A metal-semiconductor heterojunction flexible ultraviolet photodetector and its preparation method

Abstract

The present invention discloses a metal-semiconductor heterojunction flexible ultraviolet photodetector and a preparation method thereof. The detector comprises a flexible substrate, a metal electrode layer, an Al layer, a ZnO layer, a Cs3Cu2I5 layer and a PDMS polydimethylsiloxane layer. The flexible substrate is a polyethylene terephthalate film. The metal electrode layer is formed on the surface of the flexible substrate. The Al layer is formed on the surface of the metal electrode layer. The ZnO layer is formed on the surface of the Al layer. The Cs3Cu2I5 layer is formed on the surface of the ZnO layer. The PDMS polydimethylsiloxane layer is formed on the surface of the Cs3Cu2I5 layer. The present invention uses a PET flexible substrate, so that the prepared photodetector has excellent mechanical flexibility, meeting the requirements of wearable electronic devices. The present invention adopts a simple low-temperature solution method to synthesize materials, which meets the requirements of simple and easy preparation and low-cost production of optoelectronic devices, and is conducive to large-scale commercial applications.

Description

Technical Field

[0001] The present invention relates to a photoelectric detector, in particular to a metal-semiconductor heterojunction flexible ultraviolet photoelectric detector and a preparation method thereof, belonging to the technical field of photoelectric detectors. Background Art

[0002] Photodetectors, which convert light signals into electrical signals, have widespread applications across the military and the national economy. Ultraviolet (UV) photodetectors have significant applications in communications, image sensing, environmental monitoring, and missile warning. With the increasing demand for wearable electronic devices, flexible photodetectors have become a research hotspot. Currently available photodetectors are mostly based on silicon, ceramic, and ITO glass substrates, all of which have poor mechanical flexibility and are unsuitable for the performance requirements of current wearable electronics.

[0003] Lead-free halide perovskites are widely used in photodetector research due to their low dark current, wide bandgap, low toxicity, and ease of fabrication. However, photodetectors fabricated from single perovskite materials suffer from poor photoelectric performance. Therefore, perovskites are combined with ZnO, where the perovskite acts as a light-supplementing material and hole collector, while ZnO, with its high carrier mobility, serves as a carrier transport channel. This heterostructure combines the advantages of both materials and can effectively enhance the photoelectric performance of photodetectors. Summary of the Invention

[0004] The object of the present invention is to provide a metal-semiconductor heterojunction flexible ultraviolet photodetector and a preparation method thereof, so as to solve the problems raised in the above background technology.

[0005] To achieve the above-mentioned objectives, the present invention provides the following technical solution: a metal-semiconductor heterojunction flexible ultraviolet photodetector, comprising a flexible substrate, a metal electrode layer, an Al layer, a ZnO layer, a Cs3Cu2I5 layer and a PDMS polydimethylsiloxane layer, wherein the flexible substrate is a polyethylene terephthalate film, the metal electrode layer is formed on the surface of the flexible substrate, the Al layer is formed on the surface of the metal electrode layer, the ZnO layer is formed on the surface of the Al layer, the Cs3Cu2I5 layer is formed on the surface of the ZnO layer, and the PDMS polydimethylsiloxane layer is formed on the surface of the Cs3Cu2I5 layer.

[0006] As a preferred technical solution of the present invention, a method for preparing a metal-semiconductor heterojunction flexible ultraviolet photodetector comprises the following steps:

[0007] S1: Cut the PET flexible substrate into 1cm×1cm squares, clean it with acetone and alcohol in a volume ratio of 1:2, and dry it at 20℃-25℃ for 20-25min under nitrogen environment. Then, use a gas flow rate of 60-70sccm and a plasma power of 0.8-0.9W / cm 2 The PET flexible substrate is treated with oxygen plasma for 10-15 minutes.

[0008] S2: A 50 nm thick Cr metal electrode was first deposited on the flexible substrate by vacuum evaporation, followed by a 50 nm thick Au metal electrode. The vacuum evaporation conditions were: vacuum degree 5×10 -3 Pa, evaporation rate is 0.1-1A / s;

[0009] S3: The flexible substrate was vacuum-adsorbed on the center of the spin coater turntable. The spin coater speed was set to 500-800 rpm. 1 mL of 0.1 mg / mL Al·NCs solution was pipetted using a pipette. The spin coater was run for 30 seconds before spin coating was performed for 30-35 seconds. The solvent was dried under nitrogen at 20-25°C. The above spin coating operation was repeated 1-2 times to obtain a transparent thin film distributed over the entire flexible substrate, thus obtaining an Al layer on the surface of the flexible substrate.

[0010] S4: The flexible substrate was vacuum-adsorbed on the center of the spin coater turntable. The spin coater speed was set to 1000-1200 r / min. 2 mL of 2 mg / mL ZnO·QDs solution was drawn using a 5 mL disposable dropper. The spin coater was run for 30 seconds before spin coating was performed for 25-30 seconds. The device coated with ZnO QDs was annealed at 80-90°C in a nitrogen environment for 20-25 minutes. The above spin coating operation was repeated 5-6 times to obtain a white film distributed on the Al NCs coating, and a ZnO layer was obtained on the surface of the Al layer.

[0011] S5: The flexible substrate was vacuum-adsorbed on the center of the spin coater turntable. The spin coater speed was set to 800-1000 r / min. 1 mL of 8 mg / mL Cs3Cu2I5·QDs solution was drawn using a pipette. The spin coater was run for 30 seconds before spin coating was performed for 25-35 seconds. The device coated with Cs3Cu2I5·QDs was annealed at 80-90°C in a nitrogen environment for 10-15 minutes. The above spin coating operation was repeated 4-5 times to obtain a yellow thin film distributed on the ZnO·QDs coating, and a Cs3Cu2I5 layer was obtained on the surface of the ZnO layer.

[0012] S6: Vacuum adsorb the flexible substrate on the center of the spin coater turntable, set the spin coater speed to 1000-1200r / min, use a pipette to draw 1mL of PDMS mixed solution, run the spin coater for 30s, and then spin coat for 30-35s. Heat the device to 80-85℃ for 2-2.5h to obtain a PDMS layer on the surface of the Cs3Cu2I5 layer, and prepare a metal-semiconductor heterojunction flexible ultraviolet photodetector.

[0013] As a preferred technical solution of the present invention, the Al·NCs solution is prepared as follows: aluminum chloride is dissolved in mesitylene, the mixture is stirred at 80-85°C, polyethylene glycol and lithium aluminum hydride are added, the solution is heated to 140°C, and magnetic stirring is continued under a nitrogen atmosphere for 10 hours. The solvent is then washed multiple times with anhydrous acetone and centrifuged. Finally, the Al nanoparticles are dispersed in the anhydrous acetone solution to prepare a transparent Al·NCs solution.

[0014] As a preferred technical solution of the present invention, the preparation method of the ZnO·QDs solution is as follows: 2.95 g of zinc acetate dihydrate is dissolved in 125 mL of methanol at 60° C., and potassium hydroxide-methanol solution is added to the zinc acetate dihydrate solution under vigorous stirring. Stirring is continued at 60° C. for three hours, and the solution changes from translucent to a milky white suspension, and nanoparticles begin to precipitate. The precipitate is obtained by centrifugation, and then the precipitate is washed with methanol multiple times and centrifuged again. Finally, the ZnO nanocrystals are dispersed in an ethanol solution to prepare a white transparent ZnO suspension.

[0015] As a preferred technical solution of the present invention, the Cs3Cu2I5·QDs solution is prepared as follows: copper iodide and 1-octadecene are placed in a 100 mL three-necked flask and dried at 150°C under nitrogen for 1 hour. Oleic acid and oleylamine are then injected at 120°C. When the CuI is completely dissolved, the solution turns light brown. The temperature is then lowered to 70°C, and Cs-oleate preheated to 100°C is rapidly injected. After 1 minute, the reaction mixture is cooled with ice water to a temperature of 20-25°C to quench the reaction. The cooled mixture turns off-white and is centrifuged at 8000 rpm for 10 minutes. After centrifugation, the supernatant is removed, and the precipitate is dispersed in n-hexane. The precipitate is washed multiple times with n-hexane and centrifuged again at 10000 rpm for 5 minutes. Finally, the Cs3Cu2I5 nanocrystals are dispersed in the n-hexane solution to prepare a slightly yellowish, milky-white Cs3Cu2I5 suspension.

[0016] As a preferred technical solution of the present invention, the PDMS layer is prepared by mixing a PDMS prepolymer and a curing agent in a ratio of 10:1, magnetically stirring for 1-1.2 hours, placing the mixed solution in a vacuum chamber, vacuuming and placing it for 1-1.5 hours, taking the mixed solution out of the vacuum chamber, and using a pipette to draw 1 mL of the mixed solution and spin-coating it onto the device surface. The speed of the glue machine is set to 1000-1200 revolutions per minute. The glue machine runs for 30 seconds before spin coating. The spin coating time is 30-35 seconds, and then the device is heated to 80-85°C for 2-2.5 hours.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. Due to the use of PET flexible substrate, the prepared photodetector has excellent mechanical flexibility, meeting the requirements of wearable electronic devices.

[0019] 2. The present invention adopts a simple low-temperature solution method to synthesize materials, which meets the requirements of simple and easy preparation and low-cost production of optoelectronic devices, and is conducive to large-scale commercial applications.

[0020] 3. The present invention adopts a metal-semiconductor combination. Due to its high electron density, Al can exhibit strong local field enhancement. The combination of semiconductor and plasma metal components can provide opportunities based on exciton-plasmon interactions, which can effectively improve the performance of optoelectronic devices.

[0021] 4. The present invention adopts Cs3Cu2I5 material, and the lead-free halide perovskite has low toxicity, meets the requirements of being environmentally friendly and easy to degrade.

[0022] 5. The present invention combines ZnO quantum dots with Cs3Cu2I5 quantum dots to expand the device's detection range to the deep ultraviolet region. In this structure, Cs3Cu2I5 acts as a light-filling material and hole collector, while ZnO, due to its high carrier mobility, serves as a carrier transport channel. This structure greatly improves the separation efficiency of electron-hole pairs, facilitates carrier transport, thereby increasing photocurrent and enhancing the device's response detection capability. The zero-dimensional nanostructure also has good optoelectronic properties, mechanical flexibility, and stability.

[0023] In the present invention, the metal-semiconductor heterojunction flexible ultraviolet photodetector is prepared by a simple low-temperature solution method and spin coating process, has good detection capability, and is an ideal choice for high-performance flexible ultraviolet photodetectors. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 Schematic diagram of the structure of a metal-semiconductor heterojunction flexible ultraviolet photodetector;

[0025] Figure 2 This is a TEM test image of ZnO quantum dots in Example 2 of the present invention;

[0026] Figure 3 This is a SEM test image of Cs3Cu2I5 quantum dots in Example 3 of the present invention;

[0027] Figure 4 The current-voltage test curves of the flexible ultraviolet photodetectors of Examples 1-5 of the present invention with and without ZnO added;

[0028] Figure 5 1 is a current-time test curve of the metal-semiconductor heterojunction flexible ultraviolet photodetector of Examples 1-5 of the present invention;

[0029] Figure 6 Graphs showing the photoelectric performance of the metal-semiconductor heterojunction flexible ultraviolet photodetectors of Examples 1-5 of the present invention under different bending times. DETAILED DESCRIPTION

[0030] The following will clearly and completely describe the technical solutions in the embodiments of the present invention in conjunction with the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0031] See also Figure 1-6 The present invention provides a technical solution for a metal-semiconductor heterojunction flexible ultraviolet photodetector and a preparation method thereof:

[0032] It consists of a flexible substrate, a metal electrode, an Al layer, a ZnO layer, a Cs3Cu2I5 layer and a PDMS layer stacked in sequence from bottom to top, such as Figure 1 As shown;

[0033] The flexible substrate is polyethylene terephthalate (PET);

[0034] The metal electrode is Cr / Au.

[0035] Al is a metal particle that can exhibit strong local field enhancement, which is beneficial to improving the photoelectric performance of photodetectors.

[0036] ZnO is a zero-dimensional quantum dot nanocrystal with a high carrier transfer rate, which is beneficial to improving the photoelectric performance of photodetectors.

[0037] Cs3Cu2I5 is an inorganic halide perovskite with good light absorption ability, which can absorb photons and generate electron holes.

[0038] PDMS has good flexibility and is in very close contact with rough surfaces, thus protecting the photodetector.

[0039] The preparation method comprises:

[0040] S1: The flexible material was cut into 1 cm × 1 cm squares, cleaned with acetone: alcohol (volume ratio 1:2), and dried at 20°C-25°C in a nitrogen environment for 20-25 min. The plasma was then heated to 0.8-0.9 W / cm with a gas flow rate of 60-70 sccm and a plasma power of 0.8-0.9 W / cm 2 oxygen plasma treatment for 10-15 min to obtain a flexible substrate;

[0041] S2: Using vacuum evaporation coating method, a 50nm thick Cr metal electrode is first evaporated on the surface of the flexible substrate, and then an Au metal electrode is evaporated with a thickness of 50nm;

[0042] Vacuum evaporation conditions are: vacuum degree 5×10 -3 Pa, the evaporation rate is

[0043] Al thin films were prepared on the flexible substrate surface by spin coating at 20-22°C and 40% relative humidity;

[0044] The specific steps of the spin coating method are as follows:

[0045] 1) Vacuum the flexible substrate to the center of the turntable of the coating machine;

[0046] 2) Set the speed of the glue machine to 500-800r / min;

[0047] 3) Use a pipette to draw 1 mL of Al·NCs solution (0.1 mg / mL). Run the spin coater for 30 seconds before spin coating for 30-35 seconds to obtain a transparent film.

[0048] 4) The solvent was blown dry at 20°C-25°C under nitrogen atmosphere, and the above spin coating operation was repeated 1-2 times to obtain a transparent film distributed over the entire substrate;

[0049] The ZnO film was prepared on the Al film surface by spin coating at 20-22°C and 40% relative humidity;

[0050] The specific steps of the spin coating method are as follows:

[0051] 1) Vacuum the flexible substrate to the center of the turntable of the coating machine;

[0052] 2) Set the speed of the glue machine to 1000-1200r / min;

[0053] 3) Use a 5 mL disposable dropper to draw 2 mL of ZnO·QDs solution (2 mg / mL). Run the spin coater for 30 seconds before spin coating for 25-30 seconds to obtain a light white film.

[0054] 4) Anneal the device with ZnO·QDs spin-coated at 80-90°C in a nitrogen environment for 20-25 min. Repeat the above spin-coating operation 5-6 times to obtain a white film distributed on the Al NCs coating.

[0055] Cs3Cu2I5 thin film was prepared on the surface of ZnO film by spin coating at 20-22℃ and relative humidity of 40%.

[0056] The specific steps of the spin coating method are as follows:

[0057] 1) Vacuum the flexible substrate to the center of the turntable of the coating machine;

[0058] 2) Set the speed of the glue machine to 800-1000r / min;

[0059] 3) Use a pipette to draw 1 mL of Cs3Cu2I5·QDs solution (8 mg / mL). Run the spin coater for 30 seconds before spin coating for 25-35 seconds to obtain a light yellow film.

[0060] 4) The device spin-coated with the Cs3Cu2I5·QDs solution was annealed at 80-90°C in a nitrogen environment for 10-15 minutes, and the above spin-coating operation was repeated 4-5 times to obtain a yellow thin film distributed on the ZnO·QDs coating;

[0061] The PDMS layer was prepared by spin coating on the surface of the Cs3Cu2I5 film:

[0062] The specific steps of the spin coating method are as follows:

[0063] 1) Vacuum the flexible substrate to the center of the turntable of the coating machine;

[0064] 2) Set the speed of the glue machine to 1000-1200r / min;

[0065] 3) Use a pipette to draw 1 mL of PDMS solution, run the gel coater for 30 seconds, and then spin coat for 30-35 seconds.

[0066] 4) Heat the device to 80-85°C for 2-2.5 hours;

[0067] In order to make the purpose, technical solutions and advantages of the present invention more clear, the present invention is described below with reference to the accompanying drawings and embodiments.

[0068] It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0069] Example 1, Preparation of Al Nanocrystals:

[0070] Aluminum chloride (AR, 97%, 0.067 g) was dissolved in mesitylene (HPLC, ≥90.0%, 10 mL; mesitylene was washed with concentrated sulfuric acid until it became colorless, and then washed successively with deionized water and 5-8% NaOH solution, and the treated mesitylene solvent was stirred with CaH2 for 10-12 h and distilled for later use). The mixture was stirred at 80-85°C (200 r / min), and polyethylene glycol (average Mn4000) and lithium aluminum hydride (1.138 g, 30 mmol; lithium aluminum hydride was reprecipitated in 10 mL of mesitylene before use to form LiAlH4 nanoparticles) were added. The solution was heated to 140°C and magnetically stirred (200 r / min) under a nitrogen atmosphere for 10 h. The solvent was washed with anhydrous acetone several times and centrifuged (6000 r / min, 10-15 min). Finally, the Al nanoparticles were dispersed in anhydrous acetone solution to prepare a transparent Al NCs solution (0.1 mg / mL).

[0071] Example 2, Preparation of ZnO Quantum Dots:

[0072] 2.95 g of zinc acetate dihydrate (AR, 99%) was dissolved in 125 mL of methanol (AR, 99.5%) at 60°C, and potassium hydroxide (GR, ≥99.7%, 1.48 g)-methanol (65 mL) solution was added to the zinc acetate dihydrate solution under vigorous stirring. Stirring was continued at 60°C for 3 hours, and the solution changed from translucent to a milky white suspension, and nanoparticles began to precipitate. At this time, a precipitate was obtained by centrifugation (5000-6000 r / min, 5-8 min). Subsequently, the precipitate was washed with methanol several times and centrifuged again (5000 r / min, 5 min). Finally, the ZnO nanocrystals were dispersed in an ethanol solution to prepare a white transparent ZnO suspension (2 mg / mL), the transmission electron microscope (TEM) image of which is shown in FIG. Figure 2 shown.

[0073] Example 3, Preparation of Cs3Cu2I5 Quantum Dots:

[0074] 1) Preparation of Cs-oleate: Cesium carbonate (CsCO, 1 mmol), oleic acid (GC, ≥99%, 1 mL), and 1-octadecene (GC, ≥90%, 15 mL) were placed in a 100 mL three-necked flask and dried at 120°C under nitrogen for 1 hour. The solution was then maintained at 150°C for 10 minutes until the CsCO and oleic acid reacted completely.

[0075] 2) Copper iodide (CuI, 0.4 mmol) and 1-octadecene (GC, ≥90%, 10 mL) were placed in a 100 mL three-necked flask and dried at 150°C under nitrogen for 1 h. Oleic acid (GC, ≥99%, 0.5 mL) and oleylamine (C18, 80-90%, 0.5 mL) were then injected at 120°C. When the CuI was completely dissolved, the solution was light brown, and the temperature was lowered to 70°C. Cs-oleate (3 mL, prepared as described above) preheated to 100°C was quickly injected. After 1 min, the reaction was cooled with ice water and quickly cooled to 20°C-25°C to quench the reaction. The cooled mixture was off-white and centrifuged at 8000 rpm for 10 min. After centrifugation, the supernatant was removed and the precipitate was dispersed in n-hexane. The precipitate was washed several times with n-hexane and centrifuged again at 10000 rpm for 5 min. Finally, Cs3Cu2I5 nanocrystals were dispersed in n-hexane solution to prepare a slightly yellow milky white Cs3Cu2I5 suspension (8 mg / mL), the scanning electron microscope (SEM) image of which is shown in Figure 2. Figure 3 shown.

[0076] Example 4, preparation of PDMS mixed solution:

[0077] Mix the PDMS prepolymer and curing agent in a ratio of 10:1 and stir magnetically for 1-1.2 hours. Place the mixed solution in a vacuum chamber and evacuate for 1-1.5 hours.

[0078] Example 5: Preparation of a metal-heterojunction flexible ultraviolet photodetector:

[0079] 1) Cut the flexible PET substrate into 1 cm x 1 cm squares, clean it with acetone:ethanol (volume ratio 1:2), and dry it at 20°C-25°C under nitrogen for 20-25 minutes. Then, treat it with oxygen plasma at a gas flow rate of 60-70 sccm and a plasma power of 0.8-0.9 W / cm² for 10-15 minutes to obtain a flexible PET substrate.

[0080] 2) Using vacuum evaporation, a 50 nm thick Cr metal electrode is first deposited on the surface of the flexible substrate, followed by a 50 nm thick Au metal electrode. The vacuum evaporation conditions are: a vacuum degree of 5 × 10-3 Pa and an evaporation rate of 0.1-1 A / s.

[0081] 3) Vacuum the flexible substrate onto the center of the spin coater's turntable and set the spin coater speed to 500-800 rpm. Use a pipette to draw up 1 mL of the Al NCs solution (0.1 mg / mL). Run the spin coater for 30 seconds before spin coating for 30-35 seconds. Blow dry the solvent under nitrogen at 20°C-25°C. Repeat the spin coating process 1-2 times to obtain a transparent film distributed over the entire substrate, resulting in an Al film on the flexible substrate surface.

[0082] 4) Vacuum the flexible substrate onto the center of the spin coater turntable and set the spin coater speed to 1000-1200 rpm. Use a 5-mL disposable dropper to draw 2 mL of ZnO QDs solution (2 mg / mL). Run the spin coater for 30 seconds before spin coating for 25-30 seconds. Anneal the device coated with ZnO QDs at 80-90°C in a nitrogen environment for 20-25 minutes. Repeat the spin coating operation 5-6 times to obtain a white film distributed on the Al NCs coating, resulting in a ZnO film on the surface of the Al layer.

[0083] 5) Vacuum the flexible substrate onto the center of the spin coater's turntable and set the spin coater speed to 800-1000 rpm. Use a pipette to draw 1 mL of the Cs3Cu2I5·QDs solution (8 mg / mL). Run the spin coater for 30 seconds before spin coating for 25-35 seconds. Anneal the device coated with Cs3Cu2I5 QDs at 80-90°C in a nitrogen environment for 10-15 minutes. Repeat this spin coating process 4-5 times to obtain a yellowish film distributed on the ZnO QD coating, resulting in a Cs3Cu2I5 film on the surface of the ZnO layer.

[0084] 6) Vacuum the flexible substrate onto the center of the spin coater's turntable and set the spin coater speed to 1000-1200 rpm. Use a pipette to draw 1 mL of the PDMS mixture. Run the spin coater for 30 seconds before spin coating for 30-35 seconds. Heat the device to 80-85°C for 2-2.5 hours to form a PDMS film on the surface of the Cs3Cu2I5 layer, thus fabricating a metal-semiconductor heterojunction flexible UV photodetector.

[0085] The current-voltage curves of the metal-semiconductor heterojunction flexible ultraviolet photodetectors of Examples 1-5 with and without ZnO under excitation at a wavelength of 280 nm are as follows: Figure 4 As shown in Figure 2, with the addition of ZnO, the light-to-dark current ratio of the photodetector increases by more than an order of magnitude. The maximum photoresponsivity can reach 101.7 mA / W.

[0086] The current-time test curves of the metal-semiconductor heterojunction flexible ultraviolet photodetectors of Examples 1-5 under the excitation of 280nm wavelength are as follows: Figure 5 The response time of the photodetector is 0.68s (rise time) / 0.83s (fall time), which has a fast response speed and high response sensitivity.

[0087] The photoelectric performance of the metal-semiconductor heterojunction flexible ultraviolet photodetector of Examples 1-5 under different bending times is shown in the figure below. Figure 6 As shown, the photodetector still has good photoelectric performance after 300 bends, indicating that the device has good mechanical flexibility and stability.

[0088] In the description of the present invention, it should be understood that the indicated orientations or positional relationships are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0089] In the present invention, unless otherwise clearly specified and limited, for example, it can be a fixed connection, a detachable connection, or an integrated connection; it can be a mechanical connection or an electrical connection; it can be directly connected or indirectly connected through an intermediate medium, it can be internal communication between two elements or an interaction relationship between two elements. Unless otherwise clearly specified and limited, ordinary technicians in this field can understand the specific meanings of the above terms in the present invention according to specific circumstances.

[0090] While embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions, and variations may be made to these embodiments without departing from the principles and spirit of the invention, and that the scope of the invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a metal-semiconductor heterojunction flexible ultraviolet photodetector, characterized in that: The following steps are involved: S1: Cut the PET flexible substrate into 1cm×1cm squares, clean it with acetone and alcohol in a volume ratio of 1:2, and dry it at 20℃-25℃ in a nitrogen environment for 20-25min. Then, use a gas flow rate of 60-70sccm and a plasma power of 0.8-0.9W / cm 2 The PET flexible substrate is treated with oxygen plasma for 10-15 minutes. S2: A 50 nm thick Cr metal electrode was first deposited on the flexible substrate surface by vacuum evaporation method, and then a 50 nm thick Au metal electrode was deposited. The vacuum evaporation conditions were: vacuum degree 5×10 -3 Pa, evaporation rate is 0.1-1A / s; S3: The flexible substrate was vacuum-adsorbed on the center of the spin coater turntable. The spin coater speed was set to 500-800 r / min. 1 mL of 0.1 mg / mL Al·NCs solution was pipetted using a pipette. The spin coater was run for 30 s before spin coating was performed for 30-35 s. The solvent was dried under nitrogen at 20°C-25°C. The above spin coating operation was repeated 1-2 times to obtain a transparent thin film distributed over the entire flexible substrate, thus obtaining the Al layer on the surface of the flexible substrate. S4: The flexible substrate was vacuum-adsorbed on the center of the spin coater turntable, and the spin coater speed was set to 1000-1200 r / min. 2 mL of Zn0·QDs solution (2 mg / mL) was drawn using a 5 mL disposable dropper. The spin coater was run for 30 seconds before spin coating was performed for 25-30 seconds. The device coated with Zn0QDs was annealed at 80-90°C in a nitrogen environment for 20-25 minutes. The above spin coating operation was repeated 5-6 times to obtain a white film distributed on the AlNCs coating, and a Zn0 layer was obtained on the surface of the Al layer. S5: Vacuum adsorb the flexible substrate on the center of the spin coater turntable, set the spin coater speed to 800-1000 r / min, use a pipette to draw 1 mL of Cs3Cs3Cu2I5·QDs solution 8 mg / mL, run the spin coater for 30 seconds, and then spin coat for 25-35 seconds. Place the device spin-coated with Cs3Cu2I5·QDs in a nitrogen environment and anneal at 80-90°C for 10-15 minutes. Repeat the above spin coating operation 4-5 times to obtain a yellow thin film distributed on the Zn0·QDs coating, and obtain a Cs3Cu2I5 layer on the surface of the ZnO layer; S6: Vacuum adsorb the flexible substrate on the center of the spin coater turntable, set the spin coater speed to 1000-1200r / min, use a pipette to draw 1mL of PDMS mixed solution, run the spin coater for 30s and then spin coat for 30-35s. Heat the device to 80-85℃ for 2-2.5h to obtain a PDMS layer on the surface of the Cs3Cu2I5 layer, and prepare a metal-semiconductor heterojunction flexible ultraviolet photodetector.

2. The method for preparing a metal-semiconductor heterojunction flexible ultraviolet photodetector according to claim 1, characterized in that: The Al·NCs solution is prepared by dissolving aluminum chloride in mesitylene, stirring the mixture at 80-85°C, adding polyethylene glycol and lithium aluminum hydride, heating the solution to 140°C, and magnetically stirring the mixture under a nitrogen atmosphere for 10 hours. The solvent is washed multiple times with anhydrous acetone and centrifuged. Finally, Al nanoparticles are dispersed in the anhydrous acetone solution to prepare a transparent Al·NCs solution.

3. The method for preparing a metal-semiconductor heterojunction flexible ultraviolet photodetector according to claim 1, characterized in that: The preparation method of the Zn0·QDs solution is as follows: 2.95 g of zinc acetate dihydrate is dissolved in 125 mL of methanol at 60°C, and potassium hydroxide-methanol solution is added to the zinc acetate dihydrate solution under vigorous stirring. Stirring is continued at 60°C for three hours, and the solution changes from translucent to a milky white suspension, and nanoparticles begin to precipitate. The precipitate is obtained by centrifugation, and then the precipitate is washed with methanol multiple times and centrifuged again. Finally, the ZnO nanocrystals are dispersed in an ethanol solution to prepare a white transparent Zn0 suspension.

4. The method for preparing a metal-semiconductor heterojunction flexible ultraviolet photodetector according to claim 1, characterized in that: The Cs3Cu2I5·QDs solution was prepared as follows: copper iodide and 1-octadecene were placed in a 100 mL three-necked flask and dried at 150°C under nitrogen for 1 hour. Oleic acid and oleylamine were then injected at 120°C. When the CuI was completely dissolved, the solution turned light brown. The temperature was lowered to 70°C, and Cs-oleate preheated to 100°C was rapidly injected. After 1 minute, the reaction mixture was cooled with ice water to quickly cool to 20°C-25°C to quench the reaction. The cooled mixture turned off-white and was centrifuged at 8000 rpm for 10 minutes. After centrifugation, the supernatant was removed, and the precipitate was dispersed in n-hexane. The precipitate was washed multiple times with n-hexane and centrifuged again at 10000 rpm for 5 minutes. Finally, the Cs3Cu2I5 nanocrystals were dispersed in the n-hexane solution to prepare a slightly yellowish milky white Cs3Cu2I5 suspension.

5. The method for preparing a metal-semiconductor heterojunction flexible ultraviolet photodetector according to claim 1, characterized in that: The PDMS layer is prepared by mixing a PDMS prepolymer and a curing agent in a ratio of 10:1, magnetically stirring for 1-1.2 hours, placing the mixed solution in a vacuum chamber, evacuating the chamber and leaving it for 1-1.5 hours, taking the mixed solution out of the vacuum chamber, and using a pipette to draw 1 mL of the mixed solution and spin-coating it onto the device surface. The speed of the coating machine is set to 1000-1200 revolutions per minute. The coating machine is run for 30 seconds before spin coating is performed. The spin coating time is 30-35 seconds, and then the device is heated to 80-85°C for 2-2.5 hours.

6. A metal-semiconductor heterojunction flexible ultraviolet photodetector, prepared by the method according to any one of claims 1 to 5, comprising a flexible substrate, a metal electrode layer, an Al layer, a ZnO layer, a Cs3Cu2I5 layer and a PDMS polydimethylsiloxane layer, characterized in that: The flexible substrate is a polyethylene terephthalate film, the metal electrode layer is formed on the surface of the flexible substrate, the Al layer is formed on the surface of the metal electrode layer, the ZnO layer is formed on the surface of the Al layer, the Cs3Cu2I5 layer is formed on the surface of the ZnO layer, and the PDMS polydimethylsiloxane layer is formed on the surface of the Cs3Cu2I5 layer.

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