Ytterbium-doped perovskite quantum dot and preparation method thereof

Abstract

The invention discloses an ytterbium-doped perovskite quantum dot and a preparation method thereof, and the preparation method comprises the steps: mixing a lead source, an ytterbium source, a cesium source, oleic acid, first fatty amine and octadecene at a first temperature, then heating to a second temperature, and adding a first halogen source to obtain a first reaction system; keeping the reaction temperature and adding a reaction supplement to obtain a second reaction system; purifying and dispersing the second reaction system to obtain ytterbium-doped perovskite quantum dots; the reaction supplement is at least one of second fatty amine and a second halogen source. According to the invention, a Yb doped quantum dot structure is formed by using a halogen injection process, and then the alicyclic amine and / or halogen are / is used as a reaction supplement to inhibit quantum dot agglomeration, so that the reaction time is prolonged in a disguised manner, and the Yb ion doping concentration and the near-infrared luminous efficiency are increased. Meanwhile, a reaction supplement added subsequently supplements lost halogen and / or fatty amine ligands, quantum dot agglomeration is inhibited, and the size of the quantum dots and the dispersity of the solution are greatly improved.

Description

Technical Field

[0001] The patent of this invention belongs to the field of perovskite quantum dots, and specifically relates to an ytterbium-doped perovskite quantum dot and a preparation method thereof. Background Art

[0002] In recent years, in order to improve the efficiency of photoelectric conversion, the application of quantum tailored luminescent materials with theoretical photoluminescence quantum yields (PLQYs) exceeding 100% to battery components has received widespread attention. Since 2017, Yb (ytterbium)-doped lead halide perovskite quantum dots have been widely studied, and the synthesis process mainly focuses on the solution hot injection method of cesium and halogen injection. However, due to the inconsistency between the valence state of Yb ions and Pb ions in the octahedron and the low reaction activity, the actual Yb doping concentration is low and the near-infrared luminescence efficiency is low. Especially when the excitation light power is similar to the light intensity density of sunlight, the tested near-infrared quantum yield is very low, which affects the further application prospects of quantum tailored near-infrared materials in the field of photovoltaic power generation.

[0003] Increasing the reactivity of Yb ions by raising the reaction temperature is an ideal means to promote the doping of Yb into the lattice. However, due to the poor heat resistance of perovskite quantum dots themselves, they are prone to agglomeration, rapid size growth, and increased defects in high temperature environments, affecting the near-infrared quantum yield, dispersibility and storage stability of the quantum dot solution. Summary of the invention

[0004] Therefore, the technical problem to be solved by the present invention is that the existing Yb-doped lead halide perovskite quantum dots have the defects of low actual Yb doping concentration, low near-infrared luminescence efficiency, and insufficient dispersibility and storage stability, thereby providing an ytterbium-doped perovskite quantum dot and a preparation method thereof.

[0005] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0006] The present invention provides a method for preparing ytterbium-doped perovskite quantum dots, comprising:

[0007] Mixing a lead source, an ytterbium source, a cesium source, oleic acid, a first fatty amine and octadecene at a first temperature to obtain a mixed solution;

[0008] Heating the mixed solution to a second temperature and adding a first halogen source to perform a first reaction, thereby obtaining a first reaction system through the first reaction;

[0009] Keeping the reaction temperature consistent with that of the first reaction, adding a reaction supplement to the first reaction system to carry out a second reaction, and obtaining a second reaction system after the second reaction is completed;

[0010] Purifying and dispersing the second reaction system to obtain ytterbium-doped perovskite quantum dots;

[0011] The reaction supplement is at least one of the second fatty amine and the second halogen source. The reaction supplement can be a single one of the second fatty amine and the second halogen source, or a mixture of the second fatty amine and the second halogen source in any proportion.

[0012] Further,

[0013] The first temperature is 100-150° C., and the mixing is performed under vacuum for 1-2 hours.

[0014] The second temperature is 230-250° C., and the first reaction is carried out under nitrogen protection for 0.5-3 min.

[0015] The second reaction is carried out under nitrogen protection for 2 to 6 minutes.

[0016] The molar ratio of the lead source, the cesium source and the ytterbium source is 1:(1-1.4):(0.5-2);

[0017] The molar ratio of the lead source to the first halogen source is 1:(6-7.5);

[0018] The molar ratio of the first halogen source to the first fatty amine is 1:(0.6-1);

[0019] The molar ratio of the lead source to the reaction supplement is 1:(1.5-6).

[0020] The lead source includes at least one of lead oleate or lead oxide, the ytterbium source includes at least one of ytterbium oleate or ytterbium acetate, and the cesium source includes at least one of cesium acetate or cesium carbonate;

[0021] The first fatty amine includes at least one of oleylamine, butylamine, octylamine and dodecylamine;

[0022] The second fatty amine includes at least one of oleylamine, butylamine, octylamine and dodecylamine;

[0023] The first halogen source includes at least one of trimethylsilyl bromide or trimethylsilyl chloride; because trimethylsilyl bromide and trimethylsilyl chloride have lower melting points, they are generally dissolved in the solution before being added;

[0024] The second halogen source includes at least one of trimethylsilyl bromide, octylamine bromide, dodecylamine bromide, oleylamine bromide, didodecyldimethylammonium bromide, distearyldimethylammonium bromide, trimethylsilyl chloride, octylamine chloride, dodecylamine chloride, oleylamine chloride, didodecyldimethylammonium chloride, and distearyldimethylammonium chloride.

[0025] Preferably, before purifying and dispersing the second reaction system, the method further includes adding divalent metal salt of oleic acid to the second reaction system to carry out a third reaction.

[0026] The third reaction is to stir the reaction at 60-150° C. for 1-24 hours at a stirring speed of 300-500 r / min;

[0027] The molar ratio of the lead source to the divalent metal salt of oleic acid is 1:(0.1-1);

[0028] The divalent metal oleate includes at least one of lead oleate, cadmium oleate, zinc oleate, nickel oleate, chromium oleate, calcium oleate or lead oleate.

[0029] The purification dispersion is to wash the second reaction system with a dispersant, centrifuge it, take out the precipitate, and disperse and preserve it in the dispersant; the dispersant includes at least one of n-hexane or toluene.

[0030] The present invention also provides an ytterbium-doped perovskite quantum dot, which is prepared by the above preparation method.

[0031] The technical solution of the present invention has the following advantages:

[0032] (1) The present invention forms a Yb-doped quantum dot structure by using a halogen injection process, and then uses aliphatic amines and / or halogens as reaction supplements to inhibit quantum dot aggregation, thereby extending the reaction time in disguised form, increasing the Yb ion doping concentration and near-infrared luminescence efficiency. At the same time, the reaction supplements added subsequently replenish the halogen and / or aliphatic amine ligands lost in a long-term high-temperature environment, inhibit quantum dot aggregation, reduce the surface defect state density, modify the uniformity of the quantum dot lattice, and greatly improve the size of the quantum dots and the dispersibility of the solution.

[0033] (2) The present invention ensures that the ratio of the first halogen source to the lead source does not exceed 7.5:1, and the molar amount of the first fatty amine does not exceed the first halogen source, while increasing the reaction temperature to ensure that the doping of Yb ions is not affected. Considering the instrument's tolerance and energy consumption, the reaction temperature should not exceed 250°C.

[0034] (3) In the present invention, divalent metal oleate is added to the synthesized crude quantum dot solution for stirring. The divalent metal can supplement the Pb vacancies on the surface of the quantum dots, the cationic ligand can increase the steric hindrance between the quantum dots, and the oleic acid can elute and dissolve many insoluble impurities, which not only further increases the luminescence efficiency of the quantum dots, but also improves the storage stability and dispersibility of the quantum dot solution. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the specific implementation methods of the present invention or the technical solutions in the prior art, the drawings required for use in the specific implementation methods or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are some implementation methods of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0036] Figure 1 The quantum dots in Example 2 are dispersed in a solution state in n-hexane;

[0037] Figure 2 The quantum dots are dispersed in n-hexane in the solution state obtained by reacting at 250° C. for 8 minutes and then performing step (7) of Example 1 in Experimental Example 1;

[0038] Figure 3 The near-infrared quantum yield of quantum dots in Example 2 and Example 3 varies with storage time. DETAILED DESCRIPTION

[0039] The following examples are provided for a better understanding of the present invention, but are not intended to limit the best mode of implementation, nor to limit the content and protection scope of the present invention. Any product identical or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior arts shall fall within the protection scope of the present invention.

[0040] If no specific experimental steps or conditions are specified in the examples, the experiments can be carried out according to the conventional experimental steps or conditions described in the literature in the art.

[0041] Example 1

[0042] This embodiment provides an ytterbium-doped perovskite quantum dot, and the preparation method thereof is as follows:

[0043] (1) Preparation of halogen source solution: 1 ml of octadecene, 150 μl of trimethylsilyl chloride (TMS-Cl) and 50 μl of trimethylsilyl bromide (TMS-Br) were mixed and set aside.

[0044] (2) Preparation of lead oleate solution: 2 mmol of lead acetate, 2 ml of oleic acid and 18 ml of octadecene were added to a three-necked flask and mixed. The mixture was heated to 100° C. and vacuumed for 1 hour. The mixture was cooled to room temperature and sealed to avoid light.

[0045] (3) Preparation of ytterbium oleate solution: 2 mmol ytterbium acetate, 2 ml oleic acid and 38 ml octadecene were added to a three-necked flask and mixed. The mixture was heated to 100° C. and vacuumed for 1 hour. The mixture was cooled to room temperature and sealed to avoid light.

[0046] (4) Preparation of cesium acetate precursor: 10 ml of deionized water and 10 mmol of cesium acetate were mixed and ultrasonically stirred in an ultrasonic machine until the cesium acetate particles were completely dissolved and the solution was clear and transparent. The solution was sealed and stored away from light.

[0047] (5) 1 ml of the lead oleate solution obtained in step (2), 2 ml of the ytterbium oleate solution obtained in step (3), 100 μl of the cesium acetate precursor obtained in step (4), 1 ml of oleic acid, 0.5 ml of oleylamine and 5 ml of octadecene were mixed in a three-necked flask, the temperature was raised to 120° C., and vacuum was applied for 30 minutes.

[0048] (6) Then, the temperature was further raised to 250° C. under a nitrogen environment, and all the halogen source solution obtained in step (1) was injected to react for 2 minutes.

[0049] (7) 0.1 ml of oleylamine was injected into the above solution, and the solution was stirred for 6 minutes under high temperature. Finally, the solution was taken out and purified and dispersed with n-hexane to obtain ytterbium-doped perovskite quantum dots.

[0050] The above experiment was repeated for two groups, the only difference being that the heating temperatures in step (6) were changed to 230°C and 240°C respectively.

[0051] Example 2

[0052] This embodiment provides an ytterbium-doped perovskite quantum dot, and the preparation method thereof is as follows:

[0053] (1) Preparation of halogen source solution: 1 ml of octadecene, 150 μl of trimethylsilyl chloride (TMS-Cl) and 50 μl of trimethylsilyl bromide (TMS-Br) were mixed and set aside.

[0054] (2) Preparation of lead oleate: 2 mmol of lead acetate, 2 ml of oleic acid and 18 ml of octadecene were added to a three-necked flask and mixed. The mixture was heated to 100° C. and vacuumed for 1 hour. The mixture was cooled to room temperature and sealed to avoid light.

[0055] (3) Preparation of ytterbium oleate: 2 mmol ytterbium acetate, 2 ml oleic acid and 38 ml octadecene were added to a three-necked flask and mixed. The mixture was heated to 100° C. and vacuumed for 1 hour. The mixture was cooled to room temperature and sealed to avoid light.

[0056] (4) Preparation of cesium acetate precursor: 10 ml of deionized water and 10 mmol of cesium acetate were mixed and ultrasonically stirred in an ultrasonic machine until the cesium acetate particles were completely dissolved and the solution was clear and transparent. The solution was sealed and stored away from light.

[0057] (5) 1 ml of the lead oleate solution obtained in step (2), 2 ml of the ytterbium oleate solution obtained in step (3), 100 μl of the cesium acetate precursor obtained in step (4), 1 ml of oleic acid, 0.5 ml of oleylamine and 5 ml of octadecene were mixed in a three-necked flask, the temperature was raised to 120° C., and vacuum was applied for 30 minutes.

[0058] (6) Then, the temperature was continued to be raised to 250° C. under a nitrogen environment, and the halogen source from step (1) was injected to react for 2 minutes.

[0059] (7) 0.3 ml of the halogen source solution prepared in the same manner as in step (1) was injected into the above solution, stirred for 6 minutes under high temperature, and finally taken out and purified and dispersed with n-hexane to obtain ytterbium-doped perovskite quantum dots, such as Figure 1 As shown, it can be seen that the quantum dots are dispersed more evenly and the dispersion is significantly improved. The actual color in the figure is milky white.

[0060] The above experiment was repeated for two groups, the only difference being that the heating temperature in step (6) was changed to 230°C and 240°C respectively.

[0061] Example 3

[0062] This embodiment provides an ytterbium-doped perovskite quantum dot, and the preparation method thereof is as follows:

[0063] (1) Preparation of halogen source: 1 ml of octadecene, 150 μl of trimethylsilyl chloride (TMS-Cl) and 50 μl of trimethylsilyl bromide (TMS-Br) were mixed and set aside.

[0064] (2) Preparation of lead oleate: 2 mmol of lead acetate, 2 ml of oleic acid and 18 ml of octadecene were added to a three-necked flask and mixed. The mixture was heated to 100° C. and vacuumed for 1 hour. The mixture was cooled to room temperature and sealed to avoid light.

[0065] (3) Preparation of ytterbium oleate: 2 mmol ytterbium acetate, 2 mmol oleic acid and 38 ml octadecene were added to a three-necked flask and mixed. The mixture was heated to 100° C. and vacuumed for 1 hour. The mixture was cooled to room temperature and sealed to avoid light.

[0066] (4) Preparation of cesium acetate precursor: 10 ml of deionized water and 10 mmol of cesium acetate were mixed and ultrasonically stirred in an ultrasonic machine until the cesium acetate particles were completely dissolved and the solution was clear and transparent. The solution was sealed and stored away from light.

[0067] (5) 1 ml of the lead oleate solution obtained in step (2), 2 ml of the ytterbium oleate solution obtained in step (3), 100 μl of the cesium acetate precursor obtained in step (4), 1 ml of oleic acid, 0.5 ml of oleylamine and 5 ml of octadecene were mixed in a three-necked flask, the temperature was raised to 120° C., and vacuum was applied for 30 minutes.

[0068] (6) Then, the temperature was continued to be raised to 250° C. under a nitrogen environment, and the halogen source from step (1) was injected to react for 2 minutes.

[0069] (7) injecting 0.3 ml of the halogen source solution prepared in the same manner as in step (1) into the above solution and stirring for 6 minutes under high temperature;

[0070] (8) Preparation of copper oleate: Mix 1 ml of oleic acid, 1 mmol of copper acetate and 10 ml of octadecene in a three-necked flask, heat to 120°C, evacuate and stir for 1 h, and take out after the drug is completely dissolved for later use.

[0071] (9) 1 ml of copper oleate solution was added to the above solution, and the mixture was stirred at 300 r / min at 60° C. for 1 h. Finally, the solution was taken out and purified and dispersed with n-hexane to obtain ytterbium-doped perovskite quantum dots.

[0072] The above experiment was repeated for two groups, the only difference being that the heating temperature in step (6) was changed to 230°C and 240°C respectively.

[0073] Comparative Example 1

[0074] The difference between this comparative example and Example 1 is that the oleylamine added in step (7) is added together with the oleylamine in step (5).

[0075] Comparative Example 2

[0076] The difference between this comparative example and Example 2 is that the halogen source solution added in step (7) is added together with the halogen source solution in step (6).

[0077] Test Example 1

[0078] In multiple experiments, the reaction time and reaction temperature of step (6) in Example 1 were changed. After the reaction, the solution was purified and dispersed with n-hexane after step (6) was completed to obtain ytterbium-doped calcium chrysene quantum dots. The luminescence spectrum of the quantum dot solution and the near-infrared fluorescence quantum yield at 980 nm were tested using a spectrometer. The reaction temperature, reaction time and corresponding near-infrared quantum yield test data are shown in Table 1:

[0079] Table 1 Near infrared quantum yield at different reaction temperatures and reaction times

[0080]

[0081] As can be seen from the table above, the reaction time and reaction temperature determine the near-infrared luminescence efficiency. Increasing the reaction temperature and increasing the reaction time greatly improve the near-infrared quantum yield of Yb. However, the inventors found that agglomeration is likely to occur after the reaction exceeds 3 minutes. Therefore, in the case of supplementing halogen or ligand, the time of the first reaction should not exceed 3 minutes. Figure 2As shown, the quantum dots obtained after the reaction at 250° C. for 8 minutes and then step (7) of Example 1 are performed. It can be seen that the quantum dots are very obviously aggregated and the size is significantly increased. The color of the aggregates in the figure is actually yellow-green.

[0082] Test Example 2

[0083] The performance of the ytterbium-doped perovskite quantum dots obtained in Example 1 and Comparative Example 1, and in Example 2 and Comparative Example 2 were compared respectively. The luminescence spectrum of the quantum dot solution and the near-infrared fluorescence quantum yield at 980 nm were tested using a spectrometer, and the sedimentation time was calculated by timing to calculate the approximate time for the quantum dot solution to be delaminated, and the results are shown in Tables 2 and 3, respectively.

[0084] Table 2 Quantum dot performance results of Example 1 and Comparative Example 1

[0085]

[0086] Table 3 Quantum dot performance results of Example 2 and Comparative Example 2

[0087]

[0088] As can be seen from the above two tables, the reason why oleylamine cannot be excessive at the beginning is that if it is added together with the reactants at the beginning, pure CsPbX3 quantum dots are preferentially generated due to different reaction activities, and the large steric hindrance will also affect the doping of Yb ions and near-infrared quantum yield. The specific data are shown in Table 2. It can be seen that the near-infrared quantum yield in Comparative Example 1 is much lower than the quantum dot yield in Example 1; similarly, as described in Table 3, adding an excessive amount of halogen source at the beginning will also affect the quantum yield. Only when the ligand and halogen are missing, the lattice growth of CsPbX3 quantum dots is unevenly distorted, which will greatly increase the doping of Yb ions. At this time, a small amount of halogen or ligand is added to suppress the agglomeration of quantum dots in a high temperature environment, reduce the surface defect state density, and modify the uniformity of the quantum dot lattice, which greatly improves the luminous efficiency of Yb and the dispersibility of quantum dots.

[0089] Test Example 3

[0090] (1) The performance of the ytterbium-doped perovskite quantum dots obtained in Example 2 and Example 3 was compared. The luminescence spectrum of the quantum dot solution and the near-infrared fluorescence quantum yield at 980 nm were tested using a spectrometer, and the sedimentation time was calculated by timing to calculate the approximate time for the quantum dot solution to separate. The results are shown in Table 4.

[0091] Table 4 Quantum dot performance results of Example 2 and Example 3

[0092]

[0093] As can be seen from the above table, the near-infrared quantum yield of the quantum dots after stirring treatment is significantly improved due to the passivation effect of divalent metal salt of oleic acid, and the sedimentation time of the quantum dots in n-hexane is prolonged, indicating that the dispersibility of the quantum dot solution is further improved and the size of the quantum dots is reduced.

[0094] (2) Comparing Example 2 and Example 3, when the reaction temperature was 240°C, the quantum dots obtained were tested for storage stability changes. Specifically, the synthesized quantum dots were dispersed with n-hexane and centrifuged twice, and the precipitate was dispersed with n-hexane and stored in a sealed room temperature and light-proof condition. Each time the quantum dot solution was shaken and a certain amount was taken out for testing, and the remaining samples were stored under the previous conditions. The results are shown in Figure 3 As shown, it can be seen that compared with the sample in Example 2 which was not subjected to stirring treatment, the storage stability of the solution in Example 3 is improved.

[0095] Obviously, the above embodiments are merely examples for the purpose of clear explanation, and are not intended to limit the implementation methods. For those skilled in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all the implementation methods here. The obvious changes or modifications derived therefrom are still within the scope of protection of the invention.

Claims

1. A method for preparing ytterbium-doped perovskite quantum dots, characterized in that: include: Mixing a lead source, an ytterbium source, a cesium source, oleic acid, a first fatty amine and octadecene at a first temperature to obtain a mixed solution; Heating the mixed solution to a second temperature and adding a first halogen source to perform a first reaction, thereby obtaining a first reaction system through the first reaction; Keeping the reaction temperature consistent with that of the first reaction, adding a reaction supplement to the first reaction system to carry out a second reaction, and obtaining a second reaction system after the second reaction is completed; Purifying and dispersing the second reaction system to obtain ytterbium-doped perovskite quantum dots; The reaction supplement is at least one of a second fatty amine and a second halogen source.

2. The preparation method according to claim 1, characterized in that: The first temperature is 100-150° C., and the mixing is performed under vacuum for 1-2 hours.

3. The preparation method according to claim 1 or 2, characterized in that: The second temperature is 230-250° C., and the first reaction is carried out under nitrogen protection for 0.5-3 min.

4. The preparation method according to any one of claims 1 to 3, characterized in that The second reaction is carried out under nitrogen protection for 2 to 6 minutes.

5. The preparation method according to any one of claims 1 to 4, characterized in that: The molar ratio of the lead source, the cesium source and the ytterbium source is 1:(1-1.4):(0.5-2); The molar ratio of the lead source to the first halogen source is 1:(6-7.5); The molar ratio of the first halogen source to the first fatty amine is 1:(0.6-1); The molar ratio of the lead source to the reaction supplement is 1:(1.5-6).

6. The preparation method according to any one of claims 1 to 5, characterized in that: The lead source includes at least one of lead oleate or lead oxide, the ytterbium source includes at least one of ytterbium oleate or ytterbium acetate, and the cesium source includes at least one of cesium acetate or cesium carbonate; The first fatty amine includes at least one of oleylamine, butylamine, octylamine and dodecylamine; The second fatty amine includes at least one of oleylamine, butylamine, octylamine and dodecylamine; The first halogen source includes at least one of trimethylsilyl bromide or trimethylsilyl chloride; The second halogen source includes at least one of trimethylsilyl bromide, octylamine bromide, dodecylamine bromide, oleylamine bromide, didodecyldimethylammonium bromide, distearyldimethylammonium bromide, trimethylsilyl chloride, octylamine chloride, dodecylamine chloride, oleylamine chloride, didodecyldimethylammonium chloride, and distearyldimethylammonium chloride.

7. The preparation method according to any one of claims 1 to 4, characterized in that: Before purifying and dispersing the second reaction system, the method further includes adding divalent metal salt of oleic acid to the second reaction system to carry out a third reaction.

8. The preparation method according to claim 7, characterized in that: The third reaction is to stir the reaction at 60-150° C. for 1-24 hours at a stirring speed of 300-500 r / min; The molar ratio of the lead source to the divalent metal salt of oleic acid is 1:(0.1-1); The divalent metal oleate includes at least one of copper oleate, cadmium oleate, zinc oleate, nickel oleate, chromium oleate, calcium oleate or lead oleate.

9. The preparation method according to any one of claims 1 to 8, characterized in that: The purification dispersion is to wash the second reaction system with a dispersant, centrifuge, take out the precipitate, and disperse and store it in the dispersant; The dispersant includes at least one of n-hexane or toluene.

10. An ytterbium-doped perovskite quantum dot, characterized in that: Prepared by the preparation method according to any one of claims 1 to 9.

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