Two-dimensional organic / inorganic heterojunction optoelectronic devices with SHG response and their preparation

Abstract

The present invention discloses a two-dimensional organic / inorganic heterojunction optoelectronic device with SHG response and its preparation, which belongs to the technical field of nonlinear optical devices. During the preparation, the two-dimensional inorganic material is first torn onto a substrate by a mechanical stripping method to obtain a two-dimensional inorganic material / substrate structure; then, the organic molecules are induced to arrange in an orderly manner on the surface of the two-dimensional inorganic material by an epitaxial growth method to form an organic / inorganic heterojunction. The present application optimizes the charge transfer at the heterojunction interface by regulating the coverage of organic molecules and the thickness of the two-dimensional inorganic material, thereby enhancing the SHG response of the material. The SHG response intensity of the prepared Me‑PTCDI / GaSe heterojunction is better than that of a single component, and its spectral response can be extended from the original visible light range to the near-infrared band. The SHG conversion efficiency is even as high as 0.26%, which has important application potential in nonlinear optical devices.

Description

Technical Field

[0001] The invention relates to the technical field of nonlinear optical devices, in particular to a two-dimensional organic / inorganic heterojunction photoelectric device with SHG response, and discloses a specific preparation method thereof. Background Art

[0002] Second Harmonic Generation (SHG) is a typical second-order nonlinear optical phenomenon. Its essence is the process of generating frequency-doubled photons after two beams of same-frequency photons are coupled through a nonlinear medium. This effect has important value in the fields of laser frequency conversion, biological microscopic imaging and material characterization: for example, it can break through the wavelength limitation of traditional lasers to achieve ultraviolet light output; it can perform subcellular imaging of asymmetric biological tissues such as collagen fibers without fluorescent labeling; it can be used to analyze the lattice symmetry and interface characteristics of materials, etc.

[0003] However, second harmonic generation requires materials with non-centrosymmetric structures, large second-order nonlinear optical coefficients, wide optical transparency windows, and high laser damage thresholds. Although traditional materials such as lithium niobate (LiNbO3) and potassium dihydrogen phosphate (KDP) have large second-order nonlinear optical coefficients, their optical transparency windows are narrow, resulting in weak SHG response intensity of such materials. In addition, there are problems such as complex preparation processes and high costs, which greatly limit the practical application of the materials.

[0004] In recent years, two-dimensional materials have injected new vitality into the field of nonlinear optics due to their unique structure and excellent physical and chemical properties. For example, graphene, transition metal dichalcogenides (TMDs, such as MoS2, WS2, etc.) and IIIA-VIA compounds (such as GaSe, InSe, etc.) have advantages such as atomic-level thickness, interlayer van der Waals force and good mechanical flexibility, and have performed well in enhancing the interaction between light and matter, building heterostructures and preparing flexible devices. However, single-component two-dimensional materials also face problems such as weak SHG response and poor band selectivity in practical applications. For example, although monolayer MoS2 has a non-centrosymmetric structure and a large second-order nonlinear optical coefficient, the SHG response intensity is still not enough to meet the needs of practical applications, and its response band is limited to the visible light region, which seriously limits the expansion of application scenarios.

[0005] In order to make up for the shortcomings of single-component materials, this field often uses strategies such as strain engineering, electric field regulation, chemical modification and heterostructure construction to enhance the SHG response of two-dimensional materials. These strategies mainly improve the SHG response of materials by changing the material structure, inducing dipole moment, regulating electronic structure and utilizing interface effects. However, each of these strategies also has certain limitations. For example, strain engineering and electric field regulation require complex devices and are difficult to scale up; chemical modification may introduce internal defects and affect the stability of the material. Although the construction of heterojunctions helps to improve the transport properties of single materials, increase the carrier mobility of materials, and further affect the generation efficiency of their second harmonics, thereby achieving the purpose of enhancing the nonlinear optical effect of materials, the specific generation efficiency and performance are still affected by many factors, such as the structural design of heterojunctions, material selection, and preparation process.

[0006] The document "Chen X, et al. Van der Waals Nonlinear Photodetector with Quadratic Photoresponse[J]. Nano Letters, 2023. DOI: 10.1021 / acs.nanolett.2c04472." discloses a quadratic nonlinear photodetector (QNPD) composed of a van der Waals (vdW) stacked GaSe / InSe heterostructure. The material GaSe used is a layered semiconductor material. Its own structural characteristics make GaSe easy to peel into thin sheets and retain its excellent nonlinear optical properties in bulk crystals. Combining it with InSe to construct a heterojunction can further improve the electrical transport performance of GaSe and enhance its nonlinear optical effect. The additional second harmonic generation (SHG) process in GaSe / InSe leads to a quadratic nonlinear function between photocurrent and light intensity, extending the light detection wavelength from 900 nm to 1750 nm, breaking the limitation of the response band of the material itself. However, the SHG conversion efficiency of the device is not very good. The SHG efficiency of QNPD at 1500 nm is only about 0.024% (the SHG conversion efficiency of single-component GaSe is 0.016%). It is speculated that the reason why the SHG conversion efficiency is not significantly improved may be related to the construction method of the heterojunction and the inorganic / inorganic heterojunction constructed. Because the inorganic / inorganic heterojunction is first obtained by mechanical stripping and then constructed by dry transfer, the heterojunction interface is prone to charge traps or defects, which reduces the photon lifetime and leads to weak SHG intensity. However, if you want to construct such a heterojunction by changing the preparation method, there will be other problems. For example, the few-layer inorganic material itself usually has a highly symmetrical crystal structure, which is contrary to the non-centrosymmetric structure required for SHG generation. Its carrier mobility is high but the recombination time is long, which will lead to energy dissipation, which will also affect the SHG efficiency of the device.

[0007] In this context, introducing organic materials with highly conjugated systems or large dipole moments to construct organic / inorganic heterojunctions to enhance SHG response may be a feasible solution. After the introduction of organic materials, the inorganic layer provides efficient carrier transport, and the organic layer optimizes the nonlinear optical response, which helps to improve the SHG conversion efficiency of the heterojunction. However, there are few solutions in the prior art to enhance the SHG response by constructing organic / inorganic heterojunctions, which may be related to factors such as the difficulty in selecting the specific organic materials and the specific preparation process.

[0008] Organic materials such as N,N'-dimethyl-3,4,9,10-perylenetetracarboxylic acid diimide (Me-PTCDI) and 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) have significant advantages such as flexible molecular design, diverse functionalization, and simple preparation process. Combining them with inorganic materials to construct heterojunctions is expected to significantly enhance the SHG response of two-dimensional inorganic materials through mechanisms such as interface charge transfer, band regulation, and molecular arrangement optimization. In addition, the introduction of organic materials can also achieve the construction of high-quality heterojunctions through simple processes such as solution self-assembly and vapor deposition, avoiding the high cost, low stability, and poor interface quality of traditional methods.

[0009] In summary, it is speculated that if new organic / inorganic heterojunction optoelectronic devices can be constructed based on special organic materials and through process improvements, and the limitations of traditional methods can be overcome through a synergistic enhancement mechanism, it will be possible to obtain optoelectronic devices with high SHG response intensity, and it can also provide new ideas for the subsequent development of flexible and efficient nonlinear optical devices. Summary of the invention

[0010] The purpose of the present invention is to solve the problems existing in the prior art and provide a two-dimensional organic / inorganic heterojunction optoelectronic device with SHG response. The present application strictly controls the preparation conditions, constructs a Me-PTCDI / GaSe heterojunction by mechanical exfoliation and epitaxial growth, and utilizes the synergistic enhancement effect produced by the two materials to significantly enhance the SHG response of the heterojunction. The spectral response can be extended from the original visible light range to the near-infrared band, and the SHG conversion efficiency is even as high as 0.26%, and the application prospects are quite optimistic.

[0011] In order to achieve the above technical objectives, the present invention is implemented through the following technical scheme: a two-dimensional organic / inorganic heterojunction photoelectric device with SHG response, including a substrate and a two-dimensional inorganic material layer and an organic molecule functional layer arranged in sequence on the substrate, the two-dimensional inorganic material layer and the organic molecule functional layer forming a heterojunction; the selected two-dimensional inorganic material is a two-dimensional material with a non-centrosymmetric structure, selected from any one of IIIA-VIA group compounds such as GaSe, InSe, In2Se3 and Ga2Se3; the selected organic molecule has a highly conjugated system or a large dipole moment, specifically selected from any one of organic materials such as N,N'-dimethyl-3,4,9,10-perylenetetracarboxylic acid diimide (Me-PTCDI), 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA); the two-dimensional inorganic material is torn onto the substrate by a mechanical stripping method, and then the organic molecules are formed into a uniform single-layer thin film on the surface of the few-layer two-dimensional inorganic material layer by an epitaxial growth method, that is, the organic molecule functional layer is formed.

[0012] Furthermore, the thickness of the two-dimensional inorganic material layer on the substrate is 10 nm~70 nm; the thickness of the organic molecular functional layer is 0.5 nm~50 nm.

[0013] Preferably, the two-dimensional inorganic material layer is a uniform, wrinkle-free GaSe layer with a thickness of 45 nm to 55 nm; the organic molecular functional layer is a single-layer N,N'-dimethyl-3,4,9,10-perylenetetracarboxylic acid diimide (Me-PTCDI) material layer with a thickness of 0.5 nm to 5 nm.

[0014] The SHG response intensity of the two-dimensional organic / inorganic heterojunction photoelectric device is better than that of a single heterostructure component, and is several times higher than that of GaSe. The spectral response extends from the visible light range to the near-infrared band, and the SHG conversion efficiency can reach 0.26%.

[0015] The present application also discloses a method for preparing a two-dimensional organic / inorganic heterojunction optoelectronic device with SHG response, the process is as follows:

[0016] 1) Pre-treat the substrate to remove surface contaminants and oxides;

[0017] 2) Using mechanical exfoliation to tear the two-dimensional inorganic material onto the substrate to obtain a two-dimensional inorganic material / substrate structure;

[0018] 3) Place the organic source material at the center of the tube furnace, place the two-dimensional inorganic material / substrate structure obtained in the previous step downstream 1~5 cm away from the organic source, heat and sublimate the organic molecules in an inert gas atmosphere, control the heating temperature, heating time and gas flow rate, and epitaxially grow a single layer of organic molecular material on the surface of the two-dimensional material to obtain a heterojunction optoelectronic device with a single layer of organic material / a few layers of two-dimensional inorganic material / substrate structure.

[0019] Furthermore, the two-dimensional inorganic material used in step 2) is a two-dimensional material with a non-centrosymmetric structure, specifically selected from any one of IIIA-VIA compounds such as GaSe, InSe, In2Se3 and Ga2Se3, and after being torn onto the substrate, a uniform, wrinkle-free two-dimensional inorganic material with a thickness of 10 nm to 70 nm needs to be specifically selected. Controlling the thickness of the two-dimensional inorganic material can optimize the charge transfer at the heterojunction interface, thereby helping to enhance the second harmonic generation (SHG) response of the material.

[0020] Furthermore, the organic source material is an organic molecule with a highly conjugated system or a large dipole moment, selected from any one of organic materials such as N,N'-dimethyl-3,4,9,10-perylenetetracarboxylic acid diimide (Me-PTCDI), 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA), and the thickness of the organic material layer is 0.5 nm~50 nm.

[0021] Preferably, the two-dimensional inorganic material is GaSe, and the thickness of the GaSe layer on the substrate is 45 nm to 55 nm; the organic source material is N,N'-dimethyl-3,4,9,10-perylenetetracarboxylic acid diimide (Me-PTCDI), and the thickness of a single layer of organic material is 0.5 nm to 5 nm.

[0022] Furthermore, in step 3), argon gas is introduced during heating in a tube furnace, the flow rate is controlled at 80-120 sccm, and the temperature is heated to about 200-250°C, and the gas is closed and kept in vacuum for 20-40 minutes. During epitaxial growth, the coverage of organic molecules is regulated by controlling the temperature and gas flow rate, and the charge transfer at the heterojunction interface is optimized, thereby enhancing the second harmonic generation (SHG) response of the material.

[0023] Preferably, when heating in a tube furnace, the gas flow rate is controlled at 100 sccm, heated to 230°C, sealed, and kept in vacuum for 30 min, then cooled to room temperature and opened.

[0024] The beneficial effects of the present invention are:

[0025] 1. In the present application, after a few-layer GaSe is torn onto a silicon-based substrate by mechanical exfoliation, a single-layer organic molecule is directly grown on the few-layer GaSe by epitaxial growth to obtain a heterojunction optoelectronic device. The aggregated state of the epitaxially grown single-layer organic molecule has strong light absorption and charge transfer properties, which can significantly enhance the light absorption of GaSe without causing carrier capture. The combination of the conjugated system of the organic molecule and the band structure of GaSe can produce a synergistic enhancement effect, which increases the SHG response intensity of the heterojunction several times higher than that of single GaSe.

[0026] 2. This application uses organic / inorganic materials to prepare heterojunctions, combining the advantages of organic and inorganic materials, which not only makes up for the inherent low absorption problem of GaSe, but also has a higher interface charge transfer efficiency between organic molecules and inorganic materials than traditional inorganic / inorganic heterojunctions, which can induce a huge interface dipole moment and significantly enhance the SHG response;

[0027] 3. The SHG conversion efficiency of the Me-PTCDI / GaSe heterojunction designed in this application is as high as 0.26%, which is significantly better than that of single-component GaSe (0.016%) and many traditional inorganic / inorganic heterojunctions, indicating that the Me-PTCDI / GaSe heterojunction has important application potential in nonlinear optical devices;

[0028] 4. Since the Me-PTCDI / GaSe heterojunction designed in this application has a strong SHG response, its spectral response can be extended from the original visible light range to the near-infrared band, and has high sensitivity, which can meet the needs of different application scenarios;

[0029] 5. The epitaxial growth process can precisely control the temperature and argon flow rate to arrange the monolayer of organic molecules on the GaSe surface in an orderly manner, enhance the synergistic effect between molecules, reduce interface defects and scattering, and enhance the stability of the SHG signal;

[0030] 6. The preparation process of the two-dimensional organic / inorganic heterojunction optoelectronic device with SHG response disclosed in this application is simple, does not require complex equipment and high-energy consumption processes, and is suitable for large-scale production and application. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 is a flow chart of preparing an organic / inorganic heterojunction optoelectronic device in Example 1;

[0032] Figure 2 is an optical microscope photograph of the Me-PTCDI / GaSe heterojunction prepared in Example 1;

[0033] Figure 3 is the energy band diagram of Me-PTCDI / GaSe heterojunction;

[0034] Figure 4 is the PL spectrum data of Me-PTCDI / GaSe heterojunction;

[0035] Figure 5 is the SHG peak position map of Me-PTCDI / GaSe heterojunction region;

[0036] Figure 6 It is the SHG intensity mapping diagram of Me-PTCDI / GaSe heterojunction region and GaSe region;

[0037] Figure 7 is the SHG power dependence diagram of Me-PTCDI / GaSe heterojunction region;

[0038] Figure 8 This is the wavelength dependence of SHG in the Me-PTCDI / GaSe heterojunction region. DETAILED DESCRIPTION

[0039] The following examples further illustrate the content of the present invention, but should not be construed as limiting the present invention. Without departing from the essence of the present invention, modifications and substitutions made to the methods, steps or conditions of the present invention all fall within the scope of the present invention.

[0040] Example 1

[0041] This embodiment discloses a method for preparing a two-dimensional organic / inorganic heterojunction optoelectronic device with SHG response. The preparation process is referred to Figure 1 , the specific preparation steps are as follows:

[0042] Step 1) Pretreatment of silicon-based substrate: Pretreatment of silicon (500 μm thick) / silicon oxide (275 nm thick) substrate (clean the surface with propanol after wafer cutting, then clean the surface with deionized water, and blow dry the substrate with a nitrogen gun) to obtain a silicon-based substrate with a clean surface.

[0043] Step 2) Use tape to peel off the layered sample from the gallium selenide (GaSe) bulk crystal by mechanical peeling, tear it to the surface of the silicon-based substrate, observe the sample under an optical microscope, and select uniform, wrinkle-free GaSe with a thickness of about 50 nm to obtain a GaSe / substrate structure.

[0044] Step 3) Attach a 200-mesh copper mesh to the silicon wafer and place it in a high vacuum electron beam evaporation coating apparatus to evaporate 120 nm thick gold. Remove the copper mesh and use a fine needle with a tip diameter of 1 μm to cut the gold film into 500 μm × 60 μm strip films.

[0045] Step 4) On the GaSe / substrate structure, use a fine needle with a tip diameter of 15 μm to transfer the strip-shaped gold film prepared in the previous step to the GaSe side to cover part of the inorganic material.

[0046] Step 5) Place the organic source material N,N'-dimethyl-3,4,9,10-perylenetetracarboxylic acid diimide (Me-PTCDI) into a quartz boat, and then place it and the GaSe / substrate structure on both sides of the heating center of the tube furnace, with Me-PTCDI placed in the center of the furnace and the GaSe / substrate structure placed 3 cm downstream from the center. First, evacuate the tube, wait until the pressure in the tube drops to about 1 Pa, then introduce argon gas, control the gas flow rate at 100 sccm, heat to 230°C, turn off the argon switch, keep warm for 30 min, and epitaxially grow a single layer of organic material (thickness is about 3 nm) on the surface of the two-dimensional inorganic material. After cooling to room temperature, the Au / Me-PTCDI / GaSe / substrate structure is obtained, and then the gold film is picked off with a fine needle with a tip diameter of 1 μm, so that a single GaSe area and a Me-PTCDI / GaSe heterojunction area are obtained on the same structure.

[0047] The epitaxial growth process can precisely control the temperature and argon flow rate to orderly arrange a single layer of organic molecules on the GaSe surface, enhance the synergistic effect between molecules, reduce interface defects and scattering, and enhance the stability of the SHG signal.

[0048] In this embodiment, the purpose of transferring the gold film to the GaSe / substrate structure and then removing the gold film after successfully inducing the growth of organic molecules is to prepare a single GaSe area for comparison on the same device. If only a Me-PTCDI / GaSe heterojunction optoelectronic device is to be manufactured, there is no need to remove the gold film in steps 3), 4) and 5), and only a single-layer Me-PTCDI organic material layer needs to be epitaxially grown directly on the GaSe surface on the GaSe / substrate using the epitaxial growth method.

[0049] In this embodiment, a few-layer GaSe is torn onto a silicon-based substrate by mechanical stripping, and then a single layer of organic molecules is directly grown on the few-layer GaSe by epitaxial growth to obtain a heterojunction. Figure 2 That is a microscope photograph of the single-layer Me-PTCDI (MLMe-PTCDI) / few-layer GaSe (FL GaSe) heterojunction prepared in this example.

[0050] Figure 3 The energy band diagram of the single-layer Me-PTCDI (ML Me-PTCDI) / few-layer GaSe (FL GaSe) heterojunction prepared in this example. The band gap and electron affinity of GaSe (Me-PTCDI) are 2.05 eV (2.94 eV) and -3.6 eV (-3.5 eV), respectively, forming a typical type-I band. Through the SHG process (process 1), two photons with a frequency ω from the illumination light are converted into one photon with a frequency 2ω. Then, the SHG signal is absorbed by the Me-PTCDI / GaSe heterostructure to generate photocarriers (process 2), which are finally separated by the pn junction at the Me-PTCDI / GaSe interface to generate photocurrent (process 3). Through the SHG process, the response frequency limit of light is extended from ℏω>Eg to ℏω>Eg / 2, so that the Me-PTCDI / GaSe heterojunction can respond to photons with energy lower than Eg; therefore, although the Me-PTCDI / GaSe heterojunction can only absorb light in the wavelength range less than 700 nm, it can operate in the wavelength range of about 1300 nm.

[0051] Figure 4 PL spectrum data of the single-layer Me-PTCDI (ML Me-PTCDI) / few-layer GaSe (FL GaSe) heterojunction prepared in this example; it can be seen from the PL spectrum that at 2.26 eV, narrow peaks appear in Me-PTCDI and the heterojunction, and the PL intensity of the heterojunction is about 30% lower than that of Me-PTCDI. The excitons generated in Me-PTCDI dissociate at the heterojunction interface, and the charges are transferred to GaSe, and the fluorescence of the single-layer Me-PTCDI is quenched.

[0052] Figure 5SHG peak position diagram of the single-layer Me-PTCDI (ML Me-PTCDI) / few-layer GaSe (FL GaSe) heterojunction prepared in this example; SHG spectrum test was performed in the heterojunction region using a 1064 nm laser. The results showed that there was a peak at 532 nm with a half-wave width of 1 nm. This is the SHG signal with half the wavelength, indicating the generation of the SHG process in the heterojunction region, which is consistent with the Figure 3 The analysis corresponds to the process mentioned in 1.

[0053] The sample was scanned with a CCD camera to obtain the spatial distribution image of the SHG signal. The uniformity of the sample, the interface quality, and the spatial distribution characteristics of the SHG response were evaluated by analyzing the SHG image.

[0054] Figure 6 The SHG intensity mapping diagram of the single-layer Me-PTCDI (ML Me-PTCDI) / few-layer GaSe (FL GaSe) heterojunction region and the few-layer GaSe (FL GaSe) region prepared in this example; the SHG intensity test was carried out using a 1064 nm laser, and the results showed that the SHG intensity of the heterojunction region was several times that of the GaSe region; this is because when GaSe and Me-PTCDI are in contact, due to energy level matching, electrons are transferred from the valence band of GaSe to the LUMO energy level of Me-PTCDI, forming an interfacial charge transfer, and this charge transfer induces a huge interfacial dipole moment at the interface; at the same time, the interfacial charge transfer leads to the asymmetry of the electron cloud distribution, which increases the nonlinear polarizability (χ [ ² ] ), which directly increases the SHG response intensity; in addition, Me-PTCDI molecules form an orderly arrangement on the GaSe surface through π-π stacking and van der Waals forces. This orderly arrangement enhances the synergistic effect between molecules, reduces interface defects and scattering, and improves the stability of the SHG signal.

[0055] Select a 1064 nm ultrafast laser and fix the prepared Me PTCDI / GaSe / substrate structure on a three-dimensional translation stage. Adjust the laser optical path so that the laser beam is incident vertically on the sample surface, and focus the laser beam on the sample through a focusing lens. Adjust the laser power to a suitable range (1-100 nw) to avoid sample damage (this process is mainly for damage testing). Use a filter to filter out the fundamental frequency light (incident laser wavelength) and only allow the SHG signal (wavelength is half of the incident laser) to pass.

[0056] Adjust the incident laser power (refer to the power during the damage test) and measure the SHG signal intensity of the device at different powers. Draw a curve of the relationship between the SHG signal intensity and the incident laser power to verify the quadratic dependence of the SHG signal (i.e. the relationship between the SHG signal intensity and the square of the incident laser power). Evaluate the nonlinear optical conversion efficiency of the sample by fitting the power dependence curve.

[0057] Figure 7 It is a power dependence diagram of the single-layer Me-PTCDI (ML Me-PTCDI) / few-layer GaSe (FL GaSe) heterojunction region prepared in this example; the results show that the SHG signal intensity is proportional to the square of the incident laser power, the fitting curve shows a quadratic dependence, and the SHG conversion efficiency is 0.26%, which once again proves the occurrence of the SHG process.

[0058] Adjust the output wavelength of the laser (700~1300 nm) and measure the SHG signal intensity of the device at different wavelengths. Plot the relationship between the SHG signal intensity and the incident laser wavelength to analyze the band selectivity of the sample. Determine the phase matching conditions and optimal operating wavelength of the sample through wavelength dependence testing.

[0059] Figure 8 Figure 2 is the wavelength dependence of the single-layer Me-PTCDI (ML Me-PTCDI) / few-layer GaSe (FL GaSe) heterojunction region and the few-layer GaSe (FL GaSe) region prepared in this example. Since the band gap and electron affinity of GaSe (Me-PTCDI) are 2.05 eV (2.94 eV) and -3.6 eV (-3.5 eV), respectively, the spectral response range of the heterojunction is about 400~650 nm. Due to the presence of strong SHG response, the response spectrum is broadened to 700~1300 nm, which is consistent with the wavelength dependence of the single-layer Me-PTCDI (ML Me-PTCDI) / few-layer GaSe (FL GaSe) heterojunction region. Figure 3 In addition, from Figure 8 It can also be seen that the SHG intensity of the heterojunction region at different wavelengths is significantly stronger than that of single GaSe and Me-PTCDI, which fully proves the SHG enhancement effect of the heterojunction.

[0060] The above shows and describes the basic principles, main features and advantages of the present invention. However, the above is only a specific embodiment of the present invention, and the technical features of the present invention are not limited thereto. Any other implementation methods derived by any technician in the field without departing from the technical solution of the present invention should be included in the scope of the present invention.

Claims

1. A two-dimensional organic / inorganic heterojunction optoelectronic device with SHG response, characterized in that: It includes a substrate, a two-dimensional inorganic material layer and an organic molecular functional layer forming a heterojunction; The two-dimensional inorganic material is selected from any one of GaSe, InSe, In2Se3 and Ga2Se3; The organic molecule is selected from N,N'-dimethyl-3,4,9,10-perylenetetracarboxylic acid diimide or 3,4,9,10-perylenetetracarboxylic dianhydride; The few-layer two-dimensional inorganic material layer is prepared by mechanical exfoliation, and the organic molecular functional layer is a uniform single-layer film grown on the few-layer two-dimensional inorganic material layer by epitaxial growth; The thickness of the two-dimensional inorganic material layer on the substrate is 10 nm~70 nm; the thickness of the organic molecular functional layer is 0.5 nm~50 nm; The SHG spectral response of the two-dimensional organic / inorganic heterojunction optoelectronic device extends from the visible light range to the near-infrared band, and the SHG conversion efficiency can reach 0.26%.

2. The two-dimensional organic / inorganic heterojunction optoelectronic device with SHG response according to claim 1, characterized in that: The two-dimensional inorganic material layer is a uniform and wrinkle-free GaSe layer with a thickness of 45 nm to 55 nm; the organic molecular functional layer is a single-layer N,N'-dimethyl-3,4,9,10-perylenetetracarboxamide diimide material layer with a thickness of 0.5 nm to 5 nm.

3. A method for preparing a two-dimensional organic / inorganic heterojunction optoelectronic device with SHG response, characterized in that: The specific preparation process is as follows: 1) Pre-treat the substrate; 2) Using mechanical exfoliation to tear the two-dimensional inorganic material onto the substrate to obtain a two-dimensional inorganic material / substrate structure; 3) Place the organic source material at the center of the tube furnace, place the two-dimensional inorganic material / substrate structure obtained in the previous step downstream 1-5 cm away from the organic source, heat and sublimate the organic source material in an inert gas atmosphere, control the heating temperature, heating time and gas flow rate, and epitaxially grow a single layer of organic molecular material on the two-dimensional material to obtain a heterojunction optoelectronic device with a single layer of organic molecular material / few layers of two-dimensional inorganic material / substrate structure; The two-dimensional inorganic material used in step 2) is a two-dimensional material with a non-centrosymmetric structure, selected from any one of GaSe, InSe, In2Se3 and Ga2Se3, and after being torn onto the substrate, a uniform, wrinkle-free two-dimensional inorganic material with a thickness of 10 nm to 70 nm is selected; In step 3), argon gas is introduced during heating in a tube furnace, with the flow rate controlled at 80-120 sccm, and the mixture is heated to 200-250°C, and then the argon gas is turned off and the mixture is kept in vacuum for 20-40 min; The organic source material is an organic molecule with a highly conjugated system or a large dipole moment, selected from N,N'-dimethyl-3,4,9,10-perylenetetracarboxylic acid diimide or 3,4,9,10-perylenetetracarboxylic dianhydride; the thickness of a single layer of organic molecule material is 0.5 nm to 50 nm.

4. The method for preparing a two-dimensional organic / inorganic heterojunction optoelectronic device with SHG response according to claim 3, characterized in that: The two-dimensional inorganic material is GaSe, and the thickness of the GaSe layer on the substrate is 45 nm to 55 nm; the organic source material is N,N'-dimethyl-3,4,9,10-perylenetetracarboxamide, and the thickness of a single layer of organic molecular material is 0.5 nm to 5 nm.

5. The method for preparing a two-dimensional organic / inorganic heterojunction optoelectronic device with SHG response according to claim 3, characterized in that: The gas flow rate was controlled at 100 sccm, and the mixture was heated to 230 °C. The argon gas was then turned off and the mixture was kept in vacuum for 30 min. The mixture was then cooled to room temperature and the lid was opened.

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