Methylamino perovskite single crystal, preparation method and X-ray detector thereof

Abstract

The invention discloses a methylamino perovskite single crystal, a preparation method and an X-ray detector thereof. The MAX / BX2 composite material is mainly prepared by growing a precursor consisting of MAX, BX2 and an additive, wherein the molar ratio of the MAX to the BX2 to the additive is 1: 1: (0.05-0.1); the method comprises the following steps: preparing a perovskite single crystal raw material, adding MAX, BX2 and an additive prepared in the step S1 into a solvent according to a molar ratio of 1: 1: (0.05-0.1), stirring at room temperature to obtain a precursor solution for growing an MABX3 perovskite single crystal, and finally growing by using the precursor solution to obtain the methylamino perovskite single crystal. According to the method, deprotonation of methylamine cations in the precursor solution can be effectively inhibited, the methylamine perovskite single crystal with high quality, low defect density and large size can be prepared and grown, and the methylamine perovskite single crystal is used for preparing an X-ray detector with high sensitivity.

Description

Technical Field

[0001] The present invention relates to the technical field of perovskite single crystal X-ray detection, and in particular to a method for preparing a methylamine perovskite single crystal and a methylamine perovskite single crystal X-ray detector. Background Art

[0002] The potential of perovskite polycrystalline thin films in the fields of optoelectronics and photovoltaics has gradually emerged and developed rapidly. Although perovskite materials have a high defect tolerance, their degradation and ion migration problems are difficult to solve. People have gradually realized that the large number of grain boundaries and defects in perovskite polycrystalline materials are important causes of this problem. In comparison, perovskite single crystals have ultra-long carrier transmission distances, lower defect density, and higher carrier mobility. With these advantages, perovskite single crystals have also received attention in fields such as optoelectronic detection.

[0003] The crystal growth of methylamine perovskite single crystals is mainly carried out by the solution method. The solution method can not only achieve preparation at a lower temperature, but also has a competitive cost for crystal growth. However, the defects of the solution method growth cannot be ignored, such as the complex system, the large number of reactions and changes involved in the crystal growth process, and the poor controllability, which makes it difficult to grow high-quality methylamine perovskite single crystals by the solution method.

[0004] Solution growth is sensitive to environmental changes. Temperature fluctuations, vibrations, eddies, local concentration changes, supersaturation changes, substrate stress, etc. can have a great impact on it. Among them, the instability of the precursor solution is an important reason that restricts the crystallization quality of methylamine perovskite single crystals and the performance of their optoelectronic devices. Organic solvents and organic ammonium salts are necessary substances in the solution method. On the one hand, organic solvents have poor stability. For example, DMF (N, N-dimethylformamide) solvents will evaporate when heated and decompose themselves to produce HCOOH (formic acid), changing the solvent composition. In addition, MA + (Methylamine cation) reacts easily with DMF to produce DMA + (dimethylamine cation), thereby changing the composition of the precursor solution, and more importantly, MA + Deprotonation easily occurs in the solution, thus generating volatile methylamine molecules, which causes the composition and concentration of the precursor solution to change greatly with time and temperature during the growth process. It is difficult to keep the solution stable, and it is difficult to achieve high-quality, large-size crystal growth. Summary of the invention

[0005] For the MA in the solution growth of methylamine perovskite single crystals +Deprotonation leads to the problem of decreased crystal quality and difficulty in large-size growth. The present invention provides a method for achieving stable growth of methylamino perovskite single crystals by adding a deprotonation inhibitor. The growth process has high controllability, short preparation cycle, low equipment requirements, and low cost. The single crystals finally prepared have high crystallinity, large size, and good X-ray response performance.

[0006] To achieve the above objectives, the present invention is implemented through the following technical solutions: 1. A methylamine perovskite single crystal: It is mainly grown from a precursor composed of MAX, BX2 and additives, the molar ratio of MAX, BX2 and additives is 1:1:0.05-0.1, and is specifically a MABX3 perovskite single crystal.

[0007] MA in the MAX is a methylamine cation and X is a halogen anion; B in the BX2 is a lead cation, a selenium cation or a germanium cation, and X is a halogen anion; The additive is one or more of ammonium bromide, dimethylammonium bromide and methylammonium bromide.

[0008] 2. A method for preparing a methylamine perovskite single crystal, characterized in that the method comprises the following steps: Step S1, preparation of perovskite single crystal raw materials: preparation of MAX, BX2, additives and solvents; Step S2, preparation of precursor solution: adding MAX, BX2 and additives prepared in step S1 to the solvent in a molar ratio of 1:1:0.05-0.1, stirring at room temperature for 24 hours, to obtain a precursor solution that can be used to grow MABX3 perovskite single crystals; Step S3, preparation of methylamine perovskite single crystal: The precursor solution is used to grow the methylamine perovskite single crystal by adopting the seed method.

[0009] In the step S1, the cation MA of MAX is a methylamine cation, and the anion X is a halogen anion; The cation B in BX2 is a lead cation, a selenium cation or a germanium cation, and the anion X is a halogen anion; The additive is one or more of ammonium bromide, dimethylammonium bromide, and methylammonium bromide; The solvent is one or more of γ-butyrolactone, N,N-dimethylformamide, propylene carbonate or dimethyl sulfoxide; In step S2, the concentration of BX2 in the solvent is 1.2 mol / L, and the others are configured according to the proportions, such as MAX is also 1.2 mol / L.

[0010] The step S3 is specifically as follows: S31, taking a smaller volume of precursor solution, placing it on a heating table and heating it at a step heating rate of 4°C per hour, until a fixed-size seed crystal of about 1 mm appears at the bottom of the solution as an initial seed crystal; S32, taking the initial seed crystal and placing it at the bottom of a larger volume of precursor solution, and after the seed crystal size is stabilized, heating at a step rate of 1°C per day until the crystal grows to a specified size and then stops.

[0011] Specifically, the volume of the precursor solution in S32 is larger than the volume of the precursor solution in S31.

[0012] In the step S2, a precursor solution is prepared at room temperature and stirred for 24 hours. During the seed crystal growth process, the temperature of the heating stage is controlled at 60-120° C., and during the subsequent crystal growth process, the temperature of the heating stage is controlled at 40-100° C.

[0013] The step-by-step temperature increase in step S31 is from room temperature to 60-120° C., and the step-by-step temperature increase in step S32 is from room temperature to 40-100° C.

[0014] The seed crystal size stabilization treatment in step S32 is to continuously add measures so that the seed crystals in the precursor solution no longer become smaller.

[0015] Specifically, at a certain temperature, if the seed crystal placed in the precursor solution gradually dissolves in the precursor solution, then the temperature of the heating stage is increased, and the seed crystal is placed in the precursor solution again to observe whether the seed crystal dissolves and disappears again. If it disappears, the temperature of the heating stage is further increased, and another seed crystal is placed, and the above steps are repeated until the size of the seed crystal no longer decreases within 2 hours, and the seed crystal size is determined to be stable.

[0016] The seeds added in the above-mentioned addition measures are initial seeds.

[0017] 3. A methylamine perovskite single crystal X-ray detector, the X-ray detector comprising a methylamine perovskite single crystal obtained by the above-mentioned methylamine perovskite single crystal preparation method, the methylamine perovskite single crystal is used to prepare an X-ray absorption layer in the X-ray detector.

[0018] The detector is a photoconductive detector, and the structure of the photoconductive detector is an electrode, a perovskite single crystal, and an electrode. The electrode material of the photoconductive detector is one or more of gold, indium gallium alloy, bismuth, and copper.

[0019] In the specific implementation, the methylamine perovskite single crystal X-ray detector was placed under X-ray irradiation at different dose rates. A Keithley 2400 source meter was used to apply bias to the device, and the light and dark current data of the device were collected at the same time. A RADCAL ACCU GOLD + 10X6-180 ion chamber dosimeter was used to record the radiation dose rate, and the device sensitivity was fitted for testing.

[0020] In addition, X-ray diffraction (XRD) was used to characterize the structure of MABX3 perovskite single crystals, and the XRD spectrum was obtained. The rocking curve test of the single crystal was performed to obtain the half width height to characterize the crystal crystallinity. The instruments used were X' PERRT 3 MRD, Cu K α The characterization was carried out under the working conditions of 40 KV and 30 mA with radiation (λ=1.5406 Å‌). The rocking curve half-width height below 0.05° was considered to have a high degree of crystallinity.

[0021] The present invention develops a preparation method, by adding a deprotonation inhibitor as an additive, through the deprotonation process of the additive in the precursor solution and MA + competes with the deprotonation process of MA to inhibit + The deprotonation process of the precursor solution is improved to improve the stability of the precursor solution to ensure that the methylamine perovskite single crystal can grow stably in the precursor solution. The method can obtain high-quality and large-sized methylamine perovskite single crystals. The use of such single crystals to prepare devices can realize X-ray detectors with high detection sensitivity. The present invention can improve the stability of the precursor solution, which is crucial to ensuring the quality of the perovskite single crystal and the performance of its devices.

[0022] The beneficial technical effects of the present invention are as follows: The scheme of the present invention is highly operable, simple and easy to implement, and can effectively inhibit the deprotonation of methylamine cations in the precursor solution by introducing additives, thereby improving the stability of the solution.

[0023] The present invention can prepare and grow high-quality, low-defect-density, large-size methylamine-based perovskite single crystals, which can be used to prepare X-ray detectors with high sensitivity. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 The figures are the picture of MAPbBr3 perovskite single crystal grown by the method of Example 1 and its XRD rocking curve, wherein (a) represents the picture of MAPbBr3 single crystal and (b) represents the XRD rocking curve.

[0025] Figure 2 It is a schematic diagram of a MAPbBr3 single crystal X-ray detector prepared by the methods of Examples 1 and 3 and the method of Comparative Example 1.

[0026] Figure 3 It is the dark current diagram of the MAPbBr3 single crystal X-ray detector prepared by the methods of Examples 1 and 3 and the method of Comparative Example 1.

[0027] Figure 4 It is a detection step diagram and a sensitivity fitting curve diagram of the MAPbBr3 perovskite single crystal X-ray detector prepared by the method of Example 1 at different X-ray doses, wherein (a) represents the X-ray detection step diagram, and (b) represents the sensitivity fitting curve diagram.

[0028] Figure 5 It is a picture of MAPbBr3 perovskite single crystal grown by the method of Example 2 and an XRD rocking curve spectrum, wherein (a) represents the picture of MAPbBr3 single crystal, and (b) represents the XRD rocking curve.

[0029] Figure 6 It is a picture of MAPbBr3 perovskite single crystal grown by the method of Example 3 and an XRD rocking curve spectrum, wherein (a) represents the picture of MAPbBr3 single crystal, and (b) represents the XRD rocking curve.

[0030] Figure 7 It is the detection step diagram and sensitivity fitting curve diagram of the MAPbBr3 perovskite single crystal X-ray detector prepared by the method of Example 3 under different X-ray doses, wherein (a) represents the X-ray detection step diagram, and (b) represents the sensitivity fitting curve diagram.

[0031] Figure 8 These are images and XRD patterns of MAPbBr3 perovskite single crystals prepared by the method of Comparative Example 1, wherein (a) represents the image of MAPbBr3 single crystals, and (b) represents the XRD pattern.

[0032] Fig. 9 The detection step diagram and sensitivity fitting curve diagram of the MAPbBr3 perovskite single crystal X-ray detector prepared by the method of Example 1 under different X-ray doses, wherein (a) represents the X-ray detection step diagram, and (b) represents the sensitivity fitting curve diagram. DETAILED DESCRIPTION

[0033] In order to more clearly indicate the advantages and features of the embodiments of the present invention, the technical solutions in the embodiments of the present invention will be fully and clearly described below in conjunction with the drawings in the embodiments of the present invention. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Generally, the components of the embodiments of the present invention described and shown in the drawings here can be arranged and designed in different configurations.

[0034] Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings does not limit the scope of the invention claimed for protection, but merely represents a specific embodiment of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0035] It should be noted that similar reference numerals and letters denote similar items in the following drawings, and therefore, once an item is defined in one drawing, further definition and explanation thereof is not required in subsequent drawings.

[0036] In the description of the embodiments of the present invention, it should be noted that the terms "inside", "outside", "upper", etc. indicate orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, or are the orientations or positional relationships in which the inventive product is usually placed when used. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0037] The embodiments of the present invention and comparative examples are as follows: Example 1

[0038] This embodiment includes the following steps: Step S1, preparation of perovskite single crystal raw materials: prepare MABr, PbBr2 and additives, the additive is NH4Br, and the solvent is DMF.

[0039] Step S2, preparation of precursor solution: the molar ratio of MABr, PbBr2, and NH4Br is 1:1:0.05, the concentration of the precursor solution is 1.2 mol / L, and the precursor solution is prepared at room temperature.

[0040] Step S3, preparation of MAPbBr3 single crystal: take 2 ml of the precursor solution in step S2 into a bottle, heat it to 70 °C at a heating rate of 4 °C per hour, and then keep heating on a 70 °C heating table to obtain a 1 mm seed crystal. Take the 1 mm seed crystal and place it in a bottle containing 10 ml of the precursor solution. After the seed crystal size is stable, start growing on a 50 °C heating table at a heating rate of 1 °C / 24h until the length and width of the crystal are close to 10 mm.

[0041] Step S4: 100 nm Au and 100 nm Bi are deposited on both sides of the single crystal in a vacuum thermal evaporation device to obtain a ray detector and perform an X-ray detection test. Figure 1The picture and XRD rocking curve of MAPbBr3 perovskite single crystal obtained in Example 1 are shown, where (a) represents the picture of MAPbBr3 single crystal, and (b) represents the XRD rocking curve. The MAPbBr3 single crystal is orange-yellow, with a size of 8mm*8mm, and a half-width of the (100) crystal plane rocking curve of 0.03617°. The crystallinity of the MAPbBr3 single crystal is relatively high. It can be seen that the method of Example 1 successfully prepared high-quality MAPbBr3 single crystal. The addition of ammonium bromide additive increased the acidity of the solution, effectively inhibited the deprotonation of methylamine cations, ensured that the ratio of MABr and PbBr2 in the precursor solution did not change significantly during the crystal growth process, improved the stability of the solution, and obtained high-quality single crystals with low defect density.

[0042] Schematic diagram of MAPbBr3 single crystal X-ray detector Figure 2 As shown, the perovskite single crystal is a MAPbBr3 single crystal, and the two sides of the single crystal are 100nm thick metal Au and metal Bi respectively. Figure 3 The dark current graphs of the MAPbBr3 single crystal X-ray detectors prepared in Example 1, Example 3 and Comparative Example 1 are shown. The working voltage of the device for X-ray detection is negative voltage. In the range of -100V to 0V, the dark current density of the device obtained in Example 1 is less than 10 μA cm -2 The dark current of the device obtained in this embodiment is reduced by nearly an order of magnitude compared with that of Comparative Example 1, indicating that after the introduction of ammonium bromide, the obtained crystal quality is good and the device performance is excellent.

[0043] like Figure 4 The figure shows the detection step diagram and sensitivity fitting curve diagram of the MAPbBr3 perovskite single crystal X-ray detector obtained in Example 1 at a working voltage of -50V and different X-ray doses, wherein (a) represents the X-ray detection step diagram, and (b) represents the sensitivity fitting curve diagram. Figure 4 The steps of different heights in (a) represent the response current under different X-ray doses. As the X-ray dose decreases, the corresponding response current also decreases. Figure 4 and Figure 8 By comparing this embodiment with comparative example 1, it can be seen that the response current of the device obtained in this embodiment under different doses of X-rays is greater than the response current of the device obtained in comparative example 1. The different response currents obtained in this embodiment and comparative example 1 are fitted with the corresponding different X-ray doses, and good linear fits are obtained, indicating that the linearity of the response current of the device to different doses of X-rays is good. This embodiment can obtain 55030 μC Gy air -1 cm -2 The detection sensitivity is higher than that of the device obtained in Comparative Example 1 (44423 μC Gy air-1 cm -2 ), showing excellent X-ray detection performance. Example 2

[0044] This embodiment includes the following steps: Step S1, preparation of perovskite single crystal raw materials: prepare MABr, PbBr2 and additives, the additive is methyl ammonium bromide (FABr), and the solvent is DMF.

[0045] Step S2, preparation of precursor solution: the molar ratio of MABr, PbBr2, and FABr is 1:1:0.1, the concentration of the precursor solution is 1.2 mol / L, and the precursor solution is prepared at room temperature.

[0046] Step S3, preparation of MAPbBr3 single crystal: take 2 ml of the precursor solution in step S2 into a bottle, heat it to 85 °C at a heating rate of 4 °C per hour, and then keep heating on a heating table at 85 °C to obtain a 1 mm seed crystal. Take the 1 mm seed crystal and place it in a beaker containing 50 ml of the precursor solution. After the seed crystal size stabilizes, start growing it on a 65 °C heating table at a heating rate of 1 °C / 24h until the length and width of the crystal are close to 20 mm.

[0047] like Figure 5 It is a picture of MAPbBr3 perovskite single crystal grown by the method of Example 2 and an XRD rocking curve spectrum, wherein (a) represents a picture of MAPbBr3 single crystal, and (b) represents an XRD rocking curve. The size of the MAPbBr3 single crystal obtained in this example is 20mm*23mm, and the half-height width of the rocking curve is 0.0255°. The crystal quality is excellent. While ensuring a large size, the crystal quality is even better than that of Example 1 and Comparative Example 1. In the precursor solution to which methyl bromide is added, there is a competitive process of deprotonation between the methyl bromide cation and the methylamine cation, in which the methyl bromide cation is more easily deprotonated, thereby inhibiting the deprotonation of the methylamine cation, improving the stability of the solution during long-term crystal growth, and achieving inch-level growth of high-quality MAPbBr3 single crystals. Example 3

[0048] This embodiment includes the following steps: Step S1, preparation of perovskite single crystal raw materials: prepare MABr, PbBr2 and additives, the additive is dimethylamine bromide (DMABr), and the solvent is DMF.

[0049] Step S2, preparation of precursor solution: the molar ratio of MABr, PbBr2, and DMABr is 1:1:0.05, the concentration of the precursor solution is 1.2 mol / L, and the precursor solution is prepared at room temperature.

[0050] Step S3, preparation of MAPbBr3 single crystal: take 2 ml of the precursor solution in step S2 into a bottle, heat it to 80 °C at a heating rate of 4 °C per hour, and then keep heating on a heating table at 80 °C to obtain a 1 mm seed crystal. Take the 1 mm seed crystal and place it in a beaker containing 10 ml of the precursor solution. After the seed crystal size stabilizes, start growing it on a 60 °C heating table at a heating rate of 1 °C / 24h until the length and width of the crystal are close to 10 mm.

[0051] Step S4: 100 nm Au and 100 nm Bi are respectively deposited on both sides of the single crystal in a vacuum thermal evaporation device to obtain a ray detector, and an X-ray detection test is performed.

[0052] like Figure 6 The MAPbBr3 perovskite single crystal image and XRD rocking curve spectrum grown by the method of Example 3, wherein (a) represents the MAPbBr3 single crystal image, and (b) represents the XRD rocking curve. The size of the MAPbBr3 single crystal obtained in this example is 9mm*10mm, the half-height width of the XRD rocking curve is 0.0203°, and the crystal quality is optimal. It can be seen that the introduction of dimethylamine bromide additive can further improve the stability of the precursor solution. Methylamine cations easily react with each other to form dimethylamine cations during the deprotonation process. After adding dimethylamine cations to the precursor solution, the reaction of methylamine cations with each other is inhibited, and then their deprotonation is inhibited, thereby improving the crystal quality of the MAPbBr3 single crystal.

[0053] Schematic diagram of MAPbBr3 single crystal X-ray detector Figure 2 As shown, the perovskite single crystal is a MAPbBr3 single crystal, and the two sides of the single crystal are 100nm thick metal Au and metal Bi respectively. Figure 3 Shown are dark current diagrams of the MAPbBr3 single crystal X-ray detectors prepared in Example 1, Example 3 and Comparative Example 1. The operating voltage of the device for X-ray detection is negative voltage, in the range of -100V to 0V, and the dark current density of the device obtained in this example is the lowest.

[0054] like Figure 7 The following are the detection step diagrams and sensitivity fitting curves of the MAPbBr3 perovskite single crystal X-ray detector prepared by the method of Example 3 at -50 working voltage and different X-ray doses, where (a) represents the X-ray detection step diagram, and (b) represents the sensitivity fitting curve diagram. Steps of different heights represent the response currents under different X-ray doses. As the X-ray dose decreases, the corresponding response current also decreases. Figure 4 , Figure 7 , Figure 8It can be seen that the response current of the device obtained in this embodiment under different doses of X-rays is greater than the response current obtained in Comparative Example 1 and Example 1. The response current of the device in this embodiment is fitted with the corresponding X-ray dose, and a good linear relationship can be obtained, indicating that the device has good linearity in response current to different doses of X-rays. In this embodiment, 99225 μC Gy air -1 cm -2 The detection sensitivity is much higher than that of the device obtained in Comparative Example 1 (44423 μC Gy air -1 cm -2 ), showing excellent X-ray detection performance. Comparative Example 1

[0055] Step S1, preparation of perovskite single crystal raw materials: prepare MABr and PbBr2, and the solvent is DMF.

[0056] Step S2, preparation of precursor solution: the molar ratio of MABr and PbBr2 is 1:1, the concentration of the precursor solution is 1.2 mol / L, and the precursor solution is prepared at room temperature.

[0057] Step S3, preparation of MAPbBr3 single crystal: take 2 ml of the precursor solution in step S2 into a bottle, heat it to 65 °C at a heating rate of 4 °C per hour, and then keep heating on a heating table at 80 °C to obtain a 1 mm seed crystal. Take the 1 mm seed crystal and place it in a beaker containing 10 ml of the precursor solution. After the seed crystal size stabilizes, start growing it on a 48 °C heating table at a heating rate of 1 °C / 24h until the length and width of the crystal are close to 10 mm.

[0058] Step S4: 100 nm Au and 100 nm Bi are respectively deposited on both sides of the single crystal in a vacuum thermal evaporation device to obtain a ray detector, and an X-ray detection test is performed.

[0059] MAPbBr3 single crystal was successfully prepared by the comparative method. The single crystal photo and XRD spectrum are shown in Figure 8 As shown, the MAPbBr3 crystal is a single crystal.

[0060] like Figure 8 The following are images and XRD patterns of MAPbBr3 perovskite single crystals prepared by the method of Comparative Example 1, wherein (a) represents the image of MAPbBr3 single crystal, and (b) represents the XRD pattern. Figure 8 In (a), cracks can be seen inside the crystal, indicating that the crystal obtained in the comparative example has poor crystallinity. Figure 8 From the XRD pattern of (b), it can be seen that the crystal obtained in Comparative Example 1 is a single crystal.

[0061] Schematic diagram of MAPbBr3 single crystal X-ray detector Figure 2 As shown, the perovskite single crystal is a MAPbBr3 single crystal, and the two sides of the single crystal are 100nm thick metal Au and metal Bi respectively. Figure 3 The dark current graphs of the MAPbBr3 single crystal X-ray detectors prepared in Example 1, Example 3 and Comparative Example 1 are shown. The working voltage of the device for X-ray detection is negative voltage. In the range of -100V to 0V, the dark current density of the device obtained in Comparative Example 1 is the highest, indicating that the single crystal obtained in Comparative Example 1 has the worst quality and the highest defect density. Fig. 9 The following are the detection step diagram and sensitivity fitting curve diagram of the MAPbBr3 perovskite single crystal X-ray detector prepared by the method of Example 1 under different X-ray doses, wherein (a) represents the X-ray detection step diagram, and (b) represents the sensitivity fitting curve diagram. Steps of different heights represent the response current under different X-ray doses. As the X-ray dose decreases, the corresponding response current also decreases. Comparing this comparative example with Examples 1 and 3, it can be seen that under different doses of X-rays, the response current of the device obtained in this comparative example is the smallest. The response current under different doses of X-rays is fitted with the corresponding dose, and it is found that the linearity of the response current of the device obtained in this comparative example to different doses of X-rays is good. However, the X-ray detection sensitivity of the device obtained in this comparative example is 44423 μC Gy air -1 cm -2 , which are far lower than those of Example 1 and Example 3, and the X-ray detection performance is poor.

[0062] The crystal quality obtained in comparative example 1 is the lowest, the device dark current is the largest, and the X-ray response current is the lowest. Compared with the above parameters, the data obtained in Examples 1, 2, and 3 have been greatly improved. It can be seen that after the introduction of the additive, the deprotonation process of the methylamine cation is effectively suppressed, and the stability of the solution is improved. This can ensure the stable growth of the crystal, reduce the formation of crystal defects, and improve the crystal quality. The obtained MAPbBr3 single crystal can be used to prepare an X-ray detector with high detection sensitivity.

[0063] The above specific implementations are used to explain the present invention, rather than to limit the present invention. Any modifications and changes made to the present invention within the spirit of the present invention and the protection scope of the claims shall fall within the protection scope of the present invention. The above description is only a preferred implementation of the present invention, so any equivalent changes or modifications made according to the structure, features and principles described in the scope of the patent application of the present invention are included in the scope of the patent application of the present invention.

Claims

1. A methylamine perovskite single crystal, characterized in that: It is mainly grown from a precursor consisting of MAX, BX2 and additives, and the molar ratio of MAX, BX2 and additives is 1:1:0.05-0.

1.

2. The methylamine perovskite single crystal according to claim 1, characterized in that: The MA in the MAX is a methylamine cation, and X is a halogen anion; the B in the BX2 is a lead cation, a selenium cation or a germanium cation, and X is a halogen anion; and the additive is one or more of ammonium bromide, dimethylammonium bromide, and methylamine bromide.

3. A method for preparing a methylamine perovskite single crystal, characterized in that: The method comprises the following steps: Step S1, preparation of perovskite single crystal raw materials: preparation of MAX, BX2, additives and solvents; Step S2, preparation of a precursor solution: adding the MAX, BX2 and additives prepared in step S1 to a solvent in a molar ratio of 1:1:0.05-0.1, stirring at room temperature, to obtain a precursor solution that can be used to grow a MABX3 perovskite single crystal; Step S3, preparation of methylamine perovskite single crystal: using a precursor solution and adopting a seed crystal method to grow a methylamine perovskite single crystal.

4. The method for preparing a methylamine perovskite single crystal according to claim 3, characterized in that: In the step S1, MA of MAX is methylamine, and X is a halogen; B in BX2 is lead, selenium or germanium, and X is a halogen; The additive is one or more of ammonium bromide, dimethylammonium bromide, and methylammonium bromide; The solvent is one or more of γ-butyrolactone, N,N-dimethylformamide, propylene carbonate or dimethyl sulfoxide; In the step S2, the concentration of BX2 in the solvent is 1.2 mol / L.

5. The method for preparing a methylamine perovskite single crystal according to claim 3, characterized in that: The step S3 is specifically as follows: S31, taking a smaller volume of precursor solution, heating it at a step heating rate of 4° C. per hour until a seed crystal of a fixed size appears at the bottom of the solution as an initial seed crystal; S32. Take the initial seed crystal and place it at the bottom of a larger volume of precursor solution. After the seed crystal size stabilizes, increase the temperature at a step rate of 1°C per day until the crystal grows to a specified size.

6. The method for preparing a methylamine perovskite single crystal according to claim 3, characterized in that: In the step S2, a precursor solution is prepared at room temperature and stirred for 24 hours, the temperature of the heating stage is controlled at 60-120° C. during the seed crystal growth process, and the temperature of the heating stage is controlled at 40-100° C. during the subsequent crystal growth process; The step-by-step temperature increase in step S31 is from room temperature to 60-120° C.; the step-by-step temperature increase in step S32 is from room temperature to 40-100° C.

7. The method for preparing a methylamine perovskite single crystal according to claim 5, characterized in that: The size of the seed crystals in step S32 is stabilized by continuously adding measures so that the seed crystals in the precursor solution no longer become smaller.

8. A methylamine perovskite single crystal, characterized in that: The product is prepared by the preparation method described in any one of claims 3 to 7.

9. A methylamine perovskite single crystal X-ray detector, characterized in that: The X-ray detector comprises the methylamine perovskite single crystal according to any one of claims 1-2 or the methylamine perovskite single crystal obtained by the methylamine perovskite single crystal preparation method according to any one of claims 3-7.

10. The methylamine perovskite single crystal X-ray detector according to claim 9, characterized in that: The detector is a photoconductive detector, and the structure of the photoconductive detector is an electrode, a perovskite single crystal, and an electrode. The electrode material of the photoconductive detector is one or more of gold, indium gallium alloy, bismuth, and copper.

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