Novel anti-solvent-based perovskite light-emitting diode and preparation method thereof

Abstract

The invention discloses a perovskite light-emitting diode based on a novel anti-solvent and a preparation method thereof, and belongs to the technical field of light-emitting diodes. The perovskite light-emitting layer is prepared by spin coating of a perovskite precursor solution; an anti-solvent is dropwise added in the spin-coating process; the anti-solvent is a mixture of ethyl acetate doped with dimethyl phosphite (DPP) in a volume ratio of (5: 1)-(40: 1). According to the invention, the selected S-A self-adaptive solvent gives consideration to the unique advantages of an EA anti-solvent and DPP molecules, regulates and controls the growth and orientation of the Q-2D perovskite crystal, and reduces the number of grain boundary defects; the formation of low n phases is inhibited, and the energy transfer efficiency among different n phases is improved; the defects of the Q-2D perovskite are passivated, and the non-radiative recombination loss is reduced. The EQEmax of the prepared PeLEDs reaches 29.27%, and a new view angle is provided for preparation of the high-performance PeLEDs.

Description

Technical Field

[0001] This invention relates to the field of light-emitting diode technology, and in particular to a perovskite light-emitting diode based on a novel anti-solvent and its fabrication method. Background Technology

[0002] Metal halide perovskites are considered one of the most promising candidates for next-generation light-emitting diode (LED) technology due to their excellent optoelectronic properties. However, three-dimensional (3D) perovskites have relatively low exciton binding energies, meaning that most excitons can decompose into free charges at high temperatures. Therefore, the performance of 3D perovskite-based perovskite LEDs (PeLEDs) has long been unsatisfactory. Unlike 3D perovskites, quasi-two-dimensional (Q-2D) perovskites possess self-assembled multi-quantum-well structures, which can enhance exciton binding energies through quantum confinement effects, potentially leading to more ideal radiative recombination. This is crucial for the fabrication of high-performance PeLEDs. During crystallization, Q-2D perovskites readily form various n-phases with different band gaps (n represents inorganic [PbBr6]) due to kinetic and thermodynamic reasons. 4− The perovskite layer generates multiple quantum wells, with most excitons transferring from the low-n phase to the high-n phase, emitting light through radiative transitions. However, the inhomogeneity and instability of phase domain distribution easily lead to the formation of more low-n phases, while the enrichment of organic cations on the surface of the low-n phase hinders energy transfer from the low-n phase to the high-n phase. Simultaneously, the low-n phase perovskite has poor crystallinity and low carrier mobility, easily forming defects and trapped states, leading to increased non-radiative recombination and an imbalance in carrier injection, which is detrimental to improving the performance of light-emitting devices.

[0003] To fabricate high-performance Q-2D PeLEDs, researchers explored a series of interface engineering and additive strategies, including small organic molecules, polymers, and inorganic alkali metal salts. These strategies aimed to reduce the decomposition of organic ligands and interfacial effects, thereby improving device stability. They also aimed to passivate defects generated in Q-2D perovskites (such as halide vacancy defects), regulate energy transfer between different n-phases, and reduce nonradiative recombination of charge carriers. During the in-situ growth of perovskite films, the use of antisolvents helped form uniform, high-quality perovskite crystals, remove residual solvents and impurities from the film, reduce grain boundary and surface defects, and improve the photoelectric properties and stability of the perovskite.

[0004] In the fabrication of perovskite luminescent thin films, the use of antisolvents accelerates the supersaturation of the perovskite precursor solution, inducing the instantaneous and abundant formation of perovskite nuclei and accelerating the nucleation process. This is beneficial for obtaining high-quality crystalline films with more uniform grain size and fewer grain boundaries. The amount of antisolvent and the dropping time have a significant impact on the quality of the perovskite film. Adding it too early may lead to insufficient nucleation, resulting in voids or island structures. Adding it too late results in excessive supersaturation, which fails to induce uniform nucleation, leading to a rough surface and numerous defects. Excessive amounts can easily lead to over-extraction, forming a non-ideal mesophase. Residual antisolvents can become impurities in the perovskite film, acting as non-radiative recombination centers and affecting charge transport. Furthermore, in some cases, overly vigorous antisolvent treatment may lead to non-preferred orientation or introduce strain, reducing the efficiency and stability of the device.

[0005] In the prior art, CN113823751A, during the preparation of the perovskite luminescent layer, spin-coats a perovskite precursor solution onto the hole transport layer, determines the critical time by monitoring photoluminescence, and selects the antisolvent introduction time based on the critical time. The perovskite luminescent layer is then obtained through annealing. By monitoring the fluorescence phenomenon during photoluminescence, the dripping time of the introduced antisolvent can be easily determined, achieving precise control of the antisolvent dripping time. However, the antisolvent includes a chlorobenzene-trioctylphosphine oxide solution, but the addition of chlorobenzene hinders the charge transport performance of the perovskite luminescent layer, resulting in lower luminous efficiency.

[0006] CN117355159A employs a polymer-infiltrating antisolvent crystallization method, infiltrating a polymer into the perovskite layer via an antisolvent. The special polymer chains within this method form chemical bonds with the perovskite, thus slowing down perovskite grain growth and achieving the dual effects of perovskite film defect passivation and crystal growth regulation. Perovskite films prepared using this method exhibit high luminous efficiency, surface coverage, and low surface roughness, thereby improving the electroluminescence efficiency of perovskite light-emitting diodes (LEDs) and ultimately resulting in efficient and stable luminescence. However, introducing polymers into the antisolvent and perovskite precursor solution can hinder the charge transport properties of the perovskite light-emitting layer, leading to lower electroluminescence efficiency in the perovskite LED. Excessively delayed crystallization may result in increased solvent residue and the formation of amorphous or intermediate phases. Furthermore, the polymer needs to be dissolved in an antisolvent that can dissolve the polymer but not the perovskite itself or its precursor.

[0007] CN119604166A describes a perovskite precursor solution obtained by dissolving a mixture of lead iodide, lead bromide, cesium iodide, and an organic ammonium iodide salt in a polar solvent. The cesium iodide mixture includes cesium iodide and cesium triiodide. The perovskite precursor solution is drop-coated onto a substrate, which is then rotated rapidly. An antisolvent is added during the rotation process to obtain a perovskite thin film. The prepared perovskite film is denser with fewer pores, reducing the formation of low-dimensional phases, lowering defect density, and decreasing halogen migration. This improves the efficiency and brightness of pure red perovskite LEDs while achieving better spectral and operational stability. However, the relatively strong dissolving power of the ethyl acetate antisolvent can easily lead to over-dissolution and uncontrolled recrystallization. The rapid evaporation rate of the ethyl acetate antisolvent results in excessively fast crystallization kinetics of the perovskite, shortening the effective time window for controlling crystal nucleation and growth, and affecting the uniformity of the film. Furthermore, the ethyl acetate antisolvent is sensitive to specific perovskite components or additives.

[0008] In summary, the use of antisolvents in existing technologies leads to problems such as poor performance repeatability, increased interface and surface defects, and solvent residue, posing new challenges to the preparation of high-performance PeLEDs. Research on antisolvents in PeLEDs is relatively limited and warrants further investigation. Summary of the Invention

[0009] To address the problems existing in the prior art, this invention provides a perovskite light-emitting diode based on a novel antisolvent and its preparation method; it successfully solves the key problems existing in the prior art such as high solvent residue toxicity, poor solubility of functional molecules, high defect state density of thin films, and poor device efficiency and stability, thereby achieving high-efficiency and environmentally friendly preparation of high-quality, high-stability perovskite light-emitting thin films.

[0010] To solve the above-mentioned technical problems, the present invention provides the following technical solution:

[0011] On one hand, the present invention provides a perovskite light-emitting diode based on a novel anti-solvent, which comprises, from bottom to top: glass, an ITO conductive layer, a hole transport layer, a perovskite light-emitting layer, an electron transport layer, an electron injection layer, and a metal electrode; wherein the glass and the ITO conductive layer are directly purchased ITO glass substrates.

[0012] The perovskite luminescent layer was prepared by spin-coating a perovskite precursor solution onto a hole transport layer after filtering it through a 0.22 μm polytetrafluoroethylene filter. An anti-solvent was added dropwise during the spin-coating process at an appropriate time window. The perovskite precursor solution consisted of CsBr, FABr, PbBr2, 4F-PEABr, and 18-crown-6, with a good solvent (DMSO, DMF, or a mixture thereof) added. DMSO V DMFThe perovskite luminescent layer was prepared by stirring overnight with a ratio of 4:1 or 5:1 (preferably DMSO, 1 mL). The molar ratio of CsBr, FABr, PbBr2, and 4F-PEABr was 1:0.2:1:0.35, and the concentration of 18-crown-6 was 8 mg / mL. The antisolvent was a mixture of ethyl acetate and dimethyl phosphite (DPP) with a volume ratio of 20:1-40:1. The perovskite luminescent layer was prepared by: 1) spin-coating the precursor solution at 5000 rpm for 60 s; 2) preferably, rapidly injecting 0.15 mL of antisolvent or a novel antisolvent at the 30th second of spin-coating; 3) immediately annealing on a hot plate at 100°C for 10 min after spin-coating; and 4) cooling to room temperature.

[0013] The hole transport layer is made of PEDOT:PSS doped with an appropriate amount of ethanolamine; preferably, the doping ratio of ethanolamine is 980:20:4 (PEDOT:PSS solution:ethanol:ethanolamine volume ratio).

[0014] The electron transport layer is made of TPBi solid powder, prepared by vacuum evaporation, with a thickness of approximately 35 nm. The electron injection layer is made of LiF. The metal electrode uses Al metal as the cathode material, also prepared by vacuum evaporation. Finally, a LiF EIL with a thickness of 1 nm and an Al metal electrode with a thickness of 100 nm were fabricated.

[0015] On the other hand, the present invention also provides a method for fabricating the above-mentioned perovskite light-emitting diode, comprising:

[0016] S1. The glass substrate with the etched ITO conductive layer was cleaned as follows: The ITO glass substrate was ultrasonically treated sequentially with detergent, water, ultrapure water, and ethanol, twice under each solvent condition, for 20 minutes each time. After ultrasonication, the ITO side of the ITO glass substrate was placed on a 100°C hot stage to dry, removing residual organic solvents, and then transferred to a clean petri dish. S2. The petri dish containing the cleaned and dried ITO glass substrate was placed open in a UVO cleaning instrument and treated continuously for 30 minutes under the influence of ultraviolet light and ozone. S3. 50-70 μL of a PEDOT:PSS solution filtered through a 0.45 µm polyethersulfone filter was evenly coated onto the substrate and immediately spin-coated at 4000 rpm for 30 seconds. After spin-coating, it was quickly transferred to a 150°C hot stage for annealing for 20 seconds. S4, spin-coat 40-60 μL of precursor solution at 5000 rpm for 60 s, and rapidly inject 0.15 mL of antisolvent in one go at 25-30 s. After spin-coating, immediately place the substrate on a hot stage at 100 ℃ for annealing for 10 min; S5, after the light-emitting layer cools to room temperature, transfer the substrate to a vacuum evaporation chamber, and achieve the sublimation and deposition of TPBi material by heating the tungsten wire frame by controlling the current. The sublimation rate is stabilized at about 0.4 Å / s; S6, deposit LiF powder on the electron transport layer by ultra-vacuum evaporation at a deposition rate of 0.1 Å / s; S7, deposit aluminum solid wire on the electron injection layer by ultra-vacuum evaporation at a deposition rate of 2 Å / s.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] This invention addresses various challenges encountered during the crystallization of Q-2D perovskites by creating an adaptive solvent (SA) by doping an appropriate amount of dimethyl phosphonite (DPP) into the antisolvent ethyl acetate (EA). On one hand, SA regulates the crystal arrangement of Q-2D perovskites, reducing the amount of low-n phases and promoting crystallization and growth by influencing crystal distribution and orientation. On the other hand, DPP can coordinating and passivating defects in the perovskite, reducing non-radiative exciton transition losses and promoting carrier injection and transport. Simultaneously, SA inhibits the self-polymerization and phase separation of the large organic cation—4-fluorophenylethylamine bromide (4F-PEABr), reducing the defect state density of Q-2D perovskites. The prepared PeLEDs achieved a maximum brightness of 88421.17 cd / m². -2 With an initial brightness (L0) of 100 cd / m -2Under these conditions, its operating half-life (t50) reached 38.22 h, which is about 13 times that of the control group (2.98 h) device, and its maximum external quantum efficiency (EQEmax) reached 29.27%, breaking the record for PeLEDs prepared by bulk modification of Q-2D green perovskite. Attached Figure Description

[0019] Figure 1 The photoluminescence and UV-Vis absorption spectra of the perovskite thin film (SA) prepared with SA as the antisolvent and the perovskite thin film (Control) prepared with ethyl acetate as the antisolvent are shown in the present invention.

[0020] Figure 2 (a) PL and UV-vis absorption spectra of the perovskite thin film; (b) Urbach curve;

[0021] Figure 3 The figures show (a) TRPL curves and (b) PLQY vs. Knr data distributions of the perovskite thin film, with insets showing actual images of the film.

[0022] Figure 4 In-situ PL testing of perovskite films under (a) EA antisolvent treatment and (b) SA solvent treatment;

[0023] Figure 5 SEM images of perovskite films after (a) EA antisolvent treatment and (b) SA solvent treatment; AFM images of perovskite films after (c) EA antisolvent treatment and (d) SA solvent treatment;

[0024] Figure 6 The impedance curve of the perovskite thin film of the present invention is shown.

[0025] Figure 7 This is a schematic diagram of the device structure of the perovskite light-emitting diode in Embodiment 1 of the present invention;

[0026] Figure 8 The current density-voltage-brightness curves of the perovskite light-emitting diodes of Embodiment 1 (Target) and Comparative Example 1 (Control) of the present invention are shown.

[0027] Figure 9 The external quantum efficiency curves are for the perovskite light-emitting diodes of Example 1 (Target) and Comparative Example 1 (Control) of the present invention. Detailed Implementation

[0028] To make the technical problems, technical solutions and advantages of the present invention clearer, a detailed description will be given below in conjunction with specific drawings and embodiments.

[0029] Unless otherwise specified, all reagents and materials used in this invention are commercially available. The ITO glass was purchased from Xiangcheng, South China, with dimensions of 1.5 x 1.5 cm and an ITO area of ​​0.2 x 1.5 cm.

[0030] The perovskite precursor solution was prepared by the following method: 85.12 mg CsBr, 10.00 mg FABr, 146.8 mg PbBr2, 30.80 mg 4F-PEABr, and 8 mg 18-crown-6 were weighed into sample vials, and 1 mL of dimethyl sulfoxide (DMSO) was added and stirred overnight to obtain the perovskite precursor solution.

[0031] The hole transport layer solution was prepared by dissolving ethanolamine in ethanol and then mixing it thoroughly with a PEDOT:PSS solution at a volume ratio of V. 乙醇胺 V 乙醇 V PEDOT：PSS = 4:20:980. The PEDOT:PSS solution is an aqueous solution with a concentration of 1.3~1.7wt%.

[0032] The Mv of the polyethylene oxide is 600,000, purchased from aladdin.

[0033] This invention provides a perovskite light-emitting diode based on a novel antisolvent and its fabrication method, with specific embodiments as follows.

[0034] Example 1

[0035] A method for fabricating a perovskite light-emitting diode based on a novel antisolvent, comprising:

[0036] S1: Perform the following cleaning operations on the glass with the etched ITO conductive layer (ITO glass): sequentially use detergent, water, ultrapure water, and ethanol to ultrasonically treat the ITO glass substrate, ultrasonically treating twice under each solvent condition, 20 min each time; after ultrasonic treatment, place the ITO side of the ITO glass substrate face up on a hot stage at 100°C to dry, remove residual organic solvents, and then transfer it to a clean petri dish.

[0037] S2, Place the petri dish containing the cleaned and dried ITO glass substrate in the UVO cleaning instrument with the opening open, and continue to treat it for 30 min under the action of ultraviolet light and ozone.

[0038] S3, 60 μL of the hole transport layer solution filtered through a 0.45 µm polyethersulfone filter was uniformly coated onto the substrate and immediately spin-coated at 4000 rpm for 30 s. After spin-coating, it was quickly transferred to a hot plate at 150 °C for annealing for 20 min.

[0039] S4: Spin-coat 50 μL of precursor solution at 5000 rpm for 60 s, and rapidly inject 0.15 mL of antisolvent in one go at 30 s. After spin-coating, immediately place the substrate on a hot plate at 100 ℃ for annealing for 10 min, and then cool to room temperature; the antisolvent is a mixture of ethyl acetate and dimethyl phosphite (DPP) in a volume ratio of 30:1.

[0040] S5: The substrate is transferred to the vacuum evaporation chamber, and the tungsten wire frame is heated to achieve the sublimation and deposition of TPBi material. The sublimation rate is stabilized at about 0.4 Å / s, and the electron transport layer thickness is 35 nm.

[0041] S6: LiF powder was deposited on the electron transport layer by ultra-vacuum evaporation at a rate of 0.1 Å / s, and the thickness of the electron injection layer was 1 nm.

[0042] S7: Aluminum solid wires are deposited on the electron injection layer by ultra-vacuum evaporation at a rate of 2 Å / s, and the thickness of the metal electrode is 100 nm.

[0043] To further illustrate the beneficial effects of the present invention, the following comparative examples were constructed.

[0044] Comparative Example 1

[0045] In this comparative example, the antisolvent is ethyl acetate, and the other conditions are the same as in Example 1.

[0046] To investigate the reaction mechanism and performance of the light-emitting layer, the inventors first prepared a perovskite thin film. The preparation method of the perovskite thin film is as follows: a silicon wafer was used as the substrate, and the preparation method was basically the same as that used in PeLEDs: a precursor solution was spin-coated at 3000 rpm for 60 seconds, and 0.15 mL of antisolvent was rapidly injected in one go at the 30th second. After spin-coating, the substrate was immediately placed on a hot plate at 100°C for annealing for 10 minutes, and then cooled to room temperature. The antisolvent was a mixture of ethyl acetate and DPP in a volume ratio of 30:1, denoted as Target; the antisolvent was ethyl acetate, denoted as Control.

[0047] 1. To investigate the effect of novel antisolvents on perovskite crystallization.

[0048] The perovskite thin film was characterized by X-ray diffraction, such as... Figure 1As shown, diffraction peaks corresponding to the (100), (110), (200), (210), and (211) crystal planes of cubic perovskite appeared at 15.2°, 21.5°, 30.7°, 34.3°, and 37.7°, respectively. Diffraction peaks related to the low-n phase defect states of perovskite appeared at 13.8° and 26.6° in the control group. After modification with the novel antisolvent, the diffraction peaks of the perovskite shifted towards smaller angles, accompanied by changes in relative intensity. The changes were more significant in the (110) and (200) crystal planes, indicating that the adsorption of DPP molecules in the novel antisolvent expanded the lattice spacing of the perovskite and alleviated some of the lattice stress. Simultaneously, the diffraction signal of the low-n phase in the perovskite film essentially disappeared, improving the regularity of the Q-2D perovskite crystal. The results above demonstrate that the use of the novel antisolvent effectively promotes perovskite crystallization, regulates crystal arrangement and orientation, and reduces the number of low-dimensional perovskite phases that are prone to forming defects.

[0049] 2. Investigate the effect of novel antisolvents on the optical properties of perovskite thin films.

[0050] The optical properties of the above perovskite thin films were studied, and the results are shown in [the table below]. Figure 2 .

[0051] from Figure 2 (a) The photoluminescence (PL) spectrum and ultraviolet-visible (UV-vis) absorption spectrum of the perovskite thin film show that, under the same preparation conditions, the PL peak position and absorption band edge of the perovskite thin film modified with the antisolvent of the present invention both show a red shift. The PL half-width of the thin film is only about 18 nm, which shows extremely high color purity. This indicates that the novel antisolvent promotes the growth of perovskite crystals, reduces the quantum confinement effect, and reduces the band gap of perovskite.

[0052] Furthermore, it was clearly observed in the absorption spectrum that the absorption signal of n=1 in the control group essentially disappeared after SA treatment, indicating that SA optimized the energy transfer efficiency of Q-2D perovskite and suppressed the absorption of low-n phase defect states. The low-n phase in Q-2D perovskite has a low formation energy, easily leading to strong electron-phonon coupling and thus increasing nonradiative recombination. To compare the effect of SA on the strength of electron-phonon coupling in Q-2D perovskite films, the Urbach energy (Eu) was calculated by fitting the absorption band edge of the film samples, as shown below. Figure 2 As shown in (b), the Eu of the SA-modified Q-2D perovskite film decreased from 59.36 meV in the control group to 33.12 meV, indicating that DPP reduced the disorder of Q-2D perovskite, weakened electron-phonon coupling, reduced carrier scattering, and helped improve radiative recombination efficiency, thereby improving the optical properties of Q-2D perovskite.

[0053] 3. Investigate the effect of novel antisolvents on carrier recombination dynamics of perovskite thin films.

[0054] The inventors tested the photoluminescence quantum yield (PLQY) and time-resolved photoluminescence (TRPL) of the prepared perovskite thin film, such as... Figure 3 As shown, the PLQY of the control group was 62.21%, while that of the perovskite film after novel antisolvent modification increased to 84.51%, indicating that DPP optimized the radiative recombination of charge carriers. After fitting the TRPL lifetime (τ) of the perovskite film with a double exponential function, it was found that after novel antisolvent modification, the TRPL lifetime increased from τ = 45.08 ns in the control group to τ = 110.54 ns, reducing the trapping of photogenerated excitons by defects and improving carrier transport and recombination. The calculated nonradiative recombination rate (Knr) of the perovskite film increased from 8.38 × 10⁶ s in the control group. -1 The value decreased to 1.40 × 10⁶ s⁻¹ after modification with the novel antisolvent. -1 This further confirms that novel antisolvent modification can significantly reduce nonradiative recombination loss, thereby improving the optical properties of perovskite thin films.

[0055] 4. Use in-situ PL technology to track the crystal nucleation and growth process of perovskite thin films during spin coating.

[0056] like Figure 4 As shown, Figure 4 The results in (a) show that the photoluminescence (PL) intensity of the film momentarily increases upon the addition of the EA antisolvent. This is due to the instantaneous supersaturation of the perovskite precursor solution, which forms a large number of nuclei or low-dimensional phases. Subsequently, the PL intensity of the film rapidly and briefly decreases. This phenomenon is attributed to the rapid growth and recombination of the crystal, which forms a large number of nonradiative recombination centers, causing excitons to be trapped by defects and unable to emit photons. Next, as the crystal structure gradually stabilizes and the low-dimensional phase transitions, the radiative recombination pathway of the perovskite gradually recovers, and its PL intensity gradually increases. However, the overall performance has already been affected by the earlier defects. Figure 4 In (b), the effect of the SA antisolvent is relatively mild, rapidly inducing crystal nucleation without triggering drastic crystal recombination. After the addition of the SA antisolvent, the PL intensity increases rapidly, then only slightly decreases and remains stable. At this point, the perovskite crystal, after undergoing a burst of nucleation, can maintain uniform and stable crystal growth, producing only a small number of defects and non-radiative recombination centers. The phase distribution and crystal arrangement of the film are more uniform, which is beneficial for forming a stable and efficient perovskite luminescent film.

[0057] 5. Investigate the effect of novel antisolvents on the morphology of perovskite thin films.

[0058] The surface morphology of the prepared perovskite thin film was inspected, by... Figure 5 Scanning electron microscope images (a)-(b) show that the control group film consists of stacked fine grains of varying sizes and irregular shapes, with obvious gaps between the grains. This results in significant carrier loss, which is detrimental to achieving high-performance electroluminescence. After SA antisolvent modification, the perovskite film exhibits more uniform grain size, denser arrangement, and a significantly reduced number of pores. This effectively reduces non-radiative recombination loss in the luminescent layer and improves the radiative recombination efficiency of carriers. Figure 5 In the atomic force microscopy (AFM) images (c)-(d), it can be observed that the grains of the control group film are uneven in height and undulation. After SA antisolvent modification, the morphology of the film is significantly improved, the roughness is reduced from 5.69 nm to 1.37 nm, the vertical growth of the crystals is more uniform, which is beneficial to reduce carrier scattering and optical loss, and improve carrier lifetime and photoelectric conversion efficiency.

[0059] Based on the above analysis, the inventors tested the performance of the prepared perovskite light-emitting diode, and the results are as follows.

[0060] 6. The impedance spectrum of the PeLEDs device was tested under dark conditions with a 3 V bias voltage. The Nyquist plot was fitted using an equivalent circuit model consisting of series resistance (Rs), composite resistance (Rrec), and related capacitance, as shown below. Figure 6 As shown, after modification with the novel antisolvent, the Rs of PeLEDs decreased from 32.57 Ω to 20.41 Ω, while the Rrec increased from 3456.19 Ω to 11706.20 Ω. The decrease in Rs is attributed to the reduction in roughness and the increase in crystal uniformity of the perovskite film, which improves the interfacial contact between the perovskite emitting layer and the adjacent transport layer. The higher Rrec is attributed to the suppression of nonradiative recombination by the novel antisolvent, which significantly prolongs the residence time of charge carriers in the emitting layer. The conclusions obtained in PeLEDs devices are consistent with the photoelectric properties of perovskite films.

[0061] 7. The device structure of PeLEDs is as follows: Figure 7 As shown. From bottom to top, it includes: glass 1, ITO conductive layer 2, hole transport layer 3, perovskite light-emitting layer 4, electron transport layer 5, electron injection layer 6, and metal electrode 7.

[0062] This invention inserts ethanolamine into the hole transport layer of PEDOT:PSS as a bridge connecting PEDOT:PSS and perovskite. The hydroxyl groups in ethanolamine can attract Pb. 2+ The nucleation centers that form perovskite crystals, and the dipoles formed by the inserted ethanolamine, also facilitate hole injection and transport. Figure 8The current density-voltage-luminance (J−V−L) curves of PeLEDs show that SA antisolvent-modified perovskite achieved a maximum device luminance of 30238.92 cd / m² compared to the control group. -2 to 88421.17 cdm -2 The improvement in efficiency enhances the charge injection efficiency of PeLEDs devices, enabling more charge carriers to participate in effective radiative recombination.

[0063] 8. PeLEDs modified with SA antisolvent achieved a maximum external quantum efficiency (EQEmax) of 29.27%, such as... Figure 9 The EQEmax of the novel antisolvent is significantly higher than that of the control group PeLEDs devices, which have a maximum efficiency of 20.50%. These results further demonstrate that the novel antisolvent enables adaptive regulation of perovskite, reduces the defect state density of perovskite, achieves more balanced and efficient carrier transport, improves the crystal quality of perovskite and the energy transfer between different n phases, and thus successfully realizes the fabrication of high-efficiency green PeLEDs.

[0064] To further demonstrate the beneficial effects of the present invention, the following comparative examples were also constructed.

[0065] Comparative Example 2

[0066] In this comparative example, ethyl acetate was replaced with an equal volume of toluene, and the other conditions were the same as in Example 1.

[0067] Comparative Example 3

[0068] In this comparative example, ethyl acetate was replaced with an equal volume of chlorobenzene, and the other conditions were the same as in Example 1.

[0069] Comparative Example 4

[0070] In this comparative example, dimethyl phosphite was replaced with an equal volume of poly(diphenoxyphosphononitrile), and the other conditions were the same as in Example 1.

[0071] Comparative Example 5

[0072] In this comparative example, dimethyl phosphite was replaced with an equal volume of polyethylene oxide, and the other conditions were the same as in Example 1.

[0073] Comparative Example 6

[0074] In this comparative example, dimethyl phosphite was replaced with an equal volume of triphenylphosphine, and the other conditions were the same as in Example 1.

[0075] Comparative Example 7

[0076] In this comparative example, dimethyl phosphite was replaced with an equal volume of trioctylphosphine oxide, and the other conditions were the same as in Example 1.

[0077] Comparative Example 8

[0078] In this comparative example, ethanolamine in the hole transport layer solution was omitted, and the other conditions were the same as in Example 1.

[0079] The performance of the light-emitting diodes prepared in the above comparative example was tested, and the results are shown in Table 1.

[0080] Table 1

[0081]

[0082] As shown in Table 1, when the novel antisolvent of this invention is replaced with a conventional antisolvent, or when dimethyl phosphite is replaced with poly(diphenoxyphosphononitrile), polyethylene oxide, triphenylphosphine, or trioctylphosphine oxide, the maximum external quantum efficiency and maximum brightness of the prepared light-emitting diodes are significantly reduced.

[0083] The inventors also investigated the composition, amount of substances used, volume ratio of ethyl acetate to DPP in the antisolvent, and dropwise addition time of the antisolvent in the perovskite precursor solution. Details are as follows.

[0084] Example 2

[0085] In this embodiment, 4F-PEABr is replaced with an equimolar amount of PEABr, and the other conditions are the same as in Example 1.

[0086] Example 3

[0087] In this embodiment, the volume ratio of ethyl acetate to DPP is 40:1, and the other conditions are the same as in Example 1.

[0088] Example 4

[0089] In this embodiment, the volume ratio of ethyl acetate to DPP is 20:1, and the other conditions are the same as in Example 1.

[0090] Example 5

[0091] In this embodiment, the antisolvent is injected all at once at the 25th second of spin coating of the perovskite precursor solution, and the other conditions are the same as in Example 1.

[0092] Example 6

[0093] In this comparative example, the amount of FABr used was 5 mg; the other conditions were the same as in Example 1.

[0094] Comparative Example 9

[0095] In this comparative example, the amount of FABr used was 15 mg; the other conditions were the same as in Example 1.

[0096] Comparative Example 10

[0097] In this comparative example, the volume ratio of ethyl acetate to DPP was 10:1, and the other conditions were the same as in Example 1.

[0098] Comparative Example 11

[0099] In this comparative example, the antisolvent was injected all at once during the 35th second of spin coating of the perovskite precursor solution, and the remaining conditions were the same as in Example 1.

[0100] The performance of the light-emitting diodes prepared in Examples 2-6 and Comparative Examples 9-11 was tested, and the results are shown in Table 2.

[0101] Table 2

[0102]

[0103] As shown in Table 2, specific perovskite precursor solution composition, antisolvent volume ratio, and specific dropping time are required to obtain LEDs with the highest EQE.

[0104] In summary, the perovskite light-emitting diodes (PELEDs) based on a novel antisolvent and their fabrication method provided by this invention combine the unique advantages of EA antisolvent and DPP molecules. The resulting PeLEDs achieved an EQEmax of 29.27%, breaking the EQE record for PeLEDs prepared by bulk modification of Q-2D green perovskite, and achieved a maximum brightness of 88421.17 cdm. -2 This work provides a new perspective for the preparation of high-performance PeLEDs.

[0105] The above description is a preferred embodiment of the present invention. For those skilled in the art, any improvements and modifications made without departing from the principles of the present invention should also be considered within the scope of protection of the present invention.

Claims

1. A perovskite light-emitting diode based on a novel anti-solvent, wherein the perovskite light-emitting diode comprises, from bottom to top, glass, an ITO conductive layer, a hole transport layer, a perovskite light-emitting layer, an electron transport layer, an electron injection layer, and a metal electrode; characterized in that, The perovskite luminescent layer is prepared by spin coating of a perovskite precursor solution; an anti-solvent is added dropwise during the spin coating process; the anti-solvent is a mixture of ethyl acetate and dimethyl phosphite (DPP) in a volume ratio of 20:1 to 40:

1. The perovskite precursor solution was prepared by dissolving cesium bromide (CsBr), formamidinium hydrobromide (FABr), lead bromide (PbBr2), p-fluorophenylethylamine bromide (4F-PEABr), and 18-crown-6 in a polar solvent, wherein the mass ratio of CsBr, FABr, PbBr2, and 4F-PEABr was 1:0.2:1:0.35, and Pb... 2＋ The concentration is 0.2 mol / L; the concentration of 18-crown-6 is 8 mg / ml; the polar solvent is DMSO or a mixed solution of DMSO and DMF.

2. The perovskite light-emitting diode according to claim 1, characterized in that, The hole transport layer is PEDOT:PSS doped with ethanolamine.

3. The perovskite light-emitting diode according to claim 2, characterized in that, The electron transport layer is 1,3,5-tris(1-phenyl-1H-benzimidazol-2-yl)benzene (TPBi), 3,3'-[5'-[3-(3-pyridyl)phenyl][1,1':3',1''-terphenyl]-3,3''-diyl]dipyridine (TmPyPB) or di[2-((oxo)diphenylphosphino)phenyl] ether (DPEPO).

4. The perovskite light-emitting diode according to claim 3, characterized in that, The electron injection layer is LiF, and the metal electrode is aluminum.

5. The method for fabricating a perovskite light-emitting diode according to any one of claims 1-4, characterized in that, include: S1; Pretreatment of the ITO glass substrate; S2: The above-mentioned ITO glass substrate is treated under the action of ultraviolet light and ozone; S3: Dissolve ethanolamine in ethanol, then mix thoroughly with PEDOT:PSS solution, and apply the mixture to the ITO glass substrate treated with S2, at a coating amount of 22.2-31.1 μL / cm². 2 Immediately spin-coat, then anneal to obtain a hole transport layer; S4: Weigh CsBr, FABr, PbBr2, 4F-PEABr, and 18-crown-6 into sample vials, add polar solvent and stir overnight to obtain perovskite precursor solution; S5: Spin-coating precursor solution, 17.8-26.7 μL / cm³ 2 The antisolvent is rapidly injected in one go at 25-30 seconds, and annealing is performed immediately after spin coating to obtain a perovskite luminescent layer; the antisolvent is a mixture of ethyl acetate and dimethyl phosphite (DPP) with a volume ratio of 20:1-40:

1. S6: TPBi material is vacuum-deposited on the surface of the perovskite light-emitting layer to obtain the electron transport layer; S7: LiF is vacuum-deposited on the surface of the electron transport layer to obtain the electron injection layer; S8: Aluminum is vacuum-deposited on the surface of the electron injection layer to form a metal electrode; finally, a perovskite light-emitting diode is obtained.

6. The method for fabricating a perovskite light-emitting diode according to claim 5, characterized in that, In S1, the pretreatment specifically involves: sequentially ultrasonically treating the ITO glass substrate with detergent, water, ultrapure water, and ethanol, with each solvent condition being ultrasonically treated twice for 20 minutes each time; after ultrasonic treatment, the ITO side of the ITO glass substrate is placed on a hot table at 100°C to dry, removing residual organic solvents, and then set aside for later use.

7. The method for fabricating a perovskite light-emitting diode according to claim 5, characterized in that, Specifically, in S2, a culture dish containing a cleaned and dried ITO glass substrate is placed open in a UVO cleaning instrument and continuously treated for 30 minutes under the action of ultraviolet light and ozone.

8. The method for fabricating a perovskite light-emitting diode according to claim 5, characterized in that, In step S3, the spin coating speed is 4000 rpm and the time is 30 s; the annealing temperature is 150 ℃ and the time is 20 min; the volume ratio of PEDOT:PSS solution, ethanol, and ethanolamine is 980:20:

4. In step S5, the spin coating speed is 5000 rpm and the time is 60 s; the amount of antisolvent used is 0.15 mL; and the annealing treatment temperature is 100℃ and the time is 10 min.

9. The method for fabricating a perovskite light-emitting diode according to claim 5, characterized in that, In S4, the mass ratio of CsBr, FABr, PbBr2, and 4F-PEAB is 1:0.2:1:0.35, and the concentration of 18-crown-6 is 8 mg / ml; Pb 2＋ The concentration is 0.2 mol / L; the polar solvent is DMSO or a mixed solution of DMSO and DMF.

10. The method for fabricating a perovskite light-emitting diode according to claim 5, characterized in that, In S6, the sublimation rate of TPBi is 0.4 Å / s, and the electron transport layer thickness is 35 nm; in S7, the evaporation rate of LiF is 0.1 Å / s, and the electron injection layer thickness is 1 nm; in S8, the evaporation rate of aluminum is 2 Å / s, and the thickness of the metal electrode is 100 nm.

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