High performance organic electrochemical transistors based on template-sacrificial method prepared foam structure channel and preparation method and application thereof

Abstract

The present invention relates to a high performance organic electrochemical transistor (OECT) with a foam-structured channel prepared by a template-sacrifice method using ionic liquid as a template. A foam-structured PEDOT:PSS film is designed and prepared by a template-sacrifice method. By the template-sacrifice method, the domains induced by phase separation of [EMIM][PF6] ionic liquid are used as a template for the foam structure. Due to the presence of the foam structure, the transport of electrons and ions is improved. By using this foam-structured PEDOT:PSS film as a channel layer, a high performance OECT is prepared. An OECT with improved transconductance and shortened response time can be obtained. The present method provides a new and simple strategy for the preparation of high performance OECTs, which can be used for various wearable applications, including biological detection or health monitoring. The method has been proved to successfully prepare a high performance OECT with a foam-structured channel prepared by ionic liquid as a template.

Description

Technical Field

[0001] This invention relates to a high-performance organic electrochemical transistor (OECT) with a foam structure channel prepared by a template sacrifice method using an ionic liquid as a template, which is particularly applicable to the field of flexible wearable devices and belongs to the field of composite structure design and preparation technology. Background Technology

[0002] Organic electrochemical transistors (OECTs) are generally considered promising devices for the sensitive detection of chemical and biological analytes due to their high sensitivity and low operating voltage. A typical OECT consists of a source, drain, and gate electrode, with the source and drain electrodes connected through an organic semiconductor channel. During operation, ions in the electrolyte can effectively dope the semiconductor channel under an appropriate bias voltage applied to the gate electrode, thus doping or dedoping the channel. Therefore, the source and drain currents can be modulated by applying a gate voltage, facilitating analyte detection. Many parameters are used to define the sensing capability of an OECT. One key parameter is transconductance, which quantifies the ability of the gate voltage to modulate the drain current. OECTs with high transconductance typically exhibit relatively high sensitivity in sensing applications. Another key parameter is response time; a short response time usually implies fast chemical sensing and high sensitivity. Therefore, it is necessary to develop novel OECTs with both high transconductance and short response time.

[0003] Improving transconductance is crucial for achieving high-performance OECTs. Two strategies exist for enhancing OECT transconductance. One is optimizing the geometry of the channel layer. In particular, reducing the channel length can significantly improve transconductance; however, this is limited by fabrication techniques. The other strategy is improving the electrical properties of the channel layer, such as carrier mobility and volumetric capacitance. For example, synthesizing novel semiconductor polymers with higher carrier mobility and / or volumetric capacitance can improve OECT transconductance. Introducing ethylene glycol side chains onto existing semiconductor polymers can also improve OECT transconductance. Solvent treatment and physical doping with ethylene glycol or ionic liquids can both improve OECT transconductance, especially for OECTs based on poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS). Solvent treatment or physical doping can help expose more PEDOT moieties, thereby improving the channel's electrical performance. Compared to other methods, solvent treatment and physical doping are relatively simple and convenient, and have potential applications in many scenarios.

[0004] Response time is another important parameter of OECT. Generally, a shorter response time means faster and more sensitive detection. Increasing the surface area for ion doping / dedoping is an effective strategy to improve the response time of OECT. Savva et al. significantly shortened the response time of the obtained OECT by introducing hydrophilic side chains to promote ion transport in organic semiconductors. However, the expansion of semiconductor polymers may negatively affect other properties of OECT. Recently, Zhang et al. fabricated porous channels using a breathing patterning method and achieved a response time as low as 4.6 seconds. Ion doping / dedoping was promoted due to the geometric advantages of the porous structure, which explains the reduction in response time. However, this method cannot precisely control the size and density of pores, resulting in low controllability.

[0005] According to the applicant, although there are many methods for optimizing transconductance and response time, simultaneously improving transconductance and shortening response time remains a significant challenge. The [EMIM][PF6] ionic liquid phase separation-induced domain was used as a template for a foam structure. Due to the presence of the foam structure, electron and ion transport was improved. Summary of the Invention

[0006] The technical problem solved by this invention is to propose a high-performance organic electrochemical transistor (OECT) based on a template-sacrificial method for preparing foam structure channels, as well as its preparation method and application. The method of preparing foam structure channels by using the domain induced by the phase separation of [EMIM][PF6] ionic liquid as a template for the foam structure is simple to operate, highly repeatable, and highly controllable, and effectively improves the transconductance and response time of OECT.

[0007] To address the aforementioned technical problems, the present invention proposes the following technical solution: a method for fabricating a high-performance organic electrochemical transistor with a foam structure channel based on a template sacrificial method, comprising the following steps:

[0008] (1) A 49 μL solution of [EMIM][PF6] (1-ethyl-3-methylimidazolium hexafluorophosphate) was prepared by mixing with water and ethanol in a volume ratio of 1:3, wherein [EMIM][PF6] accounted for 1.3 wt.% in the alcohol-water solution. 2.5 μL of 0.5 vol.% (volume fraction of PEDOT:PSS solution) GOPS silane coupling agent solution and 2.5 μL of 90% DBSA dodecylbenzene sulfonic acid aqueous solution were added, and then mixed with 500 μL of PEDOT:PSS (3,4-ethylenedioxythiophene):poly(styrene sulfonate) solution (PEDOT:PSS accounted for 1.5 wt.% in deionized water) to prepare a film precursor with a porosity of 15 vol%. The mixture was stirred at 300 rpm for 30 minutes before use.

[0009] (2) Fabrication of organic electrochemical transistors (OECTs):

[0010] First, source and drain gold electrodes were fabricated on a PET substrate using a template mask sputtering method. Sputtering was performed on an ion sputtering device (SBC-12, KYKY). The channel length and width were controlled to be 500 μm (L) and 7000 μm (d), respectively. The gate was tested using an external Ag / AgCl device.

[0011] Then, the PEDOT:PSS mixture prepared in step (1) was dropped onto the electrode-coated PET substrate and then thermally annealed. 15 μL of the mixture was dropped onto the substrate pre-coated with gold electrodes. The dropped film was annealed at 50 °C for 30 minutes and then at 120 °C for 30 minutes. The resulting substrate was cleaned with a mixture of water and ethanol (volume ratio 1:3) by immersion and rinsing in the mixture. The thickness of the resulting foam structure film was 1 μm.

[0012] To address the aforementioned technical problems, another technical solution proposed by this invention is: a high-performance organic electrochemical transistor with a foam structure channel prepared by the method described above.

[0013] To address the aforementioned technical problems, another technical solution proposed by this invention is: the application of the high-performance organic electrochemical transistor in the foam structure channel can be used in various flexible wearable fields.

[0014] To address the aforementioned technical problems, another technical solution proposed by this invention is that it can be used for biological detection or health monitoring.

[0015] Preferably, it can be used for the detection of H2O2 and glucose.

[0016] The beneficial effects of this invention are:

[0017] A method for fabricating foam-structured channels using ionic liquids as templates is disclosed. In this method, a template sacrifice method is employed, utilizing the domains induced by phase separation of the [EMIM][PF6] ionic liquid as templates for the foam structure. The presence of the foam structure improves electron and ion transport. By using this foam-structured PEDOT:PSS film as the channel layer, OECTs with improved transconductance and shortened response times can be obtained. This method has been proven to successfully fabricate high-performance OECTs with foam-structured channels.

[0018] The separated ionic liquid was used as a template for preparing foam-structured thin films. Compared with dense PEDOT:PSS films, the conductivity of foam-structured PEDOT:PSS films increased from 0.2 to 573.7 S cm⁻¹. -1 The volume capacitance increased fivefold, reaching 71.80 F cm⁻¹. -3Furthermore, ion doping / dedoping becomes more efficient in the foam-structured PEDOT:PSS film. Results show that the transconductance of OECT based on this foam-structured PEDOT:PSS increases from 90 μS to 18 mS, while the response time decreases from 1000 ms to 300 ms. Due to the improved transconductance and shortened response time, OECT is highly sensitive for the detection of chemicals and metabolites such as hydrogen peroxide and glucose. Attached Figure Description

[0019] The present invention will be further described below with reference to the accompanying drawings.

[0020] Figure 1 The image shows a schematic diagram of a foam structure channel prepared using an ionic liquid template.

[0021] Figure 2 The process of OECT preparation based on foam structure PEDOT:PSS film.

[0022] Figure 3 Morphology of foamed PEDOT:PSS membranes with different pore contents. (a) Scanning electron microscopy (SEM) image of dense PEDOT:PSS membrane. (bf) SEM images of foamed PEDOT:PSS membranes with 8, 10, 15, 20, and 25 vol% pore contents. (g) Atomic force microscopy (AFM) height and phase images of foamed PEDOT:PSS membrane with 15 vol% pore content. (h) Cross-sectional SEM image of foamed PEDOT:PSS membrane with 15 vol% pore content. (i) Relationship between pore size and density and pore content of foamed PEDOT:PSS membranes.

[0023] Figure 4 Electrical properties of foam-structured PEDOT:PSS films. (a) The conductivity of PEDOT:PSS films varies with pore content. (b) CV curves of PEDOT:PSS films with different pore contents. (c) The volumetric capacitance of PEDOT:PSS films varies with pore content.

[0024] Figure 5 This section describes the spectroelectrochemical properties and doping kinetics of foam-structured PEDOT:PSS thin films. (a) is a schematic diagram of the measurement setup. (bc) UV-Vis-NIR spectra of foam-structured and dense PEDOT:PSS thin films, with the applied bias voltage varying from 0 to 1.0 V during the measurement. (d) Peak intensity (approximately 650 nm) of foam and dense PEDOT:PSS thin films as a function of the applied bias voltage. (ef) Doping kinetics of foam-structured and dense PEDOT:PSS thin films.

[0025] Figure 6It is the kinetic absorption spectrum of a dense PEDOT:PSS thin film.

[0026] Figure 7 OECT output performance based on foam structure channels. (a) Schematic diagram of the prepared OECT. (bc) OECT output curves based on dense and foam structure PEDOT:PSS films. (de) OECT transmission curves based on dense and foam structure PEDOT:PSS films with a drain voltage of 300mV. (fg) OECT response time based on dense and foam structure PEDOT:PSS films with a pulsed gate voltage of 20mV. (h) Stability of the OECT based on foam structure PEDOT:PSS films over 400 seconds, with the applied gate voltage varying between 0 and 20mV.

[0027] Figure 8 The flexibility of OECT based on the foam structure PEDOT:PSS channel. (a) Schematic diagram of OECT under different bending conditions. (b) Transmission curves under different bending conditions with an applied gate voltage of 300mV. (cd) Changes in relative conductivity at different radii of curvature and after 100 bending cycles.

[0028] Figure 9 Examples of OECT for H2O2 and glucose detection. (a) Schematic diagram of an OECT for H2O2 detection. (b) Transfer curves obtained in H2O2 solutions of different concentrations. VD = 100 mV. (c) Graph showing the relationship between ΔID and the logarithm of H2O2 concentration. (d) Schematic diagram of an OECT for glucose detection. (e) Transfer curves obtained in glucose solutions of different concentrations. Glucose is dissolved in 0.9% sodium chloride solution. (f) Graph showing the relationship between ΔID and the logarithm of glucose concentration.

[0029] Specific implementation methods

[0030] Example 1: Design of OECT for foam structure channels

[0031] Figure 1 The diagram shows the preparation of foam structure channels using ionic liquid templates to improve the transconductance of the corresponding OECT and shorten the response time.

[0032] Figure 2 The OECT fabrication process based on a foam-structured PEDOT:PSS thin film is described. Gold electrodes for the source and drain are fabricated by ion sputtering (mask method). A mixture of PEDOT:PSS and an ionic liquid is drop-coated and thermally annealed at 50°C for 30 minutes, followed by thermal annealing at 120°C for 30 minutes. The ionic liquid in the film is then washed away using a mixture of water and ethanol (volume ratio 1:3).

[0033] like Figure 1 As shown in Figure 2, ion doping / dedoping of the channel layer under gate voltage is a critical step in OECT operation, significantly impacting its output performance and sensing capability. To improve the ion doping / dedoping effect, we employed a template sacrificial method to fabricate foam-structured channels and assembled them into a high-performance OECT.

[0034] The preparation method is as follows:

[0035] Preparation of foam-structured thin films:

[0036] A 49 μL solution of [EMIM][PF6] (1-ethyl-3-methylimidazolium hexafluorophosphate) was prepared by mixing [EMIM][PF6] (1.3 wt.% of water and ethanol in a volume ratio of 1:3). 2.5 μL of a 0.5 vol.% (volume fraction of PEDOT:PSS solution) GOPS silane coupling agent solution and 2.5 μL of a 90% concentration DBSA dodecylbenzenesulfonic acid aqueous solution were added. This mixture was then combined with 500 μL of a PEDOT:PSS (3,4-ethylenedioxythiophene):poly(styrene sulfonate) solution (PEDOT:PSS in deionized water was 1.5 wt.%) to prepare a film precursor with a 15 vol% porosity. The mixture was stirred at 300 rpm for 30 minutes before use.

[0037] Then, 15 μL of the mixture was dropped onto a substrate pre-coated with gold electrodes. The drop-coated film was annealed at 50 °C for 30 min, and then at 120 °C for 30 min. The resulting substrate was cleaned with a mixture of water and ethanol (1:3) by immersion and rinsing in the mixture. The thickness of the resulting foam structure film was approximately 1 μm. The volume of [EMIM][PF6] was adjusted as needed (8%, 10%, 15%, 20%, 25%) to determine the pore size, which corresponds to the volume fraction of the ionic liquid [EMIM][PF6] in the PEDOT:PSS precursor as 8%, 10%, 15%, 20%, 25%, respectively. This means that after annealing and removing deionized water from the solution, the ionic liquid content of the ionic liquid in the PEDOT:PSS is 8%, 10%, 15%, 20%, 25%, respectively, to prepare foam structure films with different pore contents.

[0038] OECT fabrication: First, source and drain gold electrodes were fabricated on a PET substrate using a template mask sputtering method. Sputtering was performed on an ion sputtering apparatus (SBC-12, KYKY). The channel length and width were controlled to be 500 μm and 7000 μm, respectively. Then, the above mixture containing PEDOT:PSS was dropped onto the electrode-coated PET substrate and then thermally annealed. The gate was tested using an external Ag / AgCl test. The PEDOT:PSS mixture prepared in the above method (i.e., the above-mentioned film precursor mixture with a 15 vol% porosity content) was dropped onto the electrode-coated PET substrate and then thermally annealed. 15 μL of the mixture was dropped onto a substrate pre-coated with gold electrodes. The dropped film was annealed at 50 °C for 30 min and then at 120 °C for 30 min. The resulting substrate was cleaned by immersion and rinsing in the mixture using a mixture of water and ethanol (volume ratio 1:3). The thickness of the resulting foam structure film was 1 μm.

[0039] Example 2: Morphology of foam-structured PEDOT:PSS film

[0040] like Figure 3 As shown, to confirm the successful fabrication of the foam-structured PEDOT:PSS film, we performed morphological characterization using scanning electron microscopy (SEM). Clearly, the formation of the foam-structured PEDOT:PSS is highly dependent on the content of the ionic liquid template in the PEDOT:PSS film. When no ionic liquid [EMIM][PF6] solution was added, the PEDOT:PSS film surface was smooth. When 8 vol% of the ionic liquid was added as a template, a uniform high-density pore size of 500 ± 200 nm was formed on the film surface. When the pore content (determined by the ionic liquid template content before washing) increased to 15 vol%, the pore size increased to 1000 ± 300 nm. Further increases in the ionic liquid template content led to a further increase in pore size, and the pore size became non-uniform. Finally, the pore size reached saturation when the pore content reached 25 vol%. Furthermore, the pore density decreased with increasing pore content. High pore density and appropriate pore size are necessary for the optimization of ion transport. In Example 1, a porosity of 15 vol% was used because the sample had high output performance, as explained in later examples.

[0041] The foam-structured PEDOT:PSS film with a porosity of 15% by volume was further characterized using atomic force microscopy (AFM). AFM measurements determined a pore size of 1000 ± 300 nm, consistent with SEM measurements. A pore depth of 180 ± 60 nm was determined by cross-sectioning typical pores. Cross-sectional images of the film show that the pores are distributed not only on the surface but also uniformly throughout the entire PEDOT:PSS film.

[0042] Example 3: Electrical properties of foam-structured PEDOT:PSS films

[0043] The foam-structured PEDOT:PSS film of this embodiment was prepared according to Example 1.

[0044] The electrical properties of the channel significantly affect the performance of OECT. Therefore, it is necessary to study the electrical properties of foam-structured PEDOT:PSS films, including conductivity and volume capacitance.

[0045] like Figure 4 As shown, we first investigated the electrical conductivity of the foam-structured PEDOT:PSS film. When the porosity increased from 0 to 25% by volume, the film conductivity increased dramatically, from 0.2 to 573.7 S cm⁻¹, an increase of three orders of magnitude. During the formation of the high-density pores, ionic liquid domains were used as templates, which may have dissolved excess PSS. The dissolution of PSS leads to the exposure of more conductive PEDOT portions, thus explaining the increase in conductivity. Further increases in porosity result in a decrease in conductivity, possibly because the pores interrupt the conductive pathways of PEDOT.

[0046] The volumetric capacitance of the channel also significantly determines the performance of the corresponding OECT. We estimate the volumetric capacitance of the foam-structured PEDOT:PSS film by calculating the reversible storage capacity revealed by cyclic voltammetry (CV) curves. Figure 4 As can be seen from a, 4b, and 4c, the 15 vol% porosity content has the best performance compared to other porosities, exhibiting higher electrical and output performance.

[0047] Example 4: Ion doping kinetics in foam-structured PEDOT:PSS thin films

[0048] The foam-structured PEDOT:PSS film of this embodiment was prepared according to Example 1.

[0049] The testing method is as follows: For photoelectrochemical measurements, a channel film was prepared on a transparent PET substrate. The coated PET film was then immersed in a cuvette containing 0.1M PBS solution. Using an Ag / AgCl electrode immersed in PBS solution as the counter electrode, a positive bias was applied to a portable electrochemical analyzer (PalmSens4). The absorption spectrum of the coated PET was continuously recorded as the bias increased from 0 to 1V using a UV-Vis-NIR spectrometer (UV-3600, Shimadzu, Japan). Figure 5 This is a comparison of the spectroelectrochemistry and doping kinetics of foam-structured PEDOT:PSS and dense PEDOT:PSS. Figure 6This is the kinetic absorption spectrum of a dense PEDOT:PSS thin film. The kinetic absorption spectrum was obtained after 50 seconds following a 1.0V bias applied for 20 seconds.

[0050] like Figure 5 , Figure 6 As shown, we then investigated the ion doping of the foam-structured PEDOT:PSS film under bias voltage using UV-Vis-NIR spectroscopy. For measurements, we prepared foam-structured PEDOT:PSS films on partially metallized transparent PET substrates, and then immersed the substrates in phosphate-buffered saline (PBS) electrolyte. For comparison, we first examined the spectroelectrochemical properties of the dense PEDOT:PSS film. As the bias voltage increased from 0 to 1.0 V, the absorption peak intensity at approximately 600 nm increased, while the intensity of the broad absorption peak in the 800–1100 nm range decreased. The peak around 600 nm represents the neutral state (PEDOT). 0 The absorption of ) and the absorption peak around 970 nm is the polaron (PEDOT) absorption peak. + The absorption at >1000 nm is attributed to the bipolar (PEDOT) absorption. 2+ The above results indicate that as the bias voltage increases, PEDOT absorbs [the excess]. + The decrease in the number of PEDOTs and the increase in the number of PEDOT0s indicate that the voltage from PEDOTs decreases under positive bias. + To PEDOT 0 The transformation was observed. Similar changes were also observed in foam-structured PEDOT:PSS films, although the rate of change was faster than in dense PEDOT:PSS films. For quantitative analysis, we plotted the transformation of dense and foam-structured PEDOT:PSS films under bias voltage. 0 The absorption spectrum shows a slight increase in absorption intensity as the bias voltage increases from 0 to 0.2V. Further increasing the bias voltage from 0.2V to 0.8V results in a sharp increase in absorption intensity. When the bias voltage increases from 0.8V to 1.0V, the absorption gradually reaches saturation. Interestingly, the absorption intensity of the foamed PEDOT:PSS film increases significantly faster than that of the dense PEDOT:PSS film. This increase in absorption intensity can be attributed to PEDOT... + The intensity of neutralization and saturation indicates that neutralization has reached saturation. The faster intensity increase observed in the foam-structured PEDOT:PSS film suggests that ion doping is more favorable in this film, possibly due to the presence of a porous structure that increases the interfacial area, which is beneficial for ion doping. These results indicate that our foam-structured PEDOT:PSS film is favorable for ion doping in corresponding OECT channels, thus improving device performance.

[0051] To further investigate the kinetic differences between dense and foam PEDOT:PSS films, we applied a sharply increased bias voltage to study the rate and mechanism of ion doping. At approximately 20 seconds, we applied a positive bias of 1V to the films. The absorption spectrum of the dense PEDOT:PSS film began to decrease slowly after the bias voltage was applied, and the entire decrease was not completed even after 50 seconds. The process did not saturate until 300 seconds later. In contrast, the absorption spectrum of the foam film decreased sharply and saturated quickly. The significant reduction in the decrease time in the foam film indicates that cation implantation into the foam is faster, and the transition from the polaron to the neutral PEDOT0 state is also faster, likely due to the porous nature of the film. This rapid cation doping will result in faster response times in the corresponding OECTs, which will be discussed later.

[0052] Example 5: Output performance of OECT based on foam structure channel

[0053] The OECT of the foam structure channel in this embodiment was prepared according to Example 1.

[0054] The testing method is as follows: The output characteristics of OECT were measured on a semiconductor analyzer (B1500A, Keysight). When acquiring the output curve, the gate voltage was scanned from 0 to 1V, and the drain voltage was set from 0 to 0.5V. When acquiring the transfer curve, the drain voltage was maintained at -0.3V, and the gate voltage was scanned within the range of -1 to 1V. For H2O2 and glucose sensing tests, the drain voltage was maintained at 0.3V, and the gate voltage was scanned within the range of -0.5 to 1V. The curve fitting formula for H2O2 was y = 0.8478 + 0.00826x. The curve formula for the glucose test was y = 0.10936 + 0.00856x. For photoelectrochemical measurements, a channel film was prepared on a transparent PET substrate. The coated PET film was then immersed in a cuvette containing a PBS solution (0.1M). An Ag / AgCl electrode immersed in the PBS solution was used as the counter electrode, and a positive bias was applied on a portable electrochemical analyzer (PalmSens4). The absorption spectrum of the coated PET was continuously recorded as the bias voltage increased from 0 to 1V using a UV-Vis-NIR spectrometer (UV-3600, Shimadzu, Japan).

[0055] like Figure 7As shown, we utilize a foam-structured PEDOT:PSS film as a channel layer to fabricate a high-performance OECT. First, we deposit source and drain gold electrodes on a PET film using mask-assisted ion sputtering. The channel length and width are controlled to be 500 μm and 7 mm, respectively. Then, we coat the foam-structured PEDOT:PSS film onto the electrode-coated substrate by drop-casting a mixture of PEDOT:PSS and an ionic liquid, and then wash away the ionic liquid.

[0056] Next, we compared the output performance of OECTs based on dense and foam-structured PEDOT:PSS channels. As shown in the figure, for both dense and foam-structured PEDOT:PSS channels, the leakage current increases with increasing source-drain voltage. Furthermore, the leakage current decreases with increasing gate voltage, a typical characteristic of PEDOT:PSS-based OECTs, which operate in depletion mode. These results indicate that the OECT is on at low gate voltages and off at high gate voltages. When a positive gate voltage is applied, hole carriers in the PEDOT:PSS are annihilated by introduced cations, causing the OECT to turn off. Although the OECTs based on dense and foam-structured PEDOT:PSS exhibit similar characteristics on the output curves, the leakage current of the foam-structured PEDOT:PSS channel is generally larger than that of the dense PEDOT:PSS-based OECT (approximately 7 times greater). This increase in leakage current is likely due to the improved conductivity and volume capacitance of the foam-structured PEDOT:PSS film, as discussed earlier.

[0057] We further compared the transport curves and transconductance of the dense and foam-structured PEDOT:PSS channels. The leakage current decreased with increasing gate voltage, further confirming the depletion operating mode. In both OECTs, the leakage current dropped sharply near zero gate voltage. More importantly, the foam-structured PEDOT:PSS-based OECT exhibited a significantly higher transconductance (18 mS), approximately 200 times that of the dense PEDOT:PSS-based OECT. This improved transconductance can be explained by the improved electrical properties of the foam-structured PEDOT:PSS channel, as previously discussed. Furthermore, the presence of the porous structure increases the interfacial area between the electrolyte and the organic semiconductor channel, facilitating ion doping / dedoping processes. In addition to the high transconductance, the foam-structured PEDOT:PSS-based OECT also exhibited a shorter response time. At a pulse voltage of 20 mV, the rise and fall response times of the OECT based on dense PEDOT:PSS were 1000 and 1200 ms, respectively, while those of the OECT based on foam-structured PEDOT:PSS were reduced to 300 and 500 ms, respectively. The response time of the OECT based on foam-structured PEDOT:PSS was only 30% of that of the OECT based on dense PEDOT:PSS film, indicating that the ion doping / dedoping process of the PEDOT:PSS channel was significantly accelerated, with a speed improvement of approximately 3 times. This improvement in response time can likely be attributed to the porous structure, which makes ion doping and dedoping more efficient due to the significant increase in surface area.

[0058] Cyclic stability is another important parameter for OECTs, especially in practical applications. We tested the cyclic performance of our foam-structured PEDOT:PSS-based OECT by repeatedly applying pulsed gate voltages. During long-term operation (400 seconds), the OECT exhibited highly stable performance. The leakage current variation in the first few cycles was very consistent with that in the later cycles, indicating that our OECT has high operational stability. Therefore, our OECT may be used in practical applications in the near future.

[0059] Example 6: Flexibility of OECT based on foam structure channels

[0060] The OECT based on foam structure channels in this embodiment was prepared according to Example 1.

[0061] like Figure 8As shown, flexibility is another important parameter of OECT, especially for OECTs used in wearable sensing applications. When mounted on the human body, OECTs need to operate stably under various bending conditions, and their performance needs to remain stable after multiple bending cycles. In our case, the OECT is fabricated on a flexible PET substrate, and the channel layer is porous. All these characteristics enable our OECT to operate stably under bending conditions. We investigated the flexibility of our OECT by measuring its output performance under bending conditions. The transmission curve remained stable at different bending angles and was similar to the transmission curve under unbent conditions, indicating that our OECT has high stability under bending conditions. We then compared the transconductance of the OECT bent at different radii of curvature (R = 10, 15, 30 mm). When the OECT changed from a flat state to a bent state with a radius of 30 mm, the transconductance of the OECT decreased slightly and remained at about 90% of its original value. Furthermore, in the bent state with a radius of 15 mm, the transconductance remained stable after 100 repeated bending cycles, demonstrating the high mechanical flexibility of our OECT. Therefore, our OECT may be applied to the field of wearable electronics in the near future.

[0062] Example 7: Sensitive detection of H2O2 and glucose using OECT.

[0063] The OECT of the foam structure channel in this embodiment was prepared according to Example 1.

[0064] like Figure 9 As shown, using OECT based on the foam structure PEDOT:PSS, we can achieve sensitive detection of many chemical substances. As discussed earlier, OECT possesses high transconductance and a short response time, both of which are advantageous for sensitive detection of chemical substances. Furthermore, the maximum transconductance of OECT is obtained approximately near zero gate voltage, which helps reduce energy consumption and simplify integration requirements. This zero-gate characteristic also improves the stability of OECT sensors, as many biological elements tend to degrade at the gate when high voltages are applied.

[0065] As a proof-of-concept, we used OECT to detect hydrogen peroxide (H2O2). During detection, H2O2 undergoes an electrochemical oxidation reaction at the gate electrode. In this reaction, electrons generated during oxidation are transferred to the nearby gate electrode, while protons enter the channel layer. This electron transfer leads to a decrease in the potential near the gate, which in turn causes a further change in the drain current. By adding different concentrations of H2O2 solution, different numbers of protons and electrons are generated under a positive gate voltage, resulting in different potential decreases. Based on this principle, the concentration of H2O2 can be quantitatively determined. As shown in the figure, the drain current of our OECT shows a significant response to different concentrations of H2O2 solution. The decrease in drain current on the transfer curve (ΔI) D ΔI was used to quantify the concentration of H2O2. D The value increases with increasing H2O2 concentration. When the H2O2 concentration is 1 nM, a low concentration of H2O2 is detected, ΔI... D The value is 9.4 μA, while when the H2O2 concentration is 10 nM, ΔI D Increased to 22.6 μA. Clearly, within the concentration range of 1 nM to 100 μM, ΔI... D There is a linear relationship between the OECT result and the logarithm of the H2O2 concentration. These results indicate that our OECT can be used for the quantitative detection of H2O2.

[0066] Similarly, glucose concentration can also be measured using an OECT based on a foam-structured PEDOT:PSS channel. The gate electrode is modified with glucose oxidase (GO). x To identify glucose. ΔI D The linear correlation increases with increasing glucose concentration. Quantitatively, a wide concentration range from 1 nM to 100 μM can be detected, and a good linear correlation is observed within this concentration range.

[0067] The present invention is not limited to the specific technical solutions described in the above embodiments. All technical solutions formed by equivalent substitutions are within the scope of protection claimed by the present invention.

Claims

1. A high performance organic electrochemical transistor based on a template-sacrificial method of foam structure channel, characterized by: The preparation method steps are as follows: (1) [EMIM][PF6] (1-ethyl-3-methyl imidazole hexafluorophosphate) solution is mixed with water and ethanol in a volume ratio of 1:3 to configure a 49 μL solution, wherein [EMIM][PF6] accounts for 1.3 wt.% in the alcohol water solution, 2.5 μL of GOPS silane coupling agent solution and 2.5 μL of 90 wt.% concentration DBSA dodecylbenzenesulfonic acid aqueous solution account for 0.5 vol.% of the volume fraction of the PEDOT:PSS solution, and 500 μL of PEDOT:PSS (3,4-ethylenedioxythiophene): poly(styrene sulfonate) solution, PEDOT:PSS accounts for 1.5 wt.% in deionized water, are mixed to prepare a thin film precursor with a pore content of 15 vol%, and the mixture is stirred at a speed of 300 rpm for 30 minutes and then used; (2) Preparation of organic electrochemical transistor OECT: First, the source and drain gold electrodes are prepared on the PET substrate using a template mask sputtering method; sputtering is carried out on an ion sputtering device; the channel length and width are controlled to be 500 μm and 7000 μm, respectively; the gate is an external Ag / AgCl test; Then, the prepared PEDOT:PSS mixture in step (1) is dropped on the electrode-coated PET substrate, and then heat annealing is carried out, 15 μL of the mixture is dropped on the gold electrode-coated substrate, the dropped thin film is annealed at 50°C for 30 minutes, and then annealed at 120°C for 30 minutes, and the obtained substrate is cleaned by immersing and washing in a mixture of water and ethanol in a volume ratio of 1:3, and the obtained foam structure thin film has a thickness of 1 μm; The high-performance organic electrochemical transistor of the foam structure channel prepared by the method increases the transconductance of the foam structure PEDOT:PSS-based OECT from 90 μS to 18 mS, and the response time is reduced from 1000 milliseconds to 300 milliseconds.

2. The high performance organic electrochemical transistor application of a foam structure channel according to claim 1, characterized in that: It can be used in various flexible wearable fields.

3. The high performance organic electrochemical transistor application of a foam structure channel according to claim 1, characterized in that: It can be used for biological detection or health monitoring.

4. The high performance organic electrochemical transistor application of a foam structure channel according to claim 1, characterized in that: It can be used for detection of H2O2 and glucose.

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