Direct type perovskite single crystal linear array detector based on X rays and preparation method of direct type perovskite single crystal linear array detector

Abstract

The invention discloses an X-ray-based direct perovskite single crystal linear array detector and a preparation method thereof. The X-ray-based direct perovskite single crystal linear array detector comprises a TFT readout circuit substrate, a photodiode sensing layer and a top surface substrate, the photodiode sensing layer is a perovskite single crystal diode layer; a top electrode is arranged on the top surface substrate; an anisotropic binding layer is arranged between a connecting electrode of the TFT readout circuit substrate and the photodiode sensing layer, an anisotropic binding layer is arranged between the top surface substrate and the photodiode sensing layer, and the photodiode sensing layer is fixed between the top surface substrate and the TFT readout circuit substrate; and the anisotropic binding layer is a perovskite crystal binding layer. According to the invention, the perovskite crystal photodiode and the connecting electrode have relatively good longitudinal conductivity and very strong transverse insulativity.

Description

Technical Field

[0001] The present invention belongs to the technical field of photoelectric detection, and in particular relates to an X-ray-based direct perovskite single crystal linear detector and a preparation method thereof. Background Art

[0002] X-rays have the characteristics of short wavelength, high energy and strong transmission ability, which makes X-ray detection and imaging widely used in medical diagnosis, security inspection and scientific research. At present, X-ray detectors are divided into indirect X-ray detectors and direct X-ray detectors according to the different photoelectric conversion processes. In indirect X-ray detectors, because the scintillator itself has inevitable afterglow characteristics, fluorescence scattering will cause signal crosstalk and reduce resolution. Due to the indirect conversion process from scintillator to photodetector, the external quantum efficiency of indirect X-ray detectors will be lower than that of direct detectors.

[0003] In direct detectors, the detection material is ionized by high-energy radiation to directly generate electron-hole pairs, which form photocurrents under the action of an external electric field and are read out as images through a readout system. No additional photoelectric conversion process is required, which avoids light signal scattering. In principle, direct X-ray detectors are more conducive to miniaturization of detectors and achieve 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 complicated and expensive, especially large-area preparation has great technical difficulties. 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 X-ray detection or indirect X-ray detection, array thin film transistor (TFT) readout circuit or silicon-based CMOS readout circuit is required to obtain array imaging. Figure 1It is a typical X-ray detector TFT readout circuit, including glass substrate 1, gate 2, dielectric layer 3, drain electrode 4, semiconductor channel 5, source electrode 6, connecting electrode 7, photodiode sensing layer 8, top electrode 9, scanning signal input port 10, detection signal readout port 11 and common voltage input port 12, wherein components 1 to 7 constitute the switch circuit of the thin film transistor, and 8 and 9 constitute the photodiode sensing layer. The photodiode layer is coupled to the TFT switch circuit through the connecting electrode 7. The indirect X-ray detection imaging device sets a scintillator on the transparent top electrode 9 to convert the incident X-rays into visible light, so the photodiode sensing layer 8 only needs to convert the visible light into an electrical signal. Therefore, the indirect X-ray detection imaging device deposits an amorphous silicon or polycrystalline silicon thin film on the connecting electrode 7, and forms a visible light photodiode sensing layer 8 by doping. Since the direct X-ray detection imaging device does not have a scintillator, the sensing layer must have a strong absorption and conversion ability for high-energy X-rays to convert 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 absorption capacity for X-rays. However, the thickness of α-Se film 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 incompatible preparation technologies and cannot be directly epitaxially grown on TFT readout circuit substrates. It is usually 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, the connection electrode 7 and the photodiode sensing layer 8 have good conductivity, and the photogenerated carriers generated by the photodiode can be transmitted to the readout circuit. However, the binding layer needs to have good insulation in the lateral direction to prevent crosstalk between photogenerated carriers in different pixels, thereby affecting the imaging resolution. In other optoelectronic devices, this type of anisotropic binding can generally be achieved by methods such as anisotropic conductive glue or indium column flip-chip welding, but perovskite crystals are not resistant to high temperature and high pressure, so that these conventional binding processes cannot be applied to perovskite crystal X-ray array imaging devices. It is necessary to invent new technologies to prepare perovskite single crystal X-ray array imaging devices. Summary of the invention

[0007] The purpose of the present invention is to propose an X-ray-based direct perovskite single crystal linear detector and a preparation method thereof, in view of the fact that the existing anisotropic binding technology is not suitable for the coupling of 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 present invention is: an X-ray-based direct perovskite single crystal linear array detector, 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 disposed 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 good 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 generally the longitudinal and lateral carrier transport performances are required to 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] 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 have a height of about 50 μm and a width of about 100 μm, and their material composition is also MAPbBr3.

[0019] The method for preparing the above-mentioned X-ray-based direct perovskite single crystal linear detector comprises the following steps:

[0020] Step 1: Preparation of top substrate and TFT readout circuit substrate

[0021] The top substrate and the TFT readout circuit substrate are prepared by conventional X-ray detector methods;

[0022] Step 2: Preparation of photodiode sensing layer

[0023] The perovskite single crystal is used as the photodiode sensing layer, and the MAPbBr3 single crystal is selected. 3.36g of methyl ammonium bromide (MABr) and 11.01g of lead bromide (PbBr2) are added to 30ml of N, N-dimethylformamide methyl ammonium bromide (N, N-Dimethylformamide, 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 hole 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;

[0024] Step 3: Preparation of anisotropic binding layer

[0025] The anisotropic binding layer is completed through two processes: precursor preparation and perovskite polycrystalline particle layer preparation;

[0026] Select MAPbBr3 perovskite crystal binding layer, the precursor preparation method is as follows: pour 9 ml of pine alcohol into a beaker and place it on a heating table, and raise the temperature to 85°C; during continuous heating, add 3 g of electronic paste organic binder three times and stir evenly, and a light yellow mixed solution can be obtained after two hours; add 10 ml of MAPbBr3 precursor solution to the mixed solution, stir evenly and continue heating, and an orange-red MAPbBr3 perovskite binding layer precursor can be obtained after one hour;

[0027] The preparation method of the 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; placing the top substrate / perovskite single crystal / TFT readout circuit substrate complex on a heating platform, and raising the temperature of the heating platform 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.

[0028] Preferably, in step three, the pressure applied between the TFT circuit substrate and the top substrate is 20N.

[0029] The present invention 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 grow in the binding layer without destroying the perovskite single crystal structure. Due to the large difference in particle size and density of perovskite polycrystalline particles in different regions, it makes the carrier transport of 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 allows X-ray photogenerated carriers to be well transmitted 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.

[0030] Beneficial effects:

[0031] 1. The present invention sets a binding layer between the connecting electrode and the perovskite crystal, and grows some perovskite polycrystalline particles by appropriate heating and pressure without damaging the perovskite single crystal structure and photoelectric conversion performance. Through these perovskite polycrystalline particles, an anisotropic conductive channel is formed between the connecting electrode and the perovskite single-machine photodiode layer;

[0032] 2. The anisotropic binding layer of perovskite crystal proposed in the present invention has a simple preparation process, low cost and is easy to use.

[0033] 3. The present invention can closely 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

[0034] Figure 1 coupling the TFT readout circuit substrate with the X-ray photodiode layer;

[0035] Figure 2 The perovskite single crystal X-ray array imaging device structure proposed by the present invention;

[0036] Figure 3 A local SEM image of the binding layer between the perovskite single crystal and the TFT readout circuit;

[0037] Figure 4It is the carrier transport channel of the perovskite single crystal X-ray array imaging device proposed by the present invention;

[0038] 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 by the present invention;

[0039] 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 the present invention;

[0040] 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. Scanning 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 particles; 17. Vacant part. DETAILED DESCRIPTION

[0041] The specific implementation mode of the present invention is described in detail below with reference to the accompanying drawings. This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation mode and a specific operation process are given, but the protection scope of the present invention is not limited to the following embodiments.

[0042] like Figure 2 As shown, an X-ray based direct perovskite single crystal linear detector includes a TFT readout circuit substrate, a photodiode sensing layer 8 and a top substrate 13;

[0043] The photodiode sensing layer 8 is a perovskite single crystal diode layer, and the perovskite single crystal is MAPbBr3; a top electrode 9 is arranged on the top substrate 13; an anisotropic binding layer 14 is arranged between the connecting electrode 7 of the TFT readout circuit substrate and the photodiode sensing layer 8, and an anisotropic binding layer 14 is arranged 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.

[0044] In order to anisotropically bind the perovskite single crystal to the TFT readout circuit substrate, we set anisotropic binding layers 14 at both ends of the photodiode sensing layer 8, set a top substrate 13, and set the top electrode 9 on the top substrate 13. Apply a certain coupling pressure 15 between the glass substrate 1 and the top substrate 13, and heat to an appropriate temperature to anisotropically connect the photodiode sensing layer 8 to the TFT readout circuit. Since the binding layer has adhesiveness, it fixes the photodiode sensing layer 8 between the top substrate 13 and the TFT readout circuit substrate.

[0045] exist Figure 2 In the perovskite single crystal X-ray array imaging device shown, the key is the anisotropic binding layer 14. Figure 3 The microstructure of the anisotropic binding layer 14 between the photodiode sensing layer 8 and the connecting electrode 7 under the action of appropriate pressure and temperature in the present invention is given. There are perovskite polycrystalline particles 16 in the anisotropic binding layer, 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. The height of these perovskite polycrystalline particles 16 is about 50μm and the width is about 100μm. Their material composition is also MAPbBr3, so the perovskite polycrystalline particles 16 electrically conduct the perovskite single crystal 8 and the connecting electrode 7. The growth conditions of the perovskite polycrystalline are controlled so that there are no perovskite grains at all in the vacant part 17 or the perovskite grains are not completely covered. The perovskite polycrystalline particles 16 and the vacant part 17 constitute the anisotropic binding layer 14, which has good conductive properties in the longitudinal direction and good insulation properties in the transverse direction.

[0046] 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 longitudinal carrier channels are formed between the photodiode sensing layer 8 and the connecting electrode 7, which can smoothly transmit photogenerated holes. In the vacant part 17, the scale of the perovskite polycrystalline particles is relatively small, which is not enough to connect the photodiode sensing layer 8 and the connecting electrode 7, so the photogenerated holes in this part of the 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.

[0047] The method for preparing the above-mentioned X-ray-based direct perovskite single crystal linear detector comprises the following steps:

[0048] Step 1: Preparation of top substrate and TFT readout circuit substrate

[0049] The top substrate and the TFT readout circuit substrate are prepared by conventional X-ray detector methods;

[0050] Step 2: Preparation of photodiode sensing layer

[0051] The perovskite single crystal is used as the photodiode sensing layer, and the MAPbBr3 single crystal is selected. 3.36g of methyl ammonium bromide (MABr) and 11.01g of lead bromide (PbBr2) are added to 30ml of N, N-dimethylformamide methyl ammonium bromide (N, N-Dimethylformamide, 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 hole 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;

[0052] Step 3: Preparation of anisotropic binding layer

[0053] The anisotropic binding layer is completed through two processes: precursor preparation and perovskite polycrystalline particle layer preparation;

[0054] Select MAPbBr3 perovskite crystal binding layer, the precursor preparation method is as follows: pour 9 ml of pine alcohol into a beaker and place it on a heating table, and raise the temperature to 85°C; during continuous heating, add 3 g of electronic paste organic binder three times and stir evenly, and a light yellow mixed solution can be obtained after two hours; add 10 ml of MAPbBr3 precursor solution to the mixed solution, stir evenly and continue heating, and an orange-red MAPbBr3 perovskite binding layer precursor can be obtained after one hour;

[0055] The preparation method of the perovskite polycrystalline particle layer is as follows: coating a binding layer precursor on the top substrate, coating a binding layer precursor on the 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, with a typical value of 20N; placing the top substrate / perovskite single crystal / TFT readout circuit substrate complex on a heating platform, and raising the temperature of the heating platform to 85°C while maintaining the pressure; stopping heating when 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.

[0056] Figure 5a and 5b It is the longitudinal and transverse carrier conduction performance measured after implementing the technical solution of the present invention. 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 present invention has good conductive anisotropy.

[0057] It should be understood that those skilled in the art can make improvements or changes based on the above description, and all these improvements and changes should fall within the scope of protection of the appended claims of the present invention.

Claims

1. A direct-type perovskite single crystal linear detector based on X-rays, 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 disposed 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; The anisotropic binding layer contains perovskite polycrystalline particles.

2. The X-ray based direct perovskite single crystal linear detector according to claim 1, characterized in that: The perovskite single crystal of the photodiode sensing layer is MAPbBr3.

3. The X-ray based direct perovskite single crystal linear detector according to claim 2, characterized in that: The perovskite polycrystalline particles have a height of 50 μm and a width of 100 μm, and the material composition is MAPbBr3.

4. The method for preparing the X-ray based direct perovskite single crystal linear detector according to claim 1, 2 or 3, characterized in that: The following steps are involved: Step 1: Preparation of top substrate and TFT readout circuit substrate The top substrate and the TFT readout circuit substrate are prepared by conventional X-ray detector methods; Step 2: Preparation of photodiode sensing layer The perovskite single crystal is used as the photodiode sensing layer, and the MAPbBr3 single crystal is selected. 3.36g of methyl ammonium bromide and 11.01g of lead bromide are added to 30ml of N, N-dimethylamidomethyl ammonium bromide 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 hole 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; Step 3: Preparation of anisotropic binding layer The anisotropic binding layer is completed through two processes: precursor preparation and perovskite polycrystalline particle layer preparation; Select MAPbBr3 perovskite crystal binding layer, the precursor preparation method is as follows: pour 9 ml of pine alcohol into a beaker and place it on a heating table, and raise the temperature to 85°C; during continuous heating, add 3 g of electronic paste organic binder three times and stir evenly, and a light yellow mixed solution can be obtained after two hours; add 10 ml of MAPbBr3 precursor solution to the mixed solution, stir evenly and continue heating, and an orange-red MAPbBr3 perovskite binding layer precursor can be obtained after one hour; The method for preparing the 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; Apply pressure between the TFT circuit substrate and the top substrate; place the top substrate / perovskite single crystal / TFT readout circuit substrate complex on a heating platform, and raise the temperature of the heating platform to 85°C while maintaining pressure; stop heating after the precursor is completely solidified, and allow the top substrate / perovskite single crystal / TFT readout circuit substrate complex to cool naturally to room temperature; maintain the pressure setting during the cooling process to obtain an anisotropic binding layer.

5. The method for preparing the X-ray based direct perovskite single crystal linear detector according to claim 4, characterized in that: In the step three, the pressure applied between the TFT circuit substrate and the top substrate is 20N.

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