Perovskite quantum dot for constructing lead-containing hydroxide passivation layer in mesoporous material

Abstract

The invention provides a perovskite quantum dot for constructing a lead-containing hydroxide passivation layer in a mesoporous material. The perovskite quantum dot comprises the following components in parts by weight: 30-50 parts of mesoporous material; 4-8 parts of a hole blocking agent; 42 to 60 parts of a perovskite nanocrystal; the balance of a lead-containing hydroxide passivation layer; the hole plugging agent is a metal oxide; the perovskite nanocrystal is of an ABX3 structure; wherein A is selected from at least one of Cs < + > and CH3NH3 < + >, B is Pb, and X is at least one of Cl <->, Br <-> or I <->. According to the invention, trace water is adjusted in the pore channels of the mesoporous material, so that the perovskite quantum dots PLQY and the stability are improved.

Description

Technical Field

[0001] This invention belongs to the field of perovskite quantum dot technology, and particularly relates to a perovskite quantum dot in which a lead hydroxide passivation layer is constructed within a mesoporous material. Background Technology

[0002] All-inorganic lead-containing perovskite quantum dots have been widely studied and applied in optoelectronic devices due to their advantages such as high fluorescence efficiency, narrow emission, and wide color gamut. However, current lead halide perovskite quantum dot materials struggle to maintain good stability under harsh conditions such as humidity, oxygen, ultraviolet light, and heat, significantly hindering their practical application in the display field. Core-shell structures are considered one of the effective means to improve the stability of quantum dots; by encapsulating the quantum dots with a coating layer to isolate them from the external environment, the stability of quantum dots to water, oxygen, and heat can be greatly improved.

[0003] Perovskite quantum dots typically exhibit poor stability when exposed to water. They readily decompose in aqueous environments because perovskite quantum dots are ionic crystals, easily dissolving or dissociating in polar solvents such as water, leading to a decrease in their luminescent properties.

[0004] However, some studies have also shown that the presence of trace amounts of water can play a positive role in improving the crystallization and PLQY of lead halide perovskite quantum dots. For example, the article "Ultrasmall water-stable CsPbBr3 quantum dots with high intensity blue emission enabled by zeoliteconfinement engineering" published by Bai and Xia's team states that an appropriate amount of water can change the crystallization environment of CsPbBr3 quantum dots, resulting in higher stability and PLQY values.

[0005] However, how to regulate trace amounts of water within the pores of mesoporous materials to improve the PLQY value of perovskite quantum dots is an urgent problem to be solved. Summary of the Invention

[0006] The purpose of this invention is to provide a perovskite quantum dot with a lead hydroxide passivation layer constructed within a mesoporous material, thereby improving the PLQY and stability of the perovskite quantum dot by adjusting the amount of water within the pores of the mesoporous material.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is: a perovskite quantum dot for constructing a lead hydroxide passivation layer within a mesoporous material, comprising the following weight fractions:

[0008]

[0009] The total weight of the above amounts to 100 portions;

[0010] The plugging agent is a metal oxide;

[0011] The perovskite nanocrystals have an ABX3 structure; wherein, A is selected from Cs. + CH3NH3 + At least one of them, B is Pb, X is Cl - ,Br - Or I - At least one of them.

[0012] Furthermore, the pores of the mesoporous material contain perovskite nanocrystals and a pore-blocking agent, with a lead hydroxide passivation layer between the pore-blocking agent and the perovskite nanocrystals;

[0013] The lead hydroxide passivation layer is used to passivate surface defects of perovskite nanocrystals.

[0014] Furthermore, the mass ratio between the mesoporous material and the plugging agent is 1:(0.14-0.19).

[0015] Furthermore, the metal oxide is one or more of CaO, Al2O3, and Eu2O3.

[0016] Furthermore, the lead hydroxide passivation layer is one of lead hydroxide bromine, lead hydroxide chlorine, or lead hydroxide bromine chlorine.

[0017] Furthermore, the mesoporous material is selected from at least one of molecular sieves, mesoporous silica, mesoporous titanium dioxide, mesoporous alumina, mesoporous carbon, mesoporous transition metal oxides, mesoporous sulfides, silicates, aluminates, and transition metal nitrides.

[0018] Furthermore, the lead hydroxide passivation layer is lead bromine hydroxide (PbBrOH).

[0019] Furthermore, there is a gap between the plugging agent and the pore wall of the mesoporous material to allow water to pass through, and the plugging agent is used to limit the diffusion rate and capacity of water in the pores of the mesoporous material.

[0020] Furthermore, the lead hydroxide passivation layer is formed after the perovskite nanocrystals come into contact with water, which comes from water vapor in the air or liquid water.

[0021] The aforementioned perovskite quantum dots can be applied to perovskite diffusers, light-emitting devices, wavelength conversion films, quantum dot films, quantum dot light-emitting diodes, or quantum dot masterbatches.

[0022] In some embodiments, any commercially available method can be used to synthesize perovskite nanocrystals. Details will not be elaborated further here. Similarly, the following preparation methods can also be used (see examples below).

[0023] The beneficial effects of this invention are mainly reflected in:

[0024] (1) This invention attempts to plug pores within mesoporous materials using a plugging agent. However, this plugging is not a complete seal; gaps remain between the plugging agent and the inner wall of the mesoporous material pores. This limits the diffusion rate and capacity of water within the mesoporous material pores during post-water treatment. When perovskite nanocrystals within the mesoporous material pores encounter trace amounts of water, they partially decompose into cesium halides and lead halides, as perovskite nanocrystals are soft lattice ionic compounds. Lead halides further react with trace amounts of water to form lead hydroxides, specifically PbXOH (where X is a halogen element). Due to the low solubility of lead hydroxides, they can adhere to the surface of undecomposed perovskite quantum dots to form a lead hydroxide passivation layer.

[0025] (2) This invention regulates the diffusion rate and capacity of water in the pores of the mesoporous material by controlling the mass ratio of the mesoporous material to the plugging agent to 1:(0.14-0.19), thereby slowing down the decomposition of perovskite nanocrystals upon contact with water and allowing time for the formation of lead hydroxide PbXOH (where X is a halogen element). The perovskite quantum dots provided by this invention are expected to be used in applications such as perovskite diffuser plates, light-emitting devices, wavelength conversion films, quantum dot films, quantum dot light-emitting diodes, or quantum dot masterbatches. Attached Figure Description

[0026] Figure 1 The product prepared in Example 1 was treated with 350 mW / cm 2 Comparison of luminescence intensity after 100 hours of continuous irradiation with blue light (450nm);

[0027] Figure 2 Comparison of fluorescence quantum yield (PLQY) performance of perovskite quantum dots before and after washing for 20 samples prepared repeatedly for Comparative Example 2.

[0028] Figure 3 This is an XRD comparison image of the perovskite quantum dots of Example 1 before soaking in water (step 2) and after soaking in water (step 3). 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] In some embodiments, perovskite quantum dots can be prepared using the following method:

[0031] A method for preparing perovskite quantum dots includes the following steps:

[0032] S1. Preparation of sintering precursor: Perovskite nanocrystals, pore-blocking agent and mesoporous material are blended and ground to obtain sintering precursor; among them, the perovskite nanocrystals and the pore-blocking agent with the lowest melting point are substances A;

[0033] S2. Constructing a core-shell structure: Take the sintering precursor from step S1 and perform dynamic sintering under conditions that are higher than the melting point of substance A and lower than the failure temperature of the mesoporous material. Then cool it to room temperature to prepare perovskite nanocrystals and a plugging agent encapsulated by the mesoporous material.

[0034] S3. Post-soaking treatment: The product from step S2 is soaked and washed in water, and then dried by centrifugation to obtain post-treated perovskite quantum dots.

[0035] Furthermore, the sintering process in step S2 consists of a heating and melting stage, a heat preservation and filling stage, and a cooling and crystallization stage in sequence;

[0036] When in the heating and melting stage, the titanium dioxide nanocrystals and the pore-blocking agent form a molten liquid;

[0037] During the insulation and filling stage, the molten liquid will be absorbed into the channels of the mesoporous material;

[0038] During the cooling and crystallization stage, pore-blocking agents and perovskite nanocrystals are formed in the pores.

[0039] Among them, the plugging agent formed during the heating and melting stage and the plugging agent formed during cooling and crystallization are different substances; and the melting point of the plugging agent formed during cooling and crystallization is greater than that of the plugging agent formed during the heating and melting stage.

[0040] For example, when Ca(OH)₂ is used as the pore-blocking agent, it decomposes into CaO upon heating. When Al(OH)₃ is used, it decomposes into Al₂O₃ upon heating. Therefore, the metal oxide within the mesoporous channels of the perovskite quantum dots in this application can be derived from metal hydroxides or directly used as metal oxides; both of these methods are within the scope of protection of this application. Furthermore, the technical solutions for the preparation method have been sought for protection in other applications, which will only be briefly described here.

[0041] Example 1:

[0042] This embodiment provides a method for constructing perovskite quantum dots containing a lead hydroxide passivation layer within a mesoporous material, comprising the following preparation steps:

[0043] Step 1: CsBr (256.1g), PbBr2 (449g), and KBr (72.6g) were added to a pot mill and ground for 2 hours to form CsPbBr3 perovskite quantum dots. Then, MCM-41 molecular sieve (650g), Ca(OH)2 (67.8g), Al(OH)3 (24.1g), and Eu2O3 (38.7g) were added and ground for another 3 hours to prepare the sintering precursor.

[0044] Step 2: Place the sintering precursor from Step 1 in a rotary kiln and heat it to 560°C at a rate of 5°C / min, maintaining the temperature for 30 minutes, followed by natural cooling. Air must be introduced before heating to 450°C and again when cooling to 450°C, with a flow rate of 4L / min-8L / min, to prepare perovskite nanocrystals encapsulated by mesoporous materials.

[0045] Step 3: After cooling to room temperature, add pure water at a ratio of 1g phosphor (i.e., the product from Step 2) to 50ml pure water for heated ultrasonic washing. Heat and stir at 50℃ for 2 hours, with ultrasonic stirring for 1 hour during the process. After washing, centrifuge the product and then transfer it to a washing container for a second wash, following the same washing and centrifugation steps as above. After washing, dry the product in an 80°C oven to obtain post-treated perovskite quantum dots.

[0046] Experimental analysis: 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 75%.

[0047] The stability of the perovskite quantum dots obtained above under strong blue light irradiation was tested, as shown 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 perovskite quantum dot was able to maintain 43.78% of the initial intensity.

[0048] The thermal stability of the perovskite quantum dots obtained above was tested by heating them from room temperature to 140°C in a light-protected environment, and then allowing them to cool naturally back to room temperature. The luminescence intensity of the perovskite quantum dots retained 56.4% of the initial intensity.

[0049] Example 2:

[0050] The difference from Example 1 is that the amounts of Ca(OH)2, Al(OH)3, and Eu2O3 added in step 1 are changed. Specifically, the following limitations are imposed:

[0051] Ca(OH)2(67.8g), Al(OH)3(51.2g), Eu2O3(38.7g).

[0052] Example 3:

[0053] The difference from Example 1 is that the amounts of Ca(OH)2, Al(OH)3, and Eu2O3 added in step 1 are changed. Specifically, the following limitations are imposed:

[0054] Ca(OH)2(67.8g), Al(OH)3(24.1g), Eu2O3(23.9g).

[0055] Comparative Example 1:

[0056] The difference from Example 1 is that Ca(OH)2 is not added in step 1.

[0057] Experimental Analysis: The dry powder obtained in step 2 showed a wavelength of 511.4 nm and a PLQY of 14.7%, indicating weak luminescence. Furthermore, the powder changed from yellow to white after being soaked in water and ceased luminescence, indicating phosphor failure. This suggests that without the shrinkage effect of Ca(OH)₂, a significant amount of water enters the pores of the mesoporous material, comes into contact with the perovskite quantum dots, and decomposes many of them.

[0058] Comparative Example 2:

[0059] The difference from Example 1 is that step 3, the post-soaking treatment, is absent. That is, the washing in step 3 is not performed after step 2.

[0060] Experimental analysis: Before washing, the powder properties were: wavelength 517.4 nm, half-width at half-maximum 21.3 nm, PLQY 57.47%; after washing, the powder properties were: wavelength 517.6 nm, half-width at half-maximum 20.9 nm, PLQY 75%.

[0061] To determine the reliability of the data responses, a total of 20 replicate control experiments were conducted, details of which can be found in [link to details]. Figure 2 Experiments revealed that the fluorescence quantum yield (PLQY) performance improved after washing compared to before washing. Furthermore, the phosphor particle size also tended to decrease after washing, with D90 decreasing from 39.84 μm to 15.74 μm. Our analysis suggests that the water washing in step 3 removes substances not adsorbed by the mesoporous material (e.g., salts), which dissolve in water. Additionally, the large particles agglomerated during sintering can be broken down into fine powder by ultrasonic washing, thus reducing particle size and improving the uniformity of quantum dot size.

[0062] Comparative Example 3:

[0063] The difference from Example 1 is that Al(OH)3 and Ca(OH)2 are not added in step 1.

[0064] Experimental analysis: The produced powder is white, has almost no luminescence, and will be quenched after soaking in water, indicating that the quantum dot phosphor has become ineffective.

[0065] Table 1 shows the performance test results of the samples obtained in Examples 1-3 and Comparative Examples 1-2 of this invention. The thermal stability data was tested under the following conditions: heated from room temperature to 140°C in a light-protected environment, and then naturally cooled back to room temperature. The luminescence intensity of the perovskite quantum dots maintained a proportion of the initial intensity.

[0066] The test conditions for blue light stability were: 350mW / cm 2 After being continuously irradiated with blue light (450nm) for 100 hours, the luminescence intensity of the perovskite quantum dot was able to maintain the proportion of its initial intensity.

[0067] Table 1: Performance test results of samples from different examples (comparative examples)

[0068] Examples / Comparative Examples PLQY Thermal stability Particle size D90 Blue light stability Example 1 75％ 56.4％ 15.74μm 43.78％ Example 2 72％ 57.5％ 16.41μm 48.55％ Example 3 68％ 60.2％ 18.37μm 39.37％ Comparative Example 1 14.7％ 47.3％ 20.47μm 15.74％ Comparative Example 2 57.47％ 53％ 39.84μm 33.41％

[0069] 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 perovskite quantum dot with a passivation layer of lead hydroxide built within a mesoporous material, characterized in that, The weight fraction comprises: The pore-blocking agent is a metal oxide; The perovskite nanocrystals have an ABX3 structure; wherein, A is selected from Cs. + CH3NH3 + At least one of them, B is Pb, X is Cl - ,Br - or I - At least one of them.

2. The perovskite quantum dot with a passivation layer of lead hydroxide constructed in a mesoporous material according to claim 1, characterized in that, The mesoporous material has a perovskite nanocrystal and a pore-blocking agent in the pore, and a lead-containing hydroxide passivation layer between the pore-blocking agent and the perovskite nanocrystal; The lead-containing hydroxide passivation layer is used to passivate the surface defects of the perovskite nanocrystal.

3. The perovskite quantum dot with a passivation layer of lead hydroxide constructed in a mesoporous material according to claim 1, characterized in that, The mass ratio between the mesoporous material and the pore-blocking agent is 1:(0.14-0.19).

4. The perovskite quantum dot with a passivation layer of lead hydroxide constructed in a mesoporous material according to claim 1, characterized in that, The metal oxide is one or more of CaO, Al2O3 and Eu2O3.

5. The perovskite quantum dot with a passivation layer of lead hydroxide constructed in a mesoporous material according to claim 1, characterized in that, The lead-containing hydroxide passivation layer is one of lead hydroxide bromide, lead hydroxide chloride, and lead hydroxide bromide chloride.

6. The perovskite quantum dot with a passivation layer of lead hydroxide constructed in a mesoporous material according to claim 1, characterized in that, The mesoporous material is at least one of a molecular sieve, mesoporous silica, mesoporous titanium dioxide, mesoporous aluminum oxide, mesoporous carbon, mesoporous transition metal oxide, mesoporous sulfide, silicate, aluminate, and transition metal nitride.

7. The perovskite quantum dot with a passivation layer of lead hydroxide constructed in a mesoporous material according to claim 5, characterized in that, The lead-containing hydroxide passivation layer is lead hydroxide bromide (PbBrOH).

8. The perovskite quantum dot with a passivation layer of lead hydroxide built in the mesoporous material according to any one of claims 2-3, characterized in that, The pore-blocking agent and the pore wall of the mesoporous material have a gap for water to pass through, and the pore-blocking agent is used to limit the diffusion speed and capacity of water in the mesoporous material channel.

9. The perovskite quantum dot with a passivation layer of lead hydroxide constructed within a mesoporous material according to claim 8, characterized in that, The lead-containing hydroxide passivation layer is formed after the perovskite nanocrystal encounters water, which comes from water vapor or liquid water in the air.

10. The perovskite quantum dot with a passivation layer of lead hydroxide built in the mesoporous material according to any one of claims 1-7, characterized in that, The perovskite quantum dot can be applied to a perovskite diffusion plate, a light-emitting device, a wavelength conversion film, a quantum dot film, a quantum dot light-emitting diode, or a quantum dot master batch.

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