Perovskite solar cell and preparation method and application thereof

Abstract

The invention belongs to the technical field of perovskite cells, and particularly relates to a perovskite solar cell and a preparation method and application thereof. The perovskite solar cell comprises a substrate, a ZIF-67 modified electron transport layer, a perovskite layer, a hole transport layer and a metal back electrode which are arranged in sequence, after the ZIF-67 modifies the electron transport layer, the migration performance of electrons is improved, the transmission efficiency of photo-induced electrons is improved, and electron recombination is reduced; the ZIF-67 modified electron transport layer is connected with the perovskite layer, so that the crystallization integrity of crystal grains in the perovskite layer is improved, charge accumulation can be regulated and controlled, and the hysteresis effect is reduced; the ZIF-67 can increase the contact area between the modified electron transport layer and the perovskite layer, fill interface defects and reduce charge traps at an interface, thereby improving the photoelectric conversion efficiency of the perovskite solar cell.

Description

Technical Field

[0001] The present invention belongs to the technical field of perovskite solar cells, and particularly relates to a perovskite solar cell, a preparation method thereof, and an application thereof. Background Art

[0002] With the large consumption of non-renewable energy sources such as petroleum, the problem of energy shortage is becoming increasingly serious, and people urgently need to seek alternative energy sources. As an inexhaustible and renewable energy source, solar energy has great development potential. However, how to efficiently utilize solar energy remains a major challenge for mankind. In recent years, organic-inorganic perovskite solar cells have attracted extensive attention from scientific researchers due to their low preparation cost, easy processing, and high photoelectric conversion efficiency, and have become a very promising technology.

[0003] However, perovskite solar cells face many problems. In the electron transport layer, there are problems of energy level matching. Electrons are likely to meet with holes and recombine, resulting in poor electron transport and a poor electron migration ability, which hinders the transport of electrons. In the perovskite layer, there are problems such as uneven grain size, poor crystallinity, insufficient density, and low film coverage. Moreover, between the electron transport layer and the perovskite layer, there are also problems of interface defects, with a high electron transport barrier, which affects the transport of electrons at the interface and can also cause non-radiative recombination, ultimately resulting in a low photoelectric conversion efficiency of the solar cell.

[0004] Metal-organic framework materials (MOFs) belong to a type of coordination polymer and are a class of crystalline porous materials with a high specific surface area, high porosity, and structural designability. MOFs are usually composed of metal ions and organic ligands and can interact with a variety of interfacial reactions. However, the existing MOFs have limited effects on improving the photoelectric conversion efficiency of perovskite solar cells. Summary of the Invention

[0005] Therefore, the technical problem to be solved by the present invention is to overcome the defect of insufficient photoelectric conversion efficiency of existing perovskite solar cells, and thus provide a perovskite solar cell, a preparation method thereof, and an application thereof.

[0006] To this end, the present invention provides the following technical solutions:

[0007] In the first aspect of the present invention, a perovskite solar cell is protected. Among them, the perovskite solar cell includes a substrate, a ZIF-67 modified electron transport layer, a perovskite layer, a hole transport layer, and a metal back electrode arranged in sequence.

[0008] In the present invention, the thickness of each layer in the perovskite solar cell is a conventional thickness in the art, and the specific thickness can be adjusted according to actual needs.

[0009] In the present invention, the ZIF-67 is an existing MOF, the ligand used is 2-methylimidazole, and an example of the coordination mode in the MOF is as follows:

[0010] The second aspect of the present invention protects a method for preparing a perovskite solar cell, wherein the preparation method includes the following steps: sequentially preparing a ZIF-67 modified electron transport layer, a perovskite layer, a hole transport layer, and a metal back electrode on a substrate;

[0011] The preparation of the ZIF-67 modified electron transport layer includes the following steps: preparing an electron transport layer on a substrate; coating a ZIF-67 suspension on the electron transport layer and performing annealing to obtain a ZIF-67 modified electron transport layer.

[0012] According to the present invention, the average particle size of the ZIF-67 is 50 - 120 nm; it can be optionally 80 - 100 nm.

[0013] In the present invention, ZIF-67 is mixed with water to obtain a ZIF-67 suspension. ZIF-67 belongs to metal-organic framework materials; the water is laboratory water, generally ultrapure water or deionized water is selected; the ZIF-67 suspension is coated on the electron transport layer, and the coating methods include at least one of spin coating, blade coating, and spraying.

[0014] In the present invention, the preparation of the electron transport layer includes the following steps: coating an electron transport layer precursor solution on a substrate and performing a first annealing; the electron transport layer precursor solution is coated by a conventional coating method in the art. Typically and non-limitingly, the coating methods include at least one of spin coating, blade coating, and spraying; the electron transport layer precursor solution is a conventional electron transport layer precursor solution in the art. Typically and non-limitingly, a commercially available SnO2 colloidal solution can be used, or an electron transport layer precursor solution can be prepared by mixing SnO2 and water; the annealing conditions are conventional annealing methods in the art. Typically and non-limitingly, the temperature of the first annealing is 100 - 150 °C and the time is 15 - 30 min.

[0015] According to the present invention, the dosage ratio of ZIF-67 to water in the ZIF-67 suspension is (0.5 - 2) mg : (1 - 3) mL, and it can be optionally (0.5 - 1) mg : (1 - 3) mL.

[0016] According to the present invention, based on the area of the substrate, the dosage of the ZIF-67 suspension is 40 - 100 μL / mm 2 .

[0017] According to the present invention, the temperature of the annealing is 50 - 180 °C and the time is 3 - 15 min.

[0018] According to the present invention, the annealing temperature is 100 - 150 °C and the time is 5 - 10 min.

[0019] According to the present invention, preparing the perovskite layer includes the following steps: (1) Preheating the first perovskite precursor solution, coating the first perovskite precursor solution onto the ZIF-67 modified electron transport layer to obtain the first perovskite layer; (2) Coating the second perovskite precursor solution onto the first perovskite layer and performing annealing to obtain the perovskite layer.

[0020] In the present invention, the first perovskite precursor solution is a conventional perovskite precursor solution in the art. Typically and non-limitingly, it includes a first solute and a first solvent; the first solute includes PbI2 and CsI; the first solvent includes N,N-dimethylformamide and / or dimethyl sulfoxide. When the solvent is N,N-dimethylformamide and dimethyl sulfoxide, the volume ratio of N,N-dimethylformamide to dimethyl sulfoxide is 19 - 20:1; the dosage ratio of PbI2, CsI, and the first solvent is 1 g : (0.03 - 0.05) g : (1 - 2) mL; based on the area of the substrate, the dosage of the first perovskite precursor solution is 50 - 10 μL / mm 2 。

[0021] In the present invention, the second perovskite precursor solution includes a second solute and a second solvent; it is a conventional perovskite precursor solution in the art; the second solute includes methylammonium halide and formamidinium halide; it includes at least one of FAI, MACl, MABr, and MAI; the second solvent includes isopropyl alcohol; the dosage ratio of the second solute to the second solvent is (1 - 2) g : (15 - 20) mL; when the second solute is FAI, MACl, MABr, or MAI, the mass ratio of FAI, MAI, MABr, and MACl is (0.6 - 1) : (0.3 - 1) : (0.075 - 0.1) : (0.075 - 0.1); based on the area of the substrate, the dosage of the second perovskite precursor solution is 40 - 100 μL / mm 2 。

[0022] In the present invention, lead iodide corresponds to PbI2, formamidinium hydroiodide corresponds to FAI, methylammonium chloride corresponds to MACl, methylammonium iodide corresponds to MAI, methylammonium bromide corresponds to MABr, N,N-dimethylformamide corresponds to DMF, dimethyl sulfoxide corresponds to DMSO, and isopropyl alcohol corresponds to IPA.

[0023] In the present invention, the types and dosages of the components in the specific first perovskite precursor solution and the types and dosages of the components in the specific second perovskite precursor solution can effectively control the crystallization rate and crystallinity of the perovskite thin film, generate uniform large grains, improve the overall crystallinity of the thin film, and thereby improve the photoelectric conversion efficiency of the battery.

[0024] In the present invention, the coating methods in steps (1) and (2) are conventional coating methods in the art. Typically and non - limitatively, at least one of spin coating, blade coating, and spray coating is adopted.

[0025] In the present invention, after the components in the second perovskite precursor solution are mixed, they are stirred at a rotation speed of 500 - 700 rpm at room temperature for 5 - 6 h to ensure complete stirring.

[0026] According to the present invention, the preheating temperature is 70 - 80 °C and the time is 5 - 10 min.

[0027] According to the present invention, in step (2), the annealing temperature is 120 - 150 °C and the time is 15 - 20 min.

[0028] In the present invention, the preparation method of the hole - transporting layer is a conventional preparation method in the art. Typically and non - limitatively, a hole - transporting layer precursor solution is prepared and coated on the perovskite layer to form a hole - transporting layer; the solute in the hole - transporting layer precursor solution includes spiro - OMeTAD, and the solvent includes chlorobenzene; based on the area of the substrate, the amount of the hole - transporting layer precursor solution used is 40 - 100 μL / mm 2 。

[0029] In the present invention, the preparation method of the metal back electrode is a conventional preparation method in the art. Typically and non - limitatively, a metal is vacuum - evaporated on the hole - transporting layer to form a metal back electrode. The metal includes silver, and the evaporation thickness is 80 - 100 nm.

[0030] The third aspect of the present invention protects the application of the perovskite solar cell described above or the perovskite solar cell prepared by the preparation method described above in the photovoltaic field.

[0031] The technical solution of the present invention has the following advantages:

[0032] 1. The present invention provides a perovskite solar cell, wherein the perovskite solar cell comprises a substrate, a ZIF-67 modified electron transport layer, a perovskite layer, a hole transport layer, and a metal back electrode, which are sequentially arranged; ZIF-67 belongs to metal-organic framework materials, has good chemical stability, a highly ordered pore structure and a high specific surface area. Since ZIF-67 itself has poor conductivity, ZIF-67 is generally not selected for use in perovskite solar cells. However, the inventor unexpectedly found during research that after ZIF-67 modifies the electron transport layer, it improves the migration performance of electrons, increases the transport efficiency of photo-generated electrons, and reduces electron recombination; the ZIF-67 modified electron transport layer is connected to the perovskite layer, improving the crystal integrity of the grains in the perovskite layer and capable of regulating charge accumulation and reducing the hysteresis effect; ZIF-67 can increase the contact area between the modified electron transport layer and the perovskite layer, fill interface defects, and reduce charge traps at the interface, thereby improving the photoelectric conversion efficiency of the perovskite solar cell. In addition, compared with other metal-organic framework materials, ZIF-67 has a lower synthesis difficulty and better tunability, greatly reducing production costs and being suitable for practical applications.

[0033] 2. In the present invention, a specific particle size of ZIF-67 can make contact with the surface of the electron transport layer more fully, further improving the density of the modified layer, reducing defects and voids, and improving the interface quality; and can further improve the charge transport efficiency and enhance the battery performance.

[0034] 3. The present invention provides a preparation method for a perovskite solar cell, wherein the preparation method comprises the following steps: sequentially preparing a ZIF-67 modified electron transport layer, a perovskite layer, a hole transport layer, and a metal back electrode on a substrate; the preparation of the ZIF-67 modified electron transport layer comprises the following steps: preparing an electron transport layer on a substrate; coating a ZIF-67 suspension on the electron transport layer and annealing to obtain a ZIF-67 modified electron transport layer; coating a ZIF-67 suspension on the electron transport layer and annealing to obtain a ZIF-67 modified electron transport layer. Compared with the one-step preparation by mixing the electron transport layer material with the ZIF-67 suspension, the two-step method for preparing the ZIF-67 modified electron transport layer can reduce defects and non-uniformities, improve the crystallization quality of the thin film, thereby improving the photoelectric conversion efficiency and stability; ZIF-67 is added in the form of a suspension, which can ensure more uniform coating; and in-situ generating the perovskite layer on the ZIF-67 modified electron transport layer can precisely control the crystal growth quality of the perovskite layer. At the same time, the perovskite layer can be closely attached to the ZIF-67 modified electron transport layer, reducing electron scattering and recombination at the interface, and improving the electron transport efficiency and the stability of the battery structure.

[0035] 4. In the present invention, a specific dosage ratio of ZIF-67 to water helps the good dispersion of ZIF-67 in water, avoids particle aggregation, and makes the distribution of ZIF-67 more uniform, thereby improving the performance of ZIF-67 in perovskite solar cells.

[0036] 5. In the process of the electron transport layer modified by ZIF-67 in the present invention, specific annealing conditions can further improve the quality of the electron transport layer, promote grain growth, reduce defects, and enhance the electron mobility. In addition, specific annealing temperatures help optimize the interfacial contact between the electron transport layer and other layers, reduce the contact resistance, and improve the device efficiency. At the same time, specific annealing conditions can also enhance the stability of the electron transport layer, reduce the influence of environmental factors on its performance, and thus improve the long-term stability and photoelectric conversion efficiency of optoelectronic devices.

[0037] 6. In the preparation of the perovskite layer in the present invention, preheating the first perovskite precursor solution can further promote the dissolution of solutes, improve the uniformity and stability of the first perovskite precursor solution, and thus avoid the appearance of particles or uneven crystallization during the preparation process. Specific preheating conditions help further adjust the viscosity and surface tension of the first perovskite precursor solution, control the film-forming speed, and further affect the fluidity and growth rate of the film, so that the perovskite film forms a more uniform and dense structure, reduces film defects, and improves the photoelectric conversion efficiency. It promotes grain growth, improves the crystallinity of perovskite, makes the grains larger, and thus optimizes charge transport and photoelectric conversion efficiency. Preheating can also help remove volatile solvents or impurities in the solution and reduce their negative impact on the film quality. Therefore, preheating helps further improve the film quality and grain structure. The perovskite layer includes a first perovskite layer and a second perovskite layer. Compared with a perovskite layer with only one layer, different components are more effective in absorbing light of different wavelengths, can further provide the photoelectric conversion efficiency, and the perovskite layer with a bilayer structure also has higher mechanical strength, ensuring the long-term stability of the solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0038] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. Obviously, the drawings in the following description are some embodiments of the present invention. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0039] Figure 1 It is the AFM image of the electron transport layer modified by ZIF-67 in Example 1;

[0040] Figure 2 It is the AFM image of the electron transport layer not modified by ZIF-67 in Comparative Example 1;

[0041] Figure 3 is the J-V curve of the perovskite solar cell of Example 1 and the perovskite cell of Comparative Example 1;

[0042] Figure 4 is the SEM image of the grains in the perovskite layer of Example 1;

[0043] Figure 5 is the SEM image of the grains in the perovskite layer of Comparative Example 1. Detailed implementation manners

[0044] The following examples are provided to better further understand the present invention. It is not limited to the described best implementation manner, and does not limit the content and protection scope of the present invention. Any product that is the same as or similar to the present invention obtained by anyone under the inspiration of the present invention or by combining the features of the present invention with other prior art features falls within the protection scope of the present invention.

[0045] For those examples where specific experimental steps or conditions are not indicated, the operations or conditions of the conventional experimental steps described in the literature in this field can be followed. For the reagents or instruments whose manufacturers are not indicated, they are all conventional reagent products that can be obtained through commercial purchase.

[0046] The water used in the examples and comparative examples is ultrapure water.

[0047] The substrate is FTO conductive glass: purchased from Black Mamba Wanlian (Yingkou) Trading Co., Ltd., with the brand name FTOTEC15, and the substrate size is 2.2 mm × 20 mm × 20 mm;

[0048] The preparation method of ZIF-67 includes the following steps: Dissolve 0.45 g of cobalt nitrate in 3 mL of water to obtain solution A; dissolve 5.5 g of 2-methylimidazole in 20 mL of deionized water to obtain solution B; mix solution A and solution B, stir at room temperature for 6 h, centrifuge to collect the purple precipitate, and wash it 3 times with deionized water and methanol to obtain ZIF-67. The average particle size of ZIF-67 is 80 nm.

[0049] The preparation method of ZIF-67' includes the following steps: Dissolve 0.45 g of cobalt nitrate in 3 mL of water to obtain solution A; dissolve 5.5 g of 2-methylimidazole in 20 mL of deionized water to obtain solution B; mix solution A and solution B, stir at room temperature for 12 h, centrifuge to collect the purple precipitate, and wash it 3 times with deionized water and methanol to obtain ZIF-67'. The average particle size of ZIF-67' is 120 nm.

[0050] SnO2 colloidal solution, where the content of SnO2 is 15 wt%; purchased from Xi'an YuRi Solar Energy Technology Co., Ltd., with the brand number CAS: 18282-10-5;

[0051] PbI2 (purity 99.99%): purchased from Liaoning YouXuan New Energy Technology Co., Ltd., with the brand number CAS RN: 10101-63-0;

[0052] Spiro-OMeTAD hole transport layer: purchased from Xi'an YuRi Solar Energy Technology Co., Ltd., with the brand number CAS: 207739-72-8;

[0053] FAI: purchased from Xi'an YuRi Solar Energy Technology Co., Ltd., with the brand number CAS: 879643-71-7;

[0054] MACl: purchased from Xi'an YuRi Solar Energy Technology Co., Ltd., with the brand number CAS: 593-51-1;

[0055] Methanol, cobalt nitrate, and 2-methylimidazole were all purchased from Macklin.

[0056] Example 1

[0057] This example provides a perovskite solar cell, and the preparation method includes the following steps:

[0058] S1, Spin-coat 100 μL of the SnO2 colloidal solution onto the substrate, and perform annealing. The annealing temperature is 150 °C and the time is 15 min to obtain the electron transport layer;

[0059] S2, Mix ZIF-67 with water to obtain a ZIF-67 suspension. The dosage ratio of ZIF-67 to water is 0.5 mg: 1 mL; Spin-coat 100 μL of the ZIF-67 suspension on the electron transport layer, and perform annealing on the heating panel. The annealing temperature is 100 °C and the time is 5 min to obtain a ZIF-67 modified electron transport layer. The AFM image is as Figure 1 shown. It can be known from the AFM test that the root mean square roughness of the surface of the electron transport layer modified with ZIF-67 is 9.89 nm, while Figure 2 the root mean square roughness of the electron transport layer without ZIF-67 modification in Comparative Example 1 is 11.26 nm, which proves that ZIF-67 in Example 1 can fill and modify surface defects, improve the surface structure of the material, and make it smoother. The lower surface roughness helps the electrons migrate more smoothly in the material, reduces the recombination of electrons and holes, and helps improve the efficiency of the battery;

[0060] S3. Dissolve 7.5 g of PbI2 and 0.3 g of CsI in 11.4 mL of DMF and 0.6 mL of DMSO to obtain a first perovskite precursor solution; perform preheating, with the preheating temperature being 70 °C and the time being 5 min; use a pipette to aspirate 50 μL of the first perovskite precursor solution and spin-coat it onto the ZIF-67 modified electron transport layer at a rotation speed of 3000 rpm for 30 s to obtain a first perovskite layer; dissolve 0.6 g of FAI, 0.3 g of MAI, 0.075 g of MABr, and 0.075 g of MACl in 15 mL of IPA, and stir the mixed solution at a rotation speed of 500 rpm for 15 h at room temperature to obtain a second perovskite precursor solution; use a pipette to aspirate 100 μL of the second perovskite precursor solution and spin-coat it onto the first perovskite layer at a rotation speed of 3000 rpm for 30 s, and anneal it at 150 °C for 15 min to obtain a perovskite layer;

[0061] S4. Use a pipette to aspirate 50 μL of the Spiro-OMeTAD hole transport layer solution and spin-coat it onto the perovskite layer at a rotation speed of 3000 rpm for 30 s to obtain a hole transport layer;

[0062] S5. On the hole transport layer, vacuum deposit silver metal with a thickness of 80 nm to obtain a metal back electrode, forming a perovskite solar cell.

[0063] Example 2

[0064] This example provides a perovskite solar cell, and the preparation method includes the following steps:

[0065] S1. Spin-coat 100 μL of the SnO2 colloidal solution onto the substrate, and perform annealing, with the annealing temperature being 150 °C and the time being 30 min, to obtain an electron transport layer;

[0066] S2. Mix ZIF-67 with water to obtain a ZIF-67 suspension, and the dosage ratio of ZIF-67 to water is 1 mg:1 mL; spin-coat 100 μL of the ZIF-67 suspension onto the electron transport layer, and perform annealing on a heating panel, with the annealing temperature being 100 °C and the time being 5 min, to obtain a ZIF-67 modified electron transport layer;

[0067] S3. Dissolve 7.5 g of PbI2 and 0.3 g of CsI in 11.4 mL of DMF and 0.6 mL of DMSO to obtain a first perovskite precursor solution, and preheat it at a temperature of 70 °C for 5 min; suck 50 μL of the first perovskite precursor solution with a pipette and spin-coat it onto the ZIF-67 modified electron transport layer at a rotation speed of 3000 rpm for 30 s to obtain a first perovskite layer; dissolve 0.6 g of FAI, 0.3 g of MAI, 0.075 g of MABr and 0.075 g of MACl in 15 mL of IPA; stir the mixed solution at a rotation speed of 500 rpm for 15 h at room temperature; obtain a second perovskite precursor solution, suck 100 μL of the second perovskite precursor solution with a pipette and spin-coat it onto the first perovskite layer at a rotation speed of 3000 rpm for 30 s, and anneal it at 150 °C for 15 min to obtain a perovskite layer;

[0068] S4. Suck 50 μL of the Spiro-OMeTAD hole transport layer solution with a pipette and spin-coat it onto the perovskite layer at a rotation speed of 3000 rpm for 30 s to obtain a hole transport layer;

[0069] S5. Evaporate silver metal in vacuum on the hole transport layer with a thickness of 80 nm to obtain a metal back electrode, and form a perovskite solar cell.

[0070] Example 3

[0071] This example provides a perovskite solar cell, and the preparation method includes the following steps:

[0072] In the same manner as in Example 1, the difference is that in step S2, the dosage ratio of ZIF-67 to water is 2 mg:1 mL.

[0073] Example 4

[0074] This example provides a perovskite solar cell, and the preparation method includes the following steps:

[0075] In the same manner as in Example 1, the difference is that in step S2, the annealing temperature is 50 °C and the time is 5 min.

[0076] Example 5

[0077] This example provides a perovskite solar cell, and the preparation method includes the following steps:

[0078] In the same manner as in Example 1, the difference is that in step S3, no preheating is performed.

[0079] Example 6

[0080] This embodiment provides a perovskite solar cell, and the preparation method includes the following steps:

[0081] In the same manner as in Example 1, except that ZIF-67 is changed to ZIF-67'.

[0082] Example 7

[0083] This embodiment provides a perovskite solar cell, and the preparation method includes the following steps:

[0084] In the same manner as in Example 1, except that 100 μL of SnO2 colloidal solution, 1 mg of ZIF-67 and 1 mL of water are mixed and then spin-coated onto the substrate, followed by annealing at a temperature of 150 °C for 15 min to obtain a ZIF-67 modified electron transport layer.

[0085] Comparative Example 1

[0086] This comparative example provides a perovskite solar cell, and the preparation method includes the following steps:

[0087] S1, Spin-coat 100 μL of SnO2 colloidal solution onto the substrate and perform annealing at a temperature of 150 °C for 15 min to obtain an electron transport layer; The AFM image is as Figure 2 shown. It can be seen from Figure 2 that an atomic force microscope (AFM) test is performed on Example 1. The results show that the root mean square roughness of the surface of the electron transport layer modified by ZIF-67 is 9.89 nm. Comparing Figure 2 with the data of Comparative Example 1, the root mean square roughness of the electron transport layer without ZIF-67 modification is 11.26 nm. The experimental data show that ZIF-67 in Example 1 can fill and modify the surface defects of the electron transport layer, optimize the surface structure of the material, and make the material surface smoother. The reduction of the surface roughness of the material is beneficial to the smooth migration of electrons in the material, reduces the recombination probability of electrons and holes, and has a positive effect on improving the battery efficiency;

[0088] S2. Dissolve 7.5 g of PbI2 and 0.3 g of CsI in 11400 μL of DMF and 600 μL of DMSO to obtain a first perovskite precursor solution, and preheat it at a temperature of 70 °C for 5 min; use a pipette to aspirate 50 μL of the first perovskite precursor solution and spin-coat it onto the electron transport layer at a speed of 3000 rpm for 30 s to obtain a first perovskite layer; dissolve 0.6 g of FAI, 0.3 g of MAI, 0.075 g of MABr, and 0.075 g of MACl in 15 mL of IPA; stir the mixed solution at a speed of 500 rpm for 15 h at room temperature; obtain a second perovskite precursor solution, use a pipette to aspirate 100 μL of the second perovskite precursor solution and spin-coat it onto the first perovskite layer at a speed of 3000 rpm for 30 s, and anneal it at 150 °C for 15 min to obtain a perovskite layer;

[0089] S3. Use a pipette to aspirate 50 μL of the Spiro OMeTAD hole transport layer solution and spin-coat it onto the perovskite layer at a speed of 3000 rpm for 30 s to obtain a hole transport layer;

[0090] S4. On the hole transport layer, vacuum deposit silver metal with a thickness of 80 nm to obtain a metal back electrode, forming a perovskite solar cell.

[0091] Comparative Example 2

[0092] This comparative example provides a modified perovskite cell, and the preparation method includes the following steps:

[0093] In the same manner as in Example 3, the difference is that ZIF-67 is changed to Co-MOF-74.

[0094] Comparative Example 3

[0095] This comparative example provides a modified perovskite cell, and the preparation method includes the following steps:

[0096] In the same manner as in Example 3, the difference is that ZIF-67 is changed to ZIF-8.

[0097] Test Example

[0098] (1) Photovoltaic conversion efficiency test: Test using an electrochemical workstation, and calibrate the light intensity to AM1.5G one sun (100 mW / cm 2 ) using a standard silicon solar cell calibrated by NIM; use a metal mask made of aluminum to define the effective active area of the perovskite cells prepared in the examples and comparative examples as 0.09 cm 2 ; P inis the incident power of sunlight, and the incident power of sunlight used in the experiment is 100 mW / cm². -2 , the J-V curve is measured at a scanning rate of 100 mV / s in the range of 1.2 V to -0.1 V. Here, J is the current density (Jsc), V is the voltage (Voc), and FF is the fill factor, all of which can be directly read. The formula for the photoelectric conversion efficiency (PCE) is: PCE = (Voc × Jsc × FF / P in ) × 100%, and the specific test results are shown in Table 1 and Figure 3 as follows.

[0099] Table 1

[0100] Photoelectric conversion efficiency (%) Example 1 20.041780 Example 2 20.022461 Example 3 18.772985 Example 4 18.463229 Example 5 19.173816 Example 6 19.325484 Example 7 18.021514 Comparative Example 1 16.315982 Comparative Example 2 17.819766 Comparative Example 3 17.151852

[0101] From Figure 3 , it can be seen that the J-V curve of Example 1 with ZIF-67 modification has a significantly higher short-circuit current density (Jsc) than the J-V curve of Comparative Example 1 without ZIF-67 modification. This indicates that Example 1 has a higher short-circuit current. A higher short-circuit current density shows that the experimental group's materials or structures can generate current more effectively after absorbing photons and reduce charge recombination or resistance loss, thus proving higher efficiency in light absorption, carrier separation, or transport.

[0102] (2) Grains in the perovskite layer: The surface of the product obtained in Step 3 is tested using a scanning electron microscope (JSM-7800F, Japan). The test results of Example 1 are as shown in Figure 4 , and the test results of Comparative Example 1 are as shown in Figure 5 . It can be seen from the figures that, compared with Comparative Example 1, the average grain size of the grains in the perovskite layer of Example 1 is larger, and the crystal form is complete with fewer defects.

[0103] Obviously, the above examples are merely illustrations for clear explanation and are not limitations on the implementation methods. For those of ordinary skill in the art, other different forms of changes or modifications can be made based on the above description. It is not necessary and impossible to list all implementation methods here. The obvious changes or modifications derived therefrom are still within the protection scope of the present invention.

Claims

1. A perovskite solar cell, characterized in that, The perovskite solar cell includes a substrate, a ZIF-67 modified electron transport layer, a perovskite layer, a hole transport layer, and a metal back electrode, which are sequentially arranged.

2. A preparation method of a perovskite solar cell, characterized in that, The preparation method includes the following steps: sequentially preparing a ZIF-67 modified electron transport layer, a perovskite layer, a hole transport layer, and a metal back electrode on the substrate; The preparation of the ZIF-67 modified electron transport layer includes the following steps: preparing an electron transport layer on the substrate; coating a ZIF-67 suspension on the electron transport layer and annealing to obtain the ZIF-67 modified electron transport layer.

3. The perovskite solar cell according to claim 2, wherein The average particle size of the ZIF-67 is 50 - 120 nm; optionally 80 - 100 nm.

4. The preparation method according to claim 2 or 3, characterized in that, The dosage ratio of ZIF-67 to water in the ZIF-67 suspension is (0.5 - 2) mg : (1 - 3) mL, optionally (0.5 - 1) mg : (1 - 3) mL; Optionally, based on the area of the substrate, the dosage of the ZIF-67 suspension is 40-100 μL / mm 2 .

5. The preparation method according to claim 3 or 4, characterized in that, The annealing temperature is 50 - 180 °C and the time is 3 - 15 min.

6. The preparation method according to claim 5, characterized in that, The annealing temperature is 100 - 150 °C and the time is 5 - 10 min.

7. The preparation method according to any one of claims 3-6, characterized in that, The preparation of the perovskite layer includes the following steps: (1) preheating the first perovskite precursor solution, and coating the first perovskite precursor solution on the ZIF-67 modified electron transport layer to obtain the first perovskite layer; (2) coating the second perovskite precursor solution on the first perovskite layer and annealing to obtain the perovskite layer.

8. The preparation method according to claim 7, characterized in that, The preheating temperature is 70 - 80 °C and the time is 5 - 10 min.

9. The preparation method according to claim 7 or 8, characterized in that, In step (2), the annealing temperature is 120 - 150 °C and the time is 15 - 20 min.

10. The perovskite solar cell according to claim 1 or 2, or the perovskite solar cell prepared by the preparation method according to any one of claims 3 - 9 is applied in the photovoltaic field.

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