All-inorganic perovskite quantum dot composite film and preparation process thereof

Abstract

The invention belongs to the technical field of perovskite luminescent materials, and particularly relates to an all-inorganic perovskite quantum dot composite film and a preparation process thereof.The all-inorganic perovskite quantum dot composite film comprises a substrate film, a quantum dot film and a compact AlF3 film which are sequentially arranged from bottom to top, the chemical formula of the quantum dot film is Cs (YbaMnbZncMgdNieCay) Cl3, compared with an existing equivalent B-site doped modified perovskite CsPbCl3 nano-luminescent material, by unequal doping of metal elements, on one hand, the content of Pb < 2 + > is greatly reduced; and on the other hand, the comprehensive performance of the unequal high-entropy all-inorganic perovskite quantum dot luminescent material obtained by experiments shows more excellent stability and luminescence performance compared with the comprehensive performance of the unequal high-entropy all-inorganic perovskite quantum dot luminescent material doped with equal metal elements.

Description

Technical Field

[0001] The present invention belongs to the technical field of perovskite luminescent materials, and specifically, relates to an all-inorganic perovskite quantum dot composite film and a preparation process thereof. Background Art

[0002] Due to its unique crystal structure and excellent optoelectronic properties, all-inorganic perovskite CsPbX3 (X = Cl / Br / I) has shown great application potential in the fields of solar cells, light-emitting diodes (LEDs), photodetectors, etc. In recent years, all-inorganic perovskite luminescent materials have attracted extensive attention due to their high quantum efficiency, narrow full-width at half-maximum of luminescence, tunable emission peaks in the visible light region, and high absorption coefficients. However, traditional perovskite quantum dot luminescent materials have many challenges in terms of toxicity, luminescence intensity, stability, etc., which limit their practical applications:

[0003] In terms of performance, perovskite luminescent materials have heavy metal toxicity. Perovskite materials often contain heavy metal elements such as lead and cadmium, which pose potential threats to human health and the environment. Therefore, they may be restricted in terms of environmental protection and safety in practical applications.

[0004] In perovskite luminescent materials, the carrier transport performance has an important impact on the luminescence efficiency. High-entropy perovskite luminescent materials may have some problems in carrier transport, such as low carrier mobility, low carrier recombination efficiency. In harsh environments such as high temperature, humidity, and light, high-entropy perovskite luminescent materials are prone to degradation or decomposition, which will affect their luminescence performance and stability.

[0005] In terms of process, the synthesis of high-entropy perovskite luminescent materials mostly uses solid-phase methods and liquid-phase methods such as anion exchange methods and ligand-assisted coprecipitation methods. The preparation process is relatively complex and requires precise control of the proportion of raw materials, reaction conditions, and subsequent treatment steps. This increases the difficulty and cost of preparation and limits their large-scale production and application.

[0006] Therefore, how to improve the stability of perovskite luminescent materials, reduce the lead content, and enable mass production has become one of the current research hotspots. Summary of the Invention

[0007] To solve the above technical problems, the present invention provides a new technical solution:

[0008] An all-inorganic perovskite quantum dot composite film, comprising a substrate film, a quantum dot film, and a dense AlF3 film arranged in sequence from bottom to top. The chemical formula of the quantum dot film is Cs(Yb a Mn b Zn c Mg d Ni e Cay )Cl3, where 0 < a < 1, 0 < b < 1, 0 < c < 1, 0 < d < 1, 0 < e < 1, 0 < y < 1, and the sum of a, b, c, d, e, and y is 1.

[0009] The present invention further provides a preparation process for an all-inorganic perovskite quantum dot composite film, comprising the following steps:

[0010] S1, weighing CsCl2, YbCl3, MnCl2, MgCl2, NiCl2·6H2O, and CaCl2 as raw materials according to the ratio of the chemical formula Cs(Yb a Mn b Zn c Mg d Ni e Ca y )Cl3;

[0011] S2, putting the above raw materials into a ball milling tank and putting the ball milling tank into a vacuum drying oven for the first drying treatment;

[0012] S3, after the first drying treatment, cooling the ball milling tank and the materials inside the ball milling tank, and performing the first ball milling treatment, i.e., pre-ball milling;

[0013] S4, weighing ZnCl2 as an inorganic ligand according to the ratio of the chemical formula Cs(Yb a Mn b Zn c Mg d Ni e Ca y )Cl3, adding it to the ball milling tank, and performing the second ball milling treatment;

[0014] S5, transferring the raw materials after the second ball milling treatment to a centrifuge tube, and putting the centrifuge tube into a drying oven for the second drying treatment;

[0015] S6, transferring the raw materials after the second drying treatment to a mortar for grinding to obtain quantum dot powder, denoted as Cs(Yb a Mn b Zn c Mg d Ni e Ca y )Cl3;

[0016] S7, preparing a quantum dot solution by taking the quantum dot powder and toluene solution, and obtaining an activated quantum dot solution after ultrasonic dispersion and vacuum degassing;

[0017] S8. The fluorine-doped tin oxide film is ultrasonically cleaned successively with acetone and isopropyl alcohol. After cleaning, the fluorine-doped tin oxide film is treated with ultraviolet ozone to obtain a substrate film. The activated quantum dot solution is spin-coated onto the surface of the substrate film, and after the first annealing, a uniform thin film is formed on the substrate film surface. This uniform thin film is the quantum dot thin film, and the overall film structure formed by the quantum dot thin film and the substrate film is an unequal high-entropy all-inorganic perovskite quantum dot thin film.

[0018] S9. Under nitrogen protection, the unequal high-entropy all-inorganic perovskite quantum dot thin film is immersed in an ethanol solution of Al(NO3)3 containing oleic acid to obtain an Al 3+ adsorption film.

[0019] S10. The Al 3+ adsorption film is quickly transferred to an aqueous solution of NH4F for reaction, and a dense AlF3 shell layer is formed on the surface of the unequal high-entropy all-inorganic perovskite quantum dot thin film. This AlF3 shell layer is the dense AlF3 thin film, and the overall film structure of the dense AlF3 thin film and the unequal high-entropy all-inorganic perovskite quantum dot thin film is denoted as the composite film.

[0020] S11. The composite film is rinsed with deionized water and dried with nitrogen, and the all-inorganic perovskite quantum dot composite film is obtained after the second annealing.

[0021] Further, in step S2, the temperature of the first drying treatment is 100 - 120 °C, and the time of the first drying treatment is 30 min.

[0022] Further, in step S3, the ball milling time of the first ball milling treatment is 5 min, and the rotation speed of the high-energy ball mill used in the first ball milling treatment is 1050 rpm.

[0023] Further, in step S4, the ball milling time of the second ball milling treatment is 15 min, and the rotation speed of the high-energy ball mill used in the first ball milling treatment is 1050 rpm.

[0024] Further, in step S5, the temperature of the second drying treatment is 70 °C, and the time of the second drying treatment is 6 h.

[0025] Further, in step S7, the concentration of the quantum dot solution is 10 mg / ml, the ultrasonic dispersion time is 20 min to make the quantum dot solution fully mixed and uniform, and the temperature of vacuum degassing is 60 °C and the time is 30 min to eliminate the bubbles in the quantum dot solution.

[0026] Further, in step S8, the time of ultraviolet ozone treatment is 10 min to enhance the surface hydrophilicity of the fluorine-doped tin oxide film, and the temperature of the first annealing is 60 °C and the time is 5 min.

[0027] Further, in step S11, the composite film is rinsed three times with deionized water. The temperature of the second annealing is 80°C and the time is 10 min. The second annealing can enhance the bonding force between the multilayers of the all-inorganic perovskite quantum dot composite film.

[0028] Further, in step S6, the grinding time is 30 min to make the powder state of the quantum dot powder finer; in step S9, the unequal high-entropy all-inorganic perovskite quantum dot thin film is immersed in an ethanol solution of Al(NO3)3 containing 5% by mass of oleic acid and with a concentration of 0.1 mol / L for 30 s, so that Al 3+ is adsorbed on the surface of the unequal high-entropy all-inorganic perovskite quantum dot thin film; in step S10, the concentration of the NH4F aqueous solution is 0.3 mol / L and pH = 5, and the reaction time of the Al 3+ adsorption film in the NH4F aqueous solution is 1 min, and a dense AlF3 shell layer is formed on the surface of the unequal high-entropy all-inorganic perovskite quantum dot thin film.

[0029] The present invention also includes other devices, steps or components that can enable the normal use of the all-inorganic perovskite quantum dot composite film and its preparation process, which are all conventional technical means in the art. In addition, the high-energy ball mill and the fluorine-doped tin oxide film not defined in the present invention both adopt conventional technical means in the art.

[0030] The working principle of the present invention is that the present invention adopts the method of unequal high entropy. By using the fact that the Mn 2+ energy level structure is deep below the valence band, and the electron shell 3d 5 4T 1 to 6A 1 electron configuration transition, with a stable luminescence center and obvious exciton peaks, the luminescence performance of the all-inorganic perovskite luminescent material is improved by increasing the Mn 2+ concentration, and further reducing the lead content. At the same time, an inorganic ligand ZnCl2 is introduced to form a stable coordination structure with the uncoordinated Cl － on the surface of the perovskite to passivate surface defects; secondly, ZnCl2 regulates the crystal growth kinetics through a dynamic coordination equilibrium mechanism. Its fast ligand exchange characteristics can achieve the control of the uniformity of quantum dot size and a relatively narrow full width at half maximum at the same time; the d 10 orbital of Zn and the d-d orbital of Mn are synergistically enhanced to optimize the exciton transition path and improve the photoluminescence intensity (PL). AlF3 is selected as the encapsulating material. Using the wide bandgap of AlF3 as an energy barrier to inhibit carrier escape; making F － combine with the uncoordinated Mn 2+ on the quantum dot surface to form a stable F-Mn bridging structure to inhibit ion migration; the octahedral field of AlF3 can stabilize the 3d 2+ of Mn5 The electronic configuration reduces the interference of Jahn-Teller distortion on luminescence. In addition, in the synthesis and preparation process, a high-energy ball milling method is combined with an in-situ composite method to prepare an all-inorganic perovskite quantum dot composite film at low temperature. By using the unique "∞-shaped" running trajectory of high-energy ball milling, a large number of quantum dots can be prepared by mechanochemistry. Subsequently, through a liquid-phase reaction, an aluminum source is first introduced to coordinate with the surface of the quantum dots at 60 °C, and then fluorination is carried out slowly to avoid homogeneous nucleation of AlF3 in the solution. Compared with non-wrapped ones, this in-situ wrapping forms a heterojunction between the perovskite and AlF3 to passivate surface defects, and at the same time greatly improves the fluorescence quantum yield (PLQYs).

[0031] The beneficial effects of the present invention are as follows:

[0032] (1) Compared with the existing perovskite CsPbCl3 nanoluminescent materials doped with equal amounts of B-site modification, the present invention synthesizes stable unequal high-entropy perovskite quantum dots with excellent luminescence performance by doping metal elements in unequal amounts, increasing the Mn 2+ content to 50% - 90%, and when the performance is measured to be the best, the Mn 2+ proportion is 50%. On the one hand, this significantly reduces the Pb 2+ content. On the other hand, the comprehensive performance of the unequal high-entropy all-inorganic perovskite quantum dot luminescent materials obtained by the experiment shows more excellent stability and luminescence performance compared with the doping of equal amounts of metal elements.

[0033] (2) With the assistance of the ZnCl2 ligand, it not only helps to realize the synthesis of truly all-inorganic perovskite quantum dots, but also effectively improves the stability and luminescence performance of the quantum dots.

[0034] (3) The perovskite quantum dots are wrapped by an in-situ composite method. NH4F is used to react on the surface of the quantum dots to generate AlF3, avoiding high-temperature phase transformation, reducing surface defects, and at the same time the wrapping process improves the luminescence intensity and stability of the material.

[0035] (4) The heterojunction jointly constructed by AlF3 and Mn 2+ significantly improves the performance of perovskite quantum dots, forms a Type-I energy level structure, inhibits non-radiative recombination, and greatly improves the fluorescence quantum yield, luminescence intensity, and antioxidant ability. Description of the Drawings

[0036] The present invention will be further described below with reference to the drawings and embodiments.

[0037] Figure 1 is a process flow chart for preparing an all-inorganic perovskite quantum dot composite film.

[0038] Figure 2 is Cs(Yb 1 / 10Mn 1 / 2 Zn 1 / 10 Mg 1 / 10 Ni 1 / 10 Ca 1 / 10 ) TEM images of Cs(Yb

[0039] Figure 3 is Cs(Yb 1 / 10 Mn 1 / 2 Zn 1 / 10 Mg 1 / 10 Ni 1 / 10 Ca 1 / 10 )Cl3, Cs(Yb 4 / 25 Mn 1 / 5 Zn 4 / 25 Mg 4 / 25 Ni 4 / 25 Ca 4 / 25 )Cl3, Cs(Yb 3 / 50 Mn 7 / 10 Zn 3 / 50 Mg 3 / 50 Ni 3 / 50 Ca 3 / 50 )Cl3's luminescence intensity comparison chart.

[0040] Figure 4 is Cs(Yb 1 / 10 Mn 1 / 2 Zn 1 / 10 Mg 1 / 10 Ni 1 / 10 Ca 1 / 10 )Cl3, Cs(Mn 1 / 5 Zn 1 / 5 Mg 1 / 5 Ni 1 / 5 Pb 1 / 5 )Cl3, Cs(Mn 1 / 2 Pb 1 / 2 )Cl3, CsPbCl3's luminescence intensity comparison chart.

[0041] Figure 5 is Cs(Yb 1 / 10 Mn 1 / 2 Zn 1 / 10 Mg 1 / 10 Ni 1 / 10 Ca 1 / 10 )Cl3, Cs(Mn 1 / 5 Zn 1 / 5 Mg 1 / 5 Ni 1 / 5 Pb 1 / 5 )Cl3, Cs(Mn 1 / 2 Pb 1 / 2 )Cl3, CsPbCl3's XRD pattern. Detailed implementation manners

[0042] The present invention will be clearly described below in conjunction with the accompanying drawings in the embodiments of the present invention and specific embodiments. The description here is only used to explain the present invention, but not to limit the present invention. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative work, any modifications, equivalent replacements, improvements, etc., shall be included in the protection scope of the present invention.

[0043] Embodiment 1

[0044] This embodiment provides an all-inorganic perovskite quantum dot composite film, which includes a substrate film, a quantum dot film, and a dense AlF3 film arranged in sequence from bottom to top. The chemical formula of the quantum dot film is Cs(Yb 1 / 10 Mn 1 / 2 Zn 1 / 10 Mg 1 / 10 Ni 1 / 10 Ca 1 / 10 )Cl3.

[0045] As shown in Figure 1 , this embodiment further provides a preparation process for an all-inorganic perovskite quantum dot composite film, including the following steps:

[0046] S1, aiming to prepare 6 mmol of Cs(Yb 1 / 10 Mn 1 / 2 Zn 1 / 10 Mg 1 / 10 Ni 1 / 10 Ca 1 / 10 )Cl3 quantum dot film, according to the molar ratio of CsCl2∶YbCl3∶MnCl2∶MgCl2∶NiCl2·6H2O∶CaCl2 = 10∶1∶5∶1∶1∶1 in the chemical formula Cs(Yb 1 / 10 Mn 1 / 2 Zn 1 / 10 Mg 1 / 10 Ni 1 / 10 Ca 1 / 10 )Cl3, weigh CsCl2, YbCl3, MnCl2, MgCl2, NiCl2·6H2O, and CaCl2 as raw materials.

[0047] S2, put the above raw materials into a ball milling tank, and put the ball milling tank into a vacuum drying oven for the first drying treatment;

[0048] S3, after the first drying treatment, cool the ball milling tank and the materials in the ball milling tank, and then perform the first ball milling treatment, that is, pre-ball milling;

[0049] S4, according to the ratio of the chemical formula Cs(Yb 1 / 10 Mn 1 / 2 Zn 1 / 10 Mg 1 / 10 Ni 1 / 10 Ca 1 / 10 )Cl3, weigh ZnCl2 as an inorganic ligand in a molar ratio of CsCl2∶ZnCl2 = 10∶1, add it to the ball milling jar, and perform the second ball milling treatment;

[0050] S5, transfer the raw materials after the second ball milling treatment into a centrifuge tube, and place the centrifuge tube in an oven for the second drying treatment;

[0051] S6, transfer the raw materials after the second drying treatment into a mortar for grinding to obtain quantum dot powder, denoted as Cs(Yb 1 / 10 Mn 1 / 2 Zn 1 / 10 Mg 1 / 10 Ni 1 / 10 Ca 1 / 10 )Cl3;

[0052] S7, take the quantum dot powder and toluene solution to prepare a quantum dot solution, and after ultrasonic dispersion and vacuum degassing, obtain an activated quantum dot solution;

[0053] S8, ultrasonically clean the fluorine-doped tin oxide film successively with acetone and isopropanol, and after the cleaning, the fluorine-doped tin oxide film is treated with ultraviolet ozone to obtain a substrate film; spin-coat the activated quantum dot solution onto the surface of the substrate film, and after the first annealing, form a uniform film on the surface of the substrate film. This uniform film is the quantum dot film, and the overall film structure formed by the quantum dot film and the substrate film is an unequal high-entropy all-inorganic perovskite quantum dot film;

[0054] S9, under nitrogen protection, immerse the unequal high-entropy all-inorganic perovskite quantum dot film in an ethanol solution of Al(NO3)3 containing oleic acid to obtain an Al 3+ adsorption film;

[0055] S10, quickly transfer the Al 3+ adsorption film to a 0.3 mol / L aqueous solution of NH4F (pH = 5) for reaction, and a dense AlF3 shell layer is formed on the surface of the unequal high-entropy all-inorganic perovskite quantum dot film. This AlF3 shell layer is the dense AlF3 film, and the overall film structure of the dense AlF3 film and the unequal high-entropy all-inorganic perovskite quantum dot film is denoted as the composite film;

[0056] S11, rinse the composite film with ionized water, blow-dry the composite film with nitrogen, and obtain the all-inorganic perovskite quantum dot composite film after the second annealing, denoted as film 1.

[0057] As a further measure of this embodiment, in step S2, the temperature of the first drying treatment is 110 °C, and the time of the first drying treatment is 30 min; in step S3, the diameters of the two zirconia grinding balls for the first ball milling treatment are 16 mm, the total weight is 14.6 g, the ball milling time is 5 min, and the rotation speed of the high-energy ball mill used in the first ball milling treatment is 1050 rpm; in step S4, the diameters of the two zirconia grinding balls for the second ball milling treatment are 12 mm, the total weight is 11.2 g, the ball milling time is 15 min, and the rotation speed of the high-energy ball mill used in the first ball milling treatment is 1050 rpm; in step S5, the temperature of the second drying treatment is 70 °C, and the time of the second drying treatment is 6 h; in step S7, the concentration of the quantum dot solution is 10 mg / ml, the ultrasonic dispersion time is 20 min to fully mix and homogenize the quantum dot solution, the temperature of vacuum degassing is 60 °C and the time is 30 min to eliminate the bubbles in the quantum dot solution; in step S8, the time of ultraviolet ozone treatment is 10 min to enhance the surface hydrophilicity of the fluorine-doped tin oxide film, the temperature of the first annealing is 60 °C and the time is 5 min; in step S11, the composite film is rinsed 3 times with ionized water, the temperature of the second annealing is 80 °C and the time is 10 min, and the second annealing can enhance the bonding force between the multilayer films of the all-inorganic perovskite quantum dot composite film; in step S6, the grinding time is 30 min to make the powder state of the quantum dot powder finer; in step S9, the unequal high-entropy all-inorganic perovskite quantum dot film is immersed in an ethanol solution of Al(NO3)3 with a mass fraction of 5% oleic acid and a concentration of 0.1 mol / L, and the immersion time is 30 s to make Al 3+ adsorb on the surface of the unequal high-entropy all-inorganic perovskite quantum dot film; in step S10, the concentration of the NH4F aqueous solution is 0.3 mol / L and pH = 5, and the reaction time of the Al 3+ adsorption film in the NH4F aqueous solution is 1 min to form a dense AlF3 shell layer on the surface of the unequal high-entropy all-inorganic perovskite quantum dot film.

[0058] As Figure 2 shown, it is a TEM image of the quantum dot powder with the chemical formula Cs(Yb 1 / 10 Mn 1 / 2 Zn 1 / 10 Mg 1 / 10 Ni 1 / 10 Ca 1 / 10 )Cl3.

[0059] Example 2

[0060] This embodiment provides an all-inorganic perovskite quantum dot composite film, including a substrate film, a quantum dot film, and a dense AlF3 film sequentially arranged from bottom to top. The chemical formula of the quantum dot film is Cs(Yb4 / 25 Mn 1 / 5 Zn 4 / 25 Mg 4 / 25 Ni 4 / 25 Ca 4 / 25 )Cl3。

[0061] This embodiment further provides a preparation process for an all-inorganic perovskite quantum dot composite film, including the following steps:

[0062] S1. Taking the preparation of 6 mmol of Cs(Yb 4 / 25 Mn 1 / 5 Zn 4 / 25 Mg 4 / 25 Ni 4 / 25 Ca 4 / 25 )Cl3 quantum dot thin film as the target, according to the molar ratio of CsCl2∶YbCl3∶MnCl2∶MgCl2∶NiCl2·6H2O∶CaCl2 = 25∶4∶5∶4∶4∶4 in the chemical formula Cs(Yb 4 / 25 Mn 1 / 5 Zn 4 / 25 Mg 4 / 25 Ni 4 / 25 Ca 4 / 25 )Cl3, weigh CsCl2, YbCl3, MnCl2, MgCl2, NiCl2·6H2O and CaCl2 as raw materials.

[0063] S2. Put the above raw materials into a ball milling tank, and put the ball milling tank into a vacuum drying oven for the first drying treatment;

[0064] S3. After the first drying treatment, cool the ball milling tank and the materials in the ball milling tank, and then conduct the first ball milling treatment, that is, pre-ball milling;

[0065] S4. According to the chemical formula Cs(Yb 4 / 25 Mn 1 / 5 Zn 4 / 25 Mg 4 / 25 Ni 4 / 25 Ca 4 / 25 )Cl3, weigh ZnCl2 as an inorganic ligand according to the molar ratio of CsCl2∶ZnCl2 = 25∶4, add it to the ball milling tank, and conduct the second ball milling treatment;

[0066] S5. Transfer the raw materials after the second ball milling treatment to a centrifuge tube, and put the centrifuge tube into a drying oven for the second drying treatment;

[0067] S6. Transfer the raw materials after the second drying treatment to a mortar for grinding to obtain quantum dot powder, denoted as Cs(Yb 4 / 25Mn 1 / 5 Zn 4 / 25 Mg 4 / 25 Ni 4 / 25 Ca 4 / 25 )Cl3;

[0068] S7. Prepare a quantum dot solution by mixing the quantum dot powder and toluene solution. After ultrasonic dispersion and vacuum degassing, an activated quantum dot solution is obtained;

[0069] S8. Ultrasonically clean the fluorine-doped tin oxide film successively with acetone and isopropanol. After cleaning, the fluorine-doped tin oxide film is treated with ultraviolet ozone to obtain a substrate film. Spin-coat the activated quantum dot solution onto the surface of the substrate film. After the first annealing, a uniform film is formed on the surface of the substrate film. This uniform film is the quantum dot film. The overall film structure formed by the quantum dot film and the substrate film is an unequal high-entropy all-inorganic perovskite quantum dot film;

[0070] S9. Under nitrogen protection, immerse the unequal high-entropy all-inorganic perovskite quantum dot film in an ethanol solution of Al(NO3)3 containing oleic acid to obtain an Al 3+ adsorption film;

[0071] S10. Quickly transfer the Al 3+ adsorption film to an aqueous NH4F solution for reaction. A dense AlF3 shell layer is formed on the surface of the unequal high-entropy all-inorganic perovskite quantum dot film. This AlF3 shell layer is the dense AlF3 film. Denote the overall film structure of the dense AlF3 film and the unequal high-entropy all-inorganic perovskite quantum dot film as the composite film;

[0072] S11. Rinse the composite film with ionized water, dry the composite film with nitrogen, and obtain the all-inorganic perovskite quantum dot composite film after the second annealing, denoted as film 2.

[0073] As a further measure of this embodiment, in step S2, the temperature of the first drying treatment is 110 °C and the time of the first drying treatment is 30 min; in step S3, the diameters of the two zirconia grinding balls for the first ball milling treatment are 16 mm, the total weight is 14.6 g, the ball milling time is 5 min, and the rotation speed of the high-energy ball mill used in the first ball milling treatment is 1050 rpm; in step S4, the diameters of the two zirconia grinding balls for the second ball milling treatment are 12 mm, the total weight is 11.2 g, the ball milling time is 15 min, and the rotation speed of the high-energy ball mill used in the first ball milling treatment is 1050 rpm; in step S5, the temperature of the second drying treatment is 70 °C and the time of the second drying treatment is 6 h; in step S7, the concentration of the quantum dot solution is 10 mg / ml, the ultrasonic dispersion time is 20 min to fully mix and homogenize the quantum dot solution, the temperature of vacuum degassing is 60 °C and the time is 30 min to eliminate the bubbles in the quantum dot solution; in step S8, the time of ultraviolet ozone treatment is 10 min to enhance the surface hydrophilicity of the fluorine-doped tin oxide film, the temperature of the first annealing is 60 °C and the time is 5 min; in step S11, the composite film is rinsed 3 times with ionized water, the temperature of the second annealing is 80 °C and the time is 10 min, and the second annealing can enhance the bonding force between the multi-layers of the all-inorganic perovskite quantum dot composite film; in step S6, the grinding time is 30 min to make the powder state of the quantum dot powder finer; in step S9, the unequal high-entropy all-inorganic perovskite quantum dot thin film is immersed in an ethanol solution of Al(NO3)3 with a mass fraction of 5% oleic acid and a concentration of 0.1 mol / L, and the immersion time is 30 s to make Al 3+ adsorb on the surface of the unequal high-entropy all-inorganic perovskite quantum dot thin film; in step S10, the concentration of the NH4F aqueous solution is 0.3 mol / L and pH = 5, and the reaction time of the Al 3+ adsorption film in the NH4F aqueous solution is 1 min to form a dense AlF3 shell layer on the surface of the unequal high-entropy all-inorganic perovskite quantum dot thin film.

[0074] Example 3

[0075] This embodiment provides an all-inorganic perovskite quantum dot composite film, including a substrate film, a quantum dot thin film, and a dense AlF3 thin film arranged in sequence from bottom to top. The chemical formula of the quantum dot thin film is Cs(Yb 3 / 50 Mn 7 / 10 Zn 3 / 50 Mg 3 / 50 Ni 3 / 50 Ca 3 / 50 )Cl3.

[0076] This embodiment further provides a preparation process for an all-inorganic perovskite quantum dot composite film, including the following steps:

[0077] S1, aiming to prepare a 6 mmol Cs(Yb 3 / 50 Mn 7 / 10 Zn 3 / 50 Mg 3 / 50 Ni 3 / 50 Ca 3 / 50 )Cl3 quantum dot film, according to the molar ratio of CsCl2∶YbCl3∶MnCl2∶MgCl2∶NiCl2·6H2O∶CaCl2 = 50∶3∶35∶3∶3∶3 in the chemical formula Cs(Yb 3 / 50 Mn 7 / 10 Zn 3 / 50 Mg 3 / 50 Ni 3 / 50 Ca 3 / 50 )Cl3, weigh CsCl2, YbCl3, MnCl2, MgCl2, NiCl2·6H2O and CaCl2 as raw materials.

[0078] S2, put the above raw materials into a ball mill jar, and put the ball mill jar into a vacuum drying oven for the first drying treatment;

[0079] S3, after the first drying treatment, cool the ball mill jar and the materials in the ball mill jar, and then conduct the first ball milling treatment, that is, pre-ball milling;

[0080] S4, according to the chemical formula Cs(Yb 3 / 50 Mn 7 / 10 Zn 3 / 50 Mg 3 / 50 Ni 3 / 50 Ca 3 / 50 )Cl3, weigh ZnCl2 as an inorganic ligand according to the molar ratio of CsCl2∶ZnCl2 = 50∶3, add it to the ball mill jar, and conduct the second ball milling treatment;

[0081] S5, transfer the raw materials after the second ball milling treatment to a centrifuge tube, and put the centrifuge tube into a drying oven for the second drying treatment;

[0082] S6, transfer the raw materials after the second drying treatment to a mortar for grinding to obtain quantum dot powder, denoted as Cs(Yb 3 / 50 Mn 7 / 10 Zn 3 / 50 Mg 3 / 50 Ni 3 / 50 Ca 3 / 50 )Cl3;

[0083] S7. Prepare a quantum dot solution by mixing quantum dot powder and toluene solution. After ultrasonic dispersion and vacuum degassing, an activated quantum dot solution is obtained;

[0084] S8. Ultrasonically clean the fluorine-doped tin oxide film successively with acetone and isopropyl alcohol. After cleaning, the fluorine-doped tin oxide film is treated with ultraviolet ozone to obtain a substrate film. Spin-coat the activated quantum dot solution onto the surface of the substrate film, and form a uniform thin film on the surface of the substrate film after the first annealing. This uniform thin film is the quantum dot thin film, and the overall film structure formed by the quantum dot thin film and the substrate film is an unequal high-entropy all-inorganic perovskite quantum dot thin film;

[0085] S9. Under nitrogen protection, immerse the unequal high-entropy all-inorganic perovskite quantum dot thin film into an ethanol solution of Al(NO3)3 containing oleic acid to obtain an Al 3+ adsorption film;

[0086] S10. Quickly transfer the Al 3+ adsorption film to an aqueous solution of NH4F for reaction. A dense AlF3 shell layer is formed on the surface of the unequal high-entropy all-inorganic perovskite quantum dot thin film. This AlF3 shell layer is the dense AlF3 thin film. Denote the overall film structure of the dense AlF3 thin film and the unequal high-entropy all-inorganic perovskite quantum dot thin film as the composite film;

[0087] S11. Rinse the composite film with ionized water, dry the composite film with nitrogen, and obtain the all-inorganic perovskite quantum dot composite film after the second annealing, denoted as film 3.

[0088] As a further measure of this embodiment, in step S2, the temperature of the first drying treatment is 110 °C, and the time of the first drying treatment is 30 min; in step S3, the diameters of the two zirconia grinding balls in the first ball milling treatment are 16 mm, the total weight is 14.6 g, the ball milling time is 5 min, and the rotation speed of the high-energy ball mill used in the first ball milling treatment is 1050 rpm; in step S4, the diameters of the two zirconia grinding balls in the second ball milling treatment are 12 mm, the total weight is 11.2 g, the ball milling time is 15 min, and the rotation speed of the high-energy ball mill used in the first ball milling treatment is 1050 rpm; in step S5, the temperature of the second drying treatment is 70 °C, and the time of the second drying treatment is 6 h; in step S7, the concentration of the quantum dot solution is 10 mg / ml, the ultrasonic dispersion time is 20 min to fully mix and homogenize the quantum dot solution, the temperature of vacuum degassing is 60 °C and the time is 30 min to eliminate the bubbles in the quantum dot solution; in step S8, the time of ultraviolet ozone treatment is 10 min to enhance the surface hydrophilicity of the fluorine-doped tin oxide film, the temperature of the first annealing is 60 °C and the time is 5 min; in step S11, the composite film is rinsed 3 times with ionized water, the temperature of the second annealing is 80 °C and the time is 10 min, and the second annealing can enhance the bonding force between the multi-layers of the all-inorganic perovskite quantum dot composite film; in step S6, the grinding time is 30 min to make the powder state of the quantum dot powder finer; in step S9, the unequal high-entropy all-inorganic perovskite quantum dot film is immersed in an ethanol solution of Al(NO3)3 with a mass fraction of 5% oleic acid and a concentration of 0.1 mol / L for 30 s to make Al 3+ adsorbed on the surface of the unequal high-entropy all-inorganic perovskite quantum dot film; in step S10, the concentration of the NH4F aqueous solution is 0.3 mol / L and pH = 5, and the reaction time of the Al 3+ adsorption film in the NH4F aqueous solution is 1 min to form a dense AlF3 shell layer on the surface of the unequal high-entropy all-inorganic perovskite quantum dot film.

[0089] Characterization experiments were carried out on items such as the thickness, thermal shrinkage rate, and tensile strength of film 1, film 2, and film 3. The experimental data of the thickness, thermal shrinkage rate, tensile strength, etc. of film 1, film 2, and film 3 are shown in Table 1, and the experimental data of each item of film 1, film 2, and film 3 all fall within the range shown in Table 1.

[0090] Table 1: Experimental data table of each item of film 1, film 2, and film 3

[0091]

[0092] As Figure 3 shown is Cs(Yb 1 / 10 Mn 1 / 2 Zn1 / 10 Mg 1 / 10 Ni 1 / 10 Ca 1 / 10 )Cl3, Cs(Yb 4 / 25 Mn 1 / 5 Zn 4 / 25 Mg 4 / 25 Ni 4 / 25 Ca 4 / 25 )Cl3, Cs(Yb 3 / 50 Mn 7 / 10 Zn 3 / 50 Mg 3 / 50 Ni 3 / 50 Ca 3 / 50 )Cl3 emission intensity comparison chart.

[0093] Comparative Example 1

[0094] This comparative example aims to prepare quantum dot powder with the chemical formula Cs(Mn 1 / 5 Zn 1 / 5 Mg 1 / 5 Ni 1 / 5 Pb 1 / 5 )Cl3, including the following steps:

[0095] S1. Aiming to prepare 6 mmol of Cs(Mn 1 / 5 Zn 1 / 5 Mg 1 / 5 Ni 1 / 5 Pb 1 / 5 )Cl3 quantum dot powder, according to the molar ratio of CsCl2∶MnCl2∶MgCl2∶NiCl2·6H2O∶PbCl2 = 5∶1∶1∶1∶1 in the chemical formula Cs(Mn 1 / 5 Zn 1 / 5 Mg 1 / 5 Ni 1 / 5 Pb 1 / 5 )Cl3, weigh CsCl2, MnCl2, MgCl2, NiCl2·6H2O and PbCl2 as raw materials;

[0096] S2. Put the above raw materials into a ball milling tank, and put the ball milling tank into a vacuum drying oven for the first drying treatment.

[0097] S3. After the first drying treatment, cool the ball milling tank and the materials in the ball milling tank, and then conduct the first ball milling treatment, which is the pre-ball milling.

[0098] S4. According to the chemical formula Cs(Mn 1 / 5 Zn 1 / 5 Mg 1 / 5 Ni 1 / 5 Pb1 / 5 )The proportion of Cl3: Weigh ZnCl2 as an inorganic ligand in a molar ratio of CsCl2∶ZnCl2 = 5∶1, add it to the ball milling jar, and conduct the second ball milling treatment.

[0099] S5: Transfer the raw materials after the second ball milling treatment into a centrifuge tube, and place the centrifuge tube in a drying oven for the second drying treatment.

[0100] S6: Transfer the raw materials after the second drying treatment into a mortar for grinding to obtain quantum dot powder, denoted as Cs(Mn 1 / 5 Zn 1 / 5 Mg 1 / 5 Ni 1 / 5 Pb 1 / 5 )Cl3.

[0101] As a further measure of this embodiment, in step S2, the temperature of the first drying treatment is 110°C, and the time of the first drying treatment is 30 min; in step S3, the diameter of the zirconia grinding balls used in the first ball milling treatment is 16 mm, the total weight is 14.6 g, the ball milling time is 5 min, and the rotation speed of the high-energy ball mill used in the first ball milling treatment is 1050 rpm; in step S4, the diameter of the zirconia grinding balls used in the second ball milling treatment is 12 mm, the total weight is 11.2 g, the ball milling time is 15 min, and the rotation speed of the high-energy ball mill used in the second ball milling treatment is 1050 rpm; in step S5, the temperature of the second drying is 70°C, and the time of the second drying treatment is 6 h; in step S6, the grinding time is 30 min.

[0102] Comparative Example 2

[0103] This comparative example aims to prepare quantum dot powder with the chemical formula Cs(Mn 1 / 2 Pb 1 / 2 )Cl3, including the following steps:

[0104] S1: Aiming to prepare 6 mmol of Cs(Mn 1 / 2 Pb 1 / 2 )Cl3 quantum dot powder, weigh CsCl2, MnCl2, and PbCl2 as raw materials according to the molar ratio of CsCl2∶MnCl2∶PbCl2 = 2∶1∶1 in the chemical formula Cs(Mn 1 / 2Pb 1 / 2 )Cl3;

[0105] S2: Put the above raw materials into a ball milling jar, and place the ball milling jar in a vacuum drying oven for the first drying treatment.

[0106] S3. After the first drying treatment is completed, cool the ball milling tank and the materials inside the ball milling tank, and then perform the first ball milling treatment, which is the pre-ball milling.

[0107] S4. Without adding inorganic ligands, perform the second ball milling treatment on the materials in the ball milling tank.

[0108] S5. Transfer the raw materials after the second ball milling treatment to a centrifuge tube, and place the centrifuge tube in a drying oven for the second drying treatment.

[0109] S6. Transfer the raw materials after the second drying treatment to a mortar for grinding to obtain quantum dot powder, denoted as Cs(Mn 1 / 2 Pb 1 / 2 )Cl3.

[0110] As a further measure of this embodiment, in step S2, the temperature of the first drying treatment is 110 °C, and the time of the first drying treatment is 30 min; in step S3, the diameter of the zirconia grinding balls used in the first ball milling treatment is 16 mm, the total weight is 14.6 g, the ball milling time is 5 min, and the rotation speed of the high-energy ball mill used in the first ball milling treatment is 1050 rpm; in step S4, the diameter of the zirconia grinding balls used in the second ball milling treatment is 12 mm, the total weight is 11.2 g, the ball milling time is 15 min, and the rotation speed of the high-energy ball mill used in the second ball milling treatment is 1050 rpm; in step S5, the temperature of the second drying is 70 °C, and the time of the second drying treatment is 6 h; in step S6, the grinding time is 30 min.

[0111] Comparative Example 3

[0112] This comparative example aims to prepare quantum dot powder with the chemical formula CsPbCl3, and includes the following steps:

[0113] S1. Aiming to prepare 6 mmol of CsPbCl3 quantum dot powder, weigh CsCl2 and PbCl2 as raw materials according to the molar ratio of CsCl2∶PbCl2 = 1∶1 in the chemical formula CsPbCl3.

[0114] S2. Put the above raw materials into a ball milling tank, and place the ball milling tank in a vacuum drying oven for the first drying treatment.

[0115] S3. After the first drying treatment is completed, cool the ball milling tank and the materials inside the ball milling tank, and then perform the first ball milling treatment, which is the pre-ball milling.

[0116] S4. Without adding inorganic ligands, perform the second ball milling treatment on the materials in the ball milling tank.

[0117] S5. After the second ball milling treatment, the raw materials are transferred into a centrifuge tube, and the centrifuge tube is placed in an oven for the second drying treatment.

[0118] S6. After the second drying treatment, the raw materials are transferred into a mortar for grinding to obtain quantum dot powder, denoted as CsPbCl3.

[0119] As a further measure of this embodiment, in step S2, the temperature of the first drying treatment is 110 °C, and the time of the first drying treatment is 30 min; in step S3, the diameter of the zirconia grinding balls used in the first ball milling treatment is 16 mm, the total weight is 14.6 g, the ball milling time is 5 min, and the rotation speed of the high-energy ball mill used in the first ball milling treatment is 1050 rpm; in step S4, the diameter of the zirconia grinding balls used in the second ball milling treatment is 12 mm, the total weight is 11.2 g, the ball milling time is 15 min, and the rotation speed of the high-energy ball mill used in the second ball milling treatment is 1050 rpm; in step S5, the temperature of the second drying treatment is 70 °C, and the drying time of the second drying treatment is 6 h; in step S6, the grinding time is 30 min.

[0120] As Figure 4 、 Figure 5 shown, through the luminescence intensity spectrum and X-ray diffraction (XRD) analysis of perovskite structures with different compositions, it can be seen that Cs(Yb 1 / 10 Mn 1 / 2 Zn 1 / 10 Mg 1 / 10 Ni 1 / 10 Ca 1 / 10 )Cl3 exhibits the strongest emission peak, indicating its unique fluorescence transition characteristics, while the fluorescence intensity of CsPbCl3 is weak, indicating that the change in composition has a significant impact on the fluorescence performance; it can be seen from the XRD pattern that Cs(Yb 1 / 10 Mn 1 / 2 Zn 1 / 10 Mg 1 / 10 Ni 1 / 10 Ca 1 / 10 )Cl3 basically conforms to the peak pattern of the standard PDF card of CsPbCl3. As the doping element increases, the peak pattern becomes sharper, indicating that the quantum dot particle size is smaller and the crystal form is more perfect. In summary, it is concluded that the type and proportion of metal ions in the compound have an important regulatory effect on both the fluorescence performance and the crystal structure, providing a theoretical basis and design idea for the development of functional materials with specific optical and crystallographic properties.

[0121] The all-inorganic perovskite quantum dot composite film is prepared from quantum dot powder. The performance of the quantum dot powder directly affects the properties of the all-inorganic perovskite quantum dot composite film. The greater the luminescence intensity of the quantum dot powder, the better the luminescence performance of the all-inorganic perovskite quantum dot composite film.

[0122] The present invention adopts the method of unequal high entropy and utilizes Mn 2+ The energy level structure is deeply hidden below the valence band, and the electron shell is 3d 5 of 4T 1 to 6A 1 The characteristic of stable luminescence center and obvious exciton peak can be generated by the transition of electron configuration. By increasing the Mn 2+ concentration to improve the luminescence performance of the all-inorganic perovskite luminescent material, and further reduce the lead content.

[0123] The present invention introduces the inorganic ligand ZnCl2 to form a stable coordination structure with the uncoordinated Cl on the surface of the perovskite, passivating the surface defects; and ZnCl2 regulates the crystal growth kinetics through the dynamic coordination equilibrium mechanism. Its fast ligand exchange property can realize the control of the uniformity of quantum dot size and achieve a relatively narrow full width at half maximum at the same time; the d － orbital of Zn and the d-d orbital of Mn synergistically enhance the effect, optimize the exciton transition path, and improve the photoluminescence intensity (PL). 10

[0124] The present invention selects AlF3 as the encapsulating material, uses the wide bandgap of AlF3 as an energy barrier to inhibit the escape of carriers; makes F － combine with the uncoordinated Mn on the surface of the quantum dots 2+ to form a stable F-Mn bridging structure, inhibiting ion migration; the octahedral field of AlF3 can stabilize the 3d 2+ electron configuration of Mn 5 and reduce the interference of Jahn-Teller distortion on luminescence.

[0125] In addition, in the synthesis and preparation process, the all-inorganic perovskite quantum dot composite film is prepared at low temperature by combining high-energy ball milling method and in-situ composite method. By using the unique "∞-shaped" running track of high-energy ball milling, a large number of quantum dots can be prepared by mechanochemistry. Subsequently, through a liquid-phase reaction, the aluminum source is first introduced to coordinate with the surface of the quantum dots at 60 °C, and then slowly fluorinated to avoid the homogeneous nucleation of AlF3 in the solution. Compared with non-encapsulation, this in-situ encapsulation forms a heterojunction between the perovskite and AlF3 to passivate the surface defects, and greatly improves the fluorescence quantum yield (PLQYs).

[0126] The embodiments of the present invention have been described above. The above description is exemplary and not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations are obvious to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A fully inorganic perovskite quantum dot composite film, characterized in that: It includes a basement membrane, a quantum dot thin film, and a dense AlF3 thin film that are sequentially arranged from bottom to top. The chemical formula of the quantum dot thin film is Cs(Yb a Mn b Zn c Mg d Ni e Ca y )Cl3, where 0 < a < 1, 0 < b < 1, 0 < c < 1, 0 < d < 1, 0 < e < 1, 0 < y < 1, and the sum of a, b, c, d, e, and y is 1.

2. The preparation process of an all-inorganic perovskite quantum dot composite film according to claim 1, characterized in that, It includes the following steps: S1, according to the ratio of the chemical formula Cs(Yb a Mn b Zn c Mg d Ni e Ca y )Cl3, weigh CsCl2, YbCl3, MnCl2, MgCl2, NiCl2·6H2O and CaCl2 as raw materials; S2, put the above raw materials into a ball milling jar, and put the ball milling jar into a vacuum drying oven for the first drying treatment; S3, after the first drying treatment, cool the ball milling jar and the materials in the ball milling jar, and conduct the first ball milling treatment; S4, according to the formula Cs(Yb a Mn b Zn c Mg d Ni e Ca y )Cl3 ratio, weigh ZnCl2 as an inorganic ligand, add it to the ball milling tank, and perform the second ball milling treatment; S5, transfer the raw materials after the second ball milling treatment into a centrifuge tube, and put the centrifuge tube into a drying oven for the second drying treatment; S6. After the second drying treatment, the raw materials are transferred to a mortar for grinding to obtain quantum dot powder, denoted as Cs(Yb a Mn b Zn c Mg d Ni e Ca y )Cl3; S7, take quantum dot powder and toluene solution to prepare a quantum dot solution, and after ultrasonic dispersion and vacuum degassing, obtain an activated quantum dot solution; S8, ultrasonically clean the fluorine-doped tin oxide film successively with acetone and isopropyl alcohol. After cleaning, the fluorine-doped tin oxide film is treated with ultraviolet ozone to obtain a substrate film; spin-coat the activated quantum dot solution onto the surface of the substrate film, and after the first annealing, a uniform film is formed on the surface of the substrate film. This uniform film is the quantum dot film, and the overall film structure formed by the quantum dot film and the substrate film is an unequal high-entropy all-inorganic perovskite quantum dot film; S9, Under nitrogen protection, an unequal amount of high-entropy all-inorganic perovskite quantum dot film was immersed in an ethanol solution of Al(NO3)3 containing oleic acid to obtain an Al 3+ adsorption film; S10, Transfer the Al 3+ adsorption film quickly to an aqueous solution of NH4F for reaction, and a dense AlF3 shell layer is formed on the surface of the unequal high-entropy all-inorganic perovskite quantum dot film. This AlF3 shell layer is the dense AlF3 film. The overall film structure of the dense AlF3 film and the unequal high-entropy all-inorganic perovskite quantum dot film is denoted as the composite film; S11, rinse the composite film with ionized water, blow dry the composite film with nitrogen, and obtain the all-inorganic perovskite quantum dot composite film after the second annealing.

3. The preparation process of an all-inorganic perovskite quantum dot composite film according to claim 2, characterized in that: In step S2, the temperature of the first drying treatment is 100 - 120 °C, and the time of the first drying treatment is 30 min.

4. The preparation process of an all-inorganic perovskite quantum dot composite film according to claim 2, characterized in that: In step S3, the time of the first ball milling treatment is 5 min, and the rotation speed of the high-energy ball mill used in the first ball milling treatment is 1050 rpm.

5. The preparation process of an all-inorganic perovskite quantum dot composite film according to claim 2, characterized in that: In step S4, the time of the second ball milling treatment is 15 min, and the rotation speed of the high-energy ball mill used in the second ball milling treatment is 1050 rpm.

6. The preparation process of an all-inorganic perovskite quantum dot composite film according to claim 2, characterized in that: In step S5, the temperature of the second drying treatment is 70 °C, and the time of the second drying treatment is 6 h.

7. The preparation process of an all-inorganic perovskite quantum dot composite film according to claim 2, characterized in that: In step S7, the concentration of the quantum dot solution is 10 mg / ml, the time of ultrasonic dispersion is 20 min, the temperature of vacuum degassing is 60 °C, and the time is 30 min.

8. The preparation process of an all-inorganic perovskite quantum dot composite film according to claim 2, characterized in that: In step S8, the time of ultraviolet ozone treatment is 10 min, the temperature of the first annealing is 60 °C, and the time is 5 min.

9. The preparation process of an all-inorganic perovskite quantum dot composite film according to claim 2, characterized in that: In step S11, the composite film is rinsed with ionized water 3 times, and the temperature of the second annealing is 80 °C, and the time is 10 min.

10. The preparation process of an all-inorganic perovskite quantum dot composite film according to claim 2, characterized in that: In step S6, the grinding time is 30 min; in step S9, the unequal high-entropy all-inorganic perovskite quantum dot film is immersed in an ethanol solution of Al(NO3)3 with a mass fraction of 5% oleic acid and a concentration of 0.1 mol / L, and the immersion time is 30 s; in step S10, the concentration of the NH4F aqueous solution is 0.3 mol / L and pH = 5, and the reaction time of the Al 3+ adsorption film in the NH4F aqueous solution is 1 min.

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