A high-performance two-dimensional perovskite photodetector and its preparation method

Abstract

The present invention discloses a high-performance two-dimensional perovskite photodetector and a preparation method thereof. The preparation process of the photodetector is as follows: (1) Dissolve BAI, FAI, and PbI2 in a molar ratio of 2:1:2 in DMF, DMSO, or a mixed solvent of the two, and stir at room temperature for 7 to 10 h to obtain a precursor solution; the concentration of BA2FAPb2I7 in the solvent is 0.1 mol / L to 0.8 mol / L; (2) Preheat the cleaned glass slide on a hot plate at 150 to 250 °C for 5 to 20 minutes, take out the precursor solution, drop it on the glass slide and spin-coat it, and anneal the spin-coated film at 120 to 180 °C for 10 to 20 minutes to obtain a BA2FAPb2I7 film. The whole process is completed in a glove box; (3) Place the BA2FAPb2I7 perovskite film on a high-vacuum resistance evaporation coating machine to evaporate interdigitated electrodes, and thus obtain the product.

Description

Technical Field

[0001] The present invention belongs to the technical field of the design and preparation of lateral structure photodetectors, and particularly relates to a high-performance two-dimensional perovskite photodetector and a preparation method thereof. Background Art

[0002] Photodetectors can capture optical signals with specific spectral regions (ultraviolet, visible, and infrared light), and can instantaneously convert them into electrical signals, playing an important role in the fields of military, aerospace, optical communication, biological imaging, etc. Two-dimensional perovskites have received extensive attention in recent years due to their advantages such as adjustable bandgap, large optical absorption coefficient, high carrier mobility, and long exciton diffusion length. Among them, two-dimensional perovskite polycrystalline thin films show promising prospects in the preparation of large-area, simple, and low-cost photodetectors. However, the two-dimensional perovskite polycrystalline thin films have many surface holes, small grains, and many grain boundaries, resulting in a large trap density and low carrier mobility, which to a certain extent hinders their application in high-performance devices and is an important challenge in their commercial applications. The present invention optimizes the preparation process of perovskite, including: preheating time, annealing time, solvent, annealing temperature, preheating temperature, and precursor stoichiometry, and prepares a highly ordered and high-quality crystalline BA2FAPb2I7 polycrystalline thin film. By adjusting the morphology, the perovskite thin film is highly uniform and dense, obtaining a perovskite thin film with large grains and few grain boundaries, reducing the boundary defects of the thin film, improving charge transfer, and enhancing the performance of the photodetector. This research provides an experimental basis for the preparation of high-performance two-dimensional perovskite optoelectronic devices and is of great significance for expanding the application fields of two-dimensional perovskite materials. Summary of the Invention

[0003] In view of this, the purpose of the present invention is to provide a high-performance two-dimensional perovskite photodetector and a preparation method thereof. The present invention provides a simple manufacturing process. Using the optimized BA2FAPb2I7 thin film as the light-absorbing material, a photodetector is prepared, and excellent optoelectronic performance is obtained.

[0004] To achieve the above-mentioned invention purpose, the present invention provides the following technical solutions:

[0005] A preparation method of a high-performance two-dimensional perovskite photodetector, and the preparation process is as follows:

[0006] (1) Prepare a precursor solution

[0007] Dissolve BAI, FAI, and PbI2 in a molar ratio of 2:1:2 in DMF, DMSO, or a mixed solvent of the two. Stir at room temperature for 7 - 10 h to obtain a precursor solution; the concentration of BA2FAPb2I7 in the solvent is 0.1 mol / L - 0.8 mol / L, and the volume ratio of DMF to DMSO is (1 - 4):(1 - 4).

[0008] (2)Crystallization

[0009] Preheat the cleaned glass slide on a hot plate at 150 - 250 °C for 5 - 20 minutes. Take out the precursor solution and drop - coat it on the glass slide, then spin - coat. Place the spin - coated film in an oven at 120 - 180 °C for annealing for 10 - 20 minutes to obtain a pure BA2FAPb2I7 film. The whole process is completed in a glove box;

[0010] (3)Evaporate electrodes

[0011] Place the pure BA2FAPb2I7 perovskite film on a high - vacuum resistance evaporation coating machine to evaporate interdigital electrodes, thus obtaining the product.

[0012] Preferably, the concentration of BA2FAPb2I7 in the solvent is 0.6 mol / L. The solvent used is a mixed solvent of DMF and DMSO with a volume ratio of 1:4. The preheating temperature is 200 °C, the preheating time is 5 minutes, the annealing temperature is 150 °C, and the annealing time is 10 minutes. The area of the glass slide is 1.8 cm×1.8 cm, the spin - coating volume of the precursor solution is 80 μL, the rotation speed during spin - coating is 3000 rpm, and the spin - coating time is 30 s. The pressure in the vacuum chamber during the operation of the coating machine is 5×10 -5 Pa, the thickness of the Au electrode is 80 nm, and the width between Au electrodes is 100 μm.

[0013] The specific preparation process is as follows:

[0014] (1)Prepare the precursor solution

[0015] Dissolve 1.2 mmol BAI, 0.6 mmol FAI, and 1.2 mmol PbI2 in 0.2 ml DMF + 0.8 ml DMSO, stir at room temperature for 8 h, with a rotation speed of about 500 rpm / s, and let it stand to obtain the precursor solution G;

[0016] (2)Crystallization

[0017] Preheat the cleaned glass slide on a hot plate at 200 °C for 5 minutes. Take out 80 μL of the precursor solution and drop - coat it on the glass slide, then spin - coat at a rotation speed of 3000 rpm for 30 s. Place the spin - coated film in an oven at 150 °C for annealing for 10 minutes to obtain a pure BA2FAPb2I7 film. The whole process is completed in a glove box.

[0018] (3) Evaporation deposition of electrodes

[0019] For the above high-performance two-dimensional perovskite photodetector, a pure BA2FAPb2I7 perovskite thin film is placed on a high-vacuum resistance evaporation coating machine to deposit interdigitated electrodes. When the coating machine is working, the pressure in the vacuum chamber is 5×10 -5 Pa, the thickness of the Au electrode is 80 nm, and the width between the Au electrodes is 100 μm.

[0020] For the two-dimensional perovskite photodetector prepared by the above method, the photodetector based on the optimized BA2FAPb2I7 polycrystalline thin film has a significant on / off current ratio of 1.29 × 10 4 A, a high detectivity of 1.57 × 10 13 Jones, a high responsivity of 1.89 A / W, and a fast response speed of 5.8 / 6.2 ms.

[0021] The present invention has the following characteristics:

[0022] (1) The present invention can greatly reduce the defects of the BA2FAPb2I7 thin film. The precise control of the crystallization method can effectively regulate the morphology of the thin film, including crystal size, surface coverage, and thickness, as Figure 1 shown. These are the basic factors determining the light absorption and charge transport properties.

[0023] (2) The preparation process is simple and more conducive to large-scale commercial production.

[0024] (3) Using the optimized pure BA2FAPb2I7 thin film as the light-absorbing layer and applying it to the perovskite photodetector, excellent light response performance is obtained. Description of the Drawings

[0025] Figure 1 It is the electron microscope image and related device performance diagram of the finally optimized BA2FAPb2I7 thin film, with an excitation wavelength of 405 nm;

[0026] Figure 2 It is the I-T diagram of the corresponding device of the BA2FAPb2I7 thin film under different annealing time conditions under 8 mW / cm 2 light illumination, with an excitation wavelength of 405 nm;

[0027] Figure 3 It is the I-T diagram of the corresponding device of the BA2FAPb2I7 thin film under different preheating time conditions when the annealing time is 10 minutes under 8 mW / cm 2 light illumination, with an excitation wavelength of 405 nm;

[0028] Figure 4Absorption of (BA)2FAPb2I7 thin films with different solvents after optimizing the preheating time and annealing time, and the I-T diagrams of the corresponding perovskite devices under 8 mW / cm 2 illumination, with an excitation wavelength of 405 nm;

[0029] Figure 5 In (a), (b), (c), (d), and (e) are SEM images of (BA)2FAPb2I7 perovskite thin films with different solvents (DMF, DMF:DMSO = 4:1, DMF:DMSO = 1:1, DMF:DMSO = 1:4, DMSO);

[0030] Figure 6 I-T diagrams of the corresponding devices of (BA)2FAPb2I7 thin films under different annealing temperatures after optimizing the preheating time, annealing time, and solvent, under 8 mW / cm 2 illumination, with an excitation wavelength of 405 nm;

[0031] Figure 7 Device performance calculated based on the photocurrent and dark current of Figure 6 ;

[0032] Figure 8 Absorption, XRD of (BA)2FAPb2I7 thin films with different preheating temperatures after optimizing the preheating time, annealing time, solvent, and annealing temperature, and the I-T diagrams of the corresponding perovskite devices under 8 mW / cm 2 illumination, with an excitation wavelength of 405 nm;

[0033] Figure 9 In (a), (b), and (c) are SEM images of (BA)2FAPb2I7 perovskite thin films with different preheating temperatures (150 °C, 200 °C, 250 °C);

[0034] Figure 10 XRD of (BA)2FAPb2I7 thin films with different concentrations after optimizing the preheating time, annealing time, solvent, annealing temperature, and preheating temperature, and the I-T diagrams of the corresponding perovskite devices under 8 mW / cm 2 illumination, with an excitation wavelength of 405 nm;

[0035] Figure 11 In (a), (b), (c), and (d) are SEM images of (BA)2FAPb2I7 perovskite thin films with different concentrations (0.1 M, 0.4 M, 0.6 M, 0.8 M). Specific implementation mode

[0036] The technical solutions of the present invention will be further described in detail below in conjunction with the accompanying drawings and embodiments, but the protection scope of the present invention is not limited thereto.

[0037] In the following examples, the changed concentration amounts all refer to the doped molar amounts.

[0038] Example 1

[0039] A high-performance two-dimensional perovskite photodetector and its preparation method are as follows:

[0040] I. Preparation of perovskite precursor solution

[0041] (1) Preparation of solution A

[0042] BAI (40.2 mg, 0.2 mmol), FAI (17.2 mg, 0.1 mmol), and PbI2 (92.2 mg, 0.2 mmol) are dissolved in 1 mL of DMF, stirred at room temperature for 8 h at a rotation speed of about 500 rpm / s, and left standing for 2 hours to obtain solution A.

[0043] (2) Preparation of solution B

[0044] BAI (40.2 mg), FAI (17.2 mg), and PbI2 (92.2 mg) are dissolved in 0.8 mL of DMF:0.2 mL of DMSO, stirred at room temperature for 8 h at a rotation speed of about 500 rpm / s, and left standing for 2 hours to obtain solution B.

[0045] (3) Preparation of solution C

[0046] BAI (40.2 mg), FAI (17.2 mg), and PbI2 (92.2 mg) are dissolved in 0.5 mL of DMF:0.5 mL of DMSO, stirred at room temperature for 8 h at a rotation speed of about 500 rpm / s, and left standing for 2 hours to obtain solution C.

[0047] (4) Preparation of solution D

[0048] BAI (40.2 mg), FAI (17.2 mg), and PbI2 (92.2 mg) are dissolved in 0.2 mL of DMF:0.8 mL of DMSO, stirred at room temperature for 8 h at a rotation speed of about 500 rpm / s, and left standing for 2 hours to obtain solution D.

[0049] (5) Preparation of solution E

[0050] BAI (40.2 mg), FAI (17.2 mg), and PbI2 (92.2 mg) are dissolved in 1 mL of DMSO, stirred at room temperature for 8 h at a rotation speed of about 500 rpm / s, and left standing for 2 hours to obtain solution E.

[0051] (6) Preparation of solution F

[0052] BAI (160.8 mg, 0.8 mmol), FAI (68.8 mg, 0.4 mmol), and PbI2 (368.8 mg, 0.8 mmol) were dissolved in 0.2 ml of DMF: 0.8 ml of DMSO and stirred at room temperature for 8 h at a rotation speed of approximately 500 rpm / s. After standing for 2 h, solution F was obtained.

[0053] (7)Preparation of solution G

[0054] BAI (241.2 mg, 1.2 mmol), FAI (103.2 mg, 0.6 mol), and PbI2 (553.2 mg, 1.2 mmol) were dissolved in 0.2 ml of DMF: 0.8 ml of DMSO and stirred at room temperature for 8 h at a rotation speed of approximately 500 rpm / s. After standing for 2 h, solution G was obtained.

[0055] (8)Preparation of solution H

[0056] BAI (321.6 mg, 1.6 mmol), FAI (137.6 mg, 0.8 mmol), and PbI2 (737.6 mg, 1.6 mmol) were dissolved in 0.2 ml of DMF: 0.8 ml of DMSO and stirred at room temperature for 8 h at a rotation speed of approximately 500 rpm / s. After standing for 2 h, solution H was obtained.

[0057] II. Condition optimization

[0058] (1)Effect of different annealing times on the device

[0059] The cleaned glass slides (area 1.8 cm × 1.8 cm) were preheated on a hot plate at 150 °C for 20 min, and then 80 μL of solution A was taken out and dropped on the glass slides for spin coating at a rotation speed of 3000 rpm for 30 s. The spin-coated thin films were annealed on a hot plate at 120 °C for 10 min and 20 min respectively to obtain BA2FAPb2I7 thin films with different annealing times. The whole process was completed in a glove box.

[0060] The prepared BA2FAPb2I7 perovskite thin films were placed on a high-vacuum resistance evaporation coating machine to evaporate interdigitated electrodes. When the coating machine was working, the pressure in the vacuum chamber was 5×10 -5 Pa, the thickness of the Au electrode was 80 nm, and the width between the Au electrodes was 100 μm. Its planar structure was Au - BA2FAPb2I7 - Au.

[0061] Figure 2I-T diagram of the corresponding device for the BA2FAPb2I7 thin film under different annealing time conditions, excitation wavelength 405 nm, light intensity 8 mW / cm 2 . Figure 2 When annealed for 20 minutes, the photocurrent is 7.15×10 -8 A, the dark current is 7.2×10 -11 A, and the detectivity is 4.8×10 10 J; when annealed for 10 minutes, the photocurrent is 3.39×10 -8 A, the dark current is 1.54×10 -11 A, and the detectivity is 4.93×10 10 J. Although the photocurrent of the device annealed for 10 minutes is relatively low, it has a higher detectivity and better performance of the photodetector.

[0062] (2) Influence of different preheating times on the device

[0063] The cleaned glass slides (area 1.8 cm × 1.8 cm) were preheated on a hot plate at 150 °C for 5 minutes and 20 minutes respectively. After taking out, 80 μL of solution A was dropped on the glass slides and spin-coated at a speed of 3000 rpm for 30 s. The spin-coated thin film was annealed on a hot plate at 120 °C for 10 minutes to obtain BA2FAPb2I7 thin films with different preheating times. The whole process was completed in a glove box.

[0064] The prepared BA2FAPb2I7 perovskite thin film was placed on a high-vacuum resistance evaporation coating machine to evaporate interdigitated electrodes. When the coating machine was working, the pressure in the vacuum chamber was 5×10 -5 Pa, the thickness of the Au electrode was 80 nm, and the width between the Au electrodes was 100 μm. Its planar structure was Au - BA2FAPb2I7 - Au.

[0065] Figure 3 Device performance diagram of the BA2FAPb2I7 thin film under the preparation conditions of different preheating times and annealing for 10 minutes, excitation wavelength 405 nm. From Figure 3 it can be seen that as the preheating time increases, the on / off ratio of the light / dark current of the corresponding device gradually decreases. When preheated for 5 minutes, the performance of the photodetector of the BA2FAPb2I7 polycrystalline thin film is the best.

[0066] (3) Influence of different solvents on the device

[0067] Preheat the cleaned glass slides (area 1.8 cm × 1.8 cm) on a hot plate at 150 °C for 5 minutes. Then, take out 80 μL of solutions A, B, C, D, and E respectively, drop them on the glass slides and spin-coat them at a speed of 3000 rpm for 30 s. The spin-coated thin films are annealed on a hot plate at 120 °C for 10 minutes to obtain BA2FAPb2I7 thin films with different solvents. The whole process is completed in a glove box.

[0068] Put the obtained BA2FAPb2I7 perovskite thin film on a high-vacuum resistance evaporation coating machine to evaporate interdigital electrodes. When the coating machine is working, the pressure in the vacuum chamber is 5×10 -5 Pa, the thickness of the Au electrode is 80 nm, and the width between the Au electrodes is 100 μm. Its planar structure is Au - BA2FAPb2I7 - Au.

[0069] Figure 4 Absorption spectra and corresponding device performance diagrams of BA2FAPb2I7 thin films under the preparation conditions of preheating for 5 minutes, annealing for 10 minutes, and different solvents. The excitation wavelength is 405 nm. Figure 4 In (a), when using different solvents, the absorption edges of the BA2FAPb2I7 thin films are almost the same, about 590 nm, corresponding to a band gap of about 2.1 eV, indicating that using different solvents hardly changes the band gap of BA2FAPb2I7. Figure 4 In (b) is the I-T diagram of the corresponding device. When the solvent is DMF:DMSO = 1:4, the performance of the photodetector based on the BA2FAPb2I7 polycrystalline thin film is the best.

[0070] Figure 5 Scanning electron microscope images of BA2FAPb2I7 thin films under the preparation conditions of preheating for 5 minutes, annealing for 10 minutes, and different solvents. Among them, Figure 5 the solvents used in (a)(b)(c)(d)(e) are (DMF, DMF:DMSO = 4:1, DMF:DMSO = 1:1, DMF:DMSO = 1:4, DMSO) respectively. It can be seen from the figure that with the increase of the DMSO solvent, the grain size increases significantly and the grain boundaries decrease, improving the crystallization quality.

[0071] Comprehensive Figure 4 and Figure 5 Based on the test results, a mixed solvent of DMF and DMSO with a volume ratio of 1:4 is selected as the dissolving solvent.

[0072] (4)Effect of different annealing temperatures on the device

[0073] Preheat the cleaned glass slides (area 1.8 cm × 1.8 cm) on a hot plate at 150 °C for 5 minutes. Take out 80 μL of solution D, drop it on the glass slide and spin-coat it at a rotation speed of 3000 rpm for 30 s. The spin-coated films are respectively annealed on hot plates at 120 °C, 150 °C, and 180 °C for 10 minutes to obtain BA2FAPb2I7 films with different annealing temperatures. The whole process is completed in a glove box.

[0074] Put the obtained BA2FAPb2I7 perovskite film on a high-vacuum resistance evaporation coating machine to evaporate interdigitated electrodes. When the coating machine is working, the pressure in the vacuum chamber is 5×10 -5 Pa, the thickness of the Au electrode is 80 nm, and the width between the Au electrodes is 100 μm. Its planar structure is Au - BA2FAPb2I7 - Au.

[0075] Figure 6 It is the I-T diagram of the device for the BA2FAPb2I7 film under the preparation conditions of preheating for 5 minutes, annealing time of 10 minutes, solvent DMF:DMSO = 1:4, and different annealing temperatures; the excitation wavelength is 405 nm; Figure 7 It is the device performance calculated according to the corresponding photocurrent and dark current. It can be seen from Figure 7 that when the annealing temperature is 150 °C, the photocurrent-to-dark-current ratio, responsivity, and detectivity performance of the device are the best.

[0076] (5)Effect of different preheating temperatures on the device

[0077] Preheat the cleaned glass slides (area 1.8 cm × 1.8 cm) on hot plates at 150 °C, 200 °C, and 250 °C for 5 minutes respectively. Take out 80 μL of solution D, drop it on the glass slide and spin-coat it at a rotation speed of 3000 rpm for 30 s. The spin-coated films are annealed at 150 °C for 10 minutes to obtain BA2FAPb2I7 films with different preheating temperatures. The whole process is completed in a glove box.

[0078] Put the obtained BA2FAPb2I7 perovskite film on a high-vacuum resistance evaporation coating machine to evaporate interdigitated electrodes. When the coating machine is working, the pressure in the vacuum chamber is 5×10 -5 Pa, the thickness of the Au electrode is 80 nm, and the width between the Au electrodes is 100 μm. Its planar structure is Au - BA2FAPb2I7 - Au.

[0079] Figure 8 It is the absorption, XRD, and the corresponding I-T diagram of the device for the BA2FAPb2I7 film under the preparation conditions of preheating for 5 minutes, annealing time of 10 minutes, solvent DMF:DMSO = 1:4, annealing temperature of 150 °C, and different preheating temperatures; the excitation wavelength is 405 nm.Figure 8 In (a), as the preheating temperature increases, the absorption edge of the BA2FAPb2I7 film is almost the same. The absorption edge is approximately at 590 nm, and the corresponding bandgap is about 2.1 eV, indicating that the change in the preheating temperature hardly affects the bandgap of BA2FAPb2I7. Figure 8 In (b), the change in the preheating temperature does not affect the crystal structure of BA2FAPb2I7. Figure 8 In (c), the on / off ratio of the corresponding device's photocurrent / dark current first increases and then decreases. Under the condition of a preheating temperature of 200 °C, the performance of the BA2FAPb2I7 polycrystalline thin film photodetector is optimal.

[0080] Figure 9 SEM images of the BA2FAPb2I7 film under the preparation conditions of preheating for 5 minutes, annealing time of 10 minutes, solvent DMF:DMSO = 1:4, annealing temperature of 150 °C, and different preheating temperatures. Figure 9 In (a) 150 °C, (b) 200 °C, (c) 250 °C. From Figure 9 It can be seen that as the preheating temperature changes, the surface holes of the BA2FAPb2I7 film significantly decrease. Especially when the preheating temperature is 200 °C, the surface of the BA2FAPb2I7 film is smoother, the film-forming quality is higher, the gaps between grains are smaller, and the grain boundaries are fewer.

[0081] (6) Influence of the concentration of the perovskite precursor solution on the device

[0082] The cleaned glass slides (area 1.8 cm × 1.8 cm) were preheated on a hot plate at 200 °C for 5 minutes. Then, 80 μL of solutions D, F, G, and H were taken out and dropped onto the glass slides for spin coating at a speed of 3000 rpm for 30 s. The spin-coated films were annealed on a hot plate at 150 °C for 10 minutes to obtain BA2FAPb2I7 films with different concentrations. The whole process was completed in a glove box.

[0083] The obtained BA2FAPb2I7 perovskite film was placed on a high-vacuum resistance evaporation coating machine to evaporate interdigitated electrodes. When the coating machine was working, the pressure in the vacuum chamber was 5×10 -5 Pa, the thickness of the Au electrode was 80 nm, and the width between the Au electrodes was 100 μm. Its planar structure was Au - BA2FAPb2I7 - Au.

[0084] Figure 10 XRD of the BA2FAPb2I7 film in (a) and the corresponding I - T diagram of the device in (b) under the preparation conditions of preheating for 5 minutes, annealing time of 10 minutes, solvent DMF:DMSO = 1:4, annealing temperature of 150 °C, preheating temperature of 200 °C, and different precursor concentrations. The excitation wavelength was 405 nm. FromFigure 10 As can be seen from a in , the change in concentration does not affect the crystal structure of BA2FAPb2I7. Figure 10 b in shows that the on / off ratio of the corresponding device's photocurrent / dark current first increases and then decreases. Under the condition of a concentration of 0.6 M, the performance of the photodetector based on the BA2FAPb2I7 polycrystalline thin film is optimal.

[0085] Figure 11 SEM images of BA2FAPb2I7 thin films prepared under the conditions of preheating for 5 minutes, annealing time of 10 minutes, solvent DMF:DMSO = 1:4, annealing temperature of 150 °C, preheating temperature of 200 °C, and precursor concentrations of (a) 0.1 M, (b) 0.4 M, (c) 0.6 M, and (d) 0.8 M. As can be seen from Figure 11 it, with the change in concentration, the surface grain size of the BA2FAPb2I7 thin film increases significantly. Especially when the concentration is 0.6 M, the surface grain boundaries of the BA2FAPb2I7 thin film decrease, and the crystal grows with high quality.

[0086] Example 2

[0087] The cleaned glass slides (area 1.8 cm × 1.8 cm) were preheated on a hot plate at 200 °C for 5 minutes. Then, 80 μL of solution G was taken out and dropped on the glass slides for spin coating at a rotation speed of 3000 rpm for 30 s. The spin-coated thin film was annealed on a hot plate at 150 °C for 10 minutes to obtain the BA2FAPb2I7 thin film. The whole process was completed in a glove box.

[0088] The obtained BA2FAPb2I7 perovskite thin film was placed on a high-vacuum resistance evaporation coating machine to evaporate interdigitated electrodes. When the coating machine was working, the pressure in the vacuum chamber was 5×10 -5 Pa, the thickness of the Au electrode was 80 nm, and the width between the Au electrodes was 100 μm. Its planar structure was Au - BA2FAPb2I7 - Au, as shown in Figure 1 . Finally, the electron microscope image and the related device performance image of the optimized BA2FAPb2I7 thin film were obtained, with an excitation wavelength of 405 nm. Figure 1 In (a) in , it is the surface morphology image of the BA2FAPb2I7 thin film under the optimal preparation conditions. From Figure 1 in (a) in , it can be concluded that the surface of the BA2FAPb2I7 thin film is smoother, the grain size is larger, and the grain boundaries are fewer. Figure 1 In (b) in , it is the corresponding cross-sectional thickness image. As can be seen from the figure, the thickness of the BA2FAPb2I7 perovskite thin film is about 444 nm. Figure 1 In (c) in , at 0.5 μW / cm 2 ——8 mW / cm 2I-T diagram of the device under light intensity. When the light intensity is 0.5 μW / cm 2 , the responsivity of the device is 1.89 A / W, and the detectivity is 1.57 × 10 13 Jones. The on-off current ratio of the device gradually increases with the increase of laser power. Under the illumination condition of 8 mw / cm 2 , the on-off ratio can reach 1.29×10 4 . Figure 1 (d) I-V diagram under the same illumination condition in []. When the light intensity is 0.5 μW / cm 2 , the photocurrent of the device is 1.49×10 -9 A. Figure 1 (e) The response time of this device is 5.8 / 6.2 ms.

[0089] The above are the preferred implementation schemes of the present invention. It should be noted that for those of ordinary skill in the art, without departing from the principle of the present invention, several improvements and refinements can be made, and these improvements and refinements should also be regarded as the protection scope of the present invention.

Claims

1. A preparation method of a high-performance two-dimensional perovskite photodetector, characterized in that, The preparation process is as follows: (1) Preparation of the precursor solution Dissolve BAI, FAI, and PbI2 in a mixed solvent of DMF and DMSO at a molar ratio of 2:1:2, and stir at room temperature for 7 - 10 h to obtain the precursor solution; the concentration of BA2FAPb2I7 in the solvent is 0.6 mol / L, and the volume ratio of DMF to DMSO is 1:4; (2) Crystallization Preheat the cleaned glass slide on a hot plate at 200 °C for 5 minutes, take out the precursor solution, drop it on the glass slide and spin - coat it. The spin - coated film is annealed at 150 °C for 10 minutes to obtain the BA2FAPb2I7 film. The whole process is completed in a glove box; the area of the glass slide is 1.8 cm × 1.8 cm, the spin - coating amount of the precursor solution is 80 μL, the rotation speed during spin - coating is 3000 rpm, and the spin - coating time is 30 s; (3) Evaporation of the electrode Put the BA2FAPb2I7 perovskite thin film on a high-vacuum resistance evaporation coating machine to evaporate interdigital electrodes. When the coating machine is working, the pressure in the vacuum chamber is 5×10 -5 Pa, the thickness of the Au electrode is 80 nm, and the width between the Au electrodes is 100 μm, thus obtained.

2. The two - dimensional perovskite photodetector prepared by the method according to claim 1.

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