Method for improving fluorescence quantum yield of manganese-doped CsPbCl3 quantum dots with assistance of strontium chloride

Abstract

The invention discloses a strontium chloride-assisted method for improving the fluorescence quantum yield of manganese-doped CsPbCl3 quantum dots, which comprises the following steps: adding cesium carbonate into octadecene, heating and stirring until uniform mixing, and injecting oleic acid to obtain a cesium oleate solution; the preparation method comprises the following steps: adding different amounts of strontium chloride auxiliary dopant, manganese chloride dopant, lead chloride, oleylamine and oleic acid into octadecene, heating and stirring to uniformly mix to obtain a precursor mixed solution; injecting the cesium oleate solution into the precursor mixed solution, reacting for a certain period of time, and cooling in ice water to room temperature to form a CsPbCl3 quantum dot stock solution; a certain proportion of a flocculating agent is added into the stock solution, and a CsPbCl3 quantum dot solution is obtained through centrifugal treatment. According to the preparation method disclosed by the invention, the quantum yield of Mn-emitted fluorescence of the Mn-doped CsPbCl3 quantum dot is improved by regulating and controlling the addition amount of the doping agent, and finally, the quantum yield of Mn-emitted fluorescence of the Sr and Mn co-doped CsPbCl3 quantum dot reaches up to 100%.

Description

Technical Field

[0001] The invention belongs to the technical field of nanomaterials, and in particular relates to a method for improving the fluorescence quantum yield of Mn emitted by Mn-doped CsPbCl3 quantum dots assisted by strontium chloride. Background Art

[0002] All-inorganic lead halide perovskite (CsPbX3, X = Cl, Br, I) has attracted widespread attention due to its tunable fluorescence emission wavelength, high electron mobility and high quantum yield, and has shown great application prospects in the fields of solar cells, light-emitting diodes and lasers. However, in actual commercial applications, reducing the lead content is an important issue. B-site doping is one of the important means to reduce lead toxicity, and it can improve the luminescence performance while reducing the lead content.

[0003] In B-site doping, Mn doping can introduce a new emission center, which can give perovskite unique luminescence properties. However, it has problems such as low fluorescence quantum yield and difficulty in balancing Mn concentration and high fluorescence quantum yield. At present, relevant studies have shown that adding Mn 2+ After co-doping with other metal ions, it has shown good prospects in enhancing Mn emission and improving fluorescence quantum yield. Zhao et al. (Mater. Res. Bull. 2024, 170, 112599) found that Sr and Mn co-doped CsPbCl3 can effectively enhance Mn emission. The Mn emission fluorescence quantum yield is 72.83%, which needs to be improved, and further increase in Sr doping rate will lead to a decrease in fluorescence quantum yield.

[0004] Therefore, a strategy is needed to further improve the quantum yield of Mn emission fluorescence while increasing the Sr doping rate. Summary of the invention

[0005] Purpose of the invention: In view of the problems existing in the prior art, the present invention provides a method for improving the quantum yield of Mn fluorescence emission from Mn-doped CsPbCl3 quantum dots with the assistance of strontium chloride.

[0006] The method for improving the fluorescence quantum yield of manganese-doped CsPbCl3 quantum dots with the aid of strontium chloride comprises the following steps:

[0007] Step 1: Weigh cesium carbonate and add it into a three-necked flask containing octadecene, heat it to the dissolution temperature under vacuum and keep it warm, then introduce inert gas, inject oleic acid, evacuate the flask, fill it with inert gas and heat it to a certain temperature until the solution becomes clear and transparent, to obtain a cesium oleate solution;

[0008] Step 2: weigh strontium chloride, manganese chloride, and lead chloride, add them into a three-necked flask containing octadecene, add oleylamine and oleic acid, evacuate, heat and dissolve, and keep warm for a certain period of time, then introduce inert gas and heat to the reaction temperature, keep warm for 10 minutes, and obtain a precursor mixed solution;

[0009] Step 3: injecting the cesium oleate solution obtained in step 1 into the precursor mixed solution obtained in step 2;

[0010] Step 4: After the reaction, place it in ice water and cool it to room temperature to form Sr and Mn co-doped CsPbCl3 quantum dot stock solution;

[0011] Step 5: Add a flocculant to the quantum dot stock solution obtained in step 4, perform centrifugal washing, and add the resulting precipitate to a dispersant to obtain a Sr and Mn co-doped CsPbCl3 quantum dot solution.

[0012] Furthermore, in step 1, the molar volume ratio of cesium oleate to octadecene is 1.25-2.5 mmol:30 mL; and the volume ratio of oleic acid to octadecene is 1:(8-12).

[0013] Furthermore, in step 1, the dissolution temperature is 80-120° C., the insulation time is 60-80 minutes, and the heating temperature after injecting oleic acid is 130-150° C.

[0014] Furthermore, in step 2, the molar ratio of strontium chloride, manganese chloride and lead chloride is (0-0.5):(0.42-4):1; the molar volume ratio of the total amount of manganese chloride and lead chloride to octadecene is 0.6-1 mmol:10 mL, and the volume ratio of octadecene, oleic acid and oleylamine is (6-10):1:1.

[0015] Furthermore, the heating and dissolving temperature in step 2 is 80-120°C, the time is 60-80 minutes, and the reaction temperature is 170-200°C.

[0016] Furthermore, the inert gas in step 1 and step 2 is nitrogen, helium, neon or argon.

[0017] Furthermore, the volume of the cesium oleate solution injected in step 3 is 1 to 1.5 mL.

[0018] Furthermore, the reaction time in step 4 is 5 to 10 seconds.

[0019] Furthermore, the flocculant in step five is a mixed solution of a dispersant and a precipitant, the dispersant is n-hexane, n-octane or toluene, the precipitant is methyl acetate or ethyl acetate, and the volume ratio of the dispersant to the precipitant is 1:(1-3).

[0020] Furthermore, in step 5, the centrifugal speed is 6000-10000 rpm, and the centrifugal time is 3-5 minutes.

[0021] Principle of the invention: The present invention uses strontium chloride to assist Mn in doping CsPbCl3 quantum dots. Since the radius of strontium ions is close to that of lead ions, the co-dopant can effectively alleviate deep band gap defects, induce lattice contraction, promote the substitution of lead, and further improve the energy transfer efficiency, so that the Mn emission fluorescence quantum yield of Mn-doped CsPbCl3 quantum dots is further improved.

[0022] Beneficial effect: In the method of the present invention for improving the quantum yield of Mn emission of Mn doped CsPbCl3 quantum dots with the aid of strontium chloride, the co-doping of Sr and Mn leads to further lattice contraction of CsPbCl3 quantum dots, promotes the substitution of lead with a larger radius by doping, improves the doping rate of Sr and Mn, and the introduction of strontium chloride further improves the optical performance, and the quantum yield of Mn emission of fluorescence is as high as 100%. The conditions of the co-doping of Sr and Mn into CsPbCl3 of the present invention are controllable, with high repeatability, and the synthesized perovskite quantum dots have uniform particle size and good dispersibility. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] Figure 1 This is a comparison chart of emission spectra of Comparative Example 1, Example 12, and Example 1 of the present invention;

[0024] Figure 2 This is a comparison chart of the fluorescence quantum yield of Mn emitted by Example 12 and Example 1 of the present invention;

[0025] Figure 3 The exciton emission fluorescence lifetime diagrams of Comparative Example 1, Example 12, and Example 1 of the present invention;

[0026] Figure 4 X-ray diffraction patterns of Comparative Example 1, Example 12, and Example 1 of the present invention;

[0027] Figure 5 This is a comparison chart of emission spectra of Example 12, Example 2, Example 1, and Example 3 of the present invention;

[0028] Figure 6 This is a comparison chart of the fluorescence quantum yield of Mn emitted by Example 12, Example 2, Example 1, and Example 3 of the present invention;

[0029] Figure 7 is a transmission electron microscope image of Example 1 of the present invention;

[0030] Figure 8 This is a comparison diagram of emission spectra of Example 9 and Example 4 of the present invention;

[0031] Fig. 9This is a comparison diagram of emission spectra of Example 10 and Example 5 of the present invention;

[0032] Fig.10 This is a comparison diagram of emission spectra of Example 11 and Example 6 of the present invention;

[0033] Fig.11 This is a comparison diagram of emission spectra of Example 13 and Example 7 of the present invention;

[0034] Fig.12 This is a comparison diagram of emission spectra of Example 14 and Example 8 of the present invention;

[0035] Fig.13 This is a graph showing the replacement content ratios of Sr, Pb, and Mn in Examples 9 to 14, 1, and 4 to 8 of the present invention. DETAILED DESCRIPTION

[0036] The preferred embodiments of the present invention will be described below in conjunction with the accompanying drawings to more clearly and completely illustrate the technical solutions of the present invention.

[0037] Example 1

[0038] The method of the present invention for improving the fluorescence quantum yield of manganese-doped CsPbCl3 quantum dots with the aid of strontium chloride comprises the following steps:

[0039] Step 1: Weigh 0.814 g of cesium carbonate and place it in a 100 mL three-necked flask containing 30 mL of octadecene, dissolve it in a vacuum state, heat it to 120°C and keep it warm for 60 minutes, and remove the water and air in the three-necked flask. Then, pass nitrogen, inject 3 mL of oleic acid, evacuate again, pass nitrogen, and heat it to 150°C until the solution is clear and transparent to obtain a cesium oleate solution.

[0040] Step 2: Weigh 0.0114 g of strontium chloride, 0.0453 g of manganese chloride and 0.0667 g of lead chloride and place them in a 100 mL three-necked flask containing 10 mL of octadecene, add 1.5 mL of oleylamine and 1.5 mL of oleic acid, evacuate the three-necked flask to remove water and air, heat to 120°C to dissolve and keep warm for 60 to 80 minutes, then introduce nitrogen and raise the temperature to 190°C, keep warm for 10 minutes to obtain a precursor mixed solution.

[0041] Step 3: Take 1.2 mL of the cesium oleate precursor synthesized in step 1 and inject it into the mixed solution obtained in step 2.

[0042] Step 4: After 5 seconds of reaction time, place it in an ice water bath and cool it to room temperature to form Sr and Mn co-doped CsPbCl3 quantum dot stock solution.

[0043] Step 5: Add 10 mL of n-hexane and 20 mL of ethyl acetate to the quantum dot stock solution obtained in step 4, centrifuge and wash at 8000 rpm for 3 minutes, add the resulting precipitate to 10 mL of n-hexane dispersant to obtain a Sr and Mn co-doped quantum dot solution.

[0044] Example 2

[0045] The reaction conditions and steps are the same as those in Example 1, except that the mass of strontium chloride weighed in step 2 is 0.0038 g.

[0046] Example 3

[0047] The reaction conditions and steps are the same as those in Example 1, except that the mass of strontium chloride weighed in step 2 is 0.0190 g.

[0048] Example 4

[0049] The reaction conditions and steps are the same as those in Example 1, except that in step 2, 0.0200 g of strontium chloride, 0.0227 g of manganese chloride and 0.1168 g of lead chloride are weighed, the molar ratio of strontium chloride to lead chloride is 0.3, and the molar ratio of manganese chloride to lead chloride is 3:7.

[0050] Example 5

[0051] The reaction conditions and steps are the same as those in Example 1, except that in step 2, 0.0171 g of strontium chloride, 0.0302 g of manganese chloride and 0.1001 g of lead chloride are weighed, the molar ratio of strontium chloride to lead chloride is 0.3, and the molar ratio of manganese chloride to lead chloride is 4:6.

[0052] Example 6

[0053] The reaction conditions and steps are the same as those in Example 1, except that in step 2, 0.0143 g of strontium chloride, 0.0378 g of manganese chloride and 0.0834 g of lead chloride are weighed, the molar ratio of strontium chloride to lead chloride is 0.3, and the molar ratio of manganese chloride to lead chloride is 5:5.

[0054] Example 7

[0055] The reaction conditions and steps are the same as those in Example 1, except that in step 2, 0.0086 g of strontium chloride, 0.0529 g of manganese chloride and 0.0501 g of lead chloride are weighed, the molar ratio of strontium chloride to lead chloride is 0.3, and the molar ratio of manganese chloride to lead chloride is 7:3.

[0056] Example 8

[0057] The reaction conditions and steps are the same as those in Example 1, except that in step 2, 0.0057 g of strontium chloride, 0.0604 g of manganese chloride and 0.0334 g of lead chloride are weighed, the molar ratio of strontium chloride to lead chloride is 0.3, and the molar ratio of manganese chloride to lead chloride is 8:2.

[0058] Example 9

[0059] The reaction conditions and steps are the same as those of Example 4, except that the strontium chloride in step 2 is removed.

[0060] Example 10

[0061] The reaction conditions and steps are the same as those of Example 5, except that the strontium chloride in step 2 is removed.

[0062] Embodiment 11

[0063] The reaction conditions and steps are the same as those of Example 6, except that the strontium chloride in step 2 is removed.

[0064] Example 12

[0065] The reaction conditions and steps are the same as those in Example 1, except that the strontium chloride in step 2 is removed.

[0066] Embodiment 13

[0067] The reaction conditions and steps are the same as those of Example 7, except that the strontium chloride in step 2 is removed.

[0068] Embodiment 14

[0069] The reaction conditions and steps are the same as those of Example 8, except that the strontium chloride in step 2 is removed.

[0070] Comparative Example 1

[0071] The reaction conditions and steps were the same as those of Example 1, except that only 0.1668 g of lead chloride was weighed in step 2.

[0072] Figure 1 It can be seen that Mn-doped CsPbCl3 produces a Mn emission peak at 600nm, and Sr and Mn co-doping further increases the Mn emission peak intensity.

[0073] Figure 2 It can be seen that the PLQY of Mn emission of Mn-doped CsPbCl3 quantum dots is 85.5%, and the PLQY can reach 100% after co-doping with strontium chloride, indicating that Sr and Mn co-doping further improves the fluorescence quantum yield of Mn emission.

[0074] Figure 3It can be seen that the exciton emission fluorescence lifetime of Mn-doped CsPbCl3 is 2.02ns, which is lower than 6.93ns of pure CsPbCl3. After co-doping with Sr and Mn, the exciton emission lifetime is further reduced to 0.84ns, indicating that the energy transfer efficiency is further improved.

[0075] Figure 4 It can be seen that both Mn-doped CsPbCl3 and Sr and Mn co-doped CsPbCl3 improve crystallinity. When Mn ions are incorporated, the XRD diffraction peaks shift slightly to higher angles, confirming their doping in the perovskite lattice. Sr co-doping results in the same shift of the diffraction peaks to higher angles, due to the further lattice contraction caused by the co-existence of effective Mn ions and Sr ions.

[0076] Figure 5 It can be seen that as the molar ratio of strontium chloride to lead chloride increases from 0, 0.1, 0.3 to 0.5, the intensity of the Mn emission peak first increases and then weakens. The Mn emission peak is the strongest at 0.3, and the Mn emission peak is always enhanced when strontium chloride co-doping is in the molar ratio range of 0.1 to 0.5.

[0077] Figure 6 It can be seen that the co-doping of Sr and Mn increases the quantum yield of Mn emission fluorescence of Mn-doped CsPbCl3. Compared with Mn-doped CsPbCl3 with a molar ratio of manganese chloride to lead chloride of 6:4, the quantum yield of Mn emission fluorescence of Sr and Mn co-doped CsPbCl3 with a molar ratio of strontium chloride to lead chloride of 0.1, 0.3, and 0.5 is 96.6%, 100%, and 100%.

[0078] Figure 7 It can be seen that the microstructure of Sr and Mn co-doped CsPbCl3 has high consistency and uniformity, uniform size distribution, clear boundaries and other excellent morphological characteristics.

[0079] Figure 8 It can be seen that the addition of strontium chloride with a Sr / Pb molar ratio of 0.3 at a Mn / Pb molar ratio of 3:7 enhances the Mn emission and improves the Mn emission and its fluorescence quantum yield.

[0080] Fig. 9 It can be seen that the addition of strontium chloride with a Sr / Pb molar ratio of 0.3 at a Mn / Pb molar ratio of 4:6 enhances the Mn emission and improves the Mn emission and its fluorescence quantum yield.

[0081] Fig.10 It can be seen that the addition of strontium chloride with a Sr / Pb molar ratio of 0.3 at a Mn / Pb molar ratio of 5:5 enhances the Mn emission and improves the Mn emission and its fluorescence quantum yield.

[0082] Fig.11 It can be seen that the addition of strontium chloride with a Sr / Pb molar ratio of 0.3 at a Mn / Pb molar ratio of 7:3 enhances the Mn emission and improves the Mn emission and its fluorescence quantum yield.

[0083] Fig.12 It can be seen that the addition of strontium chloride with a Sr / Pb molar ratio of 0.3 at a Mn / Pb molar ratio of 8:2 enhances the Mn emission and improves the Mn emission and its fluorescence quantum yield.

[0084] Fig.13 It can be seen that the substitution rate of Pb after Sr and Mn co-doped CsPbCl3 is increased compared with that of single Mn doped CsPbCl3, indicating that Sr doping is beneficial to further reduce the lead content of Mn doped CsPbCl3, and the actual Sr content of Example 1 is characterized by XPS as 2.11%.

[0085] The above examples and comparative examples illustrate:

[0086] The Sr and Mn co-doped CsPbCl3 quantum dots prepared by the method of the present invention have uniform microscopic morphology, and the fluorescence quantum yield of Mn emission is as high as 100%. When the molar ratio of manganese chloride to lead chloride is fixed, the addition of strontium chloride with a molar ratio of strontium chloride to lead chloride of 0.1 to 0.5 can improve the fluorescence quantum yield of Mn emission. The addition of strontium chloride at different Mn / Pb molar ratios can improve the emission intensity of Mn and its fluorescence quantum yield.

Claims

1. A method for improving the fluorescence quantum yield of manganese-doped CsPbCl3 quantum dots with the aid of strontium chloride, characterized in that: The following steps are involved: Step 1: Weigh cesium carbonate and add it into a three-necked flask containing octadecene, heat it to the dissolution temperature under vacuum and keep it warm, then introduce inert gas, inject oleic acid, evacuate the flask, fill it with inert gas and heat it to a certain temperature until the solution becomes clear and transparent, to obtain a cesium oleate solution; Step 2: weigh strontium chloride, manganese chloride, and lead chloride, add them into a three-necked flask containing octadecene, add oleylamine and oleic acid, evacuate, heat and dissolve, and keep warm for a certain period of time, then introduce inert gas and heat to the reaction temperature, keep warm for 10 minutes, and obtain a precursor mixed solution; Step 3: injecting the cesium oleate solution obtained in step 1 into the precursor mixed solution obtained in step 2; Step 4: After the reaction, place it in ice water and cool it to room temperature to form Sr and Mn co-doped CsPbCl3 quantum dot stock solution; Step 5: Add a flocculant to the quantum dot stock solution obtained in step 4, perform centrifugal washing, and add the resulting precipitate to a dispersant to obtain a Sr and Mn co-doped CsPbCl3 quantum dot solution.

2. The method for improving the fluorescence quantum yield of manganese-doped CsPbCl3 quantum dots assisted by strontium chloride according to claim 1, characterized in that: In step 1, the molar volume ratio of cesium oleate to octadecene is 1.25-2.5 mmol:30 mL; the volume ratio of oleic acid to octadecene is 1:(8-12).

3. The method for improving the fluorescence quantum yield of manganese-doped CsPbCl3 quantum dots assisted by strontium chloride according to claim 1, characterized in that: In step 1, the dissolution temperature is 80-120° C., the insulation time is 60-80 minutes, and the heating temperature after the injection of oleic acid is 130-150° C.

4. The method for improving the fluorescence quantum yield of manganese-doped CsPbCl3 quantum dots assisted by strontium chloride according to claim 1, characterized in that: The molar ratio of strontium chloride, manganese chloride and lead chloride in step 2 is (0-0.5):(0.42-4):1; the molar volume ratio of the total amount of manganese chloride and lead chloride to octadecene is 0.6-1mmol:10mL, and the volume ratio of octadecene, oleic acid and oleylamine is (6-10):1:

1.

5. The method for improving the fluorescence quantum yield of manganese-doped CsPbCl3 quantum dots assisted by strontium chloride according to claim 1, characterized in that: The heating and dissolving temperature in step 2 is 80-120°C, the time is 60-80 minutes, and the reaction temperature is 170-200°C.

6. The method for improving the fluorescence quantum yield of manganese-doped CsPbCl3 quantum dots assisted by strontium chloride according to claim 1, characterized in that: The inert gas in step 1 and step 2 is nitrogen, helium, neon or argon.

7. The method for improving the fluorescence quantum yield of manganese-doped CsPbCl3 quantum dots assisted by strontium chloride according to claim 1, characterized in that: The volume of the cesium oleate solution injected in step 3 is 1-1.5 mL.

8. The method for improving the fluorescence quantum yield of manganese-doped CsPbCl3 quantum dots assisted by strontium chloride according to claim 1, characterized in that: The reaction time in step 4 is 5 to 10 seconds.

9. The method for improving the fluorescence quantum yield of manganese-doped CsPbCl3 quantum dots assisted by strontium chloride according to claim 1, characterized in that: The flocculant in step 5 is a mixed solution of a dispersant and a precipitant, the dispersant is n-hexane, n-octane or toluene, the precipitant is methyl acetate or ethyl acetate, and the volume ratio of the dispersant to the precipitant is 1:(1-3).

10. The method for improving the fluorescence quantum yield of manganese-doped CsPbCl3 quantum dots assisted by strontium chloride according to claim 1, characterized in that: The centrifugal speed in step 5 is 6000-10000 rpm, and the centrifugal time is 3-5 minutes.

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