A light-emitting diode based on cubic perovskite thin film and its fabrication method

Abstract

This invention belongs to the field of luminescent materials and devices, specifically relating to a light-emitting diode based on a cubic perovskite thin film and its fabrication method. The method includes the following steps: S1, preparing a precursor solution: dissolving FABr, MABr, GABr, CsBr, and PbBr2 in DMSO to obtain a mixed cationic precursor solution, then adding N-vinylpyrrolidone and azobisisobutyronitrile to obtain another precursor solution; S2, cleaning and drying the conductive substrate; S3, coating a mixed solution of PEDOT:PSS and PFI onto the conductive substrate, annealing to obtain a hole transport layer; S4, coating the precursor solution onto the hole transport layer, then adding an antisolvent, annealing to obtain a cubic perovskite thin film; S5, depositing an electron transport layer and a cathode on the perovskite thin film. The perovskite thin film prepared by this invention has a low-defect cubic phase structure, which can effectively improve device brightness and electro-optical conversion efficiency.

Description

Technical Field

[0001] This invention belongs to the field of light-emitting materials and devices, specifically relating to a light-emitting diode based on cubic perovskite thin film and its preparation method. Background Technology

[0002] Metal halide perovskites have become highly attractive semiconductor materials over the past decade due to their superior optoelectronic properties, and are widely used in various devices such as solar cells and photodetectors. As direct bandgap materials, they possess easily tunable bandgaps, high carrier mobility, and excellent color purity, making them emerging semiconductors for light-emitting diode (LED) applications. Bromine-based perovskites have been successfully applied in perovskite LEDs, achieving external quantum efficiencies exceeding 30%.

[0003] To achieve the ideal performance of perovskite light-emitting diodes (LEDs), the structure of perovskite nanocrystals can be precisely controlled to effectively confine charge carriers, thereby increasing exciton binding energy, the probability of radiative recombination, and the photoluminescence quantum yield. However, due to the inhomogeneous nucleation process and rapid crystallization of perovskite, the reduction in grain size is often accompanied by the appearance of numerous grain boundaries and high surface trap densities, leading to increased nonradiative recombination and decreased device performance. Therefore, controlling the growth of the thin film and passivating surface traps are essential steps in the fabrication of high-performance perovskite LEDs. Furthermore, controlling the crystal orientation in polycrystalline thin films can also enhance charge transport efficiency by reducing structural disorder. Various strategies have been reported for regulating the crystallization process and passivating the perovskite surface, including the use of organic or inorganic additives, optimized deposition techniques, and solvent engineering. These strategies can function as capping ligands. However, the high ion activity and bias ion migration in perovskite thin films remain another bottleneck problem to be solved. Severe ion migration generates a large number of ion vacancies, leading to lattice collapse. In addition, ion migration is also one of the reasons for the spectral shift in the emission wavelength of perovskite light-emitting diodes, especially in perovskite light-emitting diodes with mixed anions and mixed cations.

[0004] To prevent this, capping ligands can be used to confine ions within small crystals. However, most of these ligands are dynamic and have few anchoring sites on perovskites, making long-term stability difficult to guarantee and potentially leading to increased bias. In contrast, polymer-based additives with abundant anchoring sites have proven effective in encapsulating perovskite solar cells and modulating directional crystallization and surface morphology, thereby suppressing ion migration and improving device stability. Summary of the Invention

[0005] One objective of this invention is to provide a method for fabricating light-emitting diodes (LEDs) based on cubic perovskite thin films. This invention utilizes a one-step solution deposition method to fabricate three-dimensional perovskite thin films, offering a simple operation and providing technical support for the fabrication of novel, high-brightness, and stable green perovskite LEDs.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for fabricating a light-emitting diode based on a cubic perovskite thin film includes the following steps: S1. Preparation of precursor solution: Dissolve FABr, MABr, GABr, CsBr and PbBr2 in DMSO to obtain a mixed cationic precursor solution, then add N-vinylpyrrolidone and azobisisobutyronitrile to obtain the precursor solution. S2. Clean and dry the conductive substrate; S3. Coat a mixed solution of PEDOT:PSS and PFI onto a conductive substrate and anneal it to obtain a hole transport layer. S4. The precursor solution is coated on the hole transport layer, then the antisolvent is dropped in, and after annealing, a cubic perovskite film is obtained. S5. Deposit an electron transport layer and a cathode on the perovskite thin film to obtain the final product.

[0007] The reaction structure of N-vinylpyrrolidone (NVP) to polyvinylpyrrolidone (PVP) is shown in the following formula: This invention does not specifically limit the material of the electron transport layer; those skilled in the art can choose materials with similar performance to TPBi and TmPyPb. This invention also does not specifically limit the material of the cathode; those skilled in the art can choose commonly used cathode materials such as aluminum, silver, and gold.

[0008] Further, the molar ratio of FABr, MABr, GABr, CsBr, and PbBr2 in step S1 is (0.74~0.76):(0.1~0.2):(0.2~0.25):(0.1~0.13):1.

[0009] Furthermore, in step S1, the ratio of PbBr2 to DMSO is 1 mol: (1~2) mL.

[0010] Further, the amount of N-vinylpyrrolidone used in step S1 is 2.5 to 20% of the volume of DMSO.

[0011] Further, the amount of azobisisobutyronitrile used in step S1 is 0.1 to 0.5% of the mass of N-vinylpyrrolidone.

[0012] Further, the antisolvent in step S4 is a chlorobenzene solution of 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene, wherein the concentration of 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene in chlorobenzene is 0.5~2 mg / mL.

[0013] Furthermore, the annealing temperature in step S3 is 140~150℃, and the time is 30~45min.

[0014] Furthermore, the annealing temperature in step S4 is 75~85℃, and the time is 8~15min.

[0015] The second objective of this invention is to provide a light-emitting diode based on a cubic perovskite thin film. The perovskite thin film prepared by this invention has a high-quality, low-defect cubic phase structure, realizing the fabrication of a high-brightness, stable green perovskite light-emitting diode, which can effectively improve the device brightness and the electro-optical conversion efficiency of the device.

[0016] A light-emitting diode based on a cubic perovskite thin film was prepared using the above-described method.

[0017] Compared with the prior art, the beneficial effects of this invention are as follows: 1. This invention utilizes a crosslinking strategy, selecting N-vinylpyrrolidone (NVP) as a self-polymerizing additive to dope three-dimensional green perovskite films, thus preparing films with high-quality, low-defect cubic phase grains, ultimately achieving high-brightness, stable green perovskite light-emitting diodes. During spin coating, NVP repels impurities around the grains, promoting rapid perovskite nucleation and delaying crystallization. During annealing, NVP undergoes a polymerization reaction to form polyvinylpyrrolidone, encapsulating the grains. The C=O double bonds in NVP form strong hydrogen bonds with A-site cations and interact with uncoordinated Pb. 2+ It forms coordination bonds, passivates crystal surface defects, and induces the formation of cubic phase grains.

[0018] 2. Through electrical property characterization of the device, this invention reveals that after introducing NVP into the perovskite light-emitting layer, the current density decreases with increasing NVP doping concentration. This is because the incorporation of NVP affects carrier injection and transport. Furthermore, with increasing NVP doping concentration, the device brightness first increases and then decreases. This is because a small amount of NVP can effectively passivate defects, suppress non-radiative recombination, improve device performance, and enhance device stability. However, when a large amount of NVP is incorporated, the performance significantly decreases due to the low defect tolerance of NVP. After comprehensive analysis, an NVP doping concentration of 5 Vol.% is considered optimal.

[0019] 3. The self-polymerizing molecule NVP of this invention increases the exciton binding energy of the perovskite thin film, which facilitates exciton radiative recombination and effectively extends the carrier lifetime; it also yields an energy level structure that better matches the transport layer energy level, which is beneficial for carrier injection and transport. Furthermore, the introduction of NVP molecules enhances the hydrophobicity of the film, thereby improving the stability of the perovskite thin film and the device. Attached Figure Description

[0020] Figure 1 This is a flowchart illustrating the fabrication process of the perovskite light-emitting diode of the present invention. Figure 2 This is a schematic diagram of the perovskite light-emitting diode of the present invention; Figure 3 These are SEM images of the perovskite thin surfaces of Examples 1-5 and Comparative Example 1 of the present invention; Figure 4 These are SEM cross-sectional images of perovskite thin films from Embodiment 1 and Comparative Example 1 of the present invention. Figure 5 (a) Figure 5 (c) in the figure is a TEM image of the perovskite thin film in Comparative Example 1; Figure 5 (b) Figure 5 (d) in the image is a TEM image of the perovskite thin film in Example 1; Figure 6 (a) to Figure 6 (c) shows the current density-voltage characteristic curve, brightness-voltage characteristic curve, and EQE-current density characteristic curve of the PeLEDs devices in Examples 1-5 and Comparative Example 1, respectively. Figure 6 (d) in the figure represents the EL spectra of the PeLED prepared in Example 1 at different voltages; Figure 7 (a) Figure 7 (b) in the figure represents the trap state density diagrams of the perovskite thin films of Comparative Example 1 and Example 1 of the present invention, respectively. Figure 8 (a) Figure 8 (b) shows the PL spectra of the perovskite films prepared in Comparative Example 1 and Example 1, respectively. Figure 9 (a) Figure 9 (b) shows the PL and EL spectra of the thin films of Comparative Example 1 and Example 1, respectively. Figure 10 The figure shows the stability test results of the PeLEDs device under 3.4 V voltage according to the present invention. Detailed Implementation

[0021] The technical solution of the present invention will be further explained below with reference to specific embodiments, comparative examples, experimental examples and accompanying drawings.

[0022] Unless otherwise specified, the raw materials and preparation methods used in the following examples, comparative examples, and experimental cases are all conventional materials and techniques in the art.

[0023] Example 1 A method for fabricating a light-emitting diode based on a cubic perovskite thin film, specifically including the following fabrication method, the flowchart of which is shown below. Figure 1 As shown: S1. The perovskite precursor solution was prepared according to the following formula: FABr, MABr (methylammonium bromide), GABr (guanidinohydrobromide), CsBr, and PbBr2 were dissolved in 1 mL of DMSO in a molar ratio of 0.756:0.108:0.216:0.12:1 to prepare a mixed cation precursor solution (FABr). 0.7 MA 0.1 GA 0.2 ) 0.9 Cs 0.1 PbBr3 is then added to the solution along with 5% N-vinylpyrrolidone (NVP) solution (0.3wt% azobisisobutyronitrile equivalent to the mass of N-vinylpyrrolidone is added to the NVP beforehand) to obtain the perovskite precursor solution.

[0024] S2: The ITO substrate is ultrasonically cleaned in deionized water, anhydrous ethanol, acetone and isopropanol in sequence, with each ultrasonic cleaning time being 25 min. After ultrasonic cleaning, the anode substrate is placed in ozone to dry for more than 15 min until it is completely dry.

[0025] S3: A mixed solution of PEDOT:PSS (Clevios PVP Al4083) and perfluorinated ions (PFI) (PEDOT:PSS / PFI = 9:13 v / v) was spin-coated onto an O2-treated ITO substrate, and then annealed on a hot stage at 150°C for 30 min to obtain a hole transport layer. After baking, it was transferred to a glove box filled with nitrogen.

[0026] S4: Prepare the antisolvent (concentration 1 mg / mL) by dissolving TPBi (1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene) in chlorobenzene (CB). Stir the solution overnight at room temperature in an N2 glove box before use.

[0027] The above perovskite precursor solution was spin-coated onto a PEDOT:PSS coated substrate at 6000 rpm for 45 s. After a 20 s delay, 150 μL of TPBi@CB antisolvent was added, and the resulting sample was annealed at 80 °C for 10 min to form a perovskite (PNC) film.

[0028] S5: Finally, using a thermal evaporation system at <10 -4 Under high vacuum conditions of Pa, a ZADN electron transport layer (ETL) (45 nm) and LiF / Al electrodes (1 nm / 100 nm) were deposited on a perovskite thin film to obtain a perovskite light-emitting diode.

[0029] This embodiment also provides a perovskite light-emitting diode prepared by the above-described preparation method, with the structure as follows: Figure 2 As shown.

[0030] Example 2 A method for fabricating a light-emitting diode based on a cubic perovskite thin film, specifically including the following fabrication method, S1. The perovskite precursor solution was prepared according to the following formula: FABr, MABr (methylammonium bromide), GABr (guanidinohydrobromide), CsBr, and PbBr2 were dissolved in 1 mL of DMSO in a molar ratio of 0.74:0.1:0.2:0.1:1 to prepare a mixed cation precursor solution (FABr). 0.7 MA 0.1 GA 0.2 ) 0.9 Cs 0.1 PbBr3 is then added to the solution along with 2.5% N-vinylpyrrolidone (NVP) solution (0.1 wt% azobisisobutyronitrile equivalent to the mass of N-vinylpyrrolidone is added to the NVP beforehand) to obtain the perovskite precursor solution.

[0031] S2 and S3 are the same as in Example 1; S4: An antisolvent (concentration 0.5 mg / mL) was prepared by dissolving TPBi (1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene) in chlorobenzene (CB). The solution was stirred overnight at room temperature in an N2 glove box before use. Other procedures were the same as in Example 1.

[0032] S5: Finally, using a thermal evaporation system at <10 -4 Under high vacuum conditions of Pa, a ZADN electron transport layer (ETL) (45 nm) and LiF / Al electrodes (1 nm / 100 nm) were deposited on a perovskite thin film to obtain a perovskite light-emitting diode.

[0033] This embodiment also provides a perovskite light-emitting diode prepared by the above-described preparation method.

[0034] Example 3 A method for fabricating a light-emitting diode based on a cubic perovskite thin film, specifically including the following fabrication method, S1. The perovskite precursor solution was prepared according to the following formula: FABr, MABr (methylammonium bromide), GABr (guanidinohydrobromide), CsBr, and PbBr2 were dissolved in 1 mL of DMSO in a molar ratio of 0.76:0.2:0.25:0.13:1 to prepare a mixed cation precursor solution (FABr). 0.7 MA 0.1 GA 0.2 ) 0.9 Cs 0.1 PbBr3 is then added to the solution along with an N-vinylpyrrolidone (NVP) solution equivalent to 10% of the volume of DMSO (with 0.5 wt% azobisisobutyronitrile equivalent to the mass of N-vinylpyrrolidone added to the NVP beforehand), thus obtaining the perovskite precursor solution.

[0035] S2 and S3 are the same as in Example 1; S4: An antisolvent (concentration 2 mg / mL) was prepared by dissolving TPBi (1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene) in chlorobenzene (CB). The solution was stirred overnight at room temperature in an N2 glove box before use. Other procedures were the same as in Example 1.

[0036] S5: Finally, using a thermal evaporation system at <10 -4 Under high vacuum conditions of Pa, a ZADN electron transport layer (ETL) (45 nm) and LiF / Al electrodes (1 nm / 100 nm) were deposited on a perovskite thin film to obtain a perovskite light-emitting diode.

[0037] This embodiment also provides a perovskite light-emitting diode prepared by the above-described preparation method.

[0038] Example 4 A method for fabricating a light-emitting diode based on a cubic perovskite thin film, specifically including the following fabrication method, S1. The perovskite precursor solution was prepared according to the following formula: FABr, MABr (methylammonium bromide), GABr (guanidinohydrobromide), CsBr, and PbBr2 were dissolved in 1 mL of DMSO in a molar ratio of 0.75:0.11:0.22:0.12:1 to prepare a mixed cation precursor solution (FABr). 0.7 MA 0.1 GA 0.2 ) 0.9 Cs 0.1 PbBr3 is then added to the solution along with an N-vinylpyrrolidone (NVP) solution equivalent to 15% of the volume of DMSO (with 0.4 wt% azobisisobutyronitrile equivalent to the mass of N-vinylpyrrolidone added to the NVP beforehand), thus obtaining the perovskite precursor solution.

[0039] S2 and S3 are the same as in Example 1; S4: An antisolvent (concentration 1 mg / mL) was prepared by dissolving TPBi (1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene) in chlorobenzene (CB). The solution was stirred overnight at room temperature in an N2 glove box before use. Other procedures were the same as in Example 1.

[0040] S5: Finally, using a thermal evaporation system at <10 -4 Under high vacuum conditions of Pa, a ZADN electron transport layer (ETL) (45 nm) and LiF / Al electrodes (1 nm / 100 nm) were deposited on a perovskite thin film to obtain a perovskite light-emitting diode.

[0041] This embodiment also provides a perovskite light-emitting diode prepared by the above-described preparation method.

[0042] Example 5 A method for fabricating a light-emitting diode based on a cubic perovskite thin film, specifically including the following fabrication method, S1. The perovskite precursor solution was prepared according to the following formula: FABr, MABr (methylammonium bromide), GABr (guanidinohydrobromide), CsBr, and PbBr2 were dissolved in 1 mL of DMSO in a molar ratio of 0.756:0.108:0.216:0.12:1 to prepare a mixed cation precursor solution (FABr). 0.7 MA 0.1 GA 0.2 ) 0.9 Cs 0.1 PbBr3 is then added to the solution along with an N-vinylpyrrolidone (NVP) solution equivalent to 20% of the volume of DMSO (with 0.2wt% azobisisobutyronitrile equivalent to the mass of N-vinylpyrrolidone added to the NVP beforehand), thus obtaining the perovskite precursor solution.

[0043] S2 and S3 are the same as in Example 1; S4: An antisolvent (concentration 1.5 mg / mL) was prepared by dissolving TPBi (1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene) in chlorobenzene (CB). The solution was stirred overnight at room temperature in an N2 glove box before use. Other procedures were the same as in Example 1.

[0044] S5: Finally, using a thermal evaporation system at <10 -4 Under high vacuum conditions of Pa, a ZADN electron transport layer (ETL) (45 nm) and LiF / Al electrodes (1 nm / 100 nm) were deposited on a perovskite thin film to obtain a perovskite light-emitting diode.

[0045] This embodiment also provides a perovskite light-emitting diode prepared by the above-described preparation method.

[0046] Comparative Example 1 The fabrication method of the perovskite light-emitting diode in Comparative Example 1 is the same as that in Example 1, except that NVP is omitted in S1.

[0047] To verify the performance of the aforementioned light-emitting diode based on cubic perovskite thin film, the following experiment was conducted to verify its effectiveness.

[0048] Experimental Example 1 To investigate the morphology of the perovskite films prepared in Examples 1-5 and Comparative Example 1 in step S4, surface SEM analysis was performed on the corresponding films, and the results are as follows: Figure 3 As shown.

[0049] Depend on Figure 3 It can be seen that the perovskite film in Comparative Example 1 exhibits a crystal morphology with varying sizes, rounded shape, and numerous pores, with most grain sizes around 200 nm and a disordered arrangement. However, after adding the self-polymerizing additive NVP, the morphology of the perovskite films in Examples 1-5 changed significantly, transforming from the original rounded, large grains into uniform, cubic crystals, with the grain size decreasing to 100 nm. In particular, the cubic phase became more pronounced with the increase of NVP content. After reaching a certain amount (15 vol.%), the SEM images became blurry. This is because the polyvinylpyrrolidone (PVP) formed after NVP polymerization has poor conductivity. At this point, there is a large amount of polymer PVP in the perovskite film, and very few electrons are reflected back when the electron beam hits the perovskite film, resulting in very dark SEM images.

[0050] To further observe the changes in film morphology, SEM images of the corresponding films were obtained using Examples 1 and 1 (Comparative Example 1). Figure 4 As shown.

[0051] Depend on Figure 4 The thickness and grain boundary characteristics of the perovskite films can be observed. It was found that the grain size of the perovskite film in Comparative Example 1 is larger than that in Example 1, with a film thickness of approximately 280 nm. The thickness of the perovskite film in Example 1 (W / NVP) is approximately 320 nm. The grain boundaries of the perovskite film in Example 1 are significantly reduced, and the perovskite grains are more regular and dense. The black voids in the middle are cross-linked NVP.

[0052] Therefore, by adding the self-polymerizing additive NVP, the present invention can reduce the grain size of thin film perovskite and effectively increase the charge carrier confinement, which can be used to prepare PeLED devices.

[0053] Experimental Example 2 The distribution of NVP in the perovskite thin film was tested using high-resolution transmission electron microscopy (HR-TEM), and the results are as follows: Figure 5 As shown. Figure 5 (a) in the image is a TEM image of the perovskite thin film in Comparative Example 1; Figure 5 (c) in the figure is a TEM magnified image of the perovskite thin film in Comparative Example 1; Figure 5 (b) is a TEM image of the perovskite thin film in Example 1; Figure 5 (d) in the image is a magnified TEM image of the perovskite thin film in Example 1; from Figure 5 (a) Figure 5 (b) confirms that NVP undergoes in-situ polymerization in the perovskite film and exists at the grain boundaries of the perovskite. In Comparative Example 1, the perovskite edges in the film are clear and distinct, while the surface of the perovskite film with added NVP is covered by polymerized PVP. Careful observation reveals that the perovskite grains are cubically arranged and orderly, corresponding to the SEM image. Based on the magnified TEM image (e.g., Figure 5 (c) Figure 5 As shown in (d), the grain boundary edges of the film in Comparative Example 1 are clear and there is no amorphous state, while the perovskite film in Example 1 (after adding NVP) has an amorphous amorphous morphology at the edges. This indicates that the polymer PVP exists at the edges or between the perovskite grains. Selected area electron diffraction (SAD) results show that the perovskite film with added NVP is densely crystalline with a clear lattice. The lattice spacing (d) is 5.9 Å and 3.1 Å, respectively, corresponding to the (100) and (200) crystal planes of the three-dimensional perovskite. The perovskite film in Comparative Example 1 only has the (200) crystal plane. The reason for obtaining high-quality, cubic phase grains is that during the crystallization process of perovskite, the impurity phase is repelled to the edge and encapsulated by PVP. The experimental results of SEM and TEM have preliminarily confirmed that NVP undergoes a self-polymerization reaction during the perovskite annealing process, and the polymer exists in the perovskite grain boundaries.

[0054] Experimental Example 3 The green perovskite light-emitting diodes prepared in Examples 1-5 and Comparative Example 1 were placed in a glove box for electrical property characterization. The characterization results are as follows: Figure 6 and Figure 7 As shown. Figure 6 (a) to Figure 6 (c) shows the current density-voltage characteristic curve, brightness-voltage characteristic curve, and EQE-current density characteristic curve of the PeLEDs devices in Examples 1-5 and Comparative Example 1, respectively. Figure 6 (d) in the figure represents the EL spectrum of the PeLED prepared in Example 1 at different voltages.

[0055] Figure 6Figure (a) shows the current density-voltage curves. Under voltage drive, the current density of PeLEDs devices with different volume ratios and NVP doping contents varies. Specifically, as the NVP content increases, the current density first increases and then decreases. A lower current density before power-on is better, as it represents the magnitude of leakage current; a higher current density after power-on is better, indicating carrier recombination balance. Figure 6 (b) and Figure 6 As can be seen from (c), the current density is the highest and the corresponding luminous intensity is also the highest when the NVP doping volume ratio is 5 vol.%, reaching 240,000 cd / m². -2 The optimized devices achieved EQE values ​​of 4.21% (W / 2.5 vol.%), 9.32% (W / 5 vol.%), 7.43% (W / 10 vol.%), 6.32% (W / 15 vol.%), and 5.36% (W / 20 vol.%), respectively, all of which were higher than those of the comparative device 1 (3.54%).

[0056] Figure 6 (d) shows the normalized EL spectrum of PeLED under different voltages. Under the drive of 3 V to 7 V, PeLED exhibits a stable green light emission of 540 nm, consistent with the PL spectrum. The emission peak intensity of PeLED increases with the increase of voltage, and the peak position does not shift with the increase of external bias voltage, indicating that the spectrum of PeLED device after adding NVP is stable.

[0057] Figure 7 The following are density maps of trapped states in perovskite thin films of Example 1 and Comparative Example 1, wherein... Figure 7 (a) in the diagram is the density of trapped states of the perovskite thin film in Comparative Example 1. Figure 7 (b) in the diagram is the density diagram of trapped states in the perovskite thin film of Example 1. Observation Figure 7 It can be seen that, compared with the device in Comparative Example 1, the device in Example 1 (W / NVP) has a higher hole defect state density (N) due to the effective passivation of perovskite thin film defects by NVP. t The hole defect state densities of the devices in Comparative Example 1 and Example 1 are relatively low, at 2.99 × 10⁻⁶ respectively. 16 cm -3 1.07×10 16 cm -3 Trap filling threshold voltage (V) TFL The values ​​are 0.57 V and 0.45 V, respectively. TFL The decrease in the value indicates a decrease in the density of trapped states in the thin film.

[0058] Test Example 4 Ion migration in perovskites can cause the diffusion of vacancy defects and accelerate the degradation of effective carrier recombination. The degradation of PeLEDs during operation is mainly related to the quality of the perovskite film. The self-polymerizing additive NVP can improve the photostability of perovskite films. The photostability of the perovskite films of Example 1 and Comparative Example 1 was tested continuously over 30 days.

[0059] like Figure 8 (a) and Figure 8 As shown in (b), the PL intensity of the perovskite film in Comparative Example 1 decreased to 50% of its original value after 20 days, while the perovskite film with added NVP in Example 1 did not change much within 30 days, which allows the film to maintain high fluorescence emission over a long period of time.

[0060] Experimental Example 5 To further verify whether the PL and EL spectra are consistent, EL tests were performed on the devices prepared in Example 1 and Comparative Example 1 at a voltage of 4.6 V, respectively. Figure 9 (a) and Figure 9 As shown in (b), the EL spectrum of the perovskite film in Comparative Example 1 differs from the PL spectrum. The emission peaks of PL and EL are centered at 540 nm and 537 nm, respectively. The blue shift in the EL spectrum is likely caused by free carrier emission. The PL of the perovskite film in Example 1 (W / NVP) matches well with the EL of the device. The EL is broadened compared to PL, which can be attributed to the electric field-induced Stark effect. Overall, the perovskite film with the NVP additive exhibits more stable spectral performance.

[0061] Experimental Example 6 The PeLEDs prepared in Example 1 and Comparative Example 1 achieved an initial luminance of 3000 cd / m² under a constant voltage of 3.4V (in a glove box filled with N2). -2 The operational stability of the device was tested, and the results are as follows: Figure 10 As shown.

[0062] from Figure 10 It can be seen that the target device's half-life (T50) of 90 min is more than six times longer than the original device's 15 min, indicating that NVP can enhance the device's stability during operation.

[0063] The embodiments described above are some, but not all, of the embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments. All other embodiments obtained by those skilled in the art through related deductions and substitutions based on the inventive concept, without inventive effort, are within the scope of protection of the present invention.

Claims

1. A method for fabricating a light-emitting diode based on a cubic perovskite thin film, characterized in that, Includes the following steps: S1. Preparation of precursor solution: Dissolve FABr, MABr, GABr, CsBr and PbBr2 in DMSO to obtain a mixed cationic precursor solution, then add N-vinylpyrrolidone and azobisisobutyronitrile to obtain the precursor solution. S2. Clean and dry the conductive substrate; S3. Coat a mixed solution of PEDOT:PSS and PFI onto a conductive substrate and anneal it to obtain a hole transport layer. S4. The precursor solution is coated on the hole transport layer, then the antisolvent is dropped in, and after annealing, a cubic perovskite film is obtained. S5. Deposit an electron transport layer and a cathode on the perovskite thin film to obtain the desired result; The molar ratio of FABr, MABr, GABr, CsBr, and PbBr2 in step S1 is (0.74~0.76):(0.1~0.2):(0.2~0.25):(0.1~0.13):1; The amount of N-vinylpyrrolidone used is 5% of the volume of DMSO; The antisolvent is a chlorobenzene solution of 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene; wherein the concentration of 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene in chlorobenzene is 0.5~2 mg / mL; The annealing temperature in step S3 is 140~150℃, and the time is 30~45min; The annealing temperature in step S4 is 75~85℃, and the time is 8~15min.

2. The method for preparing a light-emitting diode based on a cubic perovskite thin film according to claim 1, wherein the ratio of PbBr2 to DMSO in step S1 is 1 mol: (1~2) mL.

3. The method for fabricating a light-emitting diode based on a cubic perovskite thin film according to claim 1, characterized in that, The amount of azobisisobutyronitrile used in step S1 is 0.1 to 0.5% of the mass of N-vinylpyrrolidone.

4. A light-emitting diode based on a cubic perovskite thin film, characterized in that, It is prepared by the preparation method described in any one of claims 1 to 3.

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