A high-stability metal-organic framework / nanocrystal composite material for backlight display and a preparation method thereof

Abstract

This invention discloses a highly stable metal-organic framework / nanocrystalline composite material for backlight displays and its preparation method. Specifically, it utilizes the anionic metal-organic framework material bio-MOF-100 as a matrix, and employs a two-step sequential deposition method to confine and grow perovskite nanocrystals within the metal-organic framework to prepare the metal-organic framework / nanocrystalline composite material. The preparation method of this invention is simple, the conditions are mild, and the obtained composite material exhibits good stability and ultra-pure green light emission with a full width at half maximum (FWHM) of 25.6 nm. Specifically, liquid crystal devices constructed using the ultra-pure green light-emitting metal-organic framework / nanocrystalline composite material achieve wide color gamut backlight displays, covering 122.9% of the NTSC color gamut and 91.9% of the Rec. 2020 color gamut. The metal-organic framework / nanocrystalline composite material prepared by this invention provides a novel design approach for highly stable backlight display device materials.

Description

Technical Field

[0001] This invention belongs to the field of display materials, and relates to a highly stable metal-organic framework / nanocrystalline composite material for backlight displays, its preparation method, and its application in the preparation of liquid crystal display devices. Background Technology

[0002] As modern society enters an era of information overload, display devices have become the most important information carriers in daily life and scientific fields, widely used in multimedia devices such as televisions, mobile phones, and tablets. Advances in semiconductor technology over the past few decades have driven the development of display technology towards wider color gamut, higher brightness, and longer lifespan. The International Telecommunication Union's (ITU-R) High-Definition Digital Video (HDD) standard (ITU-R BT.709) and the US National Television Standards Committee (NTSC) standard have been proposed to regulate how displays should reproduce colors. To reproduce object colors more vividly and realistically, and for the future of ultra-high-definition television, the ITU Recommendation BT 2020 (Rec. 2020) standard has been proposed. This standard requires ultra-pure light emission to meet the required wide color gamut. This poses a significant challenge, especially for ultra-pure green light emission, because the human eye is very sensitive to green and can distinguish even minute hue variations. According to Rec. 2020 standards, ultrapure green light emission needs to be within the range of 525-535 nm, with a free-wavelength (FWHM) of less than 25 nm. Commonly used green phosphors include β-SiAlON:Eu. 2+ The emission center is at 525 nm, and the FWHM is about 50 nm; the FWHM of conventional II-VI group inorganic semiconductor quantum dots is relatively wide, at 25-35 nm, making it difficult to achieve ultrapure green light emission.

[0003] The high quantum efficiency, narrow free wave size (FWHM) (<25 nm), tunable bandgap, low cost, and ease of fabrication of perovskite nanocrystals have made them a promising candidate for backlight displays. Although extensively studied CsPbBr3 and MAPbBr3 nanocrystals and their associated MOFs composites exhibit excellent optical properties, their emission wavelengths are typically less than 520 nm, deviating from the 525-535 nm ultrapure green emission defined by the Rec. 2020 standard. While perovskite nanocrystals with mixed bromine and iodine halogens can have their emission wavelength adjusted to the ultrapure green emission window by regulating the halogen stoichiometry, the incorporation of iodine not only reduces the high quantum efficiency and stability of the perovskite nanocrystals but also leads to phase separation during long-term operation. Furthermore, the halogen stoichiometry regulation of mixed halogen perovskite nanocrystals is non-quantitative, often resulting in significant spectral shifts and making fine-tuning of the emission wavelength difficult. Colloidal perovskite nanocrystals tend to aggregate and grow during long-term storage or use due to the dynamic binding of surface ligands, and this process is accelerated by light exposure, leading to an emission peak shift. Therefore, stability is the biggest factor limiting the practical application of perovskite nanocrystals for ultrapure green light emission. This is because formamidinium ions (FA...) + It has more than MA + and Cs + The larger size leads to an increased tilt angle of the Pb-X-Pb bonds, resulting in a distortion of the cubic crystal structure and a smaller band gap in FAPbX3. In 2017, Kumar et al. reported that colloidal FAPbBr3NCs prepared by ligand-assisted redeposition exhibited ultrapure green light emission with an emission center at 530 nm and an FWHM of 21.6 nm, meeting the Rec. 2020 standard. Yu et al. reported a room-temperature ion exchange-mediated self-assembly strategy and prepared FAPbBr3 nanoplates with finely tunable emission in the 525-535 nm range. However, the organic part FA in FAPbBr3 NCs... + This results in worse thermal stability compared to CsPbBr3 NCs. Colloidal FAPbBr3 nanocrystals aggregate and grow during long-term storage or use due to the dynamic binding of surface ligands, and this process is accelerated by light exposure, leading to an emission peak shift. Therefore, stability is the biggest factor limiting the practical application of FAPbBr3 nanocrystals for ultrapure green light emission. Thus, developing stable FAPbBr3 nanocrystal composite materials with ultrapure green light emission is of great significance for achieving Rec. 2020 standard displays. Summary of the Invention

[0004] Based on the shortcomings of the existing technology, the purpose of this invention is to provide a high-stability metal-organic framework / nanocrystalline composite material for backlight display and its preparation method. The metal-organic framework is used to spatially confine and surface protect the perovskite nanocrystals, and combined with the ultra-pure green light emission of perovskite, a wide color gamut backlight display can be achieved.

[0005] To achieve the above objectives, the present invention provides the following solution: One objective of this invention is to provide a highly stable metal-organic framework / nanocrystalline composite material for backlight displays, the composite material being composed of a metal-organic framework and perovskite nanocrystals, expressed as [M(L)]. x (G) y @R, Where M represents zinc ions, manganese ions, or cadmium ions. L is an organic ligand containing a carboxylic acid, and is at least one of 4,4′-biphenyl dicarboxylic acid and 2-amino-[1,1'-biphenyl]-4,4'-dicarboxylic acid, where x = 1~3. G represents a solvent molecule coordinated with a metal ion or located within a crystal channel, and is at least one of water, acetic acid, N,N-dimethylformamide, N,N-dimethylacetamide, and N,N-diethylformamide, where y = 0~6. R represents perovskite nanocrystals, which are at least one of FAPbBr3 and MAPbBr3.

[0006] This invention also provides a method for preparing the aforementioned high-stability metal-organic framework / nanocrystalline composite material. Using anionic metal-organic framework material bio-MOF-100 as a matrix, a two-step sequential deposition method is employed to confine and grow perovskite nanocrystals within the metal-organic framework, thereby preparing the metal-organic framework / nanocrystalline composite material. The method specifically includes the following steps: (1) Dissolve the metal salt and the ligand containing the carboxylic acid group in a solvent to obtain a mixed solution, and then subject the mixed solution to a thermal reaction to obtain a highly stable metal-organic framework material; (2) The prepared metal-organic framework material was immersed in a solution containing Pb. 2+ Pb was obtained by heating and soaking in a lead salt solution followed by centrifugation. 2+ The metal-organic framework crystals were added to an organic solvent containing an organoammonium bromide salt, and after standing, centrifugation was performed to obtain the metal-organic framework / nanocrystalline composite material.

[0007] Preferably, in step (1), the metal salt is zinc nitrate, zinc chloride, cadmium nitrate, or cadmium chloride; The solvent is a mixture of water and an organic solvent, wherein the organic solvent is any one of N,N-dimethylformamide, N,N-dimethylacetamide, or N,N-diethylformamide, and the volume ratio of water to organic solvent is 1:3.

[0008] In this invention, the ligands containing carboxylic acid groups are preferably 4,4′-biphenyl dicarboxylic acid or 2-amino-[1,1'-biphenyl]-4,4'-dicarboxylic acid, with the following structural formula: .

[0009] Furthermore, the molar ratio of metal ions to organic ligands in the metal salt is 1 to 4:1.

[0010] Furthermore, in step (2), during the synthesis of the metal-organic framework and perovskite nanocrystal composite material, the molar ratio of the metal salt and perovskite nanocrystals reacting in the solution is 5:1~3.

[0011] Preferably, the lead salt is one or more of lead nitrate, lead acetate, and lead halide; the added organic ammonium bromide is formamidinium bromide or methylamine bromide.

[0012] Furthermore, in step (1), the conditions for the thermal reaction are heating at 70~80℃ for 1~3 days and then naturally cooling to room temperature; In step (2), the conditions for heating and soaking are: soaking at 60°C for 1 hour; The settling time should be at least 1 hour to ensure that the perovskite nanocrystals grow in the metal-organic framework crystal.

[0013] On the other hand, the present invention also provides the application of the high-stability metal-organic framework / nanocrystalline composite material, or the high-stability metal-organic framework / nanocrystalline composite material prepared by the preparation method, in backlight displays.

[0014] On the other hand, the present invention also provides the application of the high-stability metal-organic framework / nanocrystalline composite material, or the high-stability metal-organic framework / nanocrystalline composite material prepared by the preparation method, in the preparation of liquid crystal display devices.

[0015] The metal-organic framework and perovskite nanocrystal composite material of the present invention has good stability and maintains stable green light output under light or high temperature.

[0016] The specific beneficial effects of this invention are as follows: 1. The synthesis method of the metal-organic framework and perovskite nanocrystal composite material of the present invention is simple, mild, and has a yield of up to 75%-85%. After the metal-organic framework material is synthesized, the confined growth of perovskite nanocrystals in the metal-organic framework material can be obtained at room temperature.

[0017] 2. The photoluminescence emission center of the metal-organic framework and perovskite nanocrystal composite material of the present invention is 530 nm, the full width at half maximum (FWHM) is 25.6 nm, and it emits ultrapure green light.

[0018] 3. The metal-organic framework and perovskite nanocrystal composite material prepared by this invention exhibits a high quantum efficiency of 70.9% and excellent light and thermal stability due to the effective spatial confinement and defect passivation of the metal-organic framework material.

[0019] 4. The liquid crystal display device prepared by this invention, constructed from a metal-organic framework and perovskite nanocrystal composite material emitting ultrapure green light, achieves wide color gamut backlight display, covering 122.9% of the NTSC color gamut and 91.9% of the Rec. 2020 color gamut. Attached Figure Description

[0020] Figure 1 These are TEM images of the metal-organic framework and perovskite nanocrystal composite material of Example 1 in this invention; (a) TEM image, (b) HRTEM image and (c) elemental distribution spectrum.

[0021] Figure 2 These are the ultraviolet-visible absorption and photoluminescence spectra of the metal-organic framework and perovskite nanocrystal composite material of Example 1 of this invention; where (a) represents the ultraviolet-visible absorption spectrum; and (b) represents the Tauc-plot curve.

[0022] Figure 3 This is the ultraviolet-visible absorption and photoluminescence spectrum of the metal-organic framework and perovskite nanocrystal composite material of Example 2 in this invention.

[0023] Figure 4 This is the ultraviolet-visible absorption and photoluminescence spectrum of the comparative sample in this invention.

[0024] Figure 5 These are the CIE coordinates of Embodiments 1 and 2 in this invention in the CIE 1931 color space.

[0025] Figure 6 The photostability of Example 1 and the control sample in this invention; wherein, (a) represents bMOF (a) PL spectrum of FAPbBr3 during 48 hours of continuous blue light irradiation; (b) represents bMOF The change in PL intensity of FAPbBr3 during continuous irradiation for up to 96 hours; (c) represents bMOF The PL spectrum changes of FAPbBr3 under continuous blue light irradiation; (d) represents colloidal FAPbBr3 NCs and bMOF. Comparison of changes in PL intensity during continuous irradiation of FAPbBr3.

[0026] Figure 7 This is a comparison of the thermal stability of Example 1 and the control sample in this invention; wherein, (a) represents bMOF during the heating-cooling cycle. (a) shows the PL spectrum changes of FAPbBr3; (b) represents the bMOF during the heating-cooling cycle. (c) shows the PL intensity change of FAPbBr3; (d) shows the PL spectrum change of FAPbBr3 NCs during the heating-cooling cycle.

[0027] Figure 8 This is a study of a liquid crystal display screen based on a metal-organic framework and perovskite nanocrystal composite material, as described in Example 1 of this invention. (a) MOF Schematic diagram of the structure of a Pe liquid crystal display screen. (b) MOF The white light spectrum of a Pe liquid crystal display. (c) MOF The color gamut coverage of the PE LCD screen. Detailed Implementation

[0028] The technical solution of the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0029] Example 1 Preparation of bMOF The specific synthetic route for FAPbBr3 is as follows: (1) First, prepare a 0.05 mol / L zinc acetate dihydrate solution in N,N-dimethylformamide and a 0.1 mol / L 4,4′-biphenyl dicarboxylic acid solution in N,N-dimethylformamide. Add 5 mL of zinc acetate dihydrate solution and 2.5 mL of 4,4′-biphenyl dicarboxylic acid solution to a 20 mL glass vial, then add 2.5 mL of DMF, 1 mL of anhydrous methanol and 0.25 mL of ultrapure water, and mix well. Then react in an oven at 85 °C for 24 hours. After the reaction is complete, cool to room temperature, centrifuge to separate the metal-organic framework material (bMOF), wash three times with N,N-dimethylformamide, and air dry naturally.

[0030] (2) First, 150 mg of freshly prepared bMOF was soaked in 20 mL of a 0.01 mol / L N,N-dimethylformamide solution of lead nitrate at 60 °C for 1 hour. bMOF was then obtained by centrifugation. Pb 2+The crystals were washed three times each with N,N-dimethylformamide solution and ethanol, and then air-dried. The dried bMOF... Pb 2+ The crystals were added to 15 mL of a 0.1 mol / L solution of formamidinium bromide (FABr) in n-butanol and allowed to stand for 1 hour to ensure the growth of FAPbBr3 nanocrystals in bMOF. The bMOF was then separated by centrifugation. FAPbBr3, expressed as [Zn(BPDC)(DMF)2]@FAPbBr3.

[0031] bMOF Preparation of FAPbBr3 / KSF-PMMA films (where KSF is a commercial red pigment). 1 g of polymethyl methacrylate (PMMA) was dissolved in 10 mL of ethyl acetate with the aid of heating to form a transparent solution. After cooling, 150 mg of bMOF was added. FAPbBr3 powder was stirred vigorously for 12 hours to form a yellow-green suspension. The mixture was then poured smoothly and evenly onto a glass substrate and placed in a fume hood at room temperature. After the ethyl acetate had completely evaporated, bMOF… FAPbBr3 / KSF-PMMA thin films are formed and can be peeled off from the substrate.

[0032] MOF Fabrication of PE liquid crystal display devices. A light-emitting layer consisting of a blue light chip and a light guide plate is placed on top of the reflective layer, and bMOF is then fabricated. A FAPbBr3 / KSF-PMMA thin film is placed on top as a diffuser (light conversion layer) in an LCD device. Finally, a commercial thin-film transistor liquid crystal display (TFT LCD) is placed on the diffuser to fabricate a wide color gamut display device.

[0033] bMOF Transmission electron microscopy (TEM) images of FAPbBr3 visually demonstrate the presence of bMOF. The FAPbBr3 particles contain a large number of nanocrystals with a size of 10-20 nm, and these nanocrystals are uniformly distributed within the particles. Figure 1 a).

[0034] High-resolution TEM was used to accurately identify bMOFs. Nanocrystals in FAPbBr3 particles. For example... Figure 1 As shown in b, the nanocrystals possess high-resolution lattice fringes with a crystal plane spacing of approximately 0.31 nm, and can be classified as having... Pm-3m The characteristic (200) crystal plane of the cubic phase FAPbBr3 in the space group strongly supports the formation of FAPbBr3 nanocrystals within bMOF.

[0035] In addition, bMOF The elemental distribution map of FAPbBr3 crystals shows that the distribution of the characteristic element Zn in bMOF is similar to that of the characteristic elements Pb and Br in FAPbBr3 in each bMOF. The FAPbBr3 particles largely overlap, indicating that the in-situ formed FAPbBr3 nanocrystals are located within the bMOF. Uniformly distributed in FAPbBr3 ( Figure 1 c).

[0036] bMOF The UV-Vis absorption spectrum of FAPbBr3 reveals the characteristic absorption profile of FAPbBr3 nanocrystals, exhibiting absorption for light below 550 nm. The corresponding Tauc-plot curves show the bMOF... The direct band gap of FAPbBr3 is 2.25 eV ( Figure 2 a and 2b). bMOF The wider direct band gap of FAPbBr3 indicates that the guest FAPbBr3 nanocrystals are quantum-confined by bMOF. Under 365 nm excitation, bMOF… The emission center of FAPbBr3 is located at 530 nm, with a full width at half maximum (FWHM) of 25.6 nm, which is very close to the requirements for ultrapure green light in the Rec. 2020 standard. bMOF in solution state... FAPbBr3 exhibits a PLQY of 70.9%, indicating its efficient ability to convert blue light into ultrapure green light.

[0037] Figure 8 Showcasing MOF The white light spectrum of a PE LCD, where blue, green, and red light emission belong to blue LEDs and bMOFs, respectively. FAPbBr3 and KSF, both exhibiting very narrow half-width at half-maximum (WHM). MOF The CIE coordinates of the red, green, and blue primary colors of the PE liquid crystal display are calculated to be (0.688, 0.312), (0.160, 0.753), and (0.157, 0.019) respectively. Due to bMOF... FAPbBr3 emits ultrapure green light, MOF PE LCD screens cover a very wide color gamut in the CIE 1931 color space, reaching 173.5% of the ITU-R BT.709 standard, 122.9% of the NTSC standard, and even 91.9% of the Rec.2020 standard, enabling them to present images more vividly.

[0038] Example 2 Preparation of bMOF The specific synthetic route for MAPbBr3 is as follows: (1) First, prepare a 0.05 mol / L zinc acetate dihydrate solution in N,N-dimethylformamide and a 0.1 mol / L 4,4′-biphenyl dicarboxylic acid solution in N,N-dimethylformamide. Add 5 mL of zinc acetate dihydrate solution and 2.5 mL of 4,4′-biphenyl dicarboxylic acid solution to a 20 mL glass vial, then add 2.5 mL of DMF, 1 mL of anhydrous methanol and 0.25 mL of ultrapure water, and mix well. Then react in an oven at 85 °C for 24 hours. After the reaction is complete, cool to room temperature, centrifuge to separate the metal-organic framework material (bMOF), wash three times with N,N-dimethylformamide, and air dry naturally.

[0039] (2) First, 150 mg of freshly prepared bMOF was soaked in 20 mL of a 0.01 mol / L N,N-dimethylformamide solution of lead nitrate at 60 °C for 1 hour. bMOF was then obtained by centrifugation. Pb 2+ The crystals were washed three times each with N,N-dimethylformamide solution and ethanol, and then air-dried. The dried bMOF... Pb 2+ The crystals were added to 15 mL of a 0.1 mol / L solution of methylamine bromide (MABr) in n-butanol and allowed to stand for 1 hour to ensure the growth of MAPbBr3 nanocrystals in bMOF. The bMOF was then separated by centrifugation. MAPbBr3, expressed as [Zn(BPDC)(DMF)2]@MAPbBr3.

[0040] bMOF Preparation of MAPbBr3 / KSF-PMMA films. 1 g of polymethyl methacrylate (PMMA) was dissolved in 10 mL of ethyl acetate with the aid of heating to form a transparent solution. After cooling, 150 mg of bMOF was added. MAPbBr3 powder was vigorously stirred for 12 hours to form a yellow-green suspension. The resulting mixture was then poured smoothly and evenly onto a glass substrate and placed in a fume hood at room temperature. After the ethyl acetate had completely evaporated, bMOF… A MAPbBr3 / KSF-PMMA thin film is formed and can be peeled off from the substrate.

[0041] MOF Fabrication of PE liquid crystal display devices. A light-emitting layer consisting of a blue light chip and a light guide plate is placed on top of the reflective layer, and bMOF is then fabricated. A MAPbBr3 / KSF-PMMA thin film is placed on top as a diffuser (light conversion layer) in an LCD device. Finally, a commercial thin-film transistor liquid crystal display (TFT LCD) is placed on the diffuser to fabricate a wide color gamut display device.

[0042] bMOF The UV-Vis absorption spectrum of MAPbBr3 reveals the characteristic absorption profile of MAPbBr3 nanocrystals, showing a significant blue shift compared to FAPbBr3, and exhibiting absorption for light below 530 nm. The corresponding Tauc-plot curves show that bMOF The direct band gap of MAPbBr3 is 2.34 eV ( Figure 3 bMOF The wider direct band gap of MAPbBr3 indicates that the guest MAPbBr3 nanocrystals are subject to quantum confinement by bMOF.

[0043] From the perspective of backlight display, the CIE coordinates of the green light component in the ITU-R BT.709 standard, NTSC standard, and Rec. 2020 standard are located at (0.300, 0.600), (0.210, 0.710), and (0.170, 0.797), respectively. Figure 5 The Rec. 2020 standard requires ultrapure green light emission, demanding that the emission of the conversion material under green light be in the 525-535 nm range, with a free-wavelength (FWHM) of less than 25 nm. Core-shell II-VI group inorganic semiconductor quantum dots CdSe / ZnS / CdSZnS, due to their relatively wide FWHM (25-35 nm), have CIE coordinates of (0.19, 0.71), very close to the NTSC standard, but far from the Rec. 2020 standard. CsPbBr3 NCs and MAPbBr3 NCs synthesized by thermal injection or ligand-assisted redeposition methods generally have a PL emission center less than 520 nm, deviating from the ultrapure green light range.

[0044] The CIE coordinates of MAPbBr3 NCs encapsulated with UV-curable adhesive (NOA) are (0.084, 0.732); the CIE coordinates of CsPbBr3 NCs post-treated with ZnBr2 are (0.09, 0.77); and the CIE coordinates of aluminum-doped CsPbBr3 NCs are (0.08, 0.77). Their CIE coordinates in the CIE 1931 color space are located in the bluer region, far from ultrapure green light. Due to the same luminescent center in MAPbBr3 NCs, bMOF... The CIE coordinates of MAPbBr3 are (0.110, 0.757), which also deviate from ultrapure green light. FAPbBr3 NCs with smaller band gaps are more promising materials for ultrapure green downconversion. For example, by carefully controlling the thickness of FAPbBr3 nanoplates, its PL emission center can be tuned to 530 nm, and its FWHM is 25.3 nm, which is very close to the Rec. 2020 standard.

[0045] Similarly, bMOF The PL emission center of FAPbBr3 is located at 530 nm, the FWHM is 25.6 nm, and the CIE coordinates are (0.197, 0.753), which are very close to the CIE coordinates of ultrapure green light in the Rec. 2020 standard. Figure 5 Therefore, bMOF FAPbBr3 compared to bMOF MAPbBr3 has advantages as an ultrapure green light downconversion material and has greater potential in realizing wide color gamut backlight display applications.

[0046] Comparative Example 1 Colloidal FAPbBr3 NCs were synthesized via ligand-assisted redeposition as a control. First, 0.1 mmol of FABr and 0.1 mmol of PbBr2 were dissolved in 1 mL of DMF, and 200 mL of oleic acid and 40 mL of oleylamine were added to prepare a precursor solution. 300 mL of the precursor solution was then injected into 9 mL of chloroform with vigorous stirring. The mixed solution rapidly changed from colorless and transparent to yellow-green, indicating the successful synthesis of FAPbBr3 NCs. To purify the FAPbBr3 NCs, the obtained mixed solution was added to 2.25 mL of acetonitrile and 2.25 mL of toluene, centrifuged, and the supernatant was discarded. The precipitate was dispersed in toluene for later use.

[0047] Colloidal FAPbBr3 NCs were synthesized via ligand-assisted redeposition. Their light absorption was cut off at 545 nm, and they emitted bright green light with an emission center at 532 nm upon excitation at 365 nm, with an FWHM of 19.0 nm. Figure 4 The similar absorption and emission behaviors indicate that FAPbBr3 was spatially confined by bMOF during its in-situ growth in bMOF and ultimately existed in the form of nanocrystals, exhibiting emission characteristics of FAPbBr3 NCs.

[0048] For bMOF Time-resolved dynamic spectral characterization of FAPbBr3 was performed, with colloidal FAPbBr3 NCs used as a comparison. In the double exponential function fitting, the fast fluorescence lifetime (τ1) and slow fluorescence lifetime (τ2) can be attributed to intrinsic radiative recombination and surface defect-assisted recombination, respectively. The fitting results indicate that bMOF The τ² of FAPbBr3 is 58.8 ns, which is much higher than that of colloidal FAPbBr3 NCs, proving that bMOF In FAPbBr3, the host bMOF effectively passivates the surface defects of the guest FAPbBr3 NCs. The photostability test involved placing the sample under a 450 nm blue LED lamp for extended periods of irradiation, with a blue light power density of 100 mW / cm². 2 Simultaneously, its PL spectrum is monitored. For example... Figure 6 As shown in a, bMOF The shape of the photoluminescence (PL) spectrum of FAPbBr3 did not change significantly during 48 hours of continuous blue light irradiation, and the position of its PL peak did not shift significantly. Furthermore, bMOF... The PL intensity of FAPbBr3 showed only minor fluctuations during a continuous irradiation process of up to 96 hours, and it maintained more than 97% of its initial intensity emission, demonstrating its excellent blue light irradiation stability. Figure 6 b). In contrast, the PL emission of colloidal FAPbBr3 NCs exhibits rapid quenching ( Figure 6 c). For example Figure 6 As shown in Figure d, the photosynthetic intensity (PL) of colloidal FAPbBr3 NCs is sharply quenched with increasing blue light irradiation time, and after 4 hours of irradiation, its PL intensity has dropped to less than 20% of its initial PL intensity. The unsatisfactory photosynthetic stability of colloidal FAPbBr3 NCs severely limits its practical applications.

[0049] The thermal stability of the sample was studied by subjecting it to a heating-cooling cycle from 25°C to 120°C and then from 120°C to 25°C. Figure 7 a and Figure 7 b reflects bMOF The changes in the PL spectrum and PL intensity of FAPbBr3 during a heating-cooling cycle. As temperature increases, bMOF... The PL intensity of FAPbBr3 monotonically decreases, retaining 56%, 39%, and 16% of its initial PL intensity at 60°C, 80°C, and 120°C, respectively. Furthermore, as the temperature gradually recovers to 25°C, bMOF... The thermal recovery strength of FAPbBr3 recovered to 86% of its initial strength, demonstrating excellent thermal recovery stability.

[0050] In contrast, colloidal FAPbBr3 NCs exhibited more significant fluorescence thermal quenching during heating, with almost complete PL quenching at 120°C, demonstrating significantly worse performance than bMOF. Thermal stability of FAPbBr3 Figure 7 (cd). It is noteworthy that the PL strength of colloidal FAPbBr3 NCs did not recover significantly with decreasing temperature, indicating that the weakening of PL during heating of FAPbBr3 NCs was not solely due to thermal quenching, but also accompanied by severe thermal decomposition, further demonstrating the influence of the host-guest system on bMOFs. Improved thermal stability of FAPbBr3.

Claims

1. A highly stable metal-organic framework / nanocrystalline composite material for backlight displays, characterized in that, This composite material consists of a metal-organic framework and perovskite nanocrystals, and its formula is [M(L)]. x (G) y @R, Where M represents zinc ions, manganese ions, or cadmium ions. L is an organic ligand containing a carboxylic acid, and is at least one of 4,4′-biphenyl dicarboxylic acid and 2-amino-[1,1'-biphenyl]-4,4'-dicarboxylic acid, where x = 1~3. G represents a solvent molecule coordinated with a metal ion or located within a crystal channel, and is at least one of water, acetic acid, N,N-dimethylformamide, N,N-dimethylacetamide, and N,N-diethylformamide, where y = 0~6. R represents perovskite nanocrystals, which are at least one of FAPbBr3 and MAPbBr3.

2. A method for preparing the highly stable metal-organic framework / nanocrystalline composite material according to claim 1, characterized in that, Includes the following steps: (1) Dissolve the metal salt and the ligand containing the carboxylic acid group in a solvent to obtain a mixed solution, and then subject the mixed solution to a thermal reaction to obtain a highly stable metal-organic framework material; (2) The prepared metal-organic framework material was immersed in a solution containing Pb. 2+ Pb was obtained by heating and soaking in a lead salt solution followed by centrifugation. 2+ The metal-organic framework crystals were added to an organic solvent containing an organoammonium bromide salt, and after standing, centrifugation was performed to obtain the metal-organic framework / nanocrystalline composite material.

3. The method for preparing the highly stable metal-organic framework / nanocrystalline composite material according to claim 2, characterized in that, In step (1), the metal salt is zinc nitrate, zinc chloride, cadmium nitrate, or cadmium chloride; The solvent is a mixture of water and an organic solvent.

4. The method for preparing the highly stable metal-organic framework / nanocrystalline composite material according to claim 2, characterized in that, In step (2), during the synthesis of the metal-organic framework and perovskite nanocrystal composite material, the molar ratio of the metal salt and perovskite nanocrystals reacting in the solution is 5:1 to 3.

5. The method for preparing the highly stable metal-organic framework / nanocrystalline composite material according to claim 2, characterized in that, In step (2), the lead salt is at least one of lead nitrate, lead acetate, and lead halide; The added organic ammonium bromide is formamidinium bromide or methylamine bromide.

6. The method for preparing the highly stable metal-organic framework / nanocrystalline composite material according to claim 2, characterized in that, In step (1), the thermal reaction is carried out at 70-80°C for 1-3 days, followed by natural cooling to room temperature. In step (2), the conditions for heating and soaking are: soaking at 60°C for 1 hour; The resting time should be at least 1 hour.

7. The application of the high-stability metal-organic framework / nanocrystalline composite material according to claim 1, or the high-stability metal-organic framework / nanocrystalline composite material prepared by any of the preparation methods according to claims 2 to 5, in backlight displays.

8. The application of the high-stability metal-organic framework / nanocrystalline composite material according to claim 1, or the high-stability metal-organic framework / nanocrystalline composite material prepared by any of the preparation methods according to claims 2 to 5, in the preparation of liquid crystal display devices.

Images