Organic-inorganic hybrid perovskite luminescent material, preparation method thereof and blue-light perovskite light-emitting diode

Abstract

The invention belongs to the technical field of photoelectric materials and devices, and particularly relates to an organic-inorganic hybrid perovskite luminescent material, a preparation method thereof and a blue-light perovskite light-emitting diode. In the preparation process of the organic-inorganic hybrid perovskite luminescent material, a component gradient distribution structure penetrating from a bottom interface to a bulk phase and extending to an upper interface is formed in situ through autonomous migration of a self-assembly molecule Ph-2PACz. According to the structure, excellent defect passivation, efficient carrier injection and rapid bulk phase transmission can be synchronously realized. Compared with a contrast device which does not use the technology, the blue light device prepared by the invention emits light at the wavelength of about 488 nm, the external quantum efficiency of the blue light device is improved to 18.08% or above from 5.02% of the contrast device, the stability of the device is remarkably enhanced, and the blue light device has important reference significance for development of efficient photoelectric devices.

Description

Technical Field

[0001] This invention belongs to the field of optoelectronic materials and devices technology, specifically relating to an organic-inorganic hybrid perovskite luminescent material, its preparation method, and a blue perovskite luminescent diode. Background Technology

[0002] Organic-inorganic hybrid lead-based perovskite, as an emerging semiconductor material, is a unique solution-processable crystalline material. Due to its advantages such as high carrier mobility, long exciton diffusion length, tunable band structure and emission wavelength, high fluorescence quantum yield, high color purity, and low cost, it shows broad application prospects in the field of light-emitting diodes (LEDs), providing new avenues and opportunities for large-area, low-cost, high-color-purity displays and solid-state lighting technologies.

[0003] Currently, the external quantum efficiency of green and red perovskite light-emitting diodes (LEDs) has exceeded 30%, representing significant progress. However, the development of blue perovskite LEDs, one of the three primary colors, remains relatively lagging. The fundamental reason is that the wide bandgap characteristics required to achieve blue light emission not only increase the difficulty of carrier recombination but also restrict efficient carrier injection, leading to the common problems of low external quantum efficiency and poor stability in blue LED devices.

[0004] Currently, constructing low-dimensional organic-inorganic hybrid perovskites is considered one of the effective ways to achieve blue light emission. These structures not only possess large exciton binding energies to meet the requirements of blue light emission, but their multiphase system, composed of perovskite phases with different numbers of layers, can also form a "funnel-shaped" energy transfer path, improving energy utilization efficiency. However, commonly used organic spacer cations are themselves insulating molecules, and their abundant presence in the perovskite structure hinders carrier transport between adjacent inorganic layers, limiting further improvements in device performance. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention provides an organic-inorganic hybrid perovskite luminescent material, its preparation method, and a blue perovskite luminescent diode. By introducing the organic additive quaternary ammonium salt EAX, the perovskite lattice structure is regulated, specifically improving film quality and fluorescence intensity. During spin-coating, the self-assembling molecule Ph-2PACz spontaneously undergoes directional migration and self-assembly, migrating from the bulk phase to both sides of the film surface, ultimately distributing within and on both sides of the perovskite film, forming a unique bottom-up gradient distribution structure. This structure breaks the functional boundaries between traditional interface layers and bulk passivators, achieving "multi-purpose use," where Ph-2PACz simultaneously acts as a bulk passivator and interface modifier. Through this synergistic effect, the organic-inorganic hybrid perovskite luminescent material exhibits a smooth film morphology and can be applied to blue light emitting devices, demonstrating high energy conversion efficiency. This improvement has significant implications for the development of high-efficiency optoelectronic devices.

[0006] To improve the performance of organic-inorganic hybrid perovskites, traditional improvement methods include interface modification and bulk passivation strategies. However, these two strategies are usually independent and require different methods for interface modification or bulk passivation. Furthermore, to further improve the performance of the perovskite structure, multiple different methods are often needed, making the fabrication process complex and hindering the fabrication and commercial application of high-performance blue perovskite light-emitting diodes (LEDs). Therefore, how to further improve the energy utilization efficiency of organic-inorganic hybrid perovskites through simple improvement strategies is a challenge that needs to be overcome. This invention introduces the self-assembled molecule Ph-2PACz into the perovskite precursor solution. During film formation, Ph-2PACz migrates from the bulk phase to both sides of the film surface, ultimately distributing within the perovskite film and on both sides (i.e., the interface of the light-emitting layer). It simultaneously acts as a bulk passivator and interface modifier. Compared with traditional improvement strategies, using Ph-2PACz can simultaneously achieve interface modification and bulk passivation. The method is simple, effective, and easy to implement, which is beneficial for promoting the research and industrialization of blue perovskite LEDs.

[0007] This invention is specifically achieved through the following technical solutions: The first objective of this invention is to provide an organic-inorganic hybrid perovskite luminescent material, comprising alternating stacks of several insulating organic spacer cation layers and several low-dimensional lead-based perovskite inorganic layers, wherein the low-dimensional lead-based perovskite inorganic layers are located between the insulating organic cation layers, and the low-dimensional lead-based perovskite inorganic layers are composed of lead-based perovskite octahedral cells of varying numbers; the chemical formula of the organic-inorganic hybrid perovskite luminescent material is A2Cs. n-1 Pb n X 3n+1 Where A represents an organic spacer cation, and the organic spacer cation is selected from phenylethylammonium ion (PEA).+ ) or ethylammonium ion (EA) + ); n represents the number of lead-based perovskite octahedral cells between adjacent insulating organic cation layers; X is Cl - ,Br - One or two of them; The organic-inorganic hybrid perovskite luminescent material contains Ph-2PACz. During the film formation process, Ph-2PACz migrates from the bulk phase to both sides of the film, resulting in Ph-2PACz being distributed both inside and on both sides of the final organic-inorganic hybrid perovskite luminescent material film. Ph-2PACz serves as a bulk passivating agent and interface modifier; Pb 2+ The molar ratio with Ph-2PACz is 10~40:1.

[0008] Specifically, the organic-inorganic hybrid perovskite luminescent material contains a gradient structure formed by the directional migration of organic self-assembled molecules Ph-2PACz. The gradient structure is a compositional gradient distribution structure that extends from the bottom interface through the bulk phase and to the top interface. The organic self-assembled molecule consists of an anchoring group that forms a covalent or hydrogen bond with the substrate at the tail, a carbazole group at the head, and spacer groups connected to it. Its properties are mainly related to the carbon chain length of the spacer group and the properties of the groups connected to the carbazole.

[0009] The organic-inorganic hybrid perovskite luminescent material has a band gap of 2.50 eV to 2.61 eV and a fluorescence emission wavelength of 475 nm to 495 nm.

[0010] Preferably, the center of the octahedral structure is a Pb atom, the atoms at the six vertices of the octahedron are X atoms, the octahedral structure is located inside a cube, and the atoms at the eight vertices of the cube are Cs atoms. + or EA + ion.

[0011] A second objective of this invention is to provide a method for preparing the above-mentioned organic-inorganic hybrid perovskite luminescent material, comprising the following steps: A perovskite precursor and an organic self-assembled molecule Ph-2PACz are dissolved together in a solvent to form a precursor solution; the precursor solution is coated onto a substrate; an anti-solvent is added dropwise during the coating process; and then annealing is performed; wherein, during the coating and annealing process, the organic self-assembled molecule Ph-2PACz autonomously migrates from the bulk phase to both sides of the film surface and constructs a gradient distribution structure across the perovskite film interface in situ.

[0012] This invention utilizes a precursor solution and simple spin coating to synthesize the self-assembled molecule Ph-2PACz into novel organic-inorganic hybrid perovskite luminescent materials. The steps are simple and easy to operate.

[0013] Preferably, the perovskite precursor is composed of PbX2, CsX, quaternary ammonium salt PEAX, and quaternary ammonium salt EAX, with a molar ratio of PbX2, CsX, quaternary ammonium salt PEAX, and quaternary ammonium salt EAX of 1:0.9~1.1:0.5~0.7:0.5~0.7, preferably 1:0.9:0.6:0.6. The molar ratio of PbX2 to the organic self-assembled molecule is 10~40:1. This ratio variation affects the light emission properties of the perovskite film, such as emission wavelength and intensity, and is mainly adjusted by changing the ratio to control the emission wavelength. A blue shift occurs when the amount of quaternary ammonium salt EAX increases, and a red shift occurs when the amount of quaternary ammonium salt EAX decreases. When the amount of self-assembled molecule Ph-2PACz increases, the fluorescence intensity first increases and then decreases, reaching a maximum value when the molar ratio of PbX2 to self-assembled molecule Ph-2PACz is 20:1.

[0014] More preferably, the specific preparation method of the precursor solution includes the following steps: Using PbX2, CsX, quaternary ammonium salts PEAX and EAX as raw materials, PbX2, CsX, quaternary ammonium salts PEAX and EAX, and the self-assembled molecule Ph-2PACz are mixed together in an organic solvent under an inert atmosphere. The mixture is then filtered to remove insoluble impurities, yielding a precursor solution. Preferably, the precursor solution is mixed and stirred for 4 to 6 hours, after which all solutes dissolve.

[0015] Preferably, the solvent in the precursor solution is one or both of N,N-dimethylformamide or dimethyl sulfoxide. Using highly polar aprotic solvents such as N,N-dimethylformamide or dimethyl sulfoxide ensures complete dissolution of both inorganic and organic solutes.

[0016] Preferably, the concentration of the precursor solution is 0.08 mol / L to 0.12 mol / L. More preferably, it is 0.1 mol / L. This invention can rationally adjust the emission wavelength and performance of organic-inorganic hybrid perovskite luminescent materials by controlling the amount of solute in the precursor solution.

[0017] Preferably, the annealing conditions are: annealing at 80°C to 100°C for 5 to 10 minutes. More preferably, annealing at 90°C for 6 to 10 minutes. After spin coating, the material is quickly transferred to a high-temperature annealing stage for annealing to accelerate solvent evaporation and the crystallization and shaping of the low-dimensional lead-based perovskite inorganic layer.

[0018] Preferably, the spin coating speed is 3000 rpm to 5000 rpm, and the time is 40 s to 60 s. The control of spin coating speed and spin coating time has a direct impact on the thickness and morphology formation of the organic-inorganic hybrid perovskite luminescent material.

[0019] Preferably, the antisolvent is one or more of toluene, chlorobenzene, and chloroform, and the volume ratio of the antisolvent to the precursor solution is (2~3):(100~150), with the antisolvent added at a time of 1 to 15 seconds after the start of spin coating. During spin coating, the addition of the antisolvent further promotes the crystallization and formation of perovskite octahedra, controls the crystallization atmosphere and time, and improves the quality of the organic-inorganic hybrid perovskite luminescent material.

[0020] A third objective of this invention is to provide a blue perovskite light-emitting diode, comprising a light-emitting layer made of the aforementioned organic-inorganic hybrid perovskite light-emitting material.

[0021] The blue perovskite light-emitting diode sequentially comprises an anode, a hole transport layer, an emissive layer, an electron transport layer, an electron injection layer, and a cathode. The emissive layer contains ethylammonium ions and Ph-2PACz. Ethylammonium ions are used to replace A-site cations, and Ph-2PACz is distributed at the interface between the bulk phase of the emissive layer and the emissive layer, serving as a bulk phase passivator and an interface modifier.

[0022] The blue perovskite light-emitting diode is made of ITO / PEDOT:PSS / Perovskite / PO-T2T / LiF / Al, and its external quantum efficiency reaches over 18%.

[0023] Compared with the prior art, the present invention has the following beneficial effects: 1. This invention provides a novel organic-inorganic hybrid perovskite luminescent material. The invention employs a novel functional additive, quaternary ammonium salt EAX, as a substitute for the A-site cation, specifically improving the A-site defects in perovskite, while simultaneously improving film morphology and significantly enhancing film fluorescence intensity. The core inventiveness of this invention lies in the fact that the small molecule Ph-2PACz is not simply used as an additive component, but spontaneously undergoes directional migration and self-assembly during spin-coating. Ph-2PACz migrates from the bulk phase to both sides of the film surface, ultimately forming a unique bottom-up gradient distribution structure within the perovskite film. This structure breaks the functional boundaries between traditional interface layers and bulk passivators, simultaneously acting as both a bulk passivator and an interface modifier, achieving "multi-purpose use of one material." It synergistically improves film quality, photophysical properties, and device performance, providing important reference for the design of blue light emitting devices or perovskite solar cell devices.

[0024] The distribution of Ph-2PACz in perovskites forms a "self-constructed gradient structure," which has the following three main advantages: Interface optimization: A dense layer is formed at the bottom interface to improve hole injection and enhance carrier balance. Ph-2PACz is also present in small quantities at the top interface. The Ph-2PACz at the top interface can interact with Pb on the film surface via P=O bonds. 2+This combination passivates defects at the upper interface and reduces nonradiative recombination; at the same time, it can effectively suppress nonradiative energy loss between the perovskite and the electron transport layer, and improve exciton utilization efficiency.

[0025] Bulk passivation: Distributed between perovskite grains and at grain boundaries, it effectively passivates defects and suppresses non-radiative recombination.

[0026] Energy transfer: Its gradient distribution optimizes the "funnel effect" of energy transfer from small n phase to large n phase in quasi-two-dimensional perovskites.

[0027] 2. The performance characteristics of organic-inorganic hybrid perovskite luminescent materials are: their energy transfer relies on efficient energy transfer from the small n-phase to the large n-phase; the band gap is 2.48 eV to 2.91 eV; the fluorescence emission wavelength is 425 nm to 500 nm; and the quantum fluorescence yield is relatively high. The external quantum efficiency of blue light emitting devices prepared using improved organic-inorganic hybrid perovskite luminescent materials reaches over 18.08%. Furthermore, the introduction of Ph-2PACz further enhances the energy conversion efficiency of these materials, which is of great significance for improving the performance of optoelectronic devices.

[0028] In summary, the novel organic-inorganic hybrid perovskite luminescent material of this invention effectively improves the quality and morphology of perovskite films and enhances the energy utilization and performance of corresponding perovskite devices by introducing the quaternary ammonium salt EAX and the self-assembled molecule Ph-2PACz. Furthermore, the composition and preparation method are simple, easy to operate, and the raw materials are inexpensive and readily available. Attached Figure Description

[0029] Figure 1 This is a schematic diagram of the structure of the raw material PEABr.

[0030] Figure 2 This is a schematic diagram of the structures of EABr and EACl.

[0031] Figure 3 The absorption spectrum of the organic-inorganic hybrid perovskite luminescent material in Comparative Example 1 is shown.

[0032] Figure 4 The emission spectrum of the organic-inorganic hybrid perovskite luminescent material in Comparative Example 1 is shown.

[0033] Figure 5 The fluorescence quantum yield diagram is shown for the organic-inorganic hybrid perovskite luminescent material in Comparative Example 1.

[0034] Figure 6 The images show scanning electron microscope (SEM) images of the blue perovskite luminescent film (EABr+EACl film in the figure) for Comparative Example 1 and the reference film for Comparative Example 2.

[0035] Figure 7Efficiency graphs of the device fabricated from the blue perovskite luminescent thin film of Comparative Example 1 (EABr+EACl device in the figure) and the device fabricated from the reference thin film of Comparative Example 2.

[0036] Figure 8 This is a schematic diagram of the structure of Ph-2PACz.

[0037] Figure 9 This is the absorption spectrum of the organic-inorganic hybrid perovskite luminescent material of Example 1 of the present invention.

[0038] Figure 10 The emission spectrum of the organic-inorganic hybrid perovskite luminescent material in Example 1 of this invention is shown.

[0039] Figure 11 This is a fluorescence quantum yield diagram of the organic-inorganic hybrid perovskite luminescent material of Example 1 of the present invention.

[0040] Figure 12 Time-of-flight secondary ion mass spectra of blue perovskite light-emitting diodes made from the organic-inorganic hybrid perovskite luminescent material of Example 1.

[0041] Figure 13 This is a comparison diagram of the Br vacancy formation energies on the perovskite surface of Example 1 and Comparative Example 3 of the present invention.

[0042] Figure 14 This is a graph showing the transient fluorescence of the organic-inorganic hybrid perovskite luminescent thin film of Example 1 of the present invention over time.

[0043] Figure 15 The diagram shows the perovskite-PEDOT:PSS interface energy level of the perovskite light-emitting diode prepared by Example 1 (blue light-emitting perovskite diode) and Comparative Example 2 (base film).

[0044] Figure 16 These are scanning electron microscope images of the blue perovskite luminescent film of Example 1 (Ph-2PACz film in the figure) and the film of Comparative Example 3 (EABr+EACl film in the figure).

[0045] Figure 17 The time-resolved fluorescence spectra of the blue perovskite luminescent film of Example 1 (Ph-2PACz film in the figure), Comparative Example 3 (EABr+EACl film in the figure), and the reference film of Comparative Example 2 are shown.

[0046] Figure 18 The images show the fluorescence emission spectra of the thin films in Examples 1 to 4 of this invention.

[0047] Figure 19 This is a comparison chart showing the efficiency of the device fabricated using the blue perovskite luminescent thin film of Example 1 of the present invention and the reference device fabricated using the reference thin film of Comparative Example 2.

[0048] Figure 20 This is a schematic diagram illustrating the mechanism by which the organic-inorganic hybrid perovskite luminescent material provided by this invention enhances device performance. Detailed Implementation

[0049] To enable those skilled in the art to better understand and implement the technical solutions of the present invention, the present invention will be further described below with reference to specific embodiments and accompanying drawings. However, the embodiments described are not intended to limit the present invention. Unless otherwise specified, the experimental methods and detection methods described in the following embodiments are conventional methods; unless otherwise specified, the reagents and materials described are commercially available.

[0050] In the following examples and comparative examples, the structural formula of the raw material PEABr used is as follows: Figure 1 As shown. The structural formulas of EABr and EACl are as follows. Figure 2 As shown.

[0051] Comparative Example 1 A method for preparing an organic-inorganic hybrid perovskite luminescent material includes the following steps: (1) Weigh 36.7 mg of PbBr2, 19.10 mg of CsBr, 12.10 mg of phenylethyl ammonium bromide PEABr, 5.4 mg of EABr and 0.90 mg of EACl. At this time, the molar ratio of PbBr2, CsBr, PEABr, EABr and EACl is 1:0.9:0.6:0.5:0.1. Place them together in a serum bottle. Then add 1 mL of dimethyl sulfoxide as a solvent to the serum bottle. Add a polytetrafluoroethylene magnet and stir thoroughly in a glove box filled with nitrogen. After stirring for 4 hours, filter to remove insoluble impurities and obtain the precursor solution.

[0052] (2) Use a pipette to draw 120 μL of precursor solution and drop it onto a clean glass slide. Rotate the glass slide continuously at 4000 rpm for 60 s. During this period, add 240 μL of anti-solvent toluene at the 12th second after the spin coating begins. Transfer the spin-coated glass slide to the annealing station and anneal at 90°C for 8 min to obtain a blue perovskite luminescent film, i.e., an organic-inorganic hybrid perovskite luminescent material.

[0053] Figure 3 The absorption spectrum of the organic-inorganic hybrid perovskite luminescent material prepared for Comparative Example 1 shows that the prepared organic-inorganic hybrid perovskite luminescent material has absorption peaks corresponding to different phases at different wavelengths. Among them, the two absorption peaks at 425 nm and 455 nm are more obvious, corresponding to the n=2 and n=3 phases of the organic-inorganic hybrid perovskite luminescent material, respectively.

[0054] Figure 4The emission spectrum of the organic-inorganic hybrid perovskite luminescent material prepared in Comparative Example 1 shows a strong emission peak at 484 nm with a full width at half maximum (FWHM) of 26 nm.

[0055] Figure 5 The image shows the fluorescence quantum yield of the organic-inorganic hybrid perovskite luminescent material in Comparative Example 1, which reaches a fluorescence quantum yield of 53.4%.

[0056] Comparative Example 2 A method for preparing a control film is provided, which follows the same steps as Comparative Example 1, except that EABr is not added. The prepared film is used as a reference film.

[0057] Figure 6 Scanning electron microscope (SEM) images of the blue perovskite luminescent film of Comparative Example 1 and the baseline film of Comparative Example 2 are shown. Compared with the baseline film of Comparative Example 2, the surface pores of the film in Comparative Example 1 are significantly reduced and the grains are smaller after the addition of EABr and EACl, indicating that Comparative Example 1 yields a smoother and flatter blue perovskite luminescent film. EABr and EACl, as functional additives, can replace A-site cations and specifically improve the A-site defects of perovskite, thus improving the film morphology.

[0058] Figure 7 The diagrams illustrate the EQE (External Quantum Efficiency) of the blue perovskite luminescent film of Comparative Example 1 and the reference film of Comparative Example 2 in perovskite devices. Both perovskite device structures were prepared using ITO / PEDOT:PSS / Perovskite / PO-T2T / LiF / Al. The PEDOT:PSS and Perovskite layers were formed using a one-step solution spin-coating method; the PO-T2T / LiF / Al layers were formed using vacuum evaporation at 40 nm / 1 nm / 100 nm, respectively. Compared to the reference device prepared using the control film of Comparative Example 2, the external quantum efficiency (EQE) of both the blue perovskite luminescent film prepared with EABr in Comparative Example 1 and the device prepared with the blue perovskite luminescent film was significantly improved. The EQE of the reference device prepared with the control film was 5.02%, while the EQE of the device prepared with the blue perovskite luminescent film was 11.12%.

[0059] Example 1 A method for preparing an organic-inorganic hybrid perovskite luminescent material includes the following steps: (1) Weigh 36.70 mg of PbBr2, 19.10 mg of CsBr, 12.10 mg of PEABr, 5.40 mg of EABr, 0.90 mg of EACl and 2 mg of Ph-2PACz (at this time, the molar ratio of PbX2 to Ph-2PACz is 20:1) and place them together in a serum bottle. Then add 1 mL of dimethyl sulfoxide as a solvent to the serum bottle, add polytetrafluoroethylene magnets, and stir thoroughly in a glove box filled with nitrogen. After stirring for 4 hours, filter to remove insoluble impurities to obtain the precursor solution.

[0060] (2) Using a pipette, 120 μL of the precursor solution was dropped onto a cleaned ITO glass slide. The ITO glass slide was continuously rotated at 4000 rpm for 60 s. During this period, 240 μL of the anti-solvent toluene was added 12 s after the spin coating began. The spin-coated ITO glass slide was then transferred to an annealing stage and annealed at 90 °C for 8 min to obtain a blue perovskite luminescent film, i.e., an organic-inorganic hybrid perovskite luminescent material. During the spin coating and annealing process, significant changes in the film formation kinetics were observed, with a more uniform film formation rate. This was considered to be the result of the autonomous migration and enrichment of Ph-2PACz molecules at the gas-liquid-solid interface, ultimately leading to the formation of a gradient structure.

[0061] Figure 8 The molecular structure of Ph-2PACz in Example 1 is shown below.

[0062] Figure 9 The absorption spectrum of the blue perovskite luminescent film prepared in Example 1 shows that the prepared organic-inorganic hybrid perovskite luminescent material has absorption peaks at different wavelengths with basically unchanged positions but varying in intensity. Among them, the two absorption peaks at 425 nm and 460 nm are more obvious, corresponding to the n=2 and n=3 phases of the organic-inorganic hybrid perovskite luminescent material, respectively.

[0063] Figure 10 The image shows the emission spectrum of the blue perovskite luminescent film prepared in Example 1. There is a strong emission peak at 486 nm with a full width at half maximum (FWHM) of 26 nm.

[0064] Figure 11 The fluorescence quantum yield diagram of the organic-inorganic hybrid perovskite luminescent material in Example 1 of the present invention is shown, with a fluorescence quantum yield of 72.6%.

[0065] Comparative Example 3 A method for preparing a thin film is the same as the preparation steps in Example 1, except that Ph-2PACz is not added.

[0066] The organic-inorganic hybrid perovskite luminescent material prepared in Example 1 was used to fabricate a blue perovskite luminescent diode with the structure of ITO / PEDOT:PSS / Perovskite / PO-T2T / LiF / Al. The PEDOT:PSS and Perovskite layers were formed by a one-step solution spin coating method. The three layers of PO-T2T / LiF / Al were formed by vacuum evaporation, with 40nm / 1nm / 100nm deposited respectively. Figure 12 These are the time-of-flight secondary ion mass spectrometry (TOF-SIMS) results of the blue perovskite light-emitting diode from Example 1. The test started from the top electron transport layer PO-T2T of the perovskite and ended at the bottom hole transport layer PEDOT:PSS. PbBr - As a special signal of the perovskite octahedron, SO3 exhibits higher intensity in the perovskite region. - The intensity is higher in the PEDOT:PSS region. Meanwhile, PO... - Ph-2PACz, a unique ionic signal of the small molecule, is observed to be distributed both within the perovskite layer and at the perovskite-PEDOT:PSS interface. Due to the relatively large molecular structure of Ph-2PACz, it is unsuitable for existence within the stable perovskite crystal and tends to migrate towards the upper and lower surfaces of the perovskite. A small amount of Ph-2PACz is also present at the upper interface. Figure 12 This can be seen in the time-of-flight secondary ion mass spectrum. The Ph-2PACz at the upper interface can interact with Pb on the film surface via P=O bonds. 2+ This combination passivates defects at the upper interface and reduces nonradiative recombination; at the same time, it can effectively suppress nonradiative energy loss between the perovskite and the electron transport layer, and improve exciton utilization efficiency. Figure 13 This is a comparison of the Br vacancy defect formation energies on the perovskite surfaces prepared in Example 1 and Comparative Example 3. In Example 1, the Br vacancy defect energy increased after the addition of Ph-2PACz, indicating that Br vacancies are more difficult to form. This proves that the P=O bonds of Ph-2PACz can interact with the Pb bonds on the perovskite surface. 2+ Bonding is formed, Br ion defects are passivated, thereby reducing nonradiative recombination and improving device performance. Figure 20 This is a schematic diagram illustrating the mechanism of performance improvement in blue perovskite light-emitting diodes. During the spin-coating process of perovskite film, Ph-2PACz migrates towards the hole transport layer PEDOT:PSS, resulting in Ph-2PACz distribution both within the perovskite layer and at the perovskite-PEDOT:PSS interface. This reduces the HOMO energy level at the interface and simultaneously passivates ionic defects within the perovskite layer. It is important to note that Ph-2PACz also migrates towards the electron transport layer.

[0067] Figure 14This is a graph showing the transient fluorescence spectrum of the blue perovskite thin film in Example 1 over time. The distribution of Ph-2PACz in the perovskite optimizes the small-sized perovskite in the quasi-two-dimensional perovskite. n Xiangdao Da n Phase energy transfer "funnel effect". Quasi-two-dimensional perovskite n Phase distribution concentrated in n =3 and n =4 phases, reducing energy loss caused by the "funnel effect".

[0068] Figure 15 The diagram shows the interface energy levels of the blue perovskite emitting layer and PEDOT:PSS in Example 1. It can be seen that the introduction of Ph-2PACz lowers the HOMO energy level of the interface, which is more compatible with the perovskite energy level and facilitates hole transport.

[0069] Figure 16 The image shows a scanning electron microscope (SEM) image comparing the blue perovskite luminescent film of Example 1 (the Ph-2PACz film in the figure) with the reference film of Comparative Example 3 (the EABr+EACl film in the figure). It can be seen that Example 1 has a smoother film surface with almost no obvious pores.

[0070] Figure 17 The time-resolved fluorescence spectra of the blue perovskite luminescent film of Example 1 are compared with those of the EABr+EACl film of Comparative Example 3 and the reference film of Comparative Example 2. It can be seen that the film of Example 1 containing the Ph-2PACz gradient structure exhibits a longer carrier lifetime. This indicates that defect states are effectively passivated and non-radiative recombination channels are suppressed, directly demonstrating the excellent passivation effect of this structure in bulk. The passivation of its defect states is mainly reflected in P=O and Pb. 2+ The formation of covalent bonds between them passivates the vacancy defects of halide ions.

[0071] The above data proves that Ph-2PACz not only acts as a bulk passivator, but also acts as an interface modifier because its large molecular structure is not suitable for existence inside a stable perovskite crystal. It tends to migrate to the upper and lower surfaces of the perovskite, thus achieving "multiple uses of one material". This breaks the functional boundary that interface modification strategy and bulk passivation strategy are usually independent of each other in traditional improvement strategies, making it difficult to achieve synergistic optimization.

[0072] Example 2 Compared to Example 1, the amount of Ph-2PACz was changed so that the molar ratio of PbX2 to the self-assembled molecule Ph-2PACz was 10:1.

[0073] Example 3 Compared to Example 1, the amount of Ph-2PACz was changed so that the molar ratio of PbX2 to the self-assembled molecule Ph-2PACz was 30:1.

[0074] Example 4 Compared to Example 1, the amount of Ph-2PACz was changed so that the molar ratio of PbX2 to the self-assembled molecule Ph-2PACz was 40:1.

[0075] The precursor solutions from Examples 2-4 were prepared according to the steps in Example 1, and spin-coated thin films were obtained. The fluorescence intensity of the films under different Ph-2PACz concentration gradients was then calculated. Figure 18 As shown, the amount of Ph-2PACz affects the emission performance. By changing the above parameters, the film performance can be controlled. The comparison shows that the film fluorescence intensity is the highest when the molar ratio of PbX2 to the self-assembled molecule Ph-2PACz is 20:1.

[0076] Figure 19 This diagram illustrates the EQE (External Quantum Efficiency) of the blue perovskite luminescent film from Example 1 and the reference film from Comparative Example 2, respectively, applied to devices. Both perovskite device structures are ITO / PEDOT:PSS / Perovskite / PO-T2T / LiF / Al. The PEDOT:PSS and Perovskite layers were formed using a one-step solution spin-coating method; the PO-T2T / LiF / Al layers were formed using vacuum evaporation at 40nm / 1nm / 100nm depths, respectively. Compared to the reference device prepared using the control film from Comparative Example 2, the external quantum efficiency (EQE) of both the blue perovskite luminescent film prepared using Ph-2PACz from Example 1 and the device prepared using the blue perovskite luminescent film was further improved. The EQE of the device prepared using the control film was 5.02%, and the EQE of the device prepared using the blue perovskite luminescent film was 18.08%.

[0077] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, it is intended to include any modifications and variations that fall within the scope of the claims and their equivalents.

Claims

1. An organic-inorganic hybrid perovskite luminescent material, characterized in that, The luminescent material is composed of alternating stacks of several insulating organic spacer cation layers and several low-dimensional lead-based perovskite inorganic layers. The low-dimensional lead-based perovskite inorganic layers are located between the insulating organic spacer cation layers and are composed of lead-based perovskite octahedral cells of varying numbers. The chemical formula of the organic-inorganic hybrid perovskite luminescent material is A2Cs. n-1 Pb n X 3n+1 Where A represents the organic spacer cation, selected from phenylethylammonium ion and ethylammonium ion; n represents the number of lead-based perovskite octahedral cells between adjacent insulating organic spacer cation layers; X is Cl - ,Br - One or two of them; The organic-inorganic hybrid perovskite luminescent material is in the form of a thin film, with Ph-2PACz distributed both inside and on both sides of the film. Ph-2PACz is used as a bulk passivator and interface modifier; Pb 2+ The molar ratio with Ph-2PACz is 10~40:

1.

2. The organic-inorganic hybrid perovskite luminescent material according to claim 1, characterized in that, The organic-inorganic hybrid perovskite luminescent material has a band gap of 2.50 eV to 2.61 eV and a fluorescence emission wavelength of 475 nm to 495 nm.

3. The organic-inorganic hybrid perovskite luminescent material according to claim 1, characterized in that, The center of a lead-based perovskite octahedral unit cell is a Pb atom, the atoms at the six vertices of the octahedron are X atoms, the octahedral structure is located within a cube, and the eight vertices of the cube are Cs atoms. + Or ethylammonium ions.

4. A method for preparing the organic-inorganic hybrid perovskite luminescent material according to claim 1, characterized in that, Includes the following steps: The perovskite precursor and Ph-2PACz were dissolved together in a solvent to form a precursor solution; the precursor solution was then coated onto a substrate. An antisolvent was added dropwise during the coating process, followed by annealing. Ph-2PACz migrated autonomously from the bulk phase to both sides of the film surface during the coating and annealing process, and formed a gradient distribution structure across the perovskite film interface in situ.

5. The preparation method according to claim 4, characterized in that, The perovskite precursor is composed of PbX2, CsX, quaternary ammonium salt PEAX and quaternary ammonium salt EAX. The molar ratio of PbX2, CsX, quaternary ammonium salt PEAX and quaternary ammonium salt EAX is 1:0.9~1.1:0.5~0.7:0.5~0.7, and the molar ratio of PbX2 to Ph-2PACz is 10~40:

1.

6. The preparation method according to claim 4, characterized in that, The concentration of the precursor solution is 0.08 mol / L to 0.12 mol / L.

7. The preparation method according to claim 4, characterized in that, The annealing conditions are: annealing at 80℃~100℃ for 5min~10min.

8. A blue perovskite light-emitting diode, characterized in that, It includes a light-emitting layer, which is made of the organic-inorganic hybrid perovskite light-emitting material as described in claim 1.

9. The blue perovskite light-emitting diode according to claim 8, characterized in that, It includes an anode, a hole transport layer, a light-emitting layer, an electron transport layer, an electron injection layer, and a cathode arranged in sequence. The light-emitting layer contains ethylammonium ions and Ph-2PACz. The ethylammonium ions are used to replace the A-site cations, and Ph-2PACz is distributed at the two interfaces between the bulk phase of the light-emitting layer and the light-emitting layer, serving as a bulk phase passivator and an interface modifier.

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