A preparation method of an organic-inorganic hybrid perovskite thin film

Abstract

The present invention relates to a method for preparing an organic-inorganic hybrid perovskite thin film, comprising the following steps: First, a certain amount of PbI2 powder and PEAI powder are sequentially added to a solvent and stirred in a beaker at room temperature to be fully dissolved, thereby preparing a (PEA)2PbI4 perovskite precursor solution; then, the prepared (PEA)2PbI4 precursor solution is dropped onto a cleaned thin film substrate, and the perovskite precursor solution is uniformly coated on the substrate by spin coating, and after natural drying, a (PEA)2PbI4 perovskite thin film is obtained. The (PEA)2PbI4 perovskite thin film prepared by the present invention has the characteristics of high crystallization quality, large grain size, and low defect density, and this perovskite thin film can be used in the fields of optoelectronic display, solar cells, photodetectors, etc.

Description

Technical Field

[0001] The present invention relates to the field of perovskite materials, and particularly to a method for preparing an organic-inorganic hybrid perovskite thin film. Background Art

[0002] As a new type of composite functional material, organic-inorganic hybrid perovskite combines the diversity of organic material structures and the advantages of high carrier mobility of inorganic semiconductor materials, and has characteristics such as strong light absorption ability, high extinction coefficient, long carrier diffusion distance, and excellent photoluminescence properties, which has attracted extensive attention in the fields of lighting display, photodetectors, solar cells, etc.

[0003] In organic-inorganic hybrid perovskite materials, the larger organic cations, on the one hand, act as spacers to isolate the inorganic metal halide octahedron layers, forming a quantum well superlattice structure in the energy band. The organic cations act as insulating barriers to confine charge carriers in two-dimensional space, improving the carrier mobility; on the other hand, the hydrophobic organic cations can effectively isolate the ionic lattice of the inorganic octahedrons from environmental water molecules. This unique organic-inorganic laminated structure gives it good crystallization effect and chemical stability, especially the stability to water, which is beyond the reach of traditional halogen perovskite materials.

[0004] At present, the commonly used methods for preparing perovskite thin films mainly include spraying method and spin coating method, but both the spraying method and the spin coating method have certain requirements for the thin film substrate material to varying degrees. Compared with the spraying method for preparing thin films, the spin coating method can improve the utilization rate of the perovskite precursor solution; since spin coating is carried out in a relatively closed environment, it also avoids polluting the experimental environment. Generally, an antisolvent is used during spin coating, so that perovskite can quickly nucleate and crystallize out to achieve a better film-forming effect, but this also poses a considerable challenge to the control of perovskite nucleation density and crystallization rate.

[0005] In addition, the traditional spin coating method for preparing thin films will carry out an annealing process, which puts relatively high requirements on the heat resistance of the substrate to a certain extent, and it is also necessary to avoid irreversible effects on the physical and chemical properties of the thin film during annealing. This undoubtedly puts higher requirements on the experimenter and the experimental environment, and also increases the risk of experimental failure to a certain extent. Summary of the Invention

[0006] The purpose of the present invention is to overcome the defects of the above-mentioned existing technologies, and provide a method for preparing an organic-inorganic hybrid perovskite thin film with simple operation, low cost, no selectivity for substrate materials, easy to grow large-sized grains; can be carried out only in a room-temperature atmosphere; the prepared perovskite thin film has good uniformity, high crystallization quality, and good stability.

[0007] The object of the present invention can be achieved by the following technical solutions:

[0008] A method for preparing an organic-inorganic hybrid perovskite thin film, the method comprising the following steps:

[0009] First, PbI2 powder and PEAI powder are sequentially added to a solvent, and after stirring, they are fully dissolved to obtain a (PEA)2PbI4 perovskite precursor solution;

[0010] Then, the prepared (PEA)2PbI4 perovskite precursor solution is dropped onto a substrate material, and the (PEA)2PbI4 perovskite precursor solution is uniformly coated by spin coating. After the solvent is evaporated by natural drying, a (PEA)2PbI4 organic-inorganic hybrid perovskite thin film is obtained.

[0011] Further, the solvent is a polar solvent, including N,N-dimethylformamide (DMF), γ-butyrolactone or dimethyl sulfoxide (DMSO).

[0012] PEAI has good solubility in the above three polar solvents. The formed perovskite precursor solution is a yellow transparent liquid. The required perovskite materials are uniformly mixed in the solvent in ionic form, and there is no precipitation after the solution is stored for 150 days, and it still has a good Tyndall effect. Therefore, the perovskite precursor solution can be used for a long time, with high utilization rate, without causing waste of drugs, and controlling the cost of material preparation from the source.

[0013] Further, the concentrations of PbI2 and PEAI in the (PEA)2PbI4 perovskite precursor solution are 0.8-1.2 mol / L and 1.6-2.4 mol / L respectively.

[0014] Further, the molar ratio of PbI2 to PEAI is 1:2.

[0015] Further, the stirring time is 10-20 min.

[0016] Further, the substrate material includes ordinary glass, ITO glass, FTO glass or sapphire.

[0017] Further, the substrate material is a cleaned substrate material.

[0018] Further, the cleaning process is specifically as follows: first, the substrate material is cleaned with ethanol, and then it is secondarily cleaned with the polar solvent used to prepare the precursor solution.

[0019] Further, the specific steps of the spin coating method are as follows: First, spin coat for 1 - 2 minutes at a low rotation speed, then adjust the rotation speed to a medium rotation speed and spin coat for 2 - 3 minutes, and finally spin coat for 1 minute at a high rotation speed.

[0020] Further, the low rotation speed is not higher than 500 rpm, the medium rotation speed is 800 - 1000 rpm, and the high rotation speed is 2000 rpm.

[0021] The perovskite thin film obtained by the present invention has the characteristics of large - area uniform distribution. At the same time, the growth orientation of the grains shows a single {002} crystal plane direction, which is a typical two - dimensional layered structure. The perovskite thin film has the characteristics of high crystallization quality, large grain size, and low defect density. This perovskite thin film can be used in the fields of optoelectronic display, solar cells, photodetectors, etc.

[0022] The two chemical drugs used in the present invention are PbI2 and PEAI respectively. Compared with the prior art, the solution concentration of the present invention is higher. The concentrations of PbI2 and PEAI in the solvent are 0.8 - 1.2 mol / L, that is, 369 - 553 mg / mL and 1.6 - 2.4 mol / L, that is, 340 - 598 mg / mL respectively, reaching a nearly saturated state. While the solution concentration of the prior art is often only 0.4 - 1 mol / L or 0.1 - 100 mg / mL. Therefore, the high solution concentration can be used as the driving force for crystal precipitation. So even in the ambient temperature and pressure environment, as the solvent volatilizes, the crystals will precipitate out of supersaturation without heat treatment.

[0023] Compared with the prior art, the present invention has the following advantages:

[0024] (1) When preparing the perovskite precursor solution in the present invention, any one of the polar solvents such as N,N - dimethylformamide (DMF), γ - butyrolactone or dimethyl sulfoxide (DMSO) can be used to provide the solvent environment required for the reaction of PbI2 and PEAI; there is no need to add ligands to form a complex system to control the nucleation and growth of perovskite crystals, which simplifies the operation;

[0025] (2) The method in the present invention is a one - step film - forming method, that is, dropping the perovskite precursor solution on the film substrate. Through spin coating, while the solvent evaporates, crystal growth and precipitation occur simultaneously, and the film can be formed without using an anti - solvent to induce rapid nucleation of perovskite; moreover, in the process of spin - coating the perovskite thin film in the present invention, there is no need to deposit an intermediate layer and subsequent annealing process to improve the film adhesion effect and eliminate the surface defects of the film respectively, avoiding the influence of the annealing method, temperature, and time on the perovskite crystallization process, and the process is simple;

[0026] (3) In the process of spin-coating to prepare the perovskite thin film, the present invention has no dependence on the selection of the thin film substrate, and the used thin film substrate can be any one of ordinary glass, ITO glass, FTO glass, and sapphire, with wide applicability;

[0027] (4) In the present invention, the preparation processes of the perovskite precursor solution and the thin film are both carried out at room temperature and in an atmospheric environment, without the need to control the temperature and pressure conditions. Therefore, the present invention can quickly achieve one-step film formation, which is simple, easy to operate, and low in cost, and is very suitable for industrial production. Description of the Drawings

[0028] Figure 1 XRD pattern of the (PEA)2PbI4 perovskite thin film prepared in Example 1;

[0029] Figure 2 PL spectrum of the (PEA)2PbI4 perovskite thin film prepared in Example 1;

[0030] Figure 3 UV-vis absorption spectrum of the (PEA)2PbI4 perovskite thin film prepared in Example 1;

[0031] Figure 4 Optical microscope image of the (PEA)2PbI4 perovskite thin film prepared in Example 1;

[0032] Figure 5 SEM image of the (PEA)2PbI4 perovskite thin film prepared in Example 1. Detailed Embodiments

[0033] The present invention will be described in detail below with reference to the drawings and specific embodiments. This embodiment is implemented on the premise of the technical solution of the present invention, and the detailed implementation manners and specific operation processes are given, but the protection scope of the present invention is not limited to the following embodiments.

[0034] A method for preparing an organic-inorganic hybrid perovskite thin film, the method comprising the following steps:

[0035] First, PbI2 powder and PEAI powder are sequentially added to a solvent, and stirred for 10 - 20 min to fully dissolve, obtaining a (PEA)2PbI4 perovskite precursor solution; the solvent is a polar solvent, including N,N-dimethylformamide (DMF), γ-butyrolactone, or dimethyl sulfoxide (DMSO). The concentrations of PbI2 and PEAI in the (PEA)2PbI4 perovskite precursor solution are 0.8 - 1.2 mol / L and 1.6 - 2.4 mol / L respectively. The molar ratio of PbI2 to PEAI is preferably 1:2.

[0036] Then, the prepared (PEA)2PbI4 perovskite precursor solution was dropped onto a cleaned substrate material, which included ordinary glass, ITO glass, FTO glass, or sapphire. The (PEA)2PbI4 perovskite precursor solution was evenly coated using the spin-coating method. After the solvent evaporated through natural drying, the (PEA)2PbI4 organic-inorganic hybrid perovskite thin film was obtained. The specific steps of the spin-coating method were as follows: First, spin-coat for 1 - 2 min at a low rotation speed, then adjust the rotation speed to a medium rotation speed and spin-coat for 2 - 3 min, and finally spin-coat for 1 min at a high rotation speed. The low rotation speed was not higher than 500 rpm, the medium rotation speed was 800 - 1000 rpm, and the high rotation speed was 2000 rpm.

[0037] Example 1

[0038] A method for preparing an organic-inorganic hybrid perovskite thin film specifically includes the following steps:

[0039] (1) First, 0.6915 g and 0.747 g were respectively weighed according to the molar ratio of PbI2:PEAI = 1:2 and added successively to 1 mL of γ-butyrolactone to form a solution, and stirred for 10 - 20 min. Using the solution method, PbI2 and PEAI all reacted and dissolved to generate a yellow transparent and slightly viscous precursor solution;

[0040] (2) Use a pipette to extract 1 μL of the perovskite precursor solution prepared in step (1), and then drop it onto an ordinary glass substrate that has been cleaned successively with ethanol and γ-butyrolactone. Set the initial spin-coating rotation speed to 500 rpm. After spin-coating for 90 seconds, increase the spin-coating rotation speed to 800 - 1000 rpm and continue spin-coating for 120 seconds. During this process, yellow crystals began to precipitate on the thin film substrate. Then, increase the spin-coating speed to 2000 rpm again and continue spin-coating for 60 seconds, and then gradually decrease the spin-coating speed until it reaches zero. After spin-coating is completed, a (PEA)2PbI4 perovskite thin film is obtained.

[0041] The obtained (PEA)2PbI4 perovskite thin film was tested, and the measured XRD pattern, PL spectrum, UV-vis absorption spectrum, optical microscope image, and SEM are as Figures 1-5 shown.

[0042] From Figure 1It can be seen that the XRD diffraction peaks of the (PEA)2PbI4 perovskite thin film crystals obtained in the present invention are all sharp diffraction peaks of the (00l, l = 2, 4, 6, 8,..., 20) plane series with equal spacing along the c-axis, and there are no diffraction peaks in other directions, which proves that the thin film has a relatively stable layered structure. In addition, the sharp diffraction peaks indicate a high degree of crystallinity and high phase purity of the crystal structure, with good orientation and crystallinity. At the same time, this layered structure is an inorganic layer and an organic layer that are alternately arranged in sequence along the c-axis direction and are parallel to the surface of the substrate. By analyzing the position of the diffraction peaks, the interlayer distance between the inorganic layers was determined to be approximately

[0043] From Figure 2 it can be seen that the emission center wavelength of the (PEA)2PbI4 perovskite thin film prepared in the present invention is located near 523 nm, and the peak shape is symmetric and sharp, and its full width at half maximum is relatively narrow, about 19 nm.

[0044] From Figure 3 it can be seen that the ultraviolet-visible absorption spectrum of the thin film shows that the 2D perovskite thin film has a continuous absorption edge at 521 nm, which is roughly the same as the position of the emission center wavelength of the fluorescence spectrum.

[0045] From Figure 4 it can be seen that when observing the (PEA)2PbI4 perovskite thin film under a 365 nm ultraviolet lamp with an optical microscope, it can be clearly seen that the entire thin film is composed of many flaky crystals, and the thin film under ultraviolet lamp excitation is green.

[0046] From Figure 5 it can be seen that under the observation of a scanning electron microscope (SEM), it is more accurately verified that the entire thin film is composed of many flaky crystals. The size of a single flaky crystal is about 0.15 mm, and the flatness of the crystal surface is high, and the coverage rate of the flaky crystals in the field of view reaches 85%.

[0047] Example 2

[0048] A method for preparing an organic-inorganic hybrid perovskite thin film specifically includes the following steps:

[0049] (1) First, 0.461 g and 0.498 g were weighed respectively according to the ratio of PbI2:PEAI = 1:2, and were successively added to 1 mL of γ-butyrolactone solvent, and stirred for 10 - 20 min to completely dissolve PbI2 and PEAI in γ-butyrolactone. After sufficient reaction, a precursor solution with a concentration of 1 mol / L and a yellow transparent color was formed;

[0050] (2) A small amount of the perovskite precursor solution prepared in step (1) was dropped onto a common glass substrate that had been cleaned successively with ethanol and γ-butyrolactone. The initial spin-coating speed was 500 rpm. After spin-coating for 90 seconds, the spin-coating speed was increased to 800 - 1000 rpm and spin-coating continued for 120 seconds. Then the spin-coating speed was gradually increased to 2000 rpm and spin-coating continued for 60 seconds. After that, the spin-coating speed was decreased until it reached zero, and the spin-coating was completed to obtain a (PEA)2PbI4 perovskite thin film.

[0051] Example 3

[0052] A method for preparing an organic-inorganic hybrid perovskite and its thin film specifically includes the following steps:

[0053] (1) First, 0.2305 g and 0.249 g were respectively weighed according to the ratio of PbI2:PEAI = 1:2 and successively added to 1 mL of γ-butyrolactone solution, and stirred thoroughly for 10 - 20 min. PbI2 and PEAI were all dissolved in the γ-butyrolactone solution and uniformly existed in ionic form. When the concentration of the precursor solution was decreased, the solution gradually showed a light yellow color and was slightly viscous;

[0054] (2) The perovskite precursor solution prepared in step (1) was dropped onto a common glass substrate that had been cleaned successively with ethanol and γ-butyrolactone. The initial spin-coating speed was 500 rpm. After spin-coating for 90 seconds, the spin-coating speed was increased to 800 - 1000 rpm and spin-coating continued for 120 seconds. Then the spin-coating speed was increased again to 2000 rpm and spin-coating continued for 60 seconds, and then the spin-coating speed was gradually decreased until it reached zero, and the spin-coating was completed to obtain a (PEA)2PbI4 perovskite thin film.

[0055] Example 4

[0056] First, 0.461 g and 0.498 g were respectively weighed according to the ratio of PbI2:PEAI = 1:2 and successively added to 1 mL of DMF, and stirred for 10 - 20 min to make PbI2 and PEAI all react and dissolve to form a yellow transparent and slightly viscous precursor solution with a solution concentration of 1 mol / L. The precursor solution was dropped onto a cleaned common glass substrate. The initial spin-coating speed was set at 500 rpm. After spin-coating for 90 seconds, the spin-coating speed was increased to 800 - 1000 rpm and spin-coating continued for 120 seconds. During this process, yellow crystals began to precipitate on the film substrate. Then the spin-coating speed was increased again to 2000 rpm and spin-coating continued for 60 seconds, and then the spin-coating speed was gradually decreased until it reached zero, and the spin-coating was completed to obtain a (PEA)2PbI4 perovskite thin film.

[0057] Example 5

[0058] First, weigh 0.461 g and 0.498 g respectively according to the ratio of PbI2:PEAI = 1:2, and add them successively to 1 mL of DMSO for stirring. Use the solution method to completely react and dissolve PbI2 and PEAI, and the solution concentration is 1 mol / L; drop the prepared perovskite precursor solution on a cleaned ordinary glass substrate. Spin-coat the precursor solution on the substrate by spin coating, and the spin coating process is the same as that in Example 4. After the solvent evaporates, a (PEA)2PbI4 perovskite film is obtained.

[0059] As mentioned above, it is only the preferred embodiment of the present invention, and it is not a limitation to the present invention in other forms. Any person skilled in the art may use the disclosed technical content to make changes or modifications into equivalent embodiments with equivalent changes. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention without departing from the technical solution content of the present invention still belong to the protection scope of the technical solution of the present invention.

Claims

1. A method for preparing an organic-inorganic hybrid perovskite thin film, characterized in that, The method includes the following steps: First, PbI2 powder and PEAI powder are sequentially added to a solvent, and after stirring, they are fully dissolved to obtain a (PEA)2PbI4 perovskite precursor solution; wherein, the solvent is a polar solvent selected from any one of N,N-dimethylformamide, γ-butyrolactone or dimethyl sulfoxide; Then, the prepared (PEA)2PbI4 perovskite precursor solution is dropped onto a substrate material, and the (PEA)2PbI4 perovskite precursor solution is evenly coated by spin coating. After the solvent is evaporated by natural drying, a (PEA)2PbI4 organic-inorganic hybrid perovskite thin film is obtained; During the process of spin-coating the perovskite thin film, crystal growth and precipitation occur simultaneously with the evaporation of the solvent, and the perovskite thin film can be formed without adding an antisolvent to induce rapid perovskite nucleation, nor subsequent annealing process to eliminate surface defects of the perovskite thin film.

2. The preparation method of an organic-inorganic hybrid perovskite thin film according to claim 1, characterized in that, The concentrations of PbI2 and PEAI in the (PEA)2PbI4 perovskite precursor solution are 0.8-1.2 mol / L and 1.6-2.4 mol / L respectively.

3. The preparation method of an organic-inorganic hybrid perovskite thin film according to claim 2, characterized in that, The molar ratio of the said PbI2 to PEAI is 1:

2.

4. The preparation method of an organic-inorganic hybrid perovskite thin film according to claim 1, characterized in that, The stirring time is 10-20 min.

5. The preparation method of an organic-inorganic hybrid perovskite thin film according to claim 1, characterized in that The said substrate material includes ordinary glass, ITO glass, FTO glass or sapphire.

6. The preparation method of an organic-inorganic hybrid perovskite thin film according to claim 1, characterized in that, The said substrate material is a substrate material that has been cleaned.

7. The preparation method of an organic-inorganic hybrid perovskite thin film according to claim 6, characterized in that, The cleaning process is specifically as follows: first, the substrate material is cleaned with ethanol, and then it is secondarily cleaned with the polar solvent used to prepare the precursor solution.

8. The preparation method of an organic-inorganic hybrid perovskite thin film according to claim 1, characterized in that, The specific steps of the said spin coating method are: first, spin coat at a low speed for 1-2 min, then adjust the speed to a medium speed and spin coat for 2-3 min, and finally spin coat at a high speed for 1 min.

9. The preparation method of an organic-inorganic hybrid perovskite thin film according to claim 8, wherein, The said low speed is not higher than 500 rpm, the medium speed is 800-1000 rpm, and the high speed is 2000 rpm.

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