All-inorganic lead-free two-dimensional perovskite single crystal and preparation method and application thereof

Abstract

The invention relates to the technical field of photoelectric detectors and semiconductor materials, and particularly provides an all-inorganic lead-free two-dimensional perovskite single crystal as well as a preparation method and application thereof. According to the invention, N-ethyl-N-methylpiperidine iodized salt is introduced, and an improved cooling crystallization means of introducing a seed crystal is combined, so that the crystallization kinetics and the surface state of the lead-free two-dimensional perovskite are fundamentally changed; the problems of low crystal quality and poor X-ray detection and visible light detection device performance caused by poor growth controllability and multiple surface defects of the lead-free two-dimensional perovskite are solved. The obtained single crystal is large in size, low in defect density and smooth in surface, so that electrode contact and carrier extraction are facilitated. The performance of a detector based on the single crystal is greatly improved (the sensitivity of an X-ray detector reaches nearly 60000C. Gy <-1 >. Cm <-2 >, the responsivity of a visible light dual-mode detector exceeds 4000mA / W, and the response speed is within 1ms).

Description

Technical Field

[0001] This invention relates to the field of photodetector and semiconductor material technology, and in particular to an all-inorganic lead-free two-dimensional perovskite single crystal, its preparation method and application. Background Technology

[0002] In recent years, perovskite materials have received widespread attention in the field of X-ray and visible light detection. However, the following prominent problems still exist in the existing technology: Although lead-based perovskites have excellent performance, the biotoxicity of lead limits their application in human contact scenarios such as medical imaging; the organic components in organic-inorganic hybrid perovskites are easily affected by heat, light and moisture, resulting in poor device stability and short lifespan; although lead-free two-dimensional perovskites (such as A3B2X9) are environmentally friendly, their device performance is far inferior to that of lead-based perovskites. The bottleneck lies in the poor crystal quality, specifically manifested as: (1) poor growth controllability: traditional methods are difficult to obtain large-size single crystals, usually only millimeter-sized fragments; (2) rough surface: Ra is greater than 10 nm, affecting electrode contact and reducing carrier extraction efficiency; (3) high defect density: defect density is higher than 10 nm. 11 cm -3 This leads to severe nonradiative recombination.

[0003] Existing technologies mostly use general-purpose quaternary ammonium salts for passivation, but their molecular structure has poor compatibility with the crystal surface, resulting in limited passivation effects and the potential introduction of insulating impurities. These structural defects directly lead to low detector responsivity (below 500 mA / W), slow response speed (greater than 100 ms), and poor stability. Therefore, developing a dedicated additive capable of simultaneously controlling the crystallization process and surface states from the growth source is key to overcoming the performance bottlenecks of lead-free perovskites.

[0004] Based on this, the present invention designs an all-inorganic lead-free two-dimensional perovskite single crystal, its preparation method and application. Summary of the Invention

[0005] This invention provides an all-inorganic lead-free two-dimensional perovskite single crystal, its preparation method, and its application, with the aim of solving the aforementioned problems existing in the background art.

[0006] To achieve the above objectives, embodiments of the present invention provide an all-inorganic lead-free two-dimensional perovskite single crystal, its preparation method, and its applications. The present invention introduces N-ethyl-N-methylpiperidine iodide as a surface passivating agent, combined with an improved cooling crystallization method involving rapid initial cooling followed by slower cooling and the introduction of seed crystals, fundamentally altering the crystallization kinetics and surface states of lead-free two-dimensional perovskites, successfully preparing high-quality all-inorganic lead-free type 329 perovskite single crystals. This successfully solves the problems of low crystal quality and poor performance in X-ray and visible light detection devices caused by poor growth controllability and numerous surface defects in lead-free two-dimensional perovskites. Compared with traditional linear alkyl ammonium salts or aromatic ammonium salts, the cyclic piperidine cation of N-ethyl-N-methylpiperidine iodide has a rigid spatial configuration and a suitable volume, enabling more effective selective adsorption onto specific crystal faces, significantly altering surface energy, and promoting preferential crystal growth along the two-dimensional plane. Furthermore, this cation has better interaction with halogen vacancies and metal dangling bonds on the crystal surface, thereby achieving efficient intrinsic passivation and reducing the surface defect state density.

[0007] One aspect of the present invention provides a fully inorganic lead-free two-dimensional perovskite single crystal, wherein the chemical formula of the fully inorganic lead-free two-dimensional perovskite single crystal is A3B2X9; wherein A is Rb or Cs; B is Sb or Bi; and C is I or Br; The described all-inorganic lead-free two-dimensional perovskite single crystal has a large size, low defect density, and smooth surface; its area is 3mm×6mm-5mm×12mm, and its thickness is 1-3mm; the defect density is less than 10. 9 cm -3 Ra is less than 1 nm. More preferably, the area is 5 mm × 12 mm and the thickness is 3 mm.

[0008] An embodiment of the present invention also provides a method for preparing the above-mentioned all-inorganic lead-free two-dimensional perovskite single crystal, comprising the following steps: S1: Weigh A2CO3, B2O3 and hydrohalic acid according to the stoichiometric ratio; mix A2CO3, B2O3 and N-ethyl-N-methylpiperidine iodide, add hydrohalic acid and stir the reaction at 120-150℃ for 1-4 hours, and add hypophosphoric acid to control the crystallization process to obtain a saturated precursor solution. S2: After filtering the saturated precursor solution, place it in a sealed environment and control the temperature to a supersaturated state through a program. Then, introduce the pre-prepared A3B2X9 seed crystals and slowly cool down to crystallize. Remove the residual mother liquor on the surface and dry to obtain the all-inorganic lead-free two-dimensional perovskite single crystal.

[0009] Preferably, in step S1, the amount of A2CO3 is 3-4 mmol, the amount of B2O3 is 1.5-3 mmol, the amount of hydrohalic acid is 10-15 mL, the amount of N-ethyl-N-methylpiperidine iodide is 0.1-0.3 mmol, and the amount of hypophosphoric acid is 0.2-0.6 mL.

[0010] Preferably, in step S2, the programmed temperature control conditions are a cooling rate of 1-2℃ / h for 14 days; the slow cooling rate is 0.2-0.5℃ / h. The initial rapid cooling at 1-2℃ / h to the precise supersaturation point aims to quickly overcome the metastable region prone to disordered nucleation. Then, at the moment of seed crystal introduction, the cooling rate switches to an ultra-slow rate of 0.2-0.5℃ / h, thereby maintaining the supersaturation at an extremely low and stable level for a long period, forcing crystal growth at a rate much higher than secondary nucleation. Furthermore, during crystal growth, N-ethyl-N-methylpiperidine iodide, as a crystal growth regulator and surface passivator, can more effectively and selectively adsorb onto specific crystal faces, significantly altering surface energy and promoting preferential crystal growth along a two-dimensional plane. This cation also has better interactions with halogen vacancies and metal dangling bonds on the crystal surface, thereby achieving efficient intrinsic passivation during crystal growth and reducing the surface defect state density.

[0011] Preferably, in step S2, the drying temperature is 50-70℃ and the time is 2-4 hours. During the drying process, N-ethyl-N-methylpiperidine iodide is effectively removed due to its volatility or decomposition, ultimately yielding high-quality Rb3Sb2I9 single crystals with a smooth and translucent surface, without any residual organic components.

[0012] Another aspect of the present invention provides an X-ray detector based on the above-described all-inorganic lead-free two-dimensional perovskite single crystal.

[0013] Preferably, the X-ray detector has a vertical structure, consisting of an electrode, the all-inorganic lead-free two-dimensional perovskite single crystal, and an electrode from top to bottom.

[0014] More preferably, the electrode material is a metal electrode, the metal being selected from at least one of gold, silver, or platinum, the electrode thickness is 50-200 nm, and the electrode area is 0.01 mm. 2 Up to 1mm 2 .

[0015] Preferably, the X-ray detector has a sensitivity of up to 60,000 µC·Gy. -1 ·cm -2 .

[0016] Another aspect of the embodiments of the present invention provides a visible light dual-mode detector based on the above-described all-inorganic lead-free two-dimensional perovskite single crystal.

[0017] Preferably, the visible light dual-mode detector has a horizontal structure, a responsivity exceeding 4000 mA / W, and a response speed within 1 ms.

[0018] The above-described solution of the present invention has the following beneficial effects: This invention innovatively introduces N-ethyl-N-methylpiperidine iodide as a crystal growth regulator and surface passivator, achieving a significant improvement in the quality of two-dimensional layered perovskite single crystals; the resulting single crystals have large size (area up to 5mm × 12mm, thickness 1-3mm) and low defect density (<10). 9 cm -3 Furthermore, its smooth surface (Ra < 1 nm) facilitates electrode contact and carrier extraction. Based on this single crystal, the performance of both X-ray and visible light dual-mode detectors is significantly improved (the sensitivity of the X-ray detector reaches nearly 60,000 µC·Gy). -1 ·cm -2 The responsivity of the visible light dual-mode detector exceeds 4000 mA / W, and the response speed is within 1 ms. Attached Figure Description

[0019] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0020] Figure 1 This is a photograph of a single Rb3Sb2I9 crystal from Embodiment 1 of the present invention; Figure 2 This is the Rb3Sb2I9 single crystal structure of Embodiment 1 of the present invention; Figure 3 This is a comparison diagram of the XRD pattern of the Rb3Sb2I9 single crystal in Embodiment 1 of the present invention and the simulated XRD pattern. Figure 4 This is a current response diagram of the Rb3Sb2I9 single crystal X-ray detector of Embodiment 1 of the present invention under different X-ray doses at -10V, -20V, -30V, -40V, and -50V. Figure 5 This is a graph showing the relationship between X-ray dose rate and current density of the Rb3Sb2I9 single crystal X-ray detector of Embodiment 1 of the present invention under bias voltages of -10V, -20V, -30V, -40V, and -50V. Figure 6 The Rb3Sb2I9 single-crystal X-ray detector of Embodiment 1 of the present invention operates at an X-ray dose rate of 27.5 μGy·s.-1 Graph showing the relationship between voltage and sensitivity; Figure 7 This is the photoelectric response diagram of the Rb3Sb2I9 single crystal photoelectric dual-mode detector of Embodiment 1 of the present invention under different powers of 520nm laser; Figure 8 This refers to the response speed of the Rb3Sb2I9 single-crystal photoelectric dual-mode detector of Embodiment 1 of the present invention under 520nm laser light. Figure 9 This refers to the responsivity of the Rb3Sb2I9 single-crystal photoelectric dual-mode detector of Embodiment 1 of the present invention under different powers of 520nm laser.

[0021] Figure 10 This refers to the detectivity of the Rb3Sb2I9 single-crystal photoelectric dual-mode detector of Embodiment 1 of the present invention under different powers of 520nm laser. Detailed Implementation

[0022] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with the accompanying drawings and specific embodiments.

[0023] However, it should be understood that the embodiments described are merely examples and are not intended to limit the scope of protection of the present invention. Any numerical range disclosed herein in the form of ranges (e.g., the amount of N-ethyl-N-methylpiperidine iodide salt "0.1 mL to 0.3 mL", cooling rate "0.5-2 °C / h") should be considered as having specifically disclosed all possible subranges within that range and any single value within that range. Such range descriptions are for brevity and convenience only and should not be construed as hard limitations on the present invention. For example, for the range of 0.1 mL to 0.3 mL of N-ethyl-N-methylpiperidine iodide salt, it should be considered that any single value such as 0.12 mL, 0.24 mL, 0.28 mL, etc., and any subranges such as from 0.10 mL to 0.2 mL, from 0.25 mL to 0.30 mL, etc., have been specifically disclosed. This principle applies to all numerical ranges mentioned in the present invention.

[0024] In this document, the terms “comprising,” “including,” “containing,” etc., are open-ended expressions meaning “including but not limited to.” Unless the context clearly indicates otherwise, these terms do not exclude other conditions or steps not listed. Furthermore, terms such as “first” and “second” are used only to distinguish different objects or steps and do not require or imply any actual order, hierarchy, or importance between these objects or steps.

[0025] Finally, it should be specifically noted that the above detailed description of the present invention in conjunction with the accompanying drawings and embodiments is intended to more clearly illustrate the technical solution of the present invention and its superior effects, and is not intended to limit the scope of protection of the present invention to the specific embodiments described. Based on the core principles and technical concepts of the present invention, any equivalent substitutions or reasonable modifications made by those skilled in the art to the process parameters, raw materials, equipment types, etc. involved in the above embodiments without creative effort should be considered to fall within the scope of protection of the present invention as defined by the appended claims. Unless otherwise specified, all raw materials, reagents, instruments, and equipment used in the present invention can be purchased on the market or prepared by existing methods.

[0026] This invention addresses existing problems by providing a fully inorganic lead-free two-dimensional perovskite single crystal, its preparation method, and its applications. The chemical formula of the fully inorganic lead-free two-dimensional perovskite single crystal is A3B2X9; where A is Rb or Cs; B is Sb or Bi; and C is I or Br. The fully inorganic lead-free two-dimensional perovskite single crystal described below includes any one of Rb3Sb2I9, Rb3Bi2I9, Rb3Sb2Br9, Rb3Bi2Br9, Cs3Bi2Br9, and Cs3Sb2Br9. The X-ray detector based on the above-mentioned fully inorganic lead-free two-dimensional perovskite single crystal has a vertical structure, consisting of electrodes, the fully inorganic lead-free two-dimensional perovskite single crystal, and electrodes in sequence from top to bottom. The electrodes are made of metal, with the metal selected from at least one of gold, silver, or platinum. The electrode thickness is 50-200 nm, and the electrode area is 0.01 mm². 2 Up to 1mm 2 The following describes a visible light dual-mode detector based on the aforementioned all-inorganic lead-free two-dimensional perovskite single crystal. This detector has a horizontal structure, comprising the all-inorganic lead-free two-dimensional perovskite single crystal as the visible light absorption layer and two symmetrical electrodes. The electrodes are made of metal, selected from at least one of gold, silver, or platinum, with a thickness of 50-200 nm and an area of ​​0.01 mm². 2 Up to 1 mm 2 .

[0027] Example 1 This embodiment provides a method for preparing Rb3Sb2I9 single crystal, which specifically includes the following steps: (1) Accurately weigh 0.692 g (3 mmol) of Rb2CO3, 0.583 g (2 mmol) of Sb2O3 and 0.0383 g (0.1 mmol) of N-ethyl-N-methylpiperidine iodide, add 12 mL of hydroiodic acid (HI, 47 wt%), and stir magnetically at 120 °C for 4 h. Also add 0.2 mL of hypophosphoric acid as a stabilizer to obtain the Rb3Sb2I9 precursor solution; (2) The Rb3Sb2I9 precursor solution was filtered using a polytetrafluoroethylene filter with a pore size of 0.22µm to remove any possible small insoluble particles; then it was quickly transferred to a clean, dry glass vial (with a sealed cap) and carefully placed on a shockproof platform in a temperature-controlled oven. Starting from 120°C, the solution was cooled at a rate of 1°C / h until it became supersaturated. Then, the pre-prepared Rb3Sb2I9 seed crystals were introduced, and the solution was cooled at a slow rate of 0.2°C / h. The entire cooling process lasted for about 14 days. After the cooling was completed, several large single crystals with a regular geometric shape and deep red color were observed to precipitate in the mother liquor. (3) Carefully remove the largest and most complete single crystal with tweezers, then quickly wipe it dry with lint-free paper to remove any residual mother liquor adhering to the surface; then place the crystal in a vacuum drying oven at 60℃ for 2 hours to obtain the final Rb3Sb2I9 single crystal, with a size of approximately 12mm×7mm×3mm, as shown below. Figure 1 As shown, the surface is smooth, the color is uniform, and it appears dark red when viewed under transmitted light. A single crystal was selected and characterized by XRD using a Bruker dual-microspot X-ray single-crystal diffractometer at 150K. The crystal structure was then solved directly using Olex2 software, and the resulting crystal structure is shown below. Figure 2 As shown. Figure 3 The XRD pattern of Rb3Sb2I9 single crystal shows that the diffraction peaks of the tested XRD pattern are consistent with the diffraction peaks of the theoretical simulation, indicating that the prepared single crystal material is Rb3Sb2I9.

[0028] Application Example 1 This application example provides an X-ray detector based on Embodiment 1 above, and its performance testing includes the following steps: (1) Apply bias voltages of -10V, -20V, -30V, -40V, and -50V to the X-ray detector based on the Rb3Sb2I9 single crystal, and record its performance at different X-ray dose rates (1.49 μGy·s). -1 7.66uGy·s -1 14.9uGy·s -1 21.5uGy·s -1 27.5uGy·s -1 The current response under irradiation is as follows: Figure 4As shown, when the X-ray is turned on, the current output of the X-ray detector rapidly jumps from a low level in the dark state to a stable high current state, exhibiting a sharp rising edge. The photocurrent remains stable throughout the entire X-ray irradiation cycle. When the X-ray irradiation stops, the current signal similarly drops rapidly back to the initial dark current level, showing a clear falling edge. This current switching phenomenon, which changes synchronously and rapidly with the X-ray "on" and "off" states, repeats in each cycle, fully demonstrating that the device possesses a rapid, stable, and repeatable X-ray radiation detection capability.

[0029] (2) The net photocurrent density was measured at different X-ray dose rates, and its relationship with the dose rate was plotted. The results are as follows: Figure 5 As shown, the two exhibit a good linear relationship, and the sensitivity of the detector can be calculated by fitting the curve. Figure 6 At an X-ray dose rate of 27.5 μGy·s -1 The sensitivity of the detector, calculated under different bias voltages, is 16290 µC·Gy at a bias voltage of -10V. -1 ·cm -2 The sensitivity at a bias voltage of -20V is 29236µC·Gy. -1 ·cm -2 The sensitivity at a bias voltage of -30V is 40145µC·Gy. -1 ·cm -2 The sensitivity at a bias voltage of -40V is 50327µC·Gy. -1 ·cm -2 The sensitivity at a bias voltage of -50V is 59490µC·Gy. -1 ·cm -2 It can be seen that the sensitivity of the X-ray detector is positively correlated with the applied voltage; the higher the bias voltage, the higher the sensitivity.

[0030] (3) By recording the dark current fluctuations over a period of time and defining the standard deviation as the noise current, the dose rate corresponding to the signal current with a signal-to-noise ratio of 3 is generally defined as the detection limit (the detection limit LOD is a key indicator for measuring the detector's ability to detect weak signals). Finally, the detection limit of the X-ray detector was calculated to be as low as 58.2 nC·Gy. -1 ·s -1 This indicates that it can effectively detect low doses of X-ray radiation.

[0031] Application Example 2 This application example provides a visible light dual-mode detector based on Embodiment 1 above, and its performance testing includes the following steps: (1) Using Rb3Sb2I9 single crystals grown in the same batch, a set of symmetrical gold electrodes were prepared on the surface by thermal evaporation process to obtain a planar visible light dual-mode detector.

[0032] (2) Irradiate the effective area of ​​the device with a 520nm laser and test the current-time (It) curve of the device under alternating illumination and darkness conditions at a 5V bias voltage. The results are as follows. Figure 7 As shown, the device exhibits a fast photoresponse, with response speeds on the order of microseconds, as shown in the results. Figure 8 As shown, it exhibits good switching characteristics. The maximum responsivity is 4333 mA / W, as shown in the results. Figure 9 As shown. Specific detectivity (D The value reached 9.7 × 10 11 Jones, the result is as follows Figure 10 As shown, this indicates that it has excellent low-light detection capabilities.

[0033] Comparative Example 1 The difference from Example 1 is that N-ethyl-N-methylpiperidine iodide is replaced with phenethylamine iodide, while the other steps and parameters are the same as in Example 1.

[0034] The crystals obtained in this comparative example have an average size of approximately 6 mm × 2 mm × 1.5 mm, which is significantly smaller than that of Example 1. Furthermore, the crystals have an irregular shape, poor surface light transmittance, and a defect density greater than 10. 12 cm -3 .

[0035] The X-ray detector and visible light dual-mode detector based on the single crystal of Comparative Example 1 were tested using the methods of Application Example 1 and Application Example 2. The sensitivity of this X-ray detector is 23120 µC·Gy. -1 ·cm -2 The detection limit is 94.3 nGy -1 ·s -1 The visible light dual-mode detector has a responsivity of 1284 mA / W and a detectivity of 2.3 × 10⁻⁶. 11 Jones, with a response time on the order of milliseconds, shows a decrease in performance compared to Application Examples 1 and 2.

[0036] Comparative Example 2 The difference from Example 1 is that N-ethyl-N-methylpiperidine iodide is replaced with N-methylpiperidine iodide, while the other steps and parameters are the same as in Example 1.

[0037] The crystal obtained in this comparative example has an average size of approximately 8 mm × 4 mm × 2 mm, which is significantly smaller than that of Example 1. Furthermore, it has a rough surface with obvious step-like aggregates and a defect density greater than 10. 12 cm -3 .

[0038] The X-ray detector and visible light dual-mode detector based on the single crystal of Comparative Example 1 were tested using the methods of Application Example 1 and Application Example 2. The sensitivity of this X-ray detector is 8169 µC·Gy. -1 ·cm -2 The detection limit is 115.8 nGy -1 ·s -1 The visible light dual-mode detector has a responsivity of 749 mA / W and a detectivity of 8.1 × 10⁻⁶. 10 Jones, with a response time on the order of milliseconds, shows a decrease in performance compared to Application Examples 1 and 2.

[0039] Comparative Example 3 The difference from Example 1 is that in step (2), no seed crystals are introduced and the temperature is lowered at a constant rate of 1℃ / h. The average size of the grown crystals is 5mm×3mm×1mm, which is much smaller than that of Example 1. Many irregularly shaped small single crystals can be seen clustered together in the mother liquor.

[0040] Comparative Example 4 The Rb3Sb2I9 single crystal was prepared using the method described in patent number CN110676342B. The specific preparation process is as follows: RbI and SbI3 raw materials were weighed at a molar ratio of 3:2 and dissolved in N-methyl-2-pyrrolidone organic solvent to prepare a mixed precursor solution; the mixed precursor solution was sealed and heated to 85°C and maintained for 12 hours to reach dissolution equilibrium, and the supernatant was taken as the completely saturated precursor solution; the solution was placed in an 80°C environment and the temperature was slowly increased at a rate of 2°C / day until crystals precipitated, thus obtaining Rb3Sb2I9 single crystals.

[0041] The crystals grown using this method have an average size of approximately 7 mm × 4 mm × 1.5 mm. Compared to Example 1, the crystal size is smaller, and obvious step-like growth patterns are observed on the surface, with a surface roughness Ra of approximately 3-5 nm.

[0042] Using the methods described in Application Examples 1 and 2, an X-ray and visible light dual-mode detector was constructed based on this crystal, and its performance was tested. The test results show that the sensitivity of the X-ray detector is 18500 µC·Gy. -1 ·cm -2 The detection limit is 85 nGy -1 ·s -1 The visible light dual-mode detector has a responsivity of 950 mA / W and a detectivity of 3.1 × 10⁻⁶. 11 Jones has a response time of approximately 0.6ms.

[0043] Compared to Example 1, the performance of the Rb3Sb2I9 single crystal device prepared using the method of patent number CN110676342B decreased, mainly due to differences in crystallization kinetics control and surface states. CN110676342B uses a traditional solvent cooling / heating method, relying solely on inorganic precursor growth. The N-ethyl-N-methylpiperidine iodide introduced in this invention, as a bulky cyclic quaternary ammonium salt, has cations that can selectively adsorb onto active sites during crystal growth. The comparative example lacks this passivation effect of organic molecules, making it difficult to suppress surface defects during crystal growth, thus introducing more surface roughness and trap states. Furthermore, the method used in CN110676342B mainly relies on solubility changes caused by temperature increases to drive crystallization. This can easily lead to secondary nucleation or growth streaks due to supersaturation fluctuations in the later stages of crystal growth, resulting in a less dense and smooth crystal interior and surface quality compared to Example 1 of this invention.

[0044] The above description represents the preferred embodiments of the present invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A fully inorganic, lead-free two-dimensional perovskite single crystal, characterized in that, The chemical formula of the all-inorganic lead-free two-dimensional perovskite single crystal is A3B2X9; wherein A is Rb or Cs; B is Sb or Bi; C is I or Br; and the defect density of the all-inorganic lead-free two-dimensional perovskite single crystal is less than 10. 9 cm -3 Ra is less than 1nm, the area is 3mm×6mm-5mm×12mm, and the thickness is 1-3mm.

2. A method for preparing an all-inorganic lead-free two-dimensional perovskite single crystal as described in claim 1, characterized in that, Includes the following steps: S1: Weigh out A2CO3, B2O3, and N-ethyl-N-methylpiperidine iodide salt, mix them, add hydrohalic acid, stir and react at 120-150℃ for 1-4 hours, and add hypophosphoric acid to control the crystallization process to obtain a saturated precursor solution. S2: After filtering the saturated precursor solution, place it in a sealed environment and control the temperature to a supersaturated state through a program. Then, introduce seed crystals and slowly cool down to crystallize. Remove the residual mother liquor on the surface and dry to obtain the all-inorganic lead-free two-dimensional perovskite single crystal.

3. The method for preparing an all-inorganic lead-free two-dimensional perovskite single crystal according to claim 2, characterized in that, In step S1, the amount of A2CO3 is 3-4 mmol, the amount of B2O3 is 1.5-3 mmol, the amount of hydrohalic acid is 10-15 mL, the amount of N-ethyl-N-methylpiperidine iodide is 0.1-0.3 mmol, and the amount of hypophosphoric acid is 0.2-0.6 mL.

4. The method for preparing an all-inorganic lead-free two-dimensional perovskite single crystal according to claim 2, characterized in that, In step S2, the solution is cooled to a supersaturated state at a rate of 1-2℃ / h; the cooling rate is slow at 0.2-0.5℃ / h; and the total cooling time is 7-14 days.

5. The method for preparing an all-inorganic lead-free two-dimensional perovskite single crystal according to claim 2, characterized in that, In step S2, the drying temperature is 50-70℃ and the time is 2-4 hours.

6. An X-ray detector based on the all-inorganic lead-free two-dimensional perovskite single crystal as described in claim 1.

7. The all-inorganic lead-free two-dimensional perovskite single crystal X-ray detector according to claim 6, characterized in that, The X-ray detector has a vertical structure and consists of electrodes, the all-inorganic lead-free two-dimensional perovskite single crystal, and electrodes from top to bottom.

8. The all-inorganic lead-free two-dimensional perovskite single crystal X-ray detector according to claim 6, characterized in that, The X-ray detector has a sensitivity of up to 60,000 µC·Gy -1 ·cm -2 .

9. A visible light dual-mode detector based on the all-inorganic lead-free two-dimensional perovskite single crystal as described in claim 1.

10. The all-inorganic lead-free two-dimensional perovskite single crystal visible light dual-mode detector according to claim 9, characterized in that, The visible light dual-mode detector has a horizontal structure, a responsivity exceeding 4000mA / W, and a response speed of less than 1ms.

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