A large-area halide perovskite single crystal heterojunction and its growth method and application in nuclear radiation detectors

Abstract

The present invention relates to a large-area halide perovskite single crystal heterojunction and a growth method thereof and an application in a nuclear radiation detector. The growth method of the large-area halide perovskite single crystal heterojunction comprises the following steps: placing a pretreated cesium-bromine-lead or cesium-bromine-bismuth substrate in a reagent bottle containing a perovskite precursor solution, and then sealing it; fixing the sealed reagent bottle in a water tank, and performing epitaxial growth of a large-area halide perovskite single crystal film on the substrate by an inversion crystallization method or a cooling crystallization method to obtain a large-area halide perovskite single crystal heterojunction. The method of the present invention has the advantages of low cost, simplicity and high efficiency; the perovskite single crystal heterojunction detector of the present invention can effectively suppress the dark current drift caused by ion migration under reverse bias, thereby obtaining a detection effect with high sensitivity and low detection limit.

Description

Technical Field

[0001] The invention relates to a large-area halide perovskite single crystal heterojunction and a growth method thereof and application in a nuclear radiation detector, belonging to the field of perovskite preparation technology and application. Background Art

[0002] Nuclear radiation detection is a process that uses the interaction between high-energy rays (such as X-rays, gamma rays, etc.) and matter to transform them into various forms of information that can be directly or indirectly accepted by people's senses. It plays an important role in medical diagnosis, line flaw detection, safety screening, non-destructive testing of industrial products, and food industry quality inspection. Therefore, it is crucial to select a high-performance nuclear radiation detector. Generally, nuclear radiation detectors must meet the following requirements: (1) High sensitivity: It is easier to distinguish target objects; (2) Low detection limit: Reduce radiation dose and reduce damage; (3) High stability: Stable performance ensures long-term use; (4) High quality: Reduce defects to capture carriers to improve detection efficiency; (5) Large area: It can absorb large-size focal spot rays and improve imaging accuracy. Excellent nuclear radiation detectors and detection materials complement each other. Nuclear radiation detection materials must meet the following requirements: (1) a relatively high average atomic number (Z) to achieve strong absorption of radiation; (2) a relatively high resistivity (ρ) to reduce dark current; (3) an appropriately wide bandgap (Eg) to be suitable for operation at room temperature; and (4) a large carrier mobility lifetime product (μτ) to obtain high carrier collection efficiency.

[0003] In recent years, halide perovskite, as a commercial alternative nuclear radiation detection material, has shown great potential in high-performance X-ray detectors due to its high atomic number, excellent carrier lifetime, adjustable band gap and low-temperature manufacturing process. Currently, the highest sensitivity of X-ray detectors reported is 2.2×10 8 μC Gy air -1 cm -2 MAPbI printed by 3D spraying 3Thin films have the advantages of high preparation efficiency and low production cost, but because organic cations are easily separated from the perovskite body, the stability of the detector is reduced (see: Glushkova, A.; Andricevic, P.; Smajda, R.; Nafradi, B.; Kollar, M.; Djokic, V.; Arakcheeva, A.; Forro, L.; Pugin, R.; Horvath, E., Ultrasensitive 3D Aerosol-Jet-Printed Perovskite X-ray Photodetector. ACS Nano 2021, 15 (3), 4077-4084.). The minimum detection limit is also a very important indicator in the field of X-ray detection. By eliminating the interface polarization problem of perovskite, the prepared MAPbI 3 Single crystal detector, minimum detection limit to 0.1nGy air s -1 , reaching the current high level (see: Song, Y.; Li, L.; Hao, M.; Bi, W.; Wang, A.; Kang, Y.; Li, H.; Li, X.; Fang, Y.; Yang, D.; Dong, Q., Elimination of Interfacial-Electrochemical-Reaction-Induced Polarization in Perovskite Single Crystals for Ultrasensitive and Stable X-Ray Detector Arrays. Adv. Mater. 2021, 33(52), e2103078.). Halide perovskites have also made certain progress in the field of γ detection, and all-inorganic CsPbBr 3 Single crystal pair 137The energy resolution of Cs 662-keV gamma-ray detection is 1.4% (see: He, Y.; Petryk, M.; Liu, Z.; Chica, DG; Hadar, I.; Leak, C.; Ke, W.; Spanopoulos, I.; Lin, W.; Chung, DY; Wessels, BW; He, Z.; Kanatzidis, MG, CsPbBr3perovskite detectors with 1.4% energy resolution for high-energyγ-rays. Nat. Photonics 2021, 15, 36-42.). However, when perovskite materials are currently used in radiation detectors, there is still a dark current drift problem caused by ion migration under high external electric fields, which seriously affects the working stability of the detector.

[0004] At present, there is no report on the preparation method of perovskite single crystal heterojunction, and there is no report on the use of perovskite single crystal heterojunction for nuclear radiation detection. Therefore, the present invention is proposed. Summary of the invention

[0005] In view of the shortcomings of the prior art, the present invention provides a large-area halide perovskite single crystal heterojunction and its growth method and application in nuclear radiation detectors. 3 ) or cesium bismuth bromide (Cs 3 Bi 2 Br 9 ) is used as a substrate, and chips of different sizes are cut out. After orientation and polishing, a large-area halogen perovskite single crystal heterojunction with consistent crystal orientation can be epitaxially grown on the substrate by an inversion crystallization method or a cooling crystallization method. The method of the present invention has the advantages of low cost, simplicity and high efficiency. The perovskite single crystal heterojunction detector of the present invention can effectively suppress the dark current drift caused by ion migration under reverse bias, thereby obtaining a detection effect with high sensitivity and low detection limit.

[0006] The technical solution of the present invention is as follows:

[0007] A method for growing a large-area halide perovskite single crystal heterojunction comprises the following steps:

[0008] The pretreated cesium lead bromide (CsPbBr 3 ) or cesium bismuth bromide (Cs 3 Bi 2 Br 9) The substrate is placed in a reagent bottle containing a perovskite precursor solution and then sealed; the sealed reagent bottle is fixed in a water tank, and a large-area halide perovskite single crystal thin film is epitaxially grown on the substrate by an inversion crystallization method or a cooling crystallization method to obtain a large-area halide perovskite single crystal heterojunction.

[0009] According to the present invention, the large-area halide perovskite single crystal heterojunction consists of a large-area halide perovskite single crystal thin film and a substrate.

[0010] According to the preferred embodiment of the present invention, the cesium lead bromine (CsPbBr 3 ) substrate is square, the thickness of the substrate is 1 to 6 mm; the size of the substrate is not less than 10 mm × 10 mm, and further preferably, the size of the substrate is 20 mm × 20 mm to 100 mm × 100 mm, and more preferably 20 mm × 20 mm to 50 mm × 50 mm; the cesium lead bromine (CsPbBr 3 ) substrate was prepared as follows: a large-size cesium lead bromine (CsPbBr 3 ) crystals to orient and determine <010> direction, and then cut along this direction to obtain cesium lead bromide (CsPbBr 3 ) substrate; the large size CsPbBr 3 The method for preparing crystals is prior art in the art.

[0011] According to the preferred embodiment of the present invention, the cesium bismuth bromide (Cs 3 Bi 2 Br 9 ) The substrate is square, and the thickness of the substrate is 1 to 6 mm; the size of the substrate is not less than 10 mm×10 mm, and further preferably, the size of the substrate is 10 mm×10 mm to 50 mm×50 mm, and more preferably 10 mm×10 mm to 30 mm×30 mm; the cesium bismuth bromide (Cs 3 Bi 2 Br 9 ) substrate was prepared as follows: a large-sized cesium bismuth bromide (Cs 3 Bi 2 Br 9 ) crystals to orient and determine <001> direction, and then cut along this direction to obtain cesium bismuth bromide (Cs 3 Bi 2 Br 9 ) substrate; the large size Cs 3 Bi 2 Br 9 The method for preparing crystals is prior art in the art.

[0012] According to the preferred embodiment of the present invention, the cesium lead bromine (CsPbBr3 ) or cesium bismuth bromide (Cs 3 Bi 2 Br 9 ) The pretreatment method of the substrate is: first polish the substrate with 1200 mesh coarse sandpaper to remove the scratches caused by wire cutting on the surface of the substrate, then fine polish it with 7000 mesh fine sandpaper, and finally fine polish it with 0.05μm aluminum oxide polishing powder. After polishing, clean the substrate with ethanol and dry it for use.

[0013] According to the preferred embodiment of the present invention, the perovskite precursor is MAPbBr 3-n Cl n or Cs 2 AG 6 , wherein n is 0-1; the perovskite precursor is MAPbBr 3-n Cl n When n is 0-1, the substrate used is cesium lead bromine (CsPbBr 3 ) substrate, the obtained large-area halide perovskite single crystal heterojunction is a large-area MAPbBr 3-n Cl n / CsPbBr 3 Single crystal heterojunction; the perovskite precursor is Cs 2 AG 6 When the substrate is cesium bismuth bromide (Cs 3 Bi 2 Br 9 ) substrate, the obtained large-area halide perovskite single crystal heterojunction is a large-area Cs 2 AG 6 / Cs 3 Bi 2 Br 9 Single crystal heterojunction.

[0014] Preferably, according to the present invention, the perovskite precursor solution is obtained by adding a perovskite precursor raw material into a solvent;

[0015] Further preferably, the perovskite precursor is MAPbBr 3-n Cl n When n is 0-1, the perovskite precursor solution is MABr, PbBr 2 With PbCl 2 The solution was added into a solvent in a molar ratio of 1:(1-n / 2):n / 2, and stirred and dissolved at 30-40°C. The solvent was N,N-dimethylformamide (DMF). The concentration of the perovskite precursor solution was 1.19-1.64 mol / L. MAPbBr 3-n Cl n count.

[0016] Further preferably, the perovskite precursor is Cs 2 AG 6 When the perovskite precursor solution is CsBr, BiBr 3 , AgBr in a molar ratio of 2:1:1 are added to a solvent, and stirred and dissolved at 70-80° C., wherein the solvent is a 48% by mass aqueous solution of hydrobromic acid (HBr), the concentration of the perovskite precursor solution is 0.15-0.2 mol / L, and Cs 2 AG 6 count.

[0017] According to the present invention, the amount of the perovskite precursor solution is sufficient to completely immerse the substrate, and may be slightly excessive.

[0018] The present invention controls the morphology and thickness of a single crystal heterojunction by precisely controlling the temperature change by regulating the heating (or cooling) time and the heating (or cooling) rate, thereby obtaining a large-area halide perovskite single crystal heterojunction. In the precise temperature control process of the present invention, the solubility is first tested, and different heating or cooling rates are selected through the solubility curve.

[0019] According to the preferred embodiment of the present invention, the perovskite precursor is MAPbBr 3-n Cl n When n is 0-1, the substrate used is cesium lead bromine (CsPbBr 3 ) substrate, and a large area MAPbBr was prepared on the substrate by using the inversion crystallization method. 3-n Cl n Growth of single crystal thin films to obtain large-area MAPbBr 3-n Cl n / CsPbBr 3 Single crystal heterojunction, where large area MAPbBr 3-n Cl n The thickness of the single crystal film is 10 μm to 3 mm. The specific growth process is: keep the perovskite precursor solution at 30 to 40 ° C for 12 hours, then heat it at a heating rate of 0.065 to 0.25 ° C / h to grow the single crystal film, and stop growing after growing to the target thickness. The heating time is the growth time of the single crystal film; further preferably, the heating rate for the first 72 hours is 0.065 to 0.07 ° C / h, the heating rate from 72 hours to 192 hours is 0.08 to 0.085 ° C / h, the heating rate from 192 hours to 292 hours is 0.095 to 0.1 ° C / h, and the heating rate from 292 hours to 352 hours is 0.2 to 0.25 ° C / h; the thickness of the film is controlled by the heating time, that is, the growth time. For example: epitaxial growth of MAPbBr 3The thickness of the single crystal film is 20 μm, the concentration of the perovskite precursor solution is 1.64 mol / L, and the growth time is 12 h (less than 72 h, i.e. within 72 h). That is, the temperature is increased from 30 °C at a heating rate of 0.069 °C / h for 12 h, and a large-area MAPbBr with a thickness of 20 μm is obtained. 3 Single crystal thin film; if large area MAPbBr 3 The thickness of the single crystal film is 1 mm, the concentration of the perovskite precursor solution is 1.64 mol / L, and the growth time is 108 h (more than 72 h). The temperature is first increased from 30 ° C at a heating rate of 0.069 ° C / h for 72 h, and then continued to increase from 72 h to 108 h at a heating rate of 0.083 ° C / h, that is, the heating time at a heating rate of 0.083 ° C / h is 36 h, and the total heating time is 108 h, that is, the film grows for 108 h. If a thicker film needs to be grown, follow the above procedure.

[0020] According to the preferred embodiment of the present invention, the perovskite precursor is Cs 2 AG 6 When the substrate is cesium bismuth bromide (Cs 3 Bi 2 Br 9 ) substrate, and a large area Cs 2 AG 6 Growth of single crystal thin films to obtain large area Cs 2 AG 6 / Cs 3 Bi 2 Br 9 Single crystal heterojunction, where large area Cs 2 AG 6 The thickness of the single crystal film is 10μm to 1.5mm; the specific growth conditions are: the perovskite precursor solution is kept at 70 to 80°C for 12h, and then cooled at a cooling rate of 0.045 to 0.85°C / h to grow the single crystal film, and the growth is stopped after the target thickness is grown. The cooling time is the growth time of the single crystal heterojunction; further preferably, the cooling rate for the first 20h is 0.45 to 0.5°C / h, the cooling rate from 20h to 36.5h is 0.55 to 0.6°C / h, the cooling rate from 36.5h to 50h is 0.7 to 0.75°C / h, and the cooling rate from 50h to 85h is 0.8 to 0.85°C / h; the thickness of the film is controlled by the cooling time, that is, the growth time. For example: large area Cs 2 AG 6The thickness of the single crystal film is 0.5 mm, the concentration of the perovskite precursor solution is 0.2 mol / L, and the growth time is 24 h (higher than 20 h), that is, firstly, the temperature is cooled from 80 ° C at a cooling rate of 0.5 ° C / h, and the cooling time is 20 h, and then the cooling rate is continued at 0.6 ° C / h for 4 h, that is, the cooling rate is cooled from 20 h to 24 h at a cooling rate of 0.6 ° C / h, and the total cooling time is 24 h, and a large area Cs with a thickness of 0.5 mm is obtained. 2 AG 6 Single crystal thin film; if thicker film needs to be grown, follow the above steps and so on.

[0021] According to the present invention, the perovskite precursor solution can be used only after being fully stirred and filtered, to ensure that no other nucleation points appear, no impurity crystals appear, and only crystal growth occurs.

[0022] According to the present invention, the reagent bottle is not specifically limited, and can be sealed, such as a glass bottle with a silicone sealing strip, which can ensure a very high degree of sealing and prevent air and moisture from entering the reagent bottle and affecting the growth of the heterojunction.

[0023] According to the present invention, the water tank is provided with an FP23 temperature controller, a stirrer and a real-time temperature observation display, which ensures that the entire reagent bottle is in a constant temperature environment and that all parts of the reagent bottle are heated evenly, thereby ensuring the uniformity of heterojunction growth.

[0024] A large-area halide perovskite single crystal heterojunction is prepared by using the above growth method.

[0025] According to the present invention, the large-area halide perovskite single crystal heterojunction is used to prepare a nuclear radiation detector.

[0026] According to the present invention, the thickness of the entire perovskite single crystal thin film heterojunction grown varies with time, and the thickness is adjustable from μm to mm, thanks to the precise control of temperature changes over time.

[0027] The principle of the present invention is as follows:

[0028] The present invention uses CsPbBr 3 Using single crystal as substrate, large-area MAPbBr can be achieved through the crystal growth method of inversion crystallization. 3-n Cl n / CsPbBr 3 Growth of single crystal heterojunction. 3 For example, cesium lead bromine (CsPbBr 3 ) crystal, Pnma space group, lattice constant is Methylamine lead bromide (MAPbBr 3 ) crystals, The space group and lattice constant are Cb 3 and MAPbBr 3 Lattice Figure 1 As shown, in Figure 1 It can be seen that in CsPbBr 3 Unit cell <100> The length between adjacent Pb atoms in the direction is equal to MAPbBr 3 Unit Cell <101> The length between adjacent Pb atoms in the direction of the lattice mismatch is 1.5%. 3 Single crystal materials as substrates can achieve better lattice matching with lead halide-based perovskites, which is conducive to the large-area growth of epitaxial halide perovskite heterojunctions on the substrate.

[0029] The present invention uses Cs 3 Bi 2 Br 9 Using single crystal as substrate, large-area Cs 2 AG 6 / Cs 3 Bi 2 Br 9 Growth of single crystal thin film heterojunctions by cutting oriented <001> The wafer is placed in the direction of the wafer and placed in the perovskite precursor solution, and the growth of the crystal is controlled by controlling the cooling rate.

[0030] Anything not described in detail in the present invention is the prior art in the art.

[0031] The technical features and beneficial effects of the present invention are as follows:

[0032] 1. The present invention uses cesium lead bromine (CsPbBr 3 ) or cesium bismuth bromide (Cs 3 Bi 2 Br 9 ) as the substrate, using the inversion crystallization or cooling crystallization method, it can be 3 or Cs 3 Bi 2 Br 9 A large-area, high-quality halide perovskite single crystal film is directly epitaxially grown on the substrate (i.e., on the side opposite to the contact surface between the substrate and the reagent bottle). By precisely controlling the changes in time and temperature to control the growth of the single crystal film, a uniform large-area halide perovskite single crystal heterojunction with adjustable thickness can be obtained. At the same time, the size of the single crystal heterojunction can be controlled by adjusting the size of the substrate.

[0033] 2. The method of the present invention can replace different perovskite precursor solutions to achieve the growth of perovskite single crystal heterojunctions with different compositions, and can be used for MAPbBr3 The precursor solution was replaced with MAPbBr 3-n Cl n Solution, MAPbBr 3-n Cl n / CsPbBr 3 Growth of heterojunction. In the method of the present invention, a prominent advantage is that the prepared perovskite precursor solution will not dissolve the substrate, laying a foundation for the integrity of the preparation of the heterojunction.

[0034] 3. The thickness of the entire perovskite single crystal heterojunction grown by the present invention changes with time, and the thickness is adjustable from μm to mm, thanks to the precise control of temperature changes over time.

[0035] 4. The large-area perovskite single crystal heterojunction obtained by the present invention can be used in the field of nuclear radiation detection. The conductivity type of the heterojunction can be regulated by adjusting the components. The large-area perovskite single crystal heterojunction of the present invention has an obvious rectification effect for nuclear radiation detection, which can inhibit ion migration under reverse bias, reduce the dark current of the device, and improve the stability of the detector. Experiments have shown that the present invention has a good performance in MAPbBr 3-n Xn / CsPbBr 3 , Cs 2 AG 6 / Cs 3 Bi 2 Br 9 Based on the new single crystal heterojunction, the detection of X-rays and gamma rays was studied, and the X-ray sensitivity and minimum detection limit of the heterojunction nuclear radiation detector were tested. The results showed that the prepared nuclear radiation detector has high sensitivity and low detection limit for X-rays; it has high sensitivity and energy resolution for gamma rays, providing a basis for practical applications.

[0036] 5. The method used in the present invention is simple, low-cost, easy to operate, and suitable for commercial mass production.

[0037] 6. In the present invention, the processing of the substrate and the control of the rate of temperature change are crucial in the preparation process of the single crystal heterojunction. The smoothness of the substrate determines the quality of the epitaxial film. Accurate and strict control of temperature changes within the scope of the present invention can ensure that only crystal growth is carried out without other unnecessary nucleation, which affects the preparation of the single crystal heterojunction. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] Figure 1 The CsPbBr 3 and MAPbBr 3 Lattice matching diagram.

[0039] Figure 2It is a schematic diagram of a growth device for a large-area halide perovskite single crystal heterojunction of the present invention.

[0040] Figure 3 The MAPbBr of the present invention 3 Solubility curve diagram.

[0041] Figure 4 The CsPbBr used in Example 1 3 Substrate (a) and prepared large-area MAPbBr 3 / CsPbBr 3 Optical photograph of a single crystal heterojunction (b).

[0042] Figure 5 The large-area MAPbBr prepared in Example 1 3 / CsPbBr 3 SEM images of the fracture surface (a) and cross section (b) of a single-crystal heterojunction.

[0043] Figure 6 The large-area MAPbBr prepared in Example 1 3 / CsPbBr 3 EPMA element change diagram (a), XRD spectrum (b) and pole figure (c) of single crystal heterojunction.

[0044] Figure 7 The large-area MAPbBr prepared in Example 2 3 / CsPbBr 3 Optical photograph of a single-crystal heterojunction (long growth time).

[0045] Figure 8 The large-area MAPbBr prepared in Example 3 2.9 Cl 0.1 / CsPbBr 3 Optical photograph of a single-crystal heterojunction (short growth time).

[0046] Fig. 9 The large-area MAPbBr prepared in Example 4 2.9 Cl 0.1 / CsPbBr 3 Optical photograph of a single-crystal heterojunction (long growth time).

[0047] Fig.10 The large-area MAPbBr prepared in Example 5 2.5 Cl 0.5 / CsPbBr 3 Optical photograph of a single-crystal heterojunction (short growth time).

[0048] Fig.11 The large-area MAPbBr prepared in Example 62.5 Cl 0.5 / CsPbBr 3 Optical photograph of a single-crystal heterojunction (long growth time).

[0049] Fig.12 Cs used in Example 7 3 Bi 2 Br 9 Substrate (a) and prepared large area Cs 2 AG 6 / Cs 3 Bi 2 Br 9 Optical photograph of a single crystal heterojunction (b).

[0050] Fig.13 It is the large area MAPbBr in Experiment 1 3 / CsPbBr 3 Electrical performance test of single crystal heterojunction device; where a is the IV curve, b is the KPFM test diagram, c is the defect state density and carrier mobility of the heterojunction under negative bias, and d is the carrier mobility lifetime product.

[0051] Fig.14 It is the large area MAPbBr in Experiment 2 3 / CsPbBr 3 X-ray performance test of single crystal heterojunction detection device; a is Au / CsPbBr 3 / Au detectors and Au / MAPbBr 3 / CsPbBr 3 Comparison of the time-correlated X-ray responses of Au / MAPbBr heterojunction detectors, b is Au / MAPbBr 3 / CsPbBr 3 / Au detector at -20, -40 and -60Vmm -1 Time-dependent response in electric field, c for MAPbBr 3 / CsPbBr 3 Sensitivity of heterojunction detectors in different electric fields, d for MAPbBr 3 / CsPbBr 3 The signal-to-noise ratio of the heterojunction detector under different electric fields and dose rates, e is the comparison of the X-ray detection performance of multiple perovskite X-ray detectors, and f is the comparison of MAPbBr 3 / CsPbBr 3 X-ray response stability of heterojunction detectors at room temperature. DETAILED DESCRIPTION

[0052] The present invention is further described below in conjunction with the examples and drawings. The raw material DMF used in the examples has a purity of 99.5%, MABr, PbBr 2 、PbCl 2 、CsBr、BiBr 3 , the purity of AgBr is 99.999%, and the mass fraction of HBr is 48%.

[0053] CsPbBr used in the examples 3 , Cs 3 Bi 2 Br 9 The substrate is cut from the crystal grown by the melt method of our research group. The specific preparation method is as follows: Large size CsPbBr 3 , Cs 3 Bi 2 Br 9 The single crystals were grown by our research group using the Bridgman method. First, the large-sized CsPbBr 3 , Cs 3 Bi 2 Br 9 The single crystal is oriented and the <010> Direction and <001> direction; then cut along this direction to obtain CsPbBr of the desired size 3 (010), Cs 3 Bi 2 Br 9 (001) substrate; the crystal is then polished to obtain a transparent wafer. In the embodiment, one side of the substrate is in contact with the reagent bottle, and the other side is used for epitaxial growth of a large-area halide perovskite single crystal thin film.

[0054] MAPbB 3 Solubility curve test method: First, prepare 2 mol / L MAPbBr 3 The precursor solution was then filtered to obtain a clear solution. The precursor solution was sealed and placed in a 50 °C water tank to obtain MAPbBr with different sizes. 3 The particles were taken out and ground into MAPbBr 3 Powder. Heat 10 mL of DMF to the desired temperature and, while stirring, add small amounts of MAPbBr in 0.03 g increments. 3 Perovskite powder until the solution reaches saturation. When the solute is not completely dissolved within 30 minutes after being dropped into the solution, it is considered saturated. Repeat this process from 30°C to 80°C. 3 The solubility of is reduced from 0.79 g / mL at 30 °C to 0.38 g / mL at 80 °C. Figure 3 shown.

[0055] Example 1

[0056] A large-area MAPbBr 3 / CsPbBr 3 A method for growing a single crystal heterojunction comprises the following steps:

[0057] (1) CsPbBr 3 Pretreatment of the substrate: First, polish the substrate with 1200-mesh coarse sandpaper to remove the scratches caused by wire cutting on the substrate surface, then use 7000-mesh fine sandpaper for fine polishing, and finally use 0.05μm aluminum oxide polishing powder for fine polishing. After polishing, use ethanol to remove CsPbBr 3 The substrate is cleaned, dried and ready for use. The size of the substrate is 20 mm×20 mm and the thickness is 1 mm.

[0058] (2 Large area MAPbBr 3 / CsPbBr 3 Growth of single crystal heterojunction: 6.0188g PbBr 2 、1.8368g MABr(PbBr 2 MAPbBr (1:1 molar ratio) was placed in a reagent bottle, 10 mL of DMF was added, and after sufficient stirring at 30 °C, MAPbBr was obtained by filtering with a 0.45 μm filter. 3 Precursor solution (MAPbBr 3 The concentration is 1.64 mol / L), then added to the reagent bottle, and the substrate was placed in a solution of MAPbBr 3 The reagent bottle of the precursor solution was sealed and fixed in a water tank. After being kept at 30°C for 12 h, the temperature was increased at a rate of 0.069°C / h from 30°C to start MAPbBr 3 The growth of single crystal film was stopped after heating for 12 hours, and the film growth was stopped to obtain large area MAPbBr 3 / CsPbBr 3 Single crystal heterojunction, heating time is 12h, namely MAPbBr 3 The growth time of the single crystal film is 12 h.

[0059] The MAPbBr obtained in this example 3 / CsPbBr 3 Optical photos of single crystal heterojunctions Figure 4 As shown, from Figure 4 The grown MAPbBr 3 / CsPbBr 3 The single crystal heterojunction is flat and uniform.

[0060] The MAPbBr prepared in this example 3 / CsPbBr3 The SEM image of the single crystal heterojunction is shown in Figure 5 a. Figure 5 As shown in b, from Figure 5 a. Figure 5 bIt can be seen that MAPbBr 3 Single crystal thin film and CsPbBr 3 There is a clear interface between the substrates, the crystal surface is flat, and MAPbBr 3 The thickness of the single crystal thin film is 20 μm.

[0061] The MAPbBr prepared in this example 3 / CsPbBr 3 Single crystal heterojunction has a clear interface. Figure 6 a By testing the EPMA at the interface, the interface at the heterojunction connection is confirmed by the sudden change in the content of Cs element. The XRD spectrum and pole figure are shown in Figure 6 b. Figure 6 As shown in c, it is confirmed that the obtained heterojunction has good single crystal properties.

[0062] Example 2

[0063] A large-area MAPbBr 3 / CsPbBr 3 The growth method of the single crystal heterojunction is as described in Example 1, except that: after the temperature is kept constant at 30°C for 12 hours, the temperature is increased at a heating rate of 0.069°C / h for 72 hours, and then the temperature is increased at a heating rate of 0.083°C / h from 72 hours to 108 hours, that is, the heating time at the heating rate of 0.083°C / h is 36 hours, and the temperature is stopped after a total of 108 hours, that is, the growth is stopped, and a large area MAPbBr is obtained. 3 / CsPbBr 3 Single crystal heterojunction, heating time is 108h, namely MAPbBr 3 The growth time of the single crystal film is 108h.

[0064] The MAPbBr obtained in this example 3 / CsPbBr 3 Optical photos of single crystal heterojunctions Figure 7 As shown, MAPbBr 3 The thickness of the single crystal film is 1 mm.

[0065] Example 3

[0066] A large-area MAPbBr 2.9 Cl 0.1 / CsPbBr 3 The method for growing a single crystal heterojunction is the same as that described in Example 1, except that the raw materials MABr and PbBr 2 With PbCl2 DMF (MAPbBr) was added in a molar ratio of 1:0.95:0.05 2.9 Cl 0.1 The concentration was 1.64 mol / L), and the subsequent experiments were carried out according to Example 1, with a growth time of 12 h and a film thickness of 20 μm. Figure 8 shown.

[0067] Example 4

[0068] A large-area MAPbBr 2.9 Cl 0.1 / CsPbBr 3 The growth method of the single crystal heterojunction is as described in Example 3, except that: after the temperature is kept constant at 30°C for 12 hours, the temperature is increased at a heating rate of 0.069°C / h for 72 hours, and then the temperature is increased at a heating rate of 0.083°C / h from 72 hours to 108 hours. After the temperature is increased for a total of 108 hours, the temperature is stopped, i.e., the growth is stopped to obtain a large area MAPbBr 2.9 Cl 0.1 / CsPbBr 3 Single crystal heterojunction, heating time is 108h, namely MAPbBr 2.9 Cl 0.1 The growth time of the single crystal film is 108h.

[0069] The MAPbBr obtained in this example 2.9 Cl 0.1 / CsPbBr 3 Optical photos of single crystal heterojunctions Fig. 9 As shown, MAPbBr 2.9 Cl 0.1 The thickness of the single crystal film is 1 mm.

[0070] Example 5

[0071] A large-area MAPbBr 2.5 Cl 0.5 / CsPbBr 3 The method for growing a single crystal heterojunction is the same as that described in Example 1, except that the raw materials MABr and PbBr 2 With PbCl 2 DMF (MAPbBr) was added in a molar ratio of 1:0.75:0.25 2.5 Cl 0.5 The concentration was 1.64 mol / L), and the subsequent experiments were carried out according to Example 1, with a growth time of 12 h, MAPbBr 2.5 Cl 0.5 The thickness of the single crystal film is 20 μm. Fig.10 shown.

[0072] Example 6

[0073] A large-area MAPbBr 2.5 Cl 0.5 / CsPbBr 3 The growth method of the single crystal heterojunction is as described in Example 5, except that: after the temperature is kept constant at 30°C for 12 hours, the temperature is increased at a heating rate of 0.069°C / h for 72 hours, and then the temperature is further increased at a heating rate of 0.083°C / h from 72 hours to 108 hours. After the temperature is increased for a total of 108 hours, the temperature is stopped, i.e., the growth is stopped to obtain a large area MAPbBr 2.5 Cl 0.5 / CsPbBr 3 Single crystal heterojunction, heating time is 108h, namely MAPbBr 2.5 Cl 0.5 The growth time of single crystal film is 108h, MAPbBr 2.5 Cl 0.5 The thickness of the single crystal film is 1 mm. Fig.11 shown.

[0074] Example 7

[0075] A large area Cs 2 AG 6 / Cs 3 Bi 2 Br 9 A method for growing a single crystal heterojunction comprises the following steps:

[0076] (1) Cs 3 Bi 2 Br 9 Pretreatment of the substrate: First, polish the substrate with 1200-mesh coarse sandpaper to remove the scratches caused by wire cutting on the substrate surface, then use 7000-mesh fine sandpaper for fine polishing, and finally use 0.05μm aluminum oxide polishing powder for fine polishing. After polishing, use ethanol to remove Cs 3 Bi 2 Br 9 The substrate is cleaned, dried and ready for use. The size of the substrate is 10 mm×10 mm and the thickness of the substrate is 1 mm.

[0077] (2) Cs 2 AG 6 Growth of single crystal heterojunction: 0.4236g CsBr, 0.4478g BiBr 3 , 0.1877 g AgBr was weighed and placed in a reagent bottle, 10 mL HBr aqueous solution was added, and after being stirred thoroughly at 80 °C (Cs 2 AG 6The concentration is 0.2 mol / L), and the precursor solution is filtered through a 0.45 μm filter. The substrate is placed in a 2 AG 6 After the reagent bottle of the precursor solution is sealed, it is fixed in a water tank and kept at 80°C for 12 hours. Then, the temperature is cooled from 80°C at a cooling rate of 0.5°C / h. After cooling for 20 hours, the cooling rate is then reduced from 20 hours to 24 hours at a cooling rate of 0.6°C / h. That is, the cooling time at a cooling rate of 0.6°C / h is 4 hours. After cooling for a total of 24 hours, the cooling is stopped, i.e., the film growth is stopped, and a large area of ​​Cs 2 AG 6 / Cs 3 Bi 2 Br 9 Single crystal heterojunction, cooling time is 24h, i.e. Cs 2 AG 6 The growth time of the single crystal film is 24 h.

[0078] The Cs used in this example 3 Bi 2 Br 9 Substrate Fig.12 As shown in a, the obtained Cs 2 AG 6 / Cs 3 Bi 2 Br 9 Optical photos of single crystal heterojunctions Fig.12 As shown in b, Cs 2 AG 6 The thickness of the single crystal film is 0.5 mm, and the obtained film is flat and uniform.

[0079] Test Example 1

[0080] The large-area MAPbBr prepared in Example 1 3 / CsPbBr 3 A single crystal heterojunction is prepared into a nuclear radiation detection device. The specific preparation method is as follows: the prepared single crystal heterojunction is fixed on the heterojunction using a mask with 2mm×2mm square holes, that is, the exposed area of ​​the heterojunction is 2mm×2mm, and the Au electrode is sputtered using an ion sputtering device. The current of the ion sputtering device is set to 0.2mA and the sputtering time is 180s. After the sputtering is completed, the mask is fixed at the corresponding position on the back of the heterojunction, and the sputtering operation is repeated to obtain a heterojunction device with a symmetrical Au electrode.

[0081] The large-area MAPbBr prepared in Example 1 3 / CsPbBr 3 The electrical properties of the single crystal heterojunction are tested in the following steps:

[0082] (1)MAPbBr 3 / CsPbBr 3 Single crystal heterojunction and CsPbBr 3 IV curve comparison of crystal: by preparing symmetrical Au electrodes, using 6517b test system for testing, the results are as follows Fig.13 As shown, from Fig.13 It can be seen in a that MAPbBr 3 / CsPbBr 3 The single crystal heterojunction has a very obvious rectification effect under negative pressure. The calculated rectification ratio is 45, that is, compared with the positive pressure, the symmetrical Au electrode heterojunction device has a low dark current under negative bias, laying the foundation for the subsequent preparation of high-performance nuclear radiation detection devices.

[0083] (2)MAPbBr 3 / CsPbBr 3 EPMA test of single crystal heterojunction: The test results show ( Fig.13 b), from CsPbBr 3 to MAPbBr 3 There is a significant potential increase, which is consistent with the rectification effect of the symmetrical Au electrode heterojunction device.

[0084] (3)MAPbBr 3 / CsPbBr 3 Single crystal heterojunction carrier mobility test: from Fig.13 c It can be seen that the same symmetrical Au electrode heterojunction device has a higher carrier mobility under negative bias than CsPbBr 3 Single crystal devices have been improved by 12cm 2 V -1 -1s.

[0085] (4)MAPbBr 3 / CsPbBr 3 Single crystal heterojunction carrier mobility lifetime product test: From the experimental test results, it can be seen that ( Fig.13 d), the carrier mobility lifetime product of heterojunction devices is increased by 6.76×10 -3 cm 2 V -1 .

[0086] Test Example 2

[0087] MAPbBr prepared in Example 1 3 / CsPbBr 3 Nuclear radiation detection response test of single crystal heterojunction, the specific device preparation is as described in Experimental Example 1.

[0088] (1)MAPbBr 3 / CsPbBr 3 Single crystal heterojunction and CsPbBr 3 Crystal X-ray detection performance comparison: by comparing the symmetrical Au electrode device at -125V mm -1 The X-ray response under the electric field strength ( Fig.14 a), The heterojunction device has a low and stable dark current under negative bias and can respond quickly to X-ray detection.

[0089] (2)MAPbBr 3 / CsPbBr 3 X-ray response of single crystal heterojunction under different negative bias and calculated sensitivity: By comparing the X-ray response of different biases ( Fig.14 b), -20V mm -1 、-40V mm -1 、-60V mm -1 The X-ray can also respond quickly and stably. The highest X-ray sensitivity is calculated to be 201788μC Gy air -1 cm -2 ( Fig.14 c).

[0090] (3)MAPbBr 3 / CsPbBr 3 The minimum detection limit test of single crystal heterojunction: The minimum detection limit of the heterojunction X-ray detector prepared by the present invention is 96nGy air s -1 , reaching a relatively good level at present ( Fig.14 d).

[0091] (4)MAPbBr 3 / CsPbBr 3 Single crystal heterojunction is compared with X-ray detection materials reported in the literature: This invention compares various heterojunction X-ray detection materials and other detection devices ( Fig.14 e), the heterojunction detection device prepared by the present invention has the characteristics of low detection limit and high sensitivity.

[0092] (5)MAPbBr 3 / CsPbBr 3 Stability test of single crystal heterojunction: The heterojunction X-ray detector device of the present invention can respond quickly and stably after 90 days without any packaging, and the response sensitivity has not been significantly reduced, which ensures the stability of the device ( Fig.14 f).

Claims

1. A method for growing a large-area halide perovskite single crystal heterojunction, comprising the following steps: The pretreated cesium-bromine lead substrate is placed in a reagent bottle containing a perovskite precursor solution and then sealed; the sealed reagent bottle is fixed in a water tank, and a large-area halide perovskite single crystal thin film is epitaxially grown on the substrate by an inversion crystallization method to obtain a large-area halide perovskite single crystal heterojunction; The size of the substrate is 20 mm×20 mm to 100 mm×100 mm; the perovskite precursor is MAPbBr 3-n Cl n , wherein n is 0-1, the perovskite precursor solution is prepared by adding MABr, PbBr2 and PbCl2 into a solvent at a molar ratio of 1:(1-n / 2):n / 2, and stirring and dissolving at 30-40° C., the solvent is N,N-dimethylformamide, and the concentration of the perovskite precursor solution is 1.19-1.64 mol / L; The obtained large-area halide perovskite single crystal heterojunction is a large-area MAPbBr 3-n Cl n / CsPbBr3 single crystal heterojunction, the specific growth process is: keep the perovskite precursor solution at 30~40℃ for 12h, then heat it at a heating rate of 0.065~0.25℃ / h to grow a single crystal film, and stop growing after growing to the target thickness. The heating time is the growth time of the single crystal film.

2. The method for growing a large-area halide perovskite single crystal heterojunction according to claim 1, characterized in that: The bromine-lead-cesium substrate is square and has a thickness of 1 to 6 mm. The bromine-lead-cesium substrate is prepared according to the following method: orienting a large-sized bromine-lead-cesium crystal to determine the <010> direction, and then cut along this direction to obtain a bromine lead cesium substrate.

3. The method for growing a large-area halide perovskite single crystal heterojunction according to claim 1, characterized in that: The size of the substrate is 20 mm×20 mm to 50 mm×50 mm.

4. The method for growing a large-area halide perovskite single crystal heterojunction according to claim 1, characterized in that: The pretreatment method of bromine lead cesium is as follows: firstly, the substrate is polished with 1200 mesh coarse sandpaper, then finely polished with 7000 mesh fine sandpaper, and finally finely polished with 0.05 μm aluminum oxide polishing powder. After polishing, the substrate is cleaned with ethanol and dried for standby use.

5. The method for growing a large-area halide perovskite single crystal heterojunction according to claim 1, characterized in that: The large-area MAPbBr 3-n Cl n The thickness of the single crystal film is 10μm~3mm, and the specific growth process is: the heating rate in the first 72h is 0.065~0.07℃ / h, the heating rate from 72h to 192h is 0.08~0.085℃ / h, the heating rate from 192h to 292h is 0.095~0.1℃ / h, and the heating rate from 292h to 352h is 0.2~0.25℃ / h.

6. A large-area halide perovskite single crystal heterojunction, characterized in that: The method is adopted to prepare the growth product according to any one of claims 1 to 5.

7. Application of the large-area halide perovskite single crystal heterojunction according to claim 6 to prepare nuclear radiation detectors.

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