A perovskite thin film, a preparation method thereof and an application thereof

Abstract

The present invention discloses a perovskite thin film, a preparation method thereof and an application thereof. The preparation method comprises the following steps: (1) A tin source and a halide are placed in an organic solvent, and after stirring, a tin-containing perovskite precursor solution is obtained; (2) A metal replacement powder is added to the tin-containing perovskite precursor solution, and a galvanic replacement reaction occurs to reduce tetravalent tin in the tin-containing perovskite precursor solution to divalent tin, and a replacement solution is obtained after filtration; (3) The replacement solution is spin-coated by a one-step method to obtain a tin-based perovskite thin film. The present invention can effectively inhibit the oxidation of tin elements in the thin film, reduce the defect density and non-radiative recombination centers, improve the stability of the thin film, thereby improving the photoelectric conversion efficiency of the tin-based perovskite solar cell device and enhancing the stability of the tin-based perovskite solar cell device.

Description

Technical Field

[0001] The present invention belongs to the field of optoelectronic technologies, and more specifically, relates to a perovskite thin film, a preparation method thereof, and an application thereof. Background Art

[0002] With the development of the economy and the progress of society, the demand for energy by humans is increasing day by day. The huge energy storage of solar energy, which is inexhaustible, has attracted the research interest of a large number of researchers. A solar cell is a device that converts light energy into electrical energy using the photovoltaic effect. Among them, the organic-inorganic hybrid perovskite solar cell based on solution processing has cheap raw materials and a simple preparation process, and the certified efficiency exceeds 25%, reaching an efficiency level similar to that of traditional crystalline silicon solar cells. However, such perovskite solar cells all contain the heavy metal lead element, and the toxicity and environmental harm of lead greatly limit its commercial use. Tin-based perovskite solar cells are a type of non-lead perovskite solar cells, which have the characteristics of low toxicity, suitable band gap, high absorption coefficient, and carrier mobility, and are expected to replace lead-based perovskite solar cells. However, the current tin-based perovskite materials have poor stability, and tin elements are easily oxidized from +2 valence to +4 valence, which will generate a high defect density and short minority carrier lifetime in the thin film, damaging the inherent stability and optoelectronic properties of the device, thereby reducing the output voltage of the corresponding device. It is reported that a small amount of +4-valent tin has been formed in the precursor solution before film formation. Even the formation of a small amount of +4-valent tin (molar ratio < 0.1%) will cause serious p-type self-doping, greatly reducing its optoelectronic performance. Therefore, although most current tin-containing perovskites are processed in an inert atmosphere, the oxidation problem of tin is still the main factor limiting its efficiency. Therefore, how to solve the oxidation problem of tin is of great significance for simultaneously improving the efficiency and stability of tin-based perovskite batteries. Summary of the Invention

[0003] In view of the above defects or improvement requirements of the prior art, the present invention provides a perovskite thin film, a preparation method thereof, and an application thereof, aiming to solve the technical problem of easy oxidation of tin-based materials by reducing 4-valent tin in the precursor solution to 2-valent tin.

[0004] To achieve the above object, according to one aspect of the present invention, a preparation method of a tin-based perovskite thin film is provided, including the following steps:

[0005] (1) Mix a tin source and a halide in an organic solvent, and stir to obtain a tin-containing perovskite precursor solution;

[0006] (2) Add a metal displacement powder to the tin-containing perovskite precursor solution, and an electro-galvanic displacement reaction occurs to reduce 4-valent tin in the tin-containing perovskite precursor solution to 2-valent tin, and a displacement solution is obtained after filtration;

[0007] (3) The replacement solution is used to obtain a tin-based perovskite thin film by one-step spin coating.

[0008] Preferably, the metal replacement powder is a metal powder of the second main group element or a metal powder of a transition metal element. Preferably, the metal replacement powder includes at least one of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and Zn.

[0009] Preferably, the molar ratio of the tin source to the metal replacement powder is 1:(0.01 - 0.20).

[0010] Preferably, the tin source includes at least one of SnF2, SnCl2, SnBr2, SnI2, and Sn(CH3COO)2; the halides include at least one of CH3NH3I, CH3NH3Br, CH3NH3Cl, CHNH3I, CHNH3Br, CHNH3Cl, HC(NH2)2Cl, HC(NH2)2Br, HC(NH2)2I, C6H5(CH2)2NH3Br, C6H5(CH2)2NH3Cl, C6H5(CH2)2NH3I, C4H 12 NCl, C4H 12 NBr, C4H 12 NI, C6H4(CH2NH3Cl)2, C6H4(CH2NH3Br)2, C6H4(CH2NH3I)2, CsCl, CsBr, and CsI; the organic solvent is at least one of dimethylformamide, dimethyl sulfoxide, N,N-dimethylformamide, γ-butyrolactone, and N-methylpyrrolidone.

[0011] Preferably, the tin source is SnI2, the halide is CsI, and the molar ratio of CsI to SnI2 is 1:1 - 1:2; the concentration of the tin-containing perovskite precursor solution is 0.1 - 10 mol / L; the organic solvent is a mixture of dimethyl sulfoxide and N,N-dimethylformamide, and the volume ratio of dimethyl sulfoxide to N,N-dimethylformamide is 1:1 - 1:10; preferably, the concentration of the tin-containing perovskite precursor solution is 0.7 mol / L.

[0012] Preferably, the stirring in step (1) is specifically stirring at 25°C - 80°C for 1 - 24 hours; the reaction conditions for the galvanic replacement reaction in step (2) are stirring at 25°C - 80°C for 0.5 - 24 hours; the filtration is carried out using a filter membrane with a pore size of 0.22 μm.

[0013] Preferably, the spin coating speed of the one-step spin coating method in step (3) is 3000-6000 rpm, and the spin coating time is 40-70 s; the annealing temperature is 50-100° C., and the annealing time is 10-30 min.

[0014] Preferably, the thickness of the tin-based perovskite film is 200-400 nm.

[0015] According to another aspect of the present invention, a perovskite thin film is provided.

[0016] According to another aspect of the present invention, there is provided an application of a perovskite thin film for preparing a perovskite photoelectric device, wherein the perovskite photoelectric device includes one or more integrated devices selected from the group consisting of solar cells, light-emitting diodes, sensors, transistors, and lasers.

[0017] In general, the above technical solutions conceived by the present invention can achieve at least the following beneficial effects compared with the prior art.

[0018] (1) The method provided by the present invention first prepares a tin-based perovskite material solution, then adds a metal replacement powder to the solution. The metal replacement powder and the precursor solution undergo a galvanic replacement reaction, thereby reducing all the oxidized tetravalent tin in the precursor solution to divalent tin. This method can effectively inhibit the oxidation of tin elements in the film, reduce defect density and non-radiative recombination centers, and improve the stability of the film, thereby improving the photoelectric conversion efficiency of tin-based perovskite solar cell devices and enhancing the stability of tin-based perovskite solar cell devices.

[0019] (2) The metal replacement powder selected in the present invention is a common second main group and transition metal element metal powder. Since the excessively high ionicity and electronegativity of the second main group metal elements are not conducive to the formation of perovskite films, it is preferred that the metal replacement powder is a transition metal including at least one of Sc, Ti, V, Cr, Mn, Fe, Co, Ni and Zn. Considering the common valence states and reducing abilities of the above-mentioned metals, Zn powder is preferred in the present invention.

[0020] (3) The present invention strictly limits the molar ratio of the tin source to the metal powder to 1: (0.01-0.20). This is because too little metal powder is not enough to completely reduce the +4 valent tin in the precursor solution, while excessive metal powder will cause the +2 valent tin in the solution to precipitate in the form of elemental tin, resulting in a loss of raw materials.

[0021] The present invention strictly limits the stirring time of the galvanic displacement reaction to 0.5 to 24 hours. This is because if the reaction time is too short, the metal element cannot fully reduce the +4 valent tin in the precursor solution. If the reaction time is too long, the +4 valent tin in the precursor solution will oxidize, weakening the reduction effect of the galvanic displacement reaction.

[0022] (4) The efficiency and stability of the tin-based perovskite prepared by the present invention are significantly improved. Compared with the tin-based perovskite solar cell without using the metal replacement powder, its highest conversion efficiency increases from 2.86% to 6.43%, an increase of about 225%. After being placed in air for 100 hours, the photoelectric conversion efficiency of the battery still remains above 85% of the initial value. Description of the Drawings

[0023] Figure 1 Among them, (a) is the X-ray photoelectron spectroscopy (XPS) diagram of the all-inorganic tin-based perovskite thin film prepared in Example 1 of the present invention; Figure 1 Among them, (b) is the X-ray photoelectron spectroscopy (XPS) diagram of the all-inorganic tin-based perovskite thin film prepared in Comparative Example 1;

[0024] Figure 2 is the time-resolved photoluminescence spectrum (TRPL) of the tin-based perovskite thin films prepared in Example 1 and Comparative Example 1 of the present invention;

[0025] Figure 3 is the space charge limited current measurement diagram of the tin-based perovskite solar cells prepared in Example 1 and Comparative Example 1 of the present invention;

[0026] Figure 4 Among them, (a) is the current density-voltage curve diagram of the all-inorganic tin-based perovskite solar cells prepared in Example 1 and Comparative Example 1 of the present invention; Figure 4 (b) is the diagram of the change of the photoelectric conversion efficiency of the unencapsulated devices of the all-inorganic tin-based perovskite solar cells prepared in Example 1 and Comparative Example 1 of the present invention with time;

[0027] Figure 5 is the SEM diagram of the thin films prepared after adding different metal replacement powders, among which Figure 5 Among them, (a) is the SEM diagram of the perovskite thin film prepared after adding Zn powder; Figure 5 Among them, (b) is the SEM diagram of the perovskite thin film prepared after adding Fe powder; Figure 5 Among them, (c) is the SEM diagram of the perovskite thin film prepared after adding Sr powder; Figure 5 Among them, (d) is the SEM diagram of the perovskite thin film prepared after adding Ba powder. Detailed Embodiments

[0028] In order to make the objectives, technical solutions and advantages of the present invention clearer, the present invention will be further described in detail below with reference to the drawings and embodiments. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention. In addition, the technical features involved in the various embodiments of the present invention described below can be combined with each other as long as they do not conflict with each other.

[0029] Example 1

[0030] This embodiment provides a tin-based perovskite solar cell, and its preparation method includes:

[0031] Step 1): Clean the conductive glass substrate. In the present invention, we first cut the FTO conductive glass substrate into a size of 5 cm × 10 cm, and etch it with Zn powder and hydrochloric acid. Then, the FTO glass substrate is ultrasonically cleaned successively with deionized water, detergent, ethanol, acetone, and absolute ethanol. The ultrasonic cleaning duration is about 30 min each time to remove the solid impurities on the glass substrate. Then, the cleaned FTO conductive glass is immersed in a beaker of absolute ethanol and sealed with tin foil for storage.

[0032] Step 2): Prepare a substitution perovskite precursor solution. In a dry nitrogen glove box, use an electronic analytical balance to weigh 130.50 mg of SnI2 and 91.00 mg of CsI respectively, and then use a pipette to measure 400 μL of N,N-dimethylformamide and 100 μL of dimethyl sulfoxide solution. Dissolve the weighed solid powders of SnI2 and CsI in a mixed solution with a volume ratio of dimethyl sulfoxide to N,N-dimethylformamide of 1:4 to obtain a precursor solution with a molar ratio of SnI2 to CsI of 1:1 and a concentration of 0.7 mol / L. Stir at a constant temperature of 25 °C for 12 h to fully dissolve and react the solutes. Then, measure 1.14 mg of Zn powder and add it to the above-prepared precursor solution. After stirring at 40 °C for 6 hours, filter it through a filter membrane with a pore size of 0.22 μm to obtain a substitution solution. All operations need to be completed in the glove box.

[0033] Step 3): Dry the FTO conductive glass substrate with nitrogen and perform ultraviolet ozone treatment for 30 minutes.

[0034] Step 4): Prepare a fully inorganic tin-based perovskite solar cell. Prepare a dense titanium dioxide layer on the cleaned FTO conductive glass by spray pyrolysis. Dilute titanium dioxide to a titanium ethoxide acetone ethanol solution at a volume ratio of 1:39. At a temperature of 450 °C, spray the diluted solution on the FTO conductive substrate 10 times. And anneal at 450 °C for 35 minutes.

[0035] Step 5): Dilute the titanium dioxide slurry with terpineol at a mass ratio of 1:3.5. After cooling to room temperature in Step 4), use a 400-mesh screen printing stencil to brush the diluted solution onto the dense titanium dioxide layer. And anneal at 125 °C for 15 minutes.

[0036] Step 6): After cooling to room temperature in Step 5), screen-print the alumina slurry onto the mesoporous titanium dioxide layer using the same process. And anneal at 150 °C for 15 minutes.

[0037] Step 7): After cooling to room temperature in Step 6), the nickel oxide slurry is screen-printed onto the mesoporous alumina layer using the same process. And anneal at 150 °C for 15 minutes.

[0038] Step 8): High-temperature sintering is performed on the formed dense titanium dioxide layer / mesoporous titanium dioxide layer / mesoporous alumina blocking layer / mesoporous nickel oxide hole-selective layer structure. Hold at 120 °C for 10 minutes, 180 °C for 10 minutes, 125 °C for 10 minutes, 400 °C for 20 minutes, 450 °C for 20 minutes, and 500 °C for 30 minutes.

[0039] Step 9): After cooling to room temperature in Step 8), the carbon slurry is screen-printed onto the mesoporous nickel oxide layer using the same process. And anneal at 400 °C for 35 minutes.

[0040] Step 10): After cooling to room temperature in Step 9), 5 μL of the perovskite replacement precursor solution is drop-coated into the above-obtained device, and after annealing at 70 °C for 10 minutes, the preparation of the tin-based perovskite solar cell is completed.

[0041] Example 2

[0042] The difference between this Example 2 and Example 1 is that 2.28 mg of Zn powder is added in Step 2.

[0043] Example 3

[0044] The difference between this Example 3 and Example 1 is that 0.22 mg of Zn powder is added in Step 2.

[0045] Comparative Example 1

[0046] The difference between this Comparative Example 1 and Example 1 is that no metal replacement powder Zn is added.

[0047] The open-circuit voltage, short-circuit current density, fill factor, conversion efficiency and other parameters of Examples 1, 2, 3 and Comparative Example 1 are detected, and the detection results are shown in Table 1.

[0048] Table 1 Performance table of the cells prepared in Examples 1-3 and Comparative Example 1

[0049]

[0050] As can be seen from Table 1, the tin-based perovskite solar cell prepared by adding Zn powder has a high open-circuit voltage, and both the short-circuit current density and the fill factor are improved. The highest conversion efficiency of the device increases from 2.86% to 6.43%.

[0051] The X-ray photoelectron spectroscopy (XPS) of the tin-based perovskite thin film absorption layer prepared in Example 1 and Comparative Example 1 of the present invention gives the results as Figure 1 shown in (a) and (b) in. FromFigure 1 It can be seen from (a) and (b) that the +4valent tin content of the tin-based perovskite film prepared by adding Zn powder is significantly reduced, indicating that the oxidation of tin in the precursor solution is well suppressed.

[0052] The carrier lifetime of the tin-based perovskite thin film absorption layer prepared in Example 1 of the present invention and Comparative Example 1 was tested. The results are as follows: Figure 2 As shown. Figure 2 It can be seen that the carrier lifetime of the absorption layer of the tin-based perovskite thin film prepared in Example 1 is increased from 3.98 nanoseconds to 10.03 nanoseconds, indicating that the defect state density in the film is reduced.

[0053] The defect state density of the tin-based perovskite thin film absorption layer prepared in Example 1 of the present invention and Comparative Example 1 was tested, and the results were as follows: Figure 3 As shown. Figure 3 It can be seen that the defect state density of the absorbing layer of the tin-based perovskite film prepared in Example 1 is increased from 5.81×10 18 cm -3 Reduced to 4.86×10 18 cm -3 , indicating that the defect state density in the film is reduced.

[0054] The performance of the tin-based perovskite solar cells prepared in Example 1 and Comparative Example 1 of the present invention was tested, and the test results are as follows: Figure 4 As shown in (a) and (b), thanks to the improvement of the tin oxidation problem in the film, the reduction of the defect state density and the improvement of the stability, the conversion efficiency and stability of the tin-based perovskite solar cells prepared by adding Zn powder are greatly improved.

[0055] Examples 4-7

[0056] The difference between Examples 4-7 and Example 1 is that the metal replacement powder added in Step 2 is different, see Table 2 for details.

[0057] Table 2 Performance of tin-based perovskite films prepared with different metal replacement powders

[0058]

[0059]

[0060] As can be seen from Table 2, the content of tetravalent tin in the film decreases significantly after adding the metal replacement powder, indicating that the oxidation of tin in the precursor solution is well inhibited. However, for the alkaline earth metal elements Sr and Ba in the second main group, due to their high ionicity and electronegativity, they are not conducive to perovskite film formation, resulting in smaller grain sizes of the prepared perovskite films, which is not conducive to optoelectronic applications. For the perovskite films prepared with transition metal Zn and Fe powders, the grain sizes become larger and the content of tetravalent tin in the films indicates that adding transition metal powders can improve film formation while inhibiting the oxidation of tin in the precursor solution.

[0061] The surface morphologies of the tin-based perovskite films prepared in Examples 4-7 of the present invention were detected, and the results are as Figure 5 shown in (a)-(d) below. As can be seen from Figure 5 (a)-(d) below, the surfaces of the films prepared with transition metals are flat and pore-free, while the surfaces of the films prepared with alkaline earth metal elements are rough and have more pinholes, indicating that adding transition metals to prepare perovskite films is more conducive to optoelectronic applications.

[0062] Examples 8-12

[0063] The difference between Examples 8-12 and Example 1 is that in Step 2, the stirring time of the galvanic replacement reaction is different after adding the metal Zn replacement powder. See Table 3 for details.

[0064] Table 3 Performance table of tin-based perovskite films prepared with different stirring times of galvanic replacement reactions

[0065]

[0066] As can be seen from Table 3, as the stirring time of the galvanic replacement reaction increases after adding the Zn replacement powder, the reaction becomes more complete, and the content of tetravalent tin in the film becomes lower. However, when the reaction time is too long and exceeds 12 hours, the content of tetravalent tin in the film begins to increase, indicating that the optimal stirring time for the galvanic replacement reaction is 12 hours. If the reaction time is too short, the metal elements cannot fully reduce the tetravalent tin in the precursor solution. And too long reaction time will cause the oxidation of tetravalent tin in the precursor solution, weakening the reduction effect of the galvanic replacement reaction.

[0067] Those skilled in the art can easily understand that the above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present invention should be included in the protection scope of the present invention.

Claims

1. A preparation method of a tin-based perovskite thin film, characterized in that, It includes the following steps: (1) Add a tin source and a halide into an organic solvent, and stir to obtain a tin-based perovskite precursor solution; the halide is CsI; (2) Add a metal displacement powder to the tin-based perovskite precursor solution, and an electrogalvanic displacement reaction occurs to reduce the tetravalent tin in the tin-based perovskite precursor solution to divalent tin, and a displacement solution is obtained after filtration; the metal displacement powder is Zn; the molar ratio of the tin source to the metal displacement powder is 1:(0.01 - 0.20); (3) Obtain a tin-based perovskite thin film by one-step spin coating of the displacement solution.

2. The preparation method according to claim 1, characterized in that, The tin source includes at least one of SnF2, SnCl2, SnBr2, SnI2, and Sn(CH3COO)2; the organic solvent is at least one of dimethylformamide, dimethyl sulfoxide, N,N-dimethylformamide, γ-butyrolactone, and N-methylpyrrolidone.

3. The preparation method according to claim 2, characterized in that, The tin source is SnI2, and the molar ratio of CsI to SnI2 is 1:1 - 1:2; the concentration of the tin-based perovskite precursor solution is 0.1 - 10 mol / L; the organic solvent is a mixture of dimethyl sulfoxide and N,N-dimethylformamide, and the volume ratio of dimethyl sulfoxide to N,N-dimethylformamide is 1:1 - 1:

10.

4. The preparation method according to claim 3, characterized in that, The concentration of the tin-based perovskite precursor solution is 0.7 mol / L.

5. The preparation method according to claim 1, characterized in that, In step (1), the stirring is specifically carried out at 25°C - 80°C for 1 - 24 hours; the reaction conditions for the electrogalvanic displacement reaction in step (2) are stirring at 25°C - 80°C for 0.5 - 24 hours; the filtration is carried out using a filter membrane with a pore size of 0.22 μm.

6. The preparation method according to claim 1, wherein In step (3), the spin coating speed of the one-step spin coating method is 3000 - 6000 rpm, and the spin coating time is 40 - 70 s; the temperature of the annealing treatment is 50°C - 100°C, and the annealing time is 10 - 30 min.

7. The preparation method of the tin-based perovskite thin film according to claim 1, characterized in that The thickness of the tin-based perovskite thin film is 200 - 400 nm.

8. A perovskite thin film, characterized in that, The perovskite thin film is prepared by the preparation method described in any one of claims 1 - 7.

9. Use of the perovskite thin film according to claim 8, characterized in that, It is used for preparing perovskite optoelectronic devices, and the perovskite optoelectronic devices include one or more integrations of solar cells, light-emitting diodes, sensors, transistors, and lasers.

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