Perovskite film, preparation method thereof and application of perovskite film in X-ray detector

Abstract

The invention provides a perovskite film, a preparation method thereof and application of the perovskite film in an X-ray detector. The preparation raw materials of the perovskite film contain a multifunctional synergistic regulation molecular additive, and the multifunctional synergistic regulation molecular additive comprises at least one of tannic acid, procyanidine, propyl gallate, gallic acid and baicalin. Through optimization of materials and a process, uniform and compact deposition, defect passivation and improvement of charge transfer capability of a thick film are realized, higher sensitivity and clear and rapid imaging are obtained in the field of X-ray detection, and a foundation is laid for industrial application of a high-performance X-ray detector and an imaging technology. The invention also provides a preparation method of the perovskite film and application of the perovskite film in an X-ray detector.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor material preparation and X-ray detection technology, specifically relating to a perovskite film, its preparation method, and its application in X-ray detectors. Background Technology

[0002] Halide perovskites, with their tunable bandgap, high X-ray absorption coefficient, excellent mobility-lifetime product, and long carrier diffusion length, have shown great application potential in X-ray detection, becoming a core candidate material for high-resolution imaging technologies in fields such as medical diagnostics, industrial non-destructive testing, and security inspection. Depositing uniform, large-area perovskite layers on thin-film transistors (TFTs) is a key step in realizing the industrial application of perovskite flat-panel X-ray detectors. Among these technologies, spray coating, with its unique bottom-up crystallization process, can be directly integrated with pixelated TFT backplanes without requiring post-processing steps such as hot pressing, and is considered a highly promising fabrication process.

[0003] However, the preparation and application of existing perovskite films still face many technical bottlenecks. To ensure effective X-ray absorption, the thickness of the polycrystalline perovskite film needs to reach more than 10 μm. This not only significantly increases the carrier transport path and recombination probability but also easily leads to the accumulation of lattice defects. At the same time, as an ionic crystal, perovskite has the inherent characteristics of a soft lattice and weak ionic bonds, inevitably generating a large number of bulk defects and lattice strain during the preparation process, further exacerbating the problems of carrier recombination and transport obstruction. In addition, there is a lattice mismatch and difference in thermal expansion coefficient between the perovskite material and the substrate. During temperature changes such as heating and annealing, severe lattice strain is easily generated at the interface, which may even cause the perovskite film to detach from the FTO conductive glass and TFT conductive substrate, significantly reducing the mechanical stability of the device.

[0004] Traditional solutions typically rely on adding multiple specialized additives to address each of the aforementioned individual problems. This not only increases the complexity of the fabrication process but may also affect the reproducibility of device performance, making it difficult to achieve synergistic optimization of defect passivation, stress relief, and enhanced interfacial bonding. More importantly, existing perovskite X-ray detectors exhibit significant dark current in applications, severely impacting the device's signal-to-noise ratio and limiting high-resolution imaging at low dose rates. Therefore, developing a multifunctional synergistic strategy that can simultaneously achieve defect passivation, reduce stress accumulation, enhance interfacial bonding stability, and effectively modulate semiconductor properties to reduce dark current has become a key requirement for overcoming existing technological bottlenecks and promoting the high-performance and integrated development of perovskite-based X-ray detectors. Summary of the Invention

[0005] The present invention aims to at least solve one of the aforementioned technical problems existing in the prior art. To this end, the present invention provides a perovskite film, the raw materials of which include multifunctional synergistic molecular additives, which can effectively passivate incompletely coordinated Pb. 2+ It can identify defects and vacancies, anchor related ions, and inhibit ion migration. Simultaneously, it can act as a molecular crosslinking agent, bridging adjacent perovskite particles through coordination and hydrogen bonding, suppressing disordered lattice relaxation in thick films, releasing micro-strain, and enhancing lattice stability. Furthermore, this additive can improve the wettability of the precursor solution to the substrate, enhance the interfacial bonding between the thick film and the substrate through chemical anchoring to prevent delamination, and regulate the semiconductor properties of perovskite and the energy level arrangement and interfacial barrier between the perovskite and substrate, thereby effectively reducing device dark current.

[0006] The present invention also provides a method for preparing a perovskite film.

[0007] The present invention also provides an X-ray detector containing the perovskite film of the present invention.

[0008] A first aspect of the present invention provides a perovskite film, the chemical composition of which includes MAPbI3, MAPbBr3, MAPbCl3, FAPbI3, and FA. x MA 1-x PbI3, FA x Cs 1-x PbI3, MA x FA y Cs 1-x-y At least one of PbI3 and FAPbBr3, wherein 0≤x≤1 and 0≤y≤1, the raw materials for preparing the perovskite membrane contain a multifunctional synergistic regulatory molecular additive, which includes at least one of tannic acid, proanthocyanidins, propyl gallate, gallic acid and baicalin.

[0009] The perovskite film of the present invention has at least the following beneficial effects: The perovskite film prepared by this invention contains multifunctional synergistic molecular additives, which are rich in oxygen-containing functional groups (such as hydroxyl (-OH) and carbonyl (-C=O)). These oxygen-containing functional groups interact with Pb in the perovskite film. 2+ I - (or Cl) - ,Br - ) and MA + (or Fa + The ions undergo Lewis acid-base interactions and hydrogen bonding, effectively passivating incompletely coordinated Pb. 2+ Defects, Anchoring I - and MA +Ions are passivated, vacancy defects are eliminated, and ion migration is inhibited. At the same time, the multifunctional synergistic regulatory molecular additives act as molecular crosslinking agents, bridging adjacent perovskite particles through coordination and hydrogen bonding, inhibiting the disordered lattice relaxation of perovskite thick films, releasing micro-strain, and thus enhancing the lattice stability of perovskite.

[0010] Furthermore, multifunctional synergistic regulatory molecular additives can improve the wettability of perovskite precursor solutions to the substrate and enhance the connection between the thick film and the substrate through chemical anchoring, thereby improving interfacial adhesion and preventing delamination.

[0011] Furthermore, multifunctional synergistic molecular additives can modulate the semiconductor properties of perovskites, optimize the energy level arrangement between the perovskite and the substrate, and regulate the interface barrier, thereby effectively reducing the dark current of the device.

[0012] The perovskite membrane of the present invention can achieve the above-mentioned effects simply by introducing trace amounts of multifunctional synergistic regulatory molecular additives for modification.

[0013] According to some embodiments of the present invention, in the raw materials for preparing the perovskite film, a multifunctional synergistic regulatory molecular additive reacts with Pb in the perovskite. 2+ The molar equivalent ratio is 0.01%~10%:1.

[0014] According to some embodiments of the present invention, in the raw materials for preparing the perovskite film, a multifunctional synergistic regulatory molecular additive reacts with Pb² in the perovskite. + The molar equivalent ratio is any value among 0.01%, 0.1%, 1%, 2%, 3%, 4%, 5%, 6%, 7%, 8%, 9%, and 10%, such as 5%, or any range of two values, such as 1% to 3%.

[0015] A second aspect of the present invention provides a method for preparing a perovskite film according to the first aspect of the present invention, comprising the following steps: S1: Add perovskite microcrystals corresponding to the chemical composition of the perovskite film to a solvent, and add the multifunctional synergistic regulatory molecular additive to obtain a mixed solution; S2: After spraying the mixed solution onto the substrate surface, perform annealing treatment to obtain the perovskite film.

[0016] The method for preparing perovskite films of the present invention has at least the following beneficial effects: The preparation method of the present invention does not require expensive equipment and complex process control, the reaction conditions are not harsh, the raw materials are readily available, the production cost is low, and it is easy to industrialize.

[0017] This invention introduces trace amounts of multifunctional synergistic regulatory molecular additives into perovskite solutions. These additives dissolve well in the perovskite solution, and after film formation, the additive molecules adsorb at the grain boundaries, interacting chemically with metal ions, organic cations, and halide ions in the perovskite, effectively reducing the defect density of the device and releasing lattice strain. The additive molecules also improve the wettability of the precursor solution to the substrate, resulting in a denser, thicker film and enhanced interfacial mechanical stability. The addition of the additives raises the Fermi level of the perovskite film, causing a reversal of the interfacial barrier direction with the substrate, thereby effectively reducing dark current.

[0018] According to some embodiments of the present invention, the solvent includes N,N-dimethylformamide, N-methylpyrrolidone, ethylene glycol methyl ether, or dimethyl sulfoxide.

[0019] According to some embodiments of the present invention, in step S1, perovskite microcrystals corresponding to the chemical composition of the perovskite film are added to a solvent to obtain a perovskite solution with a concentration of 0.1~5 mol / L.

[0020] According to some embodiments of the present invention, the concentration of the perovskite solution is 0.1~5 mol / L.

[0021] According to some embodiments of the present invention, the concentration of the perovskite solution is any value among 0.1 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L, and 5 mol / L, such as 2 mol / L, or any range formed by both, such as 1 mol / L to 3 mol / L.

[0022] According to some embodiments of the present invention, in step S1, after the perovskite microcrystals are added to the solvent, they are stirred overnight.

[0023] According to some embodiments of the present invention, in step S2, the mixed solution is filtered before spraying.

[0024] According to some embodiments of the present invention, in step S2, the substrate is preheated before spraying.

[0025] According to some embodiments of the present invention, in step S2, the substrate comprises FTO (fluorine-doped tin oxide) glass.

[0026] According to some embodiments of the present invention, in step S2, the spraying method is ultrasonic spraying.

[0027] According to some embodiments of the present invention, during the ultrasonic spraying process, the ultrasonic nozzle is cyclically moved on an XY moving platform to ensure uniform and complete coverage of each position of the substrate.

[0028] According to some embodiments of the present invention, during the ultrasonic spraying process, the flow rate of the mixed solution is 5~30 mL / min.

[0029] According to some embodiments of the present invention, during the ultrasonic spraying process, the flow rate of the mixed solution is any value among 5 mL / min, 8 mL / min, 10 mL / min, 12 mL / min, 15 mL / min, 18 mL / min, 20 mL / min, 22 mL / min, 25 mL / min, 28 mL / min, and 30 mL / min, such as 12 mL / min, or any range formed by both, such as 10 mL / min to 20 mL / min.

[0030] According to some embodiments of the present invention, during the ultrasonic spraying process, the carrier gas is nitrogen, and the nitrogen flow rate is 1~10L / min.

[0031] According to some embodiments of the present invention, the nitrogen flow rate is any value among 1L / min, 2L / min, 3L / min, 4L / min, 5L / min, 6L / min, 7L / min, 8L / min, 9L / min, and 10L / min, such as 5L / min, or any range formed by both, such as 3L / min to 7L / min.

[0032] According to some embodiments of the present invention, in step S2, the annealing temperature is 100~150°C.

[0033] According to some embodiments of the present invention, in step S2, the annealing temperature is any value among 100°C, 110°C, 120°C, 130°C, 140°C, and 150°C, such as 120°C, or any range formed by both, such as 110°C to 130°C.

[0034] According to some embodiments of the present invention, in step S2, the annealing time is 20-50 minutes.

[0035] According to some embodiments of the present invention, in step S2, the annealing time is any value among 20min, 25min, 30min, 35min, 40min, 45min, and 50min, such as 30min, or any range formed by both, such as 25min to 35min.

[0036] A third aspect of the present invention provides an X-ray detector comprising a perovskite film of the first aspect of the present invention or a perovskite film prepared by the method of the second aspect of the present invention.

[0037] The X-ray detector of this invention utilizes the multi-site defect passivation effect of multifunctional synergistically modulated molecular additives in the perovskite film to effectively reduce the bulk and interface defect density, decrease carrier recombination, and improve charge transport and collection efficiency. Experimental data show that the detector containing this perovskite film has significantly better sensitivity than the device without additives at a -4V bias voltage. Furthermore, for different perovskite systems (such as MAPbBr3), the sensitivity can be improved by nearly 2 times, enabling precise capture of low-dose X-ray signals and a substantial increase in detection sensitivity.

[0038] The additive modulates the Fermi level of the perovskite, flipping the orientation of its interfacial barrier with the substrate. This reverses the orientation of the built-in electric field and the applied bias voltage, counteracting the interfacial electric field strength, stabilizing ion migration, and suppressing dark current generation. This characteristic ensures that the detector maintains clear signal resolution even in low-dose-rate scenarios, providing a core guarantee for high-definition imaging.

[0039] As a molecular crosslinking agent, the additive bridges adjacent perovskite particles through coordination and hydrogen bonding, releasing lattice strain. Simultaneously, it improves precursor wettability and film-substrate interface adhesion, preventing film cracking, void formation, and delamination from the FTO / TFT substrate. Scanning electron microscopy characterization confirms that the perovskite film has a dense, defect-free surface and tight contact with the substrate, significantly improving the long-term reliability and environmental adaptability of the detector.

[0040] The perovskite film combines a high X-ray absorption coefficient with excellent charge transport properties, and can be deposited uniformly over a large area using an ultrasonic spraying process, enabling efficient integration with a pixelated TFT backplane. In actual testing, the detector can achieve clear imaging of copper knives and suitcases containing metal objects under low-dose conditions, making it suitable for high-resolution imaging needs in various scenarios such as medical diagnosis, industrial non-destructive testing, and security inspection.

[0041] The ultrasonic spraying method used eliminates the need for complex post-processing steps such as hot pressing, allowing direct integration with the TFT backplane. Furthermore, only trace amounts of additives are required to achieve multiple functional optimizations, avoiding the problems of process complexity and poor repeatability caused by traditional multi-additive solutions. It balances preparation efficiency and product consistency, laying the foundation for large-scale production.

[0042] According to some embodiments of the present invention, an X-ray detector includes a detector and an imager. Attached Figure Description

[0043] Figure 1 This is a scanning electron microscope image of the perovskite film obtained in Example 1.

[0044] Figure 2 This is a scanning electron microscope image of the perovskite film obtained in Comparative Example 1.

[0045] Figure 3 This is an energy level arrangement diagram of the perovskite thick film and electrode obtained in Comparative Example 1 and Example 1.

[0046] Figure 4 The detection sensitivity of the devices in Comparative Example 1 and Example 1 is compared under different applied bias voltages.

[0047] Figure 5 This is an X-ray imaging image of the perovskite device obtained in Example 1.

[0048] Figure 6 The results are the test results of the perovskite films of Comparative Example 2 and Example 2. Among them, a is a surface scanning electron microscope image of the perovskite thick film obtained in Comparative Example 2; b is a surface scanning electron microscope image of the perovskite thick film obtained in Example 2; and c is the relationship between the X-ray response current density and the dose rate of the perovskite devices obtained in Example 2 (red line) and Comparative Example 2 (blue line). Detailed Implementation

[0049] The following will describe the concept and technical effects of the present invention clearly and completely with reference to embodiments, so as to fully understand the purpose, features and effects of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Other embodiments obtained by those skilled in the art based on the embodiments of the present invention without creative effort are all within the scope of protection of the present invention.

[0050] In the description of this invention, the terms "one embodiment," "some embodiments," "illustrative embodiment," "example," "specific example," or "some examples," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0051] Unless otherwise specified, "room temperature" in this invention means 25℃±5℃.

[0052] Unless otherwise specified, "about" in this invention means that the allowable error is within ±2%.

[0053] Unless otherwise specified in the examples, the procedures should be performed under standard conditions or conditions recommended by the manufacturer. Reagents or instruments whose manufacturers are not specified are all commercially available products.

[0054] Example 1 A perovskite film was prepared, and the specific process is as follows: 2 mmol of FA 0.58 MA 0.42 PbI3 microcrystals were added to 4.5 mL of DMF and stirred overnight. 0.053 g of tannic acid molecules (digallicacid, DA) were weighed and added to 10 mL of DMF, and stirred overnight. Both solutions were filtered, and 0.75 mL of the DA solution was added to the perovskite solution. Stirring was continued for 2 hours. Before spraying, the solution was filtered through a 0.45 μm pore size polytetrafluoroethylene (PTFE) filter.

[0055] At the start of the ultrasonic spraying process, the UV-ozone-treated FTO glass was preheated on a 100°C heating stage for 4 minutes. Deposition was then performed using a 2.8W ultrasonic atomizing nozzle. The solution flow rate was set to 12 mL / min, and the nitrogen flow rate to approximately 5 L / min to grow a high-quality perovskite film. The ultrasonic nozzle circulated on an XY moving platform to ensure uniform and complete coverage of every location on the substrate. The thick film was annealed at 120°C for 30 minutes and then slowly cooled to room temperature at a rate of approximately 1°C / min.

[0056] Example 2 Compared with Example 1, the difference is that the multifunctional synergistic regulatory molecular additive is proanthocyanidins, and the perovskite material is MAPbBr3.

[0057] Comparative Example 1 The difference from Example 1 is that no DA molecules were added.

[0058] Comparative Example 2 The difference from Example 2 is that no proanthocyanidins were added.

[0059] Performance testing The performance of the above perovskite thick film was characterized, and the specific test items, test methods and results are as follows: Basic phase characterization Figure 1 The images shown are scanning electron microscope (SEM) images of the surface and cross-section of the membrane obtained in Example 1. It can be seen that the surface of the perovskite thick film is dense, without pores or cracks, and has a tight contact with the substrate. The film thickness is 30 μm.

[0060] Figure 2 The scanning electron microscope images of the surface and cross-section of the film obtained in Comparative Example 1 show that there are obvious pores on the surface of the perovskite thick film and obvious cracks between it and the substrate. The randomly distributed pores result in uneven film thickness.

[0061] Band structure characterization Figure 3In the diagram, 'a' represents the energy level arrangement of the perovskite thick film and electrode obtained in Comparative Example 1 and Example 1. Figure 3 In Figure 'b', we get the interfacial electric field mechanism between the perovskite thick film and the substrate obtained in Comparative Example 1. Figure 3 In the diagram, c represents the interfacial electric field mechanism between the perovskite thick film obtained in Example 1 and the substrate.

[0062] The perovskite Fermi level of Comparative Example 1 is lower than that of FTO, while the perovskite Fermi level of Example 1 is higher than that of FTO. When the perovskite and FTO come into contact, electrons spontaneously flow from the higher Fermi level to the lower Fermi level. For the perovskite in Comparative Example 1, electrons flow from the FTO surface to the perovskite, leaving a layer of positively charged holes on the FTO surface and a layer of negatively charged electrons on the perovskite surface. This generates a built-in electric field, directed from FTO to the perovskite, in the same direction as the applied bias voltage, further intensifying ion migration and defect formation at the interface. Conversely, for the perovskite in Example 1, electrons flow from the perovskite surface to FTO, leaving a layer of positively charged holes on the perovskite surface and a layer of negatively charged electrons on the FTO surface. Therefore, the built-in electric field is directed from the perovskite to FTO, opposite to the applied bias voltage, thus canceling out the magnitude of the electric field at the interface, stabilizing ion migration at the interface, and reducing dark current.

[0063] X-ray detection and imaging Devices were fabricated using the perovskite films obtained in Example 1 and Comparative Example 1, and their X-ray detection performance was characterized. The results are as follows: Figure 4 The sensitivities under different applied bias voltages were summarized, and the device corresponding to Example 1 achieved a sensitivity of 3.2 × 10⁻⁶ at -4V. 5 μCGy air -1 cm -2 This far exceeds the device in Comparative Example 1 (1.0 × 10⁻⁶). 5 μCGy air -1 cm -2 ).

[0064] The perovskite device obtained in Example 1, integrated with a TFT backplane, enables uniform and rapid imaging at a total dose of 7.18 μGy. air The image below clearly shows a pair of brass scissors, a knife, and a suitcase containing the scissors. Figure 5 ).

[0065] Universal application of similar additives To verify the universal effect of additive molecules with similar structures on different perovskite materials, MAPbBr3 perovskite thick films were prepared in Comparative Example 2, and procyanidin (PC) was added to MAPbBr3 in Example 2.

[0066] Figure 6 In the image, 'a' is a scanning electron microscope image of the perovskite film in Comparative Example 2. Figure 6 b in the figure is a scanning electron microscope image of the perovskite film in Example 2.

[0067] As can be seen, the addition of proanthocyanidins resulted in larger grain sizes and eliminated pores. X-ray response testing was performed on the obtained perovskite thick film. Figure 6 In the figure, c represents the relationship between the X-ray response current density and the dose rate of the perovskite devices obtained in Example 2 and Comparative Example 2. The device corresponding to Example 2 has a higher photocurrent density and its sensitivity is nearly twice that of Comparative Example 2, indicating the beneficial effect of proanthocyanidins on improving the photoelectric response of perovskites.

[0068] This invention proposes a multifunctional natural multi-site molecular anchoring strategy that simultaneously improves the performance and stability of perovskite X-ray detectors fabricated by spraying. Through the multidentate coordination of additive molecules and the robust bonding network structure with the perovskite, a dense and high-quality thick film is formed, enhancing the bridging effect at the substrate interface and effectively releasing lattice strain. This multifunctionality not only strengthens mechanical stability but also suppresses defect-mediated nonradiative recombination, thereby improving charge transport and collection efficiency. Furthermore, the functional additives modulate the Fermi level of the perovskite, forming a potential barrier at the perovskite / electrode interface and effectively suppressing dark current. Through optimization of materials and processes, uniform and dense deposition of the thick film, defect passivation, and improved charge transport capabilities are achieved, resulting in higher sensitivity and clearer, faster imaging in the X-ray detection field, laying the foundation for the industrial application of high-performance X-ray detectors and imaging technologies.

[0069] The present invention has been described in detail above with reference to the embodiments. However, the present invention is not limited to the above embodiments. Within the scope of knowledge possessed by those skilled in the art, various changes can be made without departing from the spirit of the present invention.

Claims

1. A perovskite film, characterized in that, The chemical composition of the perovskite film includes MAPbI3, MAPbBr3, MAPbCl3, FAPbI3, and FA. x MA 1-x PbI3, FA x Cs 1-x PbI3, MA x FA y Cs 1-x-y At least one of PbI3 and FAPbBr3, wherein 0≤x≤1 and 0≤y≤1, the raw materials for preparing the perovskite membrane contain a multifunctional synergistic regulatory molecular additive, which includes at least one of tannic acid, proanthocyanidins, propyl gallate, gallic acid and baicalin.

2. As described in claim 1, characterized in that, In the raw materials for preparing the perovskite film, multifunctional synergistic molecular additives and Pb in the perovskite are involved. 2+ The molar equivalent ratio is 0.01%~10%:

1.

3. A method for preparing a perovskite film as described in claim 1 or 2, characterized in that, Includes the following steps: S1: Add perovskite microcrystals corresponding to the chemical composition of the perovskite film to a solvent, and add the multifunctional synergistic regulatory molecular additive to obtain a mixed solution; S2: After spraying the mixed solution onto the substrate surface, perform annealing treatment to obtain the perovskite film.

4. The method according to claim 3, characterized in that, The solvent includes N,N-dimethylformamide, N-methylpyrrolidone, ethylene glycol methyl ether, or dimethyl sulfoxide.

5. The method according to claim 3, characterized in that, In step S1, after the perovskite microcrystals are added to the solvent, they are stirred overnight.

6. The method according to claim 3, characterized in that, In step S2, the mixed solution is filtered before spraying; and / or, the substrate is preheated before spraying in step S2; and / or, the substrate comprises FTO glass in step S2.

7. The method according to claim 3, characterized in that, In step S2, the spraying method is ultrasonic spraying.

8. The method according to claim 7, characterized in that, During the ultrasonic spraying process, the ultrasonic nozzle is circulated on the XY moving platform; and / or, during the ultrasonic spraying process, the flow rate of the mixed solution is 5~30mL / min; and / or, during the ultrasonic spraying process, the gas is nitrogen, and the nitrogen flow rate is 1~10L / min.

9. The method according to claim 3, characterized in that, In step S2, the annealing temperature is 100~150℃; and / or, in step S2, the annealing time is 20~50min.

10. An X-ray detector, characterized in that, The X-ray detector comprises the perovskite film as described in claim 1 or 2, or the perovskite film prepared by the method of any one of claims 3 to 9.

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