Perovskite homojunction thick film and preparation method and application thereof

Abstract

The invention provides a perovskite homojunction thick film and a preparation method and application thereof, the chemical composition of the perovskite homojunction thick film is at least one of MAPbI3, MAPbBr3, MAPbCl3, FAPbI3, FAxMA1-xPbI3, FAxCs1-xPbI3, MAxFAyCs1-x-yPbI3 and FAPbBr3, x is more than or equal to 0 and less than or equal to 1, and y is more than or equal to 0 and less than or equal to 1. According to the perovskite homojunction thick film, the hole problem in a thick film prepared by blade coating is improved, the carrier transmission performance is improved, and the perovskite homojunction thick film has higher signal-to-noise ratio and sensitivity in X-ray detection, so that the detection imaging capability is improved, and the perovskite homojunction thick film is suitable for high-performance X-ray detection devices. The invention also provides a preparation method and application of the perovskite homojunction thick film.

Description

Technical Field

[0001] The invention belongs to the technical field of perovskite homojunction thick films, and in particular relates to a perovskite homojunction thick film and a preparation method and application thereof. Background Art

[0002] X-ray detection technology is widely used in various fields such as radioactive detection, medical diagnosis, industrial non-destructive testing, scientific research, etc. Organic-inorganic hybrid perovskites show good application prospects in the field of X-ray detection due to their high X-ray absorption coefficient, excellent charge transport capacity and tunable band structure. However, perovskite single crystals are limited by the uncontrollable crystal size, long growth time, and high pressure required during wafer preparation, and are difficult to integrate with thin film transistors (TFTs). Therefore, relatively speaking, polycrystalline films are more likely to achieve large-area perovskite device preparation. In addition, in order to ensure that the material fully absorbs X-rays, a thick film with a thickness of more than 10μm needs to be prepared.

[0003] As a common method for preparing perovskite crystalline films, the scraping method can quickly and efficiently prepare large-area thick films and is expected to achieve industrial production. However, the scraping method is still limited in the preparation of thick films. On the one hand, during the preparation of thick films, the solvent evaporates faster on the upper surface, while residual solvent may remain at the bottom, which requires high-temperature annealing to solve this problem, but this may cause more holes and cracks in the film, thereby reducing performance. On the other hand, for X-ray detection, the perovskite material needs to reach a certain thickness to absorb enough X-rays, which usually requires a thickness of tens to hundreds of microns. However, the carrier transmission path will become longer as the film thickness increases, which will increase the probability of carrier recombination. Therefore, it is necessary to develop a new perovskite homojunction thick film and preparation method to improve the hole problem in the thick film prepared by scraping and improve the carrier transmission performance. Summary of the invention

[0004] The present invention aims to solve at least one of the above-mentioned technical problems existing in the prior art. To this end, the present invention provides a perovskite homojunction thick film, which improves the hole problem in the thick film prepared by scraping, improves the carrier transmission performance, has a higher signal-to-noise ratio and sensitivity in X-ray detection, thereby improving the detection imaging capability, and is suitable for high-performance X-ray detection devices.

[0005] The invention also provides a method for preparing a perovskite homojunction thick film.

[0006] The present invention also provides an application of a perovskite homojunction thick film in X-ray detection.

[0007] The first aspect of the present invention provides a perovskite homojunction thick film, wherein the chemical composition of the perovskite homojunction thick film is MAPbI3 MAPbBr 3 MAPbCl 3 , FAPbI 3 , FA x MA 1-x PbI 3 , FA x Cs 1-x PbI 3 、MA x FA y Cs 1-x-y PbI 3 , FAPbBr 3 At least one of , where 0≤x≤1, 0≤y≤1.

[0008] One of the technical solutions of the present invention regarding the perovskite homojunction thick film has at least the following beneficial effects:

[0009] Improved film density. Compared with the perovskite thick film prepared by the traditional slurry scraping method, the present invention optimizes the ink ratio and preparation process to make the obtained thick film denser, reduce holes and gaps, and improve the overall quality of the film.

[0010] By selecting solvents with different boiling points and using two scraping processes, a first layer of strong n-type and a second layer of weak n-type perovskite films were formed, realizing the construction of a type II homojunction.

[0011] There is a gradient change in the electron and hole concentrations at the homojunction interface, forming a space charge region and generating a built-in electric field, which helps to separate and directionalize carriers, reduce carrier recombination, and improve the carrier transport efficiency inside the material.

[0012] The spatial separation of electrons and holes reduces the probability of carrier recombination, thereby significantly extending the carrier lifetime and improving the optoelectronic properties of the material.

[0013] Due to the extended carrier lifetime and optimized transmission performance, the perovskite homojunction thick film of the present invention has higher signal-to-noise ratio and sensitivity in X-ray detection, thereby improving the detection imaging capability and is suitable for high-performance X-ray detection devices.

[0014] In summary, the present invention provides a method for preparing high-quality perovskite homojunction thick films, which optimizes the structure and electrical properties of the films, making them have important application value in the fields of photoelectric detection and the like.

[0015] According to some embodiments of the present invention, the thickness of the perovskite homojunction thick film is ≥10 μm.

[0016] The second aspect of the present invention provides a method for preparing the perovskite homojunction thick film of the first aspect of the present invention, comprising the following steps:

[0017] S1: dissolving perovskite microcrystals in a first solvent and a second solvent respectively according to the chemical composition to obtain a first ink and a second ink;

[0018] S2: coating the first ink on the surface of the substrate for the first time and then annealing it for the first time to form a first film;

[0019] S3: coating the second ink on the surface of the first film layer for a second time and then annealing it for a second time to obtain the perovskite homojunction thick film;

[0020] The first solvent has a higher boiling point than the second solvent.

[0021] A technical solution in the method for preparing a thick perovskite homojunction film of the present invention has at least the following beneficial effects:

[0022] On the one hand, the perovskite thick film prepared by the traditional slurry scraping method has a large number of holes and gaps, and it is necessary to prepare a denser, high-quality, large-area thick film to improve performance. The present invention regulates the semiconductor type of the perovskite film by changing the composition ratio of the perovskite precursor ink and optimizing the preparation process. On the other hand, the perovskite thick film will extend the carrier transmission distance, and the carrier transmission performance inside the material needs to be further improved. The present invention establishes a type II homojunction between the perovskite layers formed by two scrapings. At the homojunction contact interface, there is a gradient change in the electron and hole concentrations, and a space charge region is formed. In this region, the distribution of charges generates a built-in electric field, which is conducive to the separation and transmission of carriers. This spatial separation of electrons and holes significantly reduces the probability of recombination, thereby extending the carrier lifetime and enabling X-ray detection to have more outstanding imaging capabilities.

[0023] The present invention first dissolves perovskite in a first solvent with a relatively higher boiling point to form ink, and after scraping to form a film, a second solvent with a relatively lower boiling point is used to dissolve the perovskite to form ink, and then scraping is performed twice. The perovskite film formed by the two scrapings has different proportions of organic components due to different solvents and preparation processes, forming a perovskite film with a strong n-type first layer and a weak n-type second layer, thereby preparing a high-quality homojunction perovskite thick film. The construction of the homojunction enhances the carrier transport performance of the perovskite and improves the X-ray detection sensitivity of the device.

[0024] According to some embodiments of the present invention, the first solvent includes at least one of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, γ-valerolactone and 1,3-dimethyl-2-imidazolidinone.

[0025] According to some embodiments of the present invention, the second solvent includes at least one of ethylene glycol methyl ether, ethylene glycol ethyl ether, ethyl acetate, γ-butyrolactone, propylene carbonate and acetonitrile.

[0026] Both the first solvent and the second solvent have good solubility and viscosity for perovskite, which is beneficial to ensure good ink adhesion during scraping and helps to form a more uniform precursor liquid film.

[0027] The first solvent and the second solvent have the following differences: they have very different boiling points (more than 30°C) and saturated vapor pressures, and their coordination abilities with perovskites are quite different. Since different annealing temperatures are required during nucleation, high temperatures will cause the volatilization of organic components. By regulating the annealing process, the content of organic components can be cleverly utilized to form homojunction perovskites.

[0028] In semiconductors, electrical properties are mainly determined by the type of carriers. When the main carriers are holes, the semiconductor is p-type; when the main carriers are electrons, the semiconductor is n-type. From the perspective of the band structure, the Fermi level of p-type semiconductors is closer to the valence band, while the Fermi level of n-type semiconductors is closer to the conduction band.

[0029] For n-type semiconductors, the distance between the Fermi level and the bottom of the conduction band can further reflect its electrical properties. According to the relative position of the Fermi level and the conduction band, n-type semiconductors can be divided into strong n-type and weak n-type: the Fermi level of strong n-type is closer to the bottom of the conduction band than that of weak n-type.

[0030] When both layers of perovskite are n-type semiconductors, the perovskite layer with a Fermi level closer to the conduction band can be defined as a strong n-type, while the other is a weak n-type. When the two are in contact, the space charge region generated at the interface will establish a directional built-in electric field, which can effectively promote the separation and transport of photogenerated carriers in the interface region.

[0031] Specifically, after the high-boiling point solvent (first solvent) dissolves the perovskite and is scraped, it needs to be annealed at high temperature. High temperature will cause the volatilization of organic components. The lack of organic components causes the formation of strong n-type perovskite; the low-boiling point solvent (second solvent) only needs to be annealed at low temperature, and the organic component content is higher, which is conducive to the preparation of weak n-type perovskite.

[0032] According to some embodiments of the present invention, the coordination ability of the first solvent with the perovskite microcrystals is greater than the coordination ability of the second solvent with the perovskite microcrystals.

[0033] According to some embodiments of the present invention, the first solvent is a high boiling point solvent and has a strong coordination ability with perovskite, and needs to volatilize at a relatively high temperature to form a film.

[0034] According to some embodiments of the present invention, the second solvent is a low boiling point solvent and has a weak coordination ability with perovskite, and can volatilize to form a film at a relatively low temperature.

[0035] According to some embodiments of the present invention, the concentration of the first ink is 1 to 5 mol / L.

[0036] According to some embodiments of the present invention, the concentration of the first ink is any one of 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, or a range formed by any two of them, such as 2 mol / L to 4 mol / L.

[0037] According to some embodiments of the present invention, the concentration of the second ink is 1 to 5 mol / L.

[0038] According to some embodiments of the present invention, the concentration of the second ink is any one of 1 mol / L, 2 mol / L, 3 mol / L, 4 mol / L, 5 mol / L, or a range formed by any two of them, such as 2 mol / L to 4 mol / L.

[0039] According to some embodiments of the present invention, the temperature of the two annealing steps is 50°C to 300°C.

[0040] According to some embodiments of the present invention, the temperatures of the two annealing steps are any one of 50°C, 100°C, 150°C, 200°C, 250°C, 300°C, or a range formed by any two of them, such as 150°C to 250°C.

[0041] According to some embodiments of the present invention, the vacuum degree of annealing is -0.005 to -0.1 MPa.

[0042] According to some embodiments of the present invention, the temperature of the first annealing is greater than the temperature of the second annealing.

[0043] According to some embodiments of the present invention, the temperature of the first annealing is 140°C to 180°C.

[0044] According to some embodiments of the present invention, the temperature of the first annealing is any one of 140°C, 150°C, 160°C, 170°C, 180°C, or a range formed by any two of them, such as 150°C to 160°C.

[0045] According to some embodiments of the present invention, the temperature of the second annealing is 80°C to 120°C.

[0046] According to some embodiments of the present invention, the temperature of the second annealing is any one of 80°C, 90°C, 100°C, 110°C, 120°C, or a range formed by any two of them, such as 90°C to 100°C.

[0047] According to some embodiments of the present invention, the first annealing time is 0.5 to 1.5 hours.

[0048] According to some embodiments of the present invention, the first annealing time is any one of 0.5 h, 1 h, 1.5 h, or a range formed by any two of them, such as 1 h to 1.5 h.

[0049] According to some embodiments of the present invention, the second annealing time is 5 to 30 minutes.

[0050] According to some embodiments of the present invention, the second annealing time is any one of 5 min, 10 min, 15 min, 20 min, 25 min, 30 min, or a range formed by any two of them, such as 10 min to 20 min.

[0051] According to some embodiments of the present invention, the first coating and the second coating are knife coating.

[0052] According to some embodiments of the present invention, the speed of the scraping is 50-500 mm / s.

[0053] According to some embodiments of the present invention, the scraping speed is any value of 50mm / s, 100mm / s, 150mm / s, 200mm / s, 250mm / s, 300mm / s, 350mm / s, 400mm / s, 450mm / s, 500mm / s or a range formed by any two of them, such as 250mm / s to 350mm / s.

[0054] According to some embodiments of the present invention, the limitation of the scraping is 50-400 μm.

[0055] According to some embodiments of the present invention, the limit of the scraping is any value of 50 μm, 100 μm, 150 μm, 200 μm, 250 μm, 300 μm, 350 μm, 400 μm or a range formed by any two of them, such as 200 μm to 300 μm.

[0056] According to some embodiments of the present invention, the method for preparing the perovskite homojunction thick film may be:

[0057] According to the chemical composition, the perovskite crystallites are dissolved in a first solvent and stirred to form a clear first ink.

[0058] The substrate is placed on a hot table for preheating, and then a certain volume of the first ink is coated on the substrate and scraped at a uniform speed.

[0059] The first layer of liquid film is placed on a high-temperature hot stage and evacuated to a vacuum state using a vacuum reactor. After the film is formed, the vacuum reactor is removed and the film is continued to be annealed at a high temperature.

[0060] The perovskite crystallites are dissolved in a second solvent and stirred to a clear second ink.

[0061] A certain volume of the second ink is coated on the first film and formed into a film under a vacuum reactor.

[0062] The third aspect of the present invention provides the use of the perovskite homojunction thick film according to the first aspect of the present invention or the perovskite homojunction thick film prepared by the preparation method of the second aspect of the present invention in X-ray detection.

[0063] A technical solution of the present invention regarding the application of perovskite homojunction thick film in X-ray detection has at least the following beneficial effects:

[0064] The preparation method of the present invention does not require expensive equipment and complex process control, the reaction conditions are not harsh, the raw materials are easily available, the production cost is low, and it is easy to industrialize the production. Specifically:

[0065] 1. Improved X-ray detection sensitivity. Enhanced carrier separation efficiency: The built-in electric field at the homojunction interface helps to separate photogenerated electron-hole pairs and reduce recombination losses, thereby improving the signal response intensity of the X-ray detector. Reduced dark current: The effective separation of carriers reduces the dark current of the device, reduces noise, improves detection sensitivity, and makes low-dose X-ray detection possible.

[0066] 2. Improved signal-to-noise ratio. Reduced carrier recombination: The spatial separation of electrons and holes significantly reduces the probability of recombination, making the detection signal clearer and helping to obtain high-quality X-ray images. Optimized charge collection efficiency: Long-life, high-mobility carriers make charge collection more efficient, improve the signal-to-noise ratio of the device, and thus improve imaging quality.

[0067] 3. Improved spatial resolution and imaging quality. Reduced scattering effects: High-quality, low-defect perovskite thick films can reduce X-ray scattering in the detector and improve imaging clarity. Enhanced edge detection capabilities: Due to high signal-to-noise ratio and high carrier transport performance, the detector performs better in fine structure detection (such as tiny lesions in medical imaging or small defects in industrial detection).

[0068] 4. Suitable for low-dose X-ray detection. Reduced X-ray detection limit: Perovskite materials have a high absorption capacity for X-rays, and can produce stronger electrical signals at the same dose, reducing dependence on high-dose X-rays and reducing radiation risks. Suitable for medical imaging: Lower X-ray doses are safer for patients and can be used for medical applications such as low-dose CT scans and breast X-ray imaging.

[0069] 5. Improved detector stability and service life. Optimized material stability: Through reasonable perovskite layer structure design, the stability of the material under long-term X-ray irradiation is improved, degradation is reduced, and the device life is increased. Reduced power consumption: Efficient carrier transport reduces the detector's operating voltage requirements, making it more energy-efficient and more suitable for portable or long-term operating X-ray detection systems.

[0070] 6. Suitable for a variety of X-ray detection applications, such as medical imaging (low-dose CT, breast X-ray imaging, dental X-ray imaging, etc.), industrial non-destructive testing (material testing, electronic component quality testing, etc.), security inspection (baggage security inspection, border security scanning, etc.), scientific research (synchrotron radiation detection, space X-ray astronomy, etc.).

[0071] In summary, the perovskite homojunction thick film of the present invention optimizes carrier transport, improves the signal-to-noise ratio and detection sensitivity, so that the X-ray detector has higher imaging quality, lower dose requirement and longer service life, and has broad application prospects in the fields of medicine, industry and security. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] Figure 1 The following are scanning electron microscope images of the surface and cross section of the homogeneous junction film obtained in Example 1.

[0073] Figure 2 This is a scanning electron microscope image of the surface and cross section of the NMP-PVK film obtained in Comparative Example 1.

[0074] Figure 3 Schematic diagram of the Fermi level and energy band structure of Example 1 and Comparative Example 1.

[0075] Figure 4 The dynamic transient absorption attenuation curves of the films obtained in Example 1 and Comparative Examples 1 and 2.

[0076] Figure 5 It is the X-ray response curve of the detector based on the embodiment and the comparative example. DETAILED DESCRIPTION

[0077] The following will be combined with the embodiments to clearly and completely describe the concept of the present invention and the technical effects produced, so as to fully understand the purpose, characteristics and effects of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, other embodiments obtained by those skilled in the art without creative work are all within the scope of protection of the present invention.

[0078] In the description of the present invention, the description with reference to the terms "one embodiment", "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representation of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described may be combined in any one or more embodiments or examples in a suitable manner.

[0079] Unless otherwise specified, "room temperature" in the present invention means 25°C±5°C.

[0080] Unless otherwise specified, "about" in the present invention means that the allowable error is within ±2%.

[0081] If the specific conditions are not specified in the examples, the experiments were carried out under conventional conditions or conditions recommended by the manufacturer. If the manufacturers of the reagents or instruments are not specified, they are all conventional products that can be purchased commercially.

[0082] Example 1

[0083] This embodiment provides a perovskite homojunction thick film. The preparation method is based on secondary vacuum-assisted scraping, specifically:

[0084] 2.34 mmol of MAPbI 3 The microcrystals were dissolved in 1 mL of N-methylpyrrolidone (NMP) and 1 mL of ethylene glycol methyl ether (2-ME) to prepare NMP-MAPbI. 3 Ink and 2-ME-MAPbI 3 The ink was stirred at room temperature for 3 h and filtered using a polytetrafluoroethylene (PTFE) filter with a pore size of 0.45 μm.

[0085] The cleaned and UV-ozone treated FTO substrate was placed on a 100°C hot plate for 2 minutes. Then, a 100 μL NMP-MAPbI 3 The perovskite ink was uniformly coated on the FTO substrate at a speed of 200 mm / s.

[0086] The liquid film was moved to a hot stage at 160°C and evacuated to a vacuum degree of -0.1 MPa using a vacuum reactor to allow the liquid film to evaporate and take shape. The vacuum environment was then removed and annealing was continued for 1 hour.

[0087] Next, 70 μL of 2-ME-MAPbI 3The ink was coated on the first layer of film with the same applicator and speed, and then vacuum film was formed at 25°C with a vacuum degree of -0.075 MPa. The vacuum reactor was then removed and annealed at 100°C for 10 minutes.

[0088] Example 2

[0089] This embodiment provides a perovskite homojunction thick film. The preparation method is based on secondary vacuum-assisted scraping, specifically:

[0090] 2.34 mmol of MAPbI 3 The microcrystals were dissolved in 1 mL of γ-valerolactone (GVL) and 1 mL of ethylene glycol methyl ether (2-ME) to prepare GVL-MAPbI. 3 Ink and 2-ME-MAPbI 3 The ink was stirred at room temperature for 3 h and filtered using a polytetrafluoroethylene (PTFE) filter with a pore size of 0.45 μm.

[0091] The cleaned and UV-ozone treated FTO substrate was placed on a 160°C hot plate for 2 minutes. Then, 100 μL of GVL-MAPbI was coated using a 100 μm high confinement applicator. 3 The perovskite ink was uniformly coated on the FTO substrate at a speed of 200 mm / s.

[0092] The liquid film was moved to a hot stage at 120°C and evacuated to a vacuum degree of -0.1 MPa using a vacuum reactor to allow the liquid film to evaporate and take shape. The vacuum environment was then removed and annealing was continued for 1 hour.

[0093] Next, 70 μL of 2-ME-MAPbI 3 The ink was coated on the first layer of film with the same applicator and speed, and then vacuum film was formed at 25°C with a vacuum degree of -0.075 MPa. The vacuum reactor was then removed and annealed at 100°C for 10 minutes.

[0094] It should be noted that the difference between Example 2 and Example 1 is that the ink used in Example 2 for one scraping is GVL-MAPbI 3 .

[0095] Comparative Example 1

[0096] This comparative example provides a perovskite homojunction thick film. The difference from Example 1 is that 2.34 mmol of MAPbI 3 The microcrystals were dissolved in 1 mL of N-methylpyrrolidone (NMP) and the coating was applied once.

[0097] Comparative Example 2

[0098] This comparative example provides a perovskite homojunction thick film. The difference from Example 1 is that 2.34 mmol of MAPbI 3 The microcrystals were dissolved in 1 mL of ethylene glycol methyl ether (2-ME) and scraped once.

[0099] Comparative Example 3

[0100] This comparative example provides a perovskite homojunction thick film. The difference from Example 1 is that 2.34 mmol of MAPbI 3 The microcrystals were dissolved in a mixed solvent of 1 mL N-methylpyrrolidone (NMP) and 1 mL ethylene glycol methyl ether (2-ME). The coating was scraped once.

[0101] Performance Testing

[0102] The performance of the above perovskite thick film was characterized. The specific test items, test methods and results are as follows:

[0103] 1. Basic phase characterization

[0104] Figure 1 The following are scanning electron microscope images of the surface and cross section of the homogeneous junction film obtained in Example 1.

[0105] Figure 1 a in the figure is the surface morphology, from which it can be seen that the surface of the perovskite film is smooth and dense without holes. This indicates that after the second scraping, the surface of the film is more dense, which is conducive to achieving efficient carrier transport.

[0106] Figure 1 b in the figure is the cross-sectional morphology. It can be seen that the perovskite film is composed of two layers. The lower layer is composed of large-particle NMP-PVK film, and the upper layer is composed of small-particle dense 2-ME-PVK film. The thickness is 30μm. The larger thickness is conducive to the full absorption of X-rays.

[0107] Figure 2 This is a scanning electron microscope image of the surface and cross section of the NMP-PVK film obtained in Comparative Example 1.

[0108] Figure 2 a in the figure is the surface morphology. It can be seen that it is mainly composed of large grains with a grain size of about 10 to 20 μm, and there are pinholes, which means that this structure is not conducive to the preparation of the device and it is difficult to achieve high-sensitivity X-ray detection.

[0109] Figure 2 b in the figure is the cross-sectional morphology. It can be seen that the cross-section is composed of large particles with a thickness of 22 μm, indicating that the prepared thickness is suitable for X-ray detectors.

[0110] 2. Band structure characterization

[0111] from Figure 3From a in FIG, it can be seen that the Fermi level of Comparative Example 1 (NMP-PVK film) is -4.63 eV;

[0112] from Figure 3 From b in the figure, it can be seen that the Fermi level of Example 1 (homojunction film) is -4.77 eV;

[0113] from Figure 3 As shown in c, the energy band structure diagram of the two layers of perovskite in Example 1 (homojunction film) can be seen.

[0114] 3. Carrier transport and recombination characterization

[0115] The perovskite films obtained in Example 1 and Comparative Examples 1 and 2 were used to characterize the carrier transport and recombination.

[0116] Figure 4 It is the dynamic transient absorption attenuation curve of the membrane obtained in Example 1 and Comparative Examples 1 and 2.

[0117] Figure 4 In the figure, the curve of homogeneous conjunctiva is the test result of Example 1.

[0118] Figure 4 In the figure, the curve of NMP-PVK film is the test result of comparative example 1.

[0119] Figure 4 In the figure, the curve of 2-ME-PVK membrane is the test result of comparative example 2.

[0120] It can be seen that the average carrier lifetime of Example 1 is 9335 ps, which is much higher than 1272 ps of Comparative Example 1 and 2013 ps of Comparative Example 2. The long lifetime reduces carrier recombination losses and improves charge collection efficiency.

[0121] 4. X-ray detection performance

[0122] Further X-ray detection performance characterization was performed, and the results were as follows Figure 5 As shown, with the increase of X-ray dose rate, the photocurrent of the detector increases significantly. By fitting the net response current at different dose rates, the sensitivity can be calculated.

[0123] Figure 5 a in the figure is based on the X-ray response curve of the detector of Example 1. At -1V, the X-ray sensitivity of Example 1 is 14540μC Gy air -1 cm -2 .

[0124] Figure 5b is based on the X-ray response curve of the detector of comparative example 1. At -1V, the X-ray sensitivity of comparative example 1 is 8520μC Gy air -1 cm -2 .

[0125] Figure 5 c in the figure is based on the X-ray response curve of the detector of comparative example 2. At -1V, the X-ray sensitivity of comparative example 2 is 4450μC Gy air -1 cm -2 .

[0126] Figure 5 The d in the figure is based on the X-ray response curve of the detector of comparative example 3. At -1V, comparative example 3 has no obvious X-ray response.

[0127] It can be seen that Example 1 has a larger response current to X-rays of different dose rates and a flatter baseline, and has better X-ray detection performance.

[0128] The present invention has been described in detail above in conjunction with the embodiments, but the present invention is not limited to the above embodiments, and various changes can be made within the knowledge scope of ordinary technicians in the relevant technical field without departing from the purpose of the present invention.

Claims

1. A perovskite homojunction thick film, characterized in that: The chemical composition of the perovskite homojunction thick film is MAPbI3, MAPbBr3, MAPbCl3, FAPbI3, FA x MA 1-x PbI3、FA x Cs 1-x PbI3、MA x FA y Cs 1-x-y At least one of PbI3, FAPbBr3, wherein 0≤x≤1, 0≤y≤1.

2. The perovskite homojunction thick film according to claim 1, characterized in that: The thickness of the perovskite homojunction thick film is ≥10 μm.

3. A method for preparing a perovskite homojunction thick film as claimed in claim 1 or 2, characterized in that: The following steps are involved: S1: dissolving perovskite microcrystals in a first solvent and a second solvent respectively according to the chemical composition to obtain a first ink and a second ink; S2: coating the first ink on the surface of the substrate for the first time and then annealing it for the first time to form a first film; S3: coating the second ink on the surface of the first film layer for a second time and then annealing it for a second time to obtain the perovskite homojunction thick film; The first solvent has a higher boiling point than the second solvent.

4. The method according to claim 3, characterized in that: The first solvent includes at least one of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, γ-valerolactone and 1,3-dimethyl-2-imidazolidinone.

5. The method according to claim 3, characterized in that: The second solvent includes at least one of ethylene glycol methyl ether, ethylene glycol ethyl ether, ethyl acetate, γ-butyrolactone, propylene carbonate and acetonitrile.

6. The method according to claim 3, characterized in that The coordination ability of the first solvent with the perovskite microcrystals is greater than the coordination ability of the second solvent with the perovskite microcrystals.

7. The method according to claim 3, characterized in that The concentration of the first ink is 1 to 5 mol / L; and / or the concentration of the second ink is 1 to 5 mol / L.

8. The method according to claim 3, characterized in that The temperature of the first annealing is greater than the temperature of the second annealing; and / or, the temperature of the first annealing is 140°C to 180°C; and / or, the temperature of the second annealing is 80°C to 120°C; and / or, the time of the first annealing is 0.5 to 1.5 hours; and / or, the time of the second annealing is 5 to 30 minutes.

9. The method according to claim 3, characterized in that: The first coating and the second coating are scraping; and / or the scraping speed is 50-500 mm / s; and / or the scraping limit is 50-400 μm.

10. Use of the perovskite homojunction thick film according to any one of claims 1 to 2 or the perovskite homojunction thick film prepared by the preparation method according to any one of claims 3 to 9 in X-ray detection.

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