Modified halide perovskite and direct X-ray large-area imaging device and method based on modified halide perovskite

Abstract

The invention discloses modified halide perovskite and a direct X-ray large-area imaging device and method based on the modified halide perovskite, and belongs to the technical field of halide perovskite preparation. According to the modified halide perovskite disclosed by the invention, the polymer material is added into the target perovskite for modification, the added polymer material such as hydroxy propyl cellulose and carboxymethyl cellulose effectively reduces the volume expansion of the target perovskite, and through the mechanism, the volume expansion of the target perovskite is reduced; due to the introduction of the polymer material, the thermal expansion coefficient of the perovskite layer is effectively reduced, the direct thermal expansion difference between the perovskite layer and the substrate material is reduced, and the residual thermal stress of the modified perovskite material is effectively reduced.

Description

Technical Field

[0001] The present invention belongs to the technical field of halide perovskite preparation, and in particular relates to a modified halide perovskite and a direct X-ray large-area imaging device and method based thereon. Background Art

[0002] X-ray detection technology has a wide range of applications in many fields, including medical imaging, nondestructive testing, and security screening. Compared with indirect detectors, direct X-ray detectors are favored due to their high spatial resolution, fast imaging capability, and higher sensitivity. Halide perovskite materials are considered to be outstanding candidates for direct X-ray detection due to their excellent X-ray attenuation properties, tunable band gaps, and high carrier mobility-lifetime products. In recent years, in the pursuit of large-area X-ray imaging, researchers have made some progress by working hard to integrate perovskite thick films with large-area array substrates. However, there are still challenges in practical applications, especially engineering problems caused by the high thermal expansion coefficient of perovskites.

[0003] Compared with traditional semiconductor X-ray detection materials, halide perovskites such as (MAPbX 3 , X=Cl, Br, I) exhibit a larger thermal expansion coefficient, which is due to the fact that MAPbX 3 The Pb-X octahedral framework in the perovskite layer, where the weak interaction of the Pb-X bonds allows the lattice to expand and contract easily with temperature changes. During high-temperature processes such as high-temperature annealing or thermal cycling, this difference may lead to thermally induced residual stresses within the perovskite layer. If these stresses exceed the fracture energy of the material, they may cause crack initiation and propagation, ultimately leading to material failure. Given the relatively low fracture energy of perovskite materials, large-area thick perovskite films are prone to cracking under thermal stress. This not only jeopardizes the integrity of the device and may cause device failure, but can also create pathways for the penetration of environmental factors (such as gases and moisture), thereby accelerating the degradation of device performance. These challenges have limited the progress of halide perovskite materials in applications such as large-area X-ray imaging. Summary of the invention

[0004] The purpose of the present invention is to provide a modified halide perovskite and a direct X-ray large-area imaging device and method based thereon, so as to solve the problem of thermal expansion coefficient mismatch between the perovskite material and the substrate in the prior art, which may cause residual thermal stress in the perovskite layer when the temperature changes, and may lead to the rupture of the imaging device.

[0005] In order to achieve the above object, the present invention adopts the following technical solutions:

[0006] The present invention discloses a method for preparing a modified halide perovskite, comprising the following steps:

[0007] The halide perovskite slurry and the polymer material are mixed, and then the modified halide perovskite is obtained; the polymer material is one of hydroxypropyl cellulose and carboxymethyl cellulose; the halide perovskite slurry is obtained by mixing the halide perovskite powder and the solvent.

[0008] Furthermore, the chemical formula of the halide perovskite powder is ABX 3 ; wherein A is at least one of methylamine ion, formamidine ion and Cs ion; B is at least one of lead ion and bismuth ion; X is at least one of chloride ion, bromide ion and iodide ion.

[0009] Furthermore, the solvent is one or more of γ-butyrolactone, N,N-dimethylformamide and dimethyl sulfoxide; and the volume ratio of the solid to the solvent in the halide perovskite slurry is 2:1 to 5:1.

[0010] Furthermore, in the modified halide perovskite, the added amount of the polymer material is 0.1wt%-10.0wt%.

[0011] The invention also discloses the modified halide perovskite prepared by the preparation method.

[0012] The present invention also discloses a direct X-ray large-area imaging device comprising the above-mentioned modified halide perovskite, wherein the direct X-ray large-area imaging device comprises, from bottom to top, a pixelated circuit substrate, a perovskite layer and a top electrode; the perovskite layer is a modified halide perovskite.

[0013] Furthermore, the area of ​​the pixelated circuit substrate is A×B mm 2 , A, B = 10-500mm;

[0014] The pixelated circuit substrate includes N×M pixel units arranged in an array, wherein N=10-1000; M=10-1000.

[0015] Furthermore, the material of the top electrode is gold, silver, copper, indium tin oxide or fluorine-doped tin oxide;

[0016] The thickness of the perovskite layer is 50-1000 μm.

[0017] The present invention also discloses a method for preparing the above-mentioned direct X-ray large-area imaging device, comprising the following steps: coating a modified halide perovskite on a pixelated circuit substrate, followed by annealing to obtain a pre-treated device; and covering a top electrode on the surface of the pre-treated device to obtain a direct X-ray large-area imaging device.

[0018] Further, the temperature of the annealing treatment is 50° C.-200° C.; the method of coating the modified halide perovskite on the pixelated circuit substrate is by scraping, spraying or screen printing;

[0019] The method of covering the top electrode on the surface of the pre-treated device is evaporation or sputtering.

[0020] Compared with the prior art, the present invention has the following beneficial effects:

[0021] The invention discloses a modified halide perovskite, which is modified by adding a polymer material to a target perovskite. The added polymer material is such as hydroxypropyl cellulose (HPC) and carboxymethyl cellulose (CMC). These polymer materials have elastic deformable properties and can offset the stress by deformation when subjected to external stress. Therefore, when the modified perovskite material is subjected to temperature fluctuations, the polymer material at the grain boundary of the target perovskite undergoes tensile deformation under the action of tensile stress. This deformation compensates for the deformation of the target perovskite caused by lattice contraction and reduces its volume contraction. On the contrary, when the temperature rises, the polymer material undergoes compressive deformation under the action of compressive stress, which effectively reduces the volume expansion of the target perovskite. Through this mechanism, the introduction of the polymer material effectively reduces the thermal expansion coefficient of the perovskite layer, reduces the direct thermal expansion difference with the substrate material, and effectively reduces the residual thermal stress of the modified perovskite material.

[0022] The present invention also discloses a direct X-ray large-area imaging device based on the modified halide perovskite. The thermal expansion coefficient of the modified perovskite material matches that of the substrate (TFT) in the X-ray detector, thereby improving the thermal matching of the modified perovskite material and the substrate material, significantly reducing thermal stress, and improving the thermal stability of the modified perovskite material, which can effectively prevent the formation and expansion of cracks in the perovskite layer of the X-ray detector.

[0023] Furthermore, according to relevant experimental results, compared with perovskite without adding polymer materials, adding an appropriate amount of polymer can increase the resistivity of perovskite; according to relevant experimental results, by controlling the amount of polymer material added, the sensitivity of the perovskite X-ray detector can be appropriately improved, the device noise can be reduced, and the device stability can be improved.

[0024] Furthermore, according to relevant experimental results, it is shown that compared with the unmodified halide perovskite ABX 3 Compared with the modified halide perovskite ABX 3 The thermal expansion coefficient of halide perovskite ABX 3 The difference between the thermal expansion coefficient of the pixelated circuit substrate is reduced. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 It is a schematic diagram of thermal expansion of samples of Example 1 and Comparative Example 1 of the present invention during thermal cycling;

[0026] Figure 2 The thermal expansion d of the samples of Examples 2 to 4 and Comparative Example 2 at different temperatures measured by a thermal expansion analyzer L / L 0 and thermal expansion coefficients of perovskites with different HPC contents;

[0027] Where: a- thermal expansion at different temperatures d L / L 0 ; b- Thermal expansion coefficient of perovskite with different HPC contents;

[0028] Figure 3 The load-displacement curves and Young's modulus (E) of each sample obtained by nanoindentation test of samples of Examples 2 to 4 of the present invention and Comparative Example 2;

[0029] Wherein: a-load-displacement curve obtained from nanoindentation test; b-Young's modulus (E) of each sample;

[0030] Figure 4 This is a photo of the sample of Comparative Example 3 of the present invention;

[0031] Figure 5 is a photograph of a sample of Example 5 of the present invention;

[0032] Figure 6 A photograph of a sample of Example 6 of the present invention;

[0033] Figure 7 The sensitivity / noise ratios of the samples of Example 7 and Comparative Example 4 at different voltages, the signal-to-noise ratios at different dose rates, and the working stability under long-term high-dose X-ray irradiation;

[0034] Where: a-0.5-HPC-probe and MAPbI 3 - Sensitivity / noise ratio of detection at different voltages; b-0.5-HPC-detection and MAPbI 3 -Signal-to-noise ratio of detection at different dose rates; c-0.5-HPC-detection and MAPbI 3 - Detection of working stability under long-term high-dose X-ray irradiation;

[0035] Figure 8 The photographs are of the X-ray imaging device and the readout circuit of Example 8 of the present invention, as well as the imaging data of the spring capsule under different X-ray doses using the device, and the X-ray imaging results of the bat specimen and the multimeter;

[0036] Among them: a-photo of the 64×64 pixel X-ray imaging device and readout circuit; b-imaging data of the spring-containing capsule under different X-ray doses; c-X-ray imaging results of bat specimens; d-X-ray imaging results of the multimeter;

[0037] Fig. 9 The modulation transfer function of the imaging device of Example 8 of the present invention and the imaging result of the line pair test card under X-ray;

[0038] Wherein: a- Modulation Transfer Function (MTF) of the imaging device; b- Photo of the line pair test card and the imaging result under X-ray using the imaging device. DETAILED DESCRIPTION

[0039] In order to enable those skilled in the art to understand the characteristics and effects of the present invention, the following is a general description and definition of the terms and expressions mentioned in the specification and claims. Unless otherwise specified, all technical and scientific terms used in the text are the common meanings understood by those skilled in the art for the present invention. In the event of a conflict, the definition in this specification shall prevail.

[0040] The theories or mechanisms described and disclosed herein, whether correct or incorrect, should not limit the scope of the present invention in any way, that is, the present invention can be implemented without being limited by any specific theory or mechanism.

[0041] Herein, all features such as values, quantities, contents and concentrations defined in the form of numerical ranges or percentage ranges are for simplicity and convenience only. Accordingly, the description of numerical ranges or percentage ranges should be considered to have included and specifically disclosed all possible secondary ranges and individual values ​​within the range (including integers and fractions).

[0042] In this document, unless otherwise specified, “includes,” “including,” “contains,” “has,” or similar terms cover the meanings of “consisting of” and “mainly consisting of,” for example, “A includes a” covers the meanings of “A includes a and other” and “A only includes a.”

[0043] In this document, in order to make the description concise, not all possible combinations of various technical features in various embodiments or examples are described. Therefore, as long as there is no contradiction in the combination of these technical features, the various technical features in various embodiments or examples can be combined arbitrarily, and all possible combinations should be considered to be within the scope of this specification.

[0044] The modified halide perovskite disclosed in the present invention is obtained by mixing halide perovskite slurry and polymer material, wherein the halide perovskite slurry is prepared by mixing halide perovskite ABX 3Add an appropriate amount of solvent, such as γ-butyrolactone, N,N-dimethylformamide, or dimethyl sulfoxide, to the powder, and then stir and mix the powder and the solvent thoroughly to obtain a fluid material;

[0045] Among them, the amount of solvent in the halide perovskite slurry is not enough to convert the halide perovskite ABX 3 The powder is fully dissolved, and the slurry includes halide perovskite ABX 3 Powders and Halide Perovskites ABX 3 Saturated solution.

[0046] The present invention also discloses a direct X-ray large-area imaging device comprising the modified halide perovskite; the direct X-ray large-area imaging device comprises, from bottom to top, a pixelated circuit substrate, a perovskite layer and a top electrode; the perovskite layer is a modified halide perovskite;

[0047] The pixelated circuit substrate area is A×B mm 2 , A, B = 10-500mm, including N×M arrayed pixel units, each pixel unit can collect, store and transmit charges individually, the pixelated circuit substrate can collect the current value of each pixel unit individually, and by connecting the back-end circuit, the position information and current information of each pixel unit are matched one by one, and the image is formed after reorganization.

[0048] The thermal expansion coefficient of the modified halide perovskite is significantly reduced, making the halide perovskite ABX 3 The difference between the thermal expansion coefficient of the pixelated circuit substrate is reduced.

[0049] The present invention will be further described below in conjunction with specific embodiments. It should be understood that these embodiments are only used to illustrate the present invention and are not intended to limit the scope of the present invention. In addition, it should be understood that after reading the content taught by the present invention, those skilled in the art can make various changes or modifications to the present invention, and these equivalent forms fall within the scope limited by the appended claims of the application equally.

[0050] The following examples use conventional instruments and equipment in the art. The experimental methods in the following examples where specific conditions are not specified are usually carried out under conventional conditions or under conditions recommended by the manufacturer. The various raw materials used in the following examples are conventional commercial products unless otherwise specified, and their specifications are conventional specifications in the art. In the specification of the present invention and the following examples, unless otherwise specified, "%" means weight percentage, "part" means weight part, and ratio means weight ratio.

[0051] Example 1

[0052] A method for preparing a modified halide perovskite comprises the following steps:

[0053] According to the target MAPbI 3 The molar ratio of each raw material is: Weigh the corresponding raw materials, use the solvent γ-butyrolactone to dissolve the raw materials, and obtain clear and transparent MAPbI 3 Solution, MAPbI 3 The solution was added dropwise to chlorobenzene to prepare MAPbI 3 The powder was fully dried in an oven at 90 °C to obtain MAPbI 3 powder;

[0054] MAPbI 3 The powder is mixed with 0.5 wt% of hydroxypropyl cellulose (HPC), and 30 wt% of γ-butyrolactone is added to obtain a modified halide perovskite. Note that the solvent cannot dissolve the powder, that is, the obtained modified halide perovskite contains perovskite powder and perovskite saturated solution;

[0055] The modified halide perovskite obtained in this example was coated on a copper foil, and then heated on a hot plate at 110° C. for 2 h for annealing. The material obtained after the temperature dropped to room temperature was named 0.5-HPC-copper foil.

[0056] Example 2

[0057] A method for preparing a modified halide perovskite comprises the following steps:

[0058] According to the target MAPbI 3 The molar ratio of each raw material is: Weigh the corresponding raw materials, use the solvent γ-butyrolactone to dissolve the raw materials, and obtain clear and transparent MAPbI 3 Solution, MAPbI 3 The solution was added dropwise to chlorobenzene to prepare MAPbI 3 The powder was fully dried in an oven at 90 °C to obtain MAPbI 3 powder;

[0059] MAPbI 3 The powder is mixed with 0.5 wt% of hydroxypropyl cellulose (HPC), and 30 wt% of γ-butyrolactone is added to obtain a modified halide perovskite. Note that the solvent cannot dissolve the powder, that is, the obtained modified halide perovskite contains perovskite powder and perovskite saturated solution;

[0060] The modified halide perovskite obtained in this example was fully dried in a vacuum oven, then ground into powder using a mortar, and the powder was pressed into a 5×5×15 mm 3 The block is named 0.5-HPC-block.

[0061] Example 3

[0062] A method for preparing a modified halide perovskite comprises the following steps:

[0063] According to the target MAPbI 3 The molar ratio of each raw material is: Weigh the corresponding raw materials, use the solvent γ-butyrolactone to dissolve the raw materials, and obtain clear and transparent MAPbI 3 Solution, MAPbI 3 The solution was added dropwise to chlorobenzene to prepare MAPbI 3 The powder was fully dried in an oven at 90 °C to obtain MAPbI 3 powder;

[0064] MAPbI 3 The powder is mixed with 1.0 wt% of hydroxypropyl cellulose (HPC), and 30 wt% of γ-butyrolactone is added to obtain a modified halide perovskite. Note that the solvent cannot dissolve the powder, that is, the obtained modified halide perovskite contains perovskite powder and perovskite saturated solution;

[0065] The modified halide perovskite obtained in this example was fully dried in a vacuum oven, then ground into powder using a mortar, and the powder was pressed into a 5×5×15 mm 3 The block is named 1.0-HPC-block.

[0066] Example 4

[0067] A method for preparing a modified halide perovskite comprises the following steps:

[0068] According to the target MAPbI 3 The molar ratio of each raw material is: Weigh the corresponding raw materials, use the solvent γ-butyrolactone to dissolve the raw materials, and obtain clear and transparent MAPbI 3 Solution, MAPbI 3 The solution was added dropwise to chlorobenzene to prepare MAPbI 3 The powder was fully dried in an oven at 90 °C to obtain MAPbI 3 powder;

[0069] MAPbI 3 The powder is mixed with 2.0 wt% of hydroxypropyl cellulose (HPC), and 30 wt% of γ-butyrolactone is added to obtain a modified halide perovskite. Note that the solvent cannot dissolve the powder, that is, the obtained modified halide perovskite contains perovskite powder and perovskite saturated solution;

[0070] The modified halide perovskite obtained in this example was fully dried in a vacuum oven, then ground into powder using a mortar, and the powder was pressed into a 5×5×15 mm 3 The block is named 2.0-HPC-block.

[0071] Example 5

[0072] A method for preparing a modified halide perovskite comprises the following steps:

[0073] According to the target MAPbI 3 The molar ratio of each raw material is: Weigh the corresponding raw materials, use the solvent γ-butyrolactone to dissolve the raw materials, and obtain clear and transparent MAPbI 3 Solution, MAPbI 3 The solution was added dropwise to chlorobenzene to prepare MAPbI 3 The powder was fully dried in an oven at 90 °C to obtain MAPbI 3 powder;

[0074] MAPbI 3 The powder is mixed with 0.5 wt% of carboxymethyl cellulose (CMC), and 30 wt% of γ-butyrolactone is added to obtain a modified halide perovskite. Note that the solvent cannot dissolve the powder, that is, the obtained modified halide perovskite contains perovskite powder and perovskite saturated solution;

[0075] The modified halide perovskite obtained in this example was coated on ITO and then heated on a hot plate at 110°C for 2 h for annealing. The material obtained after the temperature dropped to room temperature was named MAPbI 3 -CMC-ITO.

[0076] Example 6

[0077] A method for preparing a modified halide perovskite comprises the following steps:

[0078] According to the target MAPbI 3 The molar ratio of each raw material is: Weigh the corresponding raw materials, use the solvent γ-butyrolactone to dissolve the raw materials, and obtain clear and transparent MAPbI 3 Solution, MAPbI 3 The solution was added dropwise to chlorobenzene to prepare MAPbI 3 The powder was fully dried in an oven at 90 °C to obtain MAPbI 3 powder;

[0079] MAPbI 3The powder is mixed with 0.5 wt% of hydroxypropyl cellulose (HPC), and 30 wt% of γ-butyrolactone is added to obtain a modified halide perovskite. Note that the solvent cannot dissolve the powder, that is, the obtained modified halide perovskite contains perovskite powder and perovskite saturated solution;

[0080] The modified halide perovskite obtained in this example was coated on ITO and then heated on a hot plate at 110°C for 2 h for annealing. The material obtained after the temperature dropped to room temperature was named MAPbI 3 -HPC-ITO.

[0081] Example 7

[0082] A method for preparing a modified halide perovskite comprises the following steps:

[0083] According to the target MAPbI 3 The molar ratio of each raw material is: Weigh the corresponding raw materials, use the solvent γ-butyrolactone to dissolve the raw materials, and obtain clear and transparent MAPbI 3 Solution, MAPbI 3 The solution was added dropwise to chlorobenzene to prepare MAPbI 3 The powder was fully dried in an oven at 90 °C to obtain MAPbI 3 powder;

[0084] MAPbI 3 The powder is mixed with 0.5 wt% of hydroxypropyl cellulose (HPC), and 30 wt% of γ-butyrolactone is added to obtain a modified halide perovskite. Note that the solvent cannot dissolve the powder, that is, the obtained modified halide perovskite contains perovskite powder and perovskite saturated solution;

[0085] The modified halide perovskite obtained in this example was coated on ITO and then heated on a hot plate at 110°C for 2 h for annealing. The evaporation area on the annealed film was 1×1 mm 2 The gold electrode with a thickness of 80 nm was used to obtain a modified perovskite X-ray detector device, named 0.5-HPC-detector.

[0086] Example 8

[0087] A method for preparing a modified halide perovskite comprises the following steps:

[0088] According to the target MAPbI 3 The molar ratio of each raw material is: Weigh the corresponding raw materials, use the solvent γ-butyrolactone to dissolve the raw materials, and obtain clear and transparent MAPbI 3 Solution, MAPbI 3 The solution was added dropwise to chlorobenzene to prepare MAPbI3 The powder was fully dried in an oven at 90 °C to obtain MAPbI 3 powder;

[0089] MAPbI 3 The powder is mixed with 0.5 wt% of hydroxypropyl cellulose (HPC), and 30 wt% of γ-butyrolactone is added to obtain a modified halide perovskite. Note that the solvent cannot dissolve the powder, that is, the obtained modified halide perovskite contains perovskite powder and perovskite saturated solution;

[0090] The modified halide perovskite obtained in this example was coated on a TFT substrate and then heated on a hot plate at 110°C for 2 h for annealing. The evaporation area on the annealed film was 11×11 mm 2 The gold electrode with a thickness of 80nm is named as perovskite imaging device.

[0091] Example 1

[0092] A method for preparing a modified halide perovskite comprises the following steps:

[0093] According to the target MAPbI 3 The molar ratio of each raw material is: Weigh the corresponding raw materials, dissolve the raw materials with γ-butyrolactone, and obtain clear and transparent MAPbI 3 Solution; MAPbI 3 The solution was added dropwise to anisole to prepare MAPbI 3 The powder was fully dried in an oven at 90 °C and then 3 Add 30 wt% of solvent to the powder to obtain a perovskite precursor slurry. Note that the solvent cannot dissolve the powder, that is, the obtained precursor slurry contains perovskite powder and perovskite saturated solution;

[0094] The perovskite precursor slurry was coated on copper foil and then annealed on a hot plate at 110 °C for 2 h. The resulting material was named MAPbI after the temperature dropped to room temperature. 3 -Copper foil.

[0095] Comparative Example 2

[0096] According to the target MAPbI 3 The molar ratio of each raw material is: Weigh the corresponding raw materials, use a solvent (such as γ-butyrolactone, N,N-dimethylformamide, dimethyl sulfoxide, etc.) to dissolve the raw materials to obtain clear and transparent MAPbI 3 Solution. 3 The solution was added dropwise to an anti-solvent (such as chlorobenzene, anisole, ethyl acetate, etc.) to prepare MAPbI 3The powder was fully dried in an oven at 90°C. MAPbI 3 Powder pressed into 5×5×15mm 3 The block is named MAPbI 3 -Block.

[0097] Comparative Example 3

[0098] According to the target MAPbI 3 The molar ratio of each raw material is: Weigh the corresponding raw materials, use a solvent (such as γ-butyrolactone, N,N-dimethylformamide, dimethyl sulfoxide, etc.) to dissolve the raw materials to obtain clear and transparent MAPbI 3 Solution. 3 The solution was added dropwise to an anti-solvent (such as chlorobenzene, anisole, ethyl acetate, etc.) to prepare MAPbI 3 Powder, and dry the powder thoroughly in an oven at 90°C.

[0099] In MAPbI 3 30 wt% of solvent was added to the powder to obtain a perovskite precursor slurry. Note that the solvent cannot dissolve the powder, that is, the obtained precursor slurry contains perovskite powder and perovskite saturated solution.

[0100] The perovskite precursor slurry was coated on ITO and then heated on a hot plate at 110 °C for 2 h for annealing. The material obtained after the temperature dropped to room temperature was named MAPbI 3 -ITO.

[0101] Comparative Example 4

[0102] According to the target MAPbI 3 The molar ratio of each raw material is: Weigh the corresponding raw materials, use a solvent (such as γ-butyrolactone, N,N-dimethylformamide, dimethyl sulfoxide, etc.) to dissolve the raw materials to obtain clear and transparent MAPbI 3 Solution. 3 The solution was added dropwise to an anti-solvent (such as chlorobenzene, anisole, ethyl acetate, etc.) to prepare MAPbI 3 Powder, and dry the powder thoroughly in an oven at 90°C.

[0103] In MAPbI 3 30 wt% of solvent was added to the powder to obtain a perovskite precursor slurry. Note that the solvent cannot dissolve the powder, and the obtained precursor slurry contains perovskite powder and perovskite saturated solution.

[0104] The perovskite precursor slurry was coated on ITO and then heated on a hot plate at 110 °C for 2 h for annealing. The evaporation area on the annealed film was 1 × 1 mm 2The gold electrode with a thickness of 80nm was used to obtain the perovskite X-ray detector device, named MAPbI 3 -detector.

[0105] from Figure 1 It can be seen that using MAPbI 3 The wet film prepared by 0.5-HPC slurry on copper foil was dried at 110°C to obtain a stress-free perovskite film at 110°C. 3 -copper foil), during the cooling process from 110°C to 25°C, the film begins to curl toward the perovskite side due to tensile stress, and when the temperature rises to 110°C again, the film can return to its original flat shape. It is worth noting that if the temperature continues to rise to 190°C, the shape of the film will appear arched. This is because the thermal expansion coefficient of perovskite is significantly greater than that of copper foil, and the perovskite layer shrinks to a larger scale during the cooling process, resulting in tensile stress inside it. Because the copper foil is flexible, the film will curl toward the perovskite side. On the contrary, during the heating process, the perovskite expands to a larger scale, resulting in compressive stress inside it, forming an arched film.

[0106] In contrast, Comparative Example 1 (0.5-HPC-copper foil) is insensitive to temperature changes and always maintains a flat feature. This vividly demonstrates that HPC can reduce the expansion and contraction of the volume of perovskite during temperature changes. Therefore, the addition of HPC significantly regulates the thermal expansion of perovskite, thereby preparing a large-area perovskite thick film with less thermal stress.

[0107] Figure 2 The thermal expansion coefficients of the samples of Examples 32 to 64 and Comparative Example 2 were tested using a thermal expansion analyzer. It can be seen that the thermal expansion coefficient of Comparative Example 2 is 6.51×10 -5 K -1 , which is significantly larger than 3.29×10 -5 K -1 , 2.7410 in Example 3 -5 K -1 and 2.31×10 in Example 5 -5 K -1 The results show that the addition of HPC can significantly reduce the thermal expansion coefficient of perovskite and effectively regulate the volume change of perovskite during temperature changes.

[0108] Figure 3The Young's modulus of the samples of Examples 2 to 4 and Comparative Example 2 was tested using nanoindentation. Young's modulus (E) is another key parameter for evaluating the mechanical properties of materials. Brittle materials (such as silicon) usually have higher Young's modulus values, while flexible materials (such as rubber) have lower Young's modulus values. In order to ensure the repeatability of the data, each sample was tested 5 times at different locations, and the obtained Young's modulus values ​​are summarized in Figure 3 b. The experimental results show that the Young's modulus value of Comparative Example 2 is 18.3 GPa. The Young's modulus values ​​of Examples 2-4 drop to 10.6, 9.51, and 8.18 GPa, respectively. The Young's modulus decreases with the increase of HPC content, indicating that the addition of HPC can enhance the toughness of perovskite.

[0109] The formula for calculating residual thermal stress is: where σ T is the residual thermal stress, ν is the Poisson's ratio of the perovskite, E is the Young's modulus of the perovskite, α 0 and α 11 are the thermal expansion coefficients of perovskite and substrate, and ΔT is the temperature change value. It can be seen that when other parameters remain unchanged, the residual thermal stress is positively correlated with the Young's modulus and thermal expansion coefficient of perovskite. Figure 1-Figure 3 It can be seen that the addition of HPC can reduce the residual thermal stress of perovskite.

[0110] Figure 4 This is a photo of Example 3. In order to make the cracks more clearly visible, a layer of 80nm thick gold was evaporated on the surface. It can be seen that due to the large thermal expansion coefficient of the perovskite, the volume shrinks during the cooling process after annealing. The excessive residual thermal stress causes the perovskite layer to break and form cracks. This is fatal to the perovskite X-ray detector, which will cause the device to fail. Figure 5 and Figure 6 The photos of Example 5 and Example 6 respectively show that after adding CMC and HPC, the thermal expansion coefficient of perovskite is significantly reduced, which significantly reduces the value of residual thermal stress. The surface of the film layer prepared at last is uniform and crack-free, which makes it possible to prepare large-area perovskite X-ray detectors.

[0111] Figure 7 This is the X-ray performance test of Example 7, Example 10 and Comparative Example 4. Figure 7 a It can be seen that after adding HPC, the performance of the detector at different voltages is significantly improved, and the sensitivity / noise ratio is improved. Figure 7 b It can be seen that the detection limit of the X-ray detector is from 210nGy air s -1 Reduced to 107nGy air s -1 . Figure 7c It can be seen that when exposed to large doses of X-rays, the performance of the X-ray detector does not decay significantly, proving the stability of the detector.

[0112] Figure 8 a is a photograph of Example 8 and its imaging result. Figure 8 b shows the capsule with the spring inside under low-dose X-ray irradiation (26.8-1.9 μGy air ) imaging results. At a dose of 5.8μGy air When the spring inside the capsule is clearly visible, a commercial X-ray imaging instrument usually requires 100 μGy air High-quality X-ray images can only be obtained with an X-ray dose of 100%. Therefore, the X-ray dose used here is about 1 / 20 of the dose used by commercial X-ray imaging instruments. This result confirms that the device has excellent imaging capabilities under low-dose X-ray conditions.

[0113] To demonstrate the capabilities of our device for medical imaging and nondestructive testing, we scanned a bat specimen and a commercial multimeter. Due to the lack of large-area TFT substrates, we used a 64×64 pixel device for data acquisition, resulting in streaks in the final image due to image stitching. Bats are the only mammals that can truly fly, and their bones are thinner and lighter than those of other animals. Figure 8 c clearly shows the bat's skeletal structure, especially its delicate five-finger bones, which shows the promise of our imaging device in medical imaging. Figure 8 d is the imaging result of the multimeter, which clearly shows the internal circuit structure of the multimeter. It is worth noting that the six cells inside the 9V battery used by the multimeter are also visible, which shows the practical application of our imaging equipment in non-destructive testing.

[0114] like Fig. 9 As shown, we evaluated the spatial resolution of the imaging device prepared in Example 8. When the modulation transfer function (MTF) is 0.2, the spatial resolution is 2.36 lp mm -1 In addition, the 2.5lp mm can be clearly distinguished in the X-ray imaging results of the line test card (type 81). -1 Considering that the pixel size of TFT is 200μm, the corresponding theoretical specific resolution is 2.5lp mm -1 , our device achieves a spatial resolution close to its theoretical limit, indicating that signal crosstalk can be neglected.

[0115] The above contents are only for explaining the technical idea of ​​the present invention and cannot be used to limit the protection scope of the present invention. Any changes made on the basis of the technical solution in accordance with the technical idea proposed by the present invention shall fall within the protection scope of the claims of the present invention.

Claims

1. A method for preparing a modified halide perovskite, characterized in that: The following steps are involved: The halide perovskite slurry and the polymer material are mixed, and then the modified halide perovskite is obtained; the polymer material is one of hydroxypropyl cellulose and carboxymethyl cellulose; the halide perovskite slurry is obtained by mixing the halide perovskite powder and the solvent.

2. The method for preparing a modified halide perovskite according to claim 1, characterized in that: The chemical formula of the halide perovskite powder is ABX3; wherein A is at least one of methylamine ion, formamidine ion and Cs ion; B is at least one of lead ion and bismuth ion; and X is at least one of chloride ion, bromide ion and iodide ion.

3. The method for preparing a modified halide perovskite according to claim 1, characterized in that: The solvent is one or more of γ-butyrolactone, N,N-dimethylformamide and dimethyl sulfoxide; the volume ratio of the solid to the solvent in the halide perovskite slurry is 2:1 to 5:

1.

4. The method for preparing a modified halide perovskite according to claim 1, characterized in that: In the modified halide perovskite, the added amount of the polymer material is 0.1wt%-10.0wt%.

5. A modified halide perovskite, characterized in that: The preparation method is described in any one of claims 1 to 4.

6. A direct X-ray large area imaging device, characterized in that: The direct X-ray large-area imaging device comprises, from bottom to top, a pixelated circuit substrate, a perovskite layer and a top electrode; the perovskite layer is the modified halide perovskite described in claim 5.

7. A direct X-ray large area imaging device according to claim 6, characterized in that: The area of ​​the pixelated circuit substrate is A×B mm 2 , A, B = 10-500mm; The pixelated circuit substrate includes N×M pixel units arranged in an array, wherein N=10-1000; M=10-1000.

8. A direct X-ray large area imaging device according to claim 6, characterized in that: The material of the top electrode is gold, silver, copper, indium tin oxide or fluorine-doped tin oxide; The thickness of the perovskite layer is 50-1000 μm.

9. A method for preparing a direct X-ray large area imaging device according to any one of claims 6 to 8, characterized in that: The following steps are involved: coating the modified halide perovskite on a pixelated circuit substrate, followed by annealing to obtain a pre-treated device; The surface of the pre-treated device is covered with a top electrode to obtain a direct X-ray large-area imaging device.

10. The method for preparing a direct X-ray large area imaging device according to claim 9, characterized in that: The temperature of the annealing treatment is 50° C.-200° C.; the method of coating the modified halide perovskite on the pixelated circuit substrate is by scraping, spraying or screen printing; The method of covering the top electrode on the surface of the pre-treated device is evaporation or sputtering.

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