A perovskite solar cell based on a non-fullerene acceptor material as a SnO2 interface modification layer and its fabrication method.

Abstract

A perovskite solar cell based on a non-fullerene acceptor material as a SnO2 interface modification layer and a preparation method thereof belong to the technical field of solar cells. The prepared solar cell adopts an n-i-p positive type structure of ITO / SnO2 / BDT-IC / Perovskite / Spiro-OMeTAD / Ag. In the application, a non-fullerene acceptor molecule BDT-IC based on benzodithiophene as a central core is used as an interface modification layer of the SnO2 electron transport layer, and a method for preparing a perovskite solar cell is further prepared. Using the material and device preparation method described in the application, the defects (for example, uncoordinated Pb ions) at the interface between the electron transport layer and the perovskite can be effectively passivated, the non-radiative recombination of the interface carriers is inhibited, the photovoltaic performance parameters such as open circuit voltage and short circuit current are increased, and the device performance is optimized. At the same time, the device preparation process is simplified, and the device stability is improved.

Description

Technical Field

[0001] This invention belongs to the field of solar cell technology, specifically relating to a perovskite solar cell based on a non-fullerene acceptor material as a SnO2 interface modification layer and its preparation method. Background Technology

[0002] Perovskite solar cells have attracted worldwide attention due to their unique photoelectric properties, such as low bandgap, high absorption coefficient, high carrier mobility, and long exciton diffusion length. Over the past decade, the power conversion efficiency of perovskite solar cells has rapidly increased from 3.8% to 25.2%. In perovskite solar cells, the electron transport layer extracts photogenerated electrons from the perovskite light-absorbing layer and transports them to the cathode. Therefore, the photoelectric properties of the transport layer / perovskite interface have a significant impact on the photovoltaic performance and long-term stability of the device. Traditional inorganic electron transport layer materials such as TiO2 and SnO2 have the advantage of high carrier mobility, but these materials require very high processing temperatures and suffer from drawbacks such as energy level mismatch at the perovskite interface and high interface defect state density. In contrast, n-type organic semiconductor materials have advantages such as diverse structures, easily tunable energy levels, low-temperature processing capabilities, and the ability of functional groups to effectively passivate perovskite defects, forming a complementary advantage with inorganic electron transport layer materials. Therefore, using n-type organic semiconductors to modify the interface of materials such as TiO2 and SnO2 can further improve device performance. Commonly used fullerene derivatives such as PC are employed. 61 BM modifies TiO2 and SnO2. With the rapid development of novel high-efficiency non-fullerene acceptor materials in recent years, non-fullerene acceptor materials have attracted increasing attention as efficient electron transport materials or interface modification materials. Non-fullerene n-type organic semiconductors possess some unique advantages, such as molecular structure diversity, ease of modification, tunable frontier molecular orbitals, and good stability. Therefore, the development of novel n-type organic semiconductor interface modification materials is of great significance for the development of high-efficiency and stable perovskite solar cell devices. Summary of the Invention

[0003] The purpose of this invention is to provide a perovskite solar cell based on a non-fullerene acceptor material as the SnO2 interface modification layer and its fabrication method. By using the BDT-IC non-fullerene acceptor material of this invention to modify SnO2, the electron extraction properties on the cathode side of the cell can be effectively improved, while passivating interface defects and improving the photoelectric conversion efficiency of the device.

[0004] The solar cell fabricated in this invention employs a nip positive structure of ITO conductive glass / SnO2 / BDT-IC / Perovskite / Spiro-OMeTAD / Ag, where n represents the electron transport layer SnO2, i represents the intrinsic perovskite layer Perovskite, and p represents the hole transport layer Spiro-OMeTAD. ITO conductive glass serves as the substrate (ITO: indium tin oxide), SnO2 is the electron transport layer, the non-fullerene acceptor material BDT-IC is the interface modification layer for the SnO2 electron transport layer, and Perovskite is an organic-inorganic hybrid ion (CsPbI3). 1-x-y (FAPbI3) x (MAPbBr3) y The perovskite absorber layer has x ranging from 0.5 to 1 and y ranging from 0 to 0.5, with x + y ≤ 1; Spiro-OMeTAD is a 2,2',7,7'-tetratetra[N,N-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene hole transport layer, and Ag is a silver electrode. This invention introduces a non-fullerene acceptor material, BDT-IC, as an interface modification layer between the traditional electron transport layer and the perovskite absorber layer. The aim is to passivate defects at the electron transport layer and perovskite interface and improve electron extraction efficiency, thereby enhancing the photovoltaic performance of the device. All raw materials used in this invention are commercially available.

[0005] The present invention discloses a method for preparing a perovskite solar cell based on a non-fullerene acceptor material as a SnO2 interface modification layer, the specific steps of which are as follows:

[0006] 1) The ITO conductive glass substrate (5-10nm×20-30nm) was ultrasonically treated with detergent, deionized water, acetone and isopropanol for 15-20min respectively, then dried with nitrogen, and then sent to the ultraviolet ozone cleaner for 10-15min to obtain a clean substrate.

[0007] 2) Preparation of SnO2 nanoparticle aqueous solution for electron transport layer: Measure 0.5-1.5 mL of 10%-20% SnO2 nanoparticle aqueous dispersion, add 1-4 mL of deionized water, and stir magnetically for 3-6 h to obtain SnO2 nanoparticle aqueous solution.

[0008] 3) Preparation of Spiro-OMeTAD solution for hole transport layer: Weigh 70-80 mg Spiro-OMeTAD and add it to 0.5-1.5 mL of ultra-dry chlorobenzene solvent. Stir for 5-10 h and then filter to obtain Spiro-OMeTAD filtrate solution; Weigh 520-780 mg lithium salt LiTFSI and dissolve it in 1-1.5 mL of ultra-dry acetonitrile solvent. Stir for 1-3 h to obtain LiTFSI solution; Add 15-20 μL of LiTFSI solution and 20-30 μL of 4-tert-butylpyridine (tBP) to 0.5-1.5 mL of Spiro-OMeTAD filtrate solution. Stir for 1-3 h to obtain Spiro-OMeTAD solution;

[0009] 4) Preparation of BDT-IC solution, a two-dimensional non-fullerene acceptor material: Weigh 3-10 mg of BDT-IC solid and dissolve it in 0.5-1.5 mL of ultra-dry chlorobenzene solvent. Stir under nitrogen protection for 10-12 h to obtain BDT-IC solution. The molecular structure of the two-dimensional non-fullerene acceptor material BDT-IC is shown in formula (I).

[0010]

[0011] 5) Spin-coat the ITO surface of the clean substrate in step 1) with the SnO2 nanoparticle aqueous solution obtained in step 2) for 20-40 seconds at 2000-4000 rpm, and then anneal the substrate under nitrogen protection at 140-160°C for 20-40 minutes to obtain a SnO2 electron transport layer on the ITO surface.

[0012] 6) Spin-coat the BDT-IC solution obtained in step 4) onto the surface of the SnO2 electron transport layer at 2000-4000 rpm for 20-40 seconds, then anneal the obtained device under nitrogen protection at 80-120°C for 5-10 minutes, and finally cool it to room temperature under nitrogen protection to obtain the BDT-IC interface modification layer.

[0013] 7) Preparation of the mixed ion perovskite layer: First, spin-coat the surface of the BDT-IC interface modification layer obtained in step 6) with 40-100 μL of DMF at 3000-5000 rpm for 5-15 seconds, and then rinse the BDT-IC interface modification layer with DMF solvent; then, the mixed ion (CsPbI3) layer is prepared. 1-x-y (FAPbI3) x (MAPbBr3) yThe perovskite solution (x ranges from 0.5 to 1, y ranges from 0 to 0.5, and x + y ≤ 1) was spin-coated onto the BDT-IC interface modification layer in two stages. First, it was spin-coated at a low speed of 500 to 1500 rpm for 5 to 15 seconds, followed by spin-coating at a high speed of 4000 to 6000 rpm for 30 to 40 seconds. During the first 10 to 20 seconds of the high-speed spin-coating, 50 to 150 μL of chlorobenzene anti-solvent was rapidly dropped onto the surface of the perovskite layer. Finally, the spin-coated device was annealed at 60 to 70 °C for 3 to 5 minutes, and then annealed at 130 to 150 °C for 5 to 15 minutes under nitrogen protection to obtain the perovskite light-absorbing layer.

[0014] Mixed ions (CsPbI3) 1-x-y (FAPbI3) x (MAPbBr3) y Preparation of perovskite solution: Weigh 200–500 mg of lead iodide (PbI₂) powder, 80–200 mg of formamidinium iodide (FAI) powder, 0–200 mg of lead bromide (PbBr₂) powder, 0–70 mg of methyl bromide (MABr) powder, and 0–80 mg of cesium iodide (CsI). Then add 480–640 μL of N,N-dimethylformamide and 120–160 μL of dimethyl sulfoxide solvent. Stir at room temperature for 1–3 hours to obtain a mixed-ion (CsPbI₃) solution. 1-x-y (FAPbI3) x (MAPbBr3) y The perovskite solution contains x ranging from 0.5 to 1 and y ranging from 0 to 0.5, with x + y ≤ 1; FA represents formamidinium ions and MA represents methylamine ions.

[0015] 8) The surface of the perovskite light-absorbing layer obtained in step 7) is spin-coated with the Spiro-OMeTAD solution obtained in step 3) at 3000-5000 rpm for 30-40 seconds, and then oxidized in oxygen for 4-6 hours to obtain the Spiro-OMeTAD hole transport layer.

[0016] 9) A layer of Ag with a thickness of 90-100 nanometers is vacuum deposited on the surface of the Spiro-OMeTAD hole transport layer, and then oxidized in oxygen for 4-6 hours to obtain the perovskite solar cell based on the SnO2 interface modification layer of the non-fullerene acceptor material described in this invention.

[0017] This invention introduces a non-fullerene acceptor material with n-type semiconductor properties into a perovskite solar cell as an interface modification layer between the perovskite light-absorbing layer and the electron transport layer. This modification to the device structure has the following advantages:

[0018] 1) Using BDT-IC as an interface modification layer can effectively passivate defects at the electron transport layer and perovskite interface (e.g., uncoordinated Pb ions), suppress nonradiative recombination of interface carriers, and increase photovoltaic performance parameters such as open-circuit voltage and short-circuit current.

[0019] 2) BDT-IC non-fullerene acceptors can promote electron extraction and electron transport properties.

[0020] 3) The BDT-IC non-fullerene acceptor has the lowest unoccupied molecular orbital (LUMO: 3.85 eV) and the highest occupied molecular orbital (HOMO: 5.4 eV) energy levels, which can better match the energy level structure of perovskite and reduce the energy loss during interface charge extraction.

[0021] 4) BDT-IC can provide carbonyl (C=O) and cyano (C≡N) groups, with the N and O atoms in the terminal groups acting as electron donors. Therefore, the carbonyl and cyano groups are expected to passivate uncoordinated Pb defects in the perovskite layer through coordination between Lewis acids and bases.

[0022] As a preferred experimental scope of the present invention, we first optimized the concentration of the BDT-IC solution used as the electron transport layer. In step 4), we prepared BDT-IC solutions with concentrations of 3–10 mg / mL. Then, based on the optimal BDT-IC concentration, we optimized the annealing temperature after spin-coating the BDT-IC and whether to perform DMF solvent rinsing on the BDT-IC, thereby obtaining the optimal device performance. Attached Figure Description

[0023] Figure 1 : A schematic diagram of the structure of the perovskite solar cell based on a non-fullerene acceptor material as the SnO2 interface modification layer according to the present invention; as shown. Figure 1 As shown, the solar cell prepared by the present invention consists of an ITO conductive glass substrate, a SnO2 electron transport layer, a BDT-IC interface modification layer, a Perovskite perovskite light-absorbing layer, a Spiro-OMeTAD hole transport layer, and an Ag electrode.

[0024] Figure 2 Schematic diagram of the energy levels of a perovskite solar cell based on a non-fullerene acceptor material as the SnO2 interface modification layer. As can be seen from the figure, the HOMO and LUMO energy levels of BDT-IC are energy-matched with the other functional layers, ensuring low energy loss during interface charge transport. Using BDT-IC as the interface modification layer for the SnO2 electron transport layer is beneficial for improving electron extraction.

[0025] Figure 3In Example 1 of this invention, the JV curves of SnO2-modified solar cells using solutions of different BDT-IC concentrations are shown. Curves 1-5 correspond to the control group device without a BDT-IC interface transport layer prepared according to the method of Example 1, and the devices modified with BDT-IC solutions of concentrations of 3, 5, 7, and 10 mg / mL, respectively. Figure 3 As shown in the figure, the photovoltaic performance parameters of the cell increased after adding the BDT-IC interface modification layer. The figure also shows that the efficiency of the control group device was 17.34%, and the short-circuit current was 22.3 mA / cm². 2 The open-circuit voltage was 1.08V, and the fill factor was 72%. When the BDT-IC solution concentration was 3mg / mL, the device efficiency increased to 18.74%, and the open-circuit voltage and fill factor were both improved to 1.10V and 75%. When the BDT-IC solution concentration was 5mg / mL, the device efficiency was 19.40%, and the short-circuit current was 23.1mA / cm. 2 The open-circuit voltage was 1.12V, and the fill factor was 75%. The optimal device efficiency was achieved at a BDT-IC concentration of 7 mg / mL, increasing the efficiency to 21.16%, with a short-circuit current of 23.8 mA / cm². 2 The open-circuit voltage was 1.14V, and the fill factor was 78%. Further increasing the solution concentration to 10mg / mL reduced the device efficiency to 19.93%, and the short-circuit current to 22.9mA / cm². 2 The open-circuit voltage is 1.13V, and the fill factor is 77%.

[0026] Figure 4 Example 2 of this invention shows the JV curves of solar cells prepared with a BDT-IC interface modification layer at different annealing temperatures. Curves 1-3 correspond to BDT-IC annealing temperatures of 80, 100, and 120℃, respectively. Figure 4 As shown, 1) when the annealing temperature is 80℃, the device efficiency after annealing is 19.7%, and the short-circuit current is 24mA / cm. 2 The open-circuit voltage is 1.08V, and the fill factor is 76%; 2) When the annealing temperature is 100℃, the annealing effect is optimal, which helps to reduce the structural defects of the thin film. The device efficiency is 21.16%, and the short-circuit current is 23.8mA / cm. 2 The open-circuit voltage is 1.14V, and the fill factor is 78%; 3) When the annealing temperature is 120℃, the photoelectric conversion efficiency of the annealed device is 20%, and the short-circuit current is 23.5mA / cm. 2 The open-circuit voltage is 1.15V, and the fill factor is 74%.

[0027] Figure 5The JV curves of the solar cell based on the BDT-IC interface modification layer prepared in Example 3 of this invention are shown. Curve 1 and curve 2 correspond to the "no DMF rinsing step" and the "with DMF rinsing step," respectively. Figure 5 As shown, the device efficiency without the DMF washing step is 13.72%, and the short-circuit current is 21.28 mA / cm². 2 The open-circuit voltage is 1.04V, and the fill factor is 62%. For devices with a DMF washing step, the photoelectric conversion efficiency is 21.16%, and the short-circuit current is 23.8mA / cm². 2 The open-circuit voltage was 1.14V, and the fill factor was 78%. This is because DMF washing can improve the wettability of the perovskite solution at the interface, thereby improving the film quality and film coverage. Detailed Implementation

[0028] To better understand the content of this invention, the following detailed description is provided in conjunction with specific embodiments, but the scope of protection of this invention is not limited to the following embodiments.

[0029] Example 1:

[0030] 1) The patterned ITO conductive glass (7nm×25nm) substrate was ultrasonically treated for 15 minutes with detergent (any commercially available detergent is acceptable), deionized water, acetone, and isopropanol, respectively. Then it was dried with a nitrogen gun and then sent to an ultraviolet ozone cleaner for 10 minutes.

[0031] 2) Preparation of SnO2 nanoparticle aqueous solution for electron transport layer: 1 mL of 15% SnO2 nanoparticle aqueous dispersion was taken, 4 mL of deionized water was added, and the mixture was magnetically stirred for 6 h to obtain SnO2 nanoparticle aqueous solution.

[0032] 3) Preparation of Spiro-OMeTAD solution for hole transport layer: Weigh 72.4 mg Spiro-OMeTAD and add 1 mL of ultra-dry chlorobenzene solvent. Stir for 10 h and filter to obtain Spiro-OMeTAD filtrate solution; Weigh 520 mg lithium salt LiTFSI and dissolve in 1 mL of ultra-dry acetonitrile solvent. Stir for 2 h to obtain LiTFSI solution; Add 17.6 μL of LiTFSI solution and 28.5 μL of 4-tert-butylpyridine tBP to Spiro-OMeTAD filtrate solution. Stir for 2 h to obtain Spiro-OMeTAD solution.

[0033] 4) Preparation of non-fullerene acceptor material BDT-IC solution: 3 mg, 5 mg, 7 mg and 10 mg of BDT-IC solid were weighed and dissolved in 1 mL of ultra-dry chlorobenzene solvent, and stirred for 12 h under nitrogen protection to obtain BDT-IC solutions of 3, 5, 7 and 10 mg / mL.

[0034] 5) The clean ITO surface obtained in step 1) is spin-coated with the SnO2 nanoparticle aqueous solution in step 2) at 3000 rpm for 30 seconds, and then the substrate is annealed at 150°C in nitrogen protection for 20 minutes to obtain a SnO2 electron transport layer with a thickness of about 20 nm.

[0035] 6) The BDT-IC solution prepared in step 4) was spin-coated onto the SnO2 electron transport layer at 4000 rpm for 30 seconds. The resulting device was then annealed at 100°C for 10 minutes under nitrogen protection and finally cooled to room temperature under nitrogen atmosphere to obtain the BDT-ICl interface modification layer between the electron transport layer and the perovskite layer. The film thicknesses of the interface modification layer were 5, 10, 17 and 30 nm, respectively.

[0036] 7) Preparation of mixed-ion perovskites; (CsPbI3) 0.05 (FAPbI3) 0.8 (MAPbBr3) 0.15 The perovskite solution was spin-coated onto the device obtained in step 6). Before spin-coating, the BDT-IC film was rinsed with DMF solvent, and 60 μL of DMF was dropped in and spin-coated at 4000 rpm for 10 seconds, followed by perovskite spin-coating. The spin-coating was performed in two stages: a low-speed spin-coating at 700 rpm for 6 seconds, followed by a high-speed spin-coating at 4000 rpm for 40 seconds. During the first 10 seconds of the high-speed stage, 150 μL of chlorobenzene anti-solvent was rapidly dropped onto the surface of the BDT-ICl interface modification layer. The resulting device was annealed at 60°C for 5 minutes, followed by annealing at 130°C for 10 minutes to obtain a perovskite light-absorbing layer with a thickness of approximately 450 nm.

[0037] 8) Spin-coat the Spiro-OMeTAD solution obtained in step (3) on the surface of the perovskite light-absorbing layer at 4000 rpm for 30 seconds, and then oxidize it under oxygen for 5 hours to obtain the Spiro-OMeTAD hole transport layer; the hole transport layer thickness is about 170 nm.

[0038] 9) The device is transferred to a vacuum evaporation equipment to vacuum deposit a silver electrode with a thickness of 90 nm (approximately 90 nm) on the surface of the Spiro-OMeTAD layer. Then, it is oxidized in oxygen for 4 hours to prepare the perovskite solar cell based on the SnO2 interface modification layer of the non-fullerene acceptor material described in this invention.

[0039] Example 2:

[0040] 1) The patterned ITO conductive glass (7nm×25nm) substrate was ultrasonically treated for 15 minutes with detergent (any commercially available detergent is acceptable), deionized water, acetone, and isopropanol, respectively. Then it was dried with a nitrogen gun and then sent to an ultraviolet ozone cleaner for 10 minutes.

[0041] 2) Preparation of SnO2 nanoparticle aqueous solution for electron transport layer: 1 mL of 15% SnO2 nanoparticle aqueous dispersion was taken, 4 mL of deionized water was added, and the mixture was magnetically stirred for 6 h to obtain SnO2 nanoparticle aqueous solution.

[0042] 3) Preparation of Spiro-OMeTAD solution for hole transport layer: Weigh 72.4 mg Spiro-OMeTAD and add 1 mL of ultra-dry chlorobenzene solvent. Stir for 10 h and filter to obtain Spiro-OMeTAD filtrate solution; Weigh 520 mg lithium salt LiTFSI and dissolve in 1 mL of ultra-dry acetonitrile solvent and stir for 2 h to obtain LiTFSI solution; Add 17.6 μL of LiTFSI solution and 28.5 μL of 4-tert-butylpyridine tBP to the Spiro-OMeTAD filtrate solution and stir for 2 h to obtain Spiro-OMeTAD solution;

[0043] 4) Preparation of the non-fullerene acceptor material BDT-IC solution: 7 mg of BDT-IC solid was weighed and dissolved in 1 mL of ultra-dry chlorobenzene solvent, and stirred for 12 h under nitrogen protection to obtain the BDT-IC solution. The concentration of the obtained solution was 7 mg / mL.

[0044] 5) The clean ITO surface obtained in step (1) is spin-coated with the SnO2 nanoparticle aqueous solution in step (2) at 3000 rpm for 30 seconds, and then the substrate is annealed at 150°C for 20 minutes under nitrogen protection to obtain a SnO2 electron transport layer with a thickness of about 20 nm.

[0045] 6) The BDT-IC solution prepared in step (4) was spin-coated onto the SnO2 electron transport layer at 4000 rpm for 30 seconds. The resulting device was then annealed at 80℃, 100℃ and 120℃ for 10 minutes under nitrogen protection. Finally, it was cooled to room temperature under nitrogen atmosphere to obtain the BDT-IC interface modification layer between the electron transport layer and the perovskite layer. The thickness of the obtained film was about 17 nanometers.

[0046] 7) Preparation of mixed-ion perovskites; (CsPbI3) 0.05 (FAPbI3) 0.8 (MAPbBr3) 0.15The perovskite solution was spin-coated onto the device obtained in step (6). Before spin-coating, the BDT-IC film was rinsed with DMF solvent, 60 μL of DMF was dropped in, and spin-coating was performed at 4000 rpm for 10 seconds, followed by perovskite spin-coating. The spin-coating was performed in two stages: low speed spin-coating at 700 rpm for 6 seconds, followed by high speed spin-coating at 4000 rpm for 40 seconds. During the first 10 seconds of the high speed stage, 150 μL of chlorobenzene anti-solvent was rapidly dropped onto the film surface. The obtained device was annealed at 60°C for 5 minutes, followed by annealing at 130°C for 10 minutes to obtain a perovskite light-absorbing layer with a thickness of approximately 450 nm.

[0047] 8) Spin-coat the Spiro-OMeTAD solution obtained in step (3) on the surface of the perovskite light-absorbing layer at 4000 rpm for 30 seconds, and then oxidize it under oxygen for 5 hours to obtain the Spiro-OMeTAD hole transport layer with a thickness of about 170 nm.

[0048] 9) The device is transferred to a vacuum evaporation equipment to deposit a silver electrode with a thickness of 90 nanometers on the surface of the Spiro-OMeTAD layer, and then oxidized in oxygen for 4 hours to prepare the perovskite solar cell based on the SnO2 interface modification layer of the non-fullerene acceptor material described in this invention.

[0049] Example 3:

[0050] 1) Patterned ITO conductive glass (7nm×25nm) substrates were respectively used Detergent (Any commercially available detergent can be used), deionized water, acetone, and isopropanol are ultrasonically treated for 15 minutes, then dried with a nitrogen gun, and then sent to an ultraviolet ozone cleaner for 10 minutes.

[0051] 2) Preparation of SnO2 nanoparticle aqueous solution for electron transport layer: 1 mL of 15% SnO2 nanoparticle aqueous dispersion was taken, 4 mL of deionized water was added, and the mixture was magnetically stirred for 6 h to obtain SnO2 nanoparticle aqueous solution.

[0052] 3) Preparation of Spiro-OMeTAD solution for hole transport layer: Weigh 72.4 mg Spiro-OMeTAD and add 1 mL of ultra-dry chlorobenzene solvent. Stir for 10 h and filter to obtain Spiro-OMeTAD filtrate solution; Weigh 520 mg lithium salt LiTFSI and dissolve in 1 mL of ultra-dry acetonitrile solvent and stir for 2 h to obtain LiTFSI solution; Add 17.6 μL of LiTFSI solution and 28.5 μL of 4-tert-butylpyridine tBP to the Spiro-OMeTAD filtrate solution and stir for 2 h to obtain Spiro-OMeTAD solution;

[0053] 4) Preparation of the non-fullerene acceptor material BDT-IC solution: 7 mg of BDT-IC solid was weighed and dissolved in 1 mL of ultra-dry chlorobenzene solvent, and stirred for 12 h under nitrogen protection to obtain the BDT-IC solution. The concentration of the obtained solution was 7 mg / mL.

[0054] 5) The clean ITO surface obtained in step (1) is spin-coated with the SnO2 nanoparticle aqueous solution in step (2) at 3000 rpm for 30 seconds, and then the substrate is annealed at 150°C for 20 minutes under nitrogen protection to obtain a SnO2 electron transport layer with a thickness of 20 nm.

[0055] 6) The BDT-IC solution prepared in step (4) was spin-coated onto the SnO2 electron transport layer at 4000 rpm for 30 seconds. The resulting device was then annealed at 100°C for 10 minutes under nitrogen protection. Finally, it was cooled to room temperature under nitrogen atmosphere to obtain the BDT-IC interface modification layer between the electron transport layer and the perovskite layer. The thickness of the obtained film was about 17 nanometers.

[0056] 7) Preparation of mixed-ion perovskites; (CsPbI3) 0.05 (FAPbI3) 0.8 (MAPbBr3) 0.15 The perovskite solution was spin-coated onto the device obtained in step (6). In this embodiment, the BDT-IC interface modification layer before spin-coating the perovskite was divided into two groups: "without DMF rinsing step" and "with DMF rinsing step". For the film with DMF rinsing step, 60 μL of DMF was dropped onto the film and spin-coated at 4000 rpm for 10 seconds, followed by spin-coating of the perovskite. The spin-coating was divided into two stages: low speed spin-coating at 700 rpm for 6 seconds, followed by high speed spin-coating at 4000 rpm for 40 seconds. 150 μL of chlorobenzene anti-solvent was rapidly dropped onto the film surface 10 seconds into the high speed stage. The obtained device was annealed at 60°C for 5 minutes, followed by annealing at 130°C for 10 minutes to obtain a perovskite light-absorbing layer with a thickness of approximately 450 nm.

[0057] 8) Spin-coat the surface of the perovskite light-absorbing layer with the Spiro-OMeTAD solution obtained in step (3) for 30 seconds at 4000 rpm, and then oxidize it under oxygen for 5 hours to obtain the Spiro-OMeTAD hole transport layer with a thickness of about 170 nm.

[0058] 9) The device is transferred to a vacuum evaporation equipment to deposit a silver electrode with a thickness of 90 nanometers on the surface of the Spiro-OMeTAD layer, and then oxidized in oxygen for 4 hours to prepare the perovskite solar cell based on the SnO2 interface modification layer of the non-fullerene acceptor material described in this invention.

Claims

1. A method for fabricating a perovskite solar cell based on a non-fullerene acceptor material as a SnO2 interface modification layer, the specific steps of which are as follows: 1) The ITO conductive glass substrate was ultrasonically treated with detergent, deionized water, acetone and isopropanol for 15-20 minutes respectively, then dried with nitrogen, and then sent to the ultraviolet ozone cleaner for 10-15 minutes to obtain a clean substrate. 2) In step 1), an aqueous solution of SnO2 nanoparticles was spin-coated onto the ITO surface of the cleaned substrate. The substrate was then annealed under nitrogen protection to obtain a SnO2 electron transport layer on the ITO surface. 3) A BDT-IC solution was spin-coated onto the surface of the SnO2 electron transport layer, and the resulting device was then annealed under nitrogen protection. Finally, it was cooled to room temperature under nitrogen protection to obtain the BDT-IC interface modification layer. 4) Preparation of the mixed-ion perovskite layer: First, DMF is spin-coated onto the surface of the BDT-IC interface modification layer obtained in step 3), and the BDT-IC interface modification layer is rinsed with DMF solvent; then, the mixed-ion (CsPbI3) layer is prepared. 1-x-y (FAPbI3) x (MAPbBr3) y The perovskite solution was spin-coated onto the BDT-IC interface modification layer in two stages: first, low-speed spin-coating, followed by high-speed spin-coating. During the first 10–20 seconds of the high-speed spin-coating, chlorobenzene anti-solvent was rapidly added dropwise to the perovskite layer surface. Finally, the spin-coated device was annealed at 60–70°C for 3–5 minutes, then annealed under nitrogen protection at 130–150°C for 5–15 minutes to obtain the perovskite light-absorbing layer. Here, x ranges from 0.5 to 1, y ranges from 0 to 0.5, and x + y ≤ 1; FA represents formamidinium ions, and MA represents methylamine ions. 5) Spin-coat the surface of the perovskite light-absorbing layer obtained in step 4) with Spiro-OMeTAD solution, and then oxidize it under oxygen to obtain the Spiro-OMeTAD hole transport layer. 6) Ag is vacuum deposited on the surface of the Spiro-OMeTAD hole transport layer and then oxidized under oxygen to obtain a perovskite solar cell based on a non-fullerene acceptor material as the SnO2 interface modification layer.

2. The method for preparing a perovskite solar cell based on a non-fullerene acceptor material as the SnO2 interface modification layer as described in claim 1, characterized in that: Take 0.5-1.5 mL of a 10%-20% SnO2 nanoparticle aqueous dispersion, add 1-4 mL of deionized water, and stir magnetically for 3-6 hours to obtain an aqueous solution of SnO2 nanoparticles.

3. The method for preparing a perovskite solar cell based on a non-fullerene acceptor material as the SnO2 interface modification layer as described in claim 1, characterized in that: Weigh 70–80 mg of Spiro-OMeTAD and add it to 0.5–1.5 mL of ultra-dry chlorobenzene solvent. Stir for 5–10 h and then filter to obtain a Spiro-OMeTAD filtrate solution. Weigh 520–780 mg of lithium salt LiTFSI and dissolve it in 1–1.5 mL of ultra-dry acetonitrile solvent. Stir for 1–3 h to obtain a LiTFSI solution. Add 15–20 μL of LiTFSI solution and 20–30 μL of 4-tert-butylpyridine to the 0.5–1.5 mL Spiro-OMeTAD filtrate solution and stir for 1–3 h to obtain a Spiro-OMeTAD solution.

4. The method for preparing a perovskite solar cell based on a non-fullerene acceptor material as a SnO2 interface modification layer as described in claim 1, characterized in that: The solution is obtained by weighing 3-10 mg of BDT-IC solid and dissolving it in 0.5-1.5 mL of ultra-dry chlorobenzene solvent, stirring for 10-12 h under nitrogen protection.

5. The method for preparing a perovskite solar cell based on a non-fullerene acceptor material as a SnO2 interface modification layer as described in claim 1, characterized in that: Weigh out 200–500 mg of lead iodide powder, 80–200 mg of formamidinium iodide powder, 0–200 mg of lead bromide powder, 0–70 mg of methyl bromide powder, and 0–80 mg of cesium iodide. Then add 480–640 μL of N,N-dimethylformamide and 120–160 μL of dimethyl sulfoxide solvent. Stir at room temperature for 1–3 hours to obtain a mixed ion (CsPbI3). 1-x-y (FAPbI3) x (MAPbBr3) y Perovskite solution.

6. The method for preparing a perovskite solar cell based on a non-fullerene acceptor material as the SnO2 interface modification layer as described in claim 1, characterized in that: Step 2) The spin coating speed is 2000-4000 rpm, the spin coating time is 20-40 seconds, the annealing temperature is 140-160℃, and the annealing time is 20-40 minutes.

7. The method for preparing a perovskite solar cell based on a non-fullerene acceptor material as the SnO2 interface modification layer as described in claim 1, characterized in that: Step 3) The spin coating speed is 2000-4000 rpm, the spin coating time is 20-40 seconds, and the annealing conditions are annealing at 80-120℃ for 5-10 minutes.

8. The method for preparing a perovskite solar cell based on a non-fullerene acceptor material as a SnO2 interface modification layer as described in claim 1, characterized in that: Step 4) Spin coat DMF at 3000-5000 rpm for 5-15 seconds; then spin coat at a low speed of 500-1500 rpm for 5-15 seconds, followed by spin coat at a high speed of 4000-6000 rpm for 30-40 seconds.

9. The method for preparing a perovskite solar cell based on a non-fullerene acceptor material as a SnO2 interface modification layer as described in claim 1, characterized in that: The oxidation time for steps 5) and 6) is 4 to 6 hours.

10. A perovskite solar cell based on a non-fullerene acceptor material as a SnO2 interface modification layer, characterized in that: It is prepared by the method described in any one of claims 1 to 9.

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