Multistage stacked scintillator based on perovskite quantum dots shift wave effect and preparation method thereof

Abstract

This invention relates to the field of radiation detection. To address the contradiction between the luminous efficiency and detection efficiency of existing ultrafast scintillators, which suffer from reduced external quantum yield due to self-absorption effects within the crystal, this invention proposes a multi-level stacked scintillator based on the perovskite quantum dot wave-shifting effect. The scintillator comprises an N-layer structure, serving as an X-ray absorption layer; and an N+1-layer structure, serving as a wavelength conversion layer. The N+1-layer perovskite quantum dots and the N-layer scintillator are alternately stacked to form the multi-level stacked scintillator. A transparent organic polymer encapsulation layer is disposed on the outer surface of the multi-level stacked scintillator. This effectively reduces photon self-absorption within the scintillator, improves the overall external quantum yield, and effectively solves the problem of balancing luminous efficiency and detection efficiency in scintillators. This invention also proposes a method for preparing the multi-level stacked scintillator based on the perovskite quantum dot wave-shifting effect.

Description

Technical Field

[0001] This invention relates to the field of radiation detection, specifically to a multi-level stacked scintillator based on the perovskite quantum dot wave-shifting effect and its preparation method. Background Technology

[0002] Scintillators are among the most widely used materials in nuclear radiation detection, possessing irreplaceable advantages in fields such as radiation imaging and transient pulse radiation measurement. Luminous yield and decay time are important parameters for evaluating the performance of scintillator materials, reflecting the efficiency with which the material converts radiation into a detectable light signal and its response speed to transient pulse radiation, respectively. Common scintillator materials often face a trade-off between luminous yield and decay time; fast-response scintillators, such as ZnO, GaN, and CuI, generally have lower luminous efficiency.

[0003] A major reason for the low luminous efficiency of scintillators is the significant overlap between the excitation and absorption spectra of ultrafast scintillators. This leads to the absorption of light emitted during transmission by the scintillator itself, resulting in severe self-absorption and a substantial reduction in its external quantum yield. While reducing the thickness of the scintillator can decrease self-absorption, high-energy rays, due to their strong penetrating power, require a sufficiently thick detector volume to achieve high detection efficiency. Therefore, existing ultrafast scintillators face a conflict between external quantum efficiency and detection efficiency. Effectively resolving this contradiction and improving the overall external quantum yield is crucial for optimizing ultrafast scintillators. Summary of the Invention

[0004] This invention addresses the problem of balancing luminescence efficiency and detection efficiency in existing ultrafast scintillators by proposing a multi-level stacked scintillator based on the perovskite quantum dot wave-shifting effect and its preparation method.

[0005] The design concept of this invention is as follows: perovskite quantum dot material is introduced into the scintillator material as a sandwich or coating to form a multi-level stacked conversion structure. The short-wavelength light generated by the scintillator absorbing radiation is converted into long-wavelength light through the wavelength conversion effect of perovskite. This can effectively reduce the self-absorption of photons inside the scintillator, thereby improving the overall external quantum yield and effectively solving the contradiction between the luminous efficiency and detection efficiency of the ultrafast scintillator.

[0006] To achieve the above objectives, the technical solution proposed by this invention is as follows:

[0007] A multi-level stacked scintillator based on the perovskite quantum dot wave-shifting effect, comprising a scintillator and perovskite quantum dots, is unique in that:

[0008] The scintillator consists of N layers, which serve as the radiation absorption layer; the perovskite quantum dots consist of N+1 layers, which serve as the wavelength conversion layer.

[0009] The N+1 layers of perovskite quantum dots and the N layers of scintillators are stacked alternately to form a multi-layer scintillator;

[0010] The outer surface of the multilayer scintillator is provided with a transparent organic polymer encapsulation layer.

[0011] Furthermore, the scintillator is any one of ZnO, GaN, and CuI, or a doped and modified scintillator material based on any one of ZnO, GaN, and CuI.

[0012] Furthermore, the thickness of each layer of the scintillator is 0.2mm-0.5mm.

[0013] Furthermore, the perovskite quantum dot is a CsPbX3 quantum dot, where X is Cl, Br, I, or any combination thereof.

[0014] Furthermore, the thickness of each layer of the perovskite quantum dots is 200nm-400nm.

[0015] Furthermore, the encapsulation layer is an epoxy resin sealant.

[0016] Furthermore, the number of layers N of the scintillator satisfies the following formula:

[0017]

[0018] Among them: I out The intensity of the emitted light is given by N, the number of scintillator layers is given by i, and i represents the i-th scintillator layer starting from the direction of the ray radiation. a The initial intensity of the incident X-rays is given by μ, the absorption coefficient of the scintillator for X-rays is given by d, the thickness of each scintillator layer is given by a4, and the transmission efficiency of the converted light through each scintillator layer and perovskite quantum dot is given by a4. The converted light refers to the light that the perovskite quantum dot re-emits after absorbing the light emitted by the scintillator.

[0019] Furthermore, this invention also proposes a method for preparing a multi-level stacked scintillator based on the wave-shifting effect of perovskite quantum dots, which is characterized by including the following steps:

[0020] Step 1: Polish the surface of the scintillator crystal, and then clean and dry the polished scintillator crystal.

[0021] Among them, mechanical polishing and chemical polishing are used to adjust the thickness of the scintillator wafer and reduce the surface roughness of the inorganic scintillator. The polished scintillator wafer is then cleaned with alcohol and deionized water in sequence and then dried.

[0022] Step 2: Dissolve and filter the perovskite quantum dots in an organic solution, and then add them to an organic ligand solution to form a perovskite quantum dot precursor solution;

[0023] The perovskite quantum dots are PbX2 and CsX, where X is any compound of Cl, Br, or I. PbX2 and CsX (X = Cl, Br, I) are added to DMF solvent in a set ratio and stirred to dissolve. After filtration, an organic ligand solution is added to form a precursor solution.

[0024] Step 3: Using thin-film electrostatic spraying, the perovskite quantum dot precursor solution is uniformly sprayed onto the surface of the scintillator, and then the sprayed scintillators are stacked to form a multilayer scintillator.

[0025] The inorganic scintillator is placed on a heating stage and a suitable temperature is set. The precursor solution is pushed onto the ultrasonic nozzle at a fixed rate through a tube using a syringe. The distance and moving speed of the ultrasonic nozzle are adjusted to uniformly spray the precursor solution onto the surface of the scintillator.

[0026] Step 4: Dry the multilayer scintillator after stacking, and then place the dried multilayer scintillator in a transparent organic polymer encapsulation material for curing, finally forming a multi-level stacked scintillator based on the perovskite quantum dot wave-shifting effect.

[0027] Immediately after the scintillator is sprayed, it is stacked and then placed in a negative pressure, high temperature environment to evaporate excess solvent and dry. The dried multilayer scintillator is then placed in a mold, and a low-fluorescence transparent organic polymer encapsulation material is poured into it. It is then allowed to cure at room temperature to form a complete perovskite quantum dot wave-shifting effect multilayer scintillator.

[0028] Furthermore, in step two, the organic solution is a dimethylamide solvent;

[0029] The organic ligand solution is dodecylbenzenesulfonic acid.

[0030] Furthermore, step three specifically involves: using a thin-film electrostatic spraying method to spray the first layer of scintillators on both sides, and spraying the remaining layers of scintillators on one side only, with the sprayed and unsprayed surfaces of adjacent scintillators stacked together.

[0031] The beneficial effects of this invention are:

[0032] [1] This invention introduces perovskite quantum dot material as a sandwich or coating into scintillator material to form a multi-level stacked conversion structure. Using perovskite quantum dots as a light wavelength conversion layer, the short wavelength light of the scintillator is converted into long wavelength light, which can significantly reduce the loss of light extraction efficiency caused by its original self-absorption phenomenon, improve the overall external quantum yield, and effectively reduce the self-absorption of photons inside the scintillator.

[0033] [2] The present invention uses perovskite quantum dots as a coating as a buffer layer between the scintillator and the air, thereby reducing the loss of light extraction efficiency caused by total internal reflection of the scintillator.

[0034] [3] The present invention prepares a perovskite quantum dot film on the surface of the scintillator and combines multiple thin-layer scintillators with perovskite quantum dot light conversion coatings to increase the overall thickness. This not only has a good blocking ability for high-energy rays, but also has a large external quantum efficiency.

[0035] [4] The outer surface of the multi-level stacked scintillator of the present invention is provided with a transparent organic polymer encapsulation layer, which can effectively reduce the contact between the perovskite quantum dot material and water and oxygen in the air, and is conducive to improving its long-term working stability.

[0036] [5] The present invention uses a spraying method to prepare perovskite quantum dot coatings and interlayers. The preparation process is simple and repeatable, and does not damage the original scintillator surface. The perovskite quantum dot coating can be peeled off by chemical methods to realize the reuse of the ultrafast scintillator. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the structure of an embodiment of the multi-level stacked scintillator based on the perovskite quantum dot wave-shifting effect of the present invention;

[0038] Figure 2 This is a schematic diagram of the X-ray absorption process of a multi-level stacked scintillator in an embodiment of the present invention;

[0039] Figure 3 This is a schematic diagram illustrating the light extraction efficiency of a multi-level stacked scintillator in an embodiment of the present invention;

[0040] Figure label:

[0041] 1-Scintillator, 2-Perovskite quantum dot, 3-Encapsulation layer. Detailed Implementation

[0042] Example 1

[0043] Depend on Figure 1As can be seen, the multi-level stacked scintillator based on the perovskite quantum dot wave-shifting effect includes scintillator 1 and perovskite quantum dots 2. Scintillator 1 has N layers, and the N-layer scintillator 1 serves as the X-ray absorption layer; perovskite quantum dot 2 has N+1 layers, and the N+1-layer perovskite quantum dot 2 serves as the wavelength conversion layer; the N+1-layer perovskite quantum dot 2 and the N-layer scintillator 1 are alternately stacked to form a multi-layer scintillator; the thickness of each scintillator 1 layer is 0.2mm-0.5mm, and the thickness of each perovskite quantum dot 2 layer is 200nm-400nm.

[0044] A transparent organic polymer encapsulation layer 3 is provided on the outer surface of the multilayer scintillator. The encapsulation layer 3 is preferably made of epoxy resin to form a multi-level stacked scintillator with perovskite quantum dot wave-shifting effect.

[0045] The scintillator 1 is any one of ZnO, GaN, and CuI, or a doped and modified scintillator 1 material based on any one of ZnO, GaN, and CuI. The perovskite quantum dot 2 is a CsPbX3 quantum dot, where X is Cl, Br, I, or any combination of two of them.

[0046] Depend on Figure 2 As shown, when X-rays are incident on a multi-level stacked scintillator with N layers of scintillators 1 and N+1 layers of perovskite quantum dots 2, the rays undergo attenuation inside the multi-level stacked scintillator. The X-ray intensity I deposited in the i-th layer of scintillator 1 is... i Satisfy the following formula:

[0047] I i =I a (e -μ(i-1)d -e -μid )

[0048] Where I a denoted as the initial intensity of the incident X-ray, μ as the absorption coefficient of scintillator 1 for X-rays, and d as the thickness of each layer of scintillator 1.

[0049] Since the thickness of the perovskite quantum dot 2 layer is very small, its absorption of X-rays is negligible. When considering only the conversion process of X-ray emission from the perovskite quantum dots 2 on either side of the X-ray absorption layer, assuming the efficiency of scintillator 1 in converting X-rays into light is a1, the efficiency of light propagating through scintillator 1 to the perovskite quantum dot 2 and being absorbed is a2, the efficiency of perovskite quantum dot 2 absorbing light and re-emitting the converted light is a3, and the transmission efficiency of the converted light through each layer of scintillator 1 and the +perovskite quantum dot 2 is a4. Furthermore, assuming the light emitted from the X-ray absorption layer is uniformly distributed in space, i.e., the light received by the perovskite quantum dots 2 before and after is 0.5 × I0a1a2a3, then the light intensity I emitted from the light-emitting surface of the i-th layer of scintillator 1 is... oi for:

[0050]

[0051] Let I0a1a2a3 be I a Then the total output energy I of the light-converting scintillator 1 is... out And the number of layers N of scintillator 1

[0052] Satisfy the following formula:

[0053]

[0054] Among them: I out Let N be the intensity of the emitted light, N be the number of scintillator layers 1, and i represent the i-th scintillator layer 1 starting from the direction of the ray radiation. a denoted as the initial intensity of the incident X-ray, μ as the absorption coefficient of scintillator 1 for X-rays, d as the thickness of each layer of scintillator 1, and a4 as the transmission efficiency of the converted light through each layer of scintillator 1 and perovskite quantum dot 2, where the converted light refers to the light re-emitted after the perovskite quantum dot 2 absorbs the light emitted by scintillator 1.

[0055] When the absorption coefficient, thickness, and conversion light emission efficiency of scintillator 1 are determined, the total output energy will vary with the number of layers N, and there will be a maximum value.

[0056] Simultaneously, a method for fabricating multi-level stacked scintillators based on the wave-shifting effect of perovskite quantum dots was proposed, including the following steps:

[0057] Step 1: Polish the surface of scintillator 1 crystal by mechanical polishing and chemical polishing to adjust the thickness of scintillator 1 and reduce the surface roughness of scintillator 1. After polishing, the scintillator 1 crystal is cleaned with alcohol and deionized water in sequence and then dried.

[0058] Step 2: Prepare perovskite quantum dot 2 precursor solution. Perovskite quantum dot 2 is PbX2 and CsX, where X is any compound of Cl, Br, I or any combination of two of them. PbX2 and CsX (X = Cl, Br, I) are added to dimethylamide (DMF) solvent in a set ratio and stirred to dissolve. After filtration, an organic ligand solution is added to form perovskite quantum dot 2 precursor solution.

[0059] Step 3: The perovskite quantum dot 2 precursor solution is uniformly sprayed onto the surface of scintillator 1 using a thin-film electrostatic spraying method. The scintillator 1 is placed on a heating table, a suitable temperature is set, and the perovskite quantum dot 2 precursor solution from Step 2 is pushed onto the ultrasonic nozzle at a fixed rate through a tube using a syringe. The distance and moving speed of the ultrasonic nozzle are adjusted to uniformly spray the perovskite quantum dot 2 precursor solution onto the surface of scintillator 1.

[0060] Step 4: Dry the multilayer scintillator 1 after stacking. Spray the first layer of scintillator 1 on both sides, and spray the remaining layers of scintillator 1 on one side. Stack the sprayed and unsprayed sides of adjacent scintillator 1. Stack the scintillator 1 immediately after spraying. Then place the multilayer scintillator 1 in a negative pressure and high temperature environment to evaporate excess solvent and dry it. Place the dried multilayer scintillator 1 in a mold and pour in a transparent organic polymer encapsulation material. Let it cure at room temperature to form a complete perovskite quantum dot wave-shifting effect multilevel stacked scintillator. The transparent organic polymer encapsulation material can be a low-fluorescence transparent organic polymer encapsulation material.

[0061] In this embodiment of the invention, ZnO:Ga is selected as the scintillator layer 1, with a single layer thickness of 0.4 mm and a diameter of 50 mm. Under X-ray irradiation, its emission wavelength is 380 nm.

[0062] The target signal being measured was an X-ray signal with an energy of approximately 100 keV, to which the mass absorption coefficient of ZnO:Ga was 0.1127 cm⁻¹. 2 / g.

[0063] CsPbBr3 was selected as the perovskite quantum dot 2 material, with a single quantum dot size of 10nm and an emission wavelength of 520nm.

[0064] like Figure 3 As shown, the transmittance (a4) of a 0.4 mm thick ZnO:G scintillator 1 + a 200 nm thick perovskite quantum dot 2 for 520 nm wavelength light was experimentally measured to be approximately 75%. The density of the ZnO:Ga scintillator 1 is 5.6 g / cm³. 3 When the thickness is 0.4 mm, the mass is 0.224 g / cm³. 2 The overall efficiency reaches its maximum when the number of layers is 6.

[0065] Perovskite quantum dots dispersed in a dodecylbenzenesulfonic acid (DBSA) substrate solution were uniformly transferred to the surface of ZnO:Ga scintillator 1 using a spray coating method. A thickness of 200 nm was prepared on one side only. The first ZnO:Ga scintillator was double-sided coated, while the others were single-sided coated.

[0066] After the coated ZnO:Ga scintillator 1 is stacked and pressed tightly, it is left to stand under negative pressure at room temperature to help the organic solvent evaporate.

[0067] The dried multilayer scintillator 1 is surface-encapsulated with epoxy resin 3.

[0068] The ultrafast scintillator 1, which serves as the X-ray absorption layer, and the perovskite quantum dots 2, which serve as the light conversion layer, are arranged alternately to form a multi-layer sandwich scintillator. After preparation, it is a multi-level stacked scintillator containing 6 layers of ZnO:Ga scintillator 1 and 7 layers of CsPbBr3 perovskite quantum dots 2, with a total thickness of 2.4 mm.

Claims

1. A multi-level stacked scintillator based on the perovskite quantum dot wave-shifting effect, comprising a scintillator (1) and perovskite quantum dots (2), characterized in that: The scintillator (1) is an N-layer scintillator (1) serving as a radiation absorption layer; the perovskite quantum dot (2) is an N+1-layer perovskite quantum dot (2) serving as a wavelength conversion layer. The N+1 layers of perovskite quantum dots (2) and the N layers of scintillators (1) are stacked alternately to form a multilayer scintillator; The outer surface of the multilayer scintillator is provided with a transparent organic polymer encapsulation layer (3); The scintillator (1) is any one of ZnO, GaN, and CuI, or a doped and modified scintillator material based on any one of ZnO, GaN, and CuI. The perovskite quantum dot (2) is a CsPbX3 quantum dot, wherein X is Cl, Br, I or any combination thereof.

2. The multi-level stacked scintillator based on the perovskite quantum dot wave-shifting effect according to claim 1, characterized in that: The thickness of each layer of the scintillator (1) is 0.2mm-0.5mm.

3. The multi-level stacked scintillator based on the perovskite quantum dot wave-shifting effect according to claim 2, characterized in that: The thickness of the perovskite quantum dots (2) in each layer is 200nm-400nm.

4. The multi-level stacked scintillator based on the perovskite quantum dot wave-shifting effect according to claim 3, characterized in that: The encapsulation layer (3) is an epoxy resin encapsulation layer.

5. The multi-level stacked scintillator based on the perovskite quantum dot wave-shifting effect according to claim 4, characterized in that, The number of layers N of the scintillator (1) satisfies the following formula: Among them: I out The intensity of the emitted light is N, the number of layers of scintillator (1) is N, and i represents the i-th layer of scintillator (1) starting from the direction of ray radiation. a The initial intensity of the incident X-ray is μ, the absorption coefficient of the scintillator (1) for X-rays is d, the thickness of each layer of scintillator (1) is a4, and the transmission efficiency of the converted light through each layer of scintillator (1) and perovskite quantum dot (2) is a4. The converted light refers to the light that the perovskite quantum dot (2) re-emits after absorbing the light emitted by the scintillator (1).

6. The method for preparing a multi-level stacked scintillator based on the perovskite quantum dot wave-shifting effect according to any one of claims 1-5, characterized in that, Includes the following steps: Step 1: Polish the surface of the scintillator (1) crystal, and then clean and dry the polished scintillator (1) crystal. Step 2: Dissolve and filter the perovskite quantum dots (2) in an organic solution, and then add them to an organic ligand solution to form a perovskite quantum dot (2) precursor solution; Step 3: Using thin film electrostatic spraying, the perovskite quantum dot (2) precursor solution is uniformly sprayed onto the surface of the scintillator (1), and then the sprayed scintillators (1) are stacked to form a multilayer scintillator (1). Step 4: Dry the multilayer scintillator (1) after stacking, and then place the dried multilayer scintillator (1) in a transparent organic polymer encapsulation material for curing, and finally form a multi-level stacked scintillator based on the perovskite quantum dot wave-shifting effect.

7. The method for preparing a multi-level stacked scintillator based on the perovskite quantum dot wave-shifting effect according to claim 6, characterized in that: In step two, the organic solution is a dimethylamide solvent; The organic ligand solution is dodecylbenzenesulfonic acid.

8. The method for preparing a multi-level stacked scintillator based on the perovskite quantum dot wave-shifting effect according to claim 7, characterized in that: Step 3 specifically involves: using thin-film electrostatic spraying to spray the first layer of scintillator (1) on both sides, and spraying the remaining layers of scintillator (1) on one side, with the sprayed and unsprayed surfaces of adjacent scintillator (1) stacked together.

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