A perovskite-based X-ray direct imaging detector structure with separated light and dark currents

Abstract

The present invention provides a perovskite-based X-ray direct imaging detector structure for separating light and dark currents. The structure comprises a plurality of electrode units arranged in an array, wherein the electrode unit comprises a substrate, a TFT substrate, a pixel electrode, electrodes 1 and 2 for providing a transverse electric field, a perovskite material, and a packaging structure. To address the mixed output of dark current and photocurrent in conventional perovskite devices, a dual-electrode structure that provides a differentiated electric field is added to the top surface of the TFT device, effectively separating dark current from photocurrent, thereby improving the sensitivity and response of the X-ray detector. Furthermore, the packaging structure is added to improve the operational stability of the X-ray detector.

Description

Technical Field

[0001] The present invention relates to the field of radiation detection, and in particular to a perovskite-based X-ray direct imaging detector structure for separating light and dark currents. Background Art

[0002] Metal halide perovskites, due to their strong X-ray absorption and high sensitivity, are expected to become the core technology for direct imaging detectors in next-generation digital photography systems. The low-temperature deposition process facilitates the large-scale deposition of perovskites on TFT (thin-film transistor) substrates, creating a large-area and flexible device that can accommodate a wider range of medical applications.

[0003] However, the high dark current of perovskite materials has hindered their application in X-ray imaging devices. First, the high dark current quickly fills the TFT storage capacitor, causing the actual detection information to be overwhelmed by noise. Furthermore, large dark currents significantly increase transient noise, resulting in a poor signal-to-noise ratio (SNR). Recently, numerous studies have explored methods to reduce dark current, including doping and heterojunction schemes.

[0004] Experiments have found that for traditional two-terminal perovskite devices, increasing the bias voltage will increase the photocurrent of the perovskite material in response to X-rays, thereby increasing the sensitivity of the device. However, the dark current will also increase at the same time. An ideal device should have a large signal-to-noise ratio (SNR), so the target dark current should be as low as possible. It can be seen that in two-terminal perovskite devices, dark current and sensitivity are a coupled contradiction. In conventional devices, when the X-ray energy is relatively small, the photocurrent is overwhelmed by the dark current. In order to improve the response, by increasing the bias voltage, the signal amount increases, and the dark current also increases accordingly. Therefore, it is necessary to separate the dark current and the photocurrent to effectively improve the sensitivity of the X-ray direct detector. Summary of the Invention

[0005] In response to the above-mentioned problems or shortcomings, the present invention provides a four-terminal device to solve the dark current modulation problem of perovskite-based X-ray detectors.

[0006] To achieve the above objectives, the present invention provides a perovskite-based X-ray direct imaging detector structure that separates light and dark currents. The specific technical solution is as follows:

[0007] The detector structure includes N×M electrode units arranged in an array, and the electrode unit includes a substrate, a TFT substrate, an electrode layer, a perovskite material, a top electrode, and a packaging layer; the cross-sectional view of the electrode unit is as follows Figure 1As shown, the upper surface of the substrate is a TFT substrate. The TFT substrate uses a buffer layer as a base, and the upper surface of the buffer layer is an intermediate insulating layer. The active layer is embedded on the left side of the intermediate insulating layer. Above the active layer are a source electrode, a gate dielectric layer, and a drain electrode. The source and drain electrodes are located on the left and right sides of the gate dielectric layer. Above the gate dielectric layer is a gate electrode, forming a capacitor structure, and the potential is connected through a gate-source electrode wire; the gate electrode, source electrode, and drain electrode protrude from the upper surface of the intermediate insulating layer; the upper surface of the TFT substrate is made level with the portion of the source and drain electrodes in the TFT substrate protruding from the intermediate insulating layer by coating and leveling a photosensitive PI material; the TFT substrate is connected to the pixel electrode through the potential to form a TFT device.

[0008] The upper surface of the TFT substrate is an electrode layer, which includes a pixel electrode, a lateral electric field definition structure, electrode 1, and electrode 2; the thickness of the lateral electric field definition structure is greater than the thickness of the pixel electrode; the thickness of the lateral electric field definition structure is greater than the thickness of the pixel electrode; the lateral electric field definition structure is symmetrical on the left and right sides of the pixel electrode; electrodes 1 and 2 are deposited on the upper surface of the lateral electric field definition structure or multiple surfaces except the side and bottom surfaces, and the pixel electrodes, electrodes 1, and electrodes 2 do not contact each other; the side of the lateral electric field definition structure close to the pixel electrode has a slope structure, and according to different slope angles, there are rectangles, right-angled trapezoids, and pentagons.

[0009] The upper surface of the electrode layer and the space between the electrode layers of the electrode unit are made of perovskite material, such as Figure 4 As shown; the perovskite material is attached to the upper surface of the electrode layer and between the electrode units by scraping or spraying.

[0010] The upper surface of the perovskite material is the top electrode, and the upper surface of the top electrode is the encapsulation layer.

[0011] As a preferred embodiment, the substrate may be a glass substrate or a PI (polyimide) substrate;

[0012] As a preferred embodiment, the pixel electrode material may be an ITO / Ag / ITO multilayer structure, an ITO single layer structure, or a Zn2O3 / ITO oxide multilayer structure.

[0013] As a preferred embodiment, the electrodes 1 and 2 are single-layer metal materials (Ag, Al, Au, Pt, etc.) or multi-layer metal materials (Ti / Al, Ti) with high electrical conductivity.

[0014] As a preferred embodiment, the perovskite material is lead halide perovskite (ABX3), the A-site element includes Cs, MA or FA, the B-site element is Pb, and the X-site element is I or Br.

[0015] As a preferred method, the top electrode is usually made of highly conductive metal materials (Al, Ag, Au, Pt), nanocomposite materials (nano-Ag wires, carbon nanotubes), multilayer metal materials (ITO-Ag-ITO), and the like.

[0016] As a preferred method, perovskite materials usually absorb water and oxygen, and an encapsulation layer is prepared on the top electrode to block water and oxygen, wherein the encapsulation layer is an inorganic layer material, or an inorganic layer / organic layer / inorganic layer multilayer structure, wherein the inorganic layer is SiN, SIO material, and the organic layer is a high molecular polymer material.

[0017] The present invention also provides a novel perovskite-based X-ray direct imaging detector, which includes the above-mentioned perovskite-based X-ray direct imaging detector structure for separating light and dark current.

[0018] Compared with conventional direct X-ray detectors, the detector provided by the present invention adds electrodes 1 and 2 for modulating the dark current magnitude and sensitivity received by the pixel electrode (ITO).

[0019] The beneficial effects of the present invention are as follows:

[0020] 1. When the potential of the pixel electrode (ITO) and the top electrode does not change, a differential electric field can be applied between electrodes 1 and 2 to introduce dark current into the lateral electrode, and the photogenerated current is diverted through the pixel electrode, thus achieving separation of dark current and photogenerated current;

[0021] 2. Under the action of the transverse electric field generated by electrodes 1 and 2, the number of photogenerated carriers is increased, thereby effectively improving the sensitivity of the X-ray direct detector. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] Figure 1 This is a typical cross-sectional structural diagram of the electrode unit of the present invention.

[0023] Figure 2 This is a structural diagram of the electrode unit of the present invention as an inclined electrode.

[0024] Figure 3 This is a structural diagram of the electrode unit of the present invention being a planar electrode.

[0025] Figure 4 This is a top view of the electrode layer of the present invention. DETAILED DESCRIPTION

[0026] Example 1

[0027] In the usual process, the electrodes have a certain tilt angle. Therefore, the electrode shapes that can be manufactured by electrodes 1 and 2 in the electrode unit are as follows: Figure 2 shown.

[0028] From the bottom up, there are substrate, TFT substrate, electrode layer, perovskite material layer, top electrode, and encapsulation layer;

[0029] The substrate is a glass substrate with a planar structure having a bearing function, and the upper surface of the glass substrate is a TFT substrate;

[0030] The TFT substrate uses a buffer layer as a base. The buffer layer is a multi-layer inorganic layer structure (SiNx (40nm) / Si (15A) / SiO (40nm)), which is used to prevent the substrate conductive ions from diffusing into the TFT substrate and affecting the performance of the TFT substrate.

[0031] The upper surface of the buffer layer is an intermediate insulating layer, and the active layer is embedded in the left side of the intermediate insulating layer. Above the active layer are the source, gate dielectric layer, and drain. The source and drain are located on the left and right sides of the gate dielectric layer (GI layer). Above the gate dielectric layer is the gate, forming a capacitor structure, and the potential is connected through the SD (gate-source electrode) wire; the gate, source, and drain protrude from the upper surface of the intermediate insulating layer; the upper surface of the TFT substrate is made level with the part of the source and drain protruding from the intermediate insulating layer in the TFT substrate by coating and leveling photosensitive PI (polyimide) material; the TFT substrate is connected to the pixel electrode through the potential to form a TFT device.

[0032] The upper surface of the TFT substrate is an electrode layer, which includes a pixel electrode, a transverse electric field definition structure, electrode 1, and electrode 2. The thickness of the transverse electric field definition structure is greater than that of the pixel electrode. The transverse electric field definition structure has a slope structure on the left and right sides of the pixel electrode, and the edges close to the pixel electrode have no contact with each other. The transverse electric field definition structure is a pentagon. Electrodes 1 and 2 deposited on the transverse electric field definition structure cover the three sides of the pentagon except the bottom and outer edges, forming a three-segment structure. The material of electrode 1 and electrode 2 is 100nm Ag. The pixel electrode is used to receive the photocurrent signal, and the electrode material is a 100nm Zn2O3 / ITO double-layer structure.

[0033] The perovskite material is prepared on the pixel electrode, electrode 1, and electrode 2 by scraping or spraying, wherein the perovskite material is specifically 50 μm MAPbI3.

[0034] The top electrode is located on the perovskite material and uses 1μm Ag electrode material;

[0035] 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.

[0036] Electrode 1 (+10V), electrode 2 (+12V), the top electrode 0V, and the pixel electrode 1V can be set; relative to the top electrode voltage, the voltages of electrodes 1 and 2 are greater than the pixel electrode voltage, and dark current flows to electrodes 1 and 2. Typically, the pixel electrode area is 100μm*100μm, much larger than electrodes 1 and 2 (5μm*5μm). At the pixel electrode interface, photogenerated carriers are received by the pixel electrode, achieving separation of dark current and photogenerated current, reducing pixel electrode noise.

[0037] Example 2

[0038] The electrode unit of this embodiment is as follows Figure 3 As shown, electrodes 1 and 2 are parallel plane electrode structures, which are easier to manufacture in actual processes.

[0039] From the bottom up, there are substrate, TFT substrate, electrode layer, perovskite material layer, top electrode, and encapsulation layer;

[0040] The substrate is a glass substrate with a planar structure having a bearing function, and the upper surface of the glass substrate is a TFT substrate;

[0041] The TFT substrate uses a buffer layer as a base. The buffer layer is a multi-layer inorganic layer structure (SiNx (40nm) / Si (15A) / SiO (40nm)), which is used to prevent the substrate conductive ions from diffusing into the TFT substrate and affecting the performance of the TFT substrate.

[0042] The upper surface of the buffer layer is an intermediate insulating layer, the active layer is embedded in the left side of the intermediate insulating layer, and the source, gate, and drain are located above the active layer; the gate and the active layer are isolated by the GI layer (gate dielectric layer) to form a capacitor structure, the source and drain are located on the left and right sides of the gate, and are connected to the potential through the SD (gate-source electrode) wire; the gate, source, and drain protrude from the upper surface of the intermediate insulating layer; the upper surface of the TFT substrate is made level with the part of the source and drain protruding from the intermediate insulating layer in the TFT substrate by coating and leveling photosensitive PI (polyimide) material; the TFT substrate is connected to the pixel electrode through the potential to form a TFT device.

[0043] The upper surface of the TFT substrate is an electrode layer, including a pixel electrode, a lateral electric field definition structure, and electrodes 1 and 2 deposited on the lateral electric field definition structure to provide lateral electrodes, where the material of electrodes 1 and 2 is 100nm Ag; the lateral electric field definition structure is on both sides of the pixel electrode and is a rectangular structure; electrodes 1 and 2 are deposited on part of the upper surface of the lateral electric field definition structure; the pixel electrode is used to receive photocurrent signals, and the electrode material is an ITO single-layer structure.

[0044] The perovskite material is prepared on the pixel electrode, electrode 1, and electrode 2 by scraping or spraying, wherein the perovskite material is specifically 50 μm MAPbI3.

[0045] The top electrode is located on the perovskite material and uses 1μm Ag electrode material;

[0046] 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.

[0047] Electrode 1 (+20V), electrode 2 (+22V), the top electrode at 0V, and the pixel electrode at 2V can be set; relative to the top electrode voltage, the voltages of electrodes 1 and 2 are greater than the pixel electrode voltage, and dark current flows to electrodes 1 and 2. Typically, the pixel electrode area is 80μm*80μm, much larger than electrodes 1 and 2 (8μm*8μm). At the pixel electrode interface, photogenerated carriers are received by the pixel electrode, achieving separation of dark current and photogenerated current, reducing pixel electrode noise.

[0048] Figure 4 From the top view of the electrode layer of the detector structure provided in this embodiment, it can be seen that in the electrode layer, perovskite material is filled between each electrode unit; in terms of process, the perovskite material is prepared on the pixel electrode, electrode 1, electrode 2 and around the electrode layer by scraping or spraying. The upper surface of the perovskite material is the top electrode, and an encapsulation layer is prepared on the upper surface of the top electrode to block water and oxygen.

[0049] It will be understood that the present invention is described by way of some embodiments, and it will be appreciated by 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 to the specific embodiments disclosed herein, and all embodiments falling within the scope of the claims of this application are intended to be protected by the present invention.

Claims

1. A perovskite-based X-ray direct imaging detector structure for separating light and dark currents, characterized in that: The detector structure includes N×M electrode units arranged in an array, and the electrode unit includes a substrate, a TFT substrate, an electrode layer, a perovskite material, a top electrode, and an encapsulation layer; Wherein, the upper surface of the substrate is a TFT substrate, and the upper surface of the TFT substrate is an electrode layer; The electrode layer includes a pixel electrode, a transverse electric field defining structure, an electrode 1, and an electrode 2; the thickness of the transverse electric field defining structure is greater than the thickness of the pixel electrode; the transverse electric field defining structure is symmetrical on the left and right sides of the pixel electrode; the electrode 1 and the electrode 2 are deposited on the upper surface or multiple surfaces except the side and bottom surfaces of the transverse electric field defining structure, and the pixel electrode, the electrode 1, and the electrode 2 are not in contact with each other; the voltage between the electrode 1 and the electrode 2 is greater than the voltage of the pixel electrode; The upper surface of the electrode layer and between the electrode layers of the electrode unit are formed by perovskite material; the upper surface of the perovskite material is the top electrode, and the upper surface of the top electrode is the encapsulation layer.

2. The perovskite-based X-ray direct imaging detector structure for separating light and dark current according to claim 1, characterized in that: The side of the transverse electric field defining structure close to the pixel electrode has a slope structure, which has a rectangular, right-angled trapezoidal, or pentagonal shape according to different slope angles.

3. The perovskite-based X-ray direct imaging detector structure for separating light and dark current according to claim 1, characterized in that: The perovskite material is attached to the upper surface of the electrode layer and between the electrode layers of the electrode unit by scraping or spraying.

4. The perovskite-based X-ray direct imaging detector structure for separating light and dark current according to claim 1, characterized in that: The TFT substrate uses a buffer layer as a base, the upper surface of the buffer layer is an intermediate insulating layer, the active layer is embedded on the left side of the intermediate insulating layer, and above the active layer are a source electrode, a gate dielectric layer, and a drain electrode. The source and drain electrodes are located on the left and right sides of the gate dielectric layer. Above the gate dielectric layer is a gate electrode, forming a capacitor structure, and the potential is connected through a gate-source electrode wire; the gate electrode, source electrode, and drain electrode protrude from the upper surface of the intermediate insulating layer; the upper surface of the TFT substrate is made level with the portion of the source and drain electrodes in the TFT substrate that protrudes from the intermediate insulating layer by coating and leveling a photosensitive PI material; the TFT substrate is connected to the pixel electrode through the potential to form a TFT device.

5. The perovskite-based X-ray direct imaging detector structure for separating light and dark current according to claim 1, characterized in that: The substrate is a glass substrate or a polyimide substrate.

6. The perovskite-based X-ray direct imaging detector structure for separating light and dark current according to claim 1, characterized in that: The material of the pixel electrode is ITO / Ag / ITO multilayer structure, ITO single layer structure, Zn2O3 / ITO oxide multilayer structure; the electrode 1 and the electrode 2 are metal single layer materials with high conductivity, specifically Ag, Al, Au, Pt; or multilayer metal materials, specifically Ti / Al, Ti.

7. The perovskite-based X-ray direct imaging detector structure for separating light and dark current according to claim 1, characterized in that: The perovskite material is lead halide perovskite ABX3, the A-site element includes Cs, MA or FA, the B-site element is Pb, and the X-site element is I or Br.

8. The perovskite-based X-ray direct imaging detector structure for separating light and dark current according to claim 1, characterized in that: The material of the top electrode is a highly conductive metal material, a nanocomposite material or a multilayer metal material.

9. The perovskite-based X-ray direct imaging detector structure for separating light and dark current according to claim 1, characterized in that: The encapsulation layer is an inorganic layer single layer structure or an inorganic layer / organic layer / inorganic layer multilayer structure, wherein the inorganic layer is SiN, SiO material, and the organic layer is a high molecular polymer material.

10. A novel perovskite-based X-ray direct imaging detector, characterized in that: The detector includes a perovskite-based X-ray direct imaging detector structure for separating light and dark current as described in any one of claims 1 to 9.

Images