Preparation method of two-dimensional organic semiconductor single crystal thin film and organic field-effect transistor

Abstract

The present invention provides a method for preparing a two-dimensional organic semiconductor single crystal thin film and an organic field-effect transistor. The preparation method comprises: forming an insulating layer on an n-type SiO2 / Si substrate to obtain a substrate; placing the substrate on a substrate of a doctor blade, and making the distance between the substrate and a doctor blade located above the substrate a preset distance; applying a preset mixed solution to the gap between the substrate and the doctor blade, the preset mixed solution being a mixed solution of a preset solution and polyethylene glycol octylphenyl ether, the preset solution being a solution of C8-BTBT dissolved in a preset organic solvent; controlling the doctor blade to move at a preset speed so that the curved liquid surface formed near the gap is rapidly crystallized under the guidance of the doctor blade, thereby forming a two-dimensional C8-BTBT organic semiconductor single crystal thin film. The prepared two-dimensional C8-BTBT organic semiconductor single crystal thin film has few grain boundaries and defects and a high mobility, which is sufficient to realize many applications, such as active matrix, organic light-emitting diodes, sensors, and amplifier circuits.

Description

Technical Field

[0001] The present invention relates to the technical field of preparation of organic semiconductor films, and in particular to a preparation method of a two-dimensional organic semiconductor single crystal film, an organic field effect transistor and a NAND gate circuit. Background Art

[0002] Two-dimensional organic semiconductor thin films are characterized by a single or few layers in the stack, with lateral dimensions exceeding millimeter scales through weak van der Waals interactions that enable molecular assembly. Consequently, these thin films exhibit advantages such as excellent thickness uniformity, perfect lateral continuity, and long-range molecular order. They can serve as semiconductor active layers in photovoltaic devices, nanoscale lasers, organic light-emitting diodes, and organic field-effect transistors. The active layer of organic field-effect transistors, in particular, has a wide range of applications, including flat-panel display drivers, radio frequency identification tags, sensors, and integrated circuits.

[0003] Currently, the main methods for preparing two-dimensional organic semiconductor thin films include template-induced self-assembly, inkjet printing, water-surface drag coating, and doctor blade coating. Template-induced self-assembly and inkjet printing rely primarily on crystal self-assembly. However, organic crystals interact with each other through weak van der Waals forces, making large-scale self-assembly difficult. Consequently, the resulting crystals are mostly small, on the millimeter scale, making it difficult to fabricate large-scale two-dimensional organic semiconductor thin films. The water-surface drag coating method, on the other hand, uses a water surface as a substrate and exploits the Marangoni effect, where organic solutions spread spontaneously on the surface, to enhance the lateral growth of organic crystals. This significantly increases the size of single-crystal domains and enables the large-scale fabrication of two-dimensional organic semiconductor thin films. However, this method is relatively complex and has low production efficiency. Doctor blade coating, due to its compatibility with continuous, high-throughput manufacturing techniques, offers promising applications for producing large-scale organic semiconductor thin films. However, the unidirectional induction effect of currently reported doctor blade coating methods often results in one-dimensional ribbon-like growth of organic semiconductors, which contains numerous grain boundaries and defects and is highly unfavorable for charge transport. Summary of the Invention

[0004] One object of the present invention is to provide a two-dimensional organic semiconductor thin film that has a simple process, few grain boundaries and defects, and can be produced on a large scale.

[0005] A further object of the present invention is to increase the scraping speed and further improve the mobility of the two-dimensional organic semiconductor thin film.

[0006] In particular, the present invention provides a method for preparing a two-dimensional organic semiconductor single crystal thin film, comprising the following steps:

[0007] forming an insulating layer on an n-type SiO2 / Si substrate to obtain a substrate;

[0008] Placing the substrate on a base plate of a doctor blade coating machine so that the distance between the substrate and the doctor blade located above the substrate is a preset distance;

[0009] Applying a preset mixed solution to the gap between the substrate and the scraper, wherein the preset mixed solution is a mixed solution of a preset solution and polyethylene glycol octylphenyl ether, and the preset solution is a solution of C8-BTBT dissolved in a preset organic solvent;

[0010] The scraper is controlled to move at a preset speed so that the curved liquid surface formed near the gap is rapidly crystallized under the guidance of the scraper, thereby forming a two-dimensional C8-BTBT organic semiconductor single crystal thin film.

[0011] Optionally, in the step of placing the substrate on a base plate of a doctor blade coating machine and making the distance between the substrate and the doctor blade located above the substrate a preset distance, the preset distance is any value in the range of 0.3-0.7 mm;

[0012] Optionally, the temperature of the substrate is 20-30°C.

[0013] Optionally, in the step of applying a preset mixed solution to the gap between the substrate and the scraper, the preset mixed solution is a mixed solution of a preset solution and polyethylene glycol octylphenyl ether, and the preset solution is a solution in which C8-BTBT is dissolved in a preset organic solvent. The preset organic solvent is selected to be an organic solvent that does not react with the polyethylene glycol octylphenyl ether and has a boiling point in the range of 105-115°C.

[0014] Optionally, in the step of applying a preset mixed solution to the gap between the substrate and the scraper, the preset mixed solution is a mixed solution of a preset solution and polyethylene glycol octylphenyl ether, and the preset solution is a solution of C8-BTBT dissolved in a preset organic solvent, and the mass ratio of the preset solution to the polyethylene glycol octylphenyl ether is any value in the range of 7-9:1.

[0015] Optionally, the density of the preset solution is 8-12 mg / ml, and the volume of the preset solution applied is 3-4 μL;

[0016] Optionally, the angle between the scraper and the substrate is any value in the range of 15-50°.

[0017] Optionally, in the step of controlling the scraper to move at a preset speed so that the curved liquid surface formed near the gap crystallizes rapidly under the guidance of the scraper, thereby forming a two-dimensional C8-BTBT organic semiconductor single crystal film, the preset speed is any value in the range of 1.1-1.3 mm / s.

[0018] Optionally, the step of forming an insulating layer on an n-type SiO2 / Si substrate to obtain a substrate comprises the following steps:

[0019] Place the cleaned n-type SiO2 / Si substrate on a spin coater;

[0020] An insulating layer material is spin-coated on the n-type SiO 2 / Si substrate to prepare an insulating layer on the n-type SiO 2 / Si substrate. The insulating layer material is selected to be a material with few surface defects that can be used as an insulating layer.

[0021] Optionally, the step of spin-coating an insulating layer material on the n-type SiO2 / Si substrate to form an insulating layer on the n-type SiO2 / Si substrate comprises the following steps:

[0022] Spin coating an insulating layer material on the n-type SiO2 / Si substrate at a first preset rotation speed for a first preset time;

[0023] Continuing the spin coating at a second preset speed for a second preset time, the second preset speed being greater than the first preset speed;

[0024] heating at a first predetermined temperature to remove residual solvent;

[0025] Heating at a second preset temperature for cross-linking and curing, wherein the second preset temperature is greater than the first preset temperature;

[0026] Optionally, the first preset speed is any value in the range of 300-600 rpm, the first preset time is any value in the range of 5-10 s, the second preset speed is any value in the range of 2500-3500 rpm, and the second preset time is any value in the range of 15-25 s;

[0027] Optionally, the first preset temperature is any value in the range of 130-220°C, and the second preset temperature is any value in the range of 260-280°C.

[0028] In particular, the present invention provides a method for preparing an organic field effect transistor comprising the following steps:

[0029] A two-dimensional C8-BTBT organic semiconductor single crystal thin film was prepared using the aforementioned preparation method;

[0030] fixing a metal mask on the surface of the two-dimensional C8-BTBT organic semiconductor single crystal thin film;

[0031] Thermal evaporation is used to deposit 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanodimethyl-p-benzoquinone and silver, and a conductive channel is produced.

[0032] In particular, the present invention provides a method for preparing a NAND gate circuit, comprising the following steps:

[0033] patterning the gate;

[0034] Patterning SU-8 to form a dielectric layer having a hole with a predetermined area, and positioning the hole above the gate;

[0035] A two-dimensional C8-BTBT organic semiconductor single crystal thin film was prepared using the aforementioned preparation method;

[0036] Evaporate source and drain materials.

[0037] According to the solution of the embodiment of the present invention, by making the distance between the substrate and the scraper a preset distance, a gap is formed between the substrate and the scraper, and then a preset mixed solution is applied in the gap, and the preset mixed solution is selected as a mixed solution of a preset solution and polyethylene glycol octylphenyl ether, and the preset solution is a solution of C8-BTBT dissolved in a preset organic solvent, and then the scraper is controlled to move at a preset speed, so that a curved liquid surface can be formed near the gap, and under the guidance of the scraper, it is rapidly crystallized to form a two-dimensional C8-BTBT organic semiconductor single crystal thin film. The prepared two-dimensional C8-BTBT organic semiconductor single crystal thin film has few grain boundaries and defects and a high mobility, which is sufficient to realize many applications, such as active matrix, organic light-emitting diodes, sensors and amplifier circuits. In addition, the preparation method can realize the preparation of two-dimensional C8-BTBT organic semiconductor single crystal thin films at a higher scraping speed. The key is to enhance the lateral transmission during the scraping process by using the Marangoni effect induced by the surfactant.

[0038] In some further embodiments, the mobility of the two-dimensional C8-BTBT organic semiconductor single crystal film prepared by the method of the present invention is greater than 10 square centimeters per volt per second, which far exceeds the commercial amorphous silicon (a-Si) with a mobility of 0.5-1 square centimeters per volt per second.

[0039] Based on the following detailed description of specific embodiments of the present invention in conjunction with the accompanying drawings, those skilled in the art will become more aware of the above and other objects, advantages and features of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0040] Hereinafter, some specific embodiments of the present invention will be described in detail in an exemplary and non-limiting manner with reference to the accompanying drawings. The same reference numerals in the accompanying drawings indicate the same or similar components or parts. It should be understood by those skilled in the art that these drawings are not necessarily drawn to scale. In the accompanying drawings:

[0041] Figure 1A schematic flow chart of a method for preparing a two-dimensional organic semiconductor single crystal thin film according to one embodiment of the present invention is shown;

[0042] Figure 2 A schematic flow chart illustrating steps of spin coating an insulating layer material on an n-type SiO2 / Si substrate to form an insulating layer on the n-type SiO2 / Si substrate according to one embodiment of the present invention is shown;

[0043] Figure 3 shows a polarization diagram of a two-dimensional C8-BTBT organic semiconductor single crystal film at 45° according to one embodiment of the present invention;

[0044] Figure 4 shows a polarization diagram of a two-dimensional C8-BTBT organic semiconductor single crystal film at 0° according to one embodiment of the present invention;

[0045] Figure 5 shows the UV-visible absorption spectrum of a two-dimensional C8-BTBT organic semiconductor single crystal thin film according to one embodiment of the present invention;

[0046] Figure 6 A schematic diagram of differential scanning calorimetry of a two-dimensional C8-BTBT organic semiconductor single crystal thin film according to one embodiment of the present invention is shown;

[0047] Figure 7 shows the polarization image of the C8-BTBT crystal prepared in the control experiment;

[0048] Figure 8 shows an atomic force microscope image of the C8-BTBT crystal prepared in the control experiment;

[0049] Figure 9 A schematic diagram of the mechanism of the one-dimensional ribbon-shaped C8-BTBT crystal prepared in the control experiment is shown;

[0050] Figure 10 shows a polarization diagram of a C8-BTBT crystal prepared according to one embodiment of the present invention;

[0051] Figure 11 An atomic force microscope image of a C8-BTBT crystal prepared according to one embodiment of the present invention is shown;

[0052] Figure 12 A schematic diagram of the mechanism of the two-dimensional C8-BTBT film prepared according to the present invention is shown;

[0053] Figure 13 shows an in-plane X-ray diffraction analysis diagram of a C8-BTBT crystal prepared according to one embodiment of the present invention;

[0054] Figure 14 shows an out-of-plane X-ray diffraction analysis diagram of a C8-BTBT crystal prepared according to one embodiment of the present invention;

[0055] Figure 15 A method for preparing an organic field effect transistor according to an embodiment of the present invention is shown;

[0056] Figure 16 shows a transfer characteristic curve of an organic field effect transistor prepared according to one embodiment of the present invention;

[0057] Figure 17 shows an output characteristic curve of an organic field effect transistor prepared according to one embodiment of the present invention;

[0058] Figure 18 A diagram showing a NAND gate logic circuit according to an embodiment of the present invention;

[0059] Figure 19 A microscope image of a NAND gate logic circuit according to an embodiment of the present invention is shown;

[0060] Figure 20 A microscope image of a single NAND gate logic circuit according to one embodiment of the present invention is shown;

[0061] Figure 21 shows an input-output voltage diagram of a NAND gate logic circuit according to an embodiment of the present invention;

[0062] Figure 22 shows a curve diagram of voltage variation over time of a NAND gate logic circuit according to an embodiment of the present invention;

[0063] Figure 23 A schematic flow chart of a method for preparing a NAND gate circuit according to an embodiment of the present invention is shown. DETAILED DESCRIPTION

[0064] Figure 1 FIG1 shows a schematic flow chart of a method for preparing a two-dimensional organic semiconductor single crystal thin film according to an embodiment of the present invention. Figure 1 As shown, the preparation method comprises:

[0065] Step S100, forming an insulating layer on an n-type SiO2 / Si substrate to obtain a substrate;

[0066] Step S200, placing a substrate on a base plate of a doctor blade coating machine, and making the distance between the substrate and a doctor blade located above the substrate a preset distance;

[0067] Step S300 , applying a predetermined mixed solution to the gap between the substrate and the scraper, wherein the predetermined mixed solution is a mixture of the predetermined solution and polyethylene glycol octylphenyl ether (Triton X-100), wherein the predetermined solution is a solution of C8-BTBT dissolved in a predetermined organic solvent;

[0068] In step S400 , the scraper is controlled to move at a preset speed so that the curved liquid surface formed near the gap is rapidly crystallized under the guidance of the scraper, thereby forming a two-dimensional C8-BTBT organic semiconductor single crystal thin film.

[0069] According to the solution of the embodiment of the present invention, by making the distance between the substrate and the scraper a preset distance, a gap is formed between the substrate and the scraper, and then a preset mixed solution is applied in the gap, and the preset mixed solution is selected as a mixed solution of a preset solution and polyethylene glycol octylphenyl ether, and the preset solution is a solution of C8-BTBT dissolved in a preset organic solvent, and then the scraper is controlled to move at a preset speed, so that a curved liquid surface can be formed near the gap, and under the guidance of the scraper, it is rapidly crystallized to form a two-dimensional C8-BTBT organic semiconductor single crystal thin film. The prepared two-dimensional C8-BTBT organic semiconductor single crystal thin film has few grain boundaries and defects and a high mobility, which is sufficient to realize many applications, such as active matrix, organic light-emitting diodes, sensors and amplifier circuits. In addition, the preparation method can realize the preparation of two-dimensional C8-BTBT organic semiconductor single crystal thin films at a higher scraping speed. The key is to enhance the lateral transmission during the scraping process by using the Marangoni effect induced by the surfactant.

[0070] In step S100, the insulating layer has a higher surface flatness than the n-type SiO2 / Si substrate and has fewer surface defects. The insulating layer is made of a material with fewer surface defects and capable of completely spreading the solution, such as benzocyclobutene (BCB), polyvinyl pyrrolidone (PVP), or polyvinyl chloride (PVC). Fewer surface defects facilitate carrier transport in the subsequently fabricated organic field-effect transistor, while completely spreading the solution facilitates solvent evaporation during the coating process, resulting in a faster crystallization rate and higher quality of the C8-BTBT. In some embodiments, step S100 includes the following steps: placing a cleaned n-type SiO2 / Si substrate on a spin coater; and spin-coating the insulating layer material onto the n-type SiO2 / Si substrate to form an insulating layer on the n-type SiO2 / Si substrate. The insulating layer is made of a material with fewer surface defects and capable of serving as an insulating layer.

[0071] In one embodiment, the n-type SiO2 / Si substrate is a highly doped n-type SiO2 / Si substrate. There are many methods for cleaning the n-type SiO2 / Si substrate, as long as the n-type SiO2 / Si substrate can be cleaned, an embodiment of the present invention provides a cleaning method for an n-type SiO2 / Si substrate. First, the n-type SiO2 / Si substrate is immersed in concentrated sulfuric acid at 90°C for 2 hours, and then ultrasonically cleaned in acetone, isopropanol and deionized water for 10 minutes each, dried with a nitrogen flow, and then further treated with an oxygen plasma cleaner at 100W for 300 seconds. The various parameters in the cleaning method are not limited to this, and only preferred embodiments are listed here.

[0072] In one embodiment, in the step of spin-coating an insulating layer material on an n-type SiO2 / Si substrate, the insulating layer material is BCB. This step is preceded by the step of preparing a solution of the insulating layer material. The step of preparing the insulating layer solution comprises: preparing a solution of BCB and mesitylene at a volume ratio of 1:5-20, and stirring for 2-4 hours to achieve uniform mixing.

[0073] Figure 2 A schematic flow chart of the steps of spin coating an insulating layer material on an n-type SiO2 / Si substrate to form an insulating layer on the n-type SiO2 / Si substrate according to one embodiment of the present invention is shown. The steps include:

[0074] Step S110, spin coating an insulating layer material on an n-type SiO2 / Si substrate at a first preset rotation speed for a first preset time;

[0075] Step S120, continuing the spin coating at a second preset speed for a second preset time, where the second preset speed is greater than the first preset speed;

[0076] Step S130, heating at a first preset temperature to remove residual solvent;

[0077] Step S140 , heating at a second preset temperature for cross-linking and curing, where the second preset temperature is greater than the first preset temperature.

[0078] In step S110, the first preset speed may be, for example, 300 rpm, 400 rpm, 500 rpm, or 600 rpm, or any other value within the range of 300-600 rpm. The first preset time may be, for example, 5 s, 6 s, 7 s, 8 s, 9 s, or 10 s, or any other value within the range of 5-10 s. In step S120, the second preset speed may be, for example, 2500 rpm, 2800 rpm, 3000 rpm, 3200 rpm, or 3500 rpm, or any other value within the range of 2500-3500 rpm. The second preset time may be, for example, 15 s, 18 s, 20 s, 22 s, or 25 s, or any other value within the range of 15-25 s. In step S130, the first preset temperature can be, for example, 130°C, 140°C, 160°C, 180°C, 200°C or 220°C, or any other value in the range of 130-220°C. In step S130, heating can be performed at the first preset temperature for, for example, 20 minutes, 30 minutes or 40 minutes, or any other time value in the range of 20-40 minutes. In step S140, the second preset temperature can be, for example, 260°C, 270°C or 280°C, or any other value in the range of 260-280°C. In step S140, heating can be performed at the second preset temperature for, for example, 2 hours, 3 hours, 4 hours or 5 hours, or any other value in the range of 2-5 hours. In an embodiment of the present invention, the method of spin-coating the BCB solution using a two-step method is more uniform in spin coating than one-step spin coating, and the resulting BCB insulating layer has better uniformity.

[0079] In step S200, the preset spacing can be, for example, 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, or 0.7 mm, or any other value in the range of 0.3-0.7 mm. Within this range, the solution can be limited to fill the gap, forming a meniscus, and then, under the guidance of the scraper, the meniscus is kept moving stably to obtain a high-quality film. The angle between the scraper and the substrate can be, for example, 15°, 20°, 30°, 40°, or 50°, or any other value in the range of 15-50°. The temperature of the substrate is 20°C, 25°C, or 30°C, or any other value in the range of 20-30°C.

[0080] In step S300, the distance between the substrate and the scraper is a preset distance, so that a gap can be formed between the substrate and the scraper. When applying the preset mixed solution in the gap, a micropipette can be used for application. The mass ratio of the preset solution to the polyethylene glycol octylphenyl ether in the preset mixed solution can be, for example, 7:1, 8:1 or 9:1, or any other value in the range of 7-9:1. The preset organic solvent is selected to be an organic solvent that does not react with polyethylene glycol octylphenyl ether and has a boiling point in the range of 105-115°C, for example, the boiling point can be 105°C, 107°C, 109°C, 112°C or 115°C, and the organic solvent is also required to be able to dissolve C8-BTBT well. The density of the preset solution can be, for example, 8 mg / ml, 10 mg / ml, 11 mg / ml or 12 mg / ml, or any other value in the range of 8-12 mg / ml. The volume of the preset solution applied is 3 μL, 3.5 μL or 4 μL, or any other value between 3 and 4 μL.

[0081] In step S400, the preset speed can be, for example, 1.1 mm / s, 1.2 mm / s, or 1.3 mm / s, or any other value between 1.1 and 1.3 mm / s. The scraper moves at a constant speed at the preset speed. The resulting two-dimensional C8-BTBT organic semiconductor single crystal thin film is a large-area, high-quality single crystal thin film.

[0082] Figure 3 Figure 1 shows a polarization diagram of a two-dimensional C8-BTBT organic semiconductor single crystal film at 45° according to an embodiment of the present invention. Figure 3 It can be seen that the thickness of the insulating layer is uniform, and the overall color and brightness are consistent. Figure 4 Figure 1 shows a polarization diagram of a two-dimensional C8-BTBT organic semiconductor single crystal film at 0° according to an embodiment of the present invention. Figure 4 It can be seen that at 0°, the polarization almost completely disappears, proving the long-range order of the two-dimensional C8-BTBT organic semiconductor single crystal film prepared by this method.

[0083] Figure 5 The UV-visible absorption spectrum of a two-dimensional C8-BTBT organic semiconductor single crystal film according to an embodiment of the present invention is shown. Figure 5 It can be seen that after the addition of Triton X-100, the absorption peak of the two-dimensional C8-BTBT organic semiconductor single crystal film red-shifted, indicating that there is an intermolecular interaction between Triton X-100 and C8-BTBT molecules, which increases the conjugated system of C8-BTBT molecules.

[0084] Figure 6FIG2 shows a schematic diagram of differential scanning calorimetry of a two-dimensional C8-BTBT organic semiconductor single crystal thin film according to an embodiment of the present invention. Figure 6 As shown in Figure 2, after adding Triton X-100, the melting temperature (T m ) changes from 97.1℃ to 92.6℃, and the crystallization temperature (T c ) changed from 115.3°C to 110.6°C. This indicates that there is a strong interaction between Triton X-100 and C8-BTBT molecules, which can induce the nucleation and growth of C8-BTBT and increase the grain size.

[0085] In order to compare the effects of adding Triton X-100 and not adding Triton X-100 on the final prepared C8-BTBT, the present application conducted a control experiment. Compared with the embodiment of the present invention, the control experiment is different from the embodiment of the present invention in steps S100 to S400, only step S300 and step S400. In the control experiment, step S300 is: applying a preset solution to the gap between the substrate and the scraper, and the preset solution is a solution in which C8-BTBT is dissolved in a preset organic solvent. The preset solution is the same as that used in the embodiment of the present invention. In the control experiment, only the preset speed is different in step S400, which is 0.3 mm / s. In the embodiment of the present invention, in step S400, the preset speed is selected to be 1.2 mm / s. And in the embodiment of the present invention, the density of the preset mixed solution, i.e., the C8-BTBT / Triton X-100 solution, is 10 mg / mL, and the mass ratio of C8-BTBT and Triton X-100 is 8:1. The embodiment of the present invention can increase the spin coating speed from 0.3 mm / s in the control experiment to 1.2 mm / s, which also shows that the manufacturing speed can be greatly improved.

[0086] Figure 7 The polarization diagram of the C8-BTBT crystal prepared in the control experiment is shown. Figure 8 Figure 2 shows an atomic force microscope image of the C8-BTBT crystal prepared in the control experiment. Figure 7 and Figure 8 It can be clearly observed that the crystals grow in a ribbon-like manner. This is because the nucleation and growth of crystals at the front of the curved liquid surface occur preferentially in the area with high evaporation flux, so that the solute is replenished only in the area with high evaporation flux during the solution flow, such as Figure 9 As shown (the red arrow indicates the direction of solution flow).

[0087] Figure 10 The figure shows a polarization diagram of a C8-BTBT crystal prepared according to an embodiment of the present invention. Figure 11 Figure 2 shows an atomic force microscope image of a C8-BTBT crystal prepared according to an embodiment of the present invention. Figure 10 and Figure 11 The resulting crystals appear as two-dimensional thin films, and the surface is very smooth, without pores or grain boundaries. This phenomenon is due to the interaction between C8-BTBT and Triton X-100 molecules. Figure 12 The schematic diagram of the mechanism of the two-dimensional C8-BTBT film prepared according to the present invention is shown (the red arrow indicates the direction of solution flow, the black arrow indicates the surface energy gradient from high to low, and the purple arrow indicates the Marangoni flow induced by the surface energy gradient). Figure 12 As shown in the figure, the interaction between C8-BTBT and Triton X-100 molecules causes Triton X-100 to converge toward the C8-BTBT crystal area, forming a surfactant concentration gradient at the front end of the curved liquid surface. The crystallization area with high evaporation flux has a high Triton X-100 concentration and low surface tension, while the surfactant concentration on both sides is low and the surface tension is large, forming a surface tension gradient at the front end of the curved liquid surface, and then forming a Marangoni flow flowing to both sides of the crystal. The Marangoni flow causes the reverse transport of the solute, offsetting the original directional replenishment of the solute, causing the solute to crystallize and grow in the original area, thereby obtaining a two-dimensional C8-BTBT film.

[0088] Figure 13 The figure shows an in-plane X-ray diffraction analysis diagram of a C8-BTBT crystal prepared according to one embodiment of the present invention. Figure 14 Figure 2 shows an out-of-plane X-ray diffraction analysis diagram of a C8-BTBT crystal prepared according to an embodiment of the present invention. Figure 13 and Figure 14 It can be seen that after the addition of Triton X-100, the 2θχ angle corresponding to the (020) crystal plane of C8-BTBT changes from 22.4° to 22.5°, indicating a decrease in the interplanar spacing of the (010) crystal plane. Meanwhile, the 2θ angles corresponding to the out-of-plane crystal planes all decrease, indicating an increase in the interplanar spacing of the (001) crystal plane. This result indicates that the C8-BTBT molecules are more densely packed along the in-plane direction, which is highly beneficial for carrier transport.

[0089] Figure 15 FIG. 1 shows a method for preparing an organic field effect transistor according to an embodiment of the present invention. Figure 15 As shown, the preparation method comprises:

[0090] Step S101, preparing a two-dimensional C8-BTBT organic semiconductor single crystal thin film using the aforementioned preparation method;

[0091] Step S102, fixing a metal mask on the surface of the two-dimensional C8-BTBT organic semiconductor single crystal thin film;

[0092] In step S103 , 2,3,5,6-tetrafluoro-7,7′,8,8′-tetracyanodimethyl-p-benzoquinone and silver are deposited by thermal evaporation to form a conductive channel.

[0093] In step S103, a 1.5 nm layer of 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanodimethyl-p-benzoquinone (F4-TCNQ) is deposited at a rate of 0.01 nm / s, and a 50 nm layer of silver (Ag) is deposited at a rate of 0.03 nm / s. The conductive channel is 120 µm wide and 40 µm long. The above parameters, such as 0.01 nm / s, 0.03 nm / s, 50 nm, 120 µm, and 40 µm, are specific parameters for one embodiment, but are not limited to these parameters.

[0094] The prepared organic field-effect transistors were subjected to electrical testing in accordance with an embodiment of the present invention. The electrical testing process included placing the device on a probe station (M150, Cascade), fixing it by vacuum adsorption, and performing electrical performance tests of the output and transfer curves using a semiconductor analyzer (Keithley, 4200-SCS).

[0095] Figure 16 FIG. 4 shows a transfer characteristic curve of an organic field effect transistor prepared according to an embodiment of the present invention. Figure 17 FIG1 shows the output characteristic curve of the organic field effect transistor prepared according to one embodiment of the present invention. Figure 16 and Figure 17 It can be seen that the electron mobility of the organic field-effect transistor exceeds 10, which confirms that the two-dimensional organic semiconductor film prepared by this patent has outstanding applications in the field of organic field effects and can be sufficient to realize many real-life applications, such as active matrix, organic light-emitting diodes, sensors and amplifier circuits.

[0096] The method provided by this embodiment successfully achieves the rapid preparation of high-quality, two-dimensional organic small molecule semiconductor C8-BTBT crystalline thin films, opening new possibilities for the large-scale application of organic electronics. To demonstrate this, a universal NAND logic circuit was constructed using the two-dimensional C8-BTBT crystalline thin films.

[0097] Figure 18 A diagram showing a NAND gate logic circuit according to an embodiment of the present invention is shown. Figure 19 A microscope image of a NAND gate logic circuit according to an embodiment of the present invention is shown. Figure 20 A diagram showing a single NAND gate logic circuit according to one embodiment of the present invention is shown. Figure 21FIG. 1 shows an input-output voltage diagram of a NAND gate logic circuit according to an embodiment of the present invention. Figure 22 FIG1 shows a curve diagram of voltage variation over time of a NAND gate logic circuit according to an embodiment of the present invention. Figures 18 to 22 It can be seen that the NAND gate logic circuit is composed of two inverters in parallel, and a single inverter is composed of a pair of p-type OFETs with a common source. Figure 20 and Figure 21 It can be seen that the maximum gain of a single inverter is 14.9 when VDD = 20 V, and the NAND circuit can also operate normally. The successful demonstration of these logic gate circuits provides more possibilities for the development of organic materials in the field of organic electronics.

[0098] Figure 23 FIG. 1 is a schematic flow chart showing a method for preparing a NAND gate circuit according to an embodiment of the present invention. Figure 23 As shown, the preparation method comprises:

[0099] Step S1, patterning the gate;

[0100] Step S2, patterning the SU-8 to form a dielectric layer having a hole with a predetermined area, and positioning the hole above the gate;

[0101] Step S3, preparing a two-dimensional C8-BTBT organic semiconductor single crystal thin film using the aforementioned preparation method;

[0102] Step S4: evaporating source and drain electrode materials.

[0103] In step S1, the gate may be, for example, a gold (Au) gate, and the Au gate is patterned using photolithography and etching. In step S2, the preset area may be, for example, 120*120 μm 2 In step S4, the metal mask is aligned using a mobile stage and portable CCD microscope, and 50 nm of Ag is evaporated as the top source and drain electrodes. During testing, the device is placed on a probe station, fixed by vacuum adsorption, and tested using a semiconductor analyzer.

Claims

1. A method for preparing a two-dimensional organic semiconductor single crystal thin film, characterized in that: The steps include: forming an insulating layer on an n-type SiO2 / Si substrate to obtain a substrate; Placing the substrate on a base plate of a doctor blade coating machine so that the distance between the substrate and the doctor blade located above the substrate is a preset distance; Applying a preset mixed solution to the gap between the substrate and the scraper, wherein the preset mixed solution is a mixed solution of a preset solution and polyethylene glycol octylphenyl ether, and the preset solution is a solution of C8-BTBT dissolved in a preset organic solvent; The scraper is controlled to move at a preset speed so that the curved liquid surface formed near the gap is rapidly crystallized under the guidance of the scraper, thereby forming a two-dimensional C8-BTBT organic semiconductor single crystal thin film.

2. The preparation method according to claim 1, characterized in that In the step of placing the substrate on a base plate of a doctor blade coating machine and making the distance between the substrate and the doctor blade located above the substrate a preset distance, the preset distance is any value in the range of 0.3-0.7 mm.

3. The preparation method according to claim 2, characterized in that The temperature of the substrate is 20-30°C.

4. The preparation method according to claim 1, characterized in that In the step of applying a preset mixed solution to the gap between the substrate and the scraper, the preset mixed solution is a mixed solution of a preset solution and polyethylene glycol octyl phenyl ether, and the preset solution is a solution of C8-BTBT dissolved in a preset organic solvent. The preset organic solvent is selected to be an organic solvent that does not react with the polyethylene glycol octyl phenyl ether and has a boiling point in the range of 105-115°C.

5. The preparation method according to claim 1, characterized in that In the step of applying a preset mixed solution to the gap between the substrate and the scraper, the preset mixed solution is a mixed solution of a preset solution and polyethylene glycol octyl phenyl ether, and the preset solution is a solution of C8-BTBT dissolved in a preset organic solvent. The mass ratio of the preset solution to the polyethylene glycol octyl phenyl ether is any value in the range of 7-9:

1.

6. The preparation method according to claim 1, characterized in that The density of the preset solution is 8-12 mg / ml, and the volume of the preset solution applied is 3-4 μL.

7. The preparation method according to claim 1, characterized in that The angle between the scraper and the substrate is any value in the range of 15-50°.

8. The preparation method according to claim 1, characterized in that In the step of controlling the scraper to move at a preset speed so that the curved liquid surface formed near the gap is rapidly crystallized under the guidance of the scraper, thereby forming a two-dimensional C8-BTBT organic semiconductor single crystal thin film, the preset speed is any value in the range of 1.1-1.3 mm / s.

9. The preparation method according to any one of claims 1 to 8, characterized in that The method of preparing an insulating layer on an n-type SiO2 / Si substrate to obtain a substrate comprises the following steps: Place the cleaned n-type SiO2 / Si substrate on a spin coater; An insulating layer material is spin-coated on the n-type SiO 2 / Si substrate to prepare an insulating layer on the n-type SiO 2 / Si substrate. The insulating layer material is selected to be a material with few surface defects that can be used as an insulating layer.

10. The preparation method according to claim 9, wherein The step of spin coating an insulating layer material on the n-type SiO2 / Si substrate to form an insulating layer on the n-type SiO2 / Si substrate comprises the following steps: Spin coating an insulating layer material on the n-type SiO2 / Si substrate at a first preset rotation speed for a first preset time; Continuing the spin coating at a second preset speed for a second preset time, the second preset speed being greater than the first preset speed; heating at a first predetermined temperature to remove residual solvent; Heating is performed at a second preset temperature for cross-linking and curing, and the second preset temperature is higher than the first preset temperature.

11. The preparation method according to claim 10, characterized in that: The first preset speed is any value in the range of 300-600 rpm, the first preset time is any value in the range of 5-10 s, the second preset speed is any value in the range of 2500-3500 rpm, and the second preset time is any value in the range of 15-25 s.

12. The preparation method according to claim 10, characterized in that The first preset temperature is any value in the range of 130-220°C, and the second preset temperature is any value in the range of 260-280°C.

13. A method for preparing an organic field effect transistor, characterized in that: The steps include: A two-dimensional C8-BTBT organic semiconductor single crystal thin film is prepared by the preparation method according to any one of claims 1 to 12; fixing a metal mask on the surface of the two-dimensional C8-BTBT organic semiconductor single crystal thin film; 2,3,5,6-tetrafluoro-7,7',8,8'-tetracyanodimethyl-p-benzoquinone and silver were deposited by thermal evaporation.

14. A method for preparing a NAND gate circuit, characterized in that: The steps include: patterning the gate; Patterning SU-8 to form a dielectric layer having a hole with a predetermined area, and positioning the hole above the gate; A two-dimensional C8-BTBT organic semiconductor single crystal thin film is prepared by the preparation method according to any one of claims 1 to 12; Evaporate source and drain materials.

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