X-ray detector based on narrow-band-gap perovskite and wide-band-gap perovskite heterojunction and preparation method thereof

Abstract

The invention discloses an X-ray detector based on narrow-band-gap perovskite and wide-band-gap perovskite heterojunction and a preparation method of the X-ray detector, and belongs to the technical field of perovskite. The X-ray detector based on the narrow-band-gap perovskite and the wide-band-gap perovskite heterojunction comprises a metal electrode layer, a rare earth oxide layer, a three-dimensional narrow-band-gap perovskite layer-three-dimensional wide-band-gap perovskite layer heterojunction, a rare earth oxide layer and a metal electrode layer which are stacked in sequence. According to the X-ray detector based on the narrow-band-gap perovskite and the wide-band-gap perovskite heterojunction, the active layer is a three-dimensional narrow-band-gap perovskite layer-three-dimensional wide-band-gap perovskite layer heterojunction, and the perovskite heterojunction has the characteristics of low dark current, low defect, high carrier transmission performance, high sensitivity, short response time and the like; therefore, the performances of the X-ray detector, such as sensitivity and mobility life product, are improved.

Description

Technical Field

[0001] This invention belongs to the field of perovskite technology, and in particular relates to an X-ray detector based on narrow bandgap perovskite and wide bandgap perovskite heterojunction and its fabrication method. Background Technology

[0002] Halide perovskites, as an emerging semiconductor material system, have shown great promise in the field of optoelectronic devices due to their unique crystal structure and excellent photoelectric properties. Halide perovskites possess characteristics such as direct band gaps, strong light absorption coefficients, long carrier diffusion lengths, and low defect state densities, and have been widely used in solar cells, light-emitting diodes, and photodetectors.

[0003] In contrast, the development of perovskite-based X-ray detectors in terms of photoelectric performance improvement and device engineering is still in a relatively early stage. Meanwhile, perovskite materials show significant application potential in X-ray detection. Compared with traditional amorphous selenium (α-Se), silicon-based, or cadmium telluride detectors, which have advantages such as mature processes and low dark current, perovskites possess high atomic number elemental composition and high photoelectric absorption efficiency. At the same thickness, they can achieve stronger X-ray absorption and higher charge collection efficiency, demonstrating significant advantages in key performance indicators such as sensitivity, response time, and mobility-lifetime product (μτ product). However, existing perovskite heterojunction X-ray detectors still have considerable room for improvement in sensitivity, response speed, and mobility-lifetime product. Summary of the Invention

[0004] To address the above problems, this invention provides an X-ray detector based on narrow-bandgap perovskite and wide-bandgap perovskite heterojunctions and its fabrication method.

[0005] To achieve the above-mentioned objectives, the present invention adopts the following technical solution: In a first aspect, the present invention provides an X-ray detector based on a narrow-bandgap perovskite and a wide-bandgap perovskite heterojunction, comprising a metal electrode layer, a rare earth oxide layer, a three-dimensional narrow-bandgap perovskite layer-three-dimensional wide-bandgap perovskite layer heterojunction, a rare earth oxide layer, and a metal electrode layer stacked sequentially.

[0006] Furthermore, all metal electrode layers are chromium metal electrode layers; all rare earth oxide layers are erbium oxide layers; and in the three-dimensional narrow bandgap perovskite layer-three-dimensional wide bandgap perovskite layer heterojunction, the three-dimensional narrow bandgap perovskite layer is a MAPb-tin methylamine perovskite layer. x Sn 1-x Br3), the three-dimensional wide-bandgap perovskite layer is a bromolead methylamine perovskite layer (MAPbBr3).

[0007] Furthermore, the thickness of the metal electrode layer is 120 nm; the thickness of the rare earth oxide layer is 100 nm; the thickness of the three-dimensional narrow bandgap perovskite layer-three-dimensional wide bandgap perovskite layer heterojunction is 2.5 mm, wherein the thickness of the three-dimensional narrow bandgap perovskite layer is 0.5 mm-1 mm, and the thickness of the three-dimensional wide bandgap perovskite layer is 1-1.5 mm.

[0008] Secondly, the present invention provides a method for fabricating an X-ray detector based on a narrow-bandgap perovskite and a wide-bandgap perovskite heterojunction, comprising the following steps: S1. Place the wide-bandgap perovskite crystal in a narrow-bandgap perovskite precursor solution, and use the reverse temperature crystallization method to grow narrow-bandgap perovskite on the surface of the wide-bandgap perovskite crystal to form a heterostructure. S2. After cutting and polishing the heterostructure, a three-dimensional narrow bandgap perovskite layer-three-dimensional wide bandgap perovskite layer heterojunction is obtained. S3. Rare earth oxide layers and metal electrode layers are sequentially deposited on the top and bottom surfaces of the three-dimensional narrow bandgap perovskite layer-three-dimensional wide bandgap perovskite layer heterojunction to prepare the X-ray detector based on the narrow bandgap perovskite and wide bandgap perovskite heterojunction.

[0009] This invention provides a method for preparing a narrow-bandgap perovskite and a wide-bandgap perovskite heterojunction. After preparing a narrow-bandgap perovskite precursor solution, a wide-bandgap perovskite single crystal is placed in the precursor solution, with the solution directly contacting the surface of the wide-bandgap perovskite single crystal. Narrow-bandgap perovskite crystals precipitate on the surface of the wide-bandgap perovskite single crystal, forming a new three-dimensional perovskite layer. This invention precipitates the narrow-bandgap perovskite in solution form, which not only helps ensure the equilibrium and stability of the reaction and avoids over-reaction, but also ensures that only the surface of the wide-bandgap perovskite single crystal contacts the narrow-bandgap perovskite precursor solution during the entire reaction process. Therefore, a new three-dimensional perovskite layer is formed on the surface of the wide-bandgap perovskite single crystal, resulting in a three-dimensional narrow-bandgap perovskite layer-three-dimensional wide-bandgap perovskite layer heterojunction.

[0010] This invention primarily combines the advantages of narrow-bandgap three-dimensional perovskite single crystals and wide-bandgap three-dimensional perovskite single crystals: narrow-bandgap perovskite single crystals have a longer carrier diffusion length and the ability to absorb low-energy X-rays; wide-bandgap perovskite single crystals have a higher light absorption coefficient and a stronger absorption capacity for high-energy X-rays. The three-dimensional narrow-bandgap perovskite layer-three-dimensional wide-bandgap perovskite layer heterojunction combines the wide-bandgap perovskite layer with the narrow-bandgap perovskite layer, forming a band-aligned or stepped structure, optimizing electron and hole separation, thereby reducing recombination losses and significantly improving X-ray detection sensitivity.

[0011] Further, in step S1, the wide-bandgap perovskite crystal is a MAPbBr3 perovskite single crystal. The preparation method of the MAPbBr3 perovskite single crystal includes the following steps: adding isopropanol to a mixed organic solution of lead bromide and methylammonium bromide, stirring evenly and filtering to obtain a precursor solution, and obtaining a seed crystal after a first heating; placing the seed crystal into a homogeneous precursor solution and heating a second time to prepare the MAPbBr3 perovskite single crystal.

[0012] Furthermore, the ratio of lead bromide, methylammonium bromide, and isopropanol is 4.59 g: 1.388 g: 100 μL; the initial heating temperature is 90 °C; and the secondary heating temperature is 44-52 °C.

[0013] Further, in step S1, the narrow bandgap perovskite precursor solution is MAPb. x Sn 1-x Br3 perovskite precursor solution, wherein MAPb x Sn 1-x The preparation method of Br3 perovskite precursor solution includes the following steps: mixing lead bromotin methylamine perovskite powder, tin powder, formamidinium sulfinyl D salt and N,N-dimethylformamide, stirring to dissolve after purging with argon gas, and filtering to obtain the MAPb. x Sn 1-x Br3 perovskite precursor solution.

[0014] Furthermore, the MAPb x Sn 1-x The ratio of Br3 perovskite powder, tin powder, formamidinium sulfinyl D salt and N,N-dimethylformamide is 4.5g:20mg:25mg:6mL.

[0015] Furthermore, in step S1, the temperature of the reverse temperature crystallization method is 32℃-40℃.

[0016] Compared with the prior art, the present invention has the following advantages and technical effects: The active layer of the X-ray detector based on narrow-bandgap perovskite and wide-bandgap perovskite heterojunction provided by this invention is a three-dimensional narrow-bandgap perovskite layer-three-dimensional wide-bandgap perovskite layer heterojunction. This perovskite heterojunction has characteristics such as low dark current, low defects, high carrier transport performance, high sensitivity and fast response time, thus improving the sensitivity and mobility lifetime product of the X-ray detector.

[0017] The X-ray detectors based on narrow-bandgap and wide-bandgap perovskite heterojunctions provided by this invention offer significant performance improvements in several aspects compared to ordinary perovskite single-crystal X-ray detectors, including increased sensitivity, reduced dark current, and enhanced stability. These advantages make them particularly advantageous in high-performance, long-term stable operation, especially in low-dose X-ray detection applications. Furthermore, the bandgap can be adjusted by modifying the material composition (e.g., adjusting the ratio of Pb-Sn blends) to meet the needs of various optoelectronic applications. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0019] Figure 1 A schematic diagram illustrating the performance testing of the X-ray detector based on narrow-bandgap perovskite and wide-bandgap perovskite heterostructures prepared in this invention. Figure 2 The stability test results are for the X-ray detector based on narrow-bandgap perovskite and wide-bandgap perovskite heterojunction prepared in Example 1. Figure 3 The results show the stability test results of the MAPbBr3 perovskite single crystal X-ray detector prepared for Comparative Example 1. Detailed Implementation

[0020] Various exemplary embodiments of the present invention will now be described in detail. This detailed description should not be considered as a limitation of the present invention, but rather as a more detailed description of certain aspects, features, and embodiments of the present invention.

[0021] It should be understood that the terminology used in this invention is merely for describing particular embodiments and is not intended to limit the invention. Furthermore, with respect to numerical ranges in this invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Every smaller range between any stated value or intermediate value within a stated range, and any other stated value or intermediate value within said range, is also included in this invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0022] Unless otherwise stated, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art. While only preferred methods and materials have been described herein, any methods and materials similar or equivalent to those described herein may be used in the implementation or testing of this invention. All references to this specification are incorporated by way of citation to disclose and describe methods and / or materials associated with those references. In the event of any conflict with any incorporated reference, the content of this specification shall prevail.

[0023] Various modifications and variations can be made to the specific embodiments described in this specification without departing from the scope or spirit of the invention, as will be apparent to those skilled in the art. Other embodiments derived from this specification will also be apparent to those skilled in the art. This specification and embodiments are merely exemplary.

[0024] The terms “include,” “including,” “have,” “contain,” etc., used in this article are all open-ended terms, meaning that they include but are not limited to.

[0025] The room temperature / normal temperature in this invention refers to 25±2℃.

[0026] The reagents used in the embodiments of this invention have the following purities: lead bromide: 98%; methylammonium bromide: 99.5%; N,N-dimethylformamide: 99.5%; lead monoxide: 99%; stannous oxide: 97%; methylamine hydrochloride: 98%; hydrobromic acid: 48%; hypophosphite: 50%.

[0027] This invention provides an X-ray detector based on a narrow-bandgap perovskite and a wide-bandgap perovskite heterojunction, comprising a metal electrode layer, a rare earth oxide layer, a three-dimensional narrow-bandgap perovskite layer-three-dimensional wide-bandgap perovskite layer heterojunction, a rare earth oxide layer, and a metal electrode layer stacked sequentially.

[0028] In some preferred embodiments, the metal electrode layers are all chromium metal electrode layers; the rare earth oxide layers are all erbium oxide layers; in the three-dimensional narrow bandgap perovskite layer-three-dimensional wide bandgap perovskite layer heterojunction, the three-dimensional narrow bandgap perovskite layer is a lead-tin methylamine perovskite layer, and the three-dimensional wide bandgap perovskite layer is a lead-tin methylamine perovskite layer.

[0029] In some preferred embodiments, the thickness of the metal electrode layer is 120 nm; the thickness of the rare earth oxide layer is 100 nm; the thickness of the three-dimensional narrow bandgap perovskite layer-three-dimensional wide bandgap perovskite layer heterojunction is 2.5 mm, wherein the thickness of the three-dimensional narrow bandgap perovskite layer is 0.5 mm-1 mm, and the thickness of the three-dimensional wide bandgap perovskite layer is 1-1.5 mm.

[0030] This invention also provides a method for fabricating an X-ray detector based on a narrow-bandgap perovskite and a wide-bandgap perovskite heterostructure, comprising the following steps: A wide-bandgap perovskite crystal is used as the heterostructure substrate and placed in a narrow-bandgap perovskite precursor solution. A reverse-temperature crystallization method is used to grow narrow-bandgap perovskite on the surface of the wide-bandgap perovskite substrate, forming a heterostructure. After the perovskite heterostructure is fabricated, electrodes can be deposited onto the sample using a vapor deposition apparatus to obtain an X-ray detector based on the heterostructure of narrow-bandgap perovskite and wide-bandgap perovskite. The electrode material is determined according to specific circumstances. Once the electrodes are deposited, they can be used for subsequent electrical testing.

[0031] The specific preparation method of the heterostructure based on narrow-bandgap perovskite and wide-bandgap perovskite in this embodiment of the invention is as follows: S1. Place the wide-bandgap perovskite crystal in a narrow-bandgap perovskite precursor solution, and use the reverse temperature crystallization method to grow narrow-bandgap perovskite on the surface of the wide-bandgap perovskite crystal to form a heterostructure. S2. After cutting and polishing the heterostructure, a three-dimensional narrow bandgap perovskite layer-three-dimensional wide bandgap perovskite layer heterojunction is obtained. S3. Rare earth oxide layers and metal electrode layers are sequentially deposited on the top and bottom surfaces of the three-dimensional narrow bandgap perovskite layer-three-dimensional wide bandgap perovskite layer heterojunction to prepare the X-ray detector based on the narrow bandgap perovskite and wide bandgap perovskite heterojunction.

[0032] In some preferred embodiments of the present invention, the wide bandgap perovskite crystal is a single crystal of lead bromide methylamine perovskite; the narrow bandgap perovskite precursor solution is a lead bromide tin methylamine perovskite precursor solution, the bandgap of which can be adjusted with the change of lead-tin ratio, and it is used as a narrow bandgap perovskite.

[0033] Example 1: A method for fabricating an X-ray detector based on narrow-bandgap perovskite and wide-bandgap perovskite heterostructures. S1. Add 4.590g of PbBr2 (lead bromide), 1.388g of MABr (methylammonium bromide), and 9.48g of DMF (N,N-dimethylformamide) to a 50mL low-profile beaker, place a magnetic stir bar in it, and stir at room temperature for 4 hours until the solution becomes clear. Then add 100uL of IPA (isopropanol) and stir at room temperature for another hour. Filter the solution through a 0.45um filter into another clean beaker to obtain the precursor solution. Seal the mouth of the beaker with sealing film and aluminum foil, and heat it in an oil bath at 90℃ until small and regular seed crystals are formed in the solution. S2. Prepare the precursor solution using the same method as in S1, which is the homogeneous precursor solution. Place the seed crystal prepared in S1 into the homogeneous precursor solution. Maintain the heating stage at 44°C. Place the beaker containing the seed crystal and the homogeneous precursor solution on the heating stage and increase the temperature from 44°C to 52°C, increasing by 1°C every 12 hours, until the crystal grows to 8 mm. 8mm When the thickness reaches 3mm, it can be removed to prepare MAPbBr3 (bromolead methylamine) perovskite single crystal, which is a wide-bandgap perovskite single crystal; S3. Add 0.446 g of PbO (lead monoxide), 0.269 g of SnO (stannous oxide), 0.270 g of MACl (methylaminohydrochloride), 9 mL of HBr (hydrobromic acid), and 1 mL of H3PO2 (hypophosphoric acid) to a 250 mL three-necked flask. Place a magnetic stir bar inside, purge with argon gas to remove oxygen, and place the flask on a heated magnetic stirring table. Stir at 120 °C for 1.5 h until the solution becomes clear. Then cool the solution to room temperature, pour off the supernatant, purge with argon gas, and heat at 100 °C for 2 h to dry, obtaining MAPb. 0.68 Sn 0.32 Br3 powder, in which the ratio of lead monoxide and stannous oxide is different, and the lead-tin ratio of bromolead-tin methylamine is different, in order to achieve the effect of adjusting the band gap.

[0034] S4. Using the wide-bandgap perovskite single crystal prepared in S2 as the substrate perovskite, the MAPb precipitated during cooling in S3 was taken. 0.68 Sn 0.32 4.5 g of Br3 powder, 20 mg of tin powder, 25 mg of formamidinium sulfinyl D salt, and 6 mL of DMF (N,N-dimethylformamide) were mixed in a 20 mL capped vial. After adding a magnetic stir bar and passing argon gas for 10 min, the mixture was stirred, dissolved, and filtered to obtain a bromine-lead-tin-methylamine perovskite precursor solution. The substrate perovskite was placed in this precursor solution, and then the 20 mL capped vial was placed on a heating platform and heated in an oil bath, starting at 32 °C and increasing by 2 °C daily. After 3 days of growth, a heterojunction of a three-dimensional narrow bandgap perovskite layer and a three-dimensional wide bandgap perovskite layer was formed. The thickness of the three-dimensional narrow bandgap perovskite layer was 1 mm, and the thickness of the three-dimensional wide bandgap perovskite layer was 3 mm. S5. The three-dimensional narrow-bandgap perovskite layer-three-dimensional wide-bandgap perovskite layer heterojunction prepared by epitaxial growth in S4 was cut into rectangular samples using a diamond wire saw. The resulting sample dimensions were approximately 2.5 mm thick (of which the thickness of the three-dimensional wide-bandgap perovskite layer was 1.8 mm and the thickness of the three-dimensional narrow-bandgap perovskite layer was 0.7 mm), 7 mm long, and 4 mm wide. The top and bottom surfaces of the cut sample were polished to smoothness with 3000 grit, 5000 grit, 7000 grit, and 10000 grit sandpaper, respectively. The sample was then placed in a 373 K constant temperature furnace for about 1 hour. After annealing, the sample was removed to obtain the active layer for the X-ray detector. S6. Polish the top and bottom surfaces of the active layer of the X-ray detector, and then deposit a 100 nm thick Er (erbium) metal layer on its top and bottom surfaces using a vapor deposition apparatus. After the coating is applied, the sample is exposed to air for 20 min for oxidation treatment. The originally transparent erbium layer turns gray due to oxidation. The sample is then sent back to the same vapor deposition apparatus, and a 120 nm thick chromium toothed metal electrode layer is deposited on the top and bottom surfaces of the sample using a mask. After the vapor deposition is completed, an X-ray detector based on a narrow bandgap perovskite and a wide bandgap perovskite heterojunction is obtained.

[0035] Comparative Example 1 S1. Same as Example 1; S2. Same as Example 1; S3. Using the MAPbBr3 perovskite single crystal prepared in S2 as the active layer of the X-ray detector, the sample size is approximately 4 mm thick, 4 mm long, and 2.5 mm wide. The top and bottom surfaces of the sample are polished to a smooth finish using 3000 grit, 5000 grit, 7000 grit, and 10000 grit sandpaper, respectively. A 100 nm thick Er (erbium) metal layer and a 120 nm thick Cr (chromium) metal layer are deposited sequentially on both sides of the MAPbBr3 perovskite single crystal sample using a vapor deposition apparatus. After the vapor deposition is completed, the MAPbBr3 perovskite single crystal X-ray detector is obtained.

[0036] Performance testing The X-ray detectors prepared in Example 1 and Comparative Example 1 were subjected to the following performance tests. All test steps were carried out under normal temperature and pressure atmospheric conditions.

[0037] Sensitivity Test: The X-ray detector is placed on a probe stage, with its two probes corresponding to the positive and negative electrodes, respectively, and mounted on the two ends of the X-ray detector's electrodes. A certain electric field is then applied to the detector through a source meter, and while maintaining this applied electric field, the current value output by the X-ray detector, measured by the source meter, is recorded. This current is called the dark current. Subsequently, X-rays are irradiated onto the X-ray detector, at which point the detector will output an X-ray photoresponse current. The X-ray photoresponse current value is recorded. Subtracting the dark current from this current value and then dividing by the product of the X-ray dose and the effective detection area yields the sensitivity of the X-ray detector.

[0038] Detection limit test: The X-ray detector is placed on a probe stage, with two probes corresponding to the positive and negative electrodes of the detector, respectively. A source meter applies a constant electric field to the detector, and the current value measured by the source meter is recorded; this current is called the dark current. X-rays are then irradiated onto the detector, causing it to output an X-ray photoresponse current. Using the X-ray photoresponse current-time curve, the average current density for each response window is extracted and subtracted from the corresponding dark current density; the difference between the photocurrent and dark current density is denoted as J. s The variance of the current density is processed for each response window, and the resulting current density variance is denoted as J. n The signal-to-noise ratio (SNR) of the device response signal is J. s / J n The signal-to-noise ratio of each response window is obtained, and a linear fit is performed on it. The intersection of the fitted line and the line SNR=3 is the detection limit of the device.

[0039] Mobility-Lifetime Product (IVP) Test: An X-ray detector was placed on a probe stage, with two probes corresponding to the positive and negative electrodes, respectively, and mounted on the two ends of the X-ray detector's electrodes. The probes were connected to an external circuit via a source meter. First, under no-irradiation conditions, different bias voltages were applied to the device, and the output current was recorded to obtain the dark-state IV curve. Subsequently, while keeping other conditions constant, the device was irradiated with X-rays at a constant dose rate, and the steady-state photoresponse current was recorded under different applied bias voltages. The net photocurrent under each bias voltage was obtained by subtracting the corresponding dark current from the illumination current. By changing the applied bias voltage, the relationship between the net photocurrent and voltage was obtained, according to the Hecht equation: Calculate the mobility-lifetime product.

[0040] in, Net photocurrent, This is the saturation current when all charge carriers are collected. For external bias voltage, For the thickness of perovskite devices, It is the carrier mobility lifetime product.

[0041] The net photocurrent-voltage curves obtained from the experiment were nonlinearly fitted using Origin. As fitting parameters, the device parameters are obtained by solving the least squares method. Value. When the fitted correlation coefficient R... 2 A value higher than 0.99 indicates that the fitting results have good reliability.

[0042] Figure 1This is a schematic diagram illustrating the performance testing of the X-ray detector based on narrow-bandgap perovskite and wide-bandgap perovskite heterostructure prepared in Example 1 of the present invention.

[0043] The sensitivity, detection limit, and mobility lifetime product of the X-ray detectors prepared in Example 1 and Comparative Example 1 are shown in Table 1.

[0044] Table 1 Stability Testing: The fabricated X-ray detector was fixed on a probe stage, with two probes contacting the positive and negative electrodes of the device, respectively. A constant bias voltage was applied to the device through a source meter, allowing it to operate under a fixed electric field. First, the dark current was recorded as a baseline under no-irradiation conditions. Then, while maintaining the bias voltage, the device was irradiated with X-rays at a constant dose rate, and the change in photoresponse current over time was continuously recorded. The net photoresponse current was obtained by subtracting the dark current from the irradiation current, and its trend over time was analyzed to evaluate the device's current stability and signal retention capability under continuous operating conditions. If the net photoresponse current fluctuates little and shows no significant attenuation during long-term testing, the device exhibits good operational stability.

[0045] The stability of the X-ray detectors prepared in Example 1 and Comparative Example 1 was tested using the methods described above. Figure 2 The results show the stability test results of the X-ray detector based on narrow-bandgap perovskite and wide-bandgap perovskite heterojunctions prepared in Example 1. Figure 3 The stability test results of the MAPbBr3 perovskite single-crystal X-ray detector prepared in Comparative Example 1 were obtained through... Figure 2 and Figure 3 It can be seen that the X-ray detector prepared in Example 1 showed relatively small changes in photocurrent and dark current during multiple irradiations. In contrast, the X-ray detector prepared in Comparative Example 1 showed more significant changes in photocurrent and significantly larger dark current under the same conditions.

[0046] The above are merely preferred embodiments of the present invention, but the scope of protection of the present invention is not limited thereto. Any variations or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. An X-ray detector based on narrow-bandgap perovskite and wide-bandgap perovskite heterojunctions, characterized in that, It includes a metal electrode layer, a rare earth oxide layer, a three-dimensional narrow bandgap perovskite layer-three-dimensional wide bandgap perovskite layer heterojunction, a rare earth oxide layer, and a metal electrode layer stacked sequentially.

2. The X-ray detector based on narrow-bandgap perovskite and wide-bandgap perovskite heterojunction according to claim 1, characterized in that, All metal electrode layers are chromium metal electrode layers; All rare earth oxide layers are erbium oxide layers; In the heterojunction of the three-dimensional narrow bandgap perovskite layer-three-dimensional wide bandgap perovskite layer, the three-dimensional narrow bandgap perovskite layer is a lead-tin methylamine perovskite layer, and the three-dimensional wide bandgap perovskite layer is a lead-tin methylamine perovskite layer.

3. The X-ray detector based on narrow-bandgap perovskite and wide-bandgap perovskite heterojunction according to claim 2, characterized in that, The thickness of each metal electrode layer is 120 nm; The thickness of each rare earth oxide layer is 100 nm. The thickness of the heterojunction of the three-dimensional narrow bandgap perovskite layer-three-dimensional wide bandgap perovskite layer is 2.5 mm, wherein the thickness of the three-dimensional narrow bandgap perovskite layer is 0.5 mm-1 mm, and the thickness of the three-dimensional wide bandgap perovskite layer is 1-1.5 mm.

4. A method for fabricating an X-ray detector based on a narrow-bandgap perovskite and a wide-bandgap perovskite heterojunction as described in any one of claims 1-3, characterized in that, Includes the following steps: S1. Place the wide-bandgap perovskite crystal in a narrow-bandgap perovskite precursor solution, and use the reverse temperature crystallization method to grow narrow-bandgap perovskite on the surface of the wide-bandgap perovskite crystal to form a heterostructure. S2. After cutting and polishing the heterostructure, a three-dimensional narrow bandgap perovskite layer-three-dimensional wide bandgap perovskite layer heterojunction is obtained. S3. Rare earth oxide layers and metal electrode layers are sequentially deposited on the top and bottom surfaces of the three-dimensional narrow bandgap perovskite layer-three-dimensional wide bandgap perovskite layer heterojunction to prepare the X-ray detector based on the narrow bandgap perovskite and wide bandgap perovskite heterojunction.

5. The preparation method according to claim 4, characterized in that, In step S1, the wide-bandgap perovskite crystal is a single crystal of lead bromide methylamine perovskite. The preparation method of the single crystal of lead bromide methylamine perovskite includes the following steps: adding isopropanol to a mixed organic solution of lead bromide and methylamine bromide, stirring evenly and filtering to obtain a precursor solution, and obtaining a seed crystal after a first heating; placing the seed crystal into a homogeneous precursor solution and heating a second time to prepare the single crystal of lead bromide methylamine perovskite.

6. The preparation method according to claim 5, characterized in that, The ratio of lead bromide, methylammonium bromide, and isopropanol is 4.59 g: 1.388 g: 100 μL; The initial heating temperature is 90°C; The temperature of the secondary heating is 44-52℃.

7. The preparation method according to claim 4, characterized in that, In step S1, the narrow bandgap perovskite precursor solution is a lead-tin methylamine perovskite precursor solution. The preparation method of the lead-tin methylamine perovskite precursor solution includes the following steps: mixing lead-tin methylamine perovskite powder, tin powder, formamidinium sulfinyl D salt and N,N-dimethylformamide, passing argon gas through, stirring to dissolve and filtering to obtain the lead-tin methylamine perovskite precursor solution.

8. The preparation method according to claim 7, characterized in that, The ratio of the amount of lead bromotin methylamine perovskite powder, tin powder, formamidinium sulfinyl D salt and N,N dimethylformamide is 4.5g:20mg:25mg:6mL.

9. The preparation method according to claim 4, characterized in that, In step S1, the temperature of the reverse temperature crystallization method is 32℃-40℃.

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