Preparation method of inorganic perovskite nanowire film

Abstract

The application belongs to the technical field of solar cells, and provides a preparation method of inorganic perovskite nanowire film. First, lead iodide is dissolved and stirred uniformly under constant temperature to obtain a lead iodide precursor solution; a precipitating agent is added to the lead iodide precursor solution to obtain light yellow flocculation, and the light yellow flocculation is centrifuged to obtain light yellow colloidal material, which is vacuum dried to obtain a lead iodide composite product; a precursor spin coating solution is obtained based on the lead iodide composite product, the precursor spin coating solution is spin coated on a substrate to form a film, and annealing treatment is performed to obtain a loose lead iodide film layer; the lead iodide film layer is sequentially immersed in a cesium iodide solution and a cesium bromide solution, and then annealing treatment is performed to obtain an inorganic perovskite film, so that the loose PbI2 nanostructure can fully contact and react with the cesium iodide solution and the cesium bromide solution, and a one-dimensional inorganic perovskite nanowire material with good orientation, excellent physical and chemical stability and high crystallinity is prepared.

Description

Technical Field

[0001] This application relates to the field of solar cell technology, and in particular to a method for preparing inorganic perovskite nanowire thin films. Background Technology

[0002] Metal halides with the ABX3 (A = MA, FA, Cs; B = Pb, Sn; X = Cl, Br, I) perovskite crystal structure have seen widespread research and application in recent years in fields such as perovskite solar cells, photodetectors, photoelectric water splitting, and memristors due to their excellent photoelectric properties, tunable optical band gaps, and simple low-temperature fabrication processes, showing promising development prospects. Currently, various perovskite structures are commonly used: smooth and dense perovskite thin films, perovskite colloidal quantum dots, one-dimensional perovskite nanowires, and two-dimensional perovskite nanosheets. Among these, one-dimensional perovskite nanowires have also attracted considerable attention and significant development due to their ordered orientation, good air stability, excellent carrier transport capabilities, and high crystallinity.

[0003] However, existing methods for preparing inorganic perovskite nanowires are susceptible to problems such as film agglomeration, tearing, and discontinuity due to factors like humidity and annealing atmosphere. These issues severely hinder the application and development of inorganic perovskite nanowires in fields such as solar cells and photodetectors. Summary of the Invention

[0004] The purpose of this application is to provide a method for preparing inorganic perovskite nanowire thin films, which can solve the problems of film agglomeration, film tearing, and discontinuity in existing preparation processes.

[0005] This application provides a method for preparing inorganic perovskite nanowire thin films, the method comprising:

[0006] Lead iodide was dissolved in NMP reagent and stirred evenly under constant temperature to obtain lead iodide precursor solution;

[0007] A precipitant was added to the lead iodide precursor solution, and the solution was sealed and allowed to stand to obtain a pale yellow flocculent substance.

[0008] The pale yellow flocculent substance was mixed with a pre-set organic reagent at a volume ratio of 1:4 and then centrifuged to obtain a pale yellow colloidal substance.

[0009] The pale yellow colloidal substance was vacuum dried to obtain a lead iodide composite product.

[0010] The lead iodide composite product was dissolved in a spin-coating solvent to obtain a precursor spin-coating solution of a predetermined concentration;

[0011] The precursor spin-coating solution is spin-coated onto the substrate, and the substrate is annealed to obtain a lead iodide thin film layer;

[0012] The lead iodide thin film layer was immersed in a cesium iodide solution to obtain a CsPbI3 layer, and the CsPbI3 layer was then annealed.

[0013] The CsPbI3 layer was immersed in a cesium bromide solution to obtain a CsPbBr3 layer, and the CsPbBr3 layer was annealed to obtain a perovskite film.

[0014] In one embodiment, dissolving lead iodide in NMP reagent and stirring until homogeneous under constant temperature conditions to obtain a lead iodide precursor solution includes:

[0015] Take an appropriate amount of lead iodide and dissolve it in NMP reagent under stirring, and stir it evenly under constant temperature to form a lead iodide precursor solution with a concentration of 0.52 mol / L.

[0016] In one embodiment, dissolving the lead iodide composite product in a spin-coating solvent to obtain a precursor spin-coating solution of a predetermined concentration includes:

[0017] Take an appropriate amount of lead iodide complex PbI2 (NMP) and dissolve it in a spin-coating solvent. Stir the solution evenly under constant temperature to form a lead iodide precursor solution with a concentration of 1 mol / L.

[0018] In one embodiment, the step of spin-coating the precursor spin-coating solution onto a substrate and annealing the spin-coated lead iodide thin film layer to obtain a perovskite thin film includes:

[0019] The precursor spin coating solution was filtered using a polytetrafluoroethylene filter head, and the filtered spin coating solution was placed in an environment of 65℃-75℃ for heat preservation and curing treatment.

[0020] The substrate is fixed on a spin coater, wherein the spin coater has a rotation speed range of 1000-2500 r.pm;

[0021] The precursor spin-coating solution, after heat preservation and curing treatment, is dropped onto the substrate, and the substrate is placed in a vacuum environment for annealing.

[0022] In one embodiment, the annealing temperature of the substrate is 65°C-75°C.

[0023] In one embodiment, the annealing time of the substrate is 15-30 minutes.

[0024] In one embodiment, the cesium iodide solution is formed by dissolving cesium iodide in methanol;

[0025] The lead iodide film layer is immersed in cesium iodide solution for 30-60 minutes.

[0026] In one embodiment, the annealing temperature of the CsPbI3 layer is 120℃-150℃;

[0027] The annealing time for the CsPbI3 layer is 1-2 hours.

[0028] In one embodiment, the cesium bromide solution is formed by dissolving cesium bromide in methanol;

[0029] The CsPbBr3 layer was immersed in cesium bromide solution for 20-100 minutes.

[0030] In one embodiment, the annealing temperature of the CsPbBr3 layer is 120℃-150℃;

[0031] The annealing time for the CsPbBr3 layer is 0.5-2 hours.

[0032] This application provides a method for preparing inorganic perovskite nanowire thin films. First, lead iodide is dissolved in NMP reagent and stirred evenly under constant temperature to obtain a lead iodide precursor solution. A precipitant is added to the lead iodide precursor solution to obtain a pale yellow flocculent substance. The pale yellow flocculent substance is centrifuged to obtain a pale yellow colloidal substance. The pale yellow colloidal substance is vacuum dried to obtain a lead iodide composite product. A precursor spin-coating solution is obtained based on the lead iodide composite product. The precursor spin-coating solution is spin-coated on a substrate and annealed to obtain a lead iodide thin film layer. The lead iodide thin film layer is then immersed in cesium iodide solution and cesium bromide solution in sequence and annealed to obtain a perovskite thin film. Thus, based on the loose PbI2 nanostructure, it can fully contact and react with the cesium iodide solution and cesium bromide solution to prepare a one-dimensional inorganic perovskite nanowire material with good orientation, excellent physicochemical stability, and high crystallinity. Attached Figure Description

[0033] Figure 1 A schematic flowchart illustrating the preparation method of the inorganic perovskite nanowire thin film provided in the embodiments of this application;

[0034] Figure 2 This is a schematic diagram of XRD diffraction of conventional PbI2 powder and PbI2 (NMP) synthesized in the embodiments of this application;

[0035] Figure 3 Schematic diagrams of the morphology and XRD diffraction of films prepared from conventional PbI2 powder and the embodiments of this application;

[0036] Figure 4 This is a schematic flowchart of step S600 in the method for preparing inorganic perovskite nanowire thin films provided in the embodiments of this application.

[0037] Figure 5 The morphology and XRD diffraction diagrams of CsPbI3 films synthesized by conventional PbI2 and CsPbI3 films prepared in the embodiments of this application are shown.

[0038] Figure 6 The images show the morphology and XRD diffraction patterns of CsPbBr3 films synthesized using conventional PbI2 and those prepared in the embodiments of this application. Detailed Implementation

[0039] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided in conjunction with the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the scope of this application.

[0040] In the description of this application, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include one or more of that feature.

[0041] This invention provides a method for preparing inorganic perovskite nanowire thin films. Figure 1 This is a schematic flowchart of the method for preparing perovskite thin films provided in an embodiment of the present invention, as shown below. Figure 1 As shown, the preparation method in this embodiment includes steps S100 to S800.

[0042] In step S100, lead iodide is dissolved in N-methyl-2-pyrrolidone (NMP) reagent and stirred evenly under constant temperature to obtain lead iodide precursor solution.

[0043] In one specific application embodiment, PbI2 is used as the solute and NMP reagent is used as the solvent. An appropriate amount of PbI2 is dissolved in NMP reagent under stirring, and stirred evenly under constant temperature to form a lead iodide precursor solution with a concentration of 0.52 mol / L.

[0044] In one embodiment, the isothermal temperature range of the PbI2 dissolved in the NMP reagent under isothermal stirring conditions can be 20℃-100℃.

[0045] Further, after step S100, the prepared lead iodide precursor solution can be placed in a constant temperature water bath or other constant temperature stirring device and slowly stirred for 1-3 hours at a first temperature (80°-100°).

[0046] In step S200, a precipitant is added to the lead iodide precursor solution and the mixture is sealed and allowed to stand to obtain a pale yellow flocculent substance.

[0047] In this embodiment, a precipitant is added to the lead iodide precursor solution, at which point flocculent precipitate appears in the lead iodide precursor solution. The precipitant can be an organic solvent.

[0048] In some embodiments, the precipitant may be one or a mixture of methanol, ethanol, isopropanol, or diethyl ether in a certain proportion.

[0049] In some embodiments, after adding a precipitant to the lead iodide precursor solution and letting it stand for a period of time, the upper layer solution formed after standing can be initially removed by a dropper to obtain a pale yellow flocculent substance. Specifically, the upper layer solution is mainly NMP reagent.

[0050] In step S300, the pale yellow flocculent substance is mixed with a preset organic reagent at a volume ratio of 1:4 and then centrifuged to obtain a pale yellow colloidal substance.

[0051] In some embodiments, the preset organic reagent may be one or more of diethyl ether, ethyl acetate, chlorobenzene, and toluene.

[0052] In this embodiment, the pale yellow flocculent formed in step S200 contains a small amount of NMP reagent. After removing the upper layer solution, the pale yellow flocculent is mixed with a preset organic solvent at a volume ratio of 1:4. Then, impurities are removed by centrifugation to obtain a cleaned pale yellow colloidal substance.

[0053] In practical applications, the pale yellow flocculent material should be centrifuged at least three times.

[0054] In step S400, the pale yellow colloidal substance is vacuum dried to obtain the lead iodide composite product.

[0055] In this embodiment, the pale yellow colloidal substance was vacuum dried to obtain the lead iodide composite product PbI2 (NMP).

[0056] Furthermore, in specific applications, the lead iodide composite product PbI2(NMP) obtained by vacuum drying is ground to obtain a fine powder of lead iodide composite product, and then placed in a dry vacuum environment.

[0057] When PbI2 is dissolved in NMP reagent at a certain mass ratio, since PbI2 is a Lewis acid, NMP reagent acts as both a solvent and a Lewis base. PbI2 undergoes a complexation reaction with NMP, and the product is the PbI2(NMP) complex.

[0058] After centrifugation, washing, and vacuum drying, a powdered lead iodide composite product was obtained. The powder was characterized by powder XRD, and the results were as follows: Figure 2 The XRD diffraction pattern shown shows that the diffraction peaks of the PbI2 control group powder basically conform to the basic diffraction information of standard card library number PDF#00-007-0235. The PbI2(NMP) powder in this embodiment is not completely the same as the diffraction pattern of the PbI2 standard powder in existing literature. Therefore, the PbI2(NMP) complex generated by the complexation reaction of PbI2 and NMP in this embodiment can be regarded as a novel lead iodide complex structure product PbI2(NMP).

[0059] Furthermore, combined Figure 3 As can be seen from the comparison of the film morphology images, the lead iodide composite product generated in this embodiment has the advantages of good solubility, good dispersibility and good film-forming properties, which can greatly improve the stability of the film and improve the repeatability of the experiment.

[0060] In step S500, the lead iodide composite product is dissolved in a spin-coating solvent to obtain a precursor spin-coating solution of a preset concentration.

[0061] In this embodiment, an appropriate amount of lead iodide composite product PbI2 (NMP) was dissolved in a spin-coating solvent, and then magnetically stirred for 0.5-2 hours at 65℃-75℃.

[0062] In some embodiments, the spin-coating solvent may be one or a mixture of dimethylformamide (DMF), dimethylacetamide (DMAC), and dimethyl sulfoxide (DMSO).

[0063] In step S600, the precursor spin-coating solution is spin-coated onto the substrate, and the substrate is annealed to obtain a lead iodide thin film layer.

[0064] In some embodiments, the precursor spin-coating solution is filtered using a polytetrafluoroethylene filter head to obtain the spin-coating precursor solution for the subsequent preparation of lead iodide.

[0065] In some embodiments, the pore size of the polytetrafluoroethylene filter head is 0.48 micrometers.

[0066] In some embodiments, see Figure 4 As shown, step S600 includes steps S601 to S603.

[0067] In step S601, the precursor spin coating solution is filtered using a polytetrafluoroethylene filter head, and the filtered spin coating solution is placed in an environment of 65℃-75℃ for heat preservation and curing treatment.

[0068] In step S602, the substrate is fixed on a spin coater, wherein the spin coater has a rotation speed range of 1000-2500 r.pm (1000-2500 revolutions per minute).

[0069] In step S603, the precursor spin-coating solution after heat preservation and curing is dropped onto the substrate, and the substrate is annealed.

[0070] In this embodiment, the substrate is fixed on a spin coater and rotates with the spin coater. The precursor spin coating solution is dropped onto the substrate and uniformly coated on the substrate surface to form a lead iodide thin film layer. After annealing the lead iodide thin film layer, a loose lead iodide thin film is obtained.

[0071] In some embodiments, after a lead iodide thin film layer is formed on the substrate, the substrate can be annealed in a glove box environment at 65°C-75°C.

[0072] In some embodiments, the annealing time of the substrate is 15-30 minutes.

[0073] For example, place the substrate in a 70°C heating table or other heating device for 15-30 minutes and maintain the annealing process for at least 15 minutes.

[0074] In some embodiments, the substrate may be a transparent conductive substrate, such as FTO glass.

[0075] In some embodiments, the substrate is treated with ultraviolet ozone for 20-40 minutes before spin coating with the spin coating precursor solution.

[0076] In step S700, the lead iodide thin film layer is immersed in a cesium iodide solution to obtain a CsPbI3 layer, and the CsPbI3 layer is then annealed.

[0077] In some embodiments, the cesium iodide solution is formed by dissolving cesium iodide in methanol; the lead iodide film layer is immersed in the cesium iodide solution for 30-60 minutes.

[0078] In some embodiments, the annealing temperature of the CsPbI3 layer is 120℃-150℃; the annealing time of the CsPbI3 layer is 1-2 hours.

[0079] Figure 5 SEM images and corresponding XRD phase characterization diagrams of CsPbI3 perovskite nanowires prepared from PbI2 and PbI2(NMP). Figure 5(a) and (d) are SEM images of CsPbI3 films prepared by the traditional lead iodide film process at low and high magnification, respectively. It can be seen that the agglomeration of the lead iodide film leads to the agglomeration of some nanowires, and the length and width distribution of the nanowires are relatively discrete.

[0080] On the contrary Figure 5 (b) and (e) show the morphology of the PbI2 (NMP) experimental group. It can be seen that the length of the CsPbI3 nanowires is distributed between 200-500 nm and the width is distributed between 100-150 nm. They also have a well-structured, loosely porous Wiener structure with good three-dimensional stacking, which is conducive to the subsequent halide ion replacement reaction to synthesize CsPbBr3 perovskite phase nanowires. Figure 5 (c) shows the XRD diffraction patterns of the thin film samples on the conductive glass corresponding to the two experimental groups. They are basically consistent with the diffraction peaks of the conductive substrate and CsPbI3 (PDF#00-018-0376), and there is no significant difference between the two.

[0081] In step S800, the CsPbI3 layer is immersed in a cesium bromide solution to obtain a CsPbBr3 layer, and the CsPbBr3 layer is annealed to obtain a perovskite film.

[0082] In some embodiments, the cesium bromide solution is formed by dissolving cesium bromide in methanol; the CsPbBr3 layer is immersed in the cesium bromide solution for 20-100 minutes.

[0083] In some embodiments, the annealing temperature of the CsPbBr3 layer is 120-150°C.

[0084] In some embodiments, the annealing time of the CsPbBr3 layer is 0.5-2 hours.

[0085] Figure 6 SEM images and corresponding XRD characterization images of CsPbBr3 perovskite nanowires prepared by PbI2 and PbI2(NMP). Figure 6 (a) and 6(d) are low-magnification and high-magnification SEM images of CsPbBr3 nanowires: 6(a) shows that the lengths of the nanowires vary and they are relatively short (basically only a few micrometers). Figure 6 (d) indicates that the width of the prepared perovskite nanowires is distributed between 150-300 nm, which is relatively discrete.

[0086] Figure 6(b) and 6(e) are SEM images of the perovskite nanowires corresponding to the PbI2(NMP) experimental group. The nanowires prepared by this experimental group can reach the length of tens or even hundreds of micrometers and are relatively uniformly distributed on the substrate. As can be seen from 6(e), the width of the nanowires is basically distributed between 100-150 nm and there is no significant difference in morphological changes. Relatively speaking, it is more suitable for the application of perovskite solar cells and photodetectors.

[0087] In this invention's embodiment, a novel low-temperature solution synthesis method for lead iodide complex PbI2 (NMP) nanowire thin films is provided. This method offers more nucleation sites for heterogeneous crystal nucleation and slows down crystal growth, resulting in loose, smooth, and continuous micro / nanostructured lead iodide thin films. This effectively solves problems encountered in traditional lead iodide thin film preparation processes, such as agglomeration, film tearing and discontinuity, and poor experimental repeatability due to uncontrollable factors like reduced solubility caused by solvent absorption. Based on this method, inorganic perovskite nanowires were synthesized and prepared. The obtained inorganic perovskite nanowires exhibit superior length and width distribution compared to nanowires prepared using traditional lead iodide thin films, providing positive guidance for other related research and applications of inorganic perovskite nanowires.

[0088] The above-described embodiments are only used to illustrate the technical solutions of this application, and are not intended to limit them. Although this application has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of this application, and should all be included within the protection scope of this application.

Claims

1. A method for preparing an inorganic perovskite nanowire thin film, characterized by, The preparation method comprises: Dissolve lead iodide in NMP reagent and stir uniformly under constant temperature conditions to obtain a lead iodide precursor solution; Add a precipitant to the lead iodide precursor solution and seal and stand to obtain light yellow floccules; Mix the light yellow floccules with a preset organic reagent according to a volume ratio of 1:4, and perform centrifugal treatment to obtain light yellow colloidal substances; Vacuum dry the light yellow colloidal substances to obtain a lead iodide composite product; Dissolve the lead iodide composite product in a spin coating solvent to obtain a precursor spin coating solution with a preset concentration; Filter the precursor spin coating solution using a polytetrafluoroethylene filter head, and place the filtered spin coating solution in an environment at 65-75°C for heat curing treatment; Fix a substrate on a spin coater, wherein the rotation speed of the spin coater ranges from 1000 to 2500 r.p.m; Drop the precursor spin coating solution after heat curing treatment on the substrate, and perform annealing treatment on the substrate to obtain a loose lead iodide thin film layer; Place the lead iodide thin film layer in a cesium iodide solution for immersion treatment to obtain a CsPbI3 layer, and perform annealing treatment on the CsPbI3 layer; Place the CsPbI3 layer in a cesium bromide solution for immersion treatment to obtain a CsPbBr3 layer, and perform annealing treatment on the CsPbBr3 layer to obtain an inorganic perovskite nanowire thin film. The step of dissolving the lead iodide composite product in a spin coating solvent to obtain a precursor spin coating solution with a preset concentration comprises: Dissolve an appropriate amount of lead iodide composite in a spin coating solvent, and stir uniformly under constant temperature conditions to form a lead iodide precursor solution with a concentration of 1 mol / L.

2. The production method according to claim 1, wherein The step of dissolving lead iodide in NMP reagent and stirring uniformly under constant temperature conditions to obtain a lead iodide precursor solution comprises: Dissolve an appropriate amount of lead iodide in NMP reagent in a stirring state, and stir uniformly under constant temperature conditions to form a lead iodide precursor solution with a concentration of 0.52 mol / L.

3. The production method according to claim 1, wherein The annealing temperature of the substrate is 65-75°C.

4. The production method according to claim 1, wherein The annealing time of the substrate is 15-30 minutes.

5. The production method according to claim 1, wherein The cesium iodide solution is formed by dissolving cesium iodide in methanol; The immersion treatment time of the lead iodide thin film layer in the cesium iodide solution is 30-60 minutes.

6. The production method according to claim 5, wherein The annealing temperature of the CsPbI3 layer is 120-150°C; The annealing time of the CsPbI3 layer is 1-2 hours.

7. The production method according to claim 1, wherein The cesium bromide solution is formed by dissolving cesium bromide in methanol; The immersion treatment time of the CsPbBr3 layer in the cesium bromide solution is 20-100 minutes.

8. The production method according to claim 7, wherein The annealing temperature of the CsPbBr3 layer is 120-150°C; and the annealing time of the CsPbBr3 layer is 0.5-2 hours.

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