Three-dimensional / quasi-two-dimensional perovskite thick film heterojunction and preparation method and application thereof

Abstract

The present application provides a three-dimensional / quasi-two-dimensional perovskite thick film heterojunction, its preparation method and application, belonging to the technical field of X-ray detection. It includes a three-dimensional perovskite and a quasi-two-dimensional perovskite thick film; the component of the three-dimensional perovskite thick film is MA a FA 1‑a PbI3, where 0 < a < 1; the component of the quasi-two-dimensional perovskite is A m A’ n‑1 B n X 3n+1 , the component A includes one or two of FA and MA, the component A’ includes a DJ-type amine or an RP-type amine, the component B is a lead atom Pb, the component X is one or more of halogen atoms I, Br, Cl, n is an integer greater than 1, m = 1 when the component A’ is a DJ-type amine, and m = 2 when the component A’ is an RP-type amine. By precisely regulating the n value of the upper interface two-dimensional perovskite, reducing the content of the n = 1 component, increasing the proportion of the large n value, promoting charge separation and transport at the interface, and then improving the collection efficiency of photo-generated carriers; at the same time, the high-energy band barrier of the quasi-two-dimensional structure can inhibit the leakage current injection in the dark state, thereby reducing the dark current, and finally significantly improving the sensitivity and signal-to-noise ratio of the device.

Description

Technical Field

[0001] This invention relates to the field of X-ray detection technology, specifically to a three-dimensional / quasi-two-dimensional perovskite thick film heterojunction, its preparation method, and its application. Background Technology

[0002] X-ray detectors are widely used in medical imaging, security inspection, and industrial testing. Lead halide perovskite materials possess excellent X-ray absorption cross-sections, high mobility-lifetime values ​​(high μτ product), and strong radiation stability, making them outstanding radiation detection materials. Furthermore, their low-cost solution-based fabrication process meets the practical needs of large-area integration, demonstrating broad application prospects. Direct detection based on perovskite materials utilizes the absorption of X-rays by the perovskite semiconductor, directly converting them into electrical signals. Electric field-driven charge-directed transport ensures high spatial resolution, representing the future direction of low-dose, high-resolution X-ray imaging. Compared to single-crystal perovskite materials, solution-based polycrystalline thick-film systems offer advantages such as easy area scaling and circuit integration, making them highly promising for flat-panel detectors.

[0003] To ensure effective X-ray absorption and imaging applications, perovskite films need to be over 100 micrometers thick (>100 μm). However, current methods for preparing thick perovskite films and constructing devices face the following challenges: 1. The thick film preparation method is acceptable: Most methods for preparing perovskite thick films larger than 100 micrometers use a supersaturated suspension of perovskite (concentration ~5 mol / L) for blade coating. This method suffers from intrinsic problems such as difficulty in mass transfer, difficulty in controlling nucleation and growth, and multi-component segregation, making it difficult to obtain high-quality grains and resulting in severe carrier recombination. At the same time, solvent evaporation during the preparation process forms a large number of pores, resulting in a loose and porous structure of the thick film (pore diameter ~20 μm). During the compaction process, grain breakage and film layer delamination lead to difficulties in array integration and poor electrical contact.

[0004] 2. Shortcomings in thick film structure construction: Three-dimensional perovskite materials have low resistivity (10). 6 ~10 7 The high dark current density (<1 nA·cm) due to severe ion migration leads to excessively high dark current, high noise, poor stability, and high detection limit in the detector, making it difficult to meet the dark current density (<1 nA·cm) required for commercial transistor arrays (TFTs). -2Two-dimensional perovskites, with their alternating lead halide inorganic and organic cation layers, possess interlayer quantum well structures that effectively enhance resistivity and reduce dark current. In recent years, constructing dimensional heterojunctions using two-dimensional and three-dimensional perovskites has become a research hotspot. By controlling the interface energy level matching of the heterojunction, good carrier extraction in the optical state can be ensured, while suppressing dark current injection. However, a high potential barrier (>0.3 eV) often exists between three-dimensional and two-dimensional perovskite heterojunctions, resulting in energy loss during carrier gap transitions. This affects the carrier collection efficiency of thick-film systems, leading to detector photocurrent loss, reduced device sensitivity, and limiting the minimum detection limit. Summary of the Invention

[0005] In view of the technical problems existing in the background art, this application employs a solvent evaporation method to construct a high-density, high-quality three-dimensional perovskite film, and uses thermal evaporation / liquid-phase reaction to prepare a quasi-two-dimensional perovskite thick film on the interface of the three-dimensional perovskite thick film, constructing a three-dimensional / quasi-two-dimensional thick film dimensional heterojunction structure. This aims to improve carrier collection at the interface while suppressing dark current in the device, thereby obtaining a highly sensitive and high-contrast detection device. The application aims to solve the following problems: 1. Traditional coating methods for preparing three-dimensional perovskite thick films are difficult to obtain high-quality, high-density films. Problems such as grain breakage and film detachment during the later pressing and densification process of porous perovskite thick films cause difficulties in array integration. 2. The high potential barrier difference (>0.3 eV) between the three-dimensional and two-dimensional perovskite dimensional heterojunctions leads to energy loss during carrier gap transitions, affecting the carrier collection efficiency of the thick film system, resulting in detector photocurrent loss, reduced device sensitivity, and limiting the minimum detection limit.

[0006] In a first aspect, embodiments of this application provide a three-dimensional / quasi-two-dimensional perovskite thick film heterostructure, including a three-dimensional perovskite thick film and a quasi-two-dimensional perovskite; The composition of the three-dimensional perovskite thick film is MA a FA 1-a PbI3, where 0 <a<1; The composition of the quasi-two-dimensional perovskite is A m A' n-1 B n X 3n+1 Component A includes one or two of FA and MA, component A' includes DJ-type amine or RP-type amine, component B is lead atom Pb, component X is one or more of halogen atom I, Br, Cl, n is an integer greater than 1, when component A' is DJ-type amine, m=1, when component A' is RP-type amine, m=2; RP-type amines include one or both of phenylethylamine and butylamine, while DJ-type amines include one or both of N,N-dimethyl-1,3-propanediamine and 1,4-phenylenediamine.

[0007] Secondly, embodiments of this application provide a method for preparing a three-dimensional / quasi-two-dimensional perovskite thick-film heterostructure, comprising the following steps: S1. Preparation of three-dimensional perovskite thick film: DMePDADI2 (N,N-dimethyl-1,3-propanediamine hydroiodate), MAI (methylamine iodide), FAI (formamidinium hydroiodate), PbI2 and GBL (γ-butyrolactone) were used to prepare a perovskite microcrystalline thick film growth solution. The substrate was placed in the growth solution and grains were grown by solvent evaporation. After the grain growth was completed, annealing was performed to obtain a three-dimensional perovskite thick film, forming a substrate / 3D thick film structure. S2. Mix component A, component A' and solvent, heat and stir to dissolve to obtain a three-dimensional perovskite thick film surface treatment solution. Component A is one or two of FAI and MAI. Component A' includes RP (Ruddlesden–Popper) molecules or DJ (Dion-Jacobson) molecules. RP molecules include one or more of BAI (butylammonium iodide), PEAI (phenylethylammonium iodide), and PEABr (phenylethylammonium bromide). DJ molecules include one or two of PhIDMADBr (1,4-phenylenediamine hydrobromide) and DMePDAI2 (N,N-dimethyl-1,3-propanediamine hydroiodide). S3. PbI2 is deposited on the surface of the substrate / 3D thick film structure using a thermal evaporation process, and then immersed and annealed in a surface treatment solution to obtain the substrate / 3D / Quasi-2D structure.

[0008] In the technical solution of this application embodiment, firstly, a perovskite-PVP polycrystalline layer is spin-coated to increase nucleation sites and reduce the nucleation barrier; the solvent is evaporated at 90 °C to increase the supersaturation of the solution, and nucleation is mediated on the polycrystalline layer by chemical deposition; a high-density three-dimensional perovskite thick film (100~500 μm) is prepared by grain ripening and fusion through hot-stage annealing for 3h~9h; then, PbI2 (1~5 μm) is evaporated on the three-dimensional interface as the upper reaction medium; finally, through the interface post-treatment liquid phase reaction method, a non-polar solvent is selected to dissolve different proportions of A and A' molecules, and three-dimensional and quasi-two-dimensional heterojunctions are constructed without destroying the underlying three-dimensional interface.

[0009] Preferably, the concentration of the perovskite microcrystalline thick film growth solution is 1~2 mol / L.

[0010] Preferably, the solvent evaporation method includes the following steps: after preparing the perovskite microcrystalline thick film growth solution, filtering it, placing the substrate in the growth solution at a temperature of 90~95 ℃, allowing the solvent to gradually evaporate to supersaturation and crystallize. After the first crystal precipitates, for 40~60 min, the substrate is placed in the growth solution for grain growth for 1~1.5 h; after the grain growth is completed, annealing is performed to obtain a three-dimensional perovskite thick film.

[0011] Preferably, the thickness of the three-dimensional perovskite thick film is 100~500 μm.

[0012] Preferably, the solvent in step S2 comprises the following components in volume fractions: IPA 98%~99%, DMF 1%~2%.

[0013] Preferably, the thickness of PbI2 deposited in step S3 is 1~5 μm.

[0014] Thirdly, embodiments of this application provide an X-ray detector device, comprising a glass substrate, an electron transport layer, a PVP (polyvinylpyrrolidone) & PEG (polyethylene glycol) induced adhesion layer, a three-dimensional / quasi-two-dimensional perovskite thick film heterojunction, and electrodes, which are sequentially stacked.

[0015] Fourthly, embodiments of this application provide a method for fabricating an X-ray detector device, comprising the following steps: (1) Clean the ITO glass substrate; (2) Electron transport layer preparation: SnO2 solution was spin-coated on an ITO glass substrate and annealed to obtain an electron transport layer, thus preparing an ITO / SnO2 structure; (3) Preparation of PVP-induced adhesive layer: A precursor solution was prepared using polymers PVP, PEG, PbI2, MAI and DMF. The precursor solution was spin-coated on the electron transport layer for 40~60 s to form a precursor solution layer. Chlorobenzene was added dropwise to the precursor solution layer, and spin-coating was continued for 20~30 s. After standing for 3~9 h, the layer was annealed to obtain the induced adhesive layer and prepare the ITO / SnO2 / adhesive layer structure. (4) A three-dimensional / quasi-two-dimensional perovskite thick film heterojunction was prepared on the ITO / SnO2 / adhesive layer structure according to the above method, and an ITO / SnO2 / adhesive layer / 3D / Quasi-2D structure was prepared. (5) An Au electrode was deposited on the surface of the ITO / SnO2 / adhesive layer / 3D / Quasi-2D structure to prepare an ITO / SnO2 / adhesive layer / 3D / Quasi-2D / Au structure detector device.

[0016] Preferably, in step (3), the molecular weight of the polymer PVP is 5000~50000 and the molecular weight of PEG is 200-1000. 0.1~0.3g PVP and 0.04~0.12g PEG are added to every 10mL of DMF in the precursor solution. The concentrations of PbI2 and MAI in the precursor solution are both 0.3~0.6mol / L.

[0017] The advantages of this application, which differ from existing technical solutions, include: 1. This application employs a three-step method of solvent evaporation / thermal evaporation / liquid phase reaction. First, a high-density three-dimensional perovskite thick film is prepared on the substrate through reverse-temperature nucleation, on-chip polycrystalline mediated film formation, and grain ripening and fusion. Then, PbI2 is deposited on the three-dimensional interface as the upper reaction medium. Finally, a three-dimensional and quasi-two-dimensional heterojunction is constructed without damaging the underlying three-dimensional interface through an interface post-processing liquid phase reaction method.

[0018] This application achieves a reduction in the content of the n=1 component and an increase in the proportion of high n-value components by precisely controlling the n-value of the two-dimensional perovskite at the upper interface. Different n-values ​​result in different band gaps in each layer, leading to a stepped arrangement of energy bands (gradient band gap). This causes directional energy changes in photogenerated charges (electrons and holes) between different layers. By using a heterojunction structure and laminating perovskite materials with different band gaps together to form a gradient energy band, when the device is irradiated by light or X-rays, the generated electrons migrate from the high-energy (high band gap) region to the low-energy (low band gap) region, while holes move in the opposite direction. This band gradient effectively separates electrons and holes, reducing the possibility of recombination, thereby optimizing charge separation and transport. This improves carrier extraction efficiency in the light state while suppressing dark current injection in the dark state, significantly improving device sensitivity and signal-to-noise ratio.

[0019] 2. This method is applicable to different types of two-dimensional components (RP (Ruddlesden–Popper), DJ (Dion-Jacobson) components) and lead halide components, and has universal application value.

[0020] The above description is only an overview of the technical solution of this application. In order to better understand the technical means of this application and to implement it in accordance with the contents of the specification, and to make the above and other objects, features and advantages of this application more obvious and understandable, the following are specific embodiments of this application. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of this application, the accompanying drawings used in this application will be briefly described below. Obviously, the drawings described below are merely some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without any creative effort.

[0022] Figure 1 This is a schematic diagram comparing the advantages of the three-dimensional / quasi-two-dimensional perovskite thick film heterojunction compared to the three-dimensional / two-dimensional perovskite thick film heterojunction of this application. Figure 1 (a) in the figure is a schematic diagram of electron and hole transitions in a three-dimensional / quasi-two-dimensional perovskite thick film heterostructure; Figure 1 (b) is a schematic diagram of electron and hole transitions within a three-dimensional / two-dimensional perovskite thick film heterostructure. Figure 2 This is a high-magnification microscope cross-sectional view of the thermally evaporated PbI2 thick film in Embodiment 1 of this application; Figure 3 This is a cross-sectional SEM image of the three-dimensional / quasi-two-dimensional perovskite thick film heterojunction in Embodiment 1 of this application; Figure 4 This is an EDS line scan of the cross-section of the three-dimensional / quasi-two-dimensional perovskite thick film heterojunction in Embodiment 1 of this application; Figure 5 These are the surface PL maps of the three-dimensional perovskite thick film, the three-dimensional / quasi-two-dimensional perovskite thick film heterojunction in Example 1 of this application, and the three-dimensional / two-dimensional perovskite thick film heterojunction in Comparative Example 1. Figure 6 These are It curves of the X-ray detector devices in Embodiment 2 and Comparative Example 2 of this application; Figure 7 These are the X-ray dose rate - device response photocurrent curves of the X-ray detector devices in Embodiment 2 and Comparative Example 2 of this application.

[0023] Figure 8 These are the net photocurrent versus voltage curves of the X-ray detector devices in Embodiment 2 and Comparative Example 2 of this application. Detailed Implementation

[0024] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0026] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0027] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0028] In the description of the embodiments of this application, the term "multiple" refers to two or more (including two), similarly, "multiple sets" refers to two or more (including two sets), and "multiple pieces" refers to two or more (including two pieces).

[0029] Currently, the following problems exist in the fabrication methods and device construction of perovskite thick films: 1. The thick film preparation method is acceptable: Most methods for preparing perovskite thick films larger than 100 micrometers use a supersaturated suspension of perovskite (concentration ~5 mol / L) for blade coating. This method suffers from intrinsic problems such as difficulty in mass transfer, difficulty in controlling nucleation and growth, and multi-component segregation, making it difficult to obtain high-quality grains and resulting in severe carrier recombination. At the same time, solvent evaporation during the preparation process forms a large number of pores, resulting in a loose and porous structure of the thick film (pore diameter ~20 μm). During the compaction process, grain breakage and film layer delamination lead to difficulties in array integration and poor electrical contact.

[0030] 2. Shortcomings in thick film structure construction: Three-dimensional perovskite materials have low resistivity (10). 6 ~10 7 The high dark current density (<1 nA·cm) due to severe ion migration leads to excessively high dark current, high noise, poor stability, and high detection limit in the detector, making it difficult to meet the dark current density (<1 nA·cm) required for commercial transistor arrays (TFTs). -2 Two-dimensional perovskites, with their alternating lead halide inorganic and organic cation layers, possess interlayer quantum well structures that effectively enhance resistivity and reduce dark current. In recent years, constructing dimensional heterojunctions using two-dimensional and three-dimensional perovskites has become a research hotspot. By controlling the interface energy level matching of the heterojunction, good carrier extraction in the optical state can be ensured, while suppressing dark current injection. However, a high potential barrier (>0.3 eV) often exists between three-dimensional and two-dimensional perovskite heterojunctions, resulting in energy loss during carrier gap transitions. This affects the carrier collection efficiency of thick-film systems, leading to detector photocurrent loss, reduced device sensitivity, and limiting the minimum detection limit.

[0031] To address the challenges of obtaining high-quality grains in three-dimensional perovskite thick films, severe carrier recombination, grain breakage and film detachment during the compaction process leading to difficulties in array integration and poor electrical contact, and the high potential barrier difference (>0.3 eV) between three-dimensional and two-dimensional perovskite heterojunctions resulting in energy loss during carrier gap transitions, which affects the carrier collection efficiency of thick film systems, leads to detector photocurrent loss, reduces device sensitivity, and limits the minimum detection limit, this application provides a three-dimensional / quasi-two-dimensional perovskite thick film heterojunction, its preparation method, and its application. Specifically, a high-density three-dimensional perovskite thick film (100~500 μm) is prepared on a conductive substrate through a three-step method of inverse-temperature crystallization / thermal evaporation / liquid-phase reaction, involving inverse-temperature nucleation, on-chip polycrystalline mediated film formation, and grain ripening and fusion. PbI2 (1~5 μm) was then deposited on the three-dimensional interface. Different proportions of A sites and components A' were dissolved in a non-polar solvent by means of interface post-treatment liquid phase reaction. Component A is methylamine, formamidinium, etc., and A' is phenylethylamine, butylamine, N,N-dimethyl-1,3-propanediamine hydroiodide, etc., to construct three-dimensional and quasi-two-dimensional heterojunctions without damaging the underlying three-dimensional interface.

[0032] This application achieves this by precisely controlling the n-value of the two-dimensional perovskite on the upper surface, reducing the content of the n=1 component and increasing the proportion of high n-value components. Different n-values ​​result in different band gaps in each layer, leading to a stepped arrangement of energy bands (gradient band gap). This causes directional energy changes in photogenerated charges (electrons and holes) between different layers. By employing a heterojunction structure and laminating perovskite materials with different band gaps together to form a gradient energy band, when the device is irradiated by light or X-rays, the generated electrons migrate from the high-energy (high band gap) region to the low-energy (low band gap) region, while holes move in the opposite direction. This band gradient effectively separates electrons and holes, reducing the possibility of recombination, thereby optimizing charge separation and transport. This improves carrier extraction efficiency in the light state while suppressing dark current injection in the dark state, significantly improving device sensitivity and signal-to-noise ratio.

[0033] In a first aspect, embodiments of this application provide a three-dimensional / quasi-two-dimensional perovskite thick film heterostructure, including a three-dimensional perovskite thick film and a quasi-two-dimensional perovskite; The composition of the three-dimensional perovskite thick film is MA a FA 1-a PbI3, where 0 <a<1; The composition of the quasi-two-dimensional perovskite is A m A' n-1 B n X 3n+1Component A includes one or both of FA and MA, component A' includes DJ-type amine or RP-type amine, component B is lead atom Pb, component X is iodine atom I, n is an integer greater than 1, when component A' is DJ-type amine m=1, when component A' is RP-type amine m=2; RP-type amines include one or both of phenylethylamine and butylamine, while DJ-type amines include one or both of N,N-dimethyl-1,3-propanediamine and 1,4-phenylenediamine.

[0034] Secondly, embodiments of this application provide a method for preparing a three-dimensional / quasi-two-dimensional perovskite thick-film heterostructure, comprising the following steps: S1. Preparation of three-dimensional perovskite thick film: DMePDADI2, MAI, FAI, PbI2 and GBL were mixed and heated and stirred on a hot stage at 60℃ for 8 hours to prepare a perovskite microcrystalline thick film growth solution; the substrate was placed in the growth solution and grains were grown by solvent evaporation. After the grain growth was completed, the substrate was taken out of the growth solution, wiped dry with a lint-free cloth, and placed on a hot stage at 100℃ for 8 hours to anneal, thus obtaining a three-dimensional perovskite thick film and forming a substrate / 3D thick film structure. S2. Mix component A, component A' and solvent, and stir at 50°C for 4 hours to obtain a three-dimensional perovskite thick film surface treatment solution. Component A is one or two of FAI and MAI, and component A' includes RP molecules or DJ molecules. RP molecules include one or more of BAI, PEAI and PEABr, and DJ molecules include one or two of PhIDMADBr and DMePDAI2. S3. Wipe the back of the substrate / 3D thick film structure clean with ethanol, scrape off the thick film around the perimeter with a scraper, and perform surface pretreatment by evaporating PbI2 onto the surface using a thermal evaporation process. Then, immerse the structure in the surface treatment solution at 50 °C for 20-60 min on a hot table, and anneal it at 50 °C for 1 h to obtain the substrate / 3D / Quasi-2D structure.

[0035] The preferred concentration of the perovskite microcrystalline thick film growth solution is 1~2 mol / L.

[0036] The preferred solvent evaporation method includes the following steps: after preparing the perovskite microcrystalline thick film growth solution, filter it, put the substrate into the growth solution at a temperature of 90~95 ℃, and allow the solvent to gradually evaporate to reach supersaturation and crystallize. After the first crystal precipitates, 40~60 min later, put the substrate into the growth solution for grain growth for 1~1.5 h; after the grain growth is completed, annealing is performed to obtain a three-dimensional perovskite thick film.

[0037] In the technical solution of this application embodiment, after the first crystal precipitates, another 40-60 minutes are elapsed. The crystals in the crystal growth solution grow to approximately 1 mm in diameter, but the solution has not yet reached the state of explosive crystallization. At this time, the substrate is placed in the crystal growth solution, allowing the crystals to grow on the substrate until a film is formed on the substrate surface. The film thickness is positively correlated with the crystal growth time. A 200 μm surface film typically requires a crystal growth time of 1-1.5 hours, and the film thickness can be adjusted according to the growth time.

[0038] Preferably, the thickness of the three-dimensional perovskite thick film is 100~500 μm.

[0039] Preferably, the solvent in step S2 comprises the following components in volume fractions: IPA 98%~99%, DMF 1%~2%.

[0040] Preferably, the thickness of PbI2 deposited in step S3 is 1~5 μm.

[0041] In the technical solution of this application embodiment, the perovskite microcrystalline thick film growth solution is heated at 90~95 °C to gradually evaporate the solvent and increase the concentration of the solution. After the growth solution reaches supersaturation, crystallization occurs, and crystal nuclei are formed in the growth solution. After the crystal nuclei in the growth solution grow to a certain number, the substrate is placed in the growth solution for polycrystalline mediated film formation. After the grains on the substrate grow to a certain thickness, the substrate is taken out, annealed, and the grains are ripened and fused to obtain a three-dimensional perovskite thick film. The obtained three-dimensional perovskite thick film has a high-quality, high-density thick film structure with performance no less than that of a single crystal.

[0042] PbI2 is prepared by vapor deposition without damaging the underlying perovskite thick film. PbI2 and A, A' form a quasi-two-dimensional thick film through interface treatment and medium liquid phase reaction, which forms a heterojunction with the dense perovskite thick film prepared by solvent evaporation.

[0043] PbI2 (1~5 μm) was deposited at a three-dimensional interface. Different proportions of A sites and components A' were dissolved in a non-polar solvent by means of a post-interface liquid-phase reaction. Component A was methylamine, formamidinium, etc., and A' was phenylethylamine, butylamine, N,N-dimethyl-1,3-propanediamine hydroiodide, etc., to construct three-dimensional and quasi-two-dimensional heterojunctions without damaging the underlying three-dimensional interface.

[0044] This application reduces the ratio of 2D ligands to A'-position cations by using component A (MAI, FAI), and introduces PbI2 directly from the 3D perovskite surface by adding DMF to the solvent, resulting in a more PbI2-rich surface suitable for ammonium ligand intercalation, which can generate a 2D perovskite layer containing n ≥ 3.

[0045] Figure 1In section a, a three-dimensional / two-dimensional perovskite thick film surface treatment solution containing only component A, without the addition of component A', is used to prepare a three-dimensional / quasi-two-dimensional perovskite thick film heterojunction. An X-ray detector device is fabricated using this three-dimensional / quasi-two-dimensional perovskite thick film heterojunction. Figure 1 As can be seen from a, the two-dimensional perovskite prepared by this method has only a component with n=1. There is a high potential barrier between the two-dimensional perovskite and the three-dimensional perovskite. There is energy loss during the transition between the carrier gaps under the high potential barrier, which affects the carrier transport performance of the three-dimensional perovskite thick film system. Figure 1 b represents the preparation of a three-dimensional perovskite thick film surface treatment solution using components A and A' in this application, followed by the construction of a three-dimensional / quasi-two-dimensional perovskite thick film heterojunction, and the fabrication of an X-ray detector device using this three-dimensional / quasi-two-dimensional perovskite thick film heterojunction. Figure 1 As shown in section b, this application precisely controls the n-value of the quasi-two-dimensional perovskite on the upper surface, reducing the content of the n=1 component and increasing the proportion of large n-values ​​(n=2 and n=3). Different n-values ​​result in different band gaps in each layer, leading to a stepped arrangement of energy bands (gradient band gap), which causes directional energy changes in photogenerated charges (electrons and holes) between different layers. By using a heterojunction structure to laminate perovskite materials with different band gaps together, a gradient energy band is formed. When the device is irradiated by light or X-rays, the generated electrons migrate from the high-energy (high band gap) region to the low-energy (low band gap) region, while holes move in the opposite direction. This band gradient effectively separates electrons and holes, reducing the possibility of recombination, thereby optimizing charge separation and transport. This improves carrier extraction efficiency in the light state while suppressing dark current injection in the dark state, significantly improving device sensitivity and signal-to-noise ratio.

[0046] Thirdly, embodiments of this application provide an X-ray detector device, comprising a glass substrate, an electron transport layer, an adhesive layer, a three-dimensional / quasi-two-dimensional perovskite thick film heterojunction, and electrodes stacked sequentially.

[0047] Fourthly, embodiments of this application provide a method for fabricating an X-ray detector device, comprising the following steps: (1) Clean the ITO glass substrate; (2) Electron transport layer preparation: SnO2 solution was spin-coated on an ITO glass substrate and annealed to obtain an electron transport layer, thus preparing an ITO / SnO2 structure; (3) Preparation of PVP-induced adhesive layer: A precursor solution was prepared using polymers PVP, PEG, PbI2, MAI and DMF. The precursor solution was spin-coated on the electron transport layer for 40~60 s to form a precursor solution layer. Chlorobenzene was added dropwise to the precursor solution layer, and spin-coating was continued for 20~30 s. After standing for 3~9 h, the layer was annealed to obtain the PVP-induced adhesive layer and prepare the ITO / SnO2 / adhesive layer structure. (4) A three-dimensional / quasi-two-dimensional perovskite thick film heterojunction was prepared on the ITO / SnO2 / adhesive layer structure according to the above method, and an ITO / SnO2 / adhesive layer / 3D / Quasi-2D structure was prepared. (5) An Au electrode was deposited on the surface of the ITO / SnO2 / adhesive layer / 3D / Quasi-2D structure to prepare an ITO / SnO2 / adhesive layer / 3D / Quasi-2D / Au structure detector device.

[0048] In the technical solution of this application embodiment, a polymer PVP-doped perovskite film is prepared on the SnO2 electron transport layer. On the one hand, the functional groups in the polymer PVP & PEG can form bonds with atoms or molecules on the surface of the underlying ITO glass substrate (such as amino, hydroxyl, carboxyl and other functional groups can form hydrogen bonds or covalent bonds with oxygen atoms on the ITO surface), thereby enhancing adhesion and buffering interfacial stress during annealing heating, thus solving the problem of film peeling caused by film shrinkage due to annealing heat during thick film preparation. On the other hand, the addition of MAI and PbI2 to the polymer to react and form MAPbI3 perovskite, and the doping of perovskite in the polymer also reduces the nucleation free energy of the upper interface, which is conducive to the nucleation and growth of the upper three-dimensional perovskite grains.

[0049] Preferably, in step (3), the molecular weight of the polymer PVP is 5000~50000 and the molecular weight of PEG is 200-1000. 0.1~0.3 g of PVP and 0.04~0.12 g of PEG are added to every 10 mL of DMF in the precursor solution. The concentrations of PbI2 and MAI in the precursor solution are both 0.3~0.6 mol / L.

[0050] The following are some specific embodiments. It should be noted that the embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they shall be performed in accordance with the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments whose manufacturers are not specified are all conventional products that can be obtained commercially.

[0051] I. Preparation Method Example 1 A method for preparing a three-dimensional / quasi-two-dimensional perovskite thick film heterostructure includes the following steps: (1) Preparation of three-dimensional perovskite thick film: 0.256g DMePDADI2, 1.228g MAI, 1.136g FAI, 6.914g PbI2 and 10 mL GBL were mixed and heated and stirred on a hot stage at 60℃ for 8h to prepare a 1.5 mol / L perovskite microcrystalline thick film growth solution; in a glove box, the thick film growth solution was filtered with a 0.45 μm nylon filter. The substrate was placed in the growth solution and crystallized after the solvent gradually evaporated to supersaturation at a temperature of 90~95 ℃. After the first crystal precipitated for 1h, the substrate was placed in the growth solution for grain growth for 1h; after the grain growth was completed, the substrate was annealed to obtain a three-dimensional perovskite thick film with a thickness of 100~500 μm, forming a substrate / 3D thick film structure; (2) Mix 0.2 g of MAI, 0.235 g of PEAI and solvent, and stir at 50 °C for 4 h to obtain a 20 mg / mL three-dimensional perovskite thick film surface treatment solution. The molar ratio of component A (MAI) and component A' (PEAI) is 1:1. The solvent includes 9.8 mL of IPA and 0.2 mL of DMF. (3) Wipe the back of the substrate / 3D thick film structure clean with ethanol, scrape off the thick film around the perimeter with a scraper, and perform surface pretreatment by evaporating PbI2 on the surface using a thermal evaporation process. Then, immerse the surface in the surface treatment solution at 50°C for 40 minutes and remove it. Anneal at 50°C for 1 hour to obtain a three-dimensional / quasi-two-dimensional perovskite thick film heterojunction and prepare the substrate / 3D / Quasi-2D structure.

[0052] Example 2 A method for fabricating an X-ray detector device includes the following steps: (1) Clean the ITO glass substrate and etch the ITO to an area of ​​2.5 × 2.5 cm. 2 The quartz glass was removed, cleaned with glass cleaning solution, sonicated with pure water for 30 minutes, and then sonicated with anhydrous ethanol for 30 minutes. It was then removed for use, and the ITO glass cleaning was completed. (2) Electron transport layer preparation: 2 mL of tin oxide solution was mixed with 1 mL of pure water, filtered twice through a 0.22 μm nylon filter, and sonicated for 30 min to obtain the electron transport layer spin-coating solution. 320 μL of the solution was uniformly dropped onto an ITO glass substrate treated with ozone for 30 min, and spin-coated at 3200 rpm for 1 min. The electrode area was gently wiped with anhydrous ethanol, then annealed at 150℃ for 1 h, and naturally cooled to prepare the ITO / SnO2 structure. The molecular weight of the polymer PVP was 5000~50000, and the molecular weight of PEG was 200-1000. 0.1~0.3 g of PVP and 0.04~0.12 g of PEG were added to every 10 mL of DMF in the precursor solution. The concentrations of PbI2 and MAI in the precursor solution were both 0.3~0.6 mol / L.

[0053] (3) Preparation of PVP-induced adhesive layer: 0.15 g of polymer PVP (molecular weight 24000), 0.06 g of PEG (molecular weight 200), 2.766 g of perovskite PbI2, 0.954 g of MAI and 10 mL of DMF were added to the polymer to prepare a 1.5 mol / L precursor solution. The solution was heated and stirred on a hot table at 65 ℃ for 8 h for later use. The SnO2 electron transport layer was treated with ozone for 30 min. Then, the seed layer solution was spin-coated in a glove box. 320 μL of precursor solution was taken, filtered through a 0.45 μL nylon filter, and uniformly dropped onto the glass. The spin coating was carried out at 600 rpm for 20 s, followed by 2000 rpm for 20 s. 400 μL of anhydrous chlorobenzene was then uniformly dropped onto the center of the glass to induce explosive nucleation of the seed layer. After spin coating at 2000 rpm for 20 s, the mixture was allowed to stand for 3 h, followed by annealing at 100℃ for 1 h. A 1.5 μm induced binder layer was prepared by spin coating, forming an ITO / SnO2 / binder layer structure. (4) Preparation of three-dimensional perovskite thick film: 0.256g DMePDADI2, 1.228g MAI, 1.136g FAI, 6.914g PbI2 and 10mL GBL were mixed and heated and stirred on a hot stage at 60℃ for 8h to prepare a 1.5 mol / L perovskite microcrystalline thick film growth solution; in a glove box, the thick film growth solution was filtered with a 0.45 μm nylon filter. The substrate was placed in the growth solution and crystallized after the solvent gradually evaporated to supersaturation at a temperature of 90~95℃. After the first crystal precipitated for 1h, the substrate was placed in the growth solution for grain growth for 1h; after the grain growth was completed, the substrate was annealed to obtain a three-dimensional perovskite thick film with a thickness of 100~500μm, forming an ITO / SnO2 / binder layer / 3D thick film structure; (5) Mix 0.2 g of MAI, 0.235 g of PEAI and solvent, and stir at 50 °C for 4 h to obtain a 20 mg / mL three-dimensional perovskite thick film surface treatment solution. The molar ratio of component AMAI and component A' to PEAI is 1:1. The solvent includes 9.8 mL of IPA and 0.2 mL of DMF. (6) Wipe the back of the ITO / SnO2 / adhesive layer / 3D thick film structure clean with ethanol, scrape off the thick film around the perimeter with a scraper, pre-treat the surface by depositing PbI2 on the surface using a thermal evaporation process, then immerse it in the surface treatment solution at 50°C for 40 min on a hot table, and then anneal it at 50°C for 1 h on a hot table to obtain the ITO / SnO2 / adhesive layer / 3D / Quasi-2D structure.

[0054] (7) The prepared ITO / SnO2 / binder / 3D / Quasi-2D structure was covered with a specific mask, and a 100 nm thick Au electrode was deposited by thermal evaporation to obtain an X-ray detector device with an ITO / SnO2 / binder / 3D / Quasi-2D / Au structure and an electrode area of ​​0.0706 cm². 2 .

[0055] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that, in the preparation of the three-dimensional perovskite thick film surface treatment solution, component A is MAI, and component A' is not added; the other steps are the same as in Example 1. 0.2 g of MAI was dispersed in 10 mL of isopropanol to prepare a 20 mg / mL three-dimensional perovskite thick film surface treatment solution. The solution was then used to treat the three-dimensional perovskite thick film to form a three-dimensional / quasi-two-dimensional perovskite thick film heterojunction.

[0056] Comparative Example 2 The difference between Comparative Example 2 and Example 2 is that no quasi-two-dimensional perovskite is covered on the three-dimensional perovskite thick film. The other steps are the same as in Example 2, and an X-ray detector device with an ITO / SnO2 / binder / 3D / Au structure is prepared.

[0057] II. Testing Methods 1. SEM image detection method The SEM was performed using a Hitachi SU8010 field emission scanning electron microscope with an accelerating voltage of 5kV, secondary electron mode, and a magnification of 300.

[0058] 2. EDS image detection method EDS uses an EDAX X-ray energy dispersive spectrometer with an accelerating voltage of 20kV and a line scan mode.

[0059] 3. Surface PL pattern detection method PL uses an Edinburgh FL920 xenon lamp with an excitation wavelength of 460 nm.

[0060] 4. It curve detection method The It curve was measured using a Keithley 6517B electrometer in both current and time modes.

[0061] 5. X-ray dose rate-device response photocurrent curve detection method: The X-ray dose rate is changed by altering the current of the X-ray tube (5.64, 11.20, 14.02, 22.47, 33.60, 44.94, and 56.11 μGy, respectively). air s -1 The net photocurrent of the detector under different X-ray doses was statistically analyzed (5.64, 11.20, 14.02, 22.47, 33.60, 44.94 and 56.11 μGy, respectively). air s -1 After plotting the X-ray dose rate-device response photocurrent curve, the relationship between X-ray dose rate and device response can be investigated.

[0062] 6. The IV curve was tested using a Keithley 6517B electrometer in both voltage and current modes.

[0063] III. Analysis of Test Results for Each Embodiment and Comparative Example (1) Scanning electron microscope (SEM) images of the cross-section of the three-dimensional / quasi-two-dimensional perovskite thick film heterojunction obtained in Example 1, as shown in Figure 1. Figure 3 As shown, the yellow part is a quasi-two-dimensional perovskite sheet structure, which is wrapped around the surface of a dense three-dimensional perovskite thick film, forming a dimensional heterojunction of three-dimensional and quasi-two-dimensional structures with good interfacial contact. Figure 2 High-magnification microscope image of PbI2 film prepared by thermal evaporation. PbI2 provides the reaction medium for the formation of the upper quasi-two-dimensional perovskite layer (PbI2 film thickness 1~5 μm).

[0064] (2) Perform EDS line scanning on the cross-section of the three-dimensional / quasi-two-dimensional perovskite thick film heterojunction obtained in Example 1, such as... Figure 4 As shown, the results reveal different elemental distributions at the heterojunctions on the surface of the prepared perovskite thick film. These distributions are difficult to distinguish in the all-iodine system; therefore, a bromine-containing system was used for better identification. Figure 4 As can be seen, the surface of the three-dimensional / quasi-two-dimensional perovskite thick film heterojunction is rich in bromine and carbon and exhibits a gradient distribution trend, indicating that the three-dimensional heterojunction is formed on the surface of the thick film and exhibits a gradient distribution in the film layer.

[0065] (3) Surface PL detection was performed on the three-dimensional perovskite thick film 3D, the three-dimensional / quasi-two-dimensional perovskite thick film heterojunction 3D / Quasi-2D obtained in Example 1 and the three-dimensional / two-dimensional perovskite thick film heterojunction 3D / 2D obtained in Comparative Example 1. As shown in Figure 5, the results show that the emission peak of the three-dimensional perovskite is ~800 nm. Compared with the three-dimensional / two-dimensional perovskite thick film heterojunction 3D / 2D, the structural large n value (n=2 and n=3) of the three-dimensional / quasi-two-dimensional perovskite thick film heterojunction 3D / Quasi-2D is significantly improved.

[0066] (4) The It curve was tested using the X-ray detector devices in Example 2 and Comparative Example 2 under a 5 V bias voltage, as shown below. Figure 6 As shown, the dark current density and baseline drift of the X-ray detector device in Comparative Example 2 are significantly reduced, demonstrating that the three-dimensional / quasi-two-dimensional perovskite thick film heterojunction in Example 2 can improve carrier collection efficiency, enhance device sensitivity, and suppress ion migration processes.

[0067] The relationship between X-ray dose rate and device response was tested using the X-ray detector devices in Example 2 and Comparative Example 2. The test results were processed to obtain the X-ray dose rate-device response photocurrent curve, as shown below. Figure 7 As shown in the results, the three-dimensional / quasi-two-dimensional perovskite thick-film heterojunction X-ray detector device in Example 2 exhibits good linearity in its response to X-rays at different dose rates. The sensitivity of the device based on the lead halide perovskite thick-film heterojunction is 59040 μC·Gy. air -1 ·cm -2 Compared with the three-dimensional perovskite structure X-ray detector device in Comparative Example 2, the performance is improved by 1.92 times, demonstrating excellent X-ray detection performance.

[0068] IV tests were performed using the X-ray detector devices from Example 2 and Comparative Example 2, calculating the net photocurrent in both dark and light (365 nm visible light) modes. Figure 8 As shown, the net photocurrent of the 3D perovskite thick film is less than that of the 3D / Quasi-2D perovskite thick film heterojunction system, and the carrier lifetime product μτ is 2.739 × 10⁻⁶. -5 cm 2 V -1 Significantly smaller than the 3.207 × 10⁻⁶ of the 3D / Quasi-2D system. -4 cm 2 V -1 This study confirms that three-dimensional / quasi-two-dimensional perovskite thick-film systems are more conducive to interfacial carrier separation and transport, and the high μτ product property helps to obtain highly sensitive devices.

[0069] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A method for fabricating an X-ray detector device, characterized in that, Includes the following steps: (1) Clean the ITO glass substrate; (2) Electron transport layer preparation: SnO2 solution was spin-coated on an ITO glass substrate and annealed to obtain an electron transport layer, thus preparing an ITO / SnO2 structure; (3) Preparation of polymer-induced adhesive layer: A precursor solution was prepared using polymers PVP, PEG, PbI2, MAI and DMF. The precursor solution was spin-coated on the electron transport layer for 40~60s to form a precursor solution layer. Chlorobenzene was added dropwise to the precursor solution layer, and spin-coating was continued for 20~30s. After standing for 3~9h, the layer was annealed to obtain the PVP&PEG-induced adhesive layer and prepare the ITO / SnO2 / adhesive layer structure. (4) A three-dimensional / quasi-two-dimensional perovskite thick film heterojunction was prepared on the ITO / SnO2 / adhesive layer structure to prepare an ITO / SnO2 / adhesive layer / 3D / Quasi-2D structure; (5) Au electrodes were deposited on the surface of the ITO / SnO2 / adhesive layer / 3D / Quasi-2D structure to prepare an ITO / SnO2 / adhesive layer / 3D / Quasi-2D / Au structure detector device; The three-dimensional / quasi-two-dimensional perovskite thick film heterojunction includes a three-dimensional perovskite thick film and a quasi-two-dimensional perovskite; The composition of the three-dimensional perovskite thick film is MA a FA 1-a PbI3, where 0 <a<1; The composition of the quasi-two-dimensional perovskite is A m A' n-1 B n X 3n+1 Component A includes one or two of FA and MA, component A' includes DJ-type amine or RP-type amine, component B is lead atom Pb, component X is one or more of halogen atom I, Br, Cl atom, n is an integer greater than 1, when component A' is DJ-type amine, m=1, when component A' is RP-type amine, m=2; The RP-type amine includes one or two of phenylethylamine and butylamine, and the DJ-type amine includes one or two of N,N-dimethyl-1,3-propanediamine and 1,4-phenylenediamine. The method for preparing the three-dimensional / quasi-two-dimensional perovskite thick film heterostructure includes the following steps: S1. Preparation of three-dimensional perovskite thick film: DMePDAI2, MAI, FAI, PbI2 and GBL are used to prepare a perovskite microcrystalline thick film growth solution. The substrate is placed in the growth solution and the grains are grown by solvent evaporation. After the grain growth is completed, annealing is performed to obtain a three-dimensional perovskite thick film, forming a substrate / 3D thick film structure. S2. Mix component A, component A', and the second solvent, and heat and stir to dissolve to obtain a three-dimensional perovskite thick film surface treatment solution. Component A is one or two of FAI and MAI, and component A' includes RP molecules or DJ molecules. The RP molecules include one or more of BAI, PEAI, and PEABr, and the DJ molecules include one or two of PhIDMADBr and DMePDAI2. S3. PbI2 is deposited on the surface of the substrate / 3D thick film structure using a thermal evaporation process, and then immersed and annealed in a surface treatment solution to obtain the substrate / 3D / Quasi-2D structure.

2. The method for fabricating an X-ray detector device according to claim 1, characterized in that, In step (3), the molecular weight of the polymer PVP is 5000~50000 and the molecular weight of PEG is 200-1000. 0.1~0.3g PVP and 0.04~0.12g PEG are added to every 10mL of DMF in the precursor solution. The concentrations of PbI2 and MAI in the precursor solution are both 0.3~0.6mol / L.

3. The method for fabricating an X-ray detector device according to claim 1, characterized in that, The concentration of the perovskite microcrystalline thick film growth solution is 1~2 mol / L.

4. The method for fabricating an X-ray detector device according to claim 1, characterized in that, The solvent evaporation method includes the following steps: after preparing a perovskite microcrystalline thick film growth solution, the solution is filtered. The solvent in the growth solution is gradually evaporated to supersaturation at a temperature of 90~95℃, and crystals are precipitated. After the first crystal precipitates, the substrate is placed in the growth solution for 40~60 min to grow grains for 1~1.5 h. After the grain growth is completed, the substrate is annealed to obtain a three-dimensional perovskite thick film.

5. The method for fabricating an X-ray detector device according to claim 1, characterized in that, The thickness of the three-dimensional perovskite thick film is 100~500 μm.

6. The method for fabricating an X-ray detector device according to claim 1, characterized in that, The second solvent in step S2 comprises the following components in volume fractions: IPA 98%~99%, DMF 1%~2%.

7. The method for fabricating an X-ray detector device according to claim 1, characterized in that, The thickness of PbI2 deposited in step S3 is 1~5 μm.

Images