A perovskite solar cell, a preparation method thereof, and a fabricated tandem perovskite cell

Abstract

The present invention relates to a perovskite solar cell, which includes a substrate, a hole transport layer, a perovskite film layer, an electron transport layer and an electrode layer. The perovskite film layer includes a perovskite material ABX3 and an additive. The additive contains an electron-withdrawing group. After the additive is mixed with the perovskite material, the perovskite film layer is formed. A modification material layer is provided between the perovskite film layer and the electron transport layer, and the modification material layer forms an n-type doping at the contact interface of the perovskite film layer. Diethyl (3-(trifluoromethyl)benzyl)phosphonate is doped in the perovskite film layer of the battery, so that the intrinsic weakly n-type perovskite is converted into p-type near the hole transport layer, and a surface modification material is provided between the perovskite film layer and the electron transport layer, so that the perovskite film layer near the electron transport layer is converted into n-type, forming an efficient p-n junction and improving the efficiency of the perovskite battery.

Description

Technical Field

[0001] The present invention relates to a perovskite solar cell, a preparation method thereof, and a fabricated tandem perovskite cell, belonging to the field of photovoltaics. Background Art

[0002] As a clean energy source, solar energy can meet the growing global energy demand. Among numerous optoelectronic devices, perovskite solar cells have attracted much attention due to their high power conversion efficiency and low manufacturing cost. The theoretical efficiency limit of a single-junction perovskite solar cell is approximately 31%, and the current record efficiency in the laboratory is 26.7%. According to the calculation of the Photovoltaic Association, for every 1% absolute increase in the efficiency of a photovoltaic cell, its levelized cost of electricity (LCOE) decreases by 5 - 7%. Therefore, improving the absolute efficiency of the cell is crucial for cost reduction in the photovoltaic industry.

[0003] Single-junction perovskite cells have achieved a power conversion efficiency of 26.7%, which is very close to the 27.3% efficiency of crystalline silicon. Further improving the efficiency is already very limited, and constructing tandem cells is a way to solve the above bottleneck. Perovskite-silicon tandem cells (perovskite-silicon tandem cells) have received extensive attention due to their high conversion efficiency and compatibility. For the wide-bandgap perovskite cell part in the perovskite-silicon tandem cell, there is still a large gap between its efficiency and stability and commercialization. Further improving the efficiency and stability of the wide-bandgap cell is the focus of commercialization. Compared with the service life of 20 - 30 years for crystalline silicon cells, the lifespan of perovskite is generally considered to be within 5 years, and some literature estimates that the service life of perovskite is only 2 - 3 years. At this service life, the levelized cost of electricity (LCOE) of the device will lag far behind that of commercial silicon cells. Therefore, improving the stability of perovskite cells is the top priority for promoting the commercialization of perovskite cells.

[0004] The sources of the instability and low efficiency of perovskite solar cells are mainly non-radiative recombination and ion migration in the perovskite film layer. Among them, non-radiative recombination is dominated by defects. The presence of defects significantly increases the proportion of non-radiative recombination and significantly reduces the performance of the device. Secondly, ion migration is the main factor leading to device degradation. For example, the migrating halogen ions can react with the electrodes and hinder the transport of photo-generated carriers. Therefore, considering the above two aspects, the defects inside the perovskite device are the most critical factors causing the decline of efficiency and stability. According to research, the defects of perovskite are more concentrated on the surface and grain boundaries of the perovskite film layer. In addition, the perovskite material itself tends to be an n-type crystal, which generates a large potential barrier at the interface in contact with the hole layer. The optimal situation for the perovskite film layer is that the lower interface in contact with the p-type transport layer is approximately p-type, and the upper interface in contact with the n-type transport layer is approximately n-type, so as to form an ideal p-n junction, enhance the built-in electric field and the efficiency of carrier separation and transport. Therefore, doping regulation of the perovskite film layer is one of the means to construct high-performance devices. Summary of the Invention

[0005] In order to improve the efficiency of the solar cell, the present invention provides a perovskite solar cell. Diethyl (3-(trifluoromethyl)benzyl)phosphonate is doped in the perovskite film layer, so that the intrinsic weakly n-type perovskite is converted into p-type near the hole transport layer, and a modifying material is arranged between the perovskite film layer and the electron transport layer, so that the perovskite film layer near the electron transport layer is converted into n-type, thereby improving the efficiency of the perovskite solar cell.

[0006] One of the solutions adopted is: a perovskite solar cell, including a substrate, a hole transport layer, a perovskite film layer, an electron transport layer and an electrode layer arranged in sequence, forming a p-i-n structure perovskite solar cell. In the present invention, a modifying material layer is arranged between the perovskite film layer and the electron transport layer. The modifying material layer has a suitable ammonium group, can be closely connected to the surface, and forms an n-type doping with the perovskite film layer. The material of the perovskite film layer at least includes a perovskite material and an additive. An electron-withdrawing group is arranged on the additive to convert the intrinsic perovskite material into p-type, and the distribution form of the additive on the perovskite film layer is that the content gradually decreases from near the hole transport layer to near the electron transport layer. This setting enables a gradient p-type doping to be formed inside the perovskite film layer, presenting strong p-type characteristics on the side of the hole transport layer.

[0007] The modifying material layer is arranged between the perovskite film layer and the electron transport layer material, so that the perovskite film layer near the electron transport layer presents n-type doping. On the basis of restoring the intrinsic weak n-type, the n-type characteristics are further strengthened, and the electron transport performance of the perovskite is improved.

[0008] In the perovskite material ABX3 of the present invention, A is an organic-inorganic cation, B is a lead ion, and X is a halogen. The perovskite material can directly adopt the ABX3 material, or can be two or more materials that can form ABX3 through reaction. As a preference, A is a combination of one or more of formamidinium ion, methylammonium ion, cesium ion, and rubidium ion, X is a combination of one or more of chloride ion, bromide ion, and iodide ion, and B is a lead ion. Preferably, the perovskite film layer material is composed of two or more components, and the two or more components form an ABX3-type structural material through reaction. For example, it is formed by depositing a mixed solution of two or more of lead iodide, lead bromide, cesium iodide, rubidium iodide, formamidinium iodide, methylammonium iodide, methylammonium bromide, and methylammonium chloride. Preferably, the perovskite film layer material is one or two of lead iodide and lead bromide, and one or more of cesium iodide, rubidium iodide, formamidinium iodide, methylammonium iodide, methylammonium bromide, and methylammonium chloride, which react with each other to form.

[0009] As a preferred mode, the additive containing an electron-withdrawing group is diethyl (3-(trifluoromethyl)benzyl)phosphonate, and the structural formula is:

[0010] ; This material not only contains groups such as P=O and has a strong electron-withdrawing ability, with the potential to transform the weak n-type of the perovskite into a p-type, but also can keep a relatively large amount staying at the lower interface during the formation of the perovskite film layer with the perovskite material. A variety of passivation functional groups in the material can effectively passivate the defects at the lower interface and reduce the defect density.

[0011] As a preferred mode, the material of the modification material layer is one or more combinations of EDAI2 (ethane-1,2-diammonium iodide

[0012] ), CF3-PEAI (4-trifluoromethylphenethylamine iodide), PEAI (phenethylamine iodide), F-PEAI (p-fluorophenethylamine iodide), CF3O-PEAI (4-trifluoromethoxyphenethylamine iodide salt). Further preferably, CF3O-PEAI, and the thickness of the modification material layer is 2-5 nm. The modification film layer with this thickness can make the conductivity of the material moderate. Exceeding 5 nm will cause problems in transmission, and being too thin will not play a doping role.

[0013] As a preferred mode, the hole transport layer material is one or more combinations of MeO-2PACz ([2-(3,6-dimethoxy-9H-carbazol-9-yl)ethyl]phosphonic acid), Me-4PACz ((4-(3,6-dimethyl-9H-carbazol-9-yl)butyl)phosphonic acid), PTAA (poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine]), and nickel oxide. The electron transport layer is one or more combinations of fullerene and its derivatives, tin dioxide, and titanium dioxide.

[0014] The second solution adopted by the present invention is: a preparation method of a perovskite solar cell, comprising the following steps:

[0015] S01 Obtain a substrate;

[0016] S02 Set a hole transport layer on the substrate;

[0017] S03 Set a perovskite film layer on the hole transport layer;

[0018] S04 Set a modification material layer on the perovskite film layer;

[0019] S05 Set an electron transport layer on the modification material layer;

[0020] S06 Set an electrode layer on the electron transport layer;

[0021] Among them, the preparation method of the hole transport layer is preferably:

[0022] A Mix MeO-PACz with an ethanol solution to obtain an ethanol solution of MeO-2PACz, and use a 0.45 μm filter core to filter out large particulate matter, and the filtered solution is reserved;

[0023] B Spin-coat the filtered solution on the substrate, and the substrate is preferably ITO glass;

[0024] C After annealing, a MeO-2PACz hole transport layer with a thickness of about 3 nm is obtained.

[0025] The preparation method of the perovskite film layer can be a solution method, a vacuum co-evaporation method, a combination of vacuum and solution methods. The solution method includes solution spin-coating method, solution blade-coating method, and solution spraying method. The preferred preparation method is: a Mix at least one component of lead iodide and lead bromide with at least one component of methylammonium iodide, formamidinium iodide, methylammonium bromide, and methylammonium chloride and an additive, and deposit the mixture on the hole transport layer, and the deposition method is one of spin-coating, blade-coating, and spraying; b Assist in crystal film formation: the method is one or a combination of anti-solvent dropping, vacuum drying, and heating assistance; c After the wet film is formed, perform heat annealing to evaporate the residual solvent and promote the crystallization of the perovskite film layer; d Perform post-treatment on the film formed by annealing crystallization, and dry it by heating or vacuum.

[0026] Further preferably, the preparation method of the perovskite film layer includes the following steps:

[0027] A Dissolve PbI2, FAI, PbBr2, and FABr in a mixed solution of N,N-dimethylformamide and dimethyl sulfoxide in a set molar ratio to form Solution 1;

[0028] B Add MACl to Solution 1 to form Solution 2;

[0029] C Add diethyl (3-(trifluoromethyl)benzyl)phosphonate to Solution 2 to form Solution 3;

[0030] D Heat Solution 3 and stir until a complete solution is obtained to get the perovskite film layer solution;

[0031] E Filter the perovskite film layer solution to obtain a filtrate, spin-coat the filtrate on the hole transport layer, and add the anti-solvent chlorobenzene during the spin-coating process;

[0032] F After the spin-coating is completed, anneal to obtain the perovskite film layer.

[0033] The preparation method of the modification material layer is as follows: dissolve the modification layer material in an organic solvent, and the organic solvent is one of toluene, chlorobenzene, methanol, and ethanol; b Spin-coat and deposit the modification layer solution on the perovskite film layer; c Use a heating stage for heat treatment and anneal to cure the modification layer. This preparation method can be applicable to a variety of solvents, enhance the adjustability of the solvents, select a suitable solvent type according to the crystallization rate and mode of the modification layer material, and enable the formed modification layer to better fuse with the perovskite film layer.

[0034] Further preferably, the preparation method of the modification material layer includes the following steps:

[0035] A Dissolve CF3O-PEAI in isopropanol and chlorobenzene, shake and stir until completely dissolved to form the modification layer material solution;

[0036] B Filter the modification layer material solution using a filter core to obtain a filtrate;

[0037] C Spin-coat the filtrate on the perovskite film layer;

[0038] D Anneal at 90~130 °C to obtain the modification material layer.

[0039] Based on the above first and second solutions, the perovskite solar cell prepared by the present invention is a wide-bandgap perovskite solar cell and can be used as the top cell of a tandem perovskite solar cell.

[0040] The beneficial effects of the present invention include: By adding an additive material containing amino and acidic groups into the perovskite film layer, the additive can remain in the film layer as the perovskite crystallizes. Since this molecule is easy to deposit on the lower interface of the perovskite, its content decreases with the increasing distance from the lower interface. This type of material has the following advantages: 1. The molecule contains groups such as P=O, which has strong electron-withdrawing ability and can transform the intrinsic weak n-type of perovskite into p-type; 2. The molecular structure contains a variety of passivation functional groups. Since a relatively large amount remains at the lower interface, that is, the interface in contact with the hole transport layer, a variety of groups can effectively passivate the lower interface and reduce the defect density. The present invention coats a modified material layer on the perovskite film layer. The modified materials are EDAI2 and CF3O-PEAI. On the one hand, it can passivate the defects at the interface between the perovskite and the electron transport layer, and on the other hand, it can change the weak p-type at the interface to n-type, and cooperate with the additive to regulate the energy barrier of the perovskite and improve the efficiency of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] Figure 1 Performance test chart of the batteries prepared in Example 1 and Comparative Example 1 of the present invention;

[0042] Figure 2 Side view of the performance of the batteries prepared in Example 2 and Comparative Example 2 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0043] The following further elaborates the present invention in detail with reference to the drawings and specific embodiments. However, it should be understood that the protection scope of the present invention is not limited by the specific embodiments. Unless otherwise specified, any range described in the present invention includes the end values and any values between the end values, as well as any sub-ranges formed by any values between the end values or the end values. For all raw materials of the present invention, there is no special limitation on their purity, and the present invention preferably uses analytical pure. For all raw materials of the present invention, their sources and abbreviations are all conventional sources and abbreviations in the art, and are clearly defined in the relevant fields of their uses. Those skilled in the art can purchase them from the market or prepare them by conventional methods according to the abbreviations and corresponding uses. All percentages in the present invention are mass percentages unless otherwise specified. Example

[0044] This example prepares an inverted (p-i-n) wide-bandgap perovskite (1.67 eV) solar cell. The preparation method adopted is as follows:

[0045] S01 Obtain a substrate

[0046] Using ITO glass as the substrate, the ITO glass substrate was first ultrasonically cleaned in a cleaner and deionized water for 20 minutes each, then ultrasonically cleaned in acetone for 20 minutes, and finally ultrasonically cleaned in isopropyl alcohol (IPA) for 20 minutes. Subsequently, it was dried with a nitrogen gun and placed in an ultraviolet ozone processor for 15 minutes for standby.

[0047] Preparation of the hole transport layer with S02

[0048] (1) Mix 1 mg of MeO-PACz with 1 mL of ethanol solution to obtain a 1 mg / mL MeO-2PACz solution. Use a 0.45 μm filter core to filter out large particulate matter, and the filtered solution is reserved for use.

[0049] (2) Spin-coat the filtered solution onto the ITO glass at a spin-coating rate of 3300 rpm for 30 s.

[0050] (3) Anneal at 120 °C for 10 min to obtain a MeO-2PACz hole transport layer with a thickness of approximately 3 nm.

[0051] Preparation of the perovskite film layer with S03

[0052] (1) Prepare the perovskite film layer solution

[0053] a Dissolve PbI2 (lead iodide), FAI (formamidinium iodide), PbBr2 (lead bromide), and FABr (formamidinium bromide) in a mixed solution of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) at a molar ratio of 0.75:0.75:0.25:0.25 to form Solution 1. The volume ratio of DMF to DMSO is 5:1, and the concentration of Pb 2+ in Solution 1 is 1.7 mol / L;

[0054] b Add MACl (methylammonium chloride) additive to Solution 1 to form Solution 2. The mass fraction of MACl in Solution 2 is 33.5%.

[0055] c Add diethyl (3-(trifluoromethyl)benzyl)phosphonate additive to Solution 2 to form Solution 3. The mass fraction of diethyl (3-(trifluoromethyl)benzyl)phosphonate in Solution 3 is 2%. The structural formula of diethyl (3-(trifluoromethyl)benzyl)phosphonate is: .

[0056] d Heat Solution 3 to 70 °C and stir for 70 min until completely dissolved;

[0057] e Use a 0.22 μm filter core to filter the solution to remove large particulate matter in the solution and obtain the perovskite film layer solution.

[0058] (2)Spin-coat the perovskite film layer solution on the hole transport layer at a spin-coating rate of 4000 rpm. At the 30th second of spin-coating, drop 0.4 mL of the anti-solvent chlorobenzene onto the film layer, complete the dropping within 4 s, and then continue spin-coating for a total of 40 s.

[0059] (3)After spin-coating, anneal in air at 145 °C for 20 min, control the humidity at 20 - 30%, and obtain the perovskite film layer with a thickness of about 700 nm.

[0060] S04 Preparation of the modification material layer

[0061] (1)Prepare the solution for the modification layer. Dissolve 0.6 mg of CF3O-PEAI in 0.5 mL of isopropanol and 0.5 mL of chlorobenzene, shake and stir to form a 0.6 mg / mL solution, and use a 0.45 μm filter core to filter out larger particles in the solution.

[0062] (2)Spin-coat the modification layer solution on the perovskite film layer at a speed of 2000 rpm for 30 s, and then anneal in a glove box at 100 °C for 3 minutes using a heating stage to form a modification layer with a thickness of about 5 nm.

[0063] S05 Preparation of the electron transport layer

[0064] Use a vacuum evaporation equipment and evaporate the C 60 material by thermal evaporation to form a 20-nm electron transport layer on the perovskite film layer, and the evaporation vacuum degree is below 7×10 -4 Pa.

[0065] S06 Preparation of the hole blocking layer:

[0066] Use a vacuum evaporation equipment and evaporate the BCP (2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline or bathocuproine) material by thermal evaporation to form an 8-nm hole blocking layer on the electron transport layer, and the evaporation vacuum degree is below 7×10 -4 Pa.

[0067] S07 Preparation of the electrode:

[0068] Use a vacuum evaporation equipment and evaporate 150 nm of copper (Cu) on the surface of the BCP as the electrode by thermal evaporation, and the evaporation vacuum degree is below 7×10 -4 Pa.

[0069] Comparative Example 1

[0070] The difference from Example 1 is only that diethyl (3-(trifluoromethyl)benzyl)phosphonate is not added to the perovskite film layer, and the modification material layer is not set between the perovskite film layer and the electron transport layer.

[0071] The photoelectric conversion efficiency of the perovskite solar cells in Test Example 1 and Comparative Example 1 was measured. The scanning was performed from a high voltage (1.3 V) to a low voltage (-0.1 V) with a scanning step of 0.1 V and an interval time of 20 ms. The conversion power of the cell was obtained by multiplying the voltage and the current, and the conversion efficiency of the cell was then obtained by integrating the incident power of sunlight. From Figure 1 it can be seen that the conversion efficiency of the perovskite solar cell in Example 1 was significantly improved compared with that in Comparative Example 1. In particular, the FF (fill factor) was 71.2% without adding a modification layer and increased to 78.0% after adding the modification layer, indicating that pn doping effectively accelerated the carrier transport. Example

[0072] The inverted (p-i-n) wide-bandgap perovskite (1.67 eV) solar cell was fabricated in this example. The fabrication method adopted includes the following steps:

[0073] S01 Obtain a substrate

[0074] ITO glass was used as the substrate. The ITO glass substrate was first ultrasonically cleaned in a cleaner and deionized water for 20 minutes each, then ultrasonically cleaned in acetone for 20 minutes, and finally ultrasonically cleaned in isopropyl alcohol (IPA) for 20 minutes. Subsequently, it was dried with a nitrogen gun and placed in an ultraviolet ozone processor for 15 minutes for standby.

[0075] S02 Prepare a hole transport layer

[0076] (1) 1 mg of MeO-PACz was mixed with 1 mL of ethanol solution to obtain a 1 mg / mL MeO-2PACz solution. The solution was filtered through a 0.45 μm filter core to remove large particles, and the filtered solution was reserved for use;

[0077] (2) The filtered solution was spin-coated on the ITO glass at a spin-coating rate of 3300 rpm for 30 s;

[0078] (3) Annealing was carried out at 120 °C for 10 min to obtain a MeO-2PACz hole transport layer with a thickness of about 3 nm.

[0079] S03 Prepare a perovskite film layer

[0080] (1) Prepare a perovskite film layer solution

[0081] a Dissolve PbI2 (lead iodide), FAI (formamidinium iodide), PbBr2 (lead bromide), and FABr (formamidinium bromide) in a mixed solution of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) at a molar ratio of 0.75:0.75:0.25:0.25 to form Solution 1. The volume ratio of DMF to DMSO is 5:1, and the concentration of Pb 2+ in Solution 1 is 1.7 mol / L;

[0082] b Add the MACl additive to Solution 1 to form Solution 2. The mass fraction of MACl in Solution 2 is 33.5%;

[0083] c Add diethyl (3-(trifluoromethyl)benzyl)phosphonate additive to Solution 2 to form Solution 3. The addition amount of diethyl (3-(trifluoromethyl)benzyl)phosphonate in Solution 3 is 4%; The structural formula of diethyl (3-(trifluoromethyl)benzyl)phosphonate is: .

[0084] d Heat Solution 3 to 70 °C and stir for 70 min until completely dissolved;

[0085] e Filter the solution using a 0.22 μm filter core to remove large particulate matter in the solution, obtaining the perovskite film layer solution.

[0086] (2) Spin-coat the perovskite film layer solution on the hole transport layer at a spin-coating rate of 4000 rpm. At the 30th second of spin-coating, drop 0.4 mL of the anti-solvent chlorobenzene on the film layer, complete the dropping within 4 s, and then continue spin-coating for a total of 40 s.

[0087] (3) After spin-coating, anneal in air at 145 °C for 20 min, with the humidity controlled at 20 - 30%, to obtain the perovskite film layer with a thickness of approximately 700 nm.

[0088] S04 Preparation of the modified material layer

[0089] (1) Prepare the solution for the modified material layer. Dissolve 0.3 mg of EDAI2 in 1.0 mL of isopropanol, shake and stir to form a 0.3 mg / mL solution, and use a 0.45 μm filter core to filter out larger particulate matter in the solution.

[0090] (2) Spin-coat the modified material layer solution on the perovskite film layer at a speed of 2000 rpm for 30 s, and then anneal in a glove box at 100 °C for 5 minutes using a heating stage to form a modified material layer with a thickness of approximately 3 nm.

[0091] S05 Preparation of the electron transport layer

[0092] Using a vacuum evaporation equipment, evaporate C by thermal evaporation method 60 material, form an electron transport layer with a thickness of 20 nm on the perovskite film layer, and the evaporation vacuum degree is below 7×10 -4 Pa.

[0093] Preparation of S06 hole blocking layer:

[0094] Using a vacuum evaporation equipment and an atomic layer deposition equipment, form a 20-nm SnOx layer on the electron transport layer, and the evaporation vacuum degree is below 6×10 -4 Pa.

[0095] Preparation of S07 electrode:

[0096] Using a vacuum evaporation equipment, evaporate 150 nm of silver (Ag) on the surface of SnOx as the electrode by thermal evaporation method, and the evaporation vacuum degree is below 7×10 -4 Pa;

[0097] The perovskite solar cell is fabricated.

[0098] Comparative Example 2

[0099] The differences from Example 2 are: (1) Diethyl (3-(trifluoromethyl)benzyl)phosphonate is not added to the perovskite film layer; (2) A modification material layer is not provided between the perovskite film layer and the electron transport layer.

[0100] Test the photoelectric conversion efficiency of the perovskite solar cells in Example 2 and Comparative Example 2. The scanning is carried out from a high voltage (1.3 V) to a low voltage (-0.1 V) with a scanning step of 0.1 V and an interval time of 20 ms. The conversion power of the battery is obtained from the product of voltage and current, and then the conversion efficiency of the battery is obtained by integrating the incident power of sunlight. It can be Figure 2 seen that the conversion efficiency of the perovskite solar cell in Example 2 is significantly improved compared with that in Comparative Example 2. After adding the modification layer in Example 2, the fill factor FF is 78.4%, which is significantly improved compared with the fill factor of 72.1% in Comparative Example 2, further indicating that pn doping effectively accelerates the carrier transport.

[0101] The above embodiments are only used to illustrate the technical solutions of the present invention and not to limit them. Although the present invention has been described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that the technical solutions of the present invention can be modified or equivalently replaced without departing from the spirit and scope of the technical solutions of the present invention.

Claims

1. A perovskite solar cell, comprising a substrate, a hole transport layer, a perovskite film layer, an electron transport layer and an electrode layer, characterized in that: The perovskite film layer comprises a perovskite material ABX3 and an additive, wherein A is an organic-inorganic cation, B is a lead ion, and X is a halogen. The additive contains an electron-withdrawing group, and the additive is diethyl (3-(trifluoromethyl)benzyl)phosphonate. The additive is mixed with the perovskite material to form the perovskite film layer. A modification material layer is provided between the perovskite film layer and the electron transport layer. The modification material layer forms n-type doping on the contact interface of the perovskite film layer. The structural formula of the additive is:

2. The perovskite solar cell according to claim 1, characterized in that: The material in the modification material layer is a combination of one or more of EDAI2 ethane 1,2-diammonium iodide, CF3O-PEAI4-trifluoromethoxyphenylethylamine iodide, CF3-PEAI4-trifluoromethylphenylethylamine iodide, PEAI phenylethylamine iodide, and F-PEAI p-fluorophenylethylamine iodide.

3. The perovskite solar cell according to claim 1, characterized in that: In the perovskite material ABX3 in the perovskite film layer, A is a combination of one or more of formamidinium ions, methylamine ions, cesium ions, and rubidium ions, X is a combination of one or more of chloride ions, bromide ions, and iodine ions, and B is a lead ion.

4. The perovskite solar cell according to claim 1, characterized in that: The content of the additive in the perovskite film layer gradually decreases from the side close to the hole transport layer to the side close to the electron transport layer.

5. A method for preparing a perovskite solar cell, characterized in that: The following steps are involved: S01 obtains a substrate; S02 preparing a hole transport layer on the substrate; S03 prepares a perovskite film layer on the hole transport layer, wherein the perovskite film layer is a mixed material layer of the perovskite material ABX3 and an additive, wherein A is an organic-inorganic cation, B is a lead ion, and X is a halogen. The additive contains an electron-withdrawing group, and the additive is (3-(trifluoromethyl)benzyl)phosphonic acid diethyl ester, and the structural formula of the additive is: S04 preparing a modification material layer on the perovskite film layer, wherein n-type doping is formed on the contact interface between the modification material layer and the perovskite film layer; S05: preparing an electron transport layer on the modified material layer.

6. The method for preparing a perovskite solar cell according to claim 5, characterized in that: The method for preparing the perovskite film layer comprises the following steps A. PbI2, FAI, PbBr2, and FABr are dissolved in a mixture of N,N-dimethylformamide and dimethyl sulfoxide at a set molar ratio to form solution 1; B adds MACl to solution 1 to form solution 2; C. Add diethyl (3-(trifluoromethyl)benzyl)phosphonate to solution 2 to form solution 3; D. Heat solution 3 and stir until it is completely dissolved to obtain a perovskite film solution; E. Filter the perovskite film solution to obtain a filtrate, spin-coat the filtrate on the hole transport layer, and dropwise add anti-solvent chlorobenzene during the spin-coating process; After the spin coating is completed, annealing is performed to obtain the perovskite film layer.

7. The method for preparing a perovskite solar cell according to claim 6, characterized in that: The mass concentration of diethyl (3-(trifluoromethyl)benzyl)phosphonate in solution three is 1% to 5%.

8. The method for preparing a perovskite solar cell according to claim 5, characterized in that: The material in the modified material layer is CF3O-PEAI, and the preparation method of the modified material layer is: A. Dissolve CF3O-PEAI in isopropanol and chlorobenzene, and shake and stir until fully dissolved to form a modified material layer solution; B uses a filter element to filter the modified material layer solution to obtain a filtrate; C spin-coating the filtered solution on the perovskite film layer; D is annealed at 90-130°C to obtain a modified material layer.

9. A perovskite tandem solar cell, characterized in that: The wide band gap cell is prepared by using the perovskite solar cell described in any one of claims 1 to 4 or the perovskite solar cell prepared by the preparation method described in any one of claims 5 to 8.

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