Two-dimensional organic / inorganic heterojunction photodetector and preparation method therefor

Abstract

The present invention relates to the technical field of photoelectric devices. Disclosed are a two-dimensional organic / inorganic heterojunction photodetector and a preparation method therefor. According to the present application, a few-layer two-dimensional material is transferred onto a substrate as a base material by means of a mechanical exfoliation method, a few-layer two-dimensional alloy material is transferred to one side of the two-dimensional material as the base material by means of PDMS, then the base material is put into a tubular furnace, to accurately epitaxially grow a single organic molecular layer on the two-dimensional alloy material by controlling the heating temperature and time to form a heterojunction, and finally gold films are transferred onto the organic molecular layer to obtain the photodetector. The heterojunction formed by the Van Der Waals epitaxially grown organic molecular layer and the two-dimensional alloy material is nearly defect-free, and can enhance light absorption without causing carrier trapping; thus, the photodetector has excellent detection capabilities, high light absorption and photoconductive gain, and a high response speed, can achieve high-frame-rate imaging under low-light conditions, and has broad application prospects in the field of imaging.

Description

Two-dimensional organic / inorganic heterojunction photodetector and preparation method thereof Technical Field

[0001] The present invention relates to the technical field of optoelectronic devices, and in particular to a two-dimensional organic / inorganic heterojunction photodetector and a preparation method thereof. Background Art

[0002] Photodetectors, which convert light signals into electrical signals, are widely used in various fields of military and national economy, playing a vital role in these fields. Today, people are increasingly demanding high-performance, wide-spectrum, and multi-band photodetectors. Therefore, the development and exploration of photodetectors based on new materials is of great significance.

[0003] Two-dimensional materials, such as nanofilms, superlattices, and quantum wells, are materials in which electrons can move freely only in two dimensions, at the nanoscale (1-100 nm). Commonly used two-dimensional materials include graphene, molybdenum disulfide, and boron nitride. Due to their advantages such as the absence of dangling bonds on the surface, tunable band gaps, wide spectral detection, and large-area fabrication, these materials have been widely used in the optoelectronics field in recent years. Among them, transition metal dichalcogenides (TMDCs) are ideal platforms for van der Waals heterostructures due to their tunable band gaps and profound light-matter interactions. However, the presence of internal defects in TMDCs can hinder the generation and migration of photogenerated carriers, resulting in delayed response speeds.

[0004] Further research has revealed that TMDCs-based alloys not only have high carrier mobility but also have a low density of deep-level defect states, which can effectively collect carriers and reduce unfavorable carrier capture. In addition, the low dark current of TMDC alloys is conducive to achieving higher detectivity. In addition, compared with traditional TMDCs semiconductors, organic molecular crystals have low dielectric constants and strong absorption. Therefore, it is expected that after precise control of the number of molecular semiconductor layers, exciton coupling will be significantly regulated and new optoelectronic properties will be generated. In order to overcome the limitations of weak absorption in TMDCs on the performance of photodetectors, atomically layered inorganic semiconductors can be combined with organic materials to achieve complementary advantages, such as reducing interface state binding, reducing Coulomb interactions, enhancing light absorption effects, and improving interface carrier transfer.

[0005] However, existing technologies typically use spin-coating thin-film techniques or quantum dot structures to fabricate organic-inorganic heterojunction detectors. These methods inevitably introduce harmful impurities, which can reduce the carrier mobility of TMDCs. Furthermore, insufficient spatial separation limits the enhancement of optical gain. Therefore, fabricating high-quality hybrid heterostructures with clean interfaces has become an effective strategy for maintaining the mobility of TMDCs and further improving the detection sensitivity and response speed of photodetectors.

[0006] The two-dimensional material layer is combined by covalent bonds, and the interlayer interaction is very weak, which makes it possible to separate the two-dimensional film from the bulk material by mechanical exfoliation. Among them, the PDMS exfoliation transfer method is a method that uses the viscoelastic PDMS polymer film as a carrier to transfer the material. This method is simple and easy, does not require polymer spin coating, and does not contact any solution during the entire process. It will not introduce more foreign impurities and has no special requirements for the substrate. Therefore, using this technology to transfer two-dimensional alloy materials will effectively control the reduction of TMDCs carrier mobility. It is worth noting that since the surface of the two-dimensional material is flat and there are no dangling bonds, it is itself an ideal van der Waals epitaxial substrate material. The van der Waals interaction between the two-dimensional material and the organic molecules is even more conducive to the growth of high-performance organic films.

[0007] In his master's thesis, "Epitaxial Growth and Optical Properties of Two-Dimensional Organic Semiconductor Thin Films," Tao Liu noted that vapor phase epitaxial growth based on van der Waals epitaxy can produce organic thin films with ultra-high quality and excellent interfacial properties on a variety of substrates, while also enabling precise control of film thickness to within a single atomic layer. The paper notes that single-layer Me-PTCDI organic thin films produced using high-temperature epitaxial growth exhibit high uniformity, crystallinity, stability, luminescence intensity, and quality. The paper also suggests that the resulting high-quality single-crystalline organic thin films and high-interface organic-inorganic heterostructures are promising for high-performance organic optoelectronic devices. However, the paper only explored the film-forming technology and did not conduct further applied research on single-layer Me-PTCDI organic thin films produced using high-temperature epitaxy. Further exploration of combining these thin films with other substrates to produce high-performance photodetection devices remains to be explored by those skilled in the art.

[0008] Summary of the Invention

[0009] The purpose of the present invention is to solve the problems existing in the prior art, provide a two-dimensional organic / inorganic heterojunction photodetector and disclose a specific preparation method. The heterojunction formed by the organic molecular layer grown by van der Waals epitaxy and the two-dimensional alloy material has almost no defects, can enhance light absorption and will not cause carriers to be captured, ensuring that the prepared photodetector has a high detection rate and a fast response speed.

[0010] In order to achieve the above technical objectives, the present invention is implemented by the following technical solutions: a method for preparing a two-dimensional organic / inorganic heterojunction photodetector, comprising the following steps:

[0011] 1) Pre-treat the substrate and transfer the 2D material to the substrate surface using mechanical exfoliation. Select a 2D material with a flat surface, a thickness of 5-20 nm, and no residual adhesive bubbles to form a 2D material / substrate structure.

[0012] 2) Peeling the 2D alloy material onto the blue film and pasting it repeatedly to control the thickness to 0.7-20 nm to form a 2D alloy material / blue film structure;

[0013] 3) Laminating the PDMS film onto a glass slide to obtain a PDMS / glass slide structure;

[0014] 4) Transfer the 2D alloy material to be transferred onto the PDMS film using a mechanical peeling method to form a glass slide / PDMS / 2D alloy material structure, and cut off the excess PDMS film with the 2D alloy material to be transferred as the center;

[0015] 5) Fix the glass slide with the two-dimensional alloy material into the substrate slot of the transfer platform, and place the substrate on the sample holder of the transfer platform;

[0016] 6) By controlling the bonding and separation rates of the transfer platform, the two-dimensional alloy material is separated from the PDMS and bonded to the side of the two-dimensional material on the substrate;

[0017] 7) Place the organic source material in the center of the tube furnace, and the substrate obtained in the previous step downstream 3-10 cm from the center. After evacuating the chamber, control the heating temperature and time to epitaxially grow a single layer of organic material crystals on the 2D alloy material, resulting in an organic material / 2D alloy material / 2D material / substrate structure.

[0018] 8) Transfer the two prepared gold films to the two ends of the organic material side of the structure obtained in the previous step to complete the preparation.

[0019] Furthermore, in step 1), the two-dimensional material is hexagonal boron nitride.

[0020] Furthermore, in step 2), the two-dimensional alloy material is Mo 0.1 W 0.9 S2 or Mo 0.5 W 0.5 S2.

[0021] Furthermore, before transferring the two-dimensional alloy material onto the PDMS film, the surface of the PDMS film needs to be treated with UV Ozone for 4 to 6 minutes.

[0022] Furthermore, the two-dimensional alloy material transferred onto the PDMS film is uniform and wrinkle-free, with a thickness of 0.7 to 10 nm and 1 to 12 layers.

[0023] Furthermore, in step 6), when transferring the two-dimensional alloy material, the glass slide is lowered at a constant speed of 0.5 μm every 5 s so that the two-dimensional alloy material is attached to one side of the two-dimensional material on the target substrate, and the attached state is maintained for 1 to 5 minutes. Thereafter, the glass slide is lifted at a constant speed of 0.5 μm every 5 s so that the two-dimensional alloy material is completely transferred to the surface of the target substrate.

[0024] Furthermore, in step 7), the organic source material is N,N'-dimethyl-3,4,9,10-perylenetetracarboxylic acid diimide (Me-PTCDI) or 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA).

[0025] Furthermore, in step 7), the tube furnace is heated to 210-260° C. for 15-30 min to evaporate the organic source material to epitaxially grow a single layer of organic material crystals on the two-dimensional alloy material.

[0026] Furthermore, in step 8), the distance between the two transferred gold thin films is 1-10 μm.

[0027] The two-dimensional organic / inorganic heterojunction photodetector prepared by the above preparation method has a two-dimensional material layer, a two-dimensional alloy material layer, a single layer of organic material crystal and a gold film arranged on the substrate in sequence.

[0028] The beneficial effects of the present invention are:

[0029] 1. This application is designed by Mo 0.1 W 0.9 The S2 / Me-PTCDI heterojunction fabricates a photodetector device with a simple structure. The heterojunction formed by the van der Waals epitaxially grown monolayer organic molecular layer and the two-dimensional alloy material is nearly defect-free, enhancing light absorption without causing carrier capture. Compared to conventional photodetectors, the photodetector fabricated in this application exhibits excellent detection capabilities, large light absorption and photoconductivity gain, and a fast response speed, enabling high-frame-rate rapid imaging in weak light conditions. It holds broad promise in imaging applications.

[0030] 2. This application uses two-dimensional alloy materials to prepare heterojunctions. Compared with traditional transition metal dichalcogenides, alloys based on two-dimensional materials have a lower density of deep energy level defect states, so that carriers are not trapped by deep energy level defects, and the generation and migration of photogenerated carriers are not hindered. As a result, the final optoelectronic device has a lower dark current and a faster response speed.

[0031] 3. This application constructs an organic molecular layer on the surface of a two-dimensional alloy material layer using an epitaxial growth method. Me-PTCDI organic molecular layers of different layer thicknesses have different aggregation states. The aggregation state of a single-layer Me-PTCDI has strong light absorption and charge transfer properties, which can effectively increase the photocurrent of the photodetector, improve the responsivity and detectivity;

[0032] 4. The gold electrode on the photodetector prepared in this application is in van der Waals contact with the heterojunction. This transfer contact form does not cause adverse doping of the heterojunction, has good contact, and does not change the properties of the heterojunction;

[0033] 5. This application utilizes a transfer platform to transfer two-dimensional alloy materials, which can accurately transfer the two-dimensional alloy materials to any position on the target substrate. The force during the transfer process is uniform and no new wrinkles are generated.

[0034] 6. This application uses UV Ozone to pre-treat the PDMS film, which can reduce the viscosity of the PDMS and reduce the adsorption of impurities on the surface of the material. After the two-dimensional alloy material is successfully transferred, the residual glue on the surface of the two-dimensional alloy material after transfer can be greatly reduced;

[0035] 7. The heterojunction photodetector disclosed in this application has a simple preparation process and low preparation cost, and is expected to become a feasible option for low-cost and functional photodetection or neuromorphic applications in the future, providing new ideas for the development of corresponding fields. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] FIG1 is a flow chart of the preparation of a two-dimensional organic / inorganic heterojunction photodetector;

[0037] Figure 2 is a diagram of Me-PTCDI / Mo prepared in Example 1 0.1 W 0.9 Microscope photo of the S2 heterojunction;

[0038] Figure 3 is a graph showing the Me-PTCDI / Mo prepared in Example 1. 0.1 W 0.9 PL fluorescence image of S2 heterojunction;

[0039] Figure 4: Hybrid heterojunction prepared in Example 1, Me-PTCDI organic source material and Mo 0.1 W 0.9 PL spectrum data of S2 two-dimensional alloy materials;

[0040] FIG5 is a light response test diagram of the two-dimensional organic / inorganic heterojunction photodetector prepared in Example 1;

[0041] Figure 6 is a graph showing Me-PTCDI / Mo prepared in Example 2. 0.1 W0.9 Microscope and PL fluorescence images of the S2 heterojunction;

[0042] FIG7 is a light response test diagram of the two-dimensional organic / inorganic heterojunction photodetector prepared in Example 2;

[0043] FIG8 is a photodetector prepared in Example 1, a photodetector prepared in Example 2, and a photodetector based on Mo 0.1 W 0.9 Comparison of the detectivity of two-dimensional organic photodetectors prepared by S2. DETAILED DESCRIPTION

[0044] The following examples further illustrate 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 are within the scope of the present invention.

[0045] The hexagonal boron nitride (h-BN) used in this application was purchased from Shanghai Pumi Precision Instrument Technology Co., Ltd. The two-dimensional alloy material Mo 0.1 W 0.9 S2 was purchased from Taizhou Juna Low Dimensional Materials Co., Ltd.; Me-PTCDI powder was purchased from Sigma Aldrich with a purity of 97% and no further purification was required.

[0046] Example 1: Preparation of a two-dimensional organic / inorganic heterojunction photodetector

[0047] Step 1) Pre-treat a silicon (500 μm thick) / silicon oxide (275 nm thick) substrate (after wafer dicing, clean the surface with propanol, then rinse the surface with deionized water, and blow dry the substrate with a nitrogen gun) to obtain a clean silicon substrate. Mechanically peel off a layered sample from a hexagonal boron nitride (h-BN) bulk crystal using tape. The layered sample is then peeled onto the surface of the silicon substrate. The sample is observed under an optical microscope, and h-BN with a flat surface, a thickness of 10 nm, and no residual adhesive bubbles is selected to obtain the h-BN / substrate structure.

[0048] Step 2) The two-dimensional alloy material Mo 0.1 W 0.9 S2 is peeled off on the blue film and pasted repeatedly until its thickness reaches about 20 nm to form Mo 0.1 W 0.9 S2 / blue film;

[0049] Step 3) Cut the PDMS into Remove the film on the surface of the small piece, make it stick to the glass slide, UV Ozone treat the PDMS surface, and then repeatedly stick the blue film / two-dimensional alloy material to remove the Mo on the blue film. 0.1W 0.9 S2 was transferred to PDMS, and a few layers, uniformity, and wrinkle-free Mo were found under a microscope. 0.1 W 0.9 S2 (the number of layers of the two-dimensional alloy material is 10 and the thickness is 8 nm), and the transferred Mo 0.1 W 0.9 With S2 as the center, cut the PDMS membrane into Squares of different sizes (after cutting off the excess film, a certain width must be reserved between the material boundary and the film boundary, so that the two-dimensional alloy material is as close as possible to the center of the sheared film for subsequent transfer).

[0050] Step 4) On the transfer platform (its function is to find the Mo previously observed under the microscope 0.1 W 0.9 S2 is aligned with the substrate to be transferred. The glass slide with the two-dimensional alloy material is fixed in the substrate slot of the transfer platform. The silicon-based substrate is adsorbed on the sample holder of the transfer platform. The transfer platform can be slowly raised and lowered. The minimum distance of adjustment for rising and falling is 0.5 μm, which can make the two-dimensional alloy material slowly adhere to the substrate surface. First find the transferred Mo 0.1 W 0.9 S2 is aligned with the h-BN / substrate structure to be transferred. During the transfer process, the bonding process is kept at a constant speed, decreasing by 0.5 μm every 5 s. After complete bonding, it is kept bonded for 1 min, and then separated at a constant speed of 0.5 μm every 5 s (to avoid rapid separation that causes the material to be torn or leaves a large amount of bubbles and residual glue), and Mo is obtained. 0.1 W 0.9 S2 / h-BN / substrate structure;

[0051] Step 5) Place N,N'-dimethyl-3,4,9,10-perylenetetracarboxylic acid diimide (Me-PTCDI) into a quartz boat and mix the organic source material with Mo 0.1 W 0.9 The S2 / h-BN / substrate structure is placed on both sides of the heating center of the tube furnace, the Me-PTCDI is placed in the center of the furnace, and the Mo 0.1 W 0.9 The S2 / h-BN / substrate structure was placed 3 cm downstream from the center. After the chamber was evacuated to ~1 Pa, the furnace was heated to 220 ° C to evaporate Me-PTCDI. The heating time was 30 min, and a single layer of Me-PTCDI crystal began to grow on the two-dimensional alloy material layer to obtain Me-PTCDI / Mo 0.1 W 0.9 S2 / h-BN / substrate structure;

[0052] Step 6) Attach a 200-mesh copper mesh to the silicon wafer and place it in a high-vacuum electron beam evaporation coater. Deposit a 120 nm thick layer of gold. Remove the copper mesh and use a 1 μm-diameter needle to scratch the gold film into 600 μm × 70 μm strips.

[0053] Step 7) In Me-PTCDI / Mo 0.1 W 0.9 On the S2 / h-BN / substrate structure, a fine needle with a tip diameter of 15 μm was used to transfer the strip-shaped gold film prepared in the previous step to the two ends of one side of the organic material layer. The distance between the two transferred strip-shaped gold films was 3 μm.

[0054] Figure 2 shows the single-layer Me-PTCDI (ML Me-PTCDI) / few-layer Mo prepared in this example. 0.1 W 0.9 S2(FL Mo 0.1 W 0.9 S2) Microscope photo of the heterojunction. After transferring the few-layer h-BN to the silicon substrate by mechanical exfoliation, the few-layer Mo was bonded to the silicon substrate by PDMS. 0.1 W 0.9 S2 is transferred to h-BN and then epitaxially grown on a few-layer Mo 0.1 W 0.9 A heterojunction is obtained by growing a single layer of organic material on S2.

[0055] Figure 3 is a PL fluorescence photo of the hybrid heterojunction prepared in this example. PL fluorescence microscopy shows that the single-layer Me-PTCDI on h-BN shows uniform green luminescence. 0.1 W 0.9 No green fluorescence was observed on S2 because charge transfer occurred in the heterojunction part, resulting in fluorescence quenching.

[0056] Figure 4 shows the mixed heterojunction, Me-PTCDI organic source material and Mo prepared in this embodiment. 0.1 W 0.9 PL spectrum data of S2 two-dimensional alloy material; From the PL spectrum, it can be seen that at 2.26 eV, Me-PTCDI and heterojunction have narrow peaks, and the PL intensity of the heterojunction is about 95% lower than that of Me-PTCDI. The excitons generated in Me-PTCDI dissociate at the heterojunction interface, and the charge is transferred to Mo 0.1 W 0.9 S2, Fluorescence quenching of monolayer Me-PTCDI.

[0057] Figure 5 is a light response test diagram of the two-dimensional organic / inorganic heterojunction photodetector prepared in this embodiment; the increased current after illumination is mainly contributed by photogenerated carriers. At this time, the measured rise and fall response times are 43.9 μs and 47.2 μs respectively, indicating a fast response speed.

[0058] Example 2: Preparation of a two-dimensional organic / inorganic heterojunction photodetector

[0059] Step 1) Pre-treat a silicon (500 μm thick) / silicon oxide (275 nm thick) substrate (after wafer dicing, clean the surface with propanol, then rinse the surface with deionized water, and blow dry the substrate with a nitrogen gun) to obtain a clean silicon substrate. Mechanically peel off a layered sample from a hexagonal boron nitride (h-BN) bulk crystal using tape. The layered sample is then peeled onto the surface of the silicon substrate. The sample is observed under an optical microscope, and h-BN with a flat surface, a thickness of 10 nm, and no residual adhesive bubbles is selected to obtain the h-BN / substrate structure.

[0060] Step 2) The two-dimensional alloy material Mo 0.1 W 0.9 S2 is peeled off on the blue film and pasted repeatedly until its thickness reaches about 20 nm to form Mo 0.1 W 0.9 S2 / blue film;

[0061] Step 3) Cut the PDMS into Remove the film on the surface of the small piece, make it stick to the glass slide, UV Ozone treat the PDMS surface, and then repeatedly stick the blue film / two-dimensional alloy material to remove the Mo on the blue film. 0.1 W 0.9 S2 was transferred to PDMS, and a few layers, uniformity, and wrinkle-free Mo were found under a microscope. 0.1 W 0.9 S2, and transfer Mo 0.1 W 0.9 With S2 as the center, cut the PDMS membrane into Squares of different sizes (after cutting off the excess film, a certain width must be reserved between the material boundary and the film boundary, so that the two-dimensional alloy material is as close as possible to the center of the sheared film for subsequent transfer).

[0062] Step 4) On the transfer platform (its function is to find the Mo previously observed under the microscope 0.1 W 0.9S2 is aligned with the substrate to be transferred. The glass slide with the two-dimensional alloy material is fixed in the substrate slot of the transfer platform. The silicon-based substrate is adsorbed on the sample holder of the transfer platform. The transfer platform can be slowly raised and lowered. The minimum distance of adjustment for rising and falling is 0.5 μm, which can make the two-dimensional alloy material slowly adhere to the substrate surface. First find the transferred Mo 0.1 W 0.9 S2 is aligned with the h-BN / substrate structure to be transferred. During the transfer process, the bonding process is kept at a constant speed, descending 0.5 μm every 5 s. After complete bonding, it is kept bonded for 1 min, and then separated at a constant speed of 0.5 μm every 5 s (to avoid rapid separation that may cause the material to be torn or leave a large number of bubbles and residual glue), thereby obtaining a two-dimensional material / h-BN / substrate structure;

[0063] Step 5) Place the Me-PTCDI organic source material into the quartz boat and mix the organic source material with Mo 0.1 W 0.9 The S2 / h-BN / substrate structure is placed on both sides of the heating center of the tube furnace, the Me-PTCDI is placed in the center of the furnace, and the Mo 0.1 W 0.9 The S2 / h-BN / substrate structure was placed 3 cm downstream from the center. After the chamber was evacuated to ~1 Pa, the furnace was heated to 250°C to evaporate Me-PTCDI. The temperature was maintained for 35 minutes, and a few layers of Me-PTCDI crystals (about 10 layers) were grown on the two-dimensional alloy material layer to obtain Me-PTCDI / Mo 0.1 W 0.9 S2 / h-BN / substrate structure;

[0064] Step 6) Attach a 200-mesh copper mesh to the silicon wafer and place it in a high-vacuum electron beam evaporation coater. Deposit a 120 nm thick layer of gold. Remove the copper mesh and use a 1 μm-diameter needle to scratch the gold film into 600 μm × 70 μm strips.

[0065] Step 7) In Me-PTCDI / Mo 0.1 W 0.9 On the S2 / h-BN / substrate structure, a fine needle with a tip diameter of 15 μm was used to transfer the strip-shaped gold film prepared in the previous step to the two ends of one side of the organic material layer. The distance between the two transferred strip-shaped gold films was 4 μm.

[0066] The difference between this embodiment and embodiment 1 is that in embodiment 1, 0.1 W 0.9 A single layer of organic thin film is epitaxially grown on the S2 / h-BN substrate using a high temperature method. In this embodiment, 10 layers of organic material are epitaxially grown on the substrate surface using a high temperature method by regulating the growth temperature and time.

[0067] Figure 6 shows the few-layer Me-PTCDI (FL Me-PTCDI) / few-layer Mo prepared in this example. 0.1 W 0.9 S2(FL Mo 0.1 W 0.9 S2) Microscope photo and PL fluorescence photo of the heterojunction. In this example, the few-layer h-BN was transferred to the silicon substrate by mechanical peeling, and the few-layer Mo was transferred to the silicon substrate by PDMS. 0.1 W 0.9 S2 was transferred onto h-BN, and a few-layer Me-PTCDI was grown on the two-dimensional alloy material. The upper right illustration shows that the few-layer organic material emits red light under PL fluorescence microscopy, and the few-layer Mo 0.1 W 0.9 The red light in the heterojunction region formed by S2 and a few-layer Me-PTCDI is weakened but not completely quenched. This is mainly because the fluorescence of the thick organic material layer is strong and the charge transfer is not sufficient to completely quench the fluorescence. Therefore, the fluorescence of the few-layer organic material layer can still be observed.

[0068] Figure 7 is a photoresponse test diagram of the two-dimensional organic / inorganic heterojunction photodetector prepared in this embodiment; the increased current after illumination is mainly contributed by photogenerated carriers, and the measured rise and fall response times are 555 ms and 362 ms respectively. 0.1 W 0.9 Compared with growing a single organic material layer (ML Me-PTCDI) on S2, growing a few organic material layers (FL Mo 0.1 W 0.9 S2) can further increase the photocurrent of the photodetector, improve the response and detection rate.

[0069] FIG8 is a comparison of the photodetector prepared in Example 1, the photodetector prepared in Example 2, and the photodetector based on the few-layer Mo 0.1 W 0.9 Two-dimensional organic photodetector prepared by S2 (denoted as FL Mo 0.1 W 0.9 S2, the detector used as a control, is different from the photodetector prepared in Example 1 in that no organic / inorganic heterojunction is formed during the preparation of this detector, that is, no Me-PTCDI organic material layer is grown on the two-dimensional alloy material layer. The other structures are the same as the photodetector in Example 1. 0.1 W 0.9 S2 dominates the light response, and the heterojunction photodetector based on a single layer of organic molecular layer prepared in Example 1 (denoted as FL Mo0.1 W 0.9 The detectivity of S2 / ML Me-PTCDI) is the highest, which is because the single-layer Me-PTCDI / few-layer Mo 0.1 W 0.9 The charge transfer effect of the heterojunction formed by S2 is good and there are fewer defects in the molecular layer, so the response is better than that of the heterojunction photodetector based on a few organic molecular layers prepared in Example 2 (denoted as FL Mo 0.1 W 0.9 S2 / FL Me-PTCDI); At the same time, the responsivity of the photodetector prepared in Example 1 is significantly better than that of FL Mo 0.1 W 0.9 S2 is mainly because the heterojunction formed after epitaxial growth of a single layer of organic material on a two-dimensional alloy material layer has almost no defects, which can enhance light absorption without causing carrier capture, effectively increasing the photocurrent of the photodetector, and improving the response and detection rate.

[0070] 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 person skilled in the art without departing from the technical solution of the present invention should be included in the patent scope of the present invention.

Claims

1. A method for preparing a two-dimensional organic / inorganic heterojunction photodetector, characterized in that: The steps include: 1) Pre-treat the substrate and transfer the 2D material to the substrate surface using mechanical exfoliation. Select a 2D material with a flat surface, a thickness of 5-20 nm, and no residual adhesive bubbles to form a 2D material / substrate structure. 2) Peeling the 2D alloy material onto the blue film and pasting it repeatedly to control the thickness to 0.7-20 nm to form a 2D alloy material / blue film structure; 3) Laminating the PDMS film onto a glass slide to obtain a PDMS / glass slide structure; 2) Transfer the 2D alloy material to be transferred onto the PDMS film using a mechanical peeling method to form a glass slide / PDMS / 2D alloy material structure, and then cut off the excess PDMS film with the 2D alloy material to be transferred as the center; 5) Fix the glass slide with the two-dimensional alloy material into the substrate slot of the transfer platform, and place the substrate on the sample holder of the transfer platform; 6) By controlling the bonding and separation rates of the transfer platform, the two-dimensional alloy material is separated from the PDMS and bonded to the side of the two-dimensional material on the substrate; 7) Place the organic source material in the center of the tube furnace, and the substrate obtained in the previous step downstream 3-10 cm from the center. After evacuating the chamber, control the heating temperature and time to epitaxially grow a single layer of organic material crystals on the 2D alloy material, resulting in an organic material / 2D alloy material / 2D material / substrate structure. 8) Transfer the two prepared gold films to the two ends of the organic material side of the structure obtained in the previous step to complete the preparation.

2. The method for preparing a two-dimensional organic / inorganic heterojunction photodetector according to claim 1, wherein: In step 1), the two-dimensional material is hexagonal boron nitride.

3. The method for preparing a two-dimensional organic / inorganic heterojunction photodetector according to claim 1, wherein: In step 2), the two-dimensional alloy material is Mo 0.1 W 0.9 S2 or Mo 0.5 W 0.5 S2.

4. The method for preparing a two-dimensional organic / inorganic heterojunction photodetector according to claim 1, wherein: Before transferring the two-dimensional alloy material onto the PDMS film, the surface of the PDMS film needs to be treated with UV Ozone.

5. The method for preparing a two-dimensional organic / inorganic heterojunction photodetector according to claim 1, wherein: The two-dimensional alloy material transferred to the PDMS film is uniform and wrinkle-free, with a thickness of 0.7~10 nm and 1 to 12 layers.

6. The method for preparing a two-dimensional organic / inorganic heterojunction photodetector according to claim 1, wherein: In step 6), when transferring the two-dimensional alloy material, the glass slide is lowered at a constant speed of 0.5 μm every 5 seconds so that the two-dimensional alloy material adheres to the side of the two-dimensional material on the target substrate. The adhesion state is maintained for 1 to 5 minutes, and then the glass slide is lifted at a constant speed of 0.5 μm every 5 seconds so that the two-dimensional alloy material is completely transferred to the surface of the target substrate.

7. The method for preparing a two-dimensional organic / inorganic heterojunction photodetector according to claim 1, wherein: In step 7), the organic source material is N,N'-dimethyl-3,4,9,10-perylenetetracarboxylic acid diimide or 3,4,9,10-perylenetetracarboxylic dianhydride.

8. The method for preparing a two-dimensional organic / inorganic heterojunction photodetector according to claim 1, wherein: In step 7), the tube furnace is heated to 210-260° C. for 15-30 min to evaporate the organic source material to epitaxially grow a single layer of organic material crystals on the two-dimensional alloy material.

9. The method for preparing a two-dimensional organic / inorganic heterojunction photodetector according to claim 1, wherein: In step 8), the distance between the two transferred gold film strips is 1-10 μm.

10. A two-dimensional organic / inorganic heterojunction photodetector, characterized in that: It is prepared according to the preparation method of a two-dimensional organic / inorganic heterojunction photodetector according to any one of claims 1-9, and the photodetector is obtained by sequentially arranging a two-dimensional material layer, a two-dimensional alloy material layer, a single layer of organic material crystal and a gold film on a substrate.

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