Perovskite homojunction thick film and preparation method and application thereof

Abstract

The application provides a perovskite homojunction thick film and a preparation method and application thereof, and the chemical composition of the perovskite homojunction thick film is at least one of MAPbI3, MAPbBr3, MAPbCl3, FAPbI3, FA x MA 1‑x PbI3, FA x Cs 1‑x PbI3, MA x FA y Cs 1‑x‑y PbI3, FAPbBr3, wherein 0<=x<=1 and 0<=y<=1. The perovskite homojunction thick film improves the hole problem in the preparation of the thick film by means of scraping and coating, improves the transport performance of carriers, has higher signal-to-noise ratio and sensitivity in X-ray detection, and thus improves the detection imaging capability, and is suitable for high-performance X-ray detection devices. The application further provides a preparation method and application of the perovskite homojunction thick film.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of perovskite homojunction thick films, and particularly relates to a perovskite homojunction thick film and a preparation method and application thereof. BACKGROUND

[0002] X-ray detection technology is widely used in radioactive detection, medical diagnosis, industrial non-destructive testing, scientific research and other fields. Organic-inorganic hybrid perovskite has high X-ray absorption coefficient, excellent charge transport ability and tunable energy band structure, and shows good application prospect in the field of X-ray detection. However, the perovskite single crystal is limited in crystal size control, and the growth takes a long time, and a large pressure is needed in the wafer preparation process, and it is also difficult to integrate with thin film transistor (TFT). Therefore, relatively speaking, the polycrystalline film is more expected to realize the preparation of large-area perovskite device. In addition, in order to ensure sufficient absorption of X-rays by the material, a thick film with a thickness of more than 10 microns needs to be prepared.

[0003] As a common method for preparing perovskite crystal film at present, the doctor blade method can quickly and efficiently prepare large-area thick film, and is expected to realize industrial production. However, the doctor blade method is still limited in the preparation of thick film. On the one hand, during the preparation of thick film, the solvent volatilizes faster on the upper surface, while the solvent may remain at the bottom, which needs to be solved by high-temperature annealing, but this may cause more pores and cracks in the film, and thus the performance is reduced. On the other hand, for X-ray detection, perovskite material needs to reach a certain thickness to absorb enough X-rays, which usually requires a thickness of several tens of microns to hundreds of microns. However, the transmission path of the carrier will become longer with the increase of the film thickness, which will increase the probability of carrier recombination. Therefore, a new perovskite homojunction thick film and a preparation method need to be developed to improve the pore problem in the preparation of thick film by doctor blade method, and to improve the transmission performance of the carrier. SUMMARY

[0004] The present application aims to solve at least one of the above technical problems in the prior art. To this end, the present application provides a perovskite homojunction thick film, which improves the pore problem in the preparation of thick film by doctor blade method, improves the transmission performance of the carrier, 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 device.

[0005] The present application also provides a preparation method of the perovskite homojunction thick film.

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

[0007] The first aspect of the present application provides a perovskite homojunction thick film, the chemical composition of the perovskite homojunction thick film is at least one of MAPbI3, MAPbBr3, MAPbCl3, FAPbI3, FA x MA 1-x PbI3, FA x Cs 1-x PbI3, MA x FA y Cs 1-x-y PbI3, FAPbBr3, wherein 0≤x≤1, 0≤y≤1.

[0008] The present application relates to one of the technical solutions of the perovskite homojunction thick film, which has at least the following beneficial effects:

[0009] The film density is improved. Compared with the perovskite thick film prepared by the traditional slurry coating method, the thick film obtained by optimizing the ink ratio and the preparation process is denser, the pores and voids are reduced, and the overall quality of the film is improved.

[0010] By selecting different boiling point solvents and twice coating process, a perovskite film with strong n-type in the first layer and weak n-type in the second layer is formed, and the construction of type II homojunction is realized.

[0011] There is a gradient change in the electron and hole concentration at the homojunction interface, forming a space charge region and generating a built-in electric field, which helps the separation and directional transport of carriers, reduces the carrier recombination, and improves the carrier transport efficiency inside the material.

[0012] The spatial separation of electrons and holes reduces the probability of carrier recombination, thereby significantly prolonging the carrier lifetime and improving the photoelectric performance of the material.

[0013] Due to the prolongation of carrier lifetime and optimization of transport performance, the perovskite homojunction thick film of the present application has higher signal-to-noise ratio and sensitivity in X-ray detection, thereby improving the detection imaging capability and being suitable for high-performance X-ray detection devices.

[0014] In summary, the present application provides a high-quality perovskite homojunction thick film preparation method, which optimizes the structure and electrical properties of the film, making it have important application value in the field of photoelectric detection.

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

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

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

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

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

[0020] The boiling point of the first solvent is higher than that of the second solvent.

[0021] The present application relates to a technical solution in the preparation method of the perovskite homojunction thick film, and at least has the following beneficial effects:

[0022] On the one hand, the perovskite thick film prepared by the traditional slurry coating method has a large number of pores and voids, and a denser high-quality large-area thick film needs to be prepared to improve the performance. The present application adjusts 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 prolong the carrier transport distance, and the carrier transport performance inside the material needs to be further improved. The present application establishes a type II homojunction between the perovskite layers formed by two times of coating. At the homojunction contact interface, there is a gradient change in the electron and hole concentration, and a space charge region is formed. In this region, the distribution of charges produces a built-in electric field, which is beneficial to the separation and transport of carriers. This spatial separation of electrons and holes significantly reduces the recombination probability, thereby prolonging the carrier lifetime and enabling the X-ray detector to have better imaging capability.

[0023] The present application first dissolves the perovskite to form an ink by using a first solvent with a relatively higher boiling point, then performs coating to form a film, and then dissolves the perovskite to form an ink by using a second solvent with a relatively lower boiling point, and then performs second-time coating. The perovskite films formed by two times of coating are different in the proportion of organic components due to the different solvents and preparation processes, resulting in a first layer of strong n-type perovskite film and a second layer of weak n-type perovskite film, 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 application, 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 application, 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 conducive to ensuring good ink adhesion in doctor blading and helping to form a more uniform precursor liquid film.

[0027] The first solvent and the second solvent have the following differences: they have a large difference in boiling point (more than 30℃) and saturated vapor pressure, and have a large difference in coordination ability with perovskite. Due to the need for different annealing temperatures during nucleation, high temperature will cause the volatilization of organic components, and by controlling the annealing process, the content of organic components can be ingeniously used to form homojunction perovskite.

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

[0029] For n-type semiconductors, the distance between the Fermi level and the conduction band bottom 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 conduction band bottom than that of weak n-type.

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

[0031] Specifically, after dissolving perovskite with a high-boiling-point solvent (first solvent) and doctor blading, high-temperature annealing is required, which will cause the volatilization of organic components, and the lack of organic components will cause the formation of strong n-type perovskite; low-boiling-point solvent (second solvent) only needs to be annealed at low temperature, and has a high content of organic components, which is conducive to the preparation of weak n-type perovskite.

[0032] According to some embodiments of the present application, 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 application, the first solvent is a high-boiling-point solvent and has a strong coordination ability with perovskite, and needs to be volatilized into a film at a relatively high temperature.

[0034] According to some embodiments of the present application, the second solvent is a low-boiling-point solvent and has a weak coordination ability with perovskite, and can be volatilized into a film at a relatively low temperature.

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

[0036] According to some embodiments of the present application, 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 2-4 mol / L.

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

[0038] According to some embodiments of the present application, 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 2-4 mol / L.

[0039] According to some embodiments of the present application, the temperature of the two annealings is 50-300℃.

[0040] According to some embodiments of the present application, the temperature of the two annealings is any one of 50℃, 100℃, 150℃, 200℃, 250℃, 300℃ or a range formed by any two of them, such as 150-250℃.

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

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

[0043] According to some embodiments of the present application, the temperature of the first annealing is 140-180℃.

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

[0045] According to some embodiments of the present application, the temperature of the second annealing is 80-120℃.

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

[0047] According to some embodiments of the present application, the time of the first annealing is 0.5-1.5 h.

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

[0049] According to some embodiments of the present application, the second annealing time is 5-30min.

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

[0051] According to some embodiments of the present application, the first and second coating is blade coating.

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

[0053] According to some embodiments of the present application, the blade coating speed is any one 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-350mm / s.

[0054] According to some embodiments of the present application, the blade coating limit is 50-400μm.

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

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

[0057] Dissolve perovskite microcrystals with a first solvent, and stir until a clear first ink is formed.

[0058] Preheat the substrate on a hot stage, then apply a volume of the first ink to the substrate at a constant speed.

[0059] Place the first layer of liquid film on a high-temperature hot stage, and use a vacuum reactor to extract it to a vacuum state. After the film is formed, remove the vacuum reactor and continue to anneal at high temperature.

[0060] Dissolve the perovskite microcrystals with a second solvent, stir until the second ink is clear.

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

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

[0063] The present application relates to a technical solution for the application of perovskite homojunction thick film in X-ray detection, which has at least the following beneficial effects:

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

[0065] 1. Improved X-ray detection sensitivity. Enhanced carrier separation efficiency: The built-in electric field at the homojunction interface helps to separate the photo-generated electron-hole pairs, reduces the recombination loss, and thus improves the signal response intensity of the X-ray detector. Reduce the 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. Reduce carrier recombination: The spatial separation of electrons and holes significantly reduces the recombination probability, making the detection signal clearer, which helps to obtain high-quality X-ray images. Optimize charge collection efficiency: Long-lived, high-mobility carriers make charge collection more efficient, improving the signal-to-noise ratio of the device, and thus improving the imaging quality.

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

[0068] 4. Suitable for low-dose X-ray detection. Reduce X-ray detection limit: Perovskite materials have high X-ray absorption capacity, which can generate stronger electrical signals at the same dose, reducing the dependence on high-dose X-rays and reducing radiation risk. Suitable for medical imaging: Lower X-ray dose is safer for patients and can be used for low-dose CT scanning, breast X-ray imaging and other medical applications.

[0069] 5. Improved stability and service life of the detector. Optimize material stability: By reasonable perovskite layer structure design, improve the stability of the material under long-term X-ray irradiation, reduce degradation, and improve the service life of the device. Reduce power consumption: High-efficiency carrier transport reduces the operating voltage requirement of the detector, making it more energy-efficient and more suitable for portable or long-term running X-ray detection systems.

[0070] 6. Suitable for various 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 (luggage 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 application, by optimizing carrier transport, improving signal-to-noise ratio and detection sensitivity, makes the X-ray detector have higher imaging quality, lower dose requirement and longer service life, and has wide application prospect in medical, industrial and security fields. BRIEF DESCRIPTION OF DRAWINGS

[0072] Figure 1 The scanning electron microscope images of the surface and cross-section of the homojunction film obtained in Example 1.

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

[0074] Figure 3 The Fermi level and band structure schematic diagram of Example 1 and Comparative Example 1.

[0075] Figure 4 The dynamic transient absorption decay curve of the film obtained in Example 1 and Comparative Example 1, Comparative Example 2.

[0076] Figure 5 The X-ray response curve of the detector based on Example and Comparative Example. DETAILED DESCRIPTION

[0077] The concept and technical effects of the present application will be described in detail below in combination with examples, so as to fully understand the purpose, features and effects of the present application. Obviously, the described examples are only part of the examples of the present application, but not all examples. Based on the examples of the present application, other examples obtained by those skilled in the art without creative labor are within the scope of protection of the present application.

[0078] In the description of the present application, the description of the terms "one embodiment", "some embodiments", "exemplary embodiment", "example", "specific example", or "some examples" etc. means that the specific features, structures, materials or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present application. In the present specification, the exemplary description of the above terms does not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any appropriate manner in one or more embodiments or examples.

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

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

[0081] Unless otherwise specified, the specific conditions in the examples are carried out according to the conventional conditions or the conditions recommended by the manufacturer. The reagents or instruments used are not specified by the manufacturer, and are all conventional products that can be purchased on the market.

[0082] Example 1

[0083] The present example provides a perovskite homojunction thick film. The preparation method is based on secondary vacuum-assisted blade coating, specifically:

[0084] 2.34 mmol of MAPbI3 microcrystals were respectively dissolved in 1 mL of N-methylpyrrolidone (NMP) and 1 mL of ethylene glycol methyl ether (2-ME) to prepare NMP-MAPbI3 ink and 2-ME-MAPbI3 ink, and stirred at room temperature for 3 h, and filtered with a polytetrafluoroethylene (PTFE) filter head with a pore size of 0.45 μm.

[0085] The clean and ultraviolet ozone treated FTO substrate was preheated on a 100°C hot stage for 2 minutes. Then, using a coating film applicator with a limited height of 100 μm, 100 μL of NMP-MAPbI3 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 vacuumed to a vacuum degree of -0.1 MPa using a vacuum reactor, so that the liquid film was volatilized to form a film, and then the vacuum environment was removed, and the annealing was continued for 1 hour.

[0087] Then, 70 μL of 2-ME-MAPbI3 ink was blade coated on the first layer of film using the same coating film applicator and speed, and then vacuum film forming was carried out at 25°C, with a vacuum degree of -0.075 MPa, and then the vacuum reactor was removed, and annealing was carried out at 100°C for 10 min.

[0088] Example 2

[0089] The embodiment provides a perovskite homojunction thick film. A preparation method is based on secondary vacuum-assisted blade coating, in particular:

[0090] 2.34 mmol of MAPbI3 microcrystals are respectively dissolved in 1 mL of gamma-valerolactone (GVL) and 1 mL of ethylene glycol methyl ether (2-ME) to prepare GVL-MAPbI3 ink and 2-ME-MAPbI3 ink, and the ink is stirred at room temperature for 3 h and filtered by using a polytetrafluoroethylene (PTFE) filter head with a pore size of 0.45 μm.

[0091] A clean and ultraviolet ozone treated FTO substrate is preheated on a 160°C hot stage for 2 minutes. Then, 100 μL of GVL-MAPbI3 perovskite ink is uniformly coated on the FTO substrate at a speed of 200 mm / s by using a coating film device with a limited height of 100 μm.

[0092] The liquid film is moved to a hot stage at 120°C, and is pumped to a vacuum degree of -0.1 MPa by using a vacuum reactor, so that the liquid film is volatilized to form a film, and then the vacuum environment is removed, and the annealing is continued for 1 hour.

[0093] Then, 70 μL of 2-ME-MAPbI3 ink is blade coated on the first layer of film by using the same coating film device and speed, and then vacuum film forming is performed at 25°C, and the vacuum degree is -0.075 MPa, and then the vacuum reactor is removed, and the annealing is performed at 100°C for 10 min.

[0094] It should be noted that the difference between example 2 and example 1 is that the ink used in one-time blade coating in example 2 is GVL-MAPbI3.

[0095] Comparative example 1

[0096] The comparative example provides a perovskite homojunction thick film. The difference from example 1 is that 2.34 mmol of MAPbI3 microcrystals are dissolved in 1 mL of N-methyl pyrrolidone (NMP). Blade coating is performed once.

[0097] Comparative example 2

[0098] The comparative example provides a perovskite homojunction thick film. The difference from example 1 is that 2.34 mmol of MAPbI3 microcrystals are dissolved in 1 mL of ethylene glycol methyl ether (2-ME). Blade coating is performed once.

[0099] Comparative example 3

[0100] The comparative example provides a perovskite homojunction thick film. The difference from example 1 is that 2.34 mmol of MAPbI3 microcrystals are dissolved in 1 mL of N-methyl pyrrolidone (NMP) and 1 mL of ethylene glycol methyl ether (2-ME) mixed solvents. Blade coating is performed once.

[0101] Performance test

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

[0103] 1. Basic phase characterization

[0104] Figure 1 The scanning electron microscope images of the surface and cross-section of the homojunction film obtained in Example 1.

[0105] Figure 1 In a, the surface morphology can be seen, and it can be seen that the perovskite film surface is smooth and dense, without pores. It shows that after secondary scraping, the film surface is more dense, which is conducive to realizing efficient carrier transmission.

[0106] Figure 1 In b, the cross-sectional morphology can be seen, and 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, with a thickness of 30 μm. Larger thickness is conducive to the full absorption of X-rays.

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

[0108] Figure 2 In a, the surface morphology can be seen, and it can be seen that it is mainly composed of large grains with a grain size of about 10-20 μm, with pinholes, which shows that this structure is not conducive to the preparation of devices, and it is difficult to realize high sensitivity X-ray detection.

[0109] Figure 2 In b, the cross-sectional morphology can be seen, and it can be seen that the cross-section is composed of large particles, with a thickness of 22 μm, which shows that the prepared thickness is suitable for X-ray detector.

[0110] 2. Band structure characterization

[0111] From a in FIG. 4, it can be seen that the Fermi level of Comparative Example 1 (NMP-PVK film) is -4.63 eV; Figure 3 From b in FIG. 4, it can be seen that the Fermi level of Example 1 (homojunction film) is -4.77 eV;

[0112] Figure 3 From c in FIG. 4, it can be seen that the band structure diagram of the two layers of perovskite in Example 1 (homojunction film).

[0113] From c in FIG. 4, it can be seen that the band structure diagram of the two layers of perovskite in Example 1 (homojunction film). Figure 3 3. Carrier transmission and recombination characterization

[0114]

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

[0116] Figure 4 These are the dynamic transient absorption attenuation curves of the membranes obtained in Example 1, Comparative Example 1, and Comparative Example 2.

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

[0118] Figure 4 In the figure, the curve of the NMP-PVK membrane is the test result of Comparative Example 1.

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

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

[0121] 4. X-ray detection performance

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

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

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

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

[0126] Figure 5d in the above equation is the X-ray response curve of the detector based on Comparative Example 3, which has no obvious X-ray response at -1 V.

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

[0128] The application is described in detail above in combination with the examples, but the application is not limited to the above examples, and various changes can be made within the knowledge of those skilled in the art without departing from the purpose of the application.

Claims

1. A method of preparing a perovskite homojunction thick film, characterized by, The method comprises the following steps: S1: dissolving perovskite microcrystals in a first solvent and a second solvent according to chemical composition to obtain a first ink and a second ink; S2: performing first-time coating of the first ink on a surface of a substrate and then performing first-time annealing to form a first layer of film; S3: performing second-time coating of the second ink on a surface of the first layer of film and then performing second-time annealing to obtain the perovskite homojunction thick film; The first solvent has a higher boiling point than the second solvent; The first solvent has a higher coordination ability with the perovskite microcrystals than the second solvent; The first-time annealing has a higher temperature than the second-time annealing, the first-time annealing has a temperature of 140-180℃, the second-time annealing has a temperature of 80-120℃, the first-time annealing has a time of 0.5-1.5h, and the second-time annealing has a time of 5-30min.

2. The method of claim 1, wherein, The first solvent comprises at least one of N-methylpyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide, γ-valerolactone and 1,3-dimethyl-2-imidazolidinone.

3. The method of claim 1, wherein, The second solvent comprises at least one of ethylene glycol methyl ether, ethylene glycol ethyl ether, ethyl acetate, γ-butyrolactone, propylene carbonate and acetonitrile.

4. The method of claim 1, wherein, The first ink has a concentration of 1-5mol / L; and / or, the second ink has a concentration of 1-5mol / L.

5. The method of claim 1, wherein, The first-time coating and the second-time coating are performed by doctor blading; and / or, the doctor blading has a speed of 50-500mm / s; and / or, the doctor blading has a limit of 50-400μm.

6. The method of claim 1, wherein, the perovskium homojunction thick film has a chemical composition of MAPbI3, MAPbBr3, MAPbCl3, FAPbI3, FA x MA 1-x PbI3, FA x Cs 1-x PbI3, MA x FA y Cs 1-x-y PbI3, FAPbBr3, wherein 0≤x≤1, 0≤y≤1.

7. The method of claim 1, wherein, The perovskite homojunction thick film has a thickness of ≥10μm.

8. Application of the perovskite homojunction thick film prepared by the method of any one of claims 1-7 in X-ray detection.

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