Perovskite single crystal X-ray array imager
By introducing an anisotropic binding layer into the perovskite single crystal X-ray array imager, the connection problem between the perovskite crystal and the TFT readout circuit substrate was solved, achieving high signal sensitivity and high-resolution X-ray imaging.
Patent Information
- Application Number
- CN202422509869.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-10-17
- Publication Date
- 2025-09-19
- Estimated Expiration
- 2034-10-17
AI Technical Summary
In the existing technology, the anisotropic binding technology of perovskite single crystal and TFT readout circuit substrate is not suitable, resulting in insufficient conductivity and insulation between the perovskite crystal photodiode and the connecting electrode, affecting imaging resolution and signal crosstalk.
In perovskite single crystal X-ray array imagers, an anisotropic binding layer is used to connect the perovskite crystal to the TFT readout circuit substrate. By providing good conductivity in the vertical direction and insulation in the horizontal direction, the binding layer formed by the perovskite polycrystalline particles ensures the anisotropy of carrier transport.
The signal sensitivity and imaging resolution of the X-ray detector are improved, and the signal crosstalk between different pixels is reduced.
Smart Images
Figure CN223362383U_ABST
Abstract
Description
Technical Field
[0001] The utility model belongs to the technical field of photoelectric detection, and in particular relates to a perovskite single crystal X-ray array imager. Background Art
[0002] X-rays have the characteristics of short wavelength, high energy, and strong transmission capability, making them widely used in medical diagnosis, security inspection, and scientific research. Currently, X-ray detectors are divided into indirect and direct X-ray detectors based on the photoelectric conversion process. In indirect X-ray detectors, due to the inevitable afterglow of the scintillator itself, fluorescence scattering can cause signal crosstalk and reduce resolution. Due to the indirect conversion process from scintillator to photodetector, indirect X-ray detectors have lower external quantum efficiency than direct detectors.
[0003] In direct X-ray detectors, high-energy radiation ionizes the detection material, directly generating electron-hole pairs. These electron-hole pairs, under the influence of an external electric field, generate a photocurrent, which is then read out as an image by a readout system. This eliminates the need for additional photoelectric conversion and avoids light signal scattering. In principle, direct X-ray detectors are more conducive to miniaturization, achieving higher detection efficiency and resolution.
[0004] α-Se, CdTe and CdZnTe are commonly used semiconductor materials for direct X-ray detection, but the preparation process of these materials is complex and expensive, especially for large-scale preparation. In recent years, halide perovskites have important potential applications in X-ray detection and imaging due to their low cost, simple solution growth characteristics, excellent electronic and optical properties, and strong absorption and photoelectric conversion capabilities for high-energy X-ray photons.
[0005] Whether direct or indirect X-ray detection, array thin film transistor (TFT) readout circuits or silicon-based CMOS readout circuits are required to obtain array imaging. Figure 1This is a typical X-ray detector TFT readout circuit, comprising a glass substrate 1, a gate 2, a dielectric layer 3, a drain electrode 4, a semiconductor channel 5, a source electrode 6, a connecting electrode 7, a photodiode sensing layer 8, a top electrode 9, a scanning signal input port 10, a detection signal readout port 11, and a common voltage input port 12. Components 1 through 7 constitute the thin-film transistor switching circuit, while components 8 and 9 constitute the photodiode sensing layer. The photodiode layer is coupled to the TFT switching circuit via the connecting electrode 7. Indirect X-ray detection imaging devices employ a scintillator on top of the transparent top electrode 9 to convert incident X-rays into visible light, so the photodiode sensing layer 8 only needs to convert visible light into electrical signals. Therefore, indirect X-ray detection imaging devices deposit an amorphous silicon or polycrystalline silicon thin film on the connecting electrode 7 and, through doping, form the visible light photodiode sensing layer 8. Since direct X-ray detection imaging devices lack a scintillator, the sensing layer must possess strong absorption and conversion capabilities for high-energy X-rays, converting X-ray photons into electrical signals. It is proposed to deposit an α-Se thin film on the connecting electrode 7 using a thin film process. The atomic number of Se is 34 and the mass density is about 4.8 g / cm 3 , has good X-ray absorption ability. However, the thickness of α-Se films prepared by thin film deposition is generally only micrometer-level, so α-Se detectors can usually only image soft X-rays.
[0006] Although perovskite crystals have good absorption and conversion capabilities for X-rays, they are limited by incompatibility of preparation technologies and cannot be directly epitaxially grown on TFT readout circuit substrates. Usually, it is necessary to prepare perovskite single crystals and TFT array readout circuits separately, and then bind the perovskite single crystals to the TFT readout circuit substrate. According to the application requirements of array imaging, the perovskite single crystals bound to the TFT circuit substrate need to have anisotropic conductive properties, that is, there must be good conductivity between the connecting electrode 7 and the photodiode sensing layer 8, so that the photogenerated carriers generated by the photodiode can be transmitted to the readout circuit. However, the binding layer needs to have good insulation properties in the lateral direction to prevent crosstalk between photogenerated carriers between different pixels, thereby affecting the imaging resolution. In other optoelectronic devices, this type of anisotropic binding can generally be achieved by using methods such as anisotropic conductive adhesive or indium column flip-chip bonding, but perovskite crystals cannot withstand high temperatures and high pressures, making these conventional binding processes unapplicable to perovskite crystal X-ray array imaging devices. A new utility model technology is needed to prepare perovskite single crystal X-ray array imaging devices. Utility Model Content
[0007] The purpose of the utility model is to propose a perovskite single crystal X-ray array imager to address the problem that the existing anisotropic binding technology is not suitable for coupling perovskite crystals and TFT readout circuit substrates, so that the perovskite crystal photodiode and the connecting electrode have good longitudinal conductivity and strong lateral insulation.
[0008] The technical solution adopted by the utility model is: a perovskite single crystal X-ray array imager, comprising a TFT readout circuit substrate, a photodiode sensing layer and a top substrate;
[0009] The photodiode sensing layer is a perovskite single crystal diode layer;
[0010] A top electrode is provided on the top substrate;
[0011] An anisotropic binding layer is provided between the connection electrode of the TFT readout circuit substrate and the photodiode sensing layer, an anisotropic binding layer is provided between the top substrate and the photodiode sensing layer, and the photodiode sensing layer is fixed between the top substrate and the TFT readout circuit substrate;
[0012] The anisotropic binding layer is a perovskite crystal binding layer;
[0013] The anisotropic binding layer has excellent carrier transport performance in the longitudinal direction, and X-ray photogenerated carriers can be smoothly transmitted to the TFT readout circuit; its carrier transport performance in the lateral direction is poor, and it is generally required that the longitudinal and lateral carrier transport performances differ by more than two orders of magnitude, which can effectively prevent signal crosstalk between different imaging pixels;
[0014] The anisotropic binding layer has a certain adhesiveness and can fix the perovskite crystal between the top substrate and the TFT readout circuit substrate;
[0015] The anisotropic binding layer is prepared at a temperature and pressure lower than the tolerance value of the perovskite crystal. The introduction of the anisotropic binding layer does not destroy the structure and photoelectric conversion characteristics of the perovskite crystal.
[0016] Preferably, the anisotropic binding layer contains perovskite polycrystalline particles.
[0017] Preferably, the perovskite single crystal of the photodiode sensing layer is MAPbBr3.
[0018] Preferably, the perovskite polycrystalline particles are MAPbBr3.
[0019] Preferably, the perovskite polycrystalline particles have a height of 50 μm and a width of 100 μm.
[0020] The utility model sets an anisotropic binding layer between the TFT substrate connecting electrode and the perovskite crystal, and between the top substrate and the perovskite crystal. The perovskite precursor liquid and the binder are mixed to form a binding layer precursor, and then the precursor is coated between the TFT substrate connecting electrode and the perovskite crystal, and between the top substrate and the perovskite crystal. A certain pressure and temperature are applied to the top substrate / perovskite single crystal photodiode layer / TFT readout circuit substrate, and perovskite polycrystalline particles are grown in the binding layer without destroying the perovskite single crystal structure. Due to the large differences in the particle size and density of the perovskite polycrystalline particles in different regions, it makes the carrier transport in the binding layer have good anisotropy. The test results show that the longitudinal carrier mobility is two orders of magnitude higher than the lateral carrier mobility. This anisotropy of carrier transport first enables X-ray photogenerated carriers to be well transferred to the TFT readout circuit, improving the signal sensitivity of the detector; secondly, due to the anisotropy of carrier transport, the signal crosstalk between different imaging pixels is reduced, and high-resolution X-ray array imaging can be obtained.
[0021] Beneficial effects:
[0022] 1. This invention sets a binding layer between the connecting electrode and the perovskite crystal. By applying appropriate temperature and pressure, some perovskite polycrystalline particles are grown without damaging the perovskite single crystal structure and photoelectric conversion performance. These perovskite polycrystalline particles form an anisotropic conductive channel between the connecting electrode and the perovskite single-device photodiode layer.
[0023] 2. The utility model can tightly connect the perovskite crystal and the electrode, so that each imaging pixel can work independently, reduce crosstalk between electrodes, and improve the resolution of the detector. BRIEF DESCRIPTION OF THE DRAWINGS
[0024] Figure 1 Coupling the TFT readout circuit substrate and the X-ray photodiode layer;
[0025] Figure 2 This is the structure of the perovskite single crystal X-ray array imaging device proposed in the present invention;
[0026] Figure 3 A local SEM image of the bonding layer between the perovskite single crystal and the TFT readout circuit.
[0027] Figure 4 This is the carrier transport channel of the perovskite single crystal X-ray array imaging device proposed in the utility model;
[0028] Figure 5a The carrier transport characteristics (longitudinal IV curve and carrier mobility) of the anisotropic binding layer in the perovskite single crystal X-ray array imaging device proposed in this utility model;
[0029] Figure 5b The carrier transport characteristics (lateral IV curve and carrier mobility) of the anisotropic binding layer in the perovskite single crystal X-ray array imaging device proposed in this utility model;
[0030] In the figure: 1. Glass substrate; 2. Gate; 3. Dielectric layer; 4. Drain electrode; 5. Semiconductor channel; 6. Source electrode; 7. Connecting electrode; 8. Photodiode sensing layer; 9. Top electrode; 10. Scan signal input port; 11. Detection signal readout port; 12. Common voltage input port; 13. Top substrate; 14. Anisotropic binding layer; 15. Coupling pressure; 16. Perovskite polycrystalline grains; 17. Vacant part. DETAILED DESCRIPTION
[0031] The specific implementation methods of the present invention are described in detail below with reference to the accompanying drawings. This embodiment is implemented based on the technical solution of the present invention, and provides a detailed implementation method and specific operation process. However, the protection scope of the present invention is not limited to the following embodiments.
[0032] like Figure 2 As shown, a perovskite single crystal X-ray array imager includes a TFT readout circuit substrate, a photodiode sensing layer 8 and a top substrate 13;
[0033] The photodiode sensing layer 8 is a perovskite single crystal diode layer, and the perovskite single crystal is MAPbBr3; a top electrode 9 is provided on the top substrate 13; an anisotropic binding layer 14 is provided between the connecting electrode 7 of the TFT readout circuit substrate and the photodiode sensing layer 8, and an anisotropic binding layer 14 is provided between the top substrate 13 and the photodiode sensing layer 8, and the photodiode sensing layer 8 is fixed between the top substrate 13 and the TFT readout circuit substrate; the anisotropic binding layer 14 is a perovskite crystal binding layer.
[0034] To anisotropically bond the perovskite single crystal to the TFT readout circuit substrate, anisotropic bonding layers 14 are applied to the top and bottom ends of the photodiode sensing layer 8. A top substrate 13 is then provided, and a top electrode 9 is placed on top substrate 13. By applying a certain coupling pressure 15 between the glass substrate 1 and the top substrate 13 and heating them to an appropriate temperature, the photodiode sensing layer 8 and the TFT readout circuit substrate are anisotropically bonded. The bonding layer's adhesive properties secure the photodiode sensing layer 8 between the top substrate 13 and the TFT readout circuit substrate.
[0035] exist Figure 2 In the perovskite single crystal X-ray array imaging device shown, the key is the anisotropic binding layer 14. Figure 3The microstructure of the anisotropic binding layer 14 between the photodiode sensing layer 8 and the connecting electrode 7 in the present invention, under appropriate pressure and temperature, is shown. The anisotropic binding layer contains perovskite polycrystalline particles 16, and the selected perovskite single crystal is MAPbBr3. As can be seen from the figure, some perovskite polycrystalline particles 16 grow between the perovskite single crystal and the connecting electrode 7. These perovskite polycrystalline particles 16 are approximately 50 μm in height and 100 μm in width. Their material composition is also MAPbBr3, so the perovskite polycrystalline particles 16 electrically connect the perovskite single crystal 8 and the connecting electrode 7. The growth conditions of the perovskite polycrystalline are controlled so that the vacant portion 17 is completely free of perovskite grains or is not completely covered by perovskite grains. The perovskite polycrystalline particles 16 and the vacant portion 17 constitute the anisotropic binding layer 14, which has good conductivity in the longitudinal direction and good insulation properties in the transverse direction.
[0036] Figure 4 The carrier transport mechanism of the perovskite single crystal X-ray array imaging device proposed in the present invention is explained, in which it is assumed that a positive bias voltage is applied to the common voltage input port 12. When high-energy X-rays irradiate the photodiode sensing layer 8, electron-hole pairs are generated due to the photoelectric effect. Under the action of the electric field, the electrons drift upward and the holes shift downward. The anisotropic binding layer forms different electrical connection channels between the photodiode sensing layer 8 and the connecting electrode 7. Relatively thick perovskite polycrystalline particles 16 are grown in certain areas, and a longitudinal carrier channel is formed between the photodiode sensing layer 8 and the connecting electrode 7, which can smoothly transmit photogenerated holes. In the vacant part 17, the perovskite polycrystalline particles are relatively small in size and are not enough to connect the photodiode sensing layer 8 and the connecting electrode 7, so the photogenerated holes in this area are blocked. Figure 4 By extending the carrier transport state to the entire detection array, the carriers can be conducted longitudinally but insulated laterally, which not only ensures the extraction of detection signals but also suppresses signal crosstalk between different pixels.
[0037] The method for preparing the above-mentioned perovskite single crystal X-ray array imager comprises the following steps:
[0038] Step 1: Preparation of top substrate and TFT readout circuit substrate
[0039] The top substrate and TFT readout circuit substrate are prepared using conventional X-ray detector methods;
[0040] Step 2: Preparation of photodiode sensing layer
[0041] A perovskite single crystal is used as a photodiode sensing layer, and a MAPbBr3 single crystal is selected. 3.36 g of methylammonium bromide (MABr) and 11.01 g of lead bromide (PbBr2) are added to 30 ml of N, N-dimethylformamide methylammonium bromide (DMF) solution to obtain a MAPbBr3 precursor solution. The precursor solution is stirred until the solute is fully dissolved, and the MAPbBr3 precursor solution is filtered with a filter head with a micron-sized filter to filter out impurities. After the MAPbBr3 precursor solution is poured into a clean and smooth crystallization dish, the crystallization dish is placed on a heating table, and the temperature is adjusted to rise steadily and slowly from 60°C to 80°C to obtain a MAPbBr3 single crystal. The above-mentioned MAPbBr3 single crystal is cut and polished to obtain a MAPbBr3 single crystal of the design required size.
[0042] Step 3: Preparation of anisotropic binding layer
[0043] The anisotropic binding layer is completed through two processes: precursor preparation and perovskite polycrystalline particle layer preparation;
[0044] The MAPbBr3 perovskite crystal binding layer was prepared by pouring 9 ml of terpineol into a beaker and placing it on a heating table. The temperature was raised to 85°C. During the continuous heating process, 3 g of the electronic paste organic binder was added three times and stirred evenly. After two hours, a light yellow mixed solution was obtained. 10 ml of the MAPbBr3 precursor solution was added to the mixed solution, stirred evenly, and continued to heat for one hour to obtain an orange-red MAPbBr3 perovskite binding layer precursor.
[0045] The method for preparing a perovskite polycrystalline particle layer is as follows: coating a binding layer precursor on a top substrate, coating a binding layer precursor on a TFT readout circuit substrate, placing a perovskite single crystal on the TFT readout circuit substrate, and then covering the top substrate; applying pressure between the TFT circuit substrate and the top substrate, typically 20N; placing the top substrate / perovskite single crystal / TFT readout circuit substrate complex on a heating platform, and raising the heating platform temperature to 85°C while maintaining pressure; stopping heating after the precursor is completely solidified, and allowing the top substrate / perovskite single crystal / TFT readout circuit substrate complex to naturally cool to room temperature; maintaining the pressure setting during the cooling process to obtain an anisotropic binding layer.
[0046] Figure 5a and 5b It is the longitudinal and transverse carrier conduction performance measured after implementing the technical solution of the utility model. From the carrier mobility obtained by the test, it can be seen that the longitudinal carrier transmission capacity is 128 times higher than the transverse transmission capacity. Therefore, the technical solution proposed by the utility model has good conductive anisotropy.
[0047] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all such improvements and changes should fall within the scope of protection of the claims attached to this utility model.
Claims
1. A perovskite single crystal X-ray array imager, characterized in that: It includes a TFT readout circuit substrate, a photodiode sensing layer and a top substrate; The photodiode sensing layer is a perovskite single crystal diode layer; A top electrode is provided on the top substrate; An anisotropic binding layer is provided between the connection electrode of the TFT readout circuit substrate and the photodiode sensing layer, an anisotropic binding layer is provided between the top substrate and the photodiode sensing layer, and the photodiode sensing layer is fixed between the top substrate and the TFT readout circuit substrate; The anisotropic binding layer is a perovskite crystal binding layer.
2. The perovskite single crystal X-ray array imager according to claim 1, characterized in that: The anisotropic binding layer contains perovskite polycrystalline particles.
3. The perovskite single crystal X-ray array imager according to claim 2, characterized in that: The perovskite single crystal of the photodiode sensing layer is MAPbBr3.
4. The perovskite single crystal X-ray array imager according to claim 3, characterized in that: The perovskite polycrystalline particles are MAPbBr3.
5. The perovskite single crystal X-ray array imager according to claim 4, characterized in that: The perovskite polycrystalline particles have a height of 50 μm and a width of 100 μm.