Method for growing MAPbBr3 single crystal by using mixed solvent and gamma ray detector

Abstract

The invention discloses a method for growing an MAPbBr3 single crystal through a mixed solvent and a gamma ray detector, and relates to the technical field of semiconductor material preparation and radiation detection.The method comprises the steps that a precursor solution is prepared through the mixed solvent of DMF and DMSO, and the low-defect-density and large-size MAPbBr3 single crystal is obtained through growth at the precisely-controlled heating rate through a temperature inversion crystallization technology; according to a gamma ray detector constructed based on the single crystal, a Bi / MAPbBr3 / Au asymmetric electrode structure is adopted, and surface polishing treatment and protection ring design are combined, so that dark current and noise are remarkably reduced; according to the method, the dissolution-crystallization thermodynamic and dynamic behaviors of MAPbBr3 are regulated and controlled through the DMF-DMSO mixed solvent, controllable growth of low-defect-density single crystals is achieved, and the high-performance room-temperature gamma ray detector is constructed in combination with surface defect repair and asymmetric electrode energy band engineering.

Description

Technical Field

[0001] This invention relates to the fields of semiconductor material preparation and radiation detection technology, specifically to a method for growing MAPbBr3 single crystals in a mixed solvent and a gamma ray detector. Background Technology

[0002] In recent years, organic-inorganic hybrid lead halide perovskite materials (such as CH3NH3PbBr3, or MAPbBr3 for short) have shown great potential in the field of radiation detection due to their excellent photoelectric properties—including high light absorption coefficient, long carrier diffusion length, high resistivity, and good gamma-ray response characteristics. In particular, MAPbBr3 single crystals, due to their low defect density and high crystallinity, can effectively suppress carrier recombination, significantly improving the energy resolution and sensitivity of detectors, and are therefore widely studied as sensitive materials for room-temperature gamma-ray detectors.

[0003] Currently, the mainstream methods for preparing MAPbBr3 single crystals include inverted temperature crystallization (ITC), cooling method, antisolvent vapor diffusion method, and solution surface growth method. These methods typically use a single polar solvent (such as N,N-dimethylformamide DMF, dimethyl sulfoxide DMSO, or γ-butyrolactone GBL) to dissolve the precursor, and then induce crystal nucleation and growth by controlling the temperature, solvent evaporation rate, or introducing an antisolvent (such as chlorobenzene or diethyl ether). After the obtained single crystal is cut and polished, it is often used with a metal electrode (such as gold or platinum) to form a photodetector with a vertical structure, which can collect gamma ionization signals under an applied bias voltage. However, the crystals prepared by the above methods grow too fast, resulting in a high density of internal defects (such as dislocations, vacancies, and impurity inclusions), which affects carrier mobility and lifetime. The single crystal size is limited and the morphology is irregular, making it difficult to meet the integration requirements of large-area, uniform detector arrays. Furthermore, the single solvent system has limited ability to control the solubility of precursors and crystallization kinetics, which can easily lead to too many nucleation sites, polycrystalline formation, or cracking. The resulting single crystal resistivity is low, resulting in a large dark current and a decrease in signal-to-noise ratio, which limits the sensitivity of the detector under low-dose gamma rays.

[0004] In particular, the solubility of MAPbBr3 in a single solvent system (such as DMF) exhibits a nonlinear change with temperature, leading to abrupt changes in crystal growth rate and inducing structural defects such as twins and dislocations, severely affecting single crystal quality. Existing inverse-temperature crystallization methods often use DMF as the single solvent. While DMF has good solubility for PbBr2, the solubility of MAPbBr3 in it drops sharply in the 30-50℃ range, causing unstable growth kinetics and high defect density within the crystal. Furthermore, high defect density results in low carrier mobility-lifetime product (μτ) and insufficient resistivity, leading to high dark current and poor signal-to-noise ratio in the detector, making high-resolution gamma-ray energy spectrum detection impossible. Defects (such as Br...) −Vacant, uncoordinated Pb 0 As a deep-level trap, it exacerbates nonradiative recombination, resulting in a dark current density as high as 1258 nA cm⁻¹. -3 The -100 V limit severely restricts the energy resolution capability for 511 keV gamma rays at room temperature. Traditional solution methods struggle to simultaneously achieve controllable preparation of large-size, high-transparency, and low-defect-density MAPbBr3 single crystals, resulting in poor process repeatability and hindering device integration and industrial applications. The narrow supersaturation control window of a single solvent system easily leads to multinucleation, crystal adhesion, or cracking, resulting in small, irregularly shaped single crystals that fail to meet the uniformity requirements of detector arrays. Furthermore, the crystal surface contains a corrosion layer caused by solvent residue, secondary nucleation particles, and uncoordinated lead (Pb). 0 Defects worsen the electrode-semiconductor interface contact, further increasing dark current. The single crystal surface extracted from the precursor solution exhibits selective dissolution of MA by DMF. + The formation of a non-stoichiometric surface layer was confirmed by XPS to contain Pb. 0 Deep-level defects become non-radiative recombination centers.

[0005] Meanwhile, existing electrode configurations and geometric designs fail to effectively suppress surface leakage current and bulk dark current, and there is a lack of low-damage, high-stability electrode integration processes compatible with perovskites. Symmetrical electrodes (such as Au / Perovskite / Au) are prone to bipolar injection, resulting in high dark current; while microfabrication methods such as photolithography can damage the perovskite lattice due to solvent erosion or plasma damage; high electrode-crystal contact impedance also introduces additional noise. Furthermore, there is a lack of systematic low-noise signal readout and electromagnetic shielding schemes for perovskite gamma-ray detectors, affecting the accurate acquisition and analysis of energy spectrum signals. Initial connection methods (such as copper foil) have high contact impedance, with baseline noise >50mV, making it impossible to distinguish gamma characteristic peaks; external electromagnetic interference is also not effectively isolated. Summary of the Invention

[0006] The purpose of this invention is to provide a method for growing MAPbBr3 single crystals using a mixed solvent and a gamma-ray detector, in order to solve the problem of high defect density caused by the single solvent system and uncontrollable crystallization kinetics in the solution preparation of existing MAPbBr3 perovskite single crystals, as well as the resulting technical bottlenecks of large dark current, low energy resolution and poor process repeatability of the detector.

[0007] To achieve the above objectives, the present invention provides the following technical solution:

[0008] According to a first aspect of this disclosure, a method for growing MAPbBr3 single crystals using a mixed solvent is proposed, comprising the following steps:

[0009] S1. Methylamine aqueous solution was reacted with hydrobromic acid in an ice bath, water was removed by vacuum distillation, recrystallized and dried under vacuum to obtain white methylamine bromide powder, which was then stored in a nitrogen glove box.

[0010] S2. Dissolve methylamine bromide powder and lead bromide powder in a mixed solvent of N,N-dimethylformamide and dimethyl sulfoxide to obtain a precursor solution; the volume ratio of N,N-dimethylformamide to dimethyl sulfoxide in the mixed solvent is 9:1, and the total concentration of the precursor solution is controlled at 0.7-1.3M. After stirring at 40°C for 6 hours, a clear and transparent solution is obtained and stored in the dark.

[0011] S3. Take the precursor solution and heat it to 65°C to precipitate micron-sized seed crystals. Select transparent and regular seed crystals with a size of less than 1 mm. Pour the filtered precursor solution into a glass beaker, place a clean glass plate at the bottom and place the seed crystal in the center. After equilibration at room temperature for 15 minutes, transfer it to a programmable temperature-controlled oven. First, keep it at 45°C for 2 hours, and then slowly raise the temperature to 60-70°C at a rate of 0.1-0.2°C / h. Continue to grow for 120-150 hours to obtain MAPbBr3 single crystals.

[0012] S4. Gradient mechanical polishing and precision polishing are performed on the upper and lower surfaces of the obtained MAPbBr3 single crystal using sandpaper ranging from 3000 to 10000 grit. After cleaning and drying, a single crystal with a surface roughness Ra≤1.24nm is obtained.

[0013] Furthermore, in step S2, the total concentration of the precursor solution is controlled at 1M.

[0014] Furthermore, in step S3, the heating rate in the programmable temperature-controlled oven is 0.2℃ / h, slowly increasing to 65℃, and continuing to grow for 150h.

[0015] Furthermore, in step S4, the gradient mechanical polishing uses 3000 grit, 5000 grit, 7000 grit, and 10000 grit sandpaper in sequence; the precision polishing uses polyurethane polishing cloth with diamond polishing paste, followed by wiping the surface with silk cloth, and then cleaning with isooctane and drying under nitrogen flow.

[0016] Further, in step S1, after dehydration by vacuum distillation, a white crude product is obtained. The white crude product is recrystallized twice with anhydrous ethanol and then dried under vacuum at 60°C for 24 hours to obtain high-purity white methylamine bromide crystals.

[0017] According to a second aspect of this disclosure, a gamma-ray detector is proposed, utilizing the MAPbBr3 single crystal described in the first aspect, comprising:

[0018] MAPbBr3 single crystals, used as the sensitive material layer, have centimeter-scale dimensions, surface roughness Ra ≤ 1.24 nm, and bulk defect state density ≤ 5.57 × 10⁻⁶. 9 cm -3 ;

[0019] The upper electrode, serving as the anode, is a gold thin-film electrode, deposited on the top surface of the MAPbBr3 single crystal to form an ohmic contact with the MAPbBr3 single crystal.

[0020] The lower electrode, serving as the cathode, is a bismuth thin film electrode, deposited on the bottom surface of the MAPbBr3 single crystal, forming a Schottky contact with the MAPbBr3 single crystal.

[0021] Two electrical connection wires are provided, which are fixed to the surfaces of the upper and lower electrodes respectively by conductive silver paste, and the other end of each wire is connected to an external readout circuit.

[0022] A metal shielding box is used to house the MAPbBr3 single crystal, the upper electrode, and the lower electrode;

[0023] A protective ring is used to provide a concentric ring-shaped protective electrode around the lower electrode, wherein the distance between the protective electrode and the lower electrode is 50-200 μm.

[0024] Furthermore, the MAPbBr3 single crystal is deposited with 100 nm gold as the anode on the upper surface and 100 nm bismuth as the cathode on the lower surface using a vacuum thermal evaporation method, forming an asymmetric structure.

[0025] Furthermore, the electrical connection wires are made of gold wire or flexible copper wire with a diameter of 50μm, and the contact impedance between each electrical connection wire and the corresponding electrode is <10Ω.

[0026] Furthermore, the metal shielding box is constructed of an aluminum Faraday cage, and the box body of the metal shielding box is grounded.

[0027] Furthermore, the concentric ring-shaped protective electrode and the lower electrode are made of the same bismuth material, and the same bias voltage is applied to the lower electrode during operation.

[0028] Compared with existing technologies, this invention provides a method for growing MAPbBr3 single crystals using a mixed solvent and a gamma-ray detector. By constructing a DMF-DMSO mixed solvent system, optimizing crystal growth kinetics, and combining surface defect repair with asymmetric electrode design, this invention significantly improves the quality of MAPbBr3 perovskite single crystals and their device performance in gamma-ray detection. It effectively achieves precise control of crystal growth kinetics, significantly reduces bulk defect density, and greatly improves carrier transport performance, laying the foundation for high charge collection efficiency. Furthermore, it significantly reduces detector dark current, improves signal-to-noise ratio and stability, and enables high-energy-resolution room-temperature gamma-ray spectral detection. The overall process is simple, highly reproducible, and suitable for large-size single crystal preparation, providing a complete technical path for the practical application of perovskite materials in nuclear radiation detection. Attached Figure Description

[0029] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments recorded in this invention. For those skilled in the art, other drawings can be obtained based on these drawings.

[0030] Figure 1 A schematic diagram of the device structure of the MAPbBr3 γ-ray detector provided in an embodiment of the present invention;

[0031] Figure 2 The dissolution-temperature curves and corresponding theoretical crystallization yield curves of MAPbBr3 in a single DMF solvent are provided for embodiments of the present invention.

[0032] Figure 3 A schematic diagram of the stable region, metastable region and unstable region of MAPbBr3 single crystal under reverse temperature crystallization conditions provided in an embodiment of the present invention;

[0033] Figure 4 Comparison of MAPbBr3 single crystal morphologies obtained under different heating rate conditions provided in this embodiment of the invention;

[0034] Figure 5 Physical images of MAPbBr3 single crystals grown under different precursor concentrations and their crystal quality comparison diagrams provided in this embodiment of the invention;

[0035] Figure 6 Crystal surface morphology diagrams corresponding to different polishing steps in the gradient physical polishing process provided in this embodiment of the invention;

[0036] Figure 7 The AFM test results of the surface roughness of MAPbBr3 single crystal before and after fine polishing are provided in the embodiments of the present invention;

[0037] Figure 8 The XPS energy spectrum comparison of Pb 4f before and after polishing of MAPbBr3 single crystal is provided in the embodiments of the present invention;

[0038] Figure 9 A comparison of the solubility curves of MAPbBr3 in DMF single solvent and DMF-DMSO mixed solvent systems provided in the embodiments of the present invention;

[0039] Figure 10 Powder XRD pattern and photograph of MAPbBr3 single crystals grown in a DMF-DMSO mixed solvent system provided in this embodiment of the invention;

[0040] Figure 11 Transmission spectrum and XRD rocking curve of MAPbBr3 single crystal grown using DMF-DMSO mixed solvent provided for embodiments of the present invention;

[0041] Figure 12 The present invention provides a current-voltage curve for extracting the defect state density of a MAPbBr3 single crystal device using the SCLC method, as provided in this embodiment.

[0042] Figure 13 This is a schematic diagram of the structure of the gamma-ray detector and the metal shielding box provided in an embodiment of the present invention;

[0043] Figure 14 This is a comparison diagram of the electric field distribution of detectors with and without guard rings provided in an embodiment of the present invention.

[0044] Figure 15 Dark current comparison curves of devices fabricated using DMF single solvent and DMF-DMSO mixed solvent provided in embodiments of the present invention;

[0045] Figure 16 The image shows a comparison of the pulse response and 511 keV γ-ray energy spectrum of detectors prepared by DMF single solvent and DMF-DMSO mixed solvent according to embodiments of the present invention. Detailed Implementation

[0046] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0047] Example 1:

[0048] This invention provides a method for growing MAPbBr3 single crystals using a mixed solvent, comprising the following steps:

[0049] Step 1: Synthesis of methylamine bromide (MABr) precursor

[0050] 59.5 mL of a 40 wt% methylamine aqueous solution was placed in a 250 mL three-necked flask and cooled to 0-5 °C in an ice bath with continuous magnetic stirring. 83 mL of 48 wt% hydrobromic acid (HBr) was slowly added dropwise through a dropping funnel, controlling the dropping rate to keep the reaction temperature below 10 °C. After the addition was complete, stirring in an ice bath continued for 2 hours to ensure complete formation of MABr precipitate. The mixture was then transferred to a rotary evaporator and distilled under reduced pressure at 60 °C and <10 mbar to remove water, yielding a white crude product. The crude product was recrystallized twice with anhydrous ethanol and then dried under vacuum at 60 °C for 24 hours to obtain high-purity white MABr crystals, which were sealed and stored in a nitrogen-filled glove box for later use. The purity of MABr directly affects the quality of subsequent single crystals; therefore, moisture absorption or decomposition must be avoided.

[0051] Step 2: Preparation of MAPbBr3 precursor solution

[0052] Weigh 4.47 g of methylamine bromide (MABr) (0.045 mol) and 7.34 g of lead bromide (PbBr2) (0.020 mol), and add them to a clean, dry 50 mL glass bottle. Add 18 mL of N,N-dimethylformamide (DMF) and 2 mL of dimethyl sulfoxide (DMSO) (DMF:DMSO = 9:1, v / v), bringing the total solution volume to 20 mL, corresponding to a precursor concentration of 1.0 M. Figure 5 The image shows physical images of MAPbBr3 single crystals grown under different precursor concentrations and a comparison of their crystal quality. The glass bottle was wrapped in aluminum foil to protect it from light and placed in a 40°C oil bath with magnetic stirring for 6 hours until a clear, transparent solution was formed. The solution was then filtered through a 0.2 μm pore size polytetrafluoroethylene (PTFE) membrane to remove insoluble impurities, yielding the precursor solution for crystal growth.

[0053] Through comparative experiments, such as Figure 2 and Figure 9 As shown, if only 20 mL of DMF (without DMSO) is used, the solubility curve is non-linear, which can easily lead to abrupt changes in the growth rate.

[0054] Step 3, temperature-reverse crystallization growth of MAPbBr3 single crystals (e.g.) Figure 3 (As shown)

[0055] Seed crystal preparation: Take 5 mL of the above precursor solution and place it in a small glass bottle. Heat to 65°C and let stand for 2-4 hours until multiple micron-sized crystals precipitate at the bottom. Use a clean glass pipette to select seed crystals with a diameter of about 0.5-0.8 mm that are transparent and free of cracks, as cores for subsequent epitaxial growth.

[0056] Crystal growth: Pour 20 mL of the filtered precursor solution into a 50 mL clean glass beaker, and place a 20 × 20 mm crystal at the bottom. 2A square glass slide (ultrasonically cleaned and dried with acetone and isopropanol). Gently place the selected seed crystal in the center of the slide using tweezers. Seal the mouth of the beaker with perforated plastic wrap.

[0057] Temperature-controlled growth: First, place the beaker at room temperature (25℃) for 15 minutes to allow the seed crystal surface to slightly dissolve and eliminate surface defects; then transfer it to a temperature-controlled oven and heat according to the following program: hold at 45℃ for 2 hours; slowly increase the temperature to 65℃ at a rate of 0.2℃ / h; maintain this temperature until the total growth time reaches 150 hours. Figure 4 The image shows the morphology of MAPbBr3 single crystals grown under different heating rates.

[0058] The entire process was conducted in the dark and with vibration protected. After growth was complete, a piece measuring approximately 11×10×4mm was visible attached to the bottom of the beaker. 3 High-transparency MAPbBr3 single crystals.

[0059] Crystal removal: Remove the glass slide along with the crystal from the solution, blow dry the residual liquid on the surface with nitrogen gas, then place it on a 40°C heating plate for 15 min to soften the interfacial adsorption layer, and finally gently peel off the crystal with a soft silk cloth and store it in a brown glass bottle filled with nitrogen.

[0060] Step 4: Single Crystal Surface Treatment

[0061] To remove the surface corrosion layer and uncoordinated Pb 0 Defects, gradient physical polishing of the crystal (e.g.) Figures 6-8 As shown): First, use 3000-grit (particle size ≈ 10.5μm) sandpaper to coarsely grind the upper and lower surfaces for 1 minute; then, successively use 5000-grit, 7000-grit, and 10000-grit sandpaper for fine grinding, 1 minute each; next, use polyurethane polishing cloth with diamond polishing paste to polish for 5 minutes to eliminate submicron scratches; finally, wipe the surface with silk cloth and rinse with isooctane to remove organic residues; thoroughly dry under nitrogen flow to obtain a high-quality crystal surface with a surface roughness Ra ≤ 1.24nm (as shown). Figure 7 (As shown).

[0062] XPS tests show (as...) Figure 8 As shown), Pb after polishing 0 The characteristic peak (137.1 eV) has basically disappeared, confirming that the deep energy level defects on the surface have been effectively eliminated.

[0063] Working principle: During the crystal growth stage, Pb is enhanced by introducing strongly coordinated DMSO molecules into DMF. 2+ The formation of more stable intermediate complexes with the solvent causes the solubility of MAPbBr3 to decrease approximately linearly with increasing temperature (R0). 2>0.99), thus transforming the originally nonlinear crystal growth rate into a constant, slow linear kinetic process. This effectively suppresses explosive nucleation and fluctuations in the concentration gradient at the growth front, significantly reducing the formation of bulk defects such as dislocations, twins, and vacancies.

[0064] The reverse temperature crystallization method used does not require high pressure or complex equipment. The mixed solvent system broadens the metastable growth window, and centimeter-sized, highly transparent, and non-adhesive MAPbBr3 single crystals have been successfully prepared. The batch repeatability is good, and it is feasible to scale up to industrial production.

[0065] The raw materials used in this embodiment (MABr, PbBr2, DMF, DMSO) are all commercially available analytical grade or semiconductor grade; the equipment includes a conventional magnetic stirrer, a programmable temperature-controlled oven, a vacuum thermal evaporation apparatus, a rotary evaporator, etc., all of which are common laboratory instruments. All operating steps (such as solvent ratio, heating rate, polishing process, electrode thickness) have been clearly quantified. Those skilled in the art can repeat this invention without creative effort based on the above description to obtain a MAPbBr3 gamma-ray detector with low defect density, high mobility, low dark current, and high energy resolution.

[0066] Example 2:

[0067] This invention also provides an application of MAPbBr3 single crystal in gamma-ray detection.

[0068] 1. Fabrication of gamma-ray detectors, including:

[0069] Electrode evaporation: The MAPbBr3 single crystal treated in Example 1 was fixed in an evaporation fixture. A vacuum thermal evaporation system (vacuum degree <5×10⁻⁶) was used. -4 Pa), 100 nm bismuth (Bi) is deposited on the lower surface of the crystal as the cathode, and 100 nm gold (Au) is deposited on the upper surface as the anode, forming an asymmetric structure (such as Pa). Figure 1 (As shown).

[0070] Electrical connection: Use plastic tweezers to handle the crystal to avoid scratching it. Take two 50μm diameter gold wires, dip one end in a small amount of conductive silver paste and press them onto the center of the Bi and Au electrodes respectively, and solder the other end to the SMA connector to achieve a low impedance connection (contact resistance <10Ω).

[0071] Electromagnetic shielding: The entire detector is housed in a self-made aluminum Faraday cage (e.g., Figure 13 As shown in the figure, the cage is grounded through a copper braided strip, which effectively suppresses external electromagnetic interference and completes the integration of a low-noise gamma-ray detector.

[0072] Guard ring structure: To further reduce surface leakage current, a concentric ring-shaped Bi guard electrode can be deposited around the Bi electrode using a mask. The distance between the center electrode and the guard ring electrode should be controlled within the range of 50 to 200 μm. By applying the same bias voltage, the leakage current on the crystal surface can be guided to bypass, thereby improving the breakdown voltage and signal-to-noise ratio. Figure 14 As shown.

[0073] Vacuum thermal evaporation of Bi / Au electrodes avoids the erosion of perovskite by wet processes such as photolithography; combined with low-resistance gold wire connection and aluminum Faraday shielding box, contact noise and electromagnetic interference are effectively suppressed, and the baseline noise is controlled within 10 mV to ensure accurate acquisition of pulse signals.

[0074] 2. Device performance testing

[0075] The detector was connected to a charge-sensitive preamplifier and a multichannel analyzer to test the response of a 22Na radioactive source (511keV γ-rays) under a -100V bias.

[0076] like Figure 15 As shown, the results indicate that:

[0077] Dark current density: 151 nA / cm -2 ;

[0078] Energy resolution: 14.1% @ 511 keV;

[0079] Pulse rise time: 8.3 μs (much faster than the 78.8 μs of the DMF single-solvent system, such as...) Figure 16 (As shown in the table). The performance comparison of MAPbBr3 single crystals grown in different solvent systems and their γ-ray detectors is shown in the table below:

[0080] Performance Indicator Name Single DMF solvent (control) DMF-DMSO mixed solvent (this invention) Solubility curve characteristics Nonlinear Quasi-linear Defect state density <![CDATA[1.41 × 10 11 cm −3 ]]> <![CDATA[5.57 × 10 9 cm −3 ]]> Surface roughness 15.30 nm 1.24 nm Dark current density (−100 V) <![CDATA[1258 nA cm −2 ]]> <![CDATA[151 nA cm −2 ]]> Pulse average rise time 78.8 μs 8.3 μs 511 keV energy resolution / 14.1%

[0081] This invention significantly improves the quality of MAPbBr3 perovskite single crystals and their device performance in gamma-ray detection by constructing a DMF-DMSO mixed solvent system, optimizing crystal growth kinetics, and combining surface defect repair with asymmetric electrode design. After introducing DMSO as a co-solvent, the solubility-temperature curve of MAPbBr3 changes from nonlinear to highly linear (R0). 2 >0.99), which stabilizes and controls the crystal growth rate, effectively suppressing explosive nucleation and stress-induced defects. The defect state density of the resulting single crystal is increased from 1.41 × 10¹¹ cm⁻¹ in the traditional DMF system. -3 Significantly reduced to 5.57×109cm -3 The defect density decreased by 96%, reaching the internationally advanced level in reverse temperature crystallization. The low defect density significantly reduced non-radiative recombination centers, increasing hole mobility to 89.41 cm⁻¹. 2 V-1 s -1 The hole mobility-lifetime product (μτ) reaches 8.07 × 10⁻⁶. -4 cm 2 V -1 This is far superior to crystals prepared using a single solvent system, thus ensuring efficient collection of ionized charges generated by gamma rays. Furthermore, the combination of a Bi / MAPbBr3 / Au asymmetric Schottky-Ohmic electrode structure provides dual suppression of dark-state injection of electrons and holes; simultaneously, gradient physical polishing eliminates surface Pb... 0 Deep level defects reduce the dark current density of the detector at a bias voltage of −100V from 1258 nA cm⁻¹. -2 Reduced to 151 nA cm -2 The reduction reached 88%, significantly improving the weak signal detection capability. The detector prepared based on this invention can detect weak signals at room temperature. 22 The 511 keV gamma rays emitted by the Na source exhibited an energy resolution of 14.1%, which is one of the best performances reported to date among perovskite-based gamma-ray detectors. It is the first time that the 511 keV characteristic peak has been clearly resolved, demonstrating its potential for practical energy spectrum analysis applications.

[0082] This invention not only solves the core bottleneck in material preparation, but also establishes a complete technical solution from high-quality single crystal growth to surface treatment, device fabrication, and signal readout, promoting perovskite semiconductors from laboratory research to practical applications in high-performance, low-cost room temperature radiation detectors.

[0083] The foregoing has only described certain exemplary embodiments of the present invention by way of illustration. Undoubtedly, those skilled in the art can modify the described embodiments in various ways without departing from the spirit and scope of the present invention. Therefore, the foregoing drawings and descriptions are illustrative in nature and should not be construed as limiting the scope of protection of the claims of the present invention.

Claims

1. A method for growing MAPbBr3 single crystals using a mixed solvent, characterized in that, Includes the following steps: S1. Methylamine aqueous solution was reacted with hydrobromic acid in an ice bath, water was removed by vacuum distillation, recrystallized and dried under vacuum to obtain white methylamine bromide powder, which was then stored in a nitrogen glove box. S2. Dissolve methylamine bromide powder and lead bromide powder in a mixed solvent of N,N-dimethylformamide and dimethyl sulfoxide to obtain a precursor solution; the volume ratio of N,N-dimethylformamide to dimethyl sulfoxide in the mixed solvent is 9:1, and the total concentration of the precursor solution is controlled at 0.7-1.3M. After stirring at 40°C for 6 hours, a clear and transparent solution is obtained and stored in the dark. S3. Take the precursor solution and heat it to 65°C to precipitate micron-sized seed crystals. Select transparent and regular seed crystals with a size of less than 1 mm. Pour the filtered precursor solution into a glass beaker, place a clean glass plate at the bottom and place the seed crystal in the center. After equilibration at room temperature for 15 minutes, transfer it to a programmable temperature-controlled oven. First, keep it at 45°C for 2 hours, and then slowly raise the temperature to 60-70°C at a rate of 0.1-0.2°C / h. Continue to grow for 120-150 hours to obtain MAPbBr3 single crystals. S4. Gradient mechanical polishing and precision polishing are performed on the upper and lower surfaces of the obtained MAPbBr3 single crystal using sandpaper ranging from 3000 to 10000 grit. After cleaning and drying, a single crystal with a surface roughness Ra≤1.24nm is obtained.

2. The method for growing MAPbBr3 single crystals using a mixed solvent according to claim 1, characterized in that, In step S2, the total concentration of the precursor solution is controlled at 1M.

3. The method for growing MAPbBr3 single crystals using a mixed solvent according to claim 1, characterized in that, In step S3, the heating rate in the programmable temperature-controlled oven is 0.2℃ / h, slowly increasing to 65℃, and continuing to grow for 150h.

4. The method for growing MAPbBr3 single crystals using a mixed solvent according to claim 1, characterized in that, In step S4, the gradient mechanical polishing uses 3000 grit, 5000 grit, 7000 grit, and 10000 grit sandpaper in sequence; the precision polishing uses polyurethane polishing cloth with diamond polishing paste, then wipes the surface with silk cloth, and cleans with isooctane and dries under nitrogen flow.

5. The method for growing MAPbBr3 single crystals using a mixed solvent according to claim 1, characterized in that, In step S1, after dehydration by vacuum distillation, a white crude product is obtained. The white crude product is recrystallized twice with anhydrous ethanol and then dried under vacuum at 60°C for 24 hours to obtain high-purity white methylamine bromide crystals.

6. A gamma-ray detector, characterized in that, The application of the MAPbBr3 single crystal as described in any one of claims 1-5 includes: MAPbBr3 single crystals, used as the sensitive material layer, have centimeter-scale dimensions, surface roughness Ra ≤ 1.24 nm, and bulk defect state density ≤ 5.57 × 10⁻⁶. 9 cm -3 ; The upper electrode, serving as the anode, is a gold thin-film electrode, deposited on the top surface of the MAPbBr3 single crystal to form an ohmic contact with the MAPbBr3 single crystal. The lower electrode, serving as the cathode, is a bismuth thin film electrode, deposited on the bottom surface of the MAPbBr3 single crystal, forming a Schottky contact with the MAPbBr3 single crystal. Two electrical connection wires are provided, which are fixed to the surfaces of the upper and lower electrodes respectively by conductive silver paste, and the other end of each wire is connected to an external readout circuit. A metal shielding box is used to house the MAPbBr3 single crystal, the upper electrode, and the lower electrode; A protective ring is used to provide a concentric ring-shaped protective electrode around the lower electrode, wherein the distance between the protective electrode and the lower electrode is 50-200 μm.

7. A gamma-ray detector according to claim 6, characterized in that, The MAPbBr3 single crystal was deposited with 100 nm gold as the anode on the upper surface and 100 nm bismuth as the cathode on the lower surface using a vacuum thermal evaporation method, forming an asymmetric structure.

8. A gamma-ray detector according to claim 6, characterized in that, The electrical connection wires are made of gold wire or flexible copper wire with a diameter of 50μm, and the contact impedance between each electrical connection wire and the corresponding electrode is <10Ω.

9. A gamma-ray detector according to claim 6, characterized in that, The metal shielding box is made of an aluminum Faraday cage, and the box body of the metal shielding box is grounded.

10. A gamma-ray detector according to claim 6, characterized in that, The concentric ring-shaped protective electrode and the lower electrode are made of the same bismuth material, and the same bias voltage is applied to the lower electrode during operation.

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