A ptcda / pdms composite flexible film, a preparation method thereof and an x-ray detector

Abstract

The application discloses a PTCDA / PDMS composite flexible film and a preparation method and an X-ray detector thereof, and relates to the technical fields of organic semiconductor materials and radiation detection. The method comprises the following steps: mixing 3,4,9,10-perylenetetracarboxylic dianhydride powder, polydimethylsiloxane prepolymer and a curing agent to obtain mixed slurry; performing defoaming treatment on the mixed slurry to obtain defoamed mixed slurry; injecting the defoamed mixed slurry into a mold for heating and curing, then demolding, and thus the PTCDA / PDMS composite flexible film is obtained. The PTCDA organic semiconductor material with excellent pi conjugated structure is compounded with the PDMS flexible polymer matrix, the excellent flexibility, thermal stability and interface buffering capacity of the PDMS are utilized, and the flexible detection device with the properties of flexibility, high-temperature stability and X-ray response capacity is constructed.

Description

Technical Field

[0001] This invention relates to the fields of organic semiconductor materials and radiation detection technology, specifically to a PTCDA / PDMS composite flexible thin film, its preparation method, and an X-ray detector. Background Technology

[0002] X-ray detection and imaging technology plays a vital role in fields such as medical imaging, industrial non-destructive testing, and security inspection. Current detector technologies include indirect and direct methods. Direct detectors utilize semiconductor materials to directly convert X-ray photons into electrical signals, offering high spatial resolution and sensitivity. While inorganic semiconductor materials (such as a-Se and CdZnTe) have achieved commercial applications, their use in flexible electronics and conformal attachment detection is limited by manufacturing costs, environmental toxicity, and mechanical rigidity.

[0003] 3,4,9,10-Perylenetetracarboxylic dianhydride (PTCDA), as a high-performance n-type organic semiconductor, has potential applications in the detection field due to its high carrier mobility and good thermal stability. However, PTCDA still faces the following technical limitations in practical applications: its extremely low solubility in most common organic solvents makes it difficult to directly apply conventional solution processing methods (such as spin coating, blade coating, or inkjet printing) to large-area film deposition processes; simultaneously, molecular crystal films prepared by conventional physical vapor deposition exhibit significant intrinsic brittleness, easily developing microcracks or interface failures under stress and deformation. To achieve flexible detection, current research has attempted to combine flexible polymers with sensing materials, but existing flexible X-ray composite films mostly rely on soluble organic polymers, which generally suffer from poor thermal stability and weak resistance to radiation attenuation.

[0004] Furthermore, for large-area X-ray imaging technologies (such as TFT array integration), detectors must employ a vertical device structure. This further demands that the sensing layer, while possessing a certain thickness, not only maintain low dark current and high sensitivity at high temperatures but also maintain stable charge transport during bending deformation. Due to the poor solubility of PTCDA, current research is largely limited to vapor-deposited thin films on rigid substrates. How to effectively overcome the processing difficulties and mechanical limitations of PTCDA, and develop a flexible detection film with simplified processing, mechanical reliability, and high detection sensitivity, has become an important issue in the field of flexible X-ray imaging. Summary of the Invention

[0005] To address the shortcomings of the aforementioned background technologies, this invention primarily solves the technical defects of existing inorganic X-ray detection materials, such as high preparation costs, environmental toxicity, and high mechanical rigidity, as well as the difficulty in large-area film formation of organic semiconductor PTCDA due to its extremely low solubility in common solvents, and the high brittleness of intrinsic crystalline thin films. This invention provides a PTCDA / PDMS composite flexible thin film, its preparation method, and an X-ray detector. This composite thin film overcomes the processing limitations of PTCDA through physical blending and in-situ crosslinking strategies, obtaining a flexible sensing layer that combines good mechanical flexibility, high thermal stability, and high detection sensitivity. Furthermore, this invention provides a vertical structure X-ray detector based on this thin film, aiming to achieve large-area, high-performance flexible X-ray imaging that can be integrated into a TFT array.

[0006] The first objective of this invention is to provide a method for preparing a PTCDA / PDMS composite flexible film, comprising the following steps: 3,4,9,10-perylenetetracarboxylic dianhydride powder, polydimethylsiloxane prepolymer, and curing agent are mixed to obtain a mixed slurry; The mixed slurry is degassed to obtain a degassed mixed slurry; The degassed slurry is injected into a mold for heating and curing, and then demolded to obtain a PTCDA / PDMS composite flexible film. The mass ratio of the 3,4,9,10-perylenetetracarboxylic dianhydride powder to the polydimethylsiloxane prepolymer is 1:4 to 10.

[0007] Preferably, the temperature range for heating and curing is limited to 60–100°C, and the curing time is 2–6 hours.

[0008] Preferably, during the degassing process, the mixed slurry is placed in a vacuum drying oven for vacuum degassing.

[0009] Preferably, the curing agent is a hydrosilicone addition curing agent, and its mass is 8-12% of the mass of the PDMS prepolymer; wherein, the main component of the hydrosilicone addition curing agent is low molecular weight hydrogen-containing silicone oil, and a platinum-based catalyst is added as a triggering component for the curing reaction.

[0010] Preferably, the 3,4,9,10-perylenetetracarboxylic dianhydride powder is a micron-sized powder that has undergone physical grinding. The 3,4,9,10-perylenetetracarboxylic dianhydride powder and PDMS prepolymer crosslink and cure to form a continuous charge transport network.

[0011] The second objective of this invention is to provide a PTCDA / PDMS composite flexible film.

[0012] The third objective of this invention is to provide an application of PTCDA / PDMS composite flexible thin film in X-ray detectors.

[0013] The fourth objective of this invention is to provide an X-ray detector, which is a vertically stacked device structure, including a flexible substrate, and a bottom electrode, a sensing layer and a top electrode stacked sequentially on the flexible substrate; The sensing layer is a PTCDA / PDMS composite flexible film.

[0014] Preferably, the X-ray detector is capable of maintaining an X-ray detection and imaging response without significant geometric distortion under ambient temperature conditions ranging from room temperature to 45~65℃, or under mechanical deformation conditions of bending force with a radius of curvature R≥20 mm.

[0015] The fifth objective of this invention is to provide an application of the X-ray detector of claim 8 in large-area flexible digital X-ray imaging, wherein the bottom electrode of the X-ray detector is electrically interconnected with a thin-film transistor (TFT) array to enable addressing of X-ray excitation charges and signal readout.

[0016] This invention provides a PTCDA / PDMS composite flexible thin film, its preparation method, and an X-ray detector, which have the following advantages compared with the prior art: High process compatibility and low cost: The physical blending method avoids the processing limitations caused by the extremely low solubility of PTCDA, eliminates the need for complex high-vacuum evaporation equipment, and reduces the production difficulty and cost of large-area sensing films.

[0017] Excellent thermal stability: Based on the good molecular thermal stability of PTCDA and the chemical stability of PDMS, the detector can still maintain a low dark current level and stable signal output at a high temperature of 50℃, making it suitable for continuous monitoring in complex industrial or medical environments.

[0018] Significantly improved mechanical reliability: The inherent brittleness of PTCDA materials is overcome by utilizing the highly elastic framework of the polymer matrix. Thanks to the optimized component ratio and degassing process, the sensing layer can still maintain a stable charge transport network under bending deformation with a radius of curvature R≥20mm, suppressing deformation-induced interface failure and electrical performance degradation.

[0019] Easy to integrate and apply: The design of the vertically stacked device structure enables it to achieve good signal interconnection with commercial TFT arrays. Through high pixel integration, it realizes flexible digital X-ray imaging with high spatial resolution, providing a feasible technical solution for new digital imaging systems. Attached Figure Description

[0020] Figure 1A process flow diagram for the preparation of PTCDA / PDMS composite flexible thin film provided in an embodiment of the present invention.

[0021] Figure 2 Photographs of composite films prepared under different process conditions provided in the embodiments of the present invention, wherein: (a) vacuum degassing and ultrasonic dispersion; (b) no vacuum degassing; (c) no ultrasonic dispersion.

[0022] Figure 3 The following are schematic diagrams of the device structure and detection principle of the detector provided in the embodiments of the present invention, wherein: (a) schematic diagram of the coplanar detector structure; (b) schematic diagram of the perpendicular detector structure; (c) cross-sectional view of the flexible bending state and detection principle.

[0023] Figure 4 The following are test diagrams of the basic electrical and X-ray detection performance of the coplanar structure detector provided in Embodiment 1 of the present invention, wherein: (a) IV characteristic curve; (b) current-time response; (c) on / off ratio and bias voltage relationship; (d) sensitivity and voltage relationship.

[0024] Figure 5 The following are test results of the basic electrical and X-ray detection performance of the vertical structure detector provided in Embodiment 2 of the present invention at room temperature, wherein: (a) IV characteristic curve; (b) current-time response; (c) on / off ratio and bias voltage relationship; (d) sensitivity and voltage relationship.

[0025] Figure 6 The following are test results of the electrical and X-ray detection performance of the vertical structure detector provided in Embodiment 3 of the present invention under a high temperature environment of 50°C, wherein: (a) IV characteristic curve; (b) current-time response; (c) relationship between switching ratio and bias voltage; (d) relationship between sensitivity and voltage.

[0026] Figure 7 The following are test diagrams of the electrical and X-ray detection performance of the vertical structure detector provided in Embodiment 4 of the present invention under flexible bending state, wherein: (a) IV characteristic curve; (b) current-time response; (c) on / off ratio and bias voltage relationship; (d) sensitivity and voltage relationship.

[0027] Figure 8 The X-ray imaging performance diagram of the detector provided in the embodiments of the present invention includes: (a) line pair card resolution test under different operating conditions; (b) imaging of the internal structure of the capsule under different operating conditions; (c) letter mask imaging; (d) chip internal pin imaging; and (e) biological sample imaging. Detailed Implementation

[0028] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below in conjunction with specific embodiments and accompanying drawings. However, the embodiments described are not intended to limit the present invention.

[0029] The purpose of this invention is to provide a PTCDA / PDMS composite flexible thin film, its preparation method, and an X-ray detector, in order to solve the technical defects of existing inorganic X-ray detection materials, such as high preparation cost, environmental toxicity, and high mechanical rigidity, as well as the difficulty of large-area film formation of organic semiconductor PTCDA due to its extremely low solubility in conventional solvents, and the high brittleness of intrinsic crystalline thin films.

[0030] This invention obtains the composite flexible sensing film by blending PTCDA powder with PDMS prepolymer, followed by the addition of a curing agent and vacuum degassing and thermosetting treatment. A vertical structure detector constructed based on this film effectively overcomes the intrinsic brittleness of PTCDA material by utilizing the highly elastic framework of PDMS, and circumvents the limitation of its extremely low solubility making solution processing difficult. Experimental results show that the detector maintains stable electrical response and high-resolution imaging capability even under conditions of 50℃ high temperature and bending radius R ≥ 20 mm, achieving a spatial resolution of 3.0 Lp / mm at room temperature. The detector provided by this invention has a simplified process, low cost, and good potential for TFT array integration, showing broad application prospects in the field of flexible digital X-ray imaging.

[0031] To achieve the above objectives, the first aspect of the present invention provides a method for preparing a PTCDA / PDMS composite flexible film, comprising the following steps: 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) powder, polydimethylsiloxane (PDMS) prepolymer, and curing agent are mixed to obtain a mixed slurry; The mixed slurry is degassed to obtain a degassed mixed slurry; The degassed slurry is injected into a mold for heating and curing, and then demolded to obtain a PTCDA / PDMS composite flexible film. The mass ratio of the 3,4,9,10-perylenetetracarboxylic dianhydride powder to the polydimethylsiloxane prepolymer is 1:4 to 10.

[0032] In this invention, the formation mechanism of the PTCDA composite flexible film lies in the following: utilizing the highly planar aromatic conjugated structure of the PTCDA molecules and the intermolecular π-π interactions, a continuous charge transport network is constructed within the PDMS flexible matrix; simultaneously, the flexible coating of the PDMS matrix provides stable support and interface buffering for the PTCDA conductive network, thereby achieving stable carrier transport while maintaining flexibility. Furthermore, combining the vacuum degassing and low-temperature thermosetting processes effectively reduces void defects and localized stress concentration within the composite film, maintains the continuity of the conductive network, and ultimately obtains a composite flexible film possessing high flexibility, high stability, and X-ray responsiveness.

[0033] The uniform dispersion of PTCDA particles in the PDMS matrix is ​​crucial for forming a continuous conductive network. By grinding and ultrasonically dispersing the PTCDA powder, the particle size can be reduced and the particle dispersion uniformity can be improved, thereby reducing local agglomeration, avoiding interruptions in the conductive path, and improving the continuity of carrier transport within the composite membrane.

[0034] The temperature range for heating and curing is limited to 60–100℃, and the curing time is 2–6 hours.

[0035] During the degassing process, the mixed slurry is placed in a vacuum drying oven for vacuum degassing.

[0036] The curing agent is a hydrosilicone addition curing agent, and its mass is 8-12% of the mass of the PDMS prepolymer. The main component of the hydrosilicone addition curing agent is low molecular weight hydrogen-containing silicone oil, and a platinum-based catalyst is added as a triggering component for the curing reaction.

[0037] The 3,4,9,10-perylenetetracarboxylic dianhydride powder is a micron-sized 1-5μm powder that has undergone physical grinding. The 3,4,9,10-perylenetetracarboxylic dianhydride powder and PDMS prepolymer crosslink and cure to form a continuous charge transport network.

[0038] During the preparation of the mixed slurry, mechanical stirring combined with ultrasonic dispersion is used to ensure that the PTCDA powder is uniformly suspended in the PDMS prepolymer.

[0039] The 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA) used in this invention has the molecular formula C3. 24 H8O6. Its structural formula is shown below: .

[0040] An exemplary method for preparing a PTCDA / PDMS composite flexible film includes: Step 1: Ingredient Mixing. PTCDA powder and PDMS prepolymer are mixed at a mass ratio of 1:4 to 1:10. A curing agent is then added and ultrasonically dispersed until a uniformly colored composite slurry without significant agglomeration is formed. The curing agent is a hydrosilicone addition curing agent, and its mass is 8% to 12% of the PDMS prepolymer. By adjusting the ratio of PTCDA to PDMS, both the flexibility and electrical properties of the composite film can be considered.

[0041] Step 2: Vacuum degassing. The mixed slurry obtained in Step 1 is placed in a vacuum environment for degassing treatment until the microbubbles inside the slurry are removed, in order to ensure the density, uniformity and electrical stability of the film, and to avoid the formation of pore defects during the subsequent curing process.

[0042] Step 3: Casting into mold. The degassed mixed slurry is poured into a mold of a pre-designed shape, and the film thickness is adjusted by casting or scraping to obtain a composite film with uniform thickness. The mold can be a glass mold or a polytetrafluoroethylene mold.

[0043] Step 4: Thermosetting. The mold containing the mixed slurry is placed in an environment of 60–100°C for heating and curing, allowing the PDMS matrix to fully crosslink and locking the dispersion of the PTCDA powder. Thermosetting forms a stable three-dimensional network structure, thereby improving the mechanical stability, flexibility, and environmental stability of the composite film.

[0044] Step 5: Demolding. After cooling to room temperature, demolding is performed to obtain the PTCDA / PDMS composite flexible film. The resulting film exhibits good flexibility and structural stability, and can be applied in fields such as flexible radiation detectors, flexible electronic devices, and conductive composite materials.

[0045] The PTCDA powder was purified to high purity (>99.5%) through a dissolution-filtration-recrystallization process: 2.0 g of crude PTCDA powder was added to a round-bottom flask, followed by the addition of dimethyl sulfoxide (DMSO, 30 mL). The mixture was magnetically stirred (500 rpm) for 90 minutes until completely dissolved, forming a deep red solution. The solution was then filtered through an organic filter membrane with a pore size of 0.22 μm, and subsequently dried in a vacuum oven at 60°C for 24 hours to obtain a purplish-red needle-like pure product. This purification process effectively removes impurities and improves the crystal quality and electrical properties of the PTCDA.

[0046] The pretreatment method for the PTCDA powder is as follows: the PTCDA powder is placed in an agate mortar and ground for 20-40 minutes, and then a small amount of organic solvent is added for ultrasonic dispersion for 10-30 minutes to obtain uniformly dispersed PTCDA particles.

[0047] The composite slurry is prepared by adding 0.5 g of the PTCDA powder to 3 g of the PDMS prepolymer, followed by adding the PDMS curing agent and stirring thoroughly to form a uniform composite slurry.

[0048] The mass ratio of the PTCDA powder to the PDMS prepolymer is 1:4 to 1:10.

[0049] The amount of PDMS curing agent added is 8% to 12% of the mass of the PDMS prepolymer.

[0050] The vacuum degassing method involves placing the composite slurry in a vacuum environment for 6 hours to remove air bubbles from the system and reduce void defects in the film layer.

[0051] It is understandable that the core purpose of vacuum degassing in the composite slurry is to reduce the residual bubble content inside the system, thereby avoiding the formation of voids and local stress concentration areas during the curing process. At the same time, it can improve the continuity and uniformity of the PTCDA conductive network in the PDMS matrix, reduce the impact of interface defects on carrier transport, and thus improve the dark current stability and X-ray response consistency of the device.

[0052] The method for preparing the composite flexible film is as follows: the degassed composite slurry is slowly poured into a mold, degassed under vacuum, and the film thickness is controlled by a scraper before being placed in a constant temperature oven for heat curing at 60~90℃ for 1~4 h. It is then allowed to cool naturally to room temperature and demolded to obtain the PTCDA / PDMS composite flexible film. The thickness of the composite flexible film is preferably 0.3~0.7 mm.

[0053] Understandably, the low-temperature thermosetting process can effectively reduce the internal thermal stress generated during the crosslinking of PDMS, while avoiding the local aggregation of PTCDA particles or the destruction of the conductive network under high temperature conditions, thereby helping to maintain the continuity of the internal conductive pathways and structural stability of the composite film.

[0054] A second aspect of the present invention provides a PTCDA / PDMS composite flexible film.

[0055] A third aspect of the present invention provides an application of a PTCDA / PDMS composite flexible thin film in an X-ray detector.

[0056] The fourth aspect of the present invention provides an X-ray detector, which is a vertically stacked device structure, including a flexible substrate, and a bottom electrode, a sensing layer and a top electrode stacked sequentially on the flexible substrate; The sensing layer is a PTCDA / PDMS composite flexible film.

[0057] The X-ray detector is capable of maintaining X-ray detection and imaging response without significant geometric distortion under ambient temperature conditions ranging from room temperature to 45~65℃, or under mechanical deformation conditions of bending force with a radius of curvature R≥20 mm.

[0058] The flexible X-ray detector is fabricated by vacuum evaporation onto the surface of the composite flexible film. The coplanar devices employ interdigitated electrode structures, while the vertical devices utilize a vertical stacked structure of top electrode-composite film-bottom electrode. The spacing between the interdigitated electrodes is 100–500 μm.

[0059] It is understandable that coplanar structures mainly rely on the transverse electric field to achieve carrier transport, and have the advantages of simple structure and good flexibility; while vertical structures, due to the shorter carrier transport distance, can effectively improve charge collection efficiency and reduce transverse crosstalk, making them more suitable for high-resolution flexible X-ray imaging array systems.

[0060] The fifth aspect of this invention provides an X-ray detector for large-area flexible digital X-ray imaging. "Large area" refers to a sufficiently large effective imaging area, eliminating the need for multiple image stitchings, thus improving detection efficiency and avoiding stitching errors. Industrial non-destructive testing and security inspection scenarios will adapt to even larger sizes as needed. "Flexible" refers to the use of a PDMS flexible substrate, unlike traditional silicon-based or glass-based rigid detectors. The detector itself can be freely bent and even stretched to a certain extent, conforming to irregular curved surfaces and meeting the needs of special clinical scenarios and non-destructive testing of irregularly shaped workpieces. "Digital" refers to direct digital imaging technology, where X-ray signals are directly converted into digital electrical signals by the detector, which can be processed, stored, and transmitted in real time by a computer. Compared to traditional imaging, this offers faster imaging speed, lower radiation dose, and higher resolution and dynamic range. The bottom electrode of this X-ray detector is electrically interconnected with a thin-film transistor (TFT) array to achieve X-ray excitation charge addressing and signal readout.

[0061] When the PTCDA / PDMS composite flexible film provided by this invention is used for direct X-ray detection, the PTCDA particles need to be uniformly dispersed in a PDMS flexible matrix, forming a continuous conductive network inside the composite film. The conductive network is mainly composed of π-π conjugated stacking between PTCDA molecules and interparticle contacts. Its continuous conjugated electron delocalization structure can provide a stable and efficient migration path for charge carriers generated by X-ray excitation. At the same time, the PDMS flexible matrix can provide continuous coating and flexible buffering for the PTCDA conductive network, effectively reducing the damage to the continuity of the conductive channel caused by bending stress and thermal stress, avoiding local cracks, interface peeling and transmission path breakage, thereby giving full play to the intrinsic advantages of PTCDA material's high charge transport capacity and low defect density, and meeting the core requirements of direct X-ray detectors for high sensitivity, low dark current, high stability and flexible reliability.

[0062] It is understandable that PTCDA molecules themselves have a highly planar aromatic conjugated structure, and the molecules easily form regular π-π stacks, thereby constructing continuous charge transport channels. When the PTCDA particles are uniformly dispersed inside the PDMS flexible matrix, a stable and continuous conductive network structure can be formed in the composite film, enabling electron-hole pairs generated by X-ray excitation to migrate directionally along the conjugated path, thereby improving carrier transport efficiency and charge collection efficiency. At the same time, the PDMS flexible matrix has excellent flexibility, thermal stability and interface buffering capacity, which can effectively alleviate the damage caused by bending deformation and thermal expansion mismatch to the conductive network, and maintain the continuity of the conductive path and structural stability inside the composite film to the greatest extent.

[0063] Composite films that have not undergone uniform dispersion treatment or have not formed a continuous conductive network are prone to local agglomeration of PTCDA particles, resulting in discontinuous conductive paths and hindered carrier migration. At the same time, local voids and interface defects can increase the probability of carrier recombination and device noise. In addition, under bending or high temperature conditions, discontinuous conductive networks are also prone to local fracture due to stress concentration, further damaging the carrier transport channels. This makes it difficult to meet the requirements of direct X-ray detectors for efficient carrier collection, low noise, high stability and flexible operation.

[0064] This composite structure, based on a PTCDA continuous conjugate conductive network and a PDMS flexible buffer matrix, enables the synergistic coupling of the high charge transport capacity of PTCDA material and the high flexibility and stability of PDMS. This allows the device to maintain stable X-ray response and imaging performance under planar, bending, and high-temperature conditions, thereby meeting the application requirements of flexible direct X-ray detection and flexible X-ray imaging systems.

[0065] It should be noted that, unless otherwise specified, the experimental methods used in this invention are all conventional methods; and the reagents and materials used, unless otherwise specified, are all commercially available.

[0066] The raw materials and reagents used in this embodiment are as follows: 3,4,9,10-perylenetetracarboxylic dianhydride (PTCDA, AR≥98%) was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., CAS No.: 128-69-8; dimethyl sulfoxide (DMSO, AR≥99.5%) was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., CAS No.: 67-68-5; poly(dimethylsiloxane), hydroxyl-terminated (PDMS) was purchased from Shanghai Aladdin Biochemical Technology Co., Ltd., CAS No.: 70131-67-8; hydrosilicone addition curing agent was purchased from Dow Corning Incorporated, Inc.

[0067] This embodiment uses the following instruments and testing methods to complete material characterization and performance testing: Device electrode fabrication: Gold electrodes were deposited on the surface of the composite flexible film using a vacuum evaporation method with an Auto 306 vacuum deposition equipment from HHV Company, UK.

[0068] Electrical performance and X-ray detection performance evaluation: A LIOTIMES LUX-50-50PC1-D beryllium window microfocus X-ray source was used in conjunction with a Radcal T3 Accu-Dose+ Pro dosimeter for dose rate calibration. A Keithley 6517B electrometer was used to record photocurrent data. The system evaluated key performance parameters such as the detector's sensitivity, detection limit, and stability.

[0069] Imaging performance test: Based on the ZYY-DZSZXT-100 imaging platform of Beijing Zhenyaoyan Technology Co., Ltd., and combined with the Keithley 6517B electrometer to record the transmitted X-ray photocurrent data, spatial resolution imaging results were obtained through data processing.

[0070] Example 1 See Figure 1 As shown, a method for preparing a PTCDA / PDMS composite flexible film includes the following steps: Preparation of composite slurry: Mix 0.5g PTCDA powder with 3.0g PDMS prepolymer, then add 0.3g hydrosilicone addition curing agent and ultrasonically disperse until a composite slurry with uniform color and no obvious agglomeration is formed. Then place the obtained slurry in a vacuum environment for degassing treatment to remove internal microbubbles and avoid the formation of pore defects during subsequent curing, thereby improving the film density, uniformity and electrical stability.

[0071] Film formation and curing: The degassed composite slurry is injected into a mold of a pre-designed shape, and the film thickness is adjusted by casting to obtain a composite film with a thickness of 0.6 mm. The mold can be a glass mold or a polytetrafluoroethylene mold. Subsequently, the mold is placed in an environment of 80°C for 3 hours for thermosetting, so that the PDMS matrix is ​​fully cross-linked and the dispersion state of the PTCDA powder is locked, thereby forming a stable three-dimensional network structure to improve the mechanical stability, flexibility and environmental stability of the composite film.

[0072] Demolding and shaping: After curing, the film is cooled to room temperature and then demolded to obtain a PTCDA / PDMS composite flexible film. The resulting film exhibits good flexibility, structural stability, and electrical properties, and can be applied to flexible radiation detectors, flexible electronic devices, and conductive composite materials.

[0073] By adjusting the ratio of PTCDA to PDMS, the flexibility and electrical properties of the composite film can be balanced.

[0074] Electrode structures were fabricated on the surface of the composite flexible thin film using vacuum evaporation. Example 1 employed a coplanar interdigitated structure. The evaporation process included the following steps: Substrate pretreatment: Place in an 80℃ oven to dry for later use.

[0075] Shadow Mask: A metal mask with a coplanar interdigitated pattern is applied directly to the bottom surface of the substrate to ensure that the mask and the substrate are completely and tightly bonded. Excessive gaps will cause metal diffusion during evaporation and blurry edges.

[0076] Vacuum evaporation metal: Fix the mask with the substrate attached to it onto the sample stage of the evaporation machine, and evacuate to 5×10⁻⁶. - A gold layer with a thickness of 90 nm is deposited at a pressure of ³ Pa or higher.

[0077] Demolding and removing the device: After the vapor deposition is completed, wait for the cavity to cool to room temperature, remove the sample, remove the mask, and obtain the interdigitated gold electrode device.

[0078] Example 1-1 Same as Example 1, except that, The mass ratio of PTCDA powder to PDMS prepolymer is 1:4.

[0079] Examples 1-2 Same as Example 1, except that, The mass ratio of PTCDA powder to PDMS prepolymer is 1:10.

[0080] Example 2 Flexible X-ray detectors are fabricated using the same PTCDA / PDMS composite flexible thin film as in Example 1, including: Preparation of composite slurry: Mix 0.5g PTCDA powder with 3.0g PDMS prepolymer, then add 0.3g hydrosilicone addition curing agent and ultrasonically disperse until a composite slurry with uniform color and no obvious agglomeration is formed. Then place the obtained slurry in a vacuum environment for degassing treatment to remove internal microbubbles and avoid the formation of pore defects during subsequent curing, thereby improving the film density, uniformity and electrical stability.

[0081] Film formation and curing: The degassed composite slurry is injected into a mold of a pre-designed shape, and the film thickness is adjusted by casting to obtain a composite film with a thickness of 0.5 mm. The mold can be a glass mold or a polytetrafluoroethylene mold. Subsequently, the mold is placed in an environment of 80°C for 6 hours for thermosetting, so that the PDMS matrix is ​​fully cross-linked and the dispersion state of the PTCDA powder is locked, thereby forming a stable three-dimensional network structure to improve the mechanical stability, flexibility and environmental stability of the composite film.

[0082] Demolding and shaping: After curing, the film is cooled to room temperature and then demolded to obtain a PTCDA / PDMS composite flexible film.

[0083] In the device structure fabrication stage, Example 2 uses a circular patterned metal mask for mask evaporation and a vertical stacked structure of top electrode-composite film-bottom electrode to replace the coplanar interdigitated structure.

[0084] Because the vertical structure shortens the carrier transport distance, the device exhibits a faster response speed and higher charge collection efficiency. At the same time, the vertical structure can effectively reduce lateral crosstalk, making it more suitable for flexible arrayed X-ray imaging systems. Test results show that the device can achieve a stable X-ray response under low bias conditions and has good time response characteristics.

[0085] Example 3 The vertical structure X-ray detector provided in Example 2 was placed in a 50°C constant temperature heating test cylinder for performance testing.

[0086] Test results show that the device can still maintain a stable light-dark current ratio and clear X-ray imaging capability at 50℃. Analysis suggests that the PTCDA molecule itself has a stable aromatic conjugated structure, while the PDMS matrix has excellent thermal stability and flexible buffering capacity. Therefore, it can effectively reduce the damage to the conductive network caused by thermal expansion mismatch, thereby maintaining stable carrier transport capability.

[0087] Example 4 The device provided in Example 2 was fixed to the surface of a curved mold with a curvature radius of R20 mm, and X-ray detection test was performed in the curved state.

[0088] Test results show that the device can maintain stable X-ray response performance under bending conditions, with small changes in response current and no obvious signal distortion. At the same time, the X-ray imaging images obtained under bending conditions have clear edges and small deformation and noise enhancement phenomena, indicating that the PTCDA composite flexible film has excellent mechanical flexibility and imaging capabilities.

[0089] Comparative Example 1 Same as Example 1, except that: After the composite slurry was prepared, it was directly poured and heat-cured without vacuum degassing.

[0090] Due to the large number of air bubbles remaining inside the slurry, obvious void defects are formed inside the composite film after curing, and a large number of pore structures exist on the surface of the film.

[0091] Comparative Example 2 Same as Example 1, except that: PTCDA powder was added directly to PDMS prepolymer for mixing without grinding or ultrasonic dispersion.

[0092] Because PTCDA particles are large and unevenly dispersed, they form obvious agglomeration areas inside the composite membrane, resulting in poor continuity.

[0093] To illustrate the performance and applications of the PTCDA / PDMS composite flexible film prepared by this invention, the accompanying drawings are provided.

[0094] Figure 1 The preparation process of the composite flexible film of the present invention is demonstrated. The process includes, in sequence: grinding PTCDA raw material into powder; mixing PTCDA powder, PDMS prepolymer and curing agent in proportion and ultrasonically dispersing; placing in a vacuum drying oven for vacuum degassing; pouring the slurry into a mold; heating at 80°C to crosslink and cure PDMS; and obtaining a uniform composite film with high flexibility after cooling and demolding.

[0095] Figure 2 Composite films prepared under different process conditions, among which, Figure 2 (a) is the film provided in Example 1, (b) is the film provided in Comparative Example 1, and (c) is the film provided in Comparative Example 2; from Figure 2It can be seen that (a) vacuum degassing and ultrasonic dispersion result in a film with good flexibility, structural stability and electrical properties; (b) without vacuum degassing, a large number of bubbles remain inside the slurry, and obvious void defects are formed inside the composite film after curing; (c) without ultrasonic dispersion, the PTCDA particles are large in size and unevenly dispersed, forming obvious agglomeration areas inside the composite film.

[0096] Figure 3 The device structure designed according to this invention is shown. Among them, Figure 3 (a) is the coplanar interdigitated structure device provided in Embodiment 1, and (b) is the vertical stacked structure device provided in Embodiment 2. Figure 3 As can be seen, (a) is a schematic diagram of the coplanar structure, in which interdigitated electrodes are prepared on the surface of the composite film to evaluate the intrinsic charge transport capability of the material; (b) is a schematic diagram of the vertical structure, which includes a flexible substrate, a bottom electrode, a sensing layer and a top electrode in sequence. This structure is compatible with commercial TFT array integration; (c) is a schematic diagram of the detection principle and flexible attachment cross section, showing that the device can still maintain electrode interface contact under bending deformation and stably generate and collect electrical signals under X-ray irradiation.

[0097] Figure 4 The system characterizes the performance of the coplanar structure detector in Example 1. (a) The IV characteristic curve fitting shows that the intrinsic resistivity of the material is as high as 2.97 × 10⁻⁶. 14 (a) Current-time response curves demonstrate that the device has extremely fast X-ray transient response under different bias voltages; (b) On / off ratio versus bias voltage curves show that the device still maintains a high signal-to-noise ratio at low dose rates; (c) Sensitivity versus voltage curves show that the detection sensitivity is close to 20 at a bias voltage of 100 V.

[0098] Figure 5 The performance of the vertical structure detector for TFT array integration in Example 2 was characterized at room temperature. (a) The resistivity in the vertical direction measured by the IV characteristic curve is 1.36 × 10⁻⁶. 14 (a) The current-time response curve shows a highly repeatable photocurrent step; (b) The on / off ratio is shown as a function of bias voltage; (c) The sensitivity versus voltage curve shows that the detection sensitivity of the vertical device reaches approximately 45 at a bias voltage of 150 V.

[0099] Figure 6 The operational stability of the vertical structure detector in Example 3 at a high temperature of 50°C was characterized. (a) The IV characteristic curve shows that the resistivity remains at 7.83 × 10⁻⁶ under thermal stress. 12(a) The current-time response curves demonstrate that the device can still output a stable photocurrent at high temperatures; (b) The on / off ratio evolution characteristics at high temperatures are shown; (c) The sensitivity-voltage relationship curves show that the sensitivity remains at 35 at a bias voltage of 150 V, demonstrating the excellent intrinsic thermal stability of PTCDA.

[0100] Figure 7 The reliability of the flexible detection in Example 4, where the vertical device is attached to a curvature radius R = 20 mm, was characterized. (a) The IV characteristic curve shows that no structural breakdown occurred in the thin film under bending conditions, and the resistivity remained at 9.70 × 10⁻⁶. 13 (a) The current-time response curve shows that although the substrate stretching causes a slight hysteresis in the response, the overall light-dark current contrast still meets the imaging requirements; (b) The on / off ratio change under deformation is shown; (c) The sensitivity-voltage relationship curve shows that the detection sensitivity remains at about 40 when the bias voltage is 150 V under bending conditions.

[0101] Figure 8 This invention demonstrates the actual imaging capability and spatial resolution characterization of the PTCDA / PDMS composite flexible detector provided in Embodiment 2 under complex multi-dimensional conditions. Figure 8 (a) The spatial resolution of the device was quantitatively evaluated by line-to-card imaging. At room temperature, the spatial resolution of the vertical structure device reached 3.0 Lp / mm (better than the 2.6 Lp / mm of the coplanar structure). At a high temperature of 50℃, the resolution was slightly reduced to 2.54 Lp / mm due to the influence of thermally excited carrier scattering. Under the bending state of R=20 mm, the resolution was measured to be 1.7 Lp / mm due to the change of micro spacing and substrate strain. However, the reliable imaging quality was maintained to meet the requirements of flexible conformal detection. Figure 8 (b) shows the imaging results of the detector on the capsule containing the metal wire. The internal contour of the capsule is clearly distinguishable under the four operating conditions mentioned above. Although the background baseline current increases under high temperature and extreme bending conditions, the device still maintains a high signal-to-noise ratio and no obvious geometric distortion thanks to the stable conductive percolation network formed by PTCDA powder in PDMS. In addition, Figure 8 (c), (d), and (e) further validate the wide applicability of the vertical structure detector. It can not only present extremely high edge contrast for the "XRAY" letter mask, but also clearly and non-overlappingly resolve the dense metal pin arrangement inside the integrated circuit chip, demonstrating its practicality in high-precision non-destructive testing in industry. At the same time, it can clearly restore the fine structures such as the trunk and limb joints of biological insect samples. This is due to the excellent equivalence and scattering matching between the low atomic number of organic semiconductor materials and biological tissues, which can accurately capture weak density differences, thus providing a reliable new technical solution for low-dose flexible biomedical imaging.

[0102] In summary, this invention combines PTCDA organic semiconductor material with excellent π-conjugated structure with PDMS flexible polymer matrix, and utilizes the excellent flexibility, thermal stability and interface buffering capacity of PDMS to construct a flexible detector device that combines flexibility, high temperature stability and X-ray response capability.

[0103] In this invention, PTCDA particles are uniformly dispersed within a PDMS matrix, forming a continuous conductive network. Under X-ray irradiation, the PTCDA absorbs X-rays and generates electron-hole pairs, forming a stable photocurrent output under external bias. Simultaneously, the flexible PDMS matrix effectively mitigates the damage to the conductive network caused by bending and thermal stress, thereby improving the stability of the device under bending and high-temperature conditions.

[0104] This invention describes preferred embodiments and their effects. However, those skilled in the art, once they understand the basic inventive concept, can make other changes and modifications to these embodiments.

[0105] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a PTCDA / PDMS composite flexible film, characterized in that, Includes the following steps: 3,4,9,10-perylenetetracarboxylic dianhydride powder, polydimethylsiloxane prepolymer, and curing agent are mixed to obtain a mixed slurry; The mixed slurry is degassed to obtain a degassed mixed slurry; The degassed slurry is injected into a mold for heating and curing, and then demolded to obtain a PTCDA / PDMS composite flexible film. The mass ratio of the 3,4,9,10-perylenetetracarboxylic dianhydride powder to the polydimethylsiloxane prepolymer is 1:4 to 10.

2. The method for preparing the PTCDA / PDMS composite flexible film according to claim 1, characterized in that, The temperature range for heat curing is limited to 60–100℃, and the curing time is 2–6 hours.

3. The method for preparing the PTCDA / PDMS composite flexible film according to claim 1, characterized in that, During the degassing process, the mixed slurry is placed in a vacuum drying oven for vacuum degassing.

4. The method for preparing the PTCDA / PDMS composite flexible film according to claim 1, characterized in that, The curing agent is a hydrosilicone addition curing agent, and its mass is 8-12% of the mass of the PDMS prepolymer. The main component of the hydrosilicone addition curing agent is low molecular weight hydrogen-containing silicone oil, and a platinum-based catalyst is added as a triggering component for the curing reaction.

5. The method for preparing the PTCDA / PDMS composite flexible film according to claim 1, characterized in that, The 3,4,9,10-perylenetetracarboxylic dianhydride powder is a micron-sized powder that has undergone physical grinding. The 3,4,9,10-perylenetetracarboxylic dianhydride powder and PDMS prepolymer crosslink and cure to form a continuous charge transport network.

6. A PTCDA / PDMS composite flexible film prepared by the method according to any one of claims 1 to 5.

7. The application of the PTCDA / PDMS composite flexible thin film as described in claim 6 in an X-ray detector.

8. An X-ray detector, characterized in that, The X-ray detector is a vertically stacked device structure, including a flexible substrate, and a bottom electrode, a sensing layer and a top electrode stacked sequentially on the flexible substrate; The sensing layer is the PTCDA / PDMS composite flexible film as described in claim 6.

9. The X-ray detector according to claim 8, characterized in that, The X-ray detector is capable of maintaining X-ray detection and imaging response without significant geometric distortion under ambient temperature conditions ranging from room temperature to 45~65℃, or under mechanical deformation conditions of bending force with a radius of curvature R≥20 mm.

10. An application of the X-ray detector of claim 8 in large-area flexible digital X-ray imaging, characterized in that, The bottom electrode of the X-ray detector is electrically interconnected with a thin-film transistor (TFT) array to enable addressing of X-ray excitation charges and readout of signals.

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