Method for promoting uniform epitaxial growth of large-area perovskite single crystal

Abstract

The invention discloses a method for promoting uniform epitaxial growth of a large-area perovskite single crystal, and the method comprises the following steps: 1, carrying out the solvent etching treatment of a halide substrate: placing the halide substrate into a solvent, carrying out the heating, and carrying out the heat treatment of the halide substrate, and changing the microstructure of the surface of the substrate; and 2, soaking the substrate subjected to solvent etching treatment in a perovskite single crystal growth solution. According to the method, the specific solvent is selected to perform etching treatment on the surface of the substrate to remove part of the surface atomic layer or repair lattice defects, so that the surface of the substrate is effectively activated, and the substrate is more suitable for rapid nucleation and growth of perovskite single crystals.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor materials technology, and in particular relates to a method for promoting uniform epitaxial growth of large-area perovskite single crystals. Background Technology

[0002] In recent years, perovskite single crystal materials have been widely used in optoelectronic devices such as solar cells and light-emitting diodes due to their excellent optoelectronic properties, such as low defect state density, longer carrier lifetime, diffusion length, and higher stability. To achieve high-performance devices, obtaining high-quality, large-area perovskite single crystals is crucial. Existing perovskite single crystal growth methods mainly include solution methods, vapor-phase methods, and top-down processing methods. Among these, solution methods are widely used due to their simplicity and low cost, especially showing significant advantages for perovskite material growth at low temperatures. However, single crystals grown by solution methods often face problems such as small crystal size, rough surface, and uneven growth, which limit the application of large-area, high-quality perovskite single crystals.

[0003] To address these issues, researchers have proposed optimizing single-crystal growth using lattice-matched substrate materials. When the lattice constant difference between the substrate material and the perovskite material is small (typically less than 5%), perovskite crystals can achieve ordered epitaxial growth on the substrate surface. This not only significantly improves crystal quality but also enables effective scaling up of crystal size. Therefore, using a lattice-matched substrate-assisted solution method to grow perovskite single crystals can significantly improve the crystallinity and size of the single crystals, thereby meeting the growing application demands of perovskite materials in optoelectronic devices.

[0004] In the selection of lattice-matched substrate materials, compound single-crystal substrates formed by alkali metals such as Na and K and halogens (e.g., Cl, Br, I), as well as specific transition metal compound single-crystal substrates, are favored due to their unique advantages. These materials not only possess excellent chemical stability, optical transparency, and low cost, but more importantly, their lattice constants can be well matched with perovskite materials such as MAPbX3, providing an ideal crystallographic basis for the epitaxial growth of perovskite single crystals and becoming ideal substrate materials for achieving high-quality, large-size perovskite single-crystal thin films. However, these substrates often have lattice defects and missing surface atomic layers. These surface defects significantly increase the mismatch between the perovskite material and the substrate lattice, leading to poor direct growth results. Therefore, improving the surface state of the substrate through surface modification techniques such as solvent engineering, such as etching or surface activation, is key to achieving high-quality perovskite single-crystal epitaxial growth. Summary of the Invention

[0005] In view of this, the present invention provides a method for promoting uniform epitaxial growth of large-area perovskite single crystals. This method uses a specific solvent to etch the substrate surface to remove part of the surface atomic layer or repair lattice defects, thereby effectively activating the substrate surface and making it more suitable for the rapid nucleation and growth of perovskite single crystals.

[0006] To achieve the above objectives, the technical solution of the present invention is as follows: A method for promoting uniform epitaxial growth of large-area perovskite single crystals includes the following steps: Step 1: Solvent etching of halide substrate: The halide substrate is placed in a solvent and heated to perform heat treatment on the halide substrate, thereby changing the microstructure of the substrate surface. Step 2: Immerse the solvent-etched substrate in the perovskite single crystal growth solution.

[0007] Preferably, the solvent in step 1 is any one of DMF, DMSO, methanol, ethanol, isopropanol, butanol or cyclohexanol or a mixture thereof.

[0008] Preferably, a functional additive is also added to the solvent in step 1; The functional additives are transition metal salts, metal ions, acid and basic additives, surfactants, or organic compounds.

[0009] The ratio of the functional additive to the solvent is 50 g / L to 100 g / L.

[0010] Preferably, the transition metal salt is selected from any one or a mixture of lead bromide (PbBr2), lead acetate trihydrate (Pb(CH3COO)2・3H2O), tin chloride (SnCl2), cadmium iodide (CdI2), or manganese bromide (MnBr2). The selected metal ion is: Pb 2+ Sn 2+ Cd 2+ Mn 2+ or Co 2+ ; The acid-base additives are selected from any one or a mixture of hydrobromic acid (HBr), aqueous methylamine (CH3NH2・H2O), or pyridine. The surfactant is selected from any one or a mixture of sodium dodecylbenzenesulfonate (SDBS), hexadecyltrimethylammonium bromide (CTAB), Tween-80, or Span-60; The organic compound is acetic acid or phenol.

[0011] Preferably, the heat treatment temperature in step 1 is 20-150°C, and the treatment time is 2 min-2 h.

[0012] Preferably, the solute in the perovskite single crystal growth solution in step 2 is an ABX3 type perovskite material, and the concentration of the perovskite single crystal growth solution is 1-2.5 mol / L; The solvent in the perovskite single crystal growth solution is DMF or DMSO or a mixture thereof.

[0013] Preferably, A is selected from any one or a combination of methylamine ions, methylammonium ions, or cesium ions; B is lead ions, tin ions, or a combination thereof; and X is selected from any one or a combination of chloride ions, bromide ions, or iodide ions.

[0014] Preferably, the soaking time in step 2 is 2 seconds to 10 minutes, and the growth temperature is 40 to 60°C.

[0015] Preferably, the halide substrate is a single-crystal compound composed of halides containing halogens.

[0016] Preferably, the process further includes preparing a perovskite single crystal solution prior to step 2.

[0017] Because the present invention adopts the above technical solution, it has the following advantages and positive effects compared with the prior art: Improving single crystal quality: This invention activates halide substrates through solvent etching. Through chemical dissolution and temperature changes, it removes some atomic layers on the substrate surface or repairs lattice defects, thereby changing the microstructure of the substrate surface, exposing dangling bonds, effectively activating the substrate surface, and significantly improving the lattice matching degree between the substrate and the perovskite material, thus promoting the growth of high-quality perovskite single crystals.

[0018] Promoting large-area single crystal growth: By improving the substrate surface condition, this invention effectively solves the problems of uneven growth and small crystal size in traditional methods, enabling the preparation of large-area, high-quality perovskite single crystals to meet the application requirements of optoelectronic devices.

[0019] Simple to operate and low in cost: Compared with existing perovskite single crystal growth methods, the solution etching process used in this invention is simple and low-temperature, and the solvent used has a low cost, making the method highly economical.

[0020] High adaptability: This invention is applicable to the growth of various perovskite materials, especially perovskite materials with good lattice matching with the substrate, and has broad application prospects, especially in the fields of solar cells, light-emitting diodes and other optoelectronic devices, where it has important application value.

[0021] Improved device performance: Due to the significant improvement in the quality and size of the single crystal, the perovskite single crystal prepared by this invention can further improve the performance of optoelectronic devices, such as photoelectric conversion efficiency, carrier lifetime and stability. Attached Figure Description

[0022] Figure 1 Optical characterization photograph of the large-area MAPbBr3 single crystal obtained in Comparative Example 1; Figure 2 Optical micrograph of the large-area MAPbBr3 single crystal surface obtained in Comparative Example 1; Figure 3 Optical micrograph of MAPbBr3 single crystal grown on an untreated KCl substrate in Comparative Example 2; Figure 4 This is an optical micrograph of MAPbCl3 single crystals grown on a surface-treated KCl substrate in Example 1. Figure 5 This is an optical photograph of MAPbBr3 single crystals grown on a surface-treated KCl substrate in Example 2. Figure 6 This is an optical micrograph of MAPbBr3 single crystals grown on a surface-treated KCl substrate in Example 2. Figure 7 The image shows the XRD pattern of MAPbBr3 single crystals grown on a surface-treated KCl substrate in Example 2. Figure 8 The XRD pattern of the large-area MAPbBr3 single crystal obtained in Comparative Example 1 is shown. Figure 9 The fluorescence lifetime comparison curves are shown for the MAPbBr3 single crystals obtained in Comparative Example 1 and Example 2. Figure 10 Optical photographs of MAPbBr3 single crystals grown on surface-treated NaBr substrates at different growth times in Example 3; Figure 11 These are optical micrographs of MAPbBr3 single crystals grown on a surface-treated NaBr substrate at different growth times in Example 3. Figure 12 Optical photographs of different growth times of MAPb(ClBr)3 mixed single crystals on a surface-treated NaCl substrate in Example 4; Figure 13 These are optical micrographs of MAPb(ClBr)3 mixed single crystals grown on a surface-treated NaCl substrate at different growth times in Example 4. Detailed Implementation

[0023] This invention provides a method for promoting uniform epitaxial growth of large-area perovskite single crystals by activating the substrate surface through solution etching, comprising the following steps: Step 1: Solvent etching treatment Solvents such as DMF (N,N-dimethylformamide), DMSO (dimethyl sulfoxide), methanol, ethanol, isopropanol, butanol, and cyclohexanol were used to heat-treat halide single crystal substrates such as NaCl, KCl, NaBr, and KBr. The heat treatment temperature range was 20-150°C, for example, 20, 30, 40, 50, 60, 70, 80, 90, 100, 110, 120, 130, 140, and 150°C, and the treatment time ranged from 2 min to 2 h, for example, 2 min, 10 min, 30 min, 40 min, 50 min, 1 h, and 2 h. Through chemical dissolution and temperature changes, some atomic layers on the substrate surface were removed or lattice defects were repaired, thereby changing the microstructure of the substrate surface, effectively activating the substrate surface, and improving its nucleation adaptability for perovskite single crystals.

[0024] During this process, transition metal salts, metal ions, acidic or basic additives, surfactants, or organic compounds (such as acetic acid and phenol) can be selectively added to the solvent. These additives, through selective chemical interactions with the substrate surface, precisely control the chemical properties and reaction kinetics of the solvent, thereby influencing the synergistic control of substrate etching rate, surface morphology reconstruction, and lattice defect repair. This effectively optimizes the substrate-perovskite interface characteristics and further promotes the uniform epitaxial growth of perovskite single crystals. For example, basic additives help remove surface impurities and improve surface smoothness, while surfactants reduce the interfacial tension between the solvent and the substrate, promoting uniform solvent penetration, thus improving surface smoothness and reducing uneven etching. Furthermore, organic compounds such as acetic acid and phenol can remove organic contaminants from the substrate surface and improve its chemical activity through reactions with the substrate surface. By precisely controlling the type and concentration of these additives, the etching rate, morphology changes, and lattice defect repair of the substrate surface can be effectively controlled, providing ideal surface conditions for the epitaxial growth of perovskite single crystals and promoting high-quality growth and uniform expansion of the single crystals.

[0025] Step 2: Perovskite Single Crystal Growth The solvent-treated substrate is immersed in a perovskite single crystal growth solution with a concentration of 1-2.5 M (mol / L), such as 1, 1.85, or 2.5 M. The immersion time is 2s-2h, such as 2s, 10s, 30s, 1min, 2min, 8min, 10min, 20min, 30min, 40min, 50min, 1h, or 2h. The growth temperature is 40-60℃, such as 40, 50, or 60℃. The perovskite single crystal growth solution contains perovskite materials of the ABX3 type, such as MAPbCl3 or MAPbBr3. A is methylamine ion (MA), methylammonium ion (FA), cesium ion (Cs), or other cations or mixtures thereof; B is lead (Pb) or tin (Sn) or mixtures thereof; and X is chloride ion (Cl), bromide ion (Br), iodide ion (I), or mixtures thereof. In this solution, perovskite materials rapidly nucleate and crystallize on the substrate surface, leading to epitaxial growth. By controlling the concentration, temperature, and growth time of the growth solution, epitaxial growth of perovskite materials on the substrate surface is achieved, forming high-quality, large-size single-crystal thin films.

[0026] Through the above steps, this invention can effectively activate the substrate surface, promote the growth of perovskite single crystals, and significantly improve the quality and size of the single crystals. This method is simple and efficient, and can achieve the preparation of large-area, high-quality perovskite single crystals at relatively low temperatures.

[0027] The method for promoting uniform epitaxial growth of large-area perovskite single crystals proposed in this invention will be further described in detail below with reference to the accompanying drawings and specific embodiments. The advantages and features of this invention will become clearer from the following description.

[0028] Unless otherwise specified, the experimental methods used in the following examples are conventional methods.

[0029] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0030] Comparative Example 1 1. The perovskite precursor raw materials methylamine hydrobromide (MABr) and lead bromide (PbBr2) were dissolved in N,N-dimethylformamide (DMF) at a molar ratio of 1:1, and the resulting MAPbBr3 perovskite single crystal growth solution was obtained by filtration.

[0031] 2. Add a certain amount of perovskite single crystal growth solution to a petri dish and place it on a constant temperature hot plate at 30℃ for 12 hours to obtain perovskite seed crystals with a size of less than 1 mm.

[0032] 3. Transfer the obtained perovskite seed crystal to a glass bottle, add the perovskite single crystal growth solution, and place the glass bottle in an oven. Starting from 25°C, the temperature is increased to 60°C at a rate of 2°C / day. After about 18 days of growth, a perovskite single crystal with a size of 2-3 cm is obtained.

[0033] Figure 1 and Figure 2 The images shown are optical and microscopic photographs of the obtained perovskite single crystals. It can be observed that the perovskite single crystals exhibit an irregular crystal morphology. This irregular growth is mainly due to factors such as fluctuations in solute concentration in the solution, crystal fragments, and impurity particles. These interfering factors lead to differences in the growth rate of the crystal in different directions, ultimately resulting in an irregular crystal morphology. Such irregular crystals often generate internal stress, making them more prone to cracking or fracturing under mechanical pressure, thus affecting the processability and long-term stability of perovskite materials.

[0034] Comparative Example 2 The preparation method is as follows: 1. Dissolve the perovskite precursor raw materials methylamine hydrobromide (MABr) and lead bromide (PbBr2) in N,N-dimethylformamide (DMF) at a molar ratio of 1:1, and obtain a MAPbBr3 perovskite single crystal growth solution with a concentration of 1.85 M by filtration.

[0035] 2. Place the fresh KCl substrate in a 1.85 M MAPbBr3 perovskite single crystal growth solution and grow at 40℃ for 2 min.

[0036] Figure 3 This is an optical micrograph of a KCl substrate surface, showing disordered single crystals growing on it. Although perovskite single crystals can grow under certain conditions, on an untreated KCl substrate, the growth direction of the single crystals is not effectively guided, resulting in free growth in various directions, irregular morphology, and a lack of ordered arrangement. This is because the KCl substrate surface has lattice defects and atomic layer losses, leading to poor lattice matching between the substrate and the perovskite material, thus failing to provide a stable growth platform.

[0037] Example 1 The preparation method is as follows: 1. Methylamine hydrochloride (MACl) and lead chloride (PbCl2) were dissolved in a solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) in a 1:1 molar ratio. After filtration, a MAPbCl3 perovskite single crystal growth solution with a concentration of 1 M was obtained.

[0038] 2. Select DMSO as solvent to perform slight heat treatment on KCl substrate: Place KCl substrate in DMSO solution and heat it in a hydrothermal reactor to 80°C for 20 minutes.

[0039] 3. Immerse the treated KCl substrate in the above perovskite precursor solution and grow it at 60°C for 30 seconds.

[0040] Figure 4 The image shows an optical micrograph of the MAPbCl3 perovskite single crystal prepared in Example 1. The image clearly shows a good epitaxial growth relationship between the KCl substrate and the MAPbCl3 single crystal, indicating that the MAPbCl3 single crystal has successfully achieved high-quality epitaxial growth on the KCl substrate surface.

[0041] Example 2 The preparation method is as follows: 1. Methylamine hydrobromide (MABr) and lead bromide (PbBr2) were dissolved in N,N-dimethylformamide (DMF) at a molar ratio of 1:1. After filtration, a MAPbBr3 perovskite single crystal growth solution with a concentration of 1.85 M was obtained.

[0042] 2. Using ethanol as a solvent, a slight heat treatment was performed on the KCl substrate: The KCl substrate was placed in an ethanol solution and heated to 100°C in a hydrothermal reactor for 20 minutes. This treatment process removes some atomic layers from the surface of the KCl substrate through chemical dissolution, while repairing surface lattice defects, thereby activating the KCl substrate surface and improving its adaptability to perovskite single crystal growth.

[0043] 3. Immerse the treated KCl substrate in the above perovskite single crystal growth solution and grow at 40°C for 2 min.

[0044] Figure 5 and Figure 6 Optical photographs and optical micrographs of the obtained perovskite single crystals are shown. The smooth surface of the single crystals, without obvious surface defects or irregular morphologies, demonstrates the uniformity of single crystal growth. Figure 7 The XRD patterns of perovskite single crystals grown on surface-treated KCl substrates are shown. It can be seen that the main diffraction peaks of the perovskite single crystals on the treated KCl substrate are sharper and have higher intensity, indicating improved crystal order and superior crystal quality. In contrast, Comparative Example 1 ( Figure 8 The diffraction peak intensity of perovskite single crystals grown by the traditional solution method is weak, indicating that the crystal quality is relatively poor and there are more defects. Figure 9The TRPL data for perovskite single crystals on the treated KCl substrate show that the carrier lifetime of the perovskite single crystals on the surface-treated KCl substrate is significantly longer than that of the perovskite single crystals grown by the conventional solution method in Comparative Example 1. The treated sample exhibits a longer carrier lifetime, indicating its superior photoelectric properties and lower carrier recombination rate.

[0045] Example 3 The preparation method is as follows: 1. Methylamine hydrobromide (MABr) and lead bromide (PbBr2) were dissolved in N,N-dimethylformamide (DMF) at a molar ratio of 1:1. After filtration, a MAPbBr3 perovskite single crystal growth solution with a concentration of 1.85 M was obtained.

[0046] 2. Ethanol was selected as the solvent for a mild heat treatment of the NaBr substrate. The NaBr substrate was placed in an ethanol solution containing 5 μL of HBr and heated to 100°C in a hydrothermal reactor for 20 minutes. This treatment process removes part of the atomic layer on the surface of the NaBr substrate through chemical dissolution, while repairing surface lattice defects, thereby activating the NaBr substrate surface and improving its adaptability to perovskite single crystal growth.

[0047] 3. Immerse the treated NaBr substrate in the above perovskite single crystal growth solution for 2s and 2min.

[0048] Figure 10 and Figure 11 Optical and optical microscopic images of MAPbBr3 single crystals on surface-treated NaBr substrates at different growth times are shown. The images reveal a good epitaxial growth relationship between the NaBr substrate and the MAPbBr3 single crystal. With increasing growth time, the thickness of the MAPbBr3 single crystal gradually increases, its color changes from orange-yellow to orange-red, and the crystal surface gradually becomes smoother and flatter. This indicates that the surface-treated NaBr substrate provides good lattice matching for the epitaxial growth of MAPbBr3 single crystals, promoting ordered growth of the single crystal on the substrate surface, thereby improving the quality and stability of the single crystal.

[0049] Experiment Example 4 The preparation method is as follows: 1. Methylamine hydrobromide (MABr) and lead chloride (PbCl2) were dissolved in a solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) in a molar ratio of 1:1. After filtration, a MAPb(ClBr)3 perovskite single crystal growth solution with a concentration of 2.5 M was obtained.

[0050] 2. Ethanol was selected as the solvent for a mild heat treatment of the NaCl substrate. The NaCl substrate was placed in an ethanol solution and heated to 100°C in a hydrothermal reactor for 10 minutes. This treatment process removes part of the atomic layer on the surface of the NaCl substrate through chemical dissolution, while repairing surface lattice defects to activate the NaBr substrate surface and improve its adaptability to perovskite single crystal growth.

[0051] 3. Immerse the treated NaCl substrate in the above perovskite single crystal growth solution and grow for 10 s and 8 min.

[0052] Figure 12 and Figure 13 Optical and optical micrographs of MAPb(ClBr)3 single crystals grown on surface-treated NaCl substrates at different growth times are shown. As can be observed, the thickness of the MAPb(ClBr)3 single crystal gradually increases with increasing growth time, the color changes from light yellow to a deeper yellow, and the crystal surface gradually becomes smoother. Similar to the NaBr substrate, the NaCl substrate provides excellent lattice matching for the MAPb(ClBr)3 single crystal, effectively promoting the ordered growth of the single crystal, thereby improving its quality and stability.

[0053] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings, but the present invention is not limited to the above embodiments. Even if various changes are made to the present invention, if these changes fall within the scope of the claims of the present invention and their equivalents, they shall still fall within the protection scope of the present invention.

Claims

1. A method for promoting uniform epitaxial growth of large-area perovskite single crystals, characterized in that, Includes the following steps: Step 1: Solvent etching of halide substrate: The halide substrate is placed in a solvent and heated to perform heat treatment on the halide substrate, thereby changing the microstructure of the substrate surface. Step 2: Immerse the solvent-etched substrate in the perovskite single crystal growth solution.

2. The method for promoting uniform epitaxial growth of large-area perovskite single crystals according to claim 1, characterized in that, The solvent in step 1 is any one of DMF, DMSO, methanol, ethanol, isopropanol, butanol, or cyclohexanol, or a mixture thereof.

3. The method for promoting uniform epitaxial growth of large-area perovskite single crystals according to claim 1 or 2, characterized in that, Functional additives are also added to the solvent in step 1; The functional additives are transition metal salts, metal ions, acid and basic additives, surfactants, or organic compounds. The ratio of the functional additive to the solvent is 50 g / L to 100 g / L.

4. The method for promoting uniform epitaxial growth of large-area perovskite single crystals according to claim 3, characterized in that, The transition metal salt is selected from any one or a mixture of lead bromide, lead acetate trihydrate, tin chloride, cadmium iodide, or manganese bromide. The selected metal ion is: Pb 2+ Sn 2+ Cd 2+ Mn 2+ or Co 2+ ; The acid-base additives are selected from any one or a mixture of hydrobromic acid, aqueous methylamine, or pyridine. The surfactant is selected from any one or a mixture of sodium dodecylbenzenesulfonate, hexadecyltrimethylammonium bromide, Tween-80 or Span-60; The organic compound is acetic acid or phenol.

5. The method for promoting uniform epitaxial growth of large-area perovskite single crystals according to claim 1, characterized in that, The heat treatment temperature in step 1 is 20-150°C, and the treatment time is 2 min-2 h.

6. The method for promoting uniform epitaxial growth of large-area perovskite single crystals according to claim 1, characterized in that, In step 2, the solute in the perovskite single crystal growth solution is ABX3 type perovskite material, and the concentration of the perovskite single crystal growth solution is 1-2.5 mol / L. The solvent in the perovskite single crystal growth solution is DMF or DMSO or a mixture thereof.

7. The method for promoting uniform epitaxial growth of large-area perovskite single crystals according to claim 6, characterized in that, A is any one or a combination of methylamine ions, methylammonium ions, or cesium ions; B is lead ions, tin ions, or a combination thereof; X is any one or a combination of chloride ions, bromide ions, or iodide ions.

8. The method for promoting uniform epitaxial growth of large-area perovskite single crystals according to claim 1, characterized in that, In step 2, the soaking time is 2 seconds to 10 minutes, and the growth temperature is 40 to 60°C.

9. The method for promoting uniform epitaxial growth of large-area perovskite single crystals according to claim 1, characterized in that, The halide substrate is a single-crystal compound composed of halides containing halogens.

10. The method for promoting uniform epitaxial growth of large-area perovskite single crystals according to claim 1, characterized in that, It also includes preparing a perovskite single crystal solution prior to step 2.

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