Chiral lead-free perovskite flexible X-ray detector based on enantiomer proportion regulation and preparation method thereof

Abstract

The invention discloses a chiral lead-free perovskite flexible X-ray detector based on enantiomer proportion regulation and a preparation method thereof, and belongs to the technical field of photoelectric detectors, and the method comprises the following steps: introducing proportion-adjustable chiral organic cations (S-CHEA and R-CHEA) into a Bi / Sb-based lead-free perovskite precursor to form (S1-rR r-CHEA) 4 (Bi < 0.5 > Sb < 0.5 >) 2I < 10 > perovskite; according to the method, a local asymmetric electric field and an ordered chiral environment are formed in the material by regulating and controlling the proportion and crystal structure of the enantiomers, and the local inversion symmetry of the crystal is destroyed by the effect, so that the spin degeneracy of an electron energy band is broken, the momentum overturning process related to spin is promoted, the exciton dissociation and carrier separation efficiency is enhanced, and the efficiency of the material is improved. And a new regulation and control way is provided for improving the performance of the device. According to the mechanism, the separation and transmission efficiency of current carriers is remarkably improved, the charge collection performance of the detector in X-ray detection is further enhanced, and a foundation is laid for large-scale preparation and commercial application of devices.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of photoelectric detectors, and relates to a chiral non-lead perovskite flexible X-ray detector based on enantiomer proportion regulation and a preparation method thereof. BACKGROUND

[0002] X-ray detectors are widely used in the fields of medical imaging, security detection, industrial quality control and the like. With the development of flexible electronics, flexible X-ray detectors have great potential in emerging scenarios such as wearable medical treatment and portable imaging due to their lightweight, flexibility and easy integration characteristics. The existing silicon, amorphous selenium and cadmium telluride-based detectors have high preparation temperature, high cost and high rigidity, and are difficult to meet the flexible requirements. In comparison, perovskite materials have low-temperature solution processing and excellent photoelectric performance, and are considered as an important candidate for flexible detectors. Although lead-based perovskite has excellent performance, it has toxicity and stability problems, which limit its application. Bi / Sb non-lead perovskite is more environmentally friendly and stable, but the carrier mobility and diffusion length are insufficient, and the sensitivity is limited, and how to improve the device performance is still a problem to be solved. SUMMARY

[0003] The purpose of the present application is to overcome the shortcomings of the prior art, and to provide a chiral non-lead perovskite flexible X-ray detector based on enantiomer proportion regulation and a preparation method thereof, so as to solve the problems of insufficient carrier transport and limited sensitivity of the Bi / Sb system device in the prior art.

[0004] To achieve the above purpose, the following technical solutions are adopted: A chiral non-lead perovskite flexible X-ray detector preparation method based on enantiomer proportion regulation, characterized in that it comprises the following steps: S1, mixing Bi2O3, Sb2O3 and a chiral molecule in an acidic solvent, obtaining a crystal precursor solution after heating and stirring, the chiral molecule being any one or both of S-CHEA and R-CHEA; after cooling the crystal precursor solution, a chiral non-lead perovskite single crystal is generated by crystallization, the chiral non-lead perovskite single crystal being (AEBi S 1–r R r -CHEA)4(Bi 0.5 Sb 0.5 )2I 10 (0 ≤ r ≤ 1); S2, grinding the chiral non-lead perovskite single crystal to generate a crystal powder, adding the crystal powder to an organic solvent, and obtaining a chiral non-lead perovskite precursor solution after uniform stirring; S3, filling and infiltrating a chiral non-lead perovskite precursor solution on a high polymer nylon film flexible substrate in-situ by a vacuum suction filtration method, and then heating the high polymer nylon film flexible substrate filled with the chiral non-lead perovskite precursor solution to obtain a flexible substrate distributed with a perovskite crystal network; S4, hot-pressing the flexible substrate distributed with the perovskite crystal network to obtain a chiral non-lead perovskite flexible film, wherein a film thickness of the chiral non-lead perovskite flexible film is 80-120 μm; S5, preparing a metal interdigital electrode on the chiral non-lead perovskite flexible film to obtain a chiral non-lead perovskite flexible X-ray detector.

[0005] Further improvements of the present application are as follows: Preferably, in S1, the mixing molar ratio of Bi2O3, Sb2O3 and the chiral molecule is 1:1:(4-10).

[0006] Preferably, in S1, the heating temperature is 110-130 ℃, and the heating time is 5-8 h.

[0007] Preferably, the cooling speed of the crystal precursor solution is 2-5 ℃ / day.

[0008] Preferably, in S2, the concentration of the chiral non-lead perovskite precursor solution is 0.2-1.0 mol / L.

[0009] Preferably, in S2, the chiral non-lead perovskite precursor solution is treated by filtration.

[0010] Preferably, in S3, the heating temperature is 90-110 ℃, and the heating time is 30-60 min.

[0011] Preferably, in S4, the hot-pressing temperature is 100-150 ℃, the hot-pressing pressure is 3-5 MPa, and the hot-pressing time is 10-15 min.

[0012] Preferably, in S4, the interdigital electrode is a metal electrode.

[0013] A chiral non-lead perovskite flexible X-ray detector with enantiomeric ratio control, prepared by any one of the above preparation methods, comprises a high polymer nylon film flexible substrate, wherein perovskite crystals are distributed on the high polymer nylon film flexible substrate, and the perovskite crystals are S 1–r R r -CHEA)4(Bi 0.5 Sb 0.5 )2I 10 (0 ≤ r ≤ 1).

[0014] Compared with the prior art, the present application has the following beneficial effects: The application discloses a high-performance chiral non-lead perovskite flexible X-ray detector based on enantiomer ratio regulation and a preparation method thereof. The method introduces chiral organic cations into a Bi / Sb-based non-lead perovskite precursor, regulates the chiral enantiomer ratio and the crystal structure, and prepares a chiral perovskite flexible film with excellent charge separation and transmission capacity. By introducing enantiomeric organic components (S-CHEA and R-CHEA) with adjustable ratios into the non-lead perovskite crystal structure, a local asymmetric electric field and an oriented chiral environment are formed in the material. This structural feature destroys the local inversion symmetry of the perovskite crystal, causing a clear spin splitting phenomenon around the metal center with strong spin-orbital coupling (SOC). The spin splitting causes the energy levels of the conduction band and the valence band to have a momentum-dependent spin orientation difference, thereby breaking the original spin degeneracy, limiting the spin-allowed carrier recombination channel, and promoting the spin-related carrier migration and exciton dissociation. Therefore, the application realizes the regulation of the electron spin behavior and the energy band structure through the chiral-induced local asymmetric structure, significantly improves the separation efficiency of the photo-generated carriers and the signal response performance in the device, and reduces the dark current noise level. The effect makes the local inversion symmetry of the crystal be destroyed, thereby breaking the spin degeneracy of the electron energy band, promoting the spin-related momentum flipping process, enhancing the exciton dissociation and carrier separation efficiency, and providing a new regulation approach for the performance improvement of the device. This mechanism significantly improves the separation and transmission efficiency of the carriers, further enhances the charge collection performance of the detector in X-ray detection, and lays a foundation for large-scale preparation and commercial application of the device.

[0015] By regulating the ratio of S-CHEA and R-CHEA S S-CHEA and R-CHEA R By regulating the ratio of S-CHEA and R-CHEA, precursor solutions with different chiralities can be obtained, and different chiral systems can change the nucleation and crystal face orientation behavior of the perovskite crystal, so that the obtained crystal or thin film has higher crystalline integrity and lower defect concentration, and grows high-quality single crystals or thin films. Through hot pressing and surface flattening treatment, a mechanically stable flexible perovskite layer is formed, and a high-conductivity interdigital electrode is deposited thereon to construct a flexible X-ray detector device. The method has low process temperature and simple steps, is suitable for large-area flexible substrate preparation, and is helpful for promoting the large-scale development of flexible detectors. The prepared flexible device shows ultra-low detection limit and stable sensitivity in the X-ray response process, and has good mechanical bending stability and environmental adaptability. The outstanding detection performance, lead-free environmental protection characteristics and flexibility and reliability will help promote the new generation of high-performance chiral non-lead perovskite flexible X-ray detectors to large-scale production and commercial application.

[0016] The application also discloses a high-performance chiral non-lead perovskite flexible X-ray detector based on enantiomer ratio regulation. S 1–r R r -CHEA)4(Bi 0.5 Sb 0.5 )2I 10 , wherein CHEA is a chiral organic ammonium ion, r is a chiral enantiomer ratio (0 ≤ r ≤ 1), and the enantiomer ratio is S 1–r R r -CHEA is an A-site structure in a perovskite crystal, and is combined with Bi, Sb and I to form the perovskite crystal. The structure not only ensures the photoelectric stability of the device under bending conditions, but also significantly improves the charge collection efficiency and signal-to-noise ratio performance. The application aims to solve the problems of the existing non-lead flexible X-ray detector in terms of large-scale preparation, long-term stability and application reliability, and improve the commercial application potential of the device in the fields of medical imaging, industrial detection and security and safety. BRIEF DESCRIPTION OF DRAWINGS

[0017] Figure 1 Fig. 1 is a preparation process and working principle diagram of the flexible chiral non-lead perovskite X-ray detector of the application; Figure 2 Fig. 2 is a crystal morphology photograph of the flexible chiral non-lead perovskite X-ray detector of the application; S 1–r R r -CHEA)4(Bi 0.5 Sb 0.5 )2I 10 crystal morphology photograph; Figure 3 Fig. 4 is a crystal lattice constant and X-ray diffraction analysis diagram of the sample under different chiral ratios; Figure 4 Fig. 5 is a circular dichroism (CD) and optical absorption spectrum diagram of the sample; Figure 5 Fig. 6 is a photocurrent time response and sensitivity statistical diagram of the flexible perovskite X-ray detector; Figure 6 Fig. 7 is an output signal-to-noise ratio (SNR) and dose rate response curve diagram of the detector. DETAILED DESCRIPTION

[0018] The application will be further described in detail below with reference to the drawings: To enable those skilled in the art to understand the features and effects of the present invention, the terms and expressions used in the specification and claims are explained and defined in general below. Unless otherwise specified, all technical and scientific terms used herein have the ordinary meaning understood by those skilled in the art regarding the present invention, and in case of conflict, the definitions in this specification shall prevail.

[0019] In this article, unless otherwise specified, “contains,” “includes,” “containing,” “has,” or similar terms cover the meanings of “composed of” and “mainly composed of,” for example, “A contains a” covers the meanings of “A contains a and others” and “A contains only a.”

[0020] The present invention will be further illustrated below with reference to specific embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention. Furthermore, it should be understood that after reading the teachings of this invention, those skilled in the art can make various alterations or modifications to the invention, and these equivalent forms also fall within the scope defined by the appended claims.

[0021] The following examples use instruments and equipment conventional in the art. Experimental methods in the following examples, unless otherwise specified, are generally performed under conventional conditions or as recommended by the manufacturer. All raw materials used in the following examples are conventional commercially available products with specifications conventional in the art. In this specification and the following examples, unless otherwise specified, "%" refers to weight percentage, "parts" refers to parts by weight, and "ratio" refers to weight proportion.

[0022] An embodiment of the present invention is a high-performance chiral lead-free perovskite flexible X-ray detector based on enantiomeric ratio control and its fabrication method, comprising the following steps: Step 1: Growth of chiral lead-free perovskite crystals Weigh out Bi₂O₃, Sb₂O₃, S–1–cyclohexylethylamine (S–CHEA) or R–1-cyclohexylethylamine ( ) with a purity ≥99% according to a molar ratio of 1:1:(4-10). R–CHEA) was added to an acidic solvent, namely a 57 wt% hydroiodic acid (HI) / hypophosphoric acid (H3PO2) solution, to form a 0.2 M mixed solution Z. Mixed solution Z was heated to 110-130°C to ensure complete dissolution of all reactants at this temperature. The reaction was stirred at 1000-1500 rpm for 5-8 hours to fully dissolve the reactants and form a homogeneous and transparent precursor solution. The resulting solution was then filtered through a 0.45 μm aqueous filter membrane to remove insoluble matter and particulate impurities, yielding a clear perovskite precursor solution. This precursor solution was then gradually cooled to 25-30°C at a rate of 2-5°C / day in a closed, temperature-controlled container for slow crystallization growth. Chiral lead-free perovskite single crystals were finally obtained through a continuous cooling method. S 1–r R r –CHEA)4(Bi 0.5 Sb 0.5 )2I 10 Chiral lead-free perovskite single crystals (0 ≤ r ≤ 1) with dimensions not less than 1×1×0.4 mm to 5×5×2 mm. These crystals are washed 2–3 times with anhydrous diethyl ether to remove residual solution from the surface, and then dried in an oven at 60°C for 24 hours, or at low temperature under vacuum for later use. The resulting perovskite single crystals can be further processed into flexible films or redissolved and crystallized to prepare thin films for use in the construction of flexible X-ray detectors.

[0023] Step 2, prepare the chiral lead-free perovskite precursor solution Y The chiral lead-free perovskite single crystal obtained and dried in step 1 ( S 1–r R r –CHEA)4(Bi 0.5 Sb 0.5 )2I 10(0 ≤ r ≤ 1) Grind the crystal powder into a uniform fine powder. Weigh a certain amount of the crystal powder as a solute and add it to the organic solvent N,N-dimethylformamide (DMF) to prepare a precursor solution with a concentration of 0.2–1.0 mol / L. Place the mixture on a magnetic stirrer and stir for 2–4 hours at 1000–1500 rpm to fully dissolve the crystal powder and form a uniform and transparent solution. This stirring rate can accelerate the formation of metal halide complexes in the precursor while ensuring the uniform distribution of chiral organic components in the solution. To further remove impurities and insoluble particles, the solution can be filtered through a polytetrafluoroethylene (PTFE) needle filter with a pore size of 0.22 μm to obtain a clear and stable chiral lead-free perovskite precursor solution Y, which can be used for subsequent spin-coating or filling processes to prepare high-quality chiral lead-free perovskite thin films or flexible films.

[0024] As a preferred option, the precursor solution has a concentration of 0.6–0.8 mol / L. This concentration range can ensure solution stability while promoting slow nucleation and orderly growth of crystals, resulting in a uniformly distributed perovskite crystal structure.

[0025] Step 3: Preparation of chiral lead-free perovskite thin films. Fluorine-doped tin oxide (FTO) conductive glass was selected and ultrasonically cleaned sequentially with deionized water, anhydrous ethanol, and acetone for 15 minutes each to remove surface organic residues and particulate impurities. Subsequently, it was treated in a plasma cleaner for 10 minutes to further activate the substrate surface and enhance film adhesion. 50–70 μL of chiral lead-free perovskite precursor solution Y was dropped onto the clean FTO substrate and uniformly spread using a spin-coating process (3000 rpm, 30 s). It was then annealed on a hot stage at 100–120 °C for 10–15 minutes to promote precursor solvent evaporation and crystal growth, ultimately forming a uniform and dense chiral lead-free perovskite thin film on the substrate surface.

[0026] The area of ​​the flexible polymer nylon film is 10 cm². 2 ~30 cm 2 The skeleton diameter is 5 µm to 10 µm, and the pore size is 5 µm to 10 µm. The filtration pressure is 0.1 Pa to 10 Pa, and the filtration time is 10 seconds to 60 seconds.

[0027] Step 4: Preparation of a chiral lead-free perovskite flexible membrane. A flexible polymer nylon substrate (approximately 50–80 μm thick) is fixed in the funnel of a vacuum filtration apparatus. A chiral lead-free perovskite precursor solution is slowly added dropwise to the substrate surface. Under the action of a vacuum pump, the precursor solution rapidly penetrates into the porous structure of the nylon membrane, thereby achieving in-situ filling and wetting of the chiral perovskite phase in the flexible substrate. Subsequently, the precursor-saturated nylon membrane is transferred to a hot stage and heated to 90–110 °C, held for 30–60 minutes to prevent the chiral components from being destroyed, allowing the precursor to slowly crystallize and obtain a flexible substrate with a uniformly distributed perovskite crystal network.

[0028] Step 5: Enhance the structural stability of the flexible membrane through hot pressing. The flexible perovskite membrane obtained in Step 4 is transferred to a hot press, with the temperature set at 100–150 ℃ and the pressure at 3–5 MPa for 10–15 minutes. This allows the perovskite crystals within the membrane to further densify and be oriented under the combined effects of heat and pressure, while simultaneously enhancing the interfacial bonding between the flexible substrate and the perovskite phase. The final result is a hot-pressed chiral lead-free perovskite flexible membrane with a thickness of 80–120 μm, exhibiting excellent mechanical flexibility and structural integrity.

[0029] During this temperature and pressure process, the hot-pressing parameters can, on the one hand, regulate crystal orientation. Hot pressing promotes slight plastic deformation of the perovskite crystals within the film, causing the grains to rearrange along the local stress direction and improving lattice order. On the other hand, it can induce polymer chain rearrangement on the surface through a thermo-mechanical dual effect, enhancing the interfacial bonding strength between the perovskite crystals and the flexible substrate. More importantly, the hot-pressing temperature is below the decomposition threshold of organic components (approximately 160°C), thus preventing structural deactivation of CHEA.

[0030] As a preferred embodiment, the buffer layer material includes PET (polyethylene terephthalate) and PI (polyimide). The buffer layers can be respectively disposed on both sides of the flexible film, with PET and PI arranged sequentially from the inside to the outside. The thickness of each PET or PI layer ranges from 10 to 50 μm, so that the thickness of the buffer layer on each side of the flexible film is 20-100 μm, ultimately forming a five-layer sandwich structure with the flexible film in the middle. During the hot pressing process, the pressure is shared and the strain is buffered, thereby absorbing the mechanical stress gradient under the dual action of hot and pressure, preventing the perovskite crystal from cracking or peeling off; at the same time, it improves the uniformity of heat conduction and avoids local overheating.

[0031] Step 6: Construct a flexible X-ray detector. On the surface of the flexible perovskite film obtained in Step 5, deposit interdigitated metal electrodes (such as Au, Ag, or Pt) using vacuum evaporation or magnetron sputtering. The interdigitated electrodes have a thickness of 30 nm–150 nm, a finger width of 10 nm–1 mm, a spacing of 10 nm–1 mm, a finger length of 10 nm–10 mm, and a photosensitive area of ​​200 nm. 2 ~40mm 2 To ensure the uniformity and efficiency of the charge collection channel, the fabricated device is a chiral lead-free perovskite flexible X-ray detector, possessing high sensitivity, excellent flexibility, and long-term operational stability, providing a feasible path for its commercial applications in medical imaging, security inspection, and portable detection.

[0032] Due to the significant polarity difference between chiral organic amine ions and inorganic metal oxides, phase separation or uneven local dissolution easily occurs in mixed systems, leading to an imbalance in the formation rate of metal halide complexes in the solution system. This makes the crystallization process difficult to control, easily resulting in problems such as excessively large grain size, uneven crystallization orientation, or the formation of impurity phases. This problem is more pronounced in systems containing chiral molecules, because the polarity difference of enantiomers alters the local solution potential distribution and metal-ligand coordination environment, further exacerbating crystallization instability. Therefore, this invention establishes a crystallization control strategy based on the synergistic regulation of enantiomer ratio and solvent environment. In the solution composition design, by adjusting... S –CHEA and R The proportion of CHEA is used to achieve a controllable balance between the overall chirality and polarity of the solution, thereby suppressing polar repulsion between components. HI is selected as the acidic polar solvent, and H3PO2 is added as a reducing stabilizer to prevent iodide ions (I-) from accumulating. – The iodine is oxidized to elemental iodine (I₂), stabilizing the iodide environment and Bi–I / Sb–I complex structure in the solution, thereby achieving a uniform and controlled crystallization process. In the subsequent crystallization process, by combining solution temperature gradient control and slow solvent evaporation, the crystal grows at a limited rate along the preferred crystal plane, resulting in high-quality lead-free perovskite crystals or films with smooth grain boundaries, low defect density, and uniform chirality distribution.

[0033] By controlling both the ratio and crystallization behavior, this invention significantly improves the film uniformity and crystal integrity of chiral perovskite materials, providing a reliable material basis for the stable performance of subsequent flexible devices.

[0034] The following description, in conjunction with specific embodiments, provides further details.

[0035] Example 1 See Figure 2This embodiment discloses a high-performance chiral lead-free perovskite flexible X-ray detector based on enantiomeric ratio control and its fabrication method, including the following steps: S1, Preparation of chiral lead-free perovskite crystals: Weigh out Bi2O3 (99.99%, 0.442 g), Sb2O3 (99.99%, 0.258 g) and... S S-CHEA (>99%, 0.512 g) was added to 10 mL of a 57% hydroiodic acid (HI) and hypophosphorous acid (H3PO2) solution in a molar ratio of 1:1:4 to form a homogeneous mixed solution A. Mixed solution A was heated and stirred at 120 °C for at least 5 hours to ensure complete dissolution of the oxide and full reaction with S-CHEA. Mixed solution A was filtered through an aqueous filter membrane with a pore size of 0.45 μm to obtain a clear and transparent chiral lead-free perovskite precursor solution. Subsequently, the filtered precursor solution was cooled to room temperature at a slow cooling rate of 3 °C / day to allow slow crystal growth. After crystal growth, the obtained crystals were bright orange-red and had a plate-like or blocky morphology. The crystal surface was thoroughly washed with diethyl ether to remove residual solution, and then the crystals were dried in an oven at 60 °C for 24 hours to obtain a pure and dry (… S 1 R 0–CHEA)4(Bi 0.5 Sb 0.5 )2I 10 Crystalline powder.

[0036] S2, Preparation of chiral lead-free perovskite precursor solution: Weigh out the dried ( S 1 R 0–CHEA)4(Bi 0.5 Sb 0.5 )2I 10 0.1 g of crystalline powder was dissolved in 1 mL of N,N-dimethylformamide (DMF, 99.8%) to prepare chiral lead-free perovskite precursor solution B. The solution was stirred at 1200 rpm for 3 hours to completely dissolve the crystalline powder, resulting in a homogeneous and transparent precursor solution.

[0037] S3, Preparation of chiral lead-free perovskite flexible membrane: A nylon flexible substrate (5 cm in diameter) was placed in the funnel of a vacuum filtration device. 500 μL of chiral lead-free perovskite precursor solution was dropped onto the surface of the flexible substrate. The vacuum pump was turned on to allow the precursor solution to fully penetrate the flexible substrate. Subsequently, the flexible membrane was transferred to a hot stage and annealed at 100 °C for 2 hours, allowing perovskite crystals to slowly crystallize and grow on the flexible substrate, forming a continuous and uniform flexible membrane.

[0038] S4, Hot pressing treatment: The annealed flexible film is placed in a hot press and hot-pressed at 110 ℃ and 4 MPa for 10 min to densify the flexible film, improve the intercrystalline contact, and obtain a chiral lead-free perovskite flexible film with a thickness of about 100 μm. The film surface is smooth and the color is bright orange-red.

[0039] S5, Electrode Deposition and Completion of Flexible Device: Interdigitated Au electrodes with a thickness of approximately 50 nm were deposited on the surface of the hot-pressed flexible film. Conductive electrodes were then fabricated using vacuum evaporation, forming a complete chiral lead-free perovskite flexible X-ray detector. The fabricated device exhibited ultra-low detection limit, high sensitivity, and good mechanical bending stability and environmental adaptability in X-ray response testing, providing a technological foundation for the commercial application of high-performance flexible detectors.

[0040] In this embodiment, a chiral lead-free perovskite thin film was also prepared for optical testing. The specific process was as follows: an FTO glass substrate (1 cm × 1 cm) was ultrasonically cleaned with deionized water, acetone, and isopropanol for 15 minutes each, dried, and then subjected to plasma treatment for 10 minutes. 50 μL of precursor solution B was spin-coated onto the pretreated FTO substrate (3000 rpm, spin-coating for 30 s), followed by annealing at 70 °C for 10 minutes to obtain a uniform and continuous chiral lead-free perovskite thin film. Figure 1 It can be seen that in the final X-ray detection process, electrons and holes migrate and are collected between the electrodes, respectively, during the carrier transport process.

[0041] Example 2 This embodiment describes a high-performance chiral lead-free perovskite flexible X-ray detector based on enantiomeric ratio control and its fabrication method, which includes the following fabrication steps: Preparation of chiral lead-free perovskite crystals: Weigh Bi2O3 (99.99%, 0.442 g) and Sb2O3 (99.99%, 0.258 g). S –CHEA (>99%, 0.384 g) and R –CHEA (>99%, 0.128 g), added in a molar ratio of 1:1:3:1 to 10 mL of a 57% hydroiodic acid (HI) and hypophosphorous acid (H3PO2) solution to form a homogeneous mixture A. Mixture A was heated and stirred at 120 °C for at least 5 hours to ensure complete dissolution of the oxides and homogenization. S –CHEA, R–CHEA was fully reacted. The mixed solution A was filtered through an aqueous filter membrane with a pore size of 0.45 μm to obtain a clear and transparent chiral lead-free perovskite precursor solution. Subsequently, the filtered precursor solution was cooled to room temperature at a slow cooling rate of 3 °C / day to allow for slow crystal growth. After crystal growth, the obtained crystals were bright orange-red and had a plate-like or blocky morphology. The crystal surface was thoroughly washed with diethyl ether to remove residual solution, and then the crystals were dried in an oven at 60 °C for 24 hours to obtain pure and dry (CHEA). S 0.75 R 0.25 –CHEA)4(Bi 0.5 Sb 0.5 )2I 10 Crystalline powder.

[0042] The other steps are the same as in Example 1.

[0043] Example 3 This embodiment describes a high-performance chiral lead-free perovskite flexible X-ray detector based on enantiomeric ratio control and its fabrication method, which includes the following fabrication steps: Preparation of chiral lead-free perovskite crystals: Weigh Bi2O3 (99.99%, 0.442 g) and Sb2O3 (99.99%, 0.258 g). S –CHEA (>99%, 0.256 g) and R –CHEA (>99%, 0.256 g), added in a molar ratio of 1:1:2:2 to 10 mL of a 57% hydroiodic acid (HI) and hypophosphorous acid (H3PO2) solution to form a homogeneous mixture A. Mixture A was heated and stirred at 120 °C for at least 5 hours to ensure complete dissolution of the oxides and homogenization. S –CHEA, R –CHEA was fully reacted. The mixed solution A was filtered through an aqueous filter membrane with a pore size of 0.45 μm to obtain a clear and transparent chiral lead-free perovskite precursor solution. Subsequently, the filtered precursor solution was cooled to room temperature at a slow cooling rate of 3 °C / day to allow for slow crystal growth. After crystal growth, the obtained crystals were bright orange-red and had a plate-like or blocky morphology. The crystal surface was thoroughly washed with diethyl ether to remove residual solution, and then the crystals were dried in an oven at 60 °C for 24 hours to obtain pure and dry (CHEA). S 0.5 R 0.5 –CHEA)4(Bi 0.5 Sb 0.5 )2I10 Crystalline powder.

[0044] The other steps are the same as in Example 1.

[0045] Example 4 This embodiment describes a high-performance chiral lead-free perovskite flexible X-ray detector based on enantiomeric ratio control and its fabrication method, which includes the following fabrication steps: Preparation of chiral lead-free perovskite crystals: Weigh Bi2O3 (99.99%, 0.442 g) and Sb2O3 (99.99%, 0.258 g). S –CHEA (>99%, 0.128 g) and R CHEA (>99%, 0.384 g), added in a molar ratio of 1:1:2:2 to 10 mL of a 57% hydroiodic acid (HI) and hypophosphorous acid (H3PO2) solution, forms a homogeneous mixture A. Mixture A is heated and stirred at 120 °C for at least 5 hours to ensure complete dissolution of the oxides and their homogeneity. S –CHEA, R –CHEA was fully reacted. The mixed solution A was filtered through an aqueous filter membrane with a pore size of 0.45 μm to obtain a clear and transparent chiral lead-free perovskite precursor solution. Subsequently, the filtered precursor solution was cooled to room temperature at a slow cooling rate of 3 °C / day to allow for slow crystal growth. After crystal growth, the obtained crystals were bright orange-red and had a plate-like or blocky morphology. The crystal surface was thoroughly washed with diethyl ether to remove residual solution, and then the crystals were dried in an oven at 60 °C for 24 hours to obtain pure and dry (CHEA). S 0.25 R 0.75 –CHEA)4(Bi 0.5 Sb 0.5 )2I 10 Crystalline powder.

[0046] The other steps are the same as in Example 1.

[0047] Example 5 This embodiment describes a high-performance chiral lead-free perovskite flexible X-ray detector based on enantiomeric ratio control and its fabrication method, which includes the following fabrication steps: Preparation of chiral lead-free perovskite crystals: Weigh Bi2O3 (99.99%, 0.442 g) and Sb2O3 (99.99%, 0.258 g). R–CHEA (>99%, 0.512 g), added in a molar ratio of 1:1:2:2 to 10 mL of a 57% hydroiodic acid (HI) and hypophosphorous acid (H3PO2) solution to form a homogeneous mixture A. Mixture A was heated and stirred at 120 °C for at least 5 hours to ensure complete dissolution of the oxides and homogenization. S –CHEA, R –CHEA was fully reacted. The mixed solution A was filtered through an aqueous filter membrane with a pore size of 0.45 μm to obtain a clear and transparent chiral lead-free perovskite precursor solution. Subsequently, the filtered precursor solution was cooled to room temperature at a slow cooling rate of 3 °C / day to allow for slow crystal growth. After crystal growth, the obtained crystals were bright orange-red and had a plate-like or blocky morphology. The crystal surface was thoroughly washed with diethyl ether to remove residual solution, and then the crystals were dried in an oven at 60 °C for 24 hours to obtain pure and dry (CHEA). S 0 R 1–CHEA)4(Bi 0.5 Sb 0.5 )2I 10 Crystalline powder.

[0048] The other steps are the same as in Example 1.

[0049] The characterization and analysis of a high-performance chiral lead-free perovskite flexible X-ray detector based on enantiomeric ratio control and its fabrication method, as described in this invention, includes the following: See Figure 3 Figures a and b show the lattice structure analysis under different chiral ratios. Figures a and b show the relationship between the lattice constant D and the chiral ratio; figures c and d show the corresponding XRD diffraction patterns, demonstrating the shift of the diffraction peaks of the (002) crystal plane with the chiral ratio, reflecting the systematic variation of lattice parameters and crystal order. This shows that chiral control can affect lattice orientation and crystal order, verifying the controllability of the structure.

[0050] Figure 4 Circular dichroism (CD) and absorption spectra of perovskite films. The left figure shows the CD spectra of different chiral ratios, displaying obvious chiral responses at characteristic wavelengths such as 378 nm, 451 nm, and 526 nm; the right figure shows the corresponding absorption spectrum curves, indicating the correspondence between the absorption edge and the chiral signal for each ratio of sample. This demonstrates the inherent optical chiral characteristics and stability of the material, laying the foundation for subsequent differential response analysis in devices.

[0051] Figure 5Photoelectric response performance of flexible perovskite X-ray detector. Figure a: Response curve of device output current over time under periodic X-ray irradiation, showing clear switching characteristics and repeatability; Figure b: A bar graph showing the change in response current and sensitivity as a function of the S- / R- ratio, illustrating the effect of chiral modulation on the response performance. This demonstrates that the device of this invention exhibits high sensitivity and stable response behavior under X-rays.

[0052] Figure 6 Detector dose rate response versus signal-to-noise ratio (SNR) graph. The graph shows the linear relationship between output signal intensity (or sensitivity) and incident dose rate, indicating that the detection limit of the device is 30 μGys. - ¹ This indicates that the flexible chiral perovskite detector has a wide linear response range and excellent signal-to-noise performance, making it suitable for low-dose medical or safety detection.

[0053] X-ray detection measurements were performed under ambient conditions using an X-ray tube equipped with a tungsten anode as the radiation source at room temperature. A 2 mm thick aluminum foil was placed between the X-ray source and detector as an attenuator to adjust the dose rate. All measurements were performed in a dark lead-shielded box to eliminate interference from ambient light and external electromagnetic signals. A bias voltage was applied using a Keysight B2912A source meter, and the output current was recorded for Example 1. 5. Prepared ( S 1–r R r –CHEA)4(Bi 0.5 Sb 0.5 )2I 10 The results of the X-ray detector sensitivity test of the flexible X-ray detector (0 ≤ r ≤ 1) are shown in Table 1 below.

[0054] Table 1. Test results of X-ray detector sensitivity

[0055] Example 6 In this embodiment, the concentration of the perovskite precursor solution is 0.05M, and the remaining steps are the same as in Example 1.

[0056] Example 7 In this embodiment, the concentration of the perovskite precursor solution is 0.08M, and the remaining steps are the same as in Example 1.

[0057] Example 8 In this embodiment, the concentration of the perovskite precursor solution is 0.15M, and the remaining steps are the same as in Example 1.

[0058] Example 9 In this embodiment, the concentration of the perovskite precursor solution is 0.20M, and the remaining steps are the same as in Example 1.

[0059] Example 10 In this embodiment, the concentration of the perovskite precursor solution is 0.50 M, and the remaining steps are the same as in Example 1.

[0060] Example 11 In this embodiment, Bi₂O₃, Sb₂O₃, S–CHEA, and [other ingredients] were weighed according to a molar ratio of 1:1:2:3. R –CHEA, the remaining steps are the same as in Example 1.

[0061] Example 12 In this embodiment, Bi₂O₃, Sb₂O₃, S–CHEA, and [other components] were weighed according to a molar ratio of 1:1:4:3. R –CHEA, the remaining steps are the same as in Example 1.

[0062] Example 13 In this embodiment, Bi₂O₃, Sb₂O₃, S–CHEA, and [other components] were weighed according to a molar ratio of 1:1:4:4. R –CHEA, the remaining steps are the same as in Example 1.

[0063] Example 14 In this embodiment, in S1, the heating temperature of the mixed solution z is 110°C and the heating time is 8 hours. The remaining steps are the same as in Embodiment 1.

[0064] Example 15 In this embodiment, in S1, the heating temperature of the mixed solution z is 130°C and the heating time is 5 hours. The remaining steps are the same as in Embodiment 1.

[0065] Example 16 In this embodiment, in step S1, the filtered precursor solution is cooled to room temperature at a slow cooling rate of 2 °C / day to allow the crystals to grow slowly. The remaining steps are the same as in Example 1.

[0066] Example 17 In this embodiment, in step S1, the filtered precursor solution is cooled to room temperature at a slow cooling rate of 5 °C / day to allow the crystals to grow slowly. The remaining steps are the same as in Example 1.

[0067] Example 18 In S3 of this embodiment, the heating temperature is 90°C and the heating time is 60 min. The remaining steps are the same as in Embodiment 1.

[0068] Example 19 In S3 of this embodiment, the heating temperature is 110°C and the heating time is 30 minutes. The remaining steps are the same as in Embodiment 1.

[0069] Example 20 In S4 of this embodiment, the hot pressing temperature is 100°C, the hot pressing pressure is 5 MPa, and the hot pressing time is 12 min. The remaining steps are the same as in Embodiment 1.

[0070] Example 21 In S4 of this embodiment, the hot-pressing temperature is 150°C, the heating time is 3 minutes, the hot-pressing time is 15 minutes, and the remaining steps are the same as in Embodiment 1.

[0071] This invention relates to perovskite photoelectric detection materials, specifically a high-performance chiral lead-free perovskite flexible X-ray detector based on enantiomeric ratio control and its fabrication method. Step 1: Growth of chiral lead-free perovskite ( S 1–r R r –CHEA)4(Bi 0.5 Sb 0.5 )2I 10 (0 ≤ r ≤ 1) crystal; Step 2: Prepare chiral lead-free perovskite precursor solution Y; Step 3: Prepare chiral lead-free perovskite thin film; Step 4: Prepare chiral lead-free perovskite flexible film; Step 5: Enhance the structural stability of the flexible film through hot pressing process; Step 6: Prepare flexible X-ray detector.

[0072] This invention discloses a high-performance chiral lead-free perovskite flexible X-ray detector and its fabrication method. This method involves introducing chiral organic cations into a Bi / Sb-based lead-free perovskite precursor and controlling the chiral enantiomer ratio and crystal structure to prepare a chiral perovskite flexible film with excellent charge separation and transport capabilities. This method features low processing temperature and simple steps, making it suitable for large-area flexible substrate fabrication. It contributes to the large-scale development of flexible detectors and provides a new technical path and approach for the commercial application of next-generation lead-free, high-sensitivity flexible X-ray detectors.

[0073] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A method for fabricating a chiral lead-free perovskite flexible X-ray detector based on enantiomeric ratio control, characterized in that, Includes the following steps: S1, Bi2O3, Sb2O3, and chiral molecules are mixed in an acidic solvent, and heated and stirred to obtain a crystal precursor solution. The chiral molecules are any one or both of S-CHEA and R-CHEA. After cooling the crystal precursor solution, a chiral lead-free perovskite single crystal is formed. The chiral lead-free perovskite single crystal is (…). S 1–r R r –CHEA)4(Bi 0.5 Sb 0.5 )2I 10 (0 ≤ r ≤ 1); S2, the chiral lead-free perovskite single crystal is ground to generate crystal powder, added to an organic solvent, and stirred evenly to obtain a chiral lead-free perovskite precursor solution. S3. A chiral lead-free perovskite precursor solution is filled and impregnated in situ on a flexible substrate of polymer nylon membrane by vacuum filtration. Then, the flexible substrate of polymer nylon membrane filled with chiral lead-free perovskite precursor solution is heated to obtain a flexible substrate with a perovskite crystal network. S4. A flexible substrate with a perovskite crystal network distributed thereon is hot-pressed to obtain a chiral lead-free perovskite flexible film, wherein the thickness of the chiral lead-free perovskite flexible film is 80~120μm. S5. A metal interdigitated electrode is fabricated on a chiral lead-free perovskite flexible film to obtain a chiral lead-free perovskite flexible X-ray detector.

2. The method for fabricating a chiral lead-free perovskite flexible X-ray detector based on enantiomeric ratio control according to claim 1, characterized in that, In S1, the molar ratio of Bi2O3, Sb2O3 and chiral molecules is 1:1:(4-10).

3. The method for fabricating a chiral lead-free perovskite flexible X-ray detector based on enantiomeric ratio control according to claim 1, characterized in that, In S1, the heating temperature is 110-130℃ and the heating time is 5-8h.

4. The method for fabricating a chiral lead-free perovskite flexible X-ray detector based on enantiomeric ratio control according to claim 1, characterized in that, The cooling rate of the crystal precursor solution is 2-5℃ / day.

5. The method for fabricating a chiral lead-free perovskite flexible X-ray detector based on enantiomeric ratio control according to claim 1, characterized in that, In S2, the concentration of the chiral lead-free perovskite precursor solution is 0.2–1.0 mol / L.

6. The method for fabricating a chiral lead-free perovskite flexible X-ray detector based on enantiomeric ratio control according to claim 1, characterized in that, In S2, the chiral lead-free perovskite precursor solution is filtered.

7. The method for fabricating a chiral lead-free perovskite flexible X-ray detector based on enantiomeric ratio control according to claim 1, characterized in that, In S3, the heating temperature is 90–110 ℃ and the heating time is 30–60 min.

8. The method for fabricating a chiral lead-free perovskite flexible X-ray detector based on enantiomeric ratio control according to claim 1, characterized in that, In S4, the hot-pressing temperature is 100–150 ℃, the hot-pressing pressure is 3–5 MPa, and the hot-pressing time is 10–15 min.

9. The method for fabricating a chiral lead-free perovskite flexible X-ray detector based on enantiomeric ratio control according to claim 1, characterized in that, In S4, the interdigitated electrode is a metal electrode.

10. A chiral lead-free perovskite flexible X-ray detector with enantiomeric ratio control, prepared by the method according to any one of claims 1-9, characterized in that, The substrate includes a flexible nylon film made of polymer, wherein perovskite crystals are distributed on the flexible nylon film made of polymer, wherein the perovskite crystals are ( S 1–r R r –CHEA)4(Bi 0.5 Sb 0.5 )2I 10 (0 ≤ r ≤ 1).

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