Full-solid post-processing technology of perovskite quantum dots and application thereof

Abstract

The application provides a full-solid-state post-processing technology for perovskite quantum dots, which comprises the following steps: S1, mixing a perovskite luminescent body and a post-processing additive to obtain a mixed powder; the perovskite luminescent body comprises a template agent and perovskite quantum dots in the pore channel of the template agent, and the template agent retains pores as a post-processing mass transfer path; S2, placing the mixed powder into a reaction container and heating to decompose the post-processing additive to generate HF gas, and the HF gas reacts with silicon oxide to reduce the particle size, and the HF gas diffuses into the pore channel of the template agent to passivate the surface of the perovskite quantum dots; and the template agent adopts at least one of mesoporous silicon oxide and microporous silicon oxide. The application provides a post-processing technology, which can reduce the size of the perovskite luminescent body synthesized by high-temperature solid-state synthesis and improve the light stability of the perovskite luminescent body.

Description

Technical Field

[0001] This invention belongs to the field of perovskite quantum dot post-processing technology, and particularly relates to an all-solid-state post-processing technology for perovskite quantum dots and its application. Background Technology

[0002] Metal halide perovskite (hereinafter referred to as perovskite) luminescent materials, as a novel type of light-emitting material, possess excellent luminous efficiency, narrow emission half-width, high color purity, and tunable visible light band characteristics. Furthermore, they are simple to prepare, low in cost, and easy to scale up for production, making them promising candidates for key light-emitting layer materials in the future display field. They have broad application prospects in light-emitting diodes (LEDs), solar cells, and lasers. However, because perovskite is a soft-lattice ionic compound, high humidity, high temperature, and strong light irradiation in the external environment can easily induce perovskite defects, thereby impairing its luminescent properties.

[0003] High-temperature solid-state synthesis methods are commonly used to prepare perovskite luminescent materials, offering advantages such as suitability for large-scale synthesis, high controllability, and simple procedures. Existing high-temperature solid-state synthesis methods mainly consist of two steps: 1) mixing the perovskite precursor and a template agent; 2) calcining the precursor mixture, allowing the perovskite precursor to react and melt at high temperatures, and then supercooling and crystallizing within the template agent to form the perovskite luminescent material. Due to the coating effect of the template agent, these perovskite luminescent materials can be isolated from water, oxygen, and external high temperatures, exhibiting stability against water and high temperatures.

[0004] However, strong external light exposure can still easily cause irreversible photodefects in these perovskite emitters, hindering their further development in applications requiring external light excitation, such as LEDs and photoconversion coatings. Simultaneously, high-temperature calcination (at least 400°C) easily causes template agent agglomeration and adhesion, resulting in perovskite emitters with relatively large sizes, typically ranging from tens to hundreds of micrometers, thus limiting their further application in inkjet printing, Micro LEDs, and photoconversion films. Therefore, a post-processing technique needs to be developed to improve the photostability of solid-state synthesized perovskite emitters while reducing the size of perovskite emitters prepared by high-temperature calcination, making them suitable for a wider range of applications. Summary of the Invention

[0005] The purpose of this invention is to provide an all-solid-state post-processing technology for perovskite quantum dots and its application, which can reduce the size of perovskite light emitters synthesized at high temperature and improve the photostability of perovskite light emitters.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is: an all-solid-state post-processing technology for perovskite quantum dots, comprising the following steps:

[0007] S1. Mix the perovskite luminescent material and post-treatment additives to obtain a mixed powder; the perovskite luminescent material includes a template agent and perovskite quantum dots located in the pores of the template agent, wherein the template agent retains pores for use as a mass transfer path for post-treatment.

[0008] S2. The mixed powder is placed in a reaction vessel and heated to decompose the post-treatment additives and generate HF gas. The HF gas then reacts with silicon oxide to reduce the particle size. At the same time, the HF gas diffuses into the template agent pores to passivate the surface of the perovskite quantum dots.

[0009] The template agent is at least one of mesoporous silica and microporous silica.

[0010] By employing the above method: In this application, the perovskite luminescent material can be any type of perovskite quantum dot coated with silicon oxide in the prior art, and the pores of the silicon oxide do not collapse or do not collapse completely, so as to retain pores as a mass transfer path for post-processing.

[0011] During the heating process of the mixed powder, the post-treatment additives decompose to generate HF gas. HF gas is a corrosive gas that reacts with silicon dioxide to form silicon tetrafluoride (SiF4). This etches away the large particle size originally formed by silicon dioxide clusters and agglomerations, reducing the overall particle size. Simultaneously, due to the adsorption properties of the numerous pores on the silicon dioxide, HF gas and silicon tetrafluoride (SiF4) are adsorbed into the pores, passivating the perovskite quantum dot surface.

[0012] Furthermore, the only difference between mesoporous silica and microporous silica mentioned above is the size of the pores in the silica.

[0013] Furthermore, the preparation method of the perovskite luminescent material can be found in our prior application and disclosure of a perovskite nanocrystalline fluorescent material and its preparation method and application (publication number: CN118165723A), or other related methods disclosed in the prior art. Meanwhile, the present invention also provides the following methods as examples:

[0014] A method for preparing a perovskite luminescent material includes the following steps:

[0015] Step 1: Grind and mix perovskite precursors such as cesium halide and lead halide with template agent to obtain a mixture.

[0016] Step 2: Heat the mixture to allow the precursor to react in the template agent to form a perovskite luminescent material.

[0017] The above methods are merely examples and do not constitute a limitation on the preparation methods of perovskite luminescent materials.

[0018] Furthermore, the post-treatment additive is at least one or more of NH4F, NH4HF2, KHF2, and NaHF2. In this invention, the post-treatment additive is selected as a solid, which utilizes the thermal decomposition process at the sintering temperature to generate HF gas. The HF gas reacts with the template agent, thereby reducing the clustering and adhesion of the template agent, thus achieving the purpose of reducing the size of the perovskite luminescent body prepared by high-temperature calcination. At the same time, the HF gas can also effectively diffuse into the pores of the template agent.

[0019] Furthermore, the template agent is MCM-41 molecular sieve. MCM-41 molecular sieve is a type of silica, more specifically, it is a mesoporous silica material.

[0020] Furthermore, the perovskite quantum dots have an ABX3 structure; wherein the molar ratio of A, B and X is 1:1:3, and A is Cs, B is Pb, and X is at least one of Cl, Br or I.

[0021] Furthermore, the reaction vessel is a sealed reaction vessel to prevent HF gas leakage.

[0022] Furthermore, the heating temperature in step S2 is 100-300℃.

[0023] Furthermore, in step S1, the mass ratio of the perovskite luminescent material to the post-treatment additive is (1-6):1. By specifically limiting the ratio of the two, it is ensured that the generated HF gas can simultaneously satisfy the passivation effect of etching silica to reduce particle size and diffusing into the template agent pores on the perovskite quantum dots.

[0024] Furthermore, the heating and holding time in step S2 is at least 30 minutes. By limiting the holding time, it is ensured that a sufficient amount of HF gas can be adsorbed within the pores containing the template agent.

[0025] Application of an all-solid-state post-processing technology for perovskite quantum dots in perovskite diffuser plates, inkjet printing, wavelength conversion films, quantum dot films, or Micro LEDs.

[0026] The beneficial effects of this invention are mainly reflected in:

[0027] (1) The post-processing technology of this application is aimed at: perovskite quantum dots that have been synthesized. At the same time, all the materials used in the post-processing process of this application are solid, which is suitable for the post-processing of quantum dots in the industrial scale-up stage. In other words, this application essentially provides an all-solid-state perovskite quantum dot post-processing technology.

[0028] (2) Compared with the original high-temperature solid-state synthesized perovskite light emitters, the all-solid-state post-processing technology provided by this invention enables these perovskite light emitters to not only resist water, oxygen, and heat, but also to resist the generation of photoinduced defects. The post-processing technology provided by this invention makes perovskite light emitters promising for use in inkjet printing, Micro LED, light conversion films, light conversion coatings, and other applications requiring external light excitation. Detailed Implementation

[0029] To make the objectives, technical solutions, and effects of this invention clearer and more explicit, the invention is further described in detail below. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0030] Example 1:

[0031] This embodiment provides an all-solid-state post-processing technique for perovskite quantum dots, including the following steps:

[0032] Step 1: Grind and mix 1.064g of cesium halide, 1.835g of lead halide and 3.2g of template agent MCM-41 molecular sieve for 2 hours.

[0033] Step 2: Heat the mixed powder from Step 1 to 580°C and maintain for 60 minutes, then allow it to cool naturally to obtain a perovskite luminescent material.

[0034] Step 3: Weigh 300mg of the perovskite luminescent material obtained after calcination in Step 2, add 0.15g of NH4F, and grind and blend.

[0035] Step 4: Place the perovskite luminescent material obtained after grinding in Step 3 into a sealed reaction vessel and heat it to 180 degrees Celsius. Maintain this temperature for 60 minutes and then allow it to cool naturally to obtain the post-processed product (perovskite luminescent material).

[0036] In the above, cesium halide is cesium bromide; lead halide is lead bromide.

[0037] Experimental Analysis: The perovskite luminescent material obtained after the above post-processing was subjected to particle size analysis using a Bettersize 2600 laser particle size analyzer. The results showed that the D50 of the luminescent material was 0.862 μm and the D97 was 5.326 μm. In comparison, the untreated perovskite luminescent material provided in Comparative Example 1 had a D50 of 4.665 μm and a D97 of 75.67 μm. The comparison before and after post-processing shows that all-solid-state post-processing can reduce the size of the perovskite luminescent material.

[0038] The fluorescence quantum yield (PLQY) of the sintered powder was tested, as shown in Table 1. The PLQY of this sample was 86%. In comparison, the PLQY of the untreated perovskite emitting material provided in Comparative Example 1 was 32%. The improvement in PLQY indicates that all-solid-state post-treatment can passivate defects in the perovskite CsPbBr3 emitting material.

[0039] The stability of the perovskite luminescent material obtained after the above post-processing was tested in a strong blue light irradiation environment, as shown in Table 1. The luminescent material was tested using 350 mW / cm² light. 2 After 100 hours of continuous irradiation with blue light (450 nm), the luminescence intensity of the luminescent material remained at 85% of its original intensity. In contrast, the untreated perovskite luminescent material provided in Comparative Example 1 showed a decrease in luminescence intensity to 28% of its initial intensity after 100 hours under the same blue light testing conditions. The blue light stability demonstrates that post-treatment is beneficial for improving the photostability of the CsPbBr3 luminescent material.

[0040] Example 2:

[0041] This embodiment provides an all-solid-state post-processing technique for perovskite quantum dots, including the following steps:

[0042] Step 1: Grind and mix 1.064g of cesium halide, 1.835g of lead halide and 3.2g of template agent MCM-41 molecular sieve for 2 hours.

[0043] Step 2: Heat the mixed powder from Step 1 to 580°C and maintain for 60 minutes, then allow it to cool naturally to obtain a perovskite luminescent material.

[0044] Step 3: Weigh 300mg of the perovskite luminescent material obtained after calcination in Step 2, add 0.15g of NH4HF2, and grind.

[0045] Step 4: Place the perovskite luminescent material obtained after grinding in Step 3 into a reaction vessel and heat it to 180 degrees Celsius. Maintain this temperature for 60 minutes and then allow it to cool naturally to obtain the post-processed product (perovskite luminescent material).

[0046] In the above, cesium halide is cesium bromide; lead halide is lead bromide.

[0047] Experimental Analysis: The perovskite luminescent material obtained after the above post-processing was subjected to particle size analysis using a Bettersize 2600 laser particle size analyzer. The results showed that the D50 of the luminescent material was 0.754 μm and the D97 was 4.958 μm. In comparison, the untreated perovskite luminescent material provided in Comparative Example 1 had a D50 of 4.665 μm and a D97 of 75.67 μm. The comparison before and after post-processing shows that all-solid-state post-processing can reduce the size of the perovskite luminescent material.

[0048] The fluorescence quantum yield (PLQY) of the sintered powder was tested, as shown in Table 1. The PLQY of this sample was 91%. In comparison, the PLQY of the untreated perovskite luminescent material provided in Comparative Example 1 was 32%. The increase in PLQY indicates that post-treatment can passivate defects in the perovskite CsPbBr3 luminescent material.

[0049] The stability of the perovskite luminescent material obtained after the above post-processing was tested in a strong blue light irradiation environment, as shown in Table 1. The luminescent material was tested using 350 mW / cm² light. 2 After 100 hours of continuous irradiation with blue light (450 nm), the luminescence intensity of the luminescent material remained at 83% of its original intensity. In contrast, the untreated perovskite luminescent material provided in Comparative Example 1 showed a decrease in luminescence intensity to 28% of its initial intensity after 100 hours under the same blue light testing conditions. The blue light stability demonstrates that post-treatment is beneficial for improving the photostability of the CsPbBr3 luminescent material.

[0050] Comparative Example 1:

[0051] Compared to Examples 1 and 2, this comparative example does not have a post-processing step, and includes the following steps:

[0052] Step 1: Grind and mix 1.064g of cesium halide, 1.835g of lead halide and 3.2g of template agent MCM-41 molecular sieve for 2 hours.

[0053] Step 2: Heat the mixed powder from Step 1 to 580°C and maintain for 60 minutes, then allow it to cool naturally to obtain a perovskite luminescent material.

[0054] In the above, cesium halide is cesium bromide; lead halide is lead bromide.

[0055] Experimental analysis: The perovskite luminescent material obtained by the above sintering was subjected to particle size analysis using a Bettersize 2600 laser particle size analyzer. The results showed that the D50 of the luminescent material was 4.665 μm and the D97 was 75.67 μm.

[0056] The fluorescence quantum yield (PLQY) of the powder obtained by the above sintering was tested, as shown in Table 1. The PLQY of this sample was 32%.

[0057] The stability of the perovskite luminescent material obtained above under strong blue light irradiation was tested, as detailed in Table 1, using 350 mW / cm² light. 2 After being continuously irradiated with blue light (450nm) for 100 hours, the luminescence intensity of the luminescent body can maintain 28% of the original intensity.

[0058] Comparative Example 2:

[0059] The difference from Example 1 is that the post-treatment additive (NH4F) is replaced with HF liquid.

[0060] Experimental Analysis: The sample obtained after the above treatment turned white and did not emit light. This indicates that strong acid solutions can damage the structure and degrade the performance of perovskite quantum dots. It should be noted that the intermediate product HF gas in Example 1 of this invention does not directly exhibit acidity. However, when HF gas dissolves in water, it forms hydrofluoric acid (an aqueous solution of HF), which is an acidic solution. Hydrofluoric acid solution can release hydrogen ions (H+), thus exhibiting acidity.

[0061] Comparative Example 3:

[0062] This comparative example provides an all-solid-state post-processing technique for perovskite quantum dots, including the following steps:

[0063] Step 1: Grind and mix 1.064g of cesium halide and 1.835g of lead halide for 2 hours.

[0064] Step 2: Heat the mixed powder from Step 1 to 580°C and maintain for 60 minutes, then allow it to cool naturally to obtain CsPbBr3 perovskite luminescent material (without template coating).

[0065] Step 3: Weigh 300mg of the perovskite luminescent material obtained after calcination in Step 2, and place the perovskite luminescent material in a closed reaction vessel in a hydrogen fluoride vapor environment for 60 minutes.

[0066] In the above, cesium halide is cesium bromide; lead halide is lead bromide.

[0067] Experimental analysis: Since there is no template agent (silicon oxide), hydrofluoric acid gas has no basis for reacting with silicon oxide and therefore does not change the particle size; it also does not react with silicon oxide to form silicon tetrafluoride. Hydrofluoric acid gas only effectively fills the defect sites on the perovskite surface, resulting only in a passivation effect.

[0068] Comparative Example 4:

[0069] The difference from Comparative Example 3 is that the post-processing step of HF gas in step 3 is absent.

[0070] Table 1 shows the particle size test results, PLQY test results, and the ratio of the luminescence intensity after 100 hours of blue light aging to the initial intensity of the samples obtained in Examples 1-2 and Comparative Example 1 of this invention.

[0071] Table 1

[0072]

[0073] The present invention has been illustrated with the above embodiments to explain the detailed preparation method of the present invention. However, the present invention is not limited to the above detailed preparation method, that is, it does not mean that the present invention must rely on the above product and detailed preparation method to be implemented. Those skilled in the art should understand that any improvement to the present invention, or the combination or equivalent substitution of the raw materials of the present invention, falls within the protection scope and disclosure scope of the present invention.

Claims

1. A method for all-solid-state post-processing of perovskite quantum dots, characterized in that, Includes the following steps: S1. The perovskite luminescent material and the post-treatment additive are mixed to obtain a mixed powder; the perovskite luminescent material includes a template agent and perovskite quantum dots located in the pores of the template agent, the template agent retains pores for use as a mass transfer path in the post-treatment process; the post-treatment additive is at least one of NH4F, NH4HF2, KHF2, and NaHF2; the template agent is silicon dioxide. The perovskite quantum dots have an ABX3 structure; wherein the molar ratio of A, B and X is 1:1:3, and A is Cs, B is Pb, and X is at least one of Cl, Br or I. S2. The mixed powder is placed in a reaction vessel and heated to decompose the post-treatment additives and generate HF gas. The HF gas then reacts with silicon oxide to reduce the particle size. At the same time, the HF gas diffuses into the template agent pores to passivate the surface of the perovskite quantum dots. The reaction vessel is a sealed reactor to prevent HF gas leakage.

2. The all-solid-state post-processing method for perovskite quantum dots according to claim 1, characterized in that, The template agent is MCM-41 molecular sieve.

3. The all-solid-state post-processing method for perovskite quantum dots according to claim 1, characterized in that, The heating temperature in step S2 is 100-300℃.

4. The all-solid-state post-processing method for perovskite quantum dots according to claim 1, characterized in that, The mass ratio of the perovskite luminescent material to the post-treatment additive in step S1 is (1-6):

1.

5. The all-solid-state post-processing method for perovskite quantum dots according to claim 3, characterized in that, The heating and heat preservation time in step S2 is at least 30 minutes.

6. A method for all-solid-state post-processing of perovskite quantum dots according to any one of claims 1-5, characterized in that: The perovskite luminescent material processed by the aforementioned post-processing method is used in perovskite diffuser plates, inkjet printing, or wavelength conversion films.

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