A perovskite-based X-ray detector and its preparation method

Abstract

The present application discloses a perovskite-based X-ray detector and a method for preparing the same. The perovskite-based X-ray detector of the present application comprises a conductive substrate, a low-dimensional perovskite layer, a three-dimensional perovskite layer, and a top electrode stacked in sequence. In the perovskite-based X-ray detector of the present application, the layered structure of the low-dimensional perovskite layer can effectively inhibit the migration of perovskite ions in the direct perovskite-based X-ray detector, while the vertically continuously grown three-dimensional perovskite layer is conducive to the efficient transport of carriers, so that the prepared detector has a high efficiency of up to 19530μC Gy ‑1 cm ‑2 It can read the signal stably while still maintaining high sensitivity.

Description

Technical Field

[0001] The present invention relates to the field of detector technology, and in particular to a perovskite-based X-ray detector and a preparation method thereof. Background Art

[0002] An X-ray detector is a device that converts X-ray signals into electrical signals. It has advantages such as high spatial resolution and simple structure and is widely used in scientific research, medical imaging, security inspection, and industrial non-destructive testing. For an X-ray detector, its core performance parameters mainly include: (1) sensitivity: the size of the photocurrent generated by a unit dose of X-rays; (2) detection limit: the minimum X-ray dose required to achieve a detector signal-to-noise ratio of 3; (3) response speed: the time required for the photocurrent to increase from 10% of the maximum photocurrent to 90% of the maximum photocurrent after X-ray exposure, and the time required for the photocurrent to fall from 90% of the maximum photocurrent to 10% of the maximum photocurrent after X-rays are turned off; (4) dark current; and (5) baseline drift. Ideally, an X-ray detector should have the highest possible sensitivity, the lowest possible detection limit, the fastest possible response speed, and the smallest possible dark current and baseline drift.

[0003] Currently, commercial direct-type detectors are mainly based on amorphous selenium. However, due to the small X-ray absorption coefficient and low carrier mobility-lifetime (~10 -7 cm 2 V -1 ), so it can only be applied to soft X-rays (E ph <40keV), such as breast imaging. In recent years, metal halide perovskites (abbreviated as perovskites) have been widely used due to their large X-ray absorption coefficient and high carrier mobility-lifetime product (~10- 2 cm 2 V -1 ) and other unique advantages, and is considered to be one of the most promising new X-ray absorbing materials.

[0004] In 2015, Yakunin et al. first reported the effective detection of X-rays by perovskite materials. They successfully achieved X-ray imaging of objects such as leaves by scanning a single device (x, y) point by point (Nature Photonics, 2015, 9, 444). Since then, perovskite materials of different crystal types (single crystal or polycrystalline), different compositions, and the resulting different dimensions (zero-dimensional, one-dimensional, two-dimensional, and three-dimensional) have been applied to the direct detection of X-rays, exhibiting vastly different X-ray detection properties. For example, three-dimensional perovskites typically achieve high X-ray detection sensitivity (Adv. Mater. 2019, 1904405), primarily due to their excellent carrier transport capabilities. However, due to the low film resistance of three-dimensional perovskites and the ease of ion migration, X-ray detectors based on three-dimensional perovskites typically exhibit high dark currents and significant baseline drift, making it difficult to ensure that the current signal generated by the X-rays can be read accurately and stably over a long period of time, greatly limiting their potential for practical application (Matter, 2020, 3, 1). In sharp contrast, low-dimensional perovskites typically have a relatively large film resistance and greatly inhibit ion migration within them. This gives low-dimensional perovskite detectors a stable baseline, a small dark current, and a satisfactory low detection limit, enabling them to effectively detect ultra-low doses of X-rays and operate stably for a long time (Adv. Mater. 2020, 2001981). However, due to their poor carrier transport ability, low-dimensional perovskite detectors are generally less sensitive, which is not conducive to their application in fields such as high-resolution imaging.

[0005] On the one hand, the above research highlights a bottleneck problem that needs to be overcome in the current perovskite-based X-ray detectors towards practical application, namely: the detectors cannot well balance key performances such as "high sensitivity", "low dark current", "low detection limit" and "no baseline drift"; on the other hand, it also reveals the huge potential for improving the overall performance of X-ray detectors through the comprehensive use of perovskites of different dimensions.

[0006] However, due to the extremely strong penetrating properties of X-rays, perovskites must be tens of microns or even millimeters thick to fully absorb them. Traditional methods (such as spin coating) for preparing perovskites for use in solar cells and UV-visible light detectors typically produce perovskites with a thickness of less than 1 μm, far from sufficient for effective X-ray absorption and, therefore, unsuitable for the fabrication of high-performance perovskite-based X-ray detectors. Currently, the controllable preparation of perovskite films thicker than tens of microns or even millimeters is another major bottleneck hindering the development of perovskite-based X-ray detectors.

[0007] In addition, the existing reported process methods for preparing thick perovskite films (such as hot pressing and doctor blade coating) not only have disadvantages such as harsh conditions and uncontrollable processes, but also have only achieved the preparation of single-component thick perovskite films. The layer-by-layer and continuous preparation of thick perovskite films with different components, such as low-dimensional perovskites / three-dimensional perovskites, has not been reported and there are certain challenges. For example, when preparing double-layer or multi-layer perovskites, the hot pressing method relies heavily on high temperatures to heat the perovskite precursor to a molten state. This process will destroy the first layer of perovskite when preparing the second layer of perovskite. Similarly, when doctor blade coating is used to apply multi-layer perovskites based on solution, it is difficult to ensure the integrity of the bottom perovskite. The perovskite prepared by the spin coating method is thin and has limited absorption of X-rays, making it unusable for X-ray detection. In addition, in the traditional spin coating method, if the low-dimensional perovskite is spin-coated and then the three-dimensional perovskite is spin-coated, the underlying low-dimensional perovskite will be completely destroyed. Therefore, although the coordinated use of perovskites of different dimensions has great potential for improving the overall performance of perovskite-based X-ray detectors, breakthroughs are still urgently needed in technological implementation. Summary of the Invention

[0008] This application provides a perovskite-based X-ray detector and a method for preparing the same, to improve the overall performance of the X-ray detector. The perovskite-based X-ray detector referred to in this application refers to a direct-type perovskite-based X-ray detector, particularly a direct-type perovskite-based X-ray detector having a low-dimensional perovskite / three-dimensional perovskite double-layer structure.

[0009] In a first aspect, the present application provides a perovskite-based X-ray detector comprising a conductive substrate, a low-dimensional perovskite layer, a three-dimensional perovskite layer, and a top electrode stacked in sequence.

[0010] The "low-dimensional" mentioned in this application refers to the form where n is between 1 and infinity. n = 1 is pure two-dimensional, and n equals infinity is three-dimensional. n-1 Pb n X 3n+1 For example, perovskites with n=1 are two-dimensional, such as PEA2PbI4; those with n=infinity are three-dimensional, such as MAPbI3. Perovskites with n values between 1 and infinity are called low-dimensional perovskites. The differences in their molecular arrangement are determined by the size of the molecules, resulting in pure two-dimensional, low-dimensional, or three-dimensional forms at the molecular stacking level.

[0011] In one embodiment, the material of the low-dimensional perovskite layer includes Ruddlesden-Popper perovskite (abbreviated as RP perovskite) and / or Dion-Jacobson perovskite (abbreviated as DJ perovskite). The general formula of the Ruddlesden-Popper perovskite is: A'2A n-1 Pb nX 3n+1 , n is 2-20; wherein A' is R-NH3, R can be a long-chain alkyl group (CH3-(CH2)n-, n>3), a cycloalkyl group, an aromatic group, etc. For example, A' is at least one of CH3(CH2)2NH3 (abbreviated as PA), CH3(CH2)3NH3 (abbreviated as BA), CH2CH2CH2NH3 (abbreviated as ALA), C6H5CH2CH2NH3 (abbreviated as PEA), C6H5CH2NH3 (abbreviated as PMA), and C6H5NH3 (abbreviated as Anyl), etc., A is at least one of Cs, Rb, CH3NH3 (abbreviated as MA), and (NH2)2CH (abbreviated as FA), etc., and X is at least one of Cl, Br, and I, etc.; the general formula of the Dion-Jacobson perovskite is: A'A n-1 Pb n X 3n+1 , n is 2-20; wherein A' is NH3-R-NH3, R can be a long-chain alkyl group (CH3-(CH2)n-, n>3), a cycloalkyl group, an aromatic group, etc. For example, A' is NH3-(CH2) n -NH3 (n is 2-4: when n=2, A' is NH3-(CH2)2-NH3, referred to as EDA; when n=3, A' is NH3-(CH2)3-NH3, referred to as PDA; when n=4, A' is NH3-(CH2)4-NH3, referred to as BDA), NH3CH2C6H 10 At least one of CH2NH3 and NH3C6H4NH3; A is at least one of Cs, Rb, CH3NH3 and (NH2)2CH, and X is at least one of Cl, Br and I.

[0012] The material of the low-dimensional perovskite layer is prepared from a macromolecular iodine salt, a small molecule iodine salt and PbX2, and the ratio of the three is determined by the stoichiometric ratio of the prepared low-dimensional perovskite molecular formula. n-1 Pb n X 3n+1 When n=4, the stoichiometric ratio of the three is 2:n-1:n (calculated by the molar ratio of the substances). When n=4, the stoichiometric ratio of the three is 2:3:4.

[0013] In one embodiment, the material of the three-dimensional perovskite layer mainly includes APbX3, wherein A is at least one of cesium (abbreviated as Cs), rubidium (abbreviated as Rb), CH3NH3 (abbreviated as MA), and (NH2)2CH (abbreviated as FA), and X is at least one of Cl, Br, and I. The three-dimensional perovskite described in this application mainly includes APbX3, wherein A is at least one of cesium (abbreviated as Cs), rubidium (abbreviated as Rb), CH3NH3 (abbreviated as MA), and (NH2)2CH (abbreviated as FA).

[0014] In one embodiment, the top electrode is a carbon electrode, a metal electrode, a fluorine-doped tin dioxide electrode, an indium tin oxide electrode, or an electrode made of any mixture of the above electrode materials. The top electrode is formed by blade coating to deposit a carbon top electrode, vapor deposition to deposit a metal top electrode, or sputtering to prepare fluorine-doped tin dioxide or indium tin oxide. When vapor deposition is used to deposit a metal top electrode, the metal used may include gold, silver, copper, etc.

[0015] In the perovskite-based X-ray detector described in this application, the low-dimensional perovskite layer serves as the interface material, while the three-dimensional perovskite layer serves as the X-ray absorber. Their thicknesses are controlled based on their different properties. The low-dimensional perovskite layer has a thickness of 0.05-3 μm, while the three-dimensional perovskite layer has a thickness of 20 μm-2 mm.

[0016] As a light-absorbing material, three-dimensional perovskites must be kept too thin, otherwise their absorption efficiency will be compromised. The vertical structure of three-dimensional perovskites facilitates efficient carrier transport. Low-dimensional perovskites, used as interface materials, have a layered structure that effectively inhibits the migration of perovskite ions. By combining low-dimensional and three-dimensional perovskites, it is possible to effectively read the current signal generated by X-rays while maintaining high sensitivity.

[0017] In a second aspect, the present application further provides a method for preparing the above-mentioned perovskite-based X-ray detector, characterized in that it comprises the following steps:

[0018] A. dissolving a low-dimensional perovskite precursor powder in an organic solvent to prepare a low-dimensional perovskite precursor solution, and dissolving a three-dimensional perovskite precursor powder in an organic solvent to prepare a three-dimensional perovskite precursor solution;

[0019] B. depositing the low-dimensional perovskite precursor solution onto a conductive substrate by spin coating, doctor blade coating, narrow slit coating, or aerosol thermal deposition to form a low-dimensional perovskite layer, and curing the layer;

[0020] C. Atomizing the three-dimensional perovskite precursor liquid to form three-dimensional perovskite droplets while maintaining the heating of the conductive substrate; spraying the three-dimensional perovskite droplets onto the surface of the low-dimensional perovskite layer using an inert gas as a carrier gas, so that the three-dimensional perovskite is deposited on the surface of the low-dimensional perovskite layer by aerosol thermal deposition to form a three-dimensional perovskite layer, and curing;

[0021] D. Forming a top electrode on the surface of the three-dimensional perovskite layer to obtain the perovskite-based X-ray detector.

[0022] The aerosol thermal deposition method described in this embodiment refers to a process in which a precursor liquid material is atomized and deposited on a conductive substrate. The atomization process uses a special atomization device, such as a device including an ultrasonic mist generator and an atomization container, and the atomized precursor liquid material is sprayed and deposited through a nozzle. The advantage of aerosol thermal deposition is that the thickness of the deposited perovskite can be accurately controlled according to actual needs, and the two-dimensional perovskite layer at the bottom will not be damaged when depositing the three-dimensional perovskite.

[0023] In one embodiment, in step A, the low-dimensional perovskite precursor powder includes a macromolecular iodine salt, a small molecule iodine salt, and PbX2; wherein the macromolecular iodine salt includes at least one of ethylenediamine iodine salt, 1,3-propylenediamine iodine salt, 1,4-butylenediamine iodine salt, 1,4-aminomethylcyclohexane, o-phenyldiamine, propylammonium iodide, allylammonium iodide, butylammonium iodide, benzylammonium iodide, and phenethylammonium iodide; the small molecule iodine salt includes at least one of methylammonium iodide, methylimidium iodide, rubidium iodide, and cesium iodide; in the PbX2, X is at least one of I, Br, and Cl. In the PbX2 here, Pb is lead, and X is a halogen element, that is, PbX2 is a halogen-containing lead compound. The low-dimensional perovskite precursor powder can be used to prepare the low-dimensional perovskite material (RP-type perovskite and DJ-type perovskite) required for the aforementioned perovskite-based X-ray detector.

[0024] In one embodiment, in step A, the three-dimensional perovskite precursor powder includes a small molecule iodine salt and PbX2; wherein the small molecule iodine salt includes at least one of methylammonium iodide, rubidium iodide, cesium iodide, and methylimidium ammonium iodide; and in the PbX2, X is at least one of I, Br, and Cl. The three-dimensional perovskite precursor powder can be used to prepare the three-dimensional perovskite material (APbX3 perovskite) required for the aforementioned perovskite-based X-ray detector.

[0025] In one embodiment, in step A, the organic solvent includes at least one of dimethyl sulfoxide, N,N-dimethylformamide, 1-ethyl-2-pyrrolidone, butyrolactone and methoxyethanol.

[0026] In one embodiment, in step B and step C, the heating refers to heating at a temperature of 60-300°C, preferably, heating at 120-160°C.

[0027] The purpose of heating is to maintain the conductive substrate at a certain temperature, thereby controlling the rapid volatilization of the solvent in the perovskite droplets and promoting the nucleation and crystallization growth of the perovskite. The conductive substrate can be placed on a hot plate, and the temperature and time can be controlled by the hot plate. The conductive substrate described in this application serves as the bottom electrode, which can be conductive glass or other transparent materials with conductive effects.

[0028] In one embodiment, in step B and step C, the curing refers to heating at 60-300° C. for 1-1200 minutes, preferably, heating at 100-150° C. for 10-15 minutes. The purpose of curing is to further fix the two-dimensional perovskite to the conductive substrate to form a two-dimensional perovskite layer, and to further fix the three-dimensional perovskite to the two-dimensional perovskite layer to form a three-dimensional perovskite layer.

[0029] Beneficial effects of the present invention:

[0030] This application constructs a double-layer perovskite structure of "low-dimensional perovskite interface material / three-dimensional perovskite X-ray absorption material" by sequentially depositing low-dimensional perovskite and three-dimensional perovskite on a conductive substrate. The structure is then applied to direct perovskite-based X-ray detectors. The layered structure of the low-dimensional perovskite layer effectively inhibits the migration of perovskite ions in direct perovskite-based X-ray detectors, while the vertically continuous growth of the three-dimensional perovskite layer facilitates efficient carrier transport.

[0031] This application utilizes the high film resistance, electron / hole blocking ability (band structure), ability to inhibit ion migration of low-dimensional perovskites, and excellent carrier transport properties of three-dimensional perovskites. The high film resistance and the blocking of electron / hole injection from the counter electrode effectively reduce the dark current of the detector, thereby improving the detector's on / off ratio and lowering the detector's detection limit; the inhibition of ion migration significantly improves the problem of detector baseline drift; at the same time, because the energy level of the low-dimensional perovskite ensures efficient carrier extraction, and the three-dimensional perovskite has excellent carrier transport properties, the prepared detector has a high charge transfer capacity of up to 19530μC Gy -1 cm -2 It can read the signal stably while still maintaining high sensitivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] Figure 1Schematic diagram of the present invention for preparing perovskite materials based on the aerosol thermal deposition method (Figure a) and a schematic diagram of an X-ray detector device having a low-dimensional perovskite / three-dimensional perovskite double-layer structure (Figure b);

[0033] Figure 2 : The scanning electron microscope (SEM) image (surface: Figure a; cross section: Figure b), steady-state fluorescence emission spectrum (Figure c) and X-ray diffraction (XRD) spectrum (Figure d) of the low-dimensional perovskite interface layer prepared in Example 1 of the present invention;

[0034] Figure 3 1. SEM cross-sectional images of a thick perovskite film having a low-dimensional perovskite / three-dimensional perovskite double-layer structure prepared in Example 1 of the present invention (Figures a and b) and an SEM cross-sectional image of a three-dimensional perovskite prepared in Comparative Example 1 (Figure c);

[0035] Figure 4 The XRD spectrum (Figure a), electrical properties (Figure b), and device interface energy level (Figure c) of the perovskite thick film with a low-dimensional perovskite / three-dimensional perovskite double-layer structure prepared in Comparative Example 1 and the three-dimensional perovskite prepared in Comparative Example 1 are shown;

[0036] Figure 5 The photoresponse current (Figure a) and sensitivity (Figures b and c) of the X-ray detector based on the low-dimensional perovskite / three-dimensional perovskite double-layer structure prepared in Comparative Example 1 and the three-dimensional perovskite X-ray detector prepared in Comparative Example 1 under different doses of X-rays are shown;

[0037] Figure 6 The detection limit (Figure a) and baseline drift (Figure b) of the perovskite thick film with a low-dimensional perovskite / three-dimensional perovskite double-layer structure prepared in Comparative Example 1 and the three-dimensional perovskite prepared in Comparative Example 1 are shown;

[0038] Figure 7 These are the SEM images (cross section: Figure a; surface: Figure b) and XRD spectra (Figure c) of the low-dimensional perovskite thick film in Comparative Example 2 of the present invention, as well as the photoresponse current (Figure d) and sensitivity (Figure e) of the X-ray detector based on the low-dimensional perovskite thick film under different doses of X-rays. DETAILED DESCRIPTION

[0039] The present invention is further described in detail below with reference to the accompanying drawings. In some cases, some operations related to the present application are not shown or described in the specification. This is to avoid overwhelm the core part of the present application with excessive description. For those skilled in the art, detailed description of these related operations is not necessary. They can fully understand the related operations based on the description in the specification and general technical knowledge in the field.

[0040] The preparation method of the perovskite-based X-ray detector described in this application can prepare an X-ray detector having a low-dimensional / three-dimensional perovskite double-layer structure. The specific implementation steps include:

[0041] (1) Prepare low-dimensional perovskite precursor solution and three-dimensional perovskite precursor solution. Weigh low-dimensional perovskite and three-dimensional perovskite precursor powders according to a certain stoichiometric ratio, and dissolve them in one or more solvents such as dimethyl sulfoxide, N,N-dimethylformamide, 1-ethyl-2-pyrrolidone, butyrolactone and / or methoxyethanol to prepare low-dimensional perovskite precursor solution and three-dimensional perovskite precursor solution. The stoichiometric ratio is determined by the molecular formula of the low-dimensional perovskite and three-dimensional perovskite to be prepared. When preparing low-dimensional perovskite, the macromolecular iodine salt, small molecule iodine salt and PbX2 are weighed according to the molecular stoichiometric ratio; when preparing three-dimensional perovskite, the small molecule iodine salt and PbX2 are weighed according to the molecular stoichiometric ratio. For example, in the preparation of (PEA)2MA n-1 Pb n I 3n+1 For low-dimensional RP-type perovskites, the stoichiometric ratio of the precursor powders phenylethylammonium iodide (PEAI), methylammonium iodide (MAI), and lead iodide (PbI2) is 2:n-1:n. When n = 4, the molar ratio of PEAI, MAI, and PbI2 is 2:3:4. For another example, when preparing MAPbI3 three-dimensional perovskites, methylammonium iodide (MAI) and lead iodide (PbI2) can be used in a molar ratio of 1:1, or methylammonium iodide (MAI) and lead acetate (Pb(AC)2) can be used in a molar ratio of 3:1.

[0042] (2) The low-dimensional perovskite precursor liquid is deposited on the conductive substrate by spin coating, blade coating, narrow slit coating or aerosol thermal deposition. Here, only the aerosol thermal deposition method with the best preparation effect is taken as an example: the low-dimensional perovskite precursor liquid is atomized by an atomization device. First, the low-dimensional perovskite precursor liquid is placed in an atomization container (the atomization device includes an atomization container, an ultrasonic atomizer, a nozzle, a control motor and other components, for example, the atomization thermal deposition device in 201910646084.9 can be used), and it is atomized by the ultrasonic atomizer at the bottom to form low-dimensional perovskite droplets; at the same time, the conductive substrate is placed on a hot plate and heated at 60-300°C. The conductive substrate is a bottom electrode with a conductive function, and conductive glass such as FTO, ITO or TCO can be selected. Atomization refers to the operation of dispersing a liquid into tiny droplets through a nozzle or a high-speed airflow. It should be noted that the process of atomizing the low-dimensional perovskite precursor liquid by an ultrasonic atomizer in this step is only used as an example to illustrate the implementation process of atomization. In actual operation, other atomization equipment can also be used to atomize the low-dimensional perovskite precursor liquid, which is not limited here.

[0043] (3) Deposition of low-dimensional perovskite. Using an inert gas (such as nitrogen, helium, etc.) as a carrier gas, the atomized low-dimensional perovskite droplets are carried out from the bottom of the atomizing container to a specific nozzle (the nozzle is about 5 mm vertically above the conductive glass). After the spray state stabilizes, the control motor is started to control the nozzle to sweep back and forth across the conductive glass at a speed of 0.2-1 cm / s, so that the low-dimensional perovskite precursor liquid is deposited on the conductive glass by aerosol thermal deposition, forming a low-dimensional perovskite layer. By controlling the number of times the nozzle sweeps across the conductive glass, the thickness of the low-dimensional perovskite layer is effectively controlled to be 0.05-3 μm, with a preferred value of about 1.5 μm.

[0044] (4) Solidifying the low-dimensional perovskite layer. When the desired thickness is reached, stop spraying and place the conductive glass with the low-dimensional perovskite layer on another hot plate. Heat the reaction at 100-150°C for 10-30 minutes and then cool naturally to complete the solidification process.

[0045] (5) Atomization, deposition, and solidification of the three-dimensional perovskite absorption layer. The three-dimensional perovskite precursor solution is placed in a clean atomization container, and the three-dimensional perovskite precursor solution (thickness: >20 μm) is further deposited onto the low-dimensional perovskite using steps similar to those described in (3)-(5) above to form a three-dimensional perovskite layer, thereby obtaining a perovskite thick film with a double-layer structure of "low-dimensional perovskite interface material / three-dimensional perovskite X-ray absorbing material."

[0046] (6) According to the difference in the effective area of the detector and the location and distribution of its effective area, different masks (the mask is formed by an opaque light-shielding film on a transparent substrate to form a mask pattern structure, and then the pattern information is transferred to the product substrate through an exposure process. The existing mask can be used for preparation) are used to deposit the top electrode on the perovskite thick film by scraping, evaporation or sputtering, thereby preparing a perovskite-based X-ray detector based on a low-dimensional / three-dimensional perovskite double-layer structure.

[0047] This application mainly uses spin coating, blade coating, narrow-slit coating or aerosol thermal deposition to first deposit a low-dimensional perovskite layer on conductive glass, then deposit a three-dimensional perovskite layer on the low-dimensional perovskite by aerosol thermal deposition, and finally deposit a carbon electrode by blade coating, a metal top electrode (such as gold, silver, copper, etc.) by evaporation, or fluorine-doped tin dioxide or indium tin oxide by sputtering to prepare a perovskite-based X-ray detector with a low-dimensional perovskite / three-dimensional perovskite double-layer structure. In this application, there is no particular limitation on the preparation method of the low-dimensional perovskite layer. As for the deposition of the three-dimensional perovskite layer, since it is prepared on the basis of the low-dimensional perovskite layer, the traditional preparation method is likely to damage the low-dimensional perovskite layer at the bottom, so the aerosol thermal deposition method is used to prepare the three-dimensional perovskite layer.

[0048] In this application, the low-dimensional perovskite layer has a layered structure parallel to the conductive substrate (preferably a transparent material such as conductive glass), and together with the three-dimensional perovskite layer that tends to grow perpendicular to the conductive substrate, forms a double-layer perovskite with a unique structure. The low-dimensional perovskite layer acts as an interface material, which has the effect of inhibiting the migration of perovskite ions, effectively maintaining the low dark current and zero baseline shift of the X-ray detector. The three-dimensional perovskite layer acts as an X-ray absorption material, which facilitates the efficient transmission of carriers and effectively maintains the high sensitivity and low detection limit of the X-ray detector.

[0049] In one embodiment, the thickness of the low-dimensional perovskite layer is 0.05-3 μm, preferably 1.5 μm. The thickness of the low-dimensional perovskite layer has a significant impact on the performance of the X-ray detector. If the thickness of the low-dimensional perovskite layer is too thin, there is almost no improvement in the performance of the X-ray detector, that is, the problem of perovskite ion migration cannot be solved; if the thickness is too thick, the sensitivity of the X-ray detector will be significantly reduced. A low-dimensional perovskite layer with a thickness of about 1.5 μm can effectively solve the problem of perovskite ion migration while maintaining high sensitivity. Similarly, the thickness of the three-dimensional perovskite layer also has a significant impact on the performance of the X-ray detector. If the thickness is too thin, it cannot fully absorb X-rays, resulting in low detector sensitivity; if the thickness is too thick, it will affect the efficient extraction of photogenerated carriers in the X-ray detector, which will also result in low detector sensitivity. The thickness of the three-dimensional perovskite layer should be greater than 20 μm, which should be greater than the thickness of the low-dimensional perovskite layer. Preferably, a thickness within 20-500 μm can better balance the absorption of X-rays and the extraction of X-ray-generated carriers. More preferably, a three-dimensional perovskite layer with a thickness of 50-100 μm has excellent light absorption effect and sensitivity.

[0050] Existing preparation methods, such as spin coating, doctor blade coating, and spray coating (cold deposition), are unable to precisely control the film thickness of perovskite materials over a wide range of thicknesses (from nanometers to micrometers), and thus cannot effectively guarantee the thickness of the prepared perovskite. Furthermore, existing preparation methods generally involve a complete transformation from liquid to solid phase during film formation, and different perovskite states cannot coexist during growth. Consequently, the utilization rate of the perovskite precursor solution is low, and layer-by-layer deposition of perovskites of different compositions cannot be achieved.

[0051] In the embodiments of the present application, a three-dimensional perovskite layer is directly prepared on a low-dimensional perovskite layer by means of aerosol thermal deposition. That is, a three-dimensional perovskite precursor solution formed by dissolving in a solvent is atomized to form droplets, which are deposited on the low-dimensional perovskite, and at the same time, the low-dimensional perovskite is continuously heated to volatilize the solvent while forming a three-dimensional perovskite layer without damaging the low-dimensional perovskite. The continuous deposition of droplets forms a deposit, and the continuous heating can volatilize the solvent to prepare the required three-dimensional perovskite layer. Atomization, deposition, and heat curing are carried out in real time. When dynamic equilibrium is reached during the film-forming process, a three-dimensional perovskite layer and perovskite components in which there are always three states or two of the three states of gas, liquid, and solid exist in the surrounding environment are continuously grown. The aerosol thermal deposition method used in the present invention has a unique nucleation-crystallization process, which can achieve the layer-by-layer deposition of perovskites with different components and resulting different dimensions, overcome the technical bottleneck that the traditional method can only deposit a single layer of perovskite, and realize the preparation of bilayer perovskite.

[0052] The preparation method described in the present application and the performance of the perovskite-based X-ray detector prepared are further elaborated below through specific examples and comparative examples.

[0053] Example 1

[0054] (1) Dissolve phenethylammonium iodide (PEAI), methylammonium iodide (MAI), and lead iodide (PbI2) in a mixed organic solvent according to the stoichiometric ratio in the chemical formula (PEA)2MA n-1 Pb n I 3n+1 (2 < n < 20) and stir for more than 2 hours to prepare a (PEA)2MA3Pb4I 13 low-dimensional R-P type perovskite precursor solution with a concentration of 0.4 mol / L - 0.8 mol / L; at the same time, dissolve methylammonium iodide (MAI) and lead iodide (PbI2) in a molar ratio of 1:1 or methylammonium iodide (MAI) and lead acetate (abbreviated as Pb(AC)2) in a molar ratio of 3:1 in a mixed organic solvent, stir for more than 2 hours, and prepare a MAPbI3 three-dimensional perovskite precursor solution with a concentration of 0.3 - 0.8 mol / L; the above-mentioned mixed organic solvent is dimethyl sulfoxide (DMSO) and N,N-dimethylformamide (DMF), and the mixed volume ratio is 0.5 - 1.

[0055] (2) Place 15 ml of the low-dimensional perovskite precursor solution in an atomization container and atomize it using an ultrasonic atomizer at the bottom; at the same time, place a conductive substrate (such as conductive glass) on a hot stage and heat it at 140 °C (such as Figure 1 shown in a).

[0056] (3) Using an inert gas (such as nitrogen) as a carrier gas (flow rate: 1.5-2.5 mL / min), the perovskite droplets are carried out from the bottom of the atomizing container to the nozzle (the vertical height of the nozzle from the conductive glass is about 5 mm). After the spray state is stable, the motor is started to make the nozzle sweep back and forth across the conductive glass at a speed of 0.5 cm / s, so that the low-dimensional perovskite is deposited on the conductive glass by aerosol thermal deposition.

[0057] (4) After the nozzle has swept the conductive glass for 8 cycles, stop spraying and transfer the conductive glass to another hot plate. After heating at 100°C for 10 minutes and then cooling naturally, a low-dimensional perovskite film (i.e., low-dimensional perovskite, also known as low-dimensional perovskite interface layer) is prepared. SEM characterization results show that the grain size of the low-dimensional perovskite film has reached the micron level and the thickness is about 1.5 μm. At the same time, the low-dimensional perovskite film has a unique layered structure parallel to the conductive substrate, such as Figure 2 a and b. XRD characterization shows that the obtained low-dimensional perovskite film contains two-dimensional perovskite, low-dimensional perovskite and three-dimensional perovskite, as shown in Figure 2 c. Steady-state fluorescence emission spectroscopy of the top and bottom of the perovskite film confirmed that a certain amount of two-dimensional perovskite (527nm) and low-dimensional perovskite (578nm) existed at the bottom of the film, while the top of the film was mainly three-dimensional perovskite (768nm), as shown in Figure 3. Figure 2 d, which is highly consistent with the XRD results.

[0058] (5) 40 ml of MAPbI3 3D perovskite precursor solution was placed in a clean atomizing container and further deposited onto the low-dimensional perovskite using the aforementioned spraying method. During this process, the heating stage temperature was maintained at 130°C, and the number of spraying cycles was 400.

[0059] (6) After the spraying is completed, the heating stage is immediately lowered from 130°C to 30°C at a rate of 1°C / min, thereby obtaining a perovskite thick film with a double-layer structure of "low-dimensional perovskite interface material / three-dimensional perovskite X-ray absorption material". Figure 3 (a) and (b) are SEM cross-sectional images of the bilayer perovskite thick film. As can be seen from the images, the deposition of the 3D perovskite did not destroy the quasi-2D perovskite interface layer, leaving its unique layered structure clearly visible. Furthermore, the deposited 3D perovskite tends to grow continuously perpendicular to the conductive substrate, with grain sizes reaching tens of microns and an overall thickness of approximately 50 μm.

[0060] (7) Depending on the effective area of the detector, its location, and distribution, the obtained perovskite thick film is fixed under different stainless-steel mask plates, and the carbon electrode is deposited on it by means of scraping, thereby preparing a perovskite-based X-ray detector, the device structure of which is as shown in Figure 1 shown in b.

[0061] Example 2

[0062] (1) 1,3-Propanediamine iodide (PDAI), methylammonium iodide (MAI), and lead iodide (PbI2) are dissolved in a mixed organic solvent according to the stoichiometric ratio in the chemical formula PDAMA n-1 Pb n I 3n+1 (2 < n < 20), and stirred for more than 2 hours to prepare a PDAMA n-1 Pb n I 3n+1 low-dimensional D-J type perovskite precursor solution with a concentration of 0.4 mol / L - 0.8 mol / L; at the same time, methylammonium iodide (MAI) and lead iodide (PbI2) are dissolved in a mixed organic solvent according to a molar ratio of 1:1 or methylammonium iodide (MAI) and lead acetate (Pb(AC)2) are dissolved in a mixed organic solvent according to a molar ratio of 3:1, and stirred for more than 2 hours to prepare a MAPbI3 three-dimensional perovskite precursor solution with a concentration of 0.4 - 0.8 mol / L; the above-mentioned mixed organic solvent is N,N-dimethylformamide:butyrolactone, and the mixing volume ratio is 0.5 - 1.

[0063] (2) 15 - 30 ml of the PDAMA n-1 Pb n I 3n+1 low-dimensional perovskite precursor solution is placed in an atomization container, and it is atomized by an ultrasonic atomizer at the bottom; at the same time, the transparent conductive glass is placed on a hot stage and heated at 130 °C.

[0064] (3) Using an inert gas (such as nitrogen) as the carrier gas (flow rate: 1.5 - 2.5 mL / min), the perovskite droplets are carried out from the bottom of the atomization container to the nozzle (the vertical height of the nozzle from the conductive glass is about 5 mm). When the spraying state is stable, start the motor, and make the nozzle sweep back and forth across the conductive glass at a speed of 0.5 cm / s, so that the low-dimensional perovskite is deposited on the conductive glass by aerosol thermal deposition.

[0065] (4) After the nozzle has swept across the conductive glass 6 times, stop spraying, and transfer the conductive glass to another hot stage. Heat it at 100 °C for 10 minutes and then cool it naturally to prepare a low-dimensional perovskite film.

[0066] (5) Place 40 ml of the MAPbI3 three-dimensional perovskite precursor solution in a clean atomization container, and further deposit the three-dimensional perovskite onto the low-dimensional perovskite by the above spraying method. During this process, the temperature of the heating stage is kept constant at 130 °C, and the number of spraying cycles is 400 times.

[0067] (6) After the spraying is completed, the heating stage is immediately cooled slowly from 130 °C to 30 °C at a rate of 1 °C / min, thereby obtaining a perovskite thick film with a bilayer structure of "low-dimensional perovskite interfacial material / three-dimensional perovskite X-ray absorption material".

[0068] (7) According to the differences in the effective area of the detector and the position and distribution of its effective area, fix the obtained perovskite thick film under different stainless steel mask plates, and deposit the carbon electrode on it by the doctor blade method, thereby preparing a perovskite-based X-ray detector.

[0069] Example 3

[0070] (1) Dissolve phenethylammonium iodide (PEAI), methylammonium iodide (MAI) and lead iodide (PbI2) in a mixed organic solvent according to the stoichiometric ratio in the chemical formula (PEA)2MA n-1 Pb n I 3n+1 (2 < n < 20), and stir for more than 2 hours to prepare (PEA)2MA n-1 Pb n I 3n+1 low-dimensional R-P type perovskite precursor solution with a concentration of 0.4 mol / L - 0.8 mol / L; at the same time, dissolve cesium iodide (CsI), formamidinium iodide (FAI) and lead iodide (PbI2) in a mixed organic solvent according to a molar ratio of 0.15:0.85:1, and stir for more than 2 hours to prepare Cs 0.15 FA 0.85 PbI3 three-dimensional perovskite precursor solution with a concentration of 0.4 mol / L - 0.8 mol / L; the above mixed organic solvent is N,N-dimethylformamide:butyrolactone, and the mixing volume ratio is 0.5 - 1.

[0071] (2) Place 15 ml of the (PEA)2MA n-1 Pb n I 3n+1 low-dimensional perovskite precursor solution in an atomization container, and atomize it using the ultrasonic atomizer at the bottom; at the same time, place the transparent conductive glass on a hot stage and heat it at 140 °C.

[0072] (3) Using an inert gas (such as nitrogen) as the carrier gas (flow rate: 1.5 - 2.5 mL / min), the perovskite droplets are carried from the bottom of the atomization container to the nozzle (the vertical height of the nozzle from the conductive glass is about 5 mm). When the spraying state is stable, start the motor to make the nozzle sweep back and forth across the conductive glass at a speed of 0.5 cm / s, so that the low-dimensional perovskite is deposited on the conductive glass by aerosol thermal deposition.

[0073] (4) After the nozzle has swept across the conductive glass 8 times, stop spraying and transfer the conductive glass to another hot stage. Heat it at 100 °C for 10 minutes and then let it cool naturally to obtain a low-dimensional perovskite thin film.

[0074] (5) Place 40 ml of Cs 0.15 FA 0.85 PbI3 three-dimensional perovskite precursor solution in a clean atomization container, and further deposit the three-dimensional perovskite on the low-dimensional perovskite by the above spraying method. During this process, the temperature of the hot stage is kept constant at 140 °C, and the number of spraying cycles is 400 times.

[0075] (6) After spraying is completed, the hot stage continues to be kept at a constant temperature of 140 °C for 10 min, and then slowly decreases from 140 °C to 30 °C at a rate of 1 °C / min, thereby obtaining a perovskite thick film with a bilayer structure of "low-dimensional perovskite interfacial material / three-dimensional perovskite X-ray absorption material".

[0076] (7) According to the differences in the effective area of the detector and the position and distribution of its effective area, fix the obtained perovskite thick film under different stainless steel mask plates, and deposit the metal electrode silver on it by evaporation to prepare a perovskite-based X-ray detector.

[0077] Example 4

[0078] (1) Dissolve phenethylammonium iodide (PEAI), methylammonium iodide (MAI) and lead iodide (PbI2) in a mixed organic solvent according to the stoichiometric ratio in the chemical formula (PEA)2MA n-1 Pb n I 3n+1 (2 < n < 20) and stir for more than 2 hours to prepare (PEA)2MA n-1 Pb n I 3n+1 low-dimensional R-P type perovskite precursor solution with a concentration of 0.1 mol / L - 1.4 mol / L; at the same time, dissolve cesium iodide (CsI), formamidinium iodide (FAI) and lead iodide (PbI2) in a mixed organic solvent according to a molar ratio of 0.15:0.85:1, stir for more than 2 hours, and prepare Cs 0.15 FA 0.85The concentration of the PbI3 three-dimensional perovskite precursor solution is 0.4 mol / L-0.8 mol / L; the above-mentioned mixed organic solvent is N,N-dimethylformamide:butyrolactone, and the mixing volume ratio is 0.5-1.

[0079] (2) Add 0.1 ml of (PEA)2MA n-1 Pb n I 3n+1 A low-dimensional perovskite precursor solution is placed on transparent conductive glass, and a low-dimensional perovskite thin film precursor layer is prepared by spin coating. The precursor layer is placed on a hot plate and heated and cured at 100°C for 10 minutes to 30 minutes to obtain a low-dimensional perovskite thin film. Depending on the precursor solution concentration (0.1-1.4 mol / ml) and the spin coating speed (1200-7000 rpm), its thickness can be effectively controlled between 0.05-2 μm.

[0080] (3) Add 40ml of Cs 0.15 FA 0.85 The PbI3 three-dimensional perovskite precursor liquid is placed in a clean atomization container and atomized using an ultrasonic atomizer at the bottom; at the same time, a transparent conductive glass spin-coated with a low-dimensional perovskite film is placed on a hot stage and heated at 140°C.

[0081] (4) Using an inert gas (such as helium) as a carrier gas (flow rate: 1.5-2.5 mL / min), the perovskite droplets are carried out from the bottom of the atomization container to the nozzle (the vertical height of the nozzle from the low-dimensional perovskite film is about 5 mm). After the spray state is stable, the motor is started to make the nozzle sweep back and forth across the low-dimensional perovskite film at a speed of 0.5 cm / s, so that the three-dimensional perovskite is deposited on the low-dimensional perovskite film by aerosol thermal deposition.

[0082] (5) The nozzle is sprayed in a circular motion. When the thickness of the three-dimensional perovskite film is about 40 μm, the spraying is stopped and the reaction is carried out at a constant temperature of 280°C for 10 minutes. Then, the temperature is slowly reduced from 280°C to 30°C at a rate of 1°C / min, thereby obtaining a perovskite thick film with a double-layer structure of "low-dimensional perovskite interface material / three-dimensional perovskite X-ray absorption material".

[0083] (6) According to the different effective areas of the detectors and the locations and distributions of the effective areas, the obtained perovskite thick films are fixed under different stainless steel masks, and metal electrode silver is deposited thereon by vapor deposition to prepare perovskite-based X-ray detectors.

[0084] It can be seen from the above four embodiments that a low-dimensional perovskite is deposited on a conductive substrate (such as conductive glass) serving as a bottom electrode, and three-dimensional perovskite is deposited thereon after solidification. The process of depositing the three-dimensional perovskite does not destroy the quasi-two-dimensional perovskite interface layer, and its unique layered structure is still clearly visible. At the same time, the deposited three-dimensional perovskite absorption layer tends to grow continuously perpendicular to the conductive substrate, and the grain size can reach tens of microns, and the overall thickness exceeds 20μm. In the above embodiments, the high film resistance and the blocking of hole injection to the electrode effectively reduce the dark current of the detector, thereby improving the switching ratio of the detector and reducing the detection limit of the detector; the suppression of ion migration significantly improves the problem of baseline drift of the detector; at the same time, because the energy level of the low-dimensional perovskite ensures the efficient extraction of carriers, and the three-dimensional perovskite has excellent carrier transport characteristics, the prepared detector has a power of up to 19530μC Gy -1 cm -2 sensitivity.

[0085] Within the scope of the present invention, the above-mentioned embodiments can be further exemplified. For example, further manipulation of the perovskite composition, the type and ratio of the mixed solvent, and the temperature of the heating stage can yield a thick perovskite film having a dual-layer structure of "low-dimensional perovskite interface material / three-dimensional perovskite X-ray absorbing material." For simplicity, the parameters of Example 1 are considered as the optimal choice.

[0086] Comparative Example 1

[0087] Preparation of three-dimensional perovskite-based X-ray detectors:

[0088] (1) Methylammonium iodide (MAI) and lead iodide (PbI2) in a molar ratio of 1:1 or methylammonium iodide (MAI) and lead acetate (Pb(AC)2) in a molar ratio of 3:1 are dissolved in a mixed organic solvent and stirred for more than 2 hours to prepare a MAPbI3 three-dimensional perovskite precursor solution with a concentration of 0.3-0.8 mol / L; the above-mentioned mixed organic solvent is dimethyl sulfoxide (DMSO) and N,N-dimethylformamide (DMF), and the mixing volume ratio is: 0.5-1.

[0089] (2) Place 40 ml of MAPbI3 perovskite precursor solution in a clean atomization container and atomize it using the ultrasonic atomizer at the bottom; at the same time, place the transparent conductive glass on a hot plate and heat it at 130°C.

[0090] (3) Using an inert gas (such as nitrogen) as a carrier gas (flow rate: 1.5-2.5 mL / min), the MAPbI3 perovskite droplets are carried out from the bottom of the atomization container to the nozzle (the vertical height of the nozzle from the conductive glass is about 5 mm). After the spray state is stable, the motor is started to make the nozzle sweep back and forth across the conductive glass 400 times at a speed of 0.5 cm / s, so that the MAPbI3 perovskite is deposited on the conductive glass by aerosol thermal deposition.

[0091] (4) After spraying is completed, the heating stage is immediately lowered from 130°C to 30°C at a rate of 1°C / min, thereby obtaining a MAPbI3 perovskite thick film. Figure 3 (c) is a SEM cross-sectional image of the resulting MAPbI3 perovskite thick film. As can be seen from the image, the resulting MAPbI3 perovskite thick film tends to grow continuously perpendicular to the conductive substrate, with grain sizes reaching tens of microns and an overall thickness of approximately 50 μm. Furthermore, no layered structure is observed at the bottom of the MAPbI3 perovskite thick film. Figure 4 ac respectively compares the XRD spectra, electrical properties and energy level structures of the MAPbI3 perovskite thick film and the low perovskite / three-dimensional perovskite double-layer perovskite thick film in Example 1. As can be seen from the figure, the prepared MAPbI3 perovskite thick film exhibits very strong (110) and (220) crystal plane peaks, confirming that it has high crystallinity and preferential orientation. Due to the limited penetration depth of X-rays in XRD characterization, the bottom low-dimensional perovskite cannot be detected, which makes the XRD spectrum of the low-dimensional / three-dimensional structured perovskite thick film almost completely consistent with the above-mentioned MAPbI3 perovskite thick film. However, if only a thinner MAPbI3 three-dimensional perovskite is deposited on the low-dimensional perovskite interface layer, the characteristic X-ray diffraction peaks of the two-dimensional and low-dimensional perovskites can be clearly observed. Due to the introduction of the low-dimensional perovskite interface, the film resistance of the double-layer perovskite thick film is reduced from 3.5×10 8 Ωcm increased to 3.0×10 9 Ωcm, while the carrier mobility is from 4.0cm 2 V -1 s -1 Lowered to 1.7cm 2 V -1 s -1 , which is beneficial to reducing the dark current of the detector; in addition, the valence bands of two-dimensional perovskite and low-dimensional perovskite are much lower than that of MAPbI3 perovskite, and their conduction bands are only slightly higher than that of MAPbI3 perovskite, which can not only effectively suppress the injection of holes from the conductive substrate, but also ensure the collection of holes and electrons when the detector is in working state.

[0092] (5) According to the differences in the effective area of the detector, as well as the position and distribution of its effective area, the obtained perovskite thick film is fixed under different stainless-steel mask plates, and the carbon electrode is deposited on it by means of scraping, thereby preparing a perovskite-based X-ray detector. Figure 5 The photocurrent response and sensitivity of the X-ray detectors based on the low-dimensional perovskite / three-dimensional perovskite bilayer structure in Example 1 and the MAPbI3 perovskite in Comparative Example 1 were compared. As can be seen from the figure, compared with the MAPbI3 perovskite, the dark current of the perovskite detector with the low-dimensional perovskite / three-dimensional perovskite bilayer structure in Example 1 decreased from 75.5 μA cm -2 to 5.28 μA cm -2 (25 times), the on / off ratio increased from 1.7 to 6.4 (3.8 times). At the same time, the sensitivity only decreased from 24330 μC Gy -1 cm -2 to 19503 μC Gy -1 cm -2 (80%). In addition, its detection limit decreased from 3.10 μGy / s to 480 nGy / s, and the baseline drift phenomenon was effectively suppressed, as Figure 6 shown. It can be seen that compared with the three-dimensional perovskite-based X-ray detector in Comparative Example 1, the perovskite-based X-ray detector prepared in this application can effectively reduce the dark current and increase the on / off ratio while maintaining a high sensitivity and low detection limit.

[0093] Comparative Example 2

[0094] Prepare a low-dimensional perovskite-based X-ray detector:

[0095] (1) Dissolve phenethylammonium iodide (PEAI), methylammonium iodide (MAI), and lead iodide (PbI2) in a mixed organic solvent according to the stoichiometric ratio in the chemical formula (PEA)2MA n-1 Pb n I 3n+1 (2 < n < 10) (when n = 4, the molar ratio of phenethylammonium iodide, methylammonium iodide, and lead iodide is 2:3:4), and stir for more than 2 hours to prepare a (PEA)2MA n-1 Pb n I 3n+1 low-dimensional R-P type perovskite precursor solution with a concentration of 0.4 mol / L - 0.8 mol / L.

[0096] (2) Take 40 ml of (PEA)2MA n-1 Pb n I 3n+1The low-dimensional perovskite precursor liquid is placed in a clean atomization container and atomized using an ultrasonic atomizer at the bottom; at the same time, the transparent conductive glass is placed on a hot table and heated at 140°C.

[0097] (3) Using inert gas (such as nitrogen) as carrier gas (flow rate: 1.5-2.5 mL / min), the perovskite droplets are brought out from the bottom of the atomizing container to the nozzle (the vertical height of the nozzle from the conductive glass is about 5 mm). After the spray state is stable, start the motor and make the nozzle sweep back and forth across the conductive glass 400 times at a speed of 0.5 cm / s, so that (PEA)2MA n-1 Pb n I 3n+1 Low-dimensional perovskites are deposited onto conductive glass by aerosol thermal deposition.

[0098] (4) After spraying is completed, the heating stage is immediately lowered from 140°C to 30°C at 1°C / min, thereby obtaining (PEA)2MA n-1 Pb n I 3n+1 Low-dimensional perovskite thick film, the thickness of which is about 50μm ( Figure 7 ab). XRD results show that the low-dimensional perovskite thick film has the characteristics of two-dimensional perovskite, low-dimensional perovskite, and three-dimensional perovskite, which conforms to the common laws and characteristics of low-dimensional perovskites.

[0099] Depending on the effective area of the detector and its location and distribution, the obtained perovskite thick film is fixed under a stainless steel mask plate, and a carbon electrode is deposited thereon by scraping, thereby preparing a perovskite-based X-ray detector. Figure 7 The performance of the low-dimensional perovskite-based X-ray detector in Comparative Example 2 was evaluated. As shown in the figure, although the dark current of the low-dimensional perovskite is only 0.2 μA cm -2 However, its sensitivity can only reach 153μC Gy -1 cm -2 , which is two orders of magnitude lower than the low-dimensional perovskite / three-dimensional perovskite double-layer structure perovskite in Example 1. It can be seen that compared with the low-dimensional perovskite-based X-ray detector in Comparative Example 2, the perovskite-based X-ray detector prepared in this application can maintain high sensitivity while effectively maintaining low dark current.

[0100] The above examples are used to illustrate the present invention, which are only used to help understand the present invention and are not intended to limit the present invention. Those skilled in the art can make several simple deductions, modifications or substitutions based on the concept of the present invention.

Claims

1. A perovskite-based X-ray detector, characterized in that: The perovskite-based X-ray detector comprises a conductive substrate, a low-dimensional perovskite layer, a three-dimensional perovskite layer and a top electrode stacked in sequence, wherein the perovskite-based X-ray detector has a double-layer perovskite structure; Wherein, the material of the low-dimensional perovskite layer includes Ruddlesden-Popper type perovskite and / or Dion-Jacobson type perovskite; The general formula of the Ruddlesden-Popper type perovskite is: A'2A n-1 Pb n X 3n+1 , n is 2-20; wherein A' is at least one of CH3(CH2)2NH3, CH3(CH2)3NH3, CH2CH1CH2NH3, C6H5CH2CH2NH3, C6H5CH2NH3 and C6H5NH3, A is at least one of CH3NH3, (NH2)2CH, Cs and Rb, and X is at least one of Cl, Br and I; The general formula of the Dion-Jacobson type perovskite is: A'A n-1 Pb n X 3n+1 , n is 2-20; where A' is NH3-(CH2) n -NH3 and n=2-4, NH3CH2C6H 10 At least one of CH2NH3 and NH3C6H4NH3, A is at least one of CH3NH3, (NH2)2CH, Cs and Rb, and X is at least one of Cl, Br and I.

2. The perovskite-based X-ray detector according to claim 1, wherein: The material of the three-dimensional perovskite layer includes APbX3, wherein A is at least one of CH3NH3, (NH2)2CH, Cs and Rb, and X is at least one of Cl, Br and I.

3. The perovskite-based X-ray detector according to claim 1, wherein: The top electrode is made of at least one of carbon, metal, fluorine-doped tin dioxide and indium tin oxide; wherein the metal includes at least one of gold, silver and copper.

4. The perovskite-based X-ray detector according to claim 3, characterized in that: The thickness of the low-dimensional perovskite layer is 0.05-3 μm; the thickness of the three-dimensional perovskite layer is greater than 20 μm.

5. A method for preparing a perovskite-based X-ray detector according to any one of claims 1 to 4, characterized in that: The following steps are included: A. dissolving a low-dimensional perovskite precursor powder in an organic solvent to prepare a low-dimensional perovskite precursor solution, and dissolving a three-dimensional perovskite precursor powder in an organic solvent to prepare a three-dimensional perovskite precursor solution; B. depositing the low-dimensional perovskite precursor solution onto a conductive substrate by spin coating, doctor blade coating, narrow slit coating or aerosol thermal deposition to form a low-dimensional perovskite layer, and curing the layer; C. atomizing the three-dimensional perovskite precursor solution to form three-dimensional perovskite droplets while maintaining heating of the conductive substrate; Using an inert gas as a carrier gas, the three-dimensional perovskite droplets are sprayed onto the surface of the low-dimensional perovskite layer, so that the three-dimensional perovskite is deposited on the surface of the low-dimensional perovskite layer by aerosol thermal deposition to form a three-dimensional perovskite layer, and then solidified; D. Forming a top electrode on the surface of the three-dimensional perovskite layer to obtain the perovskite-based X-ray detector.

6. The preparation method according to claim 5, characterized in that: In step A, the low-dimensional perovskite precursor powder includes a macromolecular iodine salt, a small molecule iodine salt and PbX2; wherein the macromolecular iodine salt includes at least one of ethylenediamine iodide, 1,3-propylenediamine iodide, 1,4-butylenediamine iodide, 1,4-aminomethylcyclohexane, o-phenyldiamine, propylammonium iodide, allylammonium iodide, butylammonium iodide, phenylammonium, benzylammonium iodide and phenethylammonium iodide; the small molecule iodine salt includes at least one of methylammonium iodide, formamidine ammonium iodide, cesium iodide and rubidium iodide; in the PbX2, X is at least one of I, Br and Cl.

7. The preparation method according to claim 5, wherein: In step A, the three-dimensional perovskite precursor powder includes a small molecule iodine salt and PbX2; wherein the small molecule iodine salt includes at least one of methylammonium iodide, rubidium iodide, cesium iodide and formammonium iodide; in the PbX2, X is at least one of I, Br and Cl.

8. The preparation method according to claim 5, wherein: In step A, the organic solvent includes at least one of dimethyl sulfoxide, N,N-dimethylformamide, 1-ethyl-2-pyrrolidone, butyrolactone and methoxyethanol.

9. The preparation method according to claim 5, wherein: In step B and step C, the heating refers to heating at a temperature of 60-300° C., and the curing refers to heating at 60-300° C. for 1-1200 minutes.

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