Ytterbium-doped perovskite quantum dot and preparation method and application thereof

Abstract

The invention provides an ytterbium-doped perovskite quantum dot and a preparation method and application thereof. The preparation method comprises steps as follows: a cesium source and a quaternary ammonium salt chlorine source are sequentially added to a quantum dot precursor solution, a mixed solution is obtained and heated for a reaction, the perovskite quantum dots are obtained, and the quantum dot precursor solution comprises a lead source, an ytterbium source, a halogen source, a ligand and a solvent. The cesium source and the quaternary ammonium salt chlorine source are jointly injected, effective doping of rare earth isovalent ion ytterbium in perovskite is achieved, near-infrared luminescence of the quantum dots is improved, and the storage stability of the quantum dots is enhanced.

Description

Technical Field

[0001] The present invention belongs to the field of photovoltaics or displays, and relates to a ytterbium-doped perovskite quantum dot and a preparation method and application thereof. Background Art

[0002] In recent years, perovskite semiconductor materials have received extensive attention due to their excellent capabilities and application prospects in multiple fields such as solar cells, light-emitting diodes, detectors, lasers, and display panels. Among them, perovskite luminescent materials, especially lead-based perovskite quantum dots (APbX 3 , where A generally represents a cation of a metal or an organic substance, such as a cation of cesium, formamidine, or methylamine; X generally represents a halogen, such as chlorine, bromine, or iodine), due to their narrow full-width at half-maximum of luminescence, high quantum yield, high color purity of luminescence, adjustable luminescence peak position, etc., have been explored for numerous applications in display backplanes, ray detection, photovoltaic gain, etc. since they were invented and synthesized by Protesescu et al. in 2015.

[0003] The intrinsic properties of perovskite ionic crystals make them have a relatively low internal bond energy in the lattice, which makes it possible to regulate the luminescence of perovskite by doping with other metal ions. At the same time, due to their large absorption cross-section, they can be used as excellent host materials for rare earth ions to achieve high-efficiency radiative luminescence of rare earth ion 4f energy levels.

[0004] Ytterbium-doped perovskite quantum dots can achieve near-infrared luminescence at a peak position of 980 nm, and shear the photons intrinsically absorbed by perovskite into 2 ytterbium photons through the quantum cutting effect, and theoretically can achieve a quantum efficiency of >100%, showing great application prospects in near-infrared light-emitting devices and photovoltaic gain devices. Traditional synthesis methods use organic acids and amines as quantum dot surface ligands, which play the role of dissolving and complexing precursor materials such as ytterbium, lead, and halogen sources and maintaining the morphology of quantum dots. The binding energy between the organic acid or amine ligand in the traditional synthesis method and the lead source and halogen source is usually low, and due to the simultaneous presence of protonated and non-protonated acids and amine ligands in the solution, proton exchange between the two is likely to occur, resulting in ligand detachment and affecting the luminescence efficiency and stability of quantum dots.

[0005] Therefore, it is necessary to develop a suitable ligand engineering or synthesis process to improve the long-term stability of rare earth-doped quantum dots. Summary of the Invention

[0006] The purpose of the present invention is to provide a ytterbium-doped perovskite quantum dot with high near-infrared luminescence intensity and good stability, and a preparation method and application thereof.

[0007] To achieve the purpose of this invention, the present invention adopts the following technical solutions:

[0008] One of the objectives of the present invention is to provide a method for preparing ytterbium-doped perovskite quantum dots, and the preparation method includes:

[0009] Adding a cesium source and a quaternary ammonium salt chloride source into a quantum dot precursor solution in sequence to obtain a mixed solution, heating the mixed solution for reaction to obtain the ytterbium-doped perovskite quantum dots, wherein the quantum dot precursor solution includes a lead source, an ytterbium source, a halogen source, a ligand, and a solvent.

[0010] As a common material for post-treatment passivation of perovskite quantum dots, the quaternary ammonium salt chloride source has high reaction activity, that is, it can repair the halogen vacancy defects on the surface of perovskite quantum dots. At the same time, since there are no extra protons in its ammonium root, no proton exchange occurs with other acid-based B-site ligands, which can improve the stability of the quantum dots.

[0011] In the present invention, the cesium source and the quaternary ammonium salt chloride source are co-injected to achieve effective doping of rare earth heterovalent ions ytterbium in perovskite. The surface vacancy defects are repaired by the halogen source with a quaternary ammonium salt ligand. A higher ratio of the cesium source and the quaternary ammonium salt chloride source to the lead source in the quantum dot precursor solution can enable the perovskite quantum dots to form a stable core-shell structure with a 416 phase coating a 113 phase, thereby improving the overall luminescence efficiency of the quantum dots, achieving the effect of enhancing the near-infrared luminescence of the quantum dots and enhancing the storage stability of the quantum dots.

[0012] Note: In the following text, X generally refers to halogen, A generally refers to cesium, and B generally refers to lead.

[0013] As a preferred technical solution of the present invention, the quantum dot precursor solution includes a lead source, an ytterbium source, a halogen source, a ligand, and a solvent.

[0014] The quantum dot precursor solution of the present invention uses ytterbium-doped quantum dots. The traditional synthesis of cesium ytterbium-doped quantum dots usually uses a lead source, an ytterbium source, and a halogen source as raw materials, and a ligand is added to dissolve the raw materials to form a complex form of PbX 6 4 and ytterbium ions. After heating to a high temperature, a certain amount of cesium source is added for reaction to form quantum dots. However, since the content of PbX 6 4 in the solution is much higher than the injection amount of the cesium source, the outermost layer of the quantum dots mainly consists of lead and X elements. At this time, there are many A-site vacancies on the surface of the quantum dots, which easily leads to a low quantum yield of the sample. If a large amount of cesium source is added alone, a large number of surface vacancy defects at the A-site can be supplemented, and at the same time, the reaction time can be extended to promote the continuous reaction of the cesium source with ytterbium and lead, improving the near-infrared luminescence efficiency of the quantum dots. However, since the input ratio of the cesium source, the lead source, and the halogen source is not adjusted, the newly injected excessive cesium source will react with other lead and ytterbium sources in the solution, resulting in the formation of new X-site defects on the surface of the quantum dots and reducing the long-term stability of the sample.

[0015] Therefore, while adding a cesium source to the quantum dot precursor solution of the present invention, a quaternary ammonium salt chlorine source is added to repair the defects at both the A-site and the X-site, and increase the number of surface ligands of the quantum dots, thereby enhancing the stability of the quantum dots.

[0016] Preferably, the concentration of the lead source in the mixed solution is 0.01 - 0.05 mol / L. The concentration can be 0.01 mol / L, 0.02 mol / L, 0.03 mol / L, 0.04 mol / L, 0.05 mol / L, etc., but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0017] Preferably, the concentration of the ytterbium source in the mixed solution is 0.5 - 4 times that of the lead source concentration. The multiple can be 0.5 times, 1 time, 1.5 times, 2 times, 2.5 times, 3 times, 3.5 times, or 4 times, etc., but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0018] Preferably, the concentration of the halogen source in the mixed solution is 3.5 - 14 times that of the lead source concentration. The multiple can be 3.5 times, 4 times, 5 times, 6 times, 7 times, 8 times, 9 times, 10 times, 11 times, 12 times, 13 times, or 14 times, etc., but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0019] Preferably, the concentration of the ligand in the mixed solution is 10 - 50 times that of the lead source concentration. The multiple can be 10 times, 15 times, 20 times, 25 times, 30 times, 35 times, 40 times, 45 times, or 50 times, etc., but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0020] Preferably, the concentration of the cesium source in the mixed solution is 1.5 - 2 times that of the lead source concentration. The multiple can be 1.5 times, 1.6 times, 1.7 times, 1.8 times, 1.9 times, or 2 times, etc., but is not limited to the listed values. Other unlisted values within this numerical range are equally applicable.

[0021] Note that the cesium-doped ytterbium synthesis method usually only injects 1 / 3 to 1 / 2 of the ytterbium source of the lead source to synthesize quantum dots with a 113 phase. At this time, the number of complexed PbX 2 sources in the mixed solution is relatively large, resulting in the enrichment of PbX 2 sources on the surface of the finally synthesized quantum dots, so that there are more defects at the X-site on the surface of the quantum dots, resulting in low near-infrared luminescence efficiency and low stability of the sample. The present invention adjusts the growth process of the quantum dots by increasing the input ratio of the cesium source and the lead source, so that a core-shell structure with a 416 phase coating the 113 phase is formed in-situ, further improving the storage stability.

[0022] Preferably, the concentration of the quaternary ammonium salt chlorine source in the mixed solution is 2 to 6 times that of the lead source concentration, where the multiple can be 2 times, 3 times, 4 times, 5 times or 6 times, etc., but is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0023] When the addition amount of the quaternary ammonium salt chlorine source of the present invention is too small, there are more remaining surface defects of the quantum dots, and the improvement effect on the sample stability is obvious. If the feeding amount is too large, a large amount of the quaternary ammonium salt chlorine source is difficult to fully participate in the reaction, resulting in more impurities during the purification process.

[0024] As a preferred technical solution of the present invention, the lead source includes any one or a combination of at least two of lead chloride, lead bromide, lead acetate, lead oxide, lead stearate or lead oleate, and typical but non-limiting examples of the combination are: a combination of lead chloride and lead bromide, a combination of lead bromide and lead acetate, a combination of lead acetate and lead oxide, a combination of lead oxide and lead stearate, or a combination of lead stearate and lead oleate, etc.

[0025] The ytterbium source includes any one or a combination of at least two of ytterbium chloride, ytterbium bromide, ytterbium acetate or ytterbium oleate, and typical but non-limiting examples of the combination are: a combination of ytterbium chloride and ytterbium bromide, a combination of ytterbium bromide and ytterbium acetate, or a combination of ytterbium acetate and ytterbium oleate, etc.

[0026] The halogen source includes a bromine source and / or a chlorine source.

[0027] The ligand includes octylamine, oleylamine and oleic acid.

[0028] The solvent includes octadecene.

[0029] As a preferred technical solution of the present invention, the mass ratio of the bromine source to the chlorine source is (0 to 0.2):1, where the mass ratio can be 0, 0.05:1, 0.1:1, 0.15:1 or 0.2:1, etc., but is not limited to the listed values, and other unlisted values within this value range are equally applicable.

[0030] Preferably, the chlorine source includes any one or a combination of at least two of oleylamine chloride, octylamine chloride or trimethylchlorosilane, and typical but non-limiting examples of the combination are: a combination of oleylamine chloride and octylamine chloride, a combination of octylamine chloride and trimethylchlorosilane, or a combination of oleylamine chloride and trimethylchlorosilane, etc.

[0031] The bromine source includes any one or a combination of at least two of oleylamine bromide, octylamine bromide or trimethylbromosilane, and typical but non-limiting examples of the combination are: a combination of oleylamine bromide and octylamine bromide, a combination of octylamine bromide and trimethylbromosilane, or a combination of oleylamine bromide and trimethylbromosilane, etc.

[0032] Preferably, the mass ratio of the octylamine to the oleylamine is (2 - 3):(3 - 2). The mass ratio can be 2:3, 2.5:3, 3:3, 3:2.5, 3:2, etc., but is not limited to the listed values. Other unlisted values within this range are also applicable.

[0033] Preferably, the precursor solution further includes methanol.

[0034] As a preferred technical solution of the present invention, the cesium source includes cesium oleate.

[0035] Preferably, the quaternary ammonium salt chlorine source includes any one or a combination of at least two of dioctadecyl dimethyl ammonium chloride, dodecyl dimethyl ammonium chloride, ditetradecyl dimethyl ammonium chloride, or dioctyl dimethyl ammonium chloride. Typical but non-limiting examples of the combination are: the combination of dioctadecyl dimethyl ammonium chloride and dodecyl dimethyl ammonium chloride, the combination of dodecyl dimethyl ammonium chloride and ditetradecyl dimethyl ammonium chloride, the combination of ditetradecyl dimethyl ammonium chloride and dioctyl dimethyl ammonium chloride, or the combination of dioctadecyl dimethyl ammonium chloride and dioctyl dimethyl ammonium chloride, etc.

[0036] As a preferred technical solution of the present invention, the method for preparing the quantum dot precursor solution includes: mixing a lead source, a ytterbium source, a halogen source, a ligand, and a solvent, and heating to obtain the quantum dot precursor solution at a temperature of 230 - 270 °C.

[0037] Preferably, the mixing is carried out in a vacuum environment.

[0038] Preferably, the temperature of the mixing is 100 - 140 °C. The temperature can be 100 °C, 105 °C, 110 °C, 115 °C, 120 °C, 125 °C, 130 °C, 135 °C, or 140 °C, etc., but is not limited to the listed values. Other unlisted values within this range are also applicable.

[0039] Preferably, the mixing time is 25 - 35 min. The time can be 25 min, 26 min, 27 min, 28 min, 29 min, 30 min, 31 min, 32 min, 33 min, 34 min, or 35 min, etc., but is not limited to the listed values. Other unlisted values within this range are also applicable.

[0040] As a preferred technical solution of the present invention, the time interval between adding the cesium source and the quaternary ammonium salt chlorine source to the quantum dot precursor solution is ≤5 s. The time interval can be 1 s, 2 s, 3 s, 4 s, or 5 s, etc., but is not limited to the listed values. Other unlisted values within this range are also applicable.

[0041] If the time interval between adding the cesium source and the quaternary ammonium salt chlorine source to the quantum dot precursor solution in the present invention is too small, it will affect the nucleation process of the quantum dots, resulting in the generation of some visible light quantum dots. If it is too large, the nucleation and growth process of the quantum dots cannot be effectively controlled.

[0042] Preferably, the temperature of the reaction is 230 - 270 °C. The temperature can be 230 °C, 235 °C, 240 °C, 245 °C, 250 °C, 255 °C, 260 °C, 265 °C or 270 °C, etc., but is not limited to the listed values. Other unlisted values within this range are equally applicable.

[0043] If the temperature of the thermal reaction in the present invention is too low, it is difficult to open the quantum dot lattice, and it is difficult to achieve effective doping of ytterbium. If it is too high, the reaction solvent will boil, and the ligand will be oxidized, resulting in the inability to synthesize quantum dots.

[0044] Preferably, the reaction time is 30 - 90 s. The time can be 30 s, 35 s, 40 s, 45 s, 50 s, 55 s, 60 s, 65 s, 70 s, 75 s, 80 s, 85 s or 90 s, etc., but is not limited to the listed values. Other unlisted values within this range are equally applicable.

[0045] In the present invention, the quaternary ammonium salt chlorine source halogen source with a ligand and the cesium source are added within a time interval of 5 s, and the reaction time is extended to 30 - 90 s, so that the newly added quaternary ammonium salt chlorine source and the cesium source continue to react with the existing lead source and ytterbium source in the solution together, improving the rare earth doping degree of the sample and the near-infrared luminescence efficiency. The ligand on the surface of the quaternary ammonium salt chlorine source can repair the vacancy defects on the surface of the quantum dots, further improving the quantum efficiency and stability.

[0046] In addition, since the quaternary ammonium salt chlorine source already has a quaternary ammonium salt group on its surface that cannot participate in proton exchange, it will not undergo proton exchange with the protonated acid B-site ligand, thereby improving the stability of the quantum dots.

[0047] As a preferred technical solution of the present invention, after the thermal reaction, cooling, centrifugation and standing are carried out in sequence to obtain the perovskite quantum dots.

[0048] As a preferred technical solution of the present invention, the preparation method includes:

[0049] Adding a cesium source and a quaternary ammonium salt chlorine source to a quantum dot precursor solution at a temperature of 230 - 270 °C in sequence to obtain a mixed solution, reacting the mixed solution at 230 - 270 °C for 30 - 90 s, and then carrying out cooling, centrifugation and standing in sequence to obtain the ytterbium-doped perovskite quantum dots; the quantum dot precursor solution includes a lead source, an ytterbium source, a halogen source, a ligand and a solvent.

[0050] The second object of the present invention is to provide a ytterbium-doped perovskite quantum dot, and the perovskite quantum dot is prepared by the preparation method of the ytterbium-doped perovskite quantum dot as described in the first object.

[0051] The third object of the present invention is to provide an application of the ytterbium-doped perovskite quantum dot as described in the second object, and the ytterbium-doped perovskite quantum dot is applied to the photovoltaic field or the display field.

[0052] Compared with the prior art, the present invention has the following beneficial effects:

[0053] The present invention co-injects a cesium source and a quaternary ammonium salt chlorine source to achieve effective doping of rare earth hetero-valent ions ytterbium in perovskite. The surface vacancy defects are repaired by a halogen source with a quaternary ammonium salt ligand. A higher ratio of the cesium source and the quaternary ammonium salt chlorine source to the lead source in the quantum dot precursor solution can enable the perovskite quantum dot to form a stable core-shell structure with a 416 phase coating a 113 phase, thereby improving the overall luminescence efficiency of the quantum dot, achieving the effect of enhancing the near-infrared luminescence of the quantum dot and enhancing the storage stability of the quantum dot. The quantum efficiency of the prepared perovskite quantum dot can reach more than 65%, and the storage stability can reach more than 1000 h. BRIEF DESCRIPTION OF THE DRAWINGS

[0054] Figure 1 is the near-infrared luminescence spectrum of the perovskite quantum dot prepared in Example 1 of the present invention.

[0055] Figure 2 is the near-infrared luminescence spectrum of the perovskite quantum dot prepared in Comparative Example 1 of the present invention.

[0056] Figure 3 is the near-infrared luminescence spectrum of the perovskite quantum dot prepared in Comparative Example 2 of the present invention.

[0057] Figure 4 is the near-infrared luminescence spectrum of the perovskite quantum dot prepared in Comparative Example 3 of the present invention.

[0058] Figure 5 is the quantum efficiency of the perovskite quantum dots prepared in Example 1 and Comparative Examples 1-3 of the present invention.

[0059] Figure 6 is the comparison chart of the storage stability of the perovskite quantum dots prepared in Example 1 and Comparative Example 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0060] The technical solutions of the present invention will be further described below through specific embodiments. Those skilled in the art should understand that the embodiments are only for helping to understand the present invention and should not be regarded as specific limitations on the present invention.

[0061] Example 1

[0062] This embodiment provides a method for preparing perovskite quantum dots, and the preparation method includes:

[0063] Dissolve 0.25 mmol of Pb(OAc) 2 ·3H 2 O, 0.75 mmol of YbCl 3 ·6H 2 O, 250 μL of oleylamine bromide solution in 10 mL of octadecene, add 2.5 mL of oleic acid, 1.2 mL of oleylamine, 0.8 mL of octylamine and 1.5 mL of methanol to obtain a mixture. Place the mixture in a 100 mL three-necked flask and put it on a magnetic stirring heating jacket. Heat it to 120 °C under vacuum and keep it for 30 min. Then, heat the mixture to 250 °C in a nitrogen environment to obtain a quantum dot precursor solution;

[0064] Quickly add 2.5 mL of cesium oleate solution to the quantum dot precursor solution, and then immediately add 0.8 mmol of dioctadecyldimethylammonium chloride solution after 4 s. React at 270 °C for 30 s, and then perform ice-water cooling to obtain a product. Centrifuge the obtained product at 5000 rpm for 5 min, discard the supernatant, redisperse the precipitate in 15 mL of toluene solution and shake well. Centrifuge at 8000 rpm for 5 min to obtain the supernatant, discard the supernatant, redisperse the precipitate in 10 mL of n-hexane solution and shake well, and let it stand to obtain the perovskite quantum dot solution.

[0065] This embodiment also provides preparation methods for the above-mentioned cesium oleate solution, oleylamine bromide solution and dioctadecyldimethylammonium chloride solution:

[0066] (1) Preparation method of cesium oleate solution: Dissolve 0.8 g of Cs 2 CO 3 powder in 3 mL of oleic acid and 30 mL of octadecene, place it in a 100 mL three-necked flask, heat it to 120 °C under vacuum and keep it for 60 min until the powder is completely dissolved to obtain a cesium oleate solution for standby.

[0067] (2) Preparation method of oleylamine bromide solution: Mix 0.5 mL of hydrobromic acid solution with a mass fraction of 48% and 17.5 mL of oleylamine, place it in a 100 mL three-necked flask, heat it to 120 °C under vacuum and keep it for 30 min to obtain a light yellow transparent solution to obtain an oleylamine bromide solution for standby.

[0068] (3) Preparation method of dioctadecyldimethylammonium chloride solution: Mix 4 mmol of dioctadecyldimethylammonium chloride with 2.5 mL of octadecene, place it on a hot stage at 120 °C and heat it to obtain a light yellow transparent solution for standby to obtain a dioctadecyldimethylammonium chloride solution for standby.

[0069] The near-infrared luminescence spectrum of the perovskite quantum dots prepared in this example is as follows Figure 1 shown.

[0070] Example 2

[0071] This example provides a method for preparing perovskite quantum dots, and the preparation method includes:

[0072] Dissolve 0.25 mmol of Pb(OAc) 2 ·3H 2 O, 0.75 mmol of YbCl 3 ·6H 2 O, 250 μL of oleylamine bromide solution in 10 mL of octadecene, add 2.5 mL of oleic acid, 1.2 mL of oleylamine, 0.8 mL of octylamine and 1.5 mL of methanol to obtain a mixture. Place the mixture in a 100 mL three-necked flask and put it on a magnetic stirring heating jacket. After heating to 120 °C under vacuum and maintaining for 30 min, heat the mixture to 250 °C in a nitrogen environment to obtain a quantum dot precursor solution;

[0073] Quickly add 2.5 mL of cesium oleate solution to the quantum dot precursor solution, and immediately add 1 mmol of octadecyl dimethyl ammonium chloride solution after an interval of 5 s. React at 230 °C for 90 s, and perform ice-water cooling to obtain a product. Centrifuge the obtained product at 5000 rpm for 5 min, discard the supernatant, redisperse the precipitate in 15 mL of toluene solution and shake well, centrifuge at 8000 rpm for 5 min to obtain the supernatant, discard the supernatant, redisperse the precipitate in 10 mL of n-hexane solution and shake well, and let it stand to obtain the perovskite quantum dot solution.

[0074] The preparation methods of the cesium oleate solution, oleylamine bromide solution and dioctadecyl dimethyl ammonium chloride solution in this example are the same as those in Example 1.

[0075] Example 3

[0076] This example provides a method for preparing perovskite quantum dots, and the preparation method includes:

[0077] Dissolve 0.25 mmol of Pb(OAc) 2 ·3H 2 O, 0.75 mmol of YbCl 3 ·6H 2 O, 250 μL of oleylamine bromide solution in 10 mL of octadecene, add 2.5 mL of oleic acid, 1.2 mL of oleylamine, 0.8 mL of octylamine and 1.5 mL of methanol to obtain a mixture. Place the mixture in a 100 mL three-necked flask and put it on a magnetic stirring heating jacket. After heating to 120 °C under vacuum and maintaining for 30 min, heat the mixture to 250 °C in a nitrogen environment to obtain a quantum dot precursor solution;

[0078] After quickly adding 2.5 mL of cesium oleate solution to the quantum dot precursor solution, 1.5 mmol of dioctadecyldimethylammonium chloride solution was immediately added after a 2-s interval, and the reaction was carried out at 250 °C for 1 min, followed by ice-water cooling to obtain a product. The obtained product was centrifuged at 5000 rpm for 5 min, the supernatant was discarded, the precipitate was redispersed in 15 mL of toluene solution and shaken well, and then centrifuged at 8000 rpm for 5 min to obtain the supernatant, the supernatant was discarded, the precipitate was redispersed in 10 mL of n-hexane solution and shaken well, and then allowed to stand to obtain the perovskite quantum dot solution.

[0079] The preparation methods of the cesium oleate solution, oleic acid bromide solution and dioctadecyldimethylammonium chloride solution in this example are the same as those in Example 1.

[0080] Example 4

[0081] In this example, except that the addition amount of the cesium oleate solution was replaced with 1.5 mL, other conditions were the same as those in Example 1.

[0082] Example 5

[0083] In this example, except that the addition amount of cesium oleate was replaced with 4 mL, other conditions were the same as those in Example 1.

[0084] Example 6

[0085] In this example, except that the temperature of the thermal reaction was replaced with 200 °C, other conditions were the same as those in Example 1.

[0086] Example 7

[0087] In this example, except that the addition interval between the cesium oleate solution and the dioctadecyldimethylammonium chloride solution was replaced with 5 min, other conditions were the same as those in Example 1.

[0088] Comparative Example 1

[0089] In this comparative example, only cesium oleate solution was added to the quantum dot precursor solution, and dioctadecyldimethylammonium chloride solution was not added. Other conditions were the same as those in Example 1. The near-infrared emission spectrum of the quantum dots prepared in this comparative example is as Figure 2 shown, and the near-infrared emission efficiency of the obtained quantum dot solution is about 50%.

[0090] Comparative Example 2

[0091] In this comparative example, only dioctadecyldimethylammonium chloride solution was added to the quantum dot precursor solution, and cesium oleate solution was not added. Other conditions were the same as those in Example 1. The near-infrared emission spectrum of the quantum dots prepared in this comparative example is as Figure 3 shown. Since there is no injection of cesium source, quantum dots cannot be generated.

[0092] Comparative Example 3

[0093] In this comparative example, a dioctadecyl dimethyl ammonium chloride solution was added first, and a cesium oleate solution was immediately added after a 4 s interval. Other conditions were the same as those in Example 1. The near-infrared emission spectrum of the quantum dots prepared in this comparative example is as shown in Figure 4 . Adding the quaternary ammonium salt chlorine source first and then the cesium source will induce visible light emission of the quantum dots and reduce the near-infrared emission efficiency.

[0094] The quantum yields of the quantum dot solutions prepared in Example 1 and Comparative Examples 1-3 of the present invention are as shown in Figure 5 . Figure 5 The ordinate PLQY in

[0095] refers to: photoluminescence quantum yield. The near-infrared emission efficiency of the sample in Example 1 was significantly higher than that in Comparative Example 1, indicating that the additionally injected halogen source regulated the growth of the quantum dots and passivated some defects at the same time. Meanwhile, there was obvious visible light emission in Comparative Example 3, indicating that injecting the halogen source first would induce visible light emission of the sample and affect the near-infrared emission of the sample. Figure 6 Figure 6 The storage stabilities of the quantum dot solutions prepared in Example 1 and Comparative Example 1 are as shown in Figure 6 . The ordinate represents the result after normalizing the photoluminescence quantum yield of the quantum dots. It can be seen from

[0096] that additionally injecting the quaternary ammonium salt chlorine source can significantly improve the storage stability of the quantum dots.

[0097] The test method for the quantum yield of the quantum dot solution is: using a near-infrared spectrometer to test the quantum yield, and the quantum yield is directly calculated by the instrument.

[0098] The test method for the storage stability of the quantum dot solution is: storing the quantum dot solution at room temperature in the dark, and taking it out at regular intervals for quantum yield testing. The criterion for judging stability is: when the decay value of the near-infrared quantum yield exceeds 10% of the initial value, it is considered unstable, otherwise it is considered stable.

[0099] Table 1

[0100]

[0101]

[0102] It can be seen from the data in Table 1 that: too much or too little addition of cesium oleate in Examples 4-5 will reduce the storage stability of the sample; in Example 6, the reaction temperature is too low to achieve effective doping of ytterbium; in Example 7, the long time interval between the addition of cesium oleate solution and dioctadecyldimethylammonium chloride solution results in a decrease in the near-infrared luminescence efficiency of the quantum dots; in Comparative Example 1, only adding cesium oleate solution leads to a decrease in the near-infrared luminescence efficiency of the quantum dots and a reduction in stability; in Comparative Example 2, only adding dioctadecyldimethylammonium chloride solution fails to generate quantum dots; in Comparative Example 3, changing the addition order of cesium oleate and dioctadecyldimethylammonium chloride solution induces visible light emission of the quantum dots and reduces the near-infrared luminescence efficiency.

[0103] The applicant declares that the above description is only a specific implementation manner of the present invention, but the protection scope of the present invention is not limited thereto. Those skilled in the art should understand that any changes or substitutions that can be easily conceived by any person skilled in the art within the technical scope disclosed by the present invention fall within the protection scope and the disclosure scope of the present invention.

Claims

1. A method for preparing ytterbium-doped perovskite quantum dots, characterized in that, the preparation method includes: adding a cesium source and a quaternary ammonium salt chloride source to a quantum dot precursor solution in sequence to obtain a mixed solution, and heating the mixed solution to react to obtain the ytterbium-doped perovskite quantum dots; the quantum dot precursor solution includes a lead source, a ytterbium source, a halogen source, a ligand, and a solvent.

2. The preparation method according to claim 1, characterized in that, the concentration of the lead source in the mixed solution is 0.01 - 0.05 mol / L; the concentration of the ytterbium source in the mixed solution is 0.5 - 4 times the concentration of the lead source; preferably, the concentration of the halogen source in the mixed solution is 3.5 - 14 times the concentration of the lead source; preferably, the concentration of the ligand in the mixed solution is 10 - 50 times the concentration of the lead source; preferably, the concentration of the cesium source in the mixed solution is 1.5 - 2 times the concentration of the lead source; preferably, the concentration of the quaternary ammonium salt chloride source in the mixed solution is 2 - 6 times the concentration of the lead source.

3. The preparation method according to claim 1 or 2, characterized in that, the lead source includes any one or a combination of at least two of lead chloride, lead bromide, lead acetate, lead oxide, lead stearate, or lead oleate, the ytterbium source includes any one or a combination of at least two of ytterbium chloride, ytterbium bromide, ytterbium acetate, or ytterbium oleate, the halogen source includes a bromine source and / or a chlorine source, the ligand includes octylamine, oleylamine, and oleic acid, and the solvent includes octadecene.

4. The preparation method according to claim 3, characterized in that, the mass ratio of the bromine source to the chlorine source is (0 - 0.2):1; preferably, the chlorine source includes any one or a combination of at least two of oleylamine chloride, octylamine chloride, or trimethylchlorosilane, and the bromine source includes any one or a combination of at least two of oleylamine bromide, octylamine bromide, or trimethylbromosilane; preferably, the mass ratio of octylamine to oleylamine is (2 - 3):(3 - 2); preferably, methanol is further included in the precursor solution.

5. The preparation method according to any one of claims 1 - 4, characterized in that, the cesium source includes cesium oleate; preferably, the quaternary ammonium salt chloride source includes any one or a combination of at least two of dioctadecyldimethylammonium chloride, didodecyldimethylammonium chloride, ditetradecyldimethylammonium chloride, or dioctyldimethylammonium chloride.

6. The preparation method according to any one of claims 1 - 5, characterized in that, the preparation method of the quantum dot precursor solution includes: mixing a lead source, a ytterbium source, a halogen source, a ligand, and a solvent, and heating to obtain the quantum dot precursor solution at a temperature of 230 - 270 °C; preferably, the mixing is carried out in a vacuum environment; preferably, the temperature of the mixing is 100 - 140 °C; preferably, the mixing time is 25 - 35 min.

7. The preparation method according to any one of claims 1 - 6, characterized in that, the time interval for adding the cesium source and the quaternary ammonium salt chloride source to the quantum dot precursor solution is ≤ 5 s; preferably, the reaction temperature is 230 - 270 °C; preferably, the reaction time is 30 - 90 s.

8. The preparation method according to any one of claims 1-7, characterized in that, the preparation method comprises: adding a cesium source and a quaternary ammonium salt chloride source into a quantum dot precursor solution at a temperature of 230-270 °C in sequence to obtain a mixed solution, and reacting the mixed solution at 230-270 °C for 30-90 s to obtain the ytterbium-doped perovskite quantum dots; the quantum dot precursor solution comprises a lead source, an ytterbium source, a halogen source, a ligand and a solvent.

9. An ytterbium-doped perovskite quantum dot, characterized in that, the ytterbium-doped perovskite quantum dot is prepared by the preparation method of the ytterbium-doped perovskite quantum dot according to any one of claims 1-8.

10. An application of the ytterbium-doped perovskite quantum dot according to claim 9, characterized in that, the ytterbium-doped perovskite quantum dot is applied to the photovoltaic field or the display field.

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