N-type organic semiconductor material modified based on ionic liquid additive and application of n-type organic semiconductor material in organic electrochemical transistor

Abstract

The invention belongs to the technical field of organic electrochemical transistors, and particularly relates to an n-type organic semiconductor material modified based on an ionic liquid additive and application of the n-type organic semiconductor material in an organic electrochemical transistor. According to the invention, the ionic liquid material is doped into the organic n-type organic semiconductor material to prepare the composite n-type semiconductor film, and the interaction between molecules is utilized, so that the excessive aggregation phenomenon of BBL can be effectively relieved, the crystallinity is improved, and meanwhile, the pi-pi stacking distance of a chain segment is reduced, thereby effectively improving the ion electron transmission capability of a device and improving the photoelectric conversion efficiency of the device. An organic electrochemical transistor prepared by adopting the composite n-type semiconductor thin film is stable in performance, the transconductance of the organic electrochemical transistor reaches 9.2 mS or above, the performance is expected to be matched with p-type OECT, and the high performance of expected commercial application is achieved.

Description

Technical Field

[0001] This invention belongs to the field of organic electrochemical transistor technology, specifically relating to an n-type organic semiconductor material modified with ionic liquid additives and its application in organic electrochemical transistors. Background Technology

[0002] Organic electrochemical transistors (OECTs), as an emerging device, are characterized by their core feature of constructing channels based on organic mixed ion-electron conductors (OMIECs). By modulating the migration of ions in the electrolyte through gate voltage, the doping state and carrier concentration of the channel material are altered, ultimately modulating the source and drain currents. These OECTs exhibit significant signal amplification capabilities and good compatibility with aqueous environments. To date, most reported high-performance OECT devices are based on p-type organic semiconductors poly(3,4-ethylenedioxythiophene) / poly(p-phenylene sulfonate) (PEDOT:PSS), while the development of OECTs based on n-type organic semiconductors has been severely hampered by the lack of ideal n-type materials.

[0003] In fact, n-type OMIECs are generally unstable in their surrounding environment, and their low electron affinity limits their redox capabilities in aqueous environments, making their performance far inferior to that of p-type OECT devices. To date, only a few n-type organic semiconductors have been reported to be effectively used as n-channel materials in OECTs. To address these issues, researchers typically employ the synthesis of novel n-type organic semiconductors, but this method is time-consuming, costly, and carries significant uncertainties.

[0004] Poly(benzimidazole-benzophenanthreneroline) (BBL) is a promising organic semiconductor commonly used in n-type OECTs. It is a rigid, ladder-shaped, side-chain-free n-type polymer with inherently high volumetric capacitance. As an emerging n-type conductive polymer, BBL has demonstrated superior stability and impressive electrical properties in OECTs compared to other n-channel materials. However, the electrical properties of BBL are still inferior to those of common p-type conductive polymers, and BBL is prone to over-aggregation during film formation, leading to poor stability.

[0005] Therefore, further optimization of the modified BBL is crucial for improving the performance of n-type OECT. Summary of the Invention

[0006] To address the technical challenges of low carrier mobility, easy aggregation during film formation, and lower electrical performance compared to p-type semiconductors in poly(benzimidazole-benzophenanthreneroline) (BBL), this invention provides an n-type organic semiconductor material modified with ionic liquid additives and its application in organic electrochemical transistors (OECTs). The n-type organic semiconductor material modified with ionic liquid additives possesses advantages such as high volumetric capacitance, high conductivity, high carrier mobility, and good stability. By doping the gold-based n-type organic semiconductor material with ionic liquid, intermolecular interactions effectively alleviate the excessive aggregation of BBL, improve crystallinity, and reduce the π-π stacking distance of the chain segments, thereby effectively enhancing the ion-electron transport capability of the device. Ultimately, this invention achieves a highly efficient and stable n-type OECT with a transconductance of 9.2 mS, and its performance is expected to match that of p-type OECTs.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first aspect of this invention provides a method for preparing an n-type organic semiconductor material modified with ionic liquid additives, the method comprising the following steps: (1) Add the ionic liquid and poly(benzimidazole and benzophenanthrene) to methanesulfonic acid (MSA) solvent and stir to obtain a mixed solution; (2) A solution processing film-forming method is used to form a thin film from the mixed solution; (3) The film is immersed in deionized water to remove the solvent, and then annealed to obtain a composite n-type semiconductor film.

[0008] Further, in step (1), the concentration of the poly(benzimidazole and benzophenanthrene) in the methanesulfonic acid solvent is 5-20 mg / mL.

[0009] Further, in step (1), the ionic liquid is any one of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine ([EMIM][TFSI]), 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine ([BMIM][TFSI]), and 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine ([HMIM][TFSI]), and the volume of the ionic liquid accounts for 1% to 4% of the volume of the mixed solution.

[0010] Furthermore, in step (1), the stirring time is 8-24 hours.

[0011] Furthermore, in step (2), the spin coating speed of the solution processing film method is 500-2000 rpm, and the uniform coating time is 60-120 seconds.

[0012] Furthermore, in step (3), the soaking time is 5 to 20 minutes, the annealing temperature is 150 to 200°C, and the annealing time is 1 to 2 hours.

[0013] A second aspect of the present invention provides an n-type organic semiconductor material modified with ionic liquid additives prepared by the above-described preparation method.

[0014] A third aspect of the present invention provides an application of the above-mentioned n-type organic semiconductor material modified with ionic liquid additives in organic electrochemical transistors.

[0015] A fourth aspect of the present invention provides an organic electrochemical transistor, comprising a substrate, an electrolyte solution, a source electrode and a drain electrode spaced apart, and an organic semiconductor thin film covering the source and drain electrodes, wherein the organic semiconductor thin film is an n-type organic semiconductor material modified with ionic liquid additives prepared by the preparation method according to any one of claims 1 to 6 or an n-type organic semiconductor material modified with ionic liquid additives according to claim 7.

[0016] A fifth aspect of the present invention provides a method for fabricating the above-described organic electrochemical transistor, the method comprising the following steps: 1) By patterning with a mask, titanium and gold are sputtered onto the substrate in sequence to obtain source and drain electrodes with a gap in the middle; 2) Spin-coat the n-type organic semiconductor material modified with ionic liquid additives onto the source and drain surfaces with a gap in between, immerse in deionized water, and then anneal to obtain a composite n-type organic semiconductor thin film. 3) The composite n-type organic semiconductor thin film and the Ag / AgCl electrode are simultaneously inserted into the electrolyte solution to form the organic electrochemical transistor.

[0017] Further, in step 1), the substrate is at least one of glass, polyimide, polyethylene terephthalate, and silicon / silica.

[0018] Further, in step 1), before use, the substrate is first ultrasonically cleaned in DI water, ethanol, isopropanol and acetone respectively, and then subjected to ozone plasma treatment with a power of 140-160 W for 8-15 minutes.

[0019] Further, in step 1), the thicknesses of the titanium and gold are 8-15 nm and 80-120 nm, respectively.

[0020] Furthermore, in step 2), the spin coating speed is 1000 rpm and the uniform coating time is 60 s.

[0021] Furthermore, in step 2), the soaking time in deionized water is 5-20 minutes, the annealing temperature is 200 ℃, and the time is 1 hour.

[0022] Further, in step 3), the electrolyte solution is a PBS solution.

[0023] Compared with the prior art, the beneficial effects of the present invention are: This invention provides an n-type organic semiconductor material modified with ionic liquid additives and its application in organic electrochemical transistors. This invention prepares a composite n-type semiconductor thin film by doping a gold-based organic n-type semiconductor material with an ionic liquid. Utilizing intermolecular interactions, the excessive aggregation of BBLs (Block Blower Black-Layered Electron) can be effectively alleviated, crystallinity improved, and the π-π stacking distance of chain segments reduced, thereby effectively enhancing the ion-electron transport capability of the device. The organic electrochemical transistor prepared using the composite n-type semiconductor thin film of this invention exhibits stable performance with a transconductance exceeding 9.2 mS, and its performance is expected to match that of p-type OECTs, achieving high performance suitable for commercial applications. Specifically, this invention has the following beneficial effects: (1) The present invention is based on the advantages of ionic liquid additives modifying n-type organic semiconductor materials, such as high volume capacitance, high conductivity, high carrier mobility and good stability. The material incorporates ionic liquid into the n-type organic semiconductor material film. By utilizing intermolecular interactions, the excessive aggregation of BBL can be effectively alleviated, crystallinity can be improved, and the π-π stacking distance of chain segments can be reduced, thereby effectively improving the ion electron transport capability of the device. Ultimately, the present invention realizes a highly efficient and stable n-type organic electrochemical transistor.

[0024] (2) The preparation method of n-type organic semiconductor materials modified by ionic liquid additives in this invention is simple, inexpensive and widely applicable.

[0025] (3) The organic electrochemical transistor of the present invention has stable performance and its transconductance reaches more than 9.2mS, which is high performance that is expected to be commercially applied. Attached Figure Description

[0026] Figure 1 This is a schematic diagram of the substrate and source and drain structures of an organic electrochemical transistor, where the yellow part represents the metal electrode and the green part represents the substrate.

[0027] Figure 2 This is a schematic diagram of an electrochemical transistor using n-type organic semiconductor materials modified with ionic liquid additives. In the diagram, Source and Drain are the source and drain electrodes, respectively, Ag / AgCl is the gate electrode, PBS is the electrolyte solution, and BBL / [EMIM][TFSI] is the semiconductor channel.

[0028] Figure 3The diagram shows the channel current-gate voltage (IDS-VG) transfer characteristic curves of the electrochemical transistors prepared in Comparative Examples 1 and Examples 1-4 of this invention.

[0029] Figure 4 The transconductance-gate voltage (gm-VG) curves of the electrochemical transistors prepared in Comparative Examples 1 and Examples 1-4 of this invention are shown.

[0030] Figure 5 This is an atomic force microscope (AFM) image of the ionic liquid-modified n-type organic semiconductor prepared in Example 3 of this invention. Detailed Implementation

[0031] The specific embodiments of the present invention will be further described below. It should be noted that these descriptions are for the purpose of aiding understanding the present invention, but do not constitute a limitation thereof. Furthermore, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0032] Unless otherwise specified, the experimental methods used in the following embodiments are conventional methods, and the experimental materials used in the following embodiments are all available through conventional commercial channels.

[0033] Example 1: Fabrication of an organic electrochemical transistor (1) Fabrication of source and drain electrodes with a gap in between A quartz glass substrate measuring 1.5 × 1.5 cm and approximately 0.1 cm thick was used as the device substrate. It was sequentially subjected to ultrasonic cleaning in four solvents: deionized water (DI water), anhydrous ethanol, isopropanol, and acetone. The ultrasonic treatment time in each solvent was controlled to be 15 minutes to thoroughly remove oil, dust, and other impurities adhering to the substrate surface. After cleaning, the quartz glass substrate was subjected to ozone plasma treatment. During the treatment, the plasma power was set to 150 W and the treatment lasted for 15 minutes.

[0034] Subsequently, titanium and gold layers were sequentially fabricated on the pretreated quartz glass substrate using sputtering deposition. The titanium layer was 10 nm thick, and the gold layer was 100 nm thick, forming the source and drain electrode structures of the device. The channel parameters of the fabricated device were: length 0.2 mm and width 6.0 mm. The specific channel layout is as follows: Figure 1As shown in the schematic diagram, two yellow rectangular electrode structures, each measuring 7 mm (length) × 2.5 mm (width), are distributed on the upper part of the substrate, corresponding to the source and drain electrodes, respectively. Between the two electrodes are two yellow rectangular channel regions, each measuring 11.5 mm (length) × 1 mm (width). The semiconductor thin film to be fabricated will be coated onto the surface of these channel regions using a spin-coating process. The remaining green area of ​​the substrate is the quartz glass substrate itself.

[0035] (2) Preparation of n-type organic semiconductors modified with ionic liquid additives In a nitrogen-atmospheric glove box, 10 mg of BBL was dissolved in 1 mL of MSA, and 1% [EMIM][TFSI] was added as an additive. The mixture was sealed and placed on a 70 °C heating plate with stirring for 12 hours until the BBL powder was completely dissolved, forming a homogeneous, dark-colored mixed solution without obvious particles, ensuring that [EMIM][TFSI] and BB were fully dispersed in the MSA. The mixed solution was then spin-coated onto the substrate surface covered by the source and drain electrodes described in step (1) in a nitrogen-atmospheric glove box. The spin-coating parameters were set to 1000 rpm and the spin coating time was 60 seconds.

[0036] After spin-coating, the sample was immediately immersed in deionized water for 10 minutes to rapidly remove the solvent using the water solubility of MSA. After immersion, the sample was placed on a heating stage at 200 °C for annealing for 1 hour. High-temperature annealing further removed trace amounts of MSA and moisture remaining inside the film and promoted the orderly arrangement of BBL molecular chains and the interfacial interaction between [EMIM][TFSI] and BBL, ultimately forming a modified n-type organic semiconductor film with a smooth surface, good crystallinity, and stable electrical properties.

[0037] (3) Organic electrochemical transistor assembly process After completing the fabrication of the composite n-type organic semiconductor thin film and the pretreatment of the device substrate, the assembly of the organic electrochemical transistor was carried out. The specific process is as follows: First, the previously prepared composite n-type organic semiconductor thin film (which serves as the core channel layer of the device and has been fixed to the surface of the source and drain electrode substrates through spin coating, annealing, and other processes) and the Ag / AgCl reference electrode were placed together in a PBS electrolyte solution. The composite n-type organic semiconductor thin film must ensure that its channel region (the active region between the source and drain electrodes) is completely immersed in the electrolyte solution to guarantee the efficient execution of subsequent ion migration and charge modulation processes. The Ag / AgCl electrode serves as the gate of the device, and its surface must be kept clean and in full contact with the electrolyte solution to avoid affecting the gate voltage regulation effect due to poor interfacial contact.

[0038] Through the above operations, the composite n-type organic semiconductor thin film, source / drain electrodes, Ag / AgCl gate, and electrolyte solution together constitute a complete organic electrochemical transistor structure. A schematic diagram of the structure of an electrochemical transistor based on n-type organic semiconductor materials modified with ionic liquid additives is shown below. Figure 2 As shown, Source and Drain are the source and drain electrodes, respectively, Ag / AgCl is the gate electrode of the device, PBS is the electrolyte solution, and BBL / [EMIM][TFSI] is the semiconductor channel. The electrolyte solution, as an ion transport medium, can drive ions to migrate into the interior of the composite n-type organic semiconductor thin film under the action of the gate voltage, thereby realizing the doping / dedoping state control of the channel material, thereby changing the current between the source and drain electrodes, and finally completing the ion-electron signal conversion function of the transistor.

[0039] Example 2: Fabrication of an organic electrochemical transistor (1) Fabrication of source and drain electrodes with a gap in between A quartz glass substrate measuring 1.5 × 1.5 cm and approximately 0.1 cm thick was used as the device substrate. It was sequentially subjected to ultrasonic cleaning in four solvents: deionized water (DI water), anhydrous ethanol, isopropanol, and acetone. The ultrasonic treatment time in each solvent was controlled to be 15 minutes to thoroughly remove oil, dust, and other impurities adhering to the substrate surface. After cleaning, the quartz glass substrate was subjected to ozone plasma treatment. During the treatment, the plasma power was set to 150 W and the treatment lasted for 15 minutes.

[0040] Subsequently, titanium and gold layers were sequentially fabricated on the pretreated quartz glass substrate using sputtering deposition. The titanium layer was 10 nm thick, and the gold layer was 100 nm thick, forming the source and drain electrode structures of the device. The channel parameters of the fabricated device were: length 0.2 mm and width 6.0 mm. The specific channel layout is as follows: Figure 1 As shown in the schematic diagram, two yellow rectangular electrode structures, each measuring 7 mm (length) × 2.5 mm (width), are distributed on the upper part of the substrate, corresponding to the source and drain electrodes, respectively. Between the two electrodes are two yellow rectangular channel regions, each measuring 11.5 mm (length) × 1 mm (width). The semiconductor thin film to be fabricated will be coated onto the surface of these channel regions using a spin-coating process. The remaining green area of ​​the substrate is the quartz glass substrate itself.

[0041] (2) Preparation of n-type organic semiconductors modified with ionic liquid additives In a nitrogen-atmospheric glove box, 10 mg of BBL was weighed and dissolved in 1 mL of MSA. 2% [EMIM][TFSI] (by volume) was added as an additive. The mixture was sealed and placed on a 70 °C heating plate with stirring for 12 hours until the BBL powder was completely dissolved, forming a homogeneous, dark-colored mixed solution without obvious particles, ensuring that [EMIM][TFSI] and BBL were fully dispersed in the MSA. The mixed solution was then spin-coated onto the substrate surface covered by the source and drain electrodes described in step (1) in a nitrogen-atmospheric glove box. The spin-coating parameters were set to 1000 rpm and the spin coating time to 60 seconds.

[0042] After spin-coating, the sample was immediately immersed in deionized water for 10 minutes to rapidly remove the solvent using the water solubility of MSA. After immersion, the sample was placed on a heating stage at 200 °C for annealing for 1 hour. High-temperature annealing further removed trace amounts of MSA and moisture remaining inside the film and promoted the orderly arrangement of BBL molecular chains and the interfacial interaction between [EMIM][TFSI] and BBL, ultimately forming a modified n-type organic semiconductor film with a smooth surface, good crystallinity, and stable electrical properties.

[0043] (3) Organic electrochemical transistor assembly process After completing the fabrication of the composite n-type organic semiconductor thin film and the pretreatment of the device substrate, the assembly of the organic electrochemical transistor was carried out. The specific process is as follows: First, the previously prepared composite n-type organic semiconductor thin film (which serves as the core channel layer of the device and has been fixed to the surface of the source and drain electrode substrates through spin coating, annealing, and other processes) and the Ag / AgCl reference electrode were placed together in a PBS electrolyte solution. The composite n-type organic semiconductor thin film must ensure that its channel region (the active region between the source and drain electrodes) is completely immersed in the electrolyte solution to guarantee the efficient execution of subsequent ion migration and charge modulation processes. The Ag / AgCl electrode serves as the gate of the device, and its surface must be kept clean and in full contact with the electrolyte solution to avoid affecting the gate voltage regulation effect due to poor interfacial contact.

[0044] Through the above operations, the composite n-type organic semiconductor thin film, source / drain electrodes, Ag / AgCl gate, and electrolyte solution together constitute a complete organic electrochemical transistor structure. A schematic diagram of the structure of an electrochemical transistor based on n-type organic semiconductor materials modified with ionic liquid additives is shown below. Figure 2As shown, Source and Drain are the source and drain electrodes, respectively, Ag / AgCl is the gate electrode of the device, PBS is the electrolyte solution, and BBL / [EMIM][TFSI] is the semiconductor channel. The electrolyte solution, as an ion transport medium, can drive ions to migrate into the interior of the composite n-type organic semiconductor thin film under the action of the gate voltage, thereby realizing the doping / dedoping state control of the channel material, thereby changing the current between the source and drain electrodes, and finally completing the ion-electron signal conversion function of the transistor.

[0045] Example 3: Fabrication of an organic electrochemical transistor (1) Fabrication of source and drain electrodes with a gap in between A quartz glass substrate measuring 1.5 × 1.5 cm and approximately 0.1 cm thick was used as the device substrate. It was sequentially subjected to ultrasonic cleaning in four solvents: deionized water (DI water), anhydrous ethanol, isopropanol, and acetone. The ultrasonic treatment time in each solvent was controlled to be 15 minutes to thoroughly remove oil, dust, and other impurities adhering to the substrate surface. After cleaning, the quartz glass substrate was subjected to ozone plasma treatment. During the treatment, the plasma power was set to 150 W and the treatment lasted for 15 minutes.

[0046] Subsequently, titanium and gold layers were sequentially fabricated on the pretreated quartz glass substrate using sputtering deposition. The titanium layer was 10 nm thick, and the gold layer was 100 nm thick, forming the source and drain electrode structures of the device. The channel parameters of the fabricated device were: length 0.2 mm and width 6.0 mm. The specific channel layout is as follows: Figure 1 As shown in the schematic diagram, two yellow rectangular electrode structures, each measuring 7 mm (length) × 2.5 mm (width), are distributed on the upper part of the substrate, corresponding to the source and drain electrodes, respectively. Between the two electrodes are two yellow rectangular channel regions, each measuring 11.5 mm (length) × 1 mm (width). The semiconductor thin film to be fabricated will be coated onto the surface of these channel regions using a spin-coating process. The remaining green area of ​​the substrate is the quartz glass substrate itself.

[0047] (2) Preparation of n-type organic semiconductors modified with ionic liquid additives In a nitrogen-atmospheric glove box, 10 mg of BBL was weighed and dissolved in 1 mL of MSA. 3% [EMIM][TFSI] (by volume) was added as an additive. The mixture was sealed and placed on a 70 °C heating plate with stirring for 12 hours until the BBL powder was completely dissolved, forming a homogeneous, dark-colored mixed solution without obvious particles, ensuring that [EMIM][TFSI] and BBL were fully dispersed in the MSA. The mixed solution was then spin-coated onto the substrate surface covered by the source and drain electrodes described in step (1) in a nitrogen-atmospheric glove box. The spin-coating parameters were set to 1000 rpm and the spin coating time to 60 seconds.

[0048] After spin-coating, the film was immediately immersed in deionized water for 10 minutes to rapidly remove the solvent using the water solubility of MSA. After immersion, the sample was annealed on a 200 °C heating stage for 1 hour. High-temperature annealing further removed trace amounts of residual MSA and moisture from the film and promoted the ordered arrangement of BBL molecular chains and the interfacial interaction between [EMIM][TFSI] and BBL, ultimately forming a modified n-type organic semiconductor film with a smooth surface, good crystallinity, and stable electrical properties. Atomic force microscopy (AFM) images are shown below. Figure 5 As shown.

[0049] (3) Organic electrochemical transistor assembly process After completing the fabrication of the composite n-type organic semiconductor thin film and the pretreatment of the device substrate, the assembly of the organic electrochemical transistor was carried out. The specific process is as follows: First, the previously prepared composite n-type organic semiconductor thin film (which serves as the core channel layer of the device and has been fixed to the surface of the source and drain electrode substrates through spin coating, annealing, and other processes) and the Ag / AgCl reference electrode were placed together in a PBS electrolyte solution. The composite n-type organic semiconductor thin film must ensure that its channel region (the active region between the source and drain electrodes) is completely immersed in the electrolyte solution to guarantee the efficient execution of subsequent ion migration and charge modulation processes. The Ag / AgCl electrode serves as the gate of the device, and its surface must be kept clean and in full contact with the electrolyte solution to avoid affecting the gate voltage regulation effect due to poor interfacial contact.

[0050] Through the above operations, the composite n-type organic semiconductor thin film, source / drain electrodes, Ag / AgCl gate, and electrolyte solution together constitute a complete organic electrochemical transistor structure. A schematic diagram of the structure of an electrochemical transistor based on n-type organic semiconductor materials modified with ionic liquid additives is shown below. Figure 2 As shown, Source and Drain are the source and drain electrodes, respectively, Ag / AgCl is the gate electrode of the device, PBS is the electrolyte solution, and BBL / [EMIM][TFSI] is the semiconductor channel. The electrolyte solution, as an ion transport medium, can drive ions to migrate into the interior of the composite n-type organic semiconductor thin film under the action of the gate voltage, thereby realizing the doping / dedoping state control of the channel material, thereby changing the current between the source and drain electrodes, and finally completing the ion-electron signal conversion function of the transistor.

[0051] Example 4: Fabrication of an organic electrochemical transistor (1) Fabrication of source and drain electrodes with a gap in between A quartz glass substrate measuring 1.5 × 1.5 cm and approximately 0.1 cm thick was used as the device substrate. It was sequentially subjected to ultrasonic cleaning in four solvents: deionized water (DI water), anhydrous ethanol, isopropanol, and acetone. The ultrasonic treatment time in each solvent was controlled to be 15 minutes to thoroughly remove oil, dust, and other impurities adhering to the substrate surface. After cleaning, the quartz glass substrate was subjected to ozone plasma treatment. During the treatment, the plasma power was set to 150 W and the treatment lasted for 15 minutes.

[0052] Subsequently, titanium and gold layers were sequentially fabricated on the pretreated quartz glass substrate using sputtering deposition. The titanium layer was 10 nm thick, and the gold layer was 100 nm thick, forming the source and drain electrode structures of the device. The channel parameters of the fabricated device were: length 0.2 mm and width 6.0 mm. The specific channel layout is as follows: Figure 1 As shown in the schematic diagram, two yellow rectangular electrode structures, each measuring 7 mm (length) × 2.5 mm (width), are distributed on the upper part of the substrate, corresponding to the source and drain electrodes, respectively. Between the two electrodes are two yellow rectangular channel regions, each measuring 11.5 mm (length) × 1 mm (width). The semiconductor thin film to be fabricated will be coated onto the surface of these channel regions using a spin-coating process. The remaining green area of ​​the substrate is the quartz glass substrate itself.

[0053] (2) Preparation of n-type organic semiconductors modified with ionic liquid additives In a nitrogen-atmospheric glove box, 10 mg of BBL was weighed and dissolved in 1 mL of MSA. 4% [EMIM][TFSI] (by volume) was added as an additive. The mixture was sealed and placed on a 70 °C heating plate with stirring for 12 hours until the BBL powder was completely dissolved, forming a homogeneous, dark-colored mixed solution without obvious particles, ensuring that [EMIM][TFSI] and BBL were fully dispersed in the MSA. The mixed solution was then spin-coated onto the substrate surface covered by the source and drain electrodes described in step (1) in a nitrogen-atmospheric glove box. The spin-coating parameters were set to 1000 rpm and the spin coating time to 60 seconds.

[0054] After spin-coating, the sample was immediately immersed in deionized water for 10 minutes to rapidly remove the solvent using the water solubility of MSA. After immersion, the sample was placed on a heating stage at 200 °C for annealing for 1 hour. High-temperature annealing further removed trace amounts of MSA and moisture remaining inside the film and promoted the orderly arrangement of BBL molecular chains and the interfacial interaction between [EMIM][TFSI] and BBL, ultimately forming a modified n-type organic semiconductor film with a smooth surface, good crystallinity, and stable electrical properties.

[0055] (3) Organic electrochemical transistor assembly process After completing the fabrication of the composite n-type organic semiconductor thin film and the pretreatment of the device substrate, the assembly of the organic electrochemical transistor was carried out. The specific process is as follows: First, the previously prepared composite n-type organic semiconductor thin film (which serves as the core channel layer of the device and has been fixed to the surface of the source and drain electrode substrates through spin coating, annealing, and other processes) and the Ag / AgCl reference electrode were placed together in a PBS electrolyte solution. The composite n-type organic semiconductor thin film must ensure that its channel region (the active region between the source and drain electrodes) is completely immersed in the electrolyte solution to guarantee the efficient execution of subsequent ion migration and charge modulation processes. The Ag / AgCl electrode serves as the gate of the device, and its surface must be kept clean and in full contact with the electrolyte solution to avoid affecting the gate voltage regulation effect due to poor interfacial contact.

[0056] Through the above operations, the composite n-type organic semiconductor thin film, source / drain electrodes, Ag / AgCl gate, and electrolyte solution together constitute a complete organic electrochemical transistor structure. A schematic diagram of the structure of an electrochemical transistor based on n-type organic semiconductor materials modified with ionic liquid additives is shown below. Figure 2 As shown, Source and Drain are the source and drain electrodes, respectively, Ag / AgCl is the gate electrode of the device, PBS is the electrolyte solution, and BBL / [EMIM][TFSI] is the semiconductor channel. The electrolyte solution, as an ion transport medium, can drive ions to migrate into the interior of the composite n-type organic semiconductor thin film under the action of the gate voltage, thereby realizing the doping / dedoping state control of the channel material, thereby changing the current between the source and drain electrodes, and finally completing the ion-electron signal conversion function of the transistor.

[0057] Comparative Example 1: Fabrication of Organic Electrochemical Transistors (1) Fabrication of source and drain electrodes with a gap in between A quartz glass substrate measuring 1.5 × 1.5 cm and approximately 0.1 cm thick was used as the device substrate. It was sequentially subjected to ultrasonic cleaning in four solvents: deionized water (DI water), anhydrous ethanol, isopropanol, and acetone. The ultrasonic treatment time in each solvent was controlled to be 15 minutes to thoroughly remove oil, dust, and other impurities adhering to the substrate surface. After cleaning, the quartz glass substrate was subjected to ozone plasma treatment. During the treatment, the plasma power was set to 150 W and the treatment lasted for 15 minutes.

[0058] Subsequently, titanium and gold layers were sequentially fabricated on the pretreated quartz glass substrate using sputtering deposition. The titanium layer was 10 nm thick, and the gold layer was 100 nm thick, forming the source and drain electrode structures of the device. The channel parameters of the fabricated device were: length 0.2 mm and width 6.0 mm. The specific channel layout is as follows: Figure 1As shown in the schematic diagram, two yellow rectangular electrode structures, each measuring 7 mm (length) × 2.5 mm (width), are distributed on the upper part of the substrate, corresponding to the source and drain electrodes, respectively. Between the two electrodes are two yellow rectangular channel regions, each measuring 11.5 mm (length) × 1 mm (width). The semiconductor thin film to be fabricated will be coated onto the surface of these channel regions using a spin-coating process. The remaining green area of ​​the substrate is the quartz glass substrate itself.

[0059] (2) Preparation of n-type organic semiconductors modified with ionic liquid additives In a nitrogen-atmospheric glove box, 10 mg of BBL was weighed and dissolved in 1 mL of MSA. The mixture was sealed and placed on a 70 °C heating plate with stirring for 12 hours until the BBL powder was completely dissolved, forming a homogeneous, dark-colored mixed solution without obvious particles. The mixed solution was then spin-coated onto the substrate surface covered by the source and drain electrodes described in step (1) in a nitrogen-atmospheric glove box. The spin-coating parameters were set to 1000 rpm and the spin coating time was 60 seconds.

[0060] After spin-coating, the sample is immediately immersed in deionized water for 10 minutes to rapidly remove the solvent using the water solubility of MSA. After immersion, the sample is placed on a heating stage at 200 °C for annealing for 1 hour. High-temperature annealing removes trace amounts of residual MSA and moisture from the film, forming an n-type organic semiconductor film.

[0061] (3) Organic electrochemical transistor assembly process After completing the fabrication of the n-type organic semiconductor thin film and the pretreatment of the device substrate, the assembly of the organic electrochemical transistor was carried out. The specific process is as follows: First, the previously prepared n-type organic semiconductor thin film (which serves as the core channel layer of the device and has been fixed to the surface of the source and drain electrode substrates through spin coating, annealing, and other processes) and the Ag / AgCl reference electrode were placed together in a PBS electrolyte solution. The n-type organic semiconductor thin film must ensure that its channel region (the active region between the source and drain electrodes) is completely immersed in the electrolyte solution to guarantee the efficient execution of subsequent ion migration and charge modulation processes. The Ag / AgCl electrode serves as the gate of the device, and its surface must be kept clean and in full contact with the electrolyte solution to avoid affecting the gate voltage regulation effect due to poor interfacial contact.

[0062] Through the above operations, the n-type organic semiconductor thin film, source / drain electrodes, Ag / AgCl gate, and electrolyte solution together constitute a complete organic electrochemical transistor structure: the electrolyte solution, as an ion transport medium, can drive ions to migrate into the n-type organic semiconductor thin film under the action of the gate voltage, realize the doping / dedoping state control of the channel material, thereby changing the current between the source and drain electrodes, and finally completing the ion-electron signal conversion function of the transistor.

[0063] Test Example 1: Performance Testing of Organic Electrochemical Transistors The electrical performance of the organic electrochemical transistor was tested at room temperature using a Keithley 2400 semiconductor parameter analyzer. The transfer characteristic curves of the samples during the test are shown below. Figure 3 As shown, the calculated transconductance curve of the device is as follows. Figure 4 As shown. The electrolyte used in the test was PBS solution, the gate voltage range was from 0 to 1V, and the source-drain voltage was fixed at 0.5V. Furthermore, the volumetric capacitance of the device channel material could be extracted by electrochemical impedance spectroscopy (EIS). According to the analysis, the maximum on-state current (IDS,max), maximum transconductance (gm,max), carrier mobility (μ), and volumetric capacitance (gm,max) of the measured device were obtained. As shown in Table 1 below.

[0064] Table 1 Group [EMIM][TFSI] solution volume percentage of the solvent in the composite solution (%) <![CDATA[I DS, max (mA)]]> <![CDATA[g m, max (mS)]]> <![CDATA[μ(×10 -3 cm 2 V -1 s -1 )]]> <![CDATA[C*(F cm -3 )]]> Comparative Example 1 0 1.92 3.41 75.69 642 Example 4 4 6.65 8.24 76.23 755 Example 3 3 7.66 9.26 76.65 760 Example 2 2 4.35 6.73 75.68 738 Example 1 1 2.78 5.25 75.27 667 It can be seen that the organic electrochemical transistors prepared using the composite n-type semiconductor thin film of the present invention have stable performance and a transconductance of over 9.2 mS. Their performance is expected to match that of p-type OECTs, achieving high performance that is expected to be commercially viable.

[0065] The embodiments of the present invention have been described in detail above, but the present invention is not limited to the described embodiments. For those skilled in the art, various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention, and these variations still fall within the protection scope of the present invention.

Claims

1. A method for preparing an n-type organic semiconductor material modified with ionic liquid additives, characterized in that, The preparation method includes the following steps: (1) Add the ionic liquid and poly(benzimidazole and benzophenanthrene) to methanesulfonic acid solvent and stir to obtain a mixed solution; (2) A solution processing film-forming method is used to form a thin film from the mixed solution; (3) The film is immersed in deionized water to remove the solvent, and then annealed to obtain a composite n-type semiconductor film.

2. The method for preparing an n-type organic semiconductor material modified with ionic liquid additives according to claim 1, characterized in that, In step (1), the concentration of the poly(benzimidazole and benzophenanthrene) in the methanesulfonic acid solvent is 5-20 mg / mL.

3. The method for preparing an n-type organic semiconductor material modified with ionic liquid additives according to claim 1, characterized in that, In step (1), the ionic liquid is any one of 1-ethyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine, 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine, and 1-hexyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imine, and the volume of the ionic liquid accounts for 1% to 4% of the volume of the mixed solution.

4. The method for preparing an n-type organic semiconductor material modified with ionic liquid additives according to claim 1, characterized in that, In step (1), the stirring time is 8-24 hours.

5. The method for preparing an n-type organic semiconductor material modified with ionic liquid additives according to claim 1, characterized in that, In step (2), the spin coating speed of the solution processing film method is 500-2000 rpm, and the uniform coating time is 60-120 seconds.

6. The method for preparing an n-type organic semiconductor material modified with ionic liquid additives according to claim 1, characterized in that, In step (3), the soaking time is 5 to 20 minutes, the annealing temperature is 150 to 200°C, and the annealing time is 1 to 2 hours.

7. An n-type organic semiconductor material modified with ionic liquid additives, prepared by the preparation method according to any one of claims 1 to 6.

8. The application of an n-type organic semiconductor material modified with ionic liquid additives as described in claim 7 in an organic electrochemical transistor.

9. An organic electrochemical transistor, characterized in that, The invention includes a substrate, an electrolyte solution, a source and a drain electrode spaced apart, and an organic semiconductor thin film covering the source and drain electrodes. The organic semiconductor thin film is an n-type organic semiconductor material modified with ionic liquid additives prepared by the preparation method according to any one of claims 1 to 6, or an n-type organic semiconductor material modified with ionic liquid additives according to claim 7.

10. A method for fabricating an organic electrochemical transistor as described in claim 9, characterized in that, The preparation method includes the following steps: 1) By patterning with a mask, titanium and gold are sputtered onto the substrate in sequence to obtain source and drain electrodes with a gap in the middle; 2) Spin-coat the n-type organic semiconductor material modified with ionic liquid additives prepared by the preparation method according to any one of claims 1 to 6 or the n-type organic semiconductor material modified with ionic liquid additives according to claim 7 onto the source and drain surfaces with a gap in the middle, immerse in deionized water, and then anneal to obtain a composite n-type organic semiconductor thin film. 3) The composite n-type organic semiconductor thin film and the Ag / AgCl electrode are simultaneously inserted into the electrolyte solution to form the organic electrochemical transistor.

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