Quantum dot monomer colloid as well as preparation method and application thereof

Abstract

The invention provides a quantum dot monomer colloid as well as a preparation method and application thereof. The preparation method comprises the following steps: dropwise adding a phosphoric acid dispersant and mercaptan into a quantum dot colloidal solution, and mixing to obtain a monomer colloid; the phosphoric acid dispersing agent and the thiol are used, the phosphoric acid ligand and the sulfydryl ligand which play a stabilizing role are introduced to the surface of the quantum dot colloid, and the problem that the quantum efficiency is reduced due to falling of the phosphoric acid ligand and the sulfydryl ligand on the surface of the quantum dot is solved.

Description

Technical Field

[0001] The invention belongs to the field of semiconductors and relates to a method for preparing a quantum dot monomer colloid, in particular to a quantum dot monomer colloid and a preparation method and application thereof. Background Art

[0002] Colloidal quantum dots are a type of semiconductor nanocrystals. They have excellent optoelectronic properties such as adjustable luminescence wavelength, wide luminescence wavelength coverage, high fluorescence quantum yield, high brightness, wide color gamut, and high color purity. Based on the optoelectronic properties of colloidal quantum dots, they are currently widely used in new displays. The two representative directions are electroluminescence and photoluminescence.

[0003] CN113403070A discloses a method for preparing a high-stability lead halide perovskite homojunction colloidal quantum dot. Thioacetamide and oleylamine are mixed in proportion to obtain a thioacetamide ligand solution, and cesium carbonate and octanoic acid are mixed in proportion to obtain a cesium octanoate solution; lead halide, tetra-n-octylammonium bromide, and toluene are mixed to obtain a lead halide precursor solution; the thioacetamide ligand solution is injected into the lead halide precursor solution, and a lead halide intermediate solution is obtained after reaction; the cesium octanoate solution is injected into the lead halide intermediate solution to react and obtain a coarse solution of perovskite homojunction quantum dots; the coarse solution of quantum dots is washed and centrifuged, and dissolved in a toluene solution to obtain a cesium lead halide perovskite homojunction quantum dot colloidal solution. However, the preparation method of the technical solution is complicated, the preparation cost is high, and it is not easy to achieve large-scale production. And the quantum dot colloidal solution prepared in this scheme still has the problem of agglomeration or ligand shedding after dilution.

[0004] CN110212077A discloses a method for improving the stability of quantum dots in a substrate and its application. The present invention allows quantum dots to aggregate in a substrate to form larger aggregates. The substrate can only contact the quantum dots on the surface layer of the aggregates, which will cause the surface ligands to fall off during the aging process. The quantum dots on the surface layer isolate the substrate from the internal quantum dots, which plays a role in protecting the internal quantum dots, thereby improving the luminescence stability of the quantum dots in the substrate, and further improving the service life of the quantum dots in photoluminescence applications. Although this solution improves the problem of preventing the ligands from falling off during the aging process, it has no technical enlightenment for preventing the quantum dots from agglomerating and falling off after diluting the polymer.

[0005] In photoluminescence, quantum dots are first dispersed in a monomer reagent and then prepared into a quantum dot glue for coating. However, in the process of preparing quantum dot glue, due to the low concentration of quantum dots, it is easy to cause quantum dots to agglomerate, ligands to fall off, and other unfavorable factors, resulting in fluorescence quenching, affecting the stability of quantum dot glue.

[0006] Therefore, how to prepare a method to avoid aggregation or ligand shedding when the quantum dot monomer colloid is diluted to a certain low concentration is an important research direction in this field. Summary of the invention

[0007] In view of the shortcomings of the prior art, the purpose of the present invention is to provide a quantum dot monomer colloid and its preparation method and application. The present invention prepares a quantum dot monomer colloid with high yield and high concentration, realizes the complete dispersion of quantum dot powder without obvious precipitation, reduces the agglomeration of high-concentration quantum dot monomer colloid solution, and reduces the ligand shedding on the surface of quantum dots.

[0008] To achieve this object, the present invention adopts the following technical solutions:

[0009] One of the purposes of the present invention is to provide a method for preparing a quantum dot monomer colloid, the preparation method comprising:

[0010] After adding phosphoric acid dispersant and thiol to the quantum dot colloid solution, the mixture is mixed to obtain quantum dot monomer colloid.

[0011] In the present invention, phosphoric acid dispersants are selected, and part of the ligands of the quantum dot material are phosphoric acid. The phosphoric acid dispersants and quantum dots have similar properties, and the two have better compatibility.

[0012] The present invention uses phosphoric acid dispersants and mercaptans to introduce phosphoric acid ligands and thiol ligands that play a stabilizing role on the surface of quantum dot colloids, thereby avoiding the problem of reduced quantum efficiency caused by the shedding of phosphoric acid ligands and thiol ligands on the surface of quantum dots. In the present invention, the affinity group of the quantum dot monomer colloid is not limited to a small area in the phosphoric acid dispersant molecule, but is distributed on the entire molecule in a special form. Then such an auxiliary agent plays a bridging function between the quantum dot particles. Also due to this chemical structure, the individual quantum dot particles (due to the presence of the auxiliary agent molecules) still remain separated from each other.

[0013] As a preferred technical solution of the present invention, the method for preparing the quantum dot colloidal solution comprises: dispersing quantum dot powder in a colloidal solution to obtain a quantum dot colloidal solution.

[0014] Preferably, the colloidal solution comprises any one of IBOA colloidal solution, IBOMA colloidal solution, DCPDA colloidal solution or IDA colloidal solution, or a combination of at least two of them, wherein typical but non-limiting examples of the combination include: a combination of IBOA colloidal solution and IBOMA colloidal solution, a combination of IBOMA colloidal solution and DCPDA colloidal solution, a combination of DCPDA colloidal solution and IDA colloidal solution, or a combination of IBOA colloidal solution and IDA colloidal solution, etc.

[0015] Preferably, the quantum dot powder comprises quantum dot dry powder.

[0016] Preferably, the quantum dot dry powder comprises red cadmium-based quantum dot dry powder.

[0017] As a preferred technical solution of the present invention, the mass concentration of the quantum dot colloid solution is 5 to 40%, wherein the mass concentration can be 5%, 10%, 15%, 20%, 25%, 30%, 35% or 40%, etc., but is not limited to the listed values. Other unlisted values ​​within the numerical range are also applicable, preferably 10 to 40%.

[0018] The present invention selects a high-concentration quantum dot colloid solution. When the mass concentration of the quantum dot colloid solution is lower than 5%, the quantum dots provided by the quantum dot colloid solution are dispersed in the quantum dot monomer colloid and diluted to a lower concentration required by the process, the quantum dots are easily affected by agglomeration or ligand shedding, resulting in a significant attenuation of the quantum efficiency of the quantum dots. A method of selecting a high-concentration quantum dot colloid solution of 5 to 40%, adding a dispersant and stirring and mixing at the same time, and then diluting it to a low-concentration quantum dot monomer colloid solution, the quantum efficiency of the quantum dots is not significantly reduced.

[0019] Preferably, the quantum dot dry powder comprises red cadmium-based quantum dot dry powder.

[0020] As a preferred technical solution of the present invention, the phosphoric acid dispersant includes any one of WA-8401, AFCONA-5210, AFCONA-5220, AFCONA-5251, BYK-110 or BYK-111, or a combination of at least two of them. Typical but non-limiting examples of the combination include: a combination of WA-8401 and AFCONA-5210, a combination of AFCONA-5210 and AFCONA-5220, a combination of AFCONA-5220 and AFCONA-5251, a combination of AFCONA-5251 and BYK-110, or a combination of BYK-110 and BYK-111.

[0021] As a preferred technical solution of the present invention, the mass concentration of the dispersant is 5 to 10%, wherein the mass concentration can be 5%, 6%, 7%, 8%, 9% or 10%, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0022] As a preferred technical solution of the present invention, the thiol includes any one of 1-hexyl mercaptan, 1-octyl mercaptan or n-dodecyl mercaptan, or a combination of at least two of them, wherein typical but non-limiting examples of the combination include: a combination of 1-hexyl mercaptan and 1-octyl mercaptan, a combination of 1-octyl mercaptan and n-dodecyl mercaptan, or a combination of 1-hexyl mercaptan and n-dodecyl mercaptan, etc.

[0023] As a preferred technical solution of the present invention, the mass concentration of the thiol is 2-5%, wherein the mass concentration can be 2%, 3%, 4% or 5%, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0024] As a preferred technical solution of the present invention, the mixing speed is 200-500 rpm, wherein the speed can be 200 rpm, 250 rpm, 300 rpm, 350 rpm, 400 rpm, 450 rpm or 500 rpm, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0025] Preferably, the mixing temperature is 20-30°C, wherein the temperature can be 20°C, 21°C, 22°C, 23°C, 24°C, 25°C, 26°C, 27°C, 28°C, 29°C or 30°C, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0026] Preferably, the mixing time is 5 to 8 hours, wherein the time can be 5 hours, 5.5 hours, 6 hours, 6.5 hours, 7 hours, 7.5 hours or 8 hours, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0027] The second object of the present invention is to provide a quantum dot monomer colloid, which is prepared by the preparation method as described in the first object.

[0028] The concentration of the quantum dot monomer colloid is 25-35wt%, wherein the concentration can be 25wt%, 26wt%, 27wt%, 28wt%, 29wt%, 30wt%, 31wt%, 32wt%, 33wt%, 34wt% or 35wt%, etc., but is not limited to the listed values, and other unlisted values ​​within the numerical range are also applicable.

[0029] The third object of the present invention is to provide an application of the quantum dot monomer colloid as described in the second object, wherein the quantum dot monomer colloid is applied in semiconductor materials.

[0030] The numerical range described in the present invention not only includes the point values ​​listed above, but also includes any point values ​​between the above numerical ranges that are not listed. Due to space limitations and for the sake of simplicity, the present invention no longer exhaustively lists the specific point values ​​included in the range.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] (1) The quantum dot monomer colloid of the present invention is not prone to the negative effects of aggregation or ligand shedding;

[0033] (2) The affinity groups of the quantum dot monomer colloid in the present invention are not limited to a small area in the phosphoric acid dispersant, but are distributed in a special form over the entire molecule. Such an auxiliary agent plays a bridging function between the quantum dot particles. Also due to this chemical structure, the individual quantum dot particles (due to the presence of the phosphoric acid dispersant) remain separated from each other.

[0034] (3) The quantum yield of the quantum dot monomer colloid prepared by the preparation method of the present invention can reach more than 97%. DETAILED DESCRIPTION

[0035] The technical solution of the present invention is further illustrated below through specific implementation methods.

[0036] Example 1

[0037] This embodiment provides a method for preparing a quantum dot monomer colloid, the preparation method comprising:

[0038] The red cadmium quantum dot dry powder was dispersed in IBOA to make the volume of quantum dot IBOA colloidal solution with a mass concentration of 30%.

[0039] Take a fully dispersed quantum dot IBOA colloidal solution with a mass concentration of 30%, a phosphoric acid dispersant BYK-111 and 1-octanethiol;

[0040] Place 10 g of 30% quantum dot-IBOA colloidal solution in a brown volumetric flask, then add 0.7 g of phosphoric acid dispersant BYK-111 (mass concentration is 7%) and 0.2 g of 1-octanethiol (mass concentration is 2%), add a stirring bar, set the rotation speed to 500 rpm, the temperature to 30°C, and the time to 8 hours.

[0041] Example 2

[0042] This embodiment provides a method for preparing a quantum dot monomer colloid, the preparation method comprising:

[0043] Take the red cadmium quantum dot dry powder and disperse it in IBOA to make the volume into quantum dot IBOA colloidal solution with a mass concentration of 25%;

[0044] Take a fully dispersed quantum dot IBOA colloidal solution with a mass concentration of 25%, a phosphoric acid dispersant WA-8401 and 1-octanethiol;

[0045] Place 10 g of 25% quantum dot-IBOA colloidal solution in a brown volumetric flask, then add 0.5 g of phosphoric acid dispersant WA-8401 (mass concentration is 5%) and 0.2 g of 1-octanethiol (mass concentration is 2%), add a stirring bar, set the rotation speed to 200 rpm, the temperature to 20°C, and the time to 8 hours.

[0046] Example 3

[0047] This embodiment provides a method for preparing a quantum dot monomer colloid, the preparation method comprising:

[0048] Take the red cadmium quantum dot dry powder and disperse it in IBOA to make the volume into quantum dot IBOA colloidal solution with a mass concentration of 40%;

[0049] Take a fully dispersed quantum dot IBOA colloidal solution with a mass concentration of 40%, a phosphoric acid dispersant AFCONA-5251 and 1-hexanethiol;

[0050] 10 g of 40% quantum dot-IBOA colloid solution was placed in a brown volumetric flask, and 1.0 g of phosphoric acid dispersant AFCONA-5251 (mass concentration of 10%) and 0.5 g of 1-hexanethiol (mass concentration of 5%) were added dropwise, and a stirring bar was added. The rotation speed was 500 rpm, the temperature was 30°C, and the stirring time was 5 hours.

[0051] Example 4

[0052] In this embodiment, except that the mass concentration of the quantum dot colloid solution is changed from 30% to 20%, other conditions are the same as those in Embodiment 1.

[0053] Example 5

[0054] In this embodiment, except that the mass concentration of the quantum dot colloid solution is changed from 30% to 10%, other conditions are the same as those in Embodiment 1.

[0055] Example 6

[0056] In this embodiment, except that the mass concentration of the quantum dot colloid solution is changed from 30% to 5%, other conditions are the same as those in Embodiment 1.

[0057] Example 7

[0058] In this embodiment, except that the mass concentration of the quantum dot colloid solution is changed from 30% to 1%, other conditions are the same as those in Embodiment 1.

[0059] Example 8

[0060] In this embodiment, except that the mass concentration of the quantum dot colloid solution is changed from 30% to 0.2%, other conditions are the same as those in Embodiment 1.

[0061] Example 9

[0062] In this embodiment, except that the stirring time is changed from 8 hours to 1 hour, other conditions are the same as those in Embodiment 1.

[0063] Example 10

[0064] In this embodiment, except that the stirring time is changed from 8 hours to 2 hours, other conditions are the same as those in embodiment 1.

[0065] Comparative Example 1

[0066] This comparative example provides a quantum dot monomer colloid, and the preparation method includes:

[0067] The red cadmium quantum dot dry powder was dispersed in IBOA to obtain a quantum dot-IBOA colloidal solution with a fixed volume of 30% by mass concentration.

[0068] The method for fixing the volume includes: placing the red cadmium quantum dot dry powder in a brown volumetric flask, adding the IBOA monomer reagent, adding a stirring bar, rotating at 350 rpm, at 25°C, for 2.5 hours, to ensure that the quantum dot powder is completely dispersed without obvious precipitation.

[0069] 10 g of 30% quantum dot-IBOA colloid solution was placed in a brown volumetric flask, and a stirring bar was added. The rotation speed was 500 rpm, the temperature was 30° C., and the time was 8 hours.

[0070] Comparative Example 2

[0071] In this comparative example, except that 1-octanethiol was not added dropwise, other conditions were the same as those in Example 1.

[0072] Comparative Example 3

[0073] In this comparative example, except that the phosphoric acid dispersant BYK-111 is replaced by carboxymethyl cellulose, other conditions are the same as those of Example 1.

[0074] Comparative Example 4

[0075] In this comparative example, except that the phosphoric acid dispersant BYK-111 is not added, other conditions are the same as those of Example 1.

[0076] The quantum dot monomer colloids prepared in Examples 1-10 and Comparative Examples 1-4 were tested for low-concentration quantum dot monomer colloid aggregation, quantum dot surface ligand shedding, wavelength, half-peak width, and quantum efficiency. The test results are shown in Table 1.

[0077] Among them, the test method for low concentration quantum dot monomer colloid aggregation and

[0078] The test method for the ligand shedding on the surface of quantum dots includes: using quantum dot efficiency as a criterion, when the quantum dot monomer colloid agglomerates, the quantum efficiency is greatly and seriously attenuated; using quantum dot efficiency as a criterion, when the ligand on the surface of quantum dots is shedding, the more serious the shedding degree, the more obvious the reduction in quantum efficiency;

[0079] The testing methods of wavelength, half-peak width and quantum efficiency include: using photoluminescence quantum yield spectrometer C11347 to test optical parameters, and using n-hexane solution as blank diluent.

[0080] Table 1

[0081] Wavelength / nm Half peak width / nm Quantum yield / % Reunion Ligand shedding Example 1 622 22 97 none none Example 2 622 22 95 none none Example 3 622 22 95 none none Example 4 622 22 96 none none Example 5 622 22 95 none none Example 6 622 22 94 none slight Example 7 622 22 93 none slight Example 8 622 22 91 none Moderate Example 9 622 22 93 none slight Example 10 622 22 93 none slight Comparative Example 1 623 23 56 serious / Comparative Example 2 622 22 90 none Moderate Comparative Example 3 622 22 90 slight none Comparative Example 4 622 23 85 Moderate /

[0082] It can be seen from the above table that, by comparing Example 1 with Examples 4-8, when the mass concentration of the quantum dot colloid solution drops below 10%, the quantum efficiency will decrease due to ligand shedding;

[0083] By comparing Example 1 with Examples 9-10, it can be seen that when the stirring time is low, the quantum efficiency will be lowered due to ligand shedding caused by poor treatment effect;

[0084] By comparing Example 1 with Comparative Example 1, it can be seen that when the phosphoric acid dispersant and thiol are not used, after the 30% quantum dot-IBOA colloid solution is stirred to obtain the quantum dot colloid, agglomeration occurs and the quantum efficiency decreases significantly. The damage to the quantum dots caused by agglomeration is greater than the ligand shedding in other examples.

[0085] Comparison between Example 1 and Comparative Examples 2-4 shows that when phosphoric acid dispersants or thiols are not used, the quantum efficiency will be reduced due to ligand shedding caused by poor treatment effect. Phosphoric acid dispersants are mainly used to improve the negative impact of agglomeration of quantum dot monomer colloidal solutions, and thiols are mainly used to improve the negative impact of ligand shedding of quantum dot monomer colloidal solutions. Agglomeration is more destructive to quantum dots than ligand shedding.

[0086] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above description is only a specific embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A method for preparing a quantum dot monomer colloid, characterized in that: The preparation method comprises: After adding phosphoric acid dispersant and thiol to the quantum dot colloid solution, the mixture is mixed to obtain quantum dot monomer colloid.

2. The preparation method according to claim 1, characterized in that: The method for preparing the quantum dot colloidal solution comprises: dispersing quantum dot powder in a colloidal solution to obtain a quantum dot colloidal solution; Preferably, the colloidal solution comprises any one or a combination of at least two of an IBOA colloidal solution, an IBOMA colloidal solution, a DCPDA colloidal solution or an IDA colloidal solution; Preferably, the quantum dot powder comprises a quantum dot dry powder; Preferably, the quantum dot dry powder comprises red cadmium-based quantum dot dry powder.

3. The preparation method according to claim 1 or 2, characterized in that: The mass concentration of the quantum dot colloid solution is 5 to 40%, preferably 10 to 40%.

4. The preparation method according to any one of claims 1 to 3, characterized in that The phosphoric acid dispersant includes any one of WA-8401, AFCONA-5210, AFCONA-5220, AFCONA-5251, BYK-110 or BYK-111, or a combination of at least two thereof.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The mass concentration of the dispersant is 5-10%.

6. The preparation method according to any one of claims 1 to 5, characterized in that: The thiol includes any one of 1-hexyl mercaptan, 1-octanethiol or n-dodecyl mercaptan, or a combination of at least two thereof.

7. The preparation method according to any one of claims 1 to 6, characterized in that: The mass concentration of the mercaptan is 2-5%.

8. The preparation method according to any one of claims 1 to 7, characterized in that: The mixing speed is 200-500 rpm; Preferably, the mixing temperature is 20-30°C; Preferably, the mixing time is 5 to 8 hours.

9. A quantum dot monomer colloid, characterized in that: The quantum dot monomer colloid is prepared by the preparation method according to any one of claims 1 to 8; The concentration of the quantum dot monomer colloid is 25-35 wt %.

10. An application of the quantum dot monomer colloid as claimed in claim 9, characterized in that: The quantum dot monomer colloid is used in semiconductor materials.