Bismuth-based lead-free perovskite quantum dot material and preparation method and application thereof

Abstract

The invention relates to the field of quantum dot materials, in particular to a bismuth-based lead-free perovskite quantum dot material and a preparation method and application thereof. The invention discloses a preparation method of a bismuth-based lead-free perovskite quantum dot material, which is characterized by comprising the following steps of: 1, weighing bismuth salt and salt containing halide ions, adding the bismuth salt and the salt containing halide ions into a good solvent, then adding ionic liquid, and uniformly stirring to obtain a precursor solution; 2, heating the precursor solution, rapidly injecting the precursor solution into an anti-solvent, and violently stirring for 5-15 minutes; and then cooling, precipitating, centrifuging, washing and dispersing in methylbenzene to obtain a quantum dot solution. The bismuth-based lead-free perovskite quantum dot material prepared by the invention has high quantum yield, good stability and excellent photoelectric properties, and can meet the application requirements of various photoelectric devices.

Description

Technical Field

[0001] The present invention relates to the field of quantum dot materials, and particularly to a bismuth-based lead-free perovskite quantum dot material, a preparation method thereof, and an application thereof. Background Art

[0002] Traditional lead-based perovskite quantum dots exhibit great application potential in fields such as light-emitting diodes and photodetectors due to their excellent optoelectronic properties. However, the toxicity of lead elements poses a serious threat to the environment and human health, restricting their large-scale application. Therefore, the development of lead-free perovskite quantum dot materials has become a research hotspot. Bismuth-based compounds are considered one of the potential alternatives to lead-based materials due to the low toxicity of bismuth elements and their unique electronic structures.

[0003] However, the bismuth-based lead-free perovskite quantum dot materials reported so far still have many deficiencies in aspects such as preparation methods and performance optimization, such as low quantum yield and poor stability, which limit their further application. Summary of the Invention

[0004] The purpose of the present invention is to provide a bismuth-based lead-free perovskite quantum dot material with high quantum yield, good stability, and excellent optoelectronic properties; at the same time, a preparation method of this material is provided, which is simple, efficient, and easy to control; an application of this material in optoelectronic devices such as high-power devices and heat dissipation devices is also provided.

[0005] The present application provides a preparation method of a bismuth-based lead-free perovskite quantum dot material, including the following steps, Step 1: Weigh a bismuth salt and a salt containing a halogen ion and add them to a good solvent, then add an ionic liquid and stir evenly to obtain a precursor solution; The bismuth salt is selected from at least one of bismuth trichloride (BiCl 3 ), bismuth tribromide (BiBr 3 ), and bismuth triiodide (BiI 3 ); preferably, the bismuth salt is selected from bismuth triiodide (BiI 3 ).

[0006] The salt containing a halogen ion is selected from at least one of cesium chloride (CsCl), cesium bromide (CsBr), cesium iodide (CsI), formamidinium hydroiodide (FAI), and methylammonium iodide (MAI); preferably, the salt containing a halogen ion is selected from cesium chloride (CsCl) and cesium iodide (CsI).

[0007] The molar ratio of cesium iodide, bismuth triiodide, and cesium chloride is 5-7:3-5:1; preferably, the molar ratio of cesium iodide, bismuth triiodide, and cesium chloride is 6:4:1.

[0008] The good solvent is a non-polar solvent. Specifically, the good solvent includes at least one of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO).

[0009] The good solvent also includes an amine with a carbon chain length of 5-10, preferably octylamine. In this application, the crystallization degree of quantum dots is adjusted by adding an amine with a carbon chain length of 5-10. By controlling the type and addition amount of the amine, the crystallization degree of the quantum dots reaches the best, so as to achieve the strongest emission peak and absorbance value.

[0010] The ionic liquid is selected from at least one of 1-butyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylimidazolium hexafluorophosphate, and 1-hexyl-3-methylimidazolium hexafluorophosphate.

[0011] Step 2: Heat up the precursor solution, quickly inject it into the anti-solvent, and stir vigorously for 5-15 minutes; then cool, precipitate, centrifuge, wash, and disperse in toluene to obtain a quantum dot solution.

[0012] The precursor solution is heated to 170-190 °C.

[0013] The anti-solvent is a polar solvent. Specifically, the anti-solvent includes at least one of toluene, isopropanol, and ethanol.

[0014] Preferably, the method for preparing the bismuth-based lead-free perovskite quantum dot material includes the following steps: Step 1: Weigh 0.3 mmol of CsI, 0.2 mmol of BiI 3 , 0.05 mmol of CsCl, add them to 2-10 mL of DMSO and 40-60 μL of octylamine, add 0.05-0.2 mL of 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF6, ionic liquid), stir evenly to obtain a precursor solution; Step 2: Heat up the precursor solution, quickly inject 1-5 mL of toluene, stir vigorously for 5-15 minutes; then cool to 50 °C, precipitate, centrifuge, wash, and disperse in toluene (concentration of 10 mg / mL) to obtain a quantum dot solution.

[0015] In this application, the crystallization degree of quantum dots is adjusted by adding a specific amount of octylamine, and at the same time, a small amount of CsCl is added. Due to the solubility difference between CsCl and CsI in toluene, and the concentration of added cesium chloride is lower than that of CsI, CsI precipitates from toluene earlier, and may first form Cs 3 Bi 2 I 9 nanocrystals, and Cl is mainly distributed in Cs 3 Bi 2 I9 The surface of quantum dots combines with the dangling bonds on the surface of quantum dots to passivate surface defects; at the same time, 1-butyl-3-methylimidazolium hexafluorophosphate combines with Bi³+ vacancies on the surface of quantum dots to inhibit non-radiative recombination and increase quantum yield (PLQA) and service life.

[0016] The method for preparing the bismuth-based lead-free perovskite quantum dot material also includes mixing the quantum dot solution obtained in step 2 with the boron nitride precursor and then placing the mixture in a tubular furnace, heating the mixture to 550-650° C. at a certain heating rate under an inert gas atmosphere, and keeping the mixture warm for 1-3 hours to obtain coated bismuth-based perovskite quantum dots.

[0017] The certain heating rate refers to first heating to 350°C at a rate of 10°C / min, and then heating to 550-650°C at a rate of 5°C / min.

[0018] The method for preparing the boron nitride precursor comprises the following steps: (1) 2 g of polystyrene microspheres were dispersed in 100 mL of water and ultrasonically treated for 45 minutes to obtain a dispersion; the dispersion was then dropped onto a glass substrate and allowed to stand for 24 hours; the substrate was then placed in an oven and dried to obtain a polystyrene microsphere template; (2) 1 g H 3 BO 3 and 3 g CO(NH 2 ) 2 Dissolve in 20 mL of water and stir until completely dissolved; then add 1 mL of NH 4 OH, and continue stirring for 30 minutes to form a uniform mixed solution; (3) The mixed solution was evenly dropped onto the polystyrene microsphere template, and then placed at 180°C for reaction for 12 hours to obtain a white composite; (4) The white complex was immersed in toluene and subjected to ultrasonic treatment for 1 hour; the precipitate was then washed alternately with water and ethanol and dried in vacuum to obtain a boron nitride precursor.

[0019] The high thermal conductivity of boron nitride effectively reduces the thermal quenching effect of quantum dots and improves the luminescence efficiency. The present application uses the preparation method to enable 3D-boron nitride to coat and efficiently protect bismuth-based lead-free perovskite quantum dot materials, providing good physical isolation and chemical inertness protection for quantum dot materials, and significantly improving the environmental stability of quantum dots.

[0020] The second aspect of the present application provides the application of the bismuth-based lead-free perovskite quantum dot material in high-power devices and heat dissipation devices.

[0021] The bismuth-based lead-free perovskite quantum dot material can be applied to optoelectronic devices such as light-emitting diodes, photodetectors, and fluorescence sensors. In a light-emitting diode, when the quantum dot material is used as the light-emitting layer, the light-emitting efficiency and color purity can be improved; in a photodetector, by utilizing its excellent optoelectronic conversion performance, rapid and sensitive detection of optical signals can be achieved. Beneficial effects

[0022] The bismuth-based lead-free perovskite quantum dot material prepared by the present invention has a high quantum yield, good stability, and excellent optoelectronic properties, and can meet the application requirements of various optoelectronic devices.

[0023] The preparation method is simple, efficient, and easy to control. By adjusting the composition of the precursor solution and the reaction conditions, the composition, size, and properties of the quantum dots can be precisely controlled.

[0024] This material is lead-free and non-toxic, meets environmental protection requirements, and has broad application prospects and market value. Embodiment mode Example

[0025] A preparation method of a bismuth-based lead-free perovskite quantum dot material includes the following steps: Step 1: Weigh 0.3 mmol of CsI, 0.2 mmol of BiI 3 , 0.05 mmol of CsCl, add them to 5 mL of DMSO and 50 microliters of octylamine, add 0.1 mL of 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF6, ionic liquid), stir evenly to obtain a precursor solution; Step 2: Heat the precursor solution to 180 °C, quickly inject 3 mL of toluene, and stir vigorously for 10 minutes; then cool to 50 °C, precipitate, centrifuge, wash, and disperse in toluene (concentration of 10 mg / mL) to obtain a quantum dot solution. Example

[0026] A preparation method of a bismuth-based lead-free perovskite quantum dot material includes the following steps: Step 1: Weigh 0.3 mmol of CsI, 0.2 mmol of BiI 3 , 0.01 mmol of CsCl, add them to 5 mL of DMSO and 50 microliters of octylamine, add 0.1 mL of 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF6, ionic liquid), stir evenly to obtain a precursor solution; Step 2: Heat the precursor solution to 180 °C, quickly inject 3 mL of toluene, and stir vigorously for 10 minutes; then cool to 50 °C, precipitate, centrifuge, wash, and disperse in toluene (concentration of 10 mg / mL) to obtain a quantum dot solution. Example

[0027] A preparation method of bismuth-based lead-free perovskite quantum dot material, comprising the following steps: Step 1: Weigh 0.3 mmol of CsI, 0.2 mmol of BiI 3 , 0.1 mmol of CsCl, add them into 5 mL of DMSO and 50 μL of octylamine, add 0.1 mL of 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF6, ionic liquid), stir evenly to obtain a precursor solution; Step 2: Heat the precursor solution to 180 °C, quickly inject 3 mL of toluene, stir vigorously for 10 minutes; then cool to 50 °C, precipitate, centrifuge, wash and disperse in toluene (concentration is 10 mg / mL) to obtain a quantum dot solution. Example

[0028] A preparation method of bismuth-based lead-free perovskite quantum dot material, comprising the following steps: Step 1: Weigh 0.3 mmol of CsI, 0.2 mmol of BiI 3 , 0.05 mmol of CsCl, add them into 5 mL of DMSO and 20 μL of octylamine, add 0.1 mL of 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF6, ionic liquid), stir evenly to obtain a precursor solution; Step 2: Heat the precursor solution to 180 °C, quickly inject 3 mL of toluene, stir vigorously for 10 minutes; then cool to 50 °C, precipitate, centrifuge, wash and disperse in toluene (concentration is 10 mg / mL) to obtain a quantum dot solution. Example

[0029] A preparation method of bismuth-based lead-free perovskite quantum dot material, comprising the following steps: Step 1: Weigh 0.3 mmol of CsI, 0.2 mmol of BiI 3 , 0.05 mmol of CsCl, add them into 5 mL of DMSO and 80 μL of octylamine, add 0.1 mL of 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF6, ionic liquid), stir evenly to obtain a precursor solution; Step 2: Heat the precursor solution to 180 °C, quickly inject 3 mL of toluene, stir vigorously for 10 minutes; then cool to 50 °C, precipitate, centrifuge, wash and disperse in toluene (concentration is 10 mg / mL) to obtain a quantum dot solution. Example

[0030] A preparation method of bismuth-based lead-free perovskite quantum dot material, comprising the following steps: Step 1: Weigh 0.3 mmol of CsI, 0.2 mmol of BiI 3 , 0.05 mmol of CsCl, add them into 5 mL of DMSO and 50 μL of octylamine, then add 0.1 mL of 1-butyl-3-methylimidazolium hexafluorophosphate ([BMIM]PF6, ionic liquid), stir evenly to obtain a precursor solution; Step 2: Heat the precursor solution to 180 °C, quickly inject 3 mL of toluene, and stir vigorously for 10 minutes; then cool to 50 °C, precipitate, centrifuge, wash and disperse in toluene (concentration is 10 mg / mL) to obtain a quantum dot solution.

[0031] Step 3: Mix the quantum dot solution obtained in Step 2 with a boron nitride precursor (mass ratio 1:5) evenly, then put it into a tubular furnace, heat it to 600 °C at a certain heating rate under a nitrogen atmosphere, and keep it at this temperature for 1.5 hours to obtain coated bismuth-based perovskite quantum dots.

[0032] Analyze the bismuth-based perovskite quantum dots and the coated bismuth-based perovskite quantum dots by XPS. It is found that there are no B and N peaks in the pure bismuth-based perovskite quantum dots, while the coated bismuth-based perovskite quantum dots contain B-N bonds corresponding to a binding energy of 190.5 eV and N-B bonds corresponding to a binding energy of 398.2 eV.

[0033] The said certain heating rate means heating to 350 °C at a rate of 10 °C / min first, and then heating to 600 °C at a rate of 5 °C / min.

[0034] The preparation method of the said boron nitride precursor includes the following steps: (1) Disperse 2 g of polystyrene microspheres in 100 mL of water, ultrasonically treat for 45 minutes to obtain a dispersion; then drop the dispersion on a glass substrate and let it stand for 24 hours; then place the substrate in an oven to dry to obtain a polystyrene microsphere template; (2) Dissolve 1 g of H 3 BO 3 and 3 g of CO(NH 2 ) 2 in 20 mL of water, stir until completely dissolved; then add 1 mL of NH 4 OH, continue to stir for 30 minutes to form a homogeneous mixed solution; (3) Drop the mixed solution evenly on the polystyrene microsphere template, then place it at 180 °C and react for 12 hours to obtain a white complex; (4) Immerse the white complex in toluene, ultrasonically treat for 1 hour; then wash the precipitate alternately with water and ethanol, and dry it under vacuum to obtain the boron nitride precursor. Example

[0035] A preparation method of bismuth-based lead-free perovskite quantum dot material. Steps 1 and 2 are the same as those in Example 6, with the difference being that in Step 3: the quantum dot solution obtained in Step 2 is mixed evenly with a boron nitride precursor (mass ratio 1:5), and then placed in a tube furnace. Under a nitrogen atmosphere, it is heated to 600 °C at a certain heating rate, and held for 1.5 hours to obtain coated bismuth-based perovskite quantum dots.

[0036] The so-called certain heating rate means first heating to 600 °C at a rate of 10 °C / min.

[0037] The preparation method of the boron nitride precursor includes the following steps: (1) Disperse 2 g of polystyrene microspheres in 100 mL of water, and perform ultrasonic treatment for 45 minutes to obtain a dispersion; then drop the dispersion on a glass substrate and let it stand for 24 hours; then place the substrate in an oven to dry to obtain a polystyrene microsphere template; (2) Dissolve 1 g of H 3 BO 3 and 3 g of CO(NH 2 ) 2 in 20 mL of water, and stir until completely dissolved; then add 1 mL of NH 4 OH, and continue to stir for 30 minutes to form a homogeneous mixed solution; (3) Drop the mixed solution evenly on the polystyrene microsphere template, and then place it at 180 °C for reaction for 12 hours to obtain a white complex; (4) Immerse the white complex in toluene and perform ultrasonic treatment for 1 hour; then wash the precipitate alternately with water and ethanol, and dry it under vacuum to obtain the boron nitride precursor. Example

[0038] A preparation method of bismuth-based lead-free perovskite quantum dot material. Steps 1 and 2 are the same as those in Example 6, with the difference being that in Step 3: the quantum dot solution obtained in Step 2 is mixed evenly with a boron nitride precursor (mass ratio 1:5), and then placed in a tube furnace. Under a nitrogen atmosphere, it is heated to 600 °C at a certain heating rate, and held for 1.5 hours to obtain coated bismuth-based perovskite quantum dots.

[0039] The so-called certain heating rate means first heating to 600 °C at a rate of 5 °C / min.

[0040] The preparation method of the boron nitride precursor includes the following steps: (1) Disperse 2 g of polystyrene microspheres in 100 mL of water, and perform ultrasonic treatment for 45 minutes to obtain a dispersion; then drop the dispersion on a glass substrate and let it stand for 24 hours; then place the substrate in an oven to dry to obtain a polystyrene microsphere template; (2) Dissolve 1 g of H 3 BO3 and 3 g of CO(NH 2 ) 2 is dissolved in 20 mL of water and stirred until completely dissolved; then 1 mL of NH 4 OH is added and stirring is continued for 30 minutes to form a homogeneous mixed solution; (3)The mixed solution is evenly dropped onto a polystyrene microsphere template and then placed at 180 °C for reaction for 12 hours to obtain a white complex; (4)The white complex is immersed in toluene and ultrasonically treated for 1 hour; then the precipitate is washed alternately with water and ethanol and dried in vacuo to obtain a boron nitride precursor.

[0041] Performance testing and data Quantum yield (PLQY) test: An integrating sphere system is used to test the quantum yield of the prepared bismuth-based lead-free perovskite quantum dot material. Using quinine sulfate as a standard sample, under the same excitation wavelength, the fluorescence emission spectra of the quantum dots and the standard sample are tested.

[0042] Stability test: The prepared quantum dot materials are placed in air and different humidity environments respectively, and their fluorescence emission spectra are regularly tested. After being placed in air for 30 days, the fluorescence intensity retention rate (air stability) is tested; after being placed in an environment with a relative humidity of 60% for 15 days, the fluorescence intensity retention rate (humidity stability) is tested.

[0043] Table 1 Performance test results PLQY Air stability Humidity stability Example 1 48.5% 90% 81% Example 2 40.7% 85% 75% Example 3 43.4% 88% 77% Example 4 34.6% 76% 64% Example 5 38.5% 80% 72% Example 6 59.4% 98% 89% Example 7 50.1% 95% 84% Example 8 53.8% 98% 89% The quantum dot material of Example 6 is used for an LED (excited at 450 nm), and the optoelectronic parameters are tested to obtain a luminous efficiency of 5.8 Im / W, an operating life (T50) of 150 hours, and color coordinates (0.69, 0.30).

[0044] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention and are not intended to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a bismuth-based lead-free perovskite quantum dot material, characterized in that: The following steps are involved: Step 1: Weigh a bismuth salt and a salt containing a halide ion, add them to a good solvent, then add an ionic liquid and stir evenly to obtain a precursor solution; Step 2: heating the precursor solution, rapidly injecting it into the anti-solvent, and vigorously stirring it for 5-15 minutes; then cooling it, precipitating it, centrifuging it, washing it, and dispersing it in toluene to obtain a quantum dot solution; The ionic liquid is selected from at least one of 1-butyl-3-methylimidazolium hexafluorophosphate, 1-ethyl-3-methylimidazolium hexafluorophosphate, and 1-hexyl-3-methylimidazolium hexafluorophosphate.

2. The method for preparing the bismuth-based lead-free perovskite quantum dot material according to claim 1, characterized in that: The bismuth salt is selected from at least one of bismuth trichloride, bismuth tribromide and bismuth triiodide.

3. The method for preparing the bismuth-based lead-free perovskite quantum dot material according to claim 2, characterized in that: The halide-containing salt is selected from at least one of cesium chloride, cesium bromide, cesium iodide, formamidine hydroiodide, and methylammonium iodide.

4. The method for preparing the bismuth-based lead-free perovskite quantum dot material according to claim 3, characterized in that: The halide-containing salt is selected from cesium chloride and cesium iodide.

5. The method for preparing the bismuth-based lead-free perovskite quantum dot material according to claim 4, characterized in that: The molar ratio of cesium iodide, bismuth triiodide and cesium chloride is 5-7:3-5:

1.

6. The method for preparing the bismuth-based lead-free perovskite quantum dot material according to claim 1, characterized in that: The good solvent is a non-polar solvent, and the good solvent includes at least one of N,N-dimethylformamide and dimethyl sulfoxide.

7. The method for preparing the bismuth-based lead-free perovskite quantum dot material according to claim 6, characterized in that: The good solvent also includes amines with a carbon chain length of 5-10.

8. The method for preparing bismuth-based lead-free perovskite quantum dot material according to claim 1, characterized in that: The anti-solvent is a polar solvent, and the anti-solvent includes at least one of toluene, isopropanol, and ethanol.

9. A bismuth-based lead-free perovskite quantum dot material obtained by the preparation method according to any one of claims 1 to 8.

10. An application of the bismuth-based lead-free perovskite quantum dot material as claimed in claim 9 in high-power devices and heat dissipation devices.