Method for assembling two-dimensional organic semiconductor monocrystals by limiting the spread of meniscus in atmosphere coating and application thereof

Abstract

This invention discloses a method and its application for confined assembly of two-dimensional organic semiconductor single crystals using an extended meniscus in atmosphere coating. The invention proposes that during the atmosphere coating process, a dual-solvent system generates an extended evaporation meniscus, where the nanoscale wet film confinement space can effectively regulate molecular mass transfer, thereby achieving control over the film morphology. This invention controllably prepares uniform and uniformly oriented organic semiconductor single crystal films through the construction of extended evaporation menisci. Devices prepared from the organic semiconductor single crystal films of this invention exhibit high mobility and device uniformity. Furthermore, the organic semiconductor single crystal films prepared by this invention possess strong in-plane anisotropy, enabling them to have rapid photoresponse and imaging capabilities for polarized ultraviolet light.

Description

Technical Field

[0001] This invention relates to the field of organic functional material thin films, specifically to a method for confined assembly of two-dimensional organic semiconductor single crystals in atmosphere coating and its application. Background Technology

[0002] Two-dimensional organic semiconductor single-crystal thin films (2D OSSCs) possess characteristics such as no grain boundaries, few defects, long-range order, and high mobility, thus providing efficient charge transport channels to significantly improve device performance and mitigate variations between different devices. Currently, researchers are dedicated to using 2D OSSCs to construct electronic and optoelectronic devices, such as high-performance organic field-effect transistors (OFETs) and related multifunctional applications. Numerous studies have shown that the growth mode and morphology of organic semiconductors significantly affect the electrical performance of OFETs. Therefore, high-quality 2D OSSCs with consistent orientation and uniform morphology are of great significance for constructing high-performance OFETs.

[0003] Currently, researchers tend to use meniscus-induced coating (MIC) to achieve stable coating processes and prepare highly ordered thin film morphologies. However, the complex fluid flow during the dehumidification process of MMC can lead to uncontrollable mass transfer, causing molecules to aggregate on one side and resulting in inconsistent molecular orientation, thus affecting charge transport along the optimal direction. Therefore, fluid flow must be controlled during dehumidification to avoid unfavorable mass transfer and ensure uniform deposition of organic semiconductors.

[0004] Numerous studies have explored the regulation of molecular mass transport within fluids during the printing process, with the most prevalent approaches including gas-liquid-solid multiphase surface / interface manipulation and solution system optimization. While these methods have achieved high-quality 2DOSSCs to some extent, many challenges remain. For instance, the mechanisms by which fluid flow and molecular mass transfer affect crystallization kinetics are still unclear. Furthermore, most existing fluid and mass transfer control methods require additional factors, such as specific interface selection and design, and the use of ink additives. Therefore, there is an urgent need to propose a direct and simple research strategy to create a more general research platform to elucidate the structure-property relationships between fluid flow and mass transfer behavior and the nucleation, crystallization, and deposition of thin films.

[0005] Patent document CN202011434239.1 discloses a novel atmosphere-induced coating method that generates Malaghni flow spontaneously without contact. This method demonstrates that dewetting can be achieved by locally and quantitatively releasing the atmosphere to create a surface tension difference within the spreading solution, thereby depositing molecules. However, in-depth exploration is still lacking regarding the film-spreading process of complex organic ink systems in atmosphere coating and how to controllably adjust the film morphology. Summary of the Invention

[0006] To address the complex fluid flow and uncontrollable mass transfer issues inherent in existing solution-based organic semiconductor single crystal preparation methods, this invention provides a method for confined assembly of two-dimensional organic semiconductor single crystals using an extended meniscus in an atmosphere-coated process. By constructing an extended meniscus using a dual-solvent system, a nanoscale confined wet film is generated, promoting internal molecular mass transfer and achieving the preparation of high-quality two-dimensional organic semiconductor single crystals. This method allows for nanoscale control of the two-dimensional single crystal morphology to obtain uniform and uniformly oriented two-dimensional organic semiconductor single crystal films.

[0007] To achieve the above objectives, the present invention provides a method for preparing a two-dimensional organic semiconductor single crystal, the method comprising the following steps:

[0008] 1) Place the atmosphere-containing knife perpendicular to the substrate and maintain a distance between it and the substrate in the vertical direction;

[0009] 2) A solution containing organic semiconductor materials is dropped onto a substrate and spread into a liquid film;

[0010] 3) Control the moving speed of the atmosphere cutter to gradually approach the liquid film, thereby causing the liquid film to retreat;

[0011] 4) After the liquid film has completely exited the substrate, the substrate still has a nanoscale wet film. Wait for the wet film to dry completely to obtain a two-dimensional organic semiconductor single crystal, i.e., an organic semiconductor single crystal thin film.

[0012] 5) Anneal the two-dimensional organic semiconductor single crystal obtained in step 4).

[0013] In this invention, the atmosphere in the atmosphere knife dissolves in the solution front containing organic semiconductor materials, reducing the surface tension of the liquid film front and creating a surface tension difference between the liquid film front and the solution bulk, thereby generating Malagni flow. That is, a stable Malagni flow is generated through the atmosphere field, further causing the spread liquid film to retreat uniformly and stably.

[0014] According to the present invention, the substrate in step 1) is a pretreated substrate. Preferably, the static contact angle of the substrate is not higher than 10°. The present invention does not particularly limit the substrate, as long as the static contact angle of the substrate is not higher than 10°. Preferably, the substrate can be rigid or flexible. Preferably, the substrate is transparent or opaque. Exemplarily, the substrate is one of Si / SiO2 sheet, glass sheet, PEN film, PET film, quartz sheet, aluminum sheet or copper sheet.

[0015] According to the present invention, the substrate is pretreated by treatment with a silane coupling agent or plasma treatment to obtain a pretreated substrate.

[0016] In one embodiment of the present invention, the plasma treatment time is 80-100s and the power is 80-100W.

[0017] In one embodiment of the present invention, the silane coupling agent used in the silane coupling agent treatment is phenyltrichlorosilane; the treatment conditions of the silane coupling agent are: vacuum sealing conditions, time of 2-4 hours, and temperature of 70-90°C.

[0018] According to the present invention, the atmosphere knife is a planar gas source, and the area of ​​the planar gas source is less than 10 cm². 2 .

[0019] According to the present invention, the atmosphere knife is prepared by loading a solvent that generates the atmosphere onto a gas source carrier. Preferably, the solvent that generates the atmosphere is selected from polar, nonpolar, or inert solvents with low surface tension (e.g., at 25°C, the surface tension is not higher than 33 mN / m, preferably not higher than 24 mN / m) and high vapor pressure (e.g., at 20°C, the vapor pressure is not lower than 4 kPa), such as at least one of hexaane, heptane, isopropanol, ethanol, methanol, acetone, n-butanol, acetic acid, or toluene.

[0020] According to the present invention, the gas source carrier may be, for example, filter paper.

[0021] According to the present invention, the vertical distance between the atmosphere knife and the substrate is 500-1500 μm, with examples being 500 μm, 800 μm, 1000 μm, 1200 μm, and 1500 μm; the horizontal distance between the atmosphere knife and the substrate is 0.5-5 cm, with examples being 0.5 cm, 1 cm, 1.5 cm, 2 cm, 3 cm, 4 cm, and 5 cm.

[0022] In this invention, the driving force for the directional movement of the liquid film is the diffusion of a low surface tension gas source into the interior of a high surface tension solution, creating a surface tension difference between the liquid film front and the bulk.

[0023] According to the present invention, the moving speed of the atmosphere knife is 0.1-5.0 mm / s, and exemplary speeds are 0.1 mm / s, 0.4 mm / s, 0.5 mm / s, 0.6 mm / s, 0.8 mm / s, 1.0 mm / s, 2.0 mm / s, 3.0 mm / s, 4.0 mm / s, and 5.0 mm / s.

[0024] According to the present invention, the temperature of the substrate is 25-45°C, exemplarily 25°C, 30°C, 40°C, and 45°C.

[0025] According to the present invention, in step 2), the solution containing the organic semiconductor material is composed of the organic semiconductor material, the organic solvent, and the antisolvent.

[0026] The present invention does not limit the type of organic semiconductor material, for example, it can be a conjugated / non-conjugated small molecule or a conjugated / non-conjugated polymer; preferably, the organic semiconductor material is one of thiophene conjugated small molecules, porphyrin conjugated small molecules, perylene imide conjugated small molecules, conjugated polymers based on the above conjugated units, and non-conjugated polymers with a flexible alkyl chain as the main chain.

[0027] According to an exemplary embodiment of the present invention, the organic semiconductor material is selected from one of 2,7-dioctyl[1]benzothiopheno[3,2-B]benzothiophene (C8-BTBT), 2,7-decyl[1]benzothiopheno[3,2-B]benzothiophene (C10-BTBT), 2,7-dodecyl[1]benzothiopheno[3,2-B]benzothiophene (C12-BTBT), and 2,7-dihexylalkyl[1]benzothiopheno[3,2-B]benzothiophene (C6-BTBT).

[0028] According to the present invention, in a solution containing an organic semiconductor material, the mass concentration of the organic semiconductor material is 0.1-20 mg / mL, preferably 0.5-10 mg / mL, and exemplary concentrations are 0.1 mg / mL, 0.5 mg / mL, 1 mg / mL, 3 mg / mL, 6 mg / mL, and 10 mg / mL.

[0029] The present invention does not particularly limit the type of organic solvent, and can select it appropriately as needed. Preferably, the organic solvent is one or a mixture of polar and non-polar solvents; more preferably, the organic solvent is one of chloroform, toluene, m-xylene, chlorobenzene, anisole, cyclohexanone, o-dichlorobenzene, mesitylene, and acetophenone.

[0030] According to the present invention, the antisolvent is one of N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and p-methoxybenzaldehyde.

[0031] According to the present invention, the volume of the antisolvent is 0.1% to 15% of the volume of the organic solvent, and exemplary values ​​are 0.1%, 0.6%, 1%, 4%, 6%, 10%, 12%, and 15%.

[0032] According to the present invention, the annealing temperature is 80-120°C, exemplarily 80°C, 100°C, and 120°C; the annealing time is 0.5-1 hour, exemplarily 0.5 hours, 0.8 hours, and 1 hour. Annealing can remove residual solvent from the film and improve the crystallinity of the organic semiconductor material.

[0033] The present invention also provides a two-dimensional organic semiconductor single crystal, i.e., an organic semiconductor single crystal thin film, prepared by the above preparation method.

[0034] According to the present invention, the two-dimensional organic semiconductor single crystal is deposited on the surface of the substrate to obtain an organic semiconductor single crystal thin film. Preferably, the two-dimensional organic semiconductor single crystal is uniformly deposited on the substrate.

[0035] According to the present invention, the thickness of the organic semiconductor single crystal thin film is 3nm-30nm.

[0036] The present invention also provides the application of the above-mentioned two-dimensional organic semiconductor single crystal in flexible displays, photoelectric synapses, sensors (chemical sensors, biosensors or pressure sensors, etc.) or photodetectors.

[0037] The present invention also provides a device comprising the above-mentioned two-dimensional organic semiconductor single crystal and / or prepared from the above-mentioned two-dimensional organic semiconductor single crystal.

[0038] According to embodiments of the present invention, the device may be a display, a sensor (chemical sensor, biological sensor, or pressure sensor, etc.) or a photodetector.

[0039] The beneficial effects of this invention are:

[0040] This invention proposes that an extended evaporation meniscus is generated during the atmosphere-driven film-making process, where the nanoscale wet film confinement space can effectively regulate molecular mass transfer. Through the construction of the extended evaporation meniscus, this invention controllably prepares uniform, uniformly oriented two-dimensional organic semiconductor single crystals, i.e., organic semiconductor single crystal thin films (2D OSSCs), achieving a direct transformation from one-dimensional striped crystals to two-dimensional thin film crystals. Compared with existing technologies, this invention has the following advantages:

[0041] (1) The extended curved liquid surface constructed by the present invention contains a nanoscale confined wet film region. The internal separation pressure restricts the evaporation of the wet film, thus providing sufficient time for lateral mass transfer of molecules, which is the key to the formation of organic semiconductor single crystal thin films.

[0042] (2) Devices prepared from the organic semiconductor single-crystal thin film of the present invention have high mobility and device uniformity. In addition, the organic semiconductor single-crystal thin film prepared by the present invention has strong in-plane anisotropy, which enables it to have fast photoresponse capability and imaging capability to polarized ultraviolet light. Attached Figure Description

[0043] Figure 1 These are schematic diagrams of the experimental apparatus in Examples 1-4 and Comparative Examples 1-2 of the present invention, and schematic diagrams of the extended evaporation meniscus liquid surface constructed thereunder.

[0044] Figure 2 The optical microscope and atomic force microscope images show the organic semiconductor single crystal thin film obtained in Example 1.

[0045] Figure 3 The optical microscope and atomic force microscope morphologies of the organic semiconductor single crystal thin film obtained in Comparative Example 1 are shown.

[0046] Figure 4 The optical microscope and atomic force microscope morphologies of the organic semiconductor single crystal thin film obtained in Comparative Example 2 are shown.

[0047] Figure 5 The polarization properties of the organic functional thin film prepared in Example 1 are shown in the chromatograms of angle-resolved photocurrent changes and anisotropic photocurrents.

[0048] Figure 6 The chromatograms show the polarization properties of the organic functional thin film prepared in Comparative Example 1, including the angle-resolved photocurrent variation and the anisotropic photocurrent.

[0049] Figure 7 The chromatograms show the polarization properties of the organic functional thin film prepared in Comparative Example 2, including the angle-resolved photocurrent variation and the anisotropic photocurrent. Detailed Implementation

[0050] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following embodiments are merely illustrative and explanatory of the present invention, and should not be construed as limiting the scope of protection of the present invention. All technologies implemented based on the above content of the present invention are covered within the scope of protection intended by the present invention.

[0051] Unless otherwise stated, the raw materials and reagents used in the following examples are commercially available products or can be prepared by known methods.

[0052] Example 1

[0053] (1) Preparation of pretreated substrate

[0054] Si / SiO2 wafers (2cm x 0.8cm) were ultrasonically cleaned with solvents such as water, acetone, and isopropanol. The cleaned Si / SiO2 wafers were then placed in a vacuum dryer filled with a phenyltrichlorosilane atmosphere (the phenyltrichlorosilane atmosphere was obtained by adding a few drops of phenyltrichlorosilane to the dryer and then evacuating it) for surface treatment. The treatment conditions were: vacuum sealing, time of 2 hours, and temperature of 80°C. This resulted in a pretreated SiO2 / Si substrate with a static contact angle of less than 10° with the organic solvent chlorobenzene.

[0055] (2) Preparation of atmosphere knife

[0056] A filter paper measuring 1cm x 3cm was selected as the gas source carrier, and the vertical distance between the gas source carrier and the pretreated substrate SiO2 / Si was set to 500μm. 500μL of anhydrous ethanol was dropped onto the filter paper to allow it to absorb the ethanol, thus acting as an atmosphere injector.

[0057] (3) Preparation of organic functional thin films

[0058] A chlorobenzene solution of 2,7-dioctyl[1]benzothiophene[3,2-B]benzothiophene (C8-BTBT) was prepared, with a C8-BTBT concentration of 10 mg / mL. 6% DMF (by volume) was added to the solution, and then the mixture was stirred evenly with a magnetic stirrer to obtain a mixed solution. 10 μL of the mixed solution was added dropwise to the center of the pretreated SiO2 / Si substrate using a microsyringe. Due to the low contact angle, the solution could spontaneously spread into a uniform thin film on the surface of the pretreated SiO2 / Si substrate. The horizontal distance between the atmosphere knife and the substrate was set to 1 cm, and the horizontal moving speed of the atmosphere knife was controlled at 0.4 mm / s. The substrate temperature was 30 °C. The liquid film gradually de-wetted as the atmosphere knife moved steadily, and a nanoscale wet film with a thickness of 12 nm was drawn out at the three-phase line. Molecules gradually deposited in an orderly manner inside the wet film. After 500 s, it was completely dried, resulting in a uniform two-dimensional organic semiconductor single crystal thin film. Figure 2 ).

[0059] (4) Post-processing

[0060] An annealing process was performed on a Si / SiO2 substrate with an organic semiconductor single crystal thin film deposited on its surface. The annealing temperature was 60℃ and the annealing time was 30 min to obtain a C8-BTBT thin film.

[0061] Example 2

[0062] (1) Preparation of pretreated substrate

[0063] Si / SiO2 wafers (2cm x 0.8cm) were ultrasonically cleaned with solvents such as water, acetone, and isopropanol. The cleaned Si / SiO2 wafers were then placed in a vacuum dryer filled with a phenyltrichlorosilane atmosphere (the phenyltrichlorosilane atmosphere was obtained by adding a few drops of solution to the vacuum dryer and then evacuating) for surface treatment. The treatment conditions were: vacuum sealing, time of 2 hours, and temperature of 80°C. This resulted in a pretreated SiO2 / Si substrate with a static contact angle of less than 10° with the organic solvent toluene.

[0064] (2) Preparation of atmosphere knife

[0065] A filter paper measuring 1cm x 3cm was selected as the gas source carrier, and the vertical distance between the gas source carrier and the pretreated substrate SiO2 / Si was set to 500μm. 500μL of isopropanol was dropped onto the filter paper to allow the filter paper to absorb the isopropanol as an atmosphere scalpel.

[0066] (3) Preparation of organic functional thin films

[0067] A toluene solution of 2,7-didecyl[1]benzothiophene[3,2-B]benzothiophene (C10-BTBT) was prepared, with a C10-BTBT concentration of 6 mg / mL. DMSO (4% by volume) was added to the solution, and then the mixture was stirred evenly with a magnetic stirrer to obtain a homogeneous solution. 10 μL of the homogeneous solution was added dropwise to the center of the pretreated SiO2 / Si substrate using a microsyringe. Due to the low contact angle, the solution spontaneously spreads into a uniform thin film on the surface of the pretreated SiO2 / Si substrate. The horizontal distance between the atmosphere knife and the substrate was set to 1 cm, and the horizontal moving speed of the atmosphere knife was controlled at 0.5 mm / s. The substrate temperature was 30 °C. The liquid film gradually dewetted as the atmosphere knife moved steadily, and a nanoscale wet film with a thickness of 20 nm was drawn out at the three-phase line. Molecules gradually deposited in an orderly manner inside the wet film. After 400 s, the film was completely dried, resulting in a uniform two-dimensional organic semiconductor single crystal thin film.

[0068] (4) Post-processing

[0069] An annealing process was performed on a Si / SiO2 substrate with an organic semiconductor single crystal thin film deposited on its surface. The annealing temperature was 60℃ and the annealing time was 30 min to obtain a C10-BTBT thin film.

[0070] Example 3

[0071] (1) Preparation of pretreated substrate

[0072] Si / SiO2 wafers (2cm x 0.8cm) were ultrasonically cleaned with solvents such as water, acetone, and isopropanol. The cleaned Si / SiO2 wafers were then placed in a vacuum dryer filled with a phenyltrichlorosilane surface treatment atmosphere (the phenyltrichlorosilane atmosphere was obtained by adding a few drops of solution to the vacuum dryer and then evacuating). The treatment conditions were: vacuum sealing, time of 2 hours, and temperature of 80°C. This resulted in a pretreated SiO2 / Si substrate with a static contact angle of less than 10° with the organic solvent anisole.

[0073] (2) Preparation of atmosphere knife

[0074] A filter paper measuring 1cm x 3cm was selected as the gas source carrier, and the vertical distance between the gas source carrier and the pretreated substrate SiO2 / Si was set to 1000μm. 500μL of acetone was dropped onto the filter paper to allow the filter paper to absorb the acetone as an atmosphere knife.

[0075] (3) Preparation of organic functional thin films

[0076] A solution of 2,7-dodecyl[1]benzothiophene[3,2-B]benzothiophene (C12-BTBT) in anisole was prepared, with a C12-BTBT concentration of 3 mg / mL. 1% p-methoxybenzaldehyde (by volume) was added to the solution, followed by stirring with a magnetic stirrer to obtain a mixed solution. 10 μL of the mixed solution was added dropwise to the center of the pretreated SiO2 / Si substrate using a microsyringe. Due to the low contact angle, the solution spontaneously spreads into a uniform thin film on the surface of the pretreated SiO2 / Si substrate. The horizontal distance between the atmosphere knife and the substrate was set to 1 cm, and the horizontal moving speed of the atmosphere knife was controlled at 0.6 mm / s. The substrate temperature was 30 °C. The liquid film gradually dewetted as the atmosphere knife moved steadily, drawing out a nanoscale wet film with a thickness of 10 nm at the three-phase line. Molecules gradually deposited in an ordered manner inside the wet film. After 300 s, it was completely dried, resulting in a uniform two-dimensional organic semiconductor single-crystal thin film.

[0077] (4) Post-processing

[0078] An annealing treatment was performed on a Si / SiO2 substrate with an organic semiconductor single crystal thin film deposited on its surface. The annealing temperature was 70℃ and the annealing time was 30 min to obtain a C12-BTBT thin film.

[0079] Example 4

[0080] (1) Preparation of pretreated substrate

[0081] Si / SiO2 wafers (2cm x 0.8cm) were ultrasonically cleaned with solvents such as water, acetone, and isopropanol. The cleaned Si / SiO2 wafers were then placed in a vacuum dryer filled with a phenyltrichlorosilane atmosphere (the phenyltrichlorosilane atmosphere was obtained by adding a few drops of solution to the dryer and then evacuating) for surface treatment. The treatment conditions were: vacuum sealing, time of 2 hours, and temperature of 80°C. This resulted in a pretreated SiO2 / Si substrate with a static contact angle of less than 10° with the organic solvent anisole.

[0082] (2) Preparation of atmosphere knife

[0083] A filter paper measuring 1cm x 3cm was selected as the gas source carrier, and the vertical distance between the gas source carrier and the pretreated substrate SiO2 / Si was set to 800μm. 500μL of isopropanol was dropped onto the filter paper to allow the filter paper to absorb the isopropanol as an atmosphere scalpel.

[0084] (3) Preparation of organic functional thin films

[0085] A solution of 2,7-dihexylalkyl[1]benzothiophene[3,2-B]benzothiophene (C6-BTBT) in anisole was prepared, with a C6-BTBT concentration of 10 mg / mL. 0.6% (v / v) of the antisolvent p-methoxybenzaldehyde was added to the solution, followed by stirring with a magnetic stirrer to obtain a mixed solution. 10 μL of the mixed solution was added dropwise to the center of the pretreated SiO2 / Si substrate using a microsyringe. Due to the low contact angle, the solution spontaneously spreads into a uniform thin film on the surface of the pretreated SiO2 / Si substrate. The horizontal distance between the atmosphere knife and the substrate was set to 1 cm, and the horizontal moving speed of the atmosphere knife was controlled at 0.4 mm / s. The substrate temperature was 30 °C. The liquid film gradually dewetted as the atmosphere knife moved steadily, drawing out a nanoscale wet film with a thickness of 20 nm at the three-phase line. Molecules gradually deposited and became ordered inside the wet film. After 500 s, the film was completely dried, resulting in a uniform two-dimensional organic semiconductor single-crystal thin film.

[0086] (4) Post-processing

[0087] An annealing treatment was performed on a Si / SiO2 substrate with an organic semiconductor single crystal thin film deposited on its surface. The annealing temperature was 80℃ and the annealing time was 30 min to obtain a C6-BTBT thin film.

[0088] Comparative Example 1

[0089] Organic functional films were prepared according to the method of Example 1, except that in step (3), 50% by volume of the antisolvent DMF was added to obtain organic semiconductor films. The specific steps are as follows:

[0090] (1) Preparation of pretreated substrate

[0091] Si / SiO2 wafers (2cm x 0.8cm) were ultrasonically cleaned with solvents such as water, acetone, and isopropanol. The cleaned Si / SiO2 wafers were then placed in a vacuum dryer filled with a phenyltrichlorosilane atmosphere (the phenyltrichlorosilane atmosphere was obtained by adding a few drops of solution to the vacuum dryer and then evacuating) for surface treatment. The treatment conditions were: vacuum sealing, time of 2 hours, and temperature of 80°C, resulting in a pretreated SiO2 / Si substrate with a static contact angle of less than 10° with the organic solvent.

[0092] (2) Preparation of atmosphere knife

[0093] A filter paper measuring 1cm x 3cm was selected as the gas source carrier, and the vertical distance between the gas source carrier and the pretreated substrate SiO2 / Si was set to 500μm. 500μL of anhydrous ethanol was dropped onto the filter paper to allow it to absorb the ethanol, thus acting as an atmosphere injector.

[0094] (3) Preparation of organic functional thin films

[0095] A chlorobenzene solution of 2,7-dioctyl[1]benzothiophene[3,2-B]benzothiophene (C8-BTBT) was prepared, with a C8-BTBT concentration of 10 mg / mL. 50% DMF (volume fraction) of the antisolvent was added to the solution, and then the mixture was stirred evenly with a magnetic stirrer to obtain a mixed solution. 10 μL of the mixed solution was added dropwise to the center of the pretreated SiO2 / Si substrate using a microsyringe. Due to the low contact angle, the solution could spontaneously spread into a uniform thin film on the surface of the pretreated SiO2 / Si substrate. The horizontal distance between the atmosphere knife and the substrate was set to 1 cm, and the horizontal moving speed of the atmosphere knife was controlled at 0.4 mm / s. The substrate temperature was 30 °C. The liquid film gradually de-wetted as the atmosphere knife moved steadily, and a nanoscale wet film with a thickness of 15 nm was drawn out at the three-phase line. The wet film was rapidly dried after 5 s to obtain a broken two-dimensional organic semiconductor crystal thin film. Figure 3 ).

[0096] (4) Post-processing

[0097] An annealing process was performed on a Si / SiO2 substrate with an organic semiconductor single crystal thin film deposited on its surface. The annealing temperature was 60℃ and the annealing time was 30 min to obtain a C8-BTBT thin film.

[0098] Comparative Example 2

[0099] Organic functional films were prepared according to the method of Example 1, except that in step (3), no anti-solvent was added to obtain organic semiconductor films. The specific steps are as follows:

[0100] (1) Preparation of pretreated substrate

[0101] Si / SiO2 wafers (2cm x 0.8cm) were ultrasonically cleaned with solvents such as water, acetone, and isopropanol. The cleaned Si / SiO2 wafers were then placed in a vacuum dryer filled with a phenyltrichlorosilane atmosphere (the phenyltrichlorosilane atmosphere was obtained by adding a few drops of solution to the vacuum dryer and then evacuating) for surface treatment. The treatment conditions were: vacuum sealing, time of 2 hours, and temperature of 80°C, resulting in a pretreated SiO2 / Si substrate with a static contact angle of less than 10° with the organic solvent.

[0102] (2) Preparation of atmosphere knife

[0103] A filter paper measuring 1cm x 3cm was selected as the gas source carrier, and the vertical distance between the gas source carrier and the pretreated substrate SiO2 / Si was set to 500μm. 500μL of isopropanol was dropped onto the filter paper to allow it to absorb anhydrous ethanol, thus creating an atmosphere.

[0104] (3) Preparation of organic functional thin films

[0105] A chlorobenzene solution of 2,7-dioctyl[1]benzothiophene[3,2-B]benzothiophene (C8-BTBT) was prepared, with a C8-BTBT concentration of 10 mg / mL. 10 μL of the solution was added dropwise to the center of the pretreated SiO2 / Si substrate using a microsyringe. Due to the low contact angle, the solution spontaneously spreads into a uniform thin film on the surface of the pretreated SiO2 / Si substrate. The horizontal distance between the atmosphere knife and the substrate was set to 1 cm, and the horizontal moving speed of the atmosphere knife was controlled at 0.4 mm / s. The substrate temperature was 30 °C. The liquid film gradually dewetted as the atmosphere knife moved steadily. No wet film appeared during the dewetting process; the molecules were pushed and dried immediately, resulting in uniform organic semiconductor single-crystal stripes. Figure 4 ).

[0106] (4) Post-processing

[0107] An annealing process was performed on a Si / SiO2 substrate with an organic semiconductor single crystal thin film deposited on its surface. The annealing temperature was 60℃ and the annealing time was 30 min to obtain a C8-BTBT thin film.

[0108] Application examples

[0109] Polarized ultraviolet photodetection was performed in an optical system (composed of a mercury lamp, a 360nm filter, a polarizer, a half-wave plate, and the aforementioned prepared two-dimensional organic semiconductor single-crystal thin film). A commercially available 360nm laser was used as the source for inducing the photocurrent. The laser was passed through a polarizer to obtain linearly polarized light, and the polarization angle was adjusted using a 360nm half-wave plate. In the 360nm wavelength detection, a wavelength of 20.6 mW / cm² was used. 2 A constant laser power is used to induce photocurrent. Finally, the photocurrent of the device is recorded using a semiconductor parameter analyzer.

[0110] The polarization properties of the two-dimensional organic semiconductor single-crystal thin film prepared in Example 1, including the chromatograms of angle-resolved photocurrent changes and anisotropic photocurrents, are shown below. Figure 5 As shown in the figure, the photocurrent intensity of the polarization detector device fabricated from the two-dimensional organic semiconductor single-crystal thin film of the present invention exhibits a periodic change with the polarization angle and demonstrates significant anisotropy, with a dichroism ratio as high as 2.80. The polarization performance, including the angle-resolved photocurrent variation and anisotropic photocurrent, shown by the organic semiconductor fragmented crystal thin film prepared in Comparative Example 1 and the organic semiconductor single-crystal stripes prepared in Comparative Example 2, are illustrated in the chromatograms below. Figure 6 , Figure 7 As shown in the figure, the results indicate that the polarization detection dichroism of the organic semiconductor broken crystal thin film (dichroism ratio of 1.20) in Comparative Example 1 and the organic semiconductor single crystal stripe (dichroism ratio of 1.60) in Comparative Example 2 is much lower than that of the two-dimensional organic semiconductor single crystal thin film prepared in this invention.

[0111] The embodiments of the present invention have been described above. However, the present invention is not limited to the above embodiments. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for preparing a two-dimensional organic semiconductor single crystal, characterized in that, The method includes the following steps: 1) Place the atmosphere-containing knife perpendicular to the substrate and maintain a distance between it and the substrate in the vertical direction; 2) A solution containing organic semiconductor materials is dropped onto a substrate and spread into a liquid film; 3) Control the moving speed of the atmosphere cutter to gradually approach the liquid film, thereby causing the liquid film to retreat; 4) After the liquid film has completely exited the substrate, a nanoscale wet film still exists on the substrate. Wait for the wet film to dry completely to obtain a two-dimensional organic semiconductor single crystal. 5) Anneal the two-dimensional organic semiconductor single crystal obtained in step 4).

2. The method as described in claim 1, characterized in that, The static contact angle of the substrate is less than 10°. Preferably, the substrate is one of Si / SiO2 sheet, glass sheet, PEN film, PET film, quartz sheet, aluminum sheet or copper sheet. Preferably, the substrate is used after being treated with a silane coupling agent or plasma treatment. Preferably, the plasma treatment time is 80-100s and the power is 80-100W. Preferably, the silane coupling agent used in the silane coupling agent treatment is phenyltrichlorosilane; the treatment time of the silane coupling agent is 2-4 hours, and the temperature is 70-90℃.

3. The method as described in claim 1, characterized in that, The atmosphere knife is prepared by loading a solvent that generates an atmosphere onto a gas source carrier. Preferably, the solvent for generating the atmosphere is selected from hexane, heptane, isopropanol, ethanol, methanol, acetone, n-butanol, acetic acid, or toluene, etc.

4. The method according to any one of claims 1-3, characterized in that, The vertical distance between the atmosphere knife and the substrate is 500-1500 μm; the horizontal distance between the atmosphere knife and the substrate is 0.5-5 cm. Preferably, the moving speed of the atmosphere knife is 0.1-5.0 mm / s. Preferably, the temperature of the substrate is 25-45°C.

5. The method according to any one of claims 1-4, characterized in that, The solution containing the organic semiconductor material is composed of the organic semiconductor material, an organic solvent, and an antisolvent. Preferably, the organic semiconductor material is one of the following: thiophene conjugated small molecules, porphyrin conjugated small molecules, perylene imide conjugated small molecules, conjugated polymers based on the above conjugated units, and non-conjugated polymers with a flexible alkyl chain as the main chain. Preferably, the organic semiconductor material is selected from one of 2,7-dioctyl[1]benzothiopheno[3,2-B]benzothiophene (C8-BTBT), 2,7-decyl[1]benzothiopheno[3,2-B]benzothiophene (C10-BTBT), 2,7-dodecyl[1]benzothiopheno[3,2-B]benzothiophene (C12-BTBT), and 2,7-dihexylalkyl[1]benzothiopheno[3,2-B]benzothiophene (C6-BTBT). Preferably, in the solution containing the organic semiconductor material, the mass concentration of the organic semiconductor material is 0.1-20 mg / mL. Preferably, the organic solvent is one of chloroform, toluene, m-xylene, chlorobenzene, anisole, cyclohexanone, o-dichlorobenzene, mesitylene, and acetophenone. Preferably, the antisolvent is one of N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), and p-methoxybenzaldehyde. Preferably, the volume of the antisolvent is 0.1% to 15% of the volume of the organic solvent.

6. The method according to any one of claims 1-5, characterized in that, The annealing temperature is 80-120℃; the annealing time is 0.5-1h.

7. The two-dimensional organic semiconductor single crystal prepared by the preparation method according to any one of claims 1-6.

8. The two-dimensional organic semiconductor single crystal as described in claim 7, characterized in that, The two-dimensional organic semiconductor single crystal is deposited on the surface of the substrate. Preferably, the two-dimensional organic semiconductor single crystal is uniformly deposited on the substrate. Preferably, the thickness of the organic semiconductor single crystal thin film is 3nm-30nm.

9. The application of the two-dimensional organic semiconductor single crystal according to claim 7 in flexible displays, photoelectric synapses, sensors or photodetectors.

10. A device, characterized in that, It contains the two-dimensional organic semiconductor single crystal as described in claim 7 and / or is prepared from the two-dimensional organic semiconductor single crystal as described in claim 7.

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