High-performance near-infrared luminescent perovskite thin film and preparation method thereof

Abstract

The application discloses a preparation method of a high-performance near-infrared luminescent perovskite film, which comprises the following steps: first, synthesizing all-inorganic perovskite nanocrystals; second, preparing a clean substrate and preparing a perovskite precursor solution; third, preparing an anti-solvent and doping the all-inorganic perovskite nanocrystals prepared in the first step; fourth, adopting a two-step spin coating method to drop and spin coat the perovskite precursor solution on the clean substrate in sequence, and dropping the anti-solvent for doping the all-inorganic perovskite nanocrystals prepared in the third step in the second spin coating process; and fifth, annealing and crystallizing the spin-coated substrate to obtain a perovskite film doped with all-inorganic perovskite nanocrystals. The perovskite film prepared by the method is simple, controllable and repeatable in the process.

Description

Technical Field

[0001] This invention relates to the field of photoluminescence technology, and particularly to a high-performance near-infrared luminescent perovskite thin film and its preparation method. This invention also relates to a silicon-based perovskite heterojunction light-emitting device prepared using the perovskite thin film. Background Technology

[0002] Perovskite is a direct bandgap material with an ABX3 structure. It has excellent optical properties, such as high color purity and a continuously tunable optical bandgap. It performs outstandingly in the optoelectronic field and is widely used in the fabrication of solar cells, light-emitting diodes, photodetectors, etc.

[0003] 0D and 2D perovskite materials possess excellent luminescence properties due to their large exciton binding energies. However, these low-dimensional materials generally have large optical band gaps, and the introduction of numerous insulating organic ligands or long organic chains during fabrication leads to low charge transport efficiency and poor device performance in their thin films. Traditional 3D organic-inorganic hybrid perovskites offer advantages such as uniform film formation and ease of fabrication, making them the most widely studied perovskite materials. They exhibit relatively low exciton binding energies, resulting in weaker radiative recombination compared to 0D and 2D perovskites, which hinders further improvement in luminescence performance. Furthermore, the presence of organic cations in 3D perovskites (such as MA) further complicates their development. + FA + Perovskite materials (such as aluminum, argon, and oxygen) are sensitive to water and oxygen environments, easily volatilizing and decomposing, and have poor air stability. Therefore, how to prepare perovskite materials with excellent luminescent properties suitable for high-efficiency light-emitting devices has become an urgent problem to be solved. Summary of the Invention

[0004] To address the issue of weak luminescence in organic-inorganic hybrid perovskite materials, this invention discloses a method for preparing organic-inorganic hybrid perovskite thin films by doping all-inorganic perovskite nanocrystals in an antisolvent, thereby improving the photoluminescence performance of the perovskite thin films. Furthermore, using the improved perovskite thin films, high-performance silicon-based perovskite heterojunction light-emitting devices were fabricated in air.

[0005] This invention provides a method for preparing high-performance near-infrared luminescent perovskite thin films, characterized by comprising the following steps: The first step is to synthesize all-inorganic perovskite nanocrystals; The second step is to prepare a clean substrate and a perovskite precursor solution. The third step is to prepare an antisolvent and dope it with the all-inorganic perovskite nanocrystals prepared in the first step. The fourth step involves using a two-step spin coating method to drop the spin-coating perovskite precursor solution onto a clean substrate, and during the second spin coating process, the antisolvent of the doped all-inorganic perovskite nanocrystals prepared in the third step is added. The fifth step is to anneal and crystallize the spin-coated substrate to obtain a perovskite thin film doped with all inorganic perovskite nanocrystals.

[0006] Preferably, the first step is as follows: 1) Prepare the seed solution required for the synthesis of all-inorganic perovskite nanocrystals. Add the reagents Cs salt, reducing agent and ligand required for the seed solution to a three-necked flask, and perform full vacuuming and preheating to remove moisture and air from the reagents. 2) Inert protective gas is introduced into a three-necked flask, and the mixed solution is heated to fully dissolve and mix thoroughly to obtain a seed solution; 3) Add the oleic acid, oleylamine, and octadecene reagents required for the synthesis of all-inorganic perovskite nanocrystals to a clean three-necked flask, perform thorough vacuuming and preheating, introduce inert protective gas, heat the three-necked flask, and inject the seed solution into the three-necked flask to react and grow all-inorganic perovskite nanocrystals. 4) Cool to room temperature in an ice-water bath and centrifuge to obtain an all-inorganic perovskite nanocrystal solution.

[0007] Preferably, in the second step, the method for preparing the perovskite precursor solution is as follows: dissolve monovalent cationic halide and lead halide powder in a mixed solution of N,N-dimethylformamide or N,N-dimethylformamide or dimethyl sulfoxide, and rapidly dissolve it by magnetic stirring, shaking or ultrasonic treatment to obtain the perovskite precursor solution, wherein the concentration of monovalent cationic lead halide in the perovskite precursor solution is 0.2~1M.

[0008] Preferably, the third step is as follows: first, prepare an antisolvent, then add 25 μL of all-inorganic perovskite nanocrystal solution to 1 mL of ethyl acetate, and mix thoroughly and evenly by magnetic stirring, shaking or ultrasonic treatment, so that the doping concentration of the resulting solution is 2.5%.

[0009] Preferably, the fourth step is as follows: using a two-step spin coating method, 20 μL of MAPbI3 perovskite precursor solution is dropped onto a silicon wafer substrate. The first step lasts for 10 seconds at a rotation speed of 1000 rpm, the second step lasts for 20 seconds at a rotation speed of 5000 rpm, and 200 μL of the antisolvent of the doped all-inorganic perovskite nanocrystals prepared in the third step is dropped 10 seconds before the completion of the second step.

[0010] Preferably, the antisolvent is one or more of toluene, chlorobenzene, acetonitrile, or ethyl acetate.

[0011] Preferably, the substrate is glass, quartz, a glass conductive substrate, a silicon wafer with different doping types, or a flexible substrate.

[0012] Preferably, the annealing and crystallization temperature in the fifth step is 95~120℃, and the annealing time is 10~45min, after which a perovskite thin film with improved photoluminescence performance is obtained.

[0013] Preferably, the perovskite material in the precursor fluid of the second step has the structure ABX3, where A is a monovalent cation, B is a divalent metal cation, and X is a halide anion.

[0014] Preferably, the monovalent cation is (NH2)2CH + or CH3NH3 + One or more of the following. The divalent metal cation is Pb. 2+ and / or Sn 2+ The halide anion is Cl. - ,Br - and I - One or more of them.

[0015] Preferably, the all-inorganic perovskite nanocrystals described in the second step have an ABX3 structure, wherein A is a monovalent cation, B is a divalent metal cation, and X is a halide anion.

[0016] Preferably, the monovalent cation is Cs. + The divalent metal cation is Pb. 2+ and / or Sn 2+ The halide anion is Cl. - ,Br - and I - One or more of them.

[0017] Preferably, the optical band gap of the all-inorganic perovskite nanocrystals is wider than that of organic-inorganic hybrid perovskite materials.

[0018] The present invention also discloses a silicon-based perovskite heterojunction light-emitting device, characterized in that: from bottom to top, it consists of an Al electrode layer, a hole transport layer, a light-emitting layer, an electron transport layer, and an ITO electrode layer, wherein the light-emitting layer is a perovskite thin film doped with all inorganic perovskite nanocrystals prepared by the above method.

[0019] The technical solution provided in this invention has at least the following technical effects or advantages: 1. Significantly increased carrier concentration in perovskite films: By doping all-inorganic perovskite quantum dots into the antisolvent, the carrier concentration in the perovskite film was effectively increased, reaching 15 times that of the untreated perovskite film.

[0020] 2. The photoluminescence intensity of the perovskite film is significantly improved: by doping the antisolvent with all-inorganic perovskite quantum dots, the photoluminescence intensity of the perovskite film is effectively improved, reaching 14.7 times that of the untreated perovskite film.

[0021] 3. The perovskite thin film prepared by this method is simple, controllable, and repeatable.

[0022] 4. The electroluminescence of silicon-based perovskite heterojunction light-emitting devices prepared in air using the improved perovskite thin film is significantly improved, reaching 6.5 times that of untreated perovskite thin film devices. Attached Figure Description

[0023] Figure 1 This is a comparison diagram of the carrier mobility of MAPbI3 perovskite thin films before and after antisolvent doping in an embodiment of the present invention.

[0024] Figure 2 This is a comparison of the photoluminescence intensity of the MAPbI3 perovskite thin film before and after antisolvent doping in an embodiment of the present invention.

[0025] Figure 3 This is a scanning electron microscope image of the surface morphology of the MAPbI3 perovskite film before antisolvent doping in an embodiment of the present invention.

[0026] Figure 4 This is a scanning electron microscope image of the surface morphology of the MAPbI3 perovskite film after antisolvent doping in an embodiment of the present invention.

[0027] Figure 5 This is a device structure diagram of a silicon-based perovskite heterojunction light-emitting device prepared by anti-solvent-doped MAPbI3 perovskite in an example of the present invention.

[0028] Figure 6 This is a comparison of the electroluminescence spectra of the silicon-based perovskite heterojunction light-emitting device prepared by antisolvent-doped MAPbI3 perovskite in this invention example and the original device. Implementation

[0029] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods. Example

[0030] This embodiment provides a method for preparing a high-performance near-infrared luminescent perovskite thin film, comprising the following steps: Step 1: Synthesize all-inorganic perovskite nanocrystalline materials using the hot-injection method; the specific steps are as follows: 1) Preparation of cesium oleate solution. At room temperature, add 0.8 g of cesium carbonate (Cs₂CO₃), 30 mL of octadecene, and 2.5 mL of oleic acid to a three-necked flask. Connect the first neck of the flask to a vacuum chamber and the second neck to a nitrogen atmosphere. Heat the resulting solution to 120 °C under alternating vacuum and nitrogen atmospheres, stirring continuously for 1 hour to ensure complete removal of air and moisture from the reactants. After the Cs₂CO₃ dissolves, increase the reaction temperature to 150 °C and stir continuously for 30 minutes to ensure complete dissolution of the Cs₂CO₃, yielding a pale yellow, transparent cesium oleate solution.

[0031] 2) Mix 0.168 g of lead iodide (PbI2) and 10 mL of octadecene in a three-necked flask. The first neck of the flask is connected to a vacuum, the second neck is connected to nitrogen, and the third neck is used to inject the Cs source precursor solution.

[0032] 3) Heat the mixture to 120°C in an alternating vacuum and nitrogen environment, stirring continuously for 60 minutes to ensure that air and moisture are completely removed from the mixture.

[0033] 4) Inject 1 mL each of oleic acid and oleylamine into the mixed solution. After the PbI2 is completely dissolved, heat to 180°C. Quickly inject 0.9 mL of Cs precursor into the mixed solution. The solution immediately changes from colorless to brown. The resulting mixture is kept at 180°C for 5 seconds to form a uniform brown solution.

[0034] 5) After the reaction is complete, quickly remove the three-necked flask from the oil bath and place it in an ice-water bath for rapid cooling. Remove the mixed solution and centrifuge at 7000 rpm for 3 minutes to remove impurities and unreacted precursors.

[0035] 6) Dissolve the precipitate in 5 mL of toluene and sonicate until homogeneous. Centrifuge at 7000 rpm for 10 minutes to remove large particles, obtaining an all-inorganic perovskite nanocrystal solution. Store the solution in a low-temperature environment away from light.

[0036] Step 2: Prepare a square silicon wafer substrate measuring 1.5cm × 1.5cm, clean it using the industry standard wet cleaning process (RCA), and then dry it with nitrogen.

[0037] 48 mg of methylammonium iodide (MAI) and 130 mg of lead iodide (PbI2) were dissolved in a mixed solution of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) in a ratio of 9:1. The specific volume of DMF was 635 μL and the specific volume of DMSO was 72 μL. The mixture was stirred magnetically to ensure complete dissolution. The concentration of the resulting methylamine lead iodide (MAPbI3) perovskite precursor solution was 0.3 M.

[0038] Step 3: Prepare the antisolvent by adding 25 μL of all-inorganic perovskite nanocrystal solution to 1 mL of ethyl acetate and stirring with magnetic force to mix it thoroughly. The resulting solution has a doping concentration of 2.5%.

[0039] Step 4: Using a two-step spin coating method, 20 μL of MAPbI3 perovskite precursor solution is dropped onto a silicon wafer substrate. The first step lasts 10 seconds at a spin speed of 1000 rpm, and the second step lasts 20 seconds at a spin speed of 5000 rpm. 10 seconds before the completion of the second step, 200 μL of the antisolvent of the doped all-inorganic perovskite nanocrystals prepared in the third step above is dropped.

[0040] Step 5: Transfer the spin-coated substrate to a heating stage, set the temperature to 100℃, and anneal for 10 minutes. After completion, a fully inorganic perovskite nanocrystal-doped MAPbI3 perovskite film is obtained.

[0041] The final thin film was approximately 100 nm thick, with the emission peak located at 766 nm. Figure 1 The figure shows a comparison of the photoinduced carrier concentration of MAPbI3 perovskite films before and after antisolvent doping. As can be seen from the figure, the carrier concentration of MAPbI3 perovskite films was increased by 15 times by antisolvent doping with CsPbI3 nanocrystals. Figure 2 The figure shows a comparison of the photoluminescence intensity spectra of MAPbI3 perovskite films before and after antisolvent doping. As can be seen from the figure, the fluorescence intensity of MAPbI3 perovskite films is increased by 14.7 times by antisolvent doping with CsPbI3 nanocrystals. Figure 3 and Figure 4 The images show scanning electron microscope (SEM) images of the surface morphology of MAPbI3 perovskite before and after antisolvent doping. As can be seen from the images, the perovskite film after antisolvent doping has better crystallinity and a smoother surface, which helps to reduce defects at the perovskite grain boundaries, increase the carrier concentration of the film, and enhance the photoluminescence intensity of the film. Example

[0042] In this embodiment, a silicon-based perovskite heterojunction light-emitting device is fabricated using the perovskite thin film prepared in Example 1 under an air humidity of 45%. The specific method is as follows: Step 1: Prepare a square silicon wafer substrate measuring 1.5cm × 1.5cm, clean it using the industry standard wet cleaning process (RCA), and then dry it with nitrogen.

[0043] Step 2: Place the cleaned p-silicon substrate in the magnetron sputtering sample chamber, and sputter at 3.0 × 10⁻⁶ ppm. -4 An Al electrode was fabricated on an unpolished p-silicon surface under a vacuum environment of Pa. The fabricated sample was then placed in a high-temperature environment under an argon atmosphere for 30 min for alloying treatment to achieve better ohmic contact.

[0044] Step 3: Prepare the hole transport layer solutions. Prepare the CBP solution according to the CBD / chlorobenzene ratio (6 mg / mL) and stir well; prepare the poly-TPD solution according to the poly-TPD / chlorobenzene ratio (0.5 mg / mL) and stir well.

[0045] Step 4: Prepare the hole transport layer using a two-step spin coating method. Add CBP solution to the p-silicon polished surface, spin coat at 4000 rpm for 60 seconds, and at the 30th second, add poly-TPD solution to the rotating sample and anneal for 10 minutes.

[0046] Step 5: Prepare a perovskite thin film on the hole transport layer (equivalent to the substrate of Example 1) following the steps in Example 1.

[0047] Step 6: Growth of the ZnO electron transport layer. Using a magnetron sputtering system, under a high vacuum environment (<10⁻⁶ ppm) in the chamber... -4 Ar gas is introduced and ionized to sputter high-purity ZnO target material, and an electron transport layer is grown on the sample surface.

[0048] Step 7: Growth of ITO transparent electrodes. Using a magnetron sputtering system, under a high vacuum environment (<10⁻⁶ ppm) in the chamber... -4 Ar and O2 gases are introduced and ionized to grow dot-shaped ITO electrodes on the sample surface (Pa).

[0049] The specific parameters for this experiment are as follows: Alloying treatment: 420℃, nitrogen atmosphere for 30 min.

[0050] Magnetron ZnO sputtering power: 75W, argon flow rate: 40sccm, sputtering time: 700s; Magnetron ITO sputtering power: 70W, argon flow rate 40sccm, oxygen flow rate 0.4sccm, sputtering time 1600s; The final fabricated device has an effective area of ​​3.14 mm². 2 The electroluminescence peak is located at 760 nm. Figure 5 The device structure diagram of a silicon-based perovskite heterojunction light-emitting device fabricated using antisolvent-doped MAPbI3 perovskite. Figure 6 The figure shows a comparison of the electroluminescence spectra of the silicon-based perovskite heterojunction light-emitting device prepared by antisolvent-doped MAPbI3 perovskite film with the original device. As can be seen from the figure, the electroluminescence intensity of the silicon-based perovskite heterojunction electroluminescence device prepared by antisolvent-doped CsPbI3 nanocrystals is increased by 6.5 times compared with the original device. The perovskite film after antisolvent doping has fewer defects, higher carrier concentration, and significantly improved electroluminescence intensity.

[0051] The above description is only a preferred embodiment of the present invention. It should be noted that for those skilled in the art, several improvements can be made without departing from the principle of the present invention, and these improvements should also be considered within the scope of protection of the present invention.

Claims

1. A method for preparing a high-performance near-infrared luminescent perovskite thin film, characterized in that, Includes the following steps: The first step is to synthesize all-inorganic perovskite nanocrystals, wherein the all-inorganic perovskite nanocrystals are CsPbI3 perovskite nanocrystals; The second step is to prepare a clean substrate and a perovskite precursor solution, wherein the perovskite precursor solution is a three-dimensional organic-inorganic hybrid perovskite precursor solution. The third step is to prepare an antisolvent and dope it with the all-inorganic perovskite nanocrystals prepared in the first step. The fourth step involves using a two-step spin coating method to drop the spin-coating perovskite precursor solution onto a clean substrate, and during the second spin coating process, the antisolvent of the doped all-inorganic perovskite nanocrystals prepared in the third step is added. The fifth step involves annealing and crystallizing the spin-coated substrate to obtain a perovskite thin film doped with all-inorganic perovskite nanocrystals; the first step is as follows: 1) Prepare the seed solution required for the synthesis of all-inorganic perovskite nanocrystals. Add the reagents Cs salt, reducing agent and ligand required for the seed solution to a three-necked flask, and perform full vacuuming and preheating to remove moisture and air from the reagents. 2) Inert protective gas is introduced into a three-necked flask, and the mixed solution is heated to fully dissolve and mix thoroughly to obtain a seed solution; 3) Add the oleic acid, oleylamine, and octadecene reagents required for the synthesis of all-inorganic perovskite nanocrystals to a clean three-necked flask, perform thorough vacuuming and preheating, introduce inert protective gas, heat the three-necked flask, and inject the seed solution into the three-necked flask to react and grow all-inorganic perovskite nanocrystals. 4) Cool to room temperature in an ice-water bath and centrifuge to obtain an all-inorganic perovskite nanocrystal solution.

2. The method for preparing high-performance near-infrared luminescent perovskite thin films according to claim 1, characterized in that, In the second step, the method for preparing the perovskite precursor solution is as follows: dissolve monovalent cationic halide and lead halide powder in N,N-dimethylformamide or a mixed solution of N,N-dimethylformamide and dimethyl sulfoxide, and rapidly dissolve it by magnetic stirring, shaking or ultrasonic treatment to obtain the perovskite precursor solution. The concentration of monovalent cationic lead halide in the perovskite precursor solution is 0.2~1M.

3. The method for preparing high-performance near-infrared luminescent perovskite thin films according to claim 1, characterized in that, The specific steps of the third step are as follows: First, prepare the antisolvent, then add 25 μL of all-inorganic perovskite nanocrystal solution to 1 mL of ethyl acetate, and mix it thoroughly and evenly by magnetic stirring, shaking or ultrasonic treatment. The doping concentration of the resulting solution is 2.5%.

4. The method for preparing high-performance near-infrared luminescent perovskite thin films according to claim 1, characterized in that, The fourth step specifically includes: A two-step spin coating method was used. 20 μL of MAPbI3 perovskite precursor solution was dropped onto a silicon wafer substrate. The first step lasted 10 s with a spin speed of 1000 rpm, and the second step lasted 20 s with a spin speed of 5000 rpm. 10 s before the completion of the second step, 200 μL of the antisolvent of the doped all-inorganic perovskite nanocrystals prepared in the third step was dropped.

5. The method for preparing high-performance near-infrared luminescent perovskite thin films according to claim 1, characterized in that, The antisolvent is one or more of toluene, chlorobenzene, acetonitrile, and ethyl acetate.

6. The method for preparing high-performance near-infrared luminescent perovskite thin films according to claim 1, characterized in that, The substrate can be glass, quartz, a glass conductive substrate, a silicon wafer with different doping types, or a flexible substrate.

7. A silicon-based perovskite heterojunction light-emitting device, characterized in that: From bottom to top, the layers are an Al electrode layer, a hole transport layer, a light-emitting layer, an electron transport layer, and an ITO electrode layer. The light-emitting layer is a perovskite thin film doped with all inorganic perovskite nanocrystals prepared according to any one of claims 1 to 6.

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