Cesium oleate-silver composite precursor for CsPbI3 perovskite nanocrystal synthesis and preparation method and application thereof

Abstract

The invention discloses a cesium oleate-silver composite precursor for CsPbI3 perovskite nanocrystal synthesis and a preparation method and application thereof, trace silver salt is introduced into a cesium oleate precursor system, and silver ions in the cesium oleate interact with cesium oleate to induce the cesium oleate to form a uniform reverse micelle superlattice structure. The precursor solution is not subjected to phase separation within a considerable time, and the liquid phase stability can be kept. Besides, the highly dispersed reverse micelle superlattice has a relatively uniform space structure, the dynamic environment of Cs is limited, the crystallinity of the CsPbI3 perovskite nanocrystal is improved, and the photoelectric property and the LED device performance of the CsPbI3 perovskite nanocrystal are further optimized.

Description

Technical Field

[0001] This invention belongs to the field of nanotechnology and light-emitting display, specifically relating to a cesium oleate-silver composite precursor for the synthesis of CsPbI3 perovskite nanocrystals, its preparation method, and its application. Background Technology

[0002] Halide perovskite (LHP) nanomaterials have attracted widespread attention from researchers due to their excellent optoelectronic properties, including high carrier mobility, long carrier diffusion length, tunable band gap, and high fluorescence quantum yield (PLQY). In the fields of lighting and displays, compared to other light-emitting layer materials used in commercial devices, such as group III–V inorganic semiconductors and organic molecules, LHPs exhibit narrower emission linewidths (<100 meV). For example, the emission linewidths (FWHM) of CsPbCl3, CsPbBr3, and CsPbI3 perovskite nanocrystals (PNCs) are approximately 12 nm, 20 nm, and 40 nm, respectively. They also offer a wider color gamut, covering up to 140% of the television color standard specified by the North American National Television Standards Committee (NTSC). Furthermore, they are easier to prepare; high-quality perovskite layers can be fabricated using solution methods or thin-film deposition. Currently, the external quantum efficiency (EQE) of near-infrared, red, and green perovskite light-emitting diodes (PeLEDs) has exceeded 20%, and the EQE of blue PeLEDs has also exceeded 10%. This indicates that perovskite materials have good application prospects in the fields of lighting and display, and are one of the important materials for the development of next-generation ultra-high-definition display devices.

[0003] CsPbI3 perovskite nanocrystals, which have good thermal stability, are widely used in the preparation of red LEDs.

[0004] For Cs-based LHP, cesium oleate (Cs-OA) is the most commonly used cesium source in the nanocrystal synthesis process. However, the cesium oleate precursor prepared by common methods does not dissolve after cooling to room temperature, exhibiting poor phase stability. When the molar ratio of oleic acid to Cs in the precursor solution is less than 5:1, cesium carbonate (Cs₂CO₃) and cesium bicarbonate (CsHCO₃) precipitates spontaneously form at room temperature. This makes it impossible to implement synthesis methods requiring highly stable precursors (such as layer-by-layer ion adsorption and reaction (SILAR) and microfluidic technology), as these rely on capillary injection. Insufficient stability can lead to blockage, affecting experimental safety and hindering the large-scale fabrication of perovskite devices. On the other hand, during perovskite crystallization, the Cs in the poorly dispersed precursor has a complex kinetic environment, which affects the quality of perovskite crystallization and consequently the efficiency of the fabricated LEDs. Summary of the Invention

[0005] To address the problems of poor phase stability and easy generation of byproducts in existing cesium oleate technologies, this application proposes a cesium oleate-silver composite precursor for the synthesis of CsPbI3 perovskite nanocrystals. By introducing trace amounts of silver salt into the cesium oleate precursor system, the silver ions interact with cesium oleate, inducing the formation of a uniform reverse micelle superlattice structure. This achieves phase separation-free operation of the precursor solution within a considerable time, maintaining liquid-phase stability. Furthermore, the highly dispersed reverse micelle superlattice possesses a relatively uniform spatial structure, restricting the kinetic environment of Cs, improving the crystallinity of CsPbI3 perovskite nanocrystals, and thus optimizing their optoelectronic properties and LED device performance.

[0006] One of the technical solutions of the present invention is to provide a cesium oleate-silver composite precursor for the synthesis of CsPbI3 perovskite nanocrystals, comprising cesium oleate and a silver salt, wherein the silver salt is silver nitrate or silver acetate; The amount of silver salt added is 3% to 6% of the molar amount of cesium.

[0007] The second technical solution of the present invention is to provide a method for preparing the above-mentioned cesium oleate-silver composite precursor, wherein cesium carbonate is added to 1-octadecene, and then silver salt and oleic acid are added, wherein the molar ratio of oleic acid to cesium is 1:1 to 2:1. After stirring evenly, vacuum is drawn within 5 to 10 minutes, and the temperature is raised to 110 to 120°C and heated for 1 to 2 hours. Then, an inert gas is introduced, and the temperature is raised to 140 to 150°C and heated for 1 to 2 hours. The mixture is then naturally cooled to room temperature to obtain the cesium oleate-silver composite precursor.

[0008] In some embodiments, the specific operation may be as follows: 0.83 mmol of cesium carbonate (Cs2CO3) is added to a reaction flask containing 10 mL of 1-octadecene (ODE), and then silver salt and oleic acid (OA) are added to the reaction system, wherein oleic acid is a ligand and the molar ratio of OA to cesium in the reaction system is 1.5:1. The reaction flask is placed in a heating container and stirred. Then, the system is slowly evacuated over 5 to 10 min and heated to 110 to 120 °C for 1 to 2 h. When the solution turns wine red or reddish brown, a large number of reverse micelles are formed. An inert gas is introduced into the reaction system and the temperature is raised to 140 to 150 °C for 1 to 2 h, and then the system is allowed to cool naturally to room temperature.

[0009] The third technical solution of the present invention is to provide a CsPbI3 perovskite nanocrystal, which is prepared from the above-mentioned cesium oleate-silver composite precursor.

[0010] Further, the preparation method is as follows: lead iodide is added to 1-octadecene, stirred evenly, vacuumed, and heated to 110-120℃ to remove water for 1-2 h. Then, under an inert gas atmosphere, oleylamine and oleic acid with a molar ratio of 8:1-10:1 to lead iodide are injected sequentially. After the lead iodide dissolves, the temperature is raised to 170℃, and the cesium oleate-silver composite precursor is added. After reacting for 5-7 s, the mixture is cooled to room temperature within 30-50 s to obtain CsPbI3 perovskite nanocrystals.

[0011] In some embodiments, the specific operation can be as follows: 11.19 mmol of lead iodide (PbI2) is added to a reaction flask containing 300 mL of 1-octadecene. The reaction flask is placed in a heating container, stirred, and the reaction system is evacuated and heated to 110-120°C to remove water for 1-2 h. Then, under an inert gas atmosphere, oleylamine (OLA) and oleic acid (OA) with a molar ratio of 8.14:1 to lead iodide are injected sequentially using a syringe. After the lead iodide is completely dissolved, the temperature is raised to 170°C. When the required temperature is reached, 30 mL of cesium oleate-silver composite precursor is rapidly injected into the reaction system using a syringe to make the molar ratio of cesium to lead in the system 1:1.34. After reacting for 5-7 s, the reaction flask is placed in ice water to cool the reaction system to room temperature within 30 s.

[0012] Generally, the inert gas described in this invention is nitrogen.

[0013] The fourth technical solution of this invention provides an electroluminescent diode device, prepared from the aforementioned CsPbI3 perovskite nanocrystals. The preparation method is as follows: under a nitrogen atmosphere, a hole transport layer is prepared on an etched ITO conductive glass by spin coating; subsequently, a poly(4-butyltriphenylamine) layer and the aforementioned CsPbI3 perovskite nanocrystals are prepared by spin coating; then, a 5×10⁻⁶ layer is prepared. -4 Under a vacuum of Pa, the electron transport layer and electrode layer of the device are sequentially deposited into films using a thermal evaporation system. The hole transport layer is a poly(3,4-ethylenedioxythiophene) / poly(styrene sulfonate) layer, and the electron transport layer is a 40-50 nm 1,3,5-tris(1-phenyl-1-ethylhexylene) oxide film. H -benzimidazole-2-yl)benzene; the electrode layer is LiF / Al, wherein the thickness of the LiF layer is 1 ~ 2 nm and the thickness of the Al layer is 80 ~ 150 nm; the spin coating speed of the hole transport layer, the poly(4-butyltriphenylamine) layer and the CsPbI3 perovskite nanocrystals is 1000 ~ 4000 rpm and the spin coating time is 40 ~ 60 s.

[0014] After spin-coating the hole transport layer, the device needs to be annealed at 130-160℃ for 10-17 minutes. After the device cools naturally to room temperature, a poly(4-butyltriphenylamine) layer is spin-coated, followed by annealing at 130-160℃ for 10-17 minutes. After the device cools naturally to room temperature, CsPbI3 perovskite nanocrystals are spin-coated.

[0015] Preferably, the spin-coating speed for the poly(3,4-ethylenedioxythiophene) / poly(styrene sulfonate) layer (PEDOT:PSS) and the poly(4-butyltriphenylamine) (Poly-TPD) layer is 3500 rpm, and the spin-coating time is 45 s; the spin-coating speed for the CsPbI3 perovskite nanocrystals is 1500 rpm, and the spin-coating time is 55 s. The 1,3,5-tris(1-phenyl-1-ethylhexylene) nanocrystals are deposited by vapor deposition. H The thickness of the 2-benzimidazole-2-yl)benzene (TPBi) layer is 43 nm, the thickness of the evaporated LiF layer is 1.5 nm, and the thickness of the evaporated Al layer is 120 nm.

[0016] The beneficial technical effects of this invention are as follows: By using a strategy of inducing cesium oleate to form a reverse micelle self-assembled superlattice with trace amounts of silver, this invention first achieves the goal of preventing phase separation in the composite precursor solution within a considerable time, maintaining liquid-phase stability, improving experimental safety, and enabling the large-scale synthesis of CsPbI3 perovskite nanocrystals. Furthermore, it improves the stability and dispersibility of the cesium oleate precursor. Simultaneously, the highly dispersed reverse micelle superlattice possesses a relatively uniform spatial structure, restricting the kinetic environment of Cs, improving the crystallinity of the perovskite nanocrystals, and thus optimizing their photoelectric properties and device performance. This invention plays a significant role in promoting the large-scale production of high-efficiency perovskite LEDs. Attached Figure Description

[0017] Figure 1 These are actual images of the precipitation process in Example 1 and Comparative Example 1 of the present invention within one day.

[0018] Figure 2 These are the dynamic light scattering (DLS) spectra of Embodiment 1 and Comparative Example 1 of the present invention.

[0019] Figure 3 These are transmission electron microscope (TEM) images of Embodiment 1 (A) and Comparative Example 1 (B) of the present invention.

[0020] Figure 4 This is a physical image of the photoluminescence phenomenon generated under 365 nm ultraviolet flashlight illumination in Embodiment 2 of the present invention.

[0021] Figure 5 This is the X-ray diffraction (XRD) pattern of Embodiment 2 of the present invention.

[0022] Figure 6 These are the ultraviolet-visible absorption spectra and fluorescence spectra of Example 2 and Comparative Example 2 of the present invention.

[0023] Figure 7 The images are transmission electron microscope (A) and corresponding high-resolution transmission electron microscope (HRTEM) image (B) and crystal size distribution map (C) of Embodiment 2 of the present invention, and transmission electron microscope (D) and corresponding high-resolution transmission electron microscope (HRTEM) image (E) and crystal size distribution map (F) of Comparative Example 2.

[0024] Figure 8 These are schematic diagrams (A) of the LED device structure and (B) of the corresponding energy level structure of Embodiment 3 and Comparative Example 3 of the present invention.

[0025] Figure 9 These are the brightness-current density-voltage curves (A, C) and the corresponding external quantum efficiency (EQE)-current density curves (B, D) of Embodiment 3 and Comparative Example 3 of the present invention. Detailed Implementation

[0026] The following examples are provided to further illustrate the present invention and are intended to explain the invention, not to limit its scope. Unless otherwise specified, all terms are parts by weight and weight percentages.

[0027] Unless otherwise specified, the raw materials used in this invention are all conventional commercially available products; unless otherwise specified, the methods used in this invention are all conventional methods in the field.

[0028] The embodiments of the present invention will be further described below with reference to several examples.

[0029] It should be understood that the described embodiments are merely some, not all, of the embodiments in this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0030] The terminology used in the embodiments of this application is for the purpose of describing particular embodiments only and is not intended to be limiting of this application. The singular forms “a,” “the,” and “the” used in the embodiments of this application and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0031] Example 1 (1) Add 0.83 mmol of cesium carbonate (Cs2CO3) to a reaction flask containing 10 mL of 1-octadecene (ODE); (2) Add silver nitrate (AgNO3) with a cesium molar ratio of 0.03:1 and oleic acid (OA) ligand with a cesium molar ratio of 1.5:1 to the reaction system; (3) Place the reaction flask in a heating container, stir, and then slowly evacuate the system over 8 minutes; (4) Heat to 110℃ for 1 hour; (5) When the solution turns wine red or reddish brown, a large number of reverse micelles are formed, and nitrogen gas is introduced into the reaction system; (6) Heat to 150℃ for 2 hours; (7) The cesium oleate-silver composite precursor solution was obtained by naturally cooling to room temperature.

[0032] Example 2 (1) Add 11.19 mmol of lead iodide (PbI2) to a reaction flask containing 300 mL of 1-octadecene, place the reaction flask in a heating container, stir, and evacuate the reaction system; (2) Heat to 120℃ to remove water for 1 hour; (3) Under a nitrogen atmosphere, inject oleylamine (OLA) and oleic acid (OA) in sequence with a molar ratio of 8.14:1 to lead iodide using a syringe. (4) After all the lead iodide has dissolved, raise the temperature to 170°C; (5) When the temperature reaches the required level, inject 30 ml of the cesium oleate-silver composite precursor solution from Example 1 into the reaction system using a syringe; (6) After 5 s of reaction, the reaction flask was placed in ice water to cool the reaction system to room temperature within 30 s to obtain CsPbI3 perovskite nanocrystals.

[0033] Example 3 (1) Under a nitrogen atmosphere, the hole transport layer PEDOT:PSS layer of the device was prepared on the etched ITO conductive glass by spin coating at a rotation speed of 3500 rpm and a spin coating time of 45 s. (2) Anneal the device at 150°C for 15 min; (3) After the device cools to room temperature, a Poly-TPD layer is prepared by spin coating at a speed of 3500 rpm for 45 s. (4) Anneal the device at 150°C for 15 min; (5) After the device has cooled to room temperature, a perovskite layer is prepared by spin coating CsPbI3 perovskite nanocrystals as described in Example 2. The spin coating speed is 1500 rpm and the spin coating time is 55 s. (6) In 5×10 -4Under a vacuum of Pa, an electron transport layer TPBi with a thickness of 43 nm was deposited by thermal evaporation system. (7) Under the same vacuum level, the LiF layer of the electrode is deposited by vapor deposition with a thickness of 1.5 nm; (8) Under the same vacuum, an Al layer of electrode is deposited with a thickness of 120 nm.

[0034] Example 4 1. Preparation of precursor solution (1) Add 0.83 mmol of cesium carbonate (Cs2CO3) to a reaction flask containing 10 mL of 1-octadecene (ODE); (2) Add silver nitrate (AgNO3) and oleic acid (OA) ligands with a cesium molar ratio of 0.06:1 and 1:1, respectively, to the reaction system; (3) Place the reaction flask in a heating container, stir, and then slowly evacuate the system over 10 min; (4) Heat to 120℃ for 1 hour; (5) When the solution turns wine red or reddish brown, a large number of reverse micelles are formed, and nitrogen gas is introduced into the reaction system; (6) Heat to 150℃ for 1 hour; (7) The cesium oleate-silver composite precursor solution was obtained by naturally cooling to room temperature.

[0035] 2. Preparation of CsPbI3 perovskite nanocrystals: (1) Add 11.19 mmol of lead iodide (PbI2) to a reaction flask containing 300 mL of 1-octadecene, place the reaction flask in a heating container, stir, and evacuate the reaction system; (2) Heat to 110℃ to remove water for 2 hours; (3) Under a nitrogen atmosphere, inject oleylamine (OLA) and oleic acid (OA) in a molar ratio of 10:1 to lead iodide in sequence using a syringe. (4) After all the lead iodide has dissolved, raise the temperature to 170°C; (5) When the temperature reaches the required level, inject the cesium oleate-silver composite precursor solution into the reaction system quickly with a syringe; so that the molar ratio of cesium to lead in the system is 1:1.34. (6) After 7 s of reaction, the reaction flask was placed in ice water to cool the reaction system to room temperature within 40 s to obtain CsPbI3 perovskite nanocrystals.

[0036] 3. Fabrication of electroluminescent diode devices: (1) Under a nitrogen atmosphere, the hole transport layer PEDOT:PSS layer of the device was prepared on the etched ITO conductive glass by spin coating at a rotation speed of 4000 rpm and a spin coating time of 40s. (2) Anneal the device at 130°C for 17 min; (3) After the device cools to room temperature, a Poly-TPD layer is prepared by spin coating at a speed of 3000 rpm for 50 s. (4) Anneal the device at 130°C for 17 min; (5) After the device is cooled to room temperature, a perovskite layer is prepared by spin coating CsPbI3 perovskite nanocrystals at a speed of 1500 rpm and a spin coating time of 55 s. (6) In 5×10 -4 Under a vacuum of Pa, an electron transport layer TPBi with a thickness of 40 nm was deposited by thermal evaporation system. (7) Under the same vacuum level, the LiF layer of the electrode is deposited by vapor deposition with a thickness of 1 nm; (8) Under the same vacuum, an Al layer of electrode is deposited with a thickness of 80 nm.

[0037] Example 5 1. Preparation of precursor solution (1) Add 0.83 mmol of cesium carbonate (Cs2CO3) to a reaction flask containing 10 mL of 1-octadecene (ODE); (2) Add silver nitrate (AgNO3) with a cesium molar ratio of 0.05:1 and oleic acid (OA) ligand with a cesium molar ratio of 2:1 to the reaction system; (3) Place the reaction flask in a heating container, stir, and then slowly evacuate the system over 5 minutes; (4) Heat to 115℃ for 2 hours; (5) When the solution turns wine red or reddish brown, a large number of reverse micelles are formed, and nitrogen gas is introduced into the reaction system; (6) Heat to 140℃ for 1.5 h; (7) The cesium oleate-silver composite precursor solution was obtained by naturally cooling to room temperature.

[0038] 2. Preparation of CsPbI3 perovskite nanocrystals: (1) Add 11.19 mmol of lead iodide (PbI2) to a reaction flask containing 300 mL of 1-octadecene, place the reaction flask in a heating container, stir, and evacuate the reaction system; (2) Heat to 110℃ to remove water for 2 hours; (3) Under a nitrogen atmosphere, inject oleylamine (OLA) and oleic acid (OA) in a molar ratio of 10:1 to lead iodide in sequence using a syringe. (4) After all the lead iodide has dissolved, raise the temperature to 170°C; (5) When the temperature reaches the required level, inject the cesium oleate-silver composite precursor solution into the reaction system quickly with a syringe; so that the molar ratio of cesium to lead in the system is 1:1.34. (6) After 5 s of reaction, the reaction flask was placed in ice water to cool the reaction system to room temperature within 50 s to obtain CsPbI3 perovskite nanocrystals.

[0039] 3. Fabrication of electroluminescent diode devices: (1) Under a nitrogen atmosphere, the hole transport layer PEDOT:PSS layer of the device was prepared on the etched ITO conductive glass by spin coating at a rotation speed of 4000 rpm and a spin coating time of 40s. (2) Anneal the device at 160°C for 10 min; (3) After the device cools to room temperature, a Poly-TPD layer is prepared by spin coating at a speed of 3000 rpm for 50 s. (4) Anneal the device at 160°C for 10 min; (5) After the device is cooled to room temperature, a perovskite layer is prepared by spin coating CsPbI3 perovskite nanocrystals at a speed of 1000 rpm and a spin coating time of 60 s. (6) In 5×10 -4 Under a vacuum of Pa, an electron transport layer TPBi with a thickness of 50 nm was deposited by thermal evaporation system. (7) Under the same vacuum level, the LiF layer of the electrode is deposited by vapor deposition with a thickness of 2 nm; (8) Under the same vacuum, an Al layer of electrode is deposited with a thickness of 150 nm.

[0040] Comparative Example 1 The same process as in Example 1 was used, except that silver nitrate was not added in step (2), while other conditions remained the same.

[0041] Figure 1 Figure A shows the physical state of Example 1 and Comparative Example 1 after preparation and cooling to room temperature for no more than 5 minutes. Figure 1 Figure B shows the precipitation state of the samples from Example 1 and Comparative Example 1 after being left to stand for one day at room temperature of 20-25°C and air humidity of 20%-30%. It can be seen that while Comparative Example 1 showed precipitation exceeding 50% of its sample volume, Example 1 did not show any precipitation.

[0042] Table 1. Quantitative representation of the stability of Example 1 and Comparative Example 1 The above tests show that the cesium oleate-silver precursor prepared by the method described in this invention has good macroscopic stability and dispersibility.

[0043] Figure 2 The images show the dynamic light scattering spectra of Example 1 and Comparative Example 1. The solvent used, 1-octadecene, has a molar refractive index of 85.16 and a kinematic viscosity of 4.48 × 10⁻⁶. -6 m 2 / s. The peak positions of the images of Example 1 and Comparative Example 1 are (198 nm, 56%) and (491 nm, 26%), respectively. It can be seen that Example 1 not only has a smaller average particle size than Comparative Example 1, but also a more concentrated particle size distribution. This indicates that the cesium oleate-silver precursor prepared according to the method described in this invention has good dispersibility.

[0044] Figure 3 Images A and 3B are transmission electron microscope (TEM) images of Example 1 and Comparative Example 1, respectively. It can be seen that Example 1 possesses an antimicelle structure as shown within the dashed box, and exhibits superlattice structure characteristics. The micelle structure is relatively more uniform and ordered, while Comparative Example 1 lacks an ordered, uniformly sized structure. This phenomenon corresponds to the dynamic light scattering pattern, indicating that Example 1 has better stability and dispersibility.

[0045] Comparative Example 2 Due to the low stability and low dispersibility of Comparative Example 1, it could not be used to prepare large-scale CsPbI3 perovskite nanocrystals of the same volume as in Example 2. The commonly used volume was used to prepare CsPbI3 perovskite nanocrystals, and the same process as in Example 2 was used. The difference was that in step (1), 0.37 mmol of lead iodide and 10 mL of 1-octadecene were used instead; in step (2), 1 mL of cesium oleate precursor solution of Comparative Example 1 was injected instead, and other conditions remained the same.

[0046] Figure 4 This is a photograph of the photoluminescence phenomenon produced under 365 nm ultraviolet flashlight illumination in Example 2.

[0047] Figure 5 The X-ray diffraction (XRD) pattern of Example 2 shows that the diffraction peak positions correspond to the standard card peak positions of cubic CsPbI3 crystals, indicating the successful large-scale synthesis of CsPbI3 perovskite nanocrystals.

[0048] Figure 6 These are the UV-Vis absorption and fluorescence spectra of Example 2 and Comparative Example 2. The fluorescence peaks of Example 2 and Comparative Example 2 are located at 686 nm and 684 nm, respectively, both in deep red light, with emission linewidths of 32 nm and 34 nm, respectively. It can be seen that the emission peak of Example 2 is narrower, indicating that it has good crystallinity and higher color purity.

[0049] Figure 7 A and 7D are transmission electron microscope images of Example 2 and Comparative Example 2, respectively; 7B and 7E are high-resolution transmission electron microscope images of Example 2 and Comparative Example 2, respectively; 7C and 7F are crystal grain size distribution maps of Example 2 and Comparative Example 2, respectively. Figure 7 A comparison of A and 7D shows that Example 2 has better crystallinity and more uniform grains compared to Comparative Example 2. This phenomenon can be observed through... Figure 7 The particle size distribution of C and 7F further illustrates that Example 2 has a more concentrated particle size distribution and a smaller standard deviation of particle size.

[0050] Comparative Example 3 The same process as in Example 3 was used, except that in step (5), the perovskite layer of Comparative Example 2 was spin-coated, while other conditions remained the same.

[0051] Figure 8 A is a device structure diagram of the perovskite electroluminescent diode device prepared using Example 3 and Comparative Example 3. Figure 8 B is a schematic diagram of the energy level structure of each layer in the device.

[0052] Figure 9 A shows the brightness-current density-voltage curve of the device in Example 3. Figure 9 B is the corresponding external quantum efficiency (EQE)-current density curve; Figure 9 C represents the brightness-current density-voltage curve of the device in Comparative Example 3. Figure 9 D represents the corresponding external quantum efficiency (EQE)-current density curve. The maximum luminance of Example 3 is 3804 cd / m². 2 The EQE is 21%; the maximum luminance of Comparative Example 3 is 3584 cd / m². 2 The EQE is 7%. It can be seen that Example 3 has superior device performance.

[0053] The above embodiments detail the structure, features, and effects of the present invention. The above descriptions are merely preferred embodiments of the present invention. Any changes made in accordance with the concept of the present invention, or equivalent embodiments modified to have equivalent variations, that do not exceed the scope covered by the specification should be within the protection scope of the present invention.

Claims

1. A cesium oleate-silver composite precursor for the synthesis of CsPbI3 perovskite nanocrystals, characterized in that, Includes cesium oleate and a silver salt, wherein the silver salt is silver nitrate or silver acetate; The amount of silver salt added is 3% to 6% of the molar amount of cesium.

2. A method for preparing the cesium oleate-silver composite precursor as described in claim 1, characterized in that, Cesium carbonate was added to 1-octadecene, followed by silver salt and oleic acid. The molar ratio of oleic acid to cesium was 1:1 to 2:

1. After stirring evenly, a vacuum was drawn within 5 to 10 minutes, and the temperature was raised to 110 to 120°C and heated for 1 to 2 hours. Then, an inert gas was introduced, and the temperature was raised to 140 to 150°C and heated for 1 to 2 hours. The mixture was then naturally cooled to room temperature to obtain the cesium oleate-silver composite precursor.

3. A CsPbI3 perovskite nanocrystal, characterized in that, It was prepared from the cesium oleate-silver composite precursor described in claim 1.

4. The CsPbI3 perovskite nanocrystals according to claim 3, characterized in that, The preparation method is as follows: lead iodide is added to 1-octadecene, stirred evenly, and then vacuumed. The mixture is heated to 110-120℃ to remove water for 1-2 hours. Then, under an inert gas atmosphere, oleylamine and oleic acid with a molar ratio of 8:1-10:1 to lead iodide are injected sequentially. After the lead iodide dissolves, the temperature is raised to 170℃, and the cesium oleate-silver composite precursor is added to make the molar ratio of cesium to lead in the system 1:1.

34. After reacting for 5-7 seconds, the mixture is cooled to room temperature within 30-50 seconds to obtain CsPbI3 perovskite nanocrystals.

5. An electroluminescent diode device, characterized in that, It is prepared from CsPbI3 perovskite nanocrystals as described in any one of claims 3 or 4.

6. The electroluminescent diode device according to claim 5, characterized in that, The preparation method is as follows: Under a nitrogen atmosphere, a hole transport layer is prepared on etched ITO conductive glass by spin coating; subsequently, a poly(4-butyltriphenylamine) layer and the CsPbI3 perovskite nanocrystals as described in claim 3 or 4 are prepared by spin coating; then, a 5×10⁻⁶ layer is prepared. -4 Under a vacuum of Pa, the electron transport layer and electrode layer of the device are sequentially deposited into films through a thermal evaporation system.

7. The electroluminescent diode device according to claim 6, characterized in that, The hole transport layer is a poly(3,4-ethylenedioxythiophene) / poly(styrene sulfonate) layer, and the electron transport layer is a 40-50 nm 1,3,5-tris(1-phenyl-1-ethylhexylene)-2-ethylhexylene oxide (EPDE ... H -benzimidazole-2-yl)benzene; the electrode layer is LiF / Al, wherein the thickness of the LiF layer is 1 ~ 2 nm and the thickness of the Al layer is 80 ~ 150 nm; the spin coating speed of the hole transport layer, the poly(4-butyltriphenylamine) layer and the CsPbI3 perovskite nanocrystals is 1000 ~ 4000 rpm and the spin coating time is 40 ~ 60 s.

8. The electroluminescent diode device according to claim 6, characterized in that, After spin-coating the hole transport layer, the device needs to be annealed at 130-160℃ for 10-17 minutes. After the device cools naturally to room temperature, a poly(4-butyltriphenylamine) layer is spin-coated, followed by annealing at 130-160℃ for 10-17 minutes. After the device cools naturally to room temperature, CsPbI3 perovskite nanocrystals are spin-coated.

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