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

Abstract

The invention provides a three-dimensional / quasi-two-dimensional perovskite thick film heterojunction and a preparation method and application thereof, and belongs to the technical field of X-ray detection, and the three-dimensional / quasi-two-dimensional perovskite thick film heterojunction comprises three-dimensional perovskite and a quasi-two-dimensional perovskite thick film; the component of the three-dimensional perovskite thick film is MA FA < 1-a > PbI < 3 >, wherein 0 lt; a < lt >; 1; the component of the quasi-two-dimensional perovskite is AMA 'n-1BnX3n + 1, the component A comprises one or two of FA and MA, the component A' comprises DJ type amine or RP type amine, the component B is lead atom Pb, the component X is one or more of halogen atoms I, Br and Cl, n is an integer greater than 1, m is equal to 1 when the component A 'is the DJ type amine, and m is equal to 2 when the component A' is the RP type amine. According to the invention, the n value of the two-dimensional perovskite on the upper interface is precisely regulated and controlled, the content of n = 1 component is reduced, the proportion of the large n value is improved, charge separation and transmission at the interface are promoted, and the collection efficiency of carriers in a light state is improved; and meanwhile, the quasi-two-dimensional structure high-energy band potential barrier can inhibit leakage current injection in a dark state, so that dark current is reduced, and finally, the sensitivity and the signal-to-noise ratio of the device are remarkably improved.

Description

Technical Field

[0001] The present invention relates to the field of X-ray detection technology, and in particular to a three-dimensional / quasi-two-dimensional perovskite thick film heterojunction and a preparation method and application thereof. Background Art

[0002] X-ray detectors are widely used in medical imaging, security inspection, industrial inspection and other fields. Lead halide perovskite materials have the characteristics of large X-ray absorption cross-section, high mobility-lifetime value (high μτ product), strong irradiation stability, etc. It is an extremely excellent radiation detection material. At the same time, it takes into account the low-cost preparation process of the solution method to meet the practical application needs of large-area integration, showing broad application prospects. Direct detection based on perovskite materials uses perovskite semiconductors to absorb X-rays and directly convert them into electrical signals. The directional transport of charges driven by the electric field ensures high spatial resolution. It is the future development direction of low-dose, high-resolution X-ray imaging. Compared with perovskite single crystal materials, the polycrystalline thick film system based on the solution method has the advantages of easy area enlargement and easy circuit integration, and has great application potential in flat-panel detectors.

[0003] To ensure effective absorption and imaging of X-rays, the perovskite film layer needs to be more than 100 microns (>100 μm). However, at this stage, there are the following problems in the preparation method of perovskite thick films and device construction: 1. The thick film preparation scheme is good: the preparation of perovskite thick films above 100 microns mostly adopts the scraping of perovskite supersaturated suspension (concentration ~5 mol / L), which has intrinsic problems such as difficult mass transfer, difficult to control nucleation growth, and multi-component segregation, making it difficult to obtain high-quality grains, resulting in serious carrier recombination. At the same time, the solvent evaporates during the preparation process to form a large number of holes, forming a loose and porous structure of the thick film (hole diameter ~20 μm), and the grains are broken and the film layer falls off during the compaction process, resulting in difficulty in surface array integration and poor electrical contact.

[0004] 2. Lack of thick film structure construction: three-dimensional structure perovskite material, low resistivity (10 6 ~10 7 Ω·cm), serious ion migration leads to excessively high dark current, high noise, poor stability, and high detection limit of the detector, making it difficult to meet the dark current density (<1 nA·cm) that matches commercial transistor arrays (TFTs). -2). The two-dimensional perovskite is a structure in which lead halide inorganic layers and organic cation layers are arranged alternately. The interlayer quantum well structure can effectively increase the resistivity and reduce the dark current. In recent years, the use of two-dimensional perovskites and three-dimensional perovskites to construct dimensional heterojunctions has been a hot research topic in the field. By regulating the interface energy level matching of the heterojunction, it can ensure that the carriers are well extracted in the light state, while suppressing the injection of dark current. However, there is often a high barrier difference (>0.3 eV) between the dimensional heterojunctions of three-dimensional and two-dimensional perovskites, and there is energy loss in the inter-gap transition of carriers, which affects the carrier collection efficiency of the thick film system, resulting in the loss of detector photocurrent, reducing the sensitivity of the device, and restricting the minimum detection limit. Summary of the invention

[0005] In view of the technical problems existing in the background technology, this application uses a solvent volatilization method to construct a high-density, high-quality three-dimensional perovskite film layer, 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, and constructs a three-dimensional / quasi-two-dimensional thick film dimensional heterojunction structure to achieve the purpose of improving the carrier collection at the interface while suppressing the dark current of the device, and obtaining a highly sensitive and high-contrast detection device. It aims to solve the following problems: 1. It is difficult to obtain a high-quality and high-density film layer in the preparation of a three-dimensional perovskite thick film by the traditional scraping method, and the problems of grain breakage and film layer shedding in the later film compaction process of the porous perovskite thick film make it difficult to integrate the array. 2. There is a high barrier difference (>0.3 eV) between the dimensional heterojunctions of the three-dimensional and two-dimensional perovskites, and there is energy loss in the carrier gap transition, which affects the carrier collection efficiency of the thick film system, resulting in the loss of detector photocurrent, reducing the sensitivity of the device, and restricting the minimum detection limit.

[0006] In a first aspect, the embodiments of the present application provide a three-dimensional / quasi-two-dimensional perovskite thick film heterojunction, 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 PbI 3 , where 0 <a<1; The component 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 atoms 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; The RP type amines include one or both of phenylethylamine and butylamine, and the DJ type amines include one or both of N,N-dimethyl-1,3-propylenediamine and 1,4-phenylenediamine.

[0007] In a second aspect, the present application provides a method for preparing a three-dimensional / quasi-two-dimensional perovskite thick film heterojunction, comprising the following steps: S1. Preparation of three-dimensional perovskite thick film: using DMePDADI 2 (N,N-dimethyl-1,3-propanediamine hydroiodide), MAI (methylammonium iodide), FAI (formamidine hydroiodide), PbI 2 and GBL (γ-butyrolactone) to form a perovskite microcrystalline thick film growth solution, place the substrate in the growth solution and grow grains using a solvent evaporation method, anneal after the grain growth is completed to obtain a three-dimensional perovskite thick film, forming a substrate / 3D thick film structure; S2. Component A, component A' and solvent are mixed, and after heating and stirring to dissolve, a three-dimensional perovskite thick film surface treatment solution is obtained, wherein 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 (phenethylammonium iodide), PEABr (phenethylammonium bromide), DJ molecules include PhIDMADBr (1,4-phenylenediamine hydrobromide), DMePDAI 2 (N,N-dimethyl-1,3-propanediamine hydroiodide) or both; S3: PbI is deposited on the surface of the substrate / 3D thick film structure by thermal evaporation process 2 , and then immersed in a surface treatment solution and annealed to obtain a substrate / 3D / Quasi-2D structure.

[0008] In the technical solution of the embodiment of the present application, the perovskite-PVP polycrystalline layer is firstly spin-coated to increase the nucleation sites and reduce the nucleation barrier; the solvent is volatilized at 90 °C to increase the supersaturation of the solution, and the nucleation is mediated on the polycrystalline layer by chemical deposition; a high-density three-dimensional perovskite thick film (100-500 μm) is prepared by a method of grain ripening and fusion by hot stage annealing for 3h-9h; then PbI is evaporated on the three-dimensional interface 2 (1~5 μm) as the reaction medium of the upper layer; finally, through the method of interface post-processing liquid phase reaction, non-polar solvents are 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 comprises the following steps: after preparing the perovskite microcrystalline thick film crystal growth solution, filtering, placing the substrate in the crystal growth solution at a temperature of 90-95°C, allowing the solvent to gradually evaporate to reach supersaturation and then crystallize, waiting for 40-60 minutes after the first crystal is precipitated, placing the substrate in the crystal growth solution for grain growth for 1-1.5 hours; annealing after the grain growth is completed 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% to 99%, DMF 1% to 2%.

[0013] Preferably, the PbI evaporated in step S3 2 The thickness is 1~5 μm.

[0014] In a third aspect, an embodiment of the present application provides an X-ray detector device, comprising a glass substrate, an electron transport layer, a PVP (polyvinyl pyrrolidone) & PEG (polyethylene glycol) induced adhesion layer, a three-dimensional / quasi-two-dimensional perovskite thick film heterojunction and an electrode, which are stacked in sequence.

[0015] In a fourth aspect, an embodiment of the present application provides a method for preparing an X-ray detector device, comprising the following steps: (1) Cleaning ITO glass substrate; (2) Preparation of electron transport layer: Spin coating SnO on ITO glass substrate 2 solution, and after annealing, an electron transport layer is obtained to prepare ITO / SnO 2 structure; (3) Preparation of PVP-induced bonding layer: using polymers PVP, PEG, PbI 2 The precursor solution was prepared by mixing MAI and DMF, and the precursor solution was spin-coated on the electron transport layer for 40-60 s to form a precursor solution layer. Chlorobenzene was dropped onto the precursor solution layer, and the spin coating was continued for 20-30 s. After standing for 3-9 h, annealing was performed to obtain an induced bonding layer to prepare ITO / SnO 2 / Adhesive layer structure; (4) In ITO / SnO 2 The three-dimensional / quasi-two-dimensional perovskite thick film heterojunction was prepared according to the above method on the bonding layer structure to prepare ITO / SnO 2 / Adhesive layer / 3D / Quasi-2D structure; (5) In ITO / SnO 2 / Adhesive layer / 3D / Quasi-2D structure surface evaporation Au electrode to prepare ITO / SnO 2 / adhesive layer / 3D / Quasi-2D / Au structure detector device.

[0016] Preferably, in step (3), the molecular weight of the polymer PVP is 5000-50000, the molecular weight of PEG is 200-1000, and 0.1-0.3 g PVP and 0.04-0.12 g PEG are added to each 10 mL DMF in the precursor solution. 2 The concentrations of and MAI are both 0.3~0.6mol / L.

[0017] Different from the existing technical solutions, the beneficial effects of this application include: 1. This application adopts 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 by inversion nucleation, on-chip polycrystalline mediated film formation and grain ripening fusion; then PbI is evaporated on the three-dimensional interface 2 As the reaction medium of the upper layer; finally, through the method of interface post-processing liquid phase reaction, three-dimensional and quasi-two-dimensional heterojunctions are constructed without destroying the underlying three-dimensional interface.

[0018] This application reduces the content of n=1 components and increases the proportion of large n values ​​by precisely controlling the n value of the upper interface two-dimensional perovskite. Different n values ​​result in different band gaps in each layer, resulting in a stepped arrangement (gradient band gap) between energy bands, so that the photogenerated charges (electrons and holes) have directional energy changes between different layers. A heterojunction structure is used to laminate perovskite materials with different band gaps together to form a gradient energy band. When light or X-rays irradiate the device, the generated electrons will migrate from the high energy (high band gap) region to the low energy (low band gap) region while the holes move in the opposite direction. This energy band gradient effectively separates electrons and holes, reducing the possibility of recombination, thereby optimizing charge separation and transmission, improving the carrier extraction efficiency in the light state while suppressing dark current injection in the dark state, significantly improving the 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 the present application. In order to more clearly understand the technical means of the present application, it can be implemented in accordance with the contents of the specification. In order to make the above and other purposes, features and advantages of the present application more obvious and easy to understand, the specific implementation methods of the present application are listed below. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] In order to more clearly illustrate the technical solution of the present application, the following is a brief introduction to the drawings used in the present application. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0022] Figure 1 3D / quasi-2D perovskite thick film heterojunction is a schematic diagram comparing the advantages of the present invention over the 3D / 2D perovskite thick film heterojunction. Figure 1 a is a schematic diagram of the inter-gap transition of electrons and holes in a three-dimensional / quasi-two-dimensional perovskite thick film heterojunction; Figure 1 b is a schematic diagram of the inter-gap transition of electrons and holes in a three-dimensional / two-dimensional perovskite thick film heterojunction; Figure 2 It is the thermally evaporated PbI in Example 1 of the present application. 2 High-power microscope cross-section of thick film; Figure 3 is a cross-sectional SEM image of a three-dimensional / quasi-two-dimensional perovskite thick film heterojunction in Example 1 of the present application; Figure 4 It is an EDS line scan of a cross section of a three-dimensional / quasi-two-dimensional perovskite thick film heterojunction in Example 1 of the present application; Figure 5 It is the surface PL spectrum of the three-dimensional perovskite thick film, the three-dimensional / quasi-two-dimensional perovskite thick film heterojunction in Example 1 of the present application and the three-dimensional / two-dimensional perovskite thick film heterojunction in Comparative Example 1; Figure 6 It is an It curve diagram of the X-ray detector device in Example 2 and Comparative Example 2 of the present application; Figure 7 It is the X-ray dose rate-device response photocurrent curve of the X-ray detector device in Example 2 and Comparative Example 2 of the present application.

[0023] Figure 8 It is the curve of net photocurrent changing with voltage of the X-ray detector device in Example 2 and Comparative Example 2 of the present application. DETAILED DESCRIPTION

[0024] The following embodiments of the technical solution of the present application are described in detail in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present application, and are therefore only used as examples, and cannot be used to limit the scope of protection of the present application.

[0025] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by technicians in the technical field to which this application belongs; the terms used herein are only for the purpose of describing specific embodiments and are not intended to limit this application; the terms "including" and "having" in the specification and claims of this application and the above-mentioned figure descriptions and any variations thereof are intended to cover non-exclusive inclusions.

[0026] In the description of the embodiments of the present application, the technical terms "first", "second", etc. are only used to distinguish different objects, and cannot be understood as indicating or implying relative importance or implicitly indicating the number, specific order or primary and secondary relationship of the indicated technical features. In the description of the embodiments of the present application, the meaning of "multiple" is more than two, unless otherwise clearly and specifically defined.

[0027] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0028] In the description of the embodiments of the present application, the term "multiple" refers to more than two (including two). Similarly, "multiple groups" refers to more than two groups (including two groups), and "multiple pieces" refers to more than two pieces (including two pieces).

[0029] At present, there are the following problems in the preparation method of perovskite thick film and device construction: 1. The thick film preparation scheme is good: the preparation of perovskite thick films above 100 microns mostly adopts the scraping of perovskite supersaturated suspension (concentration ~5 mol / L), which has intrinsic problems such as difficult mass transfer, difficult to control nucleation growth, and multi-component segregation, making it difficult to obtain high-quality grains, resulting in serious carrier recombination. At the same time, the solvent evaporates during the preparation process to form a large number of holes, forming a loose and porous structure of the thick film (hole diameter ~20 μm), and the grains are broken and the film layer falls off during the compaction process, resulting in difficulty in surface array integration and poor electrical contact.

[0030] 2. Lack of thick film structure construction: three-dimensional structure perovskite material, low resistivity (10 6 ~10 7 Ω·cm), serious ion migration leads to excessively high dark current, high noise, poor stability, and high detection limit of the detector, making it difficult to meet the dark current density (<1 nA·cm) that matches commercial transistor arrays (TFTs). -2). The two-dimensional perovskite is a structure in which lead halide inorganic layers and organic cation layers are arranged alternately. The interlayer quantum well structure can effectively increase the resistivity and reduce the dark current. In recent years, the use of two-dimensional perovskites and three-dimensional perovskites to construct dimensional heterojunctions has been a hot research topic in the field. By regulating the interface energy level matching of the heterojunction, it can ensure that the carriers are well extracted in the light state, while suppressing the injection of dark current. However, there is often a high barrier difference (>0.3 eV) between the dimensional heterojunctions of three-dimensional and two-dimensional perovskites, and there is energy loss in the inter-gap transition of carriers, which affects the carrier collection efficiency of the thick film system, resulting in the loss of detector photocurrent, reducing the sensitivity of the device, and restricting the minimum detection limit.

[0031] In order to solve the technical problems that it is difficult to obtain high-quality grains in three-dimensional perovskite thick films, serious carrier recombination, grain breakage and film layer shedding during the compaction process, resulting in difficulty in surface array integration and poor electrical contact; there is a high barrier difference (>0.3 eV) between the dimensional heterojunctions of three-dimensional and two-dimensional perovskites, and there is energy loss in the inter-gap transition of carriers, which affects the carrier collection efficiency of the thick film system, leads to the loss of detector photocurrent, reduces the sensitivity of the device, and restricts the minimum detection limit, this application provides a three-dimensional / quasi-two-dimensional perovskite thick film heterojunction and its preparation method and application, wherein a high-density three-dimensional perovskite thick film (100~500 μm) is first prepared on a conductive substrate by a three-step method of inversion crystallization / thermal evaporation / liquid phase reaction through inversion nucleation, on-chip polycrystalline-mediated film formation and grain ripening fusion. Then, PbI is evaporated on the three-dimensional interface. 2 (1~5 μm), through the method of interface post-treatment liquid phase reaction, non-polar solvents are selected to dissolve different proportions of A site and component A'; component A is methylamine, formamidine, etc., and A' is phenylethylamine, butylamine, N,N-dimethyl-1,3-propylenediamine hydroiodide, etc., without destroying the underlying three-dimensional interface, three-dimensional and quasi-two-dimensional heterojunctions are constructed.

[0032] This application reduces the content of n=1 components and increases the proportion of large n values ​​by precisely controlling the n value of the two-dimensional perovskite on the upper surface. Different n values ​​result in different band gaps in each layer, resulting in a stepped arrangement (gradient band gap) between energy bands, so that the photogenerated charges (electrons and holes) have directional energy changes between different layers. A heterojunction structure is used to laminate perovskite materials with different band gaps together to form a gradient energy band. When light or X-rays irradiate the device, the generated electrons will migrate from the high energy (high band gap) region to the low energy (low band gap) region while the holes move in the opposite direction. This energy band gradient effectively separates electrons and holes, reducing the possibility of recombination, thereby optimizing charge separation and transmission, improving the carrier extraction efficiency in the light state while suppressing dark current injection in the dark state, significantly improving the device sensitivity and signal-to-noise ratio.

[0033] In a first aspect, the embodiments of the present application provide a three-dimensional / quasi-two-dimensional perovskite thick film heterojunction, 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 PbI 3 , where 0 <a<1; The component 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 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; The RP type amines include one or both of phenylethylamine and butylamine, and the DJ type amines include one or both of N,N-dimethyl-1,3-propylenediamine and 1,4-phenylenediamine.

[0034] In a second aspect, the present application provides a method for preparing a three-dimensional / quasi-two-dimensional perovskite thick film heterojunction, comprising the following steps: S1. Preparation of three-dimensional perovskite thick film: using DMePDADI 2 、MAI、FAI、PbI 2 Mix with GBL, heat and stir on a hot plate at 60°C for 8 hours to prepare a perovskite microcrystalline thick film growth solution; place the substrate in the growth solution to grow grains using a solvent volatilization method, and after the grain growth is completed, remove the substrate from the growth solution, wipe the substrate dry with a dust-free cloth, place on a hot plate at 100°C, anneal for 8 hours to obtain a three-dimensional perovskite thick film, forming a substrate / 3D thick film structure; S2, component A, component A' and solvent are mixed, and stirred on a hot plate 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, component A' includes RP molecules or DJ molecules, RP molecules include one or more of BAI, PEAI, PEABr, DJ molecules include PhIDMADBr, DMePDAI 2 One or both of the following: S3. Wipe the back of the substrate / 3D thick film structure clean with ethanol, scrape the thick film around with a scraper, and evaporate PbI on the surface using a thermal evaporation process. 2 After surface pretreatment, the substrate was placed in a surface treatment solution and immersed on a hot stage at 50 °C for 20-60 min, taken out, and annealed on a hot stage at 50 °C for 1 h to obtain a substrate / 3D / Quasi-2D structure.

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

[0036] The preferred solvent evaporation method comprises the following steps: after preparing a perovskite microcrystalline thick film growth solution, filtering, placing a substrate in the growth solution at a temperature of 90-95°C, allowing the solvent to gradually evaporate to reach supersaturation and then crystallize, waiting for 40-60 minutes after the first crystal is precipitated, placing the substrate in the growth solution for grain growth for 1-1.5 hours; annealing after the grain growth is completed to obtain a three-dimensional perovskite thick film.

[0037] In the technical solution of the embodiment of the present application, after the first crystal is precipitated, after another 40 to 60 minutes, the grains in the crystal growth solution grow to about 1 mm in diameter, and the solution has not yet reached the state of burst crystallization. At this time, the substrate is placed in the crystal growth solution to allow the grains to grow on the substrate until a film is formed on the surface of the substrate. The film thickness is positively correlated with the crystal growth time. A 200 μm surface film usually requires 1 to 1.5 h of crystal growth time, and the film thickness can be adjusted with 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% to 99%, DMF 1% to 2%.

[0040] Preferably, the PbI evaporated in step S3 2 The thickness is 1~5 μm.

[0041] In the technical solution of the embodiment of the present application, the perovskite microcrystalline thick film growth solution is heated at 90~95°C to allow the solvent to gradually evaporate and increase the concentration of the solution. After the growth solution reaches supersaturation, crystallization is performed to form crystal nuclei 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 that is no less than that of a single crystal.

[0042] Preparation of PbI by evaporation 2 , will not damage the thick perovskite film formed in the lower layer, PbI 2 A and A' form a quasi-two-dimensional thick film through interface treatment and dielectric liquid phase reaction, and form a heterojunction with the dense perovskite thick film prepared by solvent evaporation method.

[0043] Three-dimensional interface evaporation PbI 2(1~5 μm), through the method of interface post-treatment liquid phase reaction, non-polar solvents are selected to dissolve different proportions of A site and component A'; component A is methylamine, formamidine, etc., and A' is phenylethylamine, butylamine, N,N-dimethyl-1,3-propylenediamine hydroiodide, etc., without destroying the underlying three-dimensional interface, three-dimensional and quasi-two-dimensional heterojunctions are constructed.

[0044] In this application, component A (MAI, FAI) is used to reduce the ratio of 2D ligands to A'-position cations, and DMF is added to the solvent to directly introduce PbI from the 3D perovskite surface. 2 , resulting in a more PbI-rich 2 The surface is suitable for ammonium ligand embedding, enabling the generation of 2D perovskite layers containing n ≥ 3.

[0045] Figure 1 a shows a three-dimensional perovskite thick film surface treatment solution containing only component A without adding component A' to prepare a three-dimensional / two-dimensional perovskite thick film heterojunction, and an X-ray detector device prepared using the three-dimensional / quasi-two-dimensional perovskite thick film heterojunction, from Figure 1 It can be seen from a that 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 in the inter-gap transition of carriers under the high potential barrier, which affects the carrier transport performance of the three-dimensional perovskite thick film system. Figure 1 b is a three-dimensional perovskite thick film surface treatment solution prepared by using component A and component A' in this application, and then constructing a three-dimensional / quasi-two-dimensional perovskite thick film heterojunction, and using the three-dimensional / quasi-two-dimensional perovskite thick film heterojunction to prepare an X-ray detector device, from Figure 1 As can be seen in b, the present application reduces the content of n=1 components and increases the proportion of large n values ​​(n=2 and n=3) by precisely controlling the n value of the quasi-two-dimensional perovskite on the upper surface. Different n values ​​result in different band gaps in each layer, leading to a stepped arrangement (gradient band gap) between energy bands, so that the photogenerated charges (electrons and holes) have directional energy changes between different layers. A heterojunction structure is used to laminate perovskite materials with different band gaps together to form a gradient energy band. When light or X-rays irradiate the device, the generated electrons will migrate from the high energy (high band gap) region to the low energy (low band gap) region while the holes move in the opposite direction. This energy band gradient effectively separates electrons and holes, reducing the possibility of recombination, thereby optimizing charge separation and transport, improving the carrier extraction efficiency in the light state while suppressing dark current injection in the dark state, significantly improving the device sensitivity and signal-to-noise ratio.

[0046] In a third aspect, an embodiment of the present application provides 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 an electrode stacked in sequence.

[0047] In a fourth aspect, an embodiment of the present application provides a method for preparing an X-ray detector device, comprising the following steps: (1) Cleaning ITO glass substrate; (2) Preparation of electron transport layer: Spin coating SnO on ITO glass substrate 2 solution, and after annealing, an electron transport layer is obtained to prepare ITO / SnO 2 structure; (3) Preparation of PVP-induced bonding layer: using polymers PVP, PEG, PbI 2 The precursor solution was prepared by mixing MAI, DMF and spin coating the precursor solution 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 the spin coating was continued for 20-30 s. After standing for 3-9 h, the PVP-induced bonding layer was obtained to prepare ITO / SnO. 2 / Adhesive layer structure; (4) In ITO / SnO 2 The three-dimensional / quasi-two-dimensional perovskite thick film heterojunction was prepared according to the above method on the bonding layer structure to prepare ITO / SnO 2 / Adhesive layer / 3D / Quasi-2D structure; (5) In ITO / SnO 2 / Adhesive layer / 3D / Quasi-2D structure surface evaporation Au electrode to prepare ITO / SnO 2 / adhesive layer / 3D / Quasi-2D / Au structure detector device.

[0048] In the technical solution of the embodiment of the present application, in SnO 2 A layer of polymer PVP doped perovskite film is prepared on the 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 and heating, thereby solving the problem of film shedding caused by film shrinkage caused by annealing heat during thick film preparation. On the other hand, MAI and PbI are added to the polymer. 2 Reaction form MAPbI 3 Perovskite, doping perovskite in polymer also reduces the upper interface nucleation free energy, which is conducive to the nucleation and growth of upper three-dimensional perovskite grains.

[0049] Preferably, in step (3), the molecular weight of the polymer PVP is 5000-50000, the molecular weight of PEG is 200-1000, and 0.1-0.3 g PVP and 0.04-0.12 g PEG are added to each 10 mL DMF in the precursor solution. 2 The concentrations of and MAI are both 0.3~0.6 mol / L.

[0050] Some specific embodiments are listed below. It should be noted that the embodiments described below are exemplary and are only used to explain the present application, and should not be construed as limiting the present application. If specific techniques or conditions are not specified in the embodiments, the techniques or conditions described in the literature in this area or the product specifications are used. The reagents or instruments used without specifying the manufacturer are all conventional products that can be obtained commercially.

[0051] 1. Preparation method Example 1 A method for preparing a three-dimensional / quasi-two-dimensional perovskite thick film heterojunction comprises the following steps: (1) Preparation of three-dimensional perovskite thick film: 0.256g DMePDADI 2 ,1.228g MAI, 1.136g FAI, 6.914gPbI 2 Mix with 10 mL GBL, heat and stir on a 60°C hot plate for 8 hours to prepare a 1.5 mol / L perovskite microcrystalline thick film growth solution; filter the thick film growth solution with a 0.45 μm nylon filter in a glove box, place the substrate in the growth solution at a temperature of 90-95°C, allow the solvent to gradually evaporate to supersaturation and then crystallize; wait for the first crystal to precipitate 1 hour, place the substrate in the growth solution for grain growth for 1 hour; anneal after the grain growth is completed to obtain a three-dimensional perovskite thick film with a thickness of 100-500 μm, forming a substrate / 3D thick film structure; (2) 0.2 g of MAI, 0.235 g of PEAI and a solvent were mixed and stirred on a hot plate at 50 °C for 4 h to obtain a 20 mg / mL three-dimensional perovskite thick film surface treatment solution, wherein the molar ratio of component A being MAI and component A' being PEAI was 1:1, and the solvent included 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 the thick film around it with a scraper, and use thermal evaporation technology to evaporate PbI on the surface 2 The surface was pretreated, then placed in a surface treatment solution and immersed on a hot plate at 50°C for 40 minutes, taken out, and annealed on a hot plate at 50°C for 1 hour to obtain a three-dimensional / quasi-two-dimensional perovskite thick film heterojunction, and a substrate / 3D / Quasi-2D structure was prepared.

[0052] Example 2 A method for preparing an X-ray detector device comprises the following steps: (1) Clean the ITO glass substrate and etch the ITO into an area of ​​2.5 × 2.5 cm 2 Take out the quartz glass, clean it with glass cleaning liquid, ultrasonicate it with pure water for 30 min, then ultrasonicate it with anhydrous ethanol for 30 min, take it out for use, and complete the ITO glass cleaning; (2) Preparation of electron transport layer: Mix 2 mL of tin oxide solution with 1 mL of pure water, filter twice with a 0.22 μm nylon filter, and ultrasonicate for 30 min to prepare the electron transport layer spin coating solution. Take 320 μL of the solution and evenly drop it on the ITO glass substrate treated with ozone for 30 min, and spin coat it at 3200 rpm for 1 min. Gently wipe the electrode area with anhydrous ethanol, then anneal on a 150°C hot plate for 1 h, and cool naturally to prepare ITO / SnO 2 Structure; The molecular weight of polymer PVP is 5000-50000, and the molecular weight of PEG is 200-1000. In every 10 mL DMF of the precursor solution, 0.1-0.3 g PVP and 0.04-0.12 g PEG are added. 2 The concentrations of and MAI are both 0.3~0.6 mol / L.

[0053] (3) Preparation of PVP-induced bonding layer: 0.15 g polymer PVP, PVP molecular weight 24000; 0.06 g PEG, PEG molecular weight 200, and 2.766 g PbI perovskite were added to the polymer. 2 , 0.954 g MAI and 10 mL DMF to prepare a 1.5 mol / L precursor solution, heated and stirred at 65 °C for 8 h. 2 The electron transport layer was treated with ozone for 30 minutes, and then the seed layer solution was spin-coated in a glove box. 320 μL of the precursor solution was taken, filtered with a 0.45 μL nylon filter, and evenly dropped on the glass. The speed was 600 rpm for 20 s, and then 2000 rpm for 20 s. 400 μL of chlorobenzene (anhydrous grade) was evenly dropped into the center of the glass to make the seed layer explosively nucleated. The spin coating was performed at 2000 rmp for 20 s and then rested for 3 h. After that, it was annealed at 100 °C for 1 h. A 1.5 μm induced bonding layer was prepared by spin coating to form ITO / SnO 2 / Adhesive layer structure; (4) Preparation of three-dimensional perovskite thick film: 0.256g DMePDADI 2 ,1.228g MAI, 1.136g FAI, 6.914gPbI 2and 10mL GBL, heated and stirred on a 60℃ hot plate 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, and the substrate was placed in the growth solution at a temperature of 90-95℃ to gradually evaporate the solvent to reach supersaturation and then crystallize. One hour after the first crystal precipitated, the substrate was placed in the growth solution for grain growth for 1h; after the grain growth was completed, annealing was performed to obtain a three-dimensional perovskite thick film with a thickness of 100-500μm, forming an ITO / SnO 2 / Adhesive layer / 3D thick film structure; (5) 0.2 g of MAI, 0.235 g of PEAI and a solvent were mixed and stirred on a hot plate at 50 °C for 4 h to obtain a 20 mg / mL three-dimensional perovskite thick film surface treatment solution, wherein the molar ratio of component AMAI and component A' is PEAI is 1:1, and the solvent includes 9.8 mL of IPA and 0.2 mL of DMF; (6) Combine ITO / SnO 2 / Adhesive layer / The back of the 3D thick film structure was wiped clean with ethanol, and the thick film around was scraped clean with a scraper. PbI was evaporated on the surface using a thermal evaporation process. 2 After surface pretreatment, the surface was placed in a surface treatment solution and immersed in a hot plate at 50°C for 40 minutes, then taken out and annealed at 50°C for 1 hour to obtain ITO / SnO 2 / Adhesive layer / 3D / Quasi-2D structure.

[0054] (7) Prepared ITO / SnO 2 / Adhesive layer / 3D / Quasi-2D structure uses a specific mask to cover ITO / SnO 2 / bonding layer / 3D / 2D structure surface, using thermal evaporation technology to evaporate 100 nm thick Au electrode to obtain ITO / SnO 2 / bonding layer / 3D / Quasi-2D / Au structured X-ray detector device with an electrode area of ​​0.0706 cm 2 .

[0055] Comparative Example 1 The difference between Comparative Example 1 and Example 1 is that, in the process of preparing 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 those 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, and the three-dimensional perovskite thick film was treated 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 the quasi-two-dimensional perovskite is not covered on the three-dimensional perovskite thick film. The other steps are the same as those in Example 2 to prepare ITO / SnO 2 / bonding layer / 3D / Au structure X-ray detector device.

[0057] 2. Test Method 1. SEM image detection method The SEM used was a Hitachi SU8010 field emission scanning electron microscope with an accelerating voltage of 5 kV, secondary electron mode, and a magnification of 300.

[0058] 2. EDS image detection method EDS used EDAX X-ray spectrometer with an acceleration voltage of 20 kV and line scanning mode.

[0059] 3. Surface PL spectrum detection method PL was performed using Edinburgh FL920 with a xenon lamp excitation wavelength of 460 nm.

[0060] 4. It curve detection method The IT curve was tested using a Keithley 6517B electrometer in current and time mode.

[0061] 5. X-ray dose rate - device response photocurrent curve detection method: by changing the current of the X-ray tube to change the X-ray dose rate (5.64, 11.20, 14.02, 22.47, 33.60, 44.94 and 56.11 μGy air s -1 ), the net photocurrent of the detector under different X-ray doses (5.64, 11.20, 14.02, 22.47, 33.60, 44.94 and 56.11 μGy air s -1 ) and then plot the X-ray dose rate-device response photocurrent curve to explore the relationship between the X-ray dose rate and the device response.

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

[0063] III. Analysis of test results of various embodiments and comparative examples (1) The scanning electron microscope (SEM) image of the cross section of the three-dimensional / quasi-two-dimensional perovskite thick film heterojunction obtained in Example 1 is as follows: Figure 3 As shown, the yellow part is a quasi-two-dimensional perovskite flake structure, which is wrapped on the surface of the brown dense three-dimensional perovskite thick film, forming a dimensional heterojunction of three-dimensional and quasi-two-dimensional structures with good interface contact. Figure 2 PbI prepared by thermal evaporation 2High-power microscope image of the film layer, PbI 2 Providing a reaction medium for the formation of the upper quasi-two-dimensional perovskite (PbI 2 Thick film 1~5 μm).

[0064] (2) Perform EDS line scan on the cross section of the three-dimensional / quasi-two-dimensional perovskite thick film heterojunction obtained in Example 1, as shown in FIG. Figure 4 As shown in the figure, the results show that the element distribution at the cross section of the prepared perovskite thick film surface heterojunction is different. The full iodine system is not easy to distinguish, so the bromine system is used here for better identification. Figure 4 It can be seen that the surface of the three-dimensional / quasi-two-dimensional perovskite thick film heterojunction is rich in bromine and carbon and shows a gradient distribution trend, indicating that the three-dimensional heterojunction is formed on the surface of the thick film and shows 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 three-dimensional / quasi-two-dimensional perovskite thick film heterojunction 3D / Quasi-2D has a significantly improved structure with large n values ​​(n=2 and n=3).

[0066] (4) The X-ray detector devices in Example 2 and Comparative Example 2 were used to test the It curve at a bias voltage of 5 V. Figure 6 As shown, the dark current density and baseline drift of the X-ray detector device in Comparative Example 2 are significantly reduced, proving that the three-dimensional / quasi-two-dimensional perovskite thick film heterojunction in Example 2 can improve the carrier collection efficiency, improve the device sensitivity and inhibit the ion migration process.

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

[0068] The X-ray detector devices in Example 2 and Comparative Example 2 were used to perform IV tests, and the net photocurrent was calculated in two modes: dark state and light state (365 nm visible light). Figure 8 As shown in Figure 2, the net photocurrent of the 3D perovskite thick film 3D is smaller than that of the 3D / Quasi-2D perovskite thick film heterojunction system, and the carrier lifetime product μτ is 2.739 × 10 -5 cm 2 V -1 Significantly smaller than 3.207 × 10 in 3D / Quasi-2D system -4 cm 2 V -1 It is confirmed that the three-dimensional / quasi-two-dimensional perovskite thick film system is more conducive to interface carrier separation and transport, and the high μτ product property is conducive to obtaining highly sensitive devices.

[0069] It should be noted that the present application is not limited to the above-mentioned embodiments. The above-mentioned embodiments are only examples, and the embodiments having the same structure as the technical idea and exerting the same effect within the scope of the technical solution of the present application are all included in the technical scope of the present application. In addition, without departing from the scope of the main purpose of the present application, various modifications that can be thought of by those skilled in the art to the embodiments and other methods of combining some of the constituent elements in the embodiments are also included in the scope of the present application.

Claims

1. A three-dimensional / quasi-two-dimensional perovskite thick film heterojunction, characterized in that: Including three-dimensional perovskite thick films and quasi-two-dimensional perovskites; The composition 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 AA' 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-propylenediamine and 1,4-phenylenediamine.

2. The method for preparing a three-dimensional / quasi-two-dimensional perovskite thick film heterojunction according to claim 1, characterized in that: The steps include: 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, and the substrate is placed in the growth solution to grow grains using a solvent evaporation method. 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, mixing component A, component A' and a solvent, heating and stirring to dissolve, obtaining a three-dimensional perovskite thick film surface treatment solution, wherein the component A is one or two of FAI and MAI, the component A' comprises RP molecules or DJ molecules, the RP molecules comprise one or more of BAI, PEAI, and PEABr, and the DJ molecules comprise one or two of PhIDMADBr and DMePDAI2; S3. PbI2 is evaporated on the surface of the substrate / 3D thick film structure by a thermal evaporation process, and then immersed and annealed in a surface treatment solution to obtain a substrate / 3D / Quasi-2D structure.

3. The method for preparing a three-dimensional / quasi-two-dimensional perovskite thick film heterojunction 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 preparing a three-dimensional / quasi-two-dimensional perovskite thick film heterojunction according to claim 1, characterized in that: The solvent evaporation method comprises the following steps: after preparing a perovskite microcrystalline thick film crystal growth solution, filtering it, placing a substrate in the crystal growth solution at a temperature of 90-95° C., allowing the solvent to gradually evaporate to reach supersaturation and then crystallize, waiting for 40-60 minutes after the first crystal is precipitated, placing the substrate in the crystal growth solution for grain growth for 1-1.5 hours, and annealing after the grain growth is completed to obtain a three-dimensional perovskite thick film.

5. The method for preparing a three-dimensional / quasi-two-dimensional perovskite thick film heterojunction according to claim 1, characterized in that: The thickness of the three-dimensional perovskite thick film is 100-500 μm.

6. The method for preparing a three-dimensional / quasi-two-dimensional perovskite thick film heterojunction according to claim 1, characterized in that: The solvent in step S2 includes the following components in volume fractions: IPA 98%-99%, DMF 1%-2%.

7. The method for preparing a three-dimensional / quasi-two-dimensional perovskite thick film heterojunction according to claim 1, characterized in that: The thickness of PbI2 evaporated in step S3 is 1-5 μm.

8. An X-ray detector device, characterized in that: It comprises a glass substrate, an electron transport layer, a polymer induced adhesion layer, the three-dimensional / quasi-two-dimensional perovskite thick film heterojunction as claimed in claim 7, and an electrode which are stacked in sequence.

9. The method for preparing an X-ray detector device according to claim 8, characterized in that: The steps include: (1) Cleaning ITO glass substrate; (2) Preparation of electron transport layer: Spin-coat SnO2 solution on ITO glass substrate, anneal to obtain electron transport layer, and prepare ITO / SnO2 structure; (3) Preparation of polymer induced bonding layer: Prepare a precursor solution using polymers PVP, PEG, PbI2, MAI and DMF, spin-coat the precursor solution on the electron transport layer for 40-60 seconds to form a precursor solution layer, drop chlorobenzene on the precursor solution layer, continue to spin-coat for 20-30 seconds, let stand for 3-9 hours and then anneal to obtain a PVP&PEG induced bonding layer, and prepare an ITO / SnO2 / bonding layer structure; (4) preparing a three-dimensional / quasi-two-dimensional perovskite thick film heterojunction on the ITO / SnO2 / adhesive layer structure according to the method of any one of claims 2 to 7 to prepare an ITO / SnO2 / adhesive layer / 3D / Quasi-2D structure; (5) An Au electrode was evaporated on the surface of the ITO / SnO2 / bonding layer / 3D / Quasi-2D structure to prepare an ITO / SnO2 / bonding layer / 3D / Quasi-2D / Au structure detector device.

10. An X-ray detector device according to claim 9, characterized in that: In the step (3), the molecular weight of the polymer PVP is 5000-50000, and the molecular weight of PEG is 200-1000. In every 10 mL of DMF in the precursor solution, 0.1-0.3 g of PVP and 0.04-0.12 g of PEG are added. The concentrations of PbI2 and MAI in the precursor solution are both 0.3-0.6 mol / L.

Images