X-ray direct detector and preparation method thereof

Abstract

The present application belongs to the field of optoelectronic technology, and in particular, relates to an X-ray direct detector and a method for preparing the same. The method for preparing the X-ray direct detector comprises the following steps: dissolving organic urea, organic ligand, halogenated carbon group metal and halogen salt in an organic solvent to form a precursor sol; the halogen salt comprises an organic ammonium halide or an alkali halide; the precursor sol is subjected to a film-forming treatment on the surface of a substrate, followed by an annealing treatment to form a quantum array film layer of a two-dimensional hybrid perovskite on the surface of the substrate; an electrode layer is prepared on the surface of the quantum array film layer away from the substrate to obtain an X-ray direct detector. In the method for preparing the X-ray direct detector of the present application, organic urea can inhibit the rapid aggregation of octahedrons in the two-dimensional hybrid perovskite, the thickness of the quantum array film layer can reach more than 100 μm, and the two-dimensional hybrid perovskite grows perpendicularly to the substrate on the surface of the substrate to form a quantum array film layer with high thickness and strong absorption of X-rays, and has high detection sensitivity.

Description

Technical Field

[0001] The present application belongs to the field of optoelectronic technology, and in particular, relates to an X-ray direct detector and a preparation method thereof. Background Art

[0002] Two-dimensional hybrid perovskite is a layered metal halide perovskite. Due to the confinement effect of the quantum well structure on carriers, two-dimensional hybrid perovskite has unique optical and electrical properties. And its stability is better than that of three-dimensional metal halide perovskite, and it is widely used in light-emitting diodes, solar cells, photoelectric sensors and other fields. X-ray direct imaging detectors directly convert X-rays passing through the object to be measured into electrical signals, and finally convert the electrical signals into images through digital processing. Two-dimensional hybrid perovskites have a high absorption coefficient for X-rays, and can generate strong electrical signals in the growth direction of the octahedral sheets. It has great application value in the field of X-ray high-definition imaging. In recent years, the application research of two-dimensional hybrid perovskites in X-ray direct imaging detectors has gradually attracted attention.

[0003] At present. The two-dimensional hybrid perovskite used in X-ray direct detectors is usually grown by slowly cooling in a saturated solution to form a single crystal, and finally an electrode is evaporated on the surface of the single crystal to collect electrical signals. However, the single crystals grown by the solution method are small in size and irregular in shape, which is not conducive to the collection of electrical signals and the final imaging of the object. In the prior art, a quantum well film with a vertical electrode orientation is prepared by spin coating a precursor solution on a hot substrate by a casting method, and the film has a linear response to X-rays. However, the thickness of the film is only 500nm, and the absorption of X-rays is weak, resulting in a lower X-ray sensitivity of the detector, affecting the final imaging. Although increasing the precursor concentration can increase the film thickness to 1.9μm, the film quality of solution casting decreases, which also leads to a weaker response to X-rays. Summary of the invention

[0004] The purpose of the present application is to provide an X-ray direct detector and a method for preparing the same, which aims to solve to a certain extent the problems of low X-ray absorption efficiency, poor electrical signal collection and imaging effects, and low detection sensitivity of the X-ray direct detector prepared by the prior art.

[0005] In order to achieve the above application purpose, the technical solution adopted in this application is as follows:

[0006] In a first aspect, the present application provides a method for preparing an X-ray direct detector, comprising the following steps:

[0007] Dissolving organic urea, organic ligand, halogenated carbon group metal and halogen salt in an organic solvent to prepare a precursor sol; the halogen salt comprises organic ammonium halide or alkali metal halide;

[0008] After the precursor sol is subjected to film-forming treatment on the surface of the substrate, annealing treatment is performed to form a quantum array film layer of a two-dimensional hybrid perovskite on the surface of the substrate;

[0009] An electrode layer is prepared on the surface of the quantum array film layer away from the substrate to obtain an X-ray direct detector.

[0010] Furthermore, the thickness of the quantum array film layer is 100-200 μm.

[0011] Furthermore, the precursor sol also includes a film-forming additive, and the film-forming additive includes at least one of an ammonium halide salt and a thiocyanate.

[0012] Furthermore, the organic urea is selected from at least one of guanidine, urea, thiourea, semicarbazide, thiosemicarbazide, cyclohexylurea, allyl urea, 1,3-dimethylurea, 4-chlorophenylurea, and ethylene urea.

[0013] Furthermore, the ammonium halide salt is selected from at least one of ammonium chloride, methylammonium chloride and formamidine chloride.

[0014] Furthermore, the thiocyanate includes ammonium thiocyanate.

[0015] Furthermore, the mass ratio of the organic urea to the halocarbon metal is (5-30):100.

[0016] Furthermore, the mass ratio of the film-forming additive to the halocarbon metal is (1-30):100.

[0017] Furthermore, the film forming process comprises: preheating the substrate at a temperature of 80 to 150° C., adding the precursor sol to the surface of the substrate, heating the substrate to 100 to 150° C., and coating the precursor sol to form a wet film.

[0018] Furthermore, the annealing step includes: keeping the temperature at 80 to 150° C. in a vacuum condition for 8 to 15 minutes to form the quantum array film layer on the surface of the substrate.

[0019] Furthermore, the step of preparing the precursor sol includes: dissolving the organic urea, the film-forming additive, the organic ligand, the halogenated carbon group metal and the halogen salt in the organic solvent, mixing and treating for 1 to 3 hours in a protective atmosphere at a temperature of 50 to 80° C., heating to 90 to 110° C. and keeping the temperature for 5 to 120 seconds to obtain the precursor sol.

[0020] Furthermore, the organic ligand is selected from at least one of n-butylamine hydroiodide, α-phenylethylamine hydroiodide, isobutylamine hydroiodide, and allylamine hydroiodide.

[0021] Furthermore, the carbon group metal halide is selected from at least one of lead chloride, lead bromide, lead iodide, tin chloride, tin bromide and tin iodide.

[0022] Furthermore, the organic halide ammonium salt is selected from: CH 3 NH 3 Cl, CH 3 NH 3 Br, CH 3 NH 3 I. CH 2 (NH 3 ) 2 Cl, CH 2 (NH 3 ) 2 Br, CH 2 (NH 3 ) 2 At least one of I;

[0023] Furthermore, the alkali metal halide is selected from at least one of CsCl, CsBr, CsI, RbCl, RbBr, and RbI.

[0024] Furthermore, the organic solvent is selected from: a mixed solvent of dimethyl sulfoxide and N,N-dimethylformamide.

[0025] Furthermore, in the organic solvent, the volume ratio of the dimethyl sulfoxide to the N,N-dimethylformamide is (1-9):(1-9).

[0026] In a second aspect, the present application provides an X-ray direct detector prepared by the above method, comprising: a substrate, a quantum array film layer in-situ vertically grown on the surface of the substrate, and an electrode layer laminated and arranged on the surface of the quantum array film layer; wherein the quantum array film layer contains a structure with a general formula of A'A n-1 B n X 3n+1 and / or A' 2 A n-1 B n X 3n+1 A two-dimensional hybrid perovskite, wherein A' is an organic ligand, A is an ammonium ion or an alkali metal ion, B is a carbon group metal ion, X is a halogen ion; and n is 2 to 10.

[0027] Furthermore, the organic ligand is selected from at least one of n-butylamine hydroiodide, α-phenylethylamine hydroiodide, isobutylamine hydroiodide, and allylamine hydroiodide.

[0028] Furthermore, the organic ammonium ion is selected from: CH 3 NH 3+ , CH 2 (NH 3 ) 2 + At least one of .

[0029] Furthermore, the alkali metal ion is selected from: Cs + , Rb + At least one of .

[0030] Furthermore, the carbon group metal ion is selected from at least one of lead and tin.

[0031] Furthermore, the halogen ion is selected from at least one of chlorine, bromine and iodine.

[0032] Furthermore, the substrate includes at least one of ITO, FTO, and P3HT:PCBM.

[0033] Furthermore, the electrode layer is selected from at least one of a carbon electrode and a metal electrode.

[0034] The first aspect of the present application provides a method for preparing an X-ray direct detector, wherein organic urea is added when configuring the precursor sol, and the organic urea can inhibit the rapid aggregation of octahedrons in the two-dimensional hybrid perovskite to form a stable precursor sol, thereby increasing the film thickness of the precursor sol on the substrate surface. After the precursor sol is processed into a wet film on the substrate surface, during the film formation and annealing process, the addition of organic urea causes the two-dimensional hybrid perovskite to form a heterogeneous crystal nucleus, causing it to grow perpendicular to the substrate orientation on the substrate surface, forming a quantum array film layer of the two-dimensional hybrid perovskite with high thickness and strong absorption of X-rays.

[0035] The second aspect of the present application provides an X-ray direct detector, comprising a substrate-quantum array film layer-electrode layer laminated and bonded, wherein a two-dimensional hybrid perovskite quantum array film layer is in-situ vertically grown on the surface of the substrate, and the confinement effect of the quantum well structure in the perovskite on the carriers causes the carriers in the quantum array film layer to migrate directionally along the growth direction of the quantum well, thereby suppressing the lateral drift and scattering of the carriers, improving the efficiency of carrier migration, and avoiding carrier loss. In addition, the thickness of the quantum array film layer can reach more than 100 μm, and the surface flatness of the quantum array film layer is high and the trap density is low. Therefore, the X-ray direct detector has high absorption efficiency for X-rays, less charge loss, high photoelectric conversion efficiency, improved imaging efficiency and clarity, and thus improved the sensitivity of the detector. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0037] Figure 1 It is a schematic flow chart of a method for preparing an X-ray direct detector provided in an embodiment of the present application;

[0038] Figure 2 is a schematic diagram of the structure of an X-ray direct detector provided in an embodiment of the present application;

[0039] Figure 3 It is a functional relationship diagram of the photocurrent density (ordinate) of the X-ray direct detector provided in Examples 1 to 3 of the present application and Comparative Example 1 and different X-ray dose rates (abscissa). DETAILED DESCRIPTION

[0040] In order to make the technical problems, technical solutions and beneficial effects to be solved by the present application more clearly understood, the present application is further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0041] In this application, the term "and / or" describes the association relationship of associated objects, indicating that there may be three relationships. For example, A and / or B can mean: A exists alone, A and B exist at the same time, and B exists alone. A and B can be singular or plural. The character " / " generally indicates that the associated objects are in an "or" relationship.

[0042] In this application, "at least one" means one or more, and "plurality" means two or more. "At least one of the following" or similar expressions refers to any combination of these items, including any combination of single items or plural items. For example, "at least one of a, b or c", or "at least one of a, b and c", can all represent: a, b, c, ab (i.e. a and b), ac, bc, or abc, where a, b, c can be single or multiple, respectively.

[0043] It should be understood that in the various embodiments of the present application, the size of the serial numbers of the above-mentioned processes does not mean the order of execution, some or all of the steps can be executed in parallel or sequentially, and the execution order of each process should be determined by its function and internal logic, and should not constitute any limitation on the implementation process of the embodiments of the present application.

[0044] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "an" and "the" used in the embodiments of the present application and the appended claims are also intended to include plural forms, unless the context clearly indicates other meanings.

[0045] The weight of the relevant components mentioned in the embodiment description of the present application can not only refer to the specific content of each component, but also represent the proportional relationship between the weights of the components. Therefore, as long as the content of the relevant components is proportionally enlarged or reduced according to the embodiment description of the present application, it is within the scope disclosed in the embodiment description of the present application. Specifically, the mass in the embodiment description of the present application can be μg, mg, g, kg and other mass units known in the chemical industry.

[0046] The terms "first" and "second" are used only for descriptive purposes to distinguish objects such as substances from each other, and should not be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. For example, without departing from the scope of the embodiments of the present application, the first XX may also be referred to as the second XX, and similarly, the second XX may also be referred to as the first XX. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features.

[0047] As attached Figure 1 According to a first aspect of an embodiment of the present application, there is provided a method for preparing an X-ray direct detector, comprising the following steps:

[0048] S10. dissolving an organic urea, an organic ligand, a halogenated carbon group metal and a halogen salt in an organic solvent to form a precursor sol; the halogen salt comprises an organic ammonium halide or an alkali metal halide;

[0049] S20. After the precursor sol is subjected to film-forming treatment on the surface of the substrate, annealing treatment is performed to form a quantum array film layer of a two-dimensional hybrid perovskite on the surface of the substrate;

[0050] S30. Prepare an electrode layer on the surface of the quantum array film layer facing away from the substrate to obtain an X-ray direct detector.

[0051] The first aspect of the present invention provides a method for preparing an X-ray direct detector, wherein organic urea is added when a precursor sol is prepared, wherein the organic urea contains -NH 2, C=O, C=S and other functional groups, which can form intermediates with larger radius with organic ligands, metal ions and other perovskite octahedral central cations in the precursor sol through the synergistic effect of Lewis acid-base pairs, so as to inhibit the rapid aggregation of octahedrons in the two-dimensional hybrid perovskite, form heterogeneous nucleation, and thus form a stable precursor sol, thereby increasing the film thickness of the precursor sol on the substrate surface. After the precursor sol is treated into a wet film on the substrate surface, during the film formation and annealing process, the octahedrons and interlayer organic cations of the two-dimensional hybrid perovskite self-assemble through intermolecular and electrostatic forces, and the addition of organic urea causes the two-dimensional hybrid perovskite to form heterogeneous nuclei, so that it grows perpendicular to the substrate on the substrate surface, forming a quantum array film layer of the two-dimensional hybrid perovskite with high thickness and strong absorption of X-rays. In addition, by controlling the annealing conditions, the volatilization rate of the solvent and additives in the precursor sol can be controlled, thereby flexibly regulating the growth rate of the two-dimensional hybrid perovskite crystal, reducing the random orientation of the crystal nucleus caused by slow solvent volatilization, and maintaining the in-situ orientation of the quantum well on the electrode while increasing the thickness of the quantum array film layer.

[0052] The general structural formula of the two-dimensional hybrid perovskite in the quantum array film prepared in the embodiment of the present application is A'A n-1 B n X 3n+1 and / or A' 2 A n-1 B n X 3n+1 The carbon group metal ion at position B and the halogen ion at position X form [BX 6 ] octahedron, the cations such as ammonium ions or alkali metal ions at the A position are distributed in the gaps formed by the top-to-top connection of the octahedron, with a coordination number of 12. The organic ligands at the A' position are bonded to the anions at the edge of the octahedron through electrostatic attraction, so that [BX 6 ] The organic spacer is formed between the octahedrons. Due to the mismatch in dielectric constants between the organic and inorganic layers, [BX 6 ] The octahedral layers form a natural quantum well structure, and n represents the well width of the quantum well, that is, the number of octahedral layers, preferably 2 to 10.

[0053] In the direct X-ray imaging detector prepared in the embodiment of the present application, the quantum array film layer of the two-dimensional hybrid perovskite grows in situ perpendicular to the substrate. On the one hand, the film thickness of the quantum array film layer is increased by the action of the organic urea added to the precursor sol, and the film thickness can reach more than 100 μm, and further 100 to 200 μm, thereby significantly improving the absorption efficiency of the detector to X-rays and improving the photoelectric conversion efficiency of the detector. On the other hand, the quantum well structure in the quantum array film layer that is perpendicular to the electrode orientation forms a natural array in situ on the substrate surface, thereby improving the collection efficiency of the quantum array film layer to electrical signals, and limiting the migration of charges perpendicular to the electrode orientation, improving the charge migration efficiency, and thus improving the imaging efficiency and clarity. The X-ray direct detector in the embodiment of the present application, due to the confinement effect of the quantum well structure on carriers in the two-dimensional hybrid perovskite and the presence of wide-bandgap organic ligands, reduces the ion mobility, greatly improves the absorption efficiency of X-rays, and can absorb X-rays and directly convert them into electrical signals. And due to the confinement effect of the two-dimensional hybrid perovskite quantum wells in the quantum array film layer, the carriers are evenly transmitted along the quantum wells in the quantum array film layer to the substrate, converting electrical signals into images, and forming high-definition images with different color depths according to the intensity of the electrical signals.

[0054] In some embodiments, the thickness of the quantum array film layer is 100 to 200 μm. This thickness greatly improves the direct X-ray imaging detector's ability to capture X-rays and improves the device's absorption and conversion efficiency of X-rays. It is difficult to obtain a vertically oriented film layer with a quantum array film layer that is too thick, and the carrier diffusion length is limited. The film layer thickness exceeds the carrier diffusion length, which will reduce its charge collection efficiency. In some specific embodiments, in a direct X-ray imaging detector, the thickness of the quantum array film layer includes but is not limited to 100 to 110 μm, 110 to 130 μm, 130 to 150 μm, 150 to 180 μm, 180 to 200 μm, etc.

[0055] In some embodiments, in the above step S10, the organic urea is selected from at least one of guanidine, urea, thiourea, semicarbazide, thiosemicarbazide, cyclohexylurea, allylurea, 1,3-dimethylurea, 4-chlorophenylurea, and ethylene urea, and semicarbazide, thiosemicarbazide, and cyclohexylurea are further preferred; these organic ureas contain -NH 2 , C=O, C=S and other functional groups. These functional groups can form intermediates with larger radius with the central cations of the perovskite octahedron such as organic ligands and metal ions in the precursor sol through the synergistic effect of Lewis acid-base pairs to inhibit the [BX 6] The octahedrons rapidly aggregate and form heterogeneous nucleation, thereby forming a stable precursor sol, thereby increasing the film thickness of the precursor sol on the substrate surface. Specifically, the C=S and C=O bonds can form coordination with carbon group metal ions, and the NH bonds can form hydrogen bonds with organic ligands and organic halide ammonium salts, thereby forming a large radius intermediate with the reaction system, inhibiting the [BX 6 ] The aggregation of octahedrons reduces the nucleation rate and can enhance the viscosity of the precursor, which is beneficial to the subsequent film-forming treatment of the precursor sol, forming a thicker film layer, while increasing the film thickness and maintaining its vertical orientation. In addition, these organic ureas containing easily decomposable or volatile components such as S, O and N are easily decomposed and removed by heat during the subsequent annealing process, and will not remain in the two-dimensional hybrid perovskite, and will not affect the crystal structure and crystal quality of the two-dimensional hybrid perovskite.

[0056] In some embodiments, the mass ratio of organic urea to halocarbon metal is (5-30):100; the amount of organic urea added can effectively optimize the [BX 6 ] octahedron aggregation rate, forming a stable precursor sol, and increasing the film thickness of the precursor sol on the substrate surface. If the amount of organic urea added is too low, the [BX 6 ] The octahedral aggregation rate is too fast, which is not conducive to the formation of a stable precursor sol, so it is difficult for the precursor solution to form a thick wet film in situ on the substrate surface at one time, and it is difficult to form a thick quantum array film layer of two-dimensional hybrid perovskite; if the amount of organic urea added is too high, the interaction with the reaction system is enhanced, and too much -NH 2 , C=O, C=S and other functional groups form intermediates with the central cation of the perovskite octahedron, which excessively suppresses the [BX 6 ] The octahedrons aggregate and evaporate too slowly in the system to form a pinhole structure, which is not conducive to the formation and growth of two-dimensional hybrid perovskite crystals, and will reduce or even prevent the formation of perovskite octahedral structures. In some specific embodiments, the mass ratio of organic urea to halocarbon metal includes but is not limited to (5-10):100, (10-15):100, (15-20):100, (20-30):100, etc.

[0057] In some embodiments, in the above step S10, the precursor sol also includes a film-forming additive, and the film-forming additive includes at least one of ammonium halide and thiocyanate. The halogen ions, ammonium ions, thiocyanate ions, etc. in the film-forming additives added to the precursor sol of the embodiment of the present application can enhance the growth orientation of the two-dimensional hybrid perovskite crystal, optimize the film-forming quality of the two-dimensional hybrid perovskite, reduce the roughness of the surface of the quantum array film layer, reduce the trap density, thereby reducing the charge loss in the detector and improving the photoelectric conversion efficiency of the X-ray direct detector. Through the combined effect of the organic urea and the film-forming additive added to the precursor sol, not only the film thickness of the quantum array film layer is increased, the film thickness can reach more than 100μm, and further 100-200μm, thereby significantly improving the absorption efficiency of the detector for X-rays; and the film quality is improved, the surface flatness of the film layer is improved, the trap density is reduced, the charge loss is reduced, and the photoelectric conversion efficiency of the detector is improved.

[0058] In some embodiments, the mass ratio of the film-forming additive to the halogenated carbon group metal is (1-30): 100, and the addition ratio of the film-forming additive can effectively improve the film flatness of the quantum array film layer of the two-dimensional hybrid perovskite, reduce the trap density of the film layer, reduce the charge loss, and improve the photoelectric conversion efficiency of the detector. If the amount of the film-forming additive added is too low, the optimization effect on the flatness, trap defects, etc. of the quantum array film layer of the two-dimensional hybrid perovskite is not good, which is not conducive to reducing the charge loss; if the amount of the film-forming additive added is too high, the excessive film-forming additive will reduce the interaction between the two-dimensional hybrid perovskite raw material components such as organic ligands, halogenated carbon group metals and halide salts in the precursor sol, and the film layer is prone to form a pinhole structure, which is also not conducive to the formation of the quantum array film layer of the two-dimensional hybrid perovskite. In some specific embodiments, the mass ratio of the film-forming additive to the halocarbon metal includes but is not limited to (5-10):100, (10-15):100, (15-20):100, (20-30):100, etc.

[0059] In some embodiments, the ammonium halide salt is selected from at least one of ammonium chloride, methylammonium chloride, and formamidine chloride, and ammonium chloride is further preferred. In some embodiments, the thiocyanate includes ammonium thiocyanate. These film-forming additives include halogen ions, ammonium ions, thiocyanate ions, etc., which can enhance the growth orientation of the two-dimensional hybrid perovskite crystal, while reducing the surface roughness of the two-dimensional hybrid perovskite crystal film, reducing the trap density, and optimizing the film quality of the two-dimensional hybrid perovskite. Specifically, film-forming additives such as ammonium halide salts and thiocyanate can be adsorbed on the (202) crystal plane of the perovskite, and the halogen ions and carbon group metal ions form intermediates, so that the perovskite octahedron grows along the (111) direction. At the same time, these film-forming additives are easy to volatilize during the annealing process, and the volatilization rate is consistent with the crystallization rate of perovskite, avoiding the formation of pinhole structure; and halogen ions will form a halogen-rich environment during the crystallization process. The electronegativity of halogen ions enables them to passivate halogen vacancies in perovskite, thereby reducing surface roughness, reducing trap density, and forming a uniform film layer, thereby reducing charge loss in the detector and improving the photoelectric conversion efficiency of the X-ray direct detector.

[0060] In some embodiments, in the above step S10, the step of preparing the precursor sol includes: dissolving the organic urea, film-forming additive, organic ligand, halogenated carbon group metal and halogen salt in an organic solvent, mixing and treating for 1 to 3 hours under a protective atmosphere at a temperature of 50 to 80°C, heating to 90 to 110°C and keeping warm for 5 to 120 seconds to obtain the precursor sol. In some specific embodiments, after dissolving the organic urea, film-forming additive, organic ligand, halogenated carbon group metal and halogen salt in an organic solvent, the resulting solution is placed in a glass bottle with a lid to prevent the solvent and additives from volatilizing, and in a glove box filled with a protective atmosphere such as nitrogen, argon, helium, etc., the temperature is 50 to 80°C and stirred for 1 to 3 hours, specifically at 65°C for 2 hours. Then the container is opened, the solution is heated to 90 to 110°C, the constant temperature time is set to 5 to 120 seconds, and the time is further preferably 10 to 30 seconds, and the solution is concentrated. Then stop heating, cover the bottle cap, make the glass bottle airtight, continue to stir the resulting solution until the solution cools to room temperature, obtain a precursor sol with high viscosity, and let it stand. It should be noted that precipitation should not occur during the concentration process. If this phenomenon occurs, reduce the concentration temperature and time.

[0061] In some embodiments, when preparing the precursor sol, the amount of organic ligand, halocarbon metal and halide salt is based on the general structure of the two-dimensional hybrid perovskite. n-1 B n X 3n+1 and / or A' 2 A n-1 B n X 3n+1The ratio of each element, i.e., the organic ligand, the carbon halide metal and the halogen salt, is 1:(n-1):n or 2:(n-1):n to prepare the precursor sol, wherein n=2 to 10, preferably 4 to 10. In some embodiments, the initial concentration of the carbon halide metal in the solvent is preferably 0.5 to 3.5 mol / L.

[0062] In some embodiments, in the above step S20, the step of forming a film of the precursor sol on the surface of the substrate includes: after preheating the substrate at a temperature of 80 to 150°C, adding the precursor sol to the surface of the substrate, heating it to 100 to 150°C, and scraping the precursor sol into a wet film. In the embodiment of the present application, the precursor sol is added to the surface of the substrate by dripping or the like at a temperature of 80 to 150°C (preferably 100 to 120°C), and the temperature is raised to 100 to 150°C (preferably 110 to 130°C), and the precursor sol is scraped into a wet film; on the one hand, the scraping method is conducive to the preparation of a high-thickness film layer, increasing the thickness of the quantum array film layer in the device, and improving the absorption efficiency of the device for X-rays; on the other hand, the preheating condition of 80 to 150°C and the wet film scraping condition of 100 to 150°C are conducive to the growth of the two-dimensional hybrid perovskite in a direction perpendicular to the substrate, forming a quantum well oriented perpendicular to the substrate. In some specific embodiments, the substrate is placed on the vacuum hole of the coating machine workbench, and the coverage rate of the vacuum hole is 1. Then the coating machine workbench is preheated to 80-150°C, preferably 100-120°C, and the precursor sol is dropped onto the hot substrate surface. The program temperature is set to adjust the substrate temperature to 100-150°C, preferably 110-130°C, and the constant temperature time is set to 30-240s, preferably 60-120s. The scraper is moved to allow the precursor sol to form a wet film of uniform thickness on the substrate surface of the substrate.

[0063] In some embodiments, the annealing step includes: keeping warm for 8 to 15 minutes under vacuum conditions of 80 to 150°C and a vacuum degree not higher than -1.78kPa, and forming a quantum array film layer of a two-dimensional hybrid perovskite on the surface of the substrate. In the embodiment of the present application, the temperature is 80 to 150°C, and the vacuum degree is not higher than -1.78kPa. The vacuum condition is kept warm for 8 to 20 minutes. On the one hand, through the thermal disturbance during the annealing process, the two-dimensional hybrid perovskite is further self-assembled, the perovskite crystal form is more ordered, the purity and structural integrity of the two-dimensional hybrid perovskite are improved, and its performance is more stable, thereby obtaining a quantum array film layer of a two-dimensional hybrid perovskite vertically grown on the surface of the substrate. On the other hand, during the annealing process, organic urea and film-forming additives are thermally decomposed and volatilized and removed from the sol. If the annealing rate is too slow or the annealing temperature is too low, the optimization effect on the crystal form, purity, etc. of the two-dimensional hybrid perovskite is not good, which is not conducive to improving the stability of the two-dimensional hybrid perovskite; if the temperature is too high, the material is easy to decompose. In some specific embodiments, after a wet film of uniform thickness is formed on the substrate surface of the substrate, the sealing rubber ring is quickly placed on the workbench of the coating machine so that the substrate is located in the center of the rubber ring and the coverage of the vacuum hole is 0. Then, the round-bottomed glass bottle is inverted on the sealing rubber ring so that the bottle mouth overlaps with the sealing rubber ring, and the coverage of the vacuum hole is 9, and a vacuum environment is constructed. The purpose of this operation is to construct a vacuum environment, reduce the partial pressure of the solvent and additives in the two-dimensional hybrid perovskite wet film during volatilization, and accelerate the volatilization and removal rate of the solvent and additives. The coating machine temperature is set to 80-150°C, preferably 100-120°C, and the temperature is kept for 8-15 minutes to anneal the wet film of the two-dimensional hybrid perovskite to form a quantum array film layer of the two-dimensional hybrid perovskite.

[0064] In some embodiments, the organic ligand is selected from at least one of n-butylamine hydroiodide, α-phenylethylamine hydroiodide, isobutylamine hydroiodide, and allylamine hydroiodide; preferably one or two of n-butylamine hydroiodide, α-phenylethylamine hydroiodide, and allylamine hydroiodide; these organic ligands are bonded to the anions at the edge of the octahedron through electrostatic attraction to form an organic spacer layer, and the dielectric constant of the spacer layer is mismatched with the octahedral sheet, so that [BX 6 ]The octahedral layers form a natural quantum well.

[0065] In some embodiments, the carbon group metal halide is selected from: at least one of lead chloride, lead bromide, lead iodide, tin chloride, tin bromide, and tin iodide; these carbon group metal halide can self-assemble with organic ammonium halides or alkali metal halides to introduce carbon group metals such as lead and tin into the lattice of the two-dimensional hybrid perovskite. Carbon group metals such as lead and tin have high absorption efficiency for X-rays, which can significantly improve the absorption efficiency of the two-dimensional hybrid perovskite for X-rays.

[0066] In some embodiments, the organic ammonium halide salt is selected from: CH 3NH 3 Cl, CH 3 NH 3 Br, CH 3 NH 3 I. CH 2 (NH 3 ) 2 Cl, CH 2 (NH 3 ) 2 Br, CH 2 (NH 3 ) 2 I at least one; these organic halide ammonium salts can form perovskite materials after self-assembly with halide carbon group metals, and CH is introduced into the perovskite material 3 NH 3 + , CH 2 (NH 3 ) 2 + Organic ammonium ions can effectively improve the thermal stability of perovskite materials.

[0067] In some embodiments, the alkali metal halide is selected from at least one of CsCl, CsBr, CsI, RbCl, RbBr, and RbI; these alkali metal halides can form a perovskite material after self-assembly with a halocarbon metal. + , Rb + Alkali metal ions can effectively improve the thermal stability of perovskite materials.

[0068] In some embodiments, the organic solvent is selected from: a mixed solvent of dimethyl sulfoxide and N,N-dimethylformamide. Further, in some embodiments, in the organic solvent, the volume ratio of dimethyl sulfoxide and N,N-dimethylformamide is (1-9): (1-9). The mixed organic solvent used in the embodiment of the present application not only has a good dissolution effect on the various raw material components, but also is conducive to the contact reaction between the components; it is also conducive to regulating the growth rate and orientation of the two-dimensional hybrid perovskite and optimizing the crystallization quality. Specifically, the S=O bond in dimethyl sulfoxide is easy to coordinate with the B-site cation in the two-dimensional hybrid perovskite to form an intermediate, preventing the perovskite [BX 6 ] octahedron such as [PbI 6] etc. Rapid aggregation. In this way, the nucleation reaction rate is reduced and the quality of the film layer is optimized, mainly the orientation goodness and grain size. The large grain size is helpful for the sensitivity of X-rays. However, due to the high boiling point of dimethyl sulfoxide and the slow volatilization rate, the roughness of the film layer will increase, which is not conducive to the X-ray response. N,N-dimethylformamide is a good solvent for perovskite precursors, and its effect is similar to that of dimethyl sulfoxide, but the effect of C=O and B-position cations is weak, and the boiling point is low, which has a poor effect on the nucleation rate of two-dimensional hybrid perovskite crystals. Therefore, a mixed solvent of dimethyl sulfoxide and N,N-dimethylformamide is used, and the ratio of the two affects the volatilization rate of the system solvent, thereby affecting the orientation goodness of the film layer. In some specific embodiments, the volume ratio of dimethyl sulfoxide and N,N-dimethylformamide includes but is not limited to 9:1, 4:1, 7:3, 3:2, 2:3, 3:7, 1:4, 1:9, etc., preferably 2:3, 1:9 or 1:4.

[0069] In some embodiments, in the above step S30, the electrode layer prepared on the surface of the quantum array film layer facing away from the substrate can be a carbon electrode or a metal electrode. In some specific embodiments, the preparation of the carbon electrode includes the steps of: applying the carbon slurry to the surface of the quantum array film layer by a scraping method, and then curing at 80 to 120°C for 5 to 45 minutes, preferably at 90 to 110°C for 20 to 30 minutes to form a carbon electrode layer. In other embodiments, the metal electrode can be prepared by vacuum evaporation or sputtering, and the electrode layer can be made of metal materials such as Al, Ag, Au, and Cu.

[0070] As attached Figure 2 As shown, the second aspect of the embodiment of the present application provides an X-ray direct detector prepared by the above method, comprising: a substrate, a quantum array film layer in-situ vertically grown on the surface of the substrate, and an electrode layer laminated and arranged on the surface of the quantum array film layer; wherein the quantum array film layer contains a structure with a general formula of A'A n-1 B n X 3n+1 and / or A' 2 A n- 1 B n X 3n+1 A two-dimensional hybrid perovskite, wherein A' is an organic ligand, A is an ammonium ion or an alkali metal ion, B is a carbon group metal ion, X is a halogen ion; and n is 2 to 10.

[0071] The X-ray direct detector provided in the second aspect of the embodiment of the present application is made by the method of the above embodiment, and includes a substrate-quantum array film layer-electrode layer arranged in a stacked manner, wherein the two-dimensional hybrid perovskite quantum array film layer is in-situ vertically grown on the surface of the substrate, and the carriers in the quantum array film layer are directed to migrate along the growth direction of the quantum well through the confinement effect of the quantum well structure in the perovskite on the carriers, thereby suppressing the lateral drift and scattering of the carriers, improving the efficiency of carrier migration, and avoiding carrier loss. In addition, the thickness of the quantum array film layer can reach more than 100μm, and the surface flatness of the quantum array film layer is high and the trap density is low. Therefore, the X-ray direct detector has high absorption efficiency for X-rays, less charge loss, high photoelectric conversion efficiency, and improved imaging efficiency and clarity, thereby improving the sensitivity of the detector.

[0072] In some embodiments, the organic ligand is selected from at least one of n-butylamine hydroiodide, α-phenylethylamine hydroiodide, isobutylamine hydroiodide, and allylamine hydroiodide; these organic ligands are bonded to the anions at the edge of the octahedron through electrostatic attraction to form an organic spacer layer, and the dielectric constant of the spacer layer is mismatched with the octahedral sheet, so that [BX 6 ]The octahedral layers form a natural quantum well.

[0073] In some embodiments, the organic ammonium ion is selected from: CH 3 NH 3 + , CH 2 (NH 3 ) 2 + At least one of; these organic ammonium ions can effectively improve the thermal stability of two-dimensional hybrid perovskite.

[0074] In some embodiments, the alkali metal ion is selected from: Cs + , Rb + At least one of; these alkali metal ions can effectively improve the thermal stability of two-dimensional hybrid perovskite.

[0075] In some embodiments, the carbon group metal ions are selected from at least one of lead and tin; these carbon group metals have high absorption efficiency for X-rays and can significantly improve the absorption efficiency of two-dimensional hybrid perovskites for X-rays.

[0076] In some embodiments, the halogen ion is selected from at least one of chlorine, bromine, and iodine; the halogen ion forms a hexa-coordinated carbon group metal element [BX 6 ] octahedron, eight [BX 6The regular octahedrons are connected by sharing vertices to form a cage. A is an ammonium ion or an alkali metal ion that occupies the center of the cage and supports the perovskite structure, forming a 12-coordination with the halogen. The organic ligand at the A' position bonds with the anion at the edge of the octahedron through electrostatic attraction to form an organic spacer.

[0077] In some embodiments, the material of the substrate includes: indium tin oxide (ITO), fluorine-doped SnO 2 At least one of conductive glass (FTO), poly (3-hexylthiophene) and a blend of fullerene derivative [6,6]-phenyl-C61-butyric acid isomethyl ester (P3HT:PCBM).

[0078] In some embodiments, the substrate further comprises a glass substrate.

[0079] In some embodiments, the electrode layer is selected from at least one of a carbon electrode and a metal electrode. In some specific embodiments, the electrode layer can be made of metal materials such as Al, Ag, Au, and Cu.

[0080] In order to enable the above implementation details and operations of the present application to be clearly understood by those skilled in the art, as well as to demonstrate the significant improvement in performance of the X-ray direct detector and its preparation method in the embodiment of the present application, the above technical solution is illustrated by means of multiple embodiments below.

[0081] Example 1

[0082] An X-ray direct detector, the preparation of which comprises the following steps:

[0083] ① Dissolve semicarbazide, ammonium chloride, n-butylamine hydroiodide, methylamine hydroiodide, and lead iodide in a mixed solvent of dimethyl sulfoxide and N,N-dimethylformamide in a volume ratio of 2:3, wherein the molar ratio of n-butylamine hydroiodide, methylamine hydroiodide, and lead iodide is 2:3:4, the initial concentration of lead iodide in the solvent is 3 mol / L, the total volume of the solvent is 0.5 ml, the amount of semicarbazide added is 10% of the lead iodide, and the amount of ammonium chloride added is 10% of the lead iodide. Place the resulting mixed solution in a glass bottle with a lid to prevent the solvent and additives from volatilizing, and stir at 65°C in a glove box filled with nitrogen for 2 hours, then open the container, heat the solution to 100°C, set the constant temperature time for 30 seconds, concentrate the solution, then stop heating, cover the bottle cap, make the glass bottle airtight, and continue to stir the resulting solution until the solution drops to room temperature to obtain a sol with high viscosity, i.e., a precursor sol.

[0084] ② Place a 15mm×15mm indium tin oxide glass on the vacuum hole of the coating machine workbench, with the hole coverage rate of 1, then preheat the coating machine workbench to 120°C, drop the precursor sol onto the hot indium tin oxide glass, set the program temperature to adjust the substrate temperature to 130°C, set the constant temperature time to 120s, move the scraper to make the precursor sol form a uniform wet film on the electrode substrate;

[0085] ③ Rapidly place a sealing rubber ring with an inner diameter of 38 mm on the workbench of the coating machine, so that the indium tin oxide glass is located in the center of the rubber ring, and the coverage rate of the vacuum hole is 0; then invert the round-bottomed glass bottle on the sealing rubber ring, so that the bottle mouth and the sealing rubber ring overlap, the coverage rate of the vacuum hole is 9, and a vacuum condition with a vacuum degree of -1.78 kPa is established. The coating machine temperature is set to 120 ° C, and the constant temperature time is 10 minutes to anneal the wet film of the two-dimensional hybrid perovskite to form a quantum array film; its thickness is 200 μm;

[0086] ④ Apply carbon paste on the surface of the quantum array film by scraping, the amount of carbon paste is 3 ml, and then cure it at 110°C for 30 minutes to form a carbon electrode to prepare an X-ray direct detector.

[0087] Example 2

[0088] An X-ray direct detector, which differs from Example 1 in that ammonium chloride is not added in step ①.

[0089] Example 3

[0090] An X-ray direct detector, which differs from Example 1 in that: in step ①, lead iodide is replaced by lead bromide.

[0091] Comparative Example 1

[0092] An X-ray direct detector, which differs from Example 1 in that no additives of semicarbazide and ammonium chloride are added in step ①.

[0093] Furthermore, in order to verify the progress of the embodiments of the present application, the photocurrent density changes of different film layers of the X-ray direct detectors prepared in embodiments 1 to 3 and comparative example 1 were measured under X-ray irradiation at different dose rates, and the X-ray sensitivity, i.e., the slope of the straight line, was calculated based on the fitting straight line. The average energy of the X-ray was about 20 keV. The test results are shown in the attached figure. Figure 3 As shown, by comparing Examples 1 to 3, Examples 1 and 3 add semicarbazide and ammonium chloride to the precursor at the same time, while Example 2 only adds semicarbazide when preparing the X-ray direct detector precursor, and the sensitivity is lower than that of Examples 1 and 3. This shows that ammonium chloride can improve the sensitivity of the film layer X-ray direct detector by improving the uniformity of the film layer. However, it can be seen from the test results that ammonium chloride has a small effect on improving the sensitivity of the device.

[0094] In addition, by comparing Example 1 and Comparative Example 1, it is found that adding aminourea to the precursor can greatly improve the X-ray sensitivity of the device because aminourea can improve the orientation goodness of the two-dimensional hybrid perovskite, thereby improving its carrier collection efficiency to achieve higher sensitivity.

[0095] The above description is only a preferred embodiment of the present application and is not intended to limit the present application. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present application should be included in the protection scope of the present application.

Claims

1. A method for preparing an X-ray direct detector, It is characterized in that The following steps are involved: Dissolving organic urea, organic ligand, halogenated carbon group metal and halogen salt in an organic solvent to prepare a precursor sol; the halogen salt comprises organic ammonium halide or alkali metal halide; After the precursor sol is subjected to film-forming treatment on the surface of the substrate, annealing treatment is performed to form a quantum array film layer of a two-dimensional hybrid perovskite on the surface of the substrate; An electrode layer is prepared on the surface of the quantum array film layer facing away from the substrate to obtain an X-ray direct detector.

2. The method for preparing the X-ray direct detector according to claim 1, It is characterized in that The thickness of the quantum array film layer is 100 to 200 μm; And / or, the precursor sol further includes a film-forming additive, and the film-forming additive includes at least one of an ammonium halide salt and a thiocyanate.

3. The method for preparing the X-ray direct detector according to claim 2, It is characterized in that The organic urea comprises at least one of guanidine, urea, thiourea, semicarbazide, thiosemicarbazide, cyclohexylurea, allylurea, 1,3-dimethylurea, 4-chlorophenylurea and ethylene urea; And / or, the ammonium halide salt comprises at least one of ammonium chloride, methylammonium chloride and formamidine chloride; And / or, the thiocyanate comprises ammonium thiocyanate.

4. The method for preparing the X-ray direct detector according to claim 3, It is characterized in that The mass ratio of the organic urea to the halogenated carbon group metal is (5-30):100; And / or, the mass ratio of the film-forming additive to the halocarbon metal is (1-30):

100.

5. The method for preparing the X-ray direct detector according to any one of claims 1 to 4, It is characterized in that The film forming process comprises: preheating the substrate at a temperature of 80 to 150° C., adding the precursor sol to the surface of the substrate, heating the substrate to 100 to 150° C., and coating the precursor sol to form a wet film; And / or, the annealing treatment step includes: keeping the temperature at 80-150° C. in a vacuum condition for 8-15 minutes to form the quantum array film layer on the surface of the substrate.

6. The method for preparing the X-ray direct detector according to any one of claims 2 to 4, It is characterized in that The step of preparing the precursor sol comprises: dissolving the organic urea, the film-forming additive, the organic ligand, the halogenated carbon group metal and the halogen salt in the organic solvent, mixing and treating for 1 to 3 hours in a protective atmosphere at a temperature of 50 to 80° C., heating to 90 to 110° C. and keeping the temperature for 5 to 120 seconds to obtain the precursor sol.

7. The method for preparing the X-ray direct detector according to claim 1, It is characterized in that The organic ligand is selected from at least one of n-butylamine hydroiodide, α-phenylethylamine hydroiodide, isobutylamine hydroiodide, and allylamine hydroiodide; And / or, the carbon group metal halide is selected from at least one of lead chloride, lead bromide, lead iodide, tin chloride, tin bromide and tin iodide; And / or, the organic ammonium halide is selected from: CH 3 NH 3 Cl, CH 3 NH 3 Br, CH 3 NH 3 I. CH 2 (NH 3 ) 2 Cl, CH 2 (NH 3 ) 2 Br, CH 2 (NH 3 ) 2 At least one of I; And / or, the alkali metal halide is selected from at least one of CsCl, CsBr, CsI, RbCl, RbBr, and RbI; And / or, the organic solvent is selected from: a mixed solvent of dimethyl sulfoxide and N,N-dimethylformamide.

8. The method for preparing the X-ray direct detector according to claim 7, It is characterized in that In the organic solvent, the volume ratio of the dimethyl sulfoxide to the N,N-dimethylformamide is (1-9):(1-9).

9. An X-ray direct detector prepared by the method according to any one of claims 1 to 8, It is characterized in that include: A substrate, a quantum array film layer in-situ vertically grown on the surface of the substrate, and an electrode layer laminated and arranged on the surface of the quantum array film layer; wherein the quantum array film layer contains a structure with a general formula of A'A n-1 B n X 3n+1 and / or A' 2 A n- 1 B n X 3n+1 A two-dimensional hybrid perovskite, wherein A' is an organic ligand, A is an ammonium ion or an alkali metal ion, B is a carbon group metal ion, X is a halogen ion; and n is 2 to 10.

10. The X-ray direct detector according to claim 9, It is characterized in that The organic ligand is selected from at least one of n-butylamine hydroiodide, α-phenylethylamine hydroiodide, isobutylamine hydroiodide, and allylamine hydroiodide; And / or, the ammonium ion is selected from: CH 3 NH 3 + , CH 2 (NH 3 ) 2 + At least one of; And / or, the alkali metal ion is selected from: Cs + , Rb + At least one of; And / or, the carbon group metal ion is selected from: at least one of lead and tin; And / or, the halogen ion is selected from at least one of chlorine, bromine and iodine; And / or, the material of the substrate includes: at least one of ITO, FTO, and P3HT:PCBM; And / or, the electrode layer is selected from at least one of a carbon electrode and a metal electrode.

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