WO2023010747A1 - Perovskite-based x-ray detector and preparation method therefor - Google Patents

Abstract

The present application relates to the field of photoelectric technologies, and in particular, to a perovskite-based X-ray detector and a preparation method therefor. The preparation method for the perovskite-based X-ray detector comprises the steps: acquiring a conductive substrate, and activating the conductive substrate to obtain an activated conductive substrate; preparing a mixed solution of a perovskite precursor, depositing the mixed solution on the activated conductive substrate, and drying and annealing to obtain a perovskite active layer containing a AnA'1-nPbZ3 perovskite material, wherein A is selected from CH3NH3 +, A' is selected from CH2(NH3)2 +, Z is selected from a halogen, and n is 0.1-0.95; and preparing a back electrode on the surface of the perovskite active layer facing away from the conductive substrate to obtain a perovskite-based X-ray detector. The preparation method in the present application is simple and efficient, has a high raw material utilization rate, and is suitable for preparing a large-area perovskite-based X-ray detector; the prepared detector has good stability and high sensitivity.

Description

Perovskite-based X-ray detector and its preparation method technical field

The application belongs to the field of optoelectronic technology, and in particular relates to a perovskite-based X-ray detector and a preparation method thereof.

Background technique

An X-ray detector is a device that converts X-ray energy into electrical signals that can be recorded. In recent years, with the large-scale promotion and use of X-ray detectors, X-ray detectors have been used more and more in small security inspection equipment, industrial parts inspection, large container inspection, medical treatment and other fields. At present, X-ray detectors are mostly used as indirect conversion X-ray detectors using scintillators, which are usually composed of scintillators, detector chips, and substrates; the working principle is that X photons enter the scintillator and are converted into visible light The output enters the detector chip, and then the photoelectric conversion is performed by the detector chip to form an electrical signal, which is transmitted to the subsequent signal processing chip through the wires on the chip and the substrate to form the final image.

In contrast, direct conversion X-ray detectors can directly convert X-ray absorption into charge carriers, and have the advantages of small radiation dose, high spatial resolution, large contrast range, and simple device structure. There are broader application prospects in terms of application. The core of the direct conversion X-ray flat panel image detector is the X-ray active layer, which is a material that directly converts X-ray absorption into charge carriers. At present, there are few types of direct conversion X-ray active materials with superior performance, and the arsenic-doped amorphous selenium material (a-Se:As) as the X-ray active layer is the mainstream method. However, devices based on this material have harsh fabrication conditions and extremely low detection efficiency for high-energy X-rays. Lead-based halide perovskite materials are regarded as the most promising next-generation X-ray active materials due to their good X-ray absorption, high carrier mobility, and long carrier lifetime. Devices based on perovskite single crystals, on the one hand, have extremely limited preparation methods, high cost and slow process methods, are not suitable for large-scale industrial production, and do not have the potential for large-scale rapid preparation; on the other hand, perovskite single crystals Crystals are based on nucleation and growth in solution, which limits the preparation of later functional layers; at the same time, in the current technology, perovskite single crystals are combined with array substrates such as thin-film transistors (TFTs) based on conductive indium tin oxide (ITO) It is unstable and easy to fall off, which seriously restricts the application prospect of perovskite-based direct conversion X-ray detector imaging.

Contents of the invention

The purpose of this application is to provide a perovskite-based X-ray detector and its preparation method, which aims to solve the difficulty in the preparation process of the existing direct-conversion X-ray detector based on perovskite single crystals, and the prepared calcium The problem of poor bonding stability between the titanium ore active layer and the substrate.

In order to realize the above-mentioned application purpose, the technical scheme adopted in this application is as follows:

In a first aspect, the present application provides a method for preparing a perovskite-based X-ray detector, comprising the following steps:

obtaining a conductive substrate, and performing an activation treatment on the conductive substrate to obtain an activated conductive substrate;

Prepare a mixed solution of the perovskite precursor, deposit the mixed solution on the activated conductive substrate, dry and anneal to obtain the active perovskite containing A _n A' _1-n PbZ ₃ perovskite material layer, wherein A is selected from CH ₃ NH ₃ ⁺ , A' is selected from CH ₂ (NH ₃ ) ₂ ⁺ , Z is selected from halogen, and n is 0.1 to 0.95;

A back electrode is prepared on the surface of the perovskite active layer away from the conductive substrate to obtain a perovskite-based X detector.

Further, the step of activation treatment includes: after cleaning the conductive substrate, heat activation treatment at a temperature of 100-130° C. for 8-10 minutes.

Further, the step of dry annealing treatment includes: after depositing the mixed solution on the activated conductive substrate, air-drying the deposited solvent in the mixed solution naturally, and then raising the temperature to 60°C at 5-10°C/s ~80°C annealing treatment for 30-120 minutes.

Further, the step of preparing the mixed solution of the perovskite precursor includes: under an inert atmosphere, CH ₃ NH ₃ Z ¹ , CH ₂ (NH ₃ ) ₂ Z ² , PbZ ₂ ³ , a surfactant and an organic The solvents are mixed to obtain a mixed solution of the perovskite precursor, wherein Z ¹ , Z ² and Z ³ are independently selected from I, Br or Cl.

Further, the molar ratio of CH ₃ NH ₃ Z ¹ , CH ₂ (NH ₃ ) ₂ Z ² and PbZ ₂ ³ is the stoichiometric ratio of the _An A' _1-n PbZ ₃ perovskite material .

Further, the mass ratio of the total mass of CH ₃ NH ₃ Z ¹ , CH ₂ (NH ₃ ) ₂ Z ² and PbZ ₂ ³ to the surfactant and the organic solvent is 100:(1.5-2.5):( 40-65).

Further, the surfactant is selected from: cetyl trimethyl ammonium bromide, cetyl trimethyl ammonium chloride, didodecyl dimethyl ammonium bromide, lauryl sulfate at least one of sodium.

Further, the organic solvent is selected from at least one of N,N-dimethylformamide, N-methylpyrrolidone, and dimethyl sulfoxide.

Further, the temperature of the mixing treatment is 50-65°C.

Further, the n is 0.1-0.2, or, the n is 0.8-0.95.

Further, the back electrode includes a metal electrode or a carbon electrode.

Further, the step of depositing the mixed solution on the activated conductive substrate includes: using a slit coating method, the distance between the slit and the activated conductive substrate is 5-500 μm, and the solution outflow rate is 1 The mixed solution is coated on the surface of the activated conductive substrate under the conditions of ˜100 μL/s and a coating rate of 1˜10 mm/s.

Further, the organic solvent is selected from a mixed solvent of N-methylpyrrolidone, N,N-dimethylformamide and/or dimethyl sulfoxide with a volume ratio of 1:(2-3).

Further, the conditions of the slit coating include: the distance between the slit and the activated conductive substrate is 250-350 μm, the outflow rate of the solution is 45-75 μL/s, and the coating rate is 3-5 mm/s.

Further, the metal electrode includes: at least one of Al, Ag, Au and Cu.

Further, the thickness of the perovskite active layer is 50-100 μm.

In a second aspect, the present application provides a perovskite-based X-ray detector, the perovskite-based X-ray detector includes a perovskite active layer, and the perovskite active layer contains A _n A' _{1 -n} PbZ ₃ perovskite material, wherein A is selected from CH ₃ NH ₃ ⁺ , A' is selected from CH ₂ (NH ₃ ) ₂ ⁺ , Z is selected from halogen, and n is 0.1-0.95.

Further, the n is 0.1-0.2, or, the n is 0.8-0.95.

Further, the Z is selected from at least one of I, Br, and Cl.

Further, the perovskite-based X-ray detector also includes a conductive base layer and a back electrode layer that are respectively bonded and arranged on both sides of the perovskite active layer.

Further, the thickness of the perovskite active layer is 50-100 μm.

Further, the back electrode layer includes: at least one of Al, Ag, Au and Cu.

Further, the conductive base layer is selected from indium tin oxide base.

In the preparation method of the perovskite-based X-ray detector provided in the first aspect of the present application, first, the conductive substrate is activated to activate the surface atoms of the conductive substrate, which is conducive to the deposition of the perovskite active layer solution on the surface and improves Carrier Mobility in Conductive Substrates. Then, the mixed solution of the perovskite precursor is deposited on the activated conductive substrate as the raw material component, and while the mixed solution is solidified and formed by drying and annealing, the perovskite precursor in the mixed solution self-assembles and forms on the surface of the conductive substrate. The perovskite active layer containing the A _n A' _1-n PbZ ₃ perovskite material is formed in situ, and the stability of the film layer is high, and at the same time, the bonding tightness between the perovskite active layer and the conductive substrate is improved. Among them, the A _n A' _1-n PbZ ₃ perovskite material has high X-ray absorption efficiency, high charge carrier mobility, long charge carrier diffusion length, and very good bulk defect tolerance, etc. characteristics, can directly absorb photons to generate electrons and hole pairs, and then these electrons and hole pairs are converted into free carriers and migrate to the electrodes under the action of an external electric field, and finally collected by their respective electrodes, with high detection sensitivity and low detection limit . Then prepare a back electrode on the surface of the perovskite active layer to obtain a perovskite-based X-ray detector. The preparation method is simple and efficient, and the utilization rate of raw materials is high. It is suitable for the preparation of large-area perovskite-based X-ray detectors, and the preparation In the perovskite-based X-ray detector, the bonding stability between functional layers is good, and the interface impedance is low, which improves the detection sensitivity of the device.

In the perovskite-based X-ray detector provided in the second aspect of the present application, the perovskite active layer comprising the A _n A' _1-n PbZ ₃ perovskite material is doped with CH ₃ NH at the same time ₃ ⁺ and CH ₂ (NH ₃ ) ₂ ⁺ two ammonium ions can improve the stability of perovskite materials, and the electrical properties such as band gap and carrier mobility of perovskite materials can be adjusted by the value of n , thereby improving the sensitivity of X-ray detection. This application contains a perovskite active layer of An _A ' _1-n PbZ ₃ perovskite material, which has high absorption efficiency for X-rays, and has high charge carrier mobility, long charge carrier diffusion length, and Very good bulk defect tolerance and other characteristics can directly absorb photons to generate electrons and hole pairs, and then these electrons and hole pairs are converted into free carriers under the action of an external electric field to migrate to the electrodes, and finally collected by their respective electrodes , to realize the direct conversion of perovskite-based X-ray detectors to X-rays, with high detection sensitivity, low detection limit and good stability.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present application, the accompanying drawings that need to be used in the descriptions of the embodiments or the prior art will be briefly introduced below. Obviously, the accompanying drawings in the following description are only for the present application For some embodiments, those of ordinary skill in the art can also obtain other drawings based on these drawings without any creative effort.

Fig. 1 is a schematic structural diagram of a perovskite-based X-ray detector provided in an embodiment of the present application;

Fig. 2 is an I-T test diagram of the perovskite-based X-ray detector provided in Example 1 of the present application.

Detailed ways

In order to make the technical problems, technical solutions and beneficial effects to be solved in the present application clearer, the present application will be further described in detail below in conjunction with the embodiments. It should be understood that the specific embodiments described here are only used to explain the present application, and are not intended to limit the present application.

In the present invention, the term "and/or" describes the relationship between associated objects, indicating that there may be three relationships, for example, A and/or B, which may mean: A exists alone, A and B exist simultaneously, and B exists alone Condition. Among them, A and B can be singular or plural. The character "/" generally indicates that the contextual objects are an "or" relationship.

In the present invention, "at least one" means one or more, and "multiple" means two or more. "At least one of the following" or similar expressions refer to any combination of these items, including any combination of single or plural items. For example, "at least one (one) of a, b or c", or "at least one (one) of a, b and c" can mean: a, b, c, a-b (that is, a and b), a-c, b-c, or a-b-c, wherein a, b, and c can be single or multiple.

It should be understood that, in various embodiments of the present invention, the size of the serial numbers of the above-mentioned processes does not mean the sequence of execution, some or all steps can be executed in parallel or sequentially, and the execution sequence of each process should be based on its function and The internal logic is determined and should not constitute any limitation to the implementation process of the embodiment of the present invention.

Terms used in the embodiments of the present invention are only for the purpose of describing specific embodiments, and are not intended to limit the present invention. As used in the embodiments of the present invention and the appended claims, the singular forms "a" and "the" are also intended to include plural forms unless the context clearly dictates otherwise.

The weight of the relevant components mentioned in the description of the embodiments of the present invention can not only refer to the specific content of each component, but also represent the proportional relationship between the weights of each component. The scaling up or down of the content of the fraction is within the scope disclosed in the description of the embodiments of the present invention. Specifically, the mass in the description of the embodiments of the present invention may be μg, mg, g, kg and other well-known mass units in the chemical industry.

The terms "first" and "second" are only used for descriptive purposes to distinguish objects such as substances from each other, and cannot be understood as indicating or implying relative importance or implicitly specifying the quantity of indicated technical features. For example, without departing from the scope of the embodiments of the present invention, the first XX can also be called the second XX, and similarly, the second XX can also be called the first XX. Thus, a feature defined as "first" and "second" may explicitly or implicitly include one or more of these features.

The first aspect of the embodiment of the present application provides a method for preparing a perovskite-based X-ray detector, comprising the following steps:

S10. Obtain a conductive substrate, perform activation treatment on the conductive substrate, and obtain an activated conductive substrate;

S20. Prepare a mixed solution of the perovskite precursor, deposit the mixed solution on the activated conductive substrate, dry and anneal to obtain a perovskite active layer containing A _n A' _1-n PbZ ₃ perovskite material, Wherein, A is selected from CH ₃ NH ₃ ⁺ , A' is selected from CH ₂ (NH ₃ ) ₂ ⁺ , Z is selected from halogen, and n is 0.1-0.95;

S30. Prepare a back electrode on the surface of the perovskite active layer away from the conductive substrate to obtain a perovskite-based X detector.

In the preparation method of the perovskite-based X-ray detector provided in the first aspect of the present application, the conductive substrate is first activated to activate the surface atoms of the conductive substrate, which is conducive to the deposition of the perovskite active layer solution on the surface and improves the conductive substrate. carrier mobility. Then, the mixed solution of the perovskite precursor is deposited on the activated conductive substrate as the raw material component, and while the mixed solution is solidified and formed by drying and annealing, the perovskite precursor in the mixed solution self-assembles and forms on the surface of the conductive substrate. The perovskite active layer containing the A _n A' _1-n PbZ ₃ perovskite material is formed in situ, and the stability of the film layer is high, and at the same time, the bonding tightness between the perovskite active layer and the conductive substrate is improved. Among them, the A _n A' _1-n PbZ ₃ perovskite material has high X-ray absorption efficiency, high charge carrier mobility, long charge carrier diffusion length, and very good bulk defect tolerance, etc. characteristics, can directly absorb photons to generate electrons and hole pairs, and then these electrons and hole pairs are converted into free carriers and migrate to the electrodes under the action of an external electric field, and finally collected by their respective electrodes, with high detection sensitivity and low detection limit . Then prepare a back electrode on the surface of the perovskite active layer to obtain a perovskite-based X-ray detector. The preparation method is simple and efficient, and the utilization rate of raw materials is high. It is suitable for the preparation of large-area perovskite-based X-ray detectors, and the preparation In the perovskite-based X-ray detector, the bonding stability between functional layers is good, and the interface impedance is low, which improves the detection sensitivity of the device.

In the _An A' _1-n PbZ ₃ perovskite material prepared in the examples of the present application, A is selected from CH ₃ NH ₃ ⁺ , A' is selected from CH ₂ (NH ₃ ) ₂ ⁺ , Z is selected from halogen, and n is 0.1～0.95; Among them, CH ₃ NH ₃ ⁺ can increase the band gap of perovskite materials and reduce the free carrier concentration, while CH ₂ (NH ₃ ) ₂ ⁺ can reduce the band gap of perovskite materials and increase the Stability; by doping both CH ₃ NH ₃ ⁺ and CH ₂ (NH ₃ ) ₂ ⁺ ammonium ions at the same time, and n is 0.1-0.95, the stability and band gap of perovskite materials can be improved in this range , Carrier mobility and other electrical properties, improve X-ray detection sensitivity. In some embodiments, n is 0.1-0.2, or, n is 0.8-0.95; this value range of n can simultaneously achieve better quality, stability and X-ray sensitivity of the perovskite active layer.

In some embodiments, in the above step S10, the activation treatment step includes: after cleaning the conductive substrate, heat activation treatment at a temperature of 100-130° C. for 8-10 minutes. In some embodiments, the conductive substrate may be an ITO indium oxide substrate. In some specific embodiments, the conductive ITO substrate is placed in detergent, deionized water, acetone and isopropanol reagents for ultrasonic cleaning for 20-25 minutes, and after standard cleaning, it is dried with nitrogen and placed in a UV ozone machine Treatment for 10-15 minutes, deep surface cleaning and work function adjustment with ultraviolet ozone, and then thermal activation treatment at a temperature of 100-130°C for 8-10 minutes to activate the surface atoms of the conductive substrate, which is beneficial to the perovskite The solution deposition of the active layer improves the bonding stability of the perovskite active layer and the conductive substrate; at the same time, the activation of the surface atoms is beneficial to improve the carrier mobility of the conductive substrate. If the activation temperature is too low or the activation time is too short, the activation effect on the conductive substrate will be poor; if the activation temperature is too high or the activation time is too long, the surface resistance of the conductive substrate will increase, which will reduce the carrier density. Migration transfer efficiency.

In some embodiments, in the above step S20, the step of preparing the mixed solution of the perovskite precursor includes: under an inert atmosphere, CH ₃ NH ₃ Z ¹ , CH ₂ (NH ₃ ) ₂ Z ² , PbZ ₂ ³ 1. The surfactant is mixed with the organic solvent to obtain a mixed solution of the perovskite precursor, wherein Z ¹ , Z ² and Z ³ are independently selected from I, Br or Cl. In the embodiment of the present application, in order to prevent the raw materials from absorbing water and deliquescence and being oxidized, the perovskite active layer was prepared with a mixed solution of perovskite precursors under an inert atmosphere instead of directly using a solution of perovskite materials to prepare a perovskite active layer. , the precursors of perovskite materials such as CH ₃ NH ₃ Z ¹ , CH ₂ (NH ₃ ) ₂ Z ² , PbZ ₂ ³ are used as the raw material components for the preparation of the active layer, and the mixed solution is dried and annealed and solidified during the forming process , the perovskite precursor material is self-assembled in situ on the surface of the conductive substrate, so that the perovskite active layer is formed in situ on the surface of the conductive substrate, which can improve the film stability, uniformity and compactness of the perovskite active layer and other properties, and can improve the bonding tightness between the perovskite active layer and the conductive substrate. In addition, the surfactant in the mixed solution can reduce the surface tension of the mixed solution, so that the mixed solution can reduce material aggregation during the crystallization and film formation process, and improve the uniformity of perovskite film formation and the quality of the film layer.

In some embodiments, CH ₃ NH ₃ Z ¹ , CH ₂ (NH ₃ ) ₂ Z ² , PbZ ₂ ³ , surfactant and organic solvent are mixed at a temperature of 50-65° C., the The mixing temperature conditions can ensure that each raw material component is fully dissolved, and in a certain supersaturated state, no crystallization will occur; if the mixing temperature is too high, the system will deteriorate, and if the mixing temperature is too low, part of the perovskite crystallization may be precipitated.

In some embodiments, the molar ratio of CH ₃ NH ₃ Z ¹ , CH ₂ (NH ₃ ) ₂ Z ² and Pb Z ³ is the ratio of the stoichiometric number of A _n A' _1-n PbZ ₃ perovskite material; Make each raw material component fully contact and react, self-assemble to form A _n A' _1-n PbZ ₃ perovskite material, and reduce the generation of by-products.

In some embodiments, the mass ratio of the total mass of CH ₃ NH ₃ Z ¹ , CH ₂ (NH ₃ ) ₂ Z ² and PbZ ₂ ³ to the surfactant and the organic solvent is 100:(1.5-2.5):(40 -65); This mass ratio not only effectively ensures the viscosity of the mixed solution, but also makes the solution easy to be deposited on the surface of the conductive substrate by scraping, spraying, etc.; and ensures the perovskite material in the perovskite active layer. content, thereby ensuring the absorption and conversion efficiency of the active layer to X-rays. If the surfactant content is too low, the uniformity of film formation of the mixed solution will be poor, and perovskite crystal aggregation will occur during deposition and film formation; if the surfactant content is too high, a diaphragm will easily form on the surface of the solution, which is not conducive to film formation Afterwards the solvent evaporates and the perovskite crystallizes. Too high or low organic solvent content will affect the viscosity of the mixed solution, which is not conducive to the deposition of the mixed solution. In some embodiments, the viscosity of the mixed solution of perovskite precursor of CH ₃ NH ₃ Z ¹ , CH ₂ (NH ₃ ) ₂ Z ² , PbZ ₂ ³ , surfactant and organic solvent is preferably 60-100 cP, This viscosity simultaneously ensures the deposition and film-forming properties of the mixed solution.

In some embodiments, the surfactant is selected from the group consisting of cetyltrimethylammonium bromide CTAB, didodecyldimethylammonium bromide DDAB, cetyltrimethylammonium chloride CTAC, At least one of sodium dialkyl sulfate SDS; these surfactants can effectively reduce the surface tension of the mixed solution, so that the mixed solution can reduce the aggregation of perovskite crystal regions during the crystallization and film formation process, and improve the uniformity of film formation and thin film quality.

In some embodiments, the organic solvent is selected from: at least one of N,N-dimethylformamide DMF, N-methylpyrrolidone NMP, and dimethyl sulfoxide DMSO, and these solvents are beneficial to the precursor of perovskite Materials and surfactants have good solubility, which is conducive to the full contact reaction of various raw material components. In some specific embodiments, the organic solvent adopts a mixed solvent of NMP and DMF and/or DMSO with a volume ratio of 1:(2～3), wherein DMF or DMSO is the main solvent, and NMP is the auxiliary solvent and ligand, which can be Better control of the crystallization rate of perovskite enables the mixed solution to have better film-forming properties and improves the film quality of the perovskite active layer.

In some embodiments, the step of depositing the mixed solution on the activated conductive substrate includes: adopting the method of slit coating, the distance between the slit and the activated conductive substrate is 5-500 μm, and the outflow rate of the solution is 1-100 μL/ s, coating the mixed solution on the surface of the activated conductive substrate under the condition of a coating rate of 1-10 mm/s. In some preferred embodiments, the conditions for slit coating include: the distance between the slit and the activated conductive substrate is 250-350 μm, the outflow rate of the solution is 45-75 μL/s, and the coating rate is 3-5 mm/s. In the embodiment of the present application, the mixed solution is deposited on the surface of the activated conductive substrate by using the slit coating method, which can realize automatic deposition, improve the repeatability of deposition, large-area deposition and increase the utilization rate of raw materials. Among them, the distance between the slit and the activated conductive substrate, the solution outflow rate and the coating rate are interrelated; the distance mainly affects the film thickness and film continuity, and the flow rate and coating speed affect the uniformity of the deposited wet film. Larger, but they influence each other, and the three parameters are highly correlated, so the main reason is that the matching degree is higher. Too high or too low will affect the thickness of the wet film, the uniformity of the film and the continuity of the film.

In some embodiments, the step of drying and annealing treatment includes: after depositing the mixed solution on the activated conductive substrate, air-drying the solvent in the deposited mixed solution, and then raising the temperature to 60-80°C at 5-10°C/s for annealing treatment After 30 to 120 minutes, dry annealing to obtain a perovskite active layer containing A _n A' _1-n PbZ ₃ perovskite material, wherein A is selected from CH ₃ NH ₃ ⁺ , and A' is selected from CH ₂ (NH ₃ ) ₂ ⁺ , Z is selected from halogen, and n is 0.1-0.95. In the process of drying and annealing the mixed solution of the perovskite precursor in the embodiment of the present application, the solvent in the mixed solution deposited under natural conditions should be air-dried at first. Crystallization, resulting in the formation of aggregates in some areas; then annealing treatment at 5-10°C/s to 60-80°C for 30-120 minutes, the perovskite solution is solidified and formed, and the A _n A' _1-n PbZ ₃ perovskite The material is further self-assembled to improve the crystal form order, structural integrity, purity, and performance stability of the A _n A' _1-n PbZ ₃ perovskite material in the perovskite active layer. If the annealing temperature is too low or the rate is too slow, the optimization effect on the perovskite crystal form and purity in the perovskite active layer is not good, which is not conducive to improving the photoelectricity and stability of the perovskite active layer; if the annealing temperature If the rate is too high or the rate is too fast, the perovskite crystallization will be unbalanced, local aggregation will occur, and the uniformity of the formed film layer will be poor, which will destroy the stability of the perovskite active layer.

In some embodiments, the thickness of the perovskite active layer is 50-100 μm, which ensures the crystallization uniformity and smoothness of the perovskite active layer, and improves the absorption and conversion efficiency of the perovskite active layer to X-rays , especially to improve the absorption and conversion efficiency of soft X-rays, thus ensuring the detection sensitivity of X-ray detectors. If the perovskite active layer is too thin, the X-ray absorption will be weak; if the perovskite active layer is too thick, it will lead to serious recombination of carriers in the perovskite active layer. In some specific embodiments, the thickness of the perovskite active layer may be 50-60 μm, 60-70 μm, 70-80 μm, 80-90 μm, 90-100 μm, etc.

In some embodiments, in the above step S30, a metal electrode or a carbon electrode is prepared on the surface of the perovskite active layer away from the conductive substrate as a back electrode to obtain a perovskite-based X detector.

In some embodiments, the step of preparing the back electrode includes: the vacuum degree is not lower than 10 ^-6 mbar, and the evaporation rate is

Under the condition that the evaporation time is 100-1500s, the metal electrode is deposited by evaporation on the surface of the perovskite active layer. If the vacuum is too low, the electrode material is easily polluted, and at the same time, the evaporation temperature will increase to decompose the perovskite material in the perovskite active layer, which will destroy the stability of the material and the functional layer. If the evaporation rate is too fast, the surface of the perovskite active layer will be damaged; if the evaporation rate is too low, the deposition efficiency will be low. In addition, on the one hand, the length of the evaporation time will affect the stability of the deposited film, and on the other hand, the length of the deposition time can be determined according to the thickness of the deposited film. The evaporation time of the embodiment of this application is 100-1500s. The stability of the film layer makes the thickness of the deposited electrode meet the application requirements of X-ray detection devices. In some specific embodiments, the metal electrodes include: at least one of Al, Ag, Au, and Cu; these metal electrodes have high charge carrier collection and transport efficiency. In other embodiments, when the back electrode is a carbon electrode, it can be prepared by doctor blade coating.

The second aspect of the embodiment of the present application provides a perovskite-based X-ray detector, the perovskite-based X-ray detector includes a perovskite active layer, and the perovskite active layer contains A _n A' _1-n PbZ ₃ Perovskite material, wherein A is selected from CH ₃ NH ₃ ⁺ , A' is selected from CH ₂ (NH ₃ ) ₂ ⁺ , Z is selected from halogen, and n is 0.1-0.95.

In the perovskite-based X-ray detector provided in the second aspect of the present application, the perovskite active layer comprising the A _n A' _1-n PbZ ₃ perovskite material is doped with CH ₃ NH at the same time ₃ ⁺ and CH ₂ (NH ₃ ) ₂ ⁺ two ammonium ions can improve the stability of perovskite materials, and the electrical properties such as band gap and carrier mobility of perovskite materials can be adjusted by the value of n , thereby improving the sensitivity of X-ray detection. The embodiment of the present application contains a perovskite active layer of A _n A' _1-n PbZ ₃ perovskite material, which has high absorption efficiency for X-rays, and has high charge carrier mobility and long charge carrier diffusion length , and very good bulk defect tolerance and other characteristics, can directly absorb photons to generate electron and hole pairs, and then these electrons and hole pairs are converted into free carriers under the action of an external electric field to migrate to the electrode, and finally are transported by their respective The electrode collection realizes the direct conversion of X-rays by perovskite-based X-ray detectors. The detector has high detection sensitivity, low detection limit and good stability.

In some embodiments, in the _An A' _1-n PbZ ₃ perovskite material, A is selected from CH ₃ NH ₃ ⁺ , A' is selected from CH ₂ (NH ₃ ) ₂ ⁺ , wherein CH ₃ NH ₃ ⁺ It can adjust the bandgap width of the perovskite material and reduce the free carrier concentration, while CH ₂ (NH ₃ ) ₂ ⁺ can adjust the narrow bandgap of the perovskite material and improve the stability of the material; n is 0.1-0.2, Alternatively, n is 0.8-0.95; this value range of n can simultaneously achieve better quality, stability and X-ray sensitivity of the perovskite active layer.

In some embodiments, Z in the A _n A' _1-n PbZ ₃ perovskite material is selected from at least one of I, Br, and Cl; the Z-position halogen forms a regular octahedron with the Pb metal element in the form of 6 coordination , eight [PbZ ₆ ] ^4- octahedrons form a cage in the form of common vertex connections, and the A and A' sites occupy the center of the cage to play a supporting role in the perovskite structure, forming 12 coordination with the Z site.

In some embodiments, the thickness of the perovskite active layer is 50-100 μm; this thickness ensures the crystallization uniformity and smoothness of the perovskite active layer, and improves the absorption and conversion efficiency of the perovskite active layer to X-rays , especially to improve the absorption and conversion efficiency of soft X-rays, thus ensuring the detection sensitivity of X-ray detectors. If the perovskite active layer is too thin, the X-ray absorption will be weak; if the perovskite active layer is too thick, it will lead to serious recombination of carriers in the perovskite active layer. In some specific embodiments, the thickness of the perovskite active layer may be 50-60 μm, 60-70 μm, 70-80 μm, 80-90 μm, 90-100 μm, etc.

In some embodiments, the perovskite-based X-ray detector also includes a conductive base layer and a back electrode layer respectively bonded on both sides of the perovskite active layer for collecting and transmitting the X-ray in the perovskite active layer. Carriers form current, and its structure is shown in Figure 1.

In some embodiments, the back electrode layer includes at least one of Al, Ag, Au, and Cu. In some embodiments, the conductive base layer is selected from an indium tin oxide base. These materials are highly efficient for carrier collection and transport.

In order to make the above-mentioned implementation details and operations of the present application clearly understood by those skilled in the art, as well as the remarkable performance of the perovskite-based X detector and its preparation method in the embodiment of the present application, the following examples are given through multiple embodiments The above-mentioned technical solution will be described.

Example 1

A perovskite-based X detector, the preparation of which comprises the steps of:

1. Place the ITO substrate in detergent, deionized water, acetone, and isopropanol reagents for ultrasonic cleaning for 25 minutes, blow dry with nitrogen and place it in a UV ozone machine for 10-15 minutes, then place it on a hot table at 120°C Heat activation for 8 minutes to obtain the activated ITO substrate;

2. Under a nitrogen atmosphere, mix CH ₃ NH ₃ I, CH ₂ (NH ₃ ) ₂ I and PbI ₂ according to (CH ₃ NH ₃ ) _0.9 (CH ₂ (NH ₃ ) ₂ ) _0.1 PbI ₃ perovskite material The ratio of the stoichiometric number is mixed, while adding CH ₃ NH ₃ I, CH ₂ (NH ₃ ) ₂ I and PbI ₂ total amount of 1.75%wt surfactant CTAB and 57%wt volume ratio of 3:1 The mixed solvent of DMF and NMP is fully stirred and mixed under the condition of 60°C to obtain a clear and transparent mixed solution of perovskite precursor;

3. Using the method of slit coating, the mixed solution is coated on the activated ITO under the conditions that the distance between the slit and the activated conductive substrate is 350 μm, the solution outflow rate is 750 μL/s, and the coating rate is 5 mm/s. base surface;

4. At a vacuum of 10 ^-6 mbar, the evaporation rate is

Under the condition that the evaporation time is 1500s, Au is vacuum-deposited on the surface of the perovskite functional layer to form an Au metal back electrode, and ITO/(CH ₃ NH ₃ ) _0.9 (CH ₂ (NH ₃ ) ₂ ) _0.1 PbI ₃ / Au-structured perovskite-based X-ray detectors.

Example 2

A perovskite-based X detector, the difference from Example 1 is that in step 2, CH ₃ NH ₃ Br, CH ₂ (NH ₃ ) ₂ Br and PbBr ₂ raw material components are used to prepare ITO/(CH ₃ NH ₃ ) _0.9 (CH ₂ (NH ₃ ) ₂ ) _0.1 Perovskite-based X-ray detector with PbBr ₃ /Au structure.

Example 3

A kind of perovskite base X detector, its difference with embodiment 1 is, adopt CH ₃ NH ₃ I, CH ₂ (NH ₃ ) ₂ I and PbI ₂ raw material components in step 2, make ITO/(CH ₃ NH ₃ ) _0.85 (CH ₂ (NH ₃ ) ₂ ) _0.15 Perovskite-based X-ray detector with PbI ₃ /Au structure.

Example 4

A kind of perovskite base X detector, its difference with embodiment 1 is, adopt CH ₃ NH ₃ I, CH ₂ (NH ₃ ) ₂ I and PbI ₂ raw material components in step 2, make ITO/(CH ₃ NH ₃ ) _0.15 (CH ₂ (NH ₃ ) ₂ ) _0.85 Perovskite-based X-ray detector with PbI ₃ /Au structure.

Example 5

A perovskite-based X detector, the difference from Example 1 is that in step 2, CH ₃ NH ₃ Br, CH ₂ (NH ₃ ) ₂ Br and PbI ₂ raw material components are used to prepare ITO/(CH ₃ NH ₃ ) _0.85 (CH ₂ (NH ₃ ) ₂ ) _0.15 Perovskite-based X-ray detector with PbBrI ₂ /Au structure.

Comparative example 1

A perovskite-based X detector, which differs from Embodiment 1 in that CH ₂ (NH ₃ ) ₂ I and PbI are calculated according to the stoichiometric ratio of CH ₂ (NH ₃ ) ₂ PbI ₃ perovskite material Mixing, adding CH ₂ (NH ₃ ) ₂ I and PbI ₂ total amount of 1.75%wt surfactant CTAB and 57%wt volume ratio are DMF and NMP mixed solvent of 3:1, at 60 ℃ condition Under the condition of thorough stirring and mixing, a clear and transparent mixed solution of perovskite precursor is obtained; a perovskite-based X-ray detector with ITO/CH ₂ (NH ₃ ) ₂ PbI ₃ /Au structure is prepared.

Comparative example 2

A perovskite-based X detector, which differs from Embodiment 1 in that in Step 1, the conductive ITO substrate is not subjected to thermal activation treatment.

Comparative example 3

A perovskite-based X detector, using CH ₃ NH ₃ I single crystal as the perovskite active layer, assembled with ITO substrate and Au metal to form a single crystal calcium of ITO/CH ₃ NH ₃ PbI ₃ single crystal/Au structure Titanium-based X-ray detectors.

Further, the X-ray detectors prepared in Examples 1-5 and Comparative Examples 1-3 were respectively subjected to photocurrent test, that is, I-t test, wherein, the I-T test diagram of Example 1 is shown in Figure 2, horizontal The coordinate is time, and the ordinate is current density. Through the I-t test, the X-ray response electricity of the detector under different doses is obtained, thereby obtaining the X-ray sensitivity (S, Sensitivity) of the detector detector respectively, and the test results are shown in Table 1 below;

In the X-ray detectors prepared in Examples 1 to 5 and Comparative Examples 1 to 3, the force required for the perovskite active layer to be peeled off from the electrode base of 1 cm × 1 cm was tested by a tensile tester, and the relationship between the perovskite active layer and the X-ray detector was studied. The size of the binding force of the conductive substrate, the test results are shown in Table 1 below:

By placing it under an inert atmosphere and regularly carrying out the i-t test every 24 hours, the defined stability time is the time point when the photocurrent intensity is 50% or lower than the initial value, for the perovskite in Examples 1-5 and Comparative Examples 1-3 The stability of the active layer of the mine was tested, and the test results are shown in Table 1 below:

In addition, the maximum preparation area of the X-ray detectors prepared in Examples 1 to 5 and Comparative Examples 1 to 3 has also been calculated, and the calculation results are shown in Table 1 below:

Table 1

It can be seen from the above test results that the examples of this application use perovskite precursor materials such as organic ammonium halide salts and lead halides as raw material components for preparing perovskite active layers, and after preparing mixed solutions with surfactants and organic solvents, deposit The A _n A' _1-n PbZ ₃ perovskite material doped with CH ₃ NH ₃ ⁺ and CH ₂ (NH ₃ ) ₂ ⁺ ammonium ions at the same time was prepared on the surface of the activated ITO conductive substrate, which not only improves the The binding force between the perovskite active layer and the surface of the conductive substrate improves the detection sensitivity of the perovskite-based X-ray detector, and is suitable for large-area preparation of the perovskite active layer.

The structure of the perovskite-based X-ray detector prepared in Comparative Example 1 is ITO/CH ₂ (NH ₃ ) ₂ PbI ₃ /Au, which is simultaneously doped with CH ₃ NH ₃ ⁺ and CH ₂ (NH ₃ ) ₂ ⁺ perovskite materials of two kinds of ammonium ions, which reduces the detection sensitivity of the detector.

In Comparative Example 2, no thermal activation treatment was performed on the conductive substrate, which reduced the binding force between the active layer and the conductive substrate in the perovskite-based X-ray detector, and also reduced the sensitivity of the detector.

The CH ₃ NH ₃ PbI ₃ single crystal perovskite-based X-ray detector provided in Comparative Example 3 has a small device and limited absorption and conversion efficiency for X-rays.

The above descriptions are only preferred embodiments of the application, and are not intended to limit the application. Any modifications, equivalent replacements and improvements made within the spirit and principles of the application should be included in the protection of the application. within range.

Claims (10)

1. A method for preparing a perovskite-based X-ray detector, comprising the following steps:

   obtaining a conductive substrate, and performing an activation treatment on the conductive substrate to obtain an activated conductive substrate;

   Prepare a mixed solution of the perovskite precursor, deposit the mixed solution on the activated conductive substrate, dry and anneal to obtain the active perovskite containing A _n A' _1-n PbZ ₃ perovskite material layer, wherein A is selected from CH ₃ NH ₃ ⁺ , A' is selected from CH ₂ (NH ₃ ) ₂ ⁺ , Z is selected from halogen, and n is 0.1 to 0.95;

   A back electrode is prepared on the surface of the perovskite active layer away from the conductive substrate to obtain a perovskite-based X detector.
2. The preparation method of perovskite-based X-ray detector according to claim 1, characterized in that, the step of activation treatment comprises: after cleaning the conductive substrate, at a temperature of 100-130°C Heat activation treatment for 8 to 10 minutes;

   And/or, the step of dry annealing treatment includes: after depositing the mixed solution on the activated conductive substrate, air-drying the solvent in the deposited mixed solution, and then raising the temperature at 5-10° C./s to Annealing at 60-80°C for 30-120 minutes.
3. The method for preparing a perovskite-based X-ray detector according to claim 1 or 2, wherein the step of preparing the mixed solution of the perovskite precursor comprises: under an inert atmosphere, CH ₃ NH ₃ Z ¹ , CH ₂ (NH ₃ ) ₂ Z ² , PbZ ₂ ³ , surfactant and organic solvent are mixed to obtain a mixed solution of perovskite precursor, wherein Z ¹ , Z ² and Z ³ are independently selected from I, Br or Cl.
4. The preparation method of perovskite-based X-ray detector according to claim 3, characterized in that, the molar ratio of said CH ₃ NH ₃ Z ¹ , CH ₂ (NH ₃ ) ₂ Z ² and PbZ ₂ ³ is as stated The stoichiometric ratio of A _n A' _1-n PbZ ₃ perovskite materials;

   And/or, the mass ratio of the total mass of CH ₃ NH ₃ Z ¹ , CH ₂ (NH ₃ ) ₂ Z ² and PbZ ₂ ³ to the surfactant and the organic solvent is 100:(1.5-2.5): (40-65);

   And/or, the surfactant is selected from: cetyl trimethyl ammonium bromide, cetyl trimethyl ammonium chloride, didodecyl dimethyl ammonium bromide, lauryl at least one of sodium sulfate;

   And/or, the organic solvent is selected from: at least one of N,N-dimethylformamide, N-methylpyrrolidone, and dimethyl sulfoxide;

   And/or, the temperature of the mixing treatment is 50-65°C.
5. The method for preparing a perovskite-based X-ray detector according to claim 4, wherein said n is 0.1-0.2, or said n is 0.8-0.95;

   And/or, the back electrode includes a metal electrode or a carbon electrode.
6. The method for preparing a perovskite-based X-ray detector according to claim 5, wherein the step of depositing the mixed solution on the activated conductive substrate comprises: adopting a slit coating method, The distance between the slit and the activated conductive substrate is 5-500 μm, the solution outflow rate is 1-100 μL/s, and the coating rate is 1-10 mm/s, and the mixed solution is coated on the activated conductive substrate. Conductive substrate surface;

   And/or, the organic solvent is selected from a mixed solvent of N-methylpyrrolidone, N,N-dimethylformamide and/or dimethyl sulfoxide with a volume ratio of 1:(2-3).
7. The method for preparing a perovskite-based X-ray detector according to claim 6, wherein the conditions for coating the slit include: the distance between the slit and the activated conductive substrate is 250-350 μm, and the solution The outflow rate is 45-75μL/s, and the coating rate is 3-5mm/s;

   And/or, the metal electrode includes: at least one of Al, Ag, Au, Cu;

   And/or, the thickness of the perovskite active layer is 50-100 μm.
8. A perovskite-based X-ray detector, characterized in that the perovskite-based X-ray detector includes a perovskite active layer, and the perovskite active layer contains A _n A' _1-n PbZ ₃ Perovskite material, wherein A is selected from CH ₃ NH ₃ ⁺ , A' is selected from CH ₂ (NH ₃ ) ₂ ⁺ , Z is selected from halogen, and n is 0.1-0.95.
9. The perovskite-based X-ray detector according to claim 8, wherein said n is 0.1-0.2, or said n is 0.8-0.95;

   And/or, said Z is selected from at least one of I, Br, Cl;

   And/or, the perovskite-based X-ray detector further includes a conductive base layer and a back electrode layer that are respectively bonded on both sides of the perovskite active layer.
10. The perovskite-based X-ray detector according to claim 9, wherein the thickness of the perovskite active layer is 50-100 μm;

    And/or, the back electrode layer includes: at least one of Al, Ag, Au, Cu;

    And/or, the conductive base layer is selected from an indium tin oxide base.

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