Perovskite scintillator material and preparation method of indirect type x-ray detector thereof

Abstract

The disclosure provides a perovskite scintillator material preparation method, which comprises the following steps: S11, spin coating a bottom perovskite nanocrystal layer and depositing a bottom polymer thin film layer; S12, spin coating a perovskite nanocrystal layer and a polymer thin film layer on the surface of the bottom polymer thin film layer in sequence, and the perovskite nanocrystal layer and the polymer thin film layer form a composite structure layer; wherein the composite structure layer is at least two layers; the uppermost layer of the composite structure layer comprises a top perovskite nanocrystal layer; wherein the band gap of the perovskite nanocrystal layer decreases layer by layer from the bottom perovskite nanocrystal layer to the top perovskite nanocrystal layer. Another aspect of the disclosure provides a method for preparing an indirect X-ray detector by using a perovskite scintillator material. The disclosure solves the self-absorption problem by introducing a perovskite nanocrystal multilayer film with a gradient change in the band gap, increases the stability of the perovskite scintillator material by using a polymer thin film, and uses a high-response light detector in combination with the perovskite scintillator part.

Description

TECHNICAL FIELD

[0001] The present disclosure provides a perovskite scintillator material and a preparation method of an indirect type X-ray detector thereof, and belongs to the field of sensors, in particular to the field of ray detectors. BACKGROUND

[0002] X-rays are widely used in the fields of industry, security check, medicine, scientific research, etc. It has strong penetration ability and can realize non-destructive detection of internal information of matter. Different substances have different absorption abilities to X-rays, so the intensity distribution information of X-rays after penetrating the object can reflect the internal material distribution of the object. The ionizing radiation of X-rays can damage genetic material and increase the risk of the irradiated person, so high sensitivity and low dose detection are the main direction of X-ray detection research. At present, the main X-ray imaging methods are direct detection imaging and indirect detection imaging, among which indirect detection imaging mainly relies on scintillators for imaging and is the most mainstream solution. The commonly used scintillator materials mainly include cesium iodide doped with thallium, sodium iodide doped with thallium, yttrium lutetium silicate doped with cerium, etc. These traditional scintillator materials have high luminous efficiency and short decay time, but it is difficult to adjust the radiation luminescence in the visible spectrum. Moreover, these scintillator materials usually need to be crystallized and synthesized at high temperature, which has the defects of complex preparation process and long preparation time. The development and use of high-performance and low-cost X-ray detection materials is the main direction of X-ray detector development.

[0003] In recent years, halide perovskites are considered to be a very competitive X-ray detection material due to their strong X-ray absorption ability and low-cost solution preparation method. Inorganic lead halide perovskite nanocrystal materials have the advantages of simple preparation, fast response speed and good spatial resolution, and are an excellent scintillator material. However, perovskite materials have a very serious self-absorption phenomenon and relatively low stability, which greatly limits their application in the field of X-rays. In addition, compared with traditional commercial scintillators, the light conversion efficiency is relatively low, that is, the same X-ray irradiation produces fewer visible light photons, in order to effectively detect fewer photons, it is necessary to develop a high-sensitivity photodetector sensitive to a small number of photons. SUMMARY

[0004] (I) Technical problems to be solved

[0005] Therefore, the present disclosure provides a perovskite scintillator material and a preparation method of an indirect type X-ray detector thereof, to solve the self-absorption phenomenon of the scintillator material, improve the stability of the scintillator material, and improve the sensitivity of the X-ray detector, etc.

[0006] (II) Technical solutions

[0007] In order to achieve the above-mentioned purpose, the present disclosure provides, in one aspect, a preparation method of a perovskite scintillator material, comprising: S11, spin-coating a bottom perovskite nanocrystal layer and depositing a bottom polymer thin film layer; S12, spin-coating a perovskite nanocrystal layer and a polymer thin film layer on the surface of the bottom polymer thin film layer in sequence, the perovskite nanocrystal layer and the polymer thin film layer forming a composite structure layer; wherein the composite structure layer is at least two layers; the uppermost layer of the composite structure layer comprises a top perovskite nanocrystal layer; wherein the band gap of the perovskite nanocrystal layer decreases layer by layer from the bottom perovskite nanocrystal layer to the top perovskite nanocrystal layer.

[0008] According to an embodiment of the present disclosure, the spin-coating of the perovskite nanocrystal layer further comprises: mixing the perovskite nanocrystal with a PMMA solution and then spin-coating.

[0009] According to an embodiment of the present disclosure, the polymer thin film at least comprises parylene.

[0010] According to an embodiment of the present disclosure, the band gap of the perovskite nanocrystal layer is adjusted by adjusting the size of quantum dots, the type and content of halogen elements.

[0011] According to an embodiment of the present disclosure, the preparation environment of the perovskite scintillator material is anhydrous and anaerobic environment.

[0012] The present disclosure provides, in a second aspect, a perovskite scintillator material prepared by the preparation method of the perovskite scintillator material, which is used to form an indirect X-ray detector together with a photodetector.

[0013] The present disclosure provides, in a third aspect, a method for preparing an indirect X-ray detector by using the perovskite scintillator material, comprising: S21, forming an embedded electrode on the surface of a substrate with a silicon oxide layer; S22, transferring graphene to the surface of the silicon oxide layer and patterning the graphene; S23, spin-coating semiconductor quantum dots and depositing a polymer thin film; S24, preparing a perovskite scintillator part, wherein the perovskite scintillator part is prepared according to the preparation method of the perovskite scintillator material; S25, depositing an aluminum thin film to coat the perovskite scintillator part and patterning the aluminum thin film; S26, etching the perovskite scintillator part and the aluminum thin film; S27, depositing an aluminum thin film to coat the sidewall of the scintillator part, thereby obtaining an indirect X-ray detector.

[0014] According to an embodiment of the present disclosure, the upper surface of the electrode in S21 is on the same plane as the upper surface of the silicon oxide layer; and the electrode is connected to a signal processing circuit.

[0015] According to an embodiment of the present disclosure, the etched-out scintillator part is a square with a side length of 10-100 μm.

[0016] The fourth aspect of the present disclosure provides an indirect X-ray detector obtained by the method of preparing an indirect X-ray detector using the perovskite scintillator material, for a single X-ray detector device or an X-ray detector device array, to realize X-ray imaging.

[0017] (III) Beneficial Effects

[0018] The present disclosure increases the stability of the perovskite scintillator material by depositing a polymer thin film on the surface of each layer of perovskite nanocrystals, solves the self-absorption problem of the perovskite scintillator material by introducing an inorganic perovskite nanocrystal multilayer thin film structure with a band gap gradient change, and solves the problem of low X-ray detection sensitivity by using a high-response graphene photodetector as a light detector of the indirect X-ray detector. BRIEF DESCRIPTION OF DRAWINGS

[0019] In order to more clearly illustrate the technical solutions in the embodiments of the present disclosure, the drawings needed in the embodiment description will be briefly introduced. Obviously, the drawings in the following description are only some embodiments of the present disclosure, and other drawings can also be obtained by those skilled in the art without creative labor.

[0020] Figure 1 A flowchart of a perovskite scintillator material preparation method provided by the embodiments of the present disclosure is schematically shown;

[0021] Figure 2 A flowchart of a perovskite scintillator material preparation method provided by the embodiments of the present disclosure is schematically shown;

[0022] Figure 3 A structure diagram of an indirect X-ray detector provided by the embodiments of the present disclosure is schematically shown;

[0023]

Explanation of reference numerals

[0024] 1-perovskite nanocrystal layer with a band gap decreasing layer by layer from the bottom layer to the top layer; 2-polymer thin film; 3-substrate; 4-electrode; 5-silicon oxide layer; 6-graphene; 7-semiconductor quantum dot; 8-aluminum thin film. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical solutions and advantages of the present disclosure more clear, the present disclosure will be further described in detail below with reference to specific embodiments and drawings.

[0026] First, the technical terms described in this document are explained and described as follows.

[0027] Bandgap: Bandgap refers to the width of an energy band, also called a bandgap, measured in electron volts (eV). Electrons bound in the valence band must acquire enough energy to jump to the conduction band to become free electrons. The energy required for an electron to go from the top of the valence band (Ev) to the bottom of the conduction band is the bandgap.

[0028] Parylene: Parylene, poly-p-xylylene, is a general term for a unique series of polymers. It is a polymer of p-xylene, which can be divided into N-type, C-type, D-type, F-type, HT-type and other types according to the difference in molecular structure.

[0029] The first aspect of the embodiment of the present disclosure provides a preparation method of a perovskite scintillator material, please refer to Figure 1 , comprising steps S11-S12.

[0030] In step S11, a bottom layer of perovskite nanocrystal layer is spin-coated, and a bottom layer of polymer thin film layer is deposited.

[0031] In step S12, a perovskite nanocrystal layer and a polymer thin film layer are spin-coated on the surface of the bottom layer of polymer thin film layer in sequence, and the perovskite nanocrystal layer and the polymer thin film layer form a composite structure layer; wherein the composite structure layer is at least two layers; the uppermost layer of the composite structure layer comprises a top layer of perovskite nanocrystal layer; wherein from the bottom layer of perovskite nanocrystal layer to the top layer of perovskite nanocrystal layer, the bandgap of the perovskite nanocrystal layer decreases layer by layer.

[0032] In this embodiment, the thickness of the 1-layer composite structure layer is 10-33 μm.

[0033] Through the embodiment of the present disclosure, the bandgap of the perovskite nanocrystal layer decreases layer by layer from the bottom layer of perovskite nanocrystal layer to the top layer of perovskite nanocrystal layer. Since the energy required for the electron of the perovskite nanocrystal with wide bandgap to reach the bottom band from the valence band is more, it is not easy to be excited, so the lower layer of perovskite nanocrystal will not absorb the light generated by the upper layer, solving the self-absorption problem of the perovskite scintillator material; at the same time, the stability of the perovskite scintillator material is increased by the polymer thin film.

[0034] On the basis of the above embodiment, the perovskite nanocrystal layer further comprises: mixing the perovskite nanocrystal with a PMMA solution and then spin-coating.

[0035] In this embodiment, the mass ratio of the PMMA solution to the perovskite nanocrystal is 1:1-100:1.

[0036] In another embodiment, the perovskite nanocrystal layer comprises: directly spin-coating perovskite nanocrystal.

[0037] Through the embodiments of the present disclosure, the PMMA solution has good transparency and optical properties, and can coat the perovskite nanocrystal thin film, thereby increasing the stability of the perovskite nanocrystal thin film without affecting the optical properties of the perovskite nanocrystal.

[0038] On the basis of the above-mentioned embodiments, the polymer thin film at least comprises parylene.

[0039] In this embodiment, the polymer thin film is a Parylene film layer, and the thickness of the Parylene thin film is 10-50 nm.

[0040] Through the embodiments of the present disclosure, the polymer thin film is prepared by a unique vacuum vapor deposition process, and a completely conformal polymer thin film coating is grown on the surface of the perovskite nanocrystal from a small active molecule. The 10-50 nm thin film coating prepared at room temperature has uniform thickness, is dense and free of pinholes, is transparent and stress-free, does not contain additives, does not damage the workpiece, has excellent electrical insulation and protection, is an effective moisture-proof, mildew-proof, corrosion-proof and salt mist-proof coating material, and helps to improve the stability of the perovskite scintillator material.

[0041] On the basis of the above-mentioned embodiments, the band gap of the perovskite nanocrystal is adjusted by adjusting the quantum dot size, the type and content of the halogen element.

[0042] In this embodiment, the band gap of CsPbCl3 is the widest, the band gap of CsPbI3 is the narrowest, the size of the perovskite nanocrystal quantum dot ranges from 2-10 nm, and the total number of the bottom layer, the intermediate layer and the top layer ranges from 3-10 layers. The band gap decreases at equal intervals from the bottom layer to the intermediate layer to the top layer.

[0043] Through the embodiments of the present disclosure, the band gap of the perovskite nanocrystal is gradually reduced layer by layer by adjusting the band gap through adjusting the quantum dot size, the type and content of the halogen element, so that the light generated by the upper layer is not absorbed by the lower layer.

[0044] On the basis of the above-mentioned embodiments, the preparation environment of the perovskite scintillator material is anhydrous and anaerobic.

[0045] In this embodiment, the perovskite scintillator material is prepared in a glove box.

[0046] Through the embodiments of the present disclosure, water and oxygen are isolated to ensure the preparation environment of the perovskite scintillator material, and to prevent water and oxygen from affecting the quality of the perovskite scintillator material.

[0047] The second aspect of the embodiments of the present disclosure provides a perovskite scintillator material prepared by the above-mentioned perovskite scintillator material preparation method, which is used to form an indirect X-ray detector with a photodetector.

[0048] Through the embodiments of the present disclosure, the self-absorption problem of the perovskite scintillator material is solved, the stability of the perovskite scintillator material is improved, and the application of the perovskite scintillator material in the X-ray field is optimized.

[0049] Please refer to Figure 2 The third aspect of the present disclosure provides a method for preparing an indirect X-ray detector by using the perovskite scintillator material, comprising: S21, forming an embedded electrode on the surface of a substrate with a silicon oxide layer; S22, transferring graphene to the surface of the silicon oxide layer and patterning the graphene; S23, spin-coating semiconductor quantum dots and depositing a polymer film; S24, preparing a perovskite scintillator part, wherein the perovskite scintillator part is prepared according to the method for preparing the perovskite scintillator material; S25, depositing an aluminum film to coat the perovskite scintillator part, and patterning the aluminum film; S26, etching the perovskite scintillator part and the aluminum film; S27, depositing an aluminum film to coat the sidewall of the scintillator part, to obtain an indirect X-ray detector.

[0050] In this embodiment, the substrate is a CMOS chip, and the thickness of the aluminum film is 100-1000 nm.

[0051] Through the embodiments of the present disclosure, the perovskite scintillator material has lower light conversion efficiency and generates fewer visible light photons compared with traditional scintillators, to solve the above problems, the graphene photodetector is creatively applied to the indirect X-ray detector, and fewer photons are effectively detected.

[0052] On the basis of the above embodiments, the upper surface of the electrode in S21 is on the same plane as the upper surface of the silicon oxide layer, and the electrode is connected to a signal processing circuit.

[0053] Through the embodiments of the present disclosure, the generated light signal is processed by the signal processing circuit connected to the electrode, and the light signal is output in the form of a digital signal, to complete the processing and reading of X-ray data.

[0054] On the basis of the above embodiments, the etched-out scintillator part is a square, and the side length of the square is 10-100 μm.

[0055] Through the embodiments of the present disclosure, the square structure has high compatibility with two-dimensional coordinates, and can be directly used as a minimum unit to process light signals, which is convenient for being used to compose an X-ray detector device array and complete X-ray detection.

[0056] The fourth aspect of the present disclosure provides an indirect X-ray detector obtained by using the method for preparing an indirect X-ray detector by using the perovskite scintillator material, which is used for a single X-ray detector device or an X-ray detector device array, and realizes X-ray imaging.

[0057] Please refer to Figure 3The indirect X-ray detector comprises, from bottom to top, a substrate 3, a silicon oxide layer 5 on the upper surface of the substrate, electrodes 5 embedded in the silicon oxide layer, graphene 6, semiconductor quantum dots 7, a polymer film 2, perovskite nanocrystal layers 1 with a band gap decreasing layer by layer from bottom to top, and a polymer film 2 on the upper surface of each perovskite nanocrystal layer, and an aluminum film 8.

[0058] By the embodiments of the present disclosure, the perovskite nanocrystal material with simple preparation, fast response speed and good spatial resolution is applied to the scintillator part, and the high-response graphene photodetector is applied to the detector part, thereby reducing the preparation difficulty of the X-ray detector and improving the response speed and spatial resolution of the X-ray detector.

[0059] It should be noted that the indirect X-ray detector provided by the embodiments of the present disclosure has at least one of the following effects and advantages:

[0060] (1) The problem of self-absorption is solved by introducing the inorganic perovskite nanocrystal multilayer film structure with a gradient change in the band gap, and the film band gap gradually decreases from the bottom layer to the top layer, ensuring that the light generated by the upper layer is not absorbed by the perovskite nanocrystal in the lower layer.

[0061] (2) The stability problem is solved by using PMMA and Parylene to coat the perovskite nanocrystal, and PMMA and Parylene do not affect the optical properties of the perovskite nanocrystal, and at the same time have excellent protection, improving the stability of the perovskite scintillator material.

[0062] (3) The problem of low X-ray detection sensitivity is solved. Compared with traditional commercial scintillators, the perovskite scintillator has lower light conversion efficiency, that is, under the same X-ray irradiation, fewer visible light photons are generated. In order to effectively detect fewer photons, a high-response graphene photodetector is used as a light detector.

[0063] The above specific embodiments further illustrate the purpose, technical solutions and advantages of the present disclosure, and it should be understood that the above description is only a specific embodiment of the present disclosure and is not intended to limit the present disclosure. Any modification, equivalent replacement, improvement, etc. made within the spirit and principles of the present disclosure shall be included in the protection scope of the present disclosure.

Claims

1. A method of preparing a perovskite scintillator material, characterized by, Comprising: S11, spin-coating a bottom perovskite nanocrystal layer, depositing a bottom polymer thin film layer; S12, spin-coating a perovskite nanocrystal layer and a polymer thin film layer on the surface of the bottom polymer thin film layer in sequence, the perovskite nanocrystal layer and the polymer thin film layer forming a composite structure layer; wherein the composite structure layer is at least two layers; the uppermost layer of the composite structure layer comprises a top perovskite nanocrystal layer; the polymer thin film layer is prepared by a vacuum vapor deposition process, and a polymer thin film coating layer is grown on the surface of the perovskite nanocrystal by active small molecules; Wherein, from the bottom perovskite nanocrystal layer to the top perovskite nanocrystal layer, the band gap of the perovskite nanocrystal layer decreases layer by layer.

2. The method of claim 1, wherein the perovskite scintillator material is prepared by a method comprising: preparing a solution of a perovskite precursor; and adding the solution of the perovskite precursor to a solution of a ligand precursor. The spin-coating perovskite nanocrystal layer further comprises: mixing the perovskite nanocrystal with a PMMA solution and then spin-coating.

3. The method of claim 1, wherein the perovskite scintillator material is prepared by a method comprising: preparing a solution of a perovskite precursor; and adding the solution of the perovskite precursor to a solution of a ligand precursor. The polymer thin film at least comprises parylene.

4. The method of claim 1, wherein the perovskite scintillator material is prepared by a method comprising: preparing a solution of a perovskite precursor; and adding the solution of the perovskite precursor to a solution of a ligand precursor. The band gap of the perovskite nanocrystal layer is adjusted by adjusting the quantum dot size, the type and content of halogen elements.

5. The method for preparing perovskite scintillator material according to claim 1, characterized in that, The perovskite scintillator material is prepared in anhydrous and oxygen-free environment.

6. A perovskite scintillator material prepared by the method of any one of claims 1-5, used for an indirect X-ray detector together with a photodetector.

7. A method of manufacturing an indirect type X-ray detector using a perovskite scintillator material, characterized by, Comprising: S21, forming an embedded substrate electrode on the surface of a substrate with a silicon oxide layer; S22, transferring graphene to the surface of the silicon oxide layer and patterning the graphene; S23, spin-coating semiconductor quantum dots and depositing a polymer thin film; S24, preparing a perovskite scintillator part, wherein the perovskite scintillator part is prepared according to the method of any one of claims 1-5; S25, depositing an aluminum thin film to coat the perovskite scintillator part and patterning the aluminum thin film; S26, etching the perovskite scintillator part and the aluminum thin film; S27, depositing an aluminum thin film to coat the sidewall of the scintillator part, to obtain an indirect X-ray detector. 8.The method of manufacturing an indirect type X-ray detector using a perovskite scintillator material according to claim 7, wherein, The upper surface of the electrode in S21 is in the same plane as the upper surface of the silicon oxide layer; the electrode is connected to a signal processing circuit. 9.The method of manufacturing an indirect type X-ray detector using a perovskite scintillator material according to claim 7, wherein, The etched scintillator part is a square, and the side length of the square is 10-100 μm.

10. An indirect X-ray detector obtained by the method of any one of claims 7-9, used for a single X-ray detector device or an X-ray detector device array, to realize X-ray imaging.

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