Sky-blue light colloidal quantum dot material, synthetic method and application in photoelectric module

Abstract

The invention discloses a pure bromine-based multiband composite sky-blue light colloidal quantum dot material and a synthesis method thereof, and belongs to the field of metal halide luminescent materials. According to the method, a composite ligand containing oleylamine and 3-aminopropyltriethoxysilane is adopted to carry out cooperative regulation and control on the reaction of a lead source, a zinc source and a cesium source. Specifically, the quantum dot material is prepared in a single reaction system through a thermal injection method. The material can generate at least three independent emission peaks within the range of 435-445 nm, 460-468 nm and 475-485 nm under exciting light of 365 nm, the three independent emission peaks are compounded to form sky blue light, and the photoluminescence quantum yield of the material can exceed 60%. Due to the existence of the silane-containing organic amine ligand, the material has excellent water stability, for example, the material can still keep higher photoluminescence quantum yield after 30 minutes in an environment with 100% relative humidity. According to the invention, the problems of single luminescence peak and poor stability of the existing blue-light perovskite material are solved.

Description

TECHNICAL FIELD

[0001] The technical field belongs to the technical field of metal halide luminescent materials, and particularly relates to a pure bromine-based multi-band composite sky blue light colloidal quantum dot material and a synthesis method thereof. BACKGROUND

[0002] Colloidal quantum dots have the advantages of low synthesis cost, high photoluminescence quantum yield (PLQY), and easy synthesis, and have very optimistic application prospects in the fields of solar cells, lighting display, light transmission, and laser.

[0003] Generally, the main existing forms of blue light colloidal quantum dots are mixed halide blue light perovskite and strong confinement perovskite. The mixed halide blue light perovskite is prone to phase separation under an applied field, which causes red shift of the emission peak, and the pure bromine-based strong confinement blue light perovskite can also achieve blue light emission. Since it is a single halogen, there is no phase separation problem, and the stability of the perovskite can be improved by changing the ligand, so that a more stable blue light emission than the mixed halide blue light perovskite is obtained. At present, although the pure bromine-based perovskite material solves the halogen phase separation problem, for example, Chinese Patent CN108531163A discloses a high quantum yield blue light perovskite colloidal quantum dot material, but it can only achieve single wavelength blue light emission, which cannot meet the demand for multi-color composite light sources in wide color gamut display and other applications. In addition, such materials generally have problems of sensitivity to water and oxygen and poor environmental stability, which greatly limits their practical application.

[0004] Therefore, how to prepare a pure bromine-based perovskite quantum dot material with multiple emission peaks, capable of composite formation of specific color (such as sky blue) light emission, and at the same time having excellent water stability in a single synthesis system is a technical problem to be solved in the field. SUMMARY

[0005] The purpose of the present application is to solve the technical problems of single light emission peak and poor water stability of the blue light perovskite material in the prior art, and to provide a pure bromine-based multi-band composite sky blue light colloidal quantum dot material with multi-band emission characteristics and excellent water stability, as well as a synthesis method and application thereof.

[0006] To achieve the above-mentioned purposes, the present application adopts the following technical solutions:

[0007] On the one hand, the present invention provides a pure bromine-based multi-band composite sky-blue colloidal quantum dot material, characterized in that the material has at least three independent emission peaks under 365nm wavelength excitation light, the emission peaks being located in the wavelength ranges of 435-445nm, 460-468nm and 475-485nm respectively; and the photoluminescence quantum yield of the material is greater than 60%.

[0008] On the other hand, the present invention provides a method for preparing the above-mentioned pure bromine-based multi-band composite sky-blue colloidal quantum dot material, characterized by comprising the following steps:

[0009] S1. Mix cesium carbonate, 1-octadecene and oleic acid, heat and stir to obtain precursor solution 1;

[0010] S2. Mix lead bromide, zinc bromide, oleic acid, oleylamine, 3-aminopropyltriethoxysilane and 1-octadecene, heat and stir to obtain precursor solution 2;

[0011] S3. Inject the precursor solution 1 into the precursor solution 2, react, and then rapidly cool to obtain a crude solution;

[0012] S4. The crude solution is purified to obtain the pure bromine-based multi-band composite sky-blue colloidal quantum dot material.

[0013] Preferably, the molar ratio of oleic acid to organic amine is 1:0.5-1:1; wherein the organic amine is oleylamine and 3-aminopropyltriethoxysilane.

[0014] Preferably, the molar ratio of PbBr2 to ZnBr2 is 1:0.5-1:2.

[0015] Preferably, the molar ratio of oleylamine to 3-aminopropyltriethoxysilane is 1:0.2-1:5.

[0016] In another aspect, the present invention provides a backlight source comprising: an ultraviolet light chip; and a perovskite quantum dot film, the film comprising the pure bromine-based multi-band composite sky-blue colloidal quantum dot material as described above, and disposed on the light emission path of the ultraviolet light chip.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] This invention achieves multi-band composite sky-blue light emission with excellent luminescence performance. By introducing ZnBr2 and controlling its ratio with PbBr2, and utilizing the synergistic effect of oleylamine and 3-aminopropyltriethoxysilane (APTES) composite ligands, a pure bromine-based perovskite quantum dot material with at least three independent emission peaks was successfully synthesized in a single reaction system. The composite of these emission peaks can produce high-quality sky-blue light, solving the problem of single emission peaks in existing pure bromine-based perovskites.

[0019] By optimizing the ligand ratio and reaction conditions, the quantum dot material prepared by this invention has a high luminescence efficiency, with a photoluminescence quantum yield that can stably exceed 60%, reaching a maximum of 68.2%, thus meeting the requirements of high-efficiency light-emitting devices.

[0020] A silane-containing organic amine ligand was introduced. This ligand not only participates in the nucleation and growth regulation of quantum dots, but the Si-O-Si network formed after its hydrolysis can also form a dense inorganic protective shell on the surface of quantum dots in situ, which greatly enhances the material's ability to resist moisture erosion and enables it to maintain long-term luminescence stability in an environment of 100% relative humidity. Attached Figure Description

[0021] Figure 1 This is a schematic diagram of the preparation process of pure bromine-based multi-band composite sky-blue colloidal quantum dot material in one embodiment of the present invention;

[0022] Figure 2 The photoluminescence spectrum of the colloidal quantum dot material prepared according to Example 1 of the present invention is shown.

[0023] Figure 3 The graph shows the comparison of the photoluminescence quantum yield of the colloidal quantum dot material prepared in Example 1 of the present invention with that of the traditional blue light colloidal quantum dot material under 100% relative humidity, in order to demonstrate the excellent water stability of the material of the present invention.

[0024] Figure 4 The photoluminescence spectrum of the colloidal quantum dot material prepared in the comparative example (Example 4);

[0025] Figure 5 This is a schematic diagram of a backlight application of the present invention, wherein 1 is a structural component, 2 is a perovskite quantum dot film, and 3 is an ultraviolet light chip. Detailed Implementation

[0026] To better understand the objectives, technical solutions, and advantages of this invention, the above technical solutions will be described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that these embodiments are for illustrative purposes only and do not constitute any limitation on the scope of this invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this invention should be included within the protection scope of this invention.

[0027] In the context of this invention, a wide range of raw materials can be selected. To support the scope of the claims, general concepts of some key raw materials are now explained:

[0028] The “cesium source” can be any compound known to those skilled in the art that can provide cesium ions, preferably a cesium carbonate, acetate, halide, etc. In a preferred embodiment of the present invention, it is specifically cesium carbonate (Cs2CO3).

[0029] The "lead source" is preferably a halide salt of divalent lead, and in a preferred embodiment of the present invention, it is specifically lead bromide (PbBr2).

[0030] The “zinc source” is preferably a halide salt of divalent zinc, and in a preferred embodiment of the present invention, it is specifically zinc bromide (ZnBr2).

[0031] The "first solvent" and "second solvent" can be high-boiling-point non-coordinating organic solvents, such as, but not limited to, 1-octadecene (ODE) and paraffin oil. In a preferred embodiment of the present invention, it is specifically 1-octadecene (ODE).

[0032] The "long-chain carboxylic acid" can be a saturated or unsaturated carboxylic acid with a carbon chain length of C8-C22, such as oleic acid (OA), stearic acid, palmitic acid, etc. In a preferred embodiment of the present invention, it is specifically oleic acid (OA).

[0033] The "long-chain fatty amine" can be a primary, secondary, or tertiary amine with a carbon chain length of C8-C22, such as oleylamine (OAm), octadecylamine, hexadecylamine, etc. In a preferred embodiment of the present invention, it is specifically oleylamine (OAm).

[0034] The term "silane-containing organic amine" refers to a compound whose molecule contains both an amino group and a hydrolyzable silane group, such as 3-aminopropyltriethoxysilane (APTES) and 3-aminopropyltrimethoxysilane. In a preferred embodiment of the present invention, it is specifically 3-aminopropyltriethoxysilane (APTES).

[0035] The following description uses specific examples and comparative models to illustrate the point.

[0036] Example 1

[0037] This embodiment provides a method for preparing a pure bromine-based multi-band composite sky-blue light colloidal quantum dot material, the steps of which are as follows:

[0038] S1. Preparation of cesium oleate precursor solution 1: 0.1 mmol Cs₂CO₃, 0.25 mL oleic acid (OA), and 4 mL 1-octadecene (ODE) were added to a 25 mL three-necked flask. The solution was heated and stirred at 120 °C for 30 min under vacuum to remove moisture and oxygen. Then, the atmosphere was switched to nitrogen, the temperature was raised to 150 °C, and the mixture was stirred for 10 min until a clear and transparent precursor solution 1 was formed. The solution was then cooled to room temperature for later use.

[0039] S2. Preparation of Zn-Pb complex precursor solution 2: 0.1 mmol PbBr2, 0.1 mmol ZnBr2, 0.5 mL ODE, 0.1 mL oleic acid (OA), 0.1 mL oleylamine (OAm), and 0.3 mL 3-aminopropyltriethoxysilane (APTES) were added to a 50 mL three-necked flask. Under an oxygen-free environment in a glove box, the mixture was stirred at 100 °C for 1 h at a stirring rate of 500 rpm. This step was to form a stable Zn-Pb complex ligand solution. Subsequently, the temperature was increased to 120 °C, and stirring was continued for 20 min to ensure that ZnBr2 and PbBr2 were fully dissolved and bound to the ligand, thereby forming a homogeneous precursor solution 2.

[0040] S3. Reaction and Cooling: Maintain the temperature of precursor solution 2 at 120°C and rapidly inject 1 mL of precursor solution 1. After the reaction proceeds for approximately 10 seconds, quickly place the three-necked flask in an ice-water bath to rapidly cool to room temperature, obtaining a solution containing crude quantum dots.

[0041] S4. Purification: Centrifuge the crude solution at 6000 rpm for 10 min and collect the supernatant. Add ethyl acetate to the supernatant until the solution becomes turbid. Then centrifuge at 8000 rpm for 10 min, discard the supernatant, and the resulting precipitate is the purified pure bromine-based multi-band composite sky-blue colloidal quantum dot material. Redisperse the material in n-hexane for storage.

[0042] Performance testing: The quantum dot material prepared in Example 1 was tested. For example... Figure 1 As shown, under 365nm excitation light, its emission spectrum exhibits three independent emission peaks, located at 440nm, 463nm, and 480nm, respectively. Figure 2 As shown, it exhibits a bright sky-blue emission under ultraviolet light. Its photoluminescence quantum yield (PLQY) was measured to be 68.2%. Figure 4 As shown, the material exhibits a uniform cubic nanocrystalline morphology.

[0043] Example 2: Adjusting the molar ratio of PbBr2 to ZnBr2

[0044] This embodiment is basically the same as Example 1, except that in step S2, the molar ratio of PbBr2 to ZnBr2 is 1:0.5. That is, 0.1 mmol PbBr2 and 0.05 mmol ZnBr2 are used. The remaining raw material amounts and operating steps are the same as in Example 1.

[0045] The prepared quantum dot material also exhibited three emission peaks under 365 nm excitation, with PLQY at 65.7%.

[0046] Example 3: Adjusting the molar ratio of PbBr2 to ZnBr2

[0047] This embodiment is basically the same as Example 1, except that in step S2, the molar ratio of PbBr2 to ZnBr2 is 1:2, i.e., 0.1 mmol PbBr2 and 0.2 mmol ZnBr2 are used. The remaining raw material amounts and operating steps are the same as in Example 1.

[0048] The prepared quantum dot material also exhibits three emission peaks under 365nm excitation, with PLQY at 63.1%.

[0049] Comparative Example 1: Lack of ZnBr2

[0050] This comparative example is basically the same as Example 1, except that ZnBr2 is not added in step S2. The amounts of other raw materials and operating steps are the same as in Example 1.

[0051] The prepared quantum dot material exhibits only one emission peak at 455 nm under 365 nm excitation, which is monochromatic blue light, with a PLQY of 58.5%.

[0052] Conclusion: The comparison between this comparative example and Example 1 shows that the introduction of ZnBr2 is a key technical feature for achieving multi-band transmission.

[0053] Comparative Example 2: Missing APTES

[0054] This comparative example is essentially the same as Example 1, except that 3-aminopropyltriethoxysilane (APTES) is not added in step S2. To maintain a similar total amount of organic amines, the amount of oleylamine is increased to 0.4 mL. The amounts of other raw materials and operating procedures are the same as in Example 1.

[0055] Although the prepared quantum dot materials also exhibited multi-peak emission, PLQY decreased significantly to 45.3%.

[0056] Conclusion: This comparative example, compared with Example 1, shows that the introduction of APTES is crucial for obtaining high photoluminescence quantum yield.

[0057] Example 4: Stability Comparison Test

[0058] The quantum dot material prepared in Example 1 (denoted as Sample A, containing APTES) and the quantum dot material prepared in Comparative Example 2 (denoted as Sample B, without APTES) were respectively fabricated into thin films. Both films were placed in a sealed environment with a relative humidity of 100%, and their PLQY was tested every 5 minutes.

[0059] The results are as follows Figure 3 As shown, after 30 minutes, the PLQY of sample A remained above 90% of the initial value (from 68.2% to about 62%), while the PLQY of sample B dropped sharply to below 20% of the initial value (from 45.3% to about 8%).

[0060] Conclusion: This comparative experiment strongly demonstrates that the introduction of silane-containing organic amines (APTES) can greatly improve the water stability of the material, which is another key technical feature of this invention.

[0061] Comparative Example 3: Ligand ratio exceeds the preferred range

[0062] This comparative example is essentially the same as Example 1, except that in step S2, the molar ratio of oleic acid to organic amine (the sum of oleylamine and APTES) is adjusted to 1:1.5. That is, 0.15 mL of oleic acid and 0.15 mL of oleylamine are used, while maintaining the APTES dosage at 0.3 mL. The remaining raw material amounts and operating procedures are the same as in Example 1.

[0063] The prepared quantum dot material PLQY has a purity of only 54.2%, and its spectral peak shape is poor, with some peaks appearing diffuse.

[0064] Conclusion: The comparison between this comparative example and Example 1 shows that controlling the ligand ratio within the preferred range helps to obtain higher quantum yield and better spectral quality.

[0065] Table 1: Summary of parameters and results for key embodiments and comparative examples

[0066]

[0067]

[0068] Example 5: Backlight Application

[0069] like Figure 5As shown, this embodiment provides a backlight source. The backlight source includes an ultraviolet light chip (3) with a center wavelength of 365nm and a perovskite quantum dot film (2), which is disposed on the light emission path of the chip (3). The film (2) is prepared by spin-coating a mixture of pure bromine-based multi-band composite sky-blue colloidal quantum dot material prepared in Example 1 and polymethyl methacrylate (PMMA) onto a glass substrate. The structural component (1) is used to fix and encapsulate the entire device. When the ultraviolet light chip (3) is powered on and emits light, the ultraviolet light emitted by it excites the perovskite quantum dot film (2), and the film (2) emits bright sky-blue light, which can be used as a backlight source for liquid crystal displays or for ambient lighting.

Claims

1. A sky-blue colloidal quantum dot material, characterized in that, The material is prepared from raw materials comprising a lead source, a zinc source, a cesium source, a first solvent, a first ligand, a second ligand, and a third ligand, wherein the third ligand is a silane-containing organic amine; Furthermore, the material has at least three independent emission peaks under 365nm wavelength excitation light, and the emission peaks are located in the wavelength ranges of 435-445nm, 460-468nm and 475-485nm, respectively. Furthermore, the photoluminescence quantum yield of the material is greater than 60%.

2. A method for preparing the sky-blue colloidal quantum dot material as described in claim 1, comprising reacting a cesium source, a lead source, a zinc source, and a halogen source under the action of an organic amine and a carboxylic acid ligand, characterized in that, The method includes the following steps: S1. Mix the cesium source, the first solvent and the first ligand, heat and stir to obtain precursor solution 1; S2. The lead source, the zinc source, the second ligand, the third ligand, and the second solvent are mixed, heated and stirred to obtain precursor solution 2, wherein the third ligand is a silane-containing organic amine; S3. Inject the precursor solution 1 into the precursor solution 2, react, and then rapidly cool to obtain a crude solution; S4. The crude solution is purified using a detergent, and the resulting precipitate is dispersed in a toluene solution to obtain the pure bromine-based multi-band composite sky-blue colloidal quantum dot material as described in claim 1.

3. The method according to claim 2, characterized in that, The cesium source is cesium carbonate, the lead source is lead bromide (PbBr2), and the zinc source is zinc bromide (ZnBr2).

4. The method according to claim 3, characterized in that, The molar ratio of PbBr2 to ZnBr2 is 1:0.5-1:

2.

5. The method according to claim 2, characterized in that, The second ligand is a long-chain fatty amine, the silane-containing organic amine is 3-aminopropyltriethoxysilane, the first ligand and / or the second ligand contains a long-chain carboxylic acid, the first solvent and the second solvent are 1-octadecene, and in step S4, the washing agent used for purification can be ethyl acetate or methyl acetate.

6. The method according to claim 5, characterized in that, The long-chain fatty amine is oleylamine.

7. The method according to claim 5, characterized in that, The long-chain carboxylic acid is oleic acid.

8. The method according to any one of claims 2, 5, and 7, characterized in that, The molar ratio of the long-chain carboxylic acid to the total molar amount of the second and third ligands is 1:0.5-1:

1.

9. The method according to any one of claims 2, 5 and 7, characterized in that, The molar ratio of the second ligand to the third ligand is 1:0.2-1:

5.

10. A backlight source, characterized in that, include: A UV chip (3); and A perovskite quantum dot film (2), the film comprising the pure bromine-based multi-band composite sky-blue colloidal quantum dot material as described in claim 1, and disposed on the light emission path of the ultraviolet light chip (3).

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