Preparation method of formamidino perovskite active layer and perovskite solar cell thereof

Abstract

The invention belongs to the technical field of formamidine perovskite cells, and particularly relates to a preparation method of a formamidine-based perovskite active layer and a perovskite solar cell thereof. According to the formamidine perovskite thin film solar cell, when a formamidine perovskite active layer is prepared, an auxiliary phase forming material 2, 4, 6-trihydroxy-1, 3, 5-triazine is added into a formamidine perovskite precursor solution. On one hand, 2, 4, 6-trihydroxy-1, 3, 5-triazine can delay the crystallization rate of perovskite through intermolecular interaction, initial nuclei with a smaller number and higher quality are formed, and the film forming quality is improved; on the other hand, the 2, 4, 6-trihydroxy-1, 3, 5-triazine generally exists in the form of a mixture of isomers of a ketone structure and an enol structure, and the two structures respectively have high-density carbonyl and nitrogen heterocyclic rings, so that different types of defects can be passivated respectively, the defect state density can be reduced, the non-radiation energy loss can be reduced, and the photoelectric conversion efficiency and the stability of the device can be improved.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of formamidinium perovskite batteries, and particularly relates to a formamidinium perovskite active layer preparation method and a perovskite solar cell. BACKGROUND

[0002] As a new type of green power generation technology, the organic-inorganic hybrid formamidinium perovskite thin film solar cell has attracted extensive attention due to its high photoelectric conversion efficiency, solution processing for large-area processing, and combination with silicon solar cells to prepare laminated solar cells. As a research hotspot in the field of solar power generation, the photoelectric conversion efficiency of the formamidinium perovskite thin film solar cell has been improved from 3.8% to 26.7% in just over a decade, and has a broad application prospect.

[0003] The formamidinium perovskite solar cell has high photoelectric conversion efficiency and good thermal stability, and is the most promising perovskite solar cell. However, on the one hand, during the preparation of the active layer, the generated crystal phase is unstable, and the alpha phase is easily converted into a yellow phase without photovoltaic activity, which leads to the failure to prepare an active layer thin film with photovoltaic activity, and the photovoltaic device prepared cannot realize photoelectric conversion or has extremely low photoelectric conversion efficiency. On the other hand, the perovskite polycrystalline ionic crystal thin film widely used at present is prepared based on a solution processing process, and the controllability of the crystallization process is poor, and problems such as excessively fast crystallization rate are prone to occur, which causes the thin film to have poor morphology and the perovskite grain boundary defect state density to be too high, thereby increasing non-radiative energy loss and affecting the photoelectric conversion efficiency and stability of the perovskite solar cell device. SUMMARY

[0004] Therefore, the technical problem to be solved by the present application is to overcome the above-mentioned defects in the prior art, and to provide a formamidinium perovskite active layer preparation method and a perovskite solar cell thereof.

[0005] To this end, the present application provides the following technical solutions:

[0006] A formamidinium perovskite active layer preparation method, the formamidinium perovskite active layer preparation method being:

[0007] 2,4,6-trihydroxy-1,3,5-triazine additive is dissolved in a perovskite active layer precursor solution with a perovskite component of FAPbI3, the precursor solution is coated on a substrate on which an electron transport layer is prepared, the substrate is rotated at high speed, an anti-solvent is added after a certain period of time, and the substrate is placed in an air environment for annealing after the rotation is stopped, to obtain the formamidinium perovskite active layer.

[0008] Optionally, the formamidine-based perovskite precursor solution is prepared by dissolving 2,4,6-trihydroxy-1,3,5-triazine, lead iodide, formamidine hydroiodide, and methylamine hydrochloride in a mixed solvent of N,N-dimethylformamide and dimethyl sulfoxide.

[0009] Optionally, the concentration of the 2,4,6-trihydroxy-1,3,5-triazine additive in the formamidinium-based perovskite precursor solution is 0.1 to 5 mg / mL.

[0010] Optionally, in the formamidine-based perovskite precursor solution, the concentration of the formamidine-based perovskite component is 1.5 to 2.0 mmol / mL, and the volume ratio of N,N-dimethylformamide to dimethyl sulfoxide is 5:1 to 10:1.

[0011] Optionally, the anti-solvent is selected from at least one of chlorobenzene, ether, acetone, toluene, ethyl acetate or chloroform.

[0012] Optionally, the rotation speed during the preparation of the formamidinium-based perovskite active layer is 2000 rpm to 8000 rpm, the rotation time is 30s to 80s, and the time for adding the anti-solvent is 5 to 40s after the start of rotation.

[0013] Optionally, during the preparation of the formamidine-based perovskite active layer, the annealing temperature is 100° C. to 180° C., the annealing time is 10 min to 60 min, the annealing atmosphere is an air environment, and the air humidity is 20% to 50%.

[0014] Optionally, the thickness of the formamidinium-based perovskite active layer is 300 nm to 1500 nm.

[0015] Optionally, the formamidinium-based perovskite solar cell includes a transparent conductive substrate layer, an electron transport layer, a formamidinium-based perovskite active layer prepared by the above method, a passivation layer, a hole transport layer and a metal back electrode, which are arranged in sequence.

[0016] Optionally, the method for preparing the formamidinium-based perovskite solar cell provided by the present invention may include the following specific steps:

[0017] Step 1: The FTO glass substrate was cleaned by ultrasonic cleaning with deionized water, acetone, and isopropyl alcohol in sequence, and the solvent remaining on the glass substrate was blown away with a nitrogen stream to obtain a clean transparent conductive substrate;

[0018] Step 2: After the conductive substrate cleaned in step 1 is UVO treated, it is placed on a coater. A pipette is used to draw up the tin dioxide nanocrystal solution and evenly coat it on the surface of the substrate. The coater is started to rotate at high speed. After the rotation stops, the substrate is placed on a hot plate and annealed in air to obtain an electron transport layer.

[0019] Step 3: After UVO treatment, place the substrate prepared in step 2 on a spin coater in a glove box. Use a pipette to draw the prepared formamidinium perovskite precursor solution and evenly apply it on the substrate surface. Start the spin coater to rotate at high speed, add anti-solvent, and after the rotation stops, place it on a hot plate in an air environment for annealing to obtain a formamidinium-based perovskite active layer.

[0020] Step 4: Place the substrate from step 3 on a coater in a glove box, use a pipette to draw up the prepared passivation layer solution, and evenly apply it on the substrate surface. Start the coater to rotate at high speed. After the rotation stops, place the substrate on a hot plate in the glove box for annealing to obtain a passivation layer.

[0021] Step 5: Place the substrate from step 4 on a coater in the glove box, use a pipette to draw up the prepared hole transport layer solution, evenly apply it on the surface of the substrate, start the coater to rotate at high speed, and after the rotation stops, the hole transport layer is obtained;

[0022] Step 6: Prepare a metal back electrode on the hole transport layer by thermal evaporation on the substrate in step 5.

[0023] Furthermore, the ultrasonic cleaning time using each solvent in step 1 is 15 minutes to 30 minutes.

[0024] Furthermore, in step 2, the rotation speed of the coating machine is 3000 rpm to 8000 rpm, the rotation time is 15 s to 60 s, the hot plate annealing temperature is 100° C. to 180° C., and the annealing time is 15 min to 60 min.

[0025] Furthermore, in step 3, the volume of the formamidine perovskite precursor solution aspirated by a pipette for each substrate (2 cm×2 cm) is 20 μL to 100 μL.

[0026] Furthermore, in step 4, the hot stage annealing temperature is 80° C. to 180° C., and the annealing time is 5 min to 60 min.

[0027] Furthermore, in step 5, the volume of the hole transport layer solution aspirated by the pipette for each substrate (2 cm×2 cm) is 30 μL to 80 μL, the rotation speed of the gel spinner is 3000 rpm to 8000 rpm, and the rotation time is 30 s to 60 s.

[0028] Furthermore, during the evaporation in step 6, the pressure in the evaporation chamber is 9×10 -5 Pa, the thickness of molybdenum oxide is 8nm, and the thickness of the metal Ag electrode is 80nm~120nm.

[0029] The technical solution of the present invention has the following advantages:

[0030] The present invention provides a formamidinium perovskite thin-film solar cell. Compared with the prior art, the present invention adds an auxiliary phase-forming material, 2,4,6-trihydroxy-1,3,5-triazine, to the formamidinium perovskite precursor solution during the preparation of the formamidinium-based perovskite active layer. The present invention has the following beneficial technical effects: on the one hand, 2,4,6-trihydroxy-1,3,5-triazine can slow the perovskite crystallization rate through intermolecular interactions, forming fewer but higher-quality initial nuclei, thereby improving film quality; on the other hand, 2,4,6-trihydroxy-1,3,5-triazine typically exists as a mixture of isomers of keto and enol structures. The two structures, respectively, have high densities of carbonyl groups and nitrogen heterocycles, which can passivate different types of defects, reduce defect state density, reduce non-radiative energy loss, and improve the device's photoelectric conversion efficiency and stability.

[0031] The preparation method of the formamidine perovskite thin-film solar cell provided by the present invention has simple process, mild conditions, easy control, and broad application prospects. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the specific embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying any creative work.

[0033] Figure 1 This is a schematic structural diagram of the formamidinium-based perovskite thin-film solar cell provided by the present invention;

[0034] Figure 2 is a JV curve diagram of the formamidinium-based perovskite thin film solar cell provided by Examples 1-3 of the present invention;

[0035] Figure 3 1 is a JV curve diagram of the formamidine perovskite thin film solar cell provided in Example 1 of the present invention and the comparative example;

[0036] Figure 4 3 is a graph showing the relationship between the normalized energy conversion efficiency of the formamidine perovskite thin-film solar cells provided in Examples 1-3 of the present invention and Comparative Example 1 and the change over time.

[0037] Reference numerals:

[0038] 1. Transparent conductive substrate layer; 2. Electron transport layer; 3. Formamidinium-based perovskite active layer; 4. Passivation layer; 5. Hole transport layer; 6. Metal back electrode. DETAILED DESCRIPTION

[0039] The following examples are provided for a better understanding of the present invention and are not intended to limit the best mode of implementation. They do not limit the content and scope of protection of the present invention. Any product identical or similar to the present invention obtained by anyone under the guidance of the present invention or by combining the features of the present invention with other prior arts shall fall within the scope of protection of the present invention.

[0040] If no specific experimental steps or conditions are specified in the examples, the conventional experimental steps or conditions described in the literature in this field can be used. If the manufacturer of the reagents or instruments is not specified, they are all commercially available conventional reagents.

[0041] The invention provides a method for preparing a formamidine-based perovskite active layer. When preparing the formamidine-based perovskite active layer, an auxiliary phase-forming material 2,4,6-trihydroxy-1,3,5-triazine is added to a formamidine perovskite precursor solution.

[0042] The structural diagram of the formamidite-based perovskite thin film solar cell provided by the present invention is as follows: Figure 1 As shown, it includes a transparent conductive substrate layer 1, an electron transport layer 2, a formamidinium-based perovskite active layer 3, a passivation layer 4, a hole transport layer 5 and a metal back electrode 6 which are arranged in sequence.

[0043] The method for preparing a formamidite-based perovskite thin-film solar cell provided by the present invention comprises the following steps:

[0044] An electron transport layer, a formamidinium-based perovskite active layer, a passivation layer, a hole transport layer, and a metal back electrode are sequentially formed on the surface of a transparent conductive substrate to obtain a formamidinium-based perovskite thin-film solar cell;

[0045] The method for preparing the formamidinium-based perovskite active layer comprises the following steps: spin-coating a formamidinium-based perovskite precursor solution on a prepared electron transport layer, dripping an antisolvent onto the rotating substrate, and annealing to obtain the formamidinium-based perovskite active layer.

[0046] In the present invention, the transparent conductive substrate is preferably ITO glass, FTO glass, AZO glass, or conductive PET, more preferably FTO glass. The present invention does not particularly limit the source of the transparent conductive substrate; commercially available products familiar to those skilled in the art can be used. In the present invention, the transparent conductive substrate is preferably cleaned with deionized water, acetone, and isopropyl alcohol for 15 to 30 minutes each before use, and then blown dry with a nitrogen gun.

[0047] In the present invention, the electron transport layer is preferably SnO2, TiO x 、NiO x 、CuO x , CuSCN, CuPc or C 60and derivatives, more preferably SnO2. The thickness of the electron transport layer is preferably 10 nm to 200 m, more preferably 20 nm to 100 nm. The method for forming the electron transport layer on the conductive substrate is not particularly limited in the present application, and a method for preparing an electron transport layer well known to those skilled in the art can be used.

[0048] In the present application, the thin film crystal structure of the formamidinium perovskite precursor solution is FAPbI3. The solvent of the formamidinium perovskite precursor solution is preferably one or more of DMF, DMSO, and more preferably the solvent of the formamidinium perovskite precursor solution is a mixed solvent of DMF and DMSO, with a volume ratio of DMF:DMSO = 7:1. The concentration of the formamidinium perovskite precursor solution is preferably 1 mmol / mL to 2 mmol / mL, and more preferably the concentration of the formamidinium perovskite precursor solution is 1.8 mmol / mL. On this basis, a formamidinium perovskite precursor solution capable of forming the formamidinium perovskite active layer well known to those skilled in the art can be used, and those skilled in the art are not particularly limited in the method for preparing the formamidinium perovskite precursor solution.

[0049] In the present application, the anti-solvent is preferably one or more of chlorobenzene, diethyl ether, acetone, toluene, ethyl acetate, and trichloromethane, and more preferably chlorobenzene.

[0050] In the present application, the method for preparing the formamidinium perovskite active layer is preferably one-step spin coating, and the process is preferably specifically as follows: after the substrate (2 cm x 2 cm) is treated with UVO for 10 min, it is placed on a spin coater in a glove box, 30 μL to 60 μL of the prepared formamidinium perovskite precursor solution added with the auxiliary phase material 2, 4, 6-trihydroxy-1, 3, 5-triazine is sucked up using a pipette, and is uniformly coated on the surface of the substrate. The spin coater is started at a high speed, the rotation speed is 3000 rpm to 6000 rpm, the rotation time is 30 to 60 s, 300 μL to 2000 μL of anti-solvent is added at the 25th to 40th second after the rotation starts, and after the rotation stops, the substrate is placed on a hot stage for annealing in an air environment, the annealing temperature is 100°C to 150°C, the annealing time is 10 min to 30 min, the air humidity is 30% to 40%, and the formamidinium perovskite active layer is obtained after the annealing is completed.

[0051] In the present application, the thickness of the formamidinium perovskite active layer is preferably 100 nm to 2000 nm, and more preferably 300 nm to 1500 nm.

[0052] In the present application, the hole transport layer is preferably Spiro-OMeTAD, P3HT, PTAA, MnO x , WO xor 2PACz layer, more preferably a Spiro-OMeTAD layer; the thickness of the hole transport layer is preferably 20 nm to 400 nm, more preferably 100 nm to 200 nm. The present invention has no particular limitation on the method for forming the hole transport layer on the formamidine perovskite active layer, and methods for preparing hole transport layers well known to those skilled in the art can be used.

[0053] The present invention has no particular restrictions on the type and formation of the counter electrode. A technical solution for forming the counter electrode on the hole transport layer that is well known to those skilled in the art can be used. In a preferred embodiment of the present invention, the substrate after the hole transport layer is prepared is transferred to a thermal evaporation device, and the vacuum degree reaches 1×10 -5 Pa, molybdenum oxide was evaporated to a thickness of 8 nm, and then an electrode (Ag) was evaporated to a thickness of 100 nm. After the evaporation was completed, a formamidinium perovskite thin film solar cell was obtained.

[0054] The present invention provides a method for preparing a formamidite active layer, comprising the following steps: dissolving a 2,4,6-trihydroxy-1,3,5-triazine additive in a perovskite active layer precursor solution whose perovskite component is FAPbI3, coating the precursor solution on a substrate on which an electron transport layer is prepared, rotating the substrate at high speed, dripping an anti-solvent after a certain period of time, and annealing the substrate in an air environment after the rotation stops, to obtain the formamidite active layer. Compared with existing methods, the present invention has the following beneficial technical effects: on the one hand, 2,4,6-trihydroxy-1,3,5-triazine can slow down the crystallization rate of perovskite through intermolecular interactions, forming fewer but higher-quality initial nuclei, thereby improving the film quality; on the other hand, 2,4,6-trihydroxy-1,3,5-triazine usually exists as a mixture of isomers of keto and enol structures, and the two structures respectively have high densities of carbonyl groups and nitrogen heterocycles, which can passivate different types of defects, reduce defect state density, reduce non-radiative energy loss, and improve device photoelectric conversion efficiency and stability. In addition, the preparation method provided by the present invention is simple in process, mild in conditions, easy to control, and has broad application prospects.

[0055] In order to further illustrate the present invention, the following examples are given below to provide a detailed description.

[0056] Example 1

[0057] This embodiment provides a formamidine perovskite thin-film solar cell, the composition and specific preparation method of which are as follows:

[0058] Step 1: Place the FTO transparent conductive glass substrate (2 cm × 2 cm) in deionized water, acetone, and isopropanol and ultrasonically clean it for 15 min each twice, blow dry it with nitrogen, and store it for later use.

[0059] Step 2: Dilute the tin dioxide (SnO2) stock solution with ultrapure water in a volume ratio of 1:5, and stir thoroughly to obtain a SnO2 precursor solution; place the FTO substrate in a UV ozone cleaner for 15 minutes; take 50 μL of SnO2 precursor solution and evenly spread it on the surface of the FTO conductive glass, and set the parameters of the coating machine to a speed of 3000 rpm / s and a time of 30 seconds; then place it on a 150°C hot plate in an air environment for annealing for 30 minutes to obtain a SnO2 film (30 nm); place the SnO2 film prepared above in a UV ozone cleaner for 15 minutes for subsequent spin coating.

[0060] Step 3: Place the substrate on the coater in the glove box, and use a pipette to draw 50 μL of the prepared formamidine perovskite precursor solution (2,4,6-trihydroxy-1,3,5-triazine, PbI2, FAI, MACl are dissolved in a mixed solvent of DMF and DMSO, with a molar ratio of PbI2:FAI:MACl=3:3:1, a volume ratio of DMF:DMSO=7:1, a FAPbI3 concentration of 1.8 mol / L, 2,4,6-trihydroxy-1,3,5-triazine, PbI2, FAI, and MACl). Trihydroxy-1,3,5-triazine (concentration 1.0 mg / mL) was evenly coated on the substrate surface, and the high-speed rotation of the coating machine was started at 5000 rpm and 60 s. 200 μL of chlorobenzene antisolvent was added dropwise 30 s after the rotation started. After the rotation stopped, it was placed on a hot plate for annealing in an air environment at an annealing temperature of 120°C, an annealing time of 60 min, and an air humidity of 40%. After annealing, a formamidinium perovskite active layer (400 nm) was obtained.

[0061] Step 4: Place the substrate on a coater in the glove box, use a pipette to draw 50 μL of the prepared phenylethylammonium iodide (PEAI) solution (solvent is isopropanol, concentration 2.0 mg / mL), and evenly apply it on the surface of the substrate. Start the coater to rotate at high speed, with a rotation speed of 5000 rpm and a rotation time of 30 s. After the rotation stops, place it on the hot stage in the glove box for annealing at an annealing temperature of 100°C and an annealing time of 10 min. After annealing is completed, a passivation layer is obtained.

[0062] Step 5: Take 60 μL of Spiro-OMeTAD solution (90 mg of spiro-OMeTAD, 21 μL of LiTFSI solution (520 mg of Li-TFSI is dissolved in 1 mL of acetonitrile), 39 μL of 4-tert-butylpyridine, and 15 μL of Co(Ⅲ)TFSI (300 mg of Co(Ⅲ)TFSI is dissolved in 1 mL of acetonitrile) and dissolved in 1 mL of chlorobenzene solvent) and spin coat it on the prepared formamidine perovskite film. The parameters of the spin coater are set to a speed of 5000 rpm / s and a time of 30 s to obtain a hole transport layer.

[0063] Step 6: Finally, use high vacuum evaporation equipment for evaporation. The pressure in the evaporation chamber is 9×10-5Pa. First, evaporate 8nm thick molybdenum oxide, and then evaporate 100nm thick metal Ag electrode to obtain a formamidinium perovskite thin film solar cell device.

[0064] Example 2

[0065] This embodiment provides a formamidine perovskite thin-film solar cell. Compared with Example 1, the difference is that the concentration of 2,4,6-trihydroxy-1,3,5-triazine in step 3 is 0.5 mg / mL.

[0066] Example 3

[0067] This embodiment provides a formamidine perovskite thin-film solar cell. Compared with Example 1, the difference is that the concentration of 2,4,6-trihydroxy-1,3,5-triazine in step 3 is 1.5 mg / mL.

[0068] Comparative Example 1

[0069] This comparative example provides a formamidite perovskite solar cell. Compared with Example 1, the difference is that when preparing the formamidite perovskite active layer in step 3, no 2,4,6-trihydroxy-1,3,5-triazine additive is added to the perovskite active layer precursor solution whose perovskite component is FAPbI3.

[0070] Test Case

[0071] The performance of the formamidine perovskite thin film solar cells provided in the embodiments of the present invention and the comparative examples was tested. The specific testing method is as follows:

[0072] The current density-voltage (JV) curves of the formamidine perovskite thin film solar cells prepared in the PCE test examples and comparative examples were tested on a Kethley 2400 system under the following test conditions: the simulated light intensity was 100 mW cm -2 (AM1.5G) scan rate 0.1V s -1 (step size of 0.02 V, time delay of 200 ms), the scanning interval was 1.2 V to -0.2 V, and the power output of the xenon lamp was calibrated by the NERL (National Renewable Energy Laboratory) standard KG5 standard Si battery.

[0073] The stability test was carried out on unencapsulated formamidine perovskite thin film solar cell devices at room temperature in a nitrogen glove box.

[0074] The specific test results are shown in the table below:

[0075] Table 1

[0076]

[0077]

[0078] From the examples and comparative examples Figure 2-4 As shown in Table 1, when preparing the formamidite active layer of the present invention, the 2,4,6-trihydroxy-1,3,5-triazine additive is dissolved in the perovskite active layer precursor solution whose perovskite component is FAPbI3 (Examples 1-3). The prepared formamidite perovskite solar cell device has improved photoelectric properties such as open circuit voltage, short circuit current density, and fill factor compared to the device prepared without adding the additive (Comparative Example 1). The formamidite thin-film solar cell device prepared by the method of the present invention has the advantages of high photoelectric conversion efficiency and strong stability.

[0079] Obviously, the above embodiments are merely examples for clarity of explanation and are not intended to limit the implementation methods. Those skilled in the art will appreciate that other variations or modifications can be made based on the above description. It is not necessary and impossible to enumerate all implementation methods here. Obvious variations or modifications arising therefrom remain within the scope of protection of the present invention.

Claims

1. A method for preparing a formamidine-based perovskite active layer, characterized in that: The method for preparing the formamidinium-based perovskite active layer is as follows: The 2,4,6-trihydroxy-1,3,5-triazine additive is dissolved in a perovskite active layer precursor solution whose perovskite component is FAPbI3, and the precursor solution is coated on a substrate on which an electron transport layer has been prepared. The substrate is rotated at high speed, and an anti-solvent is added dropwise after a certain period of time. After the rotation stops, the substrate is placed in an air environment for annealing to obtain the formamidinium-based perovskite active layer.

2. The method for preparing a formamidine-based perovskite active layer according to claim 1, wherein: The formamidine-based perovskite precursor solution is prepared by dissolving 2,4,6-trihydroxy-1,3,5-triazine, lead iodide, formamidine hydroiodide, and methylamine hydrochloride in a mixed solvent of N,N-dimethylformamide and dimethyl sulfoxide.

3. The method for preparing a formamidine-based perovskite active layer according to claim 1, wherein: The concentration of the 2,4,6-trihydroxy-1,3,5-triazine additive in the formamidinium-based perovskite precursor solution is 0.1 to 5 mg / mL.

4. The method for preparing a formamidine-based perovskite active layer according to claim 2, wherein: In the formamidine-based perovskite precursor solution, the concentration of the formamidine-based perovskite component is 1.5 to 2.0 mmol / mL, and the volume ratio of N,N-dimethylformamide to dimethyl sulfoxide is 5:1 to 10:

1.

5. The method for preparing a formamidine-based perovskite active layer according to claim 1, wherein: The anti-solvent is selected from at least one of chlorobenzene, ether, acetone, toluene, ethyl acetate or chloroform.

6. The method for preparing a formamidine-based perovskite active layer according to claim 1, wherein: During the preparation of the formamidine-based perovskite active layer, the rotation speed is 2000 rpm to 8000 rpm, the rotation time is 30s to 80s, and the time for adding the anti-solvent dropwise is 5 to 40s after the start of rotation.

7. The method for preparing a formamidine-based perovskite active layer according to claim 1, wherein: When preparing the formamidine-based perovskite active layer, the annealing temperature is 100° C. to 180° C., the annealing time is 10 min to 60 min, the annealing atmosphere is an air environment, and the air humidity is 20% to 50%.

8. The method for preparing a formamidine-based perovskite active layer according to claim 1, wherein: The thickness of the formamidinium-based perovskite active layer is 300nm to 1500nm.

9. A formamidine-based perovskite solar cell, characterized in that: The formamidinium-based perovskite solar cell comprises a transparent conductive substrate layer, an electron transport layer, a formamidinium-based perovskite active layer prepared by the preparation method according to any one of claims 1 to 8, a passivation layer, a hole transport layer and a metal back electrode, which are arranged in sequence.

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