Solid-liquid mixed packaged perovskite quantum dot and preparation method thereof

Abstract

The invention provides a solid-liquid mixed packaged perovskite quantum dot, which comprises a template agent with a pore channel, the pore channel of the template agent is internally provided with a perovskite quantum dot and an organic ligand, and the organic ligand is used for passivating surface defects of the perovskite quantum dot; the template agent further comprises stearate, the powder particle size of the stearate is larger than the pore diameter of the pore channels of the template agent, and the stearate deforms under the action of external force and then is partially embedded into the pore channels of the template agent to block the pore channels. According to the invention, the PLQY is improved by passivating uncoordinated lead on the surface of the perovskite quantum dot through an organic ligand, and then a coating layer is added on the outer layer of the perovskite quantum dot through a solid-state packaging technology, so that the perovskite quantum dot can better exist in a high-temperature and high-humidity environment.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of post-processing of perovskite quantum dots, and particularly relates to a solid-liquid mixed packaged perovskite quantum dot and a preparation method thereof. BACKGROUND

[0002] Metal halide perovskite (hereinafter referred to as perovskite) luminophore, as a new type of luminescent material, has a wide application prospect in the fields of light-emitting diodes (LEDs), solar cells, lasers, etc. due to its excellent luminous efficiency, narrow half-peak width, high color purity, visible light band adjustability, simple preparation, low cost, and easy scale-up production. However, perovskite is an ionic compound with a soft lattice, and high humidity, high temperature, and strong light in the external environment can easily induce defects in perovskite, thereby damaging its luminescent properties. Therefore, perovskite needs to meet the tests of water, oxygen stability, and light stability at the same time.

[0003] In order to further improve the PLQY and stability of perovskite quantum dots, effective passivation and packaging of perovskite quantum dots are feasible. Currently, perovskite quantum dots are usually passivated by Lewis base organic matters such as oleic acid, oleylamine, and phenylethyl iodide amine to passivate uncoordinated lead on the surface of perovskite, so as to improve the PLQY and stability of perovskite quantum dots. However, such organic matters are prone to fall off in a high-temperature and high-humidity environment and lose the passivation effect.

[0004] In order to package perovskite quantum dots, high-temperature solid-state synthesis is also used in the prior art. This method mainly includes two steps: 1) mixing perovskite precursors and a template agent; and 2) calcining the precursor mixture, reacting and melting the perovskite precursors by high temperature, and forming perovskite luminophore by undercooling crystallization in the template agent. Due to the coating effect of the template agent, these perovskite luminophores can isolate water, oxygen, and external high temperature, and show resistance to water and high temperature stability.

[0005] However, the template agent only has a coating effect and cannot effectively passivate perovskite luminophore. Therefore, perovskite luminophore still has a large number of surface defects, which can cause the fluorescence intensity of perovskite luminophore to decrease in a high-temperature or light environment. If the surface defects of perovskite luminophore are passivated in the pores of the template agent, the pores need to be reserved as a mass transfer path for post-processing (see the Chinese patent CN 118978913A of the prior application of the applicant), and the reservation of the pores makes the template agent unable to completely block water and oxygen, so that water and oxygen stability and light stability cannot be considered at the same time. Therefore, it is urgent to develop a stable surface organic ligand passivation and packaging technology for perovskite quantum dots. SUMMARY

[0006] The application aims to provide a solid-liquid mixed packaged perovskite quantum dot and a preparation method thereof.

[0007] To achieve the above-mentioned purpose, the technical solution adopted by the application is: A solid-liquid mixed packaged perovskite quantum dot comprises a template agent with a pore, and the pore of the template agent is provided with a perovskite quantum dot and an organic ligand, wherein the organic ligand is used to passivate surface defects of the perovskite quantum dot. Further, the solid-liquid mixed packaged perovskite quantum dot further comprises a stearate salt, and the stearate salt is deformed and then partially embedded in the pore of the template agent to block the pore under the action of an external force. The powder particle size of the stearate salt is greater than the pore size of the template agent, and the size of the organic ligand molecule is the smallest.

[0008] In the present application, the perovskite luminescent body can be any perovskite quantum dot coated by a template agent in the prior art, and the pore of the template agent has not collapsed or has not completely collapsed to retain the pore as a mass transfer path for post-processing. It should be pointed out that the present application is essentially a post-processing technology for a substance (i.e., a perovskite luminescent body) that has synthesized a perovskite quantum dot in a template agent. The preparation method of the perovskite luminescent body can refer to a perovskite nanocrystal fluorescent material and a preparation method and application thereof (publication number: CN118165723A) disclosed in a prior application of the applicant, or a related method disclosed in other prior art. Meanwhile, the present application also provides the following method as an enumeration: A preparation method of a perovskite luminescent body, comprising the following steps: Step 1: grinding and mixing perovskite precursors such as cesium halide and lead halide and a template agent to obtain a mixture.

[0009] Step 2: heating the mixture to make the precursors react in the template agent to form a perovskite luminescent body.

[0010] The above-mentioned method is only an enumeration, which does not constitute a limitation on the preparation method of the perovskite luminescent body.

[0011] Further, the stearate salt comprises at least one of calcium stearate, zinc stearate, magnesium stearate, and barium stearate. At room temperature, the hardness of the stearate salt powder is relatively low, and the texture is relatively soft. Therefore, the stearate salt powder is easily extruded and deformed under the action of an external force.

[0012] Further, the perovskite quantum dot has an ABX3 structure. Among them, A is at least one of Cs, Rb, FA, MA, and GA. B is at least one of Pb, Sn, Cu; X is one or two of Cl, Br or I.

[0013] Further, one end of the stearate salt is deformed under external force and then partially embedded in the pore channel of the template agent to serve as a pore blocking agent, and the other end of the stearate salt is exposed outside the template agent to serve as a lubricant.

[0014] In one aspect of the present application, the stearate salt is deformed under external force to achieve the purpose of blocking pores, and in another aspect, a plurality of stearate salt powders are grafted in the pore channel of the template agent to achieve the lubricating effect in subsequent melt processing of perovskite quantum dots. At this time, the stearate salt and the perovskite quantum dots move synchronously in the subsequent processing and melt extrusion as a whole. As known, the stearate salt is usually used as a lubricant, a release agent, etc. in plastic products (including resin products) to reduce the viscosity of the plastic melt and improve its flowability and processability. This makes the plastic more smooth in extrusion molding (such as quantum dot film, quantum dot diffusion plate, light conversion film, etc.), reduces the resistance and friction in the processing process, and thus improves the production efficiency and product quality.

[0015] Further, the deformation of the stearate salt under external force comes from external extrusion, impact or friction provided in the grinding stage; The grinding includes at least one of ball milling, manual grinding and mechanical grinding.

[0016] Further, the template agent is a microporous material and / or a mesoporous material; The microporous material is one of microporous molecular sieve, microporous silicon dioxide, microporous titanium dioxide, microporous aluminum oxide, microporous transition metal oxide, microporous sulfide, microporous silicate, microporous aluminate or microporous transition metal nitride; The mesoporous material is one of mesoporous molecular sieve, mesoporous silicon dioxide, mesoporous titanium dioxide, mesoporous aluminum oxide, mesoporous carbon, mesoporous transition metal oxide, mesoporous sulfide, mesoporous silicate, mesoporous aluminate or mesoporous transition metal nitride.

[0017] Further, the particle size of the stearate salt powder > the pore size of the pore channel of the template agent > the size of the organic ligand molecule. Under the guidance of the technical concept of the present application, those skilled in the art can flexibly adjust the particle size of the stearate salt powder, the pore size of the pore channel of the template agent and the size of the organic ligand molecule. By accurately controlling the sizes of the three, the goal of the present application can be achieved. All the specific substance selection and size adjustment of the three based on the above technical concept should be included in the protection scope of the present application.

[0018] Further, the organic ligand includes at least one of oleic acid, oleylamine, ethanolamine, dodecylamine, and trimethoxypropylamine. As generally understood by those skilled in the art, any organic ligand with a molecular size less than the pore size of the template agent can be applied to the present application, and is not limited to the above-listed examples.

[0019] A preparation method of a solid-liquid mixed packaged perovskite quantum dot, comprising the following steps: S1, mixing and soaking and stirring a perovskite luminescent body and an organic ligand to obtain a mixture; the perovskite luminescent body includes a template agent and perovskite quantum dots in the pore channel of the template agent, and the template agent has a pore for mass transfer of the organic ligand; S2, blending the mixture with a stearate salt and placing it in a grinding device for grinding treatment.

[0020] It should be pointed out that the perovskite luminescent system of the present application refers to a perovskite quantum dot with a template agent.

[0021] Further, the grinding speed of step S2 is at least 200 r / min, and the grinding time is at least 10 min.

[0022] An application of a perovskite quantum dot, which can be applied in a perovskite diffusion plate, inkjet printing, wavelength conversion film, quantum dot film, or Micro LED.

[0023] The beneficial effects of the present application mainly include: (1) The object of the post-processing technology of the present application is a perovskite quantum dot that has been synthesized (or a perovskite quantum dot with a template agent). The prepared quantum dot material has the advantages of high repeatability and high luminescent efficiency. The organic ligand in the post-processing stage interacts with Pb2+ of the perovskite quantum dot by soaking and diffusion into the pore channel of the template agent, thereby passivating the surface defects of the perovskite quantum dot. In addition, calcium stearate used in the solid-state packaging stage can form a layer of coating outside the perovskite quantum dot to isolate water and oxygen and prevent degradation of the perovskite quantum dot.

[0024] (2) The present application enables the stearate salt to simultaneously have a pore blocking effect (for the pore channel of the template agent) and a lubricating effect (for the outer periphery of the template agent) in the system, so as to improve the processability of the perovskite quantum dot material. BRIEF DESCRIPTION OF DRAWINGS

[0025] Figure 1 The spectral graph of the sample obtained in Example 1 of the present application; Figure 2 The spectral graph of the sample obtained in Comparative Example 1 of the present application; Figure 3The PL intensity-temperature curve diagram of the quantum dot diffusion plate of Example 1 of the present application is shown in the following figure: Figure 4 The PL intensity-temperature curve diagram of the quantum dot diffusion plate of Comparative Example 1 of the present application is shown in the following figure: Figure 5 The PL intensity-temperature curve diagram of the quantum dot diffusion plate of Comparative Example 2 of the present application is shown in the following figure. DETAILED DESCRIPTION

[0026] In order to make the purpose, technical scheme and effect of the present application more clear and explicit, the present application will be further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0027] Example 1: The present embodiment provides a preparation method of perovskite quantum dots with solid-liquid mixed packaging, comprising the following steps: Step 1: 233 mg of cesium bromide, 367 mg of lead bromide and 600 mg of template MCM-41 are ground and mixed, the grinding time is 2 h, and the ball milling speed is 240 r / min, to obtain the corresponding CsPbBr3 solid phase precursor (mixed powder). The mixed powder is heated to 530 degrees Celsius in an air atmosphere and maintained for 60 minutes; the temperature is lowered to crystallize to react and form CsPbBr3 perovskite quantum dots in the MCM-41 pores.

[0028] Step 2: The product obtained in step 1 and 5 mL of ethanolamine are poured into a bottle for soaking and stirring, so that the organic small molecule ligand enters the pores of MCM-41 and coordinates with the Pb on the surface of the quantum dots.

[0029] Step 3: 1.2 g of calcium stearate is blended with the product obtained in step 2 and wet ground, the grinding speed is at least 200 r / min, and the grinding time is at least 10 min. After grinding, it is placed in a 60°C oven for drying.

[0030] In the above, the particle size of the stearate powder is > the pore size of the template > the size of the organic ligand molecule.

[0031] Experimental analysis: The above treated powder is tested for fluorescence quantum yield (PLQY), and the specific values are shown in Table 1. The PLQY of the sample is 91%. As a comparison, the PLQY of the perovskite quantum dots provided in Comparative Example 1 without packaging is 52%, the PLQY of the perovskite quantum dots provided in Comparative Example 2 only with liquid packaging is 89%, and the PLQY of the perovskite quantum dots provided in Comparative Example 3 only with solid packaging is 53%. The improvement of PLQY indicates that liquid packaging can passivate CsPbBr3 perovskite quantum dot defects, and only solid packaging cannot improve PLQY.

[0032] The treated powder was tested for stability in a strong blue light irradiation environment, as shown in Table 1. After 100 hours of continuous irradiation with 350 mW / cm2blue light (450 nm), the luminescence intensity of the perovskite quantum dots was able to maintain 88% of the original intensity. As a comparison, the luminescence intensity of the perovskite quantum dots provided in Comparative Example 1 without encapsulation decreased to 32% of the initial intensity after 100 hours under the same blue light test conditions, the luminescence intensity of the perovskite quantum dots provided in Comparative Example 2 with only liquid encapsulation decreased to 67% of the initial intensity after 100 hours under the same blue light test conditions, and the luminescence intensity of the perovskite quantum dots provided in Comparative Example 3 with only solid encapsulation decreased to 78% of the initial intensity after 100 hours under the same blue light test conditions. The blue light stability test proves that the solid-phase encapsulation significantly improves the light stability of the CsPbBr3quantum dots. 2

[0033] The fluorescence quantum yield and blue light stability test data prove that the solid-liquid mixed encapsulation can improve the PLQY while improving the light stability.

[0034] Example 2: The difference from Example 1 is that the calcium stearate in step S3 is replaced by magnesium stearate.

[0035] Example 3: The difference from Example 1 is that the calcium stearate in step S3 is replaced by zinc stearate.

[0036] Example 4: The difference from Example 1 is that the calcium stearate in step S3 is replaced by barium stearate.

[0037] Comparative Example 1: The difference from Example 1 is that no encapsulation is performed.

[0038] Step 1: 233 mg of cesium bromide, 367 mg of lead bromide, and 600 mg of template MCM-41 were ground and mixed for 2 h at a ball mill speed of 240 r / min to obtain the corresponding CsPbBr3solid-phase precursor. The mixed powder was heated to 530 degrees Celsius in an air atmosphere and maintained for 60 minutes. The temperature was lowered to crystallize to react and form perovskite quantum dots in the MCM-41 channels.

[0039] Comparative Example 2: The difference from Example 1 is that only liquid encapsulation is performed.

[0040] ​Step 1: 233 mg of cesium bromide, 367 mg of lead bromide and 600 mg of template MCM-41 are mixed by grinding, the grinding time is 2 h, and the ball milling speed is 240 r / min, to obtain the corresponding CsPbBr3 solid phase precursor. The mixed powder is heated to 530 degrees Celsius in an air atmosphere and maintained for 60 minutes; cooling and crystallization to react in the MCM-41 channel and form perovskite quantum dots.

[0041] Step 2: The product obtained in step 1 and 5 mL of ethanolamine are poured into a bottle for soaking and stirring, so that the organic small molecule ligand enters the channel of MCM-41 and coordinates with the Pb on the surface of the quantum dots.

[0042] Comparative Example 3: The difference from Example 1 is that only solid encapsulation is performed.

[0043] Step 1: 233 mg of cesium bromide, 367 mg of lead bromide and 600 mg of template MCM-41 are mixed by grinding, the grinding time is 2 h, and the ball milling speed is 240 r / min, to obtain the corresponding CsPbBr3 solid phase precursor. The mixed powder is heated to 530 degrees Celsius in an air atmosphere and maintained for 60 minutes; cooling and crystallization to react in the MCM-41 channel and form perovskite quantum dots.

[0044] Step 2: 1.2 g of calcium stearate is blended with the product obtained in step 1 and wet grinding is performed, the grinding speed is at least 200 r / min, and the grinding time is at least 10 min. After grinding, it is placed in a 60°C oven for drying.

[0045] Comparing Example 1 and Comparative Examples 1-3, it can be shown that only using a single encapsulation method cannot simultaneously solve the PLQY and light stability, and using a solid-liquid mixed encapsulation method can greatly improve the perovskite PLQY and light stability.

[0046] The final products of the above examples are taken, and the PLQY and light stability of each product under 450 nm blue light laser are shown in Table 1.

[0047] Table 1: Comparison of PLQY and stability test results of samples of different examples (comparative examples) Application Example: Following the preparation methods described in Example 1, Comparative Example 1, and Comparative Example 2, the amounts of each raw material were scaled up proportionally at the same mass ratio to obtain 2 g of perovskite quantum dots. The 2 g of perovskite quantum dots prepared in Example 1, Comparative Example 1, and Comparative Example 2 were then blended with 200 g of polystyrene and 0.5 g of antioxidant, respectively. The mixture was added to an injection molding machine and extruded at 220 °C to obtain three types of perovskite quantum dot diffusion plates, designated as the quantum dot diffusion plate of Example 1, the quantum dot diffusion plate of Comparative Example 1, and the quantum dot diffusion plate of Comparative Example 2.

[0048] Experimental analysis: such as Figures 2-5 The figure shows the PL intensity-temperature curves for the three types of quantum dot diffusers mentioned above. The PL intensity-temperature curves include changes in luminescence intensity during the heating phase and changes during the cooling phase, forming a thermal recovery cycle curve. The PL intensity-temperature curves represent a normalized comparison of the quantum dot luminescence intensity during heating and cooling processes.

[0049] from Figures 3-5 As can be seen, taking the organic ligand ethanolamine provided in Example 1 as an example, the boiling point of ethanolamine is approximately 170°C. During the process of blending perovskite quantum dots with a plastic substrate and then hot-extruded at high temperature, ethanolamine is at risk of thermal volatilization. For samples that only undergo liquid encapsulation, since the template pores are not blocked, the organic ligand will gradually change from a liquid to a gaseous state and escape from the pores under conditions above its boiling point, causing the surface defects of the quantum dots to be re-exposed, and the luminescence performance to decay rapidly. However, this invention physically blocks the pores using stearate under wet milling, effectively suppressing the thermal volatilization and migration of the organic ligand, thereby ensuring the long-term luminescence stability of the quantum dots under hot processing and practical application conditions. In fact, Example 1 of this invention does not block all template agent pores.

[0050] The solid-state plugging of this invention primarily acts on the pore opening region, aiming to raise the energy barrier for the escape of small-molecule organic ligands within the pores under high-temperature processing or light irradiation conditions. By forming embedded, discretely distributed physical plugging structures in some larger pore openings, the migration and volatilization of liquid ligands can be suppressed. Furthermore, the discrete plugging structure exhibits better structural stability and failure resistance under thermal processing conditions compared to continuous plugging layers. This is because, under thermal processing conditions, continuous plugging films are prone to thermal expansion mismatch with MCM-41 due to their overall continuity, leading to the accumulation of interfacial stress and consequently, film cracking or peeling. In contrast, the discretely distributed pore opening plugging structure employed in this invention can effectively release thermal stress, thereby maintaining the stability of the plugging structure during high-temperature processing and continuously suppressing the migration and volatilization of small molecules within the pores.

[0051] The detailed preparation method of the present application is illustrated by the above examples, but the present application is not limited to the above detailed preparation method, i.e. it does not mean that the present application must rely on the above products and detailed preparation method to be implemented. It should be understood by those skilled in the art that any improvement on the present application, combination or equivalent replacement of each raw material of the product of the present application, all fall within the protection scope and disclosure scope of the present application.

Claims

1. A perovskite quantum dot encapsulated in a solid-liquid hybrid manner, characterized in that, The template agent includes a channel containing perovskite quantum dots and an organic ligand, the organic ligand being used to passivate surface defects of the perovskite quantum dots. It also includes stearates, which deform under external force and partially embed themselves in the pores of the template agent to seal the pores; The particle size of the stearate powder is greater than the pore size of the template agent, which is greater than the size of the organic ligand molecule.

2. The perovskite quantum dot with solid-liquid hybrid encapsulation according to claim 1, characterized in that, The perovskite quantum dots have an ABX3 structure; Wherein, position A is at least one of Cs, Rb, FA, MA, and GA; The B site is at least one of Pb, Sn, and Cu; X is one or two of Cl, Br, or I.

3. The perovskite quantum dot with solid-liquid hybrid encapsulation according to claim 1, characterized in that, One end of the stearate deforms under external force and is partially embedded in the pores of the template agent as a plugging agent, while the other end of the stearate is exposed outside the template agent as a lubricant.

4. The perovskite quantum dot with solid-liquid hybrid encapsulation according to claim 3, characterized in that, The deformation of the stearate under external force comes from the external extrusion, impact or friction provided during the grinding stage; The grinding includes at least one of ball milling, manual grinding, and mechanical grinding.

5. The perovskite quantum dot with solid-liquid hybrid encapsulation according to claim 1, characterized in that, The template agent is a microporous material and / or a mesoporous material; The microporous material is one of the following: microporous molecular sieve, microporous silica, microporous titanium dioxide, microporous alumina, microporous transition metal oxide, microporous sulfide, microporous silicate, microporous aluminate, or microporous transition metal nitride. The mesoporous material is one of the following: mesoporous molecular sieve, mesoporous silica, mesoporous titanium dioxide, mesoporous alumina, mesoporous carbon, mesoporous transition metal oxide, mesoporous sulfide, mesoporous silicate, mesoporous aluminate, or mesoporous transition metal nitride.

6. The perovskite quantum dot with solid-liquid hybrid encapsulation according to claim 3, characterized in that, The stearate includes at least one of calcium stearate, zinc stearate, magnesium stearate, and barium stearate.

7. The perovskite quantum dot with solid-liquid hybrid encapsulation according to claim 1, characterized in that, The organic ligand includes at least one of oleic acid, oleylamine, ethanolamine, butylamine, and trimethoxypropylamine.

8. A method for preparing perovskite quantum dots with solid-liquid hybrid encapsulation according to any one of claims 1-7, characterized in that, Includes the following steps: S1. The perovskite luminescent material and the organic ligand are mixed and soaked and stirred to obtain a mixture; the perovskite luminescent material includes a template agent and perovskite quantum dots located in the pores of the template agent, and the template agent has pores for the mass transfer pathway of the organic ligand. S2. The mixture is blended with stearate and then placed in a grinding device for grinding.

9. The method for preparing perovskite quantum dots with solid-liquid hybrid encapsulation according to claim 8, characterized in that, The grinding speed in step S2 is at least 200 r / min, and the grinding time is at least 10 min.

10. The application of a perovskite quantum dot according to any one of claims 1-7, characterized in that, The perovskite quantum dots can be used in perovskite diffusers, inkjet printing, wavelength conversion films, quantum dot films, or Micro LEDs.

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