A perovskite nuclear radiation detector optimized through interface and its preparation method

Abstract

The present invention relates to a perovskite nuclear radiation detector optimized by an interface and a preparation method thereof, characterized in that: a LiF intermediate layer is provided on one side of the perovskite crystal, and a metal anode is above the LiF intermediate layer and forms a Schottky contact with the perovskite crystal; the other side of the perovskite crystal is a metal cathode and forms an ohmic contact with the perovskite crystal. By introducing a lithium fluoride (LiF) intermediate layer between the P-type perovskite crystal and the low-work-function metal anode, the surface of the perovskite crystal is passivated, avoiding diffusion or chemical reaction between the perovskite crystal and the metal, thereby reducing the density of interface defect states, improving the charge collection efficiency of the detector, and at the same time, the LiF intermediate layer increases the Schottky barrier height at the interface, reduces the leakage current of the detector, and thus improves the energy resolution ability of the detector for charged particles and high-energy rays.

Description

Technical Field

[0001] The present invention belongs to the field of semiconductor nuclear radiation detection, and relates to a perovskite nuclear radiation detector optimized by interface and a preparation method thereof, that is, a method for improving the performance of a perovskite nuclear radiation detector by interface optimization. Background Art

[0002] The halide perovskite crystal material with the AMX3 structure has been a research hotspot in the field of nuclear radiation detection in recent years. The excellent properties of this type of perovskite material can meet the requirements of room-temperature nuclear radiation detectors for materials. For example, a relatively high atomic number can achieve better detection efficiency, a suitable band gap enables it to be used at room temperature, excellent carrier transport performance ensures its collection efficiency and energy resolution, and it has the characteristics of high defect tolerance and easy low-cost preparation, showing great application potential in the field of high-energy ray detection. However, the resistivity of the currently prepared halide perovskite crystal material is not high enough (usually less than 5×10 9 Ω·cm), and its strong ionic crystal characteristics will cause ion migration phenomena under high working bias voltages, and a junction-type detector needs to be prepared to improve the working stability and detection performance of the detector under high electric fields. In addition, interface defects of the detector will lead to a large leakage current of the detector, as well as an increase in the recombination and capture probabilities of electron-hole pairs at the interface, resulting in a decrease in the charge collection efficiency and deterioration of the detector's performance, and the performance of the detector still fails to meet the requirements of practical applications.

[0003] Document 1 "Li L, Liu X, Zhang H, et al. Enhanced X-ray Sensitivity of MAPbBr3 Detector by Tailoring the Interface-States Density. [J]. ACS applied materials & interfaces, 2019, 11: 7522-7528." discloses a method for preparing a PN junction type MAPbBr3 perovskite detector by magnetron sputtering and regulating the interface defect state density by annealing treatment. However, the leakage current of the detector is still relatively large, which is not conducive to achieving energy resolution for charged particles and high-energy rays. At the same time, the preparation and annealing processes of the N-type AZO electrode are complex, and the annealing temperature of 100 °C is higher than the phase transition temperature of the CsPbBr3 crystal and cannot be applied to the interface optimization of the CsPbBr3 detector.

[0004] Reference 2, "Pan L, Feng Y, Huang J, et al. Comparison of Zr, Bi, Ti, and Ga as Metal Contacts in Inorganic Perovskite CsPbBr3 Gamma-Ray Detector [J]. IEEE Transactions on Nuclear Science, 2020, 67(10): 2255 - 2262." discloses a method of using a low work function metal to form a Schottky contact with CsPbBr3 to improve the detector performance. However, this method does not consider the influence of detector interface defects on the Schottky contact and nuclear radiation detection performance. In addition to a large number of dangling bonds and defects existing on the crystal surface itself, interface defects will also be introduced during the detector preparation process, such as diffusion or chemical reactions between the electrode metal and the perovskite, and defects caused by ion bombardment or high temperature during the deposition process of the electrode material. Summary of the Invention

[0005] Technical Problems to be Solved

[0006] In order to avoid the deficiencies of the prior art, the present invention proposes a perovskite nuclear radiation detector and a preparation method through interface optimization, which solve the technical problems of high leakage current and large interface defect state density during the application process of current perovskite nuclear radiation detectors.

[0007] Technical Solution

[0008] A perovskite nuclear radiation detector through interface optimization, characterized in that: a LiF intermediate layer is provided on one side of the perovskite crystal, and above the LiF intermediate layer is a metal anode which forms a Schottky contact with the perovskite crystal 3; the other side of the perovskite crystal is a metal cathode which forms an ohmic contact with the perovskite crystal 3.

[0009] The thickness of the LiF intermediate layer is 5 - 40 nm.

[0010] The thickness of the metal anode is 60 - 80 nm.

[0011] The thickness of the metal cathode is 40 - 90 nm.

[0012] The metal anode is a low work function metal, which is indium In, aluminum Al, tin Sn or gallium Ga.

[0013] The metal cathode is a high work function metal, which is gold Au, platinum Pt or chromium Cr.

[0014] A method for preparing the performance of the perovskite nuclear radiation detector through interface optimization, characterized in that the steps are as follows:

[0015] Step 1: Prepare the LiF interlayer 2 on one side of the perovskite crystal 3: Using the method of vacuum evaporation, during evaporation, the vacuum degree is maintained below 5×10 -3 Pa, the evaporation boat is a tungsten boat of model #308, the evaporation current is 25 - 40 A, the evaporation material is LiF crystal particles or powder, and the mass of the evaporation material is 0.3 - 3.0 mg to obtain the LiF interlayer;

[0016] Step 2: Above the LiF interlayer 2, select a low work function metal and use the vacuum evaporation method or sputtering method to prepare the metal anode 1 to form a Schottky contact with the perovskite crystal 3;

[0017] Step 3: On the other side of the perovskite crystal 3, select a high work function metal and use the vacuum evaporation method or sputtering method to prepare the metal cathode 4;

[0018] Step 4: Use carbon paste to connect the metal cathode 4 to the S terminal of the ceramic-based PCB board, and connect the metal anode 1 to the G terminal of the ceramic-based PCB board for subsequent testing and use.

[0019] The preparation of the perovskite crystal is as follows: Use a P-type perovskite crystal 3, a CsPbBr3 all-inorganic perovskite crystal grown by the melt method or solution method, a MAPbBr3 organic-inorganic hybrid perovskite crystal grown by the solution method, or a FAPbBr3 organic-inorganic hybrid perovskite crystal grown by the solution method, and the crystal thickness is 1 - 5 mm.

[0020] Before the said Step 1, the surface of the perovskite crystal 3 is leveled and smoothed by mechanical grinding and polishing. Use SiC sandpapers of different grits to gradually grind and polish for 1 - 3 min in sequence of 3000#, 5000#, 7000#, and 9000# to make the surface of the perovskite crystal 3 flat and without a cutting damage layer. Then place the perovskite crystal 3 on a polishing cloth and use MgO powder with a particle size of about 50 nm as the abrasive for polishing, and gradually drop 1 - 2 ml of anhydrous ethanol until the surface of the perovskite crystal 3 is bright and without scratches.

[0021] After the said mechanical grinding and polishing method, soak the ground and polished perovskite crystal 3 in cyclohexane and ultrasonicate for 1 - 30 min to clean the MgO powder remaining on the surface of the perovskite crystal 3. Subsequently, place it in an ultraviolet ozone machine for 5 - 20 min to clean the organic substances attached to the surface of the perovskite crystal 3.

[0022] Beneficial effects

[0023] A perovskite nuclear radiation detector optimized by interface and its preparation method proposed by the present invention introduce a lithium fluoride (LiF) intermediate layer between the P-type perovskite crystal and the low work function metal anode to passivate the surface of the perovskite crystal, avoid diffusion or chemical reaction between the perovskite crystal and the metal, thereby reducing the density of interface defect states, improving the charge collection efficiency of the detector. At the same time, the LiF intermediate layer increases the Schottky barrier height at the interface, reduces the leakage current of the detector, and thus improves the energy resolution ability of the detector for charged particles and high-energy rays.

[0024] Mechanism of the present invention:

[0025] Introduce a LiF intermediate layer between the P-type perovskite crystal and the low work function metal anode. First, the evaporation temperature of LiF is low, which can protect the surface of the semiconductor material during the subsequent deposition process of the metal electrode, and the introduction of the LiF intermediate layer can prevent the diffusion of the metal to the semiconductor and the chemical reaction between the metal and the semiconductor. Second, LiF as an intermediate layer can change the barrier height and series resistance of the Schottky contact. This is because LiF molecules have a large dipole moment (6.33 D), and LiF molecules will be arranged orderly between the metal and the semiconductor, with Li + pointing to the semiconductor surface and F - pointing to the metal, resulting in a shift of the vacuum energy level between the metal and the semiconductor.

[0026] Advantages of the present invention:

[0027] 1. Aiming at the problems of large leakage current in perovskite nuclear radiation detectors and the deterioration of detector performance caused by interface defects, the present invention introduces an inorganic LiF intermediate layer as an interface optimization method. Compared with the existing method of introducing an organic transport layer, it has better environmental stability, low cost, and simple preparation method.

[0028] 2. The perovskite nuclear radiation detector obtained by optimizing the interface through the LiF intermediate layer of the present invention has a lower interface state density, can effectively reduce the carrier recombination and capture effects at the interface of the perovskite nuclear radiation detector, improve the carrier collection efficiency of the perovskite nuclear radiation detector. At the same time, the LiF intermediate layer increases the Schottky contact barrier height, reduces the leakage current of the perovskite nuclear radiation detector, and improves the energy resolution ability for charged particles and high-energy rays. After testing, for the CsPbBr3 perovskite nuclear radiation detector obtained by optimizing the interface through the LiF intermediate layer, at a high electric field strength of 1000 V·cm -1 , the leakage current decreased by 40.3%, and the current density was about 85.7 nA·cm -2 . For 241 the α particles of Am@5.48 MeV, the energy resolution reached 11.1%. For 241The energy resolution of γ-rays at 59.6 keV for Am reaches 27.1%, and for 137 the energy resolution of γ-rays at 662 keV for Cs reaches 12.2%. Description of the Drawings

[0029] Figure 1 is a schematic cross-sectional structure diagram of the perovskite nuclear radiation detector in the present invention; the meanings of the reference numerals in the figure are as follows: 1 is the metal anode, 2 is the LiF intermediate layer, 3 is the perovskite crystal, and 4 is the metal cathode.

[0030] Figure 2 is the binding energy spectrum diagram of In element in X-ray photoelectron spectroscopy; specifically, Figure 2 a in Figure 2 corresponds to the In / CsPbBr3 interface,

[0031] Figure 3 is the current-voltage curve diagram of the detector with and without the LiF intermediate layer under the condition of no light illumination.

[0032] Figure 4 is the conductance-frequency curve diagram of the detector with and without the LiF intermediate layer.

[0033] Figure 5 is the energy resolution spectrum diagram of the detector with and without the LiF intermediate layer for charged particles and high-energy rays; specifically, Figure 5 a in 241 corresponds to the α-particles of Am at 5.48 MeV, Figure 5 b in 241 corresponds to the γ-rays of Am at 59.6 keV, Figure 5 c in 137 corresponds to the γ-rays of Cs at 662 keV. Detailed Embodiments

[0034] The present invention will be further described below in conjunction with the embodiments and the drawings:

[0035] Embodiment 1

[0036] Step 1: Use a P-type solution-grown CsPbBr3 crystal with a size of 5×5×1 mm 3 .

[0037] Step 2: The surface of the CsPbBr3 crystal is flattened and smoothed by mechanical polishing. Use SiC sandpapers with different grit sizes to polish step by step for 1 - 3 minutes, in the order of 3000#, 5000#, 7000#, and 9000#, so that the surface of the CsPbBr3 crystal is flat and there is no cutting damage layer. Then place the CsPbBr3 crystal on the polishing cloth and polish it with MgO powder with a particle size of about 50 nm as the abrasive, and drop 1 - 2 ml of anhydrous ethanol successively until the surface of the CsPbBr3 crystal is bright and has no scratches.

[0038] Step 3: Immerse the polished CsPbBr3 crystal in cyclohexane and ultrasonicate for 10 minutes to wash the residual MgO powder on the surface of the CsPbBr3 crystal. Then place it in an ultraviolet ozone machine for 10 minutes to clean the organic matter attached to the surface of the CsPbBr3 crystal.

[0039] Step 4: Prepare a LiF intermediate layer on one side of the CsPbBr3 crystal by vacuum evaporation. The equipment is the SBC-2-1 type vacuum coating machine of Zhongke Keyi Co., Ltd. Use a square mask plate with a side length of 4 mm. During evaporation, the vacuum degree is maintained below 5×10 -3 Pa. The evaporation boat is a #308 type tungsten boat, the evaporation current is 30 A, the evaporation material is LiF crystal particles, the mass of the evaporation material is 2.0 mg, and the corresponding thickness of the LiF intermediate layer is 35 nm.

[0040] Step 5: Prepare a metal anode on the LiF intermediate layer to form a Schottky contact with the CsPbBr3 crystal. The metal anode is In, and the preparation method is vacuum evaporation. The equipment is the SBC-2-1 type vacuum coating machine of Zhongke Keyi Co., Ltd. Use a circular mask plate with a diameter of 2 mm. During evaporation, the vacuum degree is maintained below 5×10 -3 Pa, and the thickness is 80 nm.

[0041] Step 6: Prepare a metal cathode on the other side of the CsPbBr3 crystal to form an ohmic contact with the CsPbBr3 crystal. The metal cathode is Au, and the preparation method is vacuum evaporation. The equipment is the SBC-2-1 type vacuum coating machine of Zhongke Keyi Co., Ltd. Use a circular mask plate with a diameter of 2 mm. During evaporation, the vacuum degree is maintained below 5×10 -3 Pa, and the thickness is 80 nm, to obtain an In / LiF / CsPbBr3 / Au detector.

[0042] Step 7: Use carbon glue to connect the metal cathode to the S terminal of the ceramic-based PCB board and the metal anode to the G terminal of the ceramic-based PCB board for subsequent testing and use.

[0043] Example 2

[0044] Step 1: Use a CsPbBr3 crystal grown by the solution method of the P type, with dimensions of 5×5×1 mm 3 .

[0045] Step 2: Use mechanical grinding and polishing to level and smooth the surface of the CsPbBr3 crystal. Gradually polish for 1 - 3 minutes using SiC sandpapers of different grit sizes in the order of 3000#, 5000#, 7000#, and 9000# to make the surface of the CsPbBr3 crystal flat and without a cutting damage layer. Then place the CsPbBr3 crystal on a polishing cloth and polish it using MgO powder with a particle size of about 50 nm as the abrasive, and gradually drop 1 - 2 ml of anhydrous ethanol until the surface of the CsPbBr3 crystal is bright and without scratches.

[0046] Step 3: Immerse the polished CsPbBr3 crystal in cyclohexane and ultrasonicate for 10 minutes to wash away the residual MgO powder on the surface of the CsPbBr3 crystal. Then place it in an ultraviolet ozone machine for 10 minutes to clean the organic substances attached to the surface of the CsPbBr3 crystal.

[0047] Step 4: Prepare a LiF intermediate layer on one side of the CsPbBr3 crystal by vacuum evaporation. The equipment is the SBC - 2 - 1 type vacuum coating machine of Zhongke Keyi Company. Use a square mask plate with a side length of 4 mm. During evaporation, the vacuum degree is maintained below 5×10 -3 Pa. The evaporation boat is a #308 type tungsten boat, the evaporation current is 30 A, the evaporation material is LiF crystal particles, the mass of the evaporation material is 1.2 mg, and the corresponding thickness of the LiF intermediate layer is 22 nm.

[0048] Step 5: Prepare a metal anode on the LiF intermediate layer to form a Schottky contact with the CsPbBr3 crystal. The metal anode is In, and the preparation method is vacuum evaporation. The equipment is the SBC - 2 - 1 type vacuum coating machine of Zhongke Keyi Company. Use a circular mask plate with a diameter of 2 mm. During evaporation, the vacuum degree is maintained below 5×10 -3 Pa, and the thickness is 80 nm.

[0049] Step 6: Prepare a metal cathode on the other side of the CsPbBr3 crystal to form an ohmic contact with the CsPbBr3 crystal. The metal cathode is Au, and the preparation method is vacuum evaporation. The equipment is the SBC - 2 - 1 type vacuum coating machine of Zhongke Keyi Company. Use a circular mask plate with a diameter of 2 mm. During evaporation, the vacuum degree is maintained below 5×10 -3 Pa, and the thickness is 80 nm to obtain an In / LiF / CsPbBr3 / Au detector.

[0050] Step 7: Use carbon glue to connect the metal cathode to the S terminal of the ceramic-based PCB board and the metal anode to the G terminal of the ceramic-based PCB board for subsequent testing and use.

[0051] Example 3

[0052] Step 1: Use the solution method to grow CsPbBr3 crystals of P type, with a size of 5×5×1 mm 3 .

[0053] Step 2: Use mechanical grinding and polishing to level and smooth the surface of the CsPbBr3 crystal. Gradually polish for 1 - 3 minutes using SiC sandpapers of different grit sizes in the order of 3000#, 5000#, 7000#, and 9000# to make the surface of the CsPbBr3 crystal flat and without a cutting damage layer. Then place the CsPbBr3 crystal on the polishing cloth and use MgO powder with a particle size of about 50 nm as the abrasive for polishing, and gradually drop 1 - 2 ml of anhydrous ethanol until the surface of the CsPbBr3 crystal is bright and without scratches.

[0054] Step 3: Immerse the polished CsPbBr3 crystal in cyclohexane and ultrasonicate for 10 minutes to wash the residual MgO powder on the surface of the CsPbBr3 crystal. Then place it in an ultraviolet ozone machine for 10 minutes to clean the organic substances attached to the surface of the CsPbBr3 crystal.

[0055] Step 4: Prepare a LiF intermediate layer on one side of the CsPbBr3 crystal by vacuum evaporation. The equipment is the SBC - 2 - 1 type vacuum coating machine of Zhongke Keyi Co., Ltd. Use a square mask plate with a side length of 4 mm. Keep the vacuum degree below 5×10 -3 Pa during evaporation. The evaporation boat is a #308 type tungsten boat, the evaporation current is 30 A, the evaporation material is LiF crystal particles, the mass of the evaporation material is 0.3 mg, and the corresponding thickness of the LiF intermediate layer is 5 nm.

[0056] Step 5: Prepare a metal anode on the LiF intermediate layer to form a Schottky contact with the CsPbBr3 crystal. The metal anode is In, and the preparation method is vacuum evaporation. The equipment is the SBC - 2 - 1 type vacuum coating machine of Zhongke Keyi Co., Ltd. Use a circular mask plate with a diameter of 2 mm. Keep the vacuum degree below 5×10 -3 Pa during evaporation, and the thickness is 80 nm.

[0057] Step 6: Prepare a metal cathode on the other side of the CsPbBr3 crystal to form an ohmic contact with the CsPbBr3 crystal. The metal cathode is Au, and the preparation method is vacuum evaporation. The equipment is the SBC - 2 - 1 type vacuum coating machine of Zhongke Keyi Co., Ltd. Use a circular mask plate with a diameter of 2 mm. Keep the vacuum degree below 5×10-3 Below Pa, with a thickness of 80 nm, an In / LiF / CsPbBr3 / Au detector was obtained.

[0058] Step Seven: Use carbon glue to connect the metal cathode to the S terminal of the ceramic-based PCB board and the metal anode to the G terminal of the ceramic-based PCB board for subsequent testing and use.

[0059] Example 4

[0060] Step One: Use a P-type solution-grown MAPbBr3 crystal with dimensions of 5×5×2 mm 3 。

[0061] Step Two: Use mechanical polishing to flatten and smooth the surface of the MAPbBr3 crystal. Gradually polish for 1 - 3 minutes using SiC sandpapers of different grit sizes in the order of 3000#, 5000#, 7000#, and 9000# to make the surface of the MAPbBr3 crystal flat and without a cutting damage layer. Then place the MAPbBr3 crystal on a polishing cloth and polish it using MgO powder with a particle size of about 50 nm as the abrasive, and gradually drop 1 - 2 ml of anhydrous ethanol until the surface of the MAPbBr3 crystal is bright and without scratches.

[0062] Step Three: Immerse the polished MAPbBr3 crystal in cyclohexane and ultrasonicate for 10 minutes to wash away the residual MgO powder on the surface of the MAPbBr3 crystal. Then place it in an ultraviolet ozone machine for 10 minutes to clean the organic substances attached to the surface of the MAPbBr3 crystal.

[0063] Step Four: Prepare a LiF intermediate layer on one side of the MAPbBr3 crystal by vacuum evaporation. The equipment is the SBC-2-1 type vacuum coating machine of Zhongke Keyi Co., Ltd. Use a square mask plate with a side length of 4 mm. Keep the vacuum degree at 5×10 -3 Below Pa, the evaporation boat is a #308 type tungsten boat, the evaporation current is 30 A, the evaporation material is LiF crystal particles, the mass of the evaporation material is 0.8 mg, and the corresponding thickness of the LiF intermediate layer is 13 nm.

[0064] Step Five: Prepare a metal anode on the LiF intermediate layer to form a Schottky contact with the MAPbBr3 crystal. The metal anode is Al, and the preparation method is vacuum evaporation. The equipment is the SBC-2-1 type vacuum coating machine of Zhongke Keyi Co., Ltd. Use a circular mask plate with a diameter of 2 mm. Keep the vacuum degree at 5×10 -3 Below Pa, with a thickness of 80 nm.

[0065] Step 6: Prepare a metal cathode on the other side of the MAPbBr3 crystal to form an ohmic contact with the MAPbBr3 crystal. The metal cathode is Au, and the preparation method is vacuum evaporation. The equipment is the SBC-2-1 type vacuum coating machine of Zhongke Keyi Co., Ltd. A circular mask plate with a diameter of 2 mm is used. During evaporation, the vacuum degree is maintained below 5×10 -3 Pa, and the thickness is 80 nm, obtaining an Al / LiF / MAPbBr3 / Au detector.

[0066] Step 7: Use carbon paste to connect the metal cathode to the S terminal of the ceramic-based PCB board, and connect the metal anode to the G terminal of the ceramic-based PCB board for subsequent testing and use.

[0067] Comparative Example 1

[0068] Step 1: Use the In / LiF / CsPbBr3 / Au detector in Example 1.

[0069] Step 2: Use SiC sandpaper with a grit size of 9000# to remove the metal anode, metal cathode, and LiF intermediate layer on the surface of the detector. Then place the CsPbBr3 crystal on a polishing cloth and polish it with MgO powder with a particle size of about 50 nm as the abrasive, and gradually drop 1-2 ml of anhydrous ethanol until the surface of the CsPbBr3 crystal is bright and has no scratches.

[0070] Step 3: Immerse the polished CsPbBr3 crystal in cyclohexane and ultrasonically clean it for 10 min to wash away the residual MgO powder on the surface of the CsPbBr3 crystal. Then place it in an ultraviolet ozone machine for 10 min to clean the organic matter attached to the surface of the CsPbBr3 crystal.

[0071] Step 4: Prepare a metal anode on one side of the CsPbBr3 crystal to form a Schottky contact with the CsPbBr3 crystal. The metal anode is In, and the preparation method is vacuum evaporation. The equipment is the SBC-2-1 type vacuum coating machine of Zhongke Keyi Co., Ltd. A circular mask plate with a diameter of 2 mm is used. During evaporation, the vacuum degree is maintained below 5×10 -3 Pa, and the thickness is 80 nm.

[0072] Step 5: Prepare a metal cathode on the other side of the CsPbBr3 crystal to form an ohmic contact with the CsPbBr3 crystal. The metal cathode is Au, and the preparation method is vacuum evaporation. The equipment is the SBC-2-1 type vacuum coating machine of Zhongke Keyi Co., Ltd. A circular mask plate with a diameter of 2 mm is used. During evaporation, the vacuum degree is maintained below 5×10 -3 Pa, and the thickness is 80 nm, obtaining an In / CsPbBr3 / Au detector.

[0073] Step 6: Use carbon paste to connect the metal cathode to the S terminal of the ceramic-based PCB board and the metal anode to the G terminal of the ceramic-based PCB board for subsequent testing and use.

[0074] Test the In / LiF / CsPbBr3 / Au and In / CsPbBr3 / Au detectors in Example 1 and Comparative Example 1 respectively, and compare the X-ray photoelectron spectra, current-voltage characteristics, conductance-frequency characteristics, and nuclear radiation detection performance of the two detectors.

[0075] It can be seen from Figure 2 that in the In / CsPbBr3 / Au detector, there is an In-Br bond at the interface between In and the CsPbBr3 crystal at a higher binding energy, while there is no In-Br bond in the In / LiF / CsPbBr3 / Au detector, indicating that the LiF interlayer prevents the chemical reaction between the In electrode and the CsPbBr3 crystal.

[0076] It can be seen from Figure 3 that under the reverse bias conditions of the two devices, the leakage current of the In / LiF / CsPbBr3 / Au detector is significantly reduced, which is beneficial to reducing the noise of the nuclear radiation detector and improving the detection performance.

[0077] It can be seen from Figure 4 that the density of interface defect states of the In / LiF / CsPbBr3 / Au detector is significantly reduced, which is beneficial to improving the charge collection efficiency of the nuclear radiation detector and improving the detection performance.

[0078] It can be seen from Figure 5 that when the device operates under reverse bias conditions, charged particles and high-energy rays are incident on the anode of the detector. In the energy spectrum diagram, the full-energy peak channel address of the In / LiF / CsPbBr3 / Au detector is higher and the full-width at half-maximum is smaller, with better energy resolution ability. At room temperature, for 241 the energy resolution of the Am@5.48 MeV α particle is 11.1%, and for 241 the energy resolution of the Am@59.6 keV γ ray is 27.1%. For 137 the γ ray energy resolution of Cs@662 keV reaches 12.2%.

[0079] As mentioned above, the above is only the specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art within the technical scope disclosed by the present invention can easily think of various equivalent modifications or substitutions, and these modifications or substitutions should all be covered within the protection scope of the present invention.

Claims

1. A preparation method of a perovskite nuclear radiation detector optimized by interface, characterized in that: On one side of the perovskite crystal, there is a LiF intermediate layer, and above the LiF intermediate layer is a metal anode, which forms a Schottky contact with the perovskite crystal (3); on the other side of the perovskite crystal is a metal cathode, which forms an ohmic contact with the perovskite crystal (3). The preparation process of this perovskite nuclear radiation detector includes: Step 1. Prepare a LiF intermediate layer (2) on one side of the perovskite crystal (3): Using the method of vacuum evaporation, during evaporation, the vacuum degree is maintained below 5×10 -3 Pa, the evaporation boat is a tungsten boat of model #308, the evaporation current is 25 - 40 A, the evaporation material is LiF crystal particles or powder, and the mass of the evaporation material is 0.3 - 3.0 mg to obtain the LiF intermediate layer; Step 2: Above the LiF intermediate layer (2), select a low work function metal and use vacuum evaporation or sputtering to prepare the metal anode (1), which forms a Schottky contact with the perovskite crystal (3). Step 3: On the other side of the perovskite crystal (3), select a high work function metal and use vacuum evaporation or sputtering to prepare the metal cathode (4). Step 4: Use carbon paste to connect the metal cathode 4 to the S terminal of the ceramic-based PCB board, and connect the metal anode (1) to the G terminal of the ceramic-based PCB board for subsequent testing and use. The preparation of the perovskite crystal is as follows: Use a P-type perovskite crystal (3), a CsPbBr3 all-inorganic perovskite crystal grown by the melt method or solution method, a MAPbBr3 organic-inorganic hybrid perovskite crystal grown by the solution method, or a FAPbBr3 organic-inorganic hybrid perovskite crystal grown by the solution method, and the crystal thickness is 1 - 5 mm. The metal anode is a low work function metal such as indium In, aluminum Al, tin Sn, or gallium Ga. The metal cathode is a high work function metal such as gold Au, platinum Pt, or chromium Cr. The thickness of the LiF intermediate layer is 5 - 40 nm. The thickness of the metal anode is 60 - 80 nm. The thickness of the metal cathode is 40 - 90 nm. Before the said Step 1, the surface of the perovskite crystal (3) is leveled and smoothed by mechanical grinding and polishing. Use SiC sandpapers with different grits to gradually grind and polish for 1 - 3 minutes in sequence, which are 3000#, 5000#, 7000#, and 9000#, so that the surface of the perovskite crystal (3) is flat and there is no cutting damage layer. Then place the perovskite crystal (3) on the polishing cloth and use MgO powder with a particle size of about 50 nm as the abrasive for polishing, and gradually drop 1 - 2 ml of anhydrous ethanol until the surface of the perovskite crystal (3) is bright and has no scratches. After the mechanical grinding and polishing method, immerse the ground and polished perovskite crystal (3) in cyclohexane and ultrasonicate for 1 - 30 minutes to clean the MgO powder remaining on the surface of the perovskite crystal (3). Subsequently, place it in an ultraviolet ozone machine for 5 - 20 minutes to clean the organic matter attached to the surface of the perovskite crystal (3).

Images