Method for post-processing perovskite quantum dot ligand
By adding a hydrohalogenic ligand solution to perovskite quantum dot ligand exchange treatment when cooling after high temperature reaction, the problem of limited dissolution of water-soluble ligands in organic solvents is solved, and high-quality perovskites are prepared Quantum dots have enhanced their application potential in the field of display.
Patent Information
- Application Number
- CN202411228451.0
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-03
- Publication Date
- 2024-12-27
AI Technical Summary
In the prior art, water-soluble ligands cannot be directly applied to perovskite quantum dots, resulting in limited dissolution in organic solvents, and the performance and stability of perovskite quantum dots cannot be effectively improved.
After high temperature reaction, the ligand solution dissolved in hydrohalogenic acid was added during the ice bath cooling process, and quantum dot ligand exchange treatment was carried out. The perovskite quantum dot surface was passed through the acidic conditions in the hydrohalogenic acid and trace water. The defects of ligand exchange and passivation are realized.
Perovskite quantum dots with uniform particles, good crystallization quality and excellent optical performance are prepared. They are suitable for inkjet printing technology, display screens and electroluminescent diodes, which enhances the application potential of perovskite quantum dots in the display field.
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Figure CN119193137A_ABST
Abstract
Description
Technical Field
[0001] The invention belongs to the technical field of post-processing of perovskite quantum dots, and in particular relates to a method for post-processing a perovskite quantum dot ligand. Background Art
[0002] Semiconductor quantum dots have the advantages of easy solution processing, adjustable band gap, high quantum yield, and high color purity. They have application prospects in the fields of light-emitting diodes, solar cells, and biomarkers. In the display field, they are the best display luminescent materials that can be mass-produced. In recent years, metal halide perovskite quantum dots, as an emerging luminescent material, have the advantages of high color purity, high fluorescence quantum yield, adjustable luminescent wavelength, and narrow spectral half-peak width. They have broad application prospects in the fields of light-emitting diodes, solar cells, photodetectors, etc., especially in the field of new generation high-definition display, and are currently one of the most promising luminescent materials.
[0003] Ligand treatment is a key step to ensure the stability and performance of quantum dots. Ligands can not only adjust the surface properties of quantum dots, improve their solubility and dispersibility, but also improve the optical properties by interacting with the surface of quantum dots. Through ligand engineering, the electronic structure and band structure of quantum dots can be further regulated to achieve precise control of the optoelectronic properties of quantum dots. Therefore, effective ligand treatment of perovskite quantum dots is crucial to improving their performance and stability in optoelectronic devices.
[0004] Since perovskite quantum dots are a kind of soft lattice ion compound, they have poor stability in water and will decompose into cesium halide and lead halide when in contact with water. Therefore, in the prior art, in the synthesis and post-treatment process of perovskite quantum dots, the solvent used is an organic solvent, and the original ligand used is an organic compound that can be dissolved in the organic solvent, and the organic compound is an organic acid or an organic amine.
[0005] The inventors found in their research that water-soluble ligands (such as inorganic ligands and zwitterionic ligands) cannot be directly applied to perovskite quantum dots as original ligands because they are very limited in solubility in organic solvents. However, water-soluble ligands can exchange ligands with the original ligands on the surface of perovskite quantum dots under certain conditions, thereby greatly improving the performance of perovskite quantum dots. Therefore, it is urgent to find a suitable method for treating perovskite quantum dots ligands, which is of great significance for promoting the development of perovskite quantum dots in the display field. Summary of the invention
[0006] The object of the present invention is to provide a method for post-treatment of perovskite quantum dot ligands. The present invention performs post-treatment of quantum dot ligands by adding a ligand solution dissolved in hydrohalic acid during ice bath cooling at high temperature after reaction.
[0007] To achieve the above object, the technical solution adopted by the present invention is:
[0008] A method for post-processing perovskite quantum dot ligands, comprising the following steps:
[0009] S10: providing a monovalent cation precursor containing one or more of cesium (Cs), formamidine (FA), and methylammonium (MA);
[0010] S20: providing a mixed precursor, wherein the mixed precursor comprises a halogen precursor, a precursor containing a lead source, an organic acid or an organic amine;
[0011] The halogen precursor includes one of a precursor containing iodine, a precursor containing bromine, and a precursor containing both iodine and bromine;
[0012] S30: adding the monovalent cation precursor to the mixed precursor for reaction, wherein the reaction is carried out by hot injection under an inert gas, and the reaction temperature is 150°C-200°C. After the reaction, a ligand solution dissolved in hydrohalic acid is added during ice bath cooling to carry out quantum dot ligand exchange treatment to obtain perovskite quantum dots after ligand post-treatment.
[0013] By adopting the above scheme: pre-dissolving the water-soluble ligand molecules in hydrohalic acid to form a ligand solution soluble in hydrohalic acid. After the high-temperature reaction, the ligand solution soluble in hydrohalic acid is injected into the synthesized perovskite quantum dots during the cooling process. The synergistic passivation defects of the water-soluble ligands and hydrohalic acid and the screening effect of trace water in the hydrohalic acid are helpful for preparing high-quality perovskite quantum dots. The perovskite quantum dots prepared by this method have the characteristics of uniform particles, good crystal quality, and excellent optical properties. This type of perovskite quantum dots is expected to be used in inkjet printing technology, display screens, and electroluminescent diodes, accelerating the expansion of perovskite quantum dots in the display field.
[0014] In some embodiments, when adding a ligand solution dissolved in a hydrohalic acid, the temperature is preferably above 60°C, preferably 80-120°C. At a higher temperature, the surface lattice of the perovskite quantum dot and the ligand are in a higher dynamic activity, which helps the later added ligand and the original ligand on the surface of the perovskite quantum dot to fully exchange ligands. The temperature should not be too high to exceed the boiling point of the hydrohalic acid, otherwise the hydrohalic acid will volatilize in the reaction system and lose the effect of the hydrohalic acid.
[0015] In some embodiments, the precursor containing iodine element includes at least one or more of zinc iodide (ZnI2), strontium iodide (SrI2), zirconium iodide (ZrI4), and cobalt iodide (CoI2).
[0016] In some embodiments, the precursor containing bromine element includes at least one or more of zinc bromide (ZnBr2), strontium bromide (SrBr2), zirconium bromide (ZrBr4), and cobalt bromide (CoBr2).
[0017] In some embodiments, the precursor containing a lead source includes at least one or more of lead acetate (Pb(AC)2), lead iodide (PbI2), lead oleate (Pb(OA)2), and lead stearate.
[0018] In some embodiments, the organic acid is at least one of oleic acid, octanoic acid, stearic acid and palmitic acid; the organic amine is at least one of oleylamine, octylamine and dodecylamine.
[0019] In some embodiments, the volume ratio of the ligand solution dissolved in the hydrohalic acid to the reaction solution of the precursor is 1:100-1000;
[0020] The reaction solution of the precursor consists of a monovalent cation precursor and a mixed precursor.
[0021] By adopting the above technical solution: the volume ratio of the ligand solution dissolved in the hydrohalic acid to the reaction solution of the precursor is 1:100-1000. If it is less than 1:1000, the amount added is too small and the effect is minimal. If it is greater than 1:100, that is, too much hydrohalic acid is added, the introduction of too much water and HX has a destructive effect on the perovskite quantum dots, and phase transition is likely to occur, reducing the stability of the perovskite quantum dots.
[0022] In some embodiments, the ligand solution dissolved in hydrohalic acid consists of a hydrohalic acid aqueous solution and a water-soluble ligand.
[0023] In some embodiments, the hydrohalic acid aqueous solution is an aqueous solution of HX (X=Br / I), and the mass percentage of HX is 48%-57%;
[0024] The HX is at least one of hydroiodic acid and hydrobromic acid.
[0025] In some embodiments, the water-soluble ligand comprises at least one of potassium iodide, amino acid, and potassium thiocyanate.
[0026] A red light perovskite quantum dot is prepared by the above method.
[0027] Beneficial effects of the present invention: Because the hydrohalic acid aqueous solution contains a small amount of water, it helps to dissolve some water-soluble ligands (inorganic ligands and amphoteric ligands). These ligands have a stronger binding effect with perovskite quantum dots and can exchange ligands with the original ligands of perovskite quantum dots (organic acids, organic amines) and anchor to the perovskite quantum dots.
[0028] Specifically: The acidic conditions provided by hydrohalic acid help to remove or replace the original ligands on the surface of quantum dots. Under acidic conditions, the original ligands will become easily detached from the surface of quantum dots due to protonation, thereby providing space for new ligands to bind. The halogens in hydrohalic acid can fill the vacancies on the surface of perovskite quantum dots and passivate the surface defects of perovskite quantum dots. The trace water contained therein (that is, the volume ratio of the ligand solution dissolved in hydrohalic acid to the reaction solution of the precursor is 1:100-1000) will not damage the quantum dots. On the contrary, these trace waters play a role in screening the quality and size of the quantum dots, and can degrade small quantum dots of poor quality in the solution, thereby obtaining perovskite quantum dots of uniform size and excellent quality. This provides an effective and feasible solution for obtaining high-performance perovskite quantum dots and accelerates the expansion of applications of perovskite quantum dots in the display field. BRIEF DESCRIPTION OF THE DRAWINGS
[0029] Figure 1 The ultraviolet-visible spectroscopic spectrum and fluorescence spectrum of the pure red light emitting perovskite quantum dots obtained in Example 1 of the present invention. DETAILED DESCRIPTION
[0030] In order to make the purpose, technical solution and effect of the present invention clearer and more specific, the present invention is further described in detail below. It should be understood that the specific implementation methods described herein are only used to explain the present invention and are not used to limit the present invention.
[0031] In some embodiments, the monovalent cation precursor can be cesium oleate Cs (OA), and the preparation method can be: weigh 100 mg of cesium carbonate Cs2CO3 and add it to a three-necked flask, then add 0.4 mL of oleic acid (OA) to the flask to dissolve cesium carbonate (Cs2CO3) and 3.5 mL of octadecene (ODE) as a solvent, evacuate the three-necked flask and stir for a period of time, and then fill the three-necked flask with an inert atmosphere.
[0032] In some embodiments, the hydrohalic acid aqueous solution is an aqueous solution of HX (X=Br / I), and the mass percentage of HX is 50%; the HX is at least one of hydroiodic acid and hydrobromic acid, for example, hydroiodic acid: hydrobromic acid = 1:1.
[0033] In some embodiments, the monovalent cation precursor can be formamidine acetate (FA-acetate), and the preparation method can be: weigh 5 mmol FA-acetate and add it to a three-necked flask, then add 20 mL oleic acid (OA) to the flask, evacuate the three-necked flask and stir for a period of time, fill the three-necked flask with an inert atmosphere, and heat and stir.
[0034] In some embodiments, the precursor containing iodine element includes one or more mixtures of zinc iodide (ZnI2), strontium iodide (SrI2), zirconium iodide (ZrI4) and cobalt iodide (CoI2) in different proportions, for example, ZnI2 and SrI2 are mixed in a ratio of 1:1.
[0035] The precursor containing bromine element includes one or more of zinc bromide (ZnBr2), strontium bromide (SrBr2), zirconium bromide (ZrBr4), cobalt bromide (CoBr2) in different proportions. For example, ZnI2 and SrI2 are mixed in a ratio of 1:1. It can also be a mixture of bromine element and iodine element, such as ZnI2 and SrBr2 are mixed in a ratio of 2:1.
[0036] In some embodiments, the process of preparing perovskite quantum dots by hot injection includes placing the mixed precursor solution in S20 in a three-necked flask connected to a double-row tube device. The three-necked flask is evacuated for 20 minutes to remove excess water, oxygen and other components in the device, and then heated to 150-200°C in an inert atmosphere, and magnetic stirring is maintained during this process; 0.4 mL of the prepared cesium oleate precursor is quickly injected and mixed, and after reacting for 5 seconds, it is quickly cooled in an ice water bath.
[0037] In some embodiments, the process of post-treatment of quantum dot ligands includes a pre-configured ligand solution dissolved in hydrohalic acid. When the temperature of ice water cooling drops to about 80-120° C., the configured ligand solution dissolved in hydrohalic acid is quickly injected. After cooling to room temperature, a perovskite quantum dot stock solution treated with hydrohalic acid ligands is obtained.
[0038] In some embodiments, the method for purifying quantum dots may include the following steps, but is not limited to this purification method: transferring the perovskite quantum dot stock solution to a centrifuge tube for low-speed centrifugation, taking the supernatant after centrifugation, adding a certain amount of anti-solvent to precipitate the perovskite quantum dots and performing high-speed centrifugation; dispersing the precipitate in octane or toluene, and filtering and collecting with a 0.22 μm organic filter head to obtain a pure red light emitting perovskite quantum dot solution. Under certain conditions, the above steps can be repeated to continue adding anti-solvent to the perovskite quantum dot solution and centrifuging at high speed.
[0039] It should be pointed out that the above-mentioned descriptions on cesium oleate Cs (OA), formamidine acetate (FA-acetate), precursors containing iodine elements, precursors containing bromine elements, and hot injection methods, etc., are all explanations and examples of the contents of the present invention by the inventors, and do not constitute limitations on the protection scheme of this case.
[0040] It should be understood that the embodiments described in this specification are only used to illustrate the principles of the embodiments of this specification. Other variations may also fall within the scope of this specification. Therefore, as an example and not a limitation, the alternative configurations of the embodiments of this specification may be considered consistent with the teachings of this specification. Accordingly, the embodiments of this specification are not limited to the embodiments explicitly introduced and described in this specification.
[0041] Embodiment 1:
[0042] 20 mg of potassium thiocyanate (KSCN) was dissolved in 1 mL of hydrohalic acid (hydroiodic acid: hydrobromic acid = 1:1) in advance, and the mixture was shaken slightly to obtain a uniform ligand solution dissolved in the hydrohalic acid. Weigh 88mg PbI2, 319mg ZnI2, 167mg ZnBr2 into a 25mL three-necked flask, add 5mL octadecene (ODE), 2mL bis(2,4,4-trimethylpentyl)phosphonic acid (DSPA) and 2.4mL oleylamine (OAm) into the flask to obtain a mixed precursor; evacuate the three-necked flask for 20min to remove excess water, oxygen and other components in the device, and then heat to 170℃ in an inert atmosphere, and keep the magnetic stirring state during this process; take 0.4mL of the prepared cesium oleate precursor and quickly inject it into the mixed precursor to mix, react for 5s, and quickly cool it with an ice water bath. When the temperature drops to about 100℃, quickly inject 100μL of the ligand solution dissolved in hydrohalic acid, cool to room temperature, and obtain a pure red light emitting CsPb(Br / I)3 quantum dot stock solution. After subsequent purification, pure red light emitting perovskite quantum dots for testing are obtained.
[0043] like Figure 1 The UV-Visible spectra and fluorescence spectra of CsPb(Br / I)3 quantum dots in this embodiment. The perovskite quantum dots in this embodiment are subjected to the synergistic effect of halogen ion vacancy defect passivation by hydrohalic acid and inorganic KSCN inorganic ligand treatment, which reduces the surface defects of the perovskite quantum dots and greatly improves their optical properties. The fluorescence quantum yield (PLQY) can reflect the optical properties of perovskite quantum dots, see Table 1 for details. A higher PLQY value means less non-radiative recombination loss and higher luminous efficiency, that is, most of the absorbed photons can be effectively converted into emitted photons. Quantum dots with high PLQY have great application potential in the fields of displays, lighting, and optoelectronic devices.
[0044] Table 1 lists the comparison of the PLQY of quantum dots that have not been treated with ligands and the PLQY of perovskite quantum dots that have been treated in Example 1. After the ligand treatment, the PLQY of the quantum dots can be increased from the original 50% to 92%, showing excellent optical properties.
[0045] Comparative Example 1:
[0046] The difference from Example 1 is that the injection amount of 100 μL of the ligand solution dissolved in hydrohalic acid is replaced with the injection amount of 1 mL of the ligand solution dissolved in hydrohalic acid, so that an excessive amount of the ligand solution dissolved in hydrohalic acid is added.
[0047] Experimental analysis: It was found that the perovskite quantum dots appeared as a non-luminescent white emulsion. This was because the added 1 mL of ligand solution dissolved in hydrohalic acid far exceeded the proportion specified in this post-treatment method, that is, too much aqueous solution was introduced into the perovskite quantum dot system. These aqueous solutions destroyed the luminescent properties of the perovskite quantum dots and caused them to undergo a phase change.
[0048] Comparative Example 2:
[0049] The difference from Example 1 is that no hydrohalic acid is added, so that the preparation method of the ligand aqueous solution is carried out as follows:
[0050] 20 mg of potassium thiocyanate (KSCN) was dissolved in 1 mL of deionized water in advance and slightly shaken to obtain a uniform ligand aqueous solution. The rest of the preparation method was the same as in Example 1.
[0051] Experimental analysis: In this treatment method, since there is no synergistic passivation effect of hydrohalic acid, only the inorganic ligand passivation effect of KSCN, the resulting perovskite quantum dots do not show a significant improvement in optical performance, and the PLQY is only 63%. (Table 1)
[0052] Comparative Example 3:
[0053] The difference from Example 1 is that no water-soluble ligand (potassium thiocyanate) is added, and only the perovskite quantum dots are treated with a hydrohalic acid aqueous solution.
[0054] 88 mg PbI2, 319 mg ZnI2, and 167 mg ZnBr2 were weighed and added to a 25 mL three-necked flask, and 5 mL of octadecene (ODE), 2 mL of bis(2,4,4-trimethylpentyl)phosphonic acid (DSPA) and 2.4 mL of oleylamine (OAm) were added to the flask to obtain a mixed precursor; the three-necked flask was evacuated for 20 min to remove excess water, oxygen and other components in the device, and then heated to 170°C in an inert atmosphere, and magnetic stirring was maintained throughout the process; 0.4 mL of the prepared cesium oleate precursor was quickly injected into the mixed precursor and mixed, and after reacting for 5 seconds, it was quickly cooled in an ice water bath, and when the temperature dropped to around 100°C, 100 μL of hydrohalic acid aqueous solution (hydroiodic acid: hydrobromic acid = 1:1) was quickly injected, and cooled to room temperature to obtain a pure red light emitting CsPb(Br / I)3 quantum dot stock solution. After subsequent purification treatment, pure red light emitting perovskite quantum dots were obtained for testing.
[0055] Experimental analysis: In this treatment method, hydrohalic acid can fill the vacancies on the surface of perovskite quantum dots and play a role in defect passivation. Therefore, the perovskite quantum dots treated with hydrohalic acid alone also show an improvement in optical performance, with PLQY increased from the original 50% to 75% (Table 1), but it is still not as good as the synergistic improvement of combined ligand treatment.
[0056] Table 1: Fluorescence quantum yield (PLQY) of quantum dots obtained by different treatment methods
[0057]
[0058] The present invention illustrates the detailed preparation method of the present invention through the above-mentioned embodiments, but the present invention is not limited to the above-mentioned detailed preparation method, that is, it does not mean that the present invention must rely on the above-mentioned products and detailed preparation methods to be implemented. It should be clear to those skilled in the art that any improvement of the present invention, the combination or equivalent replacement of the raw materials of the product of the present invention, all fall within the protection scope and disclosure scope of the present invention.
Claims
1. A method for post-treatment of perovskite quantum dot ligands, characterized in that: The steps include: S10: providing a monovalent cation precursor containing one or more of cesium (Cs), formamidine (FA), and methylammonium (MA); S20: providing a mixed precursor, wherein the mixed precursor comprises a halogen precursor, a precursor containing a lead source, an organic acid or an organic amine; The halogen precursor includes one of a precursor containing iodine, a precursor containing bromine, and a precursor containing both iodine and bromine; S30: adding the monovalent cation precursor to the mixed precursor for reaction, wherein the reaction is carried out by hot injection under an inert gas, and the reaction temperature is 150°C-200°C. After the reaction, a ligand solution dissolved in hydrohalic acid is added during ice bath cooling to carry out quantum dot ligand exchange treatment to obtain perovskite quantum dots after ligand post-treatment.
2. The method for post-treatment of perovskite quantum dot ligands according to claim 1, characterized in that: The precursor containing iodine element includes at least one or more of zinc iodide (ZnI2), strontium iodide (SrI2), zirconium iodide (ZrI4), and cobalt iodide (CoI2).
3. The method for post-treatment of perovskite quantum dot ligands according to claim 1, characterized in that: The precursor containing bromine element includes at least one or more of zinc bromide (ZnBr2), strontium bromide (SrBr2), zirconium bromide (ZrBr4), and cobalt bromide (CoBr2).
4. The method for post-treatment of perovskite quantum dot ligands according to claim 1, characterized in that: The lead source-containing precursor includes at least one or more of lead acetate (Pb(AC)2), lead iodide (PbI2), lead oleate (Pb(OA)2), and lead stearate.
5. The method for post-treatment of perovskite quantum dot ligands according to claim 1, characterized in that: The organic acid is at least one of oleic acid, octanoic acid, stearic acid and palmitic acid; the organic amine is at least one of oleylamine, octylamine and dodecylamine.
6. The method for post-treatment of perovskite quantum dot ligands according to claim 1, characterized in that: The volume ratio of the ligand solution dissolved in the hydrohalic acid to the reaction solution of the precursor is 1:100-1000; The reaction solution of the precursor consists of a monovalent cation precursor and a mixed precursor.
7. The method for post-treatment of perovskite quantum dot ligands according to claim 6, characterized in that: The ligand solution dissolved in halogen acid consists of halogen acid aqueous solution and water-soluble ligand.
8. The method for post-treatment of perovskite quantum dot ligands according to claim 7, characterized in that: The hydrohalic acid aqueous solution is an aqueous solution of HX (X=Br / I), and the mass percentage of HX is 48%-57%; The HX is at least one of hydroiodic acid and hydrobromic acid.
9. The method for post-treatment of perovskite quantum dot ligands according to claim 8, characterized in that: The water-soluble ligand includes at least one of potassium iodide, amino acid and potassium thiocyanate.
10. A red light perovskite quantum dot, characterized in that: Prepared by the method according to any one of claims 1 to 9.