A perovskite single crystal-based unipolar barrier photodetector and a preparation method thereof
By pressure bonding MAPbI3 perovskite single crystals with two-dimensional BA2PbI4 to prepare 3D/2D/3D unipolar barrier structures, the problems of grain boundary density and dark current in perovskite photodetectors were solved, realizing a photodetector with high sensitivity and low dark current, which has excellent light detection performance and low cost.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Patents(China)
- Current Assignee / Owner
- JILIN UNIVERSITY
- Filing Date
- 2023-10-19
- Publication Date
- 2026-05-19
AI Technical Summary
In existing perovskite photodetectors, the high grain boundary density and defect state density of polycrystalline thin films lead to material degradation and increased dark current. Suppressing dark current is a challenge for high-performance detectors, and the application of unipolar barrier detectors in various materials is limited by band arrangement.
A pressure bonding method was used to combine MAPbI3 perovskite single crystals with two-dimensional BA2PbI4 to prepare 3D/2D/3D unipolar barrier structures. The difference in solubility of MAPbI3 and BA2PbI4 in acetonitrile was used for epitaxial growth to form the unipolar barrier structure, and the electrode was deposited by vapor deposition.
A photodetector with high sensitivity and low dark current has been achieved, significantly reducing the dark current of the detector and obtaining excellent photodetection performance. It is also low in cost and has an adjustable band arrangement.
Smart Images
Figure CN117320524B_ABST
Abstract
Description
Technical Field
[0001] This invention belongs to the field of photodetector technology, specifically relating to a unipolar barrier photodetector based on perovskite single crystal and its fabrication method. Background Technology
[0002] Lead halide perovskites have been widely used in the research of high-performance photodetectors due to their high extinction coefficient, long charge carrier diffusion length, tunable direct bandgap, and solution processability. In recent years, various perovskite photodetectors based on polycrystalline thin films and single crystals have been extensively studied, achieving or even surpassing commercial detectors in several performance parameters. Furthermore, based on the excellent properties of the materials, researchers have successfully revealed new device mechanisms such as narrowband detection and dual-band detection in perovskite photodetectors, enriching the application prospects of these detectors. However, the high grain boundary density and defect state density of polycrystalline thin films not only accelerate the degradation of perovskite materials by water and oxygen but also significantly increase the recombination probability and reduce the carrier diffusion length, thus affecting detector performance. Although single-crystal structures can significantly reduce grain boundary density and defect state density, suppressing dark current remains a challenge in the field of high-performance perovskite photodetectors.
[0003] Unipolar barrier photodetectors based on III-V group compounds, HgCdTe, and two-dimensional semiconductor materials exhibit excellent performance in infrared detection. By combining an absorption layer, a blocking layer, and a contact layer in a heterostructure, a barrier can be introduced in the conduction band (valence band), preventing the flow of electrons (holes) in the conduction band (valence band) in the dark state, thus blocking dark current. Simultaneously, the valence band (conduction band) alignment of the unipolar barrier mechanism does not introduce a barrier, allowing holes (electrons) to flow freely in the valence band (conduction band), thus the photocurrent of the device is unimpeded. However, the requirement for band alignment at the barrier limits the application of unipolar barrier detectors in various materials.
[0004] Perovskite materials allow for bandgap modulation by altering their composition, making them highly suitable for bandgap engineering. Furthermore, their high tolerance to defects and solution-grown characteristics make perovskite heterostructure photodetectors valuable for research. Summary of the Invention
[0005] The purpose of this invention is to provide a unipolar barrier photodetector based on perovskite single crystals and its fabrication method. Taking advantage of the simplicity of the MAPbI3 perovskite single crystal growth method, a 3D / 2D / 3D unipolar barrier structure is fabricated by combining MAPbI3 perovskite single crystals and two-dimensional BA2PbI4 using a pressure bonding method. The resulting unipolar barrier photodetector achieves high sensitivity and low dark current.
[0006] This invention is achieved through the following technical solution:
[0007] A unipolar barrier photodetector based on perovskite single crystal comprises a unipolar barrier structure formed by a two-dimensional perovskite solution and two perovskite single crystals, prepared by pressure bonding, and electrodes located on both sides of the perovskite single crystals. The perovskite single crystals are MAPbI3, and the two-dimensional perovskite solution is a BA2PbI4 acetonitrile solution. This unipolar barrier photodetector based on perovskite single crystal is prepared by the following steps:
[0008] 1) Preparation of MAPbI3 solution: MAI (methylamine iodide) and PbI2 (lead iodide) in a molar ratio of 1.15 to 1.25:1 were mixed and dissolved in γ-butyrolactone solution, and then stirred at room temperature for 8 to 12 hours until the perovskite material was completely dissolved to obtain MAPbI3 solution;
[0009] 2) Preparation of thin single crystal growth device: A polytetrafluoroethylene film with a thickness of 10 to 400 micrometers is used as a spacer between two glass substrates. The gaps around the two glass substrates are sealed with silicone, and 2 to 4 openings with a width of 0.5 to 1 cm are left.
[0010] 3) Preparation of seed crystals: The MAPbI3 solution obtained in step 1) is injected into the growth device in step 2), heated to 85-90℃ and kept for 1-4 hours to allow the solvent to evaporate from the opening until black perovskite seed crystals are produced in the solution.
[0011] 4) Single crystal growth: Continue heating the growth apparatus from step 3) where small seed crystals appeared, starting at an initial temperature of 85–90°C and increasing the temperature at a rate of 0.25–0.75°C / h for 12–24 hours. A single crystal with a thickness of 100–400 micrometers and an area of 0.04–1 cm² is obtained through reverse-temperature crystallization. 2 The MAPbI3 perovskite single crystal was then removed from the growth apparatus and cooled to room temperature.
[0012] 5) Preparation of BA2PbI4 solution: Mix BAI (n-butylamine iodide) and PbI2 (lead iodide) in a molar ratio of 1.9 to 2.1:1 and dissolve them in acetonitrile solution. Heat the solution to 55 to 62°C and stir for 3 to 8 hours. After standing at 55 to 62°C to precipitate, take the clear liquid to obtain BA2PbI4 solution.
[0013] 6) Preheat the perovskite single crystal prepared in step 4) to 55-62℃;
[0014] 7) Preparation of a unipolar barrier structure via pressure bonding process: The BA₂PbI₄ solution prepared in step 5) is dropped onto the MAPbI₃ single crystal preheated in step 6), with 0.1–0.5 μL of BA₂PbI₄ solution added per square millimeter of single crystal. This is then quickly covered with another preheated MAPbI₃ single crystal. The mixture is then heated to 60–70 °C and annealed for 1–2 hours. During annealing, a pressure of 50–150 g is applied between the two MAPbI₃ single crystal assemblies to promote the epitaxial growth of BA₂PbI₄ within the MAPbI₃ single crystal assembly. After BA₂PbI₄ dissolves part of the MAPbI₃ single crystal, BA₂MA is formed between the single crystals. n-1 Pb n I 3n+1 Where n is 1 to 3; MAPbI3 single crystal - BA2MA n-1 Pb n I 3n+1 -MAPbI3 single crystals form a unipolar barrier structure;
[0015] 8) Gold electrodes with a thickness of 18-22 nm and copper electrodes with a thickness of 80-120 nm are deposited on both sides of the single crystal assembly obtained in step 7) to obtain the unipolar barrier photodetector based on perovskite single crystal of the present invention.
[0016] Compared with existing technologies, the beneficial effects of this invention are reflected in:
[0017] This invention utilizes a glass substrate and polytetrafluoroethylene (PTFE) spacers to prepare a single-crystal growth apparatus. Silicone is used to cover the gaps in the apparatus while leaving openings. The solvent evaporation rate in the MAPbI3 solution is controlled by adjusting the size and number of openings. Solution saturation is slowly increased by solvent evaporation at 85–90°C, followed by rapid growth to obtain thin MAPbI3 perovskite single crystals. Furthermore, by utilizing the difference in solubility of MAPbI3 and BA2PbI4 in acetonitrile, two-dimensional perovskite is used as the epitaxial growth solution to bond two three-dimensional MAPbI3 perovskite single crystals together, forming a unipolar barrier structure. Electrodes are then deposited by vapor deposition to complete the perovskite single-crystal unipolar barrier photodetector. Compared with existing technologies, this invention has the following advantages:
[0018] (1) Combining solvent evaporation crystallization and reverse temperature crystallization: The opening of the growth device is controlled by silica gel, thereby controlling the solvent evaporation rate, allowing the growth solution to saturate slowly and reducing nucleation sites. After the seed crystal crystallizes, the single crystal is rapidly grown by increasing the temperature. Combining the advantages of the two growth methods, the single crystal has good quality, regular and controllable morphology, fast growth rate and low cost.
[0019] (2) Utilizing the difference in solubility of MAPbI3 and BA2PbI4 in acetonitrile, two-dimensional perovskite was used as the epitaxial growth solution to bond two three-dimensional perovskite single crystals together, forming a unipolar barrier structure. The preparation method is simple, low-cost, and the band arrangement can be controlled according to the material.
[0020] (3) The perovskite monopole barrier photodetector prepared by this method can significantly reduce the dark current of the detector and obtain excellent photodetector performance. Attached Figure Description
[0021] Figure 1 This is a schematic diagram of the process for preparing MAPbI3 perovskite single crystals in Examples 1-4 and Comparative Example 1 of the present invention.
[0022] like Figure 1 As shown, corresponding to steps 2) to 4) of the method described in the invention, the thin single crystal growth apparatus is prepared as follows: a polytetrafluoroethylene film with a thickness of 10 to 400 micrometers is used as a spacer between two glass substrates, and the gaps around the two glass substrates are sealed with silicone, leaving 2 to 4 openings with a width of 0.5 to 1 cm; seed crystal preparation: MAPbI3 solution is injected into the growth apparatus of step 2), and the temperature is raised to 85 to 90°C and maintained for 1 to 4 hours to allow the solvent to evaporate from the openings until black perovskite seed crystals are generated in the solution; single crystal growth: the growth apparatus where the seed crystals appear is further heated, starting from the initial temperature of 85 to 90°C, and heated at a rate of 0.25 to 0.75°C / h for 12 to 24 hours. A MAPbI3 perovskite single crystal with a thickness of 100 to 400 micrometers is obtained by reverse temperature crystallization, and then the growth apparatus is opened to remove the single crystal and cool it to room temperature;
[0023] Figure 2 This is a schematic diagram of the process for preparing perovskite single-crystal unipolar barrier structures in Examples 1-4 of the present invention;
[0024] like Figure 2 As shown, corresponding to steps 6) to 7) of the method described in the invention, the perovskite single crystal prepared in step 4) is preheated to 60-65°C; a unipolar barrier structure is prepared by pressure bonding process: the BA2PbI4 solution prepared in step 5) is dropped onto the MAPbI3 single crystal preheated in step 6), with 0.1-0.5 μL of BA2PbI4 solution added per square millimeter of single crystal; another preheated MAPbI3 single crystal is quickly placed on top, and then the temperature is raised to 60-70°C for annealing for 1-2 hours. During annealing, a pressure of 50-150 g is applied between the two MAPbI3 single crystal assemblies to promote the epitaxial growth of BA2PbI4 within the two MAPbI3 single crystal assemblies; after BA2PbI4 dissolves part of the MAPbI3 single crystal, BA2MA is formed between the single crystals. n-1 Pb n I3n+1 where n is 1 to 3;
[0025] Figure 3 The image shows a super-depth-of-field microscopic pseudo-color image and a laser measurement thickness curve of the MAPbI3 perovskite single crystal prepared in Example 2 of this invention (inset).
[0026] Figure 4 These are schematic diagrams of the perovskite unipolar barrier photodetectors prepared in Examples 1-4 of this invention; BA2MA in the figures n-1 Pb n I 3n+1 The product is grown after MAPbI3 single crystals are partially dissolved in BA2PbI4 solution, where n is 1 to 3.
[0027] Figure 5 The current-voltage curves are shown for the perovskite unipolar barrier photodetector prepared in Example 2 of the present invention and the perovskite photodetector prepared in Comparative Example 1.
[0028] Figure 6 The results of the external quantum efficiency test of the perovskite unipolar barrier photodetector prepared in Example 2 of this invention are shown.
[0029] Figure 7 This is a noise current curve of the perovskite unipolar barrier photodetector prepared in Example 2 of the present invention;
[0030] Figure 8 The linear dynamic range test results of the perovskite unipolar barrier photodetector prepared in Example 2 of the present invention are shown.
[0031] Figure 9 The -3dB frequency response test results of the perovskite unipolar barrier photodetector prepared in Example 2 of this invention; Detailed Implementation
[0032] The following detailed description, in conjunction with the accompanying drawings, of the specific implementation scheme of the perovskite single-crystal unipolar barrier photodetector involved in this invention.
[0033] The method for fabricating a perovskite single-crystal unipolar barrier photodetector provided by this invention includes the following steps:
[0034] Example 1
[0035] (1) Weigh 0.4388g of methylamine iodine and 1.1064g of lead iodide, add them to a glass bottle, add 2mL of γ-butyrolactone solvent, and add a magnetic stir bar; place the glass bottle on a magnetic stirring table and stir at room temperature for 8h until the perovskite material is completely dissolved to obtain MAPbI3 solution (perovskite single crystal growth solution);
[0036] (2) Preparation of thin single crystal growth device: Place four square polytetrafluoroethylene films with a side length of 0.5cm and a thickness of 100 micrometers between two glass substrates with a side length of 10cm, seal the gaps around the two glass substrates with silicone, and leave four 0.5cm long openings at the four corners.
[0037] (3) Inject the solution prepared in step 1) into the growth apparatus prepared in step 2).
[0038] (4) Place the growth device in step 3) in a preheated oven (85°C) and let it stand for 2 hours to allow the solvent to evaporate from the opening and black perovskite seed crystals to grow in the solution.
[0039] (5) Starting at 85℃, the temperature is increased at a rate of 0.5℃ / h for 15h until a MAPbI3 perovskite single crystal with a thickness of 100 micrometers is grown. The grown MAPbI3 perovskite single crystal is then taken out and cooled to room temperature.
[0040] (6) Repeat steps 1) to 5) to obtain two single crystals with a thickness of 100 micrometers, and preheat them to 60°C on a hot stage;
[0041] (7) Weigh 0.201 g of n-butylamine iodide and 0.2305 g of lead iodide, add them to a glass bottle, add 1 mL of acetonitrile solvent, and add a magnetic stir bar; place the glass bottle on a magnetic stirring table, stir at 60°C for 5 h, keep at 60°C and let it stand to precipitate, then take the clear liquid to obtain BA2PbI4 solution.
[0042] (8) Take 5 μL of the BA2PbI4 solution prepared in step 7) and drop it onto the MAPbI3 perovskite single crystal (the area of the single crystal is 25 square millimeters) preheated in step (6). Then quickly cover it with another preheated MAPbI3 perovskite single crystal. Then anneal it on a hot plate at 65°C for 1 hour. During this time, apply a weight pressure of 100g to the two MAPbI3 single crystals. BA2PbI4 partially dissolves the MAPbI3 single crystals and forms BA2MA between the single crystals. n-1 Pb n I 3n+1 , where n is 1 to 3.
[0043] (9) A 19.5 nm thick Au electrode is deposited on one side of the perovskite unipolar barrier assembly obtained in step (8), and a 100 nm thick copper electrode is deposited on the other side, thereby completing the fabrication of a unipolar barrier photodetector based on a perovskite single crystal.
[0044] Example 2
[0045] (1) Weigh 0.4388g of methylamine iodine and 1.1064g of lead iodide, add them to a glass bottle, add 2mL of γ-butyrolactone solvent, and add a magnetic stir bar; place the glass bottle on a magnetic stirring table and stir at room temperature for 5h until the perovskite material is completely dissolved to obtain MAPbI3 solution (perovskite single crystal growth solution);
[0046] (2) Preparation of thin single crystal growth device: Place four square polytetrafluoroethylene films with a side length of 0.5cm and a thickness of 210 micrometers between two glass substrates with a side length of 10cm, seal the gaps around the two glass substrates with silicone, and leave four 0.5cm long openings at the four corners.
[0047] (3) Inject the solution prepared in step 1) into the growth apparatus prepared in step 2).
[0048] (4) Place the growth device in step 3) in a preheated oven (87°C) and let it stand for 2 hours to allow the solvent to evaporate from the opening and black perovskite seed crystals to grow in the solution.
[0049] (5) Starting at 87℃, the temperature is increased at a rate of 0.5℃ / h for 18h until a perovskite single crystal with a thickness of 210 micrometers is grown. The grown MAPbI3 perovskite single crystal is then taken out and cooled to room temperature.
[0050] (6) Repeat steps 1) to 5) to obtain two single crystals with a thickness of 210 micrometers, and preheat them to 60°C on a hot stage;
[0051] (7) Weigh 0.201 g of n-butylamine iodide and 0.2305 g of lead iodide, add them to a glass bottle, add 1 mL of acetonitrile solvent, and add a magnetic stir bar; place the glass bottle on a magnetic stirring table, stir at 60°C for 5 h, keep at 60°C and let it stand to precipitate, then take the clear liquid to obtain BA2PbI4 solution.
[0052] (8) Take 4 μL of the BA2PbI4 solution prepared in step 7) and drop it onto the MAPbI3 perovskite single crystal preheated in step (6) (the area of the single crystal is 20 square millimeters). Quickly cover it with another preheated MAPbI3 perovskite single crystal, and then anneal it on a hot plate at 65°C for 1 hour, during which a weight pressure of 100g is applied to the combination of the two MAPbI3 single crystals. BA2PbI4 partially dissolves the MAPbI3 single crystal, forming BA2MA between the single crystals. n-1 Pb n I 3n+1 , where n is 1 to 3.
[0053] (9) A 19.5 nm thick Au electrode is deposited on one side of the perovskite unipolar barrier assembly obtained in step (8), and a 100 nm thick copper electrode is deposited on the other side, thereby completing the fabrication of a unipolar barrier photodetector based on a perovskite single crystal.
[0054] Example 3
[0055] (1) Weigh 0.4388g of methylamine iodine and 1.1064g of lead iodide, add them to a glass bottle, add 2mL of γ-butyrolactone solvent, and add a magnetic stir bar; place the glass bottle on a magnetic stirring table and stir at room temperature for 5h until the perovskite material is completely dissolved to obtain MAPbI3 solution (perovskite single crystal growth solution);
[0056] (2) Preparation of thin single crystal growth device: Place four square polytetrafluoroethylene films with a side length of 0.5cm and a thickness of 310 micrometers between two glass substrates with a side length of 10cm, seal the gaps around the two glass substrates with silicone, and leave four 0.8cm long openings at the four corners.
[0057] (3) Inject the solution prepared in step 1) into the growth apparatus prepared in step 2).
[0058] (4) Place the growth device in step 3) in a preheated oven (88°C) and let it stand for 2 hours to allow the solvent to evaporate from the opening and black perovskite seed crystals to grow in the solution.
[0059] (5) Starting at 88℃, the temperature is increased at a rate of 0.5℃ / h for 19h until a perovskite single crystal with a thickness of 310 micrometers is grown. The grown MAPbI3 perovskite single crystal is then taken out and cooled to room temperature.
[0060] (6) Repeat steps 1) to 5) to obtain two single crystals with a thickness of 310 micrometers, and preheat them to 60°C on a hot stage;
[0061] (7) Weigh 0.201 g of n-butylamine iodide and 0.2305 g of lead iodide, add them to a glass bottle, add 1 mL of acetonitrile solvent, and add a magnetic stir bar; place the glass bottle on a magnetic stirring table, stir at 60°C for 5 h, keep at 60°C and let it stand to precipitate, then take the clear liquid to obtain BA2PbI4 solution.
[0062] (8) Take 5 μL of the perovskite solution prepared in step 7) and drop it onto a perovskite single crystal. Press it down with another single crystal (the area of the single crystal is 25 square millimeters), and anneal it on a hot plate at 65°C for one hour, during which a weight pressure of 100g is applied to the assembly. BA2PbI4 partially dissolves the MAPbI3 single crystal, forming BA2MA between the single crystals. n-1 Pb nI 3n+1 , where n is 1 to 3.
[0063] (9) A 19.5 nm thick Au electrode is deposited on one side of the perovskite unipolar barrier assembly obtained in step (8), and a 100 nm thick copper electrode is deposited on the other side, thereby completing the fabrication of a unipolar barrier photodetector based on a perovskite single crystal.
[0064] Example 4
[0065] (1) Weigh 0.4388g of methylamine iodine and 1.1064g of lead iodide, add them to a glass bottle, add 2mL of γ-butyrolactone solvent, and add a magnetic stir bar; place the glass bottle on a magnetic stirring table and stir at room temperature for 5h until the perovskite material is completely dissolved to obtain MAPbI3 solution (perovskite single crystal growth solution);
[0066] (2) Preparation of thin single crystal growth device: Place four square polytetrafluoroethylene films with a side length of 0.5cm and a thickness of 420 micrometers between two glass substrates with a side length of 10cm, seal the gaps around the two glass substrates with silicone, and leave four 1cm long openings at the four corners.
[0067] (3) Inject the solution prepared in step 1) into the growth apparatus prepared in step 2).
[0068] (4) Place the growth device in step 3) in a preheated oven (90°C) and let it stand for 2 hours to allow the solvent to evaporate from the opening and black perovskite seed crystals to grow in the solution.
[0069] (5) Starting at 90℃, the temperature is increased at a rate of 0.5℃ / h for 20h until a perovskite single crystal with a thickness of 420 micrometers is grown. The grown MAPbI3 perovskite single crystal is then taken out and cooled to room temperature.
[0070] (6) Repeat steps 1) to 5) to obtain two single crystals with a thickness of 420 micrometers, and preheat them to 60°C on a hot stage;
[0071] (7) Weigh 0.201 g of n-butylamine iodide and 0.2305 g of lead iodide, add them to a glass bottle, add 1 mL of acetonitrile solvent, and add a magnetic stir bar; place the glass bottle on a magnetic stirring table, stir at 60°C for 5 h, keep at 60°C and let it stand to precipitate, then take the clear liquid to obtain BA2PbI4 solution.
[0072] (8) Take 6 μL of the perovskite solution prepared in step 7) and drop it onto a perovskite single crystal. Press it down with another single crystal (the area of the single crystal is 30 square millimeters), and anneal it on a hot plate at 65°C for one hour, during which a weight of 100g is applied to the assembly. BA2PbI4 partially dissolves the MAPbI3 single crystal, forming BA2MA between the single crystals. n-1 Pb n I 3n+1 , where n is 1 to 3.
[0073] (9) A 19.5 nm thick Au electrode is deposited on one side of the perovskite unipolar barrier assembly obtained in step (8), and a 100 nm thick copper electrode is deposited on the other side, thereby completing the fabrication of a unipolar barrier photodetector based on a perovskite single crystal.
[0074] Comparative Example 1
[0075] (1) Weigh 0.4388g of methylamine iodine and 1.1064g of lead iodide, add them to a glass bottle, add 2mL of γ-butyrolactone solvent, and add a magnetic stir bar; place the glass bottle on a magnetic stirring table and stir at room temperature for 5h until the perovskite material is completely dissolved to obtain MAPbI3 solution (perovskite single crystal growth solution);
[0076] (2) Preparation of thin single crystal growth device: Place four square polytetrafluoroethylene films with a side length of 0.5cm and a thickness of 420 micrometers between two glass substrates with a side length of 10cm, seal the gaps around the two glass substrates with silicone, and leave four 1cm long openings at the four corners.
[0077] (3) Inject the solution prepared in step 1) into the growth apparatus prepared in step 2).
[0078] (4) Place the growth device in step 3) in a preheated oven (88°C) and let it stand for 2 hours to allow the solvent to evaporate from the opening and black perovskite seed crystals to grow in the solution.
[0079] (5) Starting at 90℃, the temperature is increased at a rate of 0.5℃ / h for 20h until a perovskite single crystal with a thickness of 420 micrometers is grown. The grown MAPbI3 perovskite single crystal is then taken out and cooled to room temperature.
[0080] (6) A 19.5 nm thick Au electrode is deposited on one side of the perovskite single crystal obtained in step (5), and a 100 nm thick copper electrode is deposited on the other side, thereby completing the fabrication of the photodetector based on the perovskite single crystal.
[0081] In Examples 1-4, the thickness and maximum size of the obtained MAPbI3 perovskite single crystals increased with the increase of the polytetrafluoroethylene film thickness. Excessive crystal thickness affects photoelectric performance, while insufficient thickness increases fabrication difficulty. Subsequent experiments were based on the 0.21 mm thick perovskite single crystal from Example 2. A schematic diagram of single crystal growth is shown below. Figure 1 A schematic diagram of the fabrication of the unipolar barrier assembly is shown below. Figure 2 .
[0082] The ultra-depth-of-field pseudo-color micrograph and thickness measurement of the MAPbI3 perovskite single crystal prepared in Example 2 are shown below. Figure 3 As shown, the single crystal surface is flat and the edges are sharp, exhibiting good crystal quality, with a crystal thickness of 210 μm.
[0083] The unipolar barrier photodetector structure prepared in Example 2 is as follows: Figure 4 As shown, from bottom to top, the structure consists of a Cu electrode, a MAPbI3 perovskite single crystal, and a BA2MA electrode. n-1 Pb n I 3n+1 Layer, MAPbI3 perovskite single crystal, Au electrode.
[0084] The current density-voltage curves of the devices in Example 2 and Comparative Example 1 under light and dark conditions are as follows: Figure 5 As shown, it can be seen that compared with the unipolar barrier photodetector in Comparative Example 1, the dark current is significantly reduced and a larger on / off ratio is obtained.
[0085] The external quantum efficiency of the unipolar barrier photodetector prepared in Example 2 is as follows: Figure 6 As shown, this indicates that an external quantum efficiency close to 70% can be obtained.
[0086] The noise current curve of the unipolar barrier photodetector obtained in Example 2 is as follows: Figure 7 As shown, the noise current is independent of frequency, which means that the perovskite single crystals prepared in the examples have a low bulk trap density.
[0087] The linear response range of the unipolar barrier photodetector obtained in Example 2 is as follows: Figure 8 As shown, the linear response range is defined as the range between the maximum and minimum light intensity during which the photocurrent maintains linear growth, indicating that the linear response range is 160dB.
[0088] The -3dB frequency response curve of the unipolar barrier photodetector obtained in Example 2 is shown below. Figure 9 As shown, the cutoff frequency is 344kHz.
[0089] The above embodiments are merely illustrative examples of the technical solutions of the present invention. The perovskite unipolar barrier photodetector and its fabrication method involved in this invention are not limited to the content described in the above embodiments, but are defined by the scope of the claims. Any modifications, supplements, equivalent substitutions, or improvements made by those skilled in the art within the spirit and principles of this invention should be included within the protection scope of this invention.
Claims
1. A method for fabricating a unipolar barrier photodetector based on perovskite single crystal, comprising the following steps: 1) Preparation of MAPbI3 solution: Mix MAI and PbI2 in a molar ratio of 1.15 to 1.25:1 and dissolve them in a γ-butyrolactone solution. Then mix and stir at room temperature until the perovskite material is completely dissolved to obtain MAPbI3 solution. 2) Preparation of thin single crystal growth device: A polytetrafluoroethylene film with a thickness of 10 to 400 micrometers is used as a spacer between two glass substrates. The gaps around the two glass substrates are sealed with silicone, and 2 to 4 openings with a width of 0.5 to 1 cm are left. 3) Preparation of seed crystals: The MAPbI3 solution obtained in step 1) is injected into the growth device in step 2). After heating, the temperature is maintained for a period of time to allow the solvent to evaporate from the opening until black perovskite seed crystals are produced in the solution. 4) Single crystal growth: Continue heating the growth apparatus from step 3) where small seed crystals appeared for 12–24 hours, and obtain a single crystal with a thickness of 100–400 micrometers and an area of 0.04–1 cm² using the reverse temperature crystallization method. 2 The MAPbI3 perovskite single crystal was then removed from the growth apparatus and cooled to room temperature. 5) Preparation of BA2PbI4 solution: Mix BAI and PbI2 in a molar ratio of 1.9 to 2.1:1 and dissolve them in acetonitrile solution. Heat and stir, let stand to precipitate, and take the clear liquid to obtain BA2PbI4 solution. 6) Preheat the perovskite single crystal prepared in step 4); 7) Preparation of a unipolar barrier structure via pressure bonding process: The BA₂PbI₄ solution prepared in step 5) is dropped onto the MAPbI₃ single crystal preheated in step 6), and then quickly covered with another preheated MAPbI₃ single crystal. After heating, annealing is performed. During annealing, a certain pressure is applied between the two MAPbI₃ single crystal assemblies to promote the epitaxial growth of BA₂PbI₄ within the MAPbI₃ single crystal assemblies. After BA₂PbI₄ dissolves part of the MAPbI₃ single crystal, BA₂MA is formed between the single crystals. n-1 Pb n I 3n+1 Where n is 1 to 3; MAPbI3 single crystal - BA2MA n-1 Pb n I 3n+1 -MAPbI3 single crystals form a unipolar barrier structure; 8) Gold electrodes and copper electrodes are deposited on both sides of the single crystal assembly obtained in step 7) to obtain a unipolar barrier photodetector based on perovskite single crystal.
2. The method for fabricating a unipolar barrier photodetector based on perovskite single crystal as described in claim 1, characterized in that: Step 3) involves heating the temperature to 85–90°C and maintaining it for 1–4 hours to allow the solvent to evaporate from the opening.
3. The method for fabricating a unipolar barrier photodetector based on perovskite single crystal as described in claim 1, characterized in that: Step 4) Start from an initial temperature of 85-90℃ and increase the temperature at a rate of 0.25-0.75℃ / h for 12-24 hours.
4. The method for fabricating a unipolar barrier photodetector based on perovskite single crystal as described in claim 1, characterized in that: Step 5) involves heating to 55–62°C and stirring for 3–8 hours, then maintaining the temperature at 55–62°C and allowing the mixture to settle.
5. The method for fabricating a unipolar barrier photodetector based on perovskite single crystal as described in claim 1, characterized in that: Step 6) involves preheating the perovskite single crystal to 60-65°C.
6. The method for fabricating a unipolar barrier photodetector based on perovskite single crystal as described in claim 1, characterized in that: In step 7), 0.1–0.5 μL of BA2PbI4 solution is added to each square millimeter of single crystal, and then the temperature is raised to 60–70 °C for annealing for 1–2 hours. During annealing, a pressure of 50–150 g is applied between the two MAPbI3 single crystal assemblies.
7. The method for fabricating a unipolar barrier photodetector based on perovskite single crystal as described in claim 1, characterized in that: Step 8) involves vapor-depositing a gold electrode with a thickness of 18–22 nm and a copper electrode with a thickness of 80–120 nm.
8. A unipolar barrier photodetector based on perovskite single crystal, characterized in that: It is prepared by the method described in any one of claims 1 to 7.