A fluorine-substituted benzimidazolium-alkyl sulfonate derivative, preparation method and application thereof

Abstract

The present application relates to the technical field of perovskite materials, and particularly relates to a fluorine-substituted benzimidazolium-alkyl sulfonate derivative, a preparation method and application. The structural general formula of the fluorine-substituted benzimidazolium-alkyl sulfonate derivative is: wherein R1 and R2 are independently selected from hydrogen or fluorine, and L1 is selected from C1-C3 alkyl. The present application forms an ionic additive with dual-site defect passivation function by ion pairing of the fluorine-substituted benzimidazolium cation and the alkyl sulfonate anion, which can simultaneously achieve perovskite bulk phase and surface defect passivation, crystallization kinetics regulation and interface stability strengthening, and significantly improve the photoelectric conversion efficiency and long-term stability of the perovskite device. The fluorine-substituted benzimidazolium-alkyl sulfonate derivative is used as a perovskite precursor additive in a perovskite solar cell, and the highest photoelectric conversion efficiency reaches 22.93%.

Description

Technical Field

[0001] This invention relates to the field of perovskite materials technology, specifically to a fluorinated benzimidazolium-alkyl sulfonate derivative, its preparation method, and its application. Background Technology

[0002] Perovskite materials, due to their excellent photoelectric properties such as high absorption coefficient, long carrier diffusion length, and high carrier mobility, have become a research hotspot in the photovoltaic and optoelectronic device fields, and are widely used in devices such as perovskite solar cells, perovskite light-emitting diodes, and perovskite photodetectors. Among these, the photoelectric conversion efficiency (PCE) of perovskite solar cells (PSCs) has increased from an initial 3.8% to over 26% in just over a decade, demonstrating enormous potential for industrial application.

[0003] However, inherent defects in perovskite materials, such as lead vacancies, iodine vacancies, and surface dangling bonds, as well as grain boundary defects and lattice distortions that easily form during the crystallization process of perovskite films, severely restrict the performance improvement and long-term stability of perovskite devices. To address these issues, researchers have developed various defect passivation strategies, among which additive engineering has become one of the most commonly used methods due to its simplicity, low cost, and significant effects. By adding specific organic or inorganic additives to the perovskite precursor, the crystallization process of the perovskite film can be effectively controlled, bulk and surface defects can be passivated, and interfacial interactions can be strengthened, thereby improving the optoelectronic performance and stability of the device. Currently, reported perovskite additives mainly include organic ammonium salts, metal halides, and small organic molecules. However, existing perovskite additives generally suffer from poor compatibility with perovskite precursors, easily leading to uneven crystallization and pinhole defects in the perovskite film after addition, which in turn reduces device performance. Therefore, developing a perovskite additive with novel structure, significant defect passivation effect, excellent stability, simple preparation method, high yield, and controllable cost is of great significance for promoting the industrialization of perovskite devices.

[0004] Benzimidazole compounds, due to their unique heterocyclic structure, contain uncoordinated Pb in perovskites. 2+ Nitrogen atoms that form coordination interactions have been attempted as perovskite additives. However, traditional benzimidazole additives offer limited passivation effects and exhibit poor compatibility with the perovskite system. Currently, although there are a few reports of fluorinated benzimidazole compounds used in perovskite devices, these are mostly small molecules with single fluorinated benzimidazoles, which suffer from insufficient defect passivation sites and weak interactions with the perovskite lattice, making it difficult to achieve efficient passivation simultaneously. Summary of the Invention

[0005] To address the shortcomings of existing technologies, this invention provides a fluorinated benzimidazolium-alkyl sulfonate derivative, its preparation method, and its applications. This invention offers nine fluorinated benzimidazolium-alkyl sulfonate derivatives with specific structures, combining the fluorinated benzimidazolium cation with the alkyl sulfonate anion to achieve dual-site targeted passivation of defects. Simultaneously, the hydrogen bonding of fluorine atoms and the hydrophobic interaction of the alkyl chain enhance the stability of perovskite devices. The preparation method of this invention is mild, simple to operate, and has a high yield, effectively solving the problems of traditional additives having limited passivation effects and poor compatibility with perovskite systems, as well as the complexity and low yield of existing preparation processes.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first objective of this invention is to provide a fluorinated benzimidazolium-alkyl sulfonate derivative, the general structural formula of which is: In this context, R1 and R2 are independently selected from hydrogen or fluorine, and L1 is selected from C1~C3 alkyl groups.

[0007] Preferably, the fluorinated benzimidazolium-alkyl sulfonate derivatives are selected from... .

[0008] A second objective of this invention is to provide a method for preparing the above-mentioned fluorinated benzimidazolium-alkyl sulfonate derivatives, comprising the following steps: In the presence of an organic solvent, fluorinated benzimidazole is subjected to an acid-base neutralization reaction with C1-C3 alkyl sulfonic acids, followed by post-treatment to obtain fluorinated benzimidazole onium-alkyl sulfonate derivatives.

[0009] Preferably, the molar ratio of fluorinated benzimidazole to C1-C3 alkyl sulfonic acid is 1:1 to 1.2. The acid-base neutralization reaction is theoretically an equimolar reaction, but controlling the amount of alkyl sulfonic acid in a slightly excess range ensures complete protonation of the fluorinated benzimidazole feedstock and its conversion into ionic products, thereby maximizing product yield and reducing the residue of unreacted feedstock. If the amount of alkyl sulfonic acid is insufficient, the reaction will be incomplete, and unconverted fluorinated benzimidazole will remain in the product, reducing product purity and increasing the burden of subsequent purification. If the amount of alkyl sulfonic acid is excessive, residual free alkyl sulfonic acid will remain in the system, not only increasing the difficulty of post-processing, but also potentially corroding the lead-iodine framework in the perovskite lattice when used as a perovskite additive, damaging the film crystal quality, and thus impairing the photoelectric conversion performance of the device.

[0010] Preferably, the fluorinated benzimidazole is selected from 5-fluorobenzimidazole, 5,6-difluorobenzimidazole or 4,5-difluorobenzimidazole.

[0011] Preferably, the C1-C3 alkyl sulfonic acid is selected from methanesulfonic acid, ethanesulfonic acid, or propanesulfonic acid. When the carbon chain of an alkyl sulfonic acid exceeds 3 carbon atoms, the steric hindrance of the molecule increases, the reactivity decreases, and the crystallization and purification of the product becomes difficult. At the same time, the long carbon chain is too hydrophobic, which easily causes the additive to agglomerate, reduces the compatibility with the perovskite system, hinders carrier transport, destroys the film morphology, and ultimately leads to a decrease in the optoelectronic performance and stability of the device.

[0012] Preferably, the specific post-processing operation is as follows: after the acid-base neutralization reaction is completed, an alkaline reagent is first added to the system to adjust the pH to 6.5~7.5, the solvent is removed by vacuum concentration, then diethyl ether is added to disperse and crystallize, filtered, and vacuum dried at 45℃~50℃ for at least 8 hours.

[0013] A third objective of this invention is to provide a perovskite solar cell comprising a conductive substrate, a hole transport layer, a perovskite light-absorbing layer, an electron transport layer, a buffer layer, and a metal electrode, which are sequentially stacked; wherein the perovskite light-absorbing layer contains the aforementioned fluorine-substituted benzimidazolium-alkyl sulfonate derivative.

[0014] Preferably, the concentration of fluorinated benzimidazolium-alkyl sulfonate derivatives in the perovskite light-absorbing layer is 0.05 mmol / L to 0.1 mmol / L. If the concentration is too low, defect passivation will be insufficient, resulting in poor performance improvement; if the concentration is too high, additive aggregation will easily occur, damaging the perovskite film structure and hindering carrier transport, thus impairing the optoelectronic performance of the device.

[0015] Compared with the prior art, the beneficial effects of the present invention are as follows: 1. This invention provides a fluorinated benzimidazolium-alkyl sulfonate derivative with the following general structural formula: In this invention, R1 and R2 are selected from hydrogen or fluorine, and L1 is selected from C1-C3 alkyl groups. The fluorinated benzimidazolium-alkyl sulfonate derivatives of this invention, through their unique molecular structure design, possess both defect passivation and carrier transport functions, effectively regulating the crystallization behavior of perovskite thin films. Adding these fluorinated benzimidazolium-alkyl sulfonate derivatives as additives to perovskite precursor solutions can achieve dual-site targeted passivation of bulk and surface defects in perovskite thin films, regulate crystallization kinetics, and enhance interfacial stability. This significantly improves the open-circuit voltage (VOC), fill factor (FF), and power conversion efficiency (PCE) of perovskite devices, solving the technical problems of single defect passivation and poor compatibility with perovskite systems in existing perovskite additives. This provides important material support and technical solutions for the industrial application of high-performance perovskite devices.

[0016] Among them, the dual-site targeted passivation effect: the fluorine-substituted benzimidazolium cation serves as the first passivation site, and the nitrogen atom on its imidazole ring interacts with the uncoordinated Pb atoms at the perovskite grain boundaries and surface.2+ Strong coordination bonds are formed, and fluorine atoms, through the construction of a CF···H hydrogen bond network, target and anchor iodine vacancies and lead dangling bonds on the surface, effectively repairing surface defects and inhibiting non-radiative recombination; the alkyl sulfonate anion acts as a second passivation site, and its sulfonate group interacts with Pb through strong electrostatic interactions. 2+ Coordination penetrates deep into the perovskite bulk lattice, passivating bulk lead vacancies and lattice distortions, and forming hydrophobic barriers at grain boundaries via alkyl chains. The synergistic effect of cation and anion dual sites simultaneously achieves global repair of both bulk and surface defects in perovskite films, significantly reducing defect state density and improving carrier lifetime and device optoelectronic performance.

[0017] 2. This invention also provides a method for preparing fluorinated benzimidazole-onium alkyl sulfonate derivatives. In the presence of an organic solvent, fluorinated benzimidazole is reacted with a C1-C3 alkyl sulfonic acid via an acid-base neutralization reaction, followed by post-treatment to obtain the fluorinated benzimidazole-onium alkyl sulfonate derivatives. The preparation method of this invention employs a one-pot acid-base neutralization reaction, requiring no additional catalyst or harsh conditions. Its process is mild, simple to operate, and easily scaled up for industrial applications. Furthermore, the preparation method of this invention uses readily available raw materials, has controllable costs, and achieves high product yields (up to 89.6%), while avoiding high-temperature decomposition or complex purification steps, thus possessing excellent prospects for industrial production. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of a perovskite solar cell device.

[0019] Figure 2 The current-voltage curves are for the fluorinated benzimidazolium-alkyl sulfonate derivatives used in Examples 1 to 9 and for the blank control perovskite solar cells. Detailed Implementation

[0020] The technical solution of the present invention will be clearly and completely described below with reference to the data in the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0021] It should be noted that the technical terms used in this invention are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of this invention. Unless otherwise specified, all raw materials, reagents, instruments and equipment used in the following embodiments of this invention can be purchased on the market or prepared by existing methods.

[0022] While there are many types of perovskite additives in the existing technology, they generally suffer from prominent problems such as limited functionality, poor compatibility with perovskite precursors, and limited improvement in long-term device stability. Specifically, traditional benzimidazole additives are mostly neutral small organic molecules with insufficient defect passivation sites, making it difficult to simultaneously achieve effective passivation of both bulk and surface defects. Furthermore, the small amounts of fluorinated benzimidazole compounds reported so far have not formed ionic compounds with alkyl sulfonates, thus failing to fully utilize the strong interaction between anionic groups and lead ions in perovskite.

[0023] To address the problems existing in the prior art, this invention provides a fluorinated benzimidazolium-alkyl sulfonate derivative, the general structural formula of which is: In this invention, R1 and R2 are independently selected from hydrogen or fluorine, and L1 is selected from C1-C3 alkyl groups. The fluorinated benzimidazolium-alkyl sulfonate derivatives of this invention form bifunctional ionic additives with both cation and anion defect passivation sites by ion pairing the fluorinated benzimidazolium cation with the alkyl sulfonate anion. The fluorinated benzimidazolium cation interacts with uncoordinated Pb in the perovskite via the N atom on the imidazole ring. 2+ Coordinate bonds are formed, and the strong electronegativity of fluorine atoms can regulate the molecular electron cloud density and construct a hydrogen bond network, effectively passivating defects such as iodine vacancies and lead dangling bonds; the alkyl sulfonate anion further anchors Pb through the sulfonate group. 2+ Its alkyl chain forms a hydrophobic barrier at the perovskite grain boundaries, inhibiting water and oxygen erosion and ion migration. This ion-pair compound has good compatibility with the perovskite precursor and can be uniformly dispersed in the precursor solution, effectively regulating the crystallization kinetics of the perovskite film, reducing grain boundary defects, thereby significantly improving the open-circuit voltage, fill factor, and photoelectric conversion efficiency of perovskite devices, and enhancing the long-term operational stability of the devices.

[0024] To enable those skilled in the art to more clearly understand the technical solution of the present invention, the following will provide a detailed description in conjunction with specific embodiments: Example 1 A method for preparing a fluorinated benzimidazolium-alkyl sulfonate derivative, the technical route of which is shown below: This includes the following steps: 5-fluorobenzimidazole (3.0 g, 22.04 mmol) and 40 mL of ethyl acetate were added to a reaction flask and magnetically stirred for 2 h. The mixture was then cooled to 15 °C and kept at this temperature. Methylsulfonic acid (2.33 g, 24.24 mmol) was added dropwise. After the addition was complete, the mixture was reacted at 20 °C for 2 h, at which point the reaction was complete. Triethylamine was added dropwise to adjust the pH to 7. The solvent was concentrated under reduced pressure at a temperature not exceeding 45 °C until it became granular. The mixture was then cooled and ether was added and stirred to disperse the mixture. The mixture was filtered and dried under vacuum at 45 °C for 8 h to obtain a fluorinated benzimidazole onium-alkyl sulfonate derivative, namely compound A1, with a yield of 86.3% (4.42 g).

[0025] Example 2 A method for preparing a fluorinated benzimidazolium-alkyl sulfonate derivative, the technical route of which is shown below: This includes the following steps: 5-fluorobenzimidazole (3.0 g, 22.04 mmol) and 40 mL of ethyl acetate were added to a reaction flask and magnetically stirred for 2 h. The mixture was then cooled to 15 °C and kept at this temperature. Ethylsulfonic acid (2.67 g, 24.24 mmol) was added dropwise. After the addition was complete, the mixture was reacted at 20 °C for 2 h, and the reaction was then complete. Triethylamine was added dropwise to adjust the pH to 7. The solvent was concentrated under reduced pressure at a temperature not exceeding 45 °C until it became granular. The mixture was then cooled and added to diethyl ether with stirring to disperse it. The mixture was filtered and dried under vacuum at 45 °C for 8 h to obtain a fluorinated benzimidazole onium-alkyl sulfonate derivative, namely compound A2, with a yield of 77.5% (4.21 g).

[0026] Example 3 A method for preparing a fluorinated benzimidazolium-alkyl sulfonate derivative, the technical route of which is shown below: This includes the following steps: 5-fluorobenzimidazole (2 g, 14.69 mmol) and ethyl acetate (26 mL) were added to a reaction flask and magnetically stirred for 2 h. The mixture was then cooled to 15 °C and kept at this temperature. Propylene sulfonic acid (2.19 g, 17.63 mmol) was added dropwise. After the addition was complete, the mixture was reacted at 20 °C for 2 h, at which point the reaction was complete. Triethylamine was added dropwise to adjust the pH to 7. The solvent was concentrated under reduced pressure at a temperature not exceeding 45 °C until it reached a granular consistency. The mixture was then cooled and ether was added and stirred to disperse the mixture. The mixture was filtered and dried under vacuum at 45 °C for 8 h to obtain a fluorinated benzimidazole onium-alkyl sulfonate derivative, namely compound A3, with a yield of 80.2% (3.07 g).

[0027] Example 4 A method for preparing a fluorinated benzimidazolium-alkyl sulfonate derivative, the technical route of which is shown below: This includes the following steps: 5,6-Difluorobenzimidazole (2 g, 12.98 mmol) and acetonitrile (26 mL) were added to a reaction flask and magnetically stirred for 2 h. The mixture was then cooled to 15 °C and kept at this temperature. Methylsulfonic acid (1.37 g, 14.27 mmol) was added dropwise. After the addition was complete, the mixture was reacted at 20 °C for 2 h, at which point the reaction was complete. Triethylamine was added dropwise to adjust the pH to 7. The solvent was concentrated under reduced pressure at a temperature not exceeding 45 °C until it reached a granular consistency. The mixture was then cooled and ether was added and stirred to disperse the mixture. The mixture was filtered and dried under vacuum at 45 °C for 8 h to obtain a fluorinated benzimidazole onium-alkyl sulfonate derivative, namely compound B1, with a yield of 89.60% (2.91 g).

[0028] Example 5 A method for preparing a fluorinated benzimidazolium-alkyl sulfonate derivative, the technical route of which is shown below: This includes the following steps: 5,6-Difluorobenzimidazole (2 g, 12.98 mmol) and acetonitrile (26 mL) were added to a reaction flask and magnetically stirred for 2 h. The mixture was then cooled to 15 °C and kept at this temperature. Ethylsulfonic acid (1.57 g, 14.27 mmol) was added dropwise. After the addition was complete, the mixture was reacted at 20 °C for 2 h. The reaction was then complete. Triethylamine was added dropwise to adjust the pH to 7. The solvent was concentrated under reduced pressure at a temperature not exceeding 45 °C until it became granular. The mixture was then cooled and ether was added and stirred to disperse the mixture. The mixture was filtered and dried under vacuum at 45 °C for 8 h to obtain a fluorinated benzimidazole onium-alkyl sulfonate derivative, namely compound B2, with a yield of 71.4% (2.45 g).

[0029] Example 6 A method for preparing a fluorinated benzimidazolium-alkyl sulfonate derivative, the technical route of which is shown below: This includes the following steps: 5,6-Difluorobenzimidazole (2.5 g, 16.22 mmol) and acetonitrile (33 mL) were added to a reaction flask and magnetically stirred for 2 h. The mixture was then cooled to 15 °C and kept at this temperature. Propylsulfonic acid (2.22 g, 17.84 mmol) was added dropwise. After the addition was complete, the mixture was reacted at 20 °C for 2 h, at which point the reaction was complete. Triethylamine was added dropwise to adjust the pH to 7. The solvent was concentrated under reduced pressure at a temperature not exceeding 45 °C until it reached a granular consistency. The mixture was then cooled and ether was added and stirred to disperse the mixture. The mixture was filtered and dried under vacuum at 45 °C for 8 h to obtain a fluorinated benzimidazole onium-alkyl sulfonate derivative, namely compound B3, with a yield of 78.6% (3.55 g).

[0030] Example 7 A method for preparing a fluorinated benzimidazolium-alkyl sulfonate derivative is shown below: This includes the following steps: 4,5-Difluorobenzimidazole (2 g, 12.98 mmol) and acetonitrile (26 mL) were added to a reaction flask and magnetically stirred for 2 h. The mixture was then cooled to 15 °C and kept at this temperature. Methylsulfonic acid (1.31 g, 13.63 mmol) was added dropwise. After the addition was complete, the mixture was reacted at 20 °C for 2 h. The reaction was then complete. Triethylamine was added dropwise to adjust the pH to 7. The solvent was concentrated under reduced pressure at a temperature not exceeding 45 °C until it became granular. The mixture was then cooled and ether was added and stirred to disperse the mixture. The mixture was filtered and dried under vacuum at 45 °C for 8 h to obtain a fluorinated benzimidazole onium-alkyl sulfonate derivative, namely compound C1, with a yield of 83.3% (2.7 g).

[0031] Example 8 A method for preparing a fluorinated benzimidazolium-alkyl sulfonate derivative is shown below: This includes the following steps: 4,5-Difluorobenzimidazole (3.0 g, 19.47 mmol) and 40 mL of acetonitrile were added to a reaction flask and magnetically stirred for 2 h. The mixture was then cooled to 15 °C and kept at this temperature. Ethylsulfonic acid (2.25 g, 20.44 mmol) was added dropwise. After the addition was complete, the mixture was reacted at 20 °C for 2 h, at which point the reaction was complete. Triethylamine was added dropwise to adjust the pH to 7. The solvent was concentrated under reduced pressure at a temperature not exceeding 45 °C until it reached a granular consistency. The mixture was then cooled and added to diethyl ether with stirring to disperse it. The mixture was filtered and dried under vacuum at 45 °C for 8 h to obtain a fluorinated benzimidazole onium-alkyl sulfonate derivative, namely compound C2, with a yield of 46.5% (2.39 g).

[0032] Example 9 A method for preparing a fluorinated benzimidazolium-alkyl sulfonate derivative is shown below: This includes the following steps: 4,5-Difluorobenzimidazole (3.0 g, 19.47 mmol) and 40 mL of acetonitrile were added to a reaction flask and magnetically stirred for 2 h. The mixture was then cooled to 15 °C and kept at this temperature. Propylsulfonic acid (2.54 g, 20.44 mmol) was added dropwise. After the addition was complete, the mixture was reacted at 20 °C for 2 h, at which point the reaction was complete. Triethylamine was added dropwise to adjust the pH to 7. The solvent was concentrated under reduced pressure at a temperature not exceeding 45 °C until it reached a granular consistency. The mixture was then cooled and ether was added and stirred to disperse the mixture. The mixture was filtered and dried under vacuum at 45 °C for 8 h to obtain a fluorinated benzimidazole onium-alkyl sulfonate derivative, namely compound C3, with a yield of 40.7% (2.2 g).

[0033] Examples 1-9 of this invention all yielded fluorinated benzimidazolium-alkyl sulfonate derivatives with parallel effects. Taking the fluorinated benzimidazolium-alkyl sulfonate derivatives of Examples 1-9 as examples, they are applied to perovskite solar cell devices. The device structure is: ITO / hole transport layer / perovskite layer (containing compound additives) / electron transport layer / buffer layer / metal electrode, specifically as follows... Figure 1 As shown. Specifically:

[0034] ITO pretreatment: First, a 0.9mm thick ITO substrate was ultrasonically treated with deionized water, ethanol, and acetone for 15 minutes each. The cleaned ITO substrate was then placed in a forced-air drying oven and dried at 100℃ for 15 minutes. The dried ITO substrate was then placed in a UV ozone generator with a power of 30W and a treatment time of 25 minutes. Through the dual action of UV degradation and ozone oxidation, residual organic matter on the surface was further removed, while the hydrophilicity and surface energy of the substrate surface were improved. After treatment, the substrate was quickly transferred to a nitrogen glove box for later use.

[0035] Preparation of the hole transport layer: [2-(3,6-dimethoxy-9H-carbazole-9-yl)ethyl]phosphonic acid (MeO-2PACz, purity ≥99%) powder was weighed and mixed with ultra-dry ethanol in a specific ratio to prepare a hole transport material solution with a concentration of 1 mmol / L. The solution was stirred at room temperature for 30 min. 40 μL of filtered MeO-2PACz solution was uniformly dropped onto the substrate surface. The spin-coating parameters were set as follows: spin speed 4000 rpm, spin-coating time 30 s, acceleration 2000 rpm / s. The spin-coating program was started to allow the solution to spread uniformly and form a thin film. After spin-coating, the substrate was immediately transferred to a hot stage in a glove box and annealed at 100 °C for 10 min under a nitrogen atmosphere to obtain a hole transport layer with a thickness of 30 nm.

[0036] Preparation of the perovskite light-absorbing layer: PbI₂ (lead iodide, purity 99.99%), MABr (methylamine bromide, purity 99.5%), PbBr₂ (purity 99.99%), FAI (formamidinium iodide, purity 99.5%), and CsI (cesium iodide, purity 99.99%) were dissolved in a mixed solution of DMF:DMSO = 4:1. The solution was magnetically stirred at room temperature for 4 hours to form a perovskite light-absorbing layer with the chemical formula CsI. 0.05 (MA 0.05 FA 0.95 ) 0.95 Pb(Br 0.05 I 0.95A perovskite precursor solution containing fluorinated benzimidazolium-alkyl sulfonate derivatives was prepared by adding 0.1 mmol / L of the fluorinated benzimidazolium-alkyl sulfonate derivative. The substrate with the MeO-2PACz hole transport layer was fixed on a spin coater, and 50 μL of the perovskite precursor solution containing the fluorinated benzimidazolium-alkyl sulfonate derivative was added dropwise. A two-stage spin coating program was used: stage 1, 500 rpm / 5 seconds; stage 2, 4000 rpm / 30 seconds. At 15 seconds into the second stage of spin coating, 100 μL of chlorobenzene antisolvent was rapidly added dropwise using a pipette. After spin coating, the substrate was immediately transferred to a hot stage in a glove box and annealed at 120 °C for 30 min under a nitrogen atmosphere to obtain a perovskite layer with a thickness of 650 nm.

[0037] Fabrication of electron transport and buffer layers: The substrate with the perovskite layer was transferred to a thermal evaporation coating apparatus. The chamber was closed and the vacuum pump was started, and the chamber vacuum was evacuated to below 5 × 10⁻⁶. -4 Pa. With C 60 The powder was used as the evaporation source, and the evaporation rate was controlled at 0.1 nm / s. When C... 60 Evaporation was stopped when the layer thickness reached 30 nm. Then, the BCP evaporation source was switched to, and the evaporation rate was controlled at 0.05 nm / s, with a deposition thickness of 5 nm.

[0038] Preparation of metal electrode: A layer of silver (Ag) with a thickness of 100 nm is deposited on the electron transport layer.

[0039] Perovskite solar cell devices with no added fluorine-substituted benzimidazolium-alkyl sulfonate derivatives were used as blank controls (no additives added), and their performance test results are shown in Table 1.

[0040] Table 1 shows the performance data of the fluorinated benzimidazolium-alkyl sulfonate derivatives used in Examples 1-9 and the blank control perovskite solar cells. Combining the data in Table 1 and Figure 2 It was found that, through specific molecular structure design, the fluorinated benzimidazolium-alkyl sulfonate derivatives of this invention, as perovskite additives, exhibit multiple synergistic optimization effects. On one hand, the fluorinated benzimidazolium cation interacts with uncoordinated Pb via the N atom. 2+ The formation of strong coordination bonds, coupled with the ability of fluorine atoms to construct a CF…H hydrogen bond network, targets and passivates defects such as iodine vacancies and lead dangling bonds in the bulk phase and on the surface, significantly reducing non-radiative recombination losses. Furthermore, the sulfonate groups of the alkyl sulfonate anion can further anchor Pb. 2+The alkyl chains form a hydrophobic barrier at the perovskite grain boundaries, inhibiting water and oxygen erosion and ion migration, thus enhancing interfacial stability. Through the synergistic effect of these multiple mechanisms, the fill factor and photoelectric conversion efficiency of the device are significantly improved, solving the problems of single function and poor compatibility of traditional additives, and providing reliable support for the industrialization of high-performance perovskite solar cell devices.

[0041] It should be noted that when numerical ranges are involved in this invention, it should be understood that both endpoints of each numerical range, as well as any value between the two endpoints, can be selected. Since the steps and methods used are the same as in the embodiments, preferred embodiments are described here to avoid redundancy. Although preferred embodiments of the invention have been described, those skilled in the art, upon learning the basic inventive concept, can make other changes and modifications to these embodiments. Therefore, the appended claims are intended to be interpreted as including the preferred embodiments as well as all changes and modifications falling within the scope of this invention.

Claims

1. A fluorinated benzimidazolium-alkyl sulfonate derivative, characterized in that, The structural general formula of the fluoro-substituted benzimidazolium-alkyl sulfonate derivative is: wherein R1, R2 are independently selected from hydrogen or fluorine, and L1 is selected from C1-C3 alkyl.

2. The fluorinated benzimidazolium-alkyl sulfonate derivative according to claim 1, characterized in that, Fluorinated benzimidazolium-alkyl sulfonate derivatives are selected from .

3. A method for preparing the fluorinated benzimidazolium-alkyl sulfonate derivative of claim 1, characterized in that, Includes the following steps: In the presence of an organic solvent, fluorinated benzimidazole is subjected to an acid-base neutralization reaction with C1-C3 alkyl sulfonic acids, followed by post-treatment to obtain fluorinated benzimidazole onium-alkyl sulfonate derivatives.

4. The preparation method according to claim 3, characterized in that, The molar ratio of fluorinated benzimidazole to C1~C3 alkyl sulfonic acid is 1:1~1.

2.

5. The preparation method according to claim 3, characterized in that, Fluorinated benzimidazoles are selected from 5-fluorobenzimidazole, 5,6-difluorobenzimidazole, or 4,5-difluorobenzimidazole.

6. The preparation method according to claim 3, characterized in that, C1~C3 alkyl sulfonic acids are selected from methanesulfonic acid, ethanesulfonic acid, or propanesulfonic acid.

7. The preparation method according to claim 3, characterized in that, The specific post-processing steps are as follows: After the acid-base neutralization reaction is completed, add an alkaline reagent to the system to adjust the pH to 6.5~7.5, concentrate under reduced pressure to remove the solvent, add diethyl ether to disperse and crystallize, filter, and vacuum dry at 45℃~50℃ for at least 8 hours.

8. A perovskite solar cell, characterized in that, It includes a conductive substrate, a hole transport layer, a perovskite light absorption layer, an electron transport layer, a buffer layer, and a metal electrode stacked sequentially. The perovskite light-absorbing layer contains the fluorinated benzimidazolium-alkyl sulfonate derivative as described in claim 2.

9. The perovskite solar cell according to claim 8, characterized in that, In the perovskite light-absorbing layer, the concentration of fluorinated benzimidazolium-alkyl sulfonate derivatives is 0.05 mmol / L to 0.1 mmol / L.

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