Silver bismuth halide single crystal and preparation method and application thereof

Abstract

The invention belongs to the technical field of photoelectric semiconductor materials, and particularly relates to a silver bismuth halide single crystal and a preparation method and application thereof. According to the improved solution evaporation crystallization process, the size integrity of the single crystal is effectively improved and the defect density is controlled by controlling the solution concentration, the solvent evaporation rate and the annealing temperature; the method specifically comprises the following steps: preparing a precursor solution with proper concentration; measuring the precursor solution and dripping the precursor solution onto a flexible hydrophobic substrate; evaporating the liquid drops to dryness to obtain single crystals in batches; performing thermal annealing to release lattice stress; the obtained high-quality Cs2AgBiBr6 single crystal is uniform in element distribution, and has (111) crystal face preferred orientation and excellent thermal stability. According to the method, the production cycle is remarkably shortened, and the process repeatability is improved. The silver bismuth halide single crystal can be used as a core functional material of an efficient and stable photoelectric detector, and has huge application potential in the field of optical detection.

Description

Technical Field

[0001] The present invention belongs to the technical field of optoelectronic semiconductor materials, and particularly relates to silver bismuth halide single crystals, a preparation method thereof, and an application thereof. Background Art

[0002] In recent years, perovskite materials have become a research hotspot in the fields of new energy and optoelectronic technologies due to their excellent optoelectronic properties such as high light absorption coefficient, long carrier diffusion length, and flexible bandgap tunability. However, the lead toxicity and stability problems of traditional lead-based materials still severely restrict their commercialization process. The clear restriction on the use of lead in the "Administrative Measures for the Restriction of the Use of Hazardous Substances in Electrical and Electronic Products" promulgated by the Ministry of Industry and Information Technology of China has forced the academic and industrial circles to accelerate the development of environmentally friendly lead-free alternative materials. Lead-free double perovskite single crystals not only inherit the excellent optoelectronic properties of traditional perovskite materials but also overcome the disadvantages of containing lead, with better environmental friendliness and stability. However, at present, the preparation of lead-free double perovskite single crystals still faces many challenges such as low yield, high defect state density, and difficulty in batch synthesis.

[0003] Chinese Patent Application CN114657627A discloses a preparation method and application of a tunable doped lead-free double perovskite single crystal. This method solves the problems of toxicity and poor stability of organic-inorganic hybrid perovskites containing lead ions through improved crystal growth and surface treatment processes. However, this method is relatively cumbersome, requiring precise temperature control, long-time heat preservation growth, and several washes, and there are pinhole defects on the surface of the obtained single crystal. Therefore, developing a simple, efficient, and low-cost method for preparing high-quality lead-free double perovskite single crystals has become the key to promoting the practical application of such materials. Summary of the Invention

[0004] The purpose of the present invention is to provide a silver bismuth halide single crystal with low cost and high quality, a preparation method thereof, and an application thereof.

[0005] The silver bismuth halide single crystal provided by the present invention adopts a double perovskite structure, and uses an environmentally friendly combination of monovalent and trivalent metal cations (Ag + / Bi 3+ ) to replace lead elements, fundamentally solving the toxicity problem. The preparation adopts an improved solution evaporation crystallization process. By precisely controlling the solution concentration and the solvent evaporation rate, the size integrity of the single crystal is effectively improved, and the defect density is strictly controlled; and an annealing process is combined to eliminate the internal stress in the lattice and reduce the lattice distortion and defect states caused by the disordered arrangement of [AgBr6] 5- and [BiBr6] 3- two kinds of octahedra in the lattice, so as to improve the stability of the material itself and the fabricated devices.

[0006] The preparation method of the silver bismuth halide single crystal provided by the present invention specifically comprises the following steps:

[0007] (1) Prepare a perovskite precursor solution with a certain concentration at room temperature;

[0008] (2) Measure a small amount of the precursor solution in step (1) and drop it onto a flexible hydrophobic substrate;

[0009] (3) Place the substrate with the droplet in step (2) on a heating stage to evaporate the solution and batch-precipitate single crystals;

[0010] (4) Perform thermal annealing on the single crystals obtained in step (3) for a certain period of time to release lattice stress and improve stability.

[0011] Furthermore:

[0012] In step (1), for the preparation of the perovskite precursor solution, the specific method is as follows: Dissolve the metal halide raw material in a solvent and stir at room temperature until completely dissolved.

[0013] The concentration of the perovskite precursor solution is 0.02 - 0.05 mol / L.

[0014] The halide raw material is selected from cesium bromide, silver bromide, and bismuth bromide.

[0015] The solvent is hydrobromic acid.

[0016] In step (2), the amount of the precursor solution is 5 - 10 μL.

[0017] The flexible hydrophobic substrate is polydimethylsiloxane (PDMS).

[0018] In step (3), the evaporation temperature is 50 - 80 °C.

[0019] In step (3), the annealing temperature is 120 - 200 °C, and the annealing time is 0.5 - 1 h.

[0020] The present invention also provides single crystals of silver bismuth halide prepared by the above method.

[0021] The composition of the single crystal of silver bismuth halide is Cs2AgBiBr6.

[0022] The size of the single crystal is: the diameter ranges from 10 to 100 μm, and the thickness ranges from 5 to 15 μm.

[0023] The above single crystals of silver bismuth halide can be used in photodetectors.

[0024] Compared with the prior art, the features and advantages of the present invention are mainly as follows:

[0025] (1) The materials of the present invention use lead-free elements (Ag / Bi) to replace traditional lead-based perovskites, completely avoiding the biological toxicity and environmental pollution problems of lead elements, and meeting the mandatory requirements for environmentally friendly materials globally.

[0026] (2) The micron single crystals of the present invention can be batch-prepared under normal pressure and medium-low temperature (<100 °C). The equipment requirements and process complexity are greatly reduced, and the production cycle is significantly shortened. The single crystals synthesized by this method have a preferred orientation of the (111) crystal plane, with good morphology, clean surface, and high-purity phase. The crystal size distribution of the same batch is uniform, the yield exceeds 94%, and the good product rate exceeds 85%, which is suitable for large-scale production.

[0027] (3) The method of the present invention has high yield, low cost, is simple, fast, and has good repeatability. The prepared single crystals have a flat and clean surface, low defect density, and excellent and stable optoelectronic detection performance.

[0028] (4) The silver-bismuth halide single crystals of the present invention can be used in photodetectors. The obtained high-quality single crystals have good optoelectronic properties and can be used as the core functional materials of highly efficient and stable photodetectors, showing great application potential in the field of light detection. Description of the Drawings

[0029] Figure 1 is the X-ray diffraction (XRD) pattern of the obtained silver-bismuth halide Cs2AgBiBr6 perovskite single crystal.

[0030] Figure 2 is the scanning electron microscope magnification (SEM) image (left) of the obtained silver-bismuth halide Cs2AgBiBr6 perovskite single crystal and the corresponding four-element distribution maps (right).

[0031] Figure 3 is the thermogravimetric analysis (TGA) curve of the obtained silver-bismuth halide Cs2AgBiBr6 perovskite single crystal.

[0032] Figure 4 is the current-voltage (I-V) curve of the electrical property test of the obtained silver-bismuth halide Cs2AgBiBr6 perovskite single crystal.

[0033] Figure 5 is the photoluminescence (PL) spectrum of the obtained silver-bismuth halide Cs2AgBiBr6 perovskite single crystal before and after annealing.

[0034] Figure 6 is the current-time (I-t) cyclic test curve of the photodetector based on the obtained silver-bismuth halide Cs2AgBiBr6 perovskite single crystal. Detailed Embodiments

[0035] The present invention will be further introduced below through specific embodiments in combination with the drawings.

[0036] Example 1. Preparation of Cs2AgBiBr6 single crystal. The specific steps are as follows:

[0037] Step 1. Cesium bromide, silver bromide and bismuth bromide (CsBr, AgBr, BiBr3) were added to hydrobromic acid with a mass fraction of 48.0% and a purity of ≥99.99% in a molar ratio of 2:1:1, and stirred at room temperature until completely dissolved to prepare a clear precursor solution with a concentration of 0.02 mol / L.

[0038] Step 2. Use a pipette to aspirate 10 μL of the precursor solution onto a flexible hydrophobic PDMS substrate.

[0039] Step 3. Place the PDMS substrate with the droplets on a heating table at 50 °C and slowly evaporate the solution to obtain Cs2AgBiBr6 single crystals with a size of 50 - 100 μm in batches on the substrate surface.

[0040] Step 4. Further raise the temperature of the heating table to 200 °C and perform thermal annealing on the obtained Cs2AgBiBr6 single crystals for 0.5 h to release the internal stress in the lattice and reduce the degree of lattice distortion.

[0041] Figure 1 is the XRD pattern of the obtained silver bismuth halide Cs2AgBiBr6 perovskite single crystal. The inset shows that the obtained single crystal has a preferred orientation of the (111) crystal plane and a full width at half maximum (FWHM) as low as 0.03°, with consistent orientation and high crystallization quality.

[0042] Figure 2 is the SEM gray-scale magnified image and the corresponding element distribution map of the obtained silver bismuth halide Cs2AgBiBr6 perovskite single crystal. The inset shows that the obtained single crystal has a three-dimensional symmetric octahedral morphology with a triangular top surface and a hexagonal bottom surface and a flat and clean surface, with determined composition and uniform element distribution.

[0043] Example 2. The preparation method of Cs2AgBiBr6 single crystal is as follows:

[0044] Step 1. Cesium bromide, silver bromide and bismuth bromide (CsBr, AgBr, BiBr3) were added to hydrobromic acid with a mass fraction of 48.0% and a purity of ≥99.99% in a molar ratio of 2:1:1, and stirred at room temperature until completely dissolved to prepare a clear precursor solution with a concentration of 0.03 mol / L.

[0045] Step 2. Use a pipette to aspirate 7 μL of the precursor solution onto a flexible hydrophobic PDMS substrate.

[0046] Step 3. Place the PDMS substrate with the droplets on a heating table at 65 °C and evaporate the solution to obtain Cs2AgBiBr6 single crystals with a size of 30 - 50 μm in batches on the substrate surface.

[0047] Step 4: Further increase the hot stage temperature to 200 °C, and perform thermal annealing on the obtained Cs2AgBiBr6 single crystal for 1 h to release the internal stress in the lattice and reduce the degree of lattice distortion.

[0048] Figure 3 is the TGA curve of the obtained silver bismuth halide Cs2AgBiBr6 perovskite single crystal. The inset shows that the initial decomposition temperature of the obtained single crystal reaches ~460 °C, indicating excellent thermal stability compared to traditional lead-based perovskites.

[0049] Figure 4 is the I-V curve of the electrical property test of the obtained silver bismuth halide Cs2AgBiBr6 perovskite single crystal. The inset shows that the carrier transport of the obtained semiconductor single crystal is divided into three stages: the ohmic region, the trap filling region, and the space charge limited current region. The calculated defect density is as low as 1.67×10 9 cm -3 , which has a significant advantage compared to traditional perovskite single crystals (~10 11 to 10 12 cm -3 ).

[0050] Example 3: Preparation of Cs2AgBiBr6 single crystal. The specific steps are as follows:

[0051] Step 1: Add cesium bromide, silver bromide, and bismuth bromide (CsBr, AgBr, BiBr3) in a molar ratio of 2:1:1 to hydrobromic acid with a mass fraction of 48.0% and a purity of ≥99.99%, and stir at room temperature until completely dissolved to prepare a clear precursor solution with a concentration of 0.05 mol / L.

[0052] Step 2: Use a pipette to aspirate 5 μL of the precursor solution onto a flexible hydrophobic PDMS substrate.

[0053] Step 3: Place the PDMS substrate with the droplets on an 80 °C hot stage to quickly evaporate the solution, and obtain Cs2AgBiBr6 single crystals with sizes of 10 - 30 μm in batches on the substrate surface.

[0054] Step 4: Further increase the hot stage temperature to 120 °C, and perform thermal annealing on the obtained Cs2AgBiBr6 single crystal for 1 h to release the internal stress in the lattice and reduce the degree of lattice distortion.

[0055] Figure 5 is the PL spectrum of the obtained silver bismuth halide Cs2AgBiBr6 perovskite single crystal before and after annealing. The inset shows that the photoluminescence peak position of the single crystal blue-shifts after annealing, the full width at half maximum decreases, the non-radiative recombination of carriers decreases, and the crystal quality improves.

[0056] Figure 6I-t stability test curve of the obtained photodetector based on silver bismuth halide Cs2AgBiBr6 perovskite single crystal. The inset shows that the dark current is as low as pA, the photocurrent reaches nA, the on / off ratio is ~350, and the performance remains stable under cyclic testing. The unencapsulated device can still maintain >90% of its initial optoelectronic performance after being stored in an air environment for 30 days, with stability far exceeding that of traditional lead-based perovskite materials, showing great application potential.

[0057] As described above, only the specific preferred embodiments of the present invention are provided, but the scope of protection of the present invention is not limited thereto. Any modifications, equivalent replacements, and improvements made by those skilled in the art within the technical scope disclosed by the present invention shall be included within the scope of protection of the present invention.

Claims

1. A method for preparing a silver bismuth halide single crystal, characterized in that, The specific steps are as follows: (1) Prepare a perovskite precursor solution at room temperature; (2) Measure the precursor solution in step (1) and drop it onto a flexible hydrophobic substrate; (3) Place the substrate with the droplet in step (2) on a heating stage to evaporate the solution and completely precipitate single crystals; (4) Perform thermal annealing on the single crystals obtained in step (3) to release lattice stress.

2. The preparation method according to claim 1, characterized in that, In step (1): The preparation of the perovskite precursor solution specifically involves dissolving a metal halide raw material in a solvent and stirring at room temperature until completely dissolved; The concentration of the perovskite precursor solution is 0.02 - 0.05 mol / L; The halide raw material is selected from cesium bromide, silver bromide, and bismuth bromide; The solvent is hydrobromic acid.

3. The preparation method according to claim 1, characterized in that, In step (2): The amount of the precursor solution is 5 - 10 μL; The flexible hydrophobic substrate is polydimethylsiloxane (PDMS).

4. The preparation method according to claim 1, wherein In step (3), the evaporation temperature is 50 - 80 °C.

5. The preparation method according to claim 1, wherein, In step (4), the annealing temperature range is 120 - 200 °C, and the annealing time is 0.5 - 1 h.

6. A cesium silver bismuth halide single crystal obtained by the preparation method according to any one of claims 1 - 5, with the single crystal composition being Cs2AgBiBr6; single crystal size: diameter is 10 - 100 μm, and thickness is 5 - 15 μm.

7. Use of the cesium silver bismuth halide single crystal according to claim 6 in a photodetector.

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