Method for accurately regulating and controlling light-emitting wavelength of mixed halide pure red light perovskite quantum dots

Abstract

The invention provides a method for accurately regulating and controlling the light-emitting wavelength of a mixed halide pure red light perovskite quantum dot, and belongs to the technical field of photoelectric display, and the method specifically comprises the following steps: preparing a first precursor solution based on cesium carbonate, preparing a second precursor solution based on PbI2 and ZnI2, and respectively heating; injecting oleic acid and oleylamine into the second precursor solution, heating, injecting the first precursor solution into the second precursor solution, cooling, heating again, injecting hydrobromic acid to obtain a mixed halogen perovskite quantum dot coarse solution, and centrifuging for multiple times to obtain a CsPbI3-mBrm quantum dot solution. The bromine source is introduced after the quantum dots are formed, accurate regulation and control of the light-emitting wavelength of the pure red light perovskite quantum dots are achieved, the light-emitting requirement of high-color-purity red light is met, and the quantum dots are one of ideal choices of high-efficiency photoelectric devices and display technologies in the future.

Description

Technical Field

[0001] The present invention belongs to the technical field of optoelectronic display, and particularly relates to a method for precisely regulating the emission wavelength of mixed halide pure red light perovskite quantum dots. Background Art

[0002] As a new type of nanomaterial, quantum dot luminescent materials have received extensive attention in the field of optoelectronic devices in recent years. Compared with traditional semiconductor quantum dots, halide perovskite quantum dots have a narrower spectral linewidth and higher color purity, and can provide a higher-quality display effect. In addition, the synthesis process of halide perovskite quantum dots is simple and the cost is low, which has strong competitiveness in large-scale production. Therefore, halide perovskite quantum dot materials are an ideal choice for future high-performance optoelectronic devices and display technologies.

[0003] Taking high-color-purity red light as an example, the emission spectral wavelength of single-metal iodide perovskite represented by CsPbI3 is greater than 680 nm, while the emission wavelength of single-metal bromide perovskite represented by CsPbBr3 is around 520 nm. Single-metal halide perovskite quantum dots prepared by conventional methods are difficult to meet the requirements of high-color-purity red light (wavelength of 620 - 650 nm). To address the problems of perovskite quantum dots prepared by conventional methods, researchers proposed a synthesis process based on strong confinement effects in the literature (Dong, Y., et al., Precise Control of Quantum Confinement in Cesium Lead Halide Perovskite Quantum Dots via Thermodynamic Equilibrium. Nano Letters, 18(6)). By regulating the halogen ion concentration and reaction temperature, the fluorescence spectrum (PL spectrum) of quantum dots can be changed. However, the wavelength of the synthesized CsPbI3 quantum dots is still greater than 650 nm, which fails to meet the display requirements of high-color-purity red light.

[0004] Currently, the preparation of pure red light perovskite quantum dots is mainly based on the mixed halide component engineering. Existing preparation technologies of mixed halides generally achieve the regulation of red light emission wavelength by directly changing the ratio of different halogens in the raw materials. This method is complex in operation and has high precision requirements for weighing materials. When there is a weighing error, the emission wavelength shifts greatly, making it difficult to achieve precise regulation of the wavelength.

[0005] Therefore, it is of great promotional significance to provide a method for precisely regulating the emission wavelength of mixed halide pure red light perovskite quantum dots. Summary of the Invention

[0006] In view of the problem of high requirement for the weighing accuracy of raw materials in the existing mixed halide preparation technology, the present invention provides a method for precisely regulating the emission wavelength of pure red light perovskite quantum dots of mixed halides. After the quantum dots are formed, a bromine source (hydrobromic acid) is introduced to achieve precise regulation of the emission wavelength of pure red light perovskite quantum dots, meeting the requirement for high color purity red light emission.

[0007] To achieve the above object, the technical method adopted by the present invention is as follows:

[0008] A method for precisely regulating the emission wavelength of pure red light perovskite quantum dots of mixed halides, wherein the mixed halide perovskite quantum dots are CsPbI 3-m Br m quantum dots, where 0 < m < 3;

[0009] The method specifically includes the following steps:

[0010] Step 1: Add cesium carbonate to the mixed solution of octadecene and oleic acid, and stir to obtain the first precursor solution;

[0011] Step 2: Add halogen raw materials PbI2 and ZnI2 to octadecene, and stir to obtain the second precursor solution;

[0012] Step 3: Under vacuum conditions, perform stepwise heating on the first precursor solution and the second precursor solution respectively until the first precursor solution is heated to the first target temperature and kept warm, and the second precursor solution is heated to the second target temperature and kept warm, then switch to a nitrogen or inert gas environment;

[0013] Step 4: Inject oleic acid and oleylamine into the second precursor solution successively, and stir to obtain a reaction solution;

[0014] Step 5: First heat the reaction solution to the third target temperature, then quickly inject the first precursor solution into the reaction solution, and stir and cool in an ice bath to below the fourth target temperature to obtain a mixed solution;

[0015] Step 6: Reheat the mixed solution to the fifth target temperature, and inject the halogen raw material hydrobromic acid to obtain a crude solution of mixed halogen perovskite quantum dots;

[0016] Step 7: Use an anti-solvent to perform multiple centrifugations on the crude solution of mixed halogen perovskite quantum dots to obtain a dispersion of mixed halogen perovskite quantum dots dispersed in a non-polar reagent;

[0017] Step 8: Let the dispersion of mixed halogen perovskite quantum dots stand for a period of time, and then use an anti-solvent to perform multiple centrifugations again to obtain a fine dispersion of mixed halogen perovskite quantum dots dispersed in a non-polar reagent.

[0018] Further, the first target temperature is 95 - 105°C, the second target temperature is 115 - 125°C, the third target temperature is 160 - 175°C, the fourth target temperature is 40°C, and the third target temperature is 50 - 60°C.

[0019] Further, in step 2, the molar ratio of PbI2 to ZnI2 is 1:1 - 1.5.

[0020] Further, in the mixed solution in step 5, the molar ratio of Cs element to Pb element is 1:3.5 - 4.

[0021] Further, in step 1, the mass - volume ratio of cesium carbonate to oleic acid is 0.14 - 0.15 g / mL, and the mass - volume ratio of cesium carbonate to octadecene is 8 - 12 g / L; in step 2, the mass - volume ratio of PbI2 to octadecene is 16 - 18 g / L; in the reaction solution in step 4, the ratio between the total molar amount of PbI2 and ZnI2 and the total volume of oleic acid and oleylamine is 0.8 - 1 mol / L, and the volume ratio of oleic acid to oleylamine is 1:1.

[0022] Further, in step 6, the molar ratio of I element in the mixed solution to Br element in the hydrohalic acid is 1 - 3:1.

[0023] Further, the anti - solvent in steps 7 and 8 is one or more of methyl acetate, ethyl acetate, ethyl benzoate, and methyl benzoate.

[0024] Further, the non - polar solvent in steps 7 and 8 is one or more of n - octane and n - hexane.

[0025] Further, the standing time in step 8 is more than 12 h.

[0026] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0027] The present invention provides a method for precisely regulating the emission wavelength of mixed - halide pure - red perovskite quantum dots. After the formation of quantum dots, a bromine source (hydrobromic acid) is introduced. While completing the halogen exchange, hydrobromic acid provides electrons for unsaturated lead ions, passivating the lead dangling bonds on the surface of the quantum dots. While achieving precise regulation of the emission wavelength of pure - red perovskite quantum dots, the optical properties of the perovskite quantum dots are improved, meeting the requirements for high - color - purity red light emission, and it is one of the ideal choices for future high - performance optoelectronic devices and display technologies. Description of the Drawings

[0028] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings required for the description of the embodiments or the prior art. Obviously, the drawings in the following description are only some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.

[0029] Figure 1 CsPbI synthesized for Example 3 3-m Br m TEM image of red light quantum dots;

[0030] Figure 2 CsPbI synthesized for Examples 1 - 5 and Comparative Examples 1 - 3 3-m Br m Fluorescence spectrum of red light quantum dot solution;

[0031] Figure 3 CsPbI synthesized for Example 3 3-m Br m Comparison chart of photoluminescence quantum efficiency (PLQY) between red light quantum dots and CsPbI3 quantum dots synthesized in Comparative Example 4;

[0032] Figure 4 Schematic diagrams of the synthesis methods proposed for Examples 1 - 5 and Comparative Examples 1 - 3; among them, (a) is the synthesis method of Examples 1 - 5; (b) is the synthesis method of Comparative Examples 1 - 3. Detailed implementation manners

[0033] To further understand the present invention, the following describes the preferred implementation manners of the present invention in combination with embodiments. However, it should be understood that these descriptions are only for further explaining the features and advantages of the present invention, rather than limiting the claims of the invention. There are no special restrictions on the sources of all raw materials of the present invention, and they can be purchased on the market or prepared according to the conventional methods well-known to those skilled in the art.

[0034] Example 1

[0035] This example provides a method for precisely regulating the emission wavelength of mixed halide pure red light perovskite quantum dots. The synthesis method is as shown in (a) of Figure 4 Specifically, CsPbI 3-m Br m red light quantum dots are synthesized, including the following steps:

[0036] Step 1: Add 10 mL of octadecene, 0.7 mL of oleic acid, and 100 mg of cesium carbonate to a three-necked flask. Place the flask on a heating mantle and perform magnetic stirring at a speed of 250 r / min to obtain a first precursor solution;

[0037] Step 2: Put 10 mL of octadecene, 173 mg of lead iodide, and 120 mg of zinc iodide into a three-necked flask. Place the flask on a heating mantle and perform magnetic stirring at a speed of 400 r / min to obtain a second precursor solution.

[0038] Step 3: Open the vacuum pump and perform stepwise temperature elevation on the first precursor solution and the second precursor solution under vacuum conditions. The set temperatures of the first precursor solution are 40°C, 60°C, and 100°C, and the set temperatures of the second precursor solution are 40°C, 60°C, 100°C, and 120°C. Except for the set time interval of 20 min from 60°C to 100°C for the first precursor solution, the other time intervals are all 10 min. Then, fill the two flasks with nitrogen as a protective gas, evacuate the vacuum again, and maintain it for 5 min. Repeat this twice. After filling with nitrogen for the third time, close the vacuum pump and keep the nitrogen.

[0039] Step 4: Use two syringes to respectively suck 1.5 mL of oleic acid and 1.5 mL of oleylamine, and inject oleic acid and oleylamine into the second precursor solution successively. Increase the stirring speed to 700 r / min. After the precipitate dissolves, obtain a reaction solution.

[0040] Step 5: Use a syringe to suck 1.6 mL of the first precursor solution. Heat the reaction solution obtained in Step 4 to 165°C, quickly inject the first precursor solution in the syringe into the reaction solution, and immediately take out the reaction solution. Stir and cool it in an ice-water bath to below 30°C to obtain a mixed solution.

[0041] Step 6: Reheat the mixed solution obtained in Step 5 to 55°C and inject 20 μL of hydrobromic acid (with a content of 48 wt%) to obtain a crude solution of mixed-halide perovskite quantum dots.

[0042] Step 7: Add 16.25 mL of methyl acetate to the crude solution of mixed-halide perovskite quantum dots, centrifuge at a speed of 10000 r / min for 1 min, and retain the supernatant. Add another 6.25 mL of methyl acetate, centrifuge at a speed of 10000 r / min for 1 min, blow-dry the methyl acetate remaining on the precipitate at a low temperature, disperse the precipitate with 1 mL of n-octane, and centrifuge at a speed of 10000 r / min for 1 min. The obtained supernatant is a dispersion of mixed-halide perovskite quantum dots.

[0043] Step 8: Centrifuge the mixed halide perovskite quantum dot dispersion that has been left standing for 12 hours or more at a speed of 12,000 r / min for 1 minute. Retain the supernatant, add 2 mL of methyl acetate, centrifuge at a speed of 12,000 r / min for 1 minute, blow dry the methyl acetate remaining on the precipitate at low temperature, disperse the precipitate with 400 μL of n-octane, and centrifuge at a speed of 12,000 r / min for 1 minute. The resulting supernatant is the high-quality dispersion of mixed halide perovskite quantum dots, namely CsPbI 3-m Br m red light quantum dot solution.

[0044] Example 2

[0045] This example provides a method for precisely regulating the emission wavelength of mixed halide pure red light perovskite quantum dots. Specifically, CsPbI 3-m Br m red light quantum dots were synthesized. Compared with Example 1, the preparation process is only different in that: the amount of hydrobromic acid injected in Step 6 is adjusted to 40 μL; the remaining steps are the same as those in Example 1.

[0046] Example 3

[0047] This example provides a method for precisely regulating the emission wavelength of mixed halide pure red light perovskite quantum dots. Specifically, CsPbI 3-m Br m red light quantum dots were synthesized. Compared with Example 1, the preparation process is only different in that: the amount of hydrobromic acid injected in Step 6 is adjusted to 60 μL; the remaining steps are the same as those in Example 1.

[0048] Example 4

[0049] This example provides a method for precisely regulating the emission wavelength of mixed halide pure red light perovskite quantum dots. Specifically, CsPbI 3-m Br m red light quantum dots were synthesized. Compared with Example 1, the preparation process is only different in that: the amount of hydrobromic acid injected in Step 6 is adjusted to 80 μL; the remaining steps are the same as those in Example 1.

[0050] Example 5

[0051] This example provides a method for precisely regulating the emission wavelength of mixed halide pure red light perovskite quantum dots. Specifically, CsPbI 3-m Br m red light quantum dots were synthesized. Compared with Example 1, the preparation process is only different in that: the amount of hydrobromic acid injected in Step 6 is adjusted to 100 μL; the remaining steps are the same as those in Example 1.

[0052] Comparative Example 1

[0053] This comparative example provides a method for regulating the emission wavelength of mixed halide perovskite quantum dots. The synthesis method is as shown in (b) of Figure 4 Specifically, CsPbI 3-m Br m red light quantum dots were synthesized, including the following steps:

[0054] Step 1: Add 10 mL of octadecene, 0.7 mL of oleic acid, and 100 mg of cesium carbonate to a three-necked flask. Place the flask on a heating mantle and stir magnetically at a speed of 250 r / min to obtain a first precursor solution;

[0055] Step 2: Put 10 mL of octadecene, 130 mg of lead iodide, and 34.5 mg of lead bromide into a three-necked flask. Place the flask on a heating mantle and stir magnetically at a speed of 400 r / min to obtain a second precursor solution;

[0056] Step 3: Turn on the vacuum pump and perform stepwise heating on the first precursor solution and the second precursor solution under vacuum conditions. The set temperatures of the first precursor solution are 40 °C, 60 °C, and 100 °C, and the set temperatures of the second precursor solution are 40 °C, 60 °C, 100 °C, and 120 °C. Except for the set time interval of 20 min from 60 °C to 100 °C for the first precursor solution, the other time intervals are all 10 min; then fill the two flasks with nitrogen as a protective gas, evacuate again, and keep it for 5 min. Repeat this twice. After filling with nitrogen for the third time, turn off the vacuum pump and keep the nitrogen;

[0057] Step 4: Use two syringes to suck 0.75 mL of oleic acid and 0.75 mL of oleylamine respectively, and inject oleic acid and oleylamine into the second precursor solution successively. Increase the stirring speed to 700 r / min. After the precipitate dissolves, obtain a reaction solution;

[0058] Step 5: Use a syringe to suck 1.6 mL of the first precursor solution. Heat the reaction solution obtained in step 4 to 165 °C, quickly inject the first precursor solution in the syringe into the reaction solution, and immediately take out the reaction solution. Stir and cool it in an ice-water bath to below 30 °C to obtain a mixed solution;

[0059] Step 6: Add 8 mL of methyl acetate to the mixed solution, centrifuge at a speed of 10000 r / min for 1 min, and retain the supernatant. Add 3.25 mL of methyl acetate again, centrifuge at a speed of 10000 r / min for 1 min, blow dry the methyl acetate remaining on the precipitate at low temperature, disperse the precipitate with 1 mL of n-octane, and centrifuge at a speed of 10000 r / min for 1 min. The obtained supernatant is the mixed halide perovskite quantum dot dispersion;

[0060] Step 7: Centrifuge the mixed halogen perovskite quantum dot dispersion that has been left standing for more than 12 h at a speed of 12,000 r / min for 1 min. Retain the supernatant, add 2 mL of methyl acetate, centrifuge at a speed of 12,000 r / min for 1 min, blow-dry the methyl acetate remaining on the precipitate at low temperature, disperse the precipitate with 400 μL of n-octane, centrifuge at a speed of 12,000 r / min for 1 min, and the resulting supernatant is the high-quality dispersion of mixed halogen perovskite quantum dots, namely CsPbI 3-m Br m red-light quantum dot solution.

[0061] Comparative Example 2

[0062] This comparative example provides a method for regulating the emission wavelength of mixed halide perovskite quantum dots. Specifically, CsPbI 3-m Br m red-light quantum dots were synthesized. The difference in the preparation process compared with Comparative Example 1 is only that: the content of lead iodide in Step 2 was adjusted to 108.33 mg, and the content of lead bromide was adjusted to 51.75 mg; the remaining steps are the same as those in Comparative Example 1.

[0063] Comparative Example 3

[0064] This comparative example provides a method for regulating the emission wavelength of mixed halide perovskite quantum dots. Specifically, CsPbI 3-m Br m red-light quantum dots were synthesized. The difference in the preparation process compared with Comparative Example 1 is only that: the content of lead iodide in Step 2 was adjusted to 86.67 mg, and the content of lead bromide was adjusted to 68.99 mg; the remaining steps are the same as those in Comparative Example 1.

[0065] Comparative Example 4

[0066] This comparative example provides a method for regulating the emission wavelength of mixed halide perovskite quantum dots. Specifically, CsPbI3 quantum dots were synthesized. The difference in the preparation process compared with Experimental Example 3 is only that hydrobromic acid was not injected in Step 6; the remaining steps are the same as those in Experimental Example 3.

[0067] Next, the materials synthesized in Examples 1 to 4 and Comparative Examples 1 to 3 were characterized.

[0068] Figure 1 For the TEM image of the CsPbI 3-m Br m red-light quantum dots synthesized in Example 3, it can be seen that the obtained CsPbI 3-m Br m red-light quantum dots have relatively uniform size and distribution under the electric field.

[0069] Figure 2 For CsPbI synthesized in Examples 1 to 5 and Comparative Examples 1 to 33-m Br m Fluorescence spectra of the red-light quantum dot solution. It can be seen that in Examples 1-5, by adjusting the content of the halogen source - hydrobromic acid added in the second step to 20-100 μL, precise regulation of the emission wavelength from 608-668 nm can be achieved. Among them, the CsPbI 3-m Br m emission wavelength of the red-light quantum dots meets the requirements of high-color-purity red-light display; in Comparative Examples 1-3, by adjusting the content of the halogen sources lead bromide and lead iodide, specifically, the molar mass ratio changes from 0.5:1.5 to 1:1, and the obtained emission wavelength has a relatively large change range. This requires more precision when weighing the halogen source to control the emission wavelength. When there are weighing errors in actual operation, it is difficult to achieve precise regulation of the wavelength.

[0070] In contrast, the method for precisely regulating the emission wavelength of mixed-halide pure-red perovskite quantum dots proposed in Examples 1-5 is easier to implement. The precise regulation of the hydrobromic acid content can be achieved through a syringe, and the operation is also simpler. It can be used as a preferred method for precisely regulating the emission wavelength of mixed-halide pure-red perovskite quantum dots.

[0071] Figure 3 For the CsPbI 3-m Br m comparison diagram of the PLQY of the red-light quantum dots synthesized in Example 3 and the CsPbI3 quantum dots synthesized in Comparative Example 4. It can be seen that for the mixed-halide pure-red perovskite quantum dots synthesized by introducing hydrobromic acid after the formation of quantum dots in Example 3, compared with single-metal bromide perovskite quantum dots, while achieving the regulation of the emission wavelength, the optical properties of the quantum dots can be improved.

[0072] In the present invention, specific examples are used to elaborate on the principle and implementation manner of the present invention. The description of the above examples is only used to help understand the method of the present invention and its core idea, including the best mode, and also enables any person skilled in the art to practice the present invention, including manufacturing and using any device or system, and implementing any combined method. It should be noted that for those of ordinary skill in the art in this technical field, without departing from the principle of the present invention, several improvements and modifications can be made to the present invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention. The protection scope of the present invention patent is defined by the claims and may include other embodiments that can be conceived by those skilled in the art. If these other embodiments have structural elements that are not different from the literal description of the claims, or if they include equivalent structural elements that have no substantial difference from the literal description of the claims, then these other embodiments should also be included within the scope of the claims.

Claims

1. A method for precisely regulating the emission wavelength of mixed halide pure red light perovskite quantum dots, characterized in that, The mixed halide perovskite quantum dots are CsPbI 3-m Br m quantum dots, where 0 < m < 3; The method specifically includes the following steps: Step 1: Add cesium carbonate into the mixed solution of octadecene and oleic acid, and stir to obtain the first precursor solution; Step 2: Add PbI2 and ZnI2 into octadecene, and stir to obtain the second precursor solution; Step 3: Under vacuum conditions, perform stepwise heating on the first precursor solution and the second precursor solution respectively until the first precursor solution is heated to the first target temperature for heat preservation, and the second precursor solution is heated to the second target temperature for heat preservation, then switch to a nitrogen or inert gas environment; Step 4: Inject oleic acid and oleylamine into the second precursor solution successively, and stir to obtain the reaction solution; Step 5: First, heat the reaction solution to the third target temperature, then quickly inject the first precursor solution into the reaction solution, and stir and cool it in an ice-water bath to below the fourth target temperature to obtain the mixed solution; Step 6: Reheat the mixed solution to the fifth target temperature, and inject hydrobromic acid to obtain the crude solution of mixed-halide perovskite quantum dots; Step 7: Use an anti-solvent to perform multiple centrifugations on the crude solution of mixed-halide perovskite quantum dots to obtain a dispersion of mixed-halide perovskite quantum dots dispersed in a non-polar reagent; Step 8: After standing the dispersion of mixed-halide perovskite quantum dots for a period of time, perform multiple centrifugations again using the anti-solvent to obtain a high-quality dispersion of mixed-halide perovskite quantum dots dispersed in a non-polar reagent.

2. The method for precisely regulating the emission wavelength of mixed halide pure red light perovskite quantum dots according to claim 1, wherein The first target temperature is 95 - 105 °C, the second target temperature is 115 - 125 °C, the third target temperature is 160 - 175 °C, the fourth target temperature is 40 °C, and the fifth target temperature is 50 - 60 °C.

3. The method for precisely regulating the emission wavelength of the mixed halide pure red light perovskite quantum dots according to claim 2, wherein In Step 2, the molar ratio of PbI2 to ZnI2 is 1:1 - 1.

5.

4. The method for precisely regulating the emission wavelength of the mixed halide pure red light perovskite quantum dots according to claim 2, wherein In the mixed solution in Step 5, the molar ratio of Cs element to Pb element is 1:3.5 - 4.

5. The method for precisely regulating the emission wavelength of the mixed halide pure red light perovskite quantum dots according to claim 2, wherein In Step 1, the mass-volume ratio of cesium carbonate to oleic acid is 0.14 - 0.15 g / mL, and the mass-volume ratio of cesium carbonate to octadecene is 8 - 12 g / L; in Step 2, the mass-volume ratio of PbI2 to octadecene is 16 - 18 g / L; in the reaction solution in Step 4, the ratio between the total molar amount of PbI2 and ZnI2 and the total volume of oleic acid and oleylamine is 0.8 - 1 mol / L, and the volume ratio of oleic acid to oleylamine is 1:

1.

6. The method for precisely regulating the emission wavelength of the mixed halide pure red light perovskite quantum dots according to claim 2, wherein In Step 6, the molar ratio of I element in the mixed solution to Br element in the hydrohalic acid is 1 - 3:

1.

7. The method for precisely regulating the emission wavelength of mixed halide pure red light perovskite quantum dots according to any one of claims 1 to 6, characterized in that, The anti-solvent in Step 7 and Step 8 is one or more of methyl acetate, ethyl acetate, ethyl benzoate, and methyl benzoate.

8. The method for precisely regulating the emission wavelength of mixed halide pure red light perovskite quantum dots according to any one of claims 1 to 6, characterized in that, The non-polar solvent in Step 7 and Step 8 is one or more of n-octane and n-hexane.

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