X-ray imaging scintillator screen based on chiral perovskite nanocrystals and its fabrication process

Abstract

This invention relates to the field of X-ray imaging technology and discloses an X-ray imaging scintillator screen based on chiral perovskite nanocrystals and its fabrication process. The screen comprises: a flexible transparent substrate made of polyethylene terephthalate or polyimide film; a chiral perovskite nanocrystal composite layer; an inorganic oxide protective layer composed of SiO₂ or Al₂O₃; and a composite reflective layer comprising: a TiO₂ nanorod array layer located on the substrate surface; and a reflectance enhancement layer doped with 1-10 vol% rhodamine 6G or coumarin derivatives covering the surface of the TiO₂ nanorod array layer. By using a high-transmittance, low-roughness polyester or polyimide material on the flexible transparent substrate, combined with the surface-grown TiO₂ nanorod array and chiral perovskite nanocrystal composite layer, the light reflection efficiency and imaging contrast are significantly improved. Furthermore, the optimized light extraction path, achieved through a microprism structure, enhances the efficiency of X-ray conversion to visible light.

Description

Technical Field

[0001] This invention relates to the field of X-ray imaging technology, specifically to an X-ray imaging scintillator screen based on chiral perovskite nanocrystals and its manufacturing process. Background Technology

[0002] X-ray imaging technology has important applications in medical diagnosis, industrial non-destructive testing, and security inspection. As the core component of an X-ray imaging system, the performance of the scintillator screen directly determines the sensitivity and resolution of the imaging. Traditional scintillator screens are mostly based on inorganic crystal materials (such as CsI:Tl and Gd2O2S:Eu³⁺). Although these materials have high light conversion efficiency, their brittleness and rigid structure limit their application in flexible or wearable devices. In addition, the preparation process of inorganic crystal materials is complex, costly, and difficult to achieve large-scale flexible production.

[0003] In recent years, scintillator screens based on organic materials and nanocrystals have gradually attracted attention. However, these materials still have shortcomings in terms of light conversion efficiency, stability and mechanical properties. For example, organic scintillator materials usually suffer from severe light attenuation and short lifespan, while traditional nanocrystal scintillator materials have limited light extraction efficiency and are difficult to achieve high consistency due to non-uniform size and low surface ligand coverage. Summary of the Invention

[0004] To address the shortcomings of existing technologies, this invention provides an X-ray imaging scintillator screen based on chiral perovskite nanocrystals and its manufacturing process, which solves the problems of insufficient light conversion efficiency, mechanical stability and environmental stability of traditional scintillator screens.

[0005] To achieve the above objectives, the present invention provides the following technical solution:

[0006] An X-ray imaging scintillator screen based on chiral perovskite nanocrystals, comprising:

[0007] Flexible transparent substrate, with a thickness of 50-200 micrometers, light transmittance greater than 90%, surface roughness Ra<10nm, and material is polyethylene terephthalate or polyimide film;

[0008] Chiral perovskite nanocrystal composite layers, composed of general formula (R / SC) n H 2n+1 NH3) x The Cs1-yPbZ3 nanocrystals are composed of a polymer matrix, where n = 4-18, x = 0.05-0.3, y = 0.2-0.8, and Z is a mixture of Cl, Br, and I.

[0009] An inorganic oxide protective layer, composed of SiO2 or Al2O3, with a thickness of 0.5-5 micrometers and a water vapor permeability of less than 10⁻ 6 g / m² / day;

[0010] The composite reflective layer includes:

[0011] TiO2 nanorod array layers are located on the substrate surface, with a diameter of 20-100 nanometers and a height of 100-500 nanometers;

[0012] A reflection enhancement layer doped with 1-10 vol% rhodamine 6G or coumarin derivatives is used to cover the surface of the TiO2 nanorod array layer.

[0013] The chiral perovskite nanocrystal composite layer has a microprism structure on its surface with a characteristic size of 5-50 micrometers, and is formed by in-situ imprinting.

[0014] By adopting the above technical solution, using high-transmittance, low-roughness polyester or polyimide materials on a flexible transparent substrate, combined with a surface-grown TiO2 nanorod array and a chiral perovskite nanocrystal composite layer, the light reflection efficiency and imaging contrast are significantly improved. The nanocrystals are uniform in size and the surface chiral ligand coverage is controllable. Combined with the microprism structure to optimize the light extraction path, the efficiency of converting X-rays into visible light is improved. The inorganic oxide protective layer is formed into a dense film with ultra-low water vapor transmittance through atomic layer deposition technology, which can effectively isolate environmental water and oxygen and extend the device's service life.

[0015] Preferably, the chiral perovskite nanocrystals in the chiral perovskite nanocrystal composite layer have a size of 5-50 nanometers, a size dispersion of ≤8%, a surface chiral ligand coverage of 60%-95%, and the polymer matrix is ​​selected from at least one of polymethyl methacrylate, polycarbonate, and cyclic olefin copolymers, with a refractive index difference of ≤0.15 between the polymer matrix and the nanocrystals.

[0016] Preferably, the thickness of the chiral perovskite nanocrystal composite layer is 100-500 micrometers, the nanocrystal mass ratio is 25%-65%, and the composite layer is doped with 0.1-5 wt% of Eu³⁺-β-diketone complex or CdSe / ZnS core-shell quantum dot material, wherein the particle size of the quantum dot material is 3-8 nanometers and the shell thickness is 1-3 nanometers.

[0017] Preferably, in the composite reflective layer, a polyurethane resin adhesive layer is disposed between the TiO2 nanorod array and the substrate, the thickness of the polyurethane resin adhesive layer is 1-5 micrometers, and the adhesive strength is ≥5MPa.

[0018] Preferably, the tilt angle of the microprism structure on the surface of the chiral perovskite nanocrystal composite layer is 45°-60°, and the aspect ratio is 1:1 to 1:3; the surface roughness Ra of the microprism structure is <50nm.

[0019] Preferably, a fabrication process for an X-ray imaging scintillator screen based on chiral perovskite nanocrystals, used for the aforementioned X-ray imaging scintillator screen based on chiral perovskite nanocrystals, includes the following steps:

[0020] S1. Substrate pretreatment: Immerse the flexible transparent substrate in an ethanol solution containing 1-5 wt% silane coupling agent and treat it at 40-80℃ for 10-60 minutes, followed by vacuum drying at 80-120℃ for 0.5-2 hours.

[0021] S2. Preparation of reflective layer: TiO2 nanorod arrays are grown on the substrate surface by hydrothermal method, with a reaction temperature of 120-180℃ and a time of 2-12 hours.

[0022] S3. Synthesis of chiral perovskite nanocrystals: Under an inert atmosphere, CsBr, PbX2, and chiral ligand R / SC were synthesized. n H 2n+ 1NH3⁺ is dissolved in a mixed solvent of DMF and toluene at a molar ratio of 1:1.5-3 and a volume ratio of 1:3-8. The reaction temperature is controlled at 60-90℃ and the reaction time is 5-30 minutes. Microwave-assisted synthesis is used with a power of 100-500W and a frequency of 2.45GHz for 1-10 minutes.

[0023] S4. Gradient centrifugation: The synthesized nanocrystal dispersion is subjected to three-stage centrifugation. The first stage centrifugation force is 500-1000g, and the centrifugation is carried out for 3-10 minutes to remove large particles. The second stage centrifugation force is 5000-15000g, and the centrifugation is carried out for 10-30 minutes to collect the target nanocrystals. The third stage centrifugation force is 20000-40000g, and the centrifugation is carried out for 5-15 minutes to remove small-sized impurities.

[0024] S5. Preparation of composite layer: The purified nanocrystals are mixed with the polymer prepolymer, and a photoinitiator is added at a mass ratio of 1:1 to 3:1. The amount of photoinitiator added is 0.1% to 2% of the total mass. Degassing is carried out by alternating ultrasonic and vacuum treatment. The ultrasonic power is 100-300W, the vacuum degree is ≤10Pa, and the alternation cycle is 3-8 times.

[0025] S6. In-situ Imprinting: The mixture is coated on the substrate surface, covered with a mold with a microprism structure, the ultraviolet light intensity is 10-50mW / cm², the curing time is 30-180 seconds, and a microprism structure is formed on the surface of the composite layer after demolding.

[0026] S7. Protective layer deposition: An alumina layer is deposited on the surface of the composite layer using atomic layer deposition technology. The deposition temperature is 80-150℃ and the number of cycles is 50-300 times, forming a dense protective layer with a thickness of 50-200 nanometers.

[0027] S8. Annealing treatment: Anneal at 80-150℃ for 10-120 minutes under nitrogen protection, with a heating rate of 2-10℃ / min.

[0028] Preferably, 0.1-5 mol% CsBr is added simultaneously to S3 to control the lattice distortion to be 0.5-2%; the chiral ligand R / SC n H 2n+1 The molar ratio of NH3⁺ to PbX2 is 1:5 to 1:20.

[0029] Preferably, 0.1-2 wt% of photoinitiator is added to S5, and the ultrasonic-vacuum alternating treatment parameters are: ultrasonic power 100-300W, vacuum degree ≤10Pa, alternating cycle 3-8 times; the photoinitiator is selected from 2-hydroxy-2-methylphenylacetone or phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide.

[0030] Preferably, the UV curing process parameters in S6 are: light intensity 10-50mW / cm², curing time 30-180 seconds, and the feature size of the microprism structure is 5-50 micrometers.

[0031] Preferably, in S7, the deposition rate of the atomic layer deposition technology is 0.1-0.3 Å / cycle, the deposition pressure is 100-500 Pa, the oxygen source of the alumina layer is ozone, and the aluminum source is trimethylaluminum.

[0032] This invention provides an X-ray imaging scintillator screen based on chiral perovskite nanocrystals and its fabrication process. It offers the following advantages:

[0033] 1. This invention significantly improves light reflection efficiency and imaging contrast by using high-transmittance, low-roughness polyester or polyimide materials on a flexible transparent substrate, combined with a surface-grown TiO2 nanorod array and a chiral perovskite nanocrystal composite layer. The nanocrystals are uniform in size and the surface chiral ligand coverage is controllable. Combined with a microprism structure to optimize the light extraction path, the efficiency of converting X-rays into visible light is improved. The inorganic oxide protective layer is formed into a dense film with ultra-low water vapor transmittance through atomic layer deposition technology, which can effectively isolate environmental water and oxygen and extend the service life of the device.

[0034] 2. This invention precisely controls the lattice distortion and dispersion of chiral perovskite nanocrystals through gradient centrifugation and microwave-assisted synthesis processes. Combined with doping of Eu³⁺-β-diketone complexes or core-shell quantum dots, the photoluminescence intensity and wavelength stability of the composite layer are enhanced. The ultraviolet curing process, combined with the optimized selection of photoinitiators, achieves efficient bonding between the polymer matrix and the nanocrystals, reduces interface defects, and ensures the high transparency and optical uniformity of the composite layer, thereby improving imaging resolution and sensitivity.

[0035] 3. This invention enhances the mechanical bonding force between the substrate and the reflective layer by synergistically designing the polyurethane resin adhesive layer and the TiO2 nanorod array in the composite reflective layer, thereby reducing light scattering loss. The reflective enhancement layer is doped with Rhodamine 6G or coumarin derivatives to further optimize the light reflection path and wavelength matching. The synergistic effect of the flexible substrate and the protective layer enables the scintillator screen to maintain stable imaging performance under bending or dynamic conditions, making it suitable for long-term reliable applications of flexible X-ray detectors. Attached Figure Description

[0036] Figure 1 This is a process flow diagram of the fabrication process of an X-ray imaging scintillator screen based on chiral perovskite nanocrystals according to the present invention. Detailed Implementation

[0037] The technical solution of the present invention will now be clearly and completely described with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] This invention provides an X-ray imaging scintillator screen based on chiral perovskite nanocrystals, comprising:

[0039] Flexible transparent substrate, with a thickness of 50-200 micrometers, light transmittance greater than 90%, surface roughness Ra<10nm, and material is polyethylene terephthalate or polyimide film;

[0040] Chiral perovskite nanocrystal composite layers, composed of general formula (R / SC) n H 2n+1 NH3) x The Cs1-yPbZ3 nanocrystals are composed of a polymer matrix, where n = 4-18, x = 0.05-0.3, y = 0.2-0.8, and Z is a mixture of Cl, Br, and I.

[0041] An inorganic oxide protective layer, composed of SiO2 or Al2O3, with a thickness of 0.5-5 micrometers and a water vapor permeability of less than 10⁻ 6 g / m² / day;

[0042] The composite reflective layer includes:

[0043] TiO2 nanorod array layers are located on the substrate surface, with a diameter of 20-100 nanometers and a height of 100-500 nanometers;

[0044] A reflection enhancement layer doped with 1-10 vol% rhodamine 6G or coumarin derivatives is used to cover the surface of the TiO2 nanorod array layer.

[0045] The surface of the chiral perovskite nanocrystal composite layer has a microprism structure with a characteristic size of 5-50 micrometers, and it is formed by in-situ imprinting.

[0046] Specifically, by using high-transmittance (>90%) polyethylene terephthalate or polyimide films as a substrate, the overall structure is supported and optical transparency is maintained, thereby reducing light transmission loss (surface roughness Ra < 10 nm) and meeting the requirements of flexible imaging scenarios; and by introducing chiral ligands (R / SC)... n H 2n+1 NH3 regulates the lattice structure and surface energy of nanocrystals, enhancing their monodispersity and stability, resulting in high light yield and narrow emission spectrum, and improving X-ray-visible light conversion efficiency. The deposition of dense SiO2 or Al2O3 layers isolates water and oxygen permeation, inhibiting perovskite material degradation. The synergistic structure of TiO2 nanorod arrays (20-100 nm in diameter) and fluorescent dyes (Rhodamine 6G / coumarin derivatives) enables multiple light reflections and wavelength conversion. In-situ imprinting (feature size 5-50 μm) forms regular microstructures on the composite layer surface, guiding light and suppressing light scattering.

[0047] The chiral perovskite nanocrystals in the chiral perovskite nanocrystal composite layer have a size of 5-50 nanometers, a size dispersion of ≤8%, and a surface chiral ligand coverage of 60%-95%. The polymer matrix is ​​selected from polymethyl methacrylate, polycarbonate, and cyclic olefin copolymers, at least in this embodiment, and the difference between its refractive index and that of the nanocrystals is ≤0.15.

[0048] Specifically, by precisely controlling the size of chiral perovskite nanocrystals within the 5-50 nanometer range, nanocrystal growth is restricted and size uniformity is maintained, achieving a reduction in size dispersion to ≤8%, thereby improving the imaging uniformity and resolution of the scintillator screen. Achieving 60%-95% chiral ligand coverage on the surface of the chiral perovskite nanocrystals improves their optical and chemical stability, enhancing luminescence efficiency and reducing non-radiative recombination, thus increasing X-ray detection sensitivity. Finally, selecting polymethyl methacrylate, polycarbonate, or cyclic olefin copolymers with a refractive index difference ≤0.15 from the nanocrystals as the polymer matrix reduces light scattering and improves light extraction efficiency, enhancing the light output performance of the scintillator screen and optimizing imaging quality.

[0049] The thickness of the chiral perovskite nanocrystal composite layer is 100-500 micrometers, and the mass ratio of nanocrystals is 25%-65%. The composite layer is doped with 0.1-5 wt% of Eu³⁺-β-diketone complex or CdSe / ZnS core-shell quantum dot material. The particle size of the quantum dot material is 3-8 nanometers, and the shell thickness is 1-3 nanometers.

[0050] Specifically, by setting the thickness of the chiral perovskite nanocrystal composite layer to 100-500 micrometers, sufficient thickness is achieved to capture and convert X-ray energy, thereby improving light yield and imaging sensitivity and ensuring the effective operation of the scintillator screen. Adjusting the mass percentage of nanocrystals in the composite layer to 25%-65% balances the luminescence efficiency of the nanocrystals and the stability of the polymer matrix, optimizing the overall performance of the scintillator screen while maintaining good mechanical properties and ensuring high light conversion efficiency. Furthermore, by doping the composite layer with 0.1-5 wt%... Eu³⁺-β-diketone complexes or CdSe / ZnS core-shell quantum dot materials enhance emission at specific wavelengths and increase light yield, thereby improving imaging contrast and reducing the detection limit, thus enhancing the performance of scintillator screens in specific application scenarios. By selecting quantum dot materials with a particle size of 3-8 nanometers and a shell thickness of 1-3 nanometers, the quantum dot core is protected and its stability is improved. At the same time, the core-shell structure optimizes photoluminescence performance, thereby improving quantum efficiency and reducing light attenuation, thus improving the long-term stability and imaging quality of scintillator screens.

[0051] In the composite reflective layer, a polyurethane resin adhesive layer is disposed between the TiO2 nanorod array and the substrate. The thickness of the polyurethane resin adhesive layer is 1-5 micrometers, and the adhesive strength is ≥5MPa.

[0052] Specifically, by setting a polyurethane resin adhesive layer between the TiO2 nanorod array and the substrate, a strong connection between the nanorod array and the substrate is achieved, thereby improving the overall structural stability and ensuring the reliability of the composite reflective layer under various usage conditions.

[0053] The tilt angle of the microprism structure on the surface of the chiral perovskite nanocrystal composite layer is 45°-60°, and the aspect ratio is 1:1 to 1:3; the surface roughness Ra of the microprism structure is <50nm.

[0054] Specifically, by designing the microprism structure on the surface of the chiral perovskite nanocrystal composite layer with an inclination angle of 45°-60°, the reflection and refraction paths of light are optimized, thereby enhancing light extraction efficiency and reducing light scattering, thus improving the clarity and contrast of the image. By controlling the aspect ratio of the microprism structure between 1:1 and 1:3, the light-guiding function and mechanical stability of the microstructure are balanced, achieving the effect of optimizing the optical path design while maintaining structural strength, further improving the optical performance of the scintillator screen. By controlling the surface roughness Ra of the microprism structure to less than 50nm, light scattering is reduced and the uniformity of light reflection is improved, thereby enhancing the image quality and ensuring the performance of the scintillator screen in high-resolution imaging applications.

[0055] Please see the appendix Figure 1 A fabrication process for an X-ray imaging scintillator screen based on chiral perovskite nanocrystals, used in the X-ray imaging scintillator screen based on chiral perovskite nanocrystals of this embodiment according to any one of claims 1-5, includes the following steps:

[0056] S1. Substrate pretreatment: Immerse the flexible transparent substrate in an ethanol solution containing 1-5 wt% silane coupling agent and treat it at 40-80℃ for 10-60 minutes, followed by vacuum drying at 80-120℃ for 0.5-2 hours.

[0057] S2. Preparation of reflective layer: TiO2 nanorod arrays are grown on the substrate surface by hydrothermal method, with a reaction temperature of 120-180℃ and a time of 2-12 hours.

[0058] S3. Synthesis of chiral perovskite nanocrystals: Under an inert atmosphere, CsBr, PbX2, and chiral ligand R / SC were synthesized. n H 2n+ 1NH3⁺ is dissolved in a mixed solvent of DMF and toluene at a molar ratio of 1:1.5-3 and a volume ratio of 1:3-8. The reaction temperature is controlled at 60-90℃ and the reaction time is 5-30 minutes. Microwave-assisted synthesis is used with a power of 100-500W and a frequency of 2.45GHz for 1-10 minutes.

[0059] S4. Gradient centrifugation: The synthesized nanocrystal dispersion is subjected to three-stage centrifugation. The first stage centrifugation force is 500-1000g, and the centrifugation is carried out for 3-10 minutes to remove large particles. The second stage centrifugation force is 5000-15000g, and the centrifugation is carried out for 10-30 minutes to collect the target nanocrystals. The third stage centrifugation force is 20000-40000g, and the centrifugation is carried out for 5-15 minutes to remove small-sized impurities.

[0060] S5. Preparation of composite layer: The purified nanocrystals are mixed with the polymer prepolymer, and a photoinitiator is added at a mass ratio of 1:1 to 3:1. The amount of photoinitiator added is 0.1% to 2% of the total mass. Degassing is carried out by alternating ultrasonic and vacuum treatment. The ultrasonic power is 100-300W, the vacuum degree is ≤10Pa, and the alternation cycle is 3-8 times.

[0061] S6. In-situ Imprinting: The mixture is coated on the substrate surface, covered with a mold with a microprism structure, the ultraviolet light intensity is 10-50mW / cm², the curing time is 30-180 seconds, and a microprism structure is formed on the surface of the composite layer after demolding.

[0062] S7. Protective layer deposition: An alumina layer is deposited on the surface of the composite layer using atomic layer deposition technology. The deposition temperature is 80-150℃ and the number of cycles is 50-300 times, forming a dense protective layer with a thickness of 50-200 nanometers.

[0063] S8. Annealing treatment: Anneal at 80-150℃ for 10-120 minutes under nitrogen protection, with a heating rate of 2-10℃ / min.

[0064] Specifically, substrate pretreatment improves substrate surface energy and enhances subsequent interlayer bonding, thereby increasing the adhesion strength between the substrate and the reflective layer. Reflective layer fabrication constructs a high-reflectivity nanostructure, enhancing light reflection and improving imaging contrast. Chiral perovskite nanocrystal synthesis precisely controls nanocrystal size and morphology, resulting in high-efficiency chiral perovskite nanocrystals. Gradient centrifugation of the synthesized nanocrystal dispersion involves three-stage centrifugation to separate nanocrystals of different sizes and remove impurities, achieving high-purity and highly dispersed nanocrystals. Finally, composite layer preparation mixes the purified nanocrystals with a polymer prepolymer. By adding a photoinitiator and degassing through alternating ultrasonic and vacuum treatment, the nanocrystals are uniformly dispersed and the optical performance of the composite layer is improved, thus achieving the effect of preparing a high-performance scintillator screen composite layer. In-situ imprinting is used to coat the mixture onto the substrate surface, cover it with a mold containing a microprism structure, and then demold after UV curing, forming a microprism structure on the surface of the composite layer, thereby improving light extraction efficiency and imaging uniformity. A protective layer is deposited to isolate water and oxygen and protect the nanocrystals, thus improving the environmental stability and lifespan of the scintillator screen. Annealing eliminates residual stress and increases the crystallinity of the material, thereby improving the thermal stability and optical performance of the scintillator screen.

[0065] Please see the appendix Figure 1 Simultaneously adding 0.1-5 mol% CsBr to S3 to control lattice distortion at 0.5-2%; chiral ligand R / SC n H 2n+1 The molar ratio of NH3⁺ to PbX2 is 1:5 to 1:20.

[0066] Specifically, by simultaneously adding 0.1-5 mol% CsBr in step S3 of the chiral perovskite nanocrystal synthesis, the lattice distortion was adjusted, achieving a control of the lattice distortion within the range of 0.5-2%. This helps optimize the photoelectric properties of the nanocrystals and improve their light conversion efficiency in X-ray imaging scintillator screens. Furthermore, by controlling the chiral ligand R / SC... n H 2n+1 The molar ratio of NH3⁺ to PbX2 is 1:5 to 1:20, which plays a role in precisely controlling the composition and structure of nanocrystals, thereby optimizing the optical properties and stability of nanocrystals.

[0067] Please see the appendix Figure 1S5 contains 0.1-2wt% photoinitiator. The ultrasonic-vacuum alternating treatment parameters are: ultrasonic power 100-300W, vacuum degree ≤10Pa, alternating cycle 3-8 times. The photoinitiator is selected from 2-hydroxy-2-methylphenylacetone or phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide.

[0068] Specifically, in step S5 of the composite layer preparation, 0.1-2 wt% of a photoinitiator is added. This proportion is the commonly used amount of photoinitiator added in photocurable materials, ensuring that the polymer prepolymer can undergo a rapid and uniform polymerization reaction under ultraviolet light irradiation, forming a stable polymer network structure. 2-hydroxy-2-methylphenylacetone or phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide is chosen as the photoinitiator because both have good photosensitivity and initiation efficiency, enabling rapid polymerization at lower light doses, reducing material curing time, and improving production efficiency.

[0069] Please see the appendix Figure 1 The UV curing process parameters for S6 are: light intensity 10-50mW / cm², curing time 30-180 seconds, and the feature size of the microprism structure is 5-50 micrometers.

[0070] Specifically, an illumination intensity range of 10-50 mW / cm² ensures that the polymer prepolymer undergoes effective photopolymerization under ultraviolet light irradiation, forming a stable polymer network structure. The curing time depends on the illumination intensity, the amount of photoinitiator added, and the photosensitivity of the polymer prepolymer. Smaller feature sizes improve light extraction efficiency and enhance imaging clarity, while larger feature sizes reduce light scattering and improve imaging uniformity. By precisely controlling the feature size of the microprism structure, the optical performance of the scintillator screen can be optimized to meet the needs of different imaging applications.

[0071] Please see the appendix Figure 1 In S7, the deposition rate of atomic layer deposition technology is 0.1-0.3 Å / cycle, the deposition pressure is 100-500 Pa, the oxygen source of the alumina layer is ozone, and the aluminum source is trimethylaluminum.

[0072] Specifically, ozone is a strong oxidant and, as an oxygen source, can provide highly active oxygen atoms, which helps to form high-quality alumina films; trimethylaluminum is a commonly used organometallic compound and, as an aluminum source, can provide high-purity aluminum atoms.

[0073] Example 1: Infrastructure Implementation

[0074] I. Technical Solution

[0075] 1. Substrate pretreatment:

[0076] A flexible polyethylene terephthalate (PET) substrate with a thickness of 150 μm was selected, immersed in an ethanol solution containing 3 wt% KH-550 silane coupling agent, treated at 60 °C for 30 minutes, and then vacuum dried at 100 °C for 1 hour, with a surface roughness Ra=8.2 nm.

[0077] Optimization basis: The concentration and temperature of the silane coupling agent balanced the surface modification effect and the temperature resistance of the substrate.

[0078] 2. Preparation of the reflective layer:

[0079] Hydrothermal growth of TiO2 nanorod arrays: using 0.1M tetrabutyl titanate as a precursor, the reaction temperature was 150℃ and the reaction time was 8 hours. The nanorods had a diameter of 50±5nm and a height of 300±20nm.

[0080] Reflection enhancement layer: A 200 nm thick polymethyl methacrylate (PMMA) solution doped with 5 vol% Rhodamine 6G was spin-coated onto the surface of the TiO2 layer.

[0081] 3. Nanocrystal synthesis:

[0082] Molar ratio of raw materials: CsBr:PbBr2:chiral ligand SC 12 H 25 The reaction mixture consisted of NH3⁺ in a ratio of 1:2.5:0.1, DMF / toluene in a solvent (volume ratio 1:5), microwave power of 300W (2.45GHz), reaction temperature of 80℃, and reaction time of 15 minutes.

[0083] Centrifugal purification: first stage 800g×5min, second stage 10000g×20min, third stage 30000g×10min, final nanocrystal size 25±2nm, dispersion ≤7%.

[0084] 4. Composite layer molding:

[0085] Nanocrystals and cyclic olefin copolymer (COC) prepolymer were mixed at a mass ratio of 1:2, and 1 wt% phenyl bis(2,4,6-trimethylbenzoyl)phosphine oxide (Irgacure819) was added. The mixture was then subjected to ultrasonic-vacuum degassing (200W, 5Pa, alternating 5 times).

[0086] In-situ imprinting: mold microprism size 20μm (depth-to-width ratio 1:2), UV curing strength 30mW / cm²×60 seconds.

[0087] 5. Protective layer and annealing:

[0088] Atomic layer deposition of Al2O3 layer: deposition temperature 120℃, 200 cycles, thickness 150nm (deposition rate 0.2Å / cycle); nitrogen annealing 120℃×60min.

[0089] II. Implementation Results Verification

[0090] X-ray imaging resolution: Using a standard resolution test chart (line pair density 20 lp / mm), the imaging resolution reaches 18 lp / mm (ASTM E2597).

[0091] Water vapor stability: After aging at 85℃ / 85%RH for 500 hours, the light yield attenuation rate is ≤3% (GB / T21529).

[0092] Example 2: Nanocrystalline Doping Optimization

[0093] I. Adjustment of Technical Solution

[0094] 1. Nanocrystal ratio:

[0095] Chiral ligand RC 18 H 37 The proportion of NH3⁺ is increased to x=0.2, the Z component is Br / I=7:3, and the nanocrystal size is 40±3nm.

[0096] Centrifugation parameters: first stage 600g×8min, second stage 12000g×25min, third stage 35000g×12min.

[0097] 2. Composite layer doping:

[0098] Adding 3wt% CdSe / ZnS quantum dots (5nm particle size, 2nm shell) increases the nanocrystal mass ratio to 50%.

[0099] The polymer matrix was changed to polycarbonate (PC), and the refractive index matching difference Δn=0.12.

[0100] 3. Improved reflective layer:

[0101] The height of the TiO2 nanorods was increased to 400 nm, and the reflection enhancement layer was doped with coumarin derivatives (10 vol%).

[0102] II. Implementation Results Verification

[0103] Afterglow time: The time it takes for the light to decay to 10% after X-ray excitation stops is ≤2ms (ISO4037).

[0104] Photovoltaic yield: 45,000 photons / MeV (compared to 30,000 photons / MeV for undoped quantum dots).

[0105] Example 3: Optimization of Microprism Structure

[0106] I. Adjustment of Technical Solution

[0107] 1. Microprism parameters:

[0108] The tilt angle is 55°, the aspect ratio is 1:2.5, and the surface roughness Ra=35nm (controlled by plasma etching of the mold surface).

[0109] 2. Reflective layer adhesive layer:

[0110] The polyurethane resin adhesive layer has a thickness of 3μm and an adhesive strength of 7.2MPa (GB / T7124).

[0111] 3. ALD process optimization:

[0112] The deposition pressure was 300 Pa, the oxygen source used was ozone with a pulse time of 0.1 s, and the aluminum source used an ozone pulse time of 0.05 s.

[0113] II. Implementation Results Verification

[0114] Light extraction efficiency: The microprism structure increases light output by 28% (compared to unstructured samples).

[0115] Bending resistance: After bending 1000 times with a curvature radius of 3mm, the light yield retention rate is ≥98% (GB / T2423.37).

[0116] Comparative experiment

[0117] Comparative Example 1: Chiral Ligands

[0118] I. Technical Solution

[0119] 1. Adjustment points:

[0120] Chiral ligand R / SC omitted n H 2n+1 NH3⁺, the remaining preparation steps are exactly the same as in Example 1.

[0121] Nanocrystal synthesis raw materials: CsBr:PbBr2=1:2.5, solvent is DMF / toluene (volume ratio 1:5), reaction temperature is 80℃, time is 15 minutes.

[0122] 2. Testing Standards:

[0123] Nanocrystal dispersion: GB / T19077-2016 (laser particle size analyzer).

[0124] X-ray imaging resolution: ASTM E2597 (line-to-card test).

[0125] Test Project Results of Example 1 Comparative Example 1 Results Increase ratio Nanocrystal size dispersion ≤7% 15% 53% reduction X-ray resolution (lp / mm) 18 12 Increase by 50%

[0126] In summary, the absence of chiral ligands led to a significant increase in nanocrystal size dispersion (53% improvement) and a decrease in imaging resolution (50% reduction), verifying the crucial role of chiral ligands in nanocrystal monodispersity and imaging quality.

[0127] Comparative Example 2: Ordinary reflective layer replacing composite reflective layer

[0128] I. Technical Solution

[0129] 1. Adjustment points:

[0130] The reflective layer was replaced with a regular silver mirror layer (evaporated silver layer, 200nm thick), and the TiO2 nanorod array and reflective enhancement layer were omitted. The rest was the same as in Example 1.

[0131] 2. Testing Standards:

[0132] Reflectivity: GB / T26824-2011 (integrating sphere test).

[0133] Light output attenuation rate: GB / T21529 (85℃ / 85%RH aging for 500 hours).

[0134] Test Project Results of Example 1 Comparative Example 2 Results Increase ratio reflectivity 98% 85% Increase by 15% Light production decline rate ≤3% 15% Reduced by 80%

[0135] In summary, ordinary silver mirror layers have low reflectivity and are easily affected by humidity, while composite reflective layers (TiO2 nanorods + fluorescent dyes) significantly improve light utilization and environmental stability.

[0136] Comparative Example 3: Structure without microprisms

[0137] I. Technical Solution

[0138] 1. Adjustment points:

[0139] The surface of the composite layer is a planar structure (without microprisms), and the rest is the same as in Example 3.

[0140] 2. Testing Standards:

[0141] Light extraction efficiency: GB / T26180-2010 (integrating sphere + photomultiplier tube).

[0142] Bending resistance: GB / T2423.37 (bending 1000 times with a radius of curvature of 3mm).

[0143] Test Project Results of Example 3 Comparative Example 3 Results Increase ratio Light extraction efficiency 95% 72% Increased by 32% Light output retention rate after bending ≥98% 80% Increased by 22%

[0144] In summary, planar structures lead to severe light scattering, and the interface is prone to cracking after bending. Microprism structures improve output efficiency and mechanical reliability through directional light guidance.

[0145] Comparative Example 4: Undoped quantum dots

[0146] I. Technical Solution

[0147] 1. Adjustment points:

[0148] No CdSe / ZnS quantum dots were added to the composite layer; otherwise, it was the same as in Example 2.

[0149] II. Testing Standards:

[0150] Afterglow time: ISO4037 (time for light to decay to 10%).

[0151] Photovoltaic output: IEC62220-1 (Standard X-ray source excitation).

[0152] Test Project Results of Example 2 Comparative Example 4 Results Increase ratio Afterglow duration (ms) ≤2 5 Reduce by 60% Photons / MeV 45,000 30,000 Increase by 50%

[0153] In summary, quantum doping shortens afterglow time and increases light yield through energy transfer mechanisms, demonstrating its core role in enhancing fluorescence efficiency.

[0154] I. Experimental Standards and Basis:

[0155] Nanocrystal dispersion: GB / T19077-2016 "Particle size analysis by laser diffraction"

[0156] X-ray resolution: ASTM E2597 "Methods for testing the resolution of medical X-ray imaging systems"

[0157] Reflectivity testing: GB / T26824-2011 "Methods for measuring the reflectivity of optical thin films"

[0158] Optical output test: IEC 62220-1 "Performance determination of medical X-ray imaging equipment"

[0159] Bending resistance: GB / T2423.37 "Environmental testing for electrical and electronic products - Part 2: Test methods - Test L: Bending"

[0160] I. Conclusion:

[0161] Through comparative experiments with the examples and comparative examples, the experimental data shows that the proposed solution achieves verifiable performance improvements through the following technical improvements:

[0162] 1. Chiral ligands regulate nanocrystal dispersion: Nanocrystal size dispersion ≤7% (15% in Comparative Example 1), X-ray imaging resolution improved to 18 lp / mm (12 lp / mm in Comparative Example 1), an 80% improvement over traditional CsI scintillators (10 lp / mm);

[0163] 2. Composite reflective layer structure design: reflectivity 98% (comparative example 2 is 85%), light yield attenuation rate ≤3% after aging at 85℃ / 85%RH for 500 hours (comparative example 2 is 15%).

[0164] 3. Microprism light extraction optimization: Light extraction efficiency reaches 95% (comparative example 3 is 72%), and the light yield retention rate after bending test is ≥98% (comparative example 3 is 80%).

[0165] 4. Quantum doping synergistic effect: afterglow time is shortened to 2ms (comparative example 4 is 5ms), and light yield is increased to 45,000 photons / MeV (comparative example 4 is 30,000 photons / MeV).

[0166] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. An X-ray imaging scintillator screen based on chiral perovskite nanocrystals, characterized in that: include: Flexible transparent substrate, with a thickness of 50-200 micrometers, light transmittance greater than 90%, surface roughness Ra<10nm, and material is polyethylene terephthalate or polyimide film; Chiral perovskite nanocrystal composite layer, composed of general formula (R / SC) n H 2n+1 NH3) x The Cs1-yPbZ3 nanocrystals are composed of a polymer matrix, where n = 4-18, x = 0.05-0.3, y = 0.2-0.8, and Z is a mixture of Cl, Br, and I. An inorganic oxide protective layer, composed of SiO2 or Al2O3, with a thickness of 0.5-5 micrometers and a water vapor permeability of less than 10⁻ 6 g / m² / day; The composite reflective layer includes: TiO2 nanorod array layers are located on the substrate surface, with a diameter of 20-100 nanometers and a height of 100-500 nanometers; A reflection enhancement layer doped with 1-10 vol% rhodamine 6G or coumarin derivatives is used to cover the surface of the TiO2 nanorod array layer. The surface of the chiral perovskite nanocrystal composite layer has a microprism structure with a characteristic size of 5-50 micrometers, and is formed by in-situ imprinting.

2. The X-ray imaging scintillator screen based on chiral perovskite nanocrystals according to claim 1, characterized in that: The chiral perovskite nanocrystals in the chiral perovskite nanocrystal composite layer have a size of 5-50 nanometers, a size dispersion of ≤8%, and a surface chiral ligand coverage of 60%-95%. The polymer matrix is ​​selected from at least one of polymethyl methacrylate, polycarbonate, and cyclic olefin copolymers, and the difference between its refractive index and that of the nanocrystals is ≤0.

15.

3. The X-ray imaging scintillator screen based on chiral perovskite nanocrystals according to claim 1, characterized in that: The thickness of the chiral perovskite nanocrystal composite layer is 100-500 micrometers, and the nanocrystal mass ratio is 25%-65%. The composite layer is doped with 0.1-5 wt% of Eu³⁺-β-diketone complex or CdSe / ZnS core-shell quantum dot material. The particle size of the quantum dot material is 3-8 nanometers, and the shell thickness is 1-3 nanometers.

4. The X-ray imaging scintillator screen based on chiral perovskite nanocrystals according to claim 1, characterized in that: In the composite reflective layer, a polyurethane resin adhesive layer is disposed between the TiO2 nanorod array and the substrate. The thickness of the polyurethane resin adhesive layer is 1-5 micrometers, and the adhesive strength is ≥5MPa.

5. The X-ray imaging scintillator screen based on chiral perovskite nanocrystals according to claim 1, characterized in that: The tilt angle of the microprism structure on the surface of the chiral perovskite nanocrystal composite layer is 45°-60°, and the aspect ratio is 1:1 to 1:3; the surface roughness Ra of the microprism structure is <50nm.

6. A fabrication process for an X-ray imaging scintillator screen based on chiral perovskite nanocrystals, characterized in that, The X-ray imaging scintillator screen based on chiral perovskite nanocrystals as described in any one of claims 1-5 comprises the following steps: S1. Substrate pretreatment: Immerse the flexible transparent substrate in an ethanol solution containing 1-5 wt% silane coupling agent and treat it at 40-80℃ for 10-60 minutes, followed by vacuum drying at 80-120℃ for 0.5-2 hours. S2. Preparation of reflective layer: TiO2 nanorod arrays are grown on the substrate surface by hydrothermal method, with a reaction temperature of 120-180℃ and a time of 2-12 hours. S3. Synthesis of chiral perovskite nanocrystals: Under an inert atmosphere, CsBr, PbX2, and chiral ligand R / SC were synthesized. n H 2n+1 NH3⁺ is dissolved in a mixed solvent of DMF and toluene at a molar ratio of 1:1.5-3 and a volume ratio of 1:3-8. The reaction temperature is controlled at 60-90℃ and the reaction time is 5-30 minutes. Microwave-assisted synthesis is used with a power of 100-500W and a frequency of 2.45GHz for 1-10 minutes. S4. Gradient centrifugation: The synthesized nanocrystal dispersion is subjected to three-stage centrifugation. The first stage centrifugation force is 500-1000g, and the centrifugation is carried out for 3-10 minutes to remove large particles. The second stage centrifugation force is 5000-15000g, and the centrifugation is carried out for 10-30 minutes to collect the target nanocrystals. The third stage centrifugation force is 20000-40000g, and the centrifugation is carried out for 5-15 minutes to remove small-sized impurities. S5. Preparation of composite layer: The purified nanocrystals are mixed with the polymer prepolymer, and a photoinitiator is added at a mass ratio of 1:1-3:

1. The amount of photoinitiator added is 0.1%-2% of the total mass. Degassing is carried out by alternating ultrasonic and vacuum treatment. The ultrasonic power is 100-300W, the vacuum degree is ≤10Pa, and the alternation cycle is 3-8 times. S6. In-situ Imprinting: The mixture is coated on the substrate surface, covered with a mold with a microprism structure, the ultraviolet light intensity is 10-50mW / cm², the curing time is 30-180 seconds, and a microprism structure is formed on the surface of the composite layer after demolding. S7. Protective layer deposition: An alumina layer is deposited on the surface of the composite layer using atomic layer deposition technology. The deposition temperature is 80-150℃ and the number of cycles is 50-300 times, forming a dense protective layer with a thickness of 50-200 nanometers. S8. Annealing treatment: Anneal at 80-150℃ for 10-120 minutes under nitrogen protection, with a heating rate of 2-10℃ / min.

7. The fabrication process of an X-ray imaging scintillator screen based on chiral perovskite nanocrystals according to claim 6, characterized in that: Simultaneous addition of 0.1-5 mol% CsBr to S3 controls the lattice distortion to be 0.5-2%; the chiral ligand R / SC n H 2n+1 The molar ratio of NH3⁺ to PbX2 is 1:5 to 1:

20.

8. The fabrication process of an X-ray imaging scintillator screen based on chiral perovskite nanocrystals according to claim 6, characterized in that: S5 contains 0.1-2wt% of a photoinitiator. The ultrasonic-vacuum alternating treatment parameters are: ultrasonic power 100-300W, vacuum degree ≤10Pa, and alternation cycle 3-8 times. The photoinitiator is selected from 2-hydroxy-2-methylphenylacetone or phenylbis(2,4,6-trimethylbenzoyl)phosphine oxide.

9. The fabrication process of an X-ray imaging scintillator screen based on chiral perovskite nanocrystals according to claim 6, characterized in that: The UV curing process parameters for S6 are: light intensity 10-50mW / cm², curing time 30-180 seconds, and the feature size of the microprism structure is 5-50 micrometers.

10. The fabrication process of an X-ray imaging scintillator screen based on chiral perovskite nanocrystals according to claim 6, characterized in that: In S7, the deposition rate of the atomic layer deposition technology is 0.1-0.3 Å / cycle, the deposition pressure is 100-500 Pa, the oxygen source of the alumina layer is ozone, and the aluminum source is trimethylaluminum.

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