Perovskite quantum dot and preparation method thereof

Abstract

The invention relates to the technical field of photoelectric materials, in particular to a perovskite quantum dot and a preparation method thereof. The preparation method of the perovskite quantum dots comprises the following steps: mixing a post-treatment solution and rare earth element doped perovskite nanocrystals, and then carrying out passivation treatment, wherein the post-treatment liquid comprises metal cations, a first ligand and a solvent. According to the preparation method of the perovskite quantum dots, the perovskite nanocrystals doped with the rare earth elements are passivated, so that the surface defects of the perovskite nanocrystals are effectively passivated, the rare earth doping efficiency, the luminous efficiency and the stability are improved, and the preparation method is simple in step and high in repetition rate.

Description

Technical Field

[0001] The present invention relates to the technical field of optoelectronic materials, and in particular to a perovskite quantum dot and a preparation method thereof. Background Art

[0002] The best corresponding band for photovoltaic power generation is between 450nm and 1100nm. Converting high-energy photons into low-energy photons is an important way to promote the efficiency of photoelectric conversion. In the 1950s, quantum tailoring luminescence was proposed, which means that one high-energy photon can be converted into two low-energy photons. The theoretical photoluminescence quantum yield (PLQYs) exceeds 100%, which provides an effective way to improve the solar energy conversion efficiency in the photovoltaic field. Therefore, exploring high-efficiency near-infrared (NIR) emitting materials has great application prospects and market value.

[0003] Rare earth element doped perovskite quantum dots have been widely studied, and the synthesis process mainly focuses on the hot injection method of cesium and halogen solution. The luminescence at 980nm exceeds 100%, but there has been little progress in improving the conversion efficiency of solar cells based on quantum tailoring luminescence. The main reason is that the test conditions are measured under extremely low excitation light power. When the light intensity density is similar to that of sunlight, the actual QY of the test is very low. The test excitation light power is too large, which is very easy to produce light saturation, QY drops sharply, and the quantum tailoring conversion efficiency is extremely low.

[0004] The poor reproducibility of the preparation method of rare earth element-doped perovskite quantum dots is also a major obstacle. The high temperature in the synthesis process causes more surface defects in the quantum dots, affecting their near-infrared PLQYs.

[0005] In the preparation method of rare earth element doped perovskite quantum dots, trimethylsilane is generally used as the halogen source. Due to the short carbon chain and lack of ligands on the surface of trimethylsilane, many B-site, ligand and halogen defects are generated. The defect state will increase the probability of non-radiative recombination of excitons, thereby affecting the energy transfer from the perovskite host to the doping energy level and the near-infrared emission efficiency.

[0006] Doping luminescent energy levels in perovskite quantum dots to achieve dual emission has always been a research hotspot, but the actual doping concentration of doped ions needs to be improved. The existing technology can improve the emission efficiency of doped energy levels by synthesizing transition metals and rare earth elements in a one-pot form of dual doping. However, the disadvantage is also obvious. Under high-temperature synthesis conditions, the auxiliary doping ions of rare earth elements will enter the lattice first because of their smaller size, which will inhibit the actual doping effect of rare earth elements.

[0007] In view of this, the present invention is proposed. Summary of the invention

[0008] The first object of the present invention is to provide a method for preparing perovskite quantum dots, which improves the rare earth doping efficiency, luminescence efficiency and stability of rare earth element-doped perovskite nanocrystals, and the preparation method has simple steps and high repetition rate.

[0009] The second object of the present invention is to provide a perovskite quantum dot having excellent luminous efficiency and storage stability.

[0010] In order to achieve the above-mentioned purpose of the present invention, the following technical solutions are particularly adopted:

[0011] The present invention provides a method for preparing perovskite quantum dots, comprising the following steps:

[0012] The post-treatment solution and the rare earth element-doped perovskite nanocrystals are mixed and then passivated;

[0013] Wherein, the post-treatment liquid comprises metal cations, a first ligand and a solvent.

[0014] Furthermore, the metal cation includes Cd 2+ 、Zn 2+ 、Ni 2+ , Ca 2+ , Cu 2+ Cr 2+ Sn 2+ 、Co 2+ and Mn 2+ At least one of;

[0015] The first ligand includes at least one of fatty acid, sulfonic acid, sulfate ester and phosphate ester.

[0016] Furthermore, the post-treatment liquid also includes chloride ions and a second ligand; the second ligand includes a fatty amine.

[0017] Furthermore, the fatty acid includes at least one of oleic acid, butyric acid, octanoic acid and dodecanoic acid.

[0018] Furthermore, the fatty amine includes at least one of oleylamine, octylamine and dodecylamine.

[0019] Furthermore, in the rare earth element-doped perovskite nanocrystals, the perovskite nanocrystals are CsBX3, wherein B includes Pb and / or Sn, X includes at least one of Cl, Br and I; and the rare earth elements include at least one of Yb, Er, Tm, Pr, Tb, Gd, Ce, Nd and Ho.

[0020] Furthermore, in the rare earth element-doped perovskite nanocrystals, the molar ratio of the rare earth element to the perovskite nanocrystals is (0.2-4):1.

[0021] Furthermore, the molar ratio of the metal element to the rare earth element-doped perovskite nanocrystal in the post-treatment solution is (0.1-4):1.

[0022] Furthermore, the temperature of the passivation treatment is 40 to 80° C., and the time of the passivation treatment is 0.5 to 2.5 hours.

[0023] The present invention also provides a perovskite quantum dot, which is prepared by the above-mentioned preparation method of the perovskite quantum dot.

[0024] Compared with the prior art, the present invention has the following beneficial effects:

[0025] 1. The preparation method of perovskite quantum dots of the present invention can effectively passivate the B-site, ligand and halogen defects generated during the synthesis of rare earth element-doped perovskite nanocrystals, thereby improving the rare earth doping efficiency, improving the luminescence efficiency of the prepared perovskite quantum dots, and being able to improve the storage stability of the perovskite quantum dots.

[0026] 2. The preparation method of perovskite quantum dots of the present invention has simple steps and a high repetition rate, and the luminous efficiency of quantum dots prepared in different batches can be controlled to be at the same order of magnitude. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] 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.

[0028] Figure 1 The storage stability of the treated ytterbium-doped perovskite nanocrystals prepared in Examples 1 and 5 of the present invention, and the perovskite quantum dots prepared in Comparative Example 1. DETAILED DESCRIPTION

[0029] The technical scheme of the present invention will be clearly and completely described below in conjunction with the accompanying drawings and specific embodiments, but it will be understood by those skilled in the art that the following described embodiments are part of embodiments of the present invention, rather than all embodiments, and are only used to illustrate the present invention, and should not be considered as limiting the scope of the present invention. Based on the embodiments in the present invention, all other embodiments obtained by those of ordinary skill in the art without making creative work are within the scope of protection of the present invention. If specific conditions are not specified in the embodiments, they are carried out according to normal conditions or conditions recommended by the manufacturer. If the manufacturer is not specified in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0030] The following is a detailed description of a perovskite quantum dot and a preparation method thereof according to an embodiment of the present invention.

[0031] In some embodiments of the present invention, a method for preparing perovskite quantum dots is provided, comprising the following steps:

[0032] The post-treatment solution and the rare earth element-doped perovskite nanocrystals are mixed and then passivated;

[0033] The post-treatment liquid includes metal cations, a first ligand and a solvent.

[0034] The preparation method of the perovskite quantum dots of the present invention adopts a post-treatment liquid to passivate the perovskite nanocrystals doped with rare earth elements, passivates the B-site and ligand defects generated during the synthesis of the perovskite nanocrystals doped with rare earth elements, improves the doping efficiency of the rare earth elements, and improves the luminescence efficiency of the quantum dots; at the same time, the surface of the quantum dots is covered with sufficient ligands, which is beneficial to improving the stability of the quantum dots and greatly increases the storage stability of the prepared perovskite quantum dots.

[0035] For rare earth element doped perovskite nanocrystals, passivation treatment using the above post-treatment solution can enhance the energy transfer from excitons to doping energy levels, thereby facilitating improvement of the near-infrared luminescence efficiency of rare earth element doped perovskite nanocrystals.

[0036] Metal ions are doped together with rare earths. Since metal ions have a smaller radius, they are easy to enter the lattice first. The present invention adopts a metal ion post-treatment method, which will not inhibit the early doping of rare earths and is beneficial to improving the doping efficiency of rare earth elements.

[0037] In some embodiments, a post-treatment method for improving near-infrared luminescence of rare earth element-doped perovskite nanocrystals comprises the following steps:

[0038] The post-treatment solution and the rare earth element-doped perovskite nanocrystals are mixed and then passivated;

[0039] Among them, the post-treatment liquid includes metal cations, a first ligand and a solvent.

[0040] In some embodiments, the metal cation comprises Cd 2+ 、Zn 2+ 、Ni 2+ , Ca 2+ , Cu 2+ Cr 2+ Sn 2+ 、Co 2+ and Mn 2+ At least one of;

[0041] The first ligand comprises at least one of fatty acid, sulfonic acid, sulfate ester and phosphate ester; preferably fatty acid.

[0042] After the first ligand and the metal cation are mixed, fatty acid salts, sulfonates, sulfate esters and phosphate esters are formed; in addition to fatty acid salts, the present invention can also be replaced by the other three types of surfactants, sulfonates, sulfate esters and phosphate esters.

[0043] In some embodiments, the post-treatment liquid further comprises chloride ions and a second ligand; the second ligand comprises a fatty amine.

[0044] Chloride ions and fatty amines are mixed to obtain chlorinated fatty amines. The chloride ions in the post-treatment solution of the present invention can passivate halogen defects generated during the synthesis of rare earth element-doped perovskite nanocrystals, thereby improving the performance of the obtained perovskite quantum dots.

[0045] In some embodiments, the fatty acid includes at least one of oleic acid, butyric acid, octanoic acid, and lauric acid.

[0046] In some embodiments, the fatty amine includes at least one of oleylamine, octylamine, and dodecylamine.

[0047] In some embodiments, the solvent includes, but is not limited to, octadecene.

[0048] In some embodiments, the concentration of the metal element in the post-treatment liquid is 0.05 to 0.2 mol / L. Typically but not limitatively, for example, the concentration of the metal element in the post-treatment liquid can be 0.05 mol / L, 0.08 mol / L, 0.1 mol / L, 0.13 mol / L, 0.15 mol / L, 0.17 mol / L, 0.2 mol / L or a range of any two thereof.

[0049] In some embodiments, the method for preparing the post-treatment liquid comprises the following steps: a divalent metal salt, a ligand and a solvent are mixed to obtain a post-treatment liquid.

[0050] In some embodiments, the divalent metal salt comprises acetate and / or chloride; the cation in the divalent metal salt comprises Cd 2+ 、Zn 2+ 、Ni 2+ , Ca 2+ , Cu 2+ Cr 2+ Sn 2+ 、Co 2+ and Mn 2+At least one of; preferably, the divalent metal salt includes at least one of zinc acetate, nickel (II) acetate, calcium acetate, copper acetate, chromium (II) acetate, tin (II) acetate, cobalt (II) acetate, manganese (II) acetate, cadmium (II) acetate, zinc chloride, nickel (II) chloride, calcium chloride, copper chloride, chromium (II) chloride, tin (II) chloride, cobalt (II) chloride, manganese (II) chloride and cadmium chloride.

[0051] Acetate can passivate the B-site defects of rare earth element-doped perovskite nanocrystals; chloride can passivate the B-site and halogen defects of rare earth element-doped perovskite nanocrystals.

[0052] In some embodiments, the ligand comprises a first ligand and a second ligand; the first ligand comprises at least one of a fatty acid, a sulfonic acid, a sulfate ester, and a phosphate ester, and the second ligand comprises a fatty amine.

[0053] In some embodiments, the fatty acid includes at least one of oleic acid, butyric acid, octanoic acid, and dodecanoic acid; and the fatty amine includes at least one of oleylamine, octylamine, and dodecylamine.

[0054] In some embodiments, the solvent includes, but is not limited to, octadecene.

[0055] In some embodiments, the ratio of the molar number of the divalent metal salt to the sum of the molar numbers of the first ligand and the second ligand is 1:(1-6); typically but not limiting, for example, the ratio of the molar number of the divalent metal salt to the sum of the molar numbers of the first ligand and the second ligand can be 1:1, 1:2, 1:3, 1:4, 1:5, 1:6 or a range of any two thereof; the usage ratio of the divalent metal salt to the solvent is 1g:10-100mL.

[0056] In some embodiments, in the method for preparing the post-treatment liquid, the mixing includes heating under vacuum conditions; preferably, the heating temperature is 100-150° C., and the heating time is ≥30 min.

[0057] The post-treatment liquid of the present invention is mainly obtained by mixing a ligand and a divalent metal salt; wherein the first ligand (such as oleic acid) can be used as a cationic ligand, and the second ligand (such as oleylamine) can be used as an anionic ligand, and after heating, most of the insoluble divalent metal salts, such as metal chlorides, can be well dissolved, and added to an unpurified rare earth element-doped perovskite nanocrystal solution. Because the solvent of the rare earth element-doped perovskite nanocrystal solution is also composed of octadecene and a small amount of free ligands, which is the same as the environment of the post-treatment liquid, it will not cause the metal ions to precipitate due to the change of the solvent environment, which greatly reduces the difficulty of subsequent purification.

[0058] The post-treatment liquid obtained by mixing the ligand, divalent metal salt and solvent (octadecene) is added to the rare earth element doped perovskite nanocrystal solution, and the introduced solvent will not have a destructive effect on the rare earth element doped perovskite nanocrystal; in the post-treatment liquid, fatty acid salts and halogenated fatty amines passivate the B-site and halogen defects generated in the synthesis process, and enhance the energy transfer from the exciton to the doping energy level; the introduced ligand supplements the ligand defects on the surface of the nanocrystal, and the surface is covered with sufficient ligands to enhance the stability of the quantum dots, greatly increasing the near-infrared luminescence performance and storage time of the prepared rare earth doped perovskite quantum dots, achieving efficient near-infrared luminescence, and can be applied to light emitting diodes (LEDs), detectors and photovoltaic gain and other fields.

[0059] In some embodiments, in the rare earth element-doped perovskite nanocrystals, the perovskite nanocrystals are CsBX3, wherein B includes Pb and / or Sn, X includes at least one of Cl, Br and I; and the rare earth element includes at least one of Yb, Er, Tm, Pr, Tb, Gd, Ce, Nd and Ho.

[0060] In some embodiments, in the rare earth element-doped perovskite nanocrystals, the molar ratio of the rare earth element to the perovskite nanocrystals is (0.2-4):1; typically but not limitatively, for example, the molar ratio of the rare earth element to the perovskite nanocrystals can be 0.2:1, 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1 or a range of any two thereof.

[0061] The preparation method of the present invention can effectively passivate the defects on the surface of Yb-doped perovskite nanocrystals, and improve the near-infrared luminescence efficiency and storage stability.

[0062] In some embodiments, the molar ratio of the metal element and the rare earth element doped perovskite nanocrystals in the post-treatment liquid is (0.1-4):1; typically but not limitatively, for example, the molar ratio of the metal element and the rare earth element doped perovskite nanocrystals in the post-treatment liquid can be 0.1:1, 0.5:1, 1:1, 1.5:1, 2:1, 2.5:1, 3:1, 3.5:1, 4:1 or a range of any two thereof.

[0063] In some embodiments, the temperature of the passivation treatment is 40-80°C, and the time of the passivation treatment is 0.5-2.5h; typically but not limiting, for example, the temperature of the passivation treatment can be 40°C, 50°C, 60°C, 70°C, 80°C or a range between any two of them; the time of the passivation treatment can be 0.5h, 1h, 1.5h, 2h, 2.5h or a range between any two of them; preferably, the temperature of the passivation treatment is 40-60°C, and the time of the passivation treatment is 0.5-2h.

[0064] The preparation method of the present invention has the advantages of simple operation method, strong pertinence, high repetition rate, etc. Through passivation treatment, the near-infrared QY of quantum dots can be controlled at the same order of magnitude.

[0065] The passivation treatment temperature of the present invention is low, the interior of the quantum dot lattice is relatively stable, and the probability of rare earth ions (such as Yb) that have been doped into the lattice being separated is low. The added post-treatment liquid will not form a competitive occupancy relationship with the rare earth ions while passivating the defects, thereby not affecting the actual doping concentration of the rare earth and the near-infrared emission efficiency.

[0066] In some embodiments, the method for preparing perovskite quantum dots comprises the following steps:

[0067] The post-treatment liquid and the rare earth element-doped perovskite nanocrystals are mixed and then passivated, and purified and dispersed using n-hexane;

[0068] or,

[0069] After the post-treatment liquid and the rare earth element-doped perovskite nanocrystals are mixed, a first passivation treatment, centrifugation and dispersion using octadecene are sequentially performed, and then a halogen source is added for a second passivation treatment, followed by purification and dispersion using n-hexane; wherein the halogen source includes at least one of oleylamine chloride, octylamine chloride and dodecylamine chloride.

[0070] In some embodiments, the method for preparing rare earth element-doped perovskite nanocrystals comprises the following steps:

[0071] A mixed solution of a lead source, a rare earth source, a cesium source and a solvent reacts with a halogen source and is cooled to obtain a rare earth-doped perovskite nanocrystal solution.

[0072] In some embodiments, the halogen source includes at least one of trimethylchlorosilane, trimethylbromosilane, oleylamine bromide, oleylamine chloride, didodecyldimethylammonium bromide, didodecyldimethylammonium chloride, dioctadecyldimethylammonium bromide, dioctadecyldimethylammonium chloride, tetra-n-octylammonium bromide, tetra-n-octylammonium chloride, ammonium bromide and ammonium chloride.

[0073] In some embodiments, the lead source includes at least one of lead acetate, lead oxide, lead nitrate, lead carbonate, and lead oleate.

[0074] In some embodiments, the rare earth source includes at least one of ytterbium acetate, ytterbium nitrate, and ytterbium oleate.

[0075] In some embodiments, the cesium source includes at least one of cesium acetate, cesium carbonate, and cesium acetate in ethanol.

[0076] In some embodiments, the solvent includes oleic acid, oleylamine, and octadecene.

[0077] In some embodiments, in the method for preparing rare earth element-doped perovskite nanocrystals, the reaction temperature is 240 to 260° C., and the reaction time is 3 to 5 minutes.

[0078] In some specific embodiments, the method for preparing ytterbium-doped perovskite nanocrystals comprises the following steps:

[0079] Lead oleate, ytterbium oleate, cesium acetate ethanol solution, oleic acid, oleylamine and octadecene are mixed, the temperature is raised to 120°C and vacuumed for 60 minutes, the temperature is further raised to 240-260°C in a nitrogen environment, a halogen source is injected, the temperature is kept at 240-260°C for 3-5 minutes, and then cooled to room temperature in an ice water bath to obtain a rare earth doped lead halide perovskite nanocrystal solution.

[0080] In some embodiments of the present invention, a perovskite quantum dot is also provided, which is prepared using the above-mentioned method for preparing the perovskite quantum dot.

[0081] Example 1

[0082] The method for preparing perovskite quantum dots provided in this embodiment comprises the following steps:

[0083] 0.1 mL of the post-treatment solution and 2 mL of the ytterbium-doped perovskite nanocrystal solution were mixed, stirred at 60° C. for 2 h, and then purified and dispersed using n-hexane to obtain treated ytterbium-doped perovskite nanocrystals.

[0084] The method for preparing the ytterbium-doped perovskite nanocrystal solution comprises the following steps:

[0085] 0.5 mL of octadecene, 0.12 mL of trimethylsilyl chloride (TMS-Cl), and 0.08 mL of trimethylsilyl bromide (TMS-Br) were mixed to obtain a halogen source.

[0086] 4mmol lead acetate, 4mL oleic acid and 36mL octadecene are added to a three-necked flask and mixed. The mixture is heated to 120℃ and vacuumed for 1h. Then, nitrogen is passed through the flask and the temperature is raised to 150℃ for 10min until the solution is completely clear and transparent. The temperature is then lowered to below 100℃ to obtain lead oleate.

[0087] 4mmol ytterbium acetate, 4mL oleic acid and 36mL octadecene were added to a three-necked flask and mixed. The mixture was heated to 120℃ and vacuumed for 1h. Then nitrogen was introduced and the temperature was raised to 150℃ and kept for 10min until the solution was completely clear and transparent. The temperature was then lowered to 100℃ to obtain ytterbium oleate.

[0088] 10 mL of anhydrous ethanol 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, thereby obtaining an ethanol solution of cesium acetate.

[0089] 1 mL of lead oleate, 2 mL of ytterbium oleate, 0.28 mL of cesium acetate ethanol solution, 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 vacuumed for 60 min, then the temperature was continued to be raised to 260°C under a nitrogen environment, 0.08 mL of TMS-Br and 0.12 mL of TMS-Cl were injected, the temperature was kept at 260°C for 5 min, and then quickly cooled to room temperature in an ice-water bath to obtain an ytterbium-doped perovskite nanocrystal solution.

[0090] The preparation method of the post-treatment liquid comprises the following steps:

[0091] 0.266 g of cadmium acetate, 1 mL of oleic acid and 9 mL of octadecene were added to a three-necked flask, heated to 120°C and evacuated for more than 30 min until the solution was completely clear and transparent, then cooled to room temperature for use.

[0092] Example 2

[0093] The preparation method of perovskite quantum dots provided in this embodiment refers to Example 1, except that the amount of post-treatment liquid used is 0.15 mL.

[0094] Example 3

[0095] The preparation method of perovskite quantum dots provided in this embodiment refers to Example 1, except that the amount of the post-treatment liquid used is 0.2 mL.

[0096] Example 4

[0097] The preparation method of perovskite quantum dots provided in this embodiment refers to Example 1, except that the amount of post-treatment liquid used is 0.25 mL.

[0098] Example 5

[0099] The preparation method of perovskite quantum dots provided in this embodiment refers to that in Embodiment 1, except that the preparation method of the post-treatment solution is different.

[0100] The preparation method of the post-treatment liquid comprises the following steps:

[0101] 0.146 g of cadmium chloride, 2 mL of oleic acid, 2 mL of oleylamine and 16 mL of octadecene were added to a three-necked flask, heated to 120-140 °C and evacuated for more than 60 min until the solution was completely clear and transparent, then cooled to room temperature for use.

[0102] Example 6

[0103] The preparation method of perovskite quantum dots provided in this embodiment refers to Example 5, except that the amount of post-treatment liquid used is 1 mL.

[0104] Example 7

[0105] The preparation method of perovskite quantum dots provided in this embodiment refers to Example 5, except that the amount of post-treatment liquid used is 1.5 mL.

[0106] Example 8

[0107] The preparation method of perovskite quantum dots provided in this embodiment refers to Example 5, except that the amount of post-treatment liquid used is 2 mL.

[0108] Example 9

[0109] The preparation method of perovskite quantum dots provided in this embodiment refers to Example 1, with the only difference being that, in the preparation method of the post-treatment solution, cadmium acetate is replaced by calcium acetate.

[0110] Example 10

[0111] The preparation method of perovskite quantum dots provided in this embodiment refers to Example 1, with the only difference being that, in the preparation method of the post-treatment solution, cadmium acetate is replaced by nickel acetate.

[0112] Embodiment 11

[0113] The preparation method of perovskite quantum dots provided in this embodiment refers to Example 5, the only difference being that in the preparation method of the post-treatment solution, cadmium acetate is replaced by tin chloride.

[0114] Example 12

[0115] The preparation method of perovskite quantum dots provided in this embodiment refers to Example 1, with the only difference being that after the post-treatment liquid and the ytterbium-doped perovskite nanocrystal solution are mixed, they are stirred at 45°C for 2 hours, centrifuged in sequence, dispersed with octadecene, and then octylamine chloride is added, and stirred at 60°C for 20 minutes to obtain treated ytterbium-doped perovskite nanocrystals.

[0116] Embodiment 13

[0117] The preparation method of perovskite quantum dots provided in this embodiment refers to Example 1, with the only difference being that in the preparation method of ytterbium-doped perovskite nanocrystal solution, TMS-Br and TMS-Cl are replaced by didodecyldimethylammonium chloride and didecyldimethylammonium bromide.

[0118] Comparative Example 1

[0119] The preparation method of perovskite quantum dots provided in this comparative example comprises the following steps:

[0120] After centrifugation, the ytterbium-doped perovskite nanocrystal solution is purified and dispersed using n-hexane to obtain perovskite quantum dots.

[0121] The preparation method of the ytterbium-doped perovskite nanocrystal solution is the same as that in Example 1.

[0122] Comparative Example 2

[0123] The preparation method of perovskite quantum dots provided in this comparative example refers to Example 1, except that no post-treatment is performed and 0.266 g of cadmium acetate and ytterbium oleate are added together.

[0124] Test Example 1

[0125] The near-infrared luminescence properties of the treated ytterbium-doped perovskite nanocrystals prepared in Examples 1 to 13 and the perovskite quantum dots prepared in Comparative Examples 1 to 2 were tested, and the results are shown in Table 1.

[0126] The near-infrared QY test method is as follows: Use a fluorescence spectrometer that detects near-infrared bands greater than 1100nm to test the near-infrared QY and emission peak of the quantum dot solution. The excitation light wavelength is 375nm, and the wavelength test range is 700-1100nm. Dilute the quantum dot solution with n-hexane and place it in the spectrometer cuvette for testing and analysis.

[0127] The storage stability of the treated ytterbium-doped perovskite nanocrystals prepared in Example 1 and Example 5, and the perovskite quantum dots prepared in Comparative Example 1 were tested (observing the near-infrared QY changes of the quantum dot solution), and the results are as follows: Figure 1 The storage stability test method of the quantum dot solution is the same as above, ensuring that the dilution concentration of the solution tested each time is the same.

[0128] Table 1

[0129]

[0130]

[0131] As can be seen from Table 1, from the comparison between Examples 1 to 4 and Comparative Example 1, it can be seen that with the increase in the amount of cadmium oleate added, the near-infrared QY of the quantum dots increases significantly, and the exciton peak shifts to the blue. This is because the Cd ion radius is smaller than the Pb ion radius. When the ions with smaller radii replace the ions with larger radii, the lattice will shrink, the lattice spacing will increase, the bandgap will increase, and the exciton luminescence peak will shift to the blue. Cd entering the lattice can fill the defects inside and on the surface of the lattice, inhibit non-radiative recombination, and promote the transition of excited electrons in the conduction band to the Yb energy level.

[0132] Comparison of Examples 5 to 8 with Comparative Example 1 shows that with the increase in the amount of cadmium oleate and oleylamine chloride added, the near-infrared QY of the quantum dots increases significantly, and the exciton peak blue-shifts. Compared with cadmium oleate, the post-treatment solution contains halogens, which can achieve co-passivation of B-site, halogen and ligand defects. Therefore, the improvement in near-infrared QY is greater than the post-treatment effect of cadmium oleate.

[0133] Comparison between Example 1 and Comparative Example 2 shows that Cd ions can be used as auxiliary dopants and added together with Yb ions to form a one-pot synthesis in the form of dual doping, which can improve the emission efficiency of the doping energy level. However, the disadvantage is also obvious. Under high-temperature synthesis conditions, the auxiliary doped Cd ions will enter the lattice first because of their smaller size, which will inhibit the actual doping effect of Yb.

[0134] from Figure 1 It can be seen that the ytterbium-doped perovskite nanocrystals treated by the present invention have more excellent storage stability.

[0135] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing perovskite quantum dots, characterized in that: The steps include: The post-treatment solution and the rare earth element-doped perovskite nanocrystals are mixed and then passivated; Wherein, the post-treatment liquid comprises metal cations, a first ligand and a solvent.

2. The method for preparing perovskite quantum dots according to claim 1, characterized in that: The metal cations include Cd 2+ 、Zn 2+ 、Ni 2+ , Ca 2+ , Cu 2+ Cr 2+ Sn 2+ 、Co 2+ and Mn 2+ At least one of; The first ligand includes at least one of fatty acid, sulfonic acid, sulfate ester and phosphate ester.

3. The method for preparing perovskite quantum dots according to claim 1, characterized in that: The post-treatment liquid further comprises chloride ions and a second ligand; the second ligand comprises aliphatic amine.

4. The method for preparing perovskite quantum dots according to claim 2, characterized in that: The fatty acid includes at least one of oleic acid, butyric acid, octanoic acid and dodecanoic acid.

5. The method for preparing perovskite quantum dots according to claim 3, characterized in that: The fatty amine includes at least one of oleylamine, octylamine and dodecylamine.

6. The method for preparing perovskite quantum dots according to claim 1, characterized in that: In the rare earth element doped perovskite nanocrystals, the perovskite nanocrystals are CsBX3, wherein B includes Pb and / or Sn, X includes at least one of Cl, Br and I; and the rare earth element includes at least one of Yb, Er, Tm, Pr, Tb, Gd, Ce, Nd and Ho.

7. The method for preparing perovskite quantum dots according to claim 1, characterized in that: In the rare earth element doped perovskite nanocrystals, the molar ratio of the rare earth element to the perovskite nanocrystals is (0.2-4):

1.

8. The method for preparing perovskite quantum dots according to claim 1, characterized in that: The molar ratio of the metal element to the rare earth element-doped perovskite nanocrystal in the post-treatment solution is (0.1-4):

1.

9. The method for preparing perovskite quantum dots according to claim 1, characterized in that: The temperature of the passivation treatment is 40-80° C., and the time of the passivation treatment is 0.5-2.5 h.

10. A perovskite quantum dot, characterized in that: The perovskite quantum dots are prepared by the preparation method according to any one of claims 1 to 9.

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