All-fiber structure vertical organic electrochemical transistor and preparation method thereof

Abstract

The invention belongs to the technical field of electronic materials and devices, and discloses an all-fiber structure vertical organic electrochemical transistor and a preparation method thereof.The all-fiber structure vertical organic electrochemical transistor is composed of a lower electrode layer, a semiconductor active layer and an upper electrode layer, and the upper electrode layer and the lower electrode layer are ion permeable electrode layers; the porous PAN / PVP nanofiber membrane is composed of a porous PAN / PVP nanofiber substrate and a metal conductive layer, the semiconductor active layer is an electrospun PEDOT: PSS / PAm nanofiber membrane treated by DMSO (dimethylsulfoxide); the preparation method comprises the following steps: firstly, respectively preparing the ion permeable electrode layer and the semiconductor active layer, and then assembling the upper electrode layer, the semiconductor active layer and the lower electrode layer into the all-fiber structure vertical organic electrochemical transistor. The vertical organic electrochemical transistor with the all-fiber structure is more compact in structure, higher in channel utilization rate and shorter in ion transport path, and the signal amplification performance and the time response performance of a device are greatly improved.

Description

A vertical organic electrochemical transistor with an all-fiber structure and its fabrication method Technical Field

[0001] This invention belongs to the field of electronic materials and devices technology, and relates to a vertical organic electrochemical transistor with an all-fiber structure and its preparation method. Background Technology

[0002] Population aging, high incidence of chronic diseases, and increased public health awareness have created an urgent demand for "continuous, comfortable, and accessible" physiological monitoring. Simultaneously, the rapid development of home healthcare, telemedicine, and sports rehabilitation scenarios necessitates that monitoring devices seamlessly integrate into everyday clothing and remain stable and reliable during work, leisure, and special conditions (such as high temperature, high humidity, and prolonged wear). However, existing devices such as wristbands and patches often suffer from rigid encapsulation and low signal-to-noise ratios, making it difficult to simultaneously achieve comfort and high-quality signal acquisition. This is driving the evolution of sensing front-ends towards flexibility, breathability, low power consumption, and intrinsic amplification.

[0003] OECT (Organic Electrochemical Transistor) is an electrochemical device that relies on bulk ion-electron coupling to achieve functions such as modulation, acquisition, and monitoring of electrochemical signals. This device can achieve high transconductance at low voltages below 1V, enabling direct in-situ amplification of weak bioelectrical signals (such as ECG and electrooculography), reducing the need for front-end wiring and external amplification. By combining OECT with fabrics or directly achieving intrinsic fibrous structure, and developing novel fabric electronics, it is hoped that intelligent bioelectronic systems combining skin conformability and high signal amplification capabilities can be constructed, showing broad application prospects in wearable health monitoring, human-computer interaction, and intelligent biointegrated systems.

[0004] Compared to traditional rigid electrodes or field-effect transistor-based amplifiers, amplifiers integrated with OECT on textile platforms offer advantages in both materials and electronics. Their soft, flexible, stretchable, and breathable fabric substrate conforms closely to skin or curved surfaces, significantly reducing contact impedance and motion artifacts. Compared to non-breathable rigid electrodes, they offer greater comfort and stability during long-term wear and have the potential for large-area array fabrication. Compared to the dependence of field-effect transistors on dry dielectric layers and high input impedance, OECT is more electrolyte-friendly, resulting in higher signal quality and signal-to-noise ratio. Furthermore, the textile process facilitates large-scale manufacturing and integration with clothing, offering low power consumption, washability, and reusability, providing more practical system-level advantages for wearable continuous monitoring.

[0005] Despite the unique advantages of fabric OECT in terms of skin compatibility and breathability, it still faces key structural and performance challenges. Most reported fabric OECTs employ a planar configuration, which, due to the difficulty in incorporating standard photolithography and fine patterning techniques, results in large channel dimensions and insufficient morphological accuracy. Furthermore, the channel semiconductor layer is typically prepared through spraying, dip coating, drop coating, or directly using a single semiconductor fiber with a large diameter. This reduces the specific surface area of ​​the channel interface, hindering effective electrolyte penetration and ion implantation. These limitations collectively lead to slower device response time and lower transconductance. In electrophysiological monitoring such as ECG, rapid signals and small fluctuations require sensing systems with high dynamic response and high gain performance. In addition, existing fabric OECTs suffer from significant bottlenecks in electrode design and overall device architecture. Most schemes use traditional dense metals or conductive coatings as electrodes, which are inherently ion-insensitive, relying solely on the slow diffusion of electrolytes along the edges within the plane to couple with the channel region. This results in long and uneven ion implantation paths, further limiting the device's dynamic response capabilities. Encapsulation layers introduced to improve stability often sacrifice breathability and softness, making devices prone to problems such as interface lifting, sweat swelling, and signal drift under complex skin environments such as high temperature, high humidity, and sweating. On the other hand, some fabric OECTs still mainly rely on "devices attached to fabric" and have not truly achieved a fully integrated fiber design from electrodes and channels to the support skeleton. This makes it difficult for devices to be deeply compatible with textile processes. After weaving, bending, washing, and long-term cycling, the electrical performance degrades significantly, resulting in insufficient reliability.

[0006] The literature (Fast and Durable Nanofiber Mat Channel Organic Electrochemical Transistors[J].ACS Applied Materials & Interfaces, 2023, 15(33):39614-39624.) uses an electrospun PEDOT:PSS / PAm composite nanofiber membrane as the semiconductor active layer in a planar OECT structure, and works in conjunction with a hydrogel environment. Compared with traditional thin film channels, the PEDOT:PSS / PAm composite nanofiber membrane has a higher specific surface area and fibrous porous structure, thereby improving the ion exchange efficiency of the electrolyte / channel interface. However, this technology is still based on the conventional planar OECT structure, and ions mainly diffuse laterally into the channel. It does not solve the problem of vertical rapid ion injection from the overall device structure level, and it is difficult to simultaneously achieve high transconductance and high-speed response under short channel conditions. Secondly, its electrospun nanofibers are only used for the channel layer, and do not involve the multilayer electrospun integrated construction of the source, drain and channel. The overall process still relies on micro-fabrication methods such as photolithography, which is not conducive to low-cost large-scale preparation on large-area textile substrates.

[0007] Therefore, there is an urgent need to develop a vertical organic electrochemical transistor with an all-fiber structure and its fabrication method, so that the fabric made from it has a more compact structure, shorter channels, and enhanced ion transport efficiency, in order to overcome the above-mentioned bottlenecks. Summary of the Invention

[0008] The purpose of this invention is to solve the problems existing in the prior art and to provide a vertical organic electrochemical transistor with an all-fiber structure and its preparation method.

[0009] To achieve the above objectives, the technical solution adopted by the present invention is as follows:

[0010] A vertical organic electrochemical transistor (OECT) with an all-fiber structure comprises, from bottom to top, a lower electrode layer (as the source), a semiconductor active layer (as the channel), and an upper electrode layer (as the drain). Both the lower and upper electrode layers are ion-permeable electrode layers to ensure vertical ion implantation and electron conduction. The ion-permeable electrode layer is composed of a porous PAN / PVP nanofiber substrate and a metal conductive layer deposited thereon. The semiconductor active layer is an electrospun PEDOT:PSS / PAm nanofiber membrane that has been annealed and treated with DMSO. PAN / PVP refers to polyacrylonitrile / polyvinylpyrrolidone, PEDOT:PSS / PAm refers to poly(3,4-ethylenedioxythiophene) / polystyrene sulfonate-polyacrylamide, and DMSO refers to dimethyl sulfoxide.

[0011] Traditional vertical OECT devices typically employ dense metal electrodes, restricting ion transport to slow lateral diffusion through the channel sidewalls, thus reducing dynamic performance. The all-fiber vertical organic electrochemical transistor of this invention effectively overcomes this fundamental limitation by utilizing porous and ion-permeable electrodes. Furthermore, the channel region is constructed by embedding electrospun nanofiber semiconductors between vertically stacked electrodes, forming a compact three-dimensional structure that enhances ion-electron coupling and gating efficiency. Leveraging these structural advantages, the resulting all-fiber fabric OECT device exhibits high transconductance and millisecond-level response under low-voltage operation, effectively overcoming the trade-off between transconductance and response speed.

[0012] As a preferred technical solution:

[0013] The all-fiber vertical organic electrochemical transistor described above has a water vapor permeability of 1.05–2.16 kg m³ for the ion-permeable electrode layer. -2 d -1 It is significantly higher than the rate of skin sweat evaporation (0.6 kg m³). -2 d -1It has excellent breathability and skin compatibility; the all-fiber structure vertical organic electrochemical transistor can be used as a low-frequency physiological signal amplification and acquisition module, improving the signal-to-noise ratio by 30-50% when acquiring electrooculography (EOG) and electrocardiogram (ECG) signals, and can work stably under power supply voltage below 1V.

[0014] The all-fiber vertical organic electrochemical transistor described above uses a porous PAN / PVP nanofiber substrate, which is a multilayer nanofiber membrane prepared by electrospinning. The substrate consists of a PAN / PVP conductive support layer and a PVA soluble layer arranged sequentially from bottom to top. In the PAN / PVP conductive support layer, the mass ratio of PAN to PVP is 4 to 6:1. The thickness of the PVA soluble layer is 1 to 5 μm.

[0015] As described above, in a vertical organic electrochemical transistor with an all-fiber structure, the metal conductive layer consists of a Cr metal layer and an Au metal layer from bottom to top. The thickness of the Cr metal layer is 3-12 nm, and the thickness of the Au metal layer is 100-150 nm. The metal conductive layer is transferred and fixed in the nanofiber network through a sacrificial PVA layer to form a flexible electrode with high porosity and ion permeability.

[0016] In the all-fiber vertical organic electrochemical transistor described above, the mass ratio of PEDOT:PSS to PAM in the electrospun PEDOT:PSS / PAm nanofiber membrane is 100:5 to 20.

[0017] The all-fiber structure vertical organic electrochemical transistor described above is encapsulated with a PAN / PVP electrospun film of the same material to improve air permeability.

[0018] The all-fiber structure vertical organic electrochemical transistor described above has a maximum transconductance of 38–57.5 ms at a working voltage of -0.6V, a response time of 11.7–33.8 ms (preferably 11.7–32.5 ms), and retains more than 75% of its initial performance after 10,000 cycles at a bending radius of 0.5 cm.

[0019] The present invention also provides a method for fabricating a vertical organic electrochemical transistor with an all-fiber structure as described above. First, an ion-permeable electrode layer and a semiconductor active layer are prepared separately. Both the upper electrode layer and the lower electrode layer are ion-permeable electrode layers. Then, the upper electrode layer, the semiconductor active layer and the lower electrode layer are assembled into a vertical organic electrochemical transistor with an all-fiber structure.

[0020] As a preferred technical solution:

[0021] The fabrication method of the all-fiber vertical organic electrochemical transistor as described above specifically includes the following steps:

[0022] (1) Preparation of ion-permeable electrode layer;

[0023] (1.1) Preparation of electrospinning solution;

[0024] PAN is dissolved in DMF or DMAc, and then PVP is added. The mixture is magnetically stirred at room temperature (23°C) for 6–10 h to obtain a transparent and uniform spinning solution. The concentration of PAN in the spinning solution is 10–15 wt%, and the concentration of PVP is 2–3 wt%.

[0025] (1.2) Electrospinning to form a film;

[0026] The spinning solution was loaded into a syringe, and under conditions of 20–25°C and 30–40% relative humidity, the voltage was set to 12–20 kV, and the injection rate to 0.6–1.0 mL / h. -1 The volume of the spinning solution in the syringe is 1-1.5 mL, the distance between the needle and the collecting roller is 10-20 cm, and electrospinning is performed for 2-5 h to obtain PAN / PVP nanofiber membranes.

[0027] (1.3) Coating and hot pressing treatment;

[0028] A PVA layer was formed by electrospinning a PVA solution onto a PAN / PVP nanofiber membrane, followed by exposure to 120–130°C and 4–8 kg / cm² temperature. -2 Under the condition of hot pressing for 5-10 minutes, the PVA layer is partially melted to form stable interlayer bonding points, thus obtaining a porous PAN / PVP nanofiber substrate.

[0029] (1.4) Metal vapor deposition and patterning;

[0030] Using a metal masking method, chromium and gold layers are deposited sequentially in a vacuum evaporation system to form a conductive metal network. Then, the PVA layer is dissolved by spraying deionized water to obtain an ion-permeable electrode layer.

[0031] (2) Preparation of semiconductor active layer;

[0032] (2.1) Preparation of PEDOT:PSS / PAm composite electrospinning solution;

[0033] First, acrylamide (Am) was dissolved in deionized water, and then ammonium persulfate solution and tetramethylethylenediamine (TEMED) were added sequentially. The mixture was magnetically stirred at 70–80 °C to obtain a transparent, viscous PAM prepolymer solution. Then, the PEDOT:PSS aqueous solution was pre-frozen at -20–-30 °C for 24–36 h, and then freeze-dried in a freeze dryer to obtain freeze-dried PEDOT:PSS. Finally, the freeze-dried PEDOT:PSS was dissolved in deionized water and magnetically stirred to fully redisperse it to obtain a homogeneous dispersion. The PAM prepolymer solution was added to the dispersion and magnetically stirred to form a uniform, spinnable PEDOT:PSS / PAm composite electrospinning solution.

[0034] (2.2) Electrospinning to form a film;

[0035] The PEDOT:PSS / PAm composite electrospinning solution was loaded into a syringe. Under conditions of 40–45℃ and 20–25% relative humidity, the voltage was set to 10–15 kV and the injection rate to 0.4–1.0 mL / h. -1 A flat collector covered with aluminum foil was used, with the distance between the needle and the collector being 6-10 cm. Electrospinning was performed for 5 minutes to obtain a PEDOT:PSS / PAm nanofiber membrane.

[0036] (2.3) Post-treatment of electrospun film;

[0037] The PEDOT:PSS / PAm nanofiber membrane obtained by electrospinning was first annealed in an oven at 120-150℃ for 24-36 hours, and then soaked in a 4-6 wt% DMSO aqueous solution to obtain the PEDOT:PSS / PAm semiconductor active layer.

[0038] The PEDOT:PSS / PAm nanofiber membrane obtained by electrospinning is first annealed in an oven at 120-150℃ for 24-36 hours to enhance the conductivity of the PEDOT:PSS / PAm nanofiber membrane, and then soaked in a 4-6 wt% DMSO aqueous solution to promote the orderly arrangement of PEDOT segments and the hydrogen bond crosslinking of PAM, thereby improving its electrochemical stability and obtaining a semiconductor active layer.

[0039] (3) Fabrication of a fully fiber-structured vertical organic electrochemical transistor;

[0040] The composite layer is assembled in the order of ion-permeable electrode layer, semiconductor active layer, and ion-permeable electrode layer. After the assembled composite layer is heated and dried at 80-100℃ for 5-10 minutes, the interlayer bonding is tight, forming a vertical stacked structure, and a full-fiber structure vertical organic electrochemical transistor is obtained.

[0041] The nanofiber electrode of this invention is formed by an "electrospinning + vapor deposition" process, and the channel layer is formed by an "electrospinning + solvent treatment" process. Compared with combinations such as "dense metal electrode + planar channel" and "non-permeable electrode + fiber active layer", the "porous nanofiber electrode + electrospinned semiconductor active layer" has superior performance, as detailed below:

[0042] The relatively hydrophobic surface of pure PAN nanofibers hinders the spreading and penetration of electrolyte droplets. Introducing PVP significantly improves the membrane surface wetting behavior, as shown in Figure 2. The electrolyte can then enter the fiber network more quickly and in greater quantities, creating conditions for vertical ion implantation and thus enhancing the gating efficiency and response speed of OECT.

[0043] PAN, as the structural framework, possesses excellent mechanical strength and thermal stability, maintaining its fiber morphology during hot pressing at 120℃. The introduction of PVP significantly improves the hydrophilicity of the fibers, enabling electrolytes to rapidly wet and penetrate the fiber network, which is beneficial for forming efficient ion implantation channels. The composite of the two maintains the porous morphology of the nanofiber membrane while also endowing it with good wetting properties.

[0044] The PVA layer, as a soluble layer, partially melts during hot pressing, acting as a self-leveling and fiber-joint bonding agent. This gives the bilayer film strong integrity and surface smoothness, facilitating mask-based metal deposition on the PVA surface. Subsequently, the PVA layer is selectively dissolved with deionized water, allowing the metal electrode to be firmly transferred and anchored onto the PAN / PVP network, forming a porous, ion-permeable electrode. This avoids the poor conductivity problem associated with direct metal deposition on porous, rough substrates and circumvents the incompatibility limitations of traditional photolithography with fabric substrates. Because the metal is anchored at the fiber cross-linking points, the porous structure is preserved to the maximum extent, resulting in a porosity exceeding 70% for the metallized fiber membrane. This ensures that the electrode maintains conductivity while guaranteeing the device's moisture permeability and ion permeability, while also providing a simple, low-temperature, photolithography-free process suitable for large-scale fabrication.

[0045] The anchoring bond between the PAN / PVP nanofiber membrane and the metal layer, along with the interlocking structure between the fibers, results in a tighter bond between the electrode and the fiber substrate, making delamination less likely. Compared to traditional dense metal electrodes, this invention maintains stable conductivity even after repeated bending and stretching.

[0046] Both the upper and lower electrodes are composed of highly porous nanofiber networks, allowing electrolyte ions to vertically and rapidly penetrate and inject into the semiconductor active layer, avoiding the problem of long-distance lateral migration of ions in planar fabric-based OECTs. This vertical injection mode significantly shortens the response time, enabling the device to achieve millisecond-level high-speed switching even at low voltages.

[0047] The vertical stacking structure of this invention significantly shortens the equivalent channel length and improves the effective channel width-to-length ratio (W / L), enabling the device to achieve high transconductance (greater than 50 ms) at low voltage, while the response speed is within 10 to 12 ms, which is far superior to traditional fabric OECT.

[0048] The semiconductor active layer is composed of electrospun PEDOT:PSS / PAm nanofibers. After treatment with DMSO, the PEDOT segments rearrange and the π-π stacking is enhanced, significantly reducing disorder defects and improving charge transport efficiency. Compared with the uneven thickness and microcracks that are prone to occur in traditional solution-coated active layers, the semiconductor active layer of this invention is more dense and uniform, and has higher electrochemical stability.

[0049] Invention principle:

[0050] The all-fiber vertical OECT of this invention employs a vertically stacked structure consisting of upper and lower porous metallized nanofiber electrode layers and an electrospun semiconductor nanofiber active layer. The porous metallized nanofiber electrode layers possess high porosity and ion permeability, allowing the electrolyte to reach the channel along its thickness direction. This provides a longitudinal ion permeation channel for the channel, enabling efficient ion doping control. Consequently, high transconductance and millisecond-level response can be achieved at low voltages, while ensuring good moisture permeability and mechanical flexibility. The channel utilizes an electrospun PEDOT:PSS / PAm nanofiber membrane, and DMSO treatment achieves segment rearrangement and π-π stacking, significantly enhancing charge transport efficiency. The upper and lower electrode layers and the active layer work together to form a unique all-fiber vertical structure, overcoming the limitations of traditional planar OECT devices in terms of transconductance and response speed.

[0051] This invention employs a three-dimensional gated structure of "porous nanofiber electrode + electrospun semiconductor active layer". The porous nanofiber electrode allows the electrolyte to penetrate rapidly along the vertical direction, significantly shortening the ion implantation and diffusion path. The electrospun semiconductor active layer forms a connected porous network and improves π–π stacking through solvent rearrangement, significantly increasing the volumetric capacitance and dopant volume, while simultaneously improving electron transport. The synergistic effect of these two components transforms the ion path from in-plane diffusion to out-of-plane volume gating, achieving a "short path + large volume" co-directional gain. This enables the device to simultaneously achieve millisecond-level response time and high transconductance output under low-voltage drive. However, if structures such as "porous nanofiber electrode + planar channel," "dense electrode + electrospun vertical channel," and "dense electrode + planar channel" are used, it is impossible to simultaneously achieve a synergistic improvement in response time and transconductance. This is because: when porous nanofiber electrodes are combined with planar channels, the fabric substrate is difficult to be compatible with fine patterning processes such as photolithography, the channel size cannot be refined, and the planar channel is thin-film, with a limited gate volume; when dense electrodes are combined with electrospun channels, ions are hindered and need to migrate laterally from the edges, significantly slowing down the response, and the deeper parts of the channel are difficult to effectively gate; when dense electrodes are combined with planar channels, electrolyte ions need to diffuse along the in-plane of the channel to the interface to complete dedoping or doping, resulting in a limited effective gate volume and an increased diffusion distance, which in turn manifests as reduced transconductance, slower response, and limited bandwidth. In contrast, the porous nanofiber electrode of this invention allows ions to reach the electrospun bulk phase channel directly from outside the surface, achieving short-path, large-volume gate control, and can simultaneously obtain millisecond-level response and high transconductance output at low voltage. Therefore, only the vertical structure combination of "porous nanofiber electrode + electrospun semiconductor active layer" can simultaneously achieve a synergistic improvement in response time and transconductance within the same device structure.

[0052] From the OECT formula, transconductance:

[0053] Where μ: carrier mobility; C * Volumetric capacitance; W / L: Geometric ratio; d: Effective channel thickness / volume of doped ions;

[0054] Response time:

[0055] Among them, l ion Characteristic pathways of ion implantation and diffusion; D ion : Effective diffusion coefficient of ions;

[0056] The unique synergy of "porous nanofiber electrode + electrospun semiconductor active layer" lies in simultaneously increasing g m Enlarge the three multiplication factors (C*, Wd / L) in the formula, and increase the path l in the τ formula. ion Be small.

[0057] Porous electrodes change the ion pathway from horizontal to vertical, directly transferring lion Reduced to near channel thickness level (millisecond response); electrospun fiber channels provide high specific surface area and interconnected pores, reducing volume capacitance C * Simultaneously increase the effective volume d (height g) m After the two are bonded together, ions can penetrate three-dimensionally from both sides along the fiber pore-pore network. The "short path + large volume" is no longer a choice between two options, but rather a gain in the same direction, thus achieving "fast and strong".

[0058] Beneficial effects:

[0059] (1) The all-fiber structure vertical organic electrochemical transistor of the present invention adopts a vertical stacked structure composed of upper and lower electrode layers and electrospun semiconductor nanofiber active layer, which changes the ion implantation path of the all-fiber structure vertical organic electrochemical transistor from the traditional lateral diffusion to the synergy of longitudinal penetration and lateral diffusion, significantly improving the ion-electron coupling efficiency and response speed. Furthermore, through this structure, electrolyte ions can directly penetrate the porous electrode and be injected into the semiconductor active layer, achieving efficient ion doping control, thereby achieving high transconductance and millisecond-level response at low voltage. Compared with the traditional planar OECT, the structure of the present invention is more compact, the channel utilization is higher, and the ion transport path is shorter, which greatly improves the signal amplification performance and time response performance of the device.

[0060] (2) The PAN / PVP composite nanofiber substrate used in this invention has both good mechanical stability and surface wettability. PAN provides high strength and thermal stability, which can maintain the fiber morphology without collapse during hot pressing and vapor deposition. With the introduction of PVP, the surface hydrophilicity is significantly improved, which allows the electrolyte to quickly and uniformly penetrate the fiber network and improve the ion implantation rate. In addition, the composite structure maintains high porosity and has good moisture permeability, which ensures the long-term stable operation of the device in flexible, breathable and physiological environments. Compared with single PAN or PVP substrates, the conductive layer of PAN / PVP composite fiber has a stronger adhesion and better flexibility, which significantly improves the reliability and wearability of the electrode layer.

[0061] (3) The all-fiber structure vertical organic electrochemical transistor of the present invention exhibits high flexibility, high stability and long durability. The porous PAN / PVP nanofiber substrate and the metal conductive layer deposited on it form an interlocking structure at the microscopic level. The interface is firmly bonded and has excellent anti-peeling performance. The high-throughput ion regulation of the vertical stacked structure enables the device to have the characteristics of low power consumption, low noise and high amplification ratio, which is suitable for applications in wearable physiological signal amplification and textile electronics.

[0062] (4) This invention is applicable to the front-end amplification and acquisition of wearable low-frequency physiological signals. It can significantly improve the signal-to-noise ratio in the monitoring of physiological signals such as EOG / ECG and can work stably under power supply conditions of less than 1V. It has the prospect of large-scale application and textile integration. Attached Figure Description

[0063] Figure 1 is a schematic diagram of the structure of the all-fiber vertical organic electrochemical transistor prepared in Example 1 of the present invention; in the figure, I is a schematic diagram of the structure of the ion-permeable electrode layer, II is a schematic diagram of the structure of the porous PAN / PVP nanofiber substrate, III is a schematic diagram of the structure of the semiconductor active layer; in the figure, V Bio This represents the signal after a fully fiber-structured vertical organic electrochemical transistor is attached to a human body for detection, V G V represents the linear scan gate voltage. DS Indicates the source-drain voltage;

[0064] Figure 2 is a schematic diagram of the dynamic contact angle test of the PAN / PVP nanofiber membrane prepared in Example 1 of the present invention;

[0065] Figure 3 is a SEM image of the PAN / PVP nanofiber membrane prepared in Example 1 of the present invention;

[0066] Figure 4 shows the SEM images of the PAN / PVP nanofiber membrane prepared in Example 1 of the present invention before and after hot pressing; in the figure, (a) is the SEM image of the PAN / PVP nanofiber membrane before hot pressing, and (b) is the SEM image of the PAN / PVP nanofiber membrane after hot pressing.

[0067] Figure 5 is a comparison of the porosity of the porous PAN / PVP nanofiber substrate and the ion-permeable electrode layer prepared in Example 1 of the present invention.

[0068] Figure 6 is a SEM image of the PEDOT:PSS / PAm semiconductor active layer prepared in Example 1 of the present invention;

[0069] Figure 7(a) shows the XPS spectrum of the S2p peak of the PEDOT:PSS / PAm nanofiber membrane prepared in Example 1 of the present invention, and (b) shows the XPS spectrum of the S2p peak of the PEDOT:PSS / PAm semiconductor active layer prepared in Example 1 of the present invention.

[0070] Figure 8 is a schematic diagram of the all-fiber structure vertical organic electrochemical transistor obtained in Example 1 of the present invention; in the figure, I and III are encapsulation layers, and II is the all-fiber structure vertical organic electrochemical transistor in Example 1 without PAN / PVP electrospun film encapsulation.

[0071] Figure 9 shows the transconductance curve of the all-fiber structured vertical organic electrochemical transistor prepared in Example 1 of this invention at an operating voltage of -0.6V; in the figure, V DS This represents the drain-source voltage (i.e., the voltage applied across the device).

[0072] Figure 10 is a schematic diagram of the response time of the all-fiber structured vertical organic electrochemical transistor prepared in Example 1 of the present invention; in the figure, τ ON τ represents the time constant of the device conduction process, that is, the characteristic time required for the current to rise to a steady value after the gate voltage is turned on. OFF It represents the time constant of the device turn-off process, the characteristic time it takes for the current to decay to the turn-off state after the gate voltage is turned off;

[0073] Figure 11 shows the transconductance curves of the all-fiber vertical organic electrochemical transistor prepared in Example 1 of the present invention when bent for different numbers of times at a bending radius of 0.5 cm.

[0074] Figure 12 is a comparison diagram of the signal acquired using a commercial ECG acquisition system and the ECG signal processed by the all-fiber structure vertical organic electrochemical transistor prepared in Example 1 of this invention. Detailed Implementation

[0075] The present invention will be further described below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0076] To ensure that the performance of the substances used in each embodiment and comparative example is fully disclosed, the manufacturers and brands of the substances are specified. Other products from manufacturers and brands that conform to the limitations of this invention are also feasible.

[0077] The test methods for the relevant performance indicators in the following embodiments and comparative examples are as follows:

[0078] Water vapor transmission rate: After using the ion-permeable electrode layers prepared in each example as samples, 1.0 g of deionized water was added to each 10 mL glass vial, and the opening was immediately sealed with different covering materials. The samples were then fixed with rubber bands to ensure airtightness. As a control, a commercial sealing film was used under the same conditions. Finally, the vials were placed in a controlled environment of 25°C and 30% relative humidity. The mass of the remaining water in each vial was measured every 12 hours, and the mass change Δm within the test time interval Δt was recorded to evaluate the evaporation loss of water above the sample. The formula for calculating the water vapor transmission rate (WVTR) is as follows:

[0079]

[0080] Wherein, WVTR is the water vapor transmission rate (unit: kg·m). -2 ·d -1 ), where Δm is the mass of water lost (kg) during the test time Δt, and A is the effective area (m²) of the electrode layer coverage region. 2 ), where Δt is the corresponding test time (day); in actual calculations, a linear interval of the mass-time curve can be selected for linear fitting to obtain a more stable and reliable WVTR value.

[0081] Porosity: The ion-permeable electrode layers prepared in each embodiment were used as samples, and the porosity (ε) of the samples was determined by the isopropanol permeation-weighing method. The specific process was as follows: a fiber membrane sample with a known surface area (A) and average thickness (d) was taken from the sample and tested, and it was completely immersed in isopropanol (ρ = 0.7855 g cm⁻¹). -3 The membrane is then subjected to ultrasonic treatment for 20 minutes to ensure that the porous structure is fully permeated. After ultrasonic treatment, it is suspended vertically for 30 seconds to remove surface liquid. Finally, the saturated membrane mass (ω1) and dry membrane mass (ω2) are measured using a high-precision analytical balance, and the porosity is calculated based on the measured data. The porosity (in %) calculation formula is as follows:

[0082]

[0083] Shear resistance of the electrode (R) s The ion-permeable electrode layers prepared in each embodiment were used as samples. The sheet resistance of the samples was measured using the four-probe method. The specific process was as follows: First, the sample was cut into a size of 2.5cm × 2.5cm and flatly attached to a glass substrate to ensure that the surface of the sample was flat and the conductive layer was continuous. Then, the sample was placed on the four-probe test stage, and the probes were adjusted to lightly touch the membrane surface to ensure that each probe was in full contact with the membrane without damaging the fiber structure. Then, at 25°C, a constant current I was applied through the two outer probes, and the corresponding voltage drop V was measured by the two inner probes. The test instrument could then directly output the sheet resistance. In order to improve the reliability of the data, each sample was measured at least 5 times at different positions, and the average value was taken as the sheet resistance characterization result of the sample.

[0084] Maximum current and maximum transconductance between the source and drain: The all-fiber vertical organic electrochemical transistors (AMTs) without PAN / PVP electrospun film encapsulation prepared in each embodiment were used as samples. Transfer characteristics were tested using a Keithley-2450 semiconductor parameter analyzer. All electrochemical tests used a gel electrolyte (prepared from 3 wt% chitosan, 2 wt% glacial acetic acid, 3 wt% sodium trifluoromethanesulfonate, 3 wt% glycerol, and the remainder deionized water), with Ag / AgCl (manufacturer: Wuhan EEG Sensor Technology Co., Ltd., model FM010) as the gate electrode. The source-drain voltage V was fixed during the transfer characteristic test. DS = -0.6V, linear scan gate voltage V G Record the corresponding source-drain current I from -0.6V to 1V. DS Thus, the transfer characteristic curve I of the device is obtained. DS –V G The maximum current between the source and drain is obtained from this curve. Then, based on this, the transconductance under different gate voltages is calculated by numerical differentiation. The calculation formula is as follows:

[0085]

[0086] That is, using the ratio of the change in current to the change in gate voltage between adjacent test points (ΔI) DS / ΔV G Find g m With V G The change curve; in addition, to reduce the impact of test noise on the results, the original I can be modified. DS –V G The data is then appropriately smoothed before numerical differentiation is performed; finally, g is... m (V G The maximum value in the curve is the maximum transconductance g of the device at an operating voltage of -0.6V. m,peak .

[0087] Response time: Using the all-fiber vertical organic electrochemical transistors (AOTs) without PAN / PVP electrospun film encapsulation prepared in each embodiment as samples, transient response curves of the source-drain current were obtained by excitation with a square wave (step) gate voltage pulse. The change of current over time was fitted with a single exponential function to obtain the response time constant of the device. The source-drain voltage V was fixed during testing. DS = -0.6V, the gate electrode is Ag / AgCl (manufacturer: Wuhan EEG Sensor Technology Co., Ltd., model: FM010), and the electrolyte is the aforementioned gel electrolyte; a square wave pulse is applied to the gate voltage terminal to make the gate voltage at V G,low With V G,high Switching between (pulse amplitude ΔV) G =VG,high -V G,low With a duty cycle of D and a period of T, the source and drain current I are recorded synchronously. DS The time response of (t) is then used to perform a single exponential fit on the current change segment after each step: rising edge (current changes from I0 to I ∞ The calculation is performed using formula (4), and the falling edge (current is determined by I) ∞ Returning to I0), calculate using formula (5);

[0088] I DS (t)=I ∞ -(I ∞ -I0)exp(-t / τ) (4);

[0089] I DS (t)=I0+(I ∞ -I0)exp(-t / τ) (5);

[0090] Where I0 is the steady-state current before the step jump, I ∞ Let τ be the steady-state current after the step jump, and let τ be the time constant obtained by fitting. The τ obtained by fitting is defined as the response time of the device. When τ is obtained at both the rising edge and the falling edge, the larger value of the two is taken as the final response time of the device.

[0091] Performance maintained after 10,000 cycles at a bending radius of 0.5 cm: Using the all-fiber vertical organic electrochemical transistors (OLEDs) without PAN / PVP electrospun film encapsulation prepared in each embodiment as samples, the samples were fixed on a bending test device with the device channel region located at the bending center and the bending radius adjusted to 0.5 cm. The unbent, straight devices were then used as initial samples, and their transfer characteristic curves were measured using the aforementioned maximum transconductance testing method. DS –V G and transconductance curve g m –V G The maximum current and maximum transconductance between the source and drain are denoted as I, respectively. DS,0 and g m,0 The maximum transconductance of the initial sample was obtained. Then, under the fixed condition of a bending radius of 0.5 cm, the initial sample was subjected to 10,000 cyclic bending tests at a bending frequency of 1 Hz (i.e., bending-springback is one cycle). After the sample was restored to a straight state, its transfer characteristic curve I was measured under the same test conditions. DS –V G and transconductance curve g m –V G Record the maximum current I between the source and drain respectively. DS,n and maximum transconductance g m,nFinally, based on the measured data, the performance maintained after 10,000 cycles at a bending radius of 0.5 cm was calculated using the following formula:

[0092] The current retention rate and transconductance retention rate after bending cycles are calculated using the following formula:

[0093]

[0094]

[0095] Among them, ID S,0 and g m,0 The initial value when not bent, ID S,n and d m,n This represents the value after n cycles of bending at a bending radius of 0.5 cm. The retention rate obtained when n = 10000 is the data corresponding to "performance maintained after 10000 cycles at a bending radius of 0.5 cm".

[0096] Example 1

[0097] A method for fabricating a vertical organic electrochemical transistor with an all-fiber structure, comprising the following steps:

[0098] (1) Preparation of raw materials and equipment;

[0099] PAN (Polyacrylonitrile): Manufacturer is Shanghai Mairui Biochemical Technology Co., Ltd., brand name is 25014-41-9, M w =150000;

[0100] Solvent: DMF;

[0101] PVP (Polyvinylpyrrolidone): Manufacturer: Shanghai Titan Co., Ltd., Brand No.: 9003-39-8, M w =24000;

[0102] Syringe: Plastic syringe, needle specification 23G, needle length 13mm;

[0103] PVA solution: concentration 5wt%, solute is PVA (polyvinyl alcohol, manufacturer: Shanghai Titan Co., Ltd., brand name 9002-89-5, M w =205000), the solvent is deionized water;

[0104] Chromium layer: The material is chromium (Cr);

[0105] Gold layer: The material is gold (Au);

[0106] Acrylamide (Am);

[0107] Deionized water;

[0108] Ammonium persulfate solution: concentration 0.2 mol / L -1 The solvent is deionized water;

[0109] Tetramethylethylenediamine (TEMED);

[0110] PEDOT:PSS aqueous solution: concentration is 1.8wt%, solute is PEDOT:PSS (manufacturer is Heraeus, model is PH1000);

[0111] DMSO (dimethyl sulfoxide) aqueous solution;

[0112] (2) Preparation of ion-permeable electrode layer;

[0113] (2.1) Preparation of electrospinning solution;

[0114] PAN was dissolved in DMF solvent, and then PVP was added. The mixture was magnetically stirred at 23°C for 6 hours to obtain a spinning solution. The concentration of PAN in the spinning solution was 10 wt%, and the concentration of PVP was 2 wt%.

[0115] (2.2) Electrospinning to form a film;

[0116] The spinning solution was loaded into a syringe, and under conditions of 25°C and 30% relative humidity, the voltage was set to 12kV and the injection rate to 0.6mL / h. -1 The volume of the spinning solution in the syringe was 1 mL, the distance between the needle and the collecting roller was 10 cm, and electrospinning was performed for 3 h to obtain a PAN / PVP nanofiber membrane (its SEM is shown in Figure 3).

[0117] The average diameter of the PAN / PVP nanofibers in the obtained PAN / PVP nanofiber membrane is 300 nm.

[0118] The dynamic contact angle of the PAN / PVP nanofiber membrane was tested using a contact angle analyzer (Theta Flex, Sweden). The test procedure was as follows: the sample (1cm×1cm) was first fixed on a glass substrate, and 0.5μL of 0.1M NaCl solution was dropped onto its surface. Then, the spreading behavior of the electrolyte on the sample surface was recorded in real time using a high-speed imaging system. The final results are shown in Figure 2. As can be seen from Figure 2, after the introduction of PVP, the wetting and absorption process of water droplets by the PAN / PVP nanofiber membrane was significantly accelerated. The water droplets were basically flattened and absorbed within 1 second. This indicates that the PAN / PVP nanofiber membrane with PVP has better wettability for water / electrolyte, which is conducive to rapid electrolyte wetting and ion transport, thereby improving the interface stability and response speed of the device.

[0119] (2.3) Coating and hot pressing treatment;

[0120] A 5 μm thick PVA layer was formed by electrospinning a PVA solution onto one surface of a PAN / PVP nanofiber membrane, followed by curing at 120°C and 5 kg / cm². -2 Under the condition of hot pressing for 5 minutes, the PVA layer was partially melted to form stable interlayer bonding points, resulting in a porous PAN / PVP nanofiber substrate with a porosity of 80.1% (the SEM images of the PAN / PVP nanofiber membrane before and after hot pressing are shown in Figure 4).

[0121] (2.4) Metal vapor deposition and patterning;

[0122] Using a metal masking method, chromium and gold layers were sequentially deposited on a porous PAN / PVP nanofiber substrate in a vacuum evaporation system to form a metal conductive network. Subsequently, the PVA layer was dissolved by spraying deionized water to obtain an ion-permeable electrode layer. The thickness of the chromium layer was 12 nm and the thickness of the gold layer was 120 nm.

[0123] The water vapor permeability of the obtained ion-permeable electrode layer was 2.16 kg m. -2 d -1 The electrode has a sheet resistance of 1.5 Ω / sq and a porosity of 72.07%. It is compared with the porosity of the porous PAN / PVP nanofiber substrate measured using the same test method. The results are shown in Figure 5. As can be seen from the figure, after Cr / Au is vapor-deposited on the surface of the porous PAN / PVP nanofiber substrate to form a conductive network, the metal layer will cover or partially block some pores, resulting in a decrease in the overall porosity. However, the porosity of the ion-permeable electrode layer in this embodiment is still maintained at a relatively high level of 72%. This indicates that the metal vapor deposition / patterning process did not significantly damage the porous framework structure of the nanofiber. While obtaining a continuous conductive path (sheet resistance of 1.5 Ω / sq), the electrode still retains good pore connectivity and gas permeability / ion permeability, thereby meeting the requirements of rapid electrolyte permeation and ion transport for three-dimensional volume gating of the device.

[0124] (3) Prepare the semiconductor active layer;

[0125] (3.1) Preparation of PEDOT:PSS / PAm composite electrospinning solution;

[0126] (3.11) Acrylamide (Am) was dissolved in deionized water, and ammonium persulfate solution and tetramethylethylenediamine (TEMED) were added sequentially. The mixture was magnetically stirred at 70°C and 350 rpm for 2 h to obtain a PAm prepolymer solution. The mass ratio of acrylamide, deionized water, ammonium persulfate and tetramethylethylenediamine was 6800:90000:18:27.

[0127] (3.12) PEDOT:PSS aqueous solution was pre-frozen at -20℃ for 24h, and then freeze-dried in a freeze dryer for 48h to obtain freeze-dried PEDOT:PSS;

[0128] (3.13) At 25°C, the freeze-dried PEDOT:PSS was dissolved in deionized water and magnetically stirred for 12 h to fully redisperse it, resulting in a homogeneous dispersion with a concentration of 1.8 wt%. PAM prepolymer solution was added to the dispersion and magnetically stirred for another 12 h to form a PEDOT:PSS / PAm composite electrospinning solution.

[0129] (3.2) Electrospinning to form a film;

[0130] The PEDOT:PSS / PAm composite electrospinning solution was loaded into a 10 mL syringe. Under conditions of 40℃ and 20% relative humidity, the voltage was set to 10 kV and the injection rate to 0.4 mL / h. -1 The electrospinning solution in the syringe was 10 mL. A flat collector covered with aluminum foil was used, with the distance between the needle and the collector being 6 cm. Electrospinning was performed for 5 min to obtain a PEDOT:PSS / PAm nanofiber membrane. In the PEDOT:PSS / PAm nanofiber membrane, the mass ratio of PEDOT:PSS to PAM was 100:5.

[0131] (3.3) Post-treatment of electrospun film;

[0132] The PEDOT:PSS / PAm nanofiber membrane obtained by electrospinning was first annealed in an oven at 120℃ for 24h, and then soaked in a 4wt% DMSO aqueous solution to obtain the PEDOT:PSS / PAm semiconductor active layer (its SEM is shown in Figure 6).

[0133] XPS spectra of the PEDOT:PSS / PAm nanofiber membrane and the PEDOT:PSS / PAm semiconductor active layer were analyzed, and the results are shown in Figure 7. As can be seen from the figure, the nitrogen signal intensity increased after treatment, indicating that PAM was enriched on the surface. In addition, S2p energy dispersive spectroscopy analysis showed that the peak area ratio of PEDOT to PSS changed from 1:2.11 to 1:2.51, indicating that DMSO treatment induced the redistribution of polymer components, forming a denser surface structure, thereby limiting excessive ion penetration and enhancing the long-term electrochemical stability of the device.

[0134] (4) Fabrication of a fully fiber-structured vertical organic electrochemical transistor;

[0135] First, an ion-permeable electrode layer is prepared and placed flat on a clean glass substrate (with the metal conductive layer facing up). Then, a small amount of deionized water is sprayed evenly on the surface of the ion-permeable electrode layer to fully wet the surface. Next, the prepared PEDOT:PSS / PAm nanofiber membrane is placed on the ion-permeable electrode layer as the semiconductor active layer. Then, another ion-permeable electrode layer is stacked as the upper electrode layer (with its metal conductive layer facing down) to obtain a composite layer. Finally, the assembled composite layer is heated and dried at 80°C for 5 minutes to form a vertical stacked structure. Then, it is encapsulated with a PAN / PVP electrospun film (as shown in Figure 8) to obtain a vertical organic electrochemical transistor with an all-fiber structure (its structure is shown in Figure 1).

[0136] The final fabricated all-fiber vertical organic electrochemical transistor (OECT) consists of a lower electrode layer, a semiconductor active layer, and an upper electrode layer from bottom to top.

[0137] Both the lower and upper electrode layers are ion-permeable electrode layers;

[0138] The ion-permeable electrode layer consists of a porous PAN / PVP nanofiber substrate and a metal conductive layer deposited on it; the porous PAN / PVP nanofiber substrate is a multilayer nanofiber membrane prepared by electrospinning; the metal conductive layer consists of a Cr metal layer and an Au metal layer from bottom to top.

[0139] The maximum transconductance of the all-fiber vertical organic electrochemical transistor at a working voltage of -0.6V is 57.5mS (the measured transconductance curve is shown in Figure 9), the maximum current between the source and drain is -38.24mA, and the response time is 11.7ms (the measured response time is shown in Figure 10).

[0140] After 10,000 cycles at a bending radius of 0.5 cm, the maximum current retention rate between the source and drain of the all-fiber vertical organic electrochemical transistor is 87% of the initial performance, and the maximum transconductance retention rate is 85% of the initial performance (the test results are shown in Figure 11).

[0141] The above-mentioned all-fiber vertical organic electrochemical transistor and commercial Ag / AgCl ECG electrodes (manufacturer: Hangzhou Xunda Radio Equipment Co., Ltd., model X-1) were used to acquire ECG signals. The results are shown in Figure 12. As can be seen from the figure, the signal-to-noise ratio (SNR) obtained using the commercial Ag / AgCl ECG electrodes (SNR is expressed in decibels; the higher the value, the stronger the effective ECG signal relative to the background noise, the clearer the waveform, and the better the noise reduction effect) is only 16.2 dB. However, when the above-mentioned all-fiber vertical organic electrochemical transistor is used as a low-frequency physiological signal amplification module to acquire ECG signals, the SNR obtained is 23.1 dB, and it can work stably under power supply voltage below 1V. This is because the all-fiber vertical organic electrochemical transistor of the present invention can filter out some high-frequency noise, thereby improving the quality of ECG signals.

[0142] Comparative Example 1

[0143] A method for fabricating an all-fiber organic electrochemical transistor is basically the same as in Example 1, except that:

[0144] In step (2.4), source and drain electrode patterns are formed by patterning with a metal mask, with a channel length of 0.05 mm and a width of 1 mm between the source and drain electrodes.

[0145] In step (4), the semiconductor active layer is placed directly on the ion-permeable electrode layer and heated at 80°C for 5 minutes to obtain an all-fiber organic electrochemical transistor; wherein, the channel length is equal to the distance between the source electrode and the drain electrode, and the channel width is 0.8 mm.

[0146] The final fabricated all-fiber organic electrochemical transistor has a planar configuration, with the source and drain electrodes arranged horizontally on the ion-permeable electrode layer, and a semiconductor active layer filling the space between the source and drain electrodes.

[0147] The all-fiber organic electrochemical transistor has a planar configuration. When the device is working, the Ag / AgCl gate is dropped onto the channel region through the electrolyte solution, modulating the channel in the form of a planar gate. Therefore, the ions in the electrolyte diffuse mainly along the planar direction between the electrode and the channel.

[0148] The all-fiber organic electrochemical transistor has a maximum transconductance of 19.4 mS at a working voltage of -0.6 V, a maximum current between the source and drain of -7.8 mA, and a response time of 85.7 ms.

[0149] After 10,000 cycles at a bending radius of 0.5 cm, the maximum current retention rate between the source and drain of the all-fiber organic electrochemical transistor is 74.4%, and the maximum transconductance retention rate is 72.8%.

[0150] Comparing Comparative Example 1 and Example 1, it can be seen that the maximum transconductance of the all-fiber organic electrochemical transistor prepared in this comparative example is significantly reduced, the response time is greatly extended, and the performance retention rate after bending cycles is decreased. This is because in Comparative Example 1, only the ion-permeable nanofiber electrode is used as a monolayer substrate, and a planar configuration with the source / drain electrode and the PEDOT:PSS / PAm nanofiber channel coplanar is constructed on it. On the one hand, the channel length is equal to the source / drain electrode spacing, and ions diffuse mainly along the planar direction between the electrode and the channel. The ion implantation path is longer, and the ion migration time is increased, resulting in a longer transconductance and a longer response time. This results in a slower device response speed. On the other hand, the channel is only located above one side of the electrode, and it is impossible to form a three-dimensionally covered vertical short active layer structure between the upper and lower porous nanofiber electrodes as in Example 1. The equivalent volume capacitance and effective carrier modulation volume are reduced, thereby reducing the transconductance of the device. In addition, since the upper and lower symmetrical stacked layers described in Example 1 are not formed in Comparative Example 1, the interface bonding and mechanical constraint between the channel layer and the electrode layer are weak. During repeated bending, the fiber contact is prone to relaxation and microcrack accumulation, resulting in a lower performance retention rate after 10,000 bends than in Example 1.

[0151] Comparative Example 2

[0152] An organic electrochemical transistor fabrication method is basically the same as in Example 1, except that steps (2.1) to (2.3) are omitted, and the porous PAN / PVP nanofiber substrate in step (2.4) is replaced with a polyimide (PI) film with a thickness of 50 μm, finally obtaining a dense Cr / Au metal electrode layer; wherein, the channel size W = 0.5 mm and d = 0.5 mm;

[0153] The process of replacing the ion-permeable electrode layer in step (4) with the dense Cr / Au metal electrode layer prepared in this comparative example and laying the PEDOT:PSS / PAm nanofiber membrane is as follows: First, a small amount of deionized water is evenly sprayed on the surface of the source and drain electrode areas of the dense Cr / Au metal electrode layer to fully wet the surface. Then, the self-supporting PEDOT:PSS / PAm nanofiber membrane is cut to an appropriate size and laid flat on the dense Cr / Au metal electrode layer. Then, another PI-based dense Cr / Au metal electrode layer with the same structure is stacked as the upper electrode layer. After alignment, it is gently pressed to clamp the semiconductor electrospun channel between the two dense Cr / Au metal electrode layers to form a vertical stacked structure. Finally, the assembled composite layer is heated and dried at 80°C for 5 minutes to enhance the interlayer bonding, thus obtaining the organic electrochemical transistor of this comparative example.

[0154] The final organic electrochemical transistor is basically the same as in Example 1, except that: the upper electrode layer and the lower electrode layer are both dense Cr / Au metal electrode layers prepared in this comparative example, and the PEDOT:PSS / PAm nanofiber film is laid flat on the source and drain electrode regions of the lower electrode.

[0155] The organic electrochemical transistor has a maximum transconductance of only 66mS at a working voltage of -0.6V, a maximum current between the source and drain of 48.2mA, and a response time of 170ms.

[0156] After 10,000 cycles at a bending radius of 0.5 cm, the organic electrochemical transistor retains 50.2% of the maximum current between the source and drain and 60.5% of the maximum transconductance.

[0157] Comparing Comparative Example 2 with Example 1, it can be seen that the organic electrochemical transistor prepared in this comparative example has a significantly reduced maximum transconductance, a greatly prolonged response time, and a decreased performance retention rate after bending cycles. This is because this comparative example uses a dense Cr / Au metal electrode layer as the electrode layer. Although the semiconductor active layer is still a self-supporting PEDOT:PSS / PAm electrospun nanofiber membrane sandwiched between the upper and lower electrodes in a vertical stacking manner, the upper and lower electrodes themselves have almost no ion permeation channels. Moreover, ions in the electrolyte can only slowly enter the electrospun nanofiber network from the device side edge or local defects. The ion implantation path is significantly longer, and the bulk doping / dedoping process is restricted, resulting in a reduction in equivalent volume capacitance and modulated carrier volume. This leads to a decrease in device transconductance and cutoff frequency, and a longer response time. At the same time, the bending stiffness of the dense PI / Cr / Au electrode is greater than that of the porous PAN / PVP nanofiber electrode structure. Under repeated bending, especially under small bending radius conditions, the interface stress concentration is more severe, which easily leads to microcracks and contact degradation. Therefore, the performance retention rate after bending cycles is also lower than that of Example 1.

[0158] Comparative Example 3

[0159] An organic electrochemical transistor fabrication method is basically the same as in Example 1, except that steps (2.1) to (2.3) are omitted, and the porous PAN / PVP nanofiber substrate in step (2.4) is replaced with a polyimide (PI) film with a thickness of 50 μm, finally obtaining a dense Cr / Au metal electrode layer; wherein the channel length between the source electrode and the drain electrode is 0.05 mm and the width is 1 mm;

[0160] Without step (3), the semiconductor active layer of this comparative example is changed from the electrospun PEDOT:PSS / PAm nanofiber membrane to the semiconductor thin film obtained by spin coating PEDOT:PSS solution; wherein, the spin coating speed is 1500 rpm and the spin coating time is 30 s. The preparation process of PEDOT:PSS solution is as follows: 95.2 mg of 3-glycidyloxypropyltrimethoxysilane, 571.2 mg of ethylene glycol and 9.52 g of PEDOT:PSS are placed in a 20 mL glass bottle and stirred vigorously at 25 °C for 12 h to form a uniform PEDOT:PSS aqueous dispersion.

[0161] Replace the ion-permeable electrode layer used in step (4) with the dense Cr / Au metal electrode layer of this comparative example, and replace the PEDOT:PSS / PAm nanofiber membrane with the semiconductor thin film prepared in this comparative example.

[0162] The final organic electrochemical transistor consists of a lower electrode layer, a semiconductor active layer, and an upper electrode layer from bottom to top.

[0163] Both the upper and lower electrode layers are dense Cr / Au metal electrode layers prepared in this comparative example;

[0164] The ion-permeable electrode layer is a semiconductor thin film prepared in this comparative example;

[0165] The final organic electrochemical transistor has a maximum transconductance of 25.8 mS at a working voltage of -0.6 V, a maximum current between the source and drain of -12.84 mA, and a response time of 74.2 ms.

[0166] After 10,000 cycles at a bending radius of 0.5 mm, the organic electrochemical transistor retains 70.2% of the maximum current between the source and drain and 68.8% of the maximum transconductance.

[0167] Comparing Comparative Example 3 with Example 1, it can be seen that the organic electrochemical transistor prepared in this comparative example has a reduced maximum transconductance and a prolonged response time. This is because this comparative example simultaneously employs a dense metal electrode and a planar dense channel structure. Ions in the electrolyte can only participate in doping within a limited depth on the channel surface, and mainly diffuse along the planar direction between the gate, electrolyte, and planar channel, resulting in the longest ion implantation path and the smallest bulk modulation volume. At the same time, the dense PI / Cr / Au electrode has high stiffness and poor flexibility, and cannot disperse bending stress through a porous fiber network and symmetrical stacked structure as in Example 1, leading to a significant deterioration in the transconductance, bandwidth, and response speed of the device.

[0168] Comparative Example 4

[0169] A method for preparing a vertical organic electrochemical transistor with an all-fiber structure is basically the same as in Example 1, except that step (2.3) is omitted, and in step (2.4), the PAN / PVP nanofiber membrane obtained in step (2.2) is directly replaced with a porous PAN / PVP nanofiber substrate.

[0170] The water vapor permeability of the ion-permeable electrode layer obtained in step (2.4) is 3.2 kg m. -2 d -1 The sheet resistance of the electrode is 8.9 Ω / sq, and the membrane porosity is 78%.

[0171] In step (4), the ion-permeable electrode layer is replaced with the ion-permeable electrode layer prepared in this comparative example.

[0172] The final fabricated all-fiber vertical organic electrochemical transistor is basically the same as in Example 1, except that both the lower electrode layer and the upper electrode layer are ion-permeable electrode layers fabricated in this comparative example.

[0173] The all-fiber vertical organic electrochemical transistor has a maximum transconductance of 32.3 mS at a working voltage of -0.6 V, a maximum current between the source and drain of -18.56 mA, and a response time of 19.4 ms.

[0174] The all-fiber vertical organic electrochemical transistor retains 65.3% of the maximum current between the source and drain and 60.8% of the maximum transconductance after 10,000 cycles at a bending radius of 0.5 cm.

[0175] Comparing Comparative Example 4 with Example 1, it can be seen that the maximum transconductance of the all-fiber vertical organic electrochemical transistor prepared in this comparative example is reduced, the response time is prolonged, and the performance retention rate after bending cycles is decreased. This is because the PVA coating and hot pressing treatment in step (2.3) were omitted in Comparative Example 4. The PAN / PVP nanofiber membrane maintains the original electrospun state with extremely high porosity and loose network structure. On the one hand, the excessive porosity and uncontrolled pore size distribution cause the conductive network formed after metal evaporation to exhibit an "island" or local bridging morphology on the fiber surface. The in-plane current path becomes longer and the effective conductive cross-sectional area decreases, resulting in an increase in electrode sheet resistance and an increase in series resistance in the device. This weakens the effective potential modulation capability of the channel, thereby reducing the transconductance and cutoff frequency. On the other hand, the loose fiber network has poor support rigidity and large surface roughness. The actual contact area between the semiconductor electrospun active layer and the electrode layer is reduced. The fiber contact is prone to relative slippage and microcrack accumulation during bending. The interface resistance increases with cycles, resulting in a prolonged response time and a decrease in performance retention rate after 10,000 bending cycles.

[0176] Comparative Example 5

[0177] A method for preparing a vertical organic electrochemical transistor with an all-fiber structure is basically the same as in Example 1, except that: step (3.3) does not involve annealing, but instead involves low-temperature drying of the PEDOT:PSS / PAm nanofiber membrane obtained by electrospinning. The specific process is as follows: first, the PEDOT:PSS / PAm nanofiber membrane is laid flat on a clean glass slide and placed in an 80°C forced-air drying oven for 2 hours until there is no visible solvent residue on the membrane surface and the mass is basically constant, thus obtaining a dried PEDOT:PSS / PAm nanofiber membrane, which is then soaked in DMSO aqueous solution.

[0178] The PEDOT:PSS / PAm nanofiber membrane used in step (4) is replaced with the dried PEDOT:PSS / PAm nanofiber membrane prepared in this comparative example.

[0179] The final fabricated all-fiber vertical organic electrochemical transistor has a maximum transconductance of 45.34 mS at a working voltage of -0.6 V, a maximum current between the source and drain of -24.32 mA, and a response time of 29.9 ms.

[0180] After 10,000 cycles at a bending radius of 0.5 cm, the maximum current retention between the source and drain of the all-fiber vertical organic electrochemical transistor is 69.4%, and the maximum transconductance retention is 63.8%.

[0181] Comparing Comparative Example 5 with Example 1, it can be seen that the maximum transconductance of the all-fiber vertical organic electrochemical transistor prepared in this comparative example is reduced, the response time is prolonged, and the performance retention rate after bending cycles is decreased. This is because the comparative example uses drying treatment instead of annealing treatment when preparing the semiconductor active layer. There is more residual moisture and solvent inside the PEDOT:PSS / PAm nanofibers, the PAm cross-linking network is not fully formed, and the rearrangement, orientation, and phase separation of PEDOT:PSS segments are insufficient, resulting in poor continuity of the conductive network and a slight decrease in volume capacitance. This leads to a decrease in the transconductance of the device, a slower ion implantation / dedoping process, and a prolonged response time. At the same time, due to insufficient thermal annealing, the interfacial bonding force between semiconductor nanofibers and between them and the upper and lower ion-permeable electrode layers is weak. During repeated bending with a bending radius of 0.5 cm, microcracks and interfacial contact degradation are more likely to occur, resulting in a decrease in the performance retention rate after 10,000 bending cycles.

[0182] Example 2

[0183] A method for fabricating a vertical organic electrochemical transistor with an all-fiber structure, comprising the following steps:

[0184] (1) Preparation of raw materials and equipment;

[0185] PAN (Polyacrylonitrile): Manufacturer is Shanghai Mairui Biochemical Technology Co., Ltd., brand name is 25014-41-9, M w =150000;

[0186] Solvent: DMF;

[0187] PVP (Polyvinylpyrrolidone): Manufacturer: Shanghai Titan Co., Ltd., Brand No.: 9003-39-8, M w =24000;

[0188] Syringe: Plastic syringe, needle specification 23G, needle length 20mm;

[0189] PVA solution: concentration 5wt%, solute is PVA (polyvinyl alcohol, manufacturer: Shanghai Titan Co., Ltd., brand name 9002-89-5, M w =205000), the solvent is deionized water;

[0190] Chromium layer: The material is chromium (Cr);

[0191] Gold layer: The material is gold (Au);

[0192] Acrylamide (Am);

[0193] Deionized water;

[0194] Ammonium persulfate solution: concentration 0.2 mol / L -1 The solvent is deionized water;

[0195] Tetramethylethylenediamine (TEMED);

[0196] PEDOT:PSS aqueous solution: concentration is 1.8wt%, solute is PEDOT:PSS (manufacturer is Heraeus, model is PH1000);

[0197] DMSO (dimethyl sulfoxide) aqueous solution;

[0198] (2) Preparation of ion-permeable electrode layer;

[0199] (2.1) Preparation of electrospinning solution;

[0200] PAN was dissolved in DMF solvent, and then PVP was added. The mixture was magnetically stirred at 23°C for 8 hours to obtain a spinning solution. The concentration of PAN in the spinning solution was 12 wt%, and the concentration of PVP was 3 wt%.

[0201] (2.2) Electrospinning to form a film;

[0202] The spinning solution was loaded into a syringe, and under conditions of 20℃ and 35% relative humidity, the voltage was set to 12kV and the injection rate to 1mL / h. -1 The volume of the spinning solution in the syringe was 1.2 mL, the distance between the needle and the collecting roller was 15 cm, and electrospinning was performed for 3 h to obtain a PAN / PVP nanofiber membrane.

[0203] The average diameter of the PAN / PVP nanofibers in the obtained PAN / PVP nanofiber membrane is 200 nm.

[0204] (2.3) Coating and hot pressing treatment;

[0205] A 1 μm thick PVA layer was formed by electrospinning a PVA solution onto one surface of a PAN / PVP nanofiber membrane, followed by curing at 120 °C and 4 kg / cm². -2 Under the condition of hot pressing for 5 minutes, the PVA layer is partially melted to form stable interlayer bonding points, thus obtaining a porous PAN / PVP nanofiber substrate;

[0206] (2.4) Metal vapor deposition and patterning;

[0207] Using a metal masking method, chromium and gold layers were sequentially deposited on a porous PAN / PVP nanofiber substrate in a vacuum evaporation system to form a metal conductive network. Subsequently, the PVA layer was dissolved by spraying deionized water to obtain an ion-permeable electrode layer. The thickness of the chromium layer was 3 nm and the thickness of the gold layer was 100 nm.

[0208] The water vapor permeability of the obtained ion-permeable electrode layer was 1.05 kg m. -2 d -1 The sheet resistance of the electrode is 3.8 Ω / sq, and the porosity is 64%.

[0209] (3) Prepare the semiconductor active layer;

[0210] (3.1) Preparation of PEDOT:PSS / PAm composite electrospinning solution;

[0211] (3.11) Acrylamide (Am) was dissolved in deionized water, and ammonium persulfate solution and tetramethylethylenediamine (TEMED) were added sequentially. The mixture was magnetically stirred at 70°C and 350 rpm for 2 h to obtain a PAm prepolymer solution. The mass ratio of acrylamide, deionized water, ammonium persulfate and tetramethylethylenediamine was 6800:90000:18:27.

[0212] (3.12) PEDOT:PSS aqueous solution was pre-frozen at -20℃ for 24h, and then freeze-dried in a freeze dryer for 72h to obtain freeze-dried PEDOT:PSS;

[0213] (3.13) At 25°C, the freeze-dried PEDOT:PSS was dissolved in deionized water and magnetically stirred for 12 h to fully redisperse it, resulting in a homogeneous dispersion with a concentration of 1.8 wt%. PAM prepolymer solution was added to the dispersion and magnetically stirred for another 12 h to form a PEDOT:PSS / PAm composite electrospinning solution.

[0214] (3.2) Electrospinning to form a film;

[0215] The PEDOT:PSS / PAm composite electrospinning solution was loaded into a 10 mL syringe. Under conditions of 40℃ and 20% relative humidity, the voltage was set to 10 kV and the injection rate to 0.6 mL / h. -1 The electrospinning solution in the syringe was 10 mL. A flat collector covered with aluminum foil was used, with the distance between the needle and the collector being 8 cm. Electrospinning was performed for 5 min to obtain a PEDOT:PSS / PAm nanofiber membrane. In the PEDOT:PSS / PAm nanofiber membrane, the mass ratio of PEDOT:PSS to PAM was 100:5.

[0216] (3.3) Post-treatment of electrospun film;

[0217] The PEDOT:PSS / PAm nanofiber membrane obtained by electrospinning was first annealed in an oven at 120℃ for 24 hours, and then soaked in a 4wt% DMSO aqueous solution to obtain the PEDOT:PSS / PAm semiconductor active layer.

[0218] (4) Fabrication of a fully fiber-structured vertical organic electrochemical transistor;

[0219] First, an ion-permeable electrode layer is prepared and placed flat on a clean glass substrate (with the metal conductive layer facing up). Then, a small amount of deionized water is sprayed evenly on the surface of the ion-permeable electrode layer to fully wet the surface. Next, the prepared PEDOT:PSS / PAm nanofiber membrane is placed on the ion-permeable electrode layer as the semiconductor active layer. Then, another ion-permeable electrode layer is stacked as the upper electrode layer (with its metal conductive layer facing down) to obtain a composite layer. Finally, the assembled composite layer is heated and dried at 80°C for 5 minutes to form a vertical stacked structure. Then, it is encapsulated with a PAN / PVP electrospun film to obtain a vertical organic electrochemical transistor with an all-fiber structure.

[0220] The final fabricated all-fiber vertical organic electrochemical transistor (OECT) consists of a lower electrode layer, a semiconductor active layer, and an upper electrode layer from bottom to top.

[0221] Both the lower and upper electrode layers are ion-permeable electrode layers;

[0222] The ion-permeable electrode layer consists of a porous PAN / PVP nanofiber substrate and a metal conductive layer deposited on it; the porous PAN / PVP nanofiber substrate is a multilayer nanofiber membrane prepared by electrospinning; the metal conductive layer consists of a Cr metal layer and an Au metal layer from bottom to top.

[0223] The all-fiber vertical organic electrochemical transistor has a maximum transconductance of 45.5 mS at a working voltage of -0.6 V, a maximum current between the source and drain of -34.46 mA, and a response time of 22.4 ms.

[0224] The all-fiber vertical organic electrochemical transistor retains 82% of the maximum current between the source and drain and 78% of the maximum transconductance after 10,000 cycles at a bending radius of 0.5 cm.

[0225] Example 3

[0226] A method for fabricating a vertical organic electrochemical transistor with an all-fiber structure, comprising the following steps:

[0227] (1) Preparation of raw materials and equipment;

[0228] PAN (Polyacrylonitrile): Manufacturer is Shanghai Mairui Biochemical Technology Co., Ltd., brand name is 25014-41-9, M w =150000;

[0229] Solvent: DMF;

[0230] PVP (Polyvinylpyrrolidone): Manufacturer: Shanghai Titan Co., Ltd., Brand No.: 9003-39-8, M w =24000;

[0231] Syringe: Plastic syringe, needle specification 25G, needle length 20mm;

[0232] PVA solution: concentration 8wt%, solute is PVA (polyvinyl alcohol, manufacturer: Shanghai Titan Co., Ltd., brand name 9002-89-5, M) w =205000), the solvent is deionized water;

[0233] Chromium layer: The material is chromium (Cr);

[0234] Gold layer: The material is gold (Au);

[0235] Acrylamide (Am);

[0236] Deionized water;

[0237] Ammonium persulfate solution: concentration 0.2 mol / L -1 The solvent is deionized water;

[0238] Tetramethylethylenediamine (TEMED);

[0239] PEDOT:PSS aqueous solution: concentration is 1.8wt%, solute is PEDOT:PSS (manufacturer is Heraeus, model is PH1000);

[0240] DMSO (dimethyl sulfoxide) aqueous solution;

[0241] (2) Preparation of ion-permeable electrode layer;

[0242] (2.1) Preparation of electrospinning solution;

[0243] PAN was dissolved in DMF solvent, and then PVP was added. The mixture was magnetically stirred at 23°C for 8 hours to obtain a spinning solution. The concentration of PAN in the spinning solution was 12 wt%, and the concentration of PVP was 2 wt%.

[0244] (2.2) Electrospinning to form a film;

[0245] The spinning solution was loaded into a syringe, and under conditions of 25°C and 35% relative humidity, the voltage was set to 15kV and the injection rate to 1mL / h. -1 The volume of the spinning solution in the syringe was 1.2 mL, the distance between the needle and the collecting roller was 15 cm, and electrospinning was performed for 2 h to obtain a PAN / PVP nanofiber membrane.

[0246] The average diameter of the PAN / PVP nanofibers in the obtained PAN / PVP nanofiber membrane is 280 nm.

[0247] (2.3) Coating and hot pressing treatment;

[0248] A 3.4 μm thick PVA layer was formed by electrospinning a PVA solution onto one surface of a PAN / PVP nanofiber membrane, followed by curing at 125 °C and 5 kg / cm². -2 Under the condition of hot pressing for 8 minutes, the PVA layer is partially melted to form stable interlayer bonding points, thus obtaining a porous PAN / PVP nanofiber substrate;

[0249] (2.4) Metal vapor deposition and patterning;

[0250] Using a metal masking method, chromium and gold layers were sequentially deposited on a porous PAN / PVP nanofiber substrate in a vacuum evaporation system to form a metal conductive network. Subsequently, the PVA layer was dissolved by spraying deionized water to obtain an ion-permeable electrode layer. The thickness of the chromium layer was 10 nm and the thickness of the gold layer was 100 nm.

[0251] The water vapor permeability of the obtained ion-permeable electrode layer was 1.54 kg m.-2 d -1 The sheet resistance of the electrode is 7.8 Ω / sq, and the porosity is 75%.

[0252] (3) Prepare the semiconductor active layer;

[0253] (3.1) Preparation of PEDOT:PSS / PAm composite electrospinning solution;

[0254] (3.11) Acrylamide (Am) was dissolved in deionized water, and ammonium persulfate solution and tetramethylethylenediamine (TEMED) were added sequentially. The mixture was magnetically stirred at 75°C and 450 rpm for 3 h to obtain PAm prepolymer solution. The mass ratio of acrylamide, deionized water, ammonium persulfate and tetramethylethylenediamine was 6800:90000:18:27.

[0255] (3.12) PEDOT:PSS aqueous solution was pre-frozen at -30℃ for 30h, and then freeze-dried in a freeze dryer for 72h to obtain freeze-dried PEDOT:PSS;

[0256] (3.13) At 25°C, the freeze-dried PEDOT:PSS was dissolved in deionized water and magnetically stirred for 16 h to fully redisperse it, resulting in a homogeneous dispersion with a concentration of 1.8 wt%. PAM prepolymer solution was added to the dispersion and magnetically stirred for another 16 h to form a PEDOT:PSS / PAm composite electrospinning solution.

[0257] (3.2) Electrospinning to form a film;

[0258] The PEDOT:PSS / PAm composite electrospinning solution was loaded into a 10 mL syringe. Under conditions of 42℃ and 25% relative humidity, the voltage was set to 12 kV and the injection rate to 0.8 mL / h. -1 The electrospinning solution in the syringe was 15 mL. A flat collector covered with aluminum foil was used, with the distance between the needle and the collector being 8 cm. Electrospinning was performed for 5 min to obtain a PEDOT:PSS / PAm nanofiber membrane. In the PEDOT:PSS / PAm nanofiber membrane, the mass ratio of PEDOT:PSS to PAM was 100:5.

[0259] (3.3) Post-treatment of electrospun film;

[0260] The PEDOT:PSS / PAm nanofiber membrane obtained by electrospinning was first annealed in an oven at 130℃ for 30h, and then soaked in a 4wt% DMSO aqueous solution to obtain the PEDOT:PSS / PAm semiconductor active layer.

[0261] (4) Fabrication of a fully fiber-structured vertical organic electrochemical transistor;

[0262] First, an ion-permeable electrode layer is prepared and placed flat on a clean glass substrate (with the metal conductive layer facing up). Then, a small amount of deionized water is sprayed evenly on the surface of the ion-permeable electrode layer to fully wet the surface. Next, the prepared PEDOT:PSS / PAm nanofiber membrane is placed on the ion-permeable electrode layer as the semiconductor active layer. Then, another ion-permeable electrode layer is stacked as the upper electrode layer (with its metal conductive layer facing down) to obtain a composite layer. Finally, the assembled composite layer is heated and dried at 80°C for 8 minutes to form a vertical stacked structure. Then, it is encapsulated with a PAN / PVP electrospun film to obtain a vertical organic electrochemical transistor with an all-fiber structure.

[0263] The final fabricated all-fiber vertical organic electrochemical transistor (OECT) consists of a lower electrode layer, a semiconductor active layer, and an upper electrode layer from bottom to top.

[0264] Both the lower and upper electrode layers are ion-permeable electrode layers;

[0265] The ion-permeable electrode layer consists of a porous PAN / PVP nanofiber substrate and a metal conductive layer deposited on it; the porous PAN / PVP nanofiber substrate is a multilayer nanofiber membrane prepared by electrospinning; the metal conductive layer consists of a Cr metal layer and an Au metal layer from bottom to top.

[0266] The all-fiber vertical organic electrochemical transistor has a maximum transconductance of 38mS at a working voltage of -0.6V, a maximum current between the source and drain of -29mA, and a response time of 12ms.

[0267] The all-fiber vertical organic electrochemical transistor retains 80% of the maximum current between the source and drain and 76% of the maximum transconductance after 10,000 cycles at a bending radius of 0.5 cm.

[0268] Example 4

[0269] A method for fabricating a vertical organic electrochemical transistor with an all-fiber structure, comprising the following steps:

[0270] (1) Preparation of raw materials and equipment;

[0271] PAN (Polyacrylonitrile): Manufacturer is Shanghai Mairui Biochemical Technology Co., Ltd., brand name is 25014-41-9, M w =150000;

[0272] Solvent: DMAc;

[0273] PVP (Polyvinylpyrrolidone): Manufacturer: Shanghai Titan Co., Ltd., Brand No.: 9003-39-8, M w=24000;

[0274] Syringe: Plastic syringe, needle specification 27G, needle length 30mm;

[0275] PVA solution: concentration 10wt%, solute is PVA (polyvinyl alcohol, manufacturer: Shanghai Titan Co., Ltd., brand name: 9002-89-5, M) w =205000), the solvent is deionized water;

[0276] Chromium layer: The material is chromium (Cr);

[0277] Gold layer: The material is gold (Au);

[0278] Acrylamide (Am);

[0279] Deionized water;

[0280] Ammonium persulfate solution: concentration 0.2 mol / L -1 The solvent is deionized water;

[0281] Tetramethylethylenediamine (TEMED);

[0282] PEDOT:PSS aqueous solution: concentration is 1.8wt%, solute is PEDOT:PSS (manufacturer is Heraeus, model is PH1000);

[0283] DMSO (dimethyl sulfoxide) aqueous solution;

[0284] (2) Preparation of ion-permeable electrode layer;

[0285] (2.1) Preparation of electrospinning solution;

[0286] PAN was dissolved in DMF solvent, and then PVP was added. The mixture was magnetically stirred at 23°C for 10 h to obtain a spinning solution. The concentration of PAN in the spinning solution was 10 wt%, and the concentration of PVP was 2 wt%.

[0287] (2.2) Electrospinning to form a film;

[0288] The spinning solution was loaded into a syringe, and under conditions of 22℃ and 40% relative humidity, the voltage was set to 20kV and the injection rate to 0.8mL / h. -1 The volume of the spinning solution in the syringe was 1.5 mL, the distance between the needle and the collecting roller was 20 cm, and electrospinning was performed for 5 h to obtain a PAN / PVP nanofiber membrane.

[0289] The average diameter of the PAN / PVP nanofibers in the obtained PAN / PVP nanofiber membrane is 354 nm.

[0290] (2.3) Coating and hot pressing treatment;

[0291] A 2.8 μm thick PVA layer was formed by electrospinning a PVA solution onto one surface of a PAN / PVP nanofiber membrane, followed by curing at 130 °C and 8 kg / cm². -2 Under the condition of hot pressing for 10 minutes, the PVA layer is partially melted to form stable interlayer bonding points, thus obtaining a porous PAN / PVP nanofiber substrate.

[0292] (2.4) Metal vapor deposition and patterning;

[0293] Using a metal masking method, chromium and gold layers were sequentially deposited on a porous PAN / PVP nanofiber substrate in a vacuum evaporation system to form a metal conductive network. Subsequently, the PVA layer was dissolved by spraying deionized water to obtain an ion-permeable electrode layer. The thickness of the chromium layer was 12 nm and the thickness of the gold layer was 150 nm.

[0294] The water vapor permeability of the obtained ion-permeable electrode layer was 1.95 kg m. -2 d -1 The sheet resistance of the electrode is 6.5 Ω / sq, and the porosity is 70%.

[0295] (3) Prepare the semiconductor active layer;

[0296] (3.1) Preparation of PEDOT:PSS / PAm composite electrospinning solution;

[0297] (3.11) Acrylamide (Am) was dissolved in deionized water, and ammonium persulfate solution and tetramethylethylenediamine (TEMED) were added sequentially. The mixture was magnetically stirred at 80°C and 400 rpm for 2 h to obtain a PAm prepolymer solution. The mass ratio of acrylamide, deionized water, ammonium persulfate and tetramethylethylenediamine was 6800:90000:18:27.

[0298] (3.12) PEDOT:PSS aqueous solution was pre-frozen at -20℃ for 24h, and then freeze-dried in a freeze dryer for 48h to obtain freeze-dried PEDOT:PSS;

[0299] (3.13) At 25°C, the freeze-dried PEDOT:PSS was dissolved in deionized water and magnetically stirred for 12 h to fully redisperse it, resulting in a homogeneous dispersion with a concentration of 1.8 wt%. PAM prepolymer solution was added to the dispersion and magnetically stirred for another 12 h to form a PEDOT:PSS / PAm composite electrospinning solution.

[0300] (3.2) Electrospinning to form a film;

[0301] The PEDOT:PSS / PAm composite electrospinning solution was loaded into a 10 mL syringe. Under conditions of 40℃ and 20% relative humidity, the voltage was set to 12 kV and the injection rate to 0.4 mL / h. -1 The electrospinning solution in the syringe was 12 mL. A flat collector covered with aluminum foil was used, with the distance between the needle and the collector being 6 cm. Electrospinning was performed for 5 min to obtain a PEDOT:PSS / PAm nanofiber membrane. In the PEDOT:PSS / PAm nanofiber membrane, the mass ratio of PEDOT:PSS to PAM was 100:10.

[0302] (3.3) Post-treatment of electrospun film;

[0303] The PEDOT:PSS / PAm nanofiber membrane obtained by electrospinning was first annealed in an oven at 120℃ for 24 hours, and then soaked in a 5wt% DMSO aqueous solution to obtain the PEDOT:PSS / PAm semiconductor active layer.

[0304] (4) Fabrication of a fully fiber-structured vertical organic electrochemical transistor;

[0305] First, an ion-permeable electrode layer is prepared and placed flat on a clean glass substrate (with the metal conductive layer facing up). Then, a small amount of deionized water is sprayed evenly on the surface of the ion-permeable electrode layer to fully wet the surface. Next, the prepared PEDOT:PSS / PAm nanofiber membrane is placed on the ion-permeable electrode layer as the semiconductor active layer. Then, another ion-permeable electrode layer is stacked as the upper electrode layer (with its metal conductive layer facing down) to obtain a composite layer. Finally, the assembled composite layer is heated and dried at 90°C for 5 minutes to form a vertical stacked structure. Then, it is encapsulated with a PAN / PVP electrospun film to obtain a vertical organic electrochemical transistor with an all-fiber structure.

[0306] The final fabricated all-fiber vertical organic electrochemical transistor (OECT) consists of a lower electrode layer, a semiconductor active layer, and an upper electrode layer from bottom to top.

[0307] Both the lower and upper electrode layers are ion-permeable electrode layers;

[0308] The ion-permeable electrode layer consists of a porous PAN / PVP nanofiber substrate and a metal conductive layer deposited on it; the porous PAN / PVP nanofiber substrate is a multilayer nanofiber membrane prepared by electrospinning; the metal conductive layer consists of a Cr metal layer and an Au metal layer from bottom to top.

[0309] The all-fiber vertical organic electrochemical transistor has a maximum transconductance of 52.1 mS at a working voltage of -0.6 V, a maximum current between the source and drain of -29.37 mA, and a response time of 32.5 ms.

[0310] The all-fiber vertical organic electrochemical transistor retains 75% of the maximum current between the source and drain and 79% of the maximum transconductance after 10,000 cycles at a bending radius of 0.5 cm.

[0311] Example 5

[0312] A method for fabricating a vertical organic electrochemical transistor with an all-fiber structure, comprising the following steps:

[0313] (1) Preparation of raw materials and equipment;

[0314] PAN (Polyacrylonitrile): Manufacturer is Shanghai Mairui Biochemical Technology Co., Ltd., brand name is 25014-41-9, M w =150000;

[0315] Solvent: DMAc;

[0316] PVP (Polyvinylpyrrolidone): Manufacturer: Shanghai Titan Co., Ltd., Brand No.: 9003-39-8, M w =24000;

[0317] Syringe: Plastic syringe, needle specification 27G, needle length 30mm;

[0318] PVA solution: concentration 10wt%, solute is PVA (polyvinyl alcohol, manufacturer: Shanghai Titan Co., Ltd., brand name: 9002-89-5, M) w =205000), the solvent is deionized water;

[0319] Chromium layer: The material is chromium (Cr);

[0320] Gold layer: The material is gold (Au);

[0321] Acrylamide (Am);

[0322] Deionized water;

[0323] Ammonium persulfate solution: concentration 0.2 mol / L -1 The solvent is deionized water;

[0324] Tetramethylethylenediamine (TEMED);

[0325] PEDOT:PSS aqueous solution: concentration is 1.8wt%, solute is PEDOT:PSS (manufacturer is Heraeus, model is PH1000);

[0326] DMSO (dimethyl sulfoxide) aqueous solution;

[0327] (2) Preparation of ion-permeable electrode layer;

[0328] (2.1) Preparation of electrospinning solution;

[0329] PAN was dissolved in DMF solvent, and then PVP was added. The mixture was magnetically stirred at 23°C for 6 hours to obtain a spinning solution. The concentration of PAN in the spinning solution was 15 wt%, and the concentration of PVP was 3 wt%.

[0330] (2.2) Electrospinning to form a film;

[0331] The spinning solution was loaded into a syringe, and under conditions of 25°C and 40% relative humidity, the voltage was set to 20kV and the injection rate to 0.8mL / h. -1 The volume of the spinning solution in the syringe was 1.5 mL, the distance between the needle and the collecting roller was 20 cm, and electrospinning was performed for 5 h to obtain a PAN / PVP nanofiber membrane.

[0332] The average diameter of the PAN / PVP nanofibers in the obtained PAN / PVP nanofiber membrane is 450 nm.

[0333] (2.3) Coating and hot pressing treatment;

[0334] A 4.5 μm thick PVA layer was formed by electrospinning a PVA solution onto one surface of a PAN / PVP nanofiber membrane, followed by curing at 130 °C and 8 kg / cm². -2 Under the condition of hot pressing for 10 minutes, the PVA layer is partially melted to form stable interlayer bonding points, thus obtaining a porous PAN / PVP nanofiber substrate.

[0335] (2.4) Metal vapor deposition and patterning;

[0336] Using a metal masking method, chromium and gold layers were sequentially deposited on a porous PAN / PVP nanofiber substrate in a vacuum evaporation system to form a metal conductive network. Subsequently, the PVA layer was dissolved by spraying deionized water to obtain an ion-permeable electrode layer. The thickness of the chromium layer was 12 nm and the thickness of the gold layer was 150 nm.

[0337] The water vapor permeability of the obtained ion-permeable electrode layer was 1.48 kg m. -2 d -1 The sheet resistance of the electrode is 8.4 Ω / sq, and the porosity is 73%.

[0338] (3) Prepare the semiconductor active layer;

[0339] (3.1) Preparation of PEDOT:PSS / PAm composite electrospinning solution;

[0340] (3.11) Acrylamide (Am) was dissolved in deionized water, and ammonium persulfate solution and tetramethylethylenediamine (TEMED) were added sequentially. The mixture was magnetically stirred at 80°C and 400 rpm for 4 h to obtain a PAm prepolymer solution. The mass ratio of acrylamide, deionized water, ammonium persulfate and tetramethylethylenediamine was 6800:90000:18:27.

[0341] (3.12) PEDOT:PSS aqueous solution was pre-frozen at -25℃ for 36h, and then freeze-dried in a freeze dryer for 60h to obtain freeze-dried PEDOT:PSS;

[0342] (3.13) At 25°C, the freeze-dried PEDOT:PSS was dissolved in deionized water and magnetically stirred for 18 h to fully redisperse it, resulting in a homogeneous dispersion with a concentration of 1.8 wt%. PAM prepolymer solution was added to the dispersion and magnetically stirred for another 18 h to form a PEDOT:PSS / PAm composite electrospinning solution.

[0343] (3.2) Electrospinning to form a film;

[0344] The PEDOT:PSS / PAm composite electrospinning solution was loaded into a 10 mL syringe. Under conditions of 45℃ and 22% relative humidity, the voltage was set to 15 kV and the injection rate to 1.0 mL / h. -1 The volume of electrospinning solution in the syringe was 15 mL. A flat collector covered with aluminum foil was used, with the distance between the needle and the collector being 10 cm. Electrospinning was performed for 5 min to obtain a PEDOT:PSS / PAm nanofiber membrane. In the PEDOT:PSS / PAm nanofiber membrane, the mass ratio of PEDOT:PSS to PAM was 100:20.

[0345] (3.3) Post-treatment of electrospun film;

[0346] The PEDOT:PSS / PAm nanofiber membrane obtained by electrospinning was first annealed in an oven at 150℃ for 36 hours, and then soaked in a 6wt% DMSO aqueous solution to obtain the PEDOT:PSS / PAm semiconductor active layer.

[0347] (4) Fabrication of a fully fiber-structured vertical organic electrochemical transistor;

[0348] First, an ion-permeable electrode layer is prepared and placed flat on a clean glass substrate (with the metal conductive layer facing up). Then, a small amount of deionized water is sprayed evenly on the surface of the ion-permeable electrode layer to fully wet the surface. Next, the prepared PEDOT:PSS / PAm nanofiber membrane is placed on the ion-permeable electrode layer as the semiconductor active layer. Then, another ion-permeable electrode layer is stacked as the upper electrode layer (with its metal conductive layer facing down) to obtain a composite layer. Finally, the assembled composite layer is heated and dried at 100°C for 10 minutes to form a vertical stacked structure. Then, it is encapsulated with a PAN / PVP electrospun film to obtain a vertical organic electrochemical transistor with an all-fiber structure.

[0349] The final fabricated all-fiber vertical organic electrochemical transistor (OECT) consists of a lower electrode layer, a semiconductor active layer, and an upper electrode layer from bottom to top.

[0350] Both the lower and upper electrode layers are ion-permeable electrode layers;

[0351] The ion-permeable electrode layer consists of a porous PAN / PVP nanofiber substrate and a metal conductive layer deposited on it; the porous PAN / PVP nanofiber substrate is a multilayer nanofiber membrane prepared by electrospinning; the metal conductive layer consists of a Cr metal layer and an Au metal layer from bottom to top.

[0352] The all-fiber vertical organic electrochemical transistor has a maximum transconductance of 47.7 mS at a working voltage of -0.6 V, a maximum current between the source and drain of -30.48 mA, and a response time of 26.1 ms.

[0353] The all-fiber vertical organic electrochemical transistor retains 84% ​​of the maximum current between the source and drain and 75% of the maximum transconductance after 10,000 cycles at a bending radius of 0.5 cm.

Claims

1. A vertical organic electrochemical transistor with an all-fiber structure, comprising, from bottom to top, a lower electrode layer, a semiconductor active layer, and an upper electrode layer, characterized in that: Both the lower and upper electrode layers are ion-permeable electrode layers, consisting of a porous PAN / PVP nanofiber substrate and a metal conductive layer deposited on it; the semiconductor active layer is an electrospun PEDOT:PSS / PAm nanofiber membrane that has been annealed and treated with DMSO.

2. The all-fiber vertical organic electrochemical transistor according to claim 1, characterized in that, The water vapor permeability of the ion-permeable electrode layer is 1.05–2.16 kg m³. -2 d -1 .

3. The all-fiber vertical organic electrochemical transistor according to claim 1, characterized in that, The porous PAN / PVP nanofiber substrate is a multilayer nanofiber membrane prepared by electrospinning, consisting of a PAN / PVP conductive support layer and a PVA soluble layer arranged sequentially from bottom to top; in the PAN / PVP conductive support layer, the mass ratio of PAN to PVP is 4 to 6:1; the thickness of the PVA soluble layer is 1 to 5 μm.

4. The all-fiber vertical organic electrochemical transistor according to claim 1, characterized in that, The conductive metal layer consists of a Cr metal layer and an Au metal layer from bottom to top. The thickness of the Cr metal layer is 3-12 nm and the thickness of the Au metal layer is 100-150 nm.

5. The all-fiber vertical organic electrochemical transistor according to claim 1, characterized in that, In the electrospun PEDOT:PSS / PAm nanofiber membrane, the mass ratio of PEDOT:PSS to PAM is 100:5 to 20.

6. The all-fiber vertical organic electrochemical transistor according to claim 1, characterized in that, The all-fiber vertical organic electrochemical transistor is encapsulated using a PAN / PVP electrospun film.

7. The all-fiber vertical organic electrochemical transistor according to claim 1, characterized in that, The all-fiber vertical organic electrochemical transistor has a maximum transconductance of 38–57.5 ms and a response time of 11.7–33.8 ms at a working voltage of -0.6 V, and retains more than 75% of its initial performance after 10,000 cycles at a bending radius of 0.5 cm.

8. A method for fabricating a vertical organic electrochemical transistor with an all-fiber structure as described in any one of claims 1 to 7, characterized in that: First, an ion-permeable electrode layer and a semiconductor active layer are prepared separately. Both the upper and lower electrode layers are made of ion-permeable electrode layers. Then, the upper electrode layer, the semiconductor active layer, and the lower electrode layer are assembled into a vertical organic electrochemical transistor with an all-fiber structure.

9. The method for fabricating a vertical organic electrochemical transistor with an all-fiber structure according to claim 8, characterized in that, Specifically, the steps include: (1) preparing an ion-permeable electrode layer; (1.1) preparing an electrospinning solution; dissolving PAN in DMF or DMAc, then adding PVP, and stirring at room temperature for 6-10 h to obtain a spinning solution; the concentration of PAN in the spinning solution is 10-15 wt%, and the concentration of PVP is 2-3 wt%; (1.2) electrospinning to form a film; loading the spinning solution into a syringe, and under conditions of 20-25℃ and 30-40% relative humidity, setting the voltage to 12-20 kV and the injection rate to 0.6-1.0 mL / h. -1 The volume of the spinning solution in the syringe is 1-1.5 mL, the distance between the needle and the collecting roller is 10-20 cm, and electrospinning is performed for 2-5 h to obtain a PAN / PVP nanofiber membrane; (1.3) Coating and hot pressing treatment; PVA layer is formed by electrospinning on the PAN / PVP nanofiber membrane using PVA solution, and then heated at 120-130℃ for 4-8 kg / cm². -2 Under the condition of hot pressing for 5-10 minutes, the PVA layer is partially melted to obtain a porous PAN / PVP nanofiber substrate; (1.4) Metal vapor deposition and patterning; Using the metal mask method, a chromium layer and a gold layer were deposited sequentially in a vacuum evaporation system. Then, the PVA layer was dissolved by spraying deionized water to obtain an ion-permeable electrode layer; (2) Prepare a semiconductor active layer; (2.1) Prepare a PEDOT:PSS / PAm composite electrospinning solution; First, acrylamide was dissolved in deionized water, and ammonium persulfate solution and tetramethylethylenediamine were added sequentially. The solution was stirred at 70-80℃ to obtain a PAm prepolymer solution; Then, the PEDOT:PSS aqueous solution was pre-frozen at -20--30℃ for 24-36h, and then The PEDOT:PSS was freeze-dried in a freeze dryer to obtain freeze-dried PEDOT:PSS; finally, the freeze-dried PEDOT:PSS was dissolved in deionized water and stirred to obtain a uniform dispersion. PAM prepolymer solution was added to the dispersion and stirred to form PEDOT:PSS / PAm composite electrospinning solution; (2.2) Electrospinning film formation; the PEDOT:PSS / PAm composite electrospinning solution was loaded into a syringe, and under the conditions of temperature 40-45℃, relative humidity 20-25%, the voltage was set to 10-15kV and the injection rate was 0.4-1.0mL / h. -1 The volume of electrospinning solution in the syringe is 10-15 mL. A flat collector covered with aluminum foil is used, with a distance of 6-10 cm between the needle and the collector. Electrospinning is performed for 5 min to obtain a PEDOT:PSS / PAm nanofiber membrane. (2.3) Post-treatment of electrospinned membrane: The PEDOT:PSS / PAm nanofiber membrane obtained by electrospinning is first annealed in an oven at 120-150℃ for 24-36 h, and then soaked in a 4-6 wt% DMSO aqueous solution to obtain a PEDOT:PSS / PAm semiconductor active layer. (3) Preparation of vertical organic electrochemical transistor with all-fiber structure: The composite layer is assembled in the order of ion-permeable electrode layer, semiconductor active layer and ion-permeable electrode layer. The assembled composite layer is heated and dried at 80-100℃ for 5-10 min to obtain a vertical organic electrochemical transistor with all-fiber structure.

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