Preparation method of perovskite quantum dots modified by sulfonate ligands

Abstract

The present application relates to a kind of sulfonate ligand modified perovskite quantum dots, belong to perovskite quantum dot technical field.It includes the following steps:S1: cesium source, octadecene and oleic acid are mixed, vacuum drying is carried out, inert gas is passed and heated, and first mixed solution is obtained;S2: lead bromide, octadecene, oleylamine, oleic acid and octylamine methyl sulfonate are mixed, vacuum drying is carried out, under inert gas heating, first mixed solution is further added, after reaction, quenching, purification, and the solution of the sulfonate ligand modified perovskite quantum dots is obtained.The present application uses octylamine methyl sulfonate multi-ligand to passivate perovskite quantum dots in the process of quantum dot preparation, effectively reduces the vacancy defects caused by the increase of surface area due to the size reduction in the process of quantum dot synthesis, strengthens the combination between ligand and quantum dot, makes the particle size of quantum dot more uniform, and further improves the luminescent performance and stability of perovskite quantum dots.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of perovskite quantum dots, and relates to a preparation method of sulfonate ligand modified perovskite quantum dots. BACKGROUND

[0002] Quantum dots are small particles with a size of 2-10 nm made of semiconductor materials. The radius of quantum dots is smaller than or close to the Bohr radius, thus having a quantum confinement effect, so that the transport properties of carriers are limited, which affects the energy band structure of quantum dots. It is just because of this different energy band structure from conventional bulk materials and the size-adjustable energy band structure that quantum dot materials have significant advantages of high light-emitting efficiency, good light-emitting quality and adjustable light-emitting spectrum in the field of photoelectric light-emitting. As a kind of semiconductor material, all-inorganic perovskite quantum dots have characteristics such as simple synthesis, narrow emission peak (half-width of 12-42 nm), high fluorescence quantum efficiency (up to 90%) and the like, and have bright application prospects in the fields of light-emitting diodes, solar cells, photoelectric detectors, lasers and biological imaging. However, the unique ionic crystal structure of perovskite quantum dots, large surface area, weak bond strength of lead halide, and highly dynamic combination of ligands with the surface of perovskite quantum dots can easily form halide vacancy defects in the synthesis and purification process. Thus, it can cause the agglomeration and settlement of perovskite quantum dots, and further cause the decline of light-emitting performance and stability.

[0003] Improving the stability and light-emitting performance of perovskite nanocrystals through surface treatment is a common and efficient material modification method. For the traditional oleic acid / oleylamine (OA / OLA) binary ligand system, reversible proton transfer between ligands can easily occur, and in addition, the weak binding of surface ligands can cause a large amount of surface ligands to fall off and surface vacancy defects during purification and storage, which are the main reasons affecting the stability and light-emitting performance of perovskite quantum dots.

[0004] CN 116804151 A discloses a blue light emitting perovskite quantum dot and a preparation method and application thereof. The preparation method can effectively fill the vacancies caused by the loss of lead in the synthesis process by doping a specific amount of germanium ions in CsPbBr3 perovskite quantum dots. However, it does not pay attention to the stability of perovskite quantum dots. Therefore, it is necessary to seek a suitable surface ligand to passivate the surface of quantum dots. SUMMARY

[0005] In order to solve the problems existing in the prior art, the purpose of the present application is to provide a preparation method of sulfonate ligand modified perovskite quantum dots.

[0006] Another purpose of the present application is to provide a sulfonate ligand modified perovskite quantum dot.

[0007] Another object of the present application is to provide an application of the sulfonate ligand modified perovskite quantum dots in a luminescent material or a perovskite solar cell.

[0008] In order to achieve the above object, the present application adopts the following technical solution:

[0009] A preparation method of sulfonate ligand modified perovskite quantum dots, comprising the following steps:

[0010] S1: mixing a cesium source, octadecene and oleic acid, vacuum drying, passing in an inert gas and heating to obtain a first mixed solution;

[0011] S2: mixing lead bromide, octadecene, oleylamine, oleic acid and octylamine methanesulfonate, vacuum drying, adding the first mixed solution under the inert gas, quenching after reaction, and purifying to obtain a solution of the sulfonate ligand modified perovskite quantum dots.

[0012] In the preparation process of the quantum dots, the present application adopts multi-ligand passivation, and the octylamine and the methanesulfonic acid in the octylamine methanesulfonate jointly replace the oleylamine and the oleic acid to efficiently passivate the uncoordinated lead ions and bromide ions of the perovskite quantum dots, thereby improving the luminescent performance and stability of the quantum dots. Since the insulation effect of the short-chain organic ligand octylamine is weaker than that of the long-chain oleylamine, and the confinement effect of the octylamine on the quantum dots is more obvious, the perovskite quantum dots obtained by the present application have a smaller and more uniform size and better conductivity.

[0013] The octylamine and the methanesulfonic acid need to be added into the reaction system as a whole in one step, which can reduce the time for the quantum dots to be eroded by the outside world. If they are added in steps, the ligands and the perovskite quantum dots may not be combined uniformly, which affects the crystallization of the perovskite quantum dots, causes the particle size of the quantum dots to be uneven, and further reduces the crystallinity and stability of the quantum dots.

[0014] In the preparation process of the CsPbBr3 perovskite quantum dots, the octylamine methanesulfonate ligand added by the present application can strengthen the combination of the surface ligand and the quantum dots during the crystallization process, which is beneficial to reducing the defects caused by the falling of the ligands during the purification process, and further improves the luminescent performance.

[0015] Quenching can quickly reduce the growth rate of the quantum dots and control the particle size of the quantum dots. If the quantum dots are allowed to cool naturally, the particle size will be larger.

[0016] Specifically, the molar ratio of the lead bromide to the octylamine methanesulfonate is (0.8-1.1):(0.5-2).

[0017] Too little octylamine methanesulfonate salt will result in part of the lead ions unable to bond with halogen, forming vacancies, reducing the stability of perovskite quantum dots. Too much octylamine methanesulfonate salt will result in a large number of ligands between quantum dots, hindering the carrier transport between quantum dots, and reducing the luminescent performance of quantum dots.

[0018] Specifically, the molar ratio of the cesium source, octadecene and oleic acid in the step S1 is 1:6:(1-3).

[0019] As a non-coordinating solvent, octadecene can dilute the ligand, reduce the viscosity of the system, and make the material concentration in the reaction system uniform.

[0020] Specifically, the inert gas in the steps S1 and S2 is at least one of nitrogen, helium and argon.

[0021] Specifically, the cesium source in the step S1 is cesium carbonate.

[0022] Specifically, before vacuum drying in the step S1, air exchange is required, and the specific steps of air exchange include: after vacuumizing, inert gas is introduced, and the above steps are repeated more than four times.

[0023] Specifically, the temperature of vacuum drying in the step S1 is 90-130℃, and the time of vacuum drying is 1-2h.

[0024] Specifically, the heating temperature in the step S1 is 140-160℃.

[0025] Specifically, in the step S1, heating is required until the solution is completely clear.

[0026] Specifically, the first mixed solution in the step S1 needs to be kept at 90-110℃ and ready for use.

[0027] Specifically, the molar ratio of lead bromide, octadecene, oleylamine, oleic acid and octylamine methanesulfonate in the step S2 is (0.8-1.1):(60-64):(20-23):(20-24):(0.5-2).

[0028] More specifically, the molar ratio of lead bromide, octadecene, oleylamine, oleic acid and octylamine methanesulfonate in the step S2 is (0.9-1):(60-64):(20-23):(20-24):(0.5-2).

[0029] It should be noted that the main component in the first mixed solution is cesium oleate.

[0030] Specifically, the molar ratio of cesium oleate to lead bromide in the first mixed solution in the step S2 is 1:(2-3).

[0031] Specifically, the temperature of vacuum drying in the step S2 is 140℃-160℃, and the time of vacuum drying is 0.5h-1.5h.

[0032] The purpose of vacuum drying in the steps S1 and S2 is to remove air and moisture in the reaction solution, which is beneficial to reduce moisture erosion in the process of preparing quantum dots.

[0033] Specifically, the temperature of reaction in the step S2 is 110℃-140℃.

[0034] Specifically, the time of reaction in the step S2 is 20s-40s.

[0035] Specifically, the quenching treatment in the step S2 refers to placing the reaction container into an ice-water mixture for cooling.

[0036] Specifically, the temperature of quenching in the step S2 is 0℃-4℃.

[0037] Specifically, the time of quenching in the step S2 is 15s-25s.

[0038] Specifically, the specific steps of purification in the step S2 include: mixing the mixed solution after quenching with ethyl acetate, and then primary centrifuging, dispersing the separated precipitate in a dispersion liquid, adding ethyl acetate, and then secondary centrifuging and separating, and then dispersing the obtained precipitate in the dispersion liquid again to obtain the solution of the sulfonate ligand modified perovskite quantum dots.

[0039] More specifically, the dispersion liquid is n-hexane.

[0040] More specifically, the rotation speed of primary centrifuging is 7000-9000rpm, and the time of primary centrifuging is 15-25min.

[0041] More specifically, the rotation speed of secondary centrifuging is 4000-6000rpm, and the time of secondary centrifuging is 5-15min.

[0042] The application also protects a sulfonate ligand modified perovskite quantum dot prepared by the above method.

[0043] The application also protects the application of the sulfonate ligand modified perovskite quantum dot in a luminescent material or a perovskite solar cell.

[0044] Compared with the prior art, the application has the following beneficial effects:

[0045] The application uses octylamine methyl sulfonate to passivate perovskite quantum dots, effectively reduces the vacancy defects caused by the increase of surface area due to the size reduction in the process of synthesizing quantum dots, strengthens the combination between ligands and quantum dots, makes the particle size of quantum dots more uniform, and further improves the luminescent performance and stability of perovskite quantum dots. Attached Figure Description

[0046] Figure 1 The images show the fluorescence emission spectra of the quantum dots prepared in the embodiments and comparative examples of this invention.

[0047] Figure 2 These are TEM images of the quantum dots prepared in the embodiments and comparative examples of the present invention.

[0048] Figure 3 The wetting angle test results are shown for the CsPbBr3 blue quantum dots prepared in Example 3 and Comparative Example 1 of this invention.

[0049] Figure 4 The particle size distribution diagrams are for the quantum dots prepared in the embodiments and comparative examples of this invention.

[0050] Figure 5 The graph shows the luminescence properties of Example 3 and Comparative Example 1 in water. Detailed Implementation

[0051] The present invention will be further described below with reference to embodiments and comparative examples. This description is only for better illustration and not for limiting the invention. The listed embodiments are only preferred embodiments, not all embodiments. Changes, substitutions, modifications, etc., made by those skilled in the art without inventive effort are all within the protection scope of the present invention.

[0052] If the manufacturer of the reagents or instruments used is not specified, they are considered to be conventional products that can be purchased commercially.

[0053] Example 1

[0054] S1. Mix 0.825 g of Cs₂CO₃, 3.5 mL of oleic acid, and 9.6 mL of octadecene thoroughly to obtain a mixed solution. Add the mixed solution to a 100 mL three-necked flask and perform at least four gas exchanges (vacuuming and purging with argon). Then place the three-necked flask in a heating mantle and heat to 110 °C under vacuum, drying for 1.5 h. Subsequently, argon is introduced and the temperature is raised to 150 °C until the solution is completely clear, thus obtaining the cesium oleate precursor solution. Keep it at 100 °C for later use.

[0055] S2.1 Add 0.35 g PbBr2, 20 mL octadecene, 0.12 g octylamine methanesulfonate, 7 mL oleic acid, and 7 mL oleylamine to a three-necked flask. Perform at least four gas purgings (evacuation and argon purging) on ​​the flask, then dry it under vacuum at 150 °C for 1 h. Subsequently, argon gas is introduced, and the temperature is lowered to 125 °C. Then, 1 mL of cesium oleate precursor solution is rapidly injected. After reacting for 30 s, the three-necked flask containing the product solution is rapidly immersed in ice water for 20 s to obtain a crude CsPbBr3 quantum dot solution.

[0056] S2.3 Mix ethyl acetate with the CsPbBr3perovskite quantum dots crude solution with a volume ratio of 3:1, then centrifuge at 8000 rpm for 20 minutes. Collect the precipitate and re-disperse in 3 mL hexane, then, add 20 mL ethyl acetate, centrifuge at 5000 rpm for 10 min to collect the precipitate, and re-disperse in 5 mL anhydrous hexane for use.

[0057] Example 2

[0058] This example prepared sulfonate ligand modified perovskite quantum dots according to the steps of Example 1, the only difference is that 0.22 g of octylamine methanesulfonate was added in step S2.1; other steps remain unchanged.

[0059] Example 3

[0060] This example prepared sulfonate ligand modified perovskite quantum dots according to the steps of Example 1, the only difference is that 0.32 g of octylamine methanesulfonate was added in step S2.1; other steps remain unchanged.

[0061] Example 4

[0062] This example prepared sulfonate ligand modified perovskite quantum dots according to the steps of Example 1, the only difference is that 0.43 g of octylamine methanesulfonate was added in step S2.1; other steps remain unchanged.

[0063] Comparative Example 1

[0064] This example prepared sulfonate ligand modified perovskite quantum dots according to the steps of Example 1, the only difference is that no octylamine methanesulfonate was added in step S2.1; other steps remain unchanged.

[0065] Performance Test

[0066] The fluorescence emission spectra of the examples and comparative examples were all tested using a HORIBA Fluorolog-3 fluorescence spectrophotometer. And all used light with a wavelength of 365 nm as the excitation light source, before testing, the CsPbBr3solution was diluted with dimethylformamide (DMF), then the diluted solution was dropped into the cuvette.

[0067] The TEM images of the examples and comparative examples were all obtained by FEI Talos F200s microscope. Before observing the morphology of the test sample, the sample was appropriately diluted with dimethylformamide (DMF), then the diluted solution was dropped onto the carbon mesh for testing, and the test was carried out after the solvent on the carbon mesh was completely volatilized.

[0068] The wetting angle images of the examples and the comparative examples were obtained by a pco.dimax HS high-speed camera. The sample was properly diluted with dimethylformamide (DMF), and then the diluted solution was dropped to a test platform, and the image taken when the liquid drop was in a stable state was taken as the test result.

[0069] The fluorescence emission spectrum of the examples and the comparative examples is shown in Figure 1 It can be seen from the figure that the wavelength corresponding to the light emission peak is 480 nm to 510 nm, and the prepared perovskite quantum dots emit blue light. The light emission intensity of the CsPbBr3 quantum dots treated by octylamine methanesulfonate is higher than that of the original untreated quantum dots, and the light emission peak position appears different degrees of shift. This phenomenon can be attributed to the passivation of octylamine methanesulfonate to perovskite octahedral defects, which improves the probability of carrier radiative recombination. At the same time, due to the partial substitution of octylamine methanesulfonate to oleylamine, the coupling effect between each grain in the perovskite is enhanced, resulting in a certain red shift of the peak position. In addition, it can also be seen that the half peak width of the light emission peak of the crystal treated by octylamine methanesulfonate is smaller than that of the original CsPbBr3 quantum dots in the comparative example 1. This means that the crystal grain size of the perovskite treated by octylamine methanesulfonate is more uniform, so that the quantum dots have higher color purity.

[0070] The TEM images of the examples and the comparative examples are shown in Figure 2 Through the TEM observation of the morphology of the CsPbBr3 quantum dots passivated by different contents of octylamine methanesulfonate, it can be seen that the original unpassivated CsPbBr3 in the comparative example 1 and the octylamine methanesulfonate passivated CsPbBr3 quantum dots all have good monodispersity and complete cubic structure, and with the increase of the addition amount of octylamine methanesulfonate, the gap between each quantum dot becomes more obvious. This is because octylamine methanesulfonate has a certain steric hindrance, which can effectively passivate the surface of the quantum dots. It can also be seen that the quantum dots in examples 3 and 4 exhibit good crystallinity, and no obvious grain aggregation phenomenon is found. This can be attributed to the strong binding energy between the short-chain octylamine methanesulfonate and the quantum dots, which enhances the stability of the crystal grains.

[0071] The hydrophobic angle of example 3 and comparative example 1 was tested by wetting angle test. It was found that the hydrophobic angle of the perovskite quantum dots in example 3 was 89.9°, which was significantly higher than the hydrophobic angle of 40.7° of the perovskite quantum dots in comparative example 1, which benefited from the fact that octylamine methanesulfonate could provide larger steric hindrance to CsPbBr3 quantum dots than oleylamine, effectively reducing the erosion of water to the perovskite inside.

[0072] The particle size histogram of the examples and the comparative examples is shown in Figure 4The size of the CsPbBr3 nanocrystals introduced with octylamine methanesulfonate is mostly around 4.5 nm, which shows a more uniform size distribution compared with the unpassivated nanocrystals. However, it can be found that larger size grains appear in the perovskite treated with octylamine methanesulfonate due to the excessive amount of octylamine methanesulfonate. In Example 4, more grains with a size of 6.5 nm have occurred agglomeration. This means that with the increase of the amount of octylamine methanesulfonate, more oleic acid and oleylamine are replaced, the coupling force between the grains is enhanced, and the size of the nanocrystals is agglomerated and increased.

[0073] Figure 5 The luminescence performance of Example 3 and Comparative Example 1 in water is shown in the figure. It is shown in the figure that Example 3 can still emit bright sky blue light even when placed in water under the irradiation of the excitation light source, while the CsPbBr3 nanocrystal quantum dots in Comparative Example 1 have been decomposed in water and cannot exist in the form of a thin film on the glass sheet. After the original thin film structure is destroyed, the quantum dots cannot continue to aggregate, are dispersed into water, the water body becomes turbid, and cannot stably emit color under the irradiation of the excitation light source.

[0074] Obviously, the above embodiments of the present application are only examples for clearly illustrating the present application, and are not intended to limit the embodiments of the present application. Based on the above description, other different forms of changes or variations can be made by those skilled in the art. Here, all the embodiments are not required to be exhausted. Any modification, equivalent replacement and improvement made within the spirit and principle of the present application shall be included in the protection scope of the claims of the present application.

Claims

1. A method for preparing a sulfonate ligand-modified perovskite quantum dot, characterized in that, The method comprises the following steps: S1: mixing a cesium source, octadecene and oleic acid, vacuum drying, passing inert gas and heating to obtain a first mixed solution; S2: mixing lead bromide, octadecene, oleylamine, oleic acid and octylamine methyl sulfonate, vacuum drying, heating under inert gas, adding the first mixed solution, quenching after reaction, and purifying to obtain a solution of the sulfonate ligand modified perovskite quantum dots; The molar ratio of lead bromide to octylamine methyl sulfonate is (0.8-1.1):(0.5-2).

2. The method for preparing perovskite quantum dots modified with sulfonate ligands according to claim 1, characterized in that, The molar ratio of the cesium source, octadecene and oleic acid in the step S1 is 1:6:(1-3).

3. The method for preparing perovskite quantum dots modified with sulfonate ligands according to claim 1, characterized in that, The molar ratio of lead bromide, octadecene, oleylamine, oleic acid and octylamine methyl sulfonate in the step S2 is (0.8-1.1):(60-64):(20-23):(20-24):(0.5-2).

4. The method for preparing perovskite quantum dots modified with sulfonate ligands according to claim 1, characterized in that, The main component in the first mixed solution is cesium oleate, and the molar ratio of the cesium oleate in the first mixed solution to lead bromide in the step S2 is 1:(2-3).

5. The method for preparing perovskite quantum dots modified with sulfonate ligands according to claim 1, characterized in that, The heating temperature in the step S1 is 140-160℃.

6. The method for preparing perovskite quantum dots modified with sulfonate ligands according to claim 1, characterized in that, The reaction temperature in the step S2 is 110-140℃, and the reaction time is 20-40s.

7. The method for preparing perovskite quantum dots modified with sulfonate ligands according to claim 1, characterized in that, The quenching temperature in the step S2 is 0-4℃, and the quenching time is 15-25s.

8. The sulfonate ligand modified perovskite quantum dots prepared by the preparation method of any one of claims 1-7.

9. The sulfonate ligand modified perovskite quantum dots of claim 8 in a luminescent material or a perovskite solar cell.

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