Quantum shell formed by deformation of quantum dots, efficient quantum shell light-emitting diode and preparation method of efficient quantum shell light-emitting diode

Abstract

The invention discloses a quantum shell in the field of zero-dimensional nano materials, the structure of the quantum shell is CdZnSe / ZnSeS / CdSeS / CdS (C / S1 / S2 / S3, C is a CdZnSe core, and S1, S2 and S3 are respectively ZnSeS, CdSeS and CdS shell layers). The chemical components and the energy level structure are changed from inside to outside, so that the structure shows deformation from quantum dots (QDs) to quantum shells (QSs), and the quantum dots have special optical properties (such as high fluorescence quantum yield and ultra-long exciton lifetime). The external quantum efficiency of the quantum shell light emitting diodes (QS-LEDs) based on C / S1 / S2 / S3 is-22%, and is the highest value in the QS-LEDs. Therefore, the C / S1 / S2 / S3-based alloyed quantum shell is expected to replace traditional quantum dots, so that the C / S1 / S2 / S3-based alloyed quantum shell can become an emerging, attractive and efficient luminescent material for illumination and display.

Description

Technical Field

[0001] The present invention relates to the technical fields of zero-dimensional nanomaterials and light-emitting diodes, and particularly relates to a novel alloyed quantum shell and a high-efficiency quantum shell light-emitting diode. Background Art

[0002] Quantum dots with a core-shell structure have been widely used in optoelectronic devices such as biosensors, catalysis, photovoltaic devices, photodetectors, and light-emitting diodes (LEDs). Through precise control of size and chemical composition, their tunable band structures and optical properties (such as absorption and emission) enable bottom-up functional and performance design.

[0003] Core-shell type ZnS / CdSe (Cd, Se, Zn, and S represent cadmium, selenium, zinc, and sulfur respectively) quantum dots have the characteristics of reverse type-I energy level alignment, where the energy gap gradually decreases from the ZnSe core to the CdSe shell. Reverse type-I quantum dots control their optical properties by adjusting the size and chemical composition of the shell. However, since their emission centers are exposed to the surface of the nanomaterials, their excited states are easily quenched by surface defects and adverse external environments, resulting in reverse type-I quantum dots having low fluorescence quantum yields (PLQYs). Fortunately, growing a further shell on the emission shell layer of reverse type-I quantum dots to construct quantum shell materials can effectively protect the excited states from being quenched, and can well solve the challenges of reverse type-I quantum dots and improve their PLQYs. Currently, there are very few research reports on quantum shells, and they are all discrete core-shell structures, and obvious interface defects may exist at the heteromaterial interface, making their optical properties not ideal, thus restricting their application in high-performance quantum shell light-emitting diodes (QS-LEDs). Summary of the Invention

[0004] The present invention aims to provide an alloyed quantum shell (structure: CdZnSe / ZnSeS / CdSeS / CdS (C / S1 / S2 / S3, where C is the CdZnSe core, and S1-S3 are the ZnSeS, CdSeS, and CdS shell layers respectively)) and a high-efficiency quantum shell light-emitting diode. During the synthesis process of the quantum shell, there is an interesting quantum dot - quantum shell transformation. This quantum shell has special optical properties (such as: high fluorescence quantum yield (QY = 90.9%) and ultra-long exciton lifetime (τ = 215.2 ns)). The external quantum efficiency of the quantum shell light-emitting diode (QS-LEDs) based on C / S1 / S2 / S3 is ~22%, which is the highest value among QS-LEDs. Therefore, the alloyed quantum shell based on C / S1 / S2 / S3 is expected to replace traditional quantum dots and enable it to become a new, attractive, and efficient light-emitting material for lighting and display.

[0005] To achieve the above object, the present invention provides the following technical solutions:

[0006] A strategy for deforming quantum dots into quantum shells, with a designed structure: CdZnSe / ZnSeS / CdSeS / CdS (C / S1 / S2 / S3, where C is the CdZnSe core, and S1 - S3 are the ZnSeS, CdSeS, and CdS shell layers respectively). The internal CdZnSe and CdZnSe / ZnSeS are quantum dots with a traditional type-I energy level structure, CdZnSe / ZnSeS / CdSeS is a quantum shell with an inverse type-I energy level structure, and CdZnSe / ZnSeS / CdSeS / CdS is a quantum shell with a quasi-type-II structure. Therefore, during the crystal growth from the inside out, the deformation of quantum dots into quantum shells is completed.

[0007] A preparation method for deforming quantum dots into quantum shells, characterized by including:

[0008] S1: Mix cadmium acetate dihydrate, zinc oxide, oleic acid, and octadecene as initial raw materials according to a certain ratio, and heat the mixture for a period of time to remove moisture and oxygen;

[0009] S2: Raise the temperature and inject selenium-tributylphosphine into the mixture under inert gas protection to obtain a CdZnSe core solution;

[0010] S3: Add 1-dodecanethiol to the core solution and heat for a period of time to grow C / S1 nanocrystals;

[0011] S4: Add cadmium oleate Cd(OA)2 to the C / S1 nanocrystals to form C / S1 / S2 nanocrystals.

[0012] S5: Add sulfur-tributylphosphine and cadmium oleate, and heat for a period of time to obtain C / S1 / S2 / S3 nanocrystals.

[0013] In some embodiments, the following ratios are used: cadmium acetate dihydrate (Cd(OAc)2·2H2O, 0.6 mmol), zinc oxide (ZnO, 9 mmol), oleic acid (OA, 30 ml), and octadecene (ODE, 40 ml); 1 ml of 1-dodecanethiol is added in S3, 5 ml of 0.2 M Cd(OA)2 is added in S4, and 1 ml of 4 M S-TBP and 10 ml of 0.2 M Cd(OA)2 are added in S5.

[0014] In some embodiments, S1 is heated to 150 °C and maintained for 1 hour; the temperature in S2 is raised to 300 °C; S3 and S5 react at 300 °C for 30 minutes.

[0015] A highly efficient quantum shell light-emitting diode, including a CdZnSe / ZnSeS / CdSeS / CdS quantum shell.

[0016] An efficient quantum shell light-emitting diode, the device structure includes: an ITO substrate, a hole injection layer, a hole transport layer, a quantum dot light-emitting layer, an electron transport layer (electron injection layer) and a metal cathode.

[0017] In some embodiments, the light-emitting layer material is a CdZnSe / ZnSeS / CdSeS / CdS red quantum shell.

[0018] In some embodiments, the thickness of the quantum shell light-emitting layer material layer is 20 - 35 nm.

[0019] A preparation method of an efficient quantum shell light-emitting diode, including:

[0020] 1) Etching the indium tin oxide substrate: Using a laser marking method to etch the indium tin oxide (ITO) substrate with the required pattern;

[0021] 2) Cleaning the indium tin oxide substrate: The indium tin oxide (ITO) substrate (30 Ω / sq -1 ) processed in step (1) is cleaned three times in sequence with a detergent and deionized water in an ultrasonic cleaner;

[0022] 3) Preparing the hole injection layer: Preparing a PEDOT:PSS hole injection layer (HIL). First, treat the surface of the ITO substrate processed in step (2) with UV - O3 for 30 minutes, then spin - coat a PEDOT:PSS aqueous solution on the ITO surface at a speed of 3000 rpm to prepare a 30 - nm PEDOT:PSS hole injection layer, and the PEDOT:PSS film is annealed in air at 150 °C for 15 minutes;

[0023] 4) Preparing the hole transport layer: In a glove box filled with nitrogen, spin - coat a TFB solution (8 mg / mL -1 , with CB as the solvent) on the device processed in step (3) at a speed of 3000 rpm, vertically covering a 40 - nm TFB hole transport layer (HTL) on the PEDOT:PSS surface, and placing it on a hot stage at 120 °C for 10 minutes;

[0024] 5) Preparing the quantum dot light-emitting layer: Spin - coat the quantum shell solution (15 mg / mL -1 , obtained by dissolving 15 mg of CdZnSe / ZnSeS / CdSeS / CdS in 1 mL of n - octane solution) on the TFB HTL surface processed in step (4) at a speed of 3000 rpm to prepare a CdZnSe / ZnSeS / CdSeS / CdS quantum shell light-emitting layer (EML, about 20 nm), and the EML film is baked on a hot stage at 60 °C for 5 minutes;

[0025] 6) Preparing the electron transport layer (electron injection layer): The ZnMgO solution (20 mg / mL-1 , ethanol as the solvent) was spin-coated on the film treated in step (5) at a speed of 3000 rpm, and a 40-nm ZnMgO electron transport layer (ETL) was prepared on the EML surface. The ZnMgO film was annealed on a hot stage at 60 °C for 10 minutes;

[0026] 7) Fabricate the metal cathode: Under a pressure of less than 2×10 -6 torr, 100 nm of aluminum was deposited as the cathode on the film treated in step (6) by thermal evaporation;

[0027] 8) Package the QS-LED device: Apply UV glue to the four sides of the flexible packaging sheet outside the glove box, then transfer the glass packaging sheet coated with UV glue into the glove box, cover it on the device treated in step (7), and finally irradiate it with a UV lamp for 30 - 60 s for curing to perform subsequent test operations.

[0028] In some embodiments, the anode of the high-efficiency quantum dot light-emitting diode is a transparent material, the anode thickness is 10 - 100 nm, the hole injection layer thickness is 25 - 45 nm, the hole transport layer thickness is 25 - 45 nm, the electron transport layer (electron injection layer) thickness is 25 - 45 nm, and the cathode thickness is 100 - 150 nm.

[0029] In some embodiments, the PEDOT:PSS solution of the hole injection layer of the quantum dot light-emitting diode device is a 1.3 - 1.7% aqueous solution.

[0030] In some embodiments, the TFB solution of the hole transport layer of the quantum dot light-emitting diode device is usually 10 mg / ml, which is obtained by dissolving 10 mg of TFB in 1 mL of CB (chlorobenzene, CAS: 108 - 90 - 7).

[0031] In some embodiments, the quantum dot light-emitting layer of the quantum dot light-emitting diode device is a CdZnSe / ZnSeS / CdSeS / CdS red quantum dot solution, usually 15 mg / mL, which is obtained by dissolving 15 mg of CdZnSe / ZnSeS / CdSeS / CdS quantum dots in 1 mL of n-octane solution.

[0032] In some embodiments, the ZnMgO solution of the electron transport layer and electron injection layer of the quantum dot light-emitting diode device is usually 20 mg / mL, which is obtained by diluting a 50 mg / mL ZnMgO solution in absolute ethanol (CAS: 64 - 17 - 5).

[0033] The working principle and beneficial effects of the present invention:

[0034] In the CdZnSe / ZnSeS / CdSeS / CdS (C / S1 / S2 / S3, where C is the CdZnSe core, and S1 - S3 are the ZnSeS, CdSeS, and CdS shells respectively) structure, the transformation from quantum dots to quantum shells is achieved. The internal CdZnSe and CdZnSe / ZnSeS are quantum dots with a traditional type-I energy level structure, CdZnSe / ZnSeS / CdSeS is a quantum shell with an inverse type-I energy level structure, and CdZnSe / ZnSeS / CdSeS / CdS is a quantum shell with a quasi-type-II structure. The C / S1 / S2 / S3 quantum shell has a monodisperse size, a perfect nanostructure, effective defect passivation, and a unique energy level arrangement, resulting in a high photoluminescence quantum yield (90.9%), an ultra-long exciton lifetime (215.2 ns), and a slow radiative transition rate (4.2×10 6 s -1 ). The light-emitting device has ideal performance, and its external quantum efficiency (22.16%) is the highest value reported in current QS-LEDs. Based on these findings, it is believed that the emerging alloyed quantum shells can become an efficient light-emitting material for applications in the lighting and display fields. Description of the Drawings

[0035] Figure 1 Schematic diagram of the transformation of quantum dots into quantum shells.

[0036] Figure 2 HR-TEM image of the core / shell structure alloyed quantum shell of the light-emitting layer in the embodiment of the present invention.

[0037] Figure 3 HAADF-STEM image of the core / shell structure alloyed quantum shell of the light-emitting layer in the embodiment of the present invention.

[0038] Figure 4 Absorption and emission spectra of the core / shell structure alloyed quantum shell of the light-emitting layer in the embodiment of the present invention.

[0039] Figure 5 Transient spectrum of the core / shell structure alloyed quantum shell of the light-emitting layer in the embodiment of the present invention.

[0040] Figure 6 Absolute fluorescence quantum yield map of the core / shell structure alloyed quantum shell of the light-emitting layer in the embodiment of the present invention.

[0041] Figure 7 Schematic diagram of the structure of the QS-LED device in the embodiment of the present invention.

[0042] Figure 8 Current density-voltage-luminance curve of the embodiment of the present invention.

[0043] Figure 9 It is the brightness-external quantum efficiency curve graph of the embodiment of the present invention.

[0044] Figure 10 It is the working life graph of the QS-LED device of the embodiment of the present invention under high brightness (47192 cd m -2 ). Detailed implementation manners

[0045] The following is a further detailed description through specific implementation manners:

[0046] A novel alloyed quantum shell, whose structure is: CdZnSe / ZnSeS / CdSeS / CdS (C / S1 / S2 / S3, where C is the CdZnSe core, and S1-S3 are the ZnSeS, CdSeS, and CdS shell layers respectively). Its preparation method is as follows:

[0047] 1) In a 250-milliliter three-necked flask, cadmium acetate dihydrate (Cd(OAc)2·2H2O, 0.6 mmol), zinc oxide (ZnO, 9 mmol), oleic acid (OA, 30 mL), and octadecene (ODE, 40 mL) are used as starting materials. The mixture is heated to 150 °C and maintained for 1 hour to remove moisture and oxygen.

[0048] 2) The temperature is raised to 300 °C, and selenium-tributylphosphine (TBP is the abbreviation of tributylphosphine) is rapidly injected into the reaction mixture under the protection of nitrogen (N2) to form the CdZnSe core (C).

[0049] 3) After 30 minutes, 1 mL of 1-dodecanethiol (DDT) is added to the C solution, and the reaction is carried out at 300 °C for 30 minutes to grow the C / S1 nanocrystals.

[0050] 4) 5 mL of 0.2 M Cd(OA)2 is rapidly added to the C / S1 nanocrystals. After 10 minutes, the C / S1 nanocrystals are covered by the second layer of shell to form the C / S1 / S2 nanocrystals.

[0051] 5) 1 mL of 4 M S-TBP and 10 mL of 0.2 M Cd(OA)2 are rapidly added to the mixture, and it is heated at 300 °C for 30 minutes to obtain the C / S1 / S2 / S3 nanocrystals.

[0052] After sequentially growing ZnSeS (S1), CdSeS (S2), and CdS (S3) shell layers on the surface of a CdZnSe core (C), an unusual transition from quantum dots to quantum shells occurred: among them, C and CdZnSe / ZnSeS (C / S1) quantum dots have the characteristics of a conventional type-I energy level arrangement, and their emission spectra strongly depend on the CdZnSe core. However, CdZnSe / ZnSeS / CdSeS (C / S1 / S2) and CdZnSe / ZnSeS / CdSeS / CdS (C / S1 / S2 / S3) nanocrystals (NCs) exhibit an unconventional energy level arrangement, with their band gaps first increasing and then decreasing from C to S3. The band gap of S2 is smaller than those of C, S1, and S3, thus shifting the emission center from C to S2, indicating that C / S1 / S2 and C / S1 / S2 / S3 NCs belong to QS. Studies on morphology, chemical composition, and optical properties confirmed the transition from quantum dots to quantum shells.

[0053] CdZnSe, ZnSeS, and CdSeS alloys ensure highly ordered epitaxy from the inner core to the outer shell layers, enabling the C / S1 / S2 / S3 quantum shell QS to have a perfect nanostructure and efficient surface passivation. This endows the C / S1 / S2 / S3 quantum shell with excellent luminescence properties, such as a high photoluminescence quantum yield (PL QYs) exceeding 90% and an ultra-long exciton lifetime (τ) exceeding 210 ns.

[0054] Meanwhile, the outermost S3 shell layer reduces the energy level deviation between the highest occupied molecular orbital (HOMO) of the hole transport material and the valence band (VB) energy level of the quantum dots, achieving balanced recombination of charge carriers within the C / S1 / S2 / S3 QS light-emitting layer (EML).

[0055] Therefore, the quantum shell light-emitting diode (QS-LED) fabricated using C / S1 / S2 / S has a peak external quantum efficiency (EQE) of 22.16% and a long operating lifetime (37 hours) at a high initial brightness (47192 cd m -2 ), representing the current state-of-the-art QS-LED.

[0056] Combining excellent photoluminescence and electroluminescence (EL) properties, alloyed quantum shells will become a new type of highly efficient light-emitting material in the fields of lighting and display. Table 1 shows the chemical element content in C, C / S1, C / S1 / S2, and C / S1 / S2 / S3 nanocrystals

[0057] Table 1

[0058]

[0059] Example:

[0060] This example prepared a CdZnSe / ZnSeS / CdSeS / CdS gold quantum shell with a structure, and used its unique material structure and good material properties to prepare a quantum shell light-emitting diode as shown in Figure 7 The specific steps are as follows:

[0061] 1) Etch the indium tin oxide substrate: Use laser marking to etch the indium tin oxide (ITO) substrate with the required pattern;

[0062] 2) Clean the indium tin oxide substrate: The indium tin oxide (ITO) substrate (30Ωsq -1 ) processed in step (1) is cleaned three times in an ultrasonic cleaner using a detergent and deionized water in sequence;

[0063] 3) Prepare the hole injection layer: Prepare a PEDOT:PSS hole injection layer (HIL). First, treat the surface of the ITO substrate processed in step (2) with UV-O3 for 30 minutes, and then spin-coat an aqueous PEDOT:PSS solution on the ITO surface at a speed of 000rpm to prepare a 30nm PEDOT:PSS hole injection layer. The PEDOT:PSS film is annealed in air at 150°C for 15 minutes;

[0064] 4) Prepare the hole transport layer: In a glove box filled with nitrogen, spin-coat a TFB solution (8mg mL -1 , using CB as the solvent) on the device processed in step (3) at a speed of 3000rpm, and vertically cover a 40nm TFB hole transport layer (HTL) on the PEDOT:PSS surface, and place it on a hot stage at 120°C for 10 minutes;

[0065] 5) Prepare the quantum shell light-emitting layer: Spin-coat the quantum shell solution (15mg mL -1 , obtained by dissolving 15mg of CdZnSe / ZnSeS / CdSeS / CdS in 1mL of n-octane solution) on the TFB HTL surface processed in step (4) at a speed of 3000rpm to prepare a CdZnSe / ZnSeS / CdSeS / CdS quantum shell light-emitting layer (EML, about 20nm). The EML film is baked on a hot stage at 60°C for 5 minutes;

[0066] 6) Prepare the electron transport layer (electron injection layer): Spin-coat a ZnMgO solution (20mg mL -1 , using ethanol as the solvent) on the film processed in step (5) at a speed of 3000rpm, and prepare a 40nm ZnMgO electron transport layer (ETL) on the EML surface. The ZnMgO film is annealed on a hot stage at 60°C for 10 minutes;

[0067] 7) Prepare the metal cathode: At less than 2×10 -6At a pressure of torr, 100 nm of aluminum is deposited as the cathode on the film processed in step (6) by thermal evaporation method;

[0068] 8) Encapsulate the QLED device: Apply UV glue to the four sides of the flexible encapsulation sheet outside the glove box, then transfer the glass encapsulation sheet coated with UV glue into the glove box, cover it on the device processed in step (7), and finally irradiate it with a UV lamp for 30 - 60 s for curing, and then subsequent testing operations can be carried out.

[0069] Note: The volume range of the pipette is 20 - 200 μL.

[0070] Test example description

[0071] In this work, a high-resolution transmission electron microscope (HR-TEM) was used to test the morphology of the quantum shell. It can be seen from Figure 1 that the regular crystal fringes of the CdZnSe / ZnSeS / CdSeS / CdS structure confirm its good crystallinity. The lattice spacings of about 0.38 and 0.33 nm between every two crystal fringes correspond to the (100) and (002) planes of wurtzite CdS respectively. To obtain the surface morphology of C / S1 / S2 / S3 NCs at the atomic level, an atomic-resolution high-angle annular dark-field image-scanning transmission electron microscope (HAADF-STEM) was used to observe Figure 2 individual C / S1 / S2 / S3 points in. It can be clearly found that the hexagon formed by six bright spots extends regularly and periodically from the center of the C / S1 / S2 / S3 point to the edge. On the one hand, it corresponds to no obvious lattice mismatch during the epitaxial process from the core to the shell, which provides a perfect nanostructure for C / S1 / S2 / S3. On the other hand, these bright spots represent surface atoms, and the hexagon provides solid evidence for the wurtzite structure of C / S1 / S2 / S3 NCs.

[0072] As Figures 3 to 6As shown, in this work, an energy-dispersive spectrometer (EDS) was used to measure the contents of Cd, Zn, Se, and S elements. It can be found from Table 1 that after the S1, S2, and S3 shells were orderly coated on the CdZnSe core, the chemical composition changed from Zn-rich C and C / S1 to Cd-rich C / S1 / S2 and C / S1 / S2 / S3. The gradual change in chemical composition led to the change in the energy band structure of these nanomaterials. C and C / S1 quantum dots have the traditional type-I energy level structure and belong to quantum dots; C / S1 / S2 and C / S1 / S2 / S3 NCs exhibit reverse type-I and quasi-type-II energy level structures respectively and can be classified as quantum shells. The transformation from QD to QS well responds to the differences in the optical properties of C, C / S1, C / S1 / S2, and C / S1 / S2 / S3, such as redshifted emission wavelength, longer excited state lifetime, and slower radiative transition decay of C / S1 / S2 and C / S1 / S2 / S3. Due to the monodisperse size, perfect surface nanostructure, less lattice mismatch, and effective shell passivation, C / S1 / S2 / S3 QS exhibits excellent optical properties, with an emission wavelength of 630 nm, a fluorescence quantum yield of 90.9%, and an exciton lifetime of 215.2 ns.

[0073] Meanwhile, high-performance QS-LEDs were fabricated using the C / S1 / S2 / S3 quantum shell. As can be seen from Figure 10 , at a working voltage of 6 V, the brightness is as high as 45400 cd m -2 , the external quantum efficiency is 22.16%, and the initial brightness is 47912 cd m -2 When T 50 the lifetime is 37 hours. These performances are among the best in the field of QS-LEDs, demonstrating the superiority of the alloyed quantum shell designed in this invention and making it a candidate for high-performance LED luminescent materials.

[0074] In summary, in the solution provided by this invention, compared with quantum dots, quantum shells can regulate the material structure and optical properties of the alloyed quantum shell by controlling the chemical composition in their core / shell structure. Applying this material as the light-emitting layer in quantum shell light-emitting diodes shows good electroluminescent performance. Thus, it can be seen that the alloyed quantum shell can become a new, attractive, and efficient luminescent material for lighting and display.

Claims

1. A design strategy for transforming quantum dots into quantum shells, characterized in that: The designed structure is: CdZnSe / ZnSeS / CdSeS / CdS (C / S1 / S2 / S3, where C is the CdZnSe core, and S1-S3 are ZnSeS, CdSeS, and CdS shells, respectively); the internal CdZnSe and CdZnSe / ZnSeS are quantum dots with traditional I-type energy level structures, CdZnSe / ZnSeS / CdSeS are quantum shells with inverse I-type energy level structures, and CdZnSe / ZnSeS / CdSeS / CdS are quantum shells with quasi-II-type structures.

2. The method for preparing quantum dots by transforming them into quantum shells according to claim 1, characterized in that: include: S1: mixing cadmium acetate dihydrate, zinc oxide, oleic acid and octadecene as initial raw materials in a certain ratio, and heating the mixture for a period of time to remove moisture and oxygen; S2: heating up and injecting selenium-tributylphosphine into the CdZnSe core solution under inert gas protection; S3: adding 1-dodecyl mercaptan to the core solution and heating for a period of time to grow C / S1 nanocrystals; S4: Adding cadmium oleate to C / S1 nanocrystals to form C / S1 / S2 nanocrystals. S5: Add sulfur-tributylphosphine and cadmium oleate and heat for a period of time to obtain C / S1 / S2 / S3 nanocrystals.

3. The method for preparing quantum dots by transforming them into quantum shells according to claim 2, characterized in that: The following ratio is used: 0.6mmol of cadmium acetate dihydrate, 9mmol of zinc oxide, 30ml of oleic acid and 40ml of octadecene; 1ml of 1-dodecyl mercaptan is added to S3, 5ml of 0.2M cadmium oleate is added to S4, and 1ml of 4M sulfur-tributylphosphine and 10ml of 0.2M cadmium oleate are added to S5.

4. The method for preparing a quantum dot deformable quantum shell according to claim 3, characterized in that: S1 was heated to 150°C for 1 hour; the temperature of S2 was raised to 300°C; S3 and S5 were reacted at 300°C for 30 minutes.

5. A high-efficiency quantum shell light-emitting diode, comprising the CdZnSe / ZnSeS / CdSeS / CdS quantum shell according to any one of claims 1 to 4.

6. The high-efficiency quantum shell light-emitting diode according to claim 5, characterized in that: The device structure includes: an ITO substrate, a hole injection layer, a hole transport layer, a quantum dot light-emitting layer, an electron transport layer (electron injection layer) and a metal cathode.

7. The high-efficiency quantum shell light-emitting diode according to claim 6, characterized in that: The quantum dot light-emitting layer material is CdZnSe / ZnSeS / CdSeS / CdS red quantum shell.

8. The high-efficiency quantum shell light-emitting diode according to claim 7, characterized in that: The thickness of the quantum dot light-emitting layer material layer is 20-35 nm.

9. A method for preparing a high-efficiency quantum shell light-emitting diode, characterized in that: include: 1) Etching the indium tin oxide substrate: etching the desired pattern on the indium tin oxide (ITO) substrate by laser marking; 2) Cleaning the ITO substrate: The ITO substrate (30Ωsq -1 ) using detergent and deionized water in an ultrasonic cleaner three times in sequence; 3) Preparation of hole injection layer: Preparation of PEDOT:PSS hole injection layer (HIL), firstly, the surface of the ITO substrate treated in step (2) was treated with UV-O3 for 30 minutes, then a PEDOT:PSS aqueous solution was spin-coated on the ITO surface at a speed of 3000 rpm to prepare a 30 nm PEDOT:PSS hole injection layer, and the PEDOT:PSS film was annealed in air at 150°C for 15 minutes; 4) Preparation of hole transport layer: In a nitrogen-filled glove box, spin-coat the device treated in step (3) with a TFB solution (8 mg mL -1 , CB as solvent), a 40 nm TFB hole transport layer (HTL) was vertically covered on the PEDOT:PSS surface and placed on a hot stage at 120 °C for 10 min; 5) Preparation of quantum dot light-emitting layer: The quantum shell solution (15 mg mL -1 , 15 mg CdZnSe / ZnSeS / CdSeS / CdS was dissolved in 1 mL of n-octane solution) and spin coated at 3000 rpm on the surface of TFB HTL treated in step (4) to prepare CdZnSe / ZnSeS / CdSeS / CdS quantum shell light-emitting layer (EML, about 20 nm), and the EML film was baked on a hot plate at 60°C for 5 minutes; 6) Preparation of electron transport layer (electron injection layer): ZnMgO solution (20 mg mL -1 , ethanol as solvent) was spin-coated on the film treated in step (5) at a speed of 3000 rpm, a 40 nm ZnMgO electron transport layer (ETL) was prepared on the surface of the EML, and the ZnMgO film was annealed on a hot plate at 60° C. for 10 minutes; 7) Preparation of metal cathode: less than 2×10 -6 Under a pressure of 0.1 torr, a 100 nm aluminum cathode was prepared on the film treated in step (6) by thermal evaporation; 8) Encapsulating QS-LED devices: Apply UV glue to the four sides of the flexible encapsulation sheet outside the glove box, then transfer the glass encapsulation sheet coated with UV glue to the glove box, cover the device treated in step (7), and finally irradiate with UV lamp for 30-60 seconds for curing, and then proceed with subsequent testing operations.

10. The method for preparing a high-efficiency quantum shell light-emitting diode according to claim 9, characterized in that: The anode of the high-efficiency quantum shell light-emitting diode is a transparent material with an anode thickness of 10-100nm, a hole injection layer thickness of 25-45nm, a hole transport layer thickness of 25-45nm, an electron transport layer (electron injection layer) thickness of 25-45nm, and a cathode thickness of 100-150nm.

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