Fullerene derivative, method for preparing the same, and use thereof

Abstract

This invention discloses a fullerene derivative, its preparation method, and its application, belonging to the field of organic materials. The chemical structural formula of the fullerene derivative is shown in formula (I), wherein R is a chelating group, and the addition site of the pyrrolidine ring on the fullerene is at the [6,6] position. This invention uses fullerene C 60 The core is connected to the chelating group sequentially via connecting arms and connecting bridges; the n-butoxyalkyl chain is C10. 60 The molecules provide uniform steric hindrance, effectively weakening C 60 The π-π stacking interaction between molecules avoids thermally induced molecular aggregation and film degradation, and achieves synergistic regulation of steric hindrance and chelation, significantly improving the solubility and solution stability of fullerene derivatives in solvents.

Description

Technical Field

[0001] This invention relates to the field of organic materials, and in particular to a fullerene derivative, its preparation method, and its application. Background Technology

[0002] Perovskite solar cells have become a research hotspot in the photovoltaic field due to their advantages such as high photoelectric conversion efficiency and low manufacturing cost. Among them, the electron transport layer (ETL) is the core functional layer of perovskite solar cells, playing a key role in electron extraction, hole blocking, and perovskite interface protection.

[0003] Currently, C 60 PCBM and C are the most commonly used fullerene-based electron transport layer materials in perovskite solar cells. 60 While possessing advantages such as high electron mobility and good energy level matching, PCBM exhibits strong intermolecular π-π stacking interactions and extremely poor solubility. It can only be prepared using costly and inefficient thermal evaporation processes, making it unsuitable for large-scale solution processing technologies like roll-to-roll fabrication. Although PCBM achieves solution-processability, it suffers from poor photothermal stability, is prone to thermally induced dimerization and molecular aggregation, leading to microstructure degradation and hindered charge transport. Furthermore, its hydrophobic, nonpolar molecular structure interacts weakly with the polar perovskite surface, failing to effectively passivate uncoordinated Pb on the perovskite surface. 2+ The defect is severe nonradiative recombination at the interface, which limits the improvement of device efficiency.

[0004] For C 60 To address the problems associated with PCBM, researchers attempted to introduce chelating groups and alkyl side chains onto the fullerene core to enhance interfacial interactions and regulate steric hindrance to inhibit molecular aggregation, respectively. However, some shortcomings remain. For example, the coordination ability of the chelating group is not matched with the perovskite crystal, and excessively strong coordination ability can easily damage the perovskite crystal structure. Furthermore, the passivation effect of a single chelating group is limited, and it is impossible to achieve deep passivation of perovskite surface defects. Additionally, the alkyl side chain design is unreasonable, making it difficult to balance the solubility and film-forming properties of the modified product. Summary of the Invention

[0005] The present invention aims to at least solve one of the aforementioned technical problems existing in the prior art. Therefore, one object of the present invention is to provide a fullerene derivative, through C... 60 The modular design of the parent core-pyrrolidine linker-butoxyalkyl chain-chelating group enables synergistic regulation of steric hindrance and chelation, resulting in a fullerene derivative that exhibits excellent solution solubility suitable for spin-coating processes, strong interfacial defect passivation ability, and high photothermal stability. A second objective of this invention is to provide a method for preparing the fullerene derivative. A third objective of this invention is to provide an application of the fullerene derivative.

[0006] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first aspect of the present invention is to provide a fullerene derivative having the following characteristics: Figure 1 The chemical structural formula shown is given, where R is a chelating group and the addition site of the pyrrolidine ring on the fullerene is at the [6,6] position.

[0007] The fullerene derivatives described in this invention are fullerene C 60 The parent nucleus is connected to the chelating group sequentially via connecting arms and connecting bridges, wherein the parent nucleus C 60 It possesses advantages such as high electron mobility and good energy level matching; the connecting arm is a pyrrolidine ring, and the five-membered heterocyclic structure of the pyrrolidine ring has a flexible spatial configuration, which can effectively alleviate the problems of connecting bridges, chelating groups, and C. 60 The steric hindrance between the parent nuclei, along with the lone pair electrons of the N atom, enhances the interaction with the perovskite surface, improving film adhesion. The connecting bridge is a phenyl butyl ether group (-C6H4-O-(CH2)4-), where the benzene ring (-C6H4-) enhances conjugation, the ether bond (-O-) increases solubility in the solvent, and the n-butoxy chain (-O-(CH2)4-) ensures the flexibility and film-forming properties of the product. When the number of carbon atoms in the carbon chain is less than 4, the steric hindrance is insufficient, and π-π stacking cannot be significantly suppressed. When the number of carbon atoms in the carbon chain is greater than 4, the excessively long carbon chain will increase molecular entanglement and reduce electron transport performance. The n-butoxy chain of this invention is the optimal choice to simultaneously satisfy appropriate steric hindrance suppression, ensure electron transport performance, and film-forming properties.

[0008] The [6,6] site exhibits excellent electron transport properties (LUMO level matches the perovskite conduction band, resulting in high electron mobility), and the chemical stability of the [6,6]-position addition product is superior to that of the [5,6]-position, ensuring the long-term operational stability of the electron transport layer.

[0009] In some preferred embodiments, the chelating group includes thiazo[2,3-b]pyridyl, dipyrido[1,4]diazazolyl, 2,2'-bipyridyl, terpyridyl or benzothiazolyl.

[0010] Thiazolo[2,3-b]pyridyl contains S and N bicoordinate atoms, which preferentially passivate Pb-rich defects on the perovskite surface through soft-soft interactions; dipyridolo[1,4]diazazolyl contains three N atoms, and its flexible seven-membered ring adaptively fits the interface, achieving mild and stable multidentate coordination; 2,2'-bipyridyl is a bidentate chelating ligand, and the two N atoms form a five-membered chelate ring, which can efficiently passivate uncoordinated Pb. 2+ The drawback is that the tripyridyl and benzothiazolyl also have similar effects to thiazo[2,3-b]pyridyl, dipyrido[1,4]diazazolyl, and 2,2'-bipyridyl.

[0011] If the coordination ability of the chelating group is too strong, it may damage the perovskite crystal; if the coordination ability is too weak, the passivation effect will be poor. Therefore, selecting a chelating group with moderate polarity and coordination ability can optimize its application performance.

[0012] The chelating group described in this invention is connected by carbon atoms or nitrogen atoms. For example, taking 2,2'-bipyridinyl as an example, it can be connected by carbon atoms at any of the positions 3, 4, 5, 6, 3', 4', 5', and 6', or by nitrogen atoms at the positions 2 or 2'.

[0013] A second aspect of the present invention is to provide a method for preparing a fullerene derivative as described in the first aspect, comprising the following steps: (1) 4-hydroxybenzaldehyde was subjected to Williamson etherification with 1,4-dibromobutane to obtain intermediate 1; (2) Intermediate 1 undergoes an alkylation reaction with the parent molecule of the chelating group to obtain intermediate 2; (3) Intermediate 2 undergoes a Prato cycloaddition reaction with fullerene and glycine to obtain the fullerene derivative.

[0014] In some preferred embodiments, the molar ratio of 4-hydroxybenzaldehyde to 1,4-dibromobutane is 1.0:(1.1-1.3); more preferably 1.0:(1.15-1.25).

[0015] In some preferred embodiments, the reaction temperature of the Williamson etherification reaction is 20-80°C; more preferably 20-50°C.

[0016] In some preferred embodiments, the reaction time of the Williamson etherification reaction is 1-10 h; more preferably 2-5 h.

[0017] In some preferred embodiments, the molar ratio of the intermediate 1 to the parent molecule of the chelating group is 1.0:(1.0-1.2); more preferably 1.0:(1.05-1.15).

[0018] In some preferred embodiments, the alkylation reaction is carried out at a temperature of 20-80°C; more preferably, at 20-50°C.

[0019] In some preferred embodiments, the alkylation reaction takes 1-10 hours; more preferably 2-5 hours.

[0020] In some preferred embodiments, the molar ratio of intermediate 2 to the fullerene and the glycine is 1.0:(1.1-1.3):(0.9-1.1); more preferably 1.0:(1.15-1.25):(0.95-1.05).

[0021] In some preferred embodiments, the reaction temperature of the Prato cycloaddition reaction is 110-120°C; more preferably 112-118°C.

[0022] In some preferred embodiments, the reaction time of the Prato cycloaddition reaction is 18-24 hours; more preferably 20-22 hours.

[0023] A third aspect of the present invention is to provide an application of the fullerene derivative described in the first aspect, specifically as an electron transport layer material.

[0024] In some preferred embodiments, the fullerene derivatives are used as electron transport layer materials in perovskite solar cells.

[0025] In some preferred embodiments, the perovskite solar cell sequentially comprises a transparent conductive substrate, a hole transport layer, a first interface passivation layer, a perovskite light absorption layer, a second interface passivation layer, an electron transport layer, a hole blocking layer, and a transparent conductive electrode.

[0026] In some preferred embodiments, the perovskite light-absorbing layer is selected from Cs. x FA 1-x PbI3, where x satisfies 0.03 ≤ x ≤ 0.1.

[0027] The fullerene derivatives described in this invention can be applied to various perovskite light absorption layer systems, including narrow bandgap (e.g., 1.25 eV), wide bandgap (e.g., 1.80 eV), and conventional bandgap (e.g., 1.55 eV). They are highly versatile and have broad application prospects. In particular, for perovskite light absorption layer systems with conventional bandgap, the photoelectric conversion efficiency of their solar cells can reach over 25%.

[0028] In some preferred embodiments, the method for preparing the perovskite solar cell includes the following steps: S1. A hole transport layer, a first interface passivation layer, a perovskite light absorption layer, and a second interface passivation layer are sequentially formed on a transparent conductive substrate. S2. Dissolve the fullerene derivative in a solvent to obtain a fullerene derivative solution, and coat the fullerene derivative solution on the surface of the second interface passivation layer to form an electron transport layer. S3. A hole blocking layer and a transparent conductive electrode are sequentially prepared on the surface of the electron transport layer to obtain the perovskite solar cell.

[0029] In some preferred embodiments, the solvent includes one or a combination of 2-methylanisole, cyclopentyl methyl ether, and chlorobenzene.

[0030] This invention preferably uses 2-methyl anisole, cyclopentyl methyl ether, and chlorobenzene as solvents for fullerene derivatives. The polarity of these solvents matches the hydrophobicity of the fullerene derivatives described in this invention, achieving high solubility (≥10 mg / mL). Furthermore, these solvents have moderate boiling points (2-methyl anisole boiling point 170℃, cyclopentyl methyl ether boiling point 106℃), allowing for controllable solvent evaporation rates during spin coating. This enables rapid film formation while avoiding film defects (such as pinholes and orange peel texture) caused by excessive evaporation. Moreover, these solvents are low-toxicity solvents, complying with EU REACH and US EPA environmental certification standards, and are suitable for the environmental requirements of large-scale production.

[0031] In some preferred embodiments, the fullerene derivative solution is coated by spin coating.

[0032] In some preferred embodiments, the spin coating speed is 2000-5000 rpm and the spin coating time is 10-60 s; more preferably, it is 2500-4000 rpm and 20-40 s.

[0033] In some preferred embodiments, the thickness of the electron transport layer is 20-80 nm; more preferably 25-45 nm.

[0034] The beneficial effects of this invention are: (1) The fullerene derivative of the present invention is fullerene C 60 The core is connected to the chelating group sequentially via connecting arms and connecting bridges; the n-butoxyalkyl chain is C10. 60 The molecules provide uniform steric hindrance, effectively weakening C 60 The π-π stacking interaction between molecules avoids thermally induced molecular aggregation and film degradation, achieving synergistic regulation of steric hindrance and chelation, significantly improving the solubility and solution stability of fullerene derivatives in solvents, and solving the problems of traditional C 60 It addresses issues such as non-solvable spin coating and easy aggregation of PCBM, and is well-suited for the spin coating fabrication requirements of perovskite solar cells.

[0035] This invention optimizes interface compatibility, enabling the fullerene derivative to possess excellent solution solubility suitable for spin-coating processes, strong interface defect passivation capability, and high photothermal stability. Since the interface passivation layer is an ultrathin functional layer, it cannot completely isolate perovskite surface defects. The fullerene derivative of this invention can penetrate the passivation layer to achieve defect passivation, utilizing fused-ring heterocyclic chelating groups to interact with Pb on the perovskite surface. 2+The coordination effect forms stable coordination bonds. Simultaneously, the electron transport layer exhibits differentiated passivation from the side near the perovskite interface to the film surface. The defect passivation effect shows a gradual distribution from strong to weak. On the side of the film near the perovskite interface (inner side), the N and S heteroatoms in the chelating groups preferentially bind to the uncoordinated Pb atoms on the perovskite surface. 2+ In combination, deep passivation of interface defects is achieved. For the film bulk and outer surface, the n-butoxyalkyl chains form steric hindrance, inhibiting molecular aggregation, maintaining film structural stability, indirectly reducing bulk defects, realizing gradient passivation of perovskite surface defects, significantly reducing interface defects and inhibiting interfacial nonradiative recombination, and improving electron injection efficiency and interfacial bonding stability. The N / S heteroatoms have strong electronegativity, and the chelating groups of the fullerene derivatives can interact with the interface passivation layer, synergistically passivating surface defects extending from the perovskite to the interface, constructing a tightly stacked interface, inhibiting interfacial nonradiative recombination, and reducing interfacial charge recombination.

[0036] This invention enhances the thermal and humidity stability of the electron transport layer, improves the chemical stability of the electron transport material and the service life of the device through the synergistic effect of the [6,6]-position addition structure and bifunctional groups, thus meeting the requirements of industrialization for long-term device reliability.

[0037] (2) The present invention also provides a method for preparing the fullerene derivative, using a chelating group parent molecule, 4-hydroxybenzaldehyde, bromobutane, glycine and C 60 Using readily available raw materials, the product is prepared through a three-step reaction involving Williamson etherification, alkylation, and Prato 1,3-dipolar cycloaddition. The preparation process is characterized by readily available raw materials, mild reaction conditions, and simple steps, avoiding the use of high temperature, high pressure, and heavy metal catalysts. It also eliminates the need for complex functional group protection and deprotection steps, making the product easy to purify. After column chromatography and recrystallization, the purity is >98%, making it suitable for industrial-scale production.

[0038] (3) The fullerene derivative of the present invention has a parent nucleus C 60 With its high electron mobility and energy level matching, as well as its excellent solution solubility and interfacial defect passivation ability, it can be used as an electron transport material to simplify the preparation process and improve electron migration efficiency.

[0039] (4) Based on the good electron mobility and interface defect passivation ability of the fullerene derivatives described in this invention, using them as electron transport layer materials for perovskite solar cells can improve the photoelectric performance of perovskite solar cells and simplify the preparation process.

[0040] (5) The present invention also provides a method for preparing the perovskite battery, based on the good solubility and solution stability of the fullerene derivative in the solvent, to realize the spin coating preparation of the electron transport layer to replace the traditional vacuum evaporation process. Compared with evaporation, the spin coating process has the advantages of low equipment investment, high production efficiency, good uniformity of large-area preparation and reduced cost, thereby reducing the equipment investment, energy consumption and production cost of perovskite battery, and improving the uniformity and production efficiency of the thin film prepared for large-area battery.

[0041] (6) The fullerene derivatives described in this invention have a solubility of ≥10 mg / mL in solvents such as 2-methyl anisole, cyclopentyl methyl ether, and chlorobenzene. The electron transport layer can be prepared by solution spin coating process without the need for high-cost thermal evaporation equipment. It is compatible with roll-to-roll, doctor blade coating and other large-scale preparation technologies, which greatly reduces the preparation cost of perovskite solar cells. Attached Figure Description

[0042] Figure 1 The chemical structural formula of the fullerene derivative described in this invention is shown below. Figure 2 The chemical structural formula of the target fullerene derivative in Example 1 is shown below. Figure 3 The chemical reaction process for preparing the target fullerene derivative of Example 1; Figure 4 The chemical structural formula of the target fullerene derivative in Example 2 is shown below. Figure 5 The chemical reaction process for preparing the target fullerene derivative of Example 2; Figure 6 The chemical structural formula of the target fullerene derivative in Example 3 is shown below. Figure 7 The chemical reaction process for preparing the target fullerene derivative of Example 3; Figure 8 The JV curves are for the perovskite solar cells prepared in Examples 4-6 and Comparative Example 1. Detailed Implementation

[0043] The present invention will be further described in detail below through specific embodiments.

[0044] Unless otherwise specified, the raw materials, reagents, or apparatus used in the following examples and comparative examples are all available from conventional commercial sources or can be obtained by existing technical methods. Unless otherwise specified, the test or experimental methods are conventional methods in the art.

[0045] Unless otherwise specified, the term "about" in this invention actually means that the error is allowed to be within ±2%, for example, about 100 is actually 100 ± 2% × 100.

[0046] Example 1 This embodiment relates to a fullerene derivative; its chemical structural formula is shown in the appendix. Figure 2 Its preparation method includes the following steps: (1) Add 4-hydroxybenzaldehyde, 1,4-dibromobutane, potassium carbonate, and potassium iodide to anhydrous acetonitrile in a molar ratio of 1.0:1.2:1.5:0.1. Recycle under N2 protection and at room temperature for 2-3 hours. After the reaction is complete, filter to remove the inorganic solid salts (potassium carbonate and potassium iodide) in the reaction system and collect the organic filtrate. Remove the solvent from the filtrate by rotary evaporation under reduced pressure to obtain the crude product. Dissolve the crude product in dichloromethane and wash it successively with deionized water and saturated brine. Separate the organic phase and dry it with anhydrous sodium sulfate. Filter the organic phase and remove the solvent again to obtain intermediate 1. (2) The intermediate obtained in step (1) is added to anhydrous acetonitrile along with thiazo[2,3-b]pyridine, potassium carbonate, and potassium iodide in a molar ratio of 1.0:1.1:1.5:0.1. The mixture is refluxed under N2 protection and at room temperature for 2-3 hours. After the reaction is complete, the inorganic solid salts (potassium carbonate and potassium iodide) in the reaction system are removed by filtration, and the organic filtrate is collected. The solvent in the filtrate is removed by rotary evaporation under reduced pressure to obtain the crude product. The crude product is dissolved in dichloromethane and washed successively with deionized water and saturated brine. The organic phase is separated and dried with anhydrous sodium sulfate, filtered, and the solvent is removed by rotary evaporation again to obtain intermediate 2. (3) The intermediate obtained in step (2) is combined with glycine and C 60 A molar ratio of 1.0:1.2:1.0 was added to anhydrous toluene, and the mixture was refluxed at 112-118°C under N2 protection for 20-22 hours. The concentration of nitrogen was monitored by TLC. 60 The reaction was continued until complete. After the reaction was finished, the toluene solvent was removed by vacuum distillation to obtain a black product. The black product was then subjected to chromatography on a silica gel column with 200-300 mesh silica gel as the stationary phase and a mixed solvent of chloroform and n-hexane (v / v=3:7) as the mobile phase. After chromatography, the main product band was separated and collected, and recrystallized in a mixed solvent of chloroform and methanol (v / v=1:2) to obtain the target fullerene derivative. The purity of the product was determined by high performance liquid chromatography (HPLC) under the following chromatographic conditions: C18 reversed-phase column, methanol / dichloromethane mixed system as the mobile phase, and UV detector. The purity of the product was >98% by external standard method.

[0047] The chemical reaction process for preparing the target fullerene derivative is described in the appendix. Figure 3 .

[0048] Example 2 This embodiment relates to a fullerene derivative; its chemical structural formula is shown in the appendix. Figure 4The preparation method differs from that of Example 1 only in that dipyrido[1,4]diazazolide is used as the parent molecule of the chelating group, that is, dipyrido[1,4]diazazolide is used instead of thiazo[2,3-b]pyridine. The rest is the same as that of Example 1.

[0049] The chemical reaction process for preparing the target fullerene derivative is described in the appendix. Figure 5 .

[0050] Example 3 This embodiment relates to a fullerene derivative; its chemical structural formula is shown in the appendix. Figure 6 The preparation method differs from that in Example 1 only in that 2,2'-bipyridine is used as the parent molecule of the chelating group, that is, 2,2'-bipyridine is used instead of thiazo[2,3-b]pyridine, and the rest is the same as in Example 1.

[0051] The chemical reaction process for preparing the target fullerene derivative is described in the appendix. Figure 7 .

[0052] Example 4 This embodiment relates to a perovskite solar cell, the preparation method of which includes the following steps: (1) Substrate pretreatment: ITO conductive glass was used as the substrate. It was ultrasonically cleaned for 15 min each with deionized water, acetone, ethanol and isopropanol in sequence. After being dried with nitrogen, it was treated with ultraviolet ozone for 20 min to remove organic residues and impurities on the surface.

[0053] (2) Preparation of hole transport layer: Prepare 3mM Me-4PACz isopropanol solution, spin coat at 3000rpm for 60s, and then anneal at 100℃ for 20min to form hole transport layer.

[0054] (3) Preparation of the first interface passivation layer: 3-phosphonic acid pyridine (PyPA) was dissolved in anhydrous ethanol solvent to prepare a passivation solution with a concentration of 0.8 mg / mL. The passivation solution was dropped onto the surface of the hole transport layer film, spin-coated at 3500 rpm for 35 s, and annealed at 80 °C for 10 min to obtain an ultrathin first interface passivation layer with a thickness of about 1.5 nm. The first interface passivation layer is used to passivate uncoordinated defects on the surface of the hole transport layer, optimize the crystal morphology of the perovskite precursor, and reduce the recombination at the bottom interface.

[0055] (4) Preparation of perovskite light-absorbing layer; preparation of 1.2 mol / L Cs 0.06 FA 0.94 PbI3 precursor solution (V DMF V DMSO =4:1), spin-coated at 4500 rpm for 40 s, toluene anti-solvent added dropwise, annealed at 130℃ for 15 min to form a perovskite light-absorbing layer.

[0056] (5) Preparation of the second interface passivation layer: Prepare a 1 mg / mL PEAI isopropanol solution, spin-coat it on the perovskite layer at 5000 rpm for 30 s, and place it at room temperature for 5 min to form a PEAI interface passivation layer with a thickness of about 2 nm.

[0057] (6) Preparation of electron transport layer: The fullerene derivative obtained in Example 1 was dissolved in cyclopentyl methyl ether to prepare a spin coating solution of 11 mg / mL. The solution was then spin coated on the interface passivation layer at 3000 rpm for 30 s to obtain an electron transport layer of about 30 nm thickness without annealing.

[0058] (7) Preparation of hole blocking layer: 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) was dissolved in chlorobenzene solvent to prepare a BCP solution with a concentration of 0.6 mg / mL. The BCP solution was uniformly dropped onto the surface of the electron transport layer, spin-coated at 4000 rpm for 25 s, and dried naturally at room temperature to obtain a dense hole blocking layer with a thickness of 5 nm. The hole blocking layer is used to block electrons from migrating to the anode side in the reverse direction, isolate the IZO electrode from direct contact with the electron transport layer, suppress interfacial charge recombination, and improve the open circuit voltage and thermal stability of the device.

[0059] (8) Preparation of IZO transparent conductive layer: IZO transparent conductive layer was deposited on electron transport layer by radio frequency magnetron sputtering with sputtering power of 60W, argon flow rate of 20sccm, working pressure of 0.5Pa, and thickness of about 100nm; perovskite solar cell was obtained.

[0060] Example 5 This embodiment relates to a perovskite solar cell, the preparation method of which differs from that of Embodiment 4 only in step (6), the rest being the same as in Embodiment 4; step (6) of this embodiment is specifically as follows: (6) Preparation of electron transport layer: The fullerene derivative obtained in Example 2 was dissolved in chlorobenzene to prepare a spin coating solution of 10 mg / mL. The solution was then spin coated on the interface passivation layer at 2500 rpm for 30 s to obtain an electron transport layer of about 35 nm thickness without annealing.

[0061] Example 6 This embodiment relates to a perovskite solar cell, the preparation method of which differs from that of Embodiment 4 only in step (6), the rest being the same as in Embodiment 4; step (6) of this embodiment is specifically as follows: (6) Preparation of electron transport layer: The fullerene derivative obtained in Example 3 was dissolved in cyclopentyl methyl ether to prepare a spin coating solution of 12 mg / mL. The solution was then spin coated on the interface passivation layer at 3500 rpm for 30 s to obtain an electron transport layer of about 25 nm thickness without annealing.

[0062] Comparative Example 1 This comparative example relates to a perovskite solar cell, the preparation method of which differs from that of Example 4 only in step (6), while the rest is the same as that of Example 4; the specific step (6) of this example is as follows: (6) Preparation of electron transport layer: Dissolve PCBM in chlorobenzene to prepare a spin coating solution of 20 mg / mL. Spin coat the solution on the interface passivation layer at 4000 rpm for 30 s. After spin coating, anneal at 80 °C for 10 min to obtain an electron transport layer with a thickness of about 25 nm.

[0063] The performance of the perovskite solar cells prepared in Examples 4-6 and Comparative Example 1 was tested. First, the prepared solar cells were encapsulated with UV-cured adhesive and a cover plate to isolate them from water and oxygen. A solar simulator (AM 1.5G, 100 mW / cm²) was used. 2 The JV curve was tested, and the interface recombination was characterized using transient photovoltage / photocurrent testing. Stability testing was conducted using an 85℃ hot chamber and 1℃ sunlight. The test results are shown in Table 1 and Appendix. Figure 8 .

[0064] Table 1. Performance of the perovskite solar cells prepared in Examples 4-6 and Comparative Example 1

[0065] Where PCE is the photoelectric conversion efficiency, FF is the fill factor, and V oc J is the open-circuit voltage. sc This is the short-circuit current.

[0066] According to Table 1 and Appendix Figure 8 The perovskite solar cells prepared using fullerene derivatives as electron transport layers in this invention exhibit a photoelectric conversion efficiency of over 25%, a fill factor > 80%, and an open-circuit voltage > 1.04 V, demonstrating superior performance compared to traditional C-type solar cells. 60 Compared with PCBM-based devices, the device has a thermal aging time of 85℃ (T85>1000h) and a light aging time (1sun) (T85>1200h), with stability far exceeding that of PCBM-based devices.

[0067] The above embodiments are preferred embodiments of the present invention, but the embodiments of the present invention are not limited to the above embodiments. Any changes, modifications, substitutions, combinations, or simplifications made without departing from the spirit and principle of the present invention shall be considered equivalent substitutions and shall be included within the protection scope of the present invention.

Claims

1. A fullerene derivative, characterized in that, The chemical structural formula of the fullerene derivative is shown in formula (Ⅰ): （Ⅰ） Wherein, R is a chelating group, and the addition site of the pyrrolidine ring on the fullerene is at the [6,6] position.

2. A fullerene derivative according to claim 1, characterized in that, The chelating group includes thiazo[2,3-b]pyridinyl, dipyrido[1,4]diazazolyl, 2,2'-bipyridinyl, terpyridinyl or benzothiazolyl.

3. A fullerene derivative according to claim 2, characterized in that, The chelating groups are linked by carbon or nitrogen atoms.

4. A method for preparing a fullerene derivative as described in any one of claims 1-3, characterized in that, Includes the following steps: (1) 4-hydroxybenzaldehyde was subjected to Williamson etherification with 1,4-dibromobutane to obtain intermediate 1; (2) The intermediate 1 undergoes an alkylation reaction with a parent molecule containing an R chelating group to obtain intermediate 2; (3) The intermediate 2 undergoes a Prato cycloaddition reaction with fullerene and glycine to obtain a fullerene derivative with the structure shown in formula (I).

5. The method for preparing a fullerene derivative according to claim 4, characterized in that, Includes one or more of the following features: The molar ratio of 4-hydroxybenzaldehyde to 1,4-dibromobutane is 1.0:(1.1-1.3). The molar ratio of intermediate 1 to the parent molecule of the chelating group is 1.0:(1.0-1.2). The molar ratio of intermediate 2 to the fullerene and the glycine is 1.0:(1.1-1.3):(0.9-1.1).

6. An electron transport layer material, characterized in that, This includes the fullerene derivatives according to any one of claims 1-3, or the fullerene derivatives prepared by the preparation method according to any one of claims 4-5.

7. A perovskite solar cell, comprising an electron transport layer, characterized in that, The material of the electron transport layer includes the fullerene derivative as described in any one of claims 1-3, or the fullerene derivative prepared by the preparation method described in any one of claims 4-5.

8. The perovskite solar cell according to claim 7, characterized in that, It comprises, in sequence, a transparent conductive substrate, a hole transport layer, a first interface passivation layer, a perovskite light absorption layer, a second interface passivation layer, an electron transport layer, a hole blocking layer, and a transparent conductive electrode.

9. A method for preparing a perovskite solar cell as described in claim 7 or 8, characterized in that, Includes the following steps: S1. A hole transport layer, a first interface passivation layer, a perovskite light absorption layer, and a second interface passivation layer are sequentially formed on a transparent conductive substrate. S2. Dissolve the fullerene derivative in a solvent to obtain a fullerene derivative solution, and coat the fullerene derivative solution on the surface of the second interface passivation layer to form an electron transport layer. S3. A hole blocking layer and a transparent conductive electrode are sequentially prepared on the surface of the electron transport layer to obtain the perovskite solar cell.

10. The method for preparing a perovskite solar cell according to claim 9, characterized in that, The solvent includes one or a combination of 2-methyl anisole, cyclopentyl methyl ether, and chlorobenzene.

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