Search

CN-121992474-A - Mixed solvent growth MAPbBr3Method for single crystal and gamma ray detector

CN121992474ACN 121992474 ACN121992474 ACN 121992474ACN-121992474-A

Abstract

The invention discloses a method for growing MAPbBr 3 monocrystal by using a mixed solvent and a gamma ray detector, and relates to the technical field of semiconductor material preparation and radiation detection, comprising the steps of preparing a precursor solution by using a mixed solvent of DMF and DMSO, and growing to obtain the MAPbBr 3 monocrystal with low defect density and large size under the precisely controlled heating rate by a reverse temperature crystallization process; the invention regulates and controls the dissolution-crystallization thermodynamic and kinetic behaviors of MAPbBr 3 through DMF-DMSO mixed solvent, realizes the controllable growth of low defect density single crystal, and combines surface defect repair and asymmetric electrode energy band engineering to construct the high-performance room temperature gamma ray detector.

Inventors

  • FENG YANXING
  • WANG HAIBIN
  • ZHAO RUI
  • Han Shixuan
  • WEI ZHONGYU
  • YIN LI
  • LIU JU

Assignees

  • 河南省科学院先进陶瓷研究所

Dates

Publication Date
20260508
Application Date
20260225

Claims (10)

  1. 1. A method for growing MAPbBr 3 single crystals by using mixed solvent, which is characterized by comprising the following steps: s1, reacting a methylamine water solution with hydrobromic acid in an ice bath, distilling under reduced pressure to remove water, recrystallizing, and drying in vacuum to obtain white methylamine bromide powder, and storing the white methylamine bromide powder in a nitrogen glove box; S2, dissolving methylamine bromide powder and lead bromide powder in a mixed solvent of N, N-dimethylformamide and dimethyl sulfoxide to obtain a precursor solution, wherein the volume ratio of the N, N-dimethylformamide to the dimethyl sulfoxide in the mixed solvent is 9:1, the total concentration of the precursor solution is controlled to be 0.7-1.3M, and the precursor solution is stirred for 6 hours at 40 ℃ to obtain a clear and transparent solution and is stored in a dark place; S3, heating the precursor solution to 65 ℃ to separate out micron-sized seed crystals, selecting transparent regular seed crystals with the size smaller than 1mm, pouring the filtered precursor solution into a glass beaker, placing a clean glass sheet at the bottom and placing the seed crystals in the center, balancing the room temperature for 15min, transferring the precursor solution into a program temperature control oven, preserving heat for 2h at 45 ℃ before the precursor solution is heated to 60-70 ℃ at the rate of 0.1-0.2 ℃ per hour, and continuously growing for 120-150h to obtain MAPbBr 3 single crystals; And S4, sequentially using 3000-10000-mesh sand paper to carry out gradient mechanical polishing and precise polishing on the upper surface and the lower surface of the obtained MAPbBr 3 monocrystal, and cleaning and drying to obtain the monocrystal with the surface roughness Ra less than or equal to 1.24 nm.
  2. 2. The method for growing a single crystal of MAPbBr 3 using a mixed solvent according to claim 1, wherein the total concentration of the precursor solution is controlled to be 1M in the step S2.
  3. 3. The method for growing MAPbBr 3 single crystal with mixed solvent according to claim 1, wherein in the step S3, the temperature rising rate in the temperature-programmed oven is 0.2 ℃ per hour, the temperature is slowly raised to 65 ℃ and the growth is continued for 150 hours.
  4. 4. The method for growing MAPbBr 3 single crystals by using the mixed solvent according to claim 1, wherein in the step S4, 3000 mesh, 5000 mesh, 7000 mesh and 10000 mesh sand paper are sequentially used for gradient mechanical polishing, and the precise polishing adopts polyurethane polishing cloth and diamond grinding paste, then the surface is wiped by silk cloth, and the surface is cleaned by isooctane and blown dry under nitrogen flow.
  5. 5. The method for growing MAPbBr 3 single crystals by using a mixed solvent according to claim 1, wherein in the step S1, the white crude product is obtained after reduced pressure distillation and water removal, the white crude product is recrystallized twice by absolute ethyl alcohol and then vacuum-dried at 60 ℃ for 24 hours, so as to obtain the high-purity white methylamine bromide crystal.
  6. 6. A gamma ray detector employing the MAPbBr 3 single crystal of any one of claims 1-5, comprising: MAPbBr 3 monocrystal as sensitive material layer, size of cm level, surface roughness Ra less than or equal to 1.24nm and bulk defect state density less than or equal to 5.57×10 9 cm -3 ; An upper electrode, which is a gold thin film electrode as an anode, is evaporated on the top surface of the MAPbBr 3 monocrystal and forms ohmic contact with the MAPbBr 3 monocrystal; The lower electrode is a bismuth film electrode serving as a cathode, is evaporated on the bottom surface of the MAPbBr 3 monocrystal and forms Schottky contact with the MAPbBr 3 monocrystal; The two electric connection wires are respectively fixed on the surfaces of the upper electrode and the lower electrode through conductive silver paste, and the other ends of the electric connection wires are connected to an external reading circuit; the metal shielding box is used for accommodating the MAPbBr 3 single crystal, the upper electrode and the lower electrode; And the guard ring is used for arranging a concentric ring-shaped guard electrode on the periphery of the lower electrode, and the distance between the guard electrode and the lower electrode is 50-200 mu m.
  7. 7. The gamma ray detector of claim 6, wherein the MAPbBr 3 single crystal is formed in an asymmetric structure by vacuum thermal evaporation to evaporate 100nm gold on the upper surface as an anode and 100nm bismuth on the lower surface as a cathode.
  8. 8. The gamma ray detector of claim 6, wherein the electrical connection wires are gold wires or flexible copper wires with a diameter of 50 μm, and each electrical connection wire has a contact resistance of <10Ω with the corresponding electrode.
  9. 9. The gamma ray detector of claim 6, wherein the metal shielding box is constructed of aluminum faraday cage and the box body of the metal shielding box is grounded.
  10. 10. The gamma ray detector of claim 6, wherein the concentric ring guard electrode and the bottom electrode are made of the same bismuth material, and are biased in operation in the same manner as the bottom electrode.

Description

Method for growing MAPbBr 3 monocrystal by mixed solvent and gamma ray detector Technical Field The invention relates to the technical field of semiconductor material preparation and radiation detection, in particular to a method for growing MAPbBr 3 monocrystal by using a mixed solvent and a gamma ray detector. Background In recent years, organic-inorganic hybrid lead halide perovskite materials (such as CH3NH3PbBr 3, abbreviated as MAPbBr 3) have shown great potential in the radiation detection field due to their excellent photoelectric properties including high light absorption coefficient, long carrier diffusion length, high resistivity and good gamma ray response characteristics. Particularly, the MAPbBr 3 monocrystal has low defect density and high crystallization quality, can effectively inhibit carrier recombination and obviously improve the energy resolution and sensitivity of the detector, so that the MAPbBr 3 monocrystal is widely researched as a sensitive material for room temperature gamma ray detectors. Currently, the mainstream methods for preparing MAPbBr 3 single crystals include reverse temperature crystallization (ITC), temperature reduction, antisolvent vapor diffusion, solution surface growth, and the like. These methods typically employ a single polar solvent (e.g., N-dimethylformamide DMF, dimethylsulfoxide DMSO, or gamma-butyrolactone GBL) to dissolve the precursor, and then induce crystal nucleation and growth by controlling the temperature, the solvent evaporation rate, or introducing an antisolvent (e.g., chlorobenzene, diethyl ether). The obtained monocrystal is cut and polished, and then forms a photoelectric detector with a vertical structure with metal electrodes (such as gold and platinum), and ionization signal acquisition of gamma rays is realized under an externally applied bias. However, the crystal prepared by the method has the advantages of high growth speed, high density of internal defects (such as dislocation, vacancy and impurity inclusion) and influence on carrier mobility and service life, limited monocrystal size and irregular morphology, difficulty in meeting the integration requirement of a large-area uniform detector array, limited precursor solubility and crystallization dynamics regulation and control capability of a single solvent system, easiness in causing excessive nucleation points, crystallization or cracking, low resistivity of the obtained monocrystal, large dark current, reduced signal to noise ratio and limitation of the sensitivity of the detector under low-dose gamma rays. Wherein, the solubility of MAPbBr 3 in a single solvent system (such as DMF) is nonlinear along with the temperature, which causes the mutation of the crystal growth rate, induces structural defects such as twin crystal, dislocation and the like, and seriously affects the quality of single crystals. The existing reverse temperature crystallization method mostly adopts DMF single solvent, although the DMF single solvent has good solubility for PbBr 2, the solubility of MAPbBr 3 in the DMF single solvent is rapidly reduced in the range of 30-50 ℃, so that the growth dynamics is unstable, the defect density in the crystal is high, the carrier mobility-service life product (mu tau) is low due to the high defect density, the resistivity is insufficient, the dark current of a detector is high, the signal to noise ratio is poor, and the high-resolution gamma ray energy spectrum detection cannot be realized. Defects (such as Br − vacancy and uncoordinated Pb 0) are taken as deep level traps, non-radiative recombination is aggravated, so that the dark current density is up to 1258 nA cm -3 (-100V), the energy resolution capability of 511 keV gamma rays at room temperature is severely limited, the controllable preparation of MAPbBr 3 single crystals with large size, high transparency and low defect density is difficult to synchronously realize by a traditional solution method, the process repeatability is poor, and the integration and the industrialized application of devices are restricted. The supersaturation degree regulation window of a single solvent system is narrow, which is easy to cause multi-core nucleation, crystal adhesion or cracking, and the obtained single crystal has small size and irregular morphology, and is difficult to meet the requirement of a detector array on the uniformity of materials. Meanwhile, the defects of a corrosion layer, secondary nucleation particles and uncomplexed metal lead (Pb 0) caused by solvent residues exist on the surface of the crystal, so that the electrode-semiconductor interface contact is deteriorated, and the dark current is further raised. The monocrystalline surface taken out from the precursor solution forms a non-stoichiometric surface layer due to the selective dissolution of MA + by DMF, and XPS proves that Pb 0 deep level defects exist and become a non-radiative recombination center. Meanwhile, the existing electrode configuration