Copper-based halide light-emitting diode and preparation method thereof

Abstract

The present invention provides a copper-based halide light-emitting diode and a preparation method thereof, comprising: step 1, preparing an alkali metal thiocyanate solution; step 2, preparing a modified hole injection layer solution; step 3, preparing a crystallization aid; step 4, preparing a copper-based halide precursor solution; step 5, mixing the crystallization aid and the copper-based halide precursor solution; and step 6, preparing a copper-based halide light-emitting diode device. The present invention can significantly improve the hole injection capability of the light-emitting diode device, promote charge balance, and significantly increase the device brightness and external quantum efficiency. The interaction between thiocyanate and Cu ions improves the crystallization quality of the copper-based halide, thereby improving the uniformity of the film. Simultaneously, thiocyanate can increase the formation energy of halogen vacancies in the copper-based halide, thereby passivating the halogen vacancy defects and inhibiting the migration of halogen ions.

Description

Technical Field

[0001] The present invention belongs to the technical field of light emitting diodes, and in particular relates to a copper-based halide light emitting diode and a preparation method thereof. Background Art

[0002] Light-emitting diodes (LEDs) are widely used in everyday lighting and displays. Simultaneously, researchers are developing new display technologies with high color purity and a wide color gamut. In recent years, metal halide materials have attracted widespread attention due to their exceptional properties, such as continuously tunable emission wavelength, narrow half-width (FWHM), high fluorescence quantum efficiency, and low cost. Lead-based halide materials, with their high luminescence efficiency, have become a hot research area. However, the toxicity of lead, a heavy metal, limits the commercial application of lead-based halides. Consequently, non-lead halide materials have become a research focus in the field of LEDs. Current research has shown that the performance of non-lead halide LEDs cannot match that of lead-based halide diodes. Therefore, the development of efficient and stable non-lead halide LEDs is an important and urgent need in this field.

[0003] Among various non-lead halide materials, copper-based halide materials show great application prospects in the field of light-emitting diodes. However, the luminous efficiency of copper-based halide light-emitting diodes is low, mainly due to the imbalance of carrier injection in the device and the high defect density of copper-based halide materials. Copper-based halide materials have a large band gap and energy level mismatch at the interfaces of functional layers, which makes carrier injection into the light-emitting layer difficult. At the same time, halogen vacancy defects can trap carriers, reducing luminous efficiency. Therefore, the preparation of copper-based halide light-emitting diodes with superior device performance remains a major challenge in this field. Summary of the Invention

[0004] Purpose of the Invention: This invention addresses the shortcomings of existing technologies by providing a copper-based halide light-emitting diode and its preparation method. Alkali metal thiocyanate-doped poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) (PEDOT:PSS) is used to increase the hole injection rate, improve the crystallization quality of the copper-based halide, and reduce the defect density. Polyvinylpyrrolidone (PVP) and polyvinylidene fluoride (PVDF) are used as crystallization aids to improve the growth morphology of the copper-based halide.

[0005] The present invention comprises the following steps:

[0006] Step 1, preparing an alkali metal thiocyanate solution;

[0007] Step 2, preparing a modified hole injection layer solution;

[0008] Step 3, preparing a crystallization auxiliary agent;

[0009] Step 4, preparation of copper-based halide Cs x Cu2I x+2 Precursor solution;

[0010] Step 5, mixing a crystallization auxiliary agent and a copper-based halide precursor solution;

[0011] Step 6: Prepare a copper-based halide light-emitting diode device.

[0012] Step 1 comprises: dissolving an alkali metal thiocyanate solid in deionized water and stirring with a stirrer at a speed of 100 to 1000 rpm for 5 to 120 minutes to obtain an alkali metal thiocyanate solution, wherein the alkali metal thiocyanate is any one of lithium thiocyanate (LiSCN), potassium thiocyanate (KSCN), sodium thiocyanate (NaSCN), and cesium thiocyanate (CsSCN).

[0013] In step 1, the concentration of the alkali metal thiocyanate solution is 1-220 mg / mL.

[0014] Step 2 includes: mixing an alkali metal thiocyanate solution with a poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) solution (poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) is the Chinese name of the semiconductor material PEDOT:PSS, and its English name is "Poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate)"), and stirring with a stirrer at a speed of 100 to 1000 rpm for 15 to 280 minutes to obtain a modified hole injection layer solution.

[0015] In step 2, the poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) PEDOT:PSS solution has a concentration of 1.1-1.6 wt.%, is diluted with deionized water, and the volume ratio of the alkali metal thiocyanate solution to the poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) PEDOT:PSS solution is 1:X1, where the parameter X1 ranges from 2 to 5.

[0016] Step 3 comprises: preparing a polyvinyl pyrrolidone (PVP) solution or a polyvinylidene fluoride (PVDF) solution as a crystallization auxiliary agent;

[0017] The polyvinyl pyrrolidone (PVP) solution is prepared by dissolving a polyvinyl pyrrolidone (PVP) solid in dimethyl sulfoxide at a concentration of 1 to 80 mg / mL and stirring the solution with a stirrer at a speed of 100 to 1000 rpm for 10 to 60 minutes.

[0018] The polyvinylidene fluoride (PVDF) solution is prepared by dissolving polyvinylidene fluoride (PVDF) solid in dimethyl sulfoxide at a concentration of 1-80 mg / mL and stirring with a stirrer at a speed of 100-1000 rpm for 10-60 minutes.

[0019] Step 4 comprises: dissolving cesium iodide CsI and cuprous iodide CuI in a molar ratio of x:2 at a concentration of 0.1 to 0.6 M in one of the organic solvents of N,N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, methyl ethyl ketone, and dimethylacetamide, and stirring with a stirrer at a speed of 200 to 600 rpm at 50 to 70°C for 3 to 10 minutes, and then stirring at a temperature of 20 to 30°C for 5 to 18 hours to obtain a copper-based halide CsI. x Cu2I x+2 Precursor solution; where parameter x is 1 or 3.

[0020] Step 5 includes: mixing a crystallization auxiliary agent and a copper-based halide Cs x Cu2I x+2 The precursor solutions are mixed in a volume ratio of 1:X2 and stirred using a stirrer at a speed of 200-600 rpm at 20-30°C for 3-8 hours to obtain a copper-based halide precursor solution after crystallization-assisted treatment; the parameter X2 is set to 10-20.

[0021] Step 6 includes the following steps:

[0022] Step 6~1, ultrasonic cleaning of ITO conductive glass: After wiping the ITO conductive glass with a dust-free cloth, soak the ITO conductive glass in detergent, deionized water, acetone, and isopropyl alcohol in sequence and ultrasonically clean it for 10 to 40 minutes;

[0023] Step 6~2, UV-ozone treatment of ITO conductive glass: the cleaned ITO conductive glass is blown dry, then placed in a sealed, light-proof environment and irradiated with short-wave ultraviolet light; the short-wave ultraviolet light simultaneously emits two wavelengths of ultraviolet light, 180~187nm and 248~257nm;

[0024] Step 6-3, spin coating a hole injection layer: 100-400 μL of the modified hole injection layer solution prepared in step 2 was filtered through a filter head and spin coated on the surface of the ITO conductive glass at a speed of 3000-9000 rpm for 10-60 seconds. The solution was then annealed at 110-145° C. for 10-30 minutes and then cooled to room temperature to obtain a hole injection layer.

[0025] Step 6-4, spin coating a copper-based halide light-emitting layer: 100 to 300 μL of the copper-based halide precursor solution after the crystallization-assisted treatment prepared in step 5 is filtered through a filter head and then spin-coated on the surface of the hole injection layer at a first speed of 50 to 200 rpm for 5 to 12 seconds and a second speed of 1000 to 6000 rpm for 10 to 60 seconds. The solution is then annealed at 50 to 140° C. for 8 to 40 minutes and then cooled to room temperature to obtain a copper-based halide light-emitting layer.

[0026] Step 6-5, evaporation of electron transport layer: at a pressure less than 9×10 -4 Pa under high vacuum conditions, an electron transport layer was evaporated on the surface of the copper-based halide light-emitting layer at a growth rate of 0.3~0.8Å / s;

[0027] Step 6-6, evaporation of electrode modification layer: at a pressure less than 9×10 -4 Under high vacuum conditions of 1000 Pa, the electrode modification layer was evaporated on the surface of the electron transport layer at a growth rate of 0.04-0.11 Å / s;

[0028] Step 6-7, evaporation of metal electrodes: at a pressure less than 9×10 -4 Pa under high vacuum conditions, a metal electrode is evaporated on the surface of the electrode modification layer at a growth rate of 1.2~1.7Å / s;

[0029] Finally, ITO conductive glass, hole injection layer, copper-based halide light-emitting layer, electron transport layer, electrode modification layer and metal electrode are combined from bottom to top to form a copper-based halide light-emitting diode device; the hole injection layer, copper-based halide light-emitting layer, electron transport layer and electrode modification layer constitute the light-emitting unit;

[0030] The thickness of the ITO conductive glass is 40-180 nm, the thickness of the hole injection layer is 10-100 nm, the thickness of the copper-based halide light-emitting layer is 30-200 nm, the thickness of the electron transport layer is 10-100 nm, the thickness of the electrode modification layer is 0.1-20 nm, and the thickness of the metal electrode is 40-130 nm;

[0031] The material used for the electron transport layer is one of 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene TPBi and 3,3'-[5'-[3-(3-pyridyl)phenyl][1,1':3',1''-terphenyl]-3,3''-diyl]dipyridine TmPyPB;

[0032] The material used for the electrode modification layer is one of lithium fluoride LiF and 8-hydroxyquinoline-lithium Liq;

[0033] The material used for the metal electrode is one of aluminum Al, silver Ag, gold Au, and zinc Zn.

[0034] The present invention also provides a copper-based halide light-emitting diode prepared by the method, which comprises, from bottom to top, ITO conductive glass, a hole injection layer, a copper-based halide light-emitting layer, an electron transport layer, an electrode modification layer and a metal electrode; wherein the hole injection layer, the copper-based halide light-emitting layer, the electron transport layer and the electrode modification layer constitute a light-emitting unit.

[0035] Compared with the prior art, the present invention has the following advantages: 1. The copper-based halide light-emitting diode described herein modifies the hole injection layer by doping PEDOT:PSS with an alkali metal thiocyanate, lowering the hole injection barrier and significantly improving the hole injection capability of the light-emitting diode device. This balances charge injection and promotes exciton radiative recombination efficiency. Furthermore, the thiocyanate interacts with Cu ions, improving the crystallization quality of the copper-based halide and the film quality. Furthermore, the thiocyanate increases the formation energy of halogen vacancies in the copper-based halide, thereby passivating halogen vacancy defects and inhibiting halogen ion migration. As a result, the copper-based halide light-emitting diode described herein exhibits excellent luminous efficiency and stability.

[0036] 2. The copper-based halide light-emitting diode described in the present invention can improve the growth process of the copper-based halide light-emitting layer through the PVP and PVDF assisted crystallization method, thereby improving the uniformity of the film, and the size of the formed crystals is uniform, which can improve the external quantum efficiency of the device.

[0037] 3. The copper-based halide light-emitting diode described in the present invention uses a copper-based halide material as the light-emitting layer and does not contain lead elements. Therefore, it is green and environmentally friendly, conducive to sustainable environmental development, and has good application prospects.

[0038] 4. The copper-based halide light-emitting diode described in the present invention has no hole transport layer, which simplifies the device structure and preparation process, reduces the device production cost, and facilitates large-scale production. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] Figure 1 This is a schematic structural diagram of the copper-based halide light-emitting diode provided by the present invention.

[0040] Figure 2 This is a scanning electron microscope image of the copper-based halide film morphology of Example 1 of the present invention.

[0041] Figure 3 This is a scanning electron microscope image of the copper-based halide film morphology of Comparative Example 1 of the present invention.

[0042] Figure 4 Comparison of luminous brightness between the embodiment of the present invention and the comparative example.

[0043] Figure 5 Comparison of external quantum efficiencies of the embodiments of the present invention and the comparative examples.

[0044] Figure 6 The figure compares the decrease of luminous brightness over time of the embodiment of the present invention and the comparative example.

[0045] Explanation of the reference numerals: 1: ITO conductive glass, 2: hole injection layer, 3: copper-based halide light-emitting layer, 4: electron transport layer, 5: electrode modification layer, 6: metal electrode. DETAILED DESCRIPTION

[0046] The present invention will be further described below in conjunction with the accompanying drawings and specific embodiments, and the above and / or other advantages of the present invention will become more apparent.

[0047] like Figure 1 As shown, an embodiment of the present invention provides a copper-based halide light-emitting diode, which includes, from bottom to top: ITO conductive glass 1, a hole injection layer 2, a copper-based halide light-emitting layer 3, an electron transport layer 4, an electrode modification layer 5 and a metal electrode 6.

[0048] The following describes a preparation process of a copper-based halide light-emitting diode through Examples 1 to 3.

[0049] In Example 1 of the present invention, a method for preparing a copper-based halide light-emitting diode is provided, comprising the following steps:

[0050] S1, preparing a KSCN solution: dissolving KSCN solid in deionized water, and stirring with a stirrer at a speed of 300 rpm for 60 minutes to obtain a KSCN solution.

[0051] S2, preparing a modified hole injection layer solution: mixing the KSCN solution and the PEDOT:PSS solution, and stirring them with a stirrer at a speed of 300 rpm for 180 minutes to obtain a modified hole injection layer solution.

[0052] S3, preparing a crystallization auxiliary agent: preparing a PVP solution as a crystallization auxiliary agent; the PVP solution is obtained by dissolving PVP solid in dimethyl sulfoxide at a concentration of 10 mg / mL, and stirring with a stirrer at a speed of 200 rpm for 50 minutes.

[0053] S4. Prepare a copper-based halide Cs3Cu2I5 precursor solution: dissolve CsI and CuI in an N,N-dimethylformamide organic solvent at a molar ratio of 3:2 at a concentration of 0.2 M, and stir with a stirrer at a speed of 300 rpm at 55°C for 6 minutes, and then stir at 25°C for 14 hours to obtain a Cs3Cu2I5 copper-based halide precursor solution.

[0054] S5, mixing the crystallization auxiliary agent and the copper-based halide precursor solution: the crystallization auxiliary agent prepared by S3 and the copper-based halide precursor solution prepared by S4 are mixed in a volume ratio of 1:10, and stirred with a stirrer at a speed of 300 rpm at 25°C for 3 hours to obtain a copper-based halide precursor solution after crystallization auxiliary treatment.

[0055] S6, preparing a copper-based halide light-emitting diode device: forming an ITO conductive glass 1, a hole injection layer 2, a copper-based halide light-emitting layer 3, an electron transport layer 4, an electrode modification layer 5 and a metal electrode 6 from bottom to top to form a copper-based halide light-emitting diode device; wherein the hole injection layer 2, the copper-based halide light-emitting layer 3, the electron transport layer 4, and the electrode modification layer 5 constitute a light-emitting unit.

[0056] In the S6, the thickness of the ITO conductive glass is 150 nm, the thickness of the hole injection layer is 15 nm, the thickness of the copper-based halide light-emitting layer is 180 nm, the thickness of the electron transport layer is 45 nm, the thickness of the electrode modification layer is 1.5 nm, and the thickness of the metal electrode is 120 nm.

[0057] In S1, the KSCN solution is obtained by dissolving KSCN solid in deionized water, and the concentration of the KSCN solution is 120 mg / mL.

[0058] In S2, the concentration of the PEDOT:PSS solution is 1.5 wt.%, and it is diluted with deionized water, and the volume ratio of the KSCN solution to the PEDOT:PSS solution is 1:3.

[0059] In S6, the material used for the electron transport layer is TPBi.

[0060] In S6, the material used for the electrode modification layer is LiF.

[0061] In S6, the material used for the metal electrode is Al.

[0062] In said S6, preparing a copper-based halide light-emitting diode device comprises the following steps:

[0063] S61, ultrasonic cleaning of ITO conductive glass: After wiping the ITO conductive glass with a dust-free cloth, soak the ITO conductive glass in detergent, deionized water, acetone, and isopropyl alcohol in sequence and ultrasonically clean it for 15 minutes.

[0064] S62, UV-ozone treatment of ITO conductive glass: The cleaned ITO conductive glass is blown dry with a hot air blower, then placed in a sealed, light-proof environment and irradiated with short-wave ultraviolet light; the short-wave ultraviolet light simultaneously emits two wavelengths of ultraviolet light, 185nm and 254nm.

[0065] S63, spin coating of hole injection layer: 200uL of the modified hole injection layer solution prepared in S2 was filtered through a 0.22μm aqueous phase filter head, and then spin-coated on the surface of the ITO conductive glass at a speed of 4000 rpm for 50 seconds, and then annealed at 120°C for 15 minutes, and then cooled to room temperature to obtain a hole injection layer.

[0066] S64, spin coating of a copper-based halide light-emitting layer: 300 uL of the copper-based halide precursor solution after crystallization-assisted treatment prepared in S5 was filtered through a 0.45 μm polytetrafluoroethylene filter head, and then spin-coated on the surface of the hole injection layer at a first speed of 100 rpm for 7 seconds and a second speed of 4000 rpm for 60 seconds. The solution was then annealed at 70°C for 15 minutes and then cooled to room temperature to obtain a copper-based halide light-emitting layer.

[0067] S65, Evaporation of electron transport layer: at pressure <6.5×10 -4 Under high vacuum conditions of 1.5 Å Pa, an electron transport layer was evaporated on the surface of the copper-based halide light-emitting layer at a growth rate of 0.5 Å / s.

[0068] S66, evaporation electrode modification layer: at pressure <6.5×10 -4 Under high vacuum conditions of 1.5 Å Pa, the electrode modification layer was evaporated on the surface of the electron transport layer at a growth rate of 0.1 Å / s.

[0069] S67, evaporation of metal electrodes: finally at a pressure of <6.5×10 -4 Under high vacuum conditions of 1.5 Pa, metal electrodes were evaporated on the surface of the electrode modification layer at a growth rate of 1.5 Å / s.

[0070] In Example 2 of the present invention, a method for preparing a copper-based halide light-emitting diode is provided, comprising the following steps:

[0071] S1, preparing a NaSCN solution: dissolving NaSCN solid in deionized water, and stirring with a stirrer at a speed of 400 rpm for 60 minutes to obtain a NaSCN solution.

[0072] S2, preparing a modified hole injection layer solution: mixing the NaSCN solution and the PEDOT:PSS solution, and stirring with a stirrer at a speed of 400 rpm for 200 minutes to obtain a modified hole injection layer solution.

[0073] S3, preparing a crystallization auxiliary agent: preparing a PVP solution as a crystallization auxiliary agent; the PVP solution is obtained by dissolving PVP solid in dimethyl sulfoxide at a concentration of 8 mg / mL, and stirring with a stirrer at a speed of 300 rpm for 40 minutes.

[0074] S4, preparing a copper-based halide CsCu2I3 precursor solution: dissolving CsI and CuI in a dimethylacetamide organic solvent at a molar ratio of 1:2 and a concentration of 0.3 M, and stirring with a stirrer at a speed of 400 rpm at 60°C for 6 minutes, and then stirring at 20°C for 18 hours to obtain a Cs1Cu2I3 copper-based halide precursor solution.

[0075] S5, mixing the crystallization auxiliary agent and the copper-based halide precursor solution: the crystallization auxiliary agent prepared by S3 and the copper-based halide precursor solution prepared by S4 are mixed in a volume ratio of 1:15, and stirred with a stirrer at a speed of 400 rpm at 20°C for 5 hours to obtain a copper-based halide precursor solution after crystallization auxiliary treatment.

[0076] S6, preparing a copper-based halide light-emitting diode device: forming an ITO conductive glass 1, a hole injection layer 2, a copper-based halide light-emitting layer 3, an electron transport layer 4, an electrode modification layer 5 and a metal electrode 6 from bottom to top to form a copper-based halide light-emitting diode device; wherein the hole injection layer 2, the copper-based halide light-emitting layer 3, the electron transport layer 4, and the electrode modification layer 5 constitute a light-emitting unit.

[0077] In the S6, the thickness of the ITO conductive glass is 100 nm, the thickness of the hole injection layer is 20 nm, the thickness of the copper-based halide light-emitting layer is 160 nm, the thickness of the electron transport layer is 50 nm, the thickness of the electrode modification layer is 1 nm, and the thickness of the metal electrode is 100 nm.

[0078] In S1, the NaSCN solution is obtained by dissolving NaSCN solid in deionized water, and the concentration of the NaSCN solution is 20 mg / mL.

[0079] In S2, the concentration of the PEDOT:PSS solution is 1.3 wt.%, and it is diluted with deionized water, and the volume ratio of the NaSCN solution to the PEDOT:PSS solution is 1:5.

[0080] In S6, the material used for the electron transport layer is TPBi.

[0081] In the step S6, the material used for the electrode modification layer is Liq.

[0082] In S6, the material used for the metal electrode is Au.

[0083] In said S6, preparing a copper-based halide light-emitting diode device comprises the following steps:

[0084] S61, ultrasonic cleaning of ITO conductive glass: After wiping the ITO conductive glass with a dust-free cloth, soak the ITO conductive glass in detergent, deionized water, acetone, and isopropyl alcohol in sequence and ultrasonically clean it for 20 minutes.

[0085] S62, UV-ozone treatment of ITO conductive glass: The cleaned ITO conductive glass is blown dry with a hot air blower, then placed in a sealed, light-proof environment and irradiated with short-wave ultraviolet light; the short-wave ultraviolet light simultaneously emits two wavelengths of ultraviolet light, 185nm and 254nm.

[0086] S63, spin coating of hole injection layer: 300uL of the modified hole injection layer solution prepared in S2 was filtered through a 0.22μm aqueous filter head, and then spin-coated on the surface of ITO conductive glass at a speed of 4000 rpm for 50 seconds, and then annealed at 120°C for 15 minutes, and then cooled to room temperature to obtain a hole injection layer.

[0087] S64, spin coating of a copper-based halide light-emitting layer: 200 uL of the copper-based halide precursor solution after the crystallization-assisted treatment prepared in S5 was filtered through a 0.45 μm polytetrafluoroethylene filter head, and then spin-coated on the surface of the hole injection layer at a first speed of 50 rpm for 5 seconds and a second speed of 4000 rpm for 55 seconds. The solution was then annealed at 70°C for 10 minutes and then cooled to room temperature to obtain a copper-based halide light-emitting layer.

[0088] S65, Evaporation of electron transport layer: at pressure <6.5×10 -4 Under high vacuum conditions of 1.5 Å Pa, an electron transport layer was evaporated on the surface of the copper-based halide light-emitting layer at a growth rate of 0.4 Å / s.

[0089] S66, evaporation electrode modification layer: at pressure <6.5×10 -4 Under high vacuum conditions of 1.57 Pa, the electrode modification layer was evaporated on the surface of the electron transport layer at a growth rate of 0.11 Å / s.

[0090] S67, evaporation of metal electrodes: finally at a pressure of <6.5×10 -4Under high vacuum conditions of 1.5 Pa, metal electrodes were evaporated on the surface of the electrode modification layer at a growth rate of 1.3 Å / s.

[0091] In Example 3 of the present invention, a method for preparing a copper-based halide light-emitting diode is provided, comprising the following steps:

[0092] S1, preparing a LiSCN solution: dissolving LiSCN solid in deionized water, and stirring with a stirrer at a speed of 600 rpm for 50 minutes to obtain a LiSCN solution.

[0093] S2, preparing a modified hole injection layer solution: mixing the LiSCN solution and the PEDOT:PSS solution, and stirring them with a stirrer at a speed of 600 rpm for 150 minutes to obtain a modified hole injection layer solution.

[0094] S3, preparing a crystallization auxiliary agent: preparing a PVDF solution as a crystallization auxiliary agent; the PVDF solution is obtained by dissolving PVDF solid in dimethyl sulfoxide at a concentration of 20 mg / mL and stirring with a stirrer at a speed of 400 rpm for 40 minutes.

[0095] S4, preparing a copper-based halide Cs3Cu2I5 precursor solution: dissolving CsI and CuI in a dimethylacetamide organic solvent at a molar ratio of 3:2 at a concentration of 0.5 M, and stirring with a stirrer at a speed of 600 rpm at 70°C for 3 minutes, and then stirring at 30°C for 8 hours to obtain a Cs3Cu2I5 copper-based halide precursor solution.

[0096] S5, mixing the crystallization auxiliary agent and the copper-based halide precursor solution: the crystallization auxiliary agent prepared by S3 and the copper-based halide precursor solution prepared by S4 are mixed in a volume ratio of 1:20, and stirred with a stirrer at a speed of 600 rpm at 30°C for 8 hours to obtain a copper-based halide precursor solution after crystallization auxiliary treatment.

[0097] S6, preparing a copper-based halide light-emitting diode device: forming an ITO conductive glass 1, a hole injection layer 2, a copper-based halide light-emitting layer 3, an electron transport layer 4, an electrode modification layer 5 and a metal electrode 6 from bottom to top to form a copper-based halide light-emitting diode device; wherein the hole injection layer 2, the copper-based halide light-emitting layer 3, the electron transport layer 4, and the electrode modification layer 5 constitute a light-emitting unit.

[0098] In the S6, the thickness of the ITO conductive glass is 40 nm, the thickness of the hole injection layer is 15 nm, the thickness of the copper-based halide light-emitting layer is 100 nm, the thickness of the electron transport layer is 60 nm, the thickness of the electrode modification layer is 0.8 nm, and the thickness of the metal electrode is 40 nm.

[0099] In S1, the LiSCN solution is obtained by dissolving LiSCN solid in deionized water, and the concentration of the LiSCN solution is 210 mg / mL.

[0100] In S2, the concentration of the PEDOT:PSS solution is 1.6 wt.%, and it is diluted with deionized water, and the volume ratio of the LiSCN solution to the PEDOT:PSS solution is 1:2.

[0101] In S6, the material used for the electron transport layer is TmPyPB.

[0102] In S6, the material used for the electrode modification layer is LiF.

[0103] In S6, the material used for the metal electrode is Au.

[0104] In said S6, preparing a copper-based halide light-emitting diode device comprises the following steps:

[0105] S61, ultrasonic cleaning of ITO conductive glass: After wiping the ITO conductive glass with a dust-free cloth, soak the ITO conductive glass in detergent, deionized water, acetone, and isopropyl alcohol in sequence and ultrasonically clean it for 30 minutes.

[0106] S62, UV-ozone treatment of ITO conductive glass: The cleaned ITO conductive glass is blown dry with a hot air blower, then placed in a sealed, light-proof environment and irradiated with short-wave ultraviolet light; the short-wave ultraviolet light simultaneously emits two wavelengths of ultraviolet light, 185nm and 254nm.

[0107] S63, spin coating of hole injection layer: 400uL of the modified hole injection layer solution prepared in S2 was filtered through a 0.22μm aqueous phase filter head, and then spin coated on the surface of ITO conductive glass at a speed of 5000 rpm for 50 seconds, and then annealed at 130°C for 15 minutes, and then cooled to room temperature to obtain a hole injection layer.

[0108] S64, spin coating of a copper-based halide light-emitting layer: 150 uL of the copper-based halide precursor solution after the crystallization-assisted treatment prepared in S4 was filtered through a 0.45 μm polytetrafluoroethylene filter head, and then spin-coated on the surface of the hole injection layer at a first speed of 80 rpm for 12 seconds and a second speed of 5000 rpm for 30 seconds. The solution was then annealed at 90°C for 15 minutes and then cooled to room temperature to obtain a copper-based halide light-emitting layer.

[0109] S65, Evaporation of electron transport layer: at pressure <6.5×10 -4 Under high vacuum conditions of 1.57 Pa, an electron transport layer was evaporated on the surface of the copper-based halide light-emitting layer at a growth rate of 0.45 Å / s.

[0110] S66, evaporation electrode modification layer: at pressure <6.5×10 -4 Under high vacuum conditions of 500 Pa, the electrode modification layer was evaporated on the surface of the electron transport layer at a growth rate of 0.09 Å / s.

[0111] S67, evaporation of metal electrodes: finally at a pressure of <6.5×10 -4 Under high vacuum conditions of 1.5 Pa, metal electrodes were evaporated on the surface of the electrode modification layer at a growth rate of 1.25 Å / s.

[0112] Comparative Example 1: In this comparative example, a copper-based halide light-emitting diode was prepared. The preparation method and raw material amounts were the same as in Example 1, except that the hole injection layer was spin-coated using a PEDOT:PSS solution, and the copper-based halide light-emitting layer was spin-coated directly on the surface of the hole injection layer. That is, the hole injection layer was neither modified nor the copper-based halide precursor was subjected to auxiliary crystallization treatment.

[0113] Comparative Example 2: In this comparative example, a copper-based halide light-emitting diode was prepared. The preparation method and raw material amounts were the same as in Example 2, except that the hole injection layer was spin-coated using a PEDOT:PSS solution, and the copper-based halide light-emitting layer was spin-coated directly on the surface of the hole injection layer. That is, the hole injection layer was neither modified nor the copper-based halide precursor was subjected to auxiliary crystallization treatment.

[0114] Figure 2 and Figure 3 The scanning electron microscope images of the copper-based halide thin films of Example 1 and Comparative Example 1 are shown respectively. Figure 2 and Figure 3 It can be seen that the copper-based halide film of the embodiment after the hole injection layer modification and crystallization auxiliary treatment is denser than that of the comparative example, indicating that the crystallization quality of the copper-based halide in the embodiment is higher; Figure 4 The luminous brightness of the embodiment and the comparative example is shown by comparison. Figure 4It can be seen that the examples after hole injection layer modification and crystallization auxiliary treatment have higher brightness than the comparative examples. The luminous intensity of Examples 1, 2, and 3 is significantly higher than that of Comparative Examples 1 and 2 over the entire operating voltage range, indicating that the energy loss at the interfaces of the functional layers of the device is reduced and the charge injection is more balanced. Figure 5 The external quantum efficiency (EQE) of the embodiments of the present invention and the comparative example is shown. Figure 5 It can be seen that the external quantum efficiency (EQE) of the copper-based halide light-emitting diode device after hole injection layer modification and crystallization auxiliary treatment is significantly higher than that of the copper-based halide light-emitting diode device without hole injection layer modification and crystallization auxiliary treatment, indicating that the radiative recombination efficiency of the embodiment device is improved; Figure 6 The brightness of the embodiment of the present invention and the comparative example decreases over time under the operating voltage, and the ratio of the device brightness to the initial brightness is used as the measurement basis. Figure 6 It can be seen that the copper-based halide light-emitting diode device that has undergone hole injection layer modification and crystallization-assisted treatment has a smaller brightness reduction after the same period of time, indicating that the stability and service life of the device have been improved.

[0115] Working Principle: During use, the copper-based halide light-emitting diode of the present invention comprises, from bottom to top, the following: ITO conductive glass 1, hole injection layer 2, copper-based halide light-emitting layer 3, electron transport layer 4, electrode modification layer 5, and metal electrode 6. Its operating process is as follows: A positive voltage is continuously applied to the ITO conductive glass 1 end and a negative voltage is continuously applied to the metal electrode 6 end, causing holes to be injected from the ITO conductive glass 1 end and electrons to be injected from the metal electrode 6 end. Holes are injected into the copper-based halide light-emitting layer 3 through the hole injection layer 2, and electrons are injected into the copper-based halide light-emitting layer 3 through the electrode modification layer 5 and the electron transport layer 4. Because the highest occupied molecular orbital (HOMO) energy level of the electron transport layer 4 is relatively low and the lowest unoccupied molecular orbital (LUMO) energy level of the hole injection layer 2 is relatively high, the injected electrons and holes are effectively confined in the copper-based halide light-emitting layer 3. Holes and electrons recombine in the copper-based halide light-emitting layer 3 to generate excitons, which undergo radiative transitions to generate photons, which escape from the light-emitting diode device and emit light.

[0116] The above-mentioned copper-based halide light-emitting diode has good luminescence performance and can meet the needs of high-quality display. The present invention uses alkali metal thiocyanate to dope PEDOT:PSS to increase the hole injection rate, and uses PVP and PVDF as crystallization aids to improve the growth morphology of copper-based halide. The copper-based halide light-emitting diode and preparation method described in the present invention use alkali metal thiocyanate to modify PEDOT:PSS, which can significantly improve the hole injection ability of the light-emitting diode device, promote the exciton recombination process, and greatly improve the brightness and external quantum efficiency of the device; thiocyanate and Cu ions interact with each other to improve the crystallization quality of the copper-based halide precursor, inhibit crystal agglomeration, and improve the fluorescence quantum yield and film uniformity; at the same time, thiocyanate can increase the formation energy of halogen vacancies in copper-based halides, inhibit the migration of halogen ions, and thus passivate halogen vacancy defects. The copper-based halide light-emitting diode device described in the present invention has good luminescence performance and stability, and the light-emitting layer uses non-lead materials, which is green and environmentally friendly and can meet the needs of high-quality display. The data comparison diagram obtained by comparing the embodiment with the comparative example is as follows Figure 2 、 Figure 3 、 Figure 4 、 Figure 5 and Figure 6 shown.

[0117] The present invention provides a copper-based halide light-emitting diode and a method for preparing the same. While numerous methods and approaches exist for implementing this technical solution, the foregoing merely represents a preferred embodiment of the present invention. It should be noted that those skilled in the art may make various improvements and modifications without departing from the principles of the present invention, and such improvements and modifications are also within the scope of protection of the present invention. Any components not specified in this embodiment may be implemented using existing technologies.

Claims

1. A method for preparing a copper-based halide light-emitting diode, characterized in that: The following steps are involved: Step 1, preparing an alkali metal thiocyanate solution; Step 2, preparing a modified hole injection layer solution; Step 3, preparing a crystallization auxiliary agent; Step 4, preparation of copper-based halide Cs x Cu2I x+2 Precursor solution; Step 5, mixing a crystallization auxiliary agent and a copper-based halide precursor solution; Step 6, preparing a copper-based halide light-emitting diode device; Step 1 comprises: dissolving an alkali metal thiocyanate solid in deionized water and stirring with a stirrer at a speed of 100 to 1000 rpm for 5 to 120 minutes to obtain an alkali metal thiocyanate solution, wherein the alkali metal thiocyanate is any one of lithium thiocyanate, potassium thiocyanate, sodium thiocyanate, and cesium thiocyanate; In step 1, the concentration of the alkali metal thiocyanate solution is 1 to 220 mg / mL; Step 2 comprises: mixing an alkali metal thiocyanate solution with a poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) PEDOT:PSS solution, and stirring the mixture with a stirrer at a speed of 100 to 1000 rpm for 15 to 280 minutes to obtain a modified hole injection layer solution; In step 2, the poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) PEDOT:PSS solution has a concentration of 1.1 to 1.6 wt.%, is diluted with deionized water, and the volume ratio of the alkali metal thiocyanate solution to the poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid) PEDOT:PSS solution is 1:X1, where the parameter X1 is 2 to 5; Step 3 comprises: preparing a polyvinyl pyrrolidone (PVP) solution or a polyvinylidene fluoride (PVDF) solution as a crystallization auxiliary agent; The polyvinyl pyrrolidone (PVP) solution is prepared by dissolving a polyvinyl pyrrolidone (PVP) solid in dimethyl sulfoxide at a concentration of 1 to 80 mg / mL and stirring the solution with a stirrer at a speed of 100 to 1000 rpm for 10 to 60 minutes. The polyvinylidene fluoride (PVDF) solution is prepared by dissolving polyvinylidene fluoride (PVDF) solid in dimethyl sulfoxide at a concentration of 1 to 80 mg / mL and stirring with a stirrer at a speed of 100 to 1000 rpm for 10 to 60 minutes. Step 4 comprises: dissolving cesium iodide CsI and cuprous iodide CuI in a molar ratio of x:2 at a concentration of 0.1 to 0.6 M in one of the organic solvents of N,N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, methyl ethyl ketone, and dimethylacetamide, and stirring with a stirrer at a speed of 200 to 600 rpm at 50 to 70° C. for 3 to 10 minutes, and then stirring at a temperature of 20 to 30° C. for 5 to 18 hours to obtain a copper-based halide CsI. x Cu2I x+2 Precursor solution; wherein the parameter x is 1 or 3; Step 5 includes: mixing a crystallization auxiliary agent and a copper-based halide Cs x Cu2I x+2 The precursor solutions are mixed in a volume ratio of 1:X2 and stirred with a stirrer at a speed of 200 to 600 rpm at 20 to 30° C. for 3 to 8 hours to obtain a copper-based halide precursor solution after crystallization-assisted treatment; the parameter X2 is 10 to 20; Step 6 includes the following steps: Step 6-1, ultrasonic cleaning of the ITO conductive glass: After wiping the ITO conductive glass with a dust-free cloth, soak the ITO conductive glass in detergent, deionized water, acetone, and isopropyl alcohol in sequence and ultrasonically clean it for 10 to 40 minutes; Step 6-2, UV-ozone treatment of ITO conductive glass: the cleaned ITO conductive glass is blown dry, then placed in a sealed, light-proof environment and irradiated with short-wave ultraviolet light; the short-wave ultraviolet light simultaneously emits two wavelengths of ultraviolet light, 180-187 nm and 248-257 nm; Step 6-3, spin coating a hole injection layer: 100 to 400 μL of the modified hole injection layer solution prepared in step 2 is filtered through a filter head and then spin coated on the surface of the ITO conductive glass at a speed of 3000 to 9000 rpm for 10 to 60 seconds. The mixture is then annealed at 110 to 145° C. for 10 to 30 minutes and then cooled to room temperature to obtain a hole injection layer. Step 6-4, spin coating a copper-based halide light-emitting layer: 100 to 300 μL of the copper-based halide precursor solution after the crystallization-assisted treatment prepared in step 5 is filtered through a filter head, and then spin-coated on the surface of the hole injection layer at a first speed of 50 to 200 rpm for 5 to 12 seconds and a second speed of 1000 to 6000 rpm for 10 to 60 seconds, followed by annealing at 50 to 140° C. for 8 to 40 minutes, and then cooling to room temperature to obtain a copper-based halide light-emitting layer; Step 6-5, evaporation of electron transport layer: at a pressure less than 9×10 -4 Pa under high vacuum conditions, the surface of the copper-based halide luminescent layer is Growth rate of evaporated electron transport layer; Step 6-6, evaporation of electrode modification layer: at a pressure less than 9×10 -4 Pa under high vacuum conditions, the surface of the electron transport layer Growth rate of evaporated electrode modification layer; Step 6-7, evaporation of metal electrodes: at a pressure less than 9×10 -4 Pa under high vacuum conditions, the surface of the electrode modified layer Growth rate of evaporated metal electrodes; Finally, the ITO conductive glass (1), the hole injection layer (2), the copper-based halide light-emitting layer (3), the electron transport layer (4), the electrode modification layer (5) and the metal electrode (6) are combined from bottom to top to form a copper-based halide light-emitting diode device; wherein the hole injection layer (2), the copper-based halide light-emitting layer (3), the electron transport layer (4) and the electrode modification layer (5) constitute a light-emitting unit; The thickness of the ITO conductive glass is 40-180 nm, the thickness of the hole injection layer is 10-100 nm, the thickness of the copper-based halide light-emitting layer is 30-200 nm, the thickness of the electron transport layer is 10-100 nm, the thickness of the electrode modification layer is 0.1-20 nm, and the thickness of the metal electrode is 40-130 nm. The material used for the electron transport layer is one of 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene TPBi and 3,3'-[5'-[3-(3-pyridyl)phenyl][1,1':3',1"-terphenyl]-3,3"-diyl]dipyridine TmPyPB; The material used for the electrode modification layer is one of lithium fluoride LiF and 8-hydroxyquinoline-lithium Liq; The material used for the metal electrode is one of aluminum Al, silver Ag, gold Au, and zinc Zn.

2. A copper-based halide light-emitting diode prepared by the method according to claim 1, characterized in that: The invention comprises, from bottom to top, an ITO conductive glass (1), a hole injection layer (2), a copper-based halide luminescent layer (3), an electron transport layer (4), an electrode modification layer (5) and a metal electrode (6); wherein the hole injection layer (2), the copper-based halide luminescent layer (3), the electron transport layer (4) and the electrode modification layer (5) constitute a luminescent unit.

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