Fullerene pyrrolidine derivative as well as preparation method and application thereof

Abstract

The invention discloses a fullerene pyrrolidine derivative as well as a preparation method and application thereof, and relates to the field of photoelectric functional materials. The structural general formula of the fullerene pyrrolidine derivative is # imgabs0, and fullerene, amino acids with different carbon chain lengths and aromatic aldehyde are subjected to Prato reaction to generate the fullerene pyrrolidine derivative. The fullerene pyrrolidine derivative provided by the invention is used as an electron transport layer material, can significantly improve the performance of a photoelectric device, has excellent chemical stability and environmental adaptability, and greatly enhances the stability of the device. In addition, the preparation method of the fullerene pyrrolidine derivative is simple, convenient and efficient, the operation condition is mild, and the manufacturing cost of a device is reduced.

Description

Technical Field

[0001] The present invention relates to the field of photoelectric functional materials, and in particular to a novel fullerene pyrrolidine derivative and a preparation method and application thereof. Background Art

[0002] With the continuous growth of global energy demand, traditional fossil energy not only faces the problem of resource depletion, but also causes serious environmental pollution. As a clean and renewable energy source, solar energy has huge development potential. Perovskite solar cells (PSCs), as an emerging photovoltaic technology, have attracted widespread attention due to their excellent cost-effectiveness and high photoelectric conversion efficiency. However, the toxicity of lead-containing materials used in traditional PSCs limits the commercial application and development prospects of this technology. Therefore, the development of new green and friendly non-lead PSCs is imminent. Among them, tin-based perovskite solar cells (TPSCs), as a representative of non-lead perovskites, have attracted widespread attention in recent years due to their high theoretical efficiency, narrow bandgap characteristics and high carrier mobility. Despite this, TPSCs still face some key challenges, including high energy loss and insufficient stability caused by tin oxidation, which seriously limit their further performance improvement.

[0003] In traditional trans-structured lead-based PSCs, fullerenes and their derivatives are often used as electron transport layers (ETLs) and interface modification layers due to their excellent carrier mobility, good optoelectronic properties, and interface regulation capabilities. However, tin-based perovskites usually have shallower energy levels than lead-based ones, resulting in poor energy level matching between existing fullerene derivatives and TPSCs. This energy level mismatch not only hinders the effective transfer of charges, but also leads to large energy losses, thereby reducing the photovoltaic performance of the device. In addition, the interaction between traditional fullerene derivatives ETLs and perovskite layers is weak, resulting in an increase in internal defects in the device, which restricts the device stability and photovoltaic performance. Therefore, the development of new fullerene derivatives that can achieve energy level matching with tin-based perovskites and have defect passivation function has become an important way to improve the performance of TPSCs, with significant scientific significance and application potential. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the present invention provides a fullerene pyrrolidine derivative and a method for its preparation. As electron transport layer (ETL) materials, the fullerene pyrrolidine derivative of the present invention can significantly improve the performance of optoelectronic devices and exhibit excellent chemical stability and environmental adaptability, significantly enhancing device stability. Furthermore, the preparation method of the fullerene pyrrolidine derivative is simple and efficient, and the mild operating conditions help reduce device manufacturing costs.

[0005] The technical solution adopted in the present invention is as follows:

[0006] In a first aspect, the present invention provides a fullerene pyrrolidine derivative, the general structural formula of which is as follows:

[0007]

[0008] Wherein, R refers to a straight-chain or branched alkyl or alkoxy group having 1 to 10 carbon atoms, and Ar refers to an aryl or heteroaryl group having 5 to 20 carbon atoms.

[0009] This structure is based on fullerene (C60) and optimizes the electronic structure and energy level position of the molecule by introducing straight-chain or branched alkyl or alkoxy groups with different numbers of carbon atoms, as well as electron-donating groups Ar (such as triphenylamine, dimethoxybenzene, etc.), thereby enhancing the energy level matching with tin-based perovskite and improving the charge transfer performance and stability of the molecule.

[0010] Preferably, the Ar structural formula is one of the following structures:

[0011]

[0012] In a second aspect, the present invention provides a method for preparing a fullerene pyrrolidine derivative, comprising: subjecting fullerene (C60), amino acids of different carbon chain lengths and aromatic aldehydes to a Prato reaction to generate the fullerene pyrrolidine derivative.

[0013] Preferably, the molar ratio of the fullerene (C60) to the amino acids and aromatic aldehydes of different carbon chain lengths is 1:1.2 to 1.5:2.

[0014] Preferably, the Prato reaction is carried out by stirring at a temperature of 120° C. to 150° C. for 2 to 5 hours.

[0015] In a third aspect, the present invention provides an application of a fullerene pyrrolidine derivative, wherein the fullerene pyrrolidine derivative is used as an electron transport layer material for a tin-based perovskite solar cell.

[0016] Compared with the prior art, the present invention has the following beneficial effects:

[0017] The fullerene pyrrolidine derivative of the present invention is based on fullerene (C60), and introduces a pyrrolidine ring and different electron-donating groups (such as triphenylamine, dimethoxybenzene, etc.) to optimize the electronic structure and energy level position of the molecule, enhance the energy level matching degree with tin-based perovskite, and simultaneously improve the charge transport performance and stability of the molecule. Using the fullerene pyrrolidine derivative as the electron transport layer (ETL) material of tin-based perovskite solar cells can not only effectively regulate the interface energy level, improve the interface contact, and significantly improve the performance and stability of the optoelectronic device, but also because of its excellent chemical stability and environmental adaptability, it can greatly enhance the stability of the device. In addition, the present invention synthesizes the target compound through steps such as Prato reaction, Arbuzov reaction and hydrolysis reaction. Compared with traditional PCBM, the method is simple to operate, mild conditions, easy to large-scale production, with higher yield and lower production cost, which is not only conducive to reducing the manufacturing cost of the device, but also makes it more feasible in large-scale production, providing strong support for the commercial development of perovskite solar cell technology. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 Schematic diagram of the structure of a perovskite solar cell.

[0019] Figure 2 It is the molecular formula of the traditional electron transport layer material PCBM.

[0020] Figure 3 Flow chart for the preparation of fullerene derivatives.

[0021] Figure 4 Flow chart of the preparation of fullerene derivative S1.

[0022] Figure 5 This is a flow chart for the preparation of fullerene derivative S3.

[0023] Figure 6 This is a flow chart for the preparation of fullerene derivative F2.

[0024] Figure 7 This is a flow chart for the preparation of fullerene derivative F6.

[0025] Figure 8 This is a flow chart for the preparation of fullerene derivatives FN.

[0026] Figure 9 This is a flow chart for the preparation of fullerene derivative F2N.

[0027] Figure 10 This is a flow chart for the preparation of fullerene derivative F12.

[0028] Figure 11 2 are the current-voltage curves of the tin-based perovskite solar cells of Example 4 and Example 6. DETAILED DESCRIPTION

[0029] The technical solution of the present invention is further described below with reference to the accompanying drawings and specific embodiments.

[0030] Example 1: This example provides a fullerene derivative S1 and a preparation method thereof, such as Figure 4 As shown;

[0031] C 60 (0.366 g, 0.5 mmol) and 3-heptylglycine (0.347 g, 2 mmol) and 2-thiophenecarboxaldehyde (0.056 g, 0.5 mmol) were mixed in a reaction flask; 60 ml of o-dichlorobenzene was added, and the mixture was placed in an oil bath, heated to 120°C, and stirred for 2 h.

[0032] The reaction solution was poured into purified water for quenching, and the organic phase was separated using a separatory funnel. The solution in the organic phase was then removed under reduced pressure using a rotary evaporator to obtain a crude product.

[0033] The crude product was purified by silica gel column chromatography using an eluent of a mixture of petroleum ether and ethyl acetate (10 / 1 vol / vol) to obtain a brown powder solid, namely the fullerene derivative S1 (0.174 g, 29.5%).

[0034] The obtained fullerene derivative S1 was characterized by hydrogen nuclear magnetic resonance spectroscopy, and the test results were: 1 HNMR (400MHz, CDCl3), δ7.51 (d, J = 45.7Hz, 1H), 7.08 (t, J = 52.5Hz, 2H), 2.21 (dt, J = 197.0, 55.8Hz, 4H), 1.54-0.79 (m, 17H).

[0035] Example 2: This example provides a fullerene derivative S3 and a preparation method thereof, such as Figure 5 As shown;

[0036] C 60 (0.732 g, 1 mmol) and 3-heptylglycine (0.694 g, 4 mmol) and [2,2':5',2"-terthiophene]-5-carbaldehyde (0.276 g, 1 mmol) were mixed in a reaction flask; 60 ml of o-dichlorobenzene was added, and the mixture was placed in an oil bath, heated to 120°C, and stirred for 2 h.

[0037] The reaction solution was poured into purified water for quenching, and the organic phase was separated using a separatory funnel. The solution in the organic phase was then removed under reduced pressure using a rotary evaporator to obtain a crude product.

[0038] The crude product was purified by silica gel column chromatography using an eluent of a mixture of petroleum ether and ethyl acetate = 6 / 1 vol / vol to obtain a brown powder solid, namely the fullerene derivative S3 (0.174 g, 29.5%).

[0039] The obtained fullerene derivative S3 was characterized by hydrogen nuclear magnetic resonance spectroscopy, and the test results were: 1 HNMR (400MHz, CDCl3), δ7.67-7.32(m,4H), 7.26-6.98(m,3H), 2.86-2.73(m,4H), 1.78-0.83(m,17H).

[0040] Example 3: This example provides a fullerene derivative F2 and a preparation method thereof, such as Figure 6 shown.

[0041] C 60 (0.432 g, 0.6 mmol), 3-heptylglycine (0.104 g, 1.8 mmol) and 2,3-dimethoxybenzaldehyde (0.996 g, 0.6 mmol) were dissolved in 60 mL of o-dichlorobenzene and heated with stirring at 120°C for 2 h.

[0042] The reaction solution was poured into purified water for quenching, and the organic phase was separated using a separatory funnel. The solution in the organic phase was then removed under reduced pressure using a rotary evaporator to obtain a crude product.

[0043] The crude product was purified by silica gel column chromatography using a mixture of petroleum ether and ethyl acetate (3 / 1 vol / vol) as the eluent to obtain a brown powder solid, namely, the fullerene derivative F2 (0.188 g, 31.1%).

[0044] The obtained fullerene derivative F2 was characterized by hydrogen nuclear magnetic resonance spectroscopy, and the test results were: 1 HNMR (600MHz, CDCl3), δ7.65 -7.58(m,1H), 7.13(t,J=8.1Hz,1H), 6.86(dt,J=8.2,1.7Hz,1H), 5.60(d,J=5.4Hz,1H), 5.06(dd,J=9.3,3.8Hz,1H) , 4.06(dd,J=9.3,5.8Hz,1H), 3.87(d,J=8.6Hz,6H), 2.89(td,J=11.4,3.0Hz,1H), 2.44(td,J=11.8,3.2Hz, 1H), 2.04 -1.91(m,2H),1.62 -1.40(m,7H), 1.03-0.85(m,6H).

[0045] Example 4: This example provides a fullerene derivative F6 and a preparation method thereof, such as Figure 7 As shown;

[0046] C 60 (0.366 g, 0.5 mmol) and 3-heptylglycine and 4-(bis(4-methoxyphenyl)amino)benzaldehyde were dissolved in 60 mL of 1,2-dichlorobenzene and stirred vigorously at 120 °C for 2 h.

[0047] The reaction solution was poured into purified water for quenching, and the organic phase was separated using a separatory funnel. The solution in the organic phase was then removed under reduced pressure using a rotary evaporator to obtain a crude product.

[0048] The crude product was purified by silica gel column chromatography using a mixture of petroleum ether and ethyl acetate (9 / 1 vol / vol) as the eluent to obtain a brown powder solid, namely, the fullerene derivative F6 (0.174 g, 29.5%).

[0049] The obtained fullerene derivative F6 was characterized by hydrogen nuclear magnetic resonance spectroscopy, and the test results were: 1 HNMR (400MHz, CDCl3), δ7.74 -7.03(m,6H), 6.96(d,J=8.2Hz,2H), 6.81(d,J=8.5Hz,4H), 5.14-4.90(m,2H), 4.06(d,J=9.4Hz,1H), 3.80 (s, 6H), 3.10 (t, J = 11.5Hz, 1H), 2.52 (t, J = 9.9Hz, 1H), 2.20-1.89 (m, 2H), 1.46 (s, 6H), 1.13-0.98 (m, 6H).

[0050] Example 5: This example provides a fullerene derivative FN and a preparation method thereof, such as Figure 8 As shown;

[0051] C60 (0.721 g, 1 mmol), pyridinecarboxaldehyde (0.107 g, 1 mmol), 3-heptylglycine (0.516 g, mmol) and 30 mL of 1,2-dichlorobenzene as solvent were added to the reaction flask, and the mixture was stirred and refluxed in an oil bath at 120°C under nitrogen protection for 5 h.

[0052] The reaction solution was poured into purified water for quenching, and the organic phase was separated using a separatory funnel. The solution in the organic phase was then removed under reduced pressure using a rotary evaporator to obtain a crude product.

[0053] The crude product was purified by silica gel column chromatography using a mixture of petroleum ether and dichloromethane (3 / 1 vol / vol) as the eluent to obtain a brown powder solid, namely the fullerene derivative FN (0.435 g, 45.0%).

[0054] The obtained fullerene derivative FN was characterized by hydrogen nuclear magnetic resonance spectroscopy, and the test results were: 1 HNMR (400MHz, CDCl3), δ8.72 (d, J = 5.0 Hz, 2H), 7.80 (s, 2H), 4.11 (d, J = 9.5, 3.6 Hz, 1H), 2.94 (t,J=11.5Hz,1H), 2.57(d,J=11.3,7.4,3.3Hz,1H), 2.24-1.68(m,4H), 1.61-0.94(m,15H).

[0055] Example 6: This example provides a fullerene derivative F2N and a preparation method thereof, such as Figure 9 As shown;

[0056] Add C to the reaction flask 60 (0.721 g, 1 mmol), 4-(4,4′-dipyridylamino)benzaldehyde (0.183 g, 1 mmol), 3-heptylglycine (0.516 g, 3 mmol), and 50 mL of o-DCB as a solvent were added, and the mixture was stirred and refluxed in an oil bath at 120°C under nitrogen protection for 5 h.

[0057] The reaction solution was poured into purified water for quenching, and the organic phase was separated using a separatory funnel. The solution in the organic phase was then removed under reduced pressure using a rotary evaporator to obtain a crude product.

[0058] The crude product was purified by silica gel column chromatography using a mixture of petroleum ether and dichloromethane (2 / 1 vol / vol) as the eluent to obtain a brown powder solid, namely the fullerene derivative F2N (0.364 g, 31.0%).

[0059] The obtained fullerene derivative F2N was characterized by hydrogen nuclear magnetic resonance spectroscopy, and the test results were: 1 HNMR (400MHz, CDCl3), δ8.56-8.13(m,4H), 8.12-7.20(m,4H), 7.01-6.76(m,4H), 3.15(t, J=11.5Hz,1H), 2.28-0.82(m,22H).

[0060] Example 7: This example provides a fullerene derivative F12 and a preparation method thereof, such as Figure 10 As shown;

[0061] C 60(0.36 g, 0.5 mmol), 3-heptylglycine (0.264 g, 1.5 mmol) and 4-(bis(4-fluorophenyl)amino)benzaldehyde (0.155 g, 0.5 mmol) were dissolved in 30 mL of 1,2-dichlorobenzene and heated with stirring at 120°C for 2 h.

[0062] After the reaction, the reaction solution was poured into purified water for quenching, and the organic phase was separated using a separatory funnel. The solution in the organic phase was then removed under reduced pressure using a rotary evaporator to obtain a crude product.

[0063] The crude product was purified by silica gel column chromatography using a mixture of petroleum ether and dichloromethane (20 / 1 vol / vol) as the eluent to obtain a brown powder solid, namely, the fullerene derivative F12 (0.202 g, 35.0%).

[0064] The obtained fullerene derivative F2N was characterized by hydrogen nuclear magnetic resonance spectroscopy, and the test results were: 1 HNMR (500MHz, CDCl3), δ7.65 (s, 2H), 7.09-6.85 (m, 10H), 5.13-4.93 (m, 2H), 4.04 (d, J = 9.3, 4.7Hz, 1H), 3.07 (t,J=11.5Hz,1H), 2.51(d,J=12.1,9.8,3.3Hz,1H), 2.07-1.92(m,2H), 1.64-1.41(m,7H), 1.15-0.90(m,6H).

[0065] Application Example 1: Compound S1 as an electron transport layer in tin-based perovskite solar cells;

[0066] Figure 1 This is a schematic structural diagram of the tin-based perovskite solar cell involved in the present invention, which includes, from bottom to top: transparent conductive glass ITO; hole transport layer; perovskite light absorption layer; electron transport layer; BCP interface modification layer; and silver electrode.

[0067] The steps for preparing solar cells are as follows:

[0068] a. Preparation of the Hole Transport Layer: The PEDOT:PSS aqueous solution was filtered through a 0.45 μm syringe filter. The filtered solution was evenly spin-coated onto an ITO substrate at 4000 rpm for 30 seconds. After spin coating, the ITO substrate was transferred to a hot plate and annealed at 140°C for 20 minutes. After annealing, the sample was cooled to room temperature and placed in a glove box.

[0069] b. Preparation of the tin-based perovskite layer: FAI, MABr, SnI2, and SnF2 were dissolved in a DMF:DMSO (4:1, vol / vol) solvent mixture at a molar ratio of 0.75:0.25:1:0.10. 5 mg / mL of tin powder and 15 mol% of PEAI were added. The solution was stirred for 12 hours to obtain a perovskite precursor solution. After filtration, the solution was spin-coated on the prepared hole transport layer at 8000 rpm for 60 seconds. After 45 seconds, 150 μL of chlorobenzene was added. After spin coating, the film was annealed on an 80°C hotplate for 10 minutes to obtain a uniform tin-based perovskite layer.

[0070] c. Preparation of the Electron Transport Layer: Prepare a 20 mg / ml Si solution in chlorobenzene. Spin-coat the solution onto the tin-based perovskite layer at 2000 rpm for 30 seconds. Anneal the spin-coated substrate on a hot plate at 70°C for 10 minutes.

[0071] d. Preparation of the BCP interface modification layer: Weigh 5 mg of BCP into a clean glass bottle and dissolve it in 1 mL of isopropanol. Use magnetic stirring to fully dissolve the BCP until it becomes uniform and transparent. Then, spin-coat it onto the electron transport layer at 4000 rpm for 30 seconds to form a uniform BCP film.

[0072] Finally, silver electrodes with a thickness of 110 nm were deposited by thermal evaporation under vacuum conditions.

[0073] Photovoltaic device performance: Under AM1.5 G (100mW cm -2 ) Under standard conditions, the open circuit voltage (V oc )=0.65V, short-circuit current (J sc )=20.4mA cm -2 , fill factor (FF) = 60.8%, photoelectric conversion efficiency (PCE) = 8.06%.

[0074] Application Example 2: Compound S3 as an electron transport layer in tin-based perovskite solar cells;

[0075] The solution in step c of Application Example 1 was changed to a chlorobenzene solution of S3 with a concentration of 20 mg / mL. The remaining steps were the same as those in Application Example 1 to prepare a tin-based perovskite solar cell using compound S3 as an electron transport layer.

[0076] Photovoltaic device performance: Under AM1.5 G (100mW cm -2 ) Under standard conditions, the open circuit voltage (V oc )=0.73V, short-circuit current (J sc )=20.6mA cm -2, fill factor (FF) = 67.9%, photoelectric conversion efficiency (PCE) = 10.2%.

[0077] Application Example 3: Compound F2 as electron transport layer of tin-based perovskite solar cells;

[0078] The solution in step c of Application Example 1 was changed to a chlorobenzene solution of F2 with a concentration of 20 mg / mL. The remaining steps were the same as those in Application Example 1 to prepare a tin-based perovskite solar cell using compound F2 as the electron transport layer.

[0079] Photovoltaic device performance: Under AM1.5 G (100mW cm -2 ) Under standard conditions, the open circuit voltage (V oc )=0.69V, short-circuit current (J sc )=20.5mA cm -2 , fill factor (FF) = 66.5%, photoelectric conversion efficiency (PCE) = 9.4%.

[0080] Application Example 4: Compound F6 as an electron transport layer in tin-based perovskite solar cells;

[0081] The solution in step c of Application Example 1 was changed to a chlorobenzene solution of F6 with a concentration of 20 mg / mL. The remaining steps were the same as those in Application Example 1 to prepare a tin-based perovskite solar cell using compound F6 as the electron transport layer.

[0082] Photovoltaic device performance: Under AM1.5 G (100mW cm -2 ) Under standard conditions, the open circuit voltage (V oc )=0.77V, short-circuit current (J sc )=19.9mA cm -2 , fill factor (FF) = 67.2%, photoelectric conversion efficiency (PCE) = 10.2%.

[0083] Application Example 5: Compound F2N / F6 as electron transport layer for tin-based perovskite solar cells;

[0084] A hole transport layer and a perovskite layer were prepared according to Application Example 1. A F2N interlayer was then spin-coated on the perovskite layer at 2000 rpm for 30 seconds. After spin coating, the layer was annealed on a hot plate at 70°C for 10 minutes to form the F2N interlayer. An electron transport layer was then prepared on the F2N interlayer using a 20 mg / mL F6 chlorobenzene solution. The remaining steps were the same as in Application Example 1 to prepare a tin-based perovskite solar cell using compound F6 as the electron transport layer.

[0085] Photovoltaic device performance: Under AM1.5 G (100mW cm -2) Under standard conditions, the open circuit voltage (V oc )=0.78V, short-circuit current (J sc )=20.8mA cm -2 , fill factor (FF) = 66.4%, photoelectric conversion efficiency (PCE) = 10.8%.

[0086] Application Example 6: Compound F6 / F12 as electron transport layer for tin-based perovskite solar cells;

[0087] The solution in step c of Application Example 1 was changed to a mixed solution of F6 / F12. The solution was prepared by adding 20 mg of F6 and 6 mg of F12 to 1 mL of chlorobenzene solution. The remaining steps were the same as those in Application Example 1 to prepare a tin-based perovskite solar cell with compound F6 / F12 as the electron transport layer.

[0088] Photovoltaic device performance: Under AM1.5 G (100mW cm -2 ) Under standard conditions, the open circuit voltage (V oc )=0.91V, short-circuit current (J sc )=18.6mA cm -2 , fill factor (FF) = 70.6%, photoelectric conversion efficiency (PCE) = 12.0%.

[0089] Comparative Example 1

[0090] Commercialized PCBM (structural formula: Figure 2 ) is a comparative electron transport layer material. The device structure and preparation method are the same as those in Application Example 1, except that the solution in step c is replaced with a 20 mg / mL PCBM solution.

[0091] The test results are: Under AM1.5 G (100mW cm -2 ) Under standard conditions, the open circuit voltage (V oc )=0.63V, short-circuit current (J sc )=19.34mA cm -2 , fill factor (FF) = 67.2%, photoelectric conversion efficiency (PCE) = 8.2%.

[0092] In summary, the present invention significantly improves the photoelectric performance and stability of tin-based perovskite solar cells by innovatively designing and applying new fullerene derivatives as electron transport layer materials. Experimental results show that compared with traditional materials, the fullerene derivatives of the present invention perform well in improving open circuit voltage, short circuit current, fill factor and photoelectric conversion efficiency, among which the PCE of the device prepared from F6 / F12 composite material is as high as 12.0%. In addition, these derivatives also show excellent chemical stability and environmental adaptability, effectively extending the service life of the device. The preparation process of the present invention is simple and low-cost, which provides strong support for the commercialization of tin-based perovskite solar cells and promotes the development of photovoltaic technology towards high efficiency, stability and low cost.

Claims

1. A fullerene pyrrolidine derivative, characterized in that The general structural formula of the fullerene pyrrolidine derivative is as follows: Wherein, R refers to a straight-chain or branched alkyl or alkoxy group having 1 to 10 carbon atoms, and Ar refers to an aryl or heteroaryl group having 5 to 20 carbon atoms.

2. A fullerene pyrrolidine derivative according to claim 1, characterized in that: The Ar structural formula is one of the following structures:

3. A fullerene pyrrolidine derivative according to claim 1 or 2, characterized in that: The preparation method of the fullerene pyrrolidine derivative is as follows: fullerene (C60), amino acids with different carbon chain lengths and aromatic aldehydes are subjected to Prato reaction to generate the fullerene pyrrolidine derivative.

4. A fullerene pyrrolidine derivative according to claim 3, characterized in that: The molar ratio of the fullerene (C60) to the amino acids and aromatic aldehydes with different carbon chain lengths is 1:1.2 to 1.5:

2.

5. A fullerene pyrrolidine derivative according to claim 4, characterized in that: The conditions of the Prato reaction are stirring the reaction at a temperature of 120°C to 150°C for 2h to 5h.

6. A fullerene pyrrolidine derivative according to claim 1 or 2, characterized in that: The fullerene pyrrolidine derivative is used as an electron transport layer material for tin-based perovskite solar cells.

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