Nitrogen heterocyclic compound as well as preparation method and application thereof

Abstract

The invention relates to the technical field of solar cells, and particularly discloses a nitrogen heterocyclic compound and a preparation method and application thereof. Molecules of the azacyclo-compound provided by the invention have a large-pi conjugated rigid skeleton formed by a polyaza fused ring, and halogen or-CF3 is introduced as a strong electron-withdrawing substituent. According to the compound, an efficient electron transmission channel is constructed through a rigid conjugated skeleton, the electron mobility and the thermal stability are improved, and surface defects of perovskite are passivated by nitrogen atom coordination; and meanwhile, the hydrophobic substituent group can enhance the moisture resistance of the electron transport layer and improve the film forming quality and the interface compatibility, so that the photoelectric conversion efficiency and the long-term stability of the trans-perovskite solar cell are remarkably improved. According to the trans-perovskite solar cell electron transport layer and the preparation method thereof, the technical blank that the azacyclo-compound is applied to the trans-perovskite solar cell electron transport layer is filled, key material support and technical guarantee are provided for large-scale industrial popularization of the trans-perovskite solar cell, and the application prospect is wide.

Description

Technical Field

[0001] This invention relates to the field of solar cell technology, and in particular to a nitrogen heterocyclic compound, its preparation method, and its application. Background Technology

[0002] With the escalating global energy crisis and increasing environmental awareness, the development of clean, renewable, and efficient new energy sources has become a research hotspot in the field of science and technology. Among these, perovskite solar cells have become a focal point in the photovoltaic industry due to their rapid development. Since their inception in 2009, their photoelectric conversion efficiency has soared from 3.8% to 27.32% in 2025, with a theoretical single-junction efficiency exceeding 30% and tandem cells reaching over 40%, far surpassing crystalline silicon cells. This technology also boasts advantages such as low cost, simple fabrication, and lightweight flexibility, making it a promising candidate for applications in building-integrated photovoltaics (BIPV) and distributed photovoltaic systems.

[0003] Perovskite solar cells can be classified into two types based on the arrangement of their functional layers: nip (next-in) and pin (inverted). Inverted perovskite solar cells, with their unique advantages such as simple fabrication process, low-temperature fabrication capability, good compatibility with flexible substrates, excellent light stability, and compatibility with crystalline silicon cells for tandem cell fabrication, show greater promise in flexible electronic devices and large-scale commercial applications. A typical inverted perovskite solar cell structure includes, in sequence, a transparent conductive substrate, a hole transport layer, a perovskite light-absorbing layer, an electron transport layer, and a metal electrode. The electron transport layer, as one of the core functional layers, plays a crucial role in rapidly transporting photogenerated electrons generated by the perovskite light-absorbing layer, effectively blocking hole diffusion to the metal electrode, reducing non-radiative electron-hole recombination, and passivating perovskite surface defects and improving interfacial contact. Its performance directly affects the cell's photoelectric conversion efficiency, open-circuit voltage, fill factor, and long-term stability.

[0004] TiO2, as a classic electron transport layer material, possesses high electron mobility and good chemical stability. However, its preparation process typically requires high-temperature annealing, which increases preparation costs and energy consumption, and limits its application on flexible substrates. SnO2 suffers from numerous surface defects, energy level mismatches, and incomplete coverage, affecting the reproducibility and long-term stability of device performance. Fullerene materials, on the other hand, suffer from poor solubility, poor flexibility, easy phase separation, and high cost, further limiting their practical applications.

[0005] Therefore, developing a novel electron transport material with excellent electron transport performance, good interface compatibility and long-term stability, and with a simple and low-cost preparation method is of great significance for promoting the large-scale application of inverted perovskite solar cells. Summary of the Invention

[0006] To address the aforementioned problems in existing electron transport layer materials for inverted perovskite solar cells, this invention provides a nitrogen heterocyclic compound, its preparation method, and its applications.

[0007] To solve the above-mentioned technical problems, the technical solution provided by the present invention is as follows: In a first aspect, the present invention provides a nitrogen heterocyclic compound with the structure shown in formula (I):

[0008] (I) R1 is a halogen or a trifluoromethyl group.

[0009] Compared to existing technologies, this invention provides a novel nitrogen-containing heterocyclic compound with a large π-conjugated rigid framework of polynitrogenous heterocyclic rings and strong electron-withdrawing substituents such as halogens or -CF3. On one hand, the large π-conjugated rigid framework of polynitrogenous heterocyclic rings can form continuous electron transport channels, significantly improving electron mobility and accelerating photogenerated electron conduction. Simultaneously, its rigid framework structure effectively prevents molecular distortion, further optimizing charge transport efficiency. On the other hand, the aromatic structure of the nitrogen heterocycle endows the material with excellent thermal stability; thermogravimetric analysis shows that its initial decomposition temperature is above 250°C. Furthermore, multiple nitrogen atoms in the framework can form stable coordination with lead ions on the perovskite material surface, effectively passivating defect sites on the perovskite layer surface and suppressing non-radiative recombination losses of electrons and holes.

[0010] The strong hydrophobicity of halogens and -CF3 significantly improves the water contact angle of the electron transport layer, greatly reducing the risk of water and oxygen erosion of the perovskite layer and effectively extending the device's lifespan. These groups can also regulate the solubility of the compound, which is beneficial for forming a uniform and dense electron transport film and improving film quality. At the same time, these groups can also improve the interfacial compatibility and contact state between the compound and the perovskite layer, further suppressing interfacial charge recombination, thereby significantly improving the open-circuit voltage and fill factor of inverted perovskite solar cells.

[0011] The novel nitrogen heterocyclic small molecule electron transport material provided by this invention can simultaneously improve the photoelectric conversion efficiency of inverted perovskite solar cells, enhance device stability, and reduce production and application costs, providing key material support and technical guarantee for the industrialization and promotion of this type of battery.

[0012] Furthermore, the structural formula of the nitrogen heterocyclic compound is shown below: .

[0013] Secondly, the present invention provides a method for preparing nitrogen heterocyclic compounds, comprising the following steps: S1, reduce compound a as shown in formula (II) to obtain the intermediate shown in formula (III);

[0014] Wherein, R1 is a halogen or trifluoromethyl, and R2 is a nitro or amino group; S2, the intermediate and cyclohexane-1,2,3,4,5,6-hexane are subjected to a condensation cyclization reaction under acidic conditions to obtain a nitrogen-containing heterocyclic compound.

[0015] The method for preparing nitrogen heterocyclic compounds provided by this invention is simple, the raw materials are readily available, and the preparation cost is significantly lower than that of fullerene materials, making it more suitable for the actual needs of large-scale production.

[0016] As a specific embodiment of the present invention, the preparation method of the nitrogen heterocyclic compound specifically includes the following steps: S1, under an inert atmosphere, compound a and stannous salt are reduced in an aqueous ethanol solution to obtain an intermediate; S2, under an inert atmosphere, the intermediate and cyclohexane-1,2,3,4,5,6-hexane were subjected to a condensation cyclization reaction in glacial acetic acid to obtain a nitrogen-containing heterocyclic compound.

[0017] Furthermore, in S1, the stannous salt is stannous chloride.

[0018] Furthermore, in S1, the molar ratio of compound a to stannous salt is 1:3 to 1:10.

[0019] Furthermore, in S1, the volume ratio of anhydrous ethanol to water in the ethanol-water solution is 3:1 to 7:1.

[0020] Furthermore, in S1, the temperature of the reduction reaction is 70℃~100℃, and the reaction time is 3h~7h.

[0021] It should be noted that after the reduction reaction in S1 is completed, there is also a post-processing procedure: the reaction solution is adjusted to alkaline, extracted, dried and purified to obtain the intermediate.

[0022] Specifically, in S1, the extractant is dichloromethane, and the drying includes drying with anhydrous sodium sulfate and vacuum distillation. The purification is performed by column chromatography, with the eluent being petroleum ether and dichloromethane in a volume ratio of 1:1 to 3:1.

[0023] Further, in S2, the molar ratio of the intermediate to cyclohexane-1,2,3,4,5,6-hexane is 3:1 to 4:1.

[0024] Furthermore, in S2, the temperature of the condensation cyclization reaction is 110℃~135℃, and the reaction time is 15h~28h.

[0025] It should be noted that in S1 and S2 above, the inert atmosphere is provided by an inert gas, which can be any conventional inert gas in the art, such as nitrogen or argon, and the present invention does not impose any special limitations.

[0026] Thirdly, the present invention also provides the application of the above-mentioned nitrogen heterocyclic compounds in inverted perovskite solar cells.

[0027] Specifically, the application involves using nitrogen heterocyclic compounds to prepare the electron transport layer of an inverse perovskite solar cell.

[0028] As a specific embodiment of the present invention, the method for using the nitrogen heterocyclic compound to prepare the electron transport layer of an inverse perovskite solar cell includes the following steps: The above-mentioned nitrogen heterocyclic compounds were dispersed in an organic solvent to obtain an electron transport layer precursor dispersion. The electron transport layer precursor dispersion is coated onto the surface of the perovskite light absorption layer to form an electron transport layer.

[0029] Specifically, the organic solvent includes chlorobenzene, anhydrous ethanol, or isopropanol.

[0030] Specifically, the concentration of nitrogen heterocyclic compounds in the electron transport layer precursor dispersion is 3 mg / mL to 12 mg / mL.

[0031] Furthermore, before coating the electron transport layer precursor dispersion, a phenylethyl ammonium iodide solution is first coated. After spin-coating the electron transport layer precursor dispersion, the BCP solution is then spin-coated.

[0032] Specifically, the concentration of the phenylethyl ammonium iodide solution is 0.4 mg / mL to 0.6 mg / mL. The concentration of the BCP solution is 0.3 mg / mL to 0.5 mg / mL.

[0033] Fourthly, the present invention also provides an electron transport layer for an inverted perovskite solar cell, comprising the aforementioned nitrogen heterocyclic compound.

[0034] Fifthly, the present invention also provides a perovskite solar cell, comprising a transparent conductive substrate, a hole transport layer, a perovskite light-absorbing layer, the electron transport layer of the aforementioned inverted perovskite solar cell, and a metal electrode.

[0035] Optionally, the conductive substrate is ITO conductive glass. Before use, the ITO conductive glass is ultrasonically cleaned sequentially with dish soap, purified water, and isopropanol.

[0036] Optionally, the hole transport layer described above is prepared using the following method: The nickel oxide dispersion was spin-coated onto the ITO conductive glass and annealed. Then, the 2-PACz solution was coated onto the nickel oxide layer and annealed to form a hole transport layer.

[0037] Furthermore, the spin coating speed of the nickel oxide dispersion is 4800 r / min to 5200 r / min, the annealing temperature after spin coating is 110℃ to 130℃, and the annealing time is 10 min to 20 min.

[0038] Furthermore, the spin coating speed of the 2-PACz solution was 2800 r / min to 3200 r / min, the annealing temperature after spin coating was 90℃ to 110℃, and the annealing time was 8 min to 12 min.

[0039] Optionally, the above-mentioned perovskite light-absorbing layer is prepared using the following method: The perovskite active material is dispersed in an organic solution, spin-coated onto a hole transport layer, and annealed to form a perovskite light absorption layer.

[0040] Furthermore, the perovskite active material is FA. 0.8 Cs 0.2 Pb(I 0.8 Br 0.2 )3, the concentration of which is dispersed in an organic solution is 1.4M~1.6M. The organic solution is N,N-dimethylformamide and dimethyl sulfoxide in a volume ratio of 3:1~5:1.

[0041] Optionally, the back electrode layer is a gold electrode or a silver electrode, and the back electrode layer is formed on the electron transport layer by vacuum evaporation or vacuum sputtering.

[0042] Furthermore, the thickness of the back electrode layer is 100 nm.

[0043] In summary, this invention provides a nitrogen-containing heterocyclic compound for the electron transport layer of inverted perovskite solar cells. The molecule possesses a large π-conjugated rigid framework composed of multiple nitrogen-containing heterocyclic rings, and incorporates halogens or -CF3 as strong electron-withdrawing substituents. This compound constructs efficient electron transport channels through its rigid conjugated framework, enhancing electron mobility and thermal stability, and utilizes nitrogen atom coordination to passivate perovskite surface defects. Simultaneously, the hydrophobic substituents enhance the moisture resistance of the electron transport layer, improve film quality and interfacial compatibility, thereby significantly improving the photoelectric conversion efficiency and long-term stability of inverted perovskite solar cells. This invention fills the technological gap in the application of nitrogen-containing heterocyclic compounds in the electron transport layer of inverted perovskite solar cells, providing key material support and technical assurance for the large-scale industrialization and promotion of inverted perovskite solar cells, and has broad application prospects. Attached Figure Description

[0044] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0045] Figure 1 The nitrogen heterocyclic compound HATNA-51 prepared in Example 1 of this invention 1 H NMR spectrum; Figure 2 The HMRS spectrum of HATNA-51, a nitrogen heterocyclic compound prepared in Example 1 of this invention; Figure 3 The nitrogen heterocyclic compound HATNA-59 prepared in Example 1 of this invention 1 H NMR spectrum; Figure 4 The HMRS spectrum of HATNA-59, a nitrogen heterocyclic compound prepared in Example 1 of this invention; Figure 5 Thermogravimetric analysis curves and differential scanning calorimetry curves of the nitrogen heterocyclic compounds prepared in Examples 1 and 2 of this invention are shown. Figure 6 Cyclic voltammetry curves of the nitrogen heterocyclic compounds prepared in Examples 1 and 2 of this invention; Figure 7 The voltage-current density curves are for the nitrogen heterocyclic compounds prepared in Examples 1 and 2 of this invention. Figure 8 The water contact angle is the nitrogen heterocyclic compound prepared in Examples 1 and 2 of this invention. Detailed Implementation

[0046] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to embodiments. It should be understood that the specific embodiments described herein are merely illustrative and not intended to limit the invention.

[0047] To better illustrate the present invention, further examples are provided below.

[0048] Example 1 This invention provides a method for preparing the nitrogen heterocyclic compound HATNA-51, comprising the following steps: S1. Take a 100 mL single-necked round-bottom flask and add 948 mg (4 mmol) of 1,2-dichloro-4,5-dinitrobenzene and 6.06 g (32 mmol) of stannous chloride to the flask in sequence. Add 30 mL of a mixed solution of anhydrous ethanol and water (volume ratio 5:1). React in an oil bath under nitrogen protection at 80 °C for 5 h. Monitor the reaction by TLC. After the reaction is completed, cool the reaction solution to room temperature, quench the reaction with water, adjust the pH to 8.1 with NaOH solution, and then extract with dichloromethane. Dry the extract with anhydrous sodium sulfate, distill under reduced pressure, and purify by column chromatography (eluent is petroleum ether and dichloromethane in a volume ratio of 1:1). Dry to obtain 566.5 mg of pale yellow solid intermediate HATNA51-2, yield 80%. 1 H NMR (400 MHz, Chloroform-d) δ 6.76 (s, 1H), 3.19 (s, 2H). S2, Take a 100 mL single-necked round-bottom flask and add 566.50 mg (3.20 mmol) of the intermediate HATNA51-2 prepared above, 168.06 mg (1.00 mmol) of cyclohexane-1,2,3,4,5,6-hexane, and 12 mL of glacial acetic acid to the flask. Then connect a spherical condenser and a nitrogen balloon, and perform three gas exchanges using a vacuum pump to ensure an anhydrous and oxygen-free atmosphere. Heat in an oil bath at 120 °C under reflux for 16 h, and monitor with TLC. After the reaction is complete, cool the reaction solution to room temperature and add it dropwise to 70 mL of ice-cold deionized water. Stir thoroughly with a magnetic stirrer, filter through a Buchner funnel, extract the filtrate with ethyl acetate, dry the extract with anhydrous sodium sulfate, purify by vacuum distillation and column chromatography (eluent is petroleum ether and ethyl acetate in a volume ratio of 3:1), and dry to obtain 380 mg of white solid product HATNA-51, with a yield of 64.29%. 1 H NMR (400 MHz, Chloroform-d) δ 7.62(s, 6H).

[0049] The nitrogen heterocyclic compound HATNA-51 prepared in this embodiment 1 The H NMR and HRMS images are as follows: Figure 1 , Figure 2 As shown.

[0050] The preparation method of the above-mentioned nitrogen heterocyclic compound HATNA-51 can also employ other reaction conditions as defined in the specification of this invention, and as long as they are within the scope defined by this invention, equivalent effects to those described above can be achieved.

[0051] Example 2 This invention provides a method for preparing the nitrogen heterocyclic compound HATNA-59, comprising the following steps: S1. Take a 100 mL single-necked round-bottom flask and add 1.01 g (4.2 mmol) of 5-chloro-2-nitro-4-(trifluoromethyl)aniline and 3.03 g (16 mmol) of stannous chloride to the flask in sequence. Add 12 mL of a mixed solution of anhydrous ethanol and water (volume ratio 5:1) dropwise. React in an oil bath under nitrogen protection at 80 °C for 4 h. Monitor the reaction by TLC. After the reaction is completed, cool the reaction solution to room temperature, add water to quench the reaction, adjust the pH to 8.2 with NaOH solution, then extract with dichloromethane, dry with anhydrous sodium sulfate, distill under reduced pressure, and purify by column chromatography (eluent is petroleum ether and dichloromethane in a volume ratio of 1:1). Dry to obtain 1.42 g of pale yellow solid intermediate HATNA-59-2, yield 82%. 1 H NMR (500 MHz, DMSO-d6) δ 6.85 (s, 1H), 6.63 (s, 1H), 5.39 (s, 2H), 4.94 (s, 2H). S2, take a 100mL single-necked round-bottom flask and add 652.8mg (3.10mmol) of the prepared intermediate HATNA59-2, 168.06mg (1.00mmol) of cyclohexane-1,2,3,4,5,6-hexane, and 10mL of glacial acetic acid to the flask. Then connect a spherical condenser and a nitrogen balloon, and perform three gas changes using a vacuum pump to ensure an anhydrous and oxygen-free atmosphere. Heat in an oil bath at 120℃ under reflux for 16h, and perform TLC. After monitoring, the reaction solution was cooled to room temperature and then slowly added dropwise to 100 mL of ice-cold deionized water. Yellow flocculent material was immediately produced after the addition. The mixture was stirred thoroughly with a magnetic stirrer, filtered through a sintered glass funnel, and then washed with dichloromethane to obtain a brownish-yellow solution. The solution was dried over anhydrous sodium sulfate, purified by vacuum distillation and column chromatography (eluent was petroleum ether and ethyl acetate in a volume ratio of 3:1), and dried to give 288 mg of yellow solid product HATNA-59, with a yield of 41.64%. 1 H NMR (500MHz, Chloroform-d) δ 9.15 (t, J = 2.7 Hz, 3H), 8.87 (t, J = 3.0 Hz, 3H).

[0052] The nitrogen heterocyclic compound HATNA-59 prepared in this embodiment... 1 The H NMR and HRMS images are as follows: Figure 3 , Figure 4 As shown.

[0053] The preparation method of the above-mentioned nitrogen heterocyclic compound HATNA-59 can also employ other reaction conditions as defined in the specification of this invention, and as long as they are within the scope defined by this invention, equivalent effects to those described above can be achieved.

[0054] Example 3 Thermal stability test Weigh 3 mg of the dried nitrogen heterocyclic compounds prepared in Examples 1 and 2 into a crucible, add them to a thermogravimetric analyzer, and under nitrogen atmosphere, set the heating rate to 10 °C / min, and heat from room temperature to 500 °C. The thermogravimetric curves are shown below. Figure 5 As shown.

[0055] As shown in the figure, the decomposition temperatures of nitrogen heterocyclic compounds HATNA-51 and HATNA-59 are 209.03℃ and 201.98℃, respectively, indicating that both have good thermal stability. Among them, the glass transition temperatures of HATNA-51 and HATNA-59 are 252.12℃ and 364.61℃, respectively, which can effectively ensure the good film-forming properties of the compounds and provide reliable support for device stability.

[0056] Example 4 Electrochemical testing The synthesized nitrogen heterocyclic compounds HATNA-51 and HATNA-59 were electrochemically characterized using cyclic voltammetry (CV). A three-electrode system was used: a glassy carbon electrode as the working electrode, a platinum electrode as the counter electrode, and an Ag / AgCl electrode as the reference electrode. The electrolyte was a 0.1 M tetrabutylammonium hexafluorophosphate solution in acetonitrile. The scan rate was 50 mV / s, and ferrocene (with an energy level of 4.8 eV relative to vacuum) was used as an internal standard. The results are as follows: Figure 6 As shown.

[0057] The LUMO energy levels of HATNA-51 and HATNA-59 were calculated to be -3.78 eV and -3.87 eV, respectively, based on the positions of the redox peaks, indicating that they are well matched with the energy levels of the perovskite layer.

[0058] Example 5 Performance testing To better illustrate the characteristics of the nitrogen heterocyclic compounds provided in the embodiments of the present invention when applied to the electron transport layer, the nitrogen heterocyclic compounds HATNA-51 and HATNA-59 prepared in Examples 1 and 2 were used to prepare inverted perovskite solar cells, and then their performance was tested.

[0059] The above-mentioned method for fabricating inverted perovskite solar cells includes the following steps: (1) Cleaning of conductive glass substrate The ITO conductive glass was ultrasonically cleaned in sequence with dish soap, deionized water, and isopropanol to remove surface contaminants.

[0060] (2) Preparation of hole transport layer First, nickel oxide (NiO) x Disperse the 2-PACz in water to prepare a 10 mg / mL dispersion, spin-coat it onto a clean ITO surface (5000 rpm), anneal at 120 °C for 15 min, and then spin-coat it (3000 rpm) with an ethanol solution of 1 mg / mL 2-PACz, anneal at 100 °C for 10 min to form a hole transport layer.

[0061] (3) Preparation of perovskite active layer FA 0.8 Cs 0.2 Pb(I 0.8 Br 0.2 The precursor was dispersed in a mixed solvent of N,N-dimethylformamide and dimethyl sulfoxide (volume ratio 4:1) to obtain a 1.5 M perovskite precursor solution; the solution was spin-coated onto the hole transport layer (5000 rpm) and annealed at 100 °C for 45 min to form a perovskite active layer.

[0062] (4) Fabrication of the electron transport layer A 0.5 mg / mL solution of phenylethyl ammonium iodide in isopropanol was spin-coated sequentially onto the surface of the perovskite layer at a speed of 3000 rpm; then a 10 mg / mL solution of a nitrogen heterocyclic compound (chlorobenzene as solvent) was spin-coated at a speed of 4000 rpm; finally, a 0.4 mg / mL solution of BCP (anhydrous ethanol as solvent) was spin-coated at a speed of 3000 rpm to form an electron transport layer.

[0063] (5) Preparation of metal electrodes The substrate was placed in a vacuum evaporation apparatus, and an Ag electrode with a thickness of 100 nm was deposited on the surface of the electron transport layer to complete the fabrication of the device.

[0064] The structure of the inverted perovskite solar cell prepared above is ITO glass / NiO. x / 2-PACz / 1.5MFA 0.8 Cs 0.2 Pb(I 0.8 Br 0.2)3 / PEAI / ETM / BCP / Ag.

[0065] The inverted perovskite solar cell prepared above was placed under a xenon lamp solar simulator (Abet Sun 3000) at AM 1.5G and 100mW / cm². 2The photoelectric conversion efficiency was tested under standard light illumination, with a measured bias voltage of 1.25V. 0.1V, the effective area of ​​the battery is 0.06cm². 2 The voltage-current density curves obtained from the tests are as follows: Figure 7 As shown in Table 1, the test results are as follows.

[0066] Table 1

[0067] Example 6 Hydrophobicity test Using ITO transparent conductive glass as a substrate, the substrate was ultrasonically cleaned sequentially with deionized water, acetone, and anhydrous ethanol for 15 min each to obtain a clean ITO substrate. A chlorobenzene solution of the nitrogen heterocyclic compound prepared in Examples 1-2 with a concentration of 10 mg / mL was then spin-coated onto the substrate to prepare an ETM film. Water contact angle tests were then performed, and the results are as follows: Figure 8 As shown.

[0068] The results show that the water contact angles of HATNA-51 and HATNA-59 films are 77.6° and 91.0°, respectively, indicating that both have good hydrophobicity, which is beneficial to improving the stability of the device in a humid environment.

[0069] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. Any modifications, equivalent substitutions or improvements made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A nitrogen-containing heterocyclic compound, characterized in that, Its structure is shown in equation (I): （I） R1 is a halogen or a trifluoromethyl group.

2. The nitrogen heterocyclic compound as described in claim 1, characterized in that, R1 is trifluoromethyl.

3. The method for preparing the nitrogen heterocyclic compound according to claim 1 or 2, characterized in that, Includes the following steps: S1, reduce compound a as shown in formula (II) to obtain the intermediate shown in formula (III); Wherein, R1 is a halogen or trifluoromethyl, and R2 is a nitro or amino group; S2, the intermediate and cyclohexane-1,2,3,4,5,6-hexane are subjected to a condensation cyclization reaction under acidic conditions to obtain a nitrogen-containing heterocyclic compound.

4. The method for preparing nitrogen heterocyclic compounds as described in claim 3, characterized in that, Specifically, the steps include the following: S1, under an inert atmosphere, compound a and stannous salt are reduced in an aqueous ethanol solution to obtain an intermediate; S2, under an inert atmosphere, the intermediate and cyclohexane-1,2,3,4,5,6-hexane were subjected to a condensation cyclization reaction in glacial acetic acid to obtain a nitrogen-containing heterocyclic compound.

5. The method for preparing nitrogen heterocyclic compounds as described in claim 4, characterized in that, In S1, the stannous salt is stannous chloride; and / or In S1, the molar ratio of compound a to stannous salt is 1:3 to 1:10; and / or In S1, the volume ratio of anhydrous ethanol to water in the ethanol-water solution is 3:1 to 7:1; and / or In S1, the temperature of the reduction reaction is 70℃~100℃, and the reaction time is 3h~7h.

6. The method for preparing nitrogen heterocyclic compounds as described in claim 4, characterized in that, In S2, the molar ratio of the intermediate to cyclohexane-1,2,3,4,5,6-hexaone is 3:1 to 4:1; and / or In S2, the temperature of the condensation cyclization reaction is 110℃~135℃, and the reaction time is 15h~28h.

7. The application of the nitrogen heterocyclic compound according to claim 1 or 2 in inverted perovskite solar cells.

8. The application as described in claim 7, characterized in that, The nitrogen-containing heterocyclic compounds are used to prepare the electron transport layer of inverted perovskite solar cells.

9. An electron transport layer for an inverted perovskite solar cell, characterized in that, Including the nitrogen heterocyclic compounds as described in claim 1 or 2.

10. A reverse perovskite solar cell, characterized in that: It includes a transparent conductive substrate, a hole transport layer, a perovskite light-absorbing layer, an electron transport layer of the inverted perovskite solar cell as described in claim 9, and a metal electrode.

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