high specific surface area, and structural designability. However, when In-TCPP is directly used as the photosensitive gate material for OPECT, severe charge recombination and relatively low carrier mobility exist within it, which greatly limits its photoelectric conversion efficiency and photoresponse speed. By doping the In-TCPP framework with transition metal ions (such as Cu), 2+ Constructing bimetallic systems has been proven to be an effective modification strategy that can suppress charge recombination, broaden the light absorption range, and improve the charge transport rate, thereby significantly enhancing the photoelectric effect.

[0006] Therefore, overcoming the shortcomings of existing visual bionic technologies and developing a novel neuromorphic visual sensor that can operate efficiently in aquatic environments, possesses both high-sensitivity signal response and the ability to simulate complex neuromorphic functions, and exhibits good biocompatibility is a technical problem that urgently needs to be solved by those skilled in the art. Existing technologies still require improvement and development. Summary of the Invention

[0007] In view of the shortcomings of the prior art, the purpose of this invention is to provide an organic photoelectrochemical transistor neuromorphic visual sensor based on n-type semiconductor materials and its preparation method, aiming to solve the problems of separation of light sensing and information processing, single functional mode, insufficient biocompatibility, and weak adaptability in complex light environments in existing visual bionic technologies.

[0008] The technical solution of the present invention is as follows: An organic photoelectrochemical transistor neuromorphic vision sensor based on n-type semiconductor material includes a substrate; a source electrode and a drain electrode disposed on the surface of the substrate, with a channel formed between the source electrode and the drain electrode; an n-type semiconductor thin film layer covering the source electrode, the drain electrode, and part of the channel; a photosensitive gate electrode coupled to the n-type semiconductor thin film layer via electrolytic ion coupling; a photosensitive thin film disposed on the working surface of the photosensitive gate electrode, the photosensitive thin film being a metal-doped porphyrin-based metal-organic framework material; and an electrolytic cell containing the electrolyte.

[0009] The organic photoelectrochemical transistor neuromorphic visual sensor based on n-type semiconductor material, wherein the material of the n-type semiconductor thin film layer is polybenzimidazole benzophenanthrene.

[0010] The organic photoelectrochemical transistor neuromorphic visual sensor based on n-type semiconductor materials, wherein the metal-doped porphyrin-based metal-organic framework material is copper-doped indium-tetra(4-carboxyphenyl)porphyrin.

[0011] The organic photoelectrochemical transistor neuromorphic visual sensor based on n-type semiconductor material, wherein the source electrode and the drain electrode constitute an interdigital electrode pair, and the channel spacing between adjacent finger electrodes in the interdigital electrode pair is 1 μm to 20 μm.

[0012] The organic photoelectrochemical transistor neuromorphic vision sensor based on n-type semiconductor material includes a photosensitive gate electrode comprising a conductive glass substrate and an insulating layer disposed on its surface. The insulating layer has a window exposing the conductive glass substrate, and the photosensitive thin film is disposed within the window area.

[0013] The organic photoelectrochemical transistor neuromorphic vision sensor based on n-type semiconductor materials, wherein the conductive glass substrate is indium tin oxide conductive glass.

[0014] The organic photoelectrochemical transistor neuromorphic visual sensor based on n-type semiconductor materials, wherein the electrolyte is one or both of ammonium salt and phosphate.

[0015] A method for fabricating an organic photoelectrochemical crystal neuromorphic tube visual sensor based on n-type semiconductor material as described in this invention, comprising the steps of: S10. A source electrode and a drain electrode with a predetermined pattern are prepared on the surface of a substrate, and a channel is formed between the source electrode and the drain electrode. S20. An n-type organic semiconductor thin film layer is prepared on the substrate surface of the source electrode and the drain electrode; S30. Adhere insulating tape to one end of the conductive glass, use a punch to create a window on the insulating tape that exposes the conductive glass, add a metal-doped porphyrin-based metal-organic framework material solution to the window, and heat and dry to form a photosensitive film to obtain a photosensitive grid electrode. S40. The end of the substrate with an n-type organic semiconductor thin film layer and the end of the photosensitive gate electrode with a photosensitive thin film are placed in an electrolytic cell in a relative manner, and an electrolyte is injected to obtain the organic photoelectrochemical transistor neuromorphic vision sensor based on n-type semiconductor material.

[0016] The method for fabricating the organic photoelectrochemical transistor neuromorphic visual sensor based on n-type semiconductor materials, wherein the metal-doped porphyrin-based metal-organic framework material is copper-doped indium-tetra(4-carboxyphenyl)porphyrin, and the preparation of the copper-doped indium-tetra(4-carboxyphenyl)porphyrin includes the following steps: In(NO3)3·4H2O, Cu(NO3)3·3H2O and polyvinylpyrrolidone were dissolved in a mixed solvent composed of N,N-dimethylformamide and ethanol to obtain a first mixed solution. Porphyrin was dissolved in a mixed solvent consisting of N,N-dimethylformamide and ethanol to obtain a second mixed solution; After the first mixed solution and the second mixed solution are mixed and stirred evenly, they are poured into a hydrothermal reactor for hydrothermal reaction. After the hydrothermal reaction is completed, the product is centrifuged and washed with ethanol solution, and finally dried to obtain copper-doped indium-tetra(4-carboxyphenyl)porphyrin.

[0017] The method for preparing the organic photoelectrochemical transistor neuromorphic visual sensor based on n-type semiconductor material includes a hydrothermal reaction at a temperature of 70-100℃ for 1-3 hours and a drying temperature of 50-70℃.

[0018] Beneficial effects: The OPECT device constructed in this invention has the dual functions of high-sensitivity sensing and intrinsic signal amplification. The weak photocurrent change on the photosensitive gate can be significantly amplified into a large change in the channel current through the transconductance characteristics of the device. Simultaneously, by using a metal-doped porphyrin-based metal-organic framework material as the photosensitive layer, recombination of photogenerated carriers is effectively suppressed, improving photoelectric conversion efficiency and giving the sensor excellent photoelectric response performance and signal-to-noise ratio. This invention is the first to combine an n-type semiconductor BBL with a Cu-doped In-TCPP photosensitive gate to construct a neuromorphic device capable of operating in a fluid environment. The unique ion doping / dedoping kinetics and voltage-driven negative differential resistance of the BBL material allow for precise, multi-level, and non-volatile modulation of the channel conductance. This process perfectly simulates the weighting of biological synapses, i.e., learning and memory. Subsequent experiments demonstrated that the sensor of this invention can successfully simulate a series of key visual synaptic behaviors, including: short-term / long-term plasticity, pairing pulse facilitation, pulse number-dependent plasticity, and light intensity-dependent plasticity. This signifies that the device can achieve complete biomimetic functions from photosensing to information processing within a single architecture.

[0019] This invention, through meticulous design, physically and functionally separates the photosensitive gate electrode (simulating photoreceptor cells in the retina) responsible for photoreception and charge generation from the organic transistor channel (simulating bipolar cells) responsible for signal modulation and amplification. This architectural-level biomimetic design not only achieves functional decoupling, allowing the parameters of the photoreception and processing stages to be optimized independently, but also greatly enriches the functionality and flexibility of the device, providing the possibility for constructing more complex, multi-layered neuromorphic visual systems. This invention employs an n-type BBL (Browser-Based Linear Blower) to replace the traditional p-type channel material, leveraging its superior electron transport capability and stable ion modulation characteristics to overcome the stability limitations of p-type materials. Simultaneously, the use of Cu-doped In-TCPP MOF on the photosensitive gate not only enhances photoelectric performance but also strengthens the mechanical and chemical stability of the MOF framework by introducing Cu-chemical bonds, thus extending the device's lifespan. Furthermore, the use of interdigitated electrodes with micron-level (1-20 μm) channel spacing effectively reduces leakage current and enhances the accuracy and reliability of the channel current.

[0020] In summary, this invention provides a novel, high-performance, and feature-rich OPECT neuromorphic visual sensor, which has achieved breakthroughs in material selection, device structure, biomimetic function realization, and fabrication process, resulting in significant synergistic effects. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the structure of an organic photoelectrochemical transistor neuromorphic vision sensor based on n-type semiconductor materials.

[0022] Figure 2 A flowchart illustrating the fabrication method of an organic photoelectrochemical transistor neuromorphic visual sensor based on n-type semiconductor materials provided in this embodiment of the invention.

[0023] Figure 3 This is a comparison of photocurrents between Cu-doped In-TCPP and pure In-TCPP materials on the ITO gate electrode, as shown in this embodiment of the invention.

[0024] Figure 4 This is a graph showing the inverse bipolar transfer characteristics of an organic photoelectrochemical transistor based on BBL channel material in an embodiment of the present invention.

[0025] Figure 5 This is a conductivity lag characteristic curve of an organic photoelectrochemical transistor based on BBL channel material in an embodiment of the present invention.

[0026] Figure 6 The postsynaptic current change curve of the sensor provided in the embodiments of the present invention under simulated light stimulation demonstrates short-term memory characteristics.

[0027] Figure 7 The graph shows the change in the paired pulse promotion (PPF) index of the sensor provided in this embodiment of the invention under simulated paired light pulse stimulation.

[0028] Figure 8 The graph shows the postsynaptic current response of the sensor provided in this embodiment of the invention under different light intensities.

[0029] Figure 9 The graph shows the postsynaptic current response of the sensor provided in this embodiment of the invention under different numbers of light pulses. Detailed Implementation

[0030] This invention provides an organic photochemical transistor neuromorphic visual sensor based on n-type semiconductor materials and its fabrication method. To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0031] Please see Figure 1 , Figure 1 The schematic diagram of an organic photoelectrochemical transistor neuromorphic vision sensor based on n-type semiconductor material provided by the present invention is shown in the figure. The organic photoelectrochemical transistor neuromorphic vision sensor based on n-type semiconductor material includes an electrolytic cell 1 containing an electrolyte 2, a substrate 3 with one end inserted into the electrolyte 2, and a photosensitive gate electrode. A source electrode 9 and a drain electrode 10 with one end inserted into the electrolyte 2 and spaced apart are disposed on the substrate 3. A channel is formed between the source electrode 9 and the drain electrode 10. An n-type semiconductor thin film layer 4 is coated on the surface of the source electrode 9 and the drain electrode 10 inserted into the electrolyte 2 and part of the channel. The photosensitive gate electrode includes a conductive glass substrate 5 with one end inserted into the electrolyte 2 and an insulating layer 6 disposed on its surface. The insulating layer 6 has a window 7 that exposes the conductive glass substrate. A photosensitive thin film 8 is disposed in the window. The photosensitive thin film 7 is a metal-doped porphyrin-based metal-organic framework material.

[0032] In this invention, the material of the n-type semiconductor thin film layer 4 is preferably polybenzimidazole benzophenanthreneroline (BBL). BBL is an n-type conjugated polymer with a planar rigid framework, which has excellent electron mobility (typically above 10). -3 Up to 10 -2 cm 2Within the range of / V·s, it exhibits good environmental and electrochemical stability. More importantly, BBL is an organic mixed ion-electron conductor (OMIEC), which means that when the BBL channel comes into contact with the electrolyte, cations in the electrolyte (such as NH4+) will react with the electrolyte. + From NH4Br electrolyte, or Na + Ion implantation (from PBS buffer) can be injected into the BBL film under the drive of a gate voltage. The implantation of these cations compensates for the negative charge on the BBL polymer backbone, thereby altering its electrochemical doping state and precisely controlling the electronic conductivity of the channel. This process, known as ion implantation-conductivity modulation, is the physical basis for the neuromorphic functional simulation achieved in this invention. Unlike traditional p-type materials (such as PEDOT:PSS), BBL, as an n-type material, uses electrons as its working charge carriers, and its ion implantation and de-emitter processes exhibit unique kinetic behavior, which provides the possibility for achieving richer synaptic plasticity.

[0033] In the core concept of this invention, the photosensitive film 7 is a metal ion-doped porphyrin-based metal-organic framework (MOF) material. In a preferred embodiment, the photosensitive film 7 is made of copper ions (Cu). 2+ Indium-doped indium-tetra(4-carboxyphenyl)porphyrin (In-TCPP) MOF, denoted as In-TCPP(Cu), is a three-dimensional porous network structure formed by coordination bonds between secondary structural units [InO4(OH)2] and photosensitive TCPP organic ligands. This structure has the following advantages: a) High specific surface area: The porous structure of the MOF provides a large interfacial area for light trapping and ion / matter exchange, which is beneficial to improving photoelectric conversion efficiency; b) Photosensitivity: The TCPP ligand itself is a porphyrin macrocycle with broad-spectrum absorption, which can efficiently absorb photons from the ultraviolet to the visible light region and generate photogenerated electron-hole pairs; c) Charge separation and transport: By introducing a second metal ion Cu into the MOF framework... 2+ It can construct bimetallic centers, Cu 2+ The introduction of [a specific substance] can effectively trap photogenerated electrons and suppress In [a specific substance]. 3+ The severe electron-hole recombination phenomenon in the TCPP system significantly improves the separation efficiency and lifetime of photogenerated carriers. Simultaneously, In-O and Cu-O clusters can serve as channels for electron transport, promoting the rapid transport of photogenerated electrons to the conductive glass (ITO) substrate.

[0034] Therefore, the combination of the BBL channel and the In-TCPP(Cu) photogate proposed in this invention achieves perfect functional synergy and complementarity: the photogate is responsible for efficiently converting the light signal into a localized electrochemical signal (surface charge / potential change), while the BBL channel is responsible for sensitively, linearly, and amplifyingly converting this electrochemical signal into an easily readable channel current signal. This integrated architecture highly mimics the signal processing hierarchy of photoreceptor cells, bipolar cells, and ganglion cells in biological visual systems.

[0035] In some embodiments, the source electrode and the drain electrode form an interdigital electrode pair, wherein the channel spacing between adjacent finger electrodes in the interdigital electrode pair is 1 μm to 20 μm.

[0036] Specifically, the core advantage of organic photochemical transistors (OPECTs) lies in their signal amplification capability, which is quantified by transconductance. The higher the transconductance, the larger the channel current (Ic) can be induced by a small change in gate voltage (generated by the optical signal). DS The higher the sensitivity, the greater the change.

[0037] In this embodiment, the source and drain electrodes are configured as interdigital electrode pairs, and the channel spacing is set to 1μm to 20μm. This is the optimal solution after comprehensively considering transconductance enhancement, high-density integration, biomimetic scale matching, low power consumption, and process feasibility. 1μm represents the process boundary for pursuing ultimate performance (speed, sensitivity) under the premise of controllable cost; 20μm represents the performance boundary for ensuring the effectiveness of biomimetic functions (especially synaptic plasticity simulation). This design enables the OPECT vision sensor of this invention to efficiently capture the weak photoelectric signal of the photosensitive gate and amplify it into a significant, stable channel current output with rich neuromorphic information (such as time summation, pulse facilitation, etc.).

[0038] In some embodiments, the conductive glass substrate is indium tin oxide conductive glass, but it is not limited thereto.

[0039] In some embodiments, the electrolyte is one or both of ammonium salts and phosphates, but is not limited thereto. For example, the ammonium salt is selected from one or more of ammonium bromide, ammonium chloride, and ammonium nitrate; the phosphate is selected from sodium phosphate, etc.

[0040] In some embodiments, a method for fabricating an organic photoelectrochemical transistor neuromorphic visual sensor based on n-type semiconductor materials as described in this invention is also provided, such as... Figure 2 As shown, it includes the following steps: S10. A source electrode and a drain electrode with a predetermined pattern are prepared on the surface of a substrate, and a channel is formed between the source electrode and the drain electrode. S20. An n-type organic semiconductor thin film layer is prepared on the substrate surface of the source electrode and the drain electrode; S30. Adhere insulating tape to one end of the conductive glass, use a punch to create a window on the insulating tape that exposes the conductive glass, add a metal-doped porphyrin-based metal-organic framework material solution to the window, and heat and dry to form a photosensitive film to obtain a photosensitive grid electrode. S40. The end of the substrate with an n-type organic semiconductor thin film layer and the end of the photosensitive gate electrode with a photosensitive thin film are placed in an electrolytic cell in a relative manner, and an electrolyte is injected to obtain the organic photoelectrochemical transistor neuromorphic vision sensor based on n-type semiconductor material.

[0041] The sensor fabrication method of this invention is based on mature technologies such as photolithography, thermal evaporation, spin coating, and hydrothermal synthesis, with a clear and controllable process route. The materials used are relatively inexpensive, and the fabrication process does not involve complex clean environments or expensive equipment. In particular, the interdigitated electrodes defined by photolithography technology make the device easy to miniaturize and integrate in large-scale arrays, laying the foundation for the future development of high-density, high-throughput bionic vision chips.

[0042] In some embodiments, the metal-doped porphyrin-based metal-organic framework material is copper-doped indium-tetra(4-carboxyphenyl)porphyrin. The preparation of copper-doped indium-tetra(4-carboxyphenyl)porphyrin includes the following steps: dissolving In(NO3)3·4H2O, Cu(NO3)3·3H2O and polyvinylpyrrolidone in a mixed solvent composed of N,N-dimethylformamide and ethanol to obtain a first mixed solution; dissolving porphyrin in a mixed solvent composed of N,N-dimethylformamide and ethanol to obtain a second mixed solution; mixing and stirring the first mixed solution and the second mixed solution evenly, then pouring the mixture into a hydrothermal reactor for hydrothermal reaction; after the hydrothermal reaction is completed, centrifuging and washing the product with ethanol solution, and finally drying to obtain copper-doped indium-tetra(4-carboxyphenyl)porphyrin.

[0043] This embodiment uses a hydrothermal method to mix and react indium source, copper source, porphyrin ligand and surfactant (PVP) in the same reactor to directly obtain Cu-doped In-TCPP product in one step. It does not require complicated multi-step synthesis or post-processing, is simple to operate, and is suitable for large-scale preparation.

[0044] In this embodiment, copper ions directly participate in coordination during the formation of the MOF framework, achieving atomic-level uniform doping and avoiding uneven distribution that may result from later introduction. This in-situ doping method enables copper ions to be effectively embedded in the crystal lattice, forming stable bimetallic centers, thereby fully leveraging the synergistic effects of suppressing charge recombination and broadening light absorption.

[0045] In this embodiment, the hydrothermal reaction temperature is 70-100℃, and the reaction time is 1-3 hours. This temperature is much lower than the high-temperature synthesis of many inorganic materials (>300℃), resulting in low energy consumption and simple equipment requirements. The solvents used (DMF / ethanol) and water are the reaction media, making the overall process relatively mild and environmentally friendly. The polyvinylpyrrolidone (PVP) added in this embodiment acts as a morphology guiding agent and dispersant, effectively controlling the growth rate and size of MOF crystals, preventing agglomeration, and obtaining uniform and well-dispersed nanostructures. This helps to form a dense and uniform photosensitive film on the gate electrode surface, improving the consistency and stability of the photoelectric response.

[0046] The following specific embodiments illustrate the present invention's organic photoelectrochemical transistor neuromorphic visual sensor based on n-type semiconductor materials and its fabrication method: Example 1 A method for fabricating an organic photoelectrochemical transistor neuromorphic vision sensor based on n-type semiconductor materials, comprising the following steps: 1. Fabrication of source electrode, drain electrode and BBL channel layer Substrate cleaning: A 2 cm × 2 cm soda-lime glass substrate was selected and sequentially immersed in acetone, anhydrous ethanol, and deionized water, each ultrasonically cleaned for 15 minutes to remove organic and inorganic contaminants from the surface. Subsequently, the glass slide was immersed in a 1:3 (v / v) mixture of hydrogen peroxide and concentrated sulfuric acid for 15 minutes for deep cleaning and surface hydroxylation treatment. Finally, it was rinsed thoroughly with deionized water and dried with nitrogen gas for later use.

[0047] Fabrication of interdigitated electrodes: A layer of positive photoresist (e.g., AZ5214E) is uniformly spin-coated onto a clean glass substrate using the following parameters: low speed 500 rpm for 5 seconds; high speed 3000 rpm for 30 seconds. The substrate is then cured on a hot plate at 110°C for 3 minutes. The designed interdigitated electrode mask is aligned with the photoresist-coated glass and exposed using a UV exposure machine. After exposure, the glass slide is immersed in a dedicated developer to remove the photoresist from the exposed areas, exposing the glass surface and forming the interdigitated electrode pattern. After patterning, the substrate is rinsed with deionized water and dried. In this embodiment, the interdigitated electrode spacing is designed to be 20 μm. A smaller interdigitated spacing can shorten the diffusion path of ions from the electrolyte to the channel interior, improving the device's response speed and transconductance.

[0048] Next, the glass substrate with the photoresist mask was placed in a thermal evaporation deposition machine. First, a 10 nm layer of chromium (Cr) was deposited as an adhesion layer at a rate of 0.1 Å / s, followed by an 80 nm layer of gold (Au) as a conductive layer at a rate of 0.5 Å / s, forming an Au / Cr / glass electrode. After deposition, the electrode was immersed in acetone and ultrasonically removed to remove any remaining photoresist, resulting in patterned, clean interdigitated source and drain electrodes.

[0049] Preparation of the BBL channel layer: 5 mg of polybenzimidazole benzophenanthreneroline (BBL) polymer powder was weighed and dissolved in 1 mL of methanesulfonic acid (MSA). The solution was heated in a 60°C water bath and magnetically stirred for 12 hours until the BBL was completely dissolved, forming a dark brown homogeneous solution with a concentration of 5 mg / mL. The BBL solution was spin-coated onto the substrate with pre-prepared interdigitated electrodes at 3000 rpm for 30 seconds. Immediately after spin-coating, the device was immersed in deionized water for 10 minutes to extract and remove residual MSA solvent, allowing the BBL film to solidify and shrink. After removal, the surface moisture was gently blown dry with nitrogen gas, and then annealed at 110°C for 10 minutes on a heating stage to fully remove residual moisture and stabilize the film properties. Finally, a BBL organic semiconductor channel layer with a thickness of approximately 40-60 nm was formed between the source and drain electrodes.

[0050] 2. Synthesis of In-TCPP(Cu) photosensitive materials In this embodiment, a one-step hydrothermal method is used to synthesize copper-doped indium-porphyrin MOF materials.

[0051] 4.26 mg In(NO3)3·4H2O, 2.76 mg Cu(NO3)3·3H2O, and 10 mg polyvinylpyrrolidone (PVP) were dissolved in 12 mL of a mixed solvent of N,N-dimethylformamide (DMF) and ethanol (volume ratio 3:1); 4.4 mg TCPP (porphyrin) was dissolved in 4 mL of a mixed solvent of N,N-dimethylformamide (DMF) and ethanol. The solutions from the first two steps were mixed and stirred for 30 minutes, then 6 mL of the N,N-dimethylformamide (DMF)-ethanol mixture was added and stirred for 10 minutes. The mixture was then poured into a hydrothermal reactor and heated at 80 °C for 2 hours. After the hydrothermal reaction was completed, the product was washed three times by centrifugation with ethanol solution, and finally dried at 60 °C to obtain the In-TCPP(Cu) product.

[0052] 3. Fabrication of photograting electrode ITO conductive glass pretreatment: Select ITO conductive glass with dimensions of 1 cm × 3 cm, and ultrasonically clean it sequentially with acetone, anhydrous ethanol, and deionized water for 15 minutes each. After cleaning, dry it with nitrogen gas and perform oxygen plasma treatment to thoroughly remove surface organic residues and increase surface hydroxyl groups, thereby enhancing the adhesion of subsequent films.

[0053] Modification of the photosensitive film: Take a 1 cm wide piece of polyimide (PI) insulating tape and smoothly adhere it to one end of the ITO glass. Use a 5 mm diameter punch to make a circular hole in the tape, exposing the ITO surface. Disperse 3 mg of synthesized In-TCPP(Cu) powder ultrasonically in 1 mL of anhydrous ethanol to obtain a 3 mg / mL dispersion. Use a micropipette to carefully add 10 μL of this dispersion to the area within the circular hole in the PI tape. Place the gate electrode in a 40°C oven and heat for 30 minutes to evaporate the solvent, forming a uniform and dense In-TCPP(Cu) photosensitive film. The film thickness can be controlled by adjusting the dispersion concentration and the drop volume; in this example, the film thickness is approximately 500-800 nm.

[0054] 4. Construction and testing of neuromorphic visual devices Device Assembly: The substrate with the BBL channel prepared above and the photosensitive gate electrode modified with In-TCPP(Cu) were inserted together into a transparent quartz electrolytic cell. The electrolytic cell contained a 0.05 M ammonium bromide aqueous solution as the electrolyte. Ammonium bromide is a supporting electrolyte that can provide sufficient ionic conductivity, and NH4+... + Cations can be effectively injected into the BBL channel for doping. Ensure that the uninsulated portions of the source electrode, drain electrode, and photogate electrode (ITO end) are all immersed in the electrolyte, while the electrode leads are above the liquid surface. Connect the source electrode, drain electrode, and photogate electrode to the corresponding ports of a semiconductor parameter analyzer (e.g., Keithley 4200-SCS). Use a 425 nm wavelength light-emitting diode (LED) as the light source, perpendicularly aligned with the surface of the photogate electrode at a distance of approximately 2 cm, and control the LED's light pulse waveform (frequency, intensity, pulse width, etc.) using a function generator.

[0055] Electrical testing: During the test, the drain electrode is grounded, and a constant bias voltage (V0.1V to -0.6V) is applied to the source electrode. DS ), to measure channel current (I DS The photograting electrode is voltage-controlled or open-circuited via a parameter analyzer. I is recorded under different illumination conditions (no illumination, different light intensities, different pulse sequences). DSThe changes were used to evaluate the device's visual biomimetic performance. All tests were conducted at room temperature in a dark environment (except for specific light sources).

[0056] Example 2: Photoelectric performance characterization of In-TCPP(Cu) photogate To verify the effect of Cu doping on the photosensitive performance of In-TCPP, this example compares the photoresponse of OPECT devices based on pure In-TCPP and In-TCPP(Cu) photosensitive gates. Except for the photosensitive thin film material, all other conditions (including channel, electrolyte, and test conditions) were kept consistent with Example 1. During the test, a constant light pulse (wavelength 425 nm, light intensity 0.5 mW / cm²) was applied. 2 (Pulse width 1 second), and record the channel current I. DS The changes.

[0057] Experimental results are as follows Figure 3 As shown in the figure. It can be clearly seen from the figure that when illuminated by a light pulse, the Ig of the two devices... DS Both showed a rapid increase, exhibiting a typical photoinduced enhancement response. However, the photoinduced channel current change (ΔI) of the In-TCPP(Cu) gate device (dashed line) was much larger than that of the pure In-TCPP gate device (solid line). Calculations showed that the photoresponsivity of the In-TCPP(Cu) device (R=ΔI / P, where P is the incident light power) was 2.2 times that of the pure In-TCPP device. This result fully demonstrates the effectiveness of the Cu doping strategy. The mechanism is that in pure In-TCPP, photogenerated electrons and holes recombine rapidly within the MOF framework, resulting in only a few electrons being able to transfer to the ITO electrode and participate in the electrochemical reaction. The introduced Cu... 2+ Ions, acting as effective electron-trapping centers, can rapidly capture and temporarily store photogenerated electrons excited by porphyrin ligands, thereby significantly suppressing direct recombination with holes. The captured electrons can then be slowly released and transferred to the ITO electrode or participate in reduction reactions, thus significantly improving the utilization efficiency and external quantum efficiency of photogenerated carriers. Furthermore, Cu doping may introduce new energy levels, broadening the material's light absorption range and enhancing the framework's conductivity.

[0058] Example 3: Electrical Characterization of OPECT Based on BBL Channel This embodiment characterizes the key electrical properties of a BBL-channel-based OPECT device. Tests were performed in a 0.05 MNH4Br electrolyte. During testing, a constant -0.4 V bias voltage (V0.4) was applied between the source and drain electrodes. DS Simultaneously, a scan voltage (V) is applied to the gate through an Ag / AgCl reference electrode (not shown in the figure). G), and record the channel current I DS The changes.

[0059] Inverse bipolar transfer characteristics: Figure 4 The device's transfer characteristic curves (I) are shown. DS -V G A unique anti-bipolar behavior can be observed from the figure. With V... G Scanning from negative to positive, I DS First, maintain a low level (cutoff zone), when V G After exceeding a threshold (approximately 0.2 V), I DS It begins to rise sharply, reaching a peak (approximately 0.6 V), and then declines with decreasing V. G The further increase of I DS Instead, it decreases (negative resistance region). This anti-bipolar characteristic is crucial for constructing artificial synapses and neurons. The physical mechanism is as follows: Under negative gate voltage, the BBL channel is in a highly depleted state with low electron concentration, therefore I... DS Very small. When V G When the concentration of NH4+ in the electrolyte becomes positive and gradually increases, + Cations are injected into the BBL film under an electric field, compensating for the negative charge on the BBL framework and thus activating electron transport channels. DS It begins to rise. The channel's electron transport efficiency is highest when the injected cations reach an optimal concentration. DS It reaches its peak. If V continues to increase... G Excessive cation implantation can lead to enhanced ion-electron coupling scattering in BBL films or alter the internal electric field distribution of the film, resulting in a decrease in electron mobility. Therefore, I DS A decrease occurs. This peak region corresponds to the point of maximum change in synaptic weight, allowing the device to pass through V. G Simulates various states of the synapse. The figure also shows the application of different channel voltages V. DS By observing the transfer characteristic curve, it is essentially determined that the intensity and uniformity of electrochemical doping inside the device have been altered, and whether the device operates in the fast switching region with small signals or the slow-effect region with large signals and better memory effect.

[0060] Delayed reaction characteristic: Figure 5 The device's lag characteristic curve is shown. During testing, V was first... DS Scan from 0 V to 0.6 V (forward scan), record I. DS -V DS Curve; then immediately V DThe scan proceeds from 0.6 V back to 0 V (reverse scan). As clearly seen in the graph, the forward and reverse scan curves do not overlap, forming a hysteresis loop. This hysteresis indicates that the conductance state of the BBL channel is non-volatile. When the gate voltage is removed, NH4 injected into the BBL thin film... + The ions do not immediately diffuse completely but are partially trapped inside the film, thus maintaining a partially high conductivity state in the channel. V is set within this... G Three signal curves were measured at 0.3 V, 0.4 V, and 0.5 V respectively. It can be seen that V... G It affects the channel current hysteresis effect, V G By driving ions into or out of the BBL polymer film, its internal charge carrier concentration can be directly and reversibly altered. Therefore, with V... G As the ion implantation rate increases, the hysteresis effect becomes more pronounced. This ion residue effect is the physical basis for the transition from short-term to long-term synaptic plasticity and is crucial for achieving memory functionality. The size of the area enclosed by the hysteresis loop reflects the width of the device's memory window, which is essential for multi-level data storage and simulating synaptic weight updates.

[0061] Example 4: Simulation of Neuromorphic Visual Function This embodiment utilizes the sensor prepared in Example 1 to simulate several key functions of the biological vision system.

[0062] Short-term plasticity (STP) and the learning-forgetting process: Figure 6 The short-term memory behavior under visual stimulation was simulated. During the test, a single light pulse (wavelength 425 nm, light intensity 0.5 mW / cm²) was applied to the photosensitive grid. 2 (Pulse width 50 ms), and record the channel current I. DS The transient response. Figure 6 This demonstrates a typical response to single-pulse stimulation: after being triggered by a light pulse, I DS It rises rapidly to a peak (ΔPSC) ma The light stimulation initially showed an amplitude of x ≈ 0.54 μA, which then slowly decayed back to the baseline. After the light stimulation was removed, the channel current did not immediately return to the initial baseline but remained at a level slightly above the baseline. Even 30 seconds after stimulation ceased, this enhanced current retained 7.46% of its maximum peak value. This indicates that the device mimics the short-term plasticity of biological synapses: light stimulation produces a learning effect (enhanced current), and this effect is gradually forgotten over time after stimulation stops, but does not completely disappear (short-term memory). This behavior is highly similar to the phenomenon where the human eye retains a residual image of a briefly observed object in the mind.

[0063] Paired Pulse Facilitation (PPF): PPF is a typical form of short-term synaptic plasticity, which refers to the fact that two temporally closely linked presynaptic stimuli can elicit a stronger postsynaptic response than a single stimulus. Figure 7 The PPF behavior of the device of the present invention is demonstrated. We define the PPF exponent as (A2 / A1) × 100%, where A1 and A2 are the peak channel currents induced by the first and second pulses, respectively (e.g., ...). Figure 6 (As shown). We change the interval (Δt) between the two light pulses and calculate the corresponding PPF exponent. From Figure 7 It can be seen that the PPF exponent decreases exponentially with increasing Δt. When Δt = 50 ms, the PPF exponent is as high as approximately 160%; when Δt increases to 500 ms, the PPF exponent drops to approximately 110%. This trend is completely consistent with the PPF behavior observed in biological nervous systems. Its physical mechanism can be explained using the residual calcium ion model: the NH4+ injected by the first light pulse... + Ions (or accumulated photogenerated holes) create a local electric field or residual ions near the BBL channel, which is equivalent to residual calcium ions in a biological synapse. When the second pulse arrives very quickly, these residual ions / electric field work synergistically with new photogenerated carriers to generate more NH4+. + Ions can be injected into the channel more efficiently, resulting in an amplified channel current response. Longer pulse intervals lead to weaker residual effects and lower PPF exponents. This feature enables the sensor to perceive temporal information of optical signals, such as motion speed and event frequency.

[0064] Light intensity-dependent plasticity: The biological visual system can perceive the intensity of light and make corresponding physiological responses. Figure 8 The response of the device of the present invention under different light intensities is demonstrated. At the same V... DS and V G By varying the light intensity applied to the photosensitive gate and calculating the change based on the photo-excited channel current, a light intensity response curve is obtained. This intensity-dependent plasticity allows the sensor to accurately encode the absolute magnitude of the light intensity. The principle is as follows: when light shines on the photosensitive gate, its porphyrin structure absorbs photons, generating electron-hole pairs (excitons). The stronger the light, the more photons are incident per unit time, and the more electron-hole pairs are generated in In-TCPP(Cu). These photogenerated carriers separate at the gate / electrolyte interface, generating a photovoltage, equivalent to an increase in the effective gate voltage. The stronger the light, the greater this photogenerated ΔV. GThe greater the voltage, the higher the conductivity of the BBL channel. This voltage drives ions in the electrolyte to be injected into the BBL channel. Ion implantation electrochemically dops the BBL, changing its conductivity. The more ions implanted (corresponding to stronger light), the higher the conductivity of the BBL channel is modulated. Under a fixed source-drain voltage, the change in channel conductivity is amplified into a change in source-drain current, i.e., ΔPSC. Therefore, in this device, stronger light will excite more photogenerated electron-hole pairs in the In-TCPP(Cu) photosensitive gate, resulting in more negative charge (electrons) accumulating at the gate / electrolyte interface, thereby attracting more NH4+. + Cation injection into the BBL channel generates a larger channel current. This device can linearly convert the intensity of an optical signal into the amplitude of an electrical signal, directly simulating the graded response of photoreceptor cells to light intensity in biological vision. This characteristic is crucial for achieving high dynamic range image sensing.

[0065] Pulse quantity-dependent plasticity: The biological visual system produces an additive effect on continuous or repetitive stimuli. Figure 9 The response of the device of the present invention under stimulation with different numbers of light pulses is demonstrated. At the same V... DS and V G Under these conditions, 5, 10, and 20 consecutive light pulses were applied, with an interval of 0.5 s between each pulse, and the cumulative current change was calculated. The mechanism is that each light pulse causes a portion of the NH4+ to... + Ions are implanted and retained in the BBL film. When the pulse interval is short enough, ions remaining from the previous pulse have not yet fully diffused, and the next pulse introduces new ion implantation, causing the cation concentration and corresponding conductivity in the channel to continuously increase. This device can count and accumulate discrete optical pulse events. More pulses lead to a larger overall response, similar to the spatiotemporal integration of continuously input postsynaptic potentials by biological neurons. This lays the foundation for pulse-based neuromorphic computing. The number of pulses can serve as a form of information encoding; by designing patterns in the optical pulses, learning and pattern recognition functions can be directly implemented at the hardware level.

[0066] Based on the results of Examples 1-4, it can be clearly concluded that this invention successfully constructs a high-performance OPECT neuromorphic vision sensor based on an n-type semiconductor BBL and an In-TCPP (Cu) photosensitive gate. This device not only has a simple fabrication process and good biocompatibility, but more importantly, it can faithfully simulate various key information processing functions of the biological visual system in an aqueous environment, including short-term / long-term plasticity, paired pulse promotion, and light intensity / pulse number dependence. Its unique integrated architecture and working mechanism provide a new platform and highly promising solutions for developing next-generation neuromorphic vision chips, high-sensitivity photosensing systems, and biomedical interfaces.

[0067] It should be understood that the application of the present invention is not limited to the examples above. Those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. An organic photochemical transistor neuromorphic vision sensor based on n-type semiconductor material, characterized in that, Includes a substrate; a source electrode and a drain electrode disposed on the surface of the substrate, wherein a channel is formed between the source electrode and the drain electrode; An n-type semiconductor thin film layer covering the source electrode, drain electrode, and part of the channel; a photosensitive gate electrode coupled to the n-type semiconductor thin film layer via electrolytic ion coupling; a photosensitive thin film disposed on the working surface of the photosensitive gate electrode, the photosensitive thin film being a metal-doped porphyrin-based metal-organic framework material; and an electrolytic cell containing the electrolyte.

2. The organic photochemical transistor neuromorphic visual sensor based on n-type semiconductor material according to claim 1, characterized in that, The material of the n-type semiconductor thin film layer is polybenzimidazole benzophenanthrene.

3. The organic photochemical transistor neuromorphic visual sensor based on n-type semiconductor material according to claim 1, characterized in that, The metal-doped porphyrin-based metal-organic framework material is copper-doped indium-tetra(4-carboxyphenyl)porphyrin.

4. The organic photochemical transistor neuromorphic visual sensor based on n-type semiconductor material according to claim 1, characterized in that, The source electrode and drain electrode form an interdigital electrode pair, and the channel spacing between adjacent finger electrodes in the interdigital electrode pair is 1 μm to 20 μm.

5. The organic photochemical transistor neuromorphic visual sensor based on n-type semiconductor material according to claim 1, characterized in that, The photosensitive grid electrode includes a conductive glass substrate and an insulating layer disposed on its surface. The insulating layer has a window that exposes the conductive glass substrate, and the photosensitive film is disposed in the window area.

6. The organic photochemical transistor neuromorphic visual sensor based on n-type semiconductor material according to claim 5, characterized in that, The conductive glass substrate is indium tin oxide conductive glass.

7. The organic photochemical transistor neuromorphic vision sensor based on n-type semiconductor material according to claim 1, characterized in that, The electrolyte is one or both of ammonium salts and phosphates.

8. A method for fabricating an organic photochemical transistor neuromorphic visual sensor based on n-type semiconductor materials as described in any one of claims 1-7, characterized in that, Including the following steps: S10. A source electrode and a drain electrode with a predetermined pattern are prepared on the surface of a substrate, and a channel is formed between the source electrode and the drain electrode. S20. An n-type organic semiconductor thin film layer is prepared on the substrate surface of the source electrode and the drain electrode; S30. Adhere insulating tape to one end of the conductive glass, use a punch to create a window on the insulating tape that exposes the conductive glass, add a metal-doped porphyrin-based metal-organic framework material solution to the window, and heat and dry to form a photosensitive film to obtain a photosensitive grid electrode. S40. The end of the substrate with an n-type organic semiconductor thin film layer and the end of the photosensitive gate electrode with a photosensitive thin film are placed in an electrolytic cell in a relative manner, and an electrolyte is injected to obtain the organic photoelectrochemical transistor neuromorphic vision sensor based on n-type semiconductor material.

9. The method for fabricating an organic photoelectrochemical transistor neuromorphic visual sensor based on n-type semiconductor material according to claim 8, characterized in that, The metal-doped porphyrin-based metal-organic framework material is copper-doped indium-tetra(4-carboxyphenyl)porphyrin, and the preparation of the copper-doped indium-tetra(4-carboxyphenyl)porphyrin includes the following steps: In(NO3)3·4H2O, Cu(NO3)3·3H2O and polyvinylpyrrolidone were dissolved in a mixed solvent composed of N,N-dimethylformamide and ethanol to obtain a first mixed solution. Porphyrin was dissolved in a mixed solvent consisting of N,N-dimethylformamide and ethanol to obtain a second mixed solution; After the first mixed solution and the second mixed solution are mixed and stirred evenly, they are poured into a hydrothermal reactor for hydrothermal reaction. After the hydrothermal reaction is completed, the product is centrifuged and washed with ethanol solution, and finally dried to obtain copper-doped indium-tetra(4-carboxyphenyl)porphyrin.

10. The method for fabricating an organic photoelectrochemical transistor neuromorphic visual sensor based on n-type semiconductor material according to claim 9, characterized in that, The hydrothermal reaction temperature is 70-100℃, and the time is 1-3 hours; the drying temperature is 50-70℃.

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