A two-dimensional halide perovskite single crystal, a preparation method thereof and a photoelectric device

Abstract

This application discloses a two-dimensional halide perovskite single crystal with the chemical formula (C9H). 14 N)2PbBr4, where C9H 14 N + This represents the N-butylpyridine cation. This two-dimensional halide perovskite single crystal not only exhibits excellent phase stability but also produces highly efficient broadband yellow light emission.

Description

Technical Field

[0001] This application relates to the field of luminescent material preparation technology, and in particular to a two-dimensional halide perovskite single crystal, its preparation method, and optoelectronic devices. Background Technology

[0002] Organic-inorganic hybrid metal halide perovskites (OIMHs) have attracted widespread attention in the field of luminescent materials due to their tunable structure and excellent photoelectric properties. Among them, two-dimensional halide perovskites and three-dimensional halide perovskites are particularly noteworthy.

[0003] Two-dimensional halide perovskites (also known as 2D hybrid perovskites) possess a two-dimensional layered structure, namely a quantum well structure formed by alternating organic and inorganic layers. Due to their unique quantum and dielectric confinement effects, 2D halide perovskites exhibit advantages such as strong exciton binding energy, high photoluminescence quantum yield, and broadband emission, making them particularly suitable for applications such as solid-state lighting, laser gain media, and X-ray detection. Two-dimensional halide perovskites typically consist of large-volume organic cations inserted into inorganic [PbX6]. 2- The octahedral layers form a layered structure, with X representing a halogen. The organic layers not only provide structural support but also effectively isolate the inorganic light-emitting layers, reducing non-radiative recombination and improving the material's environmental stability. Compared to three-dimensional halide perovskites (3D hybrid perovskites), two-dimensional halide perovskites exhibit significantly enhanced tolerance to humidity, heat, and light, while their exciton properties are more conducive to achieving efficient luminescence.

[0004] In recent years, researchers have achieved emission control of two-dimensional halide perovskites from blue to red light by regulating organic cations, but there is still a lack of effective single-crystal systems of two-dimensional halide perovskites in the yellow light band. Summary of the Invention

[0005] This application provides a two-dimensional halide perovskite single crystal, its preparation method, and an optoelectronic device, which solves one of the technical problems of the inability of two-dimensional halide perovskites to effectively emit yellow light in related technologies.

[0006] A first aspect of this application provides a two-dimensional halide perovskite single crystal with the chemical formula (C9H10H2O). 14 N)2PbBr4, where C9H 14 N + It represents the N-butylpyridine cation.

[0007] Optionally, the emission peak wavelength of the two-dimensional halide perovskite single crystal under 350 nm wavelength excitation is 540 nm to 560 nm, and / or the CIE 1931 color coordinates of the two-dimensional halide perovskite single crystal under 350 nm wavelength excitation satisfy: x = 0.35 to 0.42, y = 0.42 to 0.48.

[0008] Optionally, the full width at half maximum (FWHM) of the emission peak is greater than 100 nm.

[0009] Optionally, the full width at half maximum (FWHM) of the (001) diffraction peak in the X-ray diffraction pattern of the two-dimensional halide perovskite single crystal is ≤0.2°, and the (001) diffraction peak is a diffraction peak with a diffraction angle 2θ in the range of 3° to 10°.

[0010] Optionally, in the X-ray diffraction pattern of the two-dimensional halide perovskite single crystal, the average background intensity of the region without diffraction peaks in the range of 2θ being 20° to 24° is not greater than 4% of the intensity of the (001) diffraction peak.

[0011] Optionally, the two-dimensional halide perovskite single crystal has a length of 2 mm to 5 mm, a width of 1 mm to 3 mm, and a thickness of 0.05 mm to 0.5 mm.

[0012] Optionally, the photoluminescence quantum efficiency of the two-dimensional halide perovskite single crystal under 350 nm excitation is ≥50%.

[0013] A second aspect of this application provides a method for preparing the two-dimensional halide perovskite single crystal described in the first aspect, comprising the following steps: N-Butylpyridine bromide and PbBr2 were placed in an aprotic polar solvent and heated until completely dissolved to obtain a perovskite precursor solution, wherein the molar ratio of N-butylpyridine bromide to PbBr2 was (1.8~2.2):1; and The perovskite precursor solution was cooled and crystallized to obtain the two-dimensional halide perovskite single crystal.

[0014] Optionally, the cooling rate of the cooling crystallization is less than or equal to 60 °C / h; and / or, The heating temperature is 80 ℃~100 ℃, the final temperature of the cooling crystallization is 20 ℃~25 ℃, and the cooling crystallization time is 1 h~2 h.

[0015] Optionally, the cooling rate is 30 ℃ / h to 60 ℃ / h.

[0016] Optionally, the aprotic polar solvent includes one or more of N,N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, γ-butyrolactone, or dimethylacetamide.

[0017] Optionally, the aprotic polar solvent is N,N-dimethylformamide.

[0018] Optionally, the amount of the aprotic polar solvent used is (2~10) L of aprotic polar solvent to dissolve 1 mol of PbBr2, or, the amount of Pb in the perovskite precursor solution is...2+ The concentration is 0.1 mol / L to 0.5 mol / L.

[0019] Optionally, the cooling crystallization is carried out under vacuum conditions.

[0020] Optionally, the step of cooling and crystallizing the perovskite precursor solution further includes washing and drying the crystals obtained by cooling and crystallization, wherein the drying temperature is 60 ℃ to 200 ℃.

[0021] In a third aspect, this application provides an optoelectronic device comprising a two-dimensional halide perovskite single crystal as described in the first aspect or a two-dimensional halide perovskite single crystal obtained by the preparation method described in the second aspect.

[0022] Compared with the prior art, the technical solution provided in this application has the following beneficial effects: The two-dimensional halide perovskite single crystal of this application, with C9H 14 N + (N-Butylpyridine cation) is an organic cation, and it reacts with [PbBr4] 2- Alternating inorganic layers form a two-dimensional layered structure. The N-butylpyridine cation possesses a hydrophobic long chain (butyl) and an aromatic ring (pyridine). This structure exhibits significant steric hindrance and rigidity, resulting in stronger support for the organic layers. Furthermore, hydrogen bonds form between the organic and inorganic layers, enhancing interlayer bonding. Therefore, this two-dimensional halide perovskite single crystal possesses excellent phase stability. In addition, steric hindrance and hydrogen bonding also induce phase changes in the inorganic [PbBr4]. 2- The octahedral structure distortion and the large steric hindrance make the inorganic layer thinner and the quantum confinement effect stronger. The quantum confinement effect, together with the structural distortion, enhances the exciton-phonon coupling and promotes the formation of self-trapped excitons (STEs). Moreover, the quantum confinement effect modulates the band gap, enabling efficient broadband yellow light emission from exciton recombination, especially under 350 nm wavelength excitation.

[0023] Traditional methods for preparing two-dimensional halide perovskite single crystals are prone to multiphase coexistence or crystal cracking. However, the method for preparing two-dimensional halide perovskite single crystals provided in this application employs cooling crystallization, further controlled by a controller with a cooling rate of less than or equal to 60 °C / h, resulting in higher quality two-dimensional halide perovskite single crystals. The single crystals prepared using this method exhibit high crystallinity, purity, and optical quality. The crystallization process is highly controllable and repeatable.

[0024] The two-dimensional halide perovskite single crystals and their preparation methods provided in this application not only contribute to in-depth research on their luminescence mechanism and structure-property relationship, but also provide an important material basis for the application of novel yellow light-emitting materials in optoelectronic devices. Attached Figure Description

[0025] The accompanying drawings, which are incorporated in and form part of this specification, illustrate embodiments consistent with this application and disclosure, and together with the description serve to explain the principles of this application and disclosure.

[0026] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, for those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0027] Figure 1 Based on some embodiments of this application (C9H) 14 Fluorescence excitation spectra of N)2PbBr4 crystal at different emission wavelengths; Figure 2 Based on some embodiments of this application (C9H) 14 Fluorescence emission spectra of N)2PbBr4 crystal at different excitation wavelengths.

[0028] Figure 3 Based on some embodiments of this application (C9H) 14 XRD pattern of N)2PbBr4 crystal.

[0029] Figure 4 Based on some embodiments of this application (C9H) 14 CIE chromaticity diagram of N)2PbBr4 crystal. Detailed Implementation

[0030] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, not all embodiments. Based on the embodiments of this application, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of this application.

[0031] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment or implementation of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments. The term "implementation" as used herein has a similar understanding.

[0032] In this application, except where expressly stated, any matters or issues not mentioned are directly applicable to those known in the art without any modification. Furthermore, any implementation described in this application can be freely combined with one or more other implementations described in this application, and the resulting technical solutions or concepts shall be considered part of the original disclosure or original record of this application, and should not be regarded as new content not disclosed or anticipated in this application, unless those skilled in the art consider the combination to be clearly unreasonable.

[0033] Any method steps, processes, and operations described in this application should not be construed as necessarily requiring them to be performed in a particular order as discussed or shown, unless explicitly specified. It should also be understood that additional or alternative steps may be used unless otherwise stated.

[0034] In this application, the technical features described in an open-ended manner include both closed technical solutions consisting of the listed features and open technical solutions that include the listed features.

[0035] Any specific numerical values ​​disclosed herein (including the endpoints of numerical ranges) are not limited to their exact values, but should be understood to also include values ​​close to the exact value, such as all possible values ​​within ±5% of the exact value. Furthermore, with respect to the disclosed numerical ranges, one or more new numerical ranges can be obtained by arbitrarily combining the endpoint values ​​of the range, the endpoint values ​​with specific point values ​​within the range, and the specific point values ​​themselves; these new numerical ranges should also be considered as specifically disclosed herein.

[0036] Unless otherwise stated, the terms used herein have the same meaning as commonly understood by those skilled in the art, and if a term is defined herein and its definition differs from the common understanding in the art, the definition herein shall prevail.

[0037] In this article, "DMF" stands for N,N-dimethylformamide.

[0038] First aspect Some embodiments of this application provide a two-dimensional halide perovskite single crystal with the chemical formula (C9H2O). 14 N)2PbBr4, where C9H 14 N + It represents the N-butylpyridine cation.

[0039] The two-dimensional halide perovskite single crystal of this application, with C9H 14 N + (N-Butylpyridine cation) is an organic cation, and it reacts with [PbBr4] 2-Alternating inorganic layers form a two-dimensional layered structure. The N-butylpyridine cation possesses a hydrophobic long chain (butyl) and an aromatic ring (pyridine). This structure exhibits significant steric hindrance and rigidity, resulting in stronger support for the organic layers. Furthermore, hydrogen bonds form between the organic and inorganic layers, enhancing interlayer bonding. Therefore, this two-dimensional halide perovskite single crystal possesses excellent phase stability. In addition, steric hindrance and hydrogen bonding also induce phase changes in the inorganic [PbBr4]. 2- The octahedral structure distortion and the large steric hindrance make the inorganic layer thinner and the quantum confinement effect stronger. The quantum confinement effect, together with the structural distortion, enhances the exciton-phonon coupling and promotes the formation of self-trapped excitons (STEs). Moreover, the quantum confinement effect modulates the band gap, enabling efficient broadband yellow light emission from exciton recombination, especially under 350 nm wavelength excitation.

[0040] In some embodiments, the emission peak wavelength of the two-dimensional halide perovskite single crystal under 350 nm excitation is 540 nm to 560 nm. This two-dimensional halide perovskite single crystal can emit yellow light.

[0041] In some implementations, the CIE 1931 color coordinates of a two-dimensional halide perovskite single crystal under 350 nm wavelength excitation satisfy: x = 0.35–0.42, y = 0.42–0.48. CIE 1931 color coordinates refer to coordinates measured using the CIE 1931 standard colorimetric system.

[0042] In some implementations, the full width at half maximum (FWHM) of the emission peak is greater than 100 nm. This two-dimensional halide perovskite single crystal exhibits broadband emission.

[0043] In some embodiments, the full width at half maximum (FWHM) of the (001) diffraction peak in the X-ray diffraction (XRD) pattern of a two-dimensional halide perovskite single crystal is ≤ 0.2°, where the (001) diffraction peak is a diffraction peak with a diffraction angle 2θ in the range of 3° to 10°. Two-dimensional halide perovskite single crystals exhibit high crystallinity. The (001) diffraction peak is a characteristic peak of the two-dimensional structure; a FWHM of ≤ 0.2° indicates a narrow and sharp peak shape. The narrower and sharper the peak, the higher the crystallinity of the single crystal, and the larger and more complete the grains.

[0044] In some embodiments, in the X-ray diffraction pattern of a two-dimensional halide perovskite single crystal, the average background intensity of the region without diffraction peaks in the 2θ range of 20° to 24° is no greater than 4% of the intensity of the (001) diffraction peak. The 2θ range of 20° to 24° is the region without diffraction peaks of the two-dimensional halide perovskite single crystal. The signal in this region can only represent the background intensity. The smaller the average background intensity of this region without diffraction peaks, the closer the baseline is to zero, the weaker the amorphous scattering, the higher the crystallinity and purity of the single crystal.

[0045] In some embodiments, the two-dimensional halide perovskite single crystal has a length of 2 mm to 5 mm, a width of 1 mm to 3 mm, and a thickness of 0.05 mm to 0.5 mm.

[0046] In some embodiments, the two-dimensional halide perovskite exhibits a photoluminescence quantum efficiency ≥50% under 350 nm excitation. This two-dimensional halide perovskite possesses high luminescence efficiency and can be widely applied in the fabrication of various optoelectronic devices.

[0047] Second aspect This application provides a method for preparing a two-dimensional halide perovskite single crystal according to any embodiment of the first aspect described above, comprising the following steps: N-Butylpyridine bromide and PbBr2 were placed in an aprotic polar solvent and heated until completely dissolved to obtain a perovskite precursor solution, wherein the molar ratio of N-butylpyridine bromide to PbBr2 was (1.8~2.2):1; and The perovskite precursor solution was cooled and crystallized to obtain a two-dimensional halide perovskite single crystal (C9H). 14 N)2PbBr4.

[0048] Traditional methods for preparing two-dimensional halide perovskite single crystals often result in multiphase coexistence or crystal cracking. However, the method for preparing two-dimensional halide perovskite single crystals provided in this application employs cooling crystallization, and further controls the cooling rate of the cooling crystallization process to obtain higher quality two-dimensional halide perovskite single crystals. The single crystals prepared by this method exhibit high crystallinity, purity, and optical quality. The crystallization process is highly controllable and reproducible.

[0049] In some embodiments, the cooling rate for cooling crystallization is less than or equal to 60 °C / h, for example 60 °C / h, 50 °C / h, 40 °C / h, 30 °C / h, 20 °C / h, or 10 °C / h, optionally 30 °C / h to 60 °C / h, and further optionally 40 °C / h. Both excessively fast and excessively slow cooling rates will lead to a decrease in the yield of two-dimensional halide perovskite single crystals.

[0050] In some embodiments, the heating temperature is 80°C to 100°C, for example, 80°C, 85°C, 90°C, 95°C, or 100°C; the final temperature for cooling crystallization is 20°C to 25°C, for example, 20°C, 21°C, 22°C, 23°C, 24°C, or 25°C; and the cooling crystallization time is 1 h to 2 h, for example, 1 h, 1.5 h, or 2 h. In some specific embodiments, the heating temperature is 80°C, the final temperature for cooling crystallization is 20°C, and the cooling crystallization time is 1 h to 2 h. In some preferred embodiments, the heating temperature is 80°C, the final temperature for cooling crystallization is 20°C, and the cooling crystallization time is 1.5 h, resulting in a higher yield of two-dimensional halide perovskite single crystals.

[0051] It should be noted that heating to complete dissolution refers to the complete dissolution of N-butylpyridine bromide and PbBr2 in an aprotic polar solvent through heating. Complete dissolution is a state that can be clearly determined by those skilled in the art, i.e., the resulting perovskite precursor solution is clear, transparent, and free of visible solids. Furthermore, the heating temperature is also the temperature of the perovskite precursor solution.

[0052] Cooling crystallization, as is known in the art, refers to the precipitation of crystals by lowering the temperature of the solution. In this application, it specifically refers to the precipitation of two-dimensional halide perovskite single crystals by lowering the temperature of the perovskite precursor solution. The endpoint temperature of cooling crystallization also has a clear, well-known meaning in the art, referring to the final system temperature reached at the end of the active cooling phase during cooling crystallization, and typically maintained (stationary) at this temperature to allow the crystals to fully precipitate.

[0053] In some embodiments, to improve the dissolution rate of N-butylpyridine bromide and PbBr2, stirring can be performed simultaneously with heating and dissolution. Furthermore, in some embodiments, to ensure that N-butylpyridine bromide and PbBr2 dissolve as completely as possible, the heating and dissolution time is 30 min to 60 min.

[0054] In some embodiments, the above preparation method includes: dissolving N-butylpyridine bromide and PbBr2 in an aprotic polar solvent by heating to 80 °C~100 °C to obtain a perovskite precursor solution, wherein the molar ratio of N-butylpyridine bromide to PbBr2 is (1.8~2.2):1; and The perovskite precursor solution was cooled to 20 ℃~25 ℃ for 1h~2h to precipitate crystals and obtain the two-dimensional halide perovskite single crystal.

[0055] In some implementations, cooling crystallization is carried out under vacuum conditions, which can further improve the quality of crystallization.

[0056] In some embodiments, the aprotic polar solvent includes one or more of N,N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, γ-butyrolactone, or dimethylacetamide. Optionally, the aprotic polar solvent includes N,N-dimethylformamide.

[0057] In some embodiments, the aprotic polar solvent is N,N-dimethylformamide, which is more conducive to crystallization.

[0058] In some embodiments, the amount of aprotic polar solvent used is (2~10) L of aprotic polar solvent to dissolve 1 mol of PbBr2. The amount of aprotic polar solvent determines the concentration of Pb in the perovskite precursor solution. 2+ The concentration of Pb in the perovskite precursor solution. In some embodiments, the concentration of Pb in the perovskite precursor solution. 2+ The concentration is 0.1 mol / L to 0.5 mol / L.

[0059] For example, 1 mol of PbBr2 is dissolved using 2 L, 3 L, 4 L, 5 L, 6 L, 7 L, 8 L, 9 L, or 10 L of aprotic polar solvent. Optionally, dissolving 1 mol of PbBr2 using (4~10) L of aprotic polar solvent can improve the yield of two-dimensional halide perovskite single crystals. More preferably, dissolving 1 mol of PbBr2 using 4 L of aprotic polar solvent can further improve the yield of two-dimensional halide perovskite single crystals.

[0060] For example, Pb in perovskite precursor solution 2+ The concentrations are 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, or 0.5 mol / L. Optionally, the Pb in the perovskite precursor solution... 2+ A concentration of 0.1 mol / L to 0.25 mol / L can improve the yield of two-dimensional halide perovskite single crystals. Further, optionally, the concentration of Pb in the perovskite precursor solution... 2+ The concentration of 0.25 mol / L further improves the yield of two-dimensional halide perovskite single crystals.

[0061] In some embodiments, the step of cooling and crystallizing the perovskite precursor solution further includes washing and drying the crystals obtained from the cooling and crystallization.

[0062] In some embodiments, the detergent used for washing may include one or more of isopropanol, toluene, or chlorobenzene to remove residual aprotic polar solvents and unreacted raw materials (including N-butylpyridine bromide and PbBr2).

[0063] In some embodiments, the drying temperature is 60 °C to 200 °C. Understandably, the drying temperature can be 60 °C, 80 °C, 100 °C, 120 °C, 140 °C, 160 °C, 180 °C, or 200 °C. Optionally, the drying temperature is 60 °C to 150 °C, more preferably 60 °C to 100 °C, and even more preferably 60 °C. The higher the drying temperature, the lower the photoluminescence quantum efficiency of the two-dimensional halide perovskite single crystal under 350 nm excitation.

[0064] Third aspect Some embodiments of this application also provide an optoelectronic device, including a two-dimensional halide perovskite single crystal obtained by any embodiment of the first aspect or a two-dimensional halide perovskite single crystal obtained by any method of the second aspect.

[0065] This optoelectronic device is based on the above-mentioned two-dimensional halide perovskite single crystal or its preparation method. The specific characteristics of the above-mentioned two-dimensional halide perovskite single crystal can be referred to the above embodiments. Since this optoelectronic device adopts some or all of the technical solutions of the above embodiments, it has at least all the beneficial effects brought about by the technical solutions of the above embodiments, which will not be elaborated here.

[0066] Example To better understand this application, the following description, in conjunction with embodiments, further illustrates this application. However, the scope of protection claimed in this application is not limited to the scope of the embodiments.

[0067] In the following examples, unless otherwise specified, all experimental instruments, raw materials, and quantities involved are commercially available products or can be prepared by known methods. Experimental methods not specifying particular conditions in the examples were performed under conventional conditions, such as those described in literature, books, or methods recommended by the manufacturer.

[0068] Unless otherwise specified, the specific parameters used in each step of the material preparation process in each embodiment and comparative example are the same.

[0069] Example 1 In an argon-atmospheric glove box, 4 mmol of N-butylpyridine bromide and 2 mmol of PbBr2 powder were weighed in a 2:1 molar ratio and placed in a 20 mL glass bottle. 2 mL of DMF solution was added, and the mixture was heated to 80 °C to obtain a clear and transparent perovskite precursor solution. The perovskite precursor solution was placed in a vacuum drying oven, and the cooling rate was controlled at 40 °C / h. After cooling to room temperature, transparent bulk crystals were obtained, with a cooling time of 1.5 h. The crystals were washed three times with isopropanol and then dried at 60 °C for 20 min to obtain (C9H) 14 N)2PbBr4 crystal.

[0070] For product (C9H) 14 Solid-state fluorescence excitation at different emission wavelengths and fluorescence emission at different excitation wavelengths were performed on N)₂PbBr₄ crystals, and the fluorescence excitation spectra are shown below. Figure 1 As shown, the fluorescence emission spectrum is as follows: Figure 2 As shown. Product (C9H) 14 The XRD pattern (i.e., X-ray diffraction pattern) of N)2PbBr4 crystal is as follows: Figure 3 As shown. Product (C9H) 14 The CIE chromaticity diagram of N)2PbBr4 crystal (measured using the CIE 1931 standard chromaticity system) is as follows: Figure 4 As shown.

[0071] like Figure 1 As shown, (C9H 14 The N)2PbBr4 crystal exhibits consistent excitation peak shapes at different emission wavelengths, indicating that (C9H) 14 N)2PbBr4 crystal is a single crystal. Figure 1 The emission wavelength corresponding to the highest intensity peak is 350 nm, and the wavelength of 350 nm is (C9H) 14 The optimal excitation wavelength for N)₂PbBr₄ crystals. (Combined with...) Figure 2 Let's look at the excitation at 350 nm wavelength, (C9H) 14 The emission peak wavelength of the N)2PbBr4 crystal is approximately 550 nm. Furthermore, the full width at half maximum (FWHM) of this emission peak is greater than 100 nm, indicating that (C9H) 14 N)2PbBr4 crystals emit broadband yellow light.

[0072] like Figure 3 As shown, (C9H 14 The XRD pattern of the N)2PbBr4 crystal shows a strong diffraction peak at 2θ = 5° and another strong diffraction peak at 2θ = 10.5°, indicating that (C9H) 14 The N)2PbBr4 crystal has a two-dimensional layered structure. The diffraction peak at 2θ = 5° is the (001) diffraction peak, and the diffraction peak at 2θ = 10.5° is the (002) diffraction peak. The full width at half maximum (FWHM) of the (001) diffraction peak is less than 0.2°, and its peak shape is relatively narrow and sharp, indicating that (C9H) 14 N)2PbBr4 crystals have high crystallinity. Figure 3 In the range of 20° to 24°, 2θ is (C9H) 14 The N)2PbBr4 crystal has a region without diffraction peaks. The average background intensity of this region is 3% of the intensity of the (001) diffraction peak, indicating that the baseline is almost zero. (C9H) 14 Amorphous scattering is very weak in N)2PbBr4 crystals, (C9H)14 N)2PbBr4 has high crystallinity and high purity.

[0073] like Figure 4 As shown, the product (C9H) 14 The x-coordinate of the N)₂PbBr₄ crystal in the CIE chromaticity diagram is 0.38, and the y-coordinate is 0.45. Further explanation: (C₁₈H₂O) 14 N)2PbBr4 crystal is a yellow light-emitting material.

[0074] Example 2 The method is basically the same as in Example 1, except that the amount of DMF solution used is replaced with 1 mL.

[0075] Example 3 The method is basically the same as in Example 1, except that the amount of DMF solution used is replaced with 5 mL.

[0076] Example 4 It is basically the same as Example 1, except that the cooling time is replaced with 1 hour.

[0077] Example 5 It is basically the same as Example 1, except that the cooling time is replaced with 2 hours.

[0078] Example 6 It is basically the same as Example 1, except that the drying temperature is replaced with 100 °C.

[0079] Example 7 It is basically the same as Example 1, except that the drying temperature is replaced with 150 °C.

[0080] Example 8 It is basically the same as Example 1, except that the drying temperature is replaced with 200 °C.

[0081] The quantum yield of the crystal fluorescence and the single crystal yield obtained using this example are 61% and 47%, respectively.

[0082] Comparative Example 1 The method is essentially the same as in Example 1, except that N-butylpyridine bromide is replaced with 1-phenylethylamine hydrobromide, with the chemical formula C6H5CH(CH3)NH3Br. 1-Phenyleneethylamine hydrobromide can be obtained by mixing 1-phenylethylamine with an equimolar amount of hydrobromic acid (HBr, 48%) in an ice-water bath.

[0083] The products (C9H) prepared in Examples 1-8 above 14 The yields and photoluminescence quantum efficiencies of the N)2PbBr4 crystal and the product obtained in Comparative Example 1 are listed in Table 1 below.

[0084] The yield was calculated using the formula: Yield = (Actual mass of collected intact single crystals / Theoretical product mass) × 100%. Theoretical product mass = Molar amount of PbBr2 × (C9H2O) / (Molar amount of PbBr2) × ... 14 The molecular weight of N)2PbBr4, (C9H 14 The molecular weight of N)2PbBr4 is calculated to be 799.24.

[0085] The photoluminescence quantum efficiency (PLQY) was measured using an absolute method (with an integrating sphere) based on a steady-state fluorescence spectrometer equipped with an integrating sphere.

[0086] The (C9H) of each embodiment was measured using vernier calipers. 14 The size of N)2PbBr4 single crystals, each (C9H 14 The length of the N)2PbBr4 crystals ranges from 2 mm to 5 mm, the width ranges from 1 mm to 3 mm, and the thickness is statistically determined by side imaging with an optical microscope, with each crystal ranging from 0.05 mm to 0.5 mm.

[0087] Table 1

[0088] As shown in Table 1, the CIE color coordinates of the crystals in Examples 1-8 indicate that the material is a yellow light emitting material, while the CIE color coordinates of the crystal in Comparative Example 1 indicate that the material is a blue light emitting material.

[0089] Comparing Examples 1-3, it can be seen that the amount of DMF used affects the crystal yield. Comparing Examples 1, 4, and 5, it can be seen that the cooling rate of cooling crystallization affects the crystal yield, preferably less than or equal to 60 ℃ / h, more preferably 30 ℃ / h to 60 ℃ / h, and even more preferably 40 ℃ / h.

[0090] Comparative Examples 1 and 6-8 show that the photoluminescence quantum efficiency of the crystals in Examples 1, 6 and 7 is greater than 45%, while the photoluminescence quantum efficiency of the crystal in Example 8 is only 25.8%, indicating that the drying temperature has a certain influence on the photoluminescence quantum efficiency of the crystal.

[0091] The above embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application.

[0092] Although preferred embodiments have been described in this specification, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this specification.

[0093] Obviously, those skilled in the art can make various modifications and variations to this specification without departing from its spirit and scope. Therefore, if such modifications and variations fall within the scope of the claims and their equivalents, this specification is also intended to include such modifications and variations.

Claims

1. A two-dimensional halide perovskite single crystal with the chemical formula (C9H2O) 14 N)2PbBr4, where C9H 14 N + It represents the N-butylpyridine cation.

2. The two-dimensional halide perovskite single crystal according to claim 1, characterized in that, The emission peak wavelength of the two-dimensional halide perovskite single crystal under 350 nm wavelength excitation is 540 nm to 560 nm; and / or, the CIE 1931 color coordinates of the two-dimensional halide perovskite single crystal under 350 nm wavelength excitation satisfy: x = 0.35 to 0.42, y = 0.42 to 0.

48.

3. The two-dimensional halide perovskite single crystal according to claim 2, characterized in that, The full width at half maximum (FWHM) of the emission peak is greater than 100 nm.

4. The two-dimensional halide perovskite single crystal according to claim 1, characterized in that, The full width at half maximum (FWHM) of the (001) diffraction peak in the X-ray diffraction pattern of the two-dimensional halide perovskite single crystal is ≤ 0.2°, and the (001) diffraction peak is a diffraction peak with a diffraction angle 2θ in the range of 3° to 10°.

5. The two-dimensional halide perovskite single crystal according to claim 1, characterized in that, In the X-ray diffraction pattern of the two-dimensional halide perovskite single crystal, the average background intensity of the region without diffraction peaks in the range of 2θ from 20° to 24° is no greater than 4% of the intensity of the (001) diffraction peak.

6. The two-dimensional halide perovskite single crystal according to claim 1, characterized in that, The single crystal has a length of 2 mm to 5 mm, a width of 1 mm to 3 mm, and a thickness of 0.05 mm to 0.5 mm.

7. The two-dimensional halide perovskite single crystal according to any one of claims 1 to 6, characterized in that, The photoluminescence quantum efficiency of the two-dimensional halide perovskite single crystal under 350 nm excitation is ≥ 50%.

8. A method for preparing a two-dimensional halide perovskite single crystal as described in any one of claims 1 to 7, characterized in that, Includes the following steps: N-Butylpyridine bromide and PbBr2 were placed in an aprotic polar solvent and heated until completely dissolved to obtain a perovskite precursor solution, wherein the molar ratio of N-butylpyridine bromide to PbBr2 was (1.8~2.2):1; and The perovskite precursor solution was cooled and crystallized to obtain the two-dimensional halide perovskite single crystal.

9. The preparation method according to claim 8, characterized in that, The cooling rate of the cooling crystallization is less than or equal to 60 °C / h; and / or, The heating temperature is 80 ℃~100 ℃, the final temperature of the cooling crystallization is 20 ℃~25 ℃, and the cooling crystallization time is 1 h~2 h.

10. The preparation method according to claim 9, characterized in that, The cooling rate for the cooling crystallization is 30 ℃ / h to 60 ℃ / h.

11. The preparation method according to any one of claims 8 to 10, characterized in that, The aprotic polar solvent includes one or more of N,N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, γ-butyrolactone, or dimethylacetamide.

12. The preparation method according to claim 11, characterized in that, The aprotic polar solvent is N,N-dimethylformamide.

13. The preparation method according to any one of claims 8 to 10, characterized in that, The amount of the aprotic polar solvent used is (2~10) L of aprotic polar solvent to dissolve 1 mol of PbBr2, or... Pb in perovskite precursor solution 2+ The concentration is 0.1 mol / L to 0.5 mol / L.

14. The preparation method according to any one of claims 8 to 10, characterized in that, The cooling crystallization is carried out under vacuum conditions.

15. The preparation method according to any one of claims 8 to 10, characterized in that, The step of cooling and crystallizing the perovskite precursor solution further includes washing and drying the crystals obtained by cooling and crystallizing, wherein the drying temperature is 60 ℃ to 200 ℃.

16. An optoelectronic device, characterized in that, Includes the two-dimensional halide perovskite single crystal as described in any one of claims 1 to 7 or the two-dimensional halide perovskite single crystal obtained by the preparation method described in any one of claims 8 to 15.

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