Preparation methods for two-dimensional tin-based perovskite microcrystal, thin film, and light-emitting diode, and light-emitting diode prepared thereby

Abstract

The present invention relates to preparation methods for a two-dimensional tin-based perovskite microcrystal, thin film, and light-emitting diode, and a light-emitting diode prepared thereby. The method comprises: dissolving phenethylammonium iodide and tin(II) iodide in a mixed organic solvent of DMSO and DMF to obtain an initial mixed solution; stirring the initial mixed solution at room temperature to obtain a homogeneous mixed solution; filtering the homogeneous mixed solution to obtain a precursor solution; and adding a multi-functional regulator to the precursor solution to precipitate a PEA2SnI4 microcrystal, wherein the multi-functional regulator has a Kd value ranging from 101 to 103 M-1 and a pKa ranging from 4 to 5.5; the Kd value is an equilibrium constant for complex dissociation, and the pKa is a negative logarithm of an acid dissociation constant (Ka). By means of the above arrangement, the present invention can significantly improve the quality of the microcrystalline thin film, and the process features simple operation, high efficiency, and good reproducibility.

Description

Methods for fabricating two-dimensional tin-based perovskite microcrystals, thin films, and light-emitting diodes, and the light-emitting diodes fabricated therefrom. Technical Field

[0001] This invention relates to the field of optoelectronic materials and devices, and in particular to a method for preparing two-dimensional tin-based perovskite microcrystals, thin films and light-emitting diodes, and the light-emitting diodes prepared therefrom. Background Technology

[0002] Perovskite materials, due to their excellent optoelectronic properties (such as high absorption coefficient, long carrier diffusion length, and tunable bandgap), have shown great potential in the field of optoelectronic conversion devices. Tin (Sn)-based perovskites, as a non-toxic alternative to lead (Pb)-based perovskites, have become a current research hotspot due to their environmental friendliness and similar optoelectronic properties. However, the thin film quality of two-dimensional tin-based perovskites (such as PEA2SnI4) is limited by their inherently high-density defect states, leading to a significant increase in nonradiative recombination, making it difficult for device performance to meet the color gamut and brightness requirements of the Rec.2020 standard in the display field.

[0003] Currently, a common method to improve the quality of two-dimensional tin-based perovskite thin films is the dropwise antisolvent method, which accelerates the crystallization of the precursor solution by adding antisolvents such as toluene and chlorobenzene to improve the film morphology. However, this method has significant limitations: First, the rapid extraction effect of the antisolvent leads to an uncontrollable crystallization process, resulting in a high density of defects such as pinholes and grain boundaries in the film, severe nonradiative recombination, generally low external quantum efficiency, and uneven tin-based perovskite films, ultimately leading to poor performance of the obtained two-dimensional tin-based perovskite LEDs. Second, the process window is narrow, and it is extremely sensitive to the antisolvent drop rate, timing, and ambient temperature and humidity, resulting in poor device performance repeatability and high process complexity. Summary of the Invention

[0004] To address the aforementioned shortcomings, this invention proposes a method for preparing two-dimensional tin-based perovskite microcrystals, thin films, and light-emitting diodes, as well as the light-emitting diodes prepared therefrom. This method enables a simple and efficient thin film preparation process with good repeatability.

[0005] The technical solution adopted in this invention is a method for preparing two-dimensional tin-based perovskite microcrystals, comprising the following steps:

[0006] S110. Phenethyl ammonium iodide and tin diiodide are dissolved in a mixed organic solvent of DMSO and DMF to obtain an initial mixed solution;

[0007] S120. Stir the initial mixed solution at room temperature to obtain a homogeneous mixed solution;

[0008] S130. Filter the homogeneous mixed solution to obtain the precursor solution;

[0009] S140. A multifunctional regulator is added to the precursor solution to precipitate PEA2SnI4 microcrystals; the Kd value of the multifunctional regulator is between 10 and 10. 1 ~10 3 M -1 Furthermore, pKa is between 4 and 5.5, Kd is the equilibrium constant for the dissociation of the complex, and pKa is the negative logarithm of the acid dissociation constant (Ka).

[0010] Furthermore, the multifunctional regulator has the following general formula: R-COOH, where R is an organic group and -COOH is a carboxyl group.

[0011] Furthermore, the multifunctional regulator is acetic acid.

[0012] Furthermore, the amount of acetic acid added is between 0.5% and 2 vol%.

[0013] Furthermore, after S140, the process further includes: S150, adding dichloromethane to the PEA2SnI4 microcrystals, and then shaking and centrifuging to obtain pure PEA2SnI4 microcrystals.

[0014] Furthermore, S110 further includes adding tin powder to the mixed organic solvent.

[0015] This invention also discloses a method for preparing two-dimensional tin-based perovskite microcrystalline thin films, comprising the following steps:

[0016] S100. PEA2SnI4 microcrystals are prepared using the above-described method for preparing microcrystals.

[0017] S200, clean the ITO substrate;

[0018] S300: Using the ITO substrate cleaned in S200, a hole transport layer is prepared;

[0019] S400: Dissolve the PEA2SnI4 microcrystals prepared in S100 in an organic solvent and stir until homogeneous to obtain a precursor solution;

[0020] S500: The precursor liquid obtained in S400 is spin-coated onto the hole transport layer prepared in step S300 and annealed to obtain a PEA2SnI4 microcrystalline film.

[0021] Furthermore, the fabrication of the hole transport layer in S300 specifically includes:

[0022] S310, ozone-treated ITO substrate;

[0023] S320: Spin-coat NiOx onto the surface of the ITO substrate treated in S310 to form a NiOx layer;

[0024] S330: Spin-coat 2PACZ onto the surface of the NiOx layer formed in S320 to form a 2PACZ layer;

[0025] S340: Spin-coat PTAA onto the surface of the 2PACZ layer formed in S330 to form a PTAA layer.

[0026] This invention also discloses a method for fabricating a two-dimensional tin-based perovskite light-emitting diode, comprising the following steps:

[0027] PEA2SnI4 microcrystalline thin films were prepared using the above-described preparation method;

[0028] An electron transport layer, an electron injection layer, and electrodes were deposited on the PEA2SnI4 microcrystalline thin film.

[0029] This invention also discloses a two-dimensional tin-based perovskite light-emitting diode, which is prepared by the above-described method.

[0030] Compared with the prior art, the present invention has the following beneficial effects:

[0031] 1. The method for preparing two-dimensional tin-based perovskite microcrystals proposed in this invention can significantly improve the quality of microcrystalline films. The process is simple, efficient, and reproducible, avoiding problems such as unevenness in the preparation of tin-based perovskite films by traditional methods.

[0032] 2. The two-dimensional tin-based perovskite microcrystalline thin film prepared by the method of the present invention can be used to prepare perovskite LED devices, which can significantly improve the performance of LEDs and meet the needs of semiconductor optoelectronic devices for the display field.

[0033] 3. Compared with PEA2SnI4 films prepared by traditional methods, the PEA2SnI4 microcrystalline thin films prepared by the method of this invention have significantly reduced pinhole density and suppressed non-radiative recombination. The external quantum efficiency of the perovskite LED prepared based on this invention reaches 0.33%, which significantly improves the performance of two-dimensional tin-based perovskite LEDs. Attached Figure Description

[0034] The present invention will now be described in detail with reference to the embodiments and accompanying drawings, wherein:

[0035] Figure 1 is a flowchart of the preparation method of two-dimensional tin-based perovskite microcrystals;

[0036] Figure 2 is a SEM image of PEA2SnI4 microcrystalline thin film prepared by conventional method (RF);

[0037] Figure 3 is a SEM image of the PEA2SnI4 microcrystalline thin film prepared by the method (ASMF) of this application;

[0038] Figure 4 compares the current density and brightness of a PEA2SnI4 microcrystalline thin-film LED prepared by the method of the present invention (ASMF) and a PEA2SnI4 thin-film LED prepared by the conventional method (RF).

[0039] Figure 5 compares the external quantum efficiency of PEA2SnI4 microcrystalline thin-film LEDs prepared by the method of the present invention (ASMF) and PEA2SnI4 thin-film LEDs prepared by the conventional method (RF). Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of the present invention clearer, the embodiments of the present invention will be further described in detail below with reference to the accompanying drawings. Examples of the embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar components or components having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present invention, and should not be construed as limiting the present invention.

[0041] This application relates to a method for preparing two-dimensional tin-based perovskite microcrystals and thin films, which can be used as high-efficiency optoelectronic thin films in the field of optoelectronic semiconductor displays, such as perovskite light-emitting diodes (LEDs).

[0042] In one embodiment, a method for preparing two-dimensional tin-based perovskite microcrystals, as shown in Figure 1, includes the following steps:

[0043] S110. Phenethyl ammonium iodide (PEAI) and tin diiodide (SnI2) are dissolved in a mixed organic solvent of DMSO and DMF to obtain an initial mixed solution.

[0044] In one exemplary embodiment, the molar ratio of PEAI to SnI2 is 2:1 to ensure the formation of the layered structure PEA2SnI4. Deviating from the ratio can easily generate impurity phases, such as PEA3SnI5.

[0045] DMSO, or dimethyl sulfoxide, stabilizes precursor micelles through strong coordination-regulated crystallization; its Kd = 10. 5 M -1DMF, or N,N-dimethylformamide, regulates viscosity through moderate coordination, preventing rapid crystallization and resulting defects. A mixture of DMSO and DMF creates a gradient coordination environment, controlling the growth rate of the Sn-I framework. The volume ratio of DMSO to DMF is between 3:1 and 5:1, preferably 4:1. A volume ratio less than 3:1 leads to excessively rapid crystallization and defects; a volume ratio greater than 5:1 hinders crystal growth, resulting in crystallites smaller than 100 nm. Experimental data show that a volume ratio of 4:1 provides the optimal control effect.

[0046] The initial concentration of the mixed solution is between 0.5 and 1.2 M, preferably 0.8 M. When the concentration is less than 0.5 M, nucleation is insufficient; when the concentration is more than 1.2 M, heterogeneous precipitation is likely to occur; when the concentration is 0.8 M, the prepared microcrystals have the highest crystallinity and the lowest defect density, achieving the optimal balance of the nucleation-growth process.

[0047] In one exemplary embodiment, step S110 further includes adding metallic tin (Sn) powder to the mixed organic solvent. The purpose of adding the Sn powder is to prevent Sn from... 2+ Oxidized to Sn 4+ Because Sn 2+ It has a certain reducing property and is easily oxidized by oxygen in the air. Excessive Sn powder can neutralize any Sn that may be generated. 4+ Restore to Sn 2+ This ensures that Sn in the precursor solution 2+ The stability of Sn powder is maintained at an amount between 40 and 60 mg, preferably 40 mg. 2+ Stable (oxidation rate <5%). When the amount of Sn powder added is <40mg, the oxidation inhibition is insufficient; when the amount of Sn powder added is >60mg, it is easy to cause metallic tin to precipitate.

[0048] S120. Stir the initial mixed solution at room temperature to obtain a homogeneous mixed solution.

[0049] Specifically, the obtained initial mixed solution is stirred overnight at room temperature for later use. The purpose is to ensure that the raw materials are fully dissolved and mixed evenly, promoting intermolecular interactions and preparing for the subsequent crystallization process. The stirring time can be adjusted according to the actual situation.

[0050] S130. Filter the homogeneous mixed solution to obtain the precursor solution.

[0051] In one exemplary embodiment, the homogeneous mixed solution is filtered through a 0.22 μm polytetrafluoroethylene filter before use to remove any impurities, particles, or undissolved substances that may be present in the solution, ensuring the purity of the solution and thus facilitating the acquisition of high-quality microcrystalline products. In other embodiments, depending on the requirements for impurity removal, filters of different pore sizes or other materials may be used for filtration.

[0052] S140. A multifunctional regulator is added to the precursor solution to precipitate PEA2SnI4 microcrystals; the Kd value of the multifunctional regulator is between 10 and 10. 1 ~10 3 M -1 Furthermore, pKa is between 4 and 5.5, Kd is the equilibrium constant for complex dissociation, and pKa is the negative logarithm of the acid dissociation constant (Ka). PEA2SnI4, or phenylethylammonium tin iodide, is a two-dimensional tin-based perovskite material. "PEA" represents phenylethylammonium, an organic cation that, together with inorganic tin (Sn) and iodine (I) ions, constitutes the perovskite structure.

[0053] Specifically, the Kd value of the multifunctional regulator is between 10. 1 ~10 3 M -1 Stronger than water but weaker than DMSO, this range allows ligands to interact with Sn. 2+ Dynamic binding and dissociation are employed to dynamically regulate the nucleation and growth rate of microcrystals through competitive coordination. If the Kd value is less than this range, the coordination is too weak, failing to effectively control crystallization (resulting in numerous defects); if the Kd value is greater than this range, the coordination is too strong, leading to excessively rapid crystallization. The pKa of this multifunctional regulator is between 4 and 5.5, which avoids the I-induced damage caused by strong acids (pKa < 4). - Vacancy (V_I) defects, while preventing weak acids (pKa>5.5) from failing to effectively protonate PEA. + This ensures the assembly of the layered structure.

[0054] Unlike rapid extraction with antisolvents, which leads to the instantaneous aggregation and crystallization of metal ions, multifunctional regulators effectively control the growth rate of microcrystals, avoiding the uncontrollability caused by rapid crystallization and reducing defects such as pinholes and grain boundaries. Appropriate acidity promotes coordination reactions between ions, resulting in a more regular microcrystal structure, reducing non-radiative recombination centers, improving the quality of the two-dimensional tin-based perovskite film, and thus enhancing the external quantum efficiency of the LED. Ultimately, this leads to a two-dimensional tin-based perovskite LED with superior performance.

[0055] This method features relatively simple operation steps. The addition of a multifunctional regulator spontaneously induces crystallization, eliminating the need for precise control of the dropping rate and complex antisolvent addition and environmental control equipment. The simplified process not only reduces operational difficulty but also improves production efficiency and product consistency, while exhibiting excellent device performance repeatability.

[0056] In one specific embodiment, the multifunctional regulator has the following general formula: R-COOH, where R is an organic group and -COOH is a carboxyl group. That is, the multifunctional regulator is a carboxylic acid ligand, and the oxygen atom of the carboxylic acid group interacts with the metal ion (such as Sn) in the tin-based perovskite precursor. 2+ Coordination slows down the reactivity of metal ions, controls the growth rate of microcrystals, promotes uniform nucleation, reduces defects such as pinholes and grain boundaries caused by excessively rapid crystallization, and improves the quality of microcrystals. -COOH dissociates to release H+. + Adjust the acidity of the precursor solution and optimize ions (such as PEA). + Sn 2+ I - The presence and reactivity of the organic group R promote ordered coordination between ions, forming well-structured PEA2SnI4 microcrystals, reducing non-radiative recombination, and improving the performance of subsequent LED devices. The structure of the organic group R (such as carbon chain and branched chain) affects the solubility of the regulator, ensuring its uniform dispersion in the precursor solution, fully interacting with each component, ensuring the uniformity of the microcrystal growth environment, reducing film defects, and improving the repeatability of device performance.

[0057] In a more specific embodiment, the multifunctional regulator is acetic acid. Specifically, acetic acid is then added to precipitate perovskite microcrystals, the supernatant is discarded, dichloromethane is added, and the mixture is shaken and centrifuged. This process is repeated twice to obtain PEA2SnI4 microcrystals. Acetic acid (Kd = 10) 2 M -1 The carboxyl group (-COOH) of DMSO competes with Sn. 2+ Coordination disrupts precursor micellar stability, slowing the crystallization rate from seconds to minutes, and promoting oriented grain alignment. Acetic acid molecules adsorb onto the grain surface, inhibiting non-radiative recombination. Acetic acid lowers the solution pH from an initial 5.2 to 3.8, promoting PEA... + Protonization (PEAH) + This reduces the solubility of acetic acid in solution, driving the assembly of layered structures. Acetic acid spontaneously induces crystallization upon addition, eliminating the need for precise control of the dropping rate.

[0058] In one exemplary embodiment, the amount of acetic acid added is between 0.5% and 2 vol%. If the amount added is less than 0.5%, precipitation may be incomplete; if the amount added is greater than 2%, it may easily cause PEA (precipitation precipitate). + Excessive protonation leads to the destruction of the layered structure.

[0059] In one exemplary embodiment, the process further includes the following step after S140:

[0060] S150. Dichloromethane is added to the PEA2SnI4 microcrystals, and the mixture is shaken and centrifuged to obtain pure PEA2SnI4 microcrystals. Specifically, dichloromethane (polarity parameter δ = 9.1) selectively dissolves residual DMSO (δ = 12.8) and acetic acid (δ = 10.5), while the microcrystals are insoluble (δ < 8), thus completing the purification of the PEA2SnI4 microcrystals.

[0061] In other embodiments, chloroform or diethyl ether can be used instead of dichloromethane, provided that the solvent polarity meets the requirement of δ = 8-10 and does not react with the microcrystals (to avoid halogen exchange), otherwise the residual coordinating agent cannot be selectively removed.

[0062] This application also discloses a method for preparing a two-dimensional tin-based perovskite microcrystalline thin film, which adopts the aforementioned method for preparing two-dimensional tin-based perovskite microcrystals.

[0063] In one embodiment, a method for preparing a two-dimensional tin-based perovskite microcrystalline thin film includes the following steps:

[0064] S100. PEA2SnI4 microcrystals are prepared using the preparation method of two-dimensional tin-based perovskite microcrystals in the above embodiments. High-purity PEA2SnI4 microcrystals with low defect density are obtained, providing high-quality raw materials for subsequent thin film preparation.

[0065] S200. Clean the ITO substrate. Specifically, place the ITO in a cleaning agent to initially remove oil and dust from the ITO surface. Then, sequentially use deionized water (to dissolve impurities), acetone (to dissolve organic matter), and isopropanol (to dehydrate) for ultrasonic cleaning for 20 minutes each, using ultrasonic energy to peel off surface deposits. The cleaned conductive glass is then placed in a dedicated oven to dry for at least 1 hour to ensure the surface is completely dry. The purpose is to improve the cleanliness and surface energy of the ITO substrate, ensuring a tight bond between the subsequent functional layers and the substrate.

[0066] S300: Using the ITO substrate cleaned in S200, a hole transport layer is prepared.

[0067] In an exemplary embodiment, the fabrication of the hole transport layer in step S300 specifically includes:

[0068] S310, Ozone treatment of ITO substrate. A 15-minute ozone treatment utilizes the strong oxidizing properties of ozone to remove residual organic matter and form hydroxyl groups on the ITO surface, enhancing its hydrophilicity. ITO stands for Indium Tin Oxide.

[0069] S320: NiOx is spin-coated onto the surface of the ITO substrate treated in S310 to form a NiOx layer. A 20 mg / ml NiOx solution is filtered through a 0.22 μm filter, spin-coated at 4000 rpm for 40 seconds, annealed at 120°C for 10 min, and cooled to form the NiOx layer. NiOx, as a hole transport material, exhibits high mobility (10... -3 cm 2 The NiOx (nickel oxide) has a suitable energy level (valence band top approximately -5.2 eV) and forms a good match with ITO (-4.7 eV), promoting hole injection.

[0070] S330: Spin-coat 2PACZ onto the surface of the NiOx layer formed in S320 to form a 2PACZ layer. A 0.3 mg / ml 2PACZ solution is spin-coated at 3000 rpm for 30 seconds, followed by annealing in a nitrogen glove box (H2O < 0.01 ppm, O2 < 0.01 ppm) for 10 minutes to form a 2PACZ layer of approximately 10 nm. 2PACZ serves as an interface modification layer; its amino groups (-NH2) can bond with the hydroxyl groups on the NiOx surface, reducing interface defects and adjusting the surface work function to -5.4 eV, further optimizing hole transport. 2PACZ is an organic hole transport material, specifically 2-[3-(9H-carbazole-9-yl)propyl]phosphonic acid.

[0071] S340: Spin-coating PTAA onto the surface of the 2PACZ layer formed in S330 to form a PTAA layer. A 5 mg / ml PTAA solution is spin-coated at an angular velocity of 3000 rpm for 40 seconds, annealed for 30 minutes, and then cooled to form a PTAA layer of approximately 30 nm. PTAA is a host material for hole transport and has high electrical conductivity (10⁻⁶ ppm). -5 With its excellent film-forming properties (S / cm), it forms a good energy level match with the perovskite layer (valence band top approximately -5.5 eV), promoting efficient hole extraction. PTAA, or poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine], is an organic hole transport polymer.

[0072] S400: Dissolve the PEA2SnI4 microcrystals prepared in S100 in an organic solvent and stir until homogeneous to obtain a precursor solution. Specifically, take 30 mg of the PEA2SnI4 microcrystals prepared in S100, dissolve them in 1 ml of DMF, and stir for 1 hour. DMF, as a high-boiling-point solvent (153℃), can delay solvent evaporation, ensure uniform dispersion of microcrystals during spin coating, and avoid agglomeration.

[0073] S500: The precursor solution obtained in S400 is spin-coated onto the hole transport layer prepared in step S300 and annealed to obtain a PEA2SnI4 microcrystalline film. Specifically, the precursor solution is spin-coated onto the hole transport layer prepared in step S300 at an angular velocity of 3000 rpm for 40 s, and then annealed at 80°C for 5 min to obtain the PEA2SnI4 film.

[0074] This method, through the synergistic effect of regulator-assisted crystallization and multilayer hole transport layer design, achieves a breakthrough improvement in the quality of tin-based perovskite thin films while ensuring process simplicity, providing a feasible path for the practical application of high-performance tin-based perovskite LEDs.

[0075] Figures 2-3 show a comparison of SEM images of PEA2SnI4 films prepared by the conventional method (RF) and PEA2SnI4 microcrystalline films prepared by the method of this invention (ASMF). Figure 2 shows obvious irregular defects on the film surface, including scattered pores and uneven areas, reflecting uncontrolled crystallization in the conventional preparation process, resulting in an irregular film structure and high defect density. Figure 3 shows significantly improved film surface uniformity and density, with a substantial reduction in the number of defects (such as pores and protrusions), demonstrating that the method of this invention optimizes the film microstructure through precise control of the crystallization process. The SEM images show that the quality of the PEA2SnI4 microcrystalline film prepared by this invention is significantly better than that prepared by the conventional method. Better film quality means a lower defect density in the emitting layer, reducing non-radiative recombination and thus improving device performance.

[0076] In one embodiment, this application also discloses a method for fabricating a two-dimensional tin-based perovskite light-emitting diode, comprising the following steps: preparing a PEA2SnI4 microcrystalline thin film using the method for preparing a two-dimensional tin-based perovskite microcrystalline thin film as described in the above embodiment; depositing an electron transport layer, an electron injection layer, and electrodes on the PEA2SnI4 microcrystalline thin film. Specifically, the PEA2SnI4 microcrystalline thin film is deposited under a vacuum of 4×10⁻⁶. -4 Under Pa conditions, TPBi 50 nm, LiF (lithium fluoride) 1 nm, and Al (aluminum) 100 nm were deposited to obtain complete tin-based perovskite LED optoelectronic devices. TPBi stands for 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene.

[0077] First, TPBi is deposited as an electron transport layer, which effectively transports electrons and promotes the recombination of electrons and holes in the perovskite layer. Next, LiF is deposited as a buffer layer to improve electron injection efficiency and device stability. Finally, Al is deposited as an electrode, providing good conductivity for current collection and transmission. This constructs a complete tin-based perovskite LED optoelectronic device, enabling electrons to be transported from the electrodes to the perovskite layer and recombine with holes to produce light emission. Simultaneously, the electrodes are used to connect to external circuits, realizing the device's photoelectric conversion and light emission functions.

[0078] In one embodiment, this application also discloses a two-dimensional tin-based perovskite light-emitting diode, which is prepared by the above-described method for preparing a two-dimensional tin-based perovskite light-emitting diode.

[0079] In Figure 4, the horizontal axis represents voltage (V), and the vertical axis on the left represents current density (mA / cm). 2 The right side shows the brightness (cd / m²). 2 As voltage increases, both current density and brightness of the two devices increase, but ASMF perovskite LEDs perform better: at the same voltage, their current density and brightness increase faster, and their maximum brightness reaches 211 cd / m². 2 It is significantly higher than the 136 cd / m² of RF perovskite LEDs. 2 .

[0080] In Figure 5, the horizontal axis represents the current density (mA / cm). 2 The vertical axis represents the external quantum efficiency (EQE, %). The maximum external quantum efficiency of ASMF perovskite LEDs is 0.33%, while that of RF perovskite LEDs is only 0.11%, showing a clear advantage for the former.

[0081] Referring to Figures 4-5, the tin perovskite LED prepared by this invention has an external quantum efficiency of 0.33% and a device brightness of 211 cd / m², which is higher than that of tin perovskite LEDs prepared by conventional methods (0.11%), with a device brightness of 136 cd / m². The turn-on voltage of the ASMF perovskite LED device (2.6V) is much lower than that of the RF perovskite LED device (4.4V), indicating that the two-dimensional tin-based perovskite thin film prepared by the acid-assisted synthesis of tin-based perovskite microcrystals has good carrier transport capability, realizing the preparation of high-performance two-dimensional tin-based perovskite LEDs.

[0082] In the description of this specification, the use of terms such as "Embodiment 1," "this embodiment," or "in one embodiment" indicates that the specific feature, structure, material, or characteristic described in connection with that embodiment or example is included in at least one embodiment or example of the invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example; moreover, the specific features, structures, materials, or characteristics described may be combined in any appropriate manner in one or more embodiments or examples.

[0083] In the description of this specification, the terms "connection," "installation," "fixing," "setting," and "having" are interpreted broadly. For example, "connection" can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium; it can be a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this application according to the specific circumstances.

[0084] In the description of this specification, relational terms such as “first” and “second” are used merely to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitation, an element defined by the phrase “comprising one…” does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0085] The above description of the embodiments is intended to enable those skilled in the art to understand and apply the technology of this invention. Those skilled in the art can readily make various modifications to these examples and apply the general principles described herein to other embodiments without creative effort. Therefore, this invention is not limited to the above embodiments. Modifications in the following situations should be within the scope of protection of this invention: ① New technical solutions implemented based on the technical solution of this invention and combined with existing common knowledge, where the technical effects of the new technical solution do not exceed the technical effects of this invention; ② Equivalent substitutions of some features of the technical solution of this invention using known technology, resulting in the same technical effects as those of this invention; ③ Extendable technical solutions based on the technical solution of this invention, where the substantive content of the extended technical solution does not exceed the technical solution of this invention; ④ Equivalent transformations made using the content of this specification and drawings, directly or indirectly applied to other related technical fields.

Claims

1. A method for preparing two-dimensional tin-based perovskite microcrystals, characterized in that, Includes the following steps: S110. Phenethyl ammonium iodide and tin diiodide are dissolved in a mixed organic solvent of DMSO and DMF to obtain an initial mixed solution; S120. Stir the initial mixed solution at room temperature to obtain a homogeneous mixed solution; S130. Filter the homogeneous mixed solution to obtain the precursor solution; S140. A multifunctional regulator is added to the precursor solution to precipitate PEA2SnI4 microcrystals; the Kd value of the multifunctional regulator is between 10 and 10. 1 ~10 3 M -1 Furthermore, pKa is between 4 and 5.5, Kd is the equilibrium constant for the dissociation of the complex, and pKa is the negative logarithm of the acid dissociation constant (Ka).

2. The method for preparing microcrystals according to claim 1, characterized in that, The multifunctional regulator has the following general formula: R-COOH, where R is an organic group and -COOH is a carboxyl group.

3. The method for preparing microcrystals according to claim 2, characterized in that, The multifunctional regulator is acetic acid.

4. The method for preparing microcrystals according to claim 3, characterized in that, The amount of acetic acid added is between 0.5% and 2 vol%.

5. The method for preparing microcrystals according to any one of claims 1-4, characterized in that, The process after S140 further includes: S150, adding dichloromethane to the PEA2SnI4 microcrystals, and then shaking and centrifuging to obtain pure PEA2SnI4 microcrystals.

6. The method for preparing microcrystals according to any one of claims 1-4, characterized in that, S110 further includes adding tin powder to the mixed organic solvent.

7. A method for preparing a two-dimensional tin-based perovskite microcrystalline thin film, characterized in that, Includes the following steps: S100. PEA2SnI4 microcrystals are prepared using the microcrystal preparation method according to any one of claims 1-6; S200, clean the ITO substrate; S300: Using the ITO substrate cleaned in S200, a hole transport layer is prepared; S400: Dissolve the PEA2SnI4 microcrystals prepared in S100 in an organic solvent and stir until homogeneous to obtain a precursor solution; S500: The precursor liquid obtained in S400 is spin-coated onto the hole transport layer prepared in step S300 and annealed to obtain a PEA2SnI4 microcrystalline film.

8. The method for preparing the thin film according to claim 7, characterized in that, The preparation of the hole transport layer in S300 specifically includes: S310, ozone-treated ITO substrate; S320: Spin-coat NiOx onto the surface of the ITO substrate treated in S310 to form a NiOx layer; S330: Spin-coat 2PACZ onto the surface of the NiOx layer formed in S320 to form a 2PACZ layer; S340: Spin-coat PTAA onto the surface of the 2PACZ layer formed in S330 to form a PTAA layer.

9. A method for fabricating a two-dimensional tin-based perovskite light-emitting diode, characterized in that, Includes the following steps: PEA2SnI4 microcrystalline thin films were prepared using the preparation method described in claim 7 or 8; An electron transport layer, an electron injection layer, and electrodes were deposited on the PEA2SnI4 microcrystalline thin film.

10. A two-dimensional tin-based perovskite light-emitting diode, characterized in that, It is prepared by the preparation method described in claim 9.

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