A CsPbBr3 perovskite nanocrystal with blue-purple photoluminescence and a preparation method thereof

Abstract

The present invention discloses a CsPbBr3 perovskite nanocrystal with blue-purple photoluminescence and a preparation method thereof. The preparation method comprises: (1) adding PbBr2 and CsBr as precursors into a good solvent for dissolution, then adding oleylamine and a polymer as surface ligands and mixing them evenly to obtain a precursor liquid; the repeating unit of the polymer contains a carboxyl group; (2) adding a poor solvent into the precursor liquid to recrystallize and obtain the CsPbBr3 perovskite nanocrystal with blue-purple photoluminescence. The present invention adopts a simple room temperature recrystallization method to prepare the perovskite nanocrystal with blue-purple photoluminescence without complicated operation steps or additional ion addition.

Description

Technical Field

[0001] The present invention belongs to the technical field of perovskites, and more specifically, relates to a CsPbBr3 perovskite nanocrystal with blue-purple photoluminescence and a preparation method thereof. Background Art

[0002] All-inorganic perovskite nanocrystals, with the general formula: CsPbX3 (X=Cl, Br, I), have unique optical advantages, such as high absorption coefficient, narrow emission spectrum, adjustable crystal size and chemical composition, adjustable emission spectrum, high quantum yield (PLQY), etc. They are the most promising optoelectronic materials in the future and are widely used in solar cells, light-emitting diodes (LEDs), photodetectors and other fields.

[0003] In 2015, the all-inorganic perovskite nanocrystals were successfully prepared for the first time by the Maksym V. Kovalenko research group through the high-temperature injection method. However, the synthesis requires high temperature, inert gas protection and hot injection operation, which is harsh and cumbersome. In 2016, Zeng Haibo's research group successfully synthesized green light CsPbBr3 NCs through a room temperature method. The principle of this method is that when the precursor salt dissolved in a good solvent encounters a poor solvent, supersaturated recrystallization occurs. Its advantages are that it does not require hot injection operation and inert gas protection, can be formed within a few seconds, is easy to operate, and can also obtain a wide color range emission from blue to red. The disadvantage of the above two methods is that this method can only produce green-emitting CsPbBr3 nanocrystals, while the quantum yield of CsPbCl3 and mixed halogen perovskites emitting in the blue light region is low and the structure is unstable, so stable, high-quantum-yield blue-violet photoluminescent perovskites are relatively scarce luminescent materials. There are also some green photoluminescence research cases, such as Pan Daocheng's research group used fatty acids of different chain lengths as ligands, cesium (I) and lead (II) fatty acid salts as cesium and lead sources, and quaternary ammonium bromide as bromine source in non-polar organic solvents to react and obtain CsPbBr3 NCs. Alexander Eychmüller's research group used partially hydrolyzed polymethyl methacrylate (h-PMMA) and highly branched polyethyleneimine (b-PEI) as dual ligands and synthesized green-emitting CsPbBr3 nanocrystals by mechanical grinding.

[0004] The CsPbBr3 prepared by the above methods all emit green photoluminescence. Meng Hong's research group used Al doping to change the band structure and obtained blue photoluminescent nanocrystals. Ward van der Stam et al. used divalent metal cation Zn 2+ Sn 2+ 、Cd 2+Doping can obtain CsPbBr3 with green to blue photoluminescence. In addition, Dong Y et al. used organic ammonium bromide as a bromine source, or added ZnBr2 to increase the additional bromine source, greatly improving the bromine-lead ratio, and obtained CsPbBr3 with quantum confinement effect, blue shift of luminescence, and high quantum yield. The disadvantage is that this method still requires high-temperature injection operation.

[0005] From the existing CsPbX3 synthesis method, ordinary CsPbBr3 nanocrystals can only emit green light under ultraviolet excitation. If you need to adjust the luminescence to the blue-violet light region, you must change the halogen to Cl or dope Cl elements, that is, CsPbCl3 or CsPb(Br / Cl)3, or dope metal elements, or reduce the dimension to produce blue-violet photoluminescence under ultraviolet excitation. The steps of metal doping and existing dimensionality reduction synthesis methods are cumbersome, and even require high-temperature injection under the protection of inert gas to complete. It is difficult to blue-shift the luminescence of CsPbBr3 without changing the chemical composition and synthesizing at room temperature. Therefore, finding a simple synthesis method to achieve the adjustment of the luminescence position of CsPbBr3 without changing the chemical composition will further deepen the understanding of the luminescence mechanism of CsPbX3 nanocrystals and expand its application in solar cells, light-emitting diodes (LEDs), photodetectors and other fields. Summary of the invention

[0006] In view of the above defects or improvement needs of the prior art, the present invention provides a method for preparing CsPbBr3 perovskite nanocrystals with blue-purple photoluminescence, which aims to provide a new method for synthesizing blue-purple photoluminescent perovskites, and realize the regulation of the luminescent position of all-inorganic perovskite nanocrystals by the synthesis method. Thus, the technical problems existing in the preparation of blue-purple photoluminescent CsPbBr3 perovskite nanocrystals are solved.

[0007] To achieve the above object, according to one aspect of the present invention, a method for preparing CsPbBr3 perovskite nanocrystals having blue-violet photoluminescence is provided, comprising:

[0008] (1) PbBr2 and CsBr are added as precursors into a good solvent to dissolve, and then oleylamine and a polymer are added as surface ligands and mixed evenly to obtain a precursor liquid; the repeating unit of the polymer contains a carboxyl group;

[0009] (2) Adding a poor solvent to the precursor solution to cause recrystallization, thereby obtaining the CsPbBr3 perovskite nanocrystals having blue-violet photoluminescence.

[0010] It should be noted that 390-450nm is the wavelength range from blue light to violet light, of which 390-435nm is violet light and 435-450nm is blue light. The maximum emission wavelength of the CsPbBr3 perovskite nanocrystal with blue-violet photoluminescence provided by the present invention fluctuates at the junction of blue light and violet light, that is, in the range of 433-438nm, and a part of each of the two intervals is widened, thus presenting blue-violet light.

[0011] Preferably, the polymer is one of polyacrylic acid, polymethacrylic acid, h-polymethyl methacrylate, poly-4-vinylbenzoic acid, and polystyrene-polyacrylic acid block copolymer.

[0012] Preferably, the good solvent has a relatively large solubility for the components in the precursor liquid; the poor solvent has a relatively small solubility for the components in the precursor liquid; preferably, the good solvent is at least one of DMF, DMA, DMSO, methanol, ethanol, n-propanol, isopropanol, ethylene glycol, propylene glycol, glycerol, formamide and acetonitrile; the poor solvent is at least one of toluene, benzene, petroleum ether, n-hexane, cyclohexane, dichloromethane, chloroform, carbon tetrachloride, dibromomethane, carbon disulfide, ether and isopropyl ether.

[0013] It should be noted that a good solvent has a relatively large solubility for the components in the precursor liquid, which means that the good solvent has a relatively large solubility for PbBr2 and CsBr in the precursor liquid, and also has a relatively large solubility for oleylamine and polymer as surface ligands; a poor solvent has a relatively small solubility for the components in the precursor liquid, which means that the good solvent has a relatively small solubility for PbBr2 and CsBr in the precursor liquid, and also has a relatively small solubility for oleylamine and polymer as surface ligands.

[0014] Preferably, the volume ratio of the poor solvent to the good solvent is (10-200):1; the mass ratio of the poor solvent to the precursor liquid is (34-20000):1.

[0015] Preferably, the molar ratio of CsBr to PbBr2 is 1:2-2:1.

[0016] Preferably, the concentration of CsBr in the precursor solution is 0.02 mmol / mL-0.04 mmol / mL, and the concentration of PbBr2 in the precursor solution is 0.02 mmol / mL-0.04 mmol / mL.

[0017] Preferably, the molecular weight of the polymer in the precursor liquid is 500-450000, and the concentration of the polymer in the precursor liquid is 0.10 mmol / mL-1.6 mmol / mL.

[0018] Preferably, the concentration of oleylamine in the precursor liquid is 0.038 mmol / mL-0.6 mmol / mL.

[0019] According to another aspect of the present invention, a CsPbBr3 perovskite nanocrystal having blue-violet photoluminescence is provided, which has a wavelength of λ ex =Emits blue-violet light under excitation at 290-400nm.

[0020] Preferably, the average particle size is 7 nm or less.

[0021] In general, compared with the prior art, the above technical solution conceived by the present invention can at least achieve the following beneficial effects.

[0022] (1) The present invention adopts a simple room temperature recrystallization method to prepare perovskite nanocrystals with blue-purple photoluminescence, without complicated operation steps or additional ion addition. The luminescence principle is that the present invention uses a polymer containing carboxyl groups in the repeating unit as the surface ligand of the nanocrystal, such as polyacrylic acid (PAA), whose abundant carboxyl groups can combine with the dangling bonds of the nanocrystal to reduce surface defects and reduce surface energy. At the same time, it acts as a ligand and encapsulation layer to limit the growth of the nanocrystal so that its particle size is smaller than the exciton Bohr radius of CsPbBr3, and a strong quantum confinement effect is produced on the surface, causing the luminescence of CsPbBr3 to blue shift. Therefore, PAA can be used as a multidentate ligand and encapsulation layer to chelate on the surface of nanocrystals, effectively producing blue-violet photoluminescent CsPbBr3 perovskite nanocrystals. It can form a coating layer on the surface of nanocrystals while the nanocrystals are growing, thereby limiting the growth of nanocrystals and obtaining zero-dimensional CsPbBr3 with a size smaller than the exciton Bohr radius of CsPbBr3. Due to the quantum confinement effect, the photoluminescence of this material undergoes a blue shift, that is, blue-violet photoluminescence is generated under ultraviolet light excitation.

[0023] (2) The mass ratio of the good solvent to the poor solvent is strictly controlled in the present invention. This is because if there is too much good solvent, it is easy to fail to form crystals due to too low supersaturation. The ratio of the poor solvent is strictly controlled in the present invention. This is because if there is too much poor solvent, the concentration of the luminescent particles is too small, the luminescence is weak, and the coordination balance is affected, causing the ligand to fall off the surface.

[0024] (3) The CsPbBr3 perovskite nanocrystals obtained by the present invention are small in size and narrow in distribution, with a particle size below 7 nm and good monodispersity. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 The appearance and particle size diagram of the upper and lower CsPbBr3 nanocrystal products of Example 2, wherein: Figure 1 (a) and (c) are TEM images of the upper and lower CsPbBr3 nanocrystalline products of Example 2, respectively. Figure 1(b) and (d) are the particle size distribution histograms of the upper and lower CsPbBr3 nanocrystalline products of Example 2, respectively;

[0026] Figure 2 (a) and (d) are respectively the UV-visible absorption spectra of the upper and lower layer products obtained by adding different precursor liquid masses during the synthesis process in the embodiments of the present invention; Figure 2 (b) and (e) are the fluorescence spectra of the corresponding upper and lower layer products, respectively; Figure 2 (c) and (f) are the CIE coordinates of the corresponding upper and lower layer products, respectively;

[0027] Figure 3 (a) and (d) are respectively the UV-visible absorption spectra of the upper and lower layer products obtained by changing the salt concentration in the precursor solution in equal proportions according to the present invention; Figure 3 (b) and (e) are the fluorescence spectra of the corresponding upper and lower layer products, respectively (b, e); Figure 3 (c) and (f) are the CIE coordinates of the corresponding upper and lower layer products, respectively;

[0028] Figure 4 (a) and (d) are respectively the UV-visible absorption spectra of the upper and lower layer products obtained by changing the [CsBr] / [PbBr2] ratio in the precursor solution according to the present invention; Figure 4 (b) and (e) are the fluorescence spectra of the corresponding upper and lower layer products, respectively; Figure 4 (c) and (f) are the CIE coordinates of the corresponding upper and lower layer products, respectively;

[0029] Figure 5 (a) and (d) are respectively the UV-visible absorption spectra of the upper and lower layer products obtained by changing the [OAm] in the precursor according to the present invention; Figure 5 (b) and (e) are the fluorescence spectra of the corresponding upper and lower layer products, respectively; Figure 5 (c) and (f) are the CIE coordinates of the corresponding upper and lower layer products, respectively;

[0030] Figure 6 (a) and (d) are respectively the UV-visible absorption spectra of the upper and lower layer products obtained by changing the [PAA] in the precursor according to the present invention; Figure 6 (b) and (e) are the fluorescence spectra of the corresponding upper and lower layer products, respectively; Figure 6 (c) and (f) are the CIE coordinates of the corresponding upper and lower layer products, respectively;

[0031] Figure 7 (a) is the UV-visible absorption spectrum of the supernatant product prepared by using DMSO as a precursor good solvent of the present invention; Figure 7 (b) is the corresponding fluorescence spectrum; Figure 7(c) is the corresponding CIE coordinate;

[0032] Figure 8 (a) is the UV-visible absorption spectrum of the supernatant product prepared by using methanol as a good solvent in the present invention; Figure 8 (b) is the corresponding fluorescence spectrum; Figure 8 (c) is the corresponding CIE coordinate. DETAILED DESCRIPTION

[0033] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0034] Example 1

[0035] This embodiment provides a method for preparing CsPbBr3 perovskite nanocrystals with blue-violet photoluminescence, the method comprising:

[0036] Weigh 0.4 mmol CsBr and 0.4 mmol PbBr2 into a centrifuge tube, add 10 mL DMF, sonicate to dissolve most of the CsBr and PbBr2, measure 0.5 mL OAm into the above centrifuge tube, continue sonication, then weigh 5 g PAA and add it to the above centrifuge tube, sonicate to dissolve all the above components to obtain a uniform, transparent, viscous precursor liquid.

[0037] The concentrations of the components in the precursor solution are: [CsBr] = [PbBr2] = 0.04 mmol / mL, [PAA] = 0.5 g / mL, [OAm] = 0.15 mmol / mL. 130 mg of the precursor solution was weighed into a centrifuge tube using an electronic balance, and 10 mL of toluene was added under vigorous stirring.

[0038] The obtained product is Figure 1 (a)-(d). Figure 1 (a) is a TEM image of the supernatant. The size distribution of the nanocrystals in the field of view is obtained by measuring the particle size of the nanocrystals. Figure 1 As shown in (b), the size distribution range of nanocrystals in the supernatant is narrow, and the average particle size is 3.8 nm. Figure 1 (c) is a TEM image of the dispersion obtained by washing and drying the lower layer product and then redispersing it in toluene. Figure 1As shown in (d), its distribution range is narrow, and the average particle size is 3.1nm. Since the exciton Bohr radius of CsPbBr3 is 7nm, a particle size smaller than this value will produce a strong quantum confinement effect, that is, the bandgap width increases as the size decreases, and the photoluminescence blue shifts. It can be seen that this luminescent material is a monodisperse nanocrystal with a strong quantum confinement effect due to its ultra-small size.

[0039] Example 2

[0040] The difference between this embodiment and embodiment 1 is that 260 mg of the precursor liquid is taken into a centrifuge tube, and 10 mL of toluene is added under vigorous stirring.

[0041] Example 3

[0042] The difference between this embodiment and embodiment 1 is that 390 mg of the precursor solution is placed in a centrifuge tube, and 10 mL of toluene is added under vigorous stirring.

[0043] After the reaction, the supernatant and the lower product were separated, and the lower product was washed and dried to prepare a dispersion. The UV-visible spectra of the supernatant and the lower product dispersion of Examples 1-3 were measured respectively ( Figure 2 (a), (d)) and fluorescence spectra ( Figure 2 (b), (e)), find the corresponding CIE coordinates ( Figure 2 In (c) and (f), the fluorescence peak position, half-peak width and CIE coordinates of each test sample are shown in Table 1.

[0044] Table 1 Performance table of embodiments 1-3

[0045]

[0046] It can be seen from the above examples that the upper and lower layer products obtained by changing the amount of precursor added both emit light in the blue-violet light region, with a narrow half-width (uniform product size distribution), realizing the synthesis of ultra-small-sized CsPbBr3 nanocrystals with blue-violet photoluminescence using CsBr and PbBr2 as raw materials.

[0047] Example 4

[0048] This embodiment provides a method for preparing CsPbBr3 perovskite nanocrystals with blue-violet photoluminescence, the method comprising:

[0049] Weigh 0.8mmol CsBr and 0.8mmol PbBr2 into a centrifuge tube, add 10mL DMF, sonicate to dissolve most of CsBr and PbBr2, weigh 0.5mL OAm into the above centrifuge tube, continue sonication, weigh 5g PAA into the above centrifuge tube, sonicate to dissolve all the above components, and obtain a uniform, transparent, viscous precursor solution. In the precursor solution, [CsBr] = [PbBr2] = 0.08mmol / mL, [PAA] = 0.5g / mL, [OAm] = 0.15mmol / mL.

[0050] Weigh 260 mg of the above precursor solution into a centrifuge tube using an electronic balance, and add 10 mL of toluene respectively under vigorous stirring. After the reaction, separate the supernatant and the lower product, wash and dry the lower product to make a dispersion, and measure the UV-visible spectra of the supernatant and the lower product dispersion ( Figure 3 (a), (d)) and fluorescence spectra ( Figure 3 (b), (e)), find the corresponding CIE coordinates ( Figure 3 In (c) and (f), the fluorescence peak position, half-peak width and CIE coordinates of each test sample are shown in Table 2.

[0051] Table 2 Performance table of embodiments 2 and 4

[0052]

[0053] According to the above process, by changing [CsBr] and [PbBr2] in the precursors year on year, the upper and lower layer products obtained both emit light in the blue-violet light region with a narrow half-width, thus realizing the synthesis of ultra-small CsPbBr3 perovskite nanocrystals with blue-violet photoluminescence using CsBr and PbBr2 as raw materials.

[0054] Example 5

[0055] This embodiment provides a method for preparing CsPbBr3 perovskite nanocrystals with blue-violet photoluminescence, the method comprising:

[0056] Weigh 0.4mmol CsBr and 0.8mmol PbBr2 into a centrifuge tube, add 10mL DMF, sonicate to dissolve most of CsBr and PbBr2, weigh 0.5mL OAm into the above centrifuge tube, continue sonication, weigh 5g PAA into the above centrifuge tube, sonicate to dissolve all the above components, and obtain a uniform, transparent, viscous precursor liquid. In the precursor liquid, [CsBr] = 0.04mmol / mL, [PbBr2] = 0.08mmol / mL, [PAA] = 0.5g / mL, [OAm] = 0.15mmol / mL.

[0057] Example 6

[0058] This embodiment provides a method for preparing CsPbBr3 perovskite nanocrystals with blue-violet photoluminescence, the method comprising:

[0059] Weigh 0.8mmol CsBr and 0.4mmol PbBr2 into a centrifuge tube, add 10mL DMF, sonicate to dissolve most of CsBr and PbBr2, weigh 0.5mL OAm into the above centrifuge tube, continue sonication, weigh 5g PAA into the above centrifuge tube, sonicate to dissolve all the above components, and obtain a uniform, transparent, viscous precursor liquid. In the precursor liquid, [CsBr] = 0.08mmol / mL, [PbBr2] = 0.04mmol / mL, [PAA] = 0.5g / mL, [OAm] = 0.15mmol / mL.

[0060] Use an electronic balance to weigh 260 mg of the above two precursor solutions into a centrifuge tube, and add 10 mL of toluene to each of them under vigorous stirring. After the reaction, separate the supernatant and the lower product, wash and dry the lower product to make a dispersion, and measure the UV-visible spectra of the supernatant and the lower product dispersion ( Figure 4 (a), (d) and fluorescence spectra ( Figure 4 (b), (e)), find the corresponding CIE coordinates ( Figure 4 In (c) and (f), the fluorescence peak position, half-peak width and CIE coordinates of each test sample are shown in Table 3.

[0061] Table 3 Performance table of Examples 2, 5-6

[0062]

[0063] According to the above process, the [CsBr] / [PbBr2] in the precursor was changed to 1:1, 1:2, and 2:1 respectively, and the upper and lower layer products obtained both emitted light in the blue-violet light region with a narrow half-width, thus realizing the synthesis of ultra-small CsPbBr3 perovskite nanocrystals with blue-violet photoluminescence using CsBr and PbBr2 as raw materials.

[0064] Example 7

[0065] The difference between this example and Example 2 is that 0.25 mL of OAm was weighed, and [OAm]=0.076 mmol / mL.

[0066] Example 8

[0067] The difference from Example 2 is that 1.0 mL of OAm was measured, and [OAm]=0.3 mmol / mL.

[0068] Use an electronic balance to weigh 260 mg of the above two precursor solutions into a centrifuge tube, and add 10 mL of toluene to each of them under vigorous stirring. After the reaction, separate the supernatant and the lower product, wash and dry the lower product to make a dispersion, and measure the UV-visible spectra of the supernatant and the lower product dispersion ( Figure 5 (a), (d)) and fluorescence spectra ( Figure 5 (b), (e)), find the corresponding CIE coordinates ( Figure 5 In (c) and (f), the fluorescence peak position, half-peak width and CIE coordinates of each test sample are shown in Table 4.

[0069] Table 4 Performance table of Examples 2, 7-8

[0070]

[0071] According to the above process, by changing [OAm] in the precursor to 0.076mmol / mL, 0.15mmol / mL, and 0.3mmol / mL, respectively, the upper and lower layer products obtained all emitted light in the blue-violet light region with a narrow half-width, thus realizing the synthesis of ultra-small CsPbBr3 perovskite nanocrystals with blue-violet photoluminescence using CsBr and PbBr2 as raw materials.

[0072] Example 9

[0073] The difference from Example 2 is that 2.5 g of PAA was weighed, and [PAA]=0.25 g / mL.

[0074] Example 10

[0075] The difference from Example 2 is that 8 g of PAA was weighed, and [PAA]=0.8 g / mL.

[0076] Use an electronic balance to weigh 260 mg of the above two precursor solutions into a centrifuge tube, and add 10 mL of toluene to each of them under vigorous stirring. After the reaction, separate the supernatant and the lower product, wash and dry the lower product to make a dispersion, and measure the UV-visible spectra of the supernatant and the lower product dispersion ( Figure 6 (a), (d)) and fluorescence spectra ( Figure 6 (b), (e)), find the corresponding CIE coordinates ( Figure 6 In (c) and (f), the fluorescence peak position, half-peak width and CIE coordinates of each test sample are shown in Table 5.

[0077] Table 5 Performance table of embodiments 2, 9-10

[0078]

[0079] According to the above process, by changing [PAA] in the precursor to 0.25g / mL, 0.5g / mL, and 0.8g / mL respectively, the upper and lower layer products obtained all emitted light in the blue-violet light region with a narrow half-width, thus realizing the synthesis of ultra-small CsPbBr3 perovskite nanocrystals with blue-violet photoluminescence using CsBr and PbBr2 as raw materials.

[0080] Examples 11-12

[0081] Preparation of precursor solution: Weigh 0.4mmol CsBr and 0.4mmol PbBr2 into a centrifuge tube, add 2mL DMSO, sonicate to dissolve most of CsBr and PbBr2, weigh 0.125mL OAm into the above centrifuge tube, continue sonication, weigh 1.25g PAA into the above centrifuge tube, sonicate to dissolve all the above components, and obtain a uniform, transparent, viscous precursor. In the precursor, [CsBr] = [PbBr2] = 0.2mmol / mL, [PAA] = 0.625g / mL, [OAm] = 0.19mmol / mL.

[0082] Use an electronic balance to weigh 27.56 and 14.95 mg of the above precursor solution into centrifuge tubes, and add 10 mL of toluene respectively under vigorous stirring. After the reaction, separate the supernatant and measure the UV-visible spectrum of the supernatant ( Figure 7 (a)) and fluorescence spectra ( Figure 7 (b)), find the corresponding CIE coordinates ( Figure 7 In (c), the fluorescence peak position, half-peak width and CIE coordinates of the samples are shown in Table 6.

[0083] Table 6 Performance table of Examples 11-12

[0084]

[0085] According to the above process, by changing the good solvent to DMSO, the obtained product can also emit light in the blue-violet light region with a narrow half-width, thus realizing the synthesis of ultra-small CsPbBr3 perovskite nanocrystals with blue-violet photoluminescence using CsBr and PbBr2 as raw materials.

[0086] Embodiment 13

[0087] Preparation of precursor solution: Weigh 0.4mmol CsBr and 0.4mmol PbBr2 into a centrifuge tube, add 10mL methanol, sonicate to dissolve most of CsBr and PbBr2, weigh 0.5mL OAm into the above centrifuge tube, continue sonication, weigh 5g PAA into the above centrifuge tube, sonicate to dissolve all the above components, and obtain a uniform, transparent, viscous precursor. In the precursor, [CsBr] = [PbBr2] = 0.2mmol / mL, [PAA] = 0.5g / mL, [OAm] = 0.15mmol / mL.

[0088] Use a pipette to measure 0.3 mL of the above precursor solution into a centrifuge tube, and add 10 mL of toluene under vigorous stirring. After the reaction, separate the supernatant and measure the UV-visible spectra of the supernatant ( Figure 8 (a)) and fluorescence spectra ( Figure 8 (b)), find the corresponding CIE coordinates ( Figure 8 In (c), the fluorescence peak position, half-peak width and CIE coordinates of the sample are shown in Table 7.

[0089] Table 7 Performance table of embodiment 13

[0090]

[0091] According to the above process, by changing the good solvent to methanol, the obtained product can also emit light in the blue-violet light region with a narrow half-width, thus realizing the synthesis of ultra-small CsPbBr3 perovskite nanocrystals with blue-violet photoluminescence using CsBr and PbBr2 as raw materials.

[0092] Embodiment 14

[0093] Preparation of precursor solution: weigh 0.4mmol CsBr and 0.4mmol PbBr2 into a centrifuge tube, add 10mL methanol, sonicate to dissolve most of CsBr and PbBr2, weigh 0.5mL OAm into the above centrifuge tube, continue sonication, weigh 5g polymethacrylic acid into the above centrifuge tube, sonicate to dissolve all the above components, and obtain a uniform, transparent, viscous precursor. In the precursor, [CsBr] = [PbBr2] = 0.2mmol / mL, [PAA] = 0.5g / mL, [OAm] = 0.15mmol / mL.

[0094] 260 mg of the above precursor solution was weighed into a centrifuge tube, and 10 mL of toluene was added under vigorous stirring. After the reaction, the supernatant was separated to obtain ultra-small CsPbBr3 perovskite nanocrystals with blue-purple photoluminescence.

[0095] Embodiment 15

[0096] Preparation of precursor solution: Weigh 0.4mmol CsBr and 0.4mmol PbBr2 into a centrifuge tube, add 10mL methanol, sonicate to dissolve most of CsBr and PbBr2, weigh 0.5mL OAm into the above centrifuge tube, continue sonication, weigh 5g h-polymethyl methacrylate into the above centrifuge tube, sonicate to dissolve all the above components, and obtain a uniform, transparent, viscous precursor. In the precursor, [CsBr] = [PbBr2] = 0.2mmol / mL, [PAA] = 0.5g / mL, [OAm] = 0.15mmol / mL.

[0097] 260 mg of the above precursor solution was weighed into a centrifuge tube, and 10 mL of toluene was added under vigorous stirring. After the reaction, the supernatant was separated to obtain ultra-small CsPbBr3 perovskite nanocrystals with blue-purple photoluminescence.

[0098] Example 16

[0099] Preparation of precursor solution: Weigh 0.4mmol CsBr and 0.4mmol PbBr2 into a centrifuge tube, add 10mL methanol, sonicate to dissolve most of CsBr and PbBr2, weigh 0.5mL OAm into the above centrifuge tube, continue sonication, weigh 5g poly 4-vinyl benzoic acid into the above centrifuge tube, sonicate to dissolve all the above components, and obtain a uniform, transparent, viscous precursor. In the precursor, [CsBr] = [PbBr2] = 0.2mmol / mL, [PAA] = 0.5g / mL, [OAm] = 0.15mmol / mL.

[0100] 260 mg of the above precursor solution was weighed into a centrifuge tube, and 10 mL of toluene was added under vigorous stirring. After the reaction, the supernatant was separated to obtain ultra-small CsPbBr3 perovskite nanocrystals with blue-purple photoluminescence.

[0101] Embodiment 17

[0102] Preparation of precursor solution: Weigh 0.4mmol CsBr and 0.4mmol PbBr2 into a centrifuge tube, add 10mL methanol, sonicate to dissolve most of CsBr and PbBr2, weigh 0.5mL OAm into the above centrifuge tube, continue sonication, weigh 5g polystyrene-polyacrylic acid block copolymer into the above centrifuge tube, sonicate to dissolve all the above components, and obtain a uniform, transparent, viscous precursor. In the precursor, [CsBr] = [PbBr2] = 0.2mmol / mL, [PAA] = 0.5g / mL, [OAm] = 0.15mmol / mL.

[0103] 260 mg of the above precursor solution was weighed into a centrifuge tube, and 10 mL of toluene was added under vigorous stirring. After the reaction, the supernatant was separated to obtain ultra-small CsPbBr3 perovskite nanocrystals with blue-purple photoluminescence.

[0104] It should be noted that the experimental results of the embodiments (such as Example 2) that appear repeatedly in the above table fluctuate within a certain range, which is a normal experimental error and does not affect the repeatability of the preparation method provided by the present invention.

[0105] It will be easily understood by those skilled in the art that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing CsPbBr3 perovskite nanocrystals with blue-violet photoluminescence, characterized in that: include: (1) PbBr2 and CsBr are added as precursors into a good solvent and dissolved, and then oleylamine and a polymer are added as surface ligands and mixed evenly to obtain a precursor liquid; the polymer is polyacrylic acid; (2) Adding a poor solvent to the precursor solution to cause recrystallization, thereby obtaining the CsPbBr3 perovskite nanocrystals having blue-violet photoluminescence.

2. The preparation method according to claim 1, characterized in that The good solvent has a relatively large solubility for the components in the precursor liquid; the poor solvent has a relatively small solubility for the components in the precursor liquid; the good solvent is at least one of DMF, DMA, DMSO, methanol, ethanol, n-propanol, isopropanol, ethylene glycol, propylene glycol, glycerol, formamide and acetonitrile; the poor solvent is at least one of toluene, benzene, petroleum ether, n-hexane, cyclohexane, dichloromethane, chloroform, carbon tetrachloride, dibromomethane, carbon disulfide, ether, ethyl acetate and isopropyl ether.

3. The preparation method according to claim 1, characterized in that: The volume ratio of the poor solvent to the good solvent is (10-200):1; the mass ratio of the poor solvent to the precursor liquid is (34-20000):

1.

4. The preparation method according to claim 1, characterized in that: The molar ratio of CsBr to PbBr2 is 1:2-2:

1.

5. The preparation method according to claim 1, characterized in that: The concentration of CsBr in the precursor solution is 0.02 mmol / mL-0.04 mmol / mL, and the concentration of PbBr2 in the precursor solution is 0.02 mmol / mL-0.04 mmol / mL.

6. The preparation method according to claim 1, characterized in that: The weight average molecular weight of the polymer in the precursor liquid is 500-450000, and the concentration of the polymer in the precursor liquid is 0.10 mmol / mL-1.6 mmol / mL.

7. The preparation method according to claim 1, characterized in that: The concentration of oleylamine in the precursor liquid is 0.038 mmol / mL-0.6 mmol / mL.

8. A CsPbBr3 perovskite nanocrystal having blue-violet photoluminescence prepared by the preparation method according to any one of claims 1 to 7, characterized in that: At the excitation wavelength λ ex =290-400 nm emits blue-violet light under excitation.

9. The CsPbBr3 perovskite nanocrystal with blue-violet photoluminescence according to claim 8, characterized in that: The average particle size is less than 7 nm.

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