Sodium salt modified nickel oxide transport layer, perovskite light-emitting diode and its preparation method

Abstract

This invention discloses a sodium salt-modified nickel oxide transport layer, a perovskite light-emitting diode, and its preparation method. The invention modifies the nickel oxide film by introducing a certain concentration of sodium salt into a dispersion of nickel oxide nanoparticles, thereby improving the quality of the nickel oxide film and enhancing the performance of the light-emitting diode. The addition of sodium polystyrene sulfonate (PSSNa) reduces the surface roughness of the nickel oxide film and improves its flatness and uniformity. Simultaneously, NiO... x - The perovskite layer interface quality is improved, the perovskite film surface is smoother and more uniform, with higher crystallinity, which inhibits NiO. x The photoluminescence quenching at the perovskite interface significantly improves the performance of the perovskite light-emitting diodes prepared based on sodium salt modification in this invention.

Description

Technical Field

[0001] This invention belongs to the field of optoelectronic materials and devices technology, specifically relating to a sodium salt modified nickel oxide transport layer, a perovskite light-emitting diode, and its preparation method. Background Technology

[0002] In recent years, metal halide perovskite materials have attracted widespread attention due to their excellent photoelectric properties, and the conversion efficiency of optoelectronic devices based on perovskite materials has achieved rapid development. Among them, perovskite light-emitting diodes (PeLEDs) are gradually becoming the focus of attention in the lighting and display fields due to their advantages such as high photoluminescence quantum yield, tunable bandgap, and high color purity.

[0003] In perovskite light-emitting diodes (LEDs), the hole transport layer (HTL) plays a crucial role in improving carrier extraction / injection efficiency and enhancing device stability. Among numerous hole transport layer materials, NiO... x As an inorganic p-type wide-bandgap semiconductor, nickel oxide (NiOx) possesses high optical transparency, good chemical and physical stability, and excellent hole transport and electron blocking capabilities, making it an ideal choice for hole transport layer materials. However, the quality of the nickel oxide film and an undesirable NiOx-perovskite interface can affect the crystallinity and stability of the perovskite layer, thus negatively impacting the optoelectronic performance of PeLEDs. Achieving low-cost preparation of nickel oxide films under low-temperature annealing conditions and employing simple and efficient methods to modify them is crucial for improving device performance. However, existing reports on the preparation and modification of nickel oxide films at low temperatures are very limited, and the performance of optoelectronic devices based on these methods remains unsatisfactory. Therefore, seeking methods for low-temperature modified nickel oxide preparation is of great significance for developing efficient and stable optoelectronic devices. Summary of the Invention

[0004] To address the aforementioned problems, the present invention aims to provide a sodium salt-modified nickel oxide transport layer, a perovskite light-emitting diode, and a method for preparing the same. By introducing a certain concentration of sodium salt into a dispersion of nickel oxide nanoparticles, the nickel oxide film is modified, thereby improving the film quality and enhancing the performance of the perovskite light-emitting diode device.

[0005] To achieve the above objectives, the present invention adopts the following technical solution.

[0006] The first aspect of the present invention provides a method for preparing a sodium salt modified nickel oxide transport layer, comprising: spin-coating a sodium salt modified nickel oxide solution onto a pretreated substrate to form a film, followed by annealing to obtain the sodium salt modified nickel oxide transport layer.

[0007] As a further illustration of the present invention, the concentration of the sodium salt modified nickel oxide solution is 16 mg / mL.

[0008] As a further explanation of the present invention, the sodium salt is one of sodium polystyrene sulfonate, sodium 4-styrene sulfonate, and sodium citrate.

[0009] As a further explanation of the present invention, the preparation method specifically includes:

[0010] 30 μL of sodium salt modified nickel oxide solution was dropped onto the pretreated ITO conductive glass and spin-coated at 4000 rpm / min for 40 s. Then, it was annealed in air at 100 °C for 10 min to obtain the sodium salt modified nickel oxide transport layer.

[0011] As a further explanation of the present invention, the preparation process of the sodium salt modified nickel oxide solution includes:

[0012] Preparation of raw nickel oxide solution: A certain amount of nickel oxide nanoparticles were taken and fully dispersed in an aqueous solution to obtain a dispersion. The dispersion was then filtered to obtain the raw nickel oxide solution.

[0013] Preparation of sodium salt modified nickel oxide solution: A certain amount of sodium salt is added to the original nickel oxide solution and mixed thoroughly to obtain a sodium salt modified nickel oxide solution.

[0014] As a further explanation of the present invention, the preparation process of the nickel oxide nanoparticles specifically includes:

[0015] 9 g of Ni(NO3)2•6H2O was weighed and dissolved in 50 mL of deionized water. The solution was stirred at 500 rpm / min for 30 min. Then, a 10 mmol / mL sodium hydroxide aqueous solution was added dropwise to the Ni(NO3)2•6H2O solution at a certain dropping rate until the pH reached 10. The green precipitate was then washed three times with deionized water. The green precipitate was refrigerated in a refrigerator for 2 h and then dried in a vacuum oven at 80 ℃ to obtain green powder. The green powder was ground for 30 min and then calcined in a muffle furnace at 270 ℃ for 2 h to obtain black nickel oxide powder. The obtained nickel oxide powder was ground for 30 min to obtain nickel oxide nanoparticles.

[0016] As a further explanation of the present invention, the preparation process of the original nickel oxide solution specifically includes:

[0017] A certain amount of nickel oxide nanoparticles were taken and dispersed in an aqueous solution at a concentration of 20 mg / mL. After stirring at room temperature for 1 h, a dispersion was obtained. The dispersion was then filtered using a syringe filter with a pore size of 0.45 μm to obtain the original nickel oxide solution.

[0018] As a further explanation of the present invention, the preparation process of the sodium salt modified nickel oxide solution specifically includes:

[0019] Take 1 mL of the original nickel oxide solution, add 16 mg of sodium polystyrene sulfonate (PSSNa), sodium 4-styrene sulfonate (SSNa), or sodium citrate (CNa), and stir at room temperature for 30 min to obtain a sodium salt modified nickel oxide solution with a concentration of 16 mg / mL.

[0020] A second aspect of the present invention provides a perovskite light-emitting diode, the light-emitting diode comprising a sodium salt modified nickel oxide transport layer obtained by any one of the above-described preparation methods.

[0021] A third aspect of this invention provides a method for fabricating a perovskite light-emitting diode, comprising:

[0022] Pretreated indium tin oxide (ITO) glass is used as the anode of a perovskite light-emitting diode. A sodium salt modified nickel oxide solution is spin-coated onto the ITO glass, and after annealing, a sodium salt modified nickel oxide transport layer as described above is formed.

[0023] A perovskite solution was spin-coated onto the sodium salt-modified nickel oxide transport layer, and then annealed to form a perovskite luminescent layer.

[0024] An electron transport layer is formed by vacuum evaporation of a TPBi layer on the perovskite light-emitting layer;

[0025] A LiF / Al electrode is vacuum-deposited on the electron transport layer to serve as the cathode of the perovskite light-emitting diode.

[0026] Compared with the prior art, the present invention has the following advantages:

[0027] 1. This invention uses sodium polystyrene sulfonate (PSSNa), sodium 4-styrene sulfonate (SSNa), or sodium citrate (CNa) to modify nickel oxide nanoparticles, and prepares nickel oxide thin films under low-temperature annealing conditions. The perovskite light-emitting diodes prepared based on sodium salt modification in this invention exhibit significantly improved performance, providing a new approach for the preparation of efficient and stable PeLEDs.

[0028] 2. Taking the modification with PSSNa as an example, within a certain concentration range, the surface roughness of the nickel oxide film is reduced by the addition of PSSNa. When the sodium salt concentration is 16 mg / mL, the surface roughness of the modified nickel oxide film is reduced from 7.49 nm to 2.75 nm. The resulting nickel oxide film has a uniform, dense, and flat surface with a significant reduction in irregular particles, improved film crystallinity, and increased film quality.

[0029] 3. The PSSNa-modified nickel oxide thin film and perovskite light-emitting diode device prepared in this invention, wherein the NiO... x - The photoluminescence quenching effect at the perovskite layer interface is suppressed, improving the device's luminous efficiency. At the same time, the carrier lifetime is extended, and the device's stability is further improved. Attached Figure Description

[0030] Figure 1 This is a schematic diagram of the structure of the perovskite light-emitting diodes prepared in Comparative Example 1 and Examples 1, 2, and 3.

[0031] Figure 2 The EQE curves are for the perovskite light-emitting diodes prepared in Comparative Example 1 and Examples 1, 2, and 3.

[0032] Figure 3 Performance curves of the perovskite light-emitting diodes prepared in Comparative Example 1 and Examples 1, 2, and 3.

[0033] Figure 4 Atomic force microscopy (AFM) images of nickel oxide films modified with different concentrations of PSSNa prepared according to the preparation method of Example 1, for comparison with Example 1.

[0034] Figure 5 The images show scanning electron microscope (SEM) images of the perovskite films deposited on nickel oxide films prepared in Comparative Example 1 and Example 1, and atomic force microscope (AFM) images of the prepared nickel oxide films.

[0035] Figure 6 Photoluminescence intensity-wavelength diagrams and normalized photoluminescence intensity-time diagrams of the perovskite films deposited on nickel oxide films prepared in Comparative Example 1 and Example 1. Implementation

[0036] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0037] The first aspect of this invention provides a method for preparing a sodium salt modified nickel oxide transport layer, comprising:

[0038] A certain amount of raw nickel oxide nanoparticles were dispersed in an aqueous solution and stirred at room temperature for 1 h to obtain a dispersion. The dispersion was then filtered using a syringe filter with a pore size of 0.45 μm to obtain a raw nickel oxide solution. 1 mL of the raw nickel oxide solution was taken and 16 mg of sodium polystyrene sulfonate (PSSNa), sodium 4-styrene sulfonate (SSNa), or sodium citrate (CNa) was added respectively. The mixture was stirred at room temperature for 30 min to obtain a sodium salt modified nickel oxide solution.

[0039] Take 30 μL of the sodium salt modified nickel oxide solution obtained above, drop it onto the pretreated substrate, spin coat it at 4000 rpm / min for 40 s, and then anneal it in air at 100 ℃ for 10 min to prepare the sodium salt modified nickel oxide transport layer.

[0040] In some feasible methods, the synthesis process of the original nickel oxide nanoparticles is as follows:

[0041] 9 g of Ni(NO3)2•6H2O was weighed and dissolved in 50 mL of deionized water. The solution was stirred at 500 rpm / min for 30 min. Then, a 10 mmol / mL sodium hydroxide aqueous solution was added dropwise to the Ni(NO3)2•6H2O solution at a certain dropping rate until the pH reached 10. The green precipitate was then washed three times with deionized water. The precipitate was refrigerated in a refrigerator for 2 h and then dried in a vacuum oven at 80 ℃ to obtain green powder. The green powder was ground for 30 min and then calcined in a muffle furnace at 270 ℃ for 2 h to obtain black nickel oxide powder. The obtained powder was ground for 30 min to obtain the original nickel oxide nanoparticles.

[0042] Preferably, the concentration of the nickel oxide dispersion is 20 mg / mL.

[0043] This invention also provides a method for fabricating a perovskite light-emitting diode, comprising: using pretreated indium tin oxide (ITO) conductive glass as the anode of the perovskite light-emitting diode; spin-coating a sodium salt modified nickel oxide solution obtained by the above preparation method onto the ITO glass as a hole transport layer; spin-coating a perovskite solution onto the hole transport layer as a perovskite light-emitting layer; depositing a layer of TPBi on the perovskite light-emitting layer using vacuum evaporation technology as an electron transport layer; and depositing a layer of LiF / Al electrode on the electron transport layer using vacuum evaporation technology as the cathode of the perovskite light-emitting diode.

[0044] In some feasible methods, the pretreatment process of indium tin oxide (ITO) conductive glass is as follows: the indium tin oxide (ITO) conductive glass is cleaned sequentially with glass cleaning solution, deionized water, acetone, isopropanol and ethanol, dried with high-purity nitrogen gas, and then treated with ultraviolet-ozone for 20 min.

[0045] In some feasible methods, the preparation process of the hole transport layer specifically includes: taking 30 μL of sodium salt modified nickel oxide solution obtained by the above preparation method and adding it dropwise onto the pretreated ITO conductive glass, spin-coating it at a speed of 4000 rpm / min for 40 s, and then annealing it in air at 100 ℃ for 10 min to obtain the hole transport layer.

[0046] In some feasible methods, the preparation process of the perovskite luminescent layer specifically includes: in a nitrogen glove box, a perovskite precursor solution is dropped onto a pretreated hole transport layer, spin-coated at 6000 rpm / min for 70 s, 300 μL of ethyl acetate is added as an antisolvent at 45 seconds, and then annealed at 80 °C for 10 min to obtain the perovskite luminescent layer.

[0047] Specifically, the perovskite precursor solution preparation process is as follows:

[0048] Phenethylammonium bromide (PEABr), formamidinium hydrobromide (FABr), methylamine hydrobromide (MABr), cesium bromide (CsBr) and lead bromide (PbBr2) were dissolved in dimethyl sulfoxide (DMSO) solvent and stirred at room temperature for 2 h to prepare a quasi-two-dimensional perovskite precursor solution.

[0049] More specifically, Pb in perovskite precursor solution 2+ The concentration was maintained at 0.20 M, and the molar ratio of PEABr∶FABr∶MABr∶CsBr∶PbBr2 was 0.4∶0.3∶0.3∶0.6∶1.

[0050] The preparation process of the perovskite light-emitting layer also includes: after the prepared hole transport layer is treated with plasma for 5 min, it is quickly transferred to a nitrogen glove box.

[0051] In some feasible methods, the electron transport layer is prepared by vacuum evaporation, with a thickness of 40 nm for the electron transport layer TPBi.

[0052] In some feasible methods, LiF / Al electrodes with a thickness of 100 nm are prepared using vacuum evaporation.

[0053] The following description is based on specific embodiments: Example

[0054] This embodiment describes a method for fabricating a perovskite light-emitting diode containing a sodium salt-modified nickel oxide transport layer, comprising the following steps:

[0055] S1: Weigh 9 g Ni(NO3)2•6H2O and dissolve it in 50 mL of deionized water. Stir at 500 rpm / min for 30 min. Then, add 10 mmol / mL sodium hydroxide aqueous solution dropwise to the Ni(NO3)2•6H2O solution at a certain dropping rate until the pH reaches 10. Wash the green precipitate three times with deionized water. Refrigerate the precipitate in a refrigerator for 2 h and then dry it in a vacuum oven at 80 ℃ to obtain green powder. Grind the green powder for 30 min and calcine it in a muffle furnace at 270 ℃ for 2 h to obtain black nickel oxide powder. Grind the obtained powder for 30 min to obtain nickel oxide nanoparticles.

[0056] S2: Take a certain amount of nickel oxide nanoparticles prepared in step S1, disperse them in an aqueous solution at a concentration of 20 mg / mL, stir at room temperature for 1 h to obtain a dispersion, filter it using a syringe filter with a pore size of 0.45 μm to obtain the original nickel oxide solution.

[0057] S3: Take 1 mL of the original nickel oxide solution prepared in step S2, add 16 mg of sodium polystyrene sulfonate (PSSNa), stir at room temperature for 30 min to obtain a PSSNa-modified nickel oxide solution with a concentration of 16 mg / mL;

[0058] S4: Clean the indium tin oxide (ITO) conductive glass. The cleaning sequence is glass cleaning solution, deionized water, acetone, isopropanol, and ethanol. Then, dry it with high-purity nitrogen and treat it with ultraviolet-ozone for 20 minutes.

[0059] S5: Take 30 μL of the PSSNa-modified nickel oxide solution prepared in step S3 and drop it onto the ITO conductive glass treated in step S4. Spin coat the glass with a spin coater at 4000 rpm / min for 40 s. Then anneal at 100 °C for 10 min to obtain the hole transport layer.

[0060] S6: After treating the hole transport layer prepared in step S5 with plasma for 5 min, quickly transfer it to a nitrogen glove box.

[0061] S7: Phenethylamine bromide (PEABr), formamidinium hydrobromide (FABr), methylamine hydrobromide (MABr), cesium bromide (CsBr), and lead bromide (PbBr2) were dissolved in dimethyl sulfoxide (DMSO) solvent and stirred at room temperature for 2 hours in a nitrogen glove box. PbBr2 was then dissolved in the solution. 2+The concentration was maintained at 0.20 M, and the molar ratio of PEABr∶FABr∶MABr∶CsBr∶PbBr2 was 0.4∶0.3∶0.3∶0.6∶1, thus preparing a quasi-two-dimensional perovskite precursor solution.

[0062] S8: The perovskite precursor solution prepared in step S7 is dropped onto the hole transport layer after step S6, and a film is formed by spin coating using a spin coater at a speed of 6000 rpm / min for 70 s. 300 μL of ethyl acetate is added as an antisolvent at 45 seconds, and then annealed at 80 °C for 10 min to obtain the perovskite luminescent layer.

[0063] S9: Using vacuum evaporation technology, an electron transport layer is deposited on the perovskite light-emitting layer prepared in step S8. The thickness of the electron transport layer TPBi is 40 nm.

[0064] S10: Using vacuum evaporation technology, a LiF / Al electrode with a thickness of 100 nm is deposited on the electron transport layer prepared in step S9 to obtain a perovskite light-emitting diode.

[0065] The nickel oxide film modified with sodium salt exhibits reduced roughness and improved density and uniformity. Based on this, the performance of the perovskite light-emitting diode prepared with it is enhanced, with the external quantum efficiency increasing from 2.13% to 6.24%, and stability significantly improved. 50 Time increased by 50%. Example

[0066] This embodiment describes a method for preparing a sodium salt-modified nickel oxide transport layer and its perovskite light-emitting diode, comprising the following steps:

[0067] S1: Weigh 9 g Ni(NO3)2•6H2O and dissolve it in 50 mL of deionized water. Stir at 500 rpm / min for 30 min. Then, add 10 mmol / mL sodium hydroxide aqueous solution dropwise to the Ni(NO3)2•6H2O solution at a certain dropping rate until the pH reaches 10. Wash the green precipitate three times with deionized water. Refrigerate the precipitate in a refrigerator for 2 h and then dry it in a vacuum oven at 80 ℃ to obtain green powder. Grind the green powder for 30 min and calcine it in a muffle furnace at 270 ℃ for 2 h to obtain black nickel oxide powder. Grind the obtained powder for 30 min to obtain nickel oxide nanoparticles.

[0068] S2: Take a certain amount of nickel oxide nanoparticles prepared in step S1, disperse them in an aqueous solution at a concentration of 20 mg / mL, stir at room temperature for 1 h to obtain a dispersion, filter it using a syringe filter with a pore size of 0.45 μm to obtain the original nickel oxide solution.

[0069] S3: Take 1 mL of the original nickel oxide solution prepared in step S2, add 16 mg of sodium 4-styrenesulfonate (SSNa), stir at room temperature for 30 min to obtain a nickel oxide solution modified with SSNa with a concentration of 16 mg / mL;

[0070] S4: Clean the indium tin oxide (ITO) conductive glass. The cleaning sequence is glass cleaning solution, deionized water, acetone, isopropanol, and ethanol. Then, dry it with high-purity nitrogen and treat it with ultraviolet-ozone for 20 minutes.

[0071] S5: Take 30 μL of the nickel oxide solution modified by SSNa prepared in step S3 and drop it onto the ITO conductive glass treated in step S4. Spin coat the glass with a spin coater at a speed of 4000 rpm / min for 40 s. Then anneal at 100 °C for 10 min to obtain the hole transport layer.

[0072] S6: After treating the hole transport layer prepared in step S5 with plasma for 5 min, quickly transfer it to a nitrogen glove box.

[0073] S7: Phenethylamine bromide (PEABr), formamidinium hydrobromide (FABr), methylamine hydrobromide (MABr), cesium bromide (CsBr), and lead bromide (PbBr2) were dissolved in dimethyl sulfoxide (DMSO) solvent and stirred at room temperature for 2 hours in a nitrogen glove box. PbBr2 was then dissolved in the solution. 2+ The concentration was maintained at 0.20 M, and the molar ratio of PEABr∶FABr∶MABr∶CsBr∶PbBr2 was 0.4∶0.3∶0.3∶0.6∶1, thus preparing a quasi-two-dimensional perovskite precursor solution.

[0074] S8: The perovskite precursor solution prepared in step S7 is dropped onto the hole transport layer after step S6, and a film is formed by spin coating using a spin coater at a speed of 6000 rpm / min for 70 s. 300 μL of ethyl acetate is added as an antisolvent at 45 seconds, and then annealed at 80 °C for 10 min to obtain the perovskite luminescent layer.

[0075] S9: Using vacuum evaporation technology, an electron transport layer is deposited on the perovskite light-emitting layer prepared in step S8. The thickness of the electron transport layer TPBi is 40 nm.

[0076] S10: Using vacuum evaporation technology, a LiF / Al electrode with a thickness of 100 nm is deposited on the electron transport layer prepared in step S9 to obtain a perovskite light-emitting diode. Example

[0077] This embodiment describes a method for preparing a sodium salt-modified nickel oxide transport layer and its perovskite light-emitting diode, comprising the following steps:

[0078] S1: Weigh 9 g Ni(NO3)2•6H2O and dissolve it in 50 mL of deionized water. Stir at 500 rpm / min for 30 min. Then, add 10 mmol / mL sodium hydroxide aqueous solution dropwise to the Ni(NO3)2•6H2O solution at a certain dropping rate until the pH reaches 10. Wash the green precipitate three times with deionized water. Refrigerate the precipitate in a refrigerator for 2 h and then dry it in a vacuum oven at 80 ℃ to obtain green powder. Grind the green powder for 30 min and calcine it in a muffle furnace at 270 ℃ for 2 h to obtain black nickel oxide powder. Grind the obtained powder for 30 min to obtain nickel oxide nanoparticles.

[0079] S2: Take a certain amount of nickel oxide nanoparticles prepared in step S1, disperse them in an aqueous solution at a concentration of 20 mg / ml, stir at room temperature for 1 h to obtain a dispersion, filter it using a syringe filter with a pore size of 0.45 μm to obtain the original nickel oxide solution.

[0080] S3: Take 1 mL of the original nickel oxide solution prepared in step S2, add 16 mg of sodium citrate (CNa), stir at room temperature for 30 min to obtain a nickel oxide solution modified with CNa with a concentration of 16 mg / mL;

[0081] S4: Clean the indium tin oxide (ITO) conductive glass in the following order: glass cleaning solution, deionized water, acetone, isopropanol, ethanol, and dry with high-purity nitrogen gas. Then treat with ultraviolet-ozone for 20 minutes.

[0082] S5: Take 30 μL of the CNa-modified nickel oxide solution prepared in step S3 and drop it onto the ITO conductive glass treated in step S4. Spin coat the glass with a spin coater at a speed of 4000 rpm / min for 40 s. Then anneal at 100 °C for 10 min to obtain the hole transport layer.

[0083] S6: After treating the hole transport layer prepared in step S5 with plasma for 5 min, quickly transfer it to a nitrogen glove box.

[0084] S7: Phenethylamine bromide (PEABr), formamidinium hydrobromide (FABr), methylamine hydrobromide (MABr), cesium bromide (CsBr), and lead bromide (PbBr2) were dissolved in dimethyl sulfoxide (DMSO) solvent and stirred at room temperature for 2 hours in a nitrogen glove box. PbBr2 was then dissolved in the solution. 2+The concentration was maintained at 0.20 M, and the molar ratio of PEABr∶FABr∶MABr∶CsBr∶PbBr2 was 0.4∶0.3∶0.3∶0.6∶1, thus preparing a quasi-two-dimensional perovskite precursor solution.

[0085] S8: The perovskite precursor solution prepared in step S7 is dropped onto the hole transport layer after step S6, and a film is formed by spin coating using a spin coater at a speed of 6000 rpm / min for 70 s. 300 μL of ethyl acetate is added as an antisolvent at 45 s, and then annealed at 80 ℃ for 10 min to obtain the perovskite luminescent layer.

[0086] S9: Using vacuum evaporation technology, an electron transport layer is deposited on the perovskite layer prepared in step S8. The thickness of the electron transport layer TPBi is 40 nm.

[0087] S10: Using vacuum evaporation technology, a LiF / Al electrode with a thickness of 100 nm is deposited on the electron transport layer prepared in step S9 to obtain a perovskite light-emitting diode.

[0088] Comparative Example 1:

[0089] This comparative example demonstrates a method for preparing a standard device, including the following steps:

[0090] S1: Weigh 9 g Ni(NO3)2•6H2O and dissolve it in 50 mL of deionized water. Stir at 500 rpm / min for 30 min. Then, add 10 mmol / mL sodium hydroxide aqueous solution dropwise to the Ni(NO3)2•6H2O solution at a certain dropping rate until the pH reaches 10. Wash the green precipitate three times with deionized water. Refrigerate the precipitate in a refrigerator for 2 h and then dry it in a vacuum oven at 80 ℃ to obtain green powder. Grind the green powder for 30 min and calcine it in a muffle furnace at 270 ℃ for 2 h to obtain black nickel oxide powder. Grind the obtained powder for 30 min to obtain nickel oxide nanoparticles.

[0091] S2: Take a certain amount of nickel oxide nanoparticles prepared in step S1, disperse them in an aqueous solution at a concentration of 20 mg / mL, stir at room temperature for 1 h to obtain a dispersion, filter it using a syringe filter with a pore size of 0.45 μm to obtain the original nickel oxide solution.

[0092] S3: Clean the indium tin oxide (ITO) conductive glass. The cleaning sequence is glass cleaning solution, deionized water, acetone, isopropanol, and ethanol. Then, dry it with high-purity nitrogen and treat it with ultraviolet-ozone for 20 minutes.

[0093] S4: Take 30 μL of the original nickel oxide solution prepared in step S2 and drop it onto the ITO conductive glass treated in step S3. Spin coat the glass with a spin coater at a speed of 4000 rpm / min for 40 s. Then anneal at 100 °C for 10 min to obtain the hole transport layer.

[0094] S5: After treating the hole transport layer prepared in step S4 with plasma for 5 min, quickly transfer it to a nitrogen glove box.

[0095] S6: Phenethylamine bromide (PEABr), formamidinium hydrobromide (FABr), methylamine hydrobromide (MABr), cesium bromide (CsBr), and lead bromide (PbBr2) were dissolved in dimethyl sulfoxide (DMSO) solvent and stirred at room temperature for 2 hours in a nitrogen glove box. PbBr2 was then dissolved in the solution. 2+ The concentration was maintained at 0.20 M, and the molar ratio of PEABr∶FABr∶MABr∶CsBr∶PbBr2 was 0.4∶0.3∶0.3∶0.6∶1, thus preparing a quasi-two-dimensional perovskite precursor solution.

[0096] S7: The perovskite precursor solution prepared in step S6 is dropped onto the hole transport layer after step S5, and a film is formed by spin coating using a spin coater at a speed of 6000 rpm / min for 70 s. 300 μL of ethyl acetate is added as an antisolvent at 45 seconds, and then annealed at 80 °C for 10 min to obtain the perovskite luminescent layer.

[0097] S8: Using vacuum evaporation technology, an electron transport layer is deposited on the perovskite light-emitting layer prepared in step S7. The thickness of the electron transport layer TPBi is 40 nm.

[0098] S9: Using vacuum evaporation technology, a LiF / Al electrode with a thickness of 100 nm is deposited on the electron transport layer prepared in step S8 to obtain a perovskite light-emitting diode.

[0099] Figure 1 This is a schematic diagram of the structure of the perovskite light-emitting diodes prepared in Comparative Example 1 and Examples 1, 2, and 3. From... Figure 1 As can be seen from the diagram, the perovskite light-emitting diode uses ITO glass as the anode, nickel oxide film as the hole transport layer, perovskite solution as the light-emitting layer, TPBi as the electron transport layer, and LiF / Al as the cathode.

[0100] Figure 2 To compare the EQE curve distribution of the perovskite light-emitting diodes prepared in Example 1 with those prepared in Examples 1, 2, and 3, we can see the following: From... Figure 2As can be seen, the EQE values ​​of the devices in Examples 1, 2, and 3 are significantly improved, reaching a maximum of 6.24%, indicating that the performance of the devices based on sodium salt modified nickel oxide films is significantly improved.

[0101] Figure 3 The graph shows the performance curves of the perovskite light-emitting diodes prepared in Comparative Example 1 and Examples 1, 2, and 3. Figure 3 As can be seen, the current density of the devices in Examples 1, 2, and 3 is lower than that in Comparative Example 1, and the maximum brightness of the devices is also reduced. This is consistent with the CV curve results. The EQE value of the devices is improved due to the introduction of sodium salt.

[0102] Figure 4 Atomic force microscopy (AFM) images of nickel oxide films modified with different concentrations of PSSNa prepared according to the method of Example 1, for Comparative Example 1 and Example 1. Figure 4 As can be seen from this, the addition of PSSNa affects NiO x Flattening is effective; the root mean square roughness of the original nickel oxide film is 7.49 nm, which is greater than that of the modified film. Furthermore, the root mean square roughness is lowest at 2.75 nm when the concentration of PSSNa added is 16 mg / mL. A smoother hole transport layer interface allows for better contact with the perovskite layer, which is beneficial for improving device performance.

[0103] Figure 5 The images show scanning electron microscope (SEM) images and atomic force microscope (AFM) images of the perovskite films deposited on nickel oxide films prepared in Comparative Example 1 and Example 1. Figure 5 AFM diagram ( Figure 5 b、 Figure 5 c. Figure 5 e Figure 5 As can be seen from f), the surface roughness of the nickel oxide film modified with a certain concentration of sodium salt decreases, the film becomes more uniform and dense, and the film quality improves; furthermore, from Figure 5 SEM image ( Figure 5 a and Figure 5 As can be seen in d), the perovskite film deposited on the surface of the nickel oxide film modified with PSSNa has fewer pinholes and is smoother and more uniform than the original nickel oxide surface.

[0104] Figure 6 Photoluminescence intensity-wavelength plots and normalized photoluminescence intensity-time plots of the perovskite films deposited on nickel oxide films prepared in Comparative Example 1 and Example 1. Figure 6 The photoluminescence intensity-wavelength diagram shows that after modification with PSSNa, NiO... x- The fluorescence quenching effect at the perovskite film interface is suppressed; furthermore, from Figure 6 The time-resolved PL decay curves show that the fluorescence intensity of the film increases with the increase of carrier lifetime. The average carrier lifetime of the perovskite film deposited on the PSSNa-modified nickel oxide film is 7.36 ns, which is higher than the 6.11 ns of the original nickel oxide film.

[0105] It should be noted that, in this document, terms such as “comprising,” “including,” or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0106] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A method for preparing a sodium salt-modified nickel oxide transport layer, characterized by, The preparation method comprises the following steps: The sodium salt modified nickel oxide solution is prepared by the following steps: The original nickel oxide solution is prepared by the following steps: a certain amount of nickel oxide nanoparticles is dispersed in an aqueous solution at a concentration of 20 mg / mL, and after stirring at room temperature for 1 h, a dispersion is prepared, and the dispersion is filtered by using a syringe filter with a pore size of 0.45 μm to obtain the original nickel oxide solution. The sodium salt modified nickel oxide solution is prepared by the following steps: 1 mL of the original nickel oxide solution is taken, 16 mg of sodium 4-styrene sulfonate or sodium citrate is added, and stirring is performed at room temperature for 30 min to obtain the sodium salt modified nickel oxide solution with a concentration of 16 mg / mL. The preparation method specifically comprises the following steps:

2. The method for preparing the sodium salt modified nickel oxide transport layer according to claim 1, characterized in that, The sodium salt modified nickel oxide solution is prepared by the following steps: 1 mL of the original nickel oxide solution is taken, 16 mg of sodium 4-styrene sulfonate or sodium citrate is added, and stirring is performed at room temperature for 30 min to obtain the sodium salt modified nickel oxide solution with a concentration of 16 mg / mL. The preparation process of the nickel oxide nanoparticles specifically comprises the following steps:

3. The method for preparing the sodium salt modified nickel oxide transport layer according to claim 1, characterized in that, 9 g of Ni (NO3) 2•6H2O is dissolved in 50 mL of deionized water, stirring is performed at a speed of 500 rpm / min for 30 min, then a sodium hydroxide aqueous solution with a concentration of 10 mmol / mL is added dropwise into the Ni (NO3) 2•6H2O solution at a certain dropwise adding speed until the pH reaches 10, then the green precipitate is washed with deionized water for 3 times, the green precipitate is taken out after being refrigerated in a refrigerator for 2 h, and the green precipitate is dried in a vacuum oven at 80 ℃ to obtain a green powder, the green powder is ground for 30 min, and then the green powder is calcined in a muffle furnace at 270 ℃ for 2 h to obtain black nickel oxide powder, and the obtained nickel oxide powder is ground for 30 min to obtain nickel oxide nanoparticles. The light emitting diode comprises the sodium salt modified nickel oxide transfer layer prepared by the preparation method in any one of claims 1-3.

4. A perovskite light emitting diode, characterized in that, The preparation method comprises the following steps:

5. A method for fabricating a perovskite light-emitting diode, characterized in that, The pre-processed indium tin oxide (ITO) glass is used as the anode of the perovskite light emitting diode, the sodium salt modified nickel oxide solution is spin-coated on the ITO glass to form the sodium salt modified nickel oxide transfer layer in any one of claims 1-3 after annealing treatment; A perovskite solution is spin-coated on the sodium salt modified nickel oxide transfer layer to form a perovskite light emitting layer after annealing treatment; An electron transfer layer is formed by vacuum evaporation of a layer of TPBi on the perovskite light emitting layer; A LiF / Al electrode is vacuum evaporated on the electron transfer layer as the cathode of the perovskite light emitting diode. ​

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