Use of a stannous halide in a perovskite quantum dot milling precursor

Abstract

The application provides application of stannous halide in a perovskite quantum dot grinding precursor, the stannous halide is blended with a perovskite quantum dot precursor to obtain a precursor mixture, the stannous halide is used as a quantum dot synthesis inhibitor in a high-energy grinding stage of the precursor mixture; the perovskite quantum dot has an ABX3 structure; wherein, the molar ratio of A, B and X is 1:1:3, A is Cs, B is Pb, and X is at least one of Cl, Br or I. The application can realize that perovskite quantum dots are not formed in advance when perovskite precursors are high-energy ground, thereby ensuring that the perovskite quantum dots have a reduced particle size and still have high optical performance.

Description

Technical Field

[0001] This invention belongs to the field of quantum dot precursor pretreatment technology, and particularly relates to the application of a tin halide in perovskite quantum dot grinding precursors. 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 thermal atmospheres, which greatly affects their practical application in the display field.

[0003] To reduce the particle size of synthesized perovskite quantum dots to meet the requirements of quantum dot applications, perovskite precursors are often subjected to high-energy grinding to reduce their size, thereby attempting to synthesize perovskite quantum dots with even smaller particle sizes. However, research has found that perovskite nanocrystals can be directly prepared by grinding the perovskite precursors, such as CN114940903A, CN115197700A, KR1020220161569A, and US6017504A.

[0004] To improve the stability of perovskite quantum dots, current techniques utilize high-temperature calcination to heat the milled perovskite precursor into a molten liquid, which is then adsorbed into the pores of a mesoporous material. Upon cooling and crystallization, this encapsulates the perovskite quantum dots with a layer of mesoporous material. However, due to the high-energy milling of the perovskite precursor, pre-synthesized perovskite quantum dots are present within it, and premature formation of these quantum dots is not desirable. For example, CsPbBr3 perovskite quantum dots are unstable at high temperatures and easily decompose into precursors (such as CsBr and PbBr2), potentially even releasing volatile halogen gases (such as Br2). During decomposition, the stoichiometric ratio of the perovskite components becomes unbalanced, preventing the reformation of a high-quality crystal structure upon cooling and consequently reducing the optical properties of the perovskite.

[0005] Therefore, it is necessary to study how to reduce the particle size of perovskite quantum dots while ensuring their high optical performance, which is an urgent technical problem to be solved. Summary of the Invention

[0006] The purpose of this invention is to provide an application of tin halide in perovskite quantum dot grinding precursors. This technology enables the high-energy grinding of perovskite precursors without the pre-formation of perovskite quantum dots, thereby ensuring that while reducing the particle size of perovskite quantum dots, they still possess high optical performance and further resist the generation of photo-induced defects.

[0007] To achieve the above objectives, the technical solution adopted by the present invention is: the application of a tin halide in a perovskite quantum dot grinding precursor, wherein the tin halide is blended with a perovskite quantum dot precursor to obtain a precursor mixture, and the tin halide is used as a quantum dot synthesis inhibitor in the high-energy grinding stage of the precursor mixture.

[0008] 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.

[0009] Furthermore, the high-energy grinding conditions are: a rotation speed of at least 200 rpm and a grinding time of at least 15 minutes; the grinding temperature generated by the high-energy grinding is at least 50°C.

[0010] Furthermore, the grinding equipment is at least one of a ball mill, a pot mill, and a grinding mill.

[0011] Furthermore, the stannous halide is at least one of stannous fluoride, stannous bromide, stannous chloride, and stannous iodide.

[0012] Furthermore, the perovskite quantum dot precursor includes a Cs source precursor, a Pb source precursor, and an X source precursor;

[0013] The Cs source precursor is one or more of cesium halide and cesium carbonate;

[0014] The Pb source precursor is one or more of lead halide and lead acetate.

[0015] The halogen source precursor is one or more of the following: cesium halide, lead halide, zinc halide, potassium halide, sodium halide, lithium halide, ammonia halide, calcium halide, strontium halide, and barium halide.

[0016] Furthermore, the precursor mixture also includes a grinding aid, which includes at least one or a combination of Ca(OH)2, Al(OH)3, and Al2O3.

[0017] Furthermore, the molar ratio of the perovskite quantum dot precursor to the stannous halide is (10-50):1.

[0018] Furthermore, the molar ratio of the perovskite quantum dot precursor to the stannous halide is 20:1.

[0019] Furthermore, the perovskite quantum dots are used in perovskite diffuser plates, light-emitting devices, wavelength conversion films, quantum dot films, quantum dot light-emitting diodes, or quantum dot masterbatches.

[0020] The beneficial effects of this invention are mainly reflected in:

[0021] (1) This invention adds stannous halides (taking stannous fluoride as an example) to the sintering precursor A for high-energy grinding, which can regulate the growth mode of perovskite quantum dots and improve crystallinity. Specifically: Since SnF2 is a reducing agent, during high-speed grinding, the reactivity increases due to mechanical force, and the oxidation reaction becomes more intense, resulting in the formation of tin oxide (SnO) in the air. It is precisely because SnF2 preferentially reacts with oxygen in the air to form SnO that it dominates the reactivity of the system. The formation of SnO further hinders the contact and reaction of the perovskite quantum dot precursors (CsBr and PbBr2) as the grinding part covers their surfaces. It should be emphasized that during high-speed grinding, the reaction rate of SnF2 is faster, and the reaction priority leads to the inhibition of the reaction of CsBr and PbBr2, weakening the motive force for the formation of CsPbBr3. This allows for the high-energy grinding of perovskite precursors without the pre-formation of perovskite quantum dots, ensuring that while reducing the particle size of perovskite quantum dots, they still possess high optical performance and further resist the generation of photo-induced defects.

[0022] (2) The rare earth metal oxides added in this invention can play a grinding aid role and a size control role (play a barrier and prevent agglomeration) during the grinding stage, thereby effectively reducing the size of mesoporous materials and perovskite quantum dots; on the other hand, they can be used as surface modifiers to improve the PLQY and stability of quantum dots.

[0023] (3) Compared with the high-temperature solid-state synthesis of perovskite quantum dots in the prior art, the synthesis technology provided by the present invention can obtain perovskite quantum dots with higher PLQY and smaller particle size. Attached Figure Description

[0024] Figure 1 The PL spectrum of the perovskite quantum dots prepared in Example 1;

[0025] Figure 2 Comparative images of the sintering precursor A powder after grinding in step 1 of Comparative Example 1 and Example 1 are shown.

[0026] Figure 3 The images show a comparison of whether the sintering precursor A powder after grinding in step 1 of Comparative Example 1 and Example 1 emits green light when irradiated with a handheld ultraviolet lamp.

[0027] Figure 4 The image shows the XRD pattern of the sintering precursor A powder after grinding in step 1 of Comparative Example 1.

[0028] Figure 5 The image shows the XRD pattern of the sintering precursor A powder after grinding in step 1 of Example 1. 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] A method for preparing perovskite quantum dots includes the following steps:

[0031] S1. Preparation of sintering precursor A: Add perovskite quantum dot precursor and stannous halide to a grinding equipment for grinding at a speed of at least 200 rpm for at least 15 minutes.

[0032] S2. Preparation of sintering precursor B: Add mesoporous material, rare earth metal oxide and grinding aid to sintering precursor A and perform co-milling at a speed of at least 200 rpm for at least 30 minutes.

[0033] S3. Synthesis of perovskite quantum dots: Take the sintering precursor B from step S2 and perform dynamic sintering at a temperature not lower than 500℃ to prepare intermediate products.

[0034] S4. Annealing treatment: Gradually reduce the temperature of the intermediate product in step S3 to the range of 400-485℃ and keep it at that temperature for at least 30 minutes to perform annealing treatment. After annealing treatment, reduce the temperature to room temperature to obtain perovskite quantum dots encapsulated by mesoporous materials.

[0035] In the above description, the grinding aid is added in step S2, but it can also be added in step S1. This is a conventional technical choice made by those skilled in the art based on the inventive concept. To clarify the role of tin halides in the system, the present invention places the tin halides and grinding aids separately in steps S1 and S2 for grinding.

[0036] In the above, 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.

[0037] In the above, the grinding aid is at least one or a combination of Ca(OH)2, Al(OH)3, and Al2O3. For example, when Ca(OH)2 is selected as the grinding aid, Ca(OH)2 decomposes into CaO and water vapor (H2O) when heated. When Al(OH)3 is selected as the grinding aid, Al(OH)3 decomposes into Al2O3 and water vapor (H2O) when heated.

[0038] In other words, the grinding aids used in the high-energy grinding stage and the grinding aids formed after the synthesis of perovskite quantum dots are different substances. Furthermore, both of these grinding aids generate water vapor after thermal decomposition, which is adsorbed by the mesoporous channels. The presence of trace amounts of water helps to improve the quantum efficiency of perovskite quantum dots.

[0039] In the above, the rare earth metal oxide includes at least one of zirconium oxide, yttrium oxide, europium oxide, zirconium-yttrium oxide, cerium oxide, neodymium oxide, samarium oxide, gadolinium oxide, terbium oxide, and scandium oxide.

[0040] Example 1:

[0041] This embodiment provides an application of stannous halides in perovskite quantum dot grinding precursors, including the following steps:

[0042] Step 1: CsBr (94.6g), PbBr2 (149.0g), and SnF2 (6.9g) were added to a ball mill and ground for 0.5h to obtain sintering precursor A. The grinding speed was 350rpm.

[0043] Step 2: Add MCM-41 molecular sieve (183.0g), Ca(OH)2 (20.5g), nanoporous Al2O3 (46.5g), and Eu2O3 (9.1g) to sintering precursor A and grind them together in a ball mill for 1 hour at a speed of 350 rpm to prepare sintering precursor B.

[0044] Step 3: Place the sintering precursor B from Step 2 into a rotary tube furnace and heat it to 550°C at a rate of 10°C / min, and maintain the temperature for 30 minutes. Then, cool it down to 480°C within 30 minutes, hold it at that temperature for 60 minutes, and then allow it to cool naturally. Air is circulated throughout the process to prepare perovskite quantum dots encapsulated by mesoporous materials.

[0045] Step 4: After cooling to room temperature, add pure water at a ratio of 1g phosphor (i.e., the product from Step 3) to 50ml pure water for heating and 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 perovskite quantum dots.

[0046] Experimental Analysis: The wavelength, fluorescence quantum yield (PLQY), and particle size of the sintered powder were tested, as shown in Table 1. For this sample, the wavelength was 518 nm, the PLQY was 93%, and the D90 was 9.8 μm. The perovskite quantum dots obtained above were mixed with PS material to prepare a quantum dot diffusion plate, and its stability under strong blue light irradiation was tested, as shown in Table 1. After continuous irradiation with 350 mW / cm² blue light (450 nm) for 100 hours, the brightness of the perovskite quantum diffusion plate maintained 95% of its initial intensity.

[0047] Comparative Example 1:

[0048] The difference from Example 1 is that SnF2 is not incorporated in step 1.

[0049] Experimental analysis: The prepared dry powder was tested to obtain a wavelength of 516.6 nm, a PLQY of 83%, and a D90 of 11.0 μm. The perovskite quantum diffusion plate, after 100 hours of blue light irradiation, retained 88% of its initial intensity. This indicates that SnF2 can primarily regulate the growth mode of perovskite quantum dots and improve crystallinity, thereby increasing the final PLQY and reducing the particle size.

[0050] Figure 2 The image on the left shows the sintering precursor A powder after grinding in step 1 of Comparative Example 1.

[0051] Figure 2 The image on the right shows the sintering precursor A powder after grinding in step 1 of Example 1.

[0052] Figure 3 The image on the left shows the sintering precursor A powder after grinding in step 1 of Comparative Example 1 inside a ball mill. The sintering precursor A powder adheres to the surface of the small balls in the ball mill jar and the inner wall of the ball mill jar. When irradiated with a handheld ultraviolet lamp, the sintering precursor A powder emits green light, indicating that CsPbBr3 quantum dots are formed in this step.

[0053] Figure 3 On the right is the sintering precursor A powder after grinding in step 1 of Example 1, inside a ball mill. The sintering precursor A powder adheres to the surface of the small balls in the ball mill jar and the inner wall of the ball mill jar. When irradiated with a handheld ultraviolet lamp, the sintering precursor A powder did not emit green light, indicating that CsPbBr3 quantum dots were not formed in this step.

[0054] Figure 4 The image shows the XRD pattern of the sintering precursor A powder after grinding in step 1 of Comparative Example 1.

[0055] Figure 5 The image shows the XRD pattern of the sintering precursor A powder after grinding in step 1 of Example 1.

[0056] Comparative Example 2:

[0057] The difference from Example 1 is that SnF2 and Eu2O3 are not incorporated in step 1.

[0058] Experimental analysis: The prepared dry powder was tested at a wavelength of 516 nm, with a PLQY of 67% and a D90 of 20.8 μm. The perovskite quantum diffusion plate, after 100 hours of blue light irradiation, retained 85% of its initial intensity. This indicates that Eu2O3 primarily functions as a grinding aid and a size control agent (blocking and preventing agglomeration) during the grinding process, effectively reducing the size of perovskite quantum dots. Secondly, it can act as a surface modifier to improve the PLQY and stability of quantum dots.

[0059] Comparative Example 3:

[0060] The difference from Example 1 is that no nanoporous Al2O3 is incorporated in step 1.

[0061] Experimental analysis: The prepared powder product changed from yellow to white after being soaked in water and stopped luminescent, indicating that the perovskite quantum dots had become ineffective. This suggests that the nanoporous Al2O3 primarily functions as a pore-blocking agent, and its abundant mesoporous structure further coats the quantum dots. Additionally, alumina itself can be used as a grinding aid. Without the pore-blocking effect of nanoporous Al2O3, a significant amount of water enters the pores of the mesoporous material, comes into contact with the perovskite quantum dots, and decomposes them.

[0062] Comparative Example 4:

[0063] The difference from Example 1 is that the amount of SnF2 added was adjusted to 14.1g.

[0064] Comparative Example 5:

[0065] The difference from Example 1 is that the amount of SnF2 added was adjusted to 2.5g.

[0066] When the sintering precursor A powder after grinding in step 1 is irradiated with a handheld ultraviolet lamp inside the ball mill, the sintering precursor A powder emits green light, indicating that CsPbBr3 quantum dots are formed in this step.

[0067] Table 1 shows the performance test results of the samples obtained in Example 1 and Comparative Examples 1-3 of this invention. Among them, blue light stability refers to the stability of the quantum dot diffusion plate, which is the perovskite quantum dots used in Example 1 and Comparative Examples 1-3 to prepare perovskite diffusion plates. The method for preparing the diffusion plates is existing technology and will not be described in detail here.

[0068] The test conditions were as follows: after being continuously irradiated with 350mW / cm2 blue light (450nm) for 100 hours, the brightness of the perovskite quantum dot diffuser plate was able to maintain the initial intensity ratio under white backlight.

[0069] The data methods for wavelength, PLQY, and particle size of the sample products are all existing technologies and will not be elaborated here.

[0070] Table 1: Performance test results of samples from different examples (comparative examples)

[0071]

[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. The application of a stannous halide in perovskite quantum dot grinding precursors, characterized in that, The tin halide is blended with the perovskite quantum dot precursor to obtain a precursor mixture, wherein the tin halide is used as a quantum dot synthesis barrier during the high-energy milling stage of the precursor mixture. 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.

2. The application of a stannous halide as described in claim 1 in a perovskite quantum dot grinding precursor, characterized in that, The high-energy grinding conditions are: a rotation speed of at least 200 rpm and a time of at least 15 minutes; the grinding temperature generated by the high-energy grinding is at least 50°C.

3. The application of a stannous halide as described in claim 2 in a perovskite quantum dot grinding precursor, characterized in that, The grinding equipment is at least one of ball mill, pot mill, and grinding mill.

4. The application of a stannous halide as described in claim 1 in a perovskite quantum dot grinding precursor, characterized in that, The stannous halide is at least one of stannous fluoride, stannous bromide, stannous chloride, and stannous iodide.

5. The application of a stannous halide according to claim 1 in a perovskite quantum dot grinding precursor, characterized in that, The perovskite quantum dot precursors include Cs source precursors, Pb source precursors, and X source precursors. The Cs source precursor is one or more of cesium halide and cesium carbonate; The Pb source precursor is one or more of lead halide and lead acetate. The halogen source precursor is one or more of the following: cesium halide, lead halide, zinc halide, potassium halide, sodium halide, lithium halide, ammonia halide, calcium halide, strontium halide, and barium halide.

6. The application of a stannous halide according to claim 1 in a perovskite quantum dot grinding precursor, characterized in that, The precursor mixture also includes a grinding aid, which includes at least one or a combination of Ca(OH)2, Al(OH)3, and Al2O3.

7. The application of a stannous halide according to claim 1 in a perovskite quantum dot grinding precursor, characterized in that, The molar ratio of the perovskite quantum dot precursor to the stannous halide is (10-50):

1.

8. The application of a stannous halide according to claim 7 in a perovskite quantum dot grinding precursor, characterized in that, The molar ratio of the perovskite quantum dot precursor to the stannous halide is 20:

1.

9. The application of a tin halide according to any one of claims 1-8 in a perovskite quantum dot grinding precursor, characterized in that, The perovskite quantum dots are used in perovskite diffusers, light-emitting devices, wavelength conversion films, quantum dot films, quantum dot light-emitting diodes, or quantum dot masterbatches.

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