Preparation method and application of FAPbBr3 heterojunction crystal with low and stable dark current

Abstract

The invention discloses a preparation method and application of an FAPbBr3 heterojunction crystal with low and stable dark current, and relates to the technical field of semiconductor heterojunctions. The method comprises the following steps: preparing an FAPbBr3 single crystal; the preparation method comprises the following steps: dissolving FABr, PbBr2 and PbCl2 in an organic solvent to obtain an epitaxial layer precursor solution; filtering the epitaxial layer precursor solution to obtain filtrate; and sealing the filtrate, placing the filtrate in a water bath, heating the filtrate to 33-36 DEG C, adding FAPbBr3 single crystals, continuously sealing the filtrate, and heating the filtrate to 43-46 DEG C to obtain the FAPbBr3 heterojunction crystal with low and stable dark current. According to the heterojunction epitaxial growth process for the FAPbBr3 single crystal, dark current can be effectively inhibited, and a radiation detection device which has good radiation detection performance on X rays and alpha particles at the same time is further obtained.

Description

Technical Field

[0001] The present invention relates to the technical field of semiconductor heterojunctions, and in particular to a method for preparing a FAPbBr3 heterogeneous crystal with low and stable dark current and an application thereof. Background Art

[0002] Radiation detection is of indispensable importance in many fields such as medical diagnosis and security inspection. In recent years, organic-inorganic halide perovskites have demonstrated outstanding performance in radiation detection applications due to their excellent optoelectronic properties, high tolerance to defects, adjustable band gaps, and ease of synthesis. Among various types of halide perovskite materials, three-dimensional FAPbBr3 has made significant progress in the field of radiation detection due to its structural stability and thermal stability at room temperature, and has gradually attracted widespread attention. However, the low bulk resistivity and high dark current problems in perovskite crystal detectors are still the main challenges.

[0003] In order to meet the demand for perovskite detectors operating at high bias voltages and with low dark currents, and to achieve efficient radiation detection performance, it is urgent to adopt a device structure that can suppress dark currents. Introducing junction structures in single crystals has become a potential solution that has attracted much attention. In addition to using asymmetric metal electrodes, it is also possible to consider building a suitable epitaxial layer on the single crystal to form a heterojunction structure to improve carrier transfer efficiency and effectively reduce dark current.

[0004] It is well known that heterojunctions can not only increase the resistivity of semiconductor materials, but also effectively reduce the dark current of optoelectronic devices. The potential difference on both sides of the heterojunction will form a built-in electric field, which is conducive to the rapid separation of photogenerated carriers. Compared with MAPbBr3-based heterojunctions, FAPbBr3-based heterojunctions have greater advantages in structural and thermal stability and carrier transport performance, and therefore have better radiation detection potential in theory. It can be seen that using FAPbBr3 crystals to construct heterojunction structures to further improve radiation detection capabilities is an important exploration direction in halide perovskite research.

[0005] Liquid phase epitaxy is simple and easy to operate, and has low growth costs. However, in the current research on the preparation of FAPbBr3 epitaxial heterojunctions, the following problems still exist: (1) The concentration of the precursor solution and the heating curve during the epitaxial process are still unclear. If the temperature rise program is not set appropriately, the seed crystal may be completely dissolved during the epitaxial process. At the same time, the heating rate and the composition of the epitaxial layer will also affect whether the heterojunction interface is tight and defect-free. The presence of defects such as holes or cracks will affect the performance of the heterogeneous crystal. (2) Compared with MAPbBr3 perovskite crystals, FAPbBr3 crystals are prone to generate a second phase during growth, and a suitable growth time needs to be set to ensure that an epitaxial heterojunction is obtained before the second phase appears. Summary of the invention

[0006] In view of the deficiencies in the above-mentioned background technology, the present invention mainly solves the problem of unstable dark current of FAPbBr3 single crystal perovskite radiation detection devices. The present invention provides a method for preparing FAPbBr3 heterogeneous crystals with low and stable dark current and its application. The method is low in cost, short in cycle, simple in operation, and can effectively suppress dark current by using a heterojunction epitaxial growth process for FAPbBr3 single crystals, thereby obtaining a radiation detection device with good radiation detection performance for both X-rays and alpha particles.

[0007] The first object of the present invention is to provide a method for preparing a FAPbBr3 heterogeneous crystal having a low and stable dark current, comprising the following steps: Preparation of FAPbBr3 single crystal; Dissolving FABr, PbBr2, and PbCl2 in an organic solvent to obtain an epitaxial layer precursor solution; filtering the epitaxial layer precursor solution to obtain a filtrate; The filtrate was sealed and placed in a water bath, heated to 33-36°C, and then FAPbBr3 single crystals were added. The filtrate was then sealed and heated to 43-46°C to obtain FAPbBr3 heterogeneous crystals with low and stable dark current.

[0008] Preferably, after adding the FAPbBr3 single crystal, the temperature is maintained at 33-36°C for 1-2 hours.

[0009] Preferably, the continuing sealing and heating to 43-46° C. is to start heating to 43-46° C. at a heating rate of 0.6-0.8° C. / h.

[0010] Preferably, the molar ratio of FABr to PbBr2+PbCl2 is 1:1; The molar ratio of PbBr2 to PbCl2 is (0.8~0.95): (0.05~0.2).

[0011] Preferably, the organic solvent is N-N-dimethylformamide and γ-valerolactone in a volume ratio of 1:0.8-1.

[0012] Preferably, the FAPbBr3 single crystal is prepared according to the following steps: Dissolve FABr and PbBr2 in a mixed solvent of N-N-dimethylformamide (DMF) and γ-valerolactone (GVL) to obtain a precursor solution; Filter the precursor solution, collect the filtrate, and seal it with a conical flask, then put it into a water tank with the mouth of the flask sticking out of the water to ensure that all the precursor solution is below the water surface of the water tank, heat it from room temperature, and start heating it to 45-50°C at a heating rate of 3-5°C / day to precipitate crystals; After the crystals are precipitated, take out the crystals, wash and dry them to obtain FAPbBr3 single crystals.

[0013] Preferably, the FABr is prepared by mixing formamidine acetate with hydrobromic acid and distilling at 80°C.

[0014] The second object of the present invention is to provide a FAPbBr3 hetero-crystal having low and stable dark current.

[0015] The third object of the present invention is to provide a FAPbBr3 heterogeneous crystal with low and stable dark current for use in radiation detection devices.

[0016] The fourth object of the present invention is to provide a radiation detector, comprising a FAPbBr3 heterogeneous crystal and gold electrodes evaporated on both sides of the FAPbBr3 heterogeneous crystal.

[0017] Compared with the prior art, the present invention has the following beneficial effects: The present invention provides a method for preparing a FAPbBr3 heterogeneous crystal with low and stable dark current and its application. The present invention uses a liquid phase epitaxy method of a seed crystal combined with inversion crystallization to prepare a FAPbBr3-based perovskite heterojunction for the first time. By finely controlling the heating rate in a liquid phase epitaxy process with simple process and low cost, a smooth and defect-free substrate is formed at the seed crystal interface, thereby obtaining a compact and non-porous heterojunction interface. The FAPbBr3-based heterogeneous crystal prepared by this method has the beneficial effects of reducing the dark current of a photodetector, maintaining a stable dark current level, improving the charge separation efficiency in a photoelectric material, and thereby improving the radiation detection efficiency. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 FAPbBr3 / FAPbBr grown in Example 1 2.9 Cl 0.1 Single crystal; Figure 2 FAPbBr3 / FAPbBr grown in Example 2 2.6 Cl 0.4 Single crystal; Figure 3 This is the FAPbBr3 single crystal grown in Comparative Example 1; Figure 4 is the dark current-voltage curve of Example 1 at -100V to +100V; Figure 5 is the dark current-voltage curve of Example 2 at -100V to +100V; Figure 6 is the dark current-voltage curve of Comparative Example 1 at -100V to +100V; Figure 7 Au / FAPbBr3 / FAPbBr prepared in Example 22.6 Cl 0.4 / Au detector to X-ray response sensitivity and α particle response spectrum, where a~c is the variable metrology X-ray source, d is 241 Am particle source.

[0019] Figure 8 The Au / FAPbBr3 / Au detector prepared in Comparative Example 1 responds to X-rays. DETAILED DESCRIPTION

[0020] In order to enable those skilled in the art to better understand and implement the technical solution of the present invention, the present invention is further described below in conjunction with specific embodiments and drawings, but the embodiments are not intended to limit the present invention.

[0021] The purpose of the present invention is to provide a method for preparing a FAPbBr3 heterogeneous crystal with low and stable dark current and its application, so as to solve the problem of unstable dark current of FAPbBr3 single crystal perovskite radiation detection device. The present invention provides a heterojunction epitaxial growth process for FAPbBr3 single crystal with low cost, short cycle, simple operation and effective dark current suppression, thereby obtaining a radiation detection device with good radiation detection performance for both X-rays and alpha particles.

[0022] In order to achieve the above object, the first aspect of the present invention provides a method for preparing a FAPbBr3 heterogeneous crystal having a low and stable dark current, comprising the following steps: Preparation of FAPbBr3 single crystal; Dissolving FABr, PbBr2, and PbCl2 in an organic solvent to obtain an epitaxial layer precursor solution; filtering the epitaxial layer precursor solution to obtain a filtrate; The filtrate was sealed and placed in a water bath, heated to 33-36°C, and then FAPbBr3 single crystals were added. The filtrate was then sealed and heated to 43-46°C to obtain FAPbBr3 heterogeneous crystals with low and stable dark current.

[0023] Among them, after adding the FAPbBr3 single crystal, the temperature is maintained at 33~36℃ for 1~2h.

[0024] The process of continuing to seal and heat to 43-46° C. is to start heating to 43-46° C. at a heating rate of 0.6-0.8° C. / h.

[0025] The molar ratio of FABr to PbBr2+PbCl2 is 1:1; The molar ratio of PbBr2 to PbCl2 is (0.8~0.95): (0.05~0.2).

[0026] The organic solvent is NN dimethylformamide and γ-valerolactone in a volume ratio of 1:0.8-1.

[0027] The FAPbBr3 single crystal is prepared according to the following steps: Dissolve FABr and PbBr2 in a mixed solvent of N-N-dimethylformamide (DMF) and γ-valerolactone (GVL) to obtain a precursor solution; Filter the precursor solution, collect the filtrate, and seal it with a conical flask, then put it into a water tank with the mouth of the flask sticking out of the water to ensure that all the precursor solution is below the water surface of the water tank, heat it from room temperature, and start heating it to 45-50°C at a heating rate of 3-5°C / day to precipitate crystals; After the crystals are precipitated, take out the crystals, wash and dry them to obtain FAPbBr3 single crystals.

[0028] The FABr was prepared by mixing formamidine acetate with hydrobromic acid and distilling at 80°C.

[0029] A second aspect of the present invention provides a FAPbBr3 heterogeneous crystal having a low and stable dark current.

[0030] A third aspect of the present invention provides an application of a FAPbBr3 heterogeneous crystal having a low and stable dark current in a radiation detection device.

[0031] A fourth aspect of the present invention provides a radiation detector comprising a FAPbBr3 heterogeneous crystal and gold electrodes evaporated on both sides of the FAPbBr3 heterogeneous crystal.

[0032] In one embodiment, a method for preparing a low and stable dark current FAPbBr3 heterogeneous crystal comprises the following steps: S1. Prepare precursor compounds: Mixing formamidine acetate and 48% by mass of hydrobromic acid and distilling at 80° C. to obtain a FABr compound; Among them, the mass of formamidine acetate is 40g, and the mass of hydrobromic acid is 45mL, and the molar ratio is 1:1.

[0033] S2. Prepare the precursor solution: FABr, PbBr2, N-N-dimethylformamide (DMF) and γ-valerolactone (GVL) are mixed to obtain a precursor solution; Among them, the molar ratio of FABr and PbBr2 is 1:1, the volume ratio of organic solvent DMF and GVL is 1:0.8, and the molar concentration of the solute is 1.2-1.55 mol / L, preferably 1.4 mol / L.

[0034] S3. Obtaining seed crystal: The nearly saturated solution obtained from S2 was filtered, and the filtrate was collected and sealed with a conical bottle, and then placed in a temperature-controlled water tank at 30-50°C, with the bottle mouth sticking out of the water surface to ensure that all the precursor solutions were below the water surface of the water tank and heated; The general heating procedure starts from room temperature and then rises to 45~50℃ at a heating rate of 3~5℃ / day to precipitate crystals; After the crystals are precipitated, they are taken out, washed and dried to obtain high-quality FAPbBr3 single crystals.

[0035] S4. Liquid phase epitaxy precursor solution: Mix FABr, PbBr2, PbCl2, N-N-dimethylformamide (DMF) and γ-valerolactone (GVL) to obtain an epitaxial layer precursor solution; The molar ratio of FABr to (PbBr2+PbCl2) is 1:1, and the volume ratio of the organic solvent DMF to GVL is 1:0.8; The FAPbBr3 / FAPbBr prepared here 3-x Cl x The x of the heterojunction is 0.1 or 0.4, where FAPbBr3 / FAPbBr 2.9 Cl 0.1 The molar ratio of PbBr2 to PbCl2 in the precursor solution is 0.95:0.05; FAPbBr3 / FAPbBr 2.6 Cl 0.4 The molar ratio of PbBr2 to PbCl2 in the precursor solution is 0.8:0.2.

[0036] S5. Heterojunction preparation: The nearly saturated solution obtained in S4 was filtered, and the filtrate was collected and sealed with a conical bottle, and then placed in a temperature-controlled water tank at 30-50°C, with the bottle mouth sticking out of the water surface to ensure that all the precursor solution is below the water surface of the water tank, and the temperature is raised; When the temperature rises to 33-36°C, the FAPbBr3 single crystal obtained in S3 is placed as a seed crystal in the epitaxial layer precursor solution, and then the conical flask is sealed and placed in the water tank. Before continuing to heat up, the temperature is kept constant at 33-36°C for 2 hours to dissolve the seed crystal back. Starting from 38°C, the temperature was raised at a rate of 0.6-0.8°C / h to precipitate an epitaxial layer; After the epitaxial layer is precipitated, the temperature is about 45°C, the heterogeneous crystals are taken out, washed and dried, and high-quality FAPbBr3 / FAPbBr is obtained. 3-x Cl x Single crystal; Among them, the epitaxial precursor solution is first heated from room temperature to 33~36℃ in order to reduce the dissolution of the seed crystal in the precursor solution and avoid the seed crystal being completely dissolved; the constant temperature program is performed before heating to ensure that the surface of the seed crystal is dissolved in a small amount so that a smooth and defect-free substrate can be obtained before the epitaxial layer grows; in order to avoid the precipitation of the FAPbBr3 second phase, the epitaxial layer growth is controlled within 10 hours.

[0037] In S3, the crystals are washed with ethanol or DMF and then dried in a vacuum drying oven.

[0038] In S3 and S5, the obtained nearly saturated solution is filtered using an organic filter with a pore size of 0.22 to 0.45 μm.

[0039] According to the present invention, it also includes: S6. Heterogeneous crystal cutting: Since the seed crystal and the epitaxial layer are both three-dimensional crystals, the epitaxial layer will grow all around the seed crystal. After the heterogeneous crystal is taken out, the epitaxial layer around the seed crystal needs to be cut to leave only the (001) surface epitaxial layer; Among them, the seed crystal is cut on all sides to ensure a single-junction heterojunction.

[0040] S7. Crystal grinding and polishing: The growth of FAPbBr3 / FAPbBr 3-x Cl x The single crystal heterojunction was polished by using 5000-7000 grit sandpaper for physical polishing, and then FAPbBr3 / FAPbBr 3-x Cl x Transfer the single crystal to the polishing cloth and add 3 to 5 drops of polishing liquid for chemical polishing.

[0041] S8. Preparation of electrodes: The polished heterogeneous crystal was evaporated on both sides with gold electrodes to obtain Au / FAPbBr3 / FAPbBr 3-x Cl x / Au sandwich heterojunction radiation detector.

[0042] In S6, a diamond wire cutting machine is used to cut the heterogeneous crystal.

[0043] In S7, the polishing liquid is ethanol.

[0044] It should be noted that the experimental methods used in the present invention are all conventional methods unless otherwise specified; the reagents and materials used are all commercially available unless otherwise specified.

[0045] Example 1 A method for preparing a low and stable dark current FAPbBr3 heterogeneous crystal, the steps are as follows: 1) At room temperature, 0.018 mol FABr, 0.018 mol PbBr2, 7.5 ml N-dimethylformamide (DMF) and 7.5 ml γ-valerolactone (GVL) were mixed to obtain a precursor solution; 2) Filter the above solution into a conical flask using a Buchner funnel and 0.22 μm organic filter paper, and seal it with plastic wrap and a rubber stopper.

[0046] 3) Place the conical flask out of the water and place it in a water tank. Heat it up from room temperature at a rate of 4°C / day. Crystals will gradually nucleate and grow in the solution. When the temperature reaches 47°C, take out the FAPbBr3 crystals.

[0047] 4) Wash the FAPbBr3 crystals with DMF and dry them in a vacuum oven for later use.

[0048] 5) at room temperature, 0.0165 mol FABr, 0.015675 mol PbBr2, 0.000825 mol PbCl2, 7.5 ml N-N dimethylformamide (DMF) and 7.5 ml γ-valerolactone (GVL) were mixed to obtain an epitaxial layer precursor solution; 6) Filter the above solution into a conical flask using a Buchner funnel and 0.22μm organic filter paper, seal it with plastic wrap and a rubber stopper, and place it in a water tank to heat. When the temperature rises to 35°C, take out the conical flask, put the FAPbBr3 crystal in, put in the seed crystal, seal it with plastic wrap and a rubber stopper, and place it in a water tank to continue the heating procedure. The epitaxial layer will gradually grow on the surface of the seed crystal. When the temperature reaches about 47°C, take out the heterogeneous crystal.

[0049] 7) Keep the (001) crystal plane of the heterogeneous crystal, cut the remaining epitaxial layers, and then grow FAPbBr3 / FAPbBr 2.9 Cl 0.1 The single crystal heterojunction was polished and Au electrodes were evaporated on the upper and lower surfaces to obtain Au / FAPbBr3 / FAPbBr 2.9 Cl 0.1 / Au detector.

[0050] Example 2 A method for preparing a low and stable dark current FAPbBr3 heterogeneous crystal, the steps are as follows: 1) At room temperature, 0.02325 mol FABr, 0.02325 mol PbBr2, 7.5 ml N-dimethylformamide (DMF) and 7.5 ml γ-valerolactone (GVL) were mixed to obtain a precursor solution; 2) Filter the above solution into a conical flask using a Buchner funnel and 0.22 μm organic filter paper, and seal it with plastic wrap and a rubber stopper.

[0051] 3) Place the conical flask out of the water and place it in a water tank. Heat it up from room temperature at a rate of 4°C / day. Crystals will gradually nucleate and grow in the solution. When the temperature reaches about 48°C, take out the crystals.

[0052] 4) Wash the crystals with DMF and dry them in a vacuum oven for later use.

[0053] 5) at room temperature, 0.021 mol FABr, 0.0168 mol PbBr2, 0.0042 mol PbCl2, 7.5 ml N-N dimethylformamide (DMF) and 7.5 ml γ-valerolactone (GVL) were mixed to obtain an epitaxial layer precursor solution; 6) Filter the above solution into a conical flask using a Buchner funnel and 0.22μm organic filter paper, seal it with plastic wrap and a rubber stopper, and place it in a water tank to heat. When the temperature rises to 35°C, take out the conical flask, put the FAPbBr3 crystal in, put in the seed crystal, seal it with plastic wrap and a rubber stopper, and place it in a water tank to continue the heating procedure. The epitaxial layer will gradually grow on the surface of the seed crystal. When the temperature reaches about 43°C, take out the heterogeneous crystal.

[0054] 7) Keep the (001) crystal plane of the heterogeneous crystal, cut the remaining epitaxial layers, and then grow FAPbBr3 / FAPbBr 2.6 Cl 0.4 The single crystal heterojunction was polished and Au electrodes were evaporated on the upper and lower surfaces to obtain Au / FAPbBr3 / FAPbBr 2.6 Cl 0.4 / Au detectors, and then the X-ray and alpha particle radiation detection performance tests were carried out.

[0055] Comparative Example 1 The preparation method of FAPbBr3 single crystal is as follows: 1) At room temperature, 0.021 mol FABr, 0.021 mol PbBr2, 7.5 ml N-dimethylformamide (DMF) and 7.5 ml γ-valerolactone (GVL) were mixed to obtain a precursor solution; 2) Filter the above solution into a conical flask using a Buchner funnel and 0.22 μm organic filter paper, and seal it with plastic wrap and a rubber stopper.

[0056] 3) Place the conical flask out of the water and place it in a water tank. Heat it up from room temperature at a rate of 4°C / day. Crystals will gradually nucleate and grow in the solution. When the temperature reaches about 49°C, take out the crystals.

[0057] 4) The grown FAPbBr3 single crystal is polished and Au electrodes are evaporated on the upper and lower surfaces to obtain an Au / FAPbBr3 / Au detector.

[0058] In order to illustrate the relevant properties of the heterogeneous crystals provided by the present invention, they are described in conjunction with the accompanying drawings.

[0059] Figure 1 FAPbBr3 / FAPbBr grown in Example 1 2.9 Cl 0.1 Single crystal; from Figure 1 It can be seen that the size of the seed crystal is 2×2 ~ 4×4 mm 2 , and it can be seen that the epitaxial layer is wrapped around the seed crystal and maintains the shape of the seed crystal. Since the composition of the epitaxial layer is slightly different from that of the seed crystal, the color of the epitaxial layer and the seed crystal is almost the same. Because the temperature when it was taken out was 47°C, the epitaxial layer growth time was relatively long and the epitaxial layer was thicker.

[0060] Figure 2 FAPbBr3 / FAPbBr grown in Example 2 2.6 Cl 0.4 Single crystal; from Figure 2 It can be seen that the size of the seed crystal is 4×4 ~ 5×5 mm 2 , and a clear boundary between the seed crystal and the epitaxial layer can be seen. The epitaxial layer wraps around the seed crystal and maintains the shape of the seed crystal. The Cl concentration in the epitaxial layer increases significantly, so the color of the epitaxial layer turns yellow significantly. And it is taken out at a temperature of 43°C, so the epitaxial layer growth time is relatively short and the epitaxial layer is thinner.

[0061] Figure 3 This is the FAPbBr3 single crystal grown in Comparative Example 1; from Figure 3 It can be seen that the size of the grown single crystal is about 4×4 ~ 5×5 mm 2 The single crystal is transparent, defect-free and cubic in shape, indicating good crystal quality.

[0062] Figure 4 is the dark current-voltage curve of Example 1 at -100V to +100V; Figure 5 is the dark current-voltage curve of Example 2 at -100V to +100V; from Figures 4 and 5It can be seen that the negative voltage region has a significant effect in suppressing dark current. When preparing a heterojunction, preparing Au electrodes on both sides of the heterojunction single crystal will obtain a clear junction current-voltage curve, that is, the current is cut off in the reverse bias (negative voltage) region. The dark current in the negative voltage region is not only significantly reduced, but can also maintain a stable low value in a wide negative voltage range, indicating that this is an effective way to obtain low and stable dark current.

[0063] Figure 6 is the dark current-voltage curve of Comparative Example 1 at -100V to +100V; Figure 6 It can be seen that the dark current density value at -100 V is significantly higher than that of Examples 1~2.

[0064] from Figure 6 It can be seen that without preparing a heterojunction, preparing Au electrodes on both sides of the FAPbBr3 single crystal will obtain a typical ohmic current-voltage curve, and the dark current at -100V is reduced by about 5 times before and after preparing the heterojunction on the same sample.

[0065] Figure 7 Au / FAPbBr3 / FAPbBr prepared in Example 2 2.6 Cl 0.4 / Au detector to X-ray response sensitivity and α particle response spectrum, where a~c is the variable metrology X-ray source, d is 241 Am particle source.

[0066] from Figure 7 It can be seen that in the On / Off current-time curve under X-ray irradiation, when the X-ray source is periodically turned off, the dark current of the device can still fall back to the level before the X-ray irradiation begins, and remains stable during this process; at the same time, thanks to the low and stable dark current brought by the heterojunction preparation, the X-ray detection response sensitivity is significantly improved. At the same time, replacing the radiation source with alpha particles can also obtain an alpha particle response energy spectrum with a good peak shape and a symmetrical Gaussian shape.

[0067] Figure 8 The Au / FAPbBr3 / Au detector prepared in Comparative Example 1 responds to X-rays; from Figure 8 It can be seen that the FAPbBr3 single crystal itself has a very weak response to X-rays and cannot maintain its own dark current level under an applied bias, but instead changes gradually over time. In this case, not only can a good X-ray response not be obtained, but it is also impossible to measure the radiation detection performance of any other radiation source.

[0068] The present invention describes preferred embodiments and their effects. However, those skilled in the art may make additional changes and modifications to these embodiments once they are aware of the basic creative concept. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments and all changes and modifications that fall within the scope of the present invention.

[0069] Although embodiments of the present invention have been shown and described, it will be appreciated by those skilled in the art that various changes, modifications, substitutions and variations may be made to the embodiments without departing from the principles and spirit of the present invention, and that the scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preparing FAPbBr3 heterogeneous crystals with low and stable dark current, characterized in that: The following steps are involved: Preparation of FAPbBr3 single crystal; Dissolving FABr, PbBr2, and PbCl2 in an organic solvent to obtain an epitaxial layer precursor solution; filtering the epitaxial layer precursor solution to obtain a filtrate; The filtrate was sealed and placed in a water bath, heated to 33-36°C, and then FAPbBr3 single crystals were added. The filtrate was then sealed and heated to 43-46°C to obtain FAPbBr3 heterogeneous crystals with low and stable dark current.

2. The method for preparing FAPbBr3 heterogeneous crystals with low and stable dark current according to claim 1, characterized in that: After adding the FAPbBr3 single crystal, maintain a constant temperature at 33~36℃ for 1~2h.

3. The method for preparing FAPbBr3 heterogeneous crystals with low and stable dark current according to claim 2, characterized in that: The process of continuing to seal and heat to 43-46° C. is to start heating to 43-46° C. at a heating rate of 0.6-0.8° C. / h.

4. The method for preparing FAPbBr3 heterogeneous crystals with low and stable dark current according to claim 1, characterized in that: The molar ratio of FABr to PbBr2+PbCl2 is 1:1; The molar ratio of PbBr2 to PbCl2 is (0.8~0.95): (0.05~0.2).

5. The method for preparing FAPbBr3 heterogeneous crystals with low and stable dark current according to claim 1, characterized in that: The organic solvent is NN dimethylformamide and γ-valerolactone in a volume ratio of 1:0.8-1.

6. The method for preparing FAPbBr3 heterogeneous crystals with low and stable dark current according to claim 1, characterized in that: The FAPbBr3 single crystal is prepared according to the following steps: Dissolve FABr and PbBr2 in a mixed solvent of N-N-dimethylformamide (DMF) and γ-valerolactone (GVL) to obtain a precursor solution; Filter the precursor solution, collect the filtrate, and seal it with a conical flask, then put it into a water tank with the mouth of the flask sticking out of the water to ensure that all the precursor solution is below the water surface of the water tank, heat it from room temperature, and start heating it to 45-50°C at a heating rate of 3-5°C / day to precipitate crystals; After the crystals are precipitated, take out the crystals, wash and dry them to obtain FAPbBr3 single crystals.

7. The method for preparing FAPbBr3 heterogeneous crystals with low and stable dark current according to claim 6, characterized in that: The FABr was prepared by mixing formamidine acetate with hydrobromic acid and distilling at 80°C.

8. A FAPbBr3 heterogeneous crystal having low and stable dark current obtained by the method according to any one of claims 1 to 7.

9. Use of the FAPbBr3 heterocrystal with low and stable dark current as claimed in claim 8 in a radiation detection device.

10. A radiation detector, characterized in that: It includes a FAPbBr3 heterogeneous crystal and gold electrodes evaporated on both sides of the FAPbBr3 heterogeneous crystal.

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