Perovskite cell based on fullerene derivative electron transport layer and preparation method thereof

Abstract

The application provides a perovskite cell based on a fullerene derivative electron transport layer and a preparation method thereof. The inverted structure perovskite cell is obtained by treating fullerene derivative with 2-methylanisole to prepare an electron transport layer. The preparation method has the advantages of being green and harmless by using 2-methylanisole to dissolve fullerene derivative to prepare a thin film. The fullerene derivative thin film prepared by using 2-methylanisole as a solvent is uniform and smooth, and can improve the short-circuit current density of the inverted structure perovskite cell, thereby improving the photoelectric conversion efficiency of the inverted structure perovskite cell.

Description

Technical Field

[0001] This application relates to the field of solar cell technology, and in particular to a perovskite solar cell based on a fullerene derivative electron transport layer and its preparation method. Background Technology

[0002] Perovskite solar cells are a type of solar cell that uses perovskite-type organometal halide semiconductors as light-absorbing materials. As a novel type of solar cell, they have advantages such as high photoelectric conversion efficiency and low production cost. Perovskite solar cells are generally divided into upright and inverted structures. In the inverted structure, the structure typically consists of, from bottom to top, a transparent substrate material, a transparent conductive oxide, a hole transport layer, a perovskite light-absorbing layer, an electron transport layer, and a top electrode.

[0003] Perovskite solar cells have enormous potential to replace crystalline silicon solar cells. However, the fabrication of perovskite solar cells, whether using spin coating or large-scale blade coating, involves solution processing. Fullerene derivatives are commonly used electron transport layer materials in high-efficiency inverted perovskite solar cells, and their processing typically employs solution methods. These methods often utilize halogen-containing organic aromatic solvents, such as chlorobenzene, o-dichlorobenzene, and chloroform. Studies have shown that long-term exposure to chlorinated organic solvents like chloroform and chlorobenzene increases the risk of cancer, and chlorobenzene (and similarly, chloroform and o-dichlorobenzene) can also have harmful effects on respiratory organs. Furthermore, these halogen elements have poor degradation capabilities in nature, polluting water sources and soil; for example, chlorobenzene causes severe ecological pollution. Halogen-containing organic aromatic solvents are not only harmful to human health but also to the environment. Therefore, avoiding the use of harmful halogen-containing organic aromatic solvents is a crucial issue that must be addressed in the development of perovskite solar cells. Summary of the Invention

[0004] The purpose of this application is to provide a perovskite solar cell based on a fullerene derivative electron transport layer and its fabrication method, so as to obtain an inverted perovskite solar cell that is more environmentally friendly and has high photoelectric conversion efficiency. The specific technical solution is as follows:

[0005] The first aspect of this application provides a method for preparing a perovskite solar cell based on a fullerene derivative electron transport layer, which includes the following steps:

[0006] A hole transport layer is prepared on the surface of a conductive substrate;

[0007] A perovskite precursor liquid is coated on the surface of the hole transport layer, and then annealed to obtain a perovskite light-absorbing layer.

[0008] A fullerene derivative and an additive are added to 2-methyl anisole and stirred for 1 to 6 hours to obtain a fullerene derivative solution; wherein the fullerene derivative is selected from at least one of [6,6]-phenyl-C61-butyrate methyl ester and [6,6]-phenyl-C71-butyrate methyl ester; the additive is selected from silane coupling agents and diiodoalkane; the silane coupling agent is selected from aminosilane coupling agents or mercaptosilane coupling agents, and the concentration of the fullerene derivative is 10 to 30 mg / mL;

[0009] The fullerene derivative solution was coated onto the surface of the perovskite light-absorbing layer and dried to obtain an electron transport layer.

[0010] A buffer layer is prepared on the surface of the electron transport layer, wherein the material of the buffer layer is selected from copper bath or N-type semiconductor metal oxide;

[0011] A metal electrode is fabricated on the surface of the buffer layer to obtain a perovskite solar cell.

[0012] In one embodiment of this application, the molar percentage of the silane coupling agent is 1% to 5% based on the mass of the fullerene derivative.

[0013] In one embodiment of this application, the diiodoalkane is selected from diiodohexane, diioheptane, diiooctane, diiononane, diiodecane, diiodoundecane, or diiodododecane.

[0014] In one embodiment of this application, the molar percentage of the diiodoalkane is 1% to 5% based on the mass of the fullerene derivative.

[0015] In one embodiment of this application, the silane coupling agent has the molecular formula Y-R1-Si(OR2)3, where Y is selected from -NH2 group or -SH group, and R1 is selected from -(CH2) group. n - indicates a chain-like alkylene group, where n is an integer from 1 to 3, and R2 is selected from a straight-chain alkyl group having 1 to 2 carbon atoms.

[0016] In one embodiment of this application, the thickness of the buffer layer is 1–30 nm.

[0017] In one embodiment of this application, the preparation method of the buffer layer includes: dissolving copper hydroxide in isopropanol, stirring until homogeneous to obtain a copper hydroxide solution, wherein the concentration of the copper hydroxide is 0.3–1 mg / mL; and coating the copper hydroxide solution onto the surface of the electron transport layer to obtain the buffer layer. Alternatively, an N-type semiconductor metal oxide is deposited on the surface of the electron transport layer by atomic layer deposition or magnetron sputtering to obtain the buffer layer, wherein the N-type semiconductor metal oxide is selected from zinc aluminum oxide, zinc tin oxide, tin oxide, zinc oxide, or titanium dioxide.

[0018] In one embodiment of this application, the perovskite precursor liquid is prepared by: adding an A-containing halide and a B-containing halide as solutes to a solvent, stirring for 3 to 10 hours to obtain the perovskite precursor liquid; wherein, the A-containing halide is selected from at least one of formamidine iodide, methylamine iodide, cesium iodide, rubidium iodide, potassium iodide, and methylamine bromide; the B-containing halide is selected from at least one of lead iodide and lead bromide; the solvent is selected from at least one of N,N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, and γ-butyrolactone; the concentration of the A-containing halide is 0.5 to 2.0 mol / L; and the concentration of the B-containing halide is 0.5 to 2.0 mol / L.

[0019] In one embodiment of this application, the annealing temperature of the perovskite light-absorbing layer is 90–200°C, and the annealing time is 10–100 min.

[0020] In one embodiment of this application, the perovskite light-absorbing layer contains a perovskite compound ABX3, wherein A in ABX3 is selected from at least one of MA, FA, Cs, Rb and K, B is selected from Pb, and X is selected from at least one of I, Br and Cl.

[0021] A second aspect of this application provides a perovskite solar cell prepared by the method described in any of the above embodiments.

[0022] The beneficial effects of this application are:

[0023] This application provides a perovskite solar cell based on a fullerene derivative electron transport layer and its preparation method. The method involves treating the fullerene derivative with 2-methylanisole instead of a halogen-containing organic aromatic ring solvent to prepare the electron transport layer, thus obtaining the perovskite solar cell. Compared to treating fullerene derivatives with chlorobenzene, treatment with 2-methylanisole results in smaller particle sizes of the fullerene derivative within the 2-methylanisole solution, leading to a more uniform and smoother film formation. This enhances the electron extraction and electron transport capabilities of the electron transport layer in the 2-methylanisole-treated fullerene derivative, which is beneficial for improving the short-circuit current density and photoelectric conversion efficiency of the inverted perovskite solar cell. The photoelectric conversion efficiency of the perovskite solar cell based on the 2-methylanisole-treated fullerene derivative electron transport layer is significantly higher than that of the perovskite solar cell using chlorobenzene as the solvent.

[0024] The perovskite solar cell preparation method provided in this application uses 2-methyl anisole instead of halogen-containing organic aromatic ring solvents, which has the advantages of being green, harmless, and environmentally friendly. The method can increase the short-circuit current density of inverted perovskite solar cells, thereby improving photoelectric conversion efficiency. The inverted perovskite solar cells prepared by the method of this application are not only more environmentally friendly but also have high photoelectric conversion efficiency. Of course, implementing any product or method of this application does not necessarily require achieving all the advantages described above simultaneously. Attached Figure Description

[0025] To more clearly illustrate the technical solutions of this application and the prior art, the accompanying drawings used in the embodiments and the prior art are briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other embodiments can be obtained based on these accompanying drawings.

[0026] Figure 1a This is a surface morphology image of the [6,6]-phenyl-C61-butyrate methyl ester (PC61BM) film in the perovskite battery prepared in Example 1 of this application;

[0027] Figure 1b The image shows the surface morphology of the PC61BM film in the perovskite solar cell prepared in Comparative Example 1 of this application.

[0028] Figure 2a This is a laser confocal microscope image of the PC61BM thin film in the perovskite solar cell prepared in Example 1 of this application;

[0029] Figure 2b Laser confocal microscopy image of the PC61BM thin film in the perovskite solar cell prepared in Comparative Example 1 of this application;

[0030] Figure 3a The current density-voltage curves of the perovskite solar cells prepared in Example 1 and Comparative Example 1 of this application are shown.

[0031] Figure 3b The current density-voltage curves of the perovskite solar cells prepared in Example 2 and Comparative Example 1 of this application are shown.

[0032] Figure 3c The current density-voltage curves of the perovskite solar cells prepared in Example 3 and Comparative Example 1 of this application are shown.

[0033] Figure 3d The current density-voltage curves of the perovskite solar cells prepared in Example 4 and Comparative Example 1 of this application are shown.

[0034] Figure 3eThe current density-voltage curves of the perovskite solar cells prepared in Example 5 and Comparative Example 1 of this application are shown.

[0035] Figure 3f The current density-voltage curves of the perovskite solar cells prepared in Example 6 and Comparative Example 1 of this application are shown.

[0036] Figure 3g The current density-voltage curves of the perovskite solar cells prepared in Example 7 and Comparative Example 1 of this application are shown.

[0037] Figure 3h The current density-voltage curves of the perovskite solar cells prepared in Example 8 and Comparative Example 1 of this application are shown.

[0038] Figure 3i The current density-voltage curves of the perovskite solar cells prepared in Example 9 and Comparative Example 1 of this application are shown.

[0039] Figure 3j This is a current density-voltage curve of the perovskite solar cells prepared in Example 10 and Comparative Example 1 of this application. Detailed Implementation

[0040] To make the objectives, technical solutions, and advantages of this application clearer, the following detailed description is provided with reference to the accompanying drawings and embodiments. Obviously, the described embodiments are merely some embodiments of this application, and not all embodiments. All other technical solutions obtained by those skilled in the art based on the embodiments of this application fall within the scope of protection of this application.

[0041] Fullerene derivatives exhibit superior performance as electron transport layers in inverted perovskite solar cells. Currently, chlorobenzene is commonly used as a solvent for fullerene derivatives in the perovskite solar cell field. However, chlorobenzene is harmful not only to humans but also to the environment. Extensive research by the inventors revealed that among common solvents, those with high solubility for fullerene derivatives are mostly halogenated organic aromatic ring solvents, while alcohols are almost insoluble. Therefore, considering the harmfulness of solvents to humans and the environment, selecting a more environmentally friendly solvent as a substitute for chlorobenzene in the preparation of inverted perovskite solar cells, while achieving higher photoelectric conversion efficiency, is of great significance for the development of inverted perovskite solar cells.

[0042] In view of this, the first aspect of this application provides a method for preparing a perovskite solar cell based on a fullerene derivative electron transport layer, which includes the following steps:

[0043] A hole transport layer is prepared on the surface of a conductive substrate;

[0044] A perovskite precursor liquid was coated on the surface of the hole transport layer, and then annealed to obtain a perovskite light-absorbing layer.

[0045] A fullerene derivative and an additive are added to 2-methyl anisole and stirred for 1 to 6 hours to obtain a fullerene derivative solution; wherein the fullerene derivative is selected from at least one of [6,6]-phenyl-C61-butyrate methyl ester and [6,6]-phenyl-C71-butyrate methyl ester; the additive is selected from silane coupling agents and diiodoalkane; the silane coupling agent is selected from aminosilane coupling agents or mercaptosilane coupling agents, and the concentration of the fullerene derivative is 10 to 30 mg / mL;

[0046] A fullerene derivative solution was coated onto the surface of a perovskite light-absorbing layer and dried to obtain an electron transport layer.

[0047] A buffer layer is prepared on the surface of the electron transport layer, and the material of the buffer layer is selected from copper bath or N-type semiconductor metal oxide;

[0048] Metal electrodes are fabricated on the surface of the buffer layer to obtain a perovskite solar cell.

[0049] In this application, the perovskite solar cell prepared according to the above method is an inverted structure, which consists of, from bottom to top, a conductive substrate, a hole transport layer, a perovskite light-absorbing layer, an electron transport layer, a buffer layer, and a metal electrode. Compared with the upright structure, the inverted perovskite solar cell has the advantages of better stability and lower hysteresis.

[0050] For example, fullerene derivatives can be selected from methyl [6,6]-phenyl-C61-butyrate or methyl [6,6]-phenyl-C71-butyrate. Selecting fullerene derivatives within the scope of this application is beneficial for obtaining perovskite solar cells with high photoelectric conversion efficiency.

[0051] In this application, by using silane coupling agents and diiodoalkane doping with fullerene derivatives, the defects formed by fullerene derivatives during film formation can be improved, thereby reducing the roughness of the electron transport layer, improving its flatness, reducing interfacial recombination, and thus improving the photoelectric conversion efficiency of perovskite solar cells.

[0052] This application does not impose any particular limitations on the steps of adding the silane coupling agent, diiodoalkane, and fullerene derivative to 2-methyl anisole, as long as the purpose of this application can be achieved. For example, the silane coupling agent (such as 3-aminopropyltriethoxysilane) and diiodoalkane (such as 1,8-diiodooctane) can be added to 2-methyl anisole, and after the silane coupling agent and diiodoalkane have dissolved, the fullerene derivative can be added and mixed evenly; or, the silane coupling agent, diiodoalkane, and fullerene derivative can be added together as solutes to 2-methyl anisole and mixed evenly; or, the silane coupling agent and diiodoalkane can be added to one part of 2-methyl anisole, stirred evenly to obtain a mixture, and then the fullerene derivative can be added to another part of 2-methyl anisole, and then the above mixture can be added and mixed evenly.

[0053] This application does not impose any particular limitation on the temperature range for stirring the fullerene derivative solution, as long as the purpose of this application can be achieved. For example, the temperature is 40–80°C. In the electron transport layer preparation step, this application does not impose any particular limitation on the drying temperature, for example, 100–110°C, as long as the purpose of this application can be achieved.

[0054] In one embodiment of this application, the molar percentage of the silane coupling agent and the molar percentage of the diiodoalkane are 1% to 5% based on the mass of the fullerene derivative. The inventors have found that when the content of the additives is within the above range, the smoothness of the electron transport layer is better, and the environmental stability and photoelectric conversion efficiency of the perovskite solar cell are higher.

[0055] In one embodiment of this application, the molecular formula of the silane coupling agent is Y-R1-Si(OR2)3, where Y is selected from -NH2 group or -SH group, and R1 is selected from -(CH2) group. n - represents a chain-like alkylene group, where n is an integer from 1 to 3, and R2 is selected from a straight-chain alkyl group having 1 to 2 carbon atoms. Exemplarily, the silane coupling agent in this application can be selected from 3-aminopropyltriethoxysilane (APTS) or 3-mercaptopropyltriethoxysilane (MPTS). By selecting a silane coupling agent as an additive within the scope of this application, perovskite solar cells can exhibit good environmental stability and photoelectric conversion efficiency.

[0056] In one embodiment of this application, the diiodoalkane is selected from at least one of diiodohexane, diioheptane, diiooctane, diiononane, diiodecane, diiodoundecane, or diiodododecane. Exemplarily, 1,8-diiooctane and 1,7-diioheptane are used as additives. By selecting the above-mentioned diiodoalkane as additives, perovskite solar cells can exhibit good environmental stability and photoelectric conversion efficiency.

[0057] In one embodiment of this application, the thickness of the buffer layer is 1–30 nm. A buffer layer thickness within this range can block hole transport, thereby improving the photoelectric conversion efficiency of the perovskite solar cell.

[0058] In one embodiment of this application, the preparation method of the buffer layer includes: dissolving copper hydroxide in isopropanol, stirring until homogeneous to obtain a copper hydroxide solution, wherein the concentration of copper hydroxide is 0.3–1 mg / mL; coating the surface of the electron transport layer with the copper hydroxide solution to obtain the buffer layer. The chemical structural formula of copper hydroxide (BCP) is as follows:

[0059]

[0060] Alternatively, an N-type semiconductor metal oxide can be deposited on the surface of the electron transport layer using atomic layer deposition or magnetron sputtering to obtain a buffer layer. The N-type semiconductor metal oxide is selected from zinc aluminum oxide, zinc tin oxide, tin dioxide, zinc oxide, or titanium dioxide. This preparation method forms a buffer layer that blocks hole transport, thereby improving the photoelectric conversion efficiency of the perovskite solar cell.

[0061] This application does not impose any particular restrictions on atomic layer deposition (ALD) or magnetron sputtering. Existing ALD deposition technology or magnetron sputtering technology can be used, as long as an N-type semiconductor metal oxide layer can be deposited on the surface of the electron transport layer to achieve the purpose of this application.

[0062] In one embodiment of this application, the perovskite precursor liquid is prepared by: adding an A-containing halide and a B-containing halide as solutes to a solvent, and stirring for 3 to 10 hours to obtain the perovskite precursor liquid; wherein the A-containing halide is selected from at least one of formamidine iodide, methylamine iodide, cesium iodide, rubidium iodide, potassium iodide, and methylamine bromide; the B-containing halide is selected from at least one of lead iodide and lead bromide; the solvent is selected from at least one of N,N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, and γ-butyrolactone; the concentration of the A-containing halide is 0.5 to 2.0 mol / L; and the concentration of the B-containing halide is 0.5 to 2.0 mol / L.

[0063] In one embodiment of this application, the annealing temperature of the perovskite light-absorbing layer is 90–200°C, and the annealing time is 10–100 min. Using the perovskite light-absorbing layer obtained through the above annealing process to prepare a perovskite solar cell is beneficial for improving the photoelectric conversion efficiency of the perovskite solar cell.

[0064] In one embodiment of this application, the perovskite light-absorbing layer contains a perovskite compound ABX3, wherein A in ABX3 is selected from at least one of MA, FA, Cs, Rb and K, B is selected from Pb, and X is selected from at least one of I, Br and Cl.

[0065] This application does not impose any particular limitation on the film formation process of the perovskite light-absorbing layer, and may include, for example, solution spin coating, solution blade coating, slot coating, or roll-to-roll coating. Of course, the film formation process of the perovskite light-absorbing layer in this application may include, but is not limited to, the examples mentioned above, as long as it achieves the purpose of this application.

[0066] This application does not impose any particular restrictions on the preparation process of the hole transport layer; it can be prepared using spin coating or atomic deposition. In one embodiment of this application, the hole transport layer is prepared by: dropping a hole transport layer material dispersion onto the surface of a conductive substrate, spin coating, and annealing to obtain the hole transport layer. The hole transport layer material can be selected from materials such as nickel oxide or cuprous oxide, the spin coating speed is 1000–4000 rpm, and the annealing temperature is 80–200°C.

[0067] This application does not impose any particular restrictions on the hole transport layer, as long as it can achieve the purpose of this application. For example, the material of the hole transport layer can be selected from nickel oxide (NiO), cuprous oxide (Cu2O), and poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), etc., and the thickness of the hole transport layer is 20-30 nm.

[0068] This application does not impose any particular restrictions on the preparation process of the metal electrode. In one embodiment of this application, the preparation process of the metal electrode is as follows: a sheet having a hole transport layer, a perovskite light-absorbing layer and an electron transport layer is placed in a thermal evaporation apparatus and a metal electrode with a diameter of 70-130 nm is obtained by evaporation under vacuum conditions.

[0069] This application does not impose any particular limitation on the material of the metal electrode; it can be any material or combination thereof known to those skilled in the art, such as any one of silver (Ag), gold (Au), aluminum (Al), or copper (Cu) electrodes. This application also does not impose any particular limitation on the thickness of the metal electrode, as long as it achieves the purpose of this application; for example, it can be 60–130 nm, with better results achieved within this range. Of course, those skilled in the art can choose an appropriate metal electrode thickness as needed.

[0070] In this application, the conductive substrate is a flexible conductive substrate, which can be a fluorinated tin oxide (FTO) flexible conductive substrate or an indium tin oxide (ITO) flexible conductive substrate. The raw material of the flexible conductive substrate is selected from any one of polyethylene terephthalate (PET), polyphthalamide (PPA), polyethylene naphthalate (PEN), or polyimide (PI). The conductive substrate can be cut to the required size. In addition, the conductive substrate can be etched to reduce the risk of short circuits due to breakdown of the upper and lower electrodes during device testing. Common etching methods in the art can be used to etch the conductive substrate, and this application does not impose any particular limitations.

[0071] In this application, since the conductive substrate is selected from flexible conductive substrates, acetone cannot be used for cleaning. For example, deionized water, ethanol, or isopropanol can be used for cleaning or rinsing.

[0072] Depending on the requirements, the perovskite solar cell prepared in this application may also contain other layers, such as a conductive layer on a conductive substrate, and electrodes may be led out from the conductive layer and the metal electrode to form a circuit.

[0073] A second aspect of this application provides a perovskite solar cell prepared by any of the above-described methods.

[0074] The embodiments and comparative examples provided below illustrate the implementation of this application in more detail. Various tests and evaluations were conducted according to the methods described below. Furthermore, unless otherwise specified, "parts" and "%" are quality standards.

[0075] Test methods and equipment

[0076] Photoelectric conversion efficiency test:

[0077] The current density (J)-voltage (V) of the perovskite solar cell was measured using a solar simulator (Newport Oriel, USA) and a digital source meter (Keithley 2400, USA). The short-circuit current density (J) can be directly obtained from the JV test curve. sc ) and open-circuit voltage (V oc Then, the fill factor and photoelectric conversion efficiency are calculated. The fill factor (FF) is the ratio of the product of the current and voltage when the perovskite cell has the maximum output power to the product of the short-circuit current and the open-circuit voltage. The photoelectric conversion efficiency (PCE) is the ratio of the maximum output power of the perovskite cell to the incident light power.

[0078] Surface morphology observation and roughness test of electron transport layer:

[0079] The fullerene derivative film was placed under a laser confocal microscope (model OLS5100) to observe the surface morphology of the fullerene derivative film on the perovskite light-absorbing layer and to test its surface roughness.

[0080] Example 1

[0081] <Preparation of Conductive Substrates>

[0082] Commercially available indium tin oxide PEN flexible conductive substrate (model Peccell) was cut into 20mm×20mm sheets. After etching and rinsing, the substrate was placed in a polytetrafluoroethylene cleaning rack and then ultrasonically cleaned for 15 minutes each with deionized water, ethanol, and isopropanol. The cleaning rack containing the conductive substrate was then placed in an oven at 75°C to dry for later use.

[0083] <Preparation of Hole Transport Layer>

[0084] 20 mg of nickel oxide nanoparticles (average particle size 8–12 nm) were added to 1 mL of deionized water and ultrasonically dispersed for 15 min to obtain a nickel oxide nanoparticle dispersion. The dried PEN flexible conductive substrate was then treated in a preheated UV ozone cleaner for 20 min before being removed and set aside.

[0085] 70 μL of nickel oxide nanoparticle dispersion was dropped onto the surface of the above-treated PEN flexible conductive substrate, and a nickel oxide hole transport layer film was prepared by spin coating. The spin coating speed was controlled at 3000 rpm and the spin coating time was 30 s to obtain a nickel oxide wet film. After annealing at 120℃ for 15 min, a hole transport layer with a thickness of 30 nm was obtained.

[0086] <Preparation of Perovskite Absorbing Layer>

[0087] First, the perovskite precursor solution was prepared according to the following steps. Solutes containing formamidinium iodide (A halide), methylamine bromide, and cesium iodide, and lead iodide and lead bromide (B halide), were added to a solvent composed of dimethylformamide and dimethyl sulfoxide. After magnetic stirring for 12 hours, the perovskite precursor solution was obtained. The volume of dimethylformamide was 800 μL, the volume of dimethyl sulfoxide was 200 μL, the concentration of formamidinium iodide in the perovskite precursor solution was 1.0 mol / L, the concentration of methylamine bromide in the perovskite precursor solution was 0.2 mol / L, the concentration of cesium iodide in the perovskite precursor solution was 0.13 mol / L, and the concentration of the A halide in the perovskite precursor solution was 1.33 mol / L. The concentration of lead iodide in the perovskite precursor fluid is 1.1 mol / L, the concentration of lead bromide in the perovskite precursor fluid is 0.2 mol / L, and the concentration of B-containing halides in the perovskite precursor fluid is 1.3 mol / L.

[0088] The sheet with the nickel oxide hole transport layer was subjected to ultraviolet ozone treatment for 10 min. Then, 50 μL of perovskite precursor liquid was dropped onto the surface of the sheet to cover the entire surface. The perovskite light-absorbing layer was prepared by spin coating. The spin coating process was as follows: spin coating was first performed at 1500 rpm for 10 s, and then at 6000 rpm for 30 s to obtain a wet film of perovskite precursor. 200 μL of anisole was dropped into the last 5 s of spin coating. The sheet was then placed on a hot plate at 100°C and annealed for 30 min to obtain a perovskite light-absorbing layer with a thickness of about 400 nm.

[0089] <Preparation of Electron Transport Layer>

[0090] 20.56 μL of 3-aminopropyltriethoxysilane (APTS) and 16 μL of 1,8-diiodooctane were added to 2 mL of 2-methyl anisole (MEA) and stirred until homogeneous to obtain a silane mixture. 20 mg of isomethyl [6,6]-phenyl-C61-butyrate (PC61BM) was added to 1 mL of 2-methyl anisole, followed by 25 μL of the above mixture. The mixture was heated and stirred at 60 °C for 3 hours (h) to obtain a PC61BM solution. In the PC61BM solution, the concentration of PC61BM was approximately 20 mg / mL. Based on PC61BM, the molar percentage of the silane coupling agent was 5%, and the molar percentage of 1,8-diiodooctane was 5%. The PC61BM solution was spin-coated onto the surface of the perovskite light-absorbing layer. The spin-coating process was to spin-coat at a speed of 2000 rpm for 30 seconds. After spin-coating, the layer was dried at 110℃ for 20 minutes to obtain an electron transport layer with a thickness of 50 nm.

[0091] <Preparation of the buffer layer>

[0092] 0.5 mg of copper hydroxide was added to 1 mL of isopropanol solution and stirred until homogeneous to obtain a copper hydroxide solution with a concentration of 0.5 mg / mL. Then, 100 μL of the copper hydroxide solution was spin-coated onto the surface of the PC61BM layer at 6000 rpm for 30 s. After spin-coating, the layer was dried at 100 °C for 20 min to obtain a buffer layer with a thickness of 10 nm.

[0093] <Preparation of Metal Electrodes>

[0094] The sheet with the prepared buffer layer was placed in a thermal evaporation apparatus (GSL-1800X-ZF) and subjected to a heat treatment of 5×10⁻⁶ ppm. -4 A 100 nm thick Ag layer was deposited under a vacuum of Pa to obtain a metal electrode, thus completing the fabrication of the perovskite solar cell.

[0095] Example 2

[0096] Except for the preparation of the electron transport layer, where the PC61BM solution was obtained by stirring for 1 hour and the concentration of PC61BM was 10 mg / mL, the rest was the same as in Example 1.

[0097] Example 3

[0098] Except for the preparation of the electron transport layer, where the PC61BM solution was obtained by stirring for 6 hours and the concentration of PC61BM was 30 mg / mL, the rest was the same as in Example 1.

[0099] Example 4

[0100] Except for the use of 3-mercaptopropyltriethoxysilane (MPTS) as the silane coupling agent in the <Preparation of Electron Transport Layer>, the rest is the same as in Example 1.

[0101] Example 5

[0102] Except for the fact that in the <Preparation of Electron Transport Layer>, the molar percentage of silane coupling agent is 1% based on PC61BM, the rest is the same as in Example 1.

[0103] Example 6

[0104] Except for the fact that in the <Preparation of Electron Transport Layer>, the molar percentage of 1,8-diiodooctane is 1% based on PC61BM, the rest is the same as in Example 1.

[0105] Example 7

[0106] Except for the preparation of the buffer layer, in which the concentration of copper hydroxide in the copper hydroxide solution is 0.8 mg / mL, the rest is the same as in Example 1.

[0107] Example 8

[0108] Except for the use of 1,7-diiodoheptane as the diiodoalkane in the <Preparation of Electron Transport Layer>, the rest is the same as in Example 1.

[0109] Example 9

[0110] Except for the preparation of the buffer layer in the <Preparation of Buffer Layer> section, where the buffer layer material is tin dioxide (SnO2), the rest is the same as in Example 1.

[0111] Preparation of the SnO2 buffer layer: The sheet with the prepared electron transport layer was used as the substrate and placed in a closed atomic layer deposition chamber. After being evacuated to a vacuum state, the substrate was preheated to 90°C. After preheating, the buffer layer was deposited. One cycle of buffer layer deposition was as follows: N2 was introduced into the closed atomic layer deposition chamber as a carrier for tetradimethylamine tin precursor for 1000 ms, followed by a 5-second reaction to allow the precursor to be uniformly attached to the substrate surface. Then, the closed atomic layer deposition chamber was rinsed with N2 for 25 seconds to remove excess metal compound precursor. Next, plasma N2 was introduced into the closed atomic layer deposition chamber as a carrier for 15 ms, followed by a 2-second reaction to allow the plasma nitrogen molecules to fully react with the metal compound precursor attached to the substrate, forming a metal compound layer. The closed atomic layer deposition chamber was rinsed with N2 again for 30 seconds to remove excess plasma nitrogen molecules, completing one cycle. After the above cycle was repeated 120 times, a SnO2 buffer layer with a thickness of 10 nm was obtained.

[0112] Example 10

[0113] Except for the use of methyl [6,6]-phenyl-C71-butyrate (PC71BM) as the fullerene derivative in the <Preparation of Electron Transport Layer>, the rest is the same as in Example 1.

[0114] Comparative Example 1

[0115] Except for replacing 2-methylanisole with chlorobenzene in the <Preparation of Electron Transport Layer> section, the rest is the same as in Example 1.

[0116] Table 1 shows the preparation parameters and performance parameters of the perovskite solar cells prepared in Examples 1-10 and Comparative Example 1. Compared with Comparative Example 1, the perovskite solar cells prepared in this application have higher photoelectric conversion efficiency. As can be seen from Examples 1-10, high photoelectric conversion efficiency perovskite solar cells can be obtained by controlling the concentration of fullerene derivatives, stirring time, type and content of additives, buffer layer material, concentration of copper bath solvent, and type of fullerene derivatives within the scope of this application. This application uses 2-methylanisole instead of chlorobenzene as the solvent for fullerene derivatives to prepare the electron transport layer of the inverted structure perovskite solar cell, which not only has the advantages of being green, harmless, and environmentally friendly, but also improves the photoelectric conversion efficiency of the inverted structure perovskite solar cell.

[0117] Table 1

[0118]

[0119] In Table 1, " / " indicates that the value is not available.

[0120] Figure 1a and Figure 1b Surface morphology images of the PC61BM thin films in the perovskite solar cells prepared in Example 1 and Comparative Example 1 are provided. Figure 1a As shown, the PC61BM prepared in Example 1 of this application exhibits a uniform thin film on the perovskite light-absorbing layer; as Figure 1b As shown, the PC61BM film prepared in Comparative Example 1 exhibited agglomeration on the perovskite light-absorbing layer, such as... Figure 1b The area within the black box is shown in the image. In summary, compared with Comparative Example 1, the PC61BM film prepared by the method of this application exhibits uniform film formation and significantly improves the agglomeration phenomenon of PC61BM, thereby contributing to the improvement of the photoelectric conversion efficiency of perovskite solar cells.

[0121] Figure 2a and Figure 2bLaser confocal microscopy images of the PC61BM thin films in the perovskite solar cells prepared in Example 1 and Comparative Example 1 are provided. The roughness Sa of the PC61BM electron transport layer on the perovskite prepared in Example 1 of this application is 36 nm, while the roughness Sa of Comparative Example 1 is 41 nm. This indicates that the PC61BM thin film prepared by the method of this application is smoother than that of Comparative Example 1, which is beneficial to improving the photoelectric conversion efficiency of the perovskite solar cell.

[0122] from Figures 3a-3j As can be seen, compared with Comparative Example 1, the perovskite solar cells prepared in Examples 1-10 of this application have higher short-circuit current density and photoelectric conversion efficiency.

[0123] The preparation method provided in this application uses 2-methylanisole to dissolve fullerene derivatives to prepare an electron transport layer to obtain an inverted perovskite solar cell, which has the advantages of being green, environmentally friendly, and harmless. The fullerene derivative film prepared using 2-methylanisole as a solvent has a uniform and flat film formation, which is beneficial to improving the current density of the perovskite solar cell and effectively improving the photoelectric conversion efficiency of the perovskite solar cell.

[0124] The above description is only a preferred embodiment of this application and is not intended to limit this application. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the scope of protection of this application.

Claims

1. A method for preparing a perovskite solar cell based on a fullerene derivative electron transport layer, comprising the following steps: A hole transport layer is prepared on the surface of a conductive substrate; A perovskite precursor liquid is coated on the surface of the hole transport layer, and then annealed to obtain a perovskite light-absorbing layer. A fullerene derivative and an additive are added to 2-methyl anisole and stirred for 1 to 6 hours to obtain a fullerene derivative solution; wherein the fullerene derivative is selected from at least one of [6,6]-phenyl-C61-butyrate methyl ester and [6,6]-phenyl-C71-butyrate methyl ester; the additive is selected from silane coupling agents and diiodoalkane; the silane coupling agent is selected from aminosilane coupling agents or mercaptosilane coupling agents, and the concentration of the fullerene derivative is 10 to 30 mg / mL; The fullerene derivative solution was coated onto the surface of the perovskite light-absorbing layer and dried to obtain an electron transport layer. A buffer layer is prepared on the surface of the electron transport layer, wherein the material of the buffer layer is selected from copper bath or N-type semiconductor metal oxide; A metal electrode is fabricated on the surface of the buffer layer to obtain a perovskite solar cell; The molecular formula of the silane coupling agent is Y-R1-Si(OR2)3, where Y is selected from -NH2 group or -SH group, and R1 is selected from -(CH2) group. n - indicates a chain-like alkylene group, where n is an integer from 1 to 3, and R2 is selected from a straight-chain alkyl group having 1 to 2 carbon atoms.

2. The preparation method according to claim 1, wherein, Based on the mass of the fullerene derivative, the molar percentage of the silane coupling agent is 1% to 5%.

3. The preparation method according to claim 1, wherein, The diiodoalkane is selected from diiodohexane, diioheptane, diiooctane, diiononane, diiodecane, diiodoundecane, or diiodododecane.

4. The preparation method according to claim 1, wherein, Based on the mass of the fullerene derivative, the molar percentage of the diiodoalkane is 1% to 5%.

5. The preparation method according to claim 1, wherein, The thickness of the buffer layer is 1–30 nm.

6. The preparation method according to claim 1, wherein the preparation method of the buffer layer comprises: Dissolve copper hydroxide in isopropanol and stir until homogeneous to obtain a copper hydroxide solution, wherein the concentration of copper hydroxide is 0.3–1 mg / mL; The buffer layer is obtained by coating the surface of the electron transport layer with the bath copper solution; Alternatively, an N-type semiconductor metal oxide can be deposited on the surface of the electron transport layer by atomic layer deposition or magnetron sputtering to obtain the buffer layer, wherein the N-type semiconductor metal oxide is selected from zinc aluminum oxide, zinc tin oxide, tin dioxide, zinc oxide, or titanium dioxide.

7. The preparation method according to claim 1, wherein, The preparation method of the perovskite precursor fluid is as follows: A halide containing A and a halide containing B are added to a solvent as solutes, and the mixture is stirred for 3 to 10 hours to obtain the perovskite precursor liquid. The halide containing A is selected from at least one of formamidine iodide, methylamine iodide, cesium iodide, rubidium iodide, potassium iodide, and methylamine bromide. The halide containing B is selected from at least one of lead iodide and lead bromide. The solvent is selected from at least one of N,N-dimethylformamide, dimethyl sulfoxide, N-methylpyrrolidone, and γ-butyrolactone. The concentration of the halide containing A is 0.5 to 2.0 mol / L, and the concentration of the halide containing B is 0.5 to 2.0 mol / L.

8. The preparation method according to claim 1, wherein, The annealing temperature of the perovskite light-absorbing layer is 90–200°C, and the annealing time is 10–100 min.

9. The preparation method according to claim 1, wherein, The perovskite light-absorbing layer contains the perovskite compound ABX3, wherein A in ABX3 is selected from at least one of MA, FA, Cs, Rb and K, B is selected from Pb, and X is selected from at least one of I, Br and Cl.

10. A perovskite solar cell prepared by the method according to any one of claims 1 to 9.

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