Perovskite nanocrystal fluorescent material, and preparation method and application thereof

Abstract

The application discloses a kind of perovskite nanocrystal fluorescent materials, including micro / intermediate pore template, matrix and perovskite nanocrystal, wherein, the micro / intermediate pore template inner wall is attached matrix, perovskite nanocrystal is grown on the matrix surface, and the melting point of the matrix is higher than the melting point of perovskite nanocrystal.The perovskite nanocrystal fluorescent material has higher luminous efficiency and higher luminous stability.The application also discloses a kind of perovskite nanocrystal fluorescent material preparation method.The preparation method provided by the application does not need organic solvent, and the preparation process is more green and environmental protection.The melting crystallization method used by the application is simple in process and strong in controllability, and is suitable for large-scale preparation of perovskite nanocrystal.The application also discloses a kind of perovskite nanocrystal fluorescent material application.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of perovskite nanocrystals, and particularly relates to a perovskite nanocrystal fluorescent material, a preparation method thereof and application thereof. BACKGROUND

[0002] The perovskite nanocrystal fluorescent material is a new emerging semiconductor material, which has high luminous efficiency, narrow luminous peak width, tunable luminous wavelength and large defect tolerance, etc., which makes the perovskite nanocrystal applicable to high-quality display and light-emitting devices, and has great commercial application value.

[0003] A Chinese patent with the publication number CN 109810703A discloses a room temperature preparation method of CsPbBr3 quantum dots, which comprises: providing a cesium source solution, a lead source solution and a polar solvent in which cationic surfactant is dispersed, mixing the three solutions, adding the obtained crude liquid of quantum dots into ethyl acetate for dispersion, and then performing separation and purification to obtain a solution containing CsPbBr3 quantum dots. The CsPbBr3 quantum dots prepared by the method exist in a solution state, and the raw materials directly react at room temperature in the solution, and the stability of the obtained product is limited. Therefore, how to make the perovskite nanocrystal fluorescent material maintain high luminous efficiency while improving the luminous stability of the perovskite nanocrystal fluorescent material has become a problem to be solved.

[0004] At present, the preparation method of the perovskite nanocrystal fluorescent material is usually a liquid phase method assisted by organic solvents. These organic solvents usually have toxicity, and the uniformity of the liquid phase reaction is difficult to control, which is not conducive to the green synthesis and large-scale preparation of the perovskite nanocrystal, and limits its development in actual commercial lighting and display devices.

[0005] The melt crystallization method is a commonly used method for large-scale preparation of semiconductor materials (such as monocrystalline silicon, germanium, etc.). In the melt crystallization process, a molten liquid is first obtained by high temperature, and when the molten liquid is cooled to the semiconductor solidification point, the target product semiconductor is supercooled and crystallized in the molten liquid. The melt crystallization method has the advantages of not needing organic solvent assistance, simple process, strong controllability of the crystallization process, etc., and is suitable for large-scale preparation of semiconductor materials.

[0006] However, two technical problems need to be solved for applying the melt crystallization method to large-scale preparation of perovskite nanocrystals: 1. The semiconductor material prepared by the melt crystallization method is usually a large-size wafer, rather than a nanocrystal with a size of nanometers. 2. The crystal formed in the melt crystallization process lacks a surface passivation mechanism. The luminescent properties of the perovskite nanocrystal are very sensitive to surface defects. Surface defects often form non-radiative recombination centers of carriers, thereby damaging the luminescent efficiency and stability of the perovskite nanocrystal. Therefore, an effective surface passivation mechanism needs to be introduced in the melt crystallization process to improve the luminescent efficiency and stability of the perovskite nanocrystal.

[0007] Therefore, it is an urgent technical problem to develop a melt crystallization method suitable for perovskite nanocrystal fluorescent materials and a preparation method thereof. SUMMARY

[0008] The application provides a perovskite nanocrystal fluorescent material with high luminescent efficiency and high luminescent stability.

[0009] The application provides a perovskite nanocrystal fluorescent material, which comprises a micro / interporous template, a matrix and perovskite nanocrystals, wherein the inner wall of the micro / interporous template is provided with the matrix, the perovskite nanocrystals are stacked with the matrix lattice to form a passivation interface, and the melting point of the matrix is higher than the melting point of the perovskite nanocrystals.

[0010] The matrix provided by the application has a high melting point, and therefore has a high lattice energy and a stable structure which is difficult to be damaged. The matrix is arranged on the inner wall of the micro / interporous template, thereby playing a role of a reinforcing rib for the micro / interporous template and improving the structural strength of the micro / interporous template, so as to facilitate subsequent production, processing and manufacturing. On the other hand, the perovskite nanocrystal / matrix interface is formed on the surface of the matrix, that is, a lattice stacking structure is formed with the perovskite nanocrystals. The structural stability of the perovskite nanocrystals is improved under the protection of the matrix. In addition, the perovskite nanocrystal / matrix interface reduces the defects on the surface of the perovskite nanocrystals, realizes surface passivation and improves the luminescent efficiency.

[0011] Further, the matrix is one or any combination of a metal oxide, a metal fluoride, a phosphate and a halide tellurium lead.

[0012] Further preferably, the metal oxide is BaO, CaO or Al2O3, the metal fluoride is CaF2 or BaF2, the phosphate is Pb3(PO4)2 or AlPO4, and the halide tellurium lead is Pb3TeO4X2, wherein X is Br, I or Cl.

[0013] Further, the melting point of the matrix is greater than 570 DEG C, and the melting point of the perovskite nanocrystal is not higher than 570 DEG C.

[0014] The matrix provided by the present application has a higher melting point than the perovskite nanocrystal, a larger lattice energy, and a crystal form that is difficult to be destroyed, thus producing a similar "reinforcing rib" effect when attached to the inner wall of the micro / mesoporous template, and having a higher structural stability. The perovskite nanocrystal fluorescent material containing the matrix also has a higher structural stability through the matrix with high structural stability.

[0015] Further, the perovskite nanocrystal includes a cesium halide perovskite nanocrystal or a mixed halide perovskite nanocrystal.

[0016] Further, the cesium halide perovskite nanocrystal has a nanocrystal structure of a perovskite structure ABX3, wherein the molar ratio of A, B and X is 1:1:3, and A is Cs, B is Pb, Sn or Cu, and X is Cl, Br or I.

[0017] Further, the mixed halide perovskite nanocrystal has a nanocrystal structure of a perovskite structure ABX y X' 3-y wherein the molar ratio of A, B, X and X' is 1:1:y:3-y, wherein 0<y<3, and A is Cs, B is Pb, Sn or Cu, and X and X' are different and each independently is Cl, Br or I.

[0018] Further, the mass ratio of the matrix and the perovskite nanocrystal is a, and 0.02

[0019] Further, the micro / mesoporous template is a microporous material and / or a mesoporous material. By adsorbing the matrix on the inner wall of the pores of the micro / mesoporous template, the size of the perovskite crystal grown in the template channel is effectively controlled through the space confinement effect of the micro / mesoporous template, and finally the nanocrystal is obtained, which can continuously adsorb a large amount of perovskite nanocrystals and improve the luminous quantity of the perovskite nanocrystal fluorescent material.

[0020] Further preferably, the microporous material is a microporous molecular sieve, microporous silica, microporous titanium dioxide, microporous aluminum oxide, microporous transition metal oxide, microporous sulfide, microporous silicate, microporous aluminate or microporous transition metal nitride.

[0021] Further preferably, the mesoporous material is a mesoporous molecular sieve, mesoporous silica, mesoporous titanium dioxide, mesoporous aluminum oxide, mesoporous carbon, mesoporous transition metal oxide, mesoporous sulfide, mesoporous silicate, mesoporous aluminate or mesoporous transition metal nitride.

[0022] The micro / mesoporous template can also be obtained by mixing the microporous material and the mesoporous material.

[0023] The application further provides a preparation method of the perovskite nanocrystal fluorescent material, comprising:

[0024] (1) mixing perovskite nanocrystal precursors, matrix precursors and the micro / mesoporous template to obtain a mixture;

[0025] (2) calcining the mixture obtained in step (1) under a condition higher than the melting point of the perovskite nanocrystal and lower than the failure temperature of the micro / mesoporous template, and then cooling to room temperature to obtain the perovskite nanocrystal fluorescent material.

[0026] The perovskite nanocrystal precursors and the matrix precursors are melted and reacted by high-temperature calcination to obtain the perovskite nanocrystal and the matrix. Since the calcination temperature is lower than the failure temperature of the micro / mesoporous template, i.e. the temperature corresponding to the collapse of the pores of the micro / mesoporous template, the pores of the template are not collapsed during the whole calcination process. The molten perovskite nanocrystal and the matrix are adsorbed into the spatial pores of the micro / mesoporous template through the adsorption capacity of the pore structure of the micro / mesoporous template. Then the calcination temperature is lowered. Since the solidification point of the matrix is higher than the solidification point of the perovskite nanocrystal, the matrix is first formed on the inner wall of the spatial pores of the micro / mesoporous template. As the temperature is lowered to the solidification point of the perovskite, the perovskite will crystallize and grow on the surface of the matrix to form a perovskite / matrix interface due to the principle of minimum energy. The perovskite / matrix interface can passivate the surface defects of the perovskite nanocrystal, thereby effectively improving the luminescent performance of the perovskite nanocrystal. The luminescent stability of the perovskite nanocrystal is improved due to the support of the lattice-stable matrix. Since the perovskite nanocrystal grows in the spatial pores of the micro / mesoporous template, the size of the perovskite nanocrystal is limited, and therefore a suitable grain size and a large amount of perovskite nanocrystal are obtained, thereby ensuring good luminescent performance.

[0027] Further, the calcination process of step (2) sequentially comprises a heating and melting stage, a heat preservation and filling stage and a cooling and growth stage.

[0028] When in the heating and melting stage and the calcination temperature is higher than the melting point of the perovskite nanocrystal, the perovskite nanocrystal precursors and the matrix precursors form a molten liquid.

[0029] When in the heat preservation and filling stage and the calcination temperature is lower than the failure temperature of the micro / mesoporous template, the molten liquid is filled into the pore structure of the micro / mesoporous template.

[0030] When in the cooling and growth stage, the matrix is first formed in the micro / mesoporous template, and then the perovskite nanocrystal is heterogeneously grown on the surface of the matrix, thereby obtaining the perovskite nanocrystal fluorescent material.

[0031] Further, the perovskite nanocrystal precursor is a cesium halide perovskite nanocrystal precursor or a mixed halide perovskite nanocrystal precursor.

[0032] Further, the cesium halide perovskite nanocrystal precursor is a precursor of ABX3 perovskite structure, wherein the molar ratio of A, B and X is 1:1:3, and A is Cs, B is Pb, Sn or Cu, and X is Cl, Br or I.

[0033] The CsPbX perovskite nanocrystal precursor comprises a Cs source precursor, a Pb source precursor and an X source precursor.

[0034] The CsSnX perovskite nanocrystal precursor comprises a Cs source precursor, a Sn source precursor and an X source precursor.

[0035] The CsCuX perovskite nanocrystal precursor comprises a Cs source precursor, a Cu source precursor and an X source precursor.

[0036] The X source precursor is a halide source precursor.

[0037] Further, the mixed halide perovskite nanocrystal precursor is a precursor of ABX y X' 3-y perovskite structure, wherein the molar ratio of A, B, X and X' is 1:1:y:3-y, wherein 0<y<3, and A is Cs, B is Pb, Sn or Cu, and X and X' are different and each independently is Cl, Br or I.

[0038] The CsPbX X' perovskite nanocrystal precursor comprises a Cs source precursor, a Pb source precursor, an X source precursor and an X' source precursor.

[0039] The CsSnX X' perovskite nanocrystal precursor comprises a Cs source precursor, a Sn source precursor, an X source precursor and an X' source precursor.

[0040] The CsCuX X' perovskite nanocrystal precursor comprises a Cs source precursor, a Cu source precursor, an X source precursor and an X' source precursor.

[0041] The X source precursor and the X' source precursor are different halide source precursors.

[0042] Further, the Cs source precursor is one or more of cesium halide, cesium carbonate;

[0043] The Pb source precursor is one or more of lead halide, lead acetate;

[0044] The Sn source precursor is tin halide;

[0045] The Cu source precursor is copper halide.

[0046] The halogen source precursor is one or more of cesium halide, lead halide, zinc halide, potassium halide, sodium halide, lithium halide, ammonia halide, calcium halide, strontium halide, barium halide.

[0047] Further, the matrix precursor is one or more of nitrate, nitrite, telluride, hydrogen phosphate.

[0048] Further, the nitrate is Ce(NO3)3, the nitrite is Ba(NO2)2 or Ca(NO2)2, the telluride is TeO2, TeCl4 or TeBr4, and the hydrogen phosphate is Al(H2PO4)3.

[0049] The matrix precursor provided by the application has a melting point lower than the calcination temperature, or the co-melting point of the matrix precursor and the perovskite nanocrystal precursor after adding a fluxing agent is lower than the calcination temperature, so that at the calcination temperature, the matrix precursor and the perovskite nanocrystal precursor are co-melted and react to obtain a molten matrix and a molten perovskite nanocrystal, respectively, so that the molten matrix and the molten perovskite nanocrystal can enter the pores of the micro / mesoporous template, and the matrix has a higher melting point than the perovskite nanocrystal, so that the matrix can play a role of reinforcing the structure of the rib.

[0050] Further, in step (1), the low-melting-point salt in the precursor can be used as a fluxing agent, and the fluxing agent can react with other salts in the precursor and has a lower melting point than the other salts.

[0051] Further, the melting point of the matrix is greater than the failure temperature of the micro / mesoporous template and the melting point of the perovskite nanocrystal.

[0052] Further, the melting point of the matrix is greater than the melting point of the matrix precursor.

[0053] The application also provides application of the perovskite nanocrystal fluorescent material in a perovskite diffusion plate, a light-emitting device, a wavelength conversion film, a quantum dot film, a quantum dot light-emitting diode or a master batch.

[0054] Compared with the prior art, the application has the following beneficial effects:

[0055] (1) The application improves the structural stability of the micro / mesoporous template by attaching a matrix with relatively stable lattice to the inner wall of the micro / mesoporous template, and heterogeneously grows perovskite nanocrystals on the crystal surface of the matrix, thereby stacking perovskite nanocrystals on the matrix to realize the passivation of surface defects of perovskite nanocrystals while improving the stability of perovskite nanocrystals, and further improving the luminous quantity and luminous stability of perovskite nanocrystal fluorescent materials. Due to the use of the micro / mesoporous template, a growth space is provided for the matrix and perovskite nanocrystals, and the grain size of the perovskite nanocrystals is limited, forming nanocrystals of the order of magnitude, so that a suitable grain size and a large amount of perovskite nanocrystals are obtained to ensure the luminous capacity of perovskite nanocrystal fluorescent materials.

[0056] (2) The application obtains a matrix with a relatively high melting point and perovskite nanocrystals with a relatively low melting point by co-melting and reaction of the matrix precursor and the perovskite nanocrystal precursor through a melt crystallization method. In the calcination process, the pores of the micro / mesoporous template are avoided from collapsing, so that the melted matrix and perovskite nanocrystals can continuously enter the pores of the micro / mesoporous template. In the cooling process, the matrix is first formed on the inner wall of the micro / mesoporous template, and then the perovskite nanocrystals are heterogeneously grown on the crystal surface of the matrix when the temperature drops to the melting point temperature of the perovskite nanocrystals, so as to finally form perovskite nanocrystal fluorescent materials. The preparation method provided by the application does not require organic solvents, and the preparation process is more green and environmentally friendly. The melt crystallization method adopted by the application is simple and controllable, and is suitable for large-scale preparation of perovskite nanocrystals.

[0057] (3) The perovskite nanocrystal fluorescent material provided by the application can be applied to perovskite diffusion plates, light-emitting devices, wavelength conversion films, quantum dot films, quantum dot light-emitting diodes and master batches, and realizes the industrialization of downstream products. BRIEF DESCRIPTION OF DRAWINGS

[0058] Figure 1 A structure schematic diagram of the perovskite nanocrystal fluorescent material provided by the embodiment of the application is shown in the figure.

[0059] Figure 2 A preparation method flowchart of the perovskite nanocrystal fluorescent material provided by the embodiment of the application is shown in the figure.

[0060] Figure 3 X-ray diffraction patterns of the samples prepared in Examples 1-4 and Comparative Example 1 of the application are shown in the figure.

[0061] Figure 4 PLQY test results of the samples prepared in Examples 1-4 and Comparative Example 1 of the application are shown in the figure.

[0062] Figure 5 The ratio of the luminous intensity of the samples prepared in Examples 1-4 and Comparative Example 1 of the application to the initial intensity after blue light aging test is shown in the figure.

[0063] Figure 6 A transmission electron microscope test image of the sample prepared for the embodiment 1 of the present application;

[0064] Figure 7 An X-ray diffraction image of the sample prepared for the embodiment 7 of the present application;

[0065] Figure 8 A transmission electron microscope test image of the sample prepared for the comparative example 2;

[0066] Figure 9 A luminescence intensity histogram of the sample prepared for the comparative example 3 with the mass ratio of CaF / CsPbBr3 being 0.02, 0.2 and 10 respectively. DETAILED DESCRIPTION

[0067] The present application is further described in conjunction with the specific embodiments, it should be noted that the embodiments are only to help understand the present application, and should not be regarded as a specific limitation on the present application.

[0068] The present application provides a perovskite nanocrystal fluorescent material, as shown in the formula (I), comprising perovskite nanocrystals, a matrix and a micro / mesoporous template, wherein the perovskite nanocrystals are heterogeneously grown at the interface of the matrix to form a perovskite / matrix interface, which is manifested as the lattice stacking of the perovskite nanocrystals and the matrix, and the matrix is attached to the inner wall of the micro / mesoporous template. Figure 1 The present application provides a perovskite nanocrystal fluorescent material, as shown in the formula (I), comprising perovskite nanocrystals, a matrix and a micro / mesoporous template, wherein the perovskite nanocrystals are heterogeneously grown at the interface of the matrix to form a perovskite / matrix interface, which is manifested as the lattice stacking of the perovskite nanocrystals and the matrix, and the matrix is attached to the inner wall of the micro / mesoporous template.

[0069] The present application further provides a preparation method of the perovskite nanocrystal fluorescent material, as shown in the formula (II), comprising: Figure 2 The present application provides a perovskite nanocrystal fluorescent material, as shown in the formula (I), comprising perovskite nanocrystals, a matrix and a micro / mesoporous template, wherein the perovskite nanocrystals are heterogeneously grown at the interface of the matrix to form a perovskite / matrix interface, which is manifested as the lattice stacking of the perovskite nanocrystals and the matrix, and the matrix is attached to the inner wall of the micro / mesoporous template.

[0070] (1) forming a precursor mixture by mixing perovskite nanocrystal precursors and matrix precursors, and mixing and grinding the precursor mixture and the micro / mesoporous template to obtain a mixture;

[0071] (2) calcining the mixture, and in the heating process, the molten liquid formed by the perovskite nanocrystal precursors and the matrix precursors enters the micro / mesoporous template, and in the cooling process, the matrix is first formed in the micro / mesoporous template, and then the perovskite nanocrystals are heterogeneously grown on the crystal surface of the matrix, thereby obtaining the perovskite nanocrystal fluorescent material. Figure 2 As can be seen from the formula (II), the perovskite nanocrystals and the matrix grow in the template, i.e., the micro / mesoporous template

[0072] In the embodiments of the present application, the calcination temperature needs to be higher than the melting point of the perovskite to obtain the melt, for example, the melting point of the all-inorganic lead halide perovskite CsPbX3 (X = Br, I, Cl) is <570℃, thus the calcination temperature is kept >570℃. On the other hand, the calcination temperature needs to be lower than the failure temperature of the growth template to ensure that the template can provide effective confinement space for the melt to obtain nanoscale size control of the final product, and due to the adsorption of the template, the melt can continue to be filled into the pore structure of the template. The failure temperature of different growth templates is different, for example, the pore of mesoporous silica (i.e. mesoporous silica) collapses at a temperature higher than 600℃, thus the calcination temperature needs to be <600℃ when mesoporous silica is used as the growth template of perovskite nanocrystals. For another example, mesoporous titanium dioxide starts to collapse at 800℃, thus the calcination temperature needs to be <800℃ when mesoporous titanium dioxide is used as the growth template of perovskite nanocrystals.

[0073] In the present application, the calcination process is divided into three stages: heating stage, holding stage, and cooling stage. In the heating stage, the perovskite precursor first reacts to form CsPbX3 crystals, and when the calcination temperature gradually exceeds the melting point of CsPbX3, these precursors will melt into a melt. In the holding stage, the calcination temperature is lower than the failure temperature of the growth template, and due to the adsorption of the growth template, the melt will be filled into the pore structure of the growth template. In the cooling stage, since the matrix has a higher solidification temperature than the perovskite, the matrix is formed in the growth template before the perovskite, and then the perovskite crystals grow heterogeneously on the surface of the matrix crystals to form nanocrystals.

[0074] Example 1

[0075] The matrix prepared in this example is BaO, and the perovskite nanocrystals prepared are CsPbBr3 perovskite nanocrystals.

[0076] 5mmol of CsBr, 5mmol of PbBr2, 5mmol of Ba(NO2)2, and 2g of mesoporous silica were ground and mixed to obtain a solid mixed powder,

[0077] The above mixed powder was placed in a muffle furnace and heated from room temperature to 585℃, and then continuously heated at 585℃ for 40 minutes, and then naturally cooled to room temperature to take out the sample powder.

[0078] During the calcination process, Ba(NO2)2 is heated and melted and adsorbed into the mesoporous silica channels, and is further heated and decomposed into BaO as the matrix of perovskite nanocrystals. The melting point of Ba(NO2)2 is 267℃, and the melting point of BaO is 1920℃. The CsBr and PbBr2 melt and react to form CsPbBr3 perovskite nanocrystals

[0079] Experimental analysis: X-ray diffraction was performed on the extracted sample powder, such as... Figure 3 As shown in (a), the sample contains not only the CsPbBr3 phase but also the BaO phase. In contrast, the X-ray diffraction pattern of the powder sample sintered without the addition of Ba(NO2)2 shows only the CsPbBr3 phase, with no BaO phase present. Figure 3 As shown in (e). X-ray diffraction confirmed the coexistence of the matrix BaO and CsPbBr3 nanocrystals in this embodiment.

[0080] The fluorescence quantum yield (PLQY) of the powder obtained from the above sintering was tested. See the detailed spectrum below. Figure 4 The PLQY of this sample was 42%. In contrast, the PLQY of the powder sample sintered without the addition of Ba(NO2)2 was 10%. The PLQY test results indicate that the presence of the matrix BaO can improve the luminescence efficiency of CsPbBr3 nanocrystals, and verify that the matrix BaO can passivate the surface of CsPbBr3 nanocrystals.

[0081] The stability of the powder obtained from the above sintering under strong blue light irradiation was tested. See the specific spectra below. Figure 5 350mW / cm 2 After 100 hours of continuous irradiation with blue light (450 nm), the luminescence intensity of the powder remained at 78% of its original intensity. In contrast, the luminescence intensity of the powder sample sintered without the addition of Ba(NO2)2 decreased to 40% of its initial intensity after 100 hours under the same blue light testing conditions. The blue light stability demonstrates that the BaO matrix is ​​beneficial for improving the photostability of CsPbBr3.

[0082] The powder obtained from the above sintering was tested using a transmission electron microscope, such as... Figure 6 As shown, the mesoporous silica channel structure is well maintained, and the perovskite nanocrystals and the matrix are stacked on each other.

[0083] Example 2

[0084] The matrix obtained in this embodiment is Pb3TeO4X2, and the perovskite nanocrystals obtained are CsPbBr3 perovskite nanocrystals.

[0085] 5 mmol CsBr, 7 mmol PbBr2, 2 mmol TeBr4, and 2 g mesoporous silica were ground and mixed to obtain a solid mixed powder.

[0086] The above mixed powder was placed in a muffle furnace and heated from room temperature to 585°C, and heated at 585°C for 40 minutes. Then it was allowed to cool naturally to room temperature and the sample powder was removed.

[0087] During calcination, the oxygen adsorbed by the mesoporous silica and TeBr4 react together with PbBr2 to form Pb3TeO4Br2, which serves as the matrix for perovskite nanocrystals. The melting point of TeBr4 is 380℃, the melting point of PbBr2 is 373℃, and the melting point of Pb3TeO4Br2 is >700℃.

[0088] Experimental analysis: The powder obtained from the above sintering was subjected to X-ray diffraction. See the detailed spectra below. Figure 3 (b) shows that the sample contains not only the CsPbBr3 phase but also the Pb3TeO4Br2 phase. In contrast, the X-ray diffraction pattern of the powder sample sintered without the addition of TeBr4 shows only the CsPbBr3 phase and no Pb3TeO4Br2 phase (see detailed pattern). Figure 3 (e). X-ray diffraction confirmed the coexistence of matrix Pb3TeO4Br2 and CsPbBr3 nanocrystals in this embodiment.

[0089] The fluorescence quantum yield (PLQY) of the powder obtained from the above sintering was tested. See the detailed spectrum below. Figure 4 The PLQY of this sample was 52%. In contrast, the PLQY of the powder sample sintered without the addition of TeBr4 was 10%. The PLQY test results indicate that the presence of the matrix Pb3TeO4Br2 can improve the luminescence efficiency of CsPbBr3 nanocrystals, verifying that the matrix Pb3TeO4Br2 can passivate the surface of CsPbBr3 nanocrystals.

[0090] The stability of the powder obtained by sintering in this embodiment under strong blue light irradiation was tested. See the specific spectra below. Figure 5 350mW / cm 2 After 100 hours of continuous irradiation with blue light (450 nm), the luminescence intensity of the powder remained at 85% of its original intensity. In contrast, the luminescence intensity of the powder sample sintered without the addition of TeBr4 decreased to 40% of its initial intensity after 100 hours under the same blue light testing conditions. The blue light stability demonstrates that the matrix Pb3TeO4Br2 is beneficial for improving the photostability of CsPbBr3.

[0091] Example 3

[0092] The matrix obtained in this embodiment is CaF2, and the perovskite nanocrystals obtained are CsPbBr3 perovskite nanocrystals.

[0093] 5 mmol CsBr, 5 mmol PbBr2, 2 mmol KF, 1 mmol CaBr2, and 2 g mesoporous silica were ground and mixed to obtain a solid mixed powder.

[0094] The mixed powder was placed in a muffle furnace and heated from room temperature to 590°C, and then heated at 590°C for 40 minutes, and then naturally cooled to room temperature to take out the sample powder.

[0095] During the calcination process, KF reacts with CaBr2 to form CaF2 as the matrix of perovskite nanocrystals. The melting point of KF is 858°C, and the melting point of CaBr2 is 730°C. PbBr2 in the system acts as a perovskite nanocrystal precursor and also as a fluxing agent, so KF and CaBr2 can co-melt below 590°C. The melting point of CaF2 generated by the reaction is 1402°C.

[0096] Experimental analysis: The powder obtained by sintering in this embodiment was taken for X-ray diffraction, and the specific spectrum is shown in FIG. 4(c). In the sample, not only CsPbBr3 phase exists, but also CaF2 phase exists. As a comparison, the X-ray diffraction spectrum of the powder sample after sintering without adding KF and CaBr2 only exists CsPbBr3 phase, and does not exist CaF2 phase (the specific spectrum is shown in FIG. 4(e)). Figure 3 Figure 3 The X-ray diffraction proves that the matrix CaF2 and CsPbBr3 nanocrystals coexist in this embodiment.

[0097] The powder obtained by sintering was taken to test the fluorescence quantum yield (PLQY), and the specific spectrum is shown in FIG. 4(d). Figure 4 The PLQY of the sample is 61%. As a comparison, the PLQY of the powder sample after sintering without adding KF and CaBr2 is 10%. The PLQY test result shows that the existence of the matrix CaF2 can improve the luminescent efficiency of the CsPbBr3 nanocrystals, and verifies that the matrix CaF2 can passivate the surface of the CsPbBr3 nanocrystals.

[0098] The powder obtained by sintering was taken to test the stability in a strong blue light irradiation environment, and the specific spectrum is shown in FIG. 4(e). Figure 5 After 100 hours of continuous irradiation with 350 mW / cm 2 of blue light (450 nm), the luminescent intensity of the powder can maintain 78% of the original intensity. As a comparison, after 100 hours under the same blue light test conditions, the luminescent intensity of the powder sample after sintering without adding KF and CaBr2 decreases to 40% of the initial intensity. The blue light stability proves that the matrix CaF2 is beneficial to improve the light stability of CsPbBr3.

[0099] Example 4

[0100] The matrix prepared in this embodiment is Pb3(PO4)2, and the perovskite nanocrystals prepared are CsPbBr3 perovskite nanocrystals.

[0101] ​5 mmol CsBr, 8 mmol PbBr2, 2 mmol H4P2O7, and 2 g mesoporous silica were ground and mixed to obtain a solid mixed powder.

[0102] The above mixed powder was placed in a muffle furnace and heated from room temperature to 580°C, and heated at 580°C for 40 minutes. Then it was allowed to cool naturally to room temperature and the sample powder was removed.

[0103] During calcination, H4P2O7 reacts with PbBr2 to form Pb3(PO4)2, which serves as the matrix for perovskite nanocrystals. The melting points of H4P2O7, PbBr2, and Pb3(PO4)2 are 61℃, 373℃, and 1014℃, respectively.

[0104] Experimental analysis: X-ray diffraction was performed on the powder obtained from the above sintering process. See the detailed spectra below. Figure 3 (d) The sample contained not only the CsPbBr3 phase but also the Pb3(PO4)2 phase. In contrast, the X-ray diffraction pattern of the powder sample sintered without the addition of H4P2O7 showed only the CsPbBr3 phase and no Pb3(PO4)2 phase (see detailed pattern). Figure 3 (e). X-ray diffraction confirmed the coexistence of matrix Pb3(PO4)2 and CsPbBr3 nanocrystals in this embodiment.

[0105] The fluorescence quantum yield (PLQY) of the powder obtained from the above sintering was tested. See the detailed spectrum below. Figure 4 The PLQY of this sample was 56%. In contrast, the PLQY of the powder sample sintered without the addition of H4P2O7 was 10%. The PLQY test results indicate that the presence of the matrix Pb3(PO4)2 can improve the luminescence efficiency of CsPbBr3 nanocrystals, verifying that the matrix Pb3(PO4)2 can passivate the surface of CsPbBr3 nanocrystals.

[0106] The stability of the powder obtained from the above sintering under strong blue light irradiation was tested. See the specific spectra below. Figure 5 350mW / cm 2 After 100 hours of continuous irradiation with blue light (450 nm), the luminescence intensity of the powder remained at 89% of its original intensity. In contrast, the luminescence intensity of the powder sample sintered without the addition of H4P2O7 decreased to 40% of its initial intensity after 100 hours under the same blue light testing conditions. The blue light stability demonstrates that the matrix Pb3(PO4)2 is beneficial for improving the photostability of CsPbBr3.

[0107] Example 5

[0108] In this embodiment, the matrix obtained was BaF2, and the perovskite nanocrystals obtained were CsPbI. 1.5 Br1.5 perovskite nanocrystals.

[0109] 5 mmol of Cs2CO3, 5 mmol of PbBr2, 5 mmol of PbI2, 2 mmol of KF, 1 mmol of Ba(OH)2, and 2 g of mesoporous silica were ground and mixed to obtain a solid mixed powder.

[0110] The above mixed powder was placed in a muffle furnace and heated from room temperature to 590°C, and then heated at 590°C for 40 minutes, and then naturally cooled to room temperature to take out the sample powder.

[0111] During the calcination process, KF reacts with Ba(OH)2 to form BaF2 as the matrix of perovskite nanocrystals. The melting point of KF is 858°C, the melting point of Ba(OH)2 is 350°C, and the melting point of BaF2 is 1354°C. In the above, PbBr2 acts as a fluxing agent while also acting as a lead source precursor. CsPbI 1.5 Br 1.5 The melting point of perovskite nanocrystals is less than 550°C

[0112] Experimental analysis: The powder obtained by sintering in this example was taken for X-ray diffraction test, and the specific spectrum is shown in Figure 7 As shown in (a) of Figure 7 , in the sample, not only CsPbI 1.5 Br 1.5 phase exists, but also BaF2 phase exists. As a comparison, as shown in (b) of Figure 7 , without adding KF and Ba(OH)2, the X-ray diffraction spectrum of the powder sample after sintering only exists CsPbI 1.5 Br 1.5 phase, and no BaF2 phase exists. The X-ray diffraction proves that the matrix BaF2 and CsPbI 1.5 Br 1.5 nanocrystals coexist.

[0113] The powder obtained by sintering in this example was taken for testing the fluorescence quantum yield (PLQY), and as shown in (a) of Figure 7 , the PLQY of the sample is 77%. As a comparison, as shown in (b) of Figure 7 , the PLQY of the sample is 18%. The PLQY test result shows that the existence of the matrix BaF2 can improve the luminescent efficiency of CsPbI 1.5 Br 1.5 nanocrystals, and verifies that the matrix BaF2 can passivate the surface of CsPbI 1.5 Br 1.5 nanocrystals. It is illustrated that the method proposed in the present application is also applicable to mixed halide perovskite nanocrystals.

[0114] Example 6

[0115] The matrix prepared in this example is BaF2, and the perovskite nanocrystal prepared is CsSnBr3 perovskite nanocrystal.

[0116] 5 mmol of CsBr, 5 mmol of SnBr2, 2 mmol of KF, 1 mmol of BaBr2, and 2 g of mesoporous silica were ground and mixed to obtain a solid mixed powder.

[0117] The mixed powder was placed in a muffle furnace in a nitrogen atmosphere, heated from room temperature to 580°C, and continuously heated at 580°C for 30 minutes, and then naturally cooled to room temperature to take out the sample powder.

[0118] During calcination, CsBr and SnBr2 react to form CsSnBr3 perovskite nanocrystal, and KF reacts with BaBr2 to form BaF2 as the matrix of the perovskite nanocrystal. The melting point of the CsSnBr3 perovskite nanocrystal is less than 550°C. In the above, SnBr2 acts as a fluxing agent at the same time as a Sn source precursor. It is illustrated that the method proposed in the present application is also applicable to cesium tin perovskite nanocrystals.

[0119] Example 7

[0120] The matrix prepared in this example is BaF2, and the perovskite nanocrystal prepared is CsCuI3 perovskite nanocrystal.

[0121] 5 mmol of CsI, 10 mmol of CuI, 2 mmol of KF, 1 mmol of Bai2, and 2 g of mesoporous titanium dioxide were ground and mixed to obtain a solid mixed powder.

[0122] The mixed powder was placed in a muffle furnace in a nitrogen atmosphere, heated from room temperature to 750°C, and continuously heated at 750°C for 30 minutes, and then naturally cooled to room temperature to take out the sample powder.

[0123] During calcination, CsI and CuI react to form CsCuI3 perovskite nanocrystal, and KF reacts with Bai2 to form BaF2 as the matrix. In the above, CuI acts as a fluxing agent at the same time as a Cu source precursor. It is illustrated that the method proposed in the present application is also applicable to copper-based perovskite nanocrystals.

[0124] The matrix prepared in Examples 5-7 is BaF2, but the matrix precursors are all different. It can be seen that under the premise of conforming to the inventive concept of the present application, the corresponding matrix precursor can be arbitrarily selected to react to form the same matrix. It can be known that a simple replacement of the matrix precursor should be included in the protection scope of the present application.

[0125] Comparative Example 1

[0126] This comparative example has no matrix, and the perovskite nanocrystals prepared in this comparative example are CsPbBr3 perovskite nanocrystals.

[0127] 5 mmol CsBr, 5 mmol PbBr2, and 2 g mesoporous silica were ground and mixed to obtain a solid mixed powder.

[0128] The above mixed powder was placed in a muffle furnace and heated from room temperature to 585°C, and heated at 585°C for 40 minutes. Then it was allowed to cool naturally to room temperature and the sample powder was removed.

[0129] Experimental analysis: X-ray diffraction was performed on the powder obtained from the above sintering process. See the detailed spectra below. Figure 3 (e) The X-ray diffraction pattern of the sintered powder sample shows only the CsPbBr3 phase and no other phases.

[0130] The fluorescence quantum yield (PLQY) of the powder obtained from the above sintering was tested. See the detailed spectrum below. Figure 4 The PLQY of this sample is 10%, indicating that the matrix-free CsPbBr3 nanocrystals lack a surface passivation matrix, and the surface defects cause severe fluorescence quenching.

[0131] The stability of the powder obtained from the above sintering under strong blue light irradiation was tested. See the specific spectra below. Figure 5 350mW / cm 2 After being continuously irradiated with blue light (450nm) for 100 hours, the luminescence intensity of the powder can maintain 40% of the original intensity, indicating that the matrix-free CsPbBr3 nanocrystals have poor stability.

[0132] Comparative Example 2

[0133] The sintering temperature provided in this comparative example is higher than the failure temperature of the micro / mesoporous template. The perovskite nanocrystals prepared in this comparative example are CsPbBr3 perovskite nanocrystals.

[0134] 5 mmol CsBr, 5 mmol PbBr2, and 2 g mesoporous silica were ground and mixed to obtain a solid mixed powder.

[0135] The above-mentioned mixed powder was placed in a muffle furnace and heated from room temperature to 620°C, and then maintained at 620°C for 40 minutes. The powder was then allowed to cool naturally to room temperature before being removed. At temperatures above 600°C, the pores of the mesoporous silica collapsed and closed.

[0136] The fluorescence quantum yield (PLQY) of the powder obtained by the above sintering was only 2%, which was less than that of the PLQY of the sintered product of Comparative Example 1 (comparative Example 1 was calcined at 585℃, which is lower than the failure temperature of the growth template, and the PLQY was 10%). This indicates that it is difficult to produce high-quality perovskite quantum dots after the mesoporous silica used as the growth template fails.

[0137] The powder obtained from the above sintering was tested using a transmission electron microscope, such as... Figure 8 As shown, the mesoporous silica channels completely collapsed, with almost no quantum dots present, further illustrating that the mesoporous silica used as a growth template is unable to adsorb precursors and grow perovskite quantum dots after it fails.

[0138] Comparative Example 3

[0139] This comparative example provides perovskite nanocrystal fluorescent materials prepared with either an excess or a small amount of matrix.

[0140] 5 mmol CsBr, 5 mmol PbBr2, 2 mmol KF, 1 mmol CaBr2, and 2 g of mesoporous silica were ground and mixed to obtain a solid powder. The powder was then placed in a muffle furnace and heated from room temperature to 590 °C, and maintained at 590 °C for 40 minutes. Afterward, the powder was allowed to cool naturally to room temperature and removed. Based on the precursor feed ratio, the CaF / CsPbBr3 ratio in the sample was found to be 1:5.

[0141] 5 mmol CsBr, 5 mmol PbBr2, 100 mmol KF, 50 mmol CaBr2, and 2 g of mesoporous silica were ground and mixed to obtain a solid powder. The powder was then heated in a muffle furnace from room temperature to 590 °C and maintained at 590 °C for 40 minutes. Afterward, the powder was allowed to cool naturally to room temperature. Based on the precursor feed ratio, the CaF / CsPbBr3 ratio in the sample was found to be 10:1.

[0142] 5 mmol CsBr, 5 mmol PbBr2, 0.2 mmol KF, 0.1 mmol CaBr2, and 2 g of mesoporous silica were ground and mixed to obtain a solid powder. The powder was then placed in a muffle furnace and heated from room temperature to 590 °C, and maintained at 590 °C for 40 minutes. The powder was then allowed to cool naturally to room temperature before being removed. Based on the precursor feed ratio, the CaF / CsPbBr3 ratio in the sample was found to be 1:50.

[0143] like Figure 9 As shown in the figure, the luminescence intensity of the three samples measured under the same excitation light is as follows: the luminescence intensity of the sample with a CaF / CsPbBr3 ratio of 5:1 is stronger than that of the samples with ratios of 1:10 and 50:1, indicating that the ratio of matrix to perovskite affects the luminescence intensity. Both excessively small and excessively large ratios will weaken the sample's luminescence. Therefore, the ratio of matrix to perovskite needs to be appropriate.

[0144] Example 8

[0145] The difference from Example 1 lies in the matrix; in this example, CaO is used as the matrix.

[0146] The matrix precursor is selected as Ca(NO2)2, the melting point of Ca(NO2)2 is 390°C, Ca(NO2)2 is melted and adsorbed into the mesoporous silica channel by heating, and is further decomposed into CaO as the matrix of perovskite nanocrystals by heating, and the melting point of CaO is 2572°C.

[0147] The powder obtained in this example is tested for PLQY, and the test result shows that the presence of the matrix CaO can improve the luminescent efficiency of the CsPbBr3 nanocrystals, and it is verified that the matrix CaO can passivate the surface of the CsPbBr3 nanocrystals.

[0148] Example 9

[0149] The difference between this example and Example 1 is the difference in the matrix, and the matrix selected in this example is Al2O3

[0150] The matrix precursor is selected as aluminum sec-butoxide, the melting point of aluminum sec-butoxide is 30°C, aluminum sec-butoxide is adsorbed into the mesoporous silica channel during heating, and is further decomposed into Al2O3 as the matrix of perovskite nanocrystals by heating, and the melting point of Al2O3 is 2054°C.

[0151] The powder obtained in this example is tested for PLQY, and the test result shows that the presence of the matrix Al2O3 can improve the luminescent efficiency of the CsPbBr3 nanocrystals, and it is verified that the matrix Al2O3 can passivate the surface of the CsPbBr3 nanocrystals.

Claims

1. A perovskite nanocrystal fluorescent material, characterized by, The micro / mesoporous template, the matrix and the perovskite nanocrystal, wherein the inner wall of the micro / mesoporous template is provided with the matrix, the perovskite nanocrystal is stacked with the matrix lattice to form a passivation interface, and the melting point of the matrix is greater than the failure temperature of the micro / mesoporous template and the melting point of the perovskite nanocrystal; The preparation method of the perovskite nanocrystal fluorescent material comprises the following steps: (1) mixing perovskite nanocrystal precursors, matrix precursors and micro / mesoporous templates to obtain a mixture; (2) calcining the mixture obtained in step (1) under conditions higher than the melting point of the perovskite nanocrystal and lower than the failure temperature of the micro / mesoporous template, and then cooling to room temperature to obtain the perovskite nanocrystal fluorescent material; The melting point of the matrix is greater than the melting point of the matrix precursor; The matrix is one or any combination of BaO, CaO, Pb3(PO4)2, Pb3TeO4X2, X is Br, I or Cl; and the matrix precursor is one or more of nitrate, nitrite, telluride and hydrogen phosphate.

2. The perovskite nanocrystal fluorescent material of claim 1, wherein, The melting point of the matrix is greater than 570 DEG C, and the melting point of the perovskite nanocrystal is not higher than 570 DEG C.

3. The perovskite nanocrystal fluorescent material of claim 1, wherein, The perovskite nanocrystal comprises cesium halide perovskite nanocrystals or mixed halide perovskite nanocrystals.

4. The perovskite nanocrystal fluorescent material of claim 3, wherein, The cesium halide perovskite nanocrystal has a perovskite structure ABX3, wherein the molar ratio of A, B and X is 1:1:3, A is Cs, B is Pb, Sn or Cu, and X is Cl, Br or I.

5. The perovskite nanocrystalline fluorescent material according to claim 3, characterized in that, The mixed halide perovskite nanocrystal has a perovskite structure ABX y X' 3-y wherein a molar ratio of A, B, X and X' is 1:1:y:3-y, wherein 0 A is Cs, B is Pb, Sn or Cu, X and X' are different and each independently is Cl, Br or I.

6. The perovskite nanocrystal fluorescent material of claim 1, wherein, The mass ratio of the matrix and the perovskite nanocrystal is a, 0.02 < a < 10.

7. The perovskite nanocrystal fluorescent material of claim 1, wherein, The micro / mesoporous template is a microporous material and / or a mesoporous material.

8. The perovskite nanocrystal fluorescent material of claim 7, wherein, The microporous material is microporous molecular sieve, microporous silica, microporous titanium dioxide, microporous aluminum oxide, microporous transition metal oxide, microporous sulfide, microporous silicate, microporous aluminate or microporous transition metal nitride.

9. The perovskite nanocrystal fluorescent material of claim 7, wherein, The mesoporous material is mesoporous molecular sieve, mesoporous silica, mesoporous titanium dioxide, mesoporous aluminum oxide, mesoporous carbon, mesoporous transition metal oxide, mesoporous sulfide, mesoporous silicate, mesoporous aluminate or mesoporous transition metal nitride.

10. The perovskite nanocrystal fluorescent material of claim 1, wherein, The calcination of the mixture obtained in step (1) comprises a heating melting stage, a heat preservation filling stage and a cooling growth stage in sequence; When in the heating melting stage and the calcination temperature is greater than the melting point of the perovskite nanocrystal, the perovskite nanocrystal precursor and the matrix precursor form a molten liquid; When in the heat preservation filling stage and the calcination temperature is lower than the failure temperature of the micro / mesoporous template, the molten liquid fills into the pore structure of the micro / mesoporous template; When in the cooling growth stage, the matrix is first formed in the micro / mesoporous template, and then the perovskite nanocrystal is heterogeneously grown on the surface of the matrix, so as to obtain the perovskite nanocrystal fluorescent material.

11. The perovskite nanocrystal fluorescent material of claim 3, wherein, The perovskite nanocrystal precursor is a cesium halide perovskite nanocrystal precursor or a mixed halide perovskite nanocrystal precursor.

12. The perovskite nanocrystal fluorescent material of claim 11, wherein, The cesium halide perovskite nanocrystal precursor is a precursor of ABX3 perovskite structure, wherein the molar ratio of A, B and X is 1:1:3, A is Cs, B is Pb, Sn or Cu, and X is Cl, Br or I. The CsPbX perovskite nanocrystal precursor includes a Cs source precursor, a Pb source precursor, and an X source precursor. The CsSnX perovskite nanocrystal precursor includes a Cs source precursor, a Sn source precursor, and an X source precursor. The CsCuX perovskite nanocrystal precursor includes a Cs source precursor, a Cu source precursor, and an X source precursor. The X source precursor is a halogen source precursor.

13. The perovskite nanocrystal fluorescent material of claim 11, wherein, The mixed halide perovskite nanocrystal precursor is ABX y X' 3-y a precursor of perovskite structure, wherein the molar ratio of A, B, X and X' is 1:1:y:3-y, wherein 0 A is Cs, B is Pb, Sn or Cu, X and X' are different and each independently is Cl, Br or I; The CsPbX X' perovskite nanocrystal precursor includes a Cs source precursor, a Pb source precursor, an X source precursor, and an X' source precursor. The CsSnX X' perovskite nanocrystal precursor includes a Cs source precursor, a Sn source precursor, an X source precursor, and an X' source precursor. The CsCuX X' perovskite nanocrystal precursor includes a Cs source precursor, a Cu source precursor, an X source precursor, and an X' source precursor. The X source precursor and the X' source precursor are different halogen source precursors.

14. The perovskite nanocrystal fluorescent material of claim 12 or 13, wherein, The Cs source precursor is one or more of cesium halide and cesium carbonate. The Pb source precursor is one or more of lead halide and lead acetate. The Sn source precursor is tin halide. The Cu source precursor is copper halide. The halogen source precursor is one or more of cesium halide, lead halide, zinc halide, potassium halide, sodium halide, lithium halide, ammonia halide, calcium halide, strontium halide, and barium halide.

15. The perovskite nanocrystal fluorescent material of claim 1, wherein, The nitrite is Ba(NO2)2 or Ca(NO2)2, and the telluride is TeO2, TeCl4, or TeBr4.

16. The perovskite nanocrystal fluorescent material of claim 1, wherein, In step (1), any low-melting salt in the perovskite nanocrystal precursor and the matrix precursor serves as a fluxing agent.

17. Use of the perovskite nanocrystal fluorescent material according to any one of claims 1-10 in a light-emitting device.

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