A method for preparing a MAPbBr3 perovskite quantum dot optical film in a water-based solvent

Abstract

The application belongs to the technical field of luminescent materials, and relates to a method for preparing a MAPbBr3 perovskite quantum dot optical film in a water-based solvent. The application selects water as the solvent, which is different from the organic solvents such as DMF, DMSO and GBL selected in the existing literature, so that the preparation cost and the pollution degree to the environment are greatly reduced. The application forms a colorless and transparent film by rapid heating first, then slowly absorbs water from the air, and realizes the controllable growth of the perovskite in the polymer PVA by adjusting the humidity and the water absorption time. The quantum dot film is optimized in performance by HBr and OABr. The HBr greatly increases the solubility of the inorganic component in water, and the OABr suppresses the agglomeration problem of the quantum dots in the heating process, so that the photoluminescence quantum efficiency of the MAPbBr3 quantum dot optical film is greatly improved, and the photoluminescence quantum efficiency is as high as 95.3%.

Description

Technical Field

[0001] This invention belongs to the field of luminescent materials technology and relates to a method for preparing MAPbBr3 perovskite quantum dot optical films in an aqueous solvent. Background Technology

[0002] Perovskite quantum dots have broad application prospects in liquid crystal backlight displays, detectors, and light emission fields due to their advantages such as high photoluminescence efficiency, tunable narrowband emission, and low cost. However, most existing synthesis methods are complex, and the products are difficult to apply directly to practical applications. In-situ synthesis, on the other hand, is considered the most suitable synthesis method for large-scale production due to its simple synthesis process, lower cost, and ability to be prepared in large sizes.

[0003] In in-situ synthesis, the use of polymers not only increases the viscosity of the precursor solution, thus improving the uniformity of the prepared film, but also effectively enhances the water and thermal stability of the film through efficient polymer coating. However, considering the solubility of the perovskite precursor and the boiling point of the solvent, the solvents used are mostly organic solvents. The resulting environmental pollution and increased costs are problems that continue to be addressed in the large-scale commercial preparation of perovskite quantum dots using in-situ synthesis methods. Therefore, a specific technology is needed to achieve the controllable preparation of perovskite quantum dots in environmentally friendly and inexpensive solvent systems. Summary of the Invention

[0004] The purpose of this invention is to address the current situation where expensive organic solvents are used in the preparation of organic-inorganic hybrid perovskite quantum dot thin films, and to propose a method for efficiently preparing MAPbBr3 quantum dot optical thin films in an aqueous solvent system.

[0005] The objective of this invention can be achieved through the following technical solution: a method for preparing MAPbBr3 perovskite quantum dot optical films in an aqueous solvent, the method comprising the following steps:

[0006] S1. Dissolve PVA in water, add MABr, PbBr2 and HBr in sequence and stir, then add octylamine bromide and stir to obtain a precursor solution;

[0007] S2. The precursor solution is filtered through micropores to obtain a transparent solution;

[0008] S3. A transparent solution is dropped onto the surface of a flat glass plate, and a liquid precursor layer is obtained by scraping. Then, a thin film is obtained by heat treatment.

[0009] S4. Place the film in the air for humidity treatment until the film turns green to obtain MAPbBr3 quantum dot film.

[0010] In the above-mentioned method for preparing MAPbBr3 perovskite quantum dot optical films in an aqueous solvent, the PVA dissolution in water in step S1 specifically involves adding PVA to water at 85-95℃ and stirring uniformly for 2-4 hours, then cooling to room temperature.

[0011] Preferably, in step S1, the solid-liquid ratio of PVA dissolved in water is (5-10) g: 100 mL.

[0012] Preferably, the stirring time is 10-20 hours. Controlling the stirring time ensures that the polymer is fully and uniformly dispersed in the solution.

[0013] In the above-described method for preparing MAPbBr3 perovskite quantum dot optical films in an aqueous solvent, the HBr content in the precursor solution in step S1 is 1.0-2 wt‰. In this invention, too little HBr results in low luminescence efficiency of the film, while too much HBr makes the film difficult to peel off from the flat glass.

[0014] In the above-described method for preparing MAPbBr3 perovskite quantum dot optical films in an aqueous solvent, the amount of octylamine bromide added in step S1 is 0.05-0.15% of the mass of MABr. In this invention, the content ratio of OABr to MABr is controlled at 5-15%. Too much ligand will cause the emission peak position to deviate from the optimal value of 530 nm, the half-peak width to increase, and the luminous efficiency to decrease; too little ligand will not have a good effect on improving optical performance.

[0015] In the above-mentioned method for preparing MAPbBr3 perovskite quantum dot optical films in an aqueous solvent, the micropore diameter in step S2 is 0.4-0.5 μm.

[0016] In the above-mentioned method for preparing MAPbBr3 perovskite quantum dot optical films in an aqueous solvent, the heating temperature in step S3 is 80-90℃ and the time is 3-5 min.

[0017] In the above-mentioned method for preparing MAPbBr3 perovskite quantum dot optical films in an aqueous solvent, the air humidity in step S4 is 30-60%.

[0018] Compared with the prior art, the present invention has the following beneficial effects:

[0019] 1. By using water as a solvent, this invention differs from existing literature which uses organic solvents such as DMF, DMSO, and GBL, thus greatly reducing preparation costs and environmental pollution.

[0020] 2. This invention achieves controllable growth of perovskite in polymer PVA by first rapidly heating to form a colorless and transparent film, and then slowly absorbing water from the air. By adjusting the humidity and water absorption time, the performance of the quantum dot film is optimized by using HBr and OABr. HBr greatly increases the solubility of inorganic components in water, and OABr suppresses the aggregation problem of quantum dots during heating. Therefore, the photoluminescence quantum efficiency of the MAPbBr3 quantum dot optical film is greatly improved, reaching as high as 95.3%.

[0021] 3. This invention significantly improves the thermal stability of MAPbBr3 quantum dot optical films by modifying them with n-octylamine bromide ligands. The MAPbBr3 quantum dot optical films can still maintain 65% of the original photoluminescence quantum efficiency after being continuously heated on a hot plate at 60°C for 300 hours.

[0022] 4. This invention completely separates the crystallization process of the polymer and perovskite quantum dots by first solidifying the polymer matrix and then slowly absorbing water. The slow growth of quantum dots inside the polymer also makes the polymer have a better coating effect on the quantum dots. Attached Figure Description

[0023] Figure 1 This is a scanning transmission electron microscope (TEM) image of the MAPbBr3 quantum dot optical thin film prepared in Example 1 of the present invention.

[0024] Figure 2 The XRD diffraction patterns are those of the MAPbBr3 quantum dot optical film and the polymer matrix PVA prepared in Example 1 of this invention.

[0025] Figure 3 The transmittance data are for the MAPbBr3 quantum dot optical thin film and the PVA substrate material prepared in Example 1 of this invention.

[0026] Figure 4 The changes in photoluminescence quantum efficiency of MAPbBr3 quantum dot optical films prepared in Comparative Examples 2-4 of this invention after adding different volume fractions of HBr are shown.

[0027] Figure 5 The changes in photoluminescence quantum efficiency of MAPbBr3 quantum dot optical films prepared in Examples 1-4 of this invention after adding different mass fractions of OABr.

[0028] Figure 6 The thermal stability changes of MAPbBr3 quantum dot optical films with and without OABr ligands prepared in Comparative Example 1 of this invention are shown.

[0029] Figure 7The photoluminescence quantum efficiency of MAPbBr3 quantum dot optical films prepared in Examples 5-19 of this invention with OABr added at 10% of the molar mass of MABr varies under different humidity levels and water absorption times.

[0030] Figure 8 The photoluminescence intensity changes of MAPbBr3 quantum dot optical films prepared in Examples 8-10 of the present invention with OABr added at 10% of the molar mass of MABr are shown in different water absorption times at 50% humidity. Detailed Implementation

[0031] The following are specific embodiments of the present invention, which further describe the technical solution of the present invention, but the present invention is not limited to these embodiments.

[0032] Examples 1-4:

[0033] S1. Add 10g PVA to 100mL of deionized water, heat at 90℃ for 3h to dissolve, and then cool to room temperature to obtain a pre-prepared PVA solution. Add 100mg MABr, 220.2mg PbBr2 and 90μL HBr to 90mL of the pre-prepared PVA solution and stir for 12 hours to prepare the precursor solution.

[0034] S2. Add 6.3 mg, 12.6 mg, 25.2 mg, and 100.8 mg of OABr to the precursor solution, mix thoroughly, and sonicate for 1 h. Then, centrifuge the sample at 3000 rpm for 3 min to remove bubbles.

[0035] S3. Filter the solution using a microporous membrane filter with a pore size of 0.45 μm to obtain a transparent and homogeneous precursor solution.

[0036] S4. Drop the precursor solution onto the surface of a flat glass plate and obtain a transparent precursor solution layer of uniform thickness using a scraping technique. Heat the flat glass plate with the precursor solution on a 90°C hot plate for 5 minutes to evaporate the solvent and form a colorless and transparent thin film.

[0037] S5. Place the flat glass with the film in an environment with a relative humidity of 50% for 90 minutes to obtain a green MAPbBr3 film.

[0038] Examples 5-7:

[0039] S1. Add 10g PVA to 100mL of deionized water, heat at 90℃ for 3h to dissolve, and then cool to room temperature to obtain a pre-prepared PVA solution. Add 100mg MABr, 220.2mg PbBr2 and 90μL HBr to 90mL of the pre-prepared PVA solution and stir for 12 hours to prepare the precursor solution.

[0040] S2. Add 12.6 mg of OABr to the precursor solution, mix thoroughly and sonicate for 1 h, then centrifuge the sample at 3000 rpm for 3 min to remove bubbles.

[0041] S3. Filter the solution using a microporous membrane filter with a pore size of 0.45 μm to obtain a transparent and homogeneous precursor solution.

[0042] S4. Drop the precursor solution onto the surface of a flat glass plate and obtain a transparent precursor solution layer of uniform thickness using a scraping technique. Heat the flat glass plate with the precursor solution on a 90°C hot plate for 5 minutes to evaporate the solvent and form a colorless and transparent thin film.

[0043] S5. Place the flat glass with the film in an environment with a relative humidity of 40% for 30 min, 60 min, and 90 min to obtain a green MAPbBr3 film.

[0044] Examples 8-10:

[0045] S1. Add 10g PVA to 100mL of deionized water, heat at 90℃ for 3h to dissolve, and then cool to room temperature to obtain a pre-prepared PVA solution. Add 100mg MABr, 220.2mg PbBr2 and 90μL HBr to 90mL of the pre-prepared PVA solution and stir for 12 hours to prepare the precursor solution.

[0046] S2. Add 12.6 mg of OABr to the precursor solution, mix thoroughly and sonicate for 1 h, then centrifuge the sample at 3000 rpm for 3 min to remove bubbles.

[0047] S3. Filter the solution using a microporous membrane filter with a pore size of 0.45 μm to obtain a transparent and homogeneous precursor solution.

[0048] S4. Drop the precursor solution onto the surface of a flat glass plate and obtain a transparent precursor solution layer of uniform thickness using a scraping technique. Heat the flat glass plate with the precursor solution on a 90°C hot plate for 5 minutes to evaporate the solvent and form a colorless and transparent thin film.

[0049] S5. Place the flat glass with the film in an environment with a relative humidity of 50% for 10 min, 30 min, and 60 min to obtain a green MAPbBr3 film.

[0050] Examples 11-13:

[0051] S1. Add 10g PVA to 100mL of deionized water, heat at 90℃ for 3h to dissolve, and then cool to room temperature to obtain a pre-prepared PVA solution. Add 100mg MABr, 220.2mg PbBr2 and 90μL HBr to 90mL of the pre-prepared PVA solution and stir for 12 hours to prepare the precursor solution.

[0052] S2. Add 12.6 mg of OABr to the precursor solution, mix thoroughly and sonicate for 1 h, then centrifuge the sample at 3000 rpm for 3 min to remove bubbles.

[0053] S3. Filter the solution using a microporous membrane filter with a pore size of 0.45 μm to obtain a transparent and homogeneous precursor solution.

[0054] S4. Drop the precursor solution onto the surface of a flat glass plate and obtain a transparent precursor solution layer of uniform thickness using a scraping technique. Heat the flat glass plate with the precursor solution on a 90°C hot plate for 5 minutes to evaporate the solvent and form a colorless and transparent thin film.

[0055] S5. Place the flat glass with the film in an environment with a relative humidity of 60% for 5 min, 35 min, and 65 min to obtain a green MAPbBr3 film.

[0056] Examples 14-16:

[0057] S1. Add 10g PVA to 100mL of deionized water, heat at 90℃ for 3h to dissolve, and then cool to room temperature to obtain a pre-prepared PVA solution. Add 100mg MABr, 220.2mg PbBr2 and 90μL HBr to 90mL of the pre-prepared PVA solution and stir for 12 hours to prepare the precursor solution.

[0058] S2. Add 12.6 mg of OABr to the precursor solution, mix thoroughly and sonicate for 1 h, then centrifuge the sample at 3000 rpm for 3 min to remove bubbles.

[0059] S3. Filter the solution using a microporous membrane filter with a pore size of 0.45 μm to obtain a transparent and homogeneous precursor solution.

[0060] S4. Drop the precursor solution onto the surface of a flat glass plate and obtain a transparent precursor solution layer of uniform thickness using a scraping technique. Heat the flat glass plate with the precursor solution on a 90°C hot plate for 5 minutes to evaporate the solvent and form a colorless and transparent thin film.

[0061] S5. Place the flat glass with the film in an environment with a relative humidity of 70% for 3 min, 5 min, and 18 min to obtain a green MAPbBr3 film.

[0062] Examples 17-19:

[0063] S1. Add 10g PVA to 100mL of deionized water, heat at 90℃ for 3h to dissolve, and then cool to room temperature to obtain a pre-prepared PVA solution. Add 100mg MABr, 220.2mg PbBr2 and 90μL HBr to 90mL of the pre-prepared PVA solution and stir for 12 hours to prepare the precursor solution.

[0064] S2. Add 12.6 mg of OABr to the precursor solution, mix thoroughly and sonicate for 1 h, then centrifuge the sample at 3000 rpm for 3 min to remove bubbles.

[0065] S3. Filter the solution using a microporous membrane filter with a pore size of 0.45 μm to obtain a transparent and homogeneous precursor solution.

[0066] S4. Drop the precursor solution onto the surface of a flat glass plate and obtain a transparent precursor solution layer of uniform thickness using a scraping technique. Heat the flat glass plate with the precursor solution on a 90°C hot plate for 5 minutes to evaporate the solvent and form a colorless and transparent thin film.

[0067] S5. Place the flat glass with the film in an environment with a relative humidity of 80% for 1 min, 3 min, and 5 min to obtain a green MAPbBr3 film.

[0068] Comparative Example 1:

[0069] S1. Add 10g PVA to 100mL of deionized water, heat at 90℃ for 3h to dissolve, and then cool to room temperature to obtain a pre-prepared PVA solution. Add 100mg MABr, 220.2mg PbBr2 and 90μL HBr to 90mL of the pre-prepared PVA solution, stir for 12h to prepare a precursor solution, mix thoroughly and sonicate for 1h, and then centrifuge the sample at 3000rpm for 3min to remove bubbles.

[0070] S2. Filter the solution using a microporous membrane filter with a pore size of 0.45 μm to obtain a transparent and homogeneous precursor solution.

[0071] S3. Drop the precursor solution onto the surface of a flat glass plate and obtain a transparent precursor solution layer of uniform thickness using a scraping technique. Heat the flat glass plate with the precursor solution on a 90°C hot plate for 5 minutes to evaporate the solvent and form a colorless and transparent thin film.

[0072] S4. Place the flat glass with the film in an environment with a relative humidity of 50% for 90 minutes to obtain a green MAPbBr3 film.

[0073] Comparative Examples 2-4:

[0074] S1. Add 10g PVA to 100mL of deionized water, heat at 90℃ for 3h to dissolve, and then cool to room temperature to obtain a pre-prepared PVA solution. Add 100mg MABr and 220.2mg PbBr2 to 90mL of the pre-prepared PVA solution and stir for 12h to prepare a precursor solution. Add 45μL, 90μL and 135μL of HBr (concentration: 48%) to the precursor solution, mix thoroughly and sonicate for 1h. Then centrifuge the sample at 3000rpm for 3min to remove bubbles.

[0075] S2. Filter the solution using a microporous membrane filter with a pore size of 0.45 μm to obtain a transparent and homogeneous precursor solution.

[0076] S3. Drop the precursor solution onto the surface of a flat glass plate and obtain a transparent precursor solution layer of uniform thickness using a scraping technique. Heat the flat glass plate with the precursor solution on a 90°C hot plate for 5 minutes to evaporate the solvent and form a colorless and transparent thin film.

[0077] S4. Place the flat glass with the film in an environment with a relative humidity of 50% for 90 minutes to obtain a green MAPbBr3 film.

[0078] Figure 1 The image shows a high-resolution transmission electron microscope (TEM) image of the MAPbBr3 quantum dot optical thin film prepared in Example 1. The image shows that the quantum dots are uniformly distributed and of uniform size, with an average diameter of about 3-5 nm.

[0079] Figure 2 The XRD diffraction patterns of the MAPbBr3 quantum dot optical thin film and the matrix material PVA prepared in Example 1 show that the obtained sample corresponds well with the standard card, proving that MAPbBr3 quantum dots with good crystallinity have indeed grown inside the polymer.

[0080] Figure 3 The transmittance data for the MAPbBr3 quantum dot optical thin film and the PVA matrix material prepared in Example 1 are shown. The high transmittance indicates that the quantum dots are well dispersed in the polymer and are small in size. The transmittance of the polymer matrix PVA in the visible light range is close to 98%, which proves its advantages as an optical matrix material.

[0081] Figure 4 For comparative examples 2-4, the PLQY of samples with different volume fractions of HBr added increased with the increase of HBr content. The PLQY of the samples maintained an upward trend. The addition of HBr can effectively increase the solubility of inorganic component PbBr2, thereby improving efficiency. However, it is worth mentioning that when the amount of HBr added is higher than 10%, the film becomes difficult to peel off from the flat glass.

[0082] Figure 5 The PLQY values ​​of samples with different mass fractions of OABr added in Examples 1-4 showed a phenomenon of first increasing and then decreasing. This is because the addition of a small amount of ligand can avoid the aggregation of precursors and quantum dots during heating, thereby increasing the efficiency of the quantum dot film. However, when the amount added exceeds 0.15 of the molar mass of MABr, it will hinder the growth of quantum dots, the peak position will gradually blue shift, and the full width at half maximum (FWHM) will gradually increase. This is because the ligand's hindering effect on the growth of quantum dots is too great, making it difficult to reach the target peak position of about 530 nm.

[0083] Figure 6 This invention demonstrates that, based on the addition of a certain amount of HBr, the addition of the ligand n-octylamine bromide can further improve thermal stability. This is because, compared with the sample without OABr, n-octylamine bromide can more effectively passivate the surface defects of perovskite quantum dots, effectively avoiding the phenomenon of thermal agglomeration and regeneration of the already grown small quantum dots, thereby increasing the thermal stability of the film.

[0084] Figure 7 The following are examples 5-19, which show the photoluminescence efficiency of MAPbBr3 quantum dot optical films with OABr added at 10% of the molar mass of MABr and HBr added at 10% of the volume fraction of the precursor solution under different humidity and treatment times. It can be seen that when the humidity is less than or equal to 60%, the optical performance of the film does not fluctuate much, which proves that this method has good environmental adaptability and versatility.

[0085] Figure 8 The experiment shows the change in photoluminescence intensity of the MAPbBr3 quantum dot optical film of the present invention, which has OABr added at 10% of the molar mass of MABr and HBr added at 10% of the volume fraction of the precursor solution, from colorless to green during the process of absorbing water. It can be seen that the present invention can effectively control the growth of quantum dots by selecting different humidity and water absorption time.

[0086] In summary, this invention significantly reduces costs and environmental pollution by using water as a solvent. It achieves high-quality photoluminescent quantum dot films by optimizing the ratio of HBr to OABr. The use of ligands effectively increases the thermal stability of the films. Furthermore, the pre-heating curing process demonstrates broad application prospects for this method in the preparation of large-size films. Controllable preparation is achieved by separating the crystallization process of polymers and perovskites and controlling the reaction conditions. This invention provides a green and reliable research approach for the field of light-emitting devices.

[0087] The embodiments described herein cover any points not exhaustively within the scope of the technical claims of this invention, as well as new technical solutions formed by equivalent substitutions of one or more technical features in the embodiments. These are all within the scope of the claims of this invention. Furthermore, in all listed or unlisted embodiments of this invention, each parameter in the same embodiment merely represents an instance (i.e., a feasible solution) of its technical solution, and there is no strict coordination or limitation relationship between the parameters. The parameters can be substituted for each other without violating axioms and the claims of this invention, unless otherwise stated.

[0088] The technical means disclosed in this invention are not limited to those described above, but also include technical solutions composed of any combination of the above technical features. The above descriptions are specific embodiments of this invention. It should be noted that those skilled in the art can make various improvements and modifications without departing from the principles of this invention, and these improvements and modifications are also considered within the scope of protection of this invention.

[0089] The specific embodiments described herein are merely illustrative of the spirit of the invention. Those skilled in the art to which this invention pertains may make various modifications or additions to the described specific embodiments or use similar methods to substitute them, without departing from the spirit of the invention or exceeding the scope defined by the appended claims.

Claims

1. A method for preparing MAPbBr3 perovskite quantum dot optical films in an aqueous solvent, the method comprising the following steps: S1. Dissolve PVA in water, add MABr, PbBr2 and HBr in sequence and stir, then add octylamine bromide and stir to obtain a precursor solution; S2. The precursor solution is filtered through micropores to obtain a transparent solution; S3. A transparent solution is dropped onto the surface of a flat glass plate, and a liquid precursor layer is obtained by scraping. Then, a thin film is obtained by heat treatment. S4. Place the film in the air for humidity treatment until the film turns green to obtain MAPbBr3 quantum dot film; In step S1, the PVA is dissolved in water by adding PVA to water at 85-95℃ and stirring evenly for 2-4 hours, then cooling to room temperature. In step S1, the solid-liquid ratio of PVA dissolved in water is (5-10) g: 100 mL; the stirring time is 10-20 h. The HBr content in the precursor solution in step S1 is 1.0-2 wt‰; In step S1, the amount of octylamine bromide added is 0.05-0.15 of the molar amount of MABr; The heating treatment in step S3 is carried out at a temperature of 80-90℃ for 3-5 minutes.

2. The method for preparing MAPbBr3 perovskite quantum dot optical films in an aqueous solvent according to claim 1, characterized in that, The micropore diameter in step S2 is 0.4-0.5 μm.

3. The method for preparing MAPbBr3 perovskite quantum dot optical films in an aqueous solvent according to claim 1, characterized in that, Step S4: Air humidity is 30-60%.

Images