A blue-violet LED device containing a perovskite material

Abstract

The present invention relates to the technical field of light-emitting devices, and particularly relates to a blue-violet LED device containing a perovskite material, which comprises an ITO anode, a hole transport layer, a perovskite layer, an electron transport layer, an electron injection layer, and a cathode material layer stacked in sequence; the perovskite layer is a quasi-two-dimensional / three-dimensional heterojunction perovskite material, which includes a three-dimensional perovskite material and a quasi-two-dimensional layered structure material wrapped on the surface of the three-dimensional perovskite material. The molecular formula of the three-dimensional perovskite material is Cs3Bi2Cl6Br3, and the molecular formula of the quasi-two-dimensional layered structure material is (4-F-PEA)2PbCl4. This quasi-two-dimensional / three-dimensional heterojunction perovskite material is a blue-violet perovskite material with high stability, high blue-violet emission efficiency, and high color purity, which is beneficial to improving the luminous color purity, luminous efficiency, and environmental tolerance of the blue-violet LED device, and enhancing the performance of the blue-violet LED device.

Description

Technical Field

[0001] The present invention relates to the technical field of light-emitting devices, and particularly to a blue-violet LED device containing a photoactive perovskite material. Background Art

[0002] Perovskite is a material with a specific crystal structure. Its original form is calcium titanate (CaTiO3), but modern perovskites generally refer to a class of compounds with similar crystal structures, expressed by the chemical formula ABX3. Here, A and B represent different-sized cations, and X is one or more halogen anions (such as Cl - 、Br - 、I - ). This structure endows perovskite with many excellent optoelectronic properties, including a high absorption coefficient, a long carrier diffusion length, an adjustable bandgap, etc. In display technology, perovskite can be used to manufacture more efficient and color-accurate displays. Especially in the application in the blue-violet region, it is crucial for improving the color expressiveness of display devices.

[0003] Traditional lead-based perovskites (such as CsPbCl3, CsPbBr3) contain a relatively large amount of highly toxic lead and have poor environmental friendliness. Therefore, researchers hope to reduce the use of lead elements. Three-dimensional perovskite (CsPbCl3) is also vulnerable to humidity, heat, and light, leading to halogen migration and phase separation, and its lifespan is less than 500h under 60% RH humidity. In terms of performance, the bandgap regulation range of pure lead-based perovskite is limited, and the quantum yield (PLQY) is less than 30% when emitting blue-violet light (<480nm). In addition, most existing technologies adopt pure three-dimensional or pure two-dimensional structures. The three-dimensional structure has a high carrier mobility but poor stability, while the two-dimensional structure has good stability but low charge transport efficiency, which affects the blue-violet light emission efficiency. To sum up, the existing perovskite materials have poor high-humidity and high-temperature stability, and the blue-violet FWHM is generally relatively wide (>25nm), resulting in insufficient color purity and low blue-violet light emission efficiency (PLQY), making it difficult to meet the requirements of high-end displays. Summary of the Invention

[0004] In view of the above-mentioned drawbacks and deficiencies of the prior art, the present invention provides a blue-violet LED device containing a photoactive perovskite material. The perovskite material has a quasi-two-dimensional / three-dimensional heterojunction structure, its main emission peak is located at 420nm, the full width at half maximum is less than 20nm, the color purity is better than that of traditional lead-based perovskites (the full width at half maximum is about 30 - 50nm), PLQY > 75%, and the performance retention rate is > 90% after 1000h under 85% RH high-humidity conditions. Thus, a blue-violet LED device with high stability, high blue-violet light emission efficiency, and high color purity is obtained, solving the technical problems of poor stability, low color purity, and low emission efficiency of existing blue-violet LED devices.

[0005] In a first aspect, the present invention provides a blue-violet light-emitting diode device containing a perovskite material, which includes an ITO anode, a hole transport layer, a perovskite layer, an electron transport layer, an electron injection layer, and a cathode material layer laminated in sequence; the perovskite layer is a blue-violet light perovskite material, and the blue-violet light perovskite material is a quasi-two-dimensional / three-dimensional heterojunction perovskite material, which includes a three-dimensional perovskite material and a quasi-two-dimensional layered structure material wrapped on the surface of the three-dimensional perovskite material. The molecular formula of the three-dimensional perovskite material is Cs3Bi2Cl6Br3, and the molecular formula of the quasi-two-dimensional layered structure material is (4-F-PEA)2PbCl4.

[0006] Among them, 4-F-PEA is the abbreviation of 4-fluorophenethylamine or p-fluorophenethylamine.

[0007] Among them, the three-dimensional perovskite material (Cs3Bi2Cl6Br3) is mainly used to provide high carrier mobility and light absorption ability. The quasi-two-dimensional structure ((4-F-PEA)2PbCl4) mainly passivates surface defects through an organic ligand layer, inhibits non-radiative recombination, and improves the fluorescence quantum yield. The halogen in the three-dimensional structure material is composed of Cl - / Br - in an atomic ratio of 6:3 (Cl6Br3) to adjust the band gap of the material to the blue-violet light range (about 400-480 nm).

[0008] Preferably, the blue-violet light perovskite material is prepared by the following method:

[0009] S1. Weigh CsCl, BiBr3, and BiCl3 in a molar ratio of 3:1:1 or weigh CsBr and BiCl3 in a molar ratio of 3:2, dissolve them in a degassed mixed solvent with a volume ratio of DMF:DMSO of 4:1, and magnetically stir at 55-60 °C for 5-10 h until completely dissolved to form a transparent solution. Then, filter out the undissolved impurities using a 0.22 μm filter membrane to obtain a solution with a substance concentration of 1-2 M.

[0010] S2. Weigh 4-fluorophenethylamine 4-F-PEA, PbCl2, and CsCl in a molar ratio of 2:1:2, dissolve them in DMSO, and stir at room temperature for 4-6 h to obtain a solution with a concentration of 1-2 M, and ultrasonically remove bubbles.

[0011] S3. Use the step-by-step spin coating method to first coat the solution prepared in S1 on a conductive substrate. After gradient annealing treatment, then coat the solution prepared in S2. After secondary annealing, a blue-violet light perovskite material with a quasi-two-dimensional / three-dimensional heterojunction composite structure is obtained, and its chemical formula is Cs3Bi2Cl6Br3@(4-F-PEA)2PbCl4.

[0012] Among them, the raw material CsCl in S2 is used to provide the lacking Cl atoms as Cl -The "carrier" itself does not participate in coordination and theoretically does not enter the product lattice. During the reaction, 4-F-PEA + (organic ammonium ion) competes with Cs + to occupy the interlayer sites of the layered perovskite. 4-F-PEA + has a larger steric hindrance and stronger van der Waals interaction, preferentially occupies the interlayer position, and thus can repel Cs + .

[0013] Preferably, the operating steps of S3 are as follows:

[0014] S31: Ultrasonically clean the substrate successively with acetone, isopropyl alcohol, and deionized water, and dry it with nitrogen gas;

[0015] S32: In a nitrogen glove box with a humidity < 1%, spin-coat the solution prepared in S1 on the substrate surface at 4000 rpm for 30 s. At the 15th second of spin-coating, add 100 - 200 μL of toluene as an anti-solvent to accelerate crystallization;

[0016] S33: Perform a uniform gradient annealing treatment at 100 °C → 80 °C for 10 min (gradient annealing promotes the orderly arrangement of halogens, promotes lattice integrity, and reduces the emission peak width), remove the residual solvent, promote the formation of a three-dimensional perovskite lattice, and obtain a three-dimensional perovskite layer on the substrate surface;

[0017] S34: In a nitrogen glove box with a humidity < 1%, continuously spin-coat the solution prepared in S2 on the surface of the three-dimensional perovskite layer formed in S33 at 2000 rpm for 20 s. At the 10th second of spin-coating, add 50 - 80 μL of toluene as an anti-solvent to accelerate crystallization;

[0018] S35: Anneal at 80 °C for 20 min to remove the residual solvent, induce the self-assembly of the quasi-two-dimensional layer, and form a heterojunction interface.

[0019] Preferably, in S32 and S34, the dropping rate of toluene should be ≤ 5 μL / s to ensure uniform crystallization.

[0020] Preferably, in S32 and S34, the oxygen content in the nitrogen glove box is < 0.1 ppm.

[0021] Preferably, the concentration of the solution prepared in S1 is 1 M; the concentration of the solution prepared in S2 is 1 M.

[0022] Preferably, in S1, DMF:DMSO = 4:1. This ratio affects the crystallization kinetics. If the ratio is too high (> 4:1), it is easy to cause the three-dimensional layer to be overly rough. The solvent is pre-bubbled with nitrogen to remove oxygen; operate in a nitrogen glove box to avoid the decomposition of perovskite caused by moisture and also avoid the oxidation of Bi 3+ to Bi 5+, an impurity phase (such as BiOCl) is generated. Among them, the annealing temperature of the three-dimensional layer needs to be higher than that of the quasi-two-dimensional layer to avoid interlayer interface interdiffusion.

[0023] Preferably, in S1, during magnetic stirring, the temperature is 60 °C and the stirring time is 6 h. In S2, during magnetic stirring, the temperature is 25 °C and the stirring time is 4 h, and ultrasonic treatment is performed for 30 min to eliminate bubbles.

[0024] Preferably, the hole transport layer is PEDOT:PSS; the electron transport layer is TPBi (1,3,5-Tris(N-phenylbenzimidazole-2-yl)benzene); the electron injection layer is LiF.

[0025] Preferably, the cathode material layer is Al or other anti-oxidant metals, such as Ag.

[0026] The beneficial effects of the present invention are:

[0027] 1. The blue-violet light perovskite material of the present invention has no lead element in its all-Bi three-dimensional perovskite layer, and the mixed halogen design is carried out with chlorine / bromine in a molar ratio of 6 / 3, which is beneficial to reducing toxicity (reducing the risk of lead pollution) and adjusting the band gap to the blue-violet light range; the Bi-O bond energy in the three-dimensional perovskite layer is higher than that of the Pb-O bond, inhibiting the formation of oxygen vacancies, enhancing the moisture and heat resistance of the material, and improving the stability of the material. The quasi-two-dimensional layered structure formed by the fluorinated phenethylamine (4-F-PEA) organic ligand wraps the surface of the three-dimensional perovskite, passivates surface defects through the organic ligand layer, inhibits non-radiative recombination, and thus improves the fluorescence quantum yield.

[0028] Due to the three-dimensional perovskite material Cs3Bi2Cl6Br3 compared with the traditional lead-based perovskite material, Bi 3+ has an ionic radius of 1.03 Å, which is smaller than that of Pb 2+ of 1.19 Å. Since the ionic radius of Bi 3+ decreases by about 13.5%, it will cause lattice contraction, and the octahedron [BiX6] 3+ unit of Bi in the three-dimensional structure is more likely to form a distorted coordination environment due to charge mismatch, which will cause the band gap to expand to the blue-violet light range. XRD detection shows that the lattice parameter a of the Cs3Bi2Cl6Br3 unit cell is 10.7 Å, while the lattice parameter a of the traditional CsPbBr3 unit cell is 11.8 Å, which also confirms the existence of lattice distortion. The high charge state of Bi 3- requires more negative charges to balance around it, so there is a problem of insufficient halogen coordination in the local Bi 3+ , resulting in the formation of unsaturated coordination bonds (Bi 3+ on the surface of the three-dimensional perovskite material 3+The dangling bonds are not conducive to PLQY. In the present invention, the F atoms in the quasi-two-dimensional perovskite material (4-F-PEA)2PbCl4 form Bi-F bonds with the uncoordinated Bi 3 + to fill the surface dangling bonds, thereby passivating the Bi defects in the pure three-dimensional perovskite material 3+ ; while the quasi-two-dimensional perovskite material can also passivate the Pb defects through fluorine atoms 2+ As a result, the defect state density of the entire composite perovskite material is greatly reduced, and the PLQY of the composite material is increased from 50% (when the surface is not coated with quasi-two-dimensional perovskite) to more than 75%.

[0029] 2. The blue-violet light perovskite material of the present invention has a quasi-two-dimensional / three-dimensional heterostructure, and there is a synergistic effect between the quasi-two-dimensional perovskite and the quasi-three-dimensional perovskite. Among them, the quasi-two-dimensional layer can limit the exciton diffusion and reduce the energy loss. The three-dimensional matrix provides a fast carrier transport channel, and the quasi-two-dimensional layer enhances the interface charge separation efficiency. The quasi-two-dimensional flexible structure relieves the lattice stress of the three-dimensional layer, and the 4-F-PEA in the quasi-two-dimensional layer inhibits the migration of halogen vacancies in the three-dimensional perovskite material through electrostatic interaction; it forms Bi-F bonds with the uncoordinated Bi 3+ to fill the surface dangling bonds; at the same time, annealing operation during the preparation process can promote the cross-interface coupling of Bi-F bonds and Pb-F bonds to enhance the material stability. The hydrophobic 4-F-PEA layer in the quasi-two-dimensional material blocks the penetration of water molecules, the Bi-O bond in the three-dimensional perovskite material enhances the lattice thermal stability, and the heterojunction inhibits the photoinduced halogen migration and phase separation, so that the blue-violet light perovskite material of the present invention has excellent wet stability and high-temperature stability.

[0030] 3. Experimental tests show that the main emission peak of the blue-violet light perovskite material prepared by the present invention is located at 420 nm (blue-violet light), the full width at half maximum (FWHM) < 20 nm, and the color purity is better than that of traditional lead-based perovskites. The quantum yield (PLQY) can reach more than 75%, which is attributed to the defect passivation effect of the quasi-two-dimensional layer. The performance retention rate reaches 90% (1000 h) at 85% RH and 85% (1000 h) at 85 °C. The external quantum efficiency (EQE) of the blue-violet light LED device prepared with the blue-violet light perovskite material of the present invention reaches more than 12%.

[0031] In addition, the preparation method of the present invention is simple. Only by first preparing a precursor solution, spin-coating and annealing in an oxygen- and water-vapor-free environment, a target thin film with a heterojunction can be obtained, and the defect state density on the surface of the target thin film is low, and the PLQY is higher than that of existing lead-based perovskites or pure three-dimensional perovskites. Description of the Drawings

[0032] Figure 1XRD analysis diagram of the three-dimensional layer (Cs3Bi2Cl6Br3) prepared by the method of Example 1.

[0033] Figure 2 EDS analysis diagram of the three-dimensional layer (Cs3Bi2Cl6Br3) prepared by the method of Example 1.

[0034] Figure 3 XRD analysis diagram of the quasi-two-dimensional layer ((4-F-PEA)2PbCl4) separately prepared on the glass substrate surface by the method of Example 1.

[0035] Figure 4 EDS analysis diagram of the quasi-two-dimensional layer ((4-F-PEA)2PbCl4) separately prepared on the glass substrate surface by the method of Example 1.

[0036] Figure 5 PL spectra of the quasi-two-dimensional / three-dimensional heterojunction perovskite material Cs3Bi2Cl6Br3@(4-F-PEA)2PbCl4 prepared in Example 1 and Cs3Bi2Cl6Br3 of Comparative Example 1.

[0037] Figure 6 External quantum efficiency (EQE) test diagrams of two blue-violet LED devices prepared in Example 3. Detailed implementation manners

[0038] For better explaining the present invention and facilitating understanding, the present invention will be described in detail below with reference to the accompanying drawings and through specific implementation manners.

[0039] In the embodiments of the present application, all reagents used are of analytical purity. Cesium salts: CsBr (purity ≥ 99.9%), CsCl (≥ 99.9%); Bismuth salts: BiBr3 (≥ 99.99%), BiCl3 (≥ 99.99%); Lead salts: PbCl2 (≥ 99.9%); Organic ligand: 4-fluorophenethylamine (4-F-PEA, ≥ 98%); Solvents: N,N-dimethylformamide (DMF, anhydrous grade), dimethyl sulfoxide (DMSO, anhydrous grade), isopropyl alcohol (IPA, ≥ 99.5%); Anti-solvent: Toluene (anhydrous grade).

[0040] Experimental equipment: Magnetic stirrer (temperature control range: 25 - 150 °C); Nitrogen glove box (oxygen content < 0.1 ppm, humidity < 1%); Spin coater (rotation speed range: 1000 - 6000 rpm); Annealing (temperature control accuracy ± 1 °C); Ultrasonic cleaner.

[0041] The following is described in conjunction with the preferred embodiments of the present invention.

[0042] Example 1

[0043] This embodiment provides a method for preparing a blue-violet light perovskite material, and the steps are as follows:

[0044] (1) Measure 4 mL of DMF and 1 mL of DMSO. After mixing, purge with nitrogen gas for 10 min to remove oxygen, then add 3 mmol of CsBr and 2 mmol of BiCl3, and stir magnetically at 60 °C for 6 h until completely dissolved to form a transparent solution. Filter through a 0.22 μm filter membrane to remove undissolved impurities to obtain a solution with a substance concentration of 1 M.

[0045] (2) Measure 5 mL of DMSO, then add 2 mmol of 4-F-PEA, 1 mmol of PbCl2, and 2 mmol of CsCl, and stir at 25 °C for 4 h to obtain a solution with a concentration of 1 M. Ultrasonic for 15 min to remove bubbles.

[0046] (3) Ultrasonically clean the surface of the glass substrate with acetone, isopropanol, and deionized water for 10 min each, and dry with nitrogen.

[0047] (4) In a nitrogen glove box with a humidity < 1%, spin-coat the solution prepared in step (1) on the substrate surface at 4000 rpm for 30 s, and add 100 μL of toluene (dropwise addition rate of 5 μL / s) as an antisolvent at the 15th second of spin-coating.

[0048] (5) Perform a uniform gradient annealing treatment at 100 °C → 80 °C for 10 min (2 °C / min) to remove residual solvents and obtain a three-dimensional perovskite layer on the substrate surface.

[0049] (6) In a nitrogen glove box with a humidity < 1%, continuously spin-coat the solution prepared in step (2) on the surface of the three-dimensional perovskite layer at 2000 rpm for 20 s, and add 50 μL of toluene as an antisolvent (dropwise addition rate of 5 μL / s) at the 10th second of spin-coating to accelerate crystallization.

[0050] (7) Anneal at 80 °C for 20 min to obtain a blue-violet light perovskite material on the glass / ITO substrate surface.

[0051] As Figure 1 shown, it is the XRD analysis pattern of the three-dimensional layer (Cs3Bi2Cl6Br3) obtained after step (5) of Example 1. Cs3Bi2Cl6Br3 belongs to the cubic crystal system, space group Pm-3m, and the unit cell parameter a = 6.11 Å; using a Cu Kα radiation source (λ = 1.5406 Å). The main diffraction peak (100) is located at 14.5° (corresponding to the (100) crystal plane, full width at half maximum 0.3), and the other peaks: peak (110) is located at 20.5°, peak (111) is located at 25.2°, peak (200) is located at 29.4°, peak (210) is located at 34.8°, and peak (211) is located at 41.2°. Figure 2EDS analysis diagram of the three-dimensional layer (Cs3Bi2Cl6Br3) obtained after step (5), where Cl / Br = 6:3 and Bi / Cs = 2:3. Figure 2 During the test, the test beam energy was 15 keV, the resolution was 100 eV, and the voltage was 15 kV.

[0052] As Figure 3 shown, to avoid interference of the three-dimensional layer (Cs3Bi2Cl6Br3) on the XRD test of the quasi-two-dimensional layer (4-F-PEA)2PbCl4) thin film on its surface, the solution prepared in step (2) of Example 1 was spin-coated on the surface of a glass substrate alone, and after annealing, a (4-F-PEA)2PbCl4) thin film was obtained. From Figure 3 it can be seen that the characteristic peak of the quasi-two-dimensional perovskite material ((4-F-PEA)2PbCl4) is located at 5.8°, which is a layered perovskite structure with a layer spacing d = 15.0 Å, monoclinic system, P21 / c space group, and the in-plane diffraction peaks (100) / (010) reflect the ordering of the organic layer; material parameters: λ = 1.5406 Å (Cu Kα), FWHM 2D = 0.15°.

[0053] As Figure 4 shown, in the EDS analysis diagram of the (4-F-PEA)2PbCl4) thin film, no Cs signal was detected (detection limit < 0.1 at%). The material crystal is monoclinic, space group P21 / c, EDS conditions: beam energy: 10 keV, resolution 80 eV, detector: SDD (30 mm²).

[0054] Example 2

[0055] This example provides a preparation method of a blue-violet light perovskite material, and the main difference from Example 1 lies in that the solution preparation steps of steps (1)-(2) are as follows:

[0056] (1) Measure 4 mL of DMF and 1 mL of DMSO, mix them, purge with nitrogen and bubble for 10 min, then add 3 mmol of CsCl, 1 mol of BiBr3 and 1 mol of BiCl3, stir magnetically at 60 °C for 6 h until completely dissolved to form a transparent solution, and filter through a 0.22 μm filter membrane to remove undissolved impurities to obtain a solution with a substance concentration of 1 M.

[0057] (2) Measure 5 mL of DMSO, then add 2 mmol of 4-F-PEA, 1 mmol of PbCl2 and 2 mmol of CsCl, stir at 25 °C for 6 h to obtain a solution with a concentration of 1 M, and ultrasonicate for 15 min to remove bubbles.

[0058] Steps (3)-(7) of this embodiment are carried out with reference to the method of Embodiment 1.

[0059] Comparative Example 1

[0060] In this comparative example, a three-dimensional perovskite layer was prepared on the surface of a glass substrate by the same method as in Embodiment 1, thus completing the preparation, corresponding to steps (1), (3)-(5), etc. of Embodiment 1. In this comparative example, a quasi-two-dimensional layer ((4-F-PEA)2PbCl4) was not covered on the surface of the three-dimensional perovskite layer.

[0061] The heterojunction perovskite material Cs3Bi2Cl6Br3@(4-F-PEA)2PbCl4 of Embodiment 1 and the pure three-dimensional perovskite material Cs3Bi2Cl6Br3 of Comparative Example 1 were analyzed by comparative photoluminescence (PL) spectroscopy using a commercial PL spectrometer (Edinburgh FLS1000), and the analysis results are as Figure 5 shown. As shown in the figure, the emission peak of the heterojunction perovskite material is 420 nm (blue-violet light), the FWHM is about 18 nm, and the quantum yield (PLQY) = 80% (integrating sphere test); the emission peak of the pure three-dimensional perovskite material of Comparative Example 1 is 450 nm, and the FWHM is 40 nm (the larger this value, the lower the color purity of the light), and the PLQY is 50%. Thus, it can be seen that the heterojunction perovskite material Cs3Bi2Cl6Br3@(4-F-PEA)2PbCl4 prepared by the present invention has an excellent interface defect passivation effect, the main emission peak of the material is located at 420 nm (blue-violet light), the full width at half maximum (FWHM) < 20 nm, and the color purity is superior to that of traditional lead-based perovskites and Comparative Example 1.

[0062] Among them, the photoluminescence test, i.e., the PL test, refers to irradiating a sample with a light source (such as a laser or an LED). In this embodiment, excitation light with a wavelength of 365 nm at room temperature is used for irradiation, so that electrons in the sample absorb photons and transition to the excited state. When these electrons return to the ground state, they will emit photons. By measuring the characteristics of these photons (such as intensity, wavelength, etc.), the photoluminescence characteristics of the material can be obtained, including information such as PLQY, the position of the main emission peak, and the full width at half maximum.

[0063] Embodiment 3

[0064] In this embodiment, a blue-violet light LED device is prepared, and its preparation method is as follows:

[0065] (1) Take a piece of glass / ITO substrate, ultrasonically clean its surface with acetone, isopropyl alcohol, and deionized water for 10 min each, dry it with nitrogen, and treat it with ultraviolet ozone for 20 minutes.

[0066] (2) Coat the PEDOT:PSS hole transport layer and dry it in a hot air oven at 40 °C.

[0067] (3)Construct a heterojunction blue-violet perovskite material layer with the chemical formula Cs3Bi2Cl6Br3@(4-F-PEA)2PbCl4 on the surface of the PEDOT:PSS hole transport layer according to the method of Example 1 or Example 2.

[0068] (4)Coat the electron transport layer as TPBi and dry it in a hot air oven at 40 °C.

[0069] (5)Sputter deposit the electron injection layer LiF.

[0070] (6)Sputter an aluminum electrode film to obtain a blue-violet LED device.

[0071] Perform an external quantum efficiency EQE test on the two blue-violet LED devices prepared in Example 3, and the test results are as Figure 6 shown. Among them, for the two blue-violet LED devices prepared in Example 3, their EQE values reach 14.2% and 13.5% respectively, the CIE color coordinates are (0.15, 0.06), and the EQE test performances of the two LED devices are relatively close. The blue-violet perovskite material layer prepared in Example 1 is assembled into a blue-violet LED device. Under a 5V DC driving voltage, the light intensity of the blue-violet light emitted by the perovskite LED device after being weighted by the human eye visual function reaches 1000 cd / m².

[0072] Furthermore, assemble the pure Cs3Bi2Cl6Br3 film of Comparative Example 1 into a blue-violet LED device according to the same method and steps as in Example 3, and test the stability of the LED light-emitting devices assembled with the three perovskite films.

[0073] The test method is as follows: Age the three LED devices at 85% humidity and 85 °C for 1000 h, conduct an aging test, and test the percentage value of the PL intensity (mainly the luminous efficiency) to the initial PL intensity to quantify the stability of the material. The test results are as follows: ;

[0074] The retention rate of the traditional lead-based perovskite after aging at 85% humidity and 85 °C for 1000 h < 30%. It can be seen that the stability of pure Cs3Bi2Cl6Br3 is generally better than that of the traditional lead-based perovskite, but weaker than that of the quasi-two-dimensional / three-dimensional heterojunction material of the present invention.

[0075] In summary, through the design of quasi-two-dimensional heterojunctions, the present invention passivates the surface of the unstable three-dimensional perovskite material Cs3Bi2Cl6Br3 and forms a physical barrier to inhibit ion migration, endowing the material with higher PLQY and environmental stability. In addition, the substitution of Bi for Pb in the three-dimensional Cs3Bi2Cl6Br3 and the regulation of the mixed halogen ratio are used to adjust the bandgap, so that the main emission peak of the blue-violet perovskite material is located at 420 nm (blue-violet light), with FWHM < 20 nm and color purity superior to that of traditional lead-based perovskites. Thus, the present invention obtains a blue-violet perovskite material and a blue-violet LED device with high stability, high blue-violet light emission efficiency, and high color purity.

[0076] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them. Although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements for some or all of the technical features. And these modifications or replacements, or when the technical features in the above embodiments do not conflict with each other, can be combined in the manner described in the embodiments, and these modifications, replacements or combinations do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A blue-violet LED device containing a perovskite material, characterized in that, It includes an ITO anode, a hole transport layer, a perovskite layer, an electron transport layer, an electron injection layer, and a cathode material layer that are stacked in sequence; the perovskite layer is a blue-violet light perovskite material, and the blue-violet light perovskite material is a quasi-two-dimensional / three-dimensional heterojunction perovskite material, which includes a three-dimensional perovskite material and a quasi-two-dimensional layered structure material wrapped on the surface of the three-dimensional perovskite material. The molecular formula of the three-dimensional perovskite material is Cs3Bi2Cl6Br3, and the molecular formula of the quasi-two-dimensional layered structure material is (4-F-PEA)2PbCl4.

2. The blue-violet LED device containing the opto-perovskite material according to claim 1, characterized in that, The preparation method of the blue-violet light perovskite material is as follows: S1. Weigh CsCl, BiBr3, BiCl3 according to the molar ratio of 3:1:1 or weigh CsBr and BiCl3 according to the molar ratio of 3:2, dissolve them in a deoxygenated mixed solvent with a volume ratio of DMF:DMSO of 4:1, magnetically stir at 55 - 60 °C for 5 - 10 h until completely dissolved to form a transparent solution, and filter with a 0.22 μm filter membrane to remove undissolved impurities to obtain a solution with a substance concentration of 1 - 2 M; S2. Weigh 4-fluorophenethylamine 4-F-PEA, PbCl2, CsCl according to the molar ratio of 2:1:2, dissolve them in DMSO, stir at room temperature for 4 - 6 h to obtain a solution with a concentration of 1 - 2 M, and ultrasonically remove bubbles; S3. Use the stepwise spin-coating method to first coat the solution prepared in S1 on a conductive substrate. After annealing treatment, then coat the solution prepared in S2. After secondary annealing, a blue-violet light perovskite material with a quasi-two-dimensional / three-dimensional heterojunction composite structure is obtained, and its chemical formula is Cs3Bi2Cl6Br3@(4-F-PEA)2PbCl4.

3. The blue-violet LED device containing a perovskite material according to claim 2, characterized in that, The steps of S3 are as follows: S31: Ultrasonically clean the substrate successively with acetone, isopropyl alcohol, and deionized water, and dry it with nitrogen; S32: In a nitrogen glove box with a humidity < 1%, spin-coat the solution prepared in S1 on the substrate surface at 4000 rpm for 30 s, and add 100 - 200 μL of toluene as an antisolvent at the 15th second of spin-coating to accelerate crystallization; S33. Carry out a uniform gradient annealing treatment at 100 °C → 80 °C for 10 min to remove residual solvents and promote the formation of the three-dimensional perovskite lattice, and obtain a three-dimensional perovskite layer on the substrate surface; S34: In a nitrogen glove box with a humidity < 1%, continuously spin-coat the solution prepared in S2 on the surface of the three-dimensional perovskite layer formed in S33 at 2000 rpm for 20 s, and add 50 - 80 μL of toluene as an antisolvent at the 10th second of spin-coating to accelerate crystallization; S35. Anneal at 80 °C for 20 min to remove residual solvents and induce the self-assembly of the quasi-two-dimensional layer and form a heterojunction interface.

4. The blue-violet LED device containing the optical perovskite material according to claim 3, characterized in that, In S32 and S34, the dropping rate of toluene should be ≤ 5 μL / s to ensure uniform crystallization.

5. The blue-violet LED device containing the optical perovskite material according to claim 3, characterized in that, In S32 and S34, the oxygen content in the nitrogen glove box is < 0.1 ppm.

6. The blue-violet LED device containing the opto-perovskite material according to claim 3, characterized in that, The concentration of the solution prepared in S1 is 1 M; the concentration of the solution prepared in S2 is 1 M.

7. The blue-violet LED device containing the opto-perovskite material according to claim 3, characterized in that, In S1, during magnetic stirring, the temperature is 60 °C and the stirring time is 6 h; in S2, during magnetic stirring, the temperature is 25 °C and the stirring time is 4 h, and ultrasonically stir for 30 min to remove bubbles.

8. The blue-violet LED device containing a perovskite material according to claim 1, wherein, The hole transport layer is PEDOT:PSS; the electron transport layer is 1,3,5-tris(N-phenylbenzimidazol-2-yl)benzene; the electron injection layer is LiF.

9. The blue-violet LED device containing a perovskite material according to claim 1, characterized in that, The cathode material layer is Al or Ag.

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