Hybrid perovskite-based X-ray imaging detector device and preparation method thereof

Abstract

The invention provides a mixed perovskite-based X-ray imaging detector device and a preparation method, and relates to the field of radiation detection. On the basis of preparing the porous perovskite thin film, the filling material is prepared, the composite perovskite structure is formed, and the transverse electrode structure is used, so that the light current transversely and alternately flows through the perovskite material and the filling material, the stability of the perovskite device is improved, and the leakage current of the perovskite device is reduced.

Description

Technical Field

[0001] The present invention relates to the field of radiation detection, and in particular to a hybrid perovskite-based X-ray imaging detector device and a preparation method thereof. Background Art

[0002] Metal halide perovskites are used as the technical core of the next generation of direct imaging detector digital photography systems due to their high X-ray absorption rate and high sensitivity. Their low-temperature deposition process is conducive to the large-area deposition of perovskites on TFT substrates (thin film transistors), forming large areas and flexibility, which can cope with more flexible medical application scenarios.

[0003] However, the high dark current of perovskite photodetectors has largely hindered the application of X-ray imaging devices. First, the high dark current will quickly fill the TFT storage capacitor, causing the actual detection information to be submerged by noise. In addition, the larger dark current will significantly increase the transient noise, resulting in a poor signal-to-noise ratio (SNR). Recently, many literatures have studied methods to reduce dark current, including doping, heterojunction and other solutions.

[0004] In addition, many tiny defect states are prone to occur during the preparation of perovskites, and these defect states will form conductive paths when an electric field is applied. From the perspective of electrical characteristics, single-layer perovskite devices will produce a large leakage current. In order to reduce the leakage current, the film quality of the thick film will be improved during the process, and the density of the thick film will be improved, but it cannot be completely improved in the end. In order to overcome the technical difficulties of leakage current, the industry needs to explore new processes and solutions for improvement. Summary of the invention

[0005] In view of the above problems or shortcomings, the present invention provides a hybrid perovskite-based X-ray imaging detector device and a preparation method to solve the problems of high dark current and device stability of perovskite-based X-ray detectors. The technical solution adopted by the present invention is:

[0006] like Figure 1 As shown, the structure of a hybrid perovskite-based X-ray imaging detector device includes a pixel unit, and the pixel unit includes a substrate, a TFT substrate, a pixel layer, a perovskite hybrid layer, a top electrode, and an encapsulation layer.

[0007] The substrate is a PI substrate, and the upper surface of the PI substrate is a buffer layer, which is a multi-layer inorganic layer structure (SiN, SiO, Si), used to prevent the conductive ions of the substrate from diffusing into the TFT device and affecting the performance of the TFT device;

[0008] The upper surface of the buffer layer is a TFT substrate, and the upper surface of the TFT substrate is a pixel electrode and a pixel definition layer; the TFT substrate includes a thin film transistor and a planarization layer PLN;

[0009] The pixel definition layer defines the area of ​​the pixel electrode; in a pixel unit, the pixel definition layer wraps the pixel electrode, that is, the pixel definition layer is located outside the pixel electrode, the pixel electrode includes a first pixel electrode and a second pixel electrode, the first pixel electrode and the second pixel electrode are not in contact with each other and are located in the same plane; between the first pixel electrode and the second pixel electrode is a perovskite mixed layer; the pixel electrode is generally an ITO transparent electrode or a metal electrode (Al, Cu, Ni, etc.);

[0010] The thin film transistor turns on the first pixel electrode, and current flows from the first pixel electrode to the second pixel electrode through the perovskite mixed layer.

[0011] The pixel definition layer and the pixel electrode are placed above the perovskite mixed layer. The perovskite material is prepared on the PI-δ-ABX3 film by scraping or spraying, wherein the perovskite material is specifically 1μm MAPbI3.

[0012] The first perovskite material exhibits non-uniform distribution and is prepared by spin coating, spray coating, scraping coating, etc. It has a porous microstructure with a pore diameter between 500nm and 2μm.

[0013] The filling layer is located above the perovskite layer, and fills the porous structure of the perovskite to obtain a composite perovskite material.

[0014] The filling material is a metal oxide material or a second perovskite material.

[0015] Perovskite materials usually absorb water and oxygen, and an encapsulation layer is prepared on the top electrode to block water and oxygen. The encapsulation layer is 1μm SiN material.

[0016] The encapsulation layer is located on the filling material and is used to prevent water and oxygen from corroding the perovskite device.

[0017] like Figure 1 As shown, the filling material forms a metal oxide film by magnetron sputtering or solution method, and the metal oxide is generally zinc oxide, titanium oxide, aluminum oxide, etc. The metal oxide material is a filling intermittent structure.

[0018] like Figure 2 As shown, in one of the pixel units, the perovskite device is viewed from above, the filling material fills the porous area, and the porous structure is non-uniformly distributed.

[0019] like Figure 3 As shown in the figure, when the perovskite film is a dispersed structure, when metal oxide is used for filling, the structure changes to the opposite structure, and the pixel unit is as follows Figure 4 As shown, the filling layer is filled on the entire surface, and the perovskite is an isolated island structure.

[0020] Both of the above structures can realize the alternating structure of perovskite and filling layer in the lateral structure.

[0021] The hybrid perovskite-based X-ray imaging detector of the present invention has the following advantages: by filling materials in the perovskite structure, the stability of the perovskite device can be improved and the leakage current of the perovskite device can be reduced. Compared with the conventional structure, the current flows from the pixel electrode to another pixel electrode, which belongs to a new type of lateral structure. After repeated alternating structures of perovskite fillers, the leakage current of the detector is reduced and the stability of the detector is improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a typical hybrid perovskite-based X-ray imaging detector pixel unit structure diagram.

[0023] Figure 2 A top view of a typical hybrid perovskite-based X-ray imaging detection pixel unit.

[0024] Figure 3 It is a filling structure on a typical dispersed perovskite material.

[0025] Figure 4 A top view of a typical dispersed perovskite film filling structure pixel unit.

[0026] Figure 5 This is a scanning electron microscope image of a typical dispersed perovskite.

[0027] Figure 6 This is a graph showing the photoelectric response characteristics of a typical hybrid perovskite-based X-ray imaging detector.

[0028] Figure 7 This is a comparison of the dark state current stability of typical hybrid perovskite and ordinary structure. DETAILED DESCRIPTION

[0029] In order to make the structure and process of the present invention easy to understand, the present invention will be described in detail below in conjunction with the accompanying drawings and specific embodiments. The following embodiments are only used to further illustrate the present invention and do not limit the content of the invention itself. Technicians in this field can make some non-essential improvements and adjustments based on the present invention.

[0030] Example 1

[0031] A hybrid perovskite-based X-ray imaging detector device of this embodiment includes a pixel unit, and the structure of the pixel unit is, from bottom to top, a substrate, a TFT substrate, a pixel layer, a perovskite hybrid layer, and an encapsulation layer; wherein the pixel layer includes a pixel definition layer and a pixel electrode.

[0032] The substrate includes a PI (polyimide) substrate and a buffer layer. The upper surface of the PI substrate is a buffer layer, which is a multi-layer inorganic layer structure (SiN, SiO, Si) and is used to prevent the conductive ions of the substrate from diffusing into the TFT device and affecting the performance of the TFT device.

[0033] The upper surface of the substrate is a TFT substrate, which includes a thin film transistor and a PLN planarization layer.

[0034] The upper surface of the TFT substrate is a pixel layer; the pixel definition layer defines the area of ​​the pixel electrode; in a pixel unit, the pixel definition layer wraps the pixel electrode, that is, the pixel definition layer is located on the outside of the pixel electrode, the pixel electrode includes a first pixel electrode and a second pixel electrode, the first pixel electrode and the second pixel electrode do not contact each other and are located in the same plane; between the first pixel electrode and the second pixel electrode is a perovskite mixed layer; the pixel electrode is a 100nm ITO transparent electrode; it can also be a metal electrode (Al, Cu, Ni, etc.).

[0035] The TFT turns on the first pixel electrode, and current flows from the first pixel electrode to the second pixel electrode through the perovskite mixed layer.

[0036] Above the pixel layer is a perovskite mixed layer, which specifically includes a first perovskite material and a filling material; Figure 5 The typical polycrystalline structure of perovskite materials is shown, providing microstructure areas for filling materials, so that the polycrystalline structure and filling materials form a composite material. By preparing filling materials in the gaps in the perovskite film, a porous filling structure is formed, such as Figure 1 , Figure 2 As shown, the filling material is mixed in the first perovskite material and is non-uniformly distributed as a whole.

[0037] The preparation method of the perovskite mixed layer is as follows:

[0038] First, a perovskite precursor solution is prepared. In this embodiment, MAI (methyl ammonium iodide) and PbI2 (lead iodide) are first added to a solvent in a 1:1 molar ratio. The solvent is specifically 2400 μL DMF (dimethylformamide) and 400 μL DMSO (dimethyl sulfoxide). The ratio of DMF to DMSO solution is 6:1. After the configuration is completed, it is stirred for 6 hours by a magnetic stirrer until MAI and PbI2 are completely dissolved to obtain a high-concentration MAPbI3 (methylamine iodide) perovskite precursor solution with a concentration greater than or equal to 1.26 mol / L.

[0039] The perovskite precursor solution is then spin-coated on top of the pixel layer by setting the spin-coating speed. Here, low-speed spin coating is performed first, with the speed set to 1000 rpm for 20 seconds, and then high-speed spin coating is performed, with the speed set to 4000 rpm for 50 seconds.

[0040] The substrate with the spin-coated perovskite precursor solution was placed on a hot plate. The hot plate was quickly heated to 100°C in 10 seconds and heated on the hot plate for 10 minutes to obtain a perovskite film. The film morphology is as follows: Figure 5 As shown, it is a porous structure and the thickness of the perovskite film is 800nm.

[0041] A filling material is prepared on the perovskite film by a spraying process, with a thickness of 2 μm, to form a porous filling structure; the filling material is specifically the second perovskite material CsPbI3 (cesium lead triiodide); Figure 2 As shown, the filling material is non-uniformly distributed according to the porous perovskite, and the filling material is filled in the first perovskite material. In the case of two perovskite materials, the second perovskite material and the first perovskite material are different semiconductor types (N-type, P-type), forming a repeated periodic body heterojunction structure.

[0042] In order to reduce leakage current, in the same pixel unit, the TFT substrate turns on the first pixel electrode, and current flows from the first pixel electrode to the second pixel electrode. The current repeatedly passes through the first perovskite material and the filling material. The filling material passivates the perovskite material, thereby improving the stability of the perovskite material.

[0043] The upper surface of the perovskite mixed layer is the top electrode. Perovskite materials usually absorb water and oxygen. An encapsulation layer is prepared on the top electrode to block water and oxygen. The encapsulation layer is 1μm SiN x Material.

[0044] In the above preparation method, the film can be controlled to have a porous structure or an isolated island structure by adjusting the solution concentration and the rotation speed.

[0045] Example 2

[0046] A hybrid perovskite-based X-ray imaging detector and a preparation method of this embodiment are different from those of Embodiment 1 in that, in the perovskite mixed layer, the first perovskite material is in an island structure. The specific preparation method is as follows:

[0047] The MAPbI3 perovskite precursor solution was prepared by the same steps. By changing the rotation speed, the first perovskite material can be controlled from a porous structure to an island structure. Specifically, the low speed was set to 1000 rpm for 20 seconds and the high speed was set to 3000 rpm for 50 seconds. The substrate with the spin-coated perovskite solution was then heated on a hot plate for 10 minutes to obtain a perovskite film. The morphology of the dispersed perovskite film is shown in FIG. Figure 4 As shown, the perovskite film is specifically 1μm MAPbI3.

[0048] Filling is performed on the first perovskite material, and a 1μm ZnO film is prepared by magnetron sputtering to form a filling structure. The specific filling method is as follows:

[0049] The process uses magnetron sputtering, and the equipment is first vacuumed to 1E -4 Pa to ensure the purity of the vacuum chamber environment; then the sputtering gas is Ar or O2, the flow ratio is set to 20 sccm:5 sccm, and 99.99% pure intrinsic zinc oxide is used as the target material, the sputtering power is set to 150 W, the sputtering pressure is set to 1 Pa, and the sputtering time is set to 4 h.

[0050] like Figure 3 As shown in the figure, when the perovskite film is a dispersed structure, when metal oxide is used for filling, the structure changes to the opposite structure, and the pixel unit is as follows Figure 4 As shown, the filling layer is filled on the entire surface, and the perovskite is an isolated island structure. When the first perovskite material is an isolated island structure, the perovskite imaging is dispersed, and the current on the perovskite cannot be conducted from any point to another point. It needs to be filled before it can be conducted from any point to another point.

[0051] like Figure 6 As shown, this is the photoelectric response curve of the perovskite device prepared in this embodiment. It can be seen that the dark state current has good stability. Under multiple X-ray radiation tests, the dark current is close to 0PA and remains stable. At the same time, the photocurrent is stable when X-rays are radiated.

[0052] like Figure 7 As shown, the conventional structure has a dark current stabilization time, which usually takes 60 seconds. It can be seen from the improved structure obtained by the present invention that the dark current has stabilized before 10 seconds.

[0053] It is to be understood that the present invention is described by some embodiments, and it is known to those skilled in the art that various changes or equivalent substitutions may be made to these features and embodiments without departing from the spirit and scope of the present invention. In addition, under the teachings of the present invention, these features and embodiments may be modified to adapt to specific circumstances and materials without departing from the spirit and scope of the present invention. Therefore, the present invention is not limited by the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are within the scope of protection of the present invention.

Claims

1. A hybrid perovskite-based X-ray imaging detector device, comprising a pixel unit, characterized in that: The structure of the pixel unit includes a thin film transistor (TFT) substrate, a pixel layer, a perovskite mixed layer, a top electrode, and an encapsulation layer; The TFT substrate includes a thin film transistor TFT and a planarization layer; The upper surface of the TFT substrate is a pixel layer, including a pixel definition layer and a pixel electrode, and the pixel definition layer defines the area of ​​the pixel electrode; in a pixel unit, the pixel definition layer wraps the pixel electrode inside, that is, the pixel definition layer is located outside the pixel electrode, and the pixel electrode includes a first pixel electrode and a second pixel electrode, and the first pixel electrode and the second pixel electrode do not contact each other and are located in the same plane; between the first pixel electrode and the second pixel electrode is a perovskite mixed layer; when the TFT turns on the first pixel electrode, current flows from the first pixel electrode to the second pixel electrode through the perovskite mixed layer; Above the pixel layer is a perovskite mixed layer, which specifically includes a first perovskite material and a filling material; The first perovskite material has a porous structure, and the filling material fills the gaps in the first perovskite material; the first perovskite material and the filling material are made of different materials; The upper surface of the perovskite mixed layer is the top electrode, and the upper surface of the top electrode is the encapsulation layer.

2. A hybrid perovskite-based X-ray imaging detector device according to claim 1, characterized in that: The first perovskite material is an island structure, and the perovskite materials are not conductive; the filling material fills and covers the gaps in the first perovskite material.

3. A hybrid perovskite-based X-ray imaging detector device according to claim 2, characterized in that: The filling material is a second perovskite material or a metal oxide. The first perovskite material and the second perovskite material are different semiconductor types, including N-type and P-type, forming a repeated periodic body heterojunction structure.

4. A method for preparing a hybrid perovskite-based X-ray imaging detector device according to any one of claims 1 to 3, characterized in that: The preparation method of the porous structure is as follows: Obtain a first perovskite precursor solution with a concentration greater than or equal to 1.26 mol / L; then spin-coat the first perovskite precursor solution on the pixel layer, set the spin-coating speed, first spin-coat at a low speed of 1000 rpm for 20 seconds, then spin-coat at a high speed of 4000 rpm for 50 seconds; place the substrate on which the perovskite precursor solution has been spin-coated on a hot plate, quickly heat the hot plate to 100° C. in 10 seconds, and heat on the hot plate for 10 minutes to obtain a first perovskite material with a porous structure; The isolated island structure is obtained by adjusting the solution concentration and the spin coating speed.

5. The method for preparing a hybrid perovskite-based X-ray imaging detector device according to claim 4, characterized in that: When preparing the isolated island structure, the low speed was set to 1000 rpm, the time was 20 s, and the high speed was set to 3000 rpm, the time was 50 s.

6. The method for preparing a hybrid perovskite-based X-ray imaging detector device according to claim 5, characterized in that: When the filling material is the second perovskite material, the gaps in the first perovskite material are filled by a spraying process; when the filling material is a metal oxide, the gaps in the first perovskite material are filled by a magnetron sputtering process.

7. The method for preparing a hybrid perovskite-based X-ray imaging detector device according to claim 6, characterized in that: The metal oxides include zinc oxide, titanium oxide and aluminum oxide.

8. The method for preparing a hybrid perovskite-based X-ray imaging detector device according to claim 7, characterized in that: The process conditions of the magnetron sputtering are as follows: the equipment is evacuated to 1E -4 Pa, the sputtering gas is Ar or O2, the flow ratio is set to 20 sccm:5 sccm, and a metal oxide with a purity of 99.99% is used as the target material. The sputtering power is set to 150 W, the sputtering pressure is set to 1 Pa, and the sputtering time is set to 4 h.

9. The method for preparing a hybrid perovskite-based X-ray imaging detector device according to claim 8, characterized in that: The pixel electrode is an ITO transparent electrode or a metal electrode, and the metal electrode specifically includes Al, Cu, and Ni.

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