Preparation method and application of surface passivation red light perovskite quantum dots

Abstract

The invention relates to a preparation method and application of surface passivation red light perovskite quantum dots, and the preparation method comprises the following steps: preparing a monovalent cation precursor from cesium carbonate, oleic acid and 1-octadecene; preparing a lead source precursor from the thiophene-sulfonamide ligand, lead halide, zinc halide, oleylamine, oleic acid and 1-octadecene; thermally injecting the monovalent cation precursor into the lead source precursor, and cooling to prepare a perovskite quantum dot solution; performing anti-solvent purification on the perovskite quantum dot solution to obtain surface passivation red light perovskite quantum dots; the invention also discloses application of the surface passivation red light perovskite quantum dot prepared by the preparation method in preparation of an electroluminescent diode. According to the invention, the purpose of preparing the halogen perovskite quantum dot with excellent optical performance, good stability and excellent performance of the prepared electroluminescent diode is achieved.

Description

Technical Field

[0001] The present invention relates to the technical field of perovskite quantum dots, and particularly to a preparation method and application of surface-passivated red perovskite quantum dots. Background Art

[0002] Halide perovskite quantum dots exhibit a series of excellent properties, such as direct bandgap, high fluorescence quantum efficiency, high emission color purity, adjustable emission color, large optical absorption coefficient, high carrier mobility, high defect tolerance, simple synthesis process, and low preparation cost. These properties make halide perovskite quantum dots show great application potential in the field of optoelectronic devices.

[0003] There are various synthesis methods for halide perovskite quantum dots, including hot injection method, ligand-assisted coprecipitation method, and ball milling method. During the synthesis process, organic ligands, such as oleic acid and oleylamine, are usually added. These ligands not only help passivate the defects on the surface of quantum dots but also prevent the aggregation of quantum dots. However, the conductivity of these organic ligands is poor, and their binding to the surface of halide perovskite quantum dots is unstable, resulting in insufficient stability of quantum dots, which is not conducive to the preparation of highly efficient and stable optoelectronic devices. Therefore, the synthesis of halide perovskite quantum dots often requires subsequent modification treatments, such as washing, ligand replacement, surface passivation, etc., to obtain halide perovskite quantum dots with high fluorescence quantum yield, good conductivity, and stability.

[0004] In order to improve the fluorescence quantum yield, conductivity, and stability of halide perovskite quantum dots, measures such as washing, ligand replacement, and surface passivation are usually taken after nucleation. For example, it has been reported that quantum dots with improved fluorescence quantum yield are obtained by washing and ligand replacement treatments after synthesizing halide perovskite quantum dots. However, the stability of the quantum dots prepared by this method is still insufficient. Therefore, achieving efficient surface passivation and preparing halide perovskite quantum dots with excellent optical properties, high stability, and suitable for highly efficient light-emitting diodes still face challenges and require further research and improvement. Summary of the Invention

[0005] Aiming at the deficiencies of the prior art, the first object of the present invention is to provide a preparation method of surface-passivated red perovskite quantum dots, which achieves the purpose of preparing halide perovskite quantum dots with excellent optical properties, good stability, and excellent performance of the prepared electroluminescent diodes.

[0006] The second object of the present invention is to provide an application of surface-passivated red perovskite quantum dots, which has the advantage of improving the luminescence performance and stability of electroluminescent diodes.

[0007] To achieve the above first object, the present invention provides the following technical solutions: A preparation method of surface-passivated red-light perovskite quantum dots, comprising the following steps: The process of preparing a monovalent cation precursor from cesium carbonate, oleic acid and 1-octadecene; The process of preparing a lead source precursor from a thiophene-sulfonamide ligand, lead halide, zinc halide, oleylamine, oleic acid and 1-octadecene; The process of thermally injecting the monovalent cation precursor into the lead source precursor and cooling to prepare a perovskite quantum dot solution; The process of obtaining surface-passivated red-light perovskite quantum dots by purifying the perovskite quantum dot solution with an anti-solvent.

[0008] Further, in the process of preparing the monovalent cation precursor, the dosage ratio of cesium carbonate, oleic acid and 1-octadecene is controlled to be 100 mg: 0.3 - 0.5 mL: 3.4 - 3.6 mL.

[0009] Furthermore, in the process of preparing the monovalent cation precursor, cesium carbonate, oleic acid and 1-octadecene are continuously stirred at a rotation speed of 600 r / min or more, heated to 70 - 90 °C and vacuum dried for 40 - 60 min, and then heated to 100 - 120 °C while maintaining nitrogen flow and held for more than 10 min to obtain the monovalent cation precursor.

[0010] Further, in the process of preparing the lead source precursor, the thiophene-sulfonamide ligand is a composition of one or more of 2-thiophenesulfonamide, 2-chlorothiophene-5-sulfonamide, 5-bromothiophene-2-sulfonamide, the lead halide is lead iodide or lead bromide, and the zinc halide is zinc iodide or zinc bromide.

[0011] Furthermore, in the process of preparing the lead source precursor, the dosage ratio of the thiophene-sulfonamide ligand, lead halide, zinc halide, oleylamine, oleic acid and 1-octadecene is controlled to be 0.1 - 2.0 mmol: 0.2 - 5.0 mmol: 0.5 - 15 mmol: 2 - 12 mL: 2 - 12 mL: 5 - 30 mL.

[0012] Most further, in the process of preparing the lead source precursor, 2-thiophenesulfonamide, lead halide, zinc halide, oleylamine, oleic acid and 1-octadecene are continuously stirred at a rotation speed of 600 r / min or more, and the nitrogen is evacuated and filled multiple times at room temperature, and then heated to 160 - 180 °C while maintaining nitrogen flow and held for more than 10 min to obtain the lead source precursor.

[0013] Further, in the process of preparing the perovskite quantum dot solution, the dosage ratio of the monovalent cation precursor and the lead source precursor is controlled to be 0.4 mL: 5 - 15 mL.

[0014] Further, in the process of preparing the perovskite quantum dot solution, the monovalent cation precursor is thermally injected into the lead source precursor under stirring at 150-180 °C, and after 5 s, an ice-water bath is used for cooling until the temperature drops below 40 °C, obtaining a perovskite quantum dot solution with a luminescence wavelength in the range of 610-660 nm.

[0015] Further, in the process of obtaining the surface-passivated red-light perovskite quantum dots, anti-solvent purification is performed 1-3 times using a 0-5 mg / mL thiophene-sulfonamide ligand solution, and the dosage ratio of the perovskite quantum dot solution to the thiophene-sulfonamide ligand solution is controlled to be 1 mL: 1-10 mL. The purified precipitate is dissolved in a mixed solvent of one or more of n-hexane, n-octane, and xylene to obtain the surface-passivated red-light perovskite quantum dots.

[0016] Still further, in the process of obtaining the surface-passivated red-light perovskite quantum dots, the thiophene-sulfonamide ligand in the thiophene-sulfonamide ligand solution is a composition of one or more of 2-thiophenesulfonamide, 2-chlorothiophene-5-sulfonamide, and 5-bromothiophene-2-sulfonamide, and the solvent is ethyl acetate and / or methyl acetate.

[0017] To achieve the above second object, the present invention provides the following technical solutions: An application of the surface-passivated red-light perovskite quantum dots, the application of the surface-passivated red-light perovskite quantum dots prepared by the above preparation method in the preparation of an electroluminescent diode.

[0018] Further, the electroluminescent diode includes a bottom electrode, a first hole transport layer, a second hole transport layer, a quantum dot light-emitting layer composed of the surface-passivated red-light perovskite quantum dots, an electron transport layer, and a top electrode arranged in sequence.

[0019] Still further, the specific implementation method in the preparation of the electroluminescent diode is as follows: S1 First, the ITO conductive glass is ultrasonically treated with acetone, deionized water, and alcohol in sequence, and then subjected to ultraviolet ozone treatment to obtain the bottom electrode; S2 The PEDOT: PSS solution is spin-coated on the surface of the bottom electrode at a rotation speed of 4000 rpm for 45 s, and annealed at 160 °C for 15 min in an air atmosphere to obtain the first hole transport layer; S3 In a glove box, a chlorobenzene solution with a PTAA concentration of 5 mg / mL is spin-coated on the first hole transport layer at a rotation speed of 2000 rpm for 45 s, and annealed at 170 °C for 20 min in a nitrogen atmosphere to obtain the second hole transport layer; S4: Spin-coat the surface passivated red light perovskite quantum dots with a concentration of 10 mg / mL on the second hole transport layer at a rotation speed of 4000 rpm for 45 s to obtain a quantum dot light-emitting layer; S5 has a vacuum degree of 1×10 -7 In a vacuum chamber of 100 torr, TPBi film, LiF film and Al film were evaporated and deposited in sequence on the quantum dot light-emitting layer. The film thicknesses were 80nm, 1.5nm and 50nm respectively. Among them, TPBi was the electron transport layer and LiF / Al was used as the top electrode to obtain an electroluminescent diode.

[0020] In summary, the beneficial technical effects of the present invention are: 1. The preparation method of the present invention provides different passivation effects by regulating different thiophene-sulfonamide ligands, and adds thiophene-sulfonamide ligands during the purification process to further enhance the passivation effect. The sulfonamide group provides a multi-point passivation effect, providing a stronger binding ability than the original ligand. At the same time, its short-chain structure and conjugated thiophene group optimize the conductivity of the perovskite quantum dots, and obtain red light perovskite quantum dots with few surface defects, good stability, good luminescence performance, and suitable for electroluminescent diodes; 2. The surface passivated red light perovskite quantum dots prepared by the present invention can be used as quantum dot light-emitting layers in the preparation of electroluminescent diodes, which effectively improves the carrier injection capacity and has the advantages of improving the luminescence performance (such as maximum brightness, external quantum efficiency, etc.) and spectral stability of electroluminescent diodes. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 is the photoluminescence spectrum of the surface passivated red light perovskite quantum dots prepared in Example 2 of the present invention; Figure 2 This is a PLQY detection diagram of the surface passivated red light perovskite quantum dots prepared in Example 2 of the present invention; Figure 3 This is an XRD detection diagram of surface passivated red light perovskite quantum dots prepared in Example 2 of the present invention; Figure 4 is a performance diagram of an LED device of an electroluminescent diode prepared in Example 2 of the present invention; Figure 5 This is a PLQY storage stability test graph of the surface passivated red light perovskite quantum dots prepared in Example 3 of the present invention; Figure 6 This is a graph showing the XRD stability of a thin film of surface-passivated red-light perovskite quantum dots prepared in Example 3 of the present invention; Figure 7 This is a PL stability test graph of a thin film of surface passivated red light perovskite quantum dots prepared in Example 3 of the present invention; Figure 8 It is the TEM detection image of the surface-passivated red-light perovskite quantum dots prepared in Example 3 of the present invention; Figure 9 It is the TRPL detection image of the surface-passivated red-light perovskite quantum dots prepared in Example 3 of the present invention; Figure 10 It is the TA detection image of the surface-passivated red-light perovskite quantum dots prepared in Example 3 of the present invention; Figure 11 It is the XPS detection image of the surface-passivated red-light perovskite quantum dots prepared in Example 3 of the present invention; Figure 12 It is the UPS, light absorption detection image and energy band distribution diagram of the LED device of the surface-passivated red-light perovskite quantum dots prepared in Example 3 of the present invention; Figure 13 It is the conductivity test image of the surface-passivated red-light perovskite quantum dots prepared in Example 3 of the present invention; Figure 14 It is the LED device performance image of the electroluminescent diode prepared in Example 3 of the present invention. Detailed implementation manners

[0022] In order to make the technical means, creative features, achieved purposes and functions of the present invention clearer and easier to understand, the present invention will be further described below in conjunction with the accompanying drawings and specific implementation manners.

[0023] Example 1: A preparation method of surface-passivated red-light perovskite quantum dots disclosed in the present invention includes the following steps. The process of preparing a monovalent cation precursor from cesium carbonate, oleic acid and 1-octadecene; The process of preparing a lead source precursor from thiophene-sulfonamide ligand, lead halide, zinc halide, oleylamine, oleic acid and 1-octadecene; The process of thermally injecting the monovalent cation precursor into the lead source precursor and cooling to prepare a perovskite quantum dot solution; The process of purifying the perovskite quantum dot solution with an antisolvent to obtain surface-passivated red-light perovskite quantum dots.

[0024] The present invention also discloses an application of surface-passivated red-light perovskite quantum dots, which is the application of the surface-passivated red-light perovskite quantum dots prepared by the above preparation method in the preparation of an electroluminescent diode. Among them, the electroluminescent diode includes a bottom electrode, a first hole transport layer, a second hole transport layer, a quantum dot light-emitting layer composed of surface-passivated red-light perovskite quantum dots, an electron transport layer and a top electrode arranged in sequence.

[0025] Example 2: A preparation method of surface-passivated red-light perovskite quantum dots disclosed in the present invention is different from Example 1 in that it includes the following steps. S1 Add 100 mg of cesium carbonate to a 25 mL three-necked flask. Then, sequentially add 3.5 mL of 1-octadecene and 0.4 mL of oleic acid. Stir continuously at a rotation speed of 850 r / min, heat to 80 °C, and vacuum dry for 30 min. Subsequently, keep purging with nitrogen and heat up to 120 °C, and maintain for more than 10 min. Place it in a 25 mL three-necked flask and keep it warm for standby to obtain a monovalent cation precursor. S2 Add 15 mg of 2-thiophenesulfonamide, 88 mg of lead iodide, 244 mg of zinc iodide, 5.0 mL of 1-octadecene, 1.8 mL of oleic acid, and 1.8 mL of oleylamine to a 25 mL three-necked flask. Stir continuously at a rotation speed of 850 r / min, and perform 1 - 5 cycles of evacuation and nitrogen filling at room temperature. Subsequently, keep purging with nitrogen and heat up to 170 °C, and maintain for more than 10 min to obtain a lead source precursor. S3 Under stirring at 170 °C, thermally inject 0.4 mL of the monovalent cation precursor into the lead source precursor. After 5 s, cool it in an ice-water bath to 40 °C to obtain a perovskite quantum dot solution. S4 Add a 10 mL xylene / methyl acetate mixed solution in a 1:1 ratio to the perovskite quantum dot solution, centrifuge at a rotation speed of 9000 r / min for 5 min. Then, take the supernatant and add 20 mL of methyl acetate, and centrifuge at a rotation speed of 9000 r / min for 5 min. Dissolve the precipitate in 1 mL of xylene to obtain a primary purified perovskite quantum dot solution. S5 Add 10 mL of methyl acetate to the primary purified perovskite quantum dot solution, centrifuge at a rotation speed of 9000 r / min for 5 min. Dissolve the precipitate in 0.6 mL of n-octane to obtain a secondary purified perovskite quantum dot solution, which is the surface-passivated red-light perovskite quantum dot.

[0026] The present invention also discloses an application of the surface-passivated red-light perovskite quantum dot, that is, the application of the surface-passivated red-light perovskite quantum dot prepared by the above preparation method in the preparation of an electroluminescent diode. Among them, the specific implementation method in the preparation of the electroluminescent diode is as follows. S1 First, ultrasonically treat the ITO conductive glass with acetone, deionized water, and alcohol in sequence, and then perform ultraviolet ozone treatment to obtain a bottom electrode. S2 Spin-coat a PEDOT:PSS solution on the surface of the bottom electrode at a rotation speed of 4000 rpm for 45 s, and anneal at 160 °C for 15 min in an atmospheric atmosphere to obtain a first hole transport layer. S3 In a glove box, spin-coat a chlorobenzene solution with a PTAA concentration of 5 mg / mL on the first hole transport layer at a rotation speed of 2000 rpm for 45 s, and anneal at 170 °C for 20 min in a nitrogen atmosphere to obtain a second hole transport layer. S4 Spin-coated surface passivated red light perovskite quantum dots with a concentration of 10 mg / mL on the second hole transport layer at a rotation speed of 4000 rpm for 45 s to obtain a quantum dot light-emitting layer; S5 In a vacuum chamber with a vacuum degree of 1×10 -7 torr, sequentially evaporate and deposit TPBi film, LiF film, and Al film on the quantum dot light-emitting layer. The film thicknesses are 80 nm, 1.5 nm, and 50 nm respectively. Among them, TPBi is the electron transport layer, and LiF / Al is used as the top electrode to obtain an electroluminescent diode Example 3: A preparation method of surface passivated red light perovskite quantum dots disclosed in the present invention, which is different from Example 2 in that it includes the following steps S1 Add 100 mg of cesium carbonate to a 25 mL three-necked flask, sequentially add 3.5 mL of 1-octadecene and 0.4 mL of oleic acid, continuously stir at a rotation speed of 850 r / min, heat to 80 °C and vacuum dry for 30 min, then keep nitrogen flowing and raise the temperature to 120 °C, keep it for more than 10 min, place it in a 25 mL three-necked flask, keep warm for standby to obtain a monovalent cation precursor; S2 Add 15.5 mg of 2-thiophenesulfonamide, 88 mg of lead iodide, 244 mg of zinc iodide, 5.0 mL of 1-octadecene, 1.6 mL of oleic acid, and 1.6 mL of oleylamine to a 25 mL three-necked flask, continuously stir at a rotation speed of 850 r / min, evacuate and fill nitrogen multiple times at room temperature, then keep nitrogen flowing and raise the temperature to 170 °C, keep it for more than 10 min to obtain a lead source precursor; S3 Under stirring at 170 °C, thermally inject 0.4 mL of the monovalent cation precursor into the lead source precursor, and perform an ice-water bath cooling after 5 s, cool to 40 °C to obtain a perovskite quantum dot solution; S4 Add a 5 mL xylene / methyl acetate mixed solution with a 1:1 ratio to the perovskite quantum dot solution, centrifuge at a rotation speed of 9000 r / min for 5 min, then take the supernatant and add 10 mL of methyl acetate, centrifuge at a rotation speed of 9000 r / min for 5 min, dissolve the precipitate in 1 mL of xylene to obtain a primary purified perovskite quantum dot solution; S5 Add 10 mL of a 2-thiophenesulfonamide-methyl acetate solution with a concentration of 1 mg / mL to the primary purified perovskite quantum dot solution, centrifuge at a rotation speed of 9000 r / min for 5 min, dissolve the precipitate in 0.6 mL of n-octane to obtain a secondary purified perovskite quantum dot solution, which is the surface passivated red light perovskite quantum dot.

[0027] The present invention also discloses an application of the surface-passivated red-light perovskite quantum dots, which is the application of the surface-passivated red-light perovskite quantum dots prepared by the above preparation method in the preparation of electroluminescent diodes. Among them, the difference from Example 2 is that in the glove box, a chlorobenzene solution with a concentration of 5 mg / mL of PTAA and TAPC is spin-coated on the first hole transport layer at a rotation speed of 2000 rpm for 45 s, and annealed at 170 °C for 20 min in a nitrogen atmosphere to obtain the second hole transport layer.

[0028] Example 4: A preparation method of the surface-passivated red-light perovskite quantum dots disclosed in the present invention, which is different from Example 2 and includes the following steps: S1 Add 100 mg of cesium carbonate to a 25 mL three-necked flask, successively add 3.5 mL of 1-octadecene and 0.4 mL of oleic acid, continuously stir at a rotation speed of 850 r / min, heat to 80 °C and vacuum dry for 30 min, then keep purging nitrogen and raise the temperature to 120 °C, keep for more than 10 min, place it in a 25 mL three-necked flask, keep warm for standby to obtain the monovalent cation precursor; S2 Add 31 mg of 2-thiophenesulfonamide, 88 mg of lead iodide, 244 mg of zinc iodide, 86 mg of iodine bromide, 5.0 mL of 1-octadecene, 1.6 mL of oleic acid and 1.6 mL of oleylamine to a 25 mL three-necked flask, continuously stir at a rotation speed of 850 r / min, evacuate and fill nitrogen multiple times at room temperature, then keep purging nitrogen and raise the temperature to 170 °C, keep for more than 10 min to obtain the lead source precursor; S3 Under stirring at 170 °C, inject 0.5 mL of the monovalent cation precursor into the lead source precursor, perform an ice-water bath cooling after 5 s, and cool to 40 °C to obtain the perovskite quantum dot solution; S4 Add a 5 mL toluene / methyl acetate mixed solution with a ratio of 1:2 to the perovskite quantum dot solution, centrifuge at a rotation speed of 9000 r / min for 5 min, then take the supernatant and add 10 mL of methyl acetate, centrifuge at a rotation speed of 9000 r / min for 5 min, and dissolve the precipitate in 1 mL of xylene to obtain the primary purified perovskite quantum dot solution; S5 Add 10 mL of a 5- bromothiophene-2-sulfonamide-methyl acetate solution with a concentration of 5 mg / mL to the primary purified perovskite quantum dot solution, centrifuge at a rotation speed of 9000 r / min for 5 min, and dissolve the precipitate in 0.6 mL of n-octane to obtain the secondary purified perovskite quantum dot solution, which is the surface-passivated red-light perovskite quantum dots.

[0029] Test Example 1: Irradiate the surface-passivated red-light perovskite quantum dots prepared in Example 2 with an excitation light source of 450 nm, collect the spectrum generated after irradiation, and obtain Figure 1The photoluminescence spectrum diagram with an emission peak at 645 nm and a full width at half maximum of 34.1 nm as shown.

[0030] Test Example 2: A blank solvent cuvette and the surface - passivated red - light perovskite quantum dots prepared in Example 2 were irradiated with an excitation light source of 450 nm. By collecting the spectra of both, the photoluminescence spectrum diagram as shown in Figure 2 was obtained. By converting the light intensities of the blank and the sample of Example 2 into the number of photons, and then dividing the number of photons after the photoluminescence of the surface - passivated red - light perovskite quantum dots by the number of photons of the photoluminescence when irradiating the blank solvent, the corresponding photoluminescence quantum yield (PLQY) was finally obtained. The surface - passivated red - light perovskite quantum dots prepared in Example 2 had a PLQY increased from 89.6% to 99.6% compared with the non - surface - passivated perovskite quantum dots, indicating that this surface - passivation treatment can effectively improve the PLQY of perovskite quantum dots and reduce the defects existing in perovskite quantum dots themselves.

[0031] Test Example 3: The surface - passivated red - light perovskite quantum dots prepared in Example 2 were dropped into an XRD cell and air - dried naturally. The surface - passivated red - light perovskite quantum dots were characterized by XRD, and the XRD image as shown in Figure 3 was obtained. It can be seen that the XRD diffraction peaks of the perovskite quantum dots correspond to those of α - phase CsPbI3.

[0032] Test Example 4: The luminous performance of the light - emitting diodes obtained in Example 2 was further tested. Figure 4 are the J - L - V curve diagram and the EQE - L curve diagram of the PeLEDs device. Compared with the PeLEDs not treated with thiophene - sulfonamide ligands, the turn - on voltage of the device decreased from 4.2 V to 3.3 V. At the same time, the maximum brightness of the device without ligand treatment was 494 cd / m 2 which was much lower than 2924 cd / m 2 after passivation with thiophene - sulfonamide ligands. In addition, the PeLEDs based on thiophene - sulfonamide ligand passivation showed a higher device efficiency: 20.9%, which was much higher than 8.9% of the non - treated device. These experiments all proved that thiophene - sulfonamide ligand passivation effectively reduced the surface defects of quantum dots, and the short - chain conjugated thiophene - sulfonamide ligand effectively increased the conductivity of the light - emitting layer compared with the original oleic acid oleylamine ligand.

[0033] Test Example 5: The non - treated perovskite quantum dots and the surface - passivated red - light perovskite quantum dots prepared in Example 3 were placed in an atmospheric environment, and the PLQY of the perovskite quantum dots was tested at regular intervals to compare the stability before and after ligand passivation treatment. From Figure 5It can be seen that the PLQY of the surface-passivated red-light perovskite quantum dots prepared in Example 3 can still maintain 85.5% after being placed for 30 days, while the PLQY of the blank perovskite quantum dots drops rapidly on the 15th day after being placed.

[0034] Test Example 6: By forming films of untreated perovskite quantum dots and the surface-passivated red-light perovskite quantum dots prepared in Example 3 and placing them in an atmospheric environment, the XRD of the perovskite was tested at the beginning and one day later to compare the stability before and after ligand passivation treatment. From Figure 7 it can be seen that the passivated perovskite quantum dots can still maintain a complete α-phase, while other-phase impurity peaks appear in the control group. This shows that the ligand-passivated perovskite quantum dots have better phase stability.

[0035] Test Example 7: By forming films of untreated perovskite quantum dots and the surface-passivated red-light perovskite quantum dots prepared in Example 3 and placing them in an atmospheric environment, the PL of the perovskite was tested at the beginning and one day later to compare the stability before and after ligand passivation treatment, as Figure 7 shown. It can be seen that the PL peak position of the passivated perovskite quantum dots does not change much, while the PL peak of the blank control group shows an obvious red shift. This shows that ligand passivation effectively improves the spectral stability of the perovskite quantum dot film.

[0036] Test Example 8: The perovskite quantum dot solution prepared in Example 3 was dropped onto an ultra-thin carbon film and air-dried naturally, and the perovskite was characterized by TEM to obtain the TEM image as Figure 8 shown. It can be seen that whether there is 2-thiophenesulfonamide treatment or not, the crystal plane spacing of the quantum dots is 0.63 nm, and the quantum dots show a regular cubic phase. At the same time, after 2-thiophenesulfonamide treatment, the average particle size of the quantum dots is slightly reduced, which may be due to the slight inhibition of the nucleation and growth of the quantum dots by 2-thiophenesulfonamide during the synthesis process.

[0037] Test Example 9: By performing fluorescence lifetime tests on the perovskite quantum dot solution prepared in Example 3, the PL decay diagram as Figure 9 shown was obtained. It can be seen that after the introduction of 2-thiophenesulfonamide, the decay trend of the perovskite quantum dots changes from double-exponential decay to single-exponential decay, and at the same time, the fluorescence lifetime increases from 10.4 ns to 15.3 ns. This shows that the introduction of 2-thiophenesulfonamide reduces the non-radiative decay channels of the perovskite quantum dots and increases the fluorescence lifetime.

[0038] Test Example 10: By performing transient absorption tests on the perovskite quantum dot solution prepared in Example 3, the result as Figure 10The ground state bleach recovery curve shown. It can be seen that on the ps scale, the perovskite quantum dots passivated by 2-thiophenesulfonamide ligands exhibit a more gentle downward trend, demonstrating that 2-thiophenesulfonamide effectively passivates the surface defects of perovskite quantum dots.

[0039] Experimental Example 11: The surface-passivated red-light perovskite quantum dots prepared in Example 3 were spin-coated onto a quartz glass at a speed of 2000 rpm, and XPS tests were performed to obtain the Figure 11 XPS spectra of S, N, Pb, and I elements as shown. It can be seen that an S spectrum appears after the introduction of 2-thiophenesulfonamide, indicating that 2-thiophenesulfonamide has been successfully introduced into the perovskite quantum dots; the peak representing -NH2 in the N spectrum increases, indicating that 2-thiophenesulfonamide mainly binds to the quantum dots in the form of -NH2; the Pb and I elements shift to higher energies after the introduction of 2-thiophenesulfonamide, indicating that there are interactions between 2-thiophenesulfonamide and Pb, I.

[0040] Experimental Example 12: The surface-passivated red-light perovskite quantum dots prepared in Example 3 were spin-coated onto an 80-nm Au film at a speed of 2000 rpm, and UPS and absorbance tests were performed on it. After processing, the Figure 12 UPS and light absorption spectra as shown in a, b, and c were obtained. Based on this, the energy band diagram as shown in Figure 12 d was calculated, proving that the introduction of 2-thiophenesulfonamide is beneficial to the recombination of electrons and holes in the light-emitting layer.

[0041] Experimental Example 13: The surface-passivated red-light perovskite quantum dots prepared in Example 3 were used to prepare an ITO / quantum dot / Ag electroluminescent diode device structure for conductivity testing. The Figure 13 current-voltage curve after applying voltage as shown was tested. The greater the slope of the curve, the better the conductivity of the quantum dot film. The quantum dots passivated by 2-thiophenesulfonamide have a greater slope, indicating that they have better conductivity.

[0042] Experimental Example 14: Through the optoelectronic performance characterization of the electroluminescent diode prepared in Example 3, the Figure 14 EL curve as shown in a was obtained. In addition, Figure 14 b shows that the electroluminescent diode passivated by 2-thiophenesulfonamide has good spectral stability and can maintain spectral stability during the process of increasing the voltage from 3.5 V to 8 V. The LED device performance curve is as shown in Figure 14 c and d. Compared with the electroluminescent diode treated without 2-thiophenesulfonamide, the device with perovskite quantum dots passivated has a higher current density, and the device efficiency is increased from 18.44% to 28.73%, and the maximum brightness is increased from 857 cd / m 2 to 2747 cd / m 2 .

[0043] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention rather than to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention, and they should all be covered within the scope of the claims of the present invention.

Claims

1. A method for preparing surface passivated red light perovskite quantum dots, characterized in that: The following steps are included: A process for preparing a monovalent cation precursor from cesium carbonate, oleic acid and 1-octadecene; A process for preparing a lead source precursor from a thiophene-sulfonamide ligand, a lead halide, a zinc halide, oleylamine, oleic acid and 1-octadecene; The process of hot injecting the monovalent cation precursor into the lead source precursor and cooling to prepare a perovskite quantum dot solution; The perovskite quantum dot solution is purified by anti-solvent to obtain surface passivated red light perovskite quantum dots.

2. The method for preparing surface passivated red light perovskite quantum dots according to claim 1, characterized in that: In the process of preparing the monovalent cation precursor, the dosage ratio of cesium carbonate, oleic acid and 1-octadecene is controlled to be 100 mg: 0.3-0.5 mL: 3.4-3.6 mL.

3. The method for preparing surface passivated red light perovskite quantum dots according to claim 2, characterized in that: In the process of preparing the monovalent cation precursor, cesium carbonate, oleic acid and 1-octadecene are continuously stirred at a speed of more than 600 r / min, heated to 70-90° C. and vacuum dried for 40-60 min, then heated to 100-120° C. while maintaining nitrogen flow and maintained for more than 10 min to obtain a monovalent cation precursor.

4. The method for preparing surface passivated red light perovskite quantum dots according to claim 1, characterized in that: In the process of preparing the lead source precursor, the thiophene-sulfonamide ligand is one or a combination of 2-thiophenesulfonamide, 2-chlorothiophene-5-sulfonamide, and 5-bromothiophene-2-sulfonamide, the lead halide is lead iodide or lead bromide, and the zinc halide is zinc iodide or zinc bromide.

5. The method for preparing surface passivated red light perovskite quantum dots according to claim 4, characterized in that: In the process of preparing the lead source precursor, the dosage ratio of thiophene-sulfonamide ligand, lead halide, zinc halide, oleylamine, oleic acid and 1-octadecene is controlled to be 0.1-2.0 mmol: 0.2-5.0 mmol: 0.5-15 mmol: 2-12 mL: 2-12 mL: 5-30 mL.

6. The method for preparing surface passivated red light perovskite quantum dots according to claim 5, characterized in that: In the process of preparing the lead source precursor, the thiophene-sulfonamide ligand, lead halide, zinc halide, oleylamine, oleic acid and 1-octadecene are continuously stirred at a speed of more than 600 r / min, and nitrogen is pumped and charged for multiple cycles at room temperature. Then, the temperature is raised to 160-180° C. while nitrogen is passed through, and maintained for more than 10 minutes to obtain the lead source precursor.

7. The method for preparing surface passivated red light perovskite quantum dots according to claim 1, characterized in that: In the process of preparing the perovskite quantum dot solution, the dosage ratio of the monovalent cation precursor and the lead source precursor is controlled to be 0.4 mL: 5-15 mL.

8. The method for preparing surface passivated red light perovskite quantum dots according to claim 1, characterized in that: In the process of preparing the perovskite quantum dot solution, the monovalent cation precursor is hot injected into the lead source precursor under stirring at 150-180° C., and after 5 seconds, the solution is cooled in an ice water bath to below 40° C. to obtain a perovskite quantum dot solution with a luminescent wavelength of 610-660 nm.

9. The method for preparing surface passivated red light perovskite quantum dots according to claim 1, characterized in that: In the process of obtaining surface passivated red light perovskite quantum dots, 0-5 mg / mL thiophene-sulfonamide ligand solution is used for anti-solvent purification 1-3 times, and the dosage ratio of the perovskite quantum dot solution and the thiophene-sulfonamide ligand solution is controlled to be 1 mL: 1-10 mL. The purified precipitate is dissolved in one or more mixed solvents of n-hexane, n-octane, and xylene to obtain surface passivated red light perovskite quantum dots.

10. An application of surface passivated red light perovskite quantum dots, characterized in that: Use of surface passivated red light perovskite quantum dots prepared by the preparation method according to any one of claims 1 to 9 in the preparation of an electroluminescent diode, the electroluminescent diode comprising a bottom electrode, a first hole transport layer, a second hole transport layer, a quantum dot light-emitting layer composed of the surface passivated red light perovskite quantum dots, an electron transport layer and a top electrode arranged in sequence.

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