A thick-film heterojunction absorption layer for X-ray direct detection and a composite preparation method and application thereof

Abstract

This invention discloses a thick-film heterojunction absorption layer for direct X-ray detection, its composite preparation method, and its applications. The core of this invention is its process system. A first semiconductor functional layer, formed through rapid curing, supports subsequent thick-film coating, reducing the risk of interlayer solvent erosion during multilayer thick-film fabrication. A second semiconductor functional layer is formed using a thick-film coating process, retaining the efficiency and thickness advantages of thick-film coating in the fabrication of large-area, thicker absorption layers. This allows the first and second semiconductor functional layers to form a heterojunction in the thickness direction, which is beneficial for balancing dark current suppression and photogenerated carrier collection in direct X-ray conversion detection. This invention does not rely on a single material combination; the semiconductor functional layer can be selected according to different X-ray detection material systems and can be integrated with conductive glass, flexible substrates, metal electrodes, or readout backplanes for direct conversion X-ray detection and flat panel imaging, improving low-dose response, dynamic response, and continuous operation stability.

Description

Technical Field

[0001] This invention belongs to the technical fields of semiconductor radiation detection materials, thick film deposition processes and direct conversion X-ray detectors, specifically relating to a composite preparation method and application of a thick film heterojunction absorption layer for direct X-ray detection. Background Technology

[0002] Direct-conversion X-ray detectors convert incident X-ray photons directly into electrical signals through a semiconductor absorption layer, making them suitable for applications such as medical imaging, industrial non-destructive testing, and security inspection. Unlike ordinary thin-film optoelectronic devices, direct-conversion X-ray detectors typically require an absorption layer on the order of tens to hundreds of micrometers to ensure effective absorption of high-energy photons.

[0003] To balance dark current suppression, carrier separation, and signal collection efficiency in a thicker absorption layer, heterojunction structures can be constructed within the absorption layer. Heterojunctions can improve dark-state charge injection and photogenerated carrier transport through differences in composition, band gap, energy level, or conductivity type between different semiconductor functional layers. However, for thick-film heterojunctions used in X-ray detection, the fabrication challenge lies not only in material design but also in obtaining stable, clear, and tightly connected interlayer interfaces at the thick-film scale.

[0004] Solution and slurry methods are suitable for large-area fabrication of thick X-ray detection films, but in multilayer or heterojunction structures, the second wet film or slurry typically contains a high solvent load. If the second semiconductor slurry is directly coated onto a rough, porous, or insufficiently solvent-resistant first film layer, the second solvent layer may penetrate, swell, undergo secondary dissolution, or erode the first film layer, leading to blurred heterojunction interfaces, deteriorated interlayer contacts, increased interface defects, and weakened heterojunction control over dark current and carrier separation.

[0005] Comparative optical images of thick films prepared by single-coating and composite processes before and after drying are shown below. Figure 1 .like Figure 1 As shown in (a) and (c), in continuous film formation using a single blade coating process, the top layer slurry can undergo capillary wetting along the pores or rough areas of the bottom layer before drying, which easily leads to macroscopic pores, roughness, or local discontinuities after drying; such as Figure 1 As shown in (b) and (d), when a rapid curing deposition is used to form the bottom layer before thick film coating, the wet film edge is more continuous, and the integrity of the film layer after drying is better. This comparison intuitively shows that the key issue in the preparation of thick film heterojunctions is not just the material ratio, but the secondary erosion of the first film layer by the second wet film and the resulting interface damage.

[0006] Single-layer coating processes such as blade coating, slot coating, or casting offer advantages such as high deposition efficiency, easy thickness scaling, and compatibility with readout backplanes. However, they are prone to interlayer solvent erosion and interface stability issues when continuously fabricating multilayer thick films. Single-layer spraying or atomization deposition processes can form relatively continuous lower layers, but when relying solely on these processes to fabricate complete X-ray absorbing thick films, they may be limited by droplet fusion, deposition efficiency, and solvent evaporation kinetics.

[0007] Therefore, there is an urgent need for a composite preparation method for thick film heterojunction absorption layers for direct X-ray detection, which can solve the problems of interlayer solvent erosion, interface contact deterioration, and absorption thickness in the preparation of thick film heterojunctions without limiting the protection scope to a specific material combination. Summary of the Invention

[0008] This invention aims to solve the problems of secondary erosion of interlayer solvents, poor contact of heterojunctions, difficulty in maintaining interlayer interfaces with single thick film coating, and difficulty in achieving absorption thickness with single rapid curing deposition when preparing thick film heterojunctions for X-ray direct conversion detection using solution or slurry methods. It provides a composite preparation method and thick film heterojunction absorption layer that takes into account both interface bearing capacity and X-ray absorption thickness.

[0009] To address the aforementioned technical problems, this invention provides a method for preparing a composite thick-film heterojunction absorption layer for direct X-ray detection, comprising the following steps:

[0010] Step 1: The first semiconductor precursor solution is deposited on a conductive substrate or readout backplane to form the first semiconductor functional layer through a rapid curing deposition process;

[0011] Step 2: Coat the second semiconductor paste thick film onto the first semiconductor functional layer, and dry it to obtain the second semiconductor functional layer;

[0012] This composite preparation process enables the first layer to be responsible for interfacial support and solvent resistance, while the second layer is responsible for thick film absorption and functional stack construction.

[0013] The first semiconductor functional layer differs from the second semiconductor functional layer in at least one of the following: composition, doping, phase structure, energy level, band gap, carrier type, or conductivity type, and forms a thick-film heterojunction for direct X-ray conversion detection in the thickness direction. The specific material combination can be selected based on X-ray absorption capacity, dark current suppression requirements, carrier transport characteristics, and process compatibility.

[0014] In this invention, the primary function of the first semiconductor functional layer is to provide a continuous or dense surface for supporting subsequent thick film coating and to reduce the penetration, swelling, secondary dissolution, or interface erosion of the underlying layer by the solvent in the second semiconductor paste. The primary function of the second semiconductor functional layer is to provide the thickness required for X-ray absorption and, together with the first semiconductor functional layer, constitute a thick film heterojunction.

[0015] In one embodiment, the rapid curing deposition process includes ultrasonic spraying, atomized spraying, aerosol deposition, spray pyrolysis, or other droplet deposition processes that enable semiconductor precursor droplets to be deposited and cured on a heated substrate.

[0016] In one embodiment, the thick film coating includes blade coating, slit coating, screen printing, casting, or a combination thereof.

[0017] In one embodiment, the drying temperature is 50-120 °C and the drying time is 0.5-10 h.

[0018] In one embodiment, at least one of the first semiconductor functional layer and the second semiconductor functional layer is a metal halide semiconductor layer, a metal halide perovskite layer, a lead halide perovskite layer, a tin-based halide semiconductor layer, a bismuth-based halide semiconductor layer, an antimony-based halide semiconductor layer, or a composite layer thereof.

[0019] In one embodiment, both the first semiconductor functional layer and the second semiconductor functional layer are metal halide perovskite layers, and they differ in at least one of the following: halogen composition, A-site composition, B-site composition, additive composition, or crystal phase structure.

[0020] In one embodiment, the first semiconductor functional layer and the second semiconductor functional layer may be metal halide semiconductor layers, particularly metal halide perovskite layers, lead halide perovskite layers, or other semiconductor layers suitable for direct conversion X-ray detection.

[0021] In one embodiment, step 1 is specifically as follows:

[0022] A conductive substrate or readout backplane is selected as the bottom substrate, and the bottom substrate is cleaned, dried and surface pretreated; a first semiconductor precursor solution is provided, and the first semiconductor precursor solution is delivered to an atomizing or spraying device to form droplets and deposit on the heated bottom substrate surface to form a continuous or dense first semiconductor functional layer.

[0023] In one embodiment, step 2 is specifically as follows:

[0024] A second semiconductor slurry is provided, the second semiconductor slurry comprising a second semiconductor microcrystalline powder, a precursor powder, a dispersed phase or a combination thereof, and an organic solvent capable of forming a coatable slurry; a thick film of the second semiconductor slurry is coated onto a first semiconductor functional layer to form a second wet film, and the second semiconductor functional layer is obtained by drying.

[0025] The present invention also provides a thick film heterojunction absorption layer for direct X-ray detection, which is prepared by the above-described composite preparation method. The thick film heterojunction absorption layer includes a first semiconductor functional layer formed by a rapid curing deposition process and a second semiconductor functional layer formed by a thick film coating process.

[0026] The present invention also provides an application of a thick film heterojunction absorption layer for direct X-ray detection in the preparation of X-ray direct conversion detectors, direct conversion type X-ray flat panel imaging devices, medical imaging devices, industrial non-destructive testing devices, security inspection devices or scientific research radiation detection devices, wherein the thick film heterojunction absorption layer serves as an X-ray absorption and charge generation layer.

[0027] The beneficial effects of this invention are as follows:

[0028] 1. This invention takes the process system as its core, and utilizes the first semiconductor functional layer formed by rapid curing to carry the subsequent thick film coating, thereby reducing the risk of interlayer solvent erosion in the preparation of multilayer thick films.

[0029] 2. This invention utilizes a thick film coating process to form a second semiconductor functional layer, retaining the efficiency and thickness advantages of thick film coating in the preparation of large-area, thicker absorber layers.

[0030] 3. The present invention enables the first semiconductor functional layer and the second semiconductor functional layer to form a heterojunction in the thickness direction, which is beneficial for both dark current suppression and photogenerated carrier collection in X-ray direct conversion detection.

[0031] 4. This invention does not rely on a single material combination. The semiconductor functional layer can be selected according to different X-ray detection material systems, and it can be integrated with conductive glass, flexible substrate, metal electrode or readout backplane.

[0032] 5. The thick film heterojunction absorption layer obtained by the composite preparation method of the present invention can be used for direct conversion X-ray detection and flat panel imaging, improving low-dose response, dynamic response and continuous operation stability. Attached Figure Description

[0033] Figure 1 Optical images of perovskite thick films prepared by single-coating and composite processes before and after drying. (a) Before drying of film prepared by single-coating process; (b) Before drying of film prepared by composite process; (c) After drying of film prepared by single-coating process; (d) After drying of film prepared by composite process.

[0034] Figure 2 The images show the cross-sectional morphology of perovskite and EDS linear scans. (a) Cross-sectional morphology of δ-CsPbI₂Br; (b) Cross-sectional morphology of δ-CsPbI₂Br. 2.5 Br 0.5 Cross-sectional morphology diagram and enlarged view of a portion; (c) δ-CsPbI2Br / δ-CsPbI 2.5 Br 0.5 Cross-sectional morphology of heterojunction; (d)δ-CsPbI2Br / δ-CsPbI 2.5 Br 0.5 Cross-sectional EDS linear scan diagram.

[0035] Figure 3 The graph shows the current density versus electric field intensity curves for different thick-film devices.

[0036] Figure 4 This is a semi-logarithmic curve of dark-state current density versus electric field intensity for different thick-film devices.

[0037] Figure 5 The image shows the dark-state current drift test results for different thick-film devices under a constant electric field.

[0038] Figure 6 X-ray response characteristics of the device. (a) IT curve of δ-CsPbI₂Br; (b) Sensitivity of δ-CsPbI₂Br; (c) X-ray response characteristics of δ-CsPbI₂Br. 2.5 Br 0.5 IT curve; (d)δ-CsPbI 2.5 Br 0.5 (e) The sensitivity of the heterojunction; (f) The IT curve of the heterojunction.

[0039] Figure 7 The images show the physical optical image and X-ray image of a thick-film heterojunction flat panel detector. Detailed Implementation

[0040] The present invention will be further described below with reference to specific embodiments. It should be understood that the following embodiments are only for illustrating the composite film formation process system of the present invention and are not intended to limit the scope of protection of the present invention. The specific parameters listed in the embodiments are non-limiting examples and do not represent optimal sample parameters or the only feasible parameters. Equivalent substitutions or conventional adjustments made by those skilled in the art to the type of semiconductor material, precursor solvent, rapid curing deposition method, thick film coating method, conductive substrate, electrode material, and readout backplane form without departing from the concept of the present invention should all fall within the scope of protection of the present invention.

[0041] Example 1

[0042] This embodiment provides a composite preparation method for a thick-film heterojunction absorption layer for direct X-ray detection, including the following steps:

[0043] Step 1: Form the first semiconductor functional layer by rapid curing deposition.

[0044] Conductive glass, metal electrode substrate, flexible conductive substrate, or readout backplane are selected as the bottom substrate. The bottom substrate is cleaned, dried, and pretreated to give it a clean surface suitable for semiconductor precursor droplet deposition.

[0045] A first semiconductor precursor solution is provided. The first semiconductor precursor solution may contain an A-site cation source, a metal source, a halogen source, and a polar solvent, or may employ other precursor systems suitable for forming functional layers of X-ray detection semiconductors.

[0046] A first semiconductor precursor solution is delivered to an atomizing or spraying device, where it forms droplets and is deposited on a heated conductive substrate or readout backplane surface. Upon reaching the heated surface, the droplets undergo rapid solvent evaporation, precursor solidification, and crystal growth, forming a continuous or dense first semiconductor functional layer.

[0047] In a non-limiting example, the rapid curing deposition process is ultrasonic spraying. The A-site cation source, metal source, and halogen source are dissolved in a polar solvent according to a feeding relationship required for metal halide semiconductor film formation, to prepare a solution with a total concentration of 0.42 mol / L. -1 The precursor stock solution was then diluted with amide or sulfoxide solvents to obtain a concentration of 0.18 mol / L. -1 The spraying precursor solution. As a non-preferred example, the molar ratio of iodine source to bromine source can be set to 1.3:1.

[0048] In a non-limiting example, the ultrasonic atomization power is 4.5 W and the robotic arm movement speed is 65 mm / s. -1 The heating stage temperature was 90 ℃. After deposition, the temperature was maintained at 2 ℃ for 1 minute. -1 The cooling rate is reduced to room temperature to decrease the risk of stress cracking caused by rapid cooling. The above parameters are only used to illustrate that the rapid curing deposition process is feasible, and the resulting first semiconductor functional layer can serve as a carrier substrate for subsequent thick film coating.

[0049] Step 2: Form a second semiconductor functional layer by thick film coating.

[0050] A second semiconductor paste is provided. The second semiconductor paste comprises a second semiconductor microcrystalline powder, a precursor powder, a dispersed phase, or a combination thereof, and an organic solvent capable of forming a coatable paste. The second semiconductor material differs from the first semiconductor functional layer in at least one of the following: composition, doping, phase structure, energy level, band gap, carrier type, or conductivity type.

[0051] A second semiconductor paste is coated onto the first semiconductor functional layer to form a second wet film, and then dried to obtain the second semiconductor functional layer. The coating method can be blade coating, slit coating, screen printing, or casting. The drying temperature can be 50-120 ℃, and the drying time can be 0.5-10 h.

[0052] In a non-limiting example, the second semiconductor material is a metal halide perovskite material with a different halogen composition relative to the first semiconductor functional layer. The second semiconductor microcrystalline powder is mixed with a coatable organic solvent to obtain a slurry with a solid content of 55 wt%; a wet film is formed using a doctor blade spacing of 180 μm and dried at 80 °C for 3 h. Depending on the film formation requirements, auxiliary film-forming additives may also be added to the slurry to improve coating continuity.

[0053] When using the aforementioned composite preparation method, the first semiconductor functional layer can reduce the possibility of organic solvents in the second semiconductor slurry penetrating downwards along the underlying pores or rough regions. An interlayer interface is formed between the first and second semiconductor functional layers, which can be identified by cross-sectional morphology, elemental distribution, compositional gradient, or electrical response, ensuring that the thick-film heterojunction interface maintains an identifiable hierarchical structure and compositional differences. Compared to continuous thick-film coating of bilayer films, the composite-prepared thick-film heterojunction exhibits reduced interlayer separation and large-size pores, which helps to reduce the impact of interface defects on dark current and carrier recombination.

[0054] Example 2: A set of examples of preparation of lead halide perovskite thick film heterojunctions.

[0055] Based on Example 1, the first semiconductor functional layer can be CsPb(I) formed by ultrasonic spraying. 0.46 Br 0.54 The third layer, the second semiconductor functional layer, can be CsPb(I) formed by scraping. 0.71 Br 0.29 (3 layers) This exemplary material combination is only used to illustrate that the composite preparation method of the present invention can be used to construct lead halide perovskite thick film heterostructures, and does not represent the optimal material design, nor does it limit the present invention to using only this material system.

[0056] In the preparation process, a first semiconductor precursor droplet is first deposited on a cleaned and dried conductive substrate using ultrasonic spraying. The substrate is then heated to promote rapid solidification of the droplet, resulting in a continuous first semiconductor functional layer. Subsequently, a second semiconductor paste is coated onto the surface of the first semiconductor functional layer and dried at 50-120 °C to obtain the second semiconductor functional layer.

[0057] The cross-sectional morphology of films obtained by different film-forming methods varies significantly, as shown in the EDS linear scan images of their cross-sections. Figure 2 As shown in (d). Figure 2 As shown in (a), the first semiconductor functional layer formed by rapid curing deposition has high density, and no obvious large-sized pores were observed inside the film, which can provide a stable bearing surface for subsequent thick film coating; as Figure 2 As shown in (b), although the film layer formed by direct thick film coating can achieve a large thickness, pores or local loose areas can still be observed in the cross section, indicating that it is more likely to cause solvent penetration and interface damage when used as the bottom layer of multilayer preparation.

[0058] After adopting this composite process, the first semiconductor functional layer can still exist as an identifiable bottom layer during the coating and drying of the second semiconductor paste. The thick film heterojunction retains its hierarchical structure and compositional differences along the thickness direction. The cross-sectional morphology and elemental distribution are shown in [reference needed]. Figure 2 (c) In comparison with direct continuous thick film coating, the composite process can reduce secondary erosion of the substrate by the second wet film, interlayer mixing and large-sized pores, and form a thick film heterojunction structure with clear interfaces and tight bonding.

[0059] The specific material combination described above is only used to illustrate one possible embodiment of the present invention. For other semiconductor materials that can be used for X-ray direct conversion detection, as long as a thick film heterojunction is constructed by combining a rapidly cured deposition of the bottom layer with a thick film coating of the top layer, the process logic of the present invention can be followed.

[0060] Example 3: Direct conversion X-ray detector and photoelectric testing effect.

[0061] The thick film heterojunction absorption layer obtained in Example 2 is integrated onto a pretreated ITO conductive glass, a flexible conductive substrate, a metal electrode substrate, or a readout backplane, and a top electrode is formed on the surface of the thick film heterojunction absorption layer to obtain a vertically structured direct conversion X-ray detector.

[0062] In this embodiment, the device comprises, from bottom to top, a conductive substrate, a first semiconductor functional layer, a second semiconductor functional layer, and a metal top electrode. The metal top electrode can be formed by screen printing, vapor deposition, sputtering, blade coating, or spraying; the effective test area, top electrode thickness, and post-processing conditions can be adjusted according to the test fixture and readout method.

[0063] The obtained thick-film heterojunction device was subjected to dark-state current, resistivity, and dark-state baseline stability tests. The current density-electric field intensity curves are shown in [reference needed]. Figure 3 Linear fitting showed that the resistivity of the thick-film heterojunction device was 2.36 × 10⁻⁶. 12 Ω cm, compared to 8.28 × 10⁻⁶ for the two monolayer control devices. 10 Ω cm and 2.19×10 11 Ω cm, representing increases of approximately 28 times and 11 times respectively; the semi-logarithmic curves of dark-state current density versus electric field intensity are shown below. Figure 4 Under the same electric field, the dark-state current density of thick-film heterojunction devices decreases by more than an order of magnitude. Dark-state current drift testing is shown in [link to test]. Figure 5 In dark-state baseline testing, the dark current drift rate of the thick-film heterojunction device was 3.5 fA cm⁻¹. -1 s -1 V -1 Compared to the 104.6 fA cm⁻¹ of the two monolayer control devices, -1 s -1 V -1 and 84.6 fA cm -1 s -1 V -1 The reductions were approximately 30 times and 24 times, respectively.

[0064] The obtained thick-film heterojunction device was subjected to X-ray dynamic response and sensitivity tests. The X-ray response curve and sensitivity fitting are shown in [reference needed]. Figure 6 Test results show that at 27 V mm -1 Under the specified electric field strength, the sensitivity of the thick-film heterojunction device is 185.3 μC Gy. air -1 cm -2 This is higher than the 137.3 μC Gy of the two monolayer control devices. air -1 cm -2 and 149.7 μC Gy air -1 cm -2 ; at 54 V mm -1 Under the specified electric field strength, the sensitivity of thick-film heterojunction devices can reach 221.8 μC Gy. air -1 cm -2 The above results demonstrate that the thick-film heterojunction absorption layer formed by the composite process can improve the performance of direct conversion X-ray detection.

[0065] Example 4: Application of X-ray flat panel imaging.

[0066] Integrating the thick-film heterojunction absorption layer obtained in Example 2 onto a thin-film transistor readout backplane yields a direct-conversion X-ray flat panel imaging device. In one specific embodiment, the device comprises, from bottom to top, a TFT sensing substrate, a first semiconductor functional layer, a second semiconductor functional layer, and a top electrode.

[0067] The readout backplane is used to collect and store the charge signals generated by X-ray irradiation, and to read and reconstruct images through back-end circuitry. The number of pixels, pixel size, and readout method of the readout backplane can be adjusted according to the imaging application and do not constitute a core limitation of this invention.

[0068] In a specific imaging test, the thick-film heterojunction flat panel detector can output grayscale images under X-ray irradiation. The actual optical image and X-ray imaging are shown below. Figure 7 The resulting X-ray images can show the overall outline of the object under test and the grayscale contrast caused by local thickness differences. This result indicates that the thick film heterojunction absorption layer is suitable for direct conversion X-ray flat panel imaging.

[0069] This invention focuses on a composite preparation route combining rapid curing deposition and thick film coating, which is compatible with platforms such as conductive glass, metal electrodes, flexible substrates, and readout backplanes. The resulting thick film heterojunction absorption layer can be used as an absorption and charge generation layer in direct conversion X-ray detectors to reduce dark current, improve low-dose response, enhance dynamic response capabilities, and realize digital X-ray flat panel imaging, demonstrating industrial applicability.

[0070] It is understood that the present invention has been described through some embodiments, and those skilled in the art will recognize that various changes or equivalent substitutions can be made to these features and embodiments without departing from the spirit and scope of the invention. Furthermore, under the teachings of the present invention, these features and embodiments can be modified to adapt to specific situations and materials without departing from the spirit and scope of the invention. Therefore, the present invention is not limited to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the protection scope of the present invention.

Claims

1. A method for preparing a composite thick-film heterojunction absorption layer for direct X-ray detection, characterized in that, Includes the following steps: Step 1: The first semiconductor precursor solution is deposited on a conductive substrate or readout backplane to form the first semiconductor functional layer through a rapid curing deposition process; Step 2: Coat the second semiconductor paste thick film onto the first semiconductor functional layer, and dry it to obtain the second semiconductor functional layer; The first semiconductor functional layer and the second semiconductor functional layer differ in at least one of composition, doping, phase structure, energy level, band gap, carrier type or conductivity type, and form a thick film heterojunction for X-ray direct conversion detection in the thickness direction.

2. The method for preparing a composite thick-film heterojunction absorption layer for direct X-ray detection according to claim 1, characterized in that, The rapid curing deposition process includes ultrasonic spraying, atomized spraying, aerosol deposition, spray pyrolysis, or other droplet deposition processes that enable semiconductor precursor droplets to be deposited and cured on a heated substrate.

3. The method for preparing a composite thick-film heterojunction absorption layer for direct X-ray detection according to claim 1, characterized in that, The thick film coating includes blade coating, slit coating, screen printing, casting, or a combination thereof.

4. The method for preparing a composite thick-film heterojunction absorption layer for direct X-ray detection according to claim 3, characterized in that, The drying temperature is 50-120 ℃, and the drying time is 0.5-10 h.

5. The method for preparing a composite thick-film heterojunction absorption layer for direct X-ray detection according to claim 1, characterized in that, At least one of the first semiconductor functional layer and the second semiconductor functional layer is a metal halide semiconductor layer, a metal halide perovskite layer, a lead halide perovskite layer, a tin-based halide semiconductor layer, a bismuth-based halide semiconductor layer, an antimony-based halide semiconductor layer, or a composite layer thereof.

6. The method for preparing a composite thick-film heterojunction absorption layer for direct X-ray detection according to claim 1, characterized in that, Both the first semiconductor functional layer and the second semiconductor functional layer are metal halide perovskite layers, and they differ in at least one of the following: halogen composition, A-site composition, B-site composition, additive composition, or crystal phase structure.

7. The method for preparing a composite thick-film heterojunction absorption layer for direct X-ray detection according to claim 1, characterized in that, Step 1 is described in detail as follows: A conductive substrate or readout backplane is selected as the bottom substrate, and the bottom substrate is cleaned, dried and surface pretreated; a first semiconductor precursor solution is provided, and the first semiconductor precursor solution is delivered to an atomizing or spraying device to form droplets and deposit on the heated bottom substrate surface to form a continuous or dense first semiconductor functional layer.

8. The method for preparing a composite thick-film heterojunction absorption layer for direct X-ray detection according to claim 1, characterized in that, Step 2 is described in detail below: A second semiconductor slurry is provided, the second semiconductor slurry comprising a second semiconductor microcrystalline powder, a precursor powder, a dispersed phase or a combination thereof, and an organic solvent capable of forming a coatable slurry; a thick film of the second semiconductor slurry is coated onto a first semiconductor functional layer to form a second wet film, and the second semiconductor functional layer is obtained by drying.

9. A thick-film heterojunction absorption layer for direct X-ray detection, characterized in that, The thick film heterojunction absorber layer, prepared by any one of claims 1-7, comprises a first semiconductor functional layer formed by a rapid curing deposition process and a second semiconductor functional layer formed by a thick film coating process.

10. The application of the thick-film heterojunction absorption layer for direct X-ray detection as described in claim 9 in the fabrication of X-ray direct conversion detectors, direct conversion X-ray flat panel imaging devices, medical imaging devices, industrial non-destructive testing devices, security inspection devices, or scientific research radiation detection devices, characterized in that... The thick film heterojunction absorption layer serves as an X-ray absorption and charge generation layer.

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