Formamidino perovskite solar cell and preparation method thereof

Abstract

The invention belongs to the technical field of perovskite solar cells, and particularly relates to a formamidino perovskite solar cell and a preparation method thereof. The formamidino perovskite solar cell comprises a formamidino perovskite active layer, and when the formamidino perovskite active layer is prepared, a lead iodide film is coated with a formamidino hydriodate solution mixed with butadiene sulfone. Compared with the prior art, the invention has the following beneficial technical effects: on one hand, butadiene sulfone can regulate and control crystallization kinetics, delay crystallization rate and improve film forming quality through interaction with perovskite molecules, thereby fundamentally reducing perovskite crystal defect state density; and on the other hand, by adopting the treatment process, butadiene sulfone can be fully permeated to the perovskite crystal boundary in the crystallization process, sulfonyl in molecules can play a passivation role on defects at the crystal boundary, the defect state density is reduced, the non-radiation energy loss is reduced, and the photoelectric conversion efficiency and stability of the device are improved.

Description

Technical Field

[0001] This invention belongs to the field of perovskite solar cell technology, specifically relating to a formamidinium-based perovskite solar cell and its preparation method. Background Technology

[0002] Metal halide perovskite solar cells, as a novel green energy power generation technology, have attracted widespread attention due to their high photoelectric conversion efficiency, large-area solution processing capability, and ability to be combined with silicon solar cells to fabricate tandem solar cells. As a research hotspot in the field of solar power generation, the photoelectric conversion efficiency of perovskite solar cells has increased from the initial 3.8% to 26.7% in just over a decade, demonstrating broad application prospects.

[0003] Currently, most widely used perovskite polycrystalline ionic thin films are prepared based on solution processing technology. The crystallization process has weak controllability and is prone to problems such as excessively fast crystallization rate. This results in poor film morphology and excessively high perovskite grain boundary defect state density, which increases non-radiative energy loss and affects the photoelectric conversion efficiency and stability of perovskite solar cell devices.

[0004] Defect passivation strategies have proven to be effective in improving the photoelectric performance and stability of halide perovskites. However, most existing processes perform passivation on the film surface. Due to the diverse types of defect sites, there is an urgent need for an efficient passivation strategy that can penetrate to various grain boundaries to reduce defect state density and non-radiative energy loss, thereby improving the photoelectric properties and stability of perovskite solar cells. Furthermore, most existing processes perform passivation after the perovskite layer is prepared, without considering minimizing defect formation during the fabrication process. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the above-mentioned defects in the existing perovskite solar cells and their preparation process, thereby providing a formamidinium-based perovskite solar cell and its preparation method.

[0006] Therefore, the present invention provides the following technical solution:

[0007] This invention provides a formamidinium-based perovskite solar cell, comprising a formamidinium-based perovskite active layer, wherein the formamidinium-based perovskite active layer is prepared by coating a lead iodide film with a formamidinium hydroiodate solution mixed with cyclobutene sulfone additive.

[0008] Optionally, the formamidinium-based perovskite solar cell includes a transparent conductive substrate layer, an electron transport layer, a formamidinium-based perovskite active layer, a hole transport layer, and a metal back electrode arranged sequentially.

[0009] The present invention provides a method for preparing the above-mentioned formamidine perovskite solar cell, comprising the following steps: sequentially preparing an electron transport layer, a formamidine perovskite active layer, a hole transport layer and a metal back electrode on the surface of a transparent conductive substrate layer;

[0010] The formamidinium-based perovskite active layer is prepared using a two-step continuous deposition method, the preparation steps of which include:

[0011] A lead iodide solution is coated onto the surface of the electron transport layer, annealed, and cooled. A formamidinium hydroiodate solution mixed with cyclobutene sulfone additive is coated onto the lead iodide film and annealed to obtain the formamidinium-based perovskite active layer.

[0012] Optionally, in the formamidine hydroiodide solution containing sulfolane additive, the solvent is selected from at least one of isopropanol, ethanol, n-butanol, chlorobenzene, and ethyl acetate.

[0013] Optionally, in the formamidine hydroiodide solution containing sulfolane additive, the concentration of sulfolane additive is 0.1 mg / mL to 5 mg / mL.

[0014] Optionally, the annealing temperature is 70℃ to 150℃, and the annealing time is 1 min to 30 min.

[0015] Optionally, the thickness of the formamidinium perovskite active layer is 100 nm to 1000 nm.

[0016] Specifically, the preparation method of the above-mentioned formamidinium-based perovskite solar cell provided by the present invention includes the following steps:

[0017] Step 1: Clean the FTO glass substrate with deionized water, acetone and isopropanol in sequence using ultrasonic cleaning. Then blow away the solvent remaining on the glass substrate with nitrogen gas to obtain a clean transparent conductive substrate.

[0018] Step 2: After cleaning the conductive substrate in Step 1 and treating it with UVO, place it on a spin coater. Use a pipette to draw up the tin dioxide nanocrystal solution and spread it evenly on the substrate surface. Start the spin coater to rotate at high speed. After the rotation stops, place the substrate on a hot plate and anneal it in air to obtain the electron transport layer.

[0019] Step 3: After UVO treatment of the substrate in Step 2, place it on a spin coater in the glove box. Use a pipette to draw up the prepared lead iodide (PbI2) solution and spread it evenly on the substrate surface. Start the spin coater to rotate at high speed. After the rotation stops, place the substrate on the hot plate in the glove box for annealing. After annealing is completed and the substrate has cooled to room temperature, place the substrate back on the spin coater. Use a pipette to draw up the prepared formamidine hydroiodide (FAI) solution mixed with sulfolane cyclobutene additive and spread it evenly on the substrate surface. Quickly start the spin coater to rotate at high speed. After the rotation stops, place the substrate on the hot plate for annealing in air to obtain the formamidine-based perovskite active layer.

[0020] Step 4: Place the substrate from Step 3 on the spin coater inside the glove box. Use a pipette to draw up the prepared hole transport layer solution and spread it evenly on the substrate surface. Start the spin coater to rotate at high speed. After the rotation stops, the hole transport layer is obtained.

[0021] Step 5: A metal back electrode is fabricated on the hole transport layer on the substrate of Step 4 using a thermal evaporation method.

[0022] Furthermore, the ultrasonic cleaning time for each solvent in step 1 is 10 min to 30 min.

[0023] Furthermore, in step 2, the spin coater speed is 3000rpm~8000rpm, the rotation time is 15s~60s, the annealing temperature of the hot table is 100℃~180℃, and the annealing time is 15min~60min.

[0024] Further, in step 3, the pipette is used to draw 20 μL to 100 μL of PbI2 solution or FAI solution mixed with sulfolane cyclobutene additive, the spin coater speed is 1000 rpm to 6000 rpm, the rotation time is 20 s to 60 s, the hot plate annealing temperature is 70 ℃ to 150 ℃, and the annealing time is 1 min to 30 min.

[0025] Furthermore, in step 4, the pipette draws 30 μL to 80 μL of the hole transport layer solution, the spin coater rotates at 2000 rpm to 8000 rpm, and the rotation time is 20 s to 60 s.

[0026] Furthermore, in step 5, the pressure inside the vapor deposition chamber during vapor deposition is 9 × 10⁻⁶. -5 Pa, the thickness of molybdenum oxide is 8 nm, and the thickness of the metal Ag electrode is 80 nm to 120 nm.

[0027] The technical solution of this invention has the following advantages:

[0028] The formamidinium-based perovskite solar cell provided by this invention includes a formamidinium-based perovskite active layer. During the preparation of the formamidinium-based perovskite active layer, a formamidinium hydroiodide solution mixed with cyclobutene sulfone additive is coated onto a lead iodide film. Compared with the prior art, this invention has the following beneficial technical effects: On the one hand, cyclobutene sulfone can regulate crystallization kinetics, slow down the crystallization rate, and improve film quality through interactions with perovskite molecules, fundamentally reducing the defect state density of perovskite crystals; on the other hand, this processing technology allows cyclobutene sulfone to fully penetrate into the perovskite grain boundaries during crystallization, and the sulfonyl groups in the molecule can passivate defects at the grain boundaries, reducing the defect state density, reducing non-radiative energy loss, and improving the photoelectric conversion efficiency and stability of the device.

[0029] The method for preparing formamidine-based perovskite solar cells provided by this invention is simple, with mild and easily controllable conditions, and has broad application prospects. Attached Figure Description

[0030] To more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0031] Figure 1 This is a schematic diagram of the structure of the formamidinium-based perovskite solar cell provided by the present invention;

[0032] Figure 2 These are the JV curves of the perovskite solar cells provided in Embodiments 1, 2, and 3 of this invention;

[0033] Figure 3 These are JV curves of the perovskite solar cells of Embodiment 1 and Comparative Examples 1 and 2 of the present invention.

[0034] Figure 4 This is a graph showing the normalized power conversion efficiency of the perovskite solar cells in Examples 1-3 and Comparative Examples 1-2 of the present invention as a function of time.

[0035] Figure label:

[0036] 1. Transparent conductive substrate layer; 2. Electron transport layer; 3. Formamidinium perovskite active layer; 4. Hole transport layer; 5. Metal back electrode. Detailed Implementation

[0037] The following embodiments are provided to better understand the present invention and are not limited to the preferred embodiments described. They do not constitute a limitation on the content and scope of protection of the present invention. Any product that is the same as or similar to the present invention, derived by any person under the guidance of the present invention or by combining the features of the present invention with other prior art, falls within the protection scope of the present invention.

[0038] For experiments not specifically described in the examples, the procedures or conditions should be followed according to the conventional experimental procedures described in the literature in this field. Reagents or instruments whose manufacturers are not specified are all commercially available conventional reagent products.

[0039] The present invention provides a formamidine-based perovskite solar cell, comprising a formamidine-based perovskite active layer, wherein the formamidine-based perovskite active layer is prepared by coating a lead iodide film with a formamidine hydroiodate solution mixed with cyclobutene sulfone additive.

[0040] The structural schematic diagram of the formamidinium-based perovskite solar cell provided by this invention is shown below. Figure 1 As shown, it includes a transparent conductive substrate layer 1, an electron transport layer 2, a formamidinium perovskite active layer 3, a hole transport layer 4, and a metal back electrode 5, which are arranged sequentially.

[0041] This invention provides a method for preparing a formamidinium-based perovskite solar cell, comprising the following steps:

[0042] An electron transport layer, a formamidinium perovskite active 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 perovskite solar cell.

[0043] During the preparation of the formamidinium-based perovskite active layer, a formamidinium hydroiodate solution mixed with cyclobutene sulfone additive is coated onto a lead iodide film.

[0044] In this invention, the transparent conductive substrate is preferably ITO glass, FTO glass, AZO glass, or conductive PET, and more preferably FTO glass. This invention does not impose any special restrictions on the source of the transparent conductive substrate; commercially available products well-known to those skilled in the art can be used. In this invention, the transparent conductive substrate is preferably cleaned with deionized water, acetone, and isopropanol for 15-30 minutes each before use, and then dried with a nitrogen gun.

[0045] In this invention, the electron transport layer is preferably SnO2, TiOx, NiOx, CuOx, CuSCN, CuPc, or C. 60The electron transport layer and its derivatives, more preferably SnO2, are used. The thickness of the electron transport layer is preferably 10 nm to 200 nm, more preferably 20 nm to 100 nm. This invention does not impose any particular limitation on the method for forming the electron transport layer on a conductive substrate; any electron transport layer preparation method well known to those skilled in the art can be used.

[0046] In this invention, the preferred method for preparing the FAI solution containing cyclobutene sulfone is as follows: FAI, MACl, and cyclobutene sulfone are dissolved in a solvent, stirred at room temperature until completely dissolved, and then impurities in the mixed solution are filtered out using a polytetrafluoroethylene filter (0.22 μm) to obtain a pure solution.

[0047] In this invention, the organic solvent used in the FAI solution containing cyclobutene sulfone is preferably one of isopropanol (IPA), ethanol, and ethyl acetate, and more preferably, the solvent of the solution is IPA.

[0048] In this invention, the concentration of cyclobutene sulfone in the organic salt solution is preferably 0.1 mg / mL to 5 mg / mL, more preferably 0.5 mg / mL to 2 mg / mL.

[0049] In this invention, the preferred method for preparing the formamidine-based perovskite active layer is a two-step continuous deposition method. The preferred preparation process is as follows: A substrate (2cm × 2cm) is placed on a spin coater inside a glove box. 20μL–100μL of prepared PbI₂ solution is pipetted onto the substrate surface. The spin coater is then started at high speed (1000 rpm–5000 rpm) for 10–60 seconds. After rotation stops, the substrate is placed on a heated platform inside the glove box for annealing at 80℃–150℃ for 5–30 minutes. After annealing and cooling the substrate to room temperature, place the substrate back onto the spin coater in the glove box. Use a pipette to draw 20 μL to 100 μL of the prepared FAI solution mixed with cyclobutene sulfone, spread it evenly on the substrate surface, and quickly start the spin coater to rotate at high speed of 1000 rpm to 5000 rpm for 10 to 60 seconds. After rotation stops, place the substrate on a hot plate for annealing in air at a temperature of 80℃ to 150℃ for 5 to 30 minutes and an air humidity of 30% to 40%. After annealing, a formamidinium perovskite active layer is obtained.

[0050] In this invention, the hole transport layer is preferably a Spiro-OMeTAD, P3HT, PTAA, MnOx, WOx, or 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. This invention does not impose any particular limitation on the method for forming the hole transport layer on the formamidinium perovskite active layer; any hole transport layer preparation method well known to those skilled in the art can be used.

[0051] This invention does not impose any special limitations on the type or formation method of the back electrode; any technique well-known to those skilled in the art for forming the back electrode on the hole transport layer can be used. In a preferred embodiment of this invention, the hole transport layer is transferred to a thermal evaporation apparatus, where the vacuum level reaches 9 × 10⁻⁶. -5 Under the condition of Pa, molybdenum oxide is deposited by vapor deposition to a thickness of 8 nm, and then electrode (Ag) is deposited to a thickness of 100 nm; after the vapor deposition is completed, formamidinium-based perovskite solar cell is obtained.

[0052] This invention provides a method for fabricating a formamidine-based perovskite solar cell, comprising the following steps: sequentially forming an electron transport layer, a formamidine-based perovskite active layer, a hole transport layer, and a back electrode on the surface of a transparent conductive substrate to obtain a formamidine-based perovskite solar cell. Compared with the prior art, the fabrication method provided by this invention involves coating a lead iodide film with a formamidine hydroiodate solution mixed with cyclobutene sulfone additive during the fabrication of the formamidine-based perovskite active layer. This invention has the following beneficial technical effects: on the one hand, cyclobutene sulfone can regulate crystallization kinetics, slow down the crystallization rate, and improve film quality through interactions with perovskite molecules, fundamentally reducing the defect state density of perovskite crystals; on the other hand, this processing technology allows cyclobutene sulfone to fully penetrate into the perovskite grain boundaries during crystallization, and the sulfonyl groups in the molecule can passivate defects at the grain boundaries, reducing the defect state density, reducing non-radiative energy loss, and improving the photoelectric conversion efficiency and stability of the device.

[0053] In addition, the preparation method provided by this invention is simple, mild and easy to control, and has broad application prospects.

[0054] To further illustrate the present invention, the following embodiments will be described in detail.

[0055] Example 1

[0056] This embodiment provides a formamidinium-based perovskite solar cell, the composition of which and its specific fabrication method are as follows:

[0057] Step 1: Place the FTO transparent conductive glass (2cm×2cm) in deionized water, acetone, and isopropanol and ultrasonically clean it twice for 15 minutes each. After drying with nitrogen, store it for later use.

[0058] Step 2: Dilute the tin dioxide (SnO2) stock solution with ultrapure water at a volume ratio of 1:5 and stir thoroughly to obtain a SnO2 precursor solution; place the FTO substrate in an ultraviolet ozone cleaner for 15 min; take 50 μL of SnO2 precursor solution and spread it evenly on the surface of the FTO conductive glass, and set the spin coater parameters to 3000 rpm / s and 30 s; then place it on a 150℃ hot stage in air environment for annealing for 30 min to obtain a SnO2 thin film (30 nm); place the SnO2 thin film prepared above in an ultraviolet ozone cleaner for 15 min for subsequent spin coating.

[0059] Step 3: Place the substrate on the spin coater in the glove box. Use a pipette to draw 50 μL of PbI2 solution (solvent is a mixture of DMF and DMSO with a volume ratio of DMF:DMSO = 9:1, concentration 1.5M, containing 5 mol% RbCl) and spread it evenly on the substrate surface. Start the spin coater to rotate at high speed. Set the spin coater parameters to 1500 rpm and 30 s. After the rotation stops, place the substrate on the hot plate in the glove box for annealing at 70℃ for 1 min. After annealing and cooling the substrate to room temperature, place the substrate on a spin coater. Use a pipette to draw 50 μL of a FAI solution containing cyclobutene sulfone (solvent is IPA, FAI concentration is 90 mg / mL, cyclobutene sulfone concentration is 1 mg / mL, and 18 mg of MACl is dissolved in each 1 mL of solution), and uniformly coat it onto the PbI2 film. Quickly start the spin coater to rotate at high speed. The spin coater parameters are set as follows: rotation speed 1800 rpm, time 30 s. After rotation stops, place the substrate on a hot stage and anneal in air at a temperature of 150℃ for 15 min and an air humidity of 30%–40%. After annealing, a formamidinium perovskite active layer (400 nm) is obtained.

[0060] Step 4: Take 60 μL of Spiro-OMeTAD solution (prepared by dissolving 90 mg Spiro-OMeTAD, 21 μL of LiTFSI solution (520 mg Li-TFSI dissolved in 1 mL of acetonitrile), 39 μL of 4-tert-butylpyridine, and 15 μL of Co(III)TFSI (300 mg Co(III)TFSI dissolved in 1 mL of acetonitrile) in 1 mL of chlorobenzene solvent) and spin coat it onto the prepared formamidinium perovskite film. Set the spin coater parameters to 5000 rpm / s and 30 s to obtain the hole transport layer.

[0061] Step 5: Finally, perform vapor deposition using a high-vacuum evaporation equipment, with a pressure of 9 × 10⁻⁶ ppm inside the deposition chamber. -5Pa first deposits molybdenum oxide to a thickness of 8 nm, then deposits a metal Ag electrode to a thickness of 100 nm to obtain a perovskite solar cell device.

[0062] Example 2

[0063] This embodiment provides a formamidine-based perovskite solar cell, which differs from Embodiment 1 in that the concentration of cyclobutene sulfone in step 3 is 0.5 mg / mL.

[0064] Example 3

[0065] This embodiment provides a formamidine-based perovskite solar cell, which differs from Embodiment 1 in that the concentration of cyclobutene sulfone in step 3 is 1.5 mg / mL.

[0066] Comparative Example 1

[0067] This comparative example provides a formamidine-based perovskite solar cell, which differs from Example 1 in that the FAI solution in step 3 does not contain cyclobutene sulfone.

[0068] Comparative Example 2

[0069] This comparative example provides a formamidine-based perovskite solar cell. The difference from Example 1 is that in step 3, when preparing the formamidine-based perovskite active layer, there is no cyclobutene sulfone in the FAI solution. Instead, a cyclobutene sulfone film is deposited on the surface of the prepared perovskite active layer as a modification layer.

[0070] The specific steps for preparing a sulfolane film as a modification layer are as follows: Place the substrate (2cm×2cm) with the prepared perovskite active layer on a spin coater in a glove box. Use a pipette to draw 50μL of the prepared sulfolane solution (solvent is IPA, concentration 1.0mg / mL) and spread it evenly on the substrate surface. Start the spin coater to rotate at high speed of 5000rpm for 30s. After the rotation stops, place it on a hot plate in the glove box for annealing at 100℃ for 10min. After annealing, the sulfolane modified layer is obtained.

[0071] Test case

[0072] The perovskite solar cells provided in the embodiments and comparative examples of this invention were subjected to performance testing. The specific testing methods are as follows:

[0073] The current density-voltage (JV) curves of the perovskite solar cells prepared in the PCE test examples and comparative examples were obtained. The tests were conducted on a Kethley 2400 system under the following conditions: simulated light intensity of 100 mW / cm². -2 (AM 1.5G) Scan rate is 0.1V s -1(Step size 0.02V, time delay 200ms), scan range 1.2V to -0.2V, xenon lamp power output calibrated by NERL (National Renewable Energy Laboratory) standard KG5 Si cell.

[0074] Stability testing was conducted on unencapsulated perovskite solar cell devices at room temperature in a nitrogen glove box.

[0075] The specific test results are shown in the table below:

[0076] Table 1

[0077]

[0078] From the examples and comparative examples Figure 2-4 As shown in Table 1, in the preparation of the formamidinium-based perovskite active layer, a formamidinium hydroiodide solution mixed with cyclobutene sulfone is coated onto the lead iodide film (Examples 1-3). Compared with devices without this additive (Comparative Example 1) and devices where a cyclobutene sulfone film is deposited as a modification layer on the surface of the prepared perovskite active layer instead of using the cyclobutene sulfone additive (Comparative Example 2), the photoelectric properties such as open-circuit voltage, short-circuit current density, and fill factor are all improved. The perovskite solar cell devices prepared using the method of this invention have the advantages of high photoelectric conversion efficiency and strong stability.

[0079] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

Claims

1. A formamidinium-based perovskite solar cell, comprising a formamidinium-based perovskite active layer, characterized in that, During the preparation of the formamidinium-based perovskite active layer, a formamidinium hydroiodate solution mixed with cyclobutene sulfone additive is coated onto a lead iodide film.

2. The formamidinium-based perovskite solar cell according to claim 1, characterized in that, It includes a transparent conductive substrate layer, an electron transport layer, a formamidinium perovskite active layer, a hole transport layer, and a metal back electrode arranged sequentially.

3. A method for preparing the formamidinium-based perovskite solar cell according to claim 2, characterized in that, The process includes the following steps: sequentially fabricating an electron transport layer, a formamidinium perovskite active layer, a hole transport layer, and a metal back electrode on the surface of a transparent conductive substrate; The preparation steps of the formamidinium-based perovskite active layer include: A lead iodide solution is coated onto the surface of the electron transport layer, annealed, and cooled. A formamidinium hydroiodate solution mixed with cyclobutene sulfone additive is coated onto the lead iodide film and annealed to obtain the formamidinium-based perovskite active layer.

4. The method for preparing a formamidinium-based perovskite solar cell according to claim 3, characterized in that, In the formamidinium hydroiodide solution containing sulfolane additive, the solvent is selected from at least one of isopropanol, ethanol, n-butanol, chlorobenzene, and ethyl acetate.

5. The method for preparing a formamidinium-based perovskite solar cell according to claim 3, characterized in that, In the formamidinium hydroiodide solution containing sulfolane additive, the concentration of sulfolane additive is 0.1 mg / mL to 5 mg / mL.

6. The method for preparing a formamidinium-based perovskite solar cell according to claim 3, characterized in that, The annealing temperature is 70℃~150℃, and the annealing time is 1min~30min.

7. The method for preparing a formamidinium-based perovskite solar cell according to claim 3, characterized in that, The thickness of the formamidinium perovskite active layer is 100 nm to 1000 nm.

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