Core-shell type perovskite quantum dot powder and preparation method thereof
By preparing core-shell perovskite quantum dot powder and using high-temperature sintering to form a dense shell, the problem of poor stability of CsPbBr3 quantum dots was solved, resulting in longer fluorescence lifetime and higher humidity stability, thus improving luminescence performance.
Patent Information
- Application Number
- CN202511619512.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-11-06
- Publication Date
- 2026-02-10
AI Technical Summary
In the existing technology, CsPbBr3 quantum dots have poor stability, many surface defects, short fluorescence lifetime, and are difficult to maintain luminescence performance in high humidity environments.
A multi-ligand synergistic regulation method was adopted to prepare core-shell perovskite quantum dot powder, including high-temperature sintering to form a dense inorganic protective shell, repairing surface defects, and optimizing material properties through high-temperature sintering process.
It significantly improves the water stability and fluorescence lifetime of quantum dots, narrows the half-width at half-maximum, and has excellent luminescence performance. It can maintain a high luminescence intensity at 100% relative humidity, achieving a longer fluorescence decay lifetime and purer green light emission.
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Figure CN121495580A_ABST
Abstract
Description
TECHNICAL FIELD
[0001] The technical field belongs to the technical field of metal halide luminescent materials, and particularly relates to a core-shell perovskite quantum dot powder and a preparation method thereof. BACKGROUND
[0002] All-inorganic perovskite quantum dots CsPbBr3 have become a research hotspot of a new generation of luminescent materials due to their excellent photoelectric properties such as high photoluminescence quantum yield (PLQY), narrow emission full width at half maximum (FWHM) and high color purity. However, the surface ligand of CsPbBr3 quantum dots is easy to fall off, and there are many defect states, which leads to poor stability, and especially under light, heating or high humidity environment, fluorescence quenching and structure degradation are easy to occur, which seriously restricts its commercial application.
[0003] At present, the strategies for improving the stability of CsPbBr3 quantum dots mainly include surface ligand engineering, inorganic shell coating and matrix encapsulation. For example, long-chain organic acids / amines are used for surface passivation, or metal oxides such as SiO2 and Al2O3 are used for surface wrapping. However, the silica coating layer formed at low temperature based on the traditional sol-gel method often has problems such as loose structure, non-dense, and many surface residual hydroxyl groups, which limits its blocking ability to water and oxygen, and it is difficult to fundamentally solve the long-term stability problem. These methods are often complex in process, and the compactness of the coating layer is not good and will affect the luminescence of perovskite quantum dots to some extent. In addition, the traditional purification process often cannot effectively remove surface defects, and the agglomeration between quantum dots also affects its long-term stability.
[0004] Therefore, it is necessary to develop a post-processing method which is relatively simple in process, can effectively passivate surface defects and enhance stability, and can maintain or even enhance the intrinsic luminescent performance. SUMMARY
[0005] The purpose of the present application is to solve the problems of insufficient stability, short fluorescence lifetime and many surface defects of CsPbBr3 quantum dots in the prior art. Specifically, the present application aims to provide a kind of CsPbBr3 perovskite quantum dot powder which has a narrow half peak width, a longer fluorescence decay lifetime and excellent water stability by the synergistic regulation of multiple ligands.
[0006] Another purpose of the present application is to provide a stable and controllable preparation method of the above-mentioned material.
[0007] To achieve the above-mentioned purposes of the present application, the technical solutions adopted by the present application are as follows:
[0008] A core-shell perovskite quantum dot powder and a preparation method thereof, the preparation raw materials of which comprise: cesium carbonate (Cs2CO3), 1-octadecene (ODE), oleic acid (OA), lead bromide (PbBr2), zinc bromide (ZnBr2), oleylamine (OAm), 3-aminopropyl triethoxysilane (APTES), hydrobromic acid (HBr), a toluene solution of didodecylamine (DDDAM), tetramethoxysilane (TMOS), and methyl acetate.
[0009] The application also provides a synthesis and post-processing method of the above material, characterized by comprising the following ordered steps:
[0010] First, a cesium precursor solution (precursor solution 1) is prepared by heating and stirring cesium salt, 1-octadecene, and oleic acid in an oxygen-free environment.
[0011] Second, a lead-zinc composite precursor solution (precursor solution 2) is prepared by heating and stirring PbBr2, ZnBr2, oleic acid, oleylamine, 3-aminopropyl triethoxysilane, and 1-octadecene in an oxygen-free environment. In this step, the molar ratio of PbBr2 to ZnBr2, the molar ratio of oleic acid to the composite organic amine, and the molar ratio of oleylamine to 3-aminopropyl triethoxysilane are precisely controlled, which is an important guarantee for obtaining the target quantum dot size distribution and luminous efficiency.
[0012] Third, the preheated precursor solution 1 is quickly injected into the precursor solution 2, and reacted at a specific reaction temperature (for example, 110-150°C) for a very short time (for example, 5-15 seconds), and then quickly cooled by an ice water bath to obtain a crude solution containing quantum dot material.
[0013] Next, the crude solution is subjected to purification treatment, for example, centrifugation and washing with a washing agent such as ethyl acetate, and finally the obtained quantum dot precipitate is dispersed in a non-polar solvent (such as toluene) for storage, to obtain a perovskite quantum dot toluene solution.
[0014] Then, tetramethoxysilane is added to the perovskite quantum dot toluene solution, stirred to natural dryness, and ground to obtain a powder.
[0015] Finally, the powder is sintered at a specific temperature (125-200°C) for a certain time (1-3h) in an oxygen-free environment, and after cooling to room temperature, a CsPbBr3 perovskite quantum dot powder with excellent water stability is obtained.
[0016] In the above method, in order to further optimize the performance of the material, the reaction temperature, reaction time, stirring rate, and molar ratio of each component of each step can be preferably limited.
[0017] The molar ratio of 3-aminopropyltriethoxysilane to tetramethoxysilane in the precursor solution 2 is 1:3-1:5, and the molar ratio of PbBr2 to ZnBr2 is 1:0.5-1:1.
[0018] Compared with the original unsintered powder, the high water stability CsPbBr3 perovskite quantum dot powder based on the high-temperature sintering process has an increased fluorescence decay time from 7.622 ns to 21.83 ns and a decreased half-peak width from 35.75 nm to 19.23 nm; high-efficiency and pure green light emission can be achieved under excitation light, and a relatively high relative light intensity can be stably maintained for 150 minutes in a 100% relative humidity environment.
[0019] In addition, the high water stability CsPbBr3 perovskite quantum dot powder based on the high-temperature sintering process can be prepared into a high-efficiency and pure perovskite quantum dot fluorescent film for backlight source material application.
[0020] Compared with the prior art, the present application has the following beneficial effects:
[0021] 1. The present application performs high-temperature sintering treatment on the quantum dot powder after silane coating, so that the silane hydrolysis product (silicon dioxide) on the surface of the quantum dot is restructured to form a more compact and uniform inorganic protective shell layer, and the defect state on the surface of the quantum dot is repaired. This scheme effectively solves the problem of poor stability of quantum dots due to ligand shedding and surface defects in the prior art, so that the prepared quantum dot powder exhibits extremely high water stability, for example, it can maintain more than 85% of the original light intensity for 150 minutes under 100% relative humidity.
[0022] 2. The high-temperature sintering process also has the effect of "thermal annealing" purification of the quantum dot size, so that the size distribution is more uniform. This scheme solves the problem of low color purity of quantum dot light emission in the prior art, so that the half-peak width of the emission spectrum of the material is significantly narrowed, for example, from 35.75 nm before sintering to 19.23 nm, realizing more pure green light emission.
[0023] 3. Due to the effective passivation of surface defects and the protection of the compact shell layer, the non-radiative recombination path is inhibited, which solves the problem of short fluorescence lifetime of quantum dots in the prior art, so that the fluorescence decay lifetime of the material is greatly extended, for example, from 7.622 ns to 21.83 ns. BRIEF DESCRIPTION OF DRAWINGS
[0024] Figure 1 The transmission electron microscopy (TEM) comparison chart of the powders obtained in Example One and Example Four is shown in the figure. Figure 1 a is the TEM chart of the powder obtained in Example One, Figure 1 b is the TEM chart of the powder obtained in Example Four.
[0025] Figure 2 X-ray diffraction (XRD) comparison chart of the powders obtained in Example One to Example Five of the present application;
[0026] Figure 3 Photoluminescence (PL) spectrum comparison chart of the powders obtained in Example One to Example Five of the present application;
[0027] Figure 4 Photoluminescence fluorescence lifetime decay comparison chart of the powders obtained in Example One to Example Five of the present application;
[0028] Figure 5 Photoluminescence (PL) spectrum chart of the powder obtained in Example One of the present application at different time points under 100% relative humidity;
[0029] Figure 6 Photoluminescence (PL) spectrum chart of the powder obtained in Example Four of the present application at different time points under 100% relative humidity;
[0030] Figure 7 Water contact angle test chart of the powders obtained in Example One and Example Four of the present application; wherein Figure a is the water contact angle test chart of the powder obtained in Example One, and Figure b is the water contact angle test chart of the powder obtained in Example Four. DETAILED DESCRIPTION
[0031] In order to better understand the purpose, technical scheme and advantages of the present application, the above technical scheme will be described in detail below in combination with the drawings and specific embodiments.
[0032] The core-shell type perovskite quantum dot powder and the preparation method thereof, raw materials of which comprise 1-octadecene, oleic acid, oleylamine, PbBr2, 3-aminopropyl triethoxysilane, tetramethoxysilane, didodecylamine, HBr, ZnBr2 and Cs2CO3. The molar ratio of 3-aminopropyl triethoxysilane to tetramethoxysilane is 1:3-1:5, and the molar ratio of PbBr2 to ZnBr2 is 1:0.5-1:1.
[0033] Example One
[0034] The steps for preparing the high water stability CsPbBr3 perovskite quantum dot powder based on the high-temperature sintering process are as follows:
[0035] S1, 0.1 g Cs2CO3 was put into a 150 ml three-necked flask, a magnetic stirrer was added, and 700 μL of oleic acid and 10 mL of 1-octadecene were measured by using a syringe and added into the flask. To fully dissolve the Cs2CO3, the flask was heated to 100 °C and stirred at a speed of 500 rpm for 1 h in an oxygen-free environment in a glove box to remove water and oxygen in the solution. Subsequently, the temperature was raised to 120 °C, and stirring was continued for 20 min (to complete the formation of the precursor) at a stirring speed of 500 rpm to obtain a precursor solution 1.
[0036] S2, 0.084 g of ZnBr2 and 0.138 g of PbBr2 (the molar ratio of PbBr2 to ZnBr2 was adjusted to 1:0.5) were added into a 150 ml three-necked flask, a magnetic stirrer was added, and 1 mL of oleic acid, 1 mL of oleylamine, 3 mL of 3-aminopropyltriethoxysilane (the molar ratio of oleic acid to organic amine was 1:1), and 10 mL of 1-octadecene were measured by using a syringe and added into the flask. Stirring was carried out at a speed of 500 rpm for 1 h at a temperature of 100 °C in an oxygen-free environment in a glove box (to form a stable Zn-Pb complex ligand solution). Subsequently, the temperature was raised to 120 °C, and stirring was continued for 20 min to ensure that ZnBr2 and PbBr2 were fully dissolved and combined with the ligand to form a uniform precursor solution 2.
[0037] S3, the Cs precursor solution 1 prepared in S1 was preheated to 105 °C, and was quickly injected into 1.6 mL of the Zn-Pb precursor solution 2 in S2. After injection, the reaction temperature was quickly raised to 120 °C and maintained for 10 s, 30 ul of HBr was added, the reaction was carried out for 10 s, and then 0.5 M dilaurylamine toluene solution was added to quickly generate a CsPbBr3 quantum dot colloidal solution. After the reaction was completed, the solution was immediately cooled to room temperature in an ice water bath to terminate the reaction and prevent the quantum dots from aggregating.
[0038] S4, the crude solution obtained by mixing the reaction in the flask in S3 was added into an equal volume of methyl acetate (as a washing agent), and after being uniformly mixed, centrifugation was carried out at 8000 rpm for 5 min to precipitate the target quantum dots. The precipitate was washed for 3 times, and finally the target quantum dots were obtained, which were stored in a toluene solution. Through this purification process, unreacted raw materials, ligands and by-products were effectively removed, and the non-radiative recombination centers on the surface of the quantum dots were reduced. At the same time, the purification process also created conditions for the hydrolysis of 3-aminopropyltriethoxysilane on the surface of the quantum dots to form a protective layer.
[0039] S5, 900 ul of tetramethoxysilane (the molar ratio of 3-aminopropyltriethoxysilane to tetramethoxysilane was 1:5) was added dropwise to the perovskite quantum dot toluene solution in S4, and stirring was carried out to dry naturally, the stirring speed was 500 rpm, and grinding was carried out to obtain a powder.
[0040] like Figure 1 As shown in the TEM image of a, the surface of the quantum dots is unevenly coated with amorphous organosilane binders, and there is obvious adhesion between the particles, failing to form an independent, well-defined shell structure.
[0041] like Figure 5 As shown, the relative intensity of the luminescence of the quantum dot powder almost disappears after 50 minutes at 100% relative humidity.
[0042] like Figure 7 As shown in Figure a, the water contact angle of the above quantum dot powder was tested, and the contact angle was 33.5 degrees, which shows that it is hydrophilic.
[0043] Example 2
[0044] The preparation steps in this embodiment are basically the same as those in Example 1, except that:
[0045] After step S5, the powder obtained in S5 is sintered at 125°C for 2 hours in an oxygen-free environment.
[0046] Example 3
[0047] The preparation steps in this embodiment are basically the same as those in Example 1, except that:
[0048] After step S5, the powder obtained in S5 is sintered at 150°C for 2 hours in an oxygen-free environment.
[0049] Example 4
[0050] The preparation steps in this embodiment are basically the same as those in Example 1, except that:
[0051] After step S5, the powder obtained in S5 is sintered at 175°C for 2 hours in an oxygen-free environment.
[0052] like Figure 1 As shown in the TEM image of b, after high-temperature sintering, the quantum dots exhibit well-dispersed, uniformly sized, independent spherical individuals. A uniformly thick and clearly defined shell layer forms on the surface of each quantum dot, demonstrating that high-temperature sintering promotes the formation of a dense silica shell.
[0053] like Figure 2 As shown, Example 1 is a sintered sample, in which the cesium lead bromine phase is a mixed phase of 113 and 125. After sintering, the cesium lead bromine phase gradually becomes purer. Example 4 is the relatively purest phase, that is, the best effect is achieved when the sintering temperature is 175℃.
[0054] like Figure 3As shown, the half-peak width of Example 4 is the narrowest compared to the other examples, decreasing from 35.75nm to 19.23nm, which means that the effect is best when the sintering temperature is 175°C.
[0055] like Figure 4 As shown, the fluorescence decay lifetime of Example 4 is the longest compared to other examples, increasing from 7.622ns to 21.83ns, which means that the best effect is achieved at a sintering temperature of 175°C.
[0056] like Figure 6 As shown, the relative intensity of the quantum dot powder remains above 85% after 150 minutes at 100% relative humidity.
[0057] like Figure 7 As shown in Figure b, the water contact angle of the above quantum dot powder was tested, and the contact angle was 69.6 degrees, which shows a certain degree of hydrophobicity.
[0058] Example 5
[0059] The preparation steps in this embodiment are basically the same as those in Example 1, except that:
[0060] After step S5, the powder obtained in S5 is sintered at 200°C for 2 hours in an oxygen-free environment.
[0061] Compared to Example 4, the above adjustments resulted in a wider half-peak width and a shorter fluorescence decay lifetime, as the excessively high temperature affected the luminescence of the quantum dot powder.
[0062] Example 6
[0063] The preparation steps in this embodiment are basically the same as those in Example 1, except that:
[0064] After step S5, the powder obtained in S5 is dried in a vacuum drying oven at 60°C for 4 hours.
[0065] Despite the above adjustments, the powder remained sticky during grinding, resulting in a narrower half-peak width and increased decay lifetime compared to Example 1. However, it lost its luminescence in water after 60 minutes, indicating that water stability was not significantly improved.
[0066] Example 7
[0067] The preparation steps in this embodiment are basically the same as those in Example 1, except that:
[0068] In S5, the molar ratio of 3-aminopropyltriethoxysilane to tetramethoxysilane is adjusted to 1:2.
[0069] The aforementioned quantum dot materials cannot be dried into quantum dot powder; they remain a quantum dot toluene solution.
[0070] Example 8
[0071] The preparation steps in this embodiment are basically the same as those in Example 1, except that:
[0072] In S5, the molar ratio of 3-aminopropyltriethoxysilane to tetramethoxysilane is adjusted to 1:6.
[0073] The aforementioned quantum dot material, after drying, appears as a white powder, which is a non-luminescent powder, thus destroying the quantum dots themselves.
[0074] Example 9
[0075] The preparation steps in this embodiment are basically the same as those in Example 1, except that:
[0076] After step S5, the powder obtained in S5 is sintered at 100°C for 2 hours in an oxygen-free environment.
[0077] The luminescence properties of the quantum dot materials after sintering are basically the same as those in Example 1.
[0078] Example 10
[0079] The preparation steps in this embodiment are basically the same as those in Example 1, except that:
[0080] After step S5, the powder obtained in S5 is sintered at 225°C for 2 hours in an oxygen-free environment.
[0081] The luminescence properties of the aforementioned quantum dot materials decreased significantly after sintering, becoming almost non-luminescent powder, with only a few powder particles capable of emitting light.
[0082] Example 11
[0083] The preparation steps in this embodiment are basically the same as those in Embodiment 4, except that:
[0084] In step S5, the molar ratio of 3-aminopropyltriethoxysilane to tetramethoxysilane is adjusted to 1:3. The resulting quantum dot powder, after testing, showed significant improvements in full width at half maximum (FWHM), fluorescence lifetime, and water stability compared to Example 1.
[0085] Example 12
[0086] The preparation steps in this embodiment are basically the same as those in Embodiment 4, except that:
[0087] In step S2, the molar ratio of PbBr2 to ZnBr2 is adjusted to 1:1. The resulting quantum dot powder also exhibits excellent luminescent properties and stability.
[0088] Example 12
[0089] The preparation steps in this embodiment are basically the same as those in Example 1, except that:
[0090] In step S4, ethyl acetate is used as the washing agent for purification. The target quantum dots can ultimately be obtained as well.
Claims
1. A core-shell perovskite quantum dot powder and its preparation method, wherein the powder comprises: a CsPbBr3 quantum dot core; and a dense silica shell formed by high-temperature sintering and coating the surface of the CsPbBr3 quantum dot core.
2. The powder according to claim 1, characterized in that, The high-temperature sintering temperature is between 125°C and 200°C.
3. The powder according to claim 1 or 2, characterized in that, When the powder is excited at a wavelength of 365 nm, the half-width of its emission spectrum is less than 20 nm.
4. A method for preparing core-shell perovskite quantum dot powder as described in claim 1, comprising the following steps: S1. Mix Cs2CO3, 1-octadecene and oleic acid, heat to a certain temperature, and stir for 1.5 h in an oxygen-free environment in a glove box to obtain precursor solution 1; S2. PbBr2, ZnBr2, oleic acid, oleylamine, 3-aminopropyltriethoxysilane and 1-octadecene are mixed, heated to a certain temperature, and stirred for 0.5 h in an oxygen-free environment in a glove box to obtain precursor solution 2. S3. After preheating solution 1, quickly inject it into solution 2. React at 110℃-150℃ for 5-15 seconds, then add hydrobromic acid. After reacting for another 5-10 seconds, add 0.5M dodecylamine toluene solution. Continue to react for 5-10 seconds, then cool in an ice-water bath to obtain a crude solution. S4. The crude solution was purified using a detergent. After purification, the resulting precipitate was dispersed in toluene solution to obtain a perovskite quantum dot toluene solution. S5. Add tetramethoxysilane to the toluene solution of perovskite quantum dots, stir until naturally dried, and grind to obtain powder; S6. Under a nitrogen atmosphere, the powder is sintered at a certain temperature for 1-3 hours to obtain high water stability CsPbBr3 perovskite quantum dot powder based on a high-temperature sintering process.
5. The method according to claim 4, characterized in that, In steps S2 and S5, the molar ratio of 3-aminopropyltriethoxysilane to tetramethoxysilane is 1:3 to 1:
5.
6. The method according to claim 4, characterized in that, In step S6, the sintering temperature is between 125°C and 200°C.
7. The method according to claim 4, characterized in that, The sintering time in step S6 is 1 to 3 hours.
8. A backlight source, characterized in that, The backlight comprises high water-stability CsPbBr3 perovskite quantum dot powder according to any one of claims 1 to 3.