Pure blue light perovskite thin film material with stable spectrum and preparation method and application thereof

Abstract

The invention discloses a pure blue light perovskite thin film material with a stable spectrum, and a preparation method and application of the pure blue light perovskite thin film material with the stable spectrum. The spectrum-stable pure blue light perovskite thin film material is prepared from the following raw materials: cesium halide, lead halide, an organic ligand, formamidine hydrobromide, lithium halide and 2-phenylmalonamide. According to the invention, 2-phenylmalonamide is introduced into the mixed halogen perovskite precursor as a functional additive, so that the pure blue light perovskite light-emitting diode with stable spectrum is realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of microelectronic devices, and in particular relates to a spectrally stable pure blue light perovskite thin film material and a preparation method and application thereof. Background Art

[0002] Metal halide perovskites with high color purity are considered to be ideal emitters for future ultra-high-definition displays because of their ability to precisely control the band gap and emission color, covering the entire visible light range, especially their significant advantages in blue and red light emission. According to the International Telecommunication Union's ultra-high-definition television recommendation standard, monochromatic red, green, and blue light must be strictly located in the predetermined color coordinates and spectral regions, and mixed halide perovskites can achieve this requirement by simply mixing different halide anions. Compared with the complex methods of traditional quantum dots, they show great potential. However, despite the many advantages of mixed halide perovskites, their spectral stability issues have become a key factor restricting their practical applications. CsPb(Br x Cl 1-x )3 system as an example, the difference in ion radius between Cl and Br makes it difficult to form a stable mixed halide perovskite. During the operation of perovskite light-emitting diode (PeLED) devices, the uniformly mixed halide perovskite phase is prone to shift, forming Cl-rich phase and Br-rich phase, which have lower and higher band gaps, respectively, leading to band gap drift, emission spectrum shift and device performance degradation. This halogen anion migration behavior not only causes color instability, but also significantly reduces the electroluminescence efficiency through non-radiative loss or the formation of injection barriers at the interface.

[0003] Phase shift is a core factor affecting the spectral instability of PeLED devices, and it manifests itself in two forms: photoinduced phase shift and electrically induced phase shift. Photoinduced phase shift mainly occurs under illumination conditions. Due to the action of photogenerated carriers, thermodynamic drive, and defect assistance, halogen ions migrate to form phase separation regions, changing the optical properties of the material. Electrically induced phase shift occurs under the action of an electric field, and its impact is more significant. Under the combined action of electric field drive, carrier injection, and interface effects, halogen ion migration intensifies, forming phase separation regions, which not only causes real-time changes in the emission spectrum, resulting in a shift in the PeLED's luminous color, but also accelerates the lifetime decay of the PeLED, causing performance fluctuations. The intensification of electrically induced phase shift is closely related to the operating conditions of the PeLED, and has become a key issue that needs to be addressed in current research.

[0004] In summary, the color instability of hybrid halogen PeLEDs is a major obstacle to their commercial application. Although some strategies have been proposed to alleviate or overcome spectral instability, achieving stable spectral emission still faces many challenges. Summary of the Invention

[0005] The present invention aims to solve at least one of the technical problems existing in the above-mentioned prior art. To this end, the present invention proposes a spectrally stable pure blue light perovskite thin film material, and the PeLED device prepared with the material realizes a spectrally stable pure blue light PeLED.

[0006] The present invention also provides a method for preparing a spectrally stable pure blue light perovskite thin film material.

[0007] The present invention also proposes a perovskite light-emitting diode comprising a conductive glass layer, a hole transport layer, an interface modification layer, a perovskite light-emitting layer, an electron transport layer, an electrode modification layer and an electrode layer stacked in sequence, wherein the perovskite light-emitting layer is the perovskite film.

[0008] According to a first aspect of the present invention, a spectrally stable pure blue light perovskite thin film material is proposed. The raw materials for preparing the spectrally stable pure blue light perovskite thin film material include: cesium halide, lead halide, organic ligand, formamidine hydrobromide, lithium halide and 2-phenylmalonamide.

[0009] According to the embodiment of the first aspect of the present invention, there are at least the following beneficial effects:

[0010] The present invention achieves spectrally stable pure blue PeLED by introducing 2-phenylmalonamide (PMDA) as a functional additive into the mixed halogen (Br / Cl) perovskite precursor. Specifically, the introduction of PMDA additive has a dual effect: on the one hand, it can effectively passivate the defects in the perovskite material, reduce non-radiative recombination centers, and thus improve the luminous efficiency of PeLED; on the other hand, PMDA can significantly inhibit the migration and phase shift of halogen ions, prevent the formation of Cl-rich phase and Br-rich phase, and maintain the phase stability of the perovskite material. The carbonyl group (C=O) in PMDA can react with Pb 2+ Form coordination bonds, fill halogen vacancies, and reduce non-radiative recombination centers; at the same time, amino groups (-NH2) form coordination bonds with the perovskite inorganic framework ([PbX6] 4- The PMDA additive effectively solves the spectral instability problem caused by phase shift in mixed halogen perovskite PeLEDs through a simple additive engineering strategy, while simultaneously solving the two major problems of defect passivation and phase shift suppression in mixed halogen perovskite PeLEDs, providing an efficient and feasible solution for achieving spectrally stable pure blue PeLEDs. This innovation not only promotes the application of mixed halogen perovskite materials in display technology, but also provides new ideas for the development of high-performance, long-life PeLED devices.

[0011] In some embodiments of the present invention, the molar ratio of the cesium halide, the lead halide, the organic ligand, the formamidine hydrobromide, the lithium halide and the 2-phenylmalonamide is: 1:1:0.9:0.3:0.1:0.1-0.5.

[0012] Under the above ratio, PMDA is ensured to anchor halide ions, suppressing the phase separation induced by electric field or light, so that the electroluminescence spectrum does not drift under voltage changes.

[0013] In some embodiments of the present invention, the molar ratio of the cesium halide, the lead halide, the organic ligand, the formamidine hydrobromide, the lithium halide, and the 2-phenylmalonamide is 1:1:0.9:0.3:0.1:0.1-0.5. Furthermore, the molar ratio of the 2-phenylmalonamide is 0.15-0.4, for example, 0.15, 0.2, 0.25, 0.3, 0.35, or 0.4. Furthermore, the organic ligand is selected from phenylethylamine iodide, n-butylamine iodide, or a combination thereof; the lithium halide is selected from lithium iodide, lithium bromide, or a mixture thereof; and the halogen in the cesium halide and the lead halide is independently selected from iodine, bromine, or a combination thereof.

[0014] In some embodiments of the present invention, the organic ligand material includes at least one of fluorophenethylammonium bromide and phenethylammonium bromide.

[0015] In some embodiments of the present invention, the cesium halide includes at least one of cesium bromide, cesium chloride, and cesium iodide.

[0016] In some embodiments of the present invention, the lead halide comprises lead bromide and lead chloride.

[0017] In some embodiments of the present invention, the raw materials for preparing the spectrally stable pure blue light perovskite thin film material also include: a solvent, and the solvent includes: at least one of dimethyl sulfoxide, N,N-dimethylformamide, N-methylpyrrolidone and N,N-dimethylpropylene urea.

[0018] In some embodiments of the present invention, in solution, Pb 2+ The concentration of Pb is 0.08 to 0.2 mol / L. 2+ The concentration is 0.09 to 0.15 mol / L, for example 0.09, 0.10, 0.11, 0.12, 0.13, 0.14 or 0.15 mol / L.

[0019] According to a second aspect of the present invention, a method for preparing a spectrally stable pure blue light perovskite thin film material is proposed, comprising the following steps:

[0020] S1. In a solution state, mixing cesium halide, lead halide, organic ligand, formamidine hydrobromide, lithium halide, and 2-phenylmalonamide to obtain a perovskite precursor solution;

[0021] S2. The perovskite precursor solution is auxiliary-coated on the interface layer and then annealed to obtain a spectrally stable pure blue light perovskite thin film material.

[0022] In some embodiments of the present invention, in step S1, the mixing temperature is 30-80°C.

[0023] In some embodiments of the present invention, in step S1, the mixing time is 4 to 6 hours.

[0024] In some embodiments of the present invention, in step S2, the coating method includes spin coating; the spin coating time is 30 to 200 seconds.

[0025] In some embodiments of the present invention, in step S2, the rotation speed of the spin coating is 3000-5000 rpm.

[0026] In some embodiments of the present invention, in step S2, the spin coating temperature is 60-70°C.

[0027] According to a third aspect of the present invention, a perovskite light-emitting diode is proposed, comprising a substrate layer, a hole transport layer, an interface modification layer, a perovskite light-emitting layer, an electron transport layer, an electrode modification layer and an electrode layer stacked in sequence.

[0028] In some embodiments of the present invention, the substrate layer is a substrate layer obtained after pre-treatment.

[0029] In some embodiments of the present invention, the pre-treatment step comprises the following steps:

[0030] A1. Clean the substrate by immersing the ITO substrate in a cleaning solution and then ultrasonically cleaning the substrate in ultrapure water;

[0031] A2. Dry the substrate. Place the cleaned substrate on a hot plate or in an oven at 100-200°C to dry it, ensuring that there is no moisture on the entire substrate.

[0032] A3. Surface treatment: plasma clean the dried substrate for 5 to 30 minutes.

[0033] In some embodiments of the present invention, the preparation method of the hole transport layer includes: spin coating a thin film hole transport layer material on a substrate layer, the spin coating speed is 3000-5000 rpm, the spin coating time is 30-50s, and annealing is performed immediately after the rotation is completed, the annealing temperature is 120-150°C, the annealing time is 20-30min, and the hole transport layer film is obtained after cooling.

[0034] In some embodiments of the present invention, the raw materials for preparing the hole transport layer include poly(9-vinylcarbazole), N,N'-diphenyl-N,N'-di(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine and chlorobenzene.

[0035] In some embodiments of the present invention, the method for preparing the interface modification layer comprises: spin coating the interface material on the hole transport layer at a spin coating speed of 3000 to 5000 rpm for a spin coating time of 30 to 50 s.

[0036] In some embodiments of the present invention, the raw materials for preparing the interface modification layer include 1,4-dioxane.

[0037] In some embodiments of the present invention, the method for preparing the electron transport layer comprises: depositing the electron transport layer on the perovskite light-emitting layer by thermal evaporation.

[0038] In some embodiments of the present invention, the raw material for preparing the electron transport layer includes 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene.

[0039] In some embodiments of the present invention, the method for preparing the electrode modification layer comprises: depositing the electrode modification layer on the electron transport layer by thermal evaporation.

[0040] In some embodiments of the present invention, the raw material for preparing the electrode modification layer includes lithium fluoride.

[0041] In some embodiments of the present invention, the method for preparing the electrode layer comprises: depositing the electrode layer on the electrode modification layer by thermal evaporation.

[0042] In some embodiments of the present invention, the raw material for preparing the electrode layer includes aluminum. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] The present invention will be further described below with reference to the accompanying drawings and embodiments, in which:

[0044] Figure 1 UV-visible absorption spectra of the films before and after PMDA modification;

[0045] Figure 2 X-ray diffraction (XRD) patterns of the films before and after PMDA modification;

[0046] Figure 3 Photoluminescence (PL) spectra of the films before and after PMDA modification;

[0047] Figure 4 Normalized PL spectra of the film before and after PMDA modification;

[0048] Figure 5 Time-resolved photoluminescence (TRPL) spectra of the films before and after PMDA modification;

[0049] Figure 6 The current density-voltage-luminance (JVL) curves of the PeLED device before and after PMDA modification;

[0050] Figure 7 The external quantum efficiency-current density (EQE-J) curves of PeLED devices before and after PMDA modification;

[0051] Figure 8 Normalized electroluminescence (EL) spectra of PeLED devices before and after PMDA modification;

[0052] Figure 9 The color coordinate diagram of the PeLED device before and after PMDA modification;

[0053] Figure 10 EL spectra of the unmodified PeLED device at different voltages;

[0054] Figure 11 EL spectra of PMDA-modified PeLED devices at different voltages;

[0055] Figure 12 The two-dimensional EL spectra of the PeLED device at different voltages without the auxiliary spin coating process;

[0056] Figure 13 EL spectra of the PeLED device without auxiliary spin coating and PMDA at different voltages;

[0057] Figure 14 EQE-J curves of PeLED devices modified with different PMDA concentrations;

[0058] Figure 15 This is the EQE-J curve of the PeLED device modified with o-formamidobenzoic acid (PTAA). DETAILED DESCRIPTION

[0059] The terms "preferably," "more preferably," and the like, used herein refer to embodiments of the present invention that may provide certain benefits under certain circumstances. However, other embodiments may also be preferred under the same or other circumstances. Furthermore, the recitation of one or more preferred embodiments does not imply that other embodiments are not useful, nor is it intended to exclude other embodiments from the scope of the present invention.

[0060] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values of the range is included. In addition, when multiple ranges are provided to describe a feature or characteristic, the ranges can be combined. In other words, unless otherwise indicated, all ranges disclosed herein are understood to include any and all subranges subsumed therein.

[0061] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. All other embodiments obtained by ordinary technicians in this field based on the embodiments of the present invention without making any creative efforts are within the scope of the present invention.

[0062] Unless otherwise specified, the reagents, methods and equipment used in the present invention are conventional reagents, methods and equipment in the art.

[0063] Example 1

[0064] This embodiment provides a spectrally stable pure blue light perovskite thin film material, specifically:

[0065] S1. Mix CsBr, PbBr2, PbCl2, pF-PEABr, FABr, LiBr, and PMDA in a molar ratio of 1:0.68:0.32:0.9:0.3:0.1:0.3, and finally keep the perovskite precursor solution Pb 2+ The concentration is 0.1 mol / L;

[0066] S2. Drop the prepared perovskite precursor solution onto the pretreated substrate surface, then start the spin coating process, set the rotation speed to 5000 rpm, and the spin coating time to 100 s. 30 s before the start of spin coating, heat the sample stage on which the substrate is placed to 60°C and maintain a constant temperature. When the spin coating process is started, the solution is subjected to the dual effects of high-speed rotation and heating, and the solvent evaporation rate is precisely controlled. Annealing is performed immediately after the rotation is completed. The annealing temperature is 50°C and the annealing time is 7 minutes. After cooling, a pure blue light perovskite light-emitting layer film is obtained.

[0067] This embodiment also provides a perovskite light-emitting diode, specifically:

[0068] A1. Clean the ITO substrate by soaking it in a cleaning solution and ultrasonically cleaning it for 60 minutes. Then, soak the substrate in ultrapure water and ultrasonically clean it for another 60 minutes (the ultrapure water needs to be replaced every 20 minutes during this process).

[0069] A2. Dry the ITO substrate. Place the cleaned ITO substrate on a hot plate or in an oven at 150°C for drying to ensure that there is no moisture on the entire ITO substrate.

[0070] A3. Surface treatment: plasma clean the dried ITO substrate for no less than 10 minutes.

[0071] A4. Spin-coat a thin film of hole transport layer material (PVK:TPD = 7:1, chlorobenzene solvent, 6 mg / ml) at a spin speed of 3000 rpm for 30 s. Anneal immediately after the spin cycle at 135°C for 20 min. After cooling, a PVK:TPD hole transport layer film was obtained.

[0072] PVK: poly(9-vinylcarbazole), CAS: 25067-59-8.

[0073] TPD: N,N'-diphenyl-N,N'-di(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine, CAS: 65181-78-4.

[0074] A5. Spin-coat the interface material (pure DOA solution, 1,4-dioxane, CAS: 123-91-1) at a speed of 3000 rpm for 30 s.

[0075] A6. Spin-coating the perovskite light-emitting layer, the preparation steps are the same as the above-mentioned preparation method of the spectrally stable pure blue light perovskite thin film material.

[0076] A7. Deposit an electron transport layer (TPBi, 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene, CAS: 192198-85-9) by thermal evaporation on the perovskite light-emitting layer. The vacuum degree should be less than 5×10 -4 Pa was deposited to a thickness of 40 nm.

[0077] A8. Thermally evaporate and deposit an electrode modification layer (LiF, lithium fluoride, CAS: 7789-24-4) on the electron transport layer. The vacuum degree should be less than 5×10 -4 Pa was deposited with a thickness of 1 nm.

[0078] A9. Thermally evaporate the electrode layer (Al, aluminum) on the electrode modification layer. The vacuum degree should be less than 5×10 -4 Pa was deposited to a thickness of 120 nm.

[0079] Example 2

[0080] The difference between this embodiment and Example 1 is that the content of PMDA in the configuration of the perovskite precursor is different. CsBr, PbBr2, PbCl2, pF-PEABr, FABr, LiBr, and PMDA are mixed in a molar ratio of 1:0.68:0.32:0.9:0.3:0.1:0.2, and the rest remain unchanged.

[0081] Example 3

[0082] The difference between this embodiment and Example 1 is that the content of PMDA in the configuration of the perovskite precursor is different. CsBr, PbBr2, PbCl2, pF-PEABr, FABr, LiBr, and PMDA are mixed in a molar ratio of 1:0.68:0.32:0.9:0.3:0.1:0.4, and the rest remain unchanged.

[0083] Comparative Example 1

[0084] The difference between this comparative example and Example 1 is that the configuration of the titanium ore precursor does not contain PMDA material, and the rest remains unchanged.

[0085] Comparative Example 2

[0086] The difference between this embodiment and embodiment 1 is that the spin coating is performed at room temperature in step S2, and the rest remain unchanged.

[0087] Comparative Example 3

[0088] The difference between this embodiment and embodiment 1 is that the luminescent material does not contain PMDA material and room temperature spin coating is used in the preparation process, and the rest remains unchanged.

[0089] Comparative Example 4

[0090] The difference between this embodiment and embodiment 1 is that o-formamidobenzoic acid (PTAA) is used to replace PMDA material in the preparation process, and the rest remains unchanged.

[0091] Test Case

[0092] Figure 1 This is the UV-visible absorption spectrum of the film before and after PMDA modification.

[0093] The unmodified sample (Comparative Example 1) exhibited three characteristic absorption peaks at 395nm, 424nm, and 449nm, corresponding to the n=1, n=2, and n≥3 phases, respectively, with the n=1 phase predominating. After PMDA modification (Example 1), the characteristic absorption intensity of the phase decreased significantly, while the absorption peak of the n=2 phase was relatively retained, indicating that PMDA selectively inhibited the low-n and high-n phases and stabilized the preferential growth of the n=2 phase. Furthermore, after PMDA modification, the n≥3 phase was suppressed, indicating improved phase purity.

[0094] Figure 2 X-ray diffraction (XRD) patterns of the films before and after PMDA modification.

[0095] Both the unmodified (Comparative Example 1) and PMDA-modified (Example 1) films exhibited diffraction peaks at 10.59°, 12.38°, 15.30°, 29.79°, 30.77°, and 31.93°. Comparison with a standard CsPbBr3 card (PDF#18-0364) revealed that the peak positions remained unchanged before and after PMDA addition, indicating that the introduction of PMDA did not alter the perovskite crystal lattice constant. PMDA was not directly incorporated into the perovskite lattice, but rather localized at grain boundaries or on the surface. Furthermore, the addition of PMDA significantly reduced the diffraction intensity of the corresponding three-dimensional phase and the n=1 phase. Surface PMDA plays a role in regulating the n-value phase, optimizing and narrowing the n-value phase distribution.

[0096] Figure 3 The photoluminescence (PL) spectra of the films before and after PMDA modification are as follows. The unmodified sample (Comparative Example 1) exhibits a weak luminescence peak at 482 nm (originating from n≥3 phase band edge emission). After PMDA modification (Example 1), the photoluminescence spectrum blue-shifts to 476 nm and the intensity is greatly improved. The enhanced quantum confinement effect and the suppression of non-radiative recombination pathways jointly contribute to the improvement of luminescence efficiency.

[0097] Figure 4 : Normalized photoluminescence spectra of the film before and after PMDA modification. The comparison of normalized photoluminescence spectra shows that the luminescence intensity of the n=2 phase decreases significantly, which is consistent with the absorption spectrum results, further confirming that PMDA achieves phase purity optimization by regulating the quantum confinement effect of the inorganic layer.

[0098] Figure 5 : Time-resolved photoluminescence (TRPL) spectra of the films before and after PMDA modification. The time-resolved photoluminescence spectra show that the film modified with PMDA (Example 1) has a significantly longer lifespan than the unmodified film (Comparative Example 1), indicating that PMDA can effectively reduce non-radiative recombination paths and increase the radiative recombination rate of carriers.

[0099] Figure 6: Current density-voltage-brightness (JVL) curves of PeLED devices before and after PMDA modification. The current density-voltage curves of PMDA-modified devices (Example 1 and Comparative Example 1) show that the current density is significantly decreased, indicating that the PMDA additive reduces non-radiative recombination losses by regulating carrier injection balance and suppressing leakage current.

[0100] Figure 7 : External quantum efficiency-current density (EQE-J) curve of PeLED devices before and after PMDA modification. The maximum external quantum efficiency of the PMDA-modified device increased from 1.22% (Comparative Example 1) to 8.22% (Example 1). This increase is due to the defect suppression effect of the PMDA additive.

[0101] Figure 8 : Normalized electroluminescence (EL) spectra of PeLED devices before and after PMDA modification. The electroluminescence peak of the PMDA device blue-shifted from 487nm (Comparative Example 1) to 476nm (Example 1), and its half-peak width narrowed from 36nm (Comparative Example 1) to 27nm (Example 1), confirming that it reduces the quantum well width and enhances the quantum confinement effect through hydrogen bond anchoring and phase distribution regulation.

[0102] Figure 9 : Color coordinate diagram of PeLED devices before and after PMDA modification. The color coordinates of the device modified with PMDA (Example 1) are (0.111, 0.119), and the color coordinates of the device without additive modification (Comparative Example 1) are (0.080, 0.280).

[0103] Figure 10 : Electroluminescence spectra of unmodified PeLED devices at different voltages. The spectrum of the PeLED device without PMDA modification (Comparative Example 1) drifts from 500nm to 485nm as the voltage increases, resulting in a huge drift of 15nm, indicating spectral instability.

[0104] Figure 11 : Electroluminescence spectra of PMDA-modified PeLED devices at different voltages. The spectrum of the PMDA-modified PeLED device (Example 1) did not drift as the voltage increased, and the spectrum was stable around 476nm, indicating that the addition of PMDA enhanced the stability of the spectrum.

[0105] Figure 12 The two-dimensional electroluminescence spectra of the PeLED device modified with PMDA but without the auxiliary spin coating process (Comparative Example 2) at different voltages are shown. When the PeLED device modified with PMDA does not use the auxiliary spin coating temperature process, the device drifts by 6nm with the increase of voltage, which proves the importance of the auxiliary spin coating temperature process in the preparation process.

[0106] Figure 13 : Electroluminescence spectra of the PeLED device without assisted spin coating and PMDA (Comparative Example 3) at different voltages. The spectral stability of the PeLED device is extremely poor when the assisted spin coating temperature process is not used and the modification does not contain PMDA additives. As the voltage continues to increase, the spectrum drifts by 21nm, indicating the importance of optimizing the preparation process and the PMDA additive strategy.

[0107] Figure 14 : External quantum efficiency-current density (EQE-J) curves of PeLED devices modified with different PMDA concentrations, PMDA concentration optimization analysis. As the PMDA concentration increases from 0.02M (Example 2) to 0.04M (Example 3), the device's maximum EQE is optimal in performance at 0.03M (Example 1), with a maximum EQE of 8.22%.

[0108] Figure 15 : The external quantum efficiency-current density (EQE-J) curve of the device modified with PTAA, a similar additive to PMAD (Comparative Example 4) shows that the maximum EQE of the device modified with PTAA additive is only 3.06%, which is lower than that of the device modified with PMAD additive, reflecting the superiority of PMAD additive among similar additives.

Claims

1. A spectrally stable pure blue light perovskite thin film material, characterized in that: The raw materials for preparing the spectrum-stable pure blue light perovskite thin film material include: cesium halide, lead halide, organic ligand, formamidine hydrobromide, lithium halide and 2-phenylmalonamide.

2. The spectrally stable pure blue light perovskite thin film material according to claim 1, characterized in that: In terms of molar ratio, the cesium halide, the lead halide, the organic ligand, the formamidine hydrobromide, the lithium halide and the 2-phenylmalonamide are: 1:1:0.9:0.3:0.1:0.1-0.

5.

3. The spectrally stable pure blue light perovskite thin film material according to claim 1, characterized in that: The organic ligand includes at least one of fluorophenethylammonium bromide and phenethylammonium bromide.

4. The spectrally stable pure blue light perovskite thin film material according to claim 1, characterized in that: The raw materials for preparing the spectrally stable pure blue light perovskite thin film material also include: a solvent, and the solvent includes: at least one of dimethyl sulfoxide, N,N-dimethylformamide, N-methylpyrrolidone and N,N-dimethylpropylene urea.

5. A method for preparing a spectrally stable pure blue light perovskite thin film material according to any one of claims 1 to 4, characterized in that: The following steps are involved: S1. In a solution state, mixing cesium halide, lead halide, organic ligand, formamidine hydrobromide, lithium halide, and 2-phenylmalonamide to obtain a perovskite precursor solution; S2. The perovskite precursor solution is coated on the interface layer and then annealed to obtain a spectrally stable pure blue light perovskite thin film material.

6. The preparation method according to claim 5, characterized in that In step S1, the mixing temperature is 30-80°C.

7. The preparation method according to claim 5, characterized in that In step S2, the coating method includes spin coating; the spin coating time is 30 to 200 seconds.

8. The preparation method according to claim 5, characterized in that In step S2, the rotation speed of the spin coating is 3000-5000 rpm.

9. The preparation method according to claim 5, characterized in that In step S2, the spin coating temperature is 60-70°C.

10. A perovskite light-emitting diode, characterized in that: The invention comprises a substrate layer, a hole transport layer, an interface modification layer, a perovskite light-emitting layer, an electron transport layer, an electrode modification layer and an electrode layer which are stacked in sequence, wherein the perovskite light-emitting layer is the spectrally stable pure blue light perovskite thin film material according to any one of claims 1 to 4.

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