Dibenzofuran-carbazolyl compound, preparation method and trans-perovskite solar cell

Abstract

The invention discloses a dibenzofuran-carbazolyl compound, a preparation method and a trans-perovskite solar cell, and belongs to the technical field of perovskite solar cells. The core molecular structure of the dibenzofuran-carbazolyl compound provided by the invention is based on a dibenzofuran-carbazole fused or connected skeleton; and multi-functional integration is realized by introducing phosphorus-oxygen groups. In the aspect of energy level matching, the fused ring system has a relatively high highest occupied molecular orbital energy level, can realize more optimized energy level alignment with the valence band top of the perovskite light absorption layer, and effectively reduces the interface potential barrier of hole extraction, thereby facilitating the improvement of the open-circuit voltage of the device.

Description

Technical Field

[0001] This invention relates to the field of perovskite solar cell technology, specifically to dibenzofuran-carbazole compounds and their preparation methods, and trans-perovskite solar cells. Background Technology

[0002] Perovskite solar cells have become a research hotspot in the photovoltaic field due to their outstanding advantages such as low manufacturing cost, high photoelectric conversion efficiency, and flexibility. To date, the photoelectric conversion efficiency of laboratory-grade perovskite solar cells has exceeded 27%, demonstrating enormous commercial potential. However, their poor long-term stability and severe interfacial charge recombination remain key bottlenecks restricting their large-scale application.

[0003] Self-assembled monomolecular films (SAMs), as key materials for the hole-selective layer in perovskite solar cells, can form ordered thin films on the surface of transparent conductive oxide (TCO) substrates through intermolecular and substrate-substrate interactions. This not only efficiently extracts photogenerated holes and lowers the substrate work function, but also passivates interface defects and prevents direct contact between the substrate and the perovskite layer, which is crucial for improving cell efficiency and stability. Currently, SAM materials used in perovskite cells are mainly carbazole derivatives. Although carbazole compounds possess strong electron-donating capabilities and large π-conjugated systems, existing carbazole SAM materials generally suffer from loose molecular stacking, uneven coverage, and weak resistance to solvent desorption. Under high temperature and high humidity environments, molecular shedding easily occurs, leading to substrate exposure and accelerated perovskite layer decomposition, resulting in severe efficiency degradation of the cell under harsh conditions. Summary of the Invention

[0004] This invention provides a dibenzofuran-carbazole-based compound and its preparation method, as well as an inverted perovskite solar cell. It effectively solves the technical problem that existing carbazole-based SAM materials suffer from severe efficiency degradation in high-temperature and high-humidity environments due to loose molecular stacking, uneven coverage, and weak resistance to solvent desorption. At the same time, it provides an indole-carbazole compound for hole transport layer materials in perovskite solar cells, thereby effectively improving the hole mobility, fill factor, and photoelectric conversion efficiency of inverted perovskite solar cells.

[0005] The first objective of this invention is to provide a dibenzofuran-carbazole compound, the general structural formula of which is: or Among them, L1, L2, and L3 are each independently C0 to C4 alkylene groups.

[0006] In a preferred embodiment, L1, L2, and L3 are each independently a C1-C4 straight-chain alkylene group.

[0007] In a preferred embodiment, the dibenzofuran-carbazole compound is any one of the following structural formulas: , , , .

[0008] A second objective of this invention is to provide a method for preparing the above-mentioned dibenzofuran-carbazole compound, comprising the following steps: Using compounds of formula 3 and formula 4 as starting materials, the compounds are dissolved in an organic solvent at room temperature and coupled under the action of a base and a catalyst to attach carbazole to dibenzofuran, yielding compound 5. Using compound 5 and an lipid compound as starting materials, the mixture is refluxed at 130℃–160℃ to yield compound 6. Using compound 6 and trimethylbromosilane of formula 7 as starting materials, a substitution reaction is carried out in an organic solvent at room temperature, followed by hydrolysis in an aqueous methanol solution to yield dibenzofuran-carbazole compound of formula 1. The synthetic route for dibenzofuran-carbazole compound of formula 1 is as follows: .

[0009] Alternatively, using compounds of formula 8 and formula 4 as starting materials, they are dissolved in an organic solvent at room temperature and coupled under the action of a base and a catalyst to attach carbazole to dibenzofuran, yielding compound 9; using compound 9 and an lipid compound as starting materials, a reflux reaction is carried out at 130℃~160℃ to yield compound 10; using compound 10 and trimethylbromosilane of formula 7 as starting materials, a substitution reaction is carried out in an organic solvent at room temperature, followed by hydrolysis in an aqueous methanol solution to yield dibenzofuran-carbazole compound of formula 2. The synthetic route for dibenzofuran-carbazole compound of formula 2 is as follows: Among them, L1, L2, and L3 are each independently C0 to C4 alkylene groups.

[0010] In a preferred embodiment, the molar ratio of the compound of Formula 3 to the compound of Formula 4 is 1:2 to 10; the molar ratio of the compound of Formula 8 to the compound of Formula 4 is 1:2 to 10.

[0011] In a preferred embodiment, the molar ratio of the compound of Formula 5 to the lipid compound is 1:2 to 5; the molar ratio of the compound of Formula 9 to the lipid compound is 1:2 to 5.

[0012] In a preferred embodiment, the molar ratio of the compound of Formula 6 to the trimethylbromosilane of Formula 7 is 1:2 to 5; the molar ratio of the compound of Formula 10 to the trimethylbromosilane of Formula 7 is 1:2 to 5.

[0013] In a preferred embodiment, the lipid compound is selected from diethyl 2-bromoethylphosphonate or triethyl phosphite; the organic solvent is 1,4-dioxane.

[0014] The third objective of this invention is to provide an inverted perovskite solar cell, which comprises, from bottom to top, a conductive substrate, a hole transport layer, a perovskite light-absorbing layer, an electron transport layer, and a metal electrode, wherein the hole transport layer is constructed using the dibenzofuran-carbazole compound as a self-assembled monolayer material.

[0015] As a preferred embodiment, the hole transport layer is prepared by dissolving a dibenzofuran-carbazole compound in an organic solvent under a nitrogen atmosphere to obtain a coating solution with a concentration of 0.5 mg / mL to 6 mg / mL, spin-coating the coating solution onto a conductive substrate at a speed of 1000 rpm to 5000 rpm, and annealing at 100°C to 150°C to obtain the hole transport layer.

[0016] Compared with the prior art, the beneficial effects of the present invention are as follows: Based on the strong electron-donating ability and large π-conjugated system of carbazole compounds, and the unique oxocyclic conjugated structure of dibenzofuran compounds, which possess excellent electron transport performance, high chemical stability, and good molecular planarity, this invention fuses the structures of carbazole and dibenzofuran compounds to achieve complementary performance. This invention provides a dibenzofuran-carbazole-based compound, whose core molecular structure is based on a dibenzofuran-carbazole fused or linked framework, and achieves multifunctional integration by introducing phosphoroxane groups. Applying the dibenzofuran-carbazole-based compound as a self-assembled monolayer material to the hole transport layer induces the directional growth of perovskite crystals, significantly reduces the hole extraction barrier, suppresses non-radiative recombination, and achieves a stable photoelectric conversion efficiency exceeding 25%. Furthermore, the film deposition process is low-temperature and simple, with low material consumption, and is highly compatible with flexible substrates and tandem battery processes, demonstrating outstanding industrial application value.

[0017] In terms of energy level matching, this fused ring system has a high highest occupied molecular orbital energy level, which can achieve more optimized energy level alignment with the valence band top of the perovskite light-absorbing layer, effectively reducing the interface barrier for hole extraction, thereby helping to improve the open-circuit voltage of the device.

[0018] In terms of interface passivation, the polar phosphoro-oxygen bonds (P=O) and other electron-donating groups (C=O, carbazole nitrogen atoms) present in the molecule act as Lewis base sites, which specifically coordinate with the defects of uncoordinated lead ions and halogen vacancies on the lower surface of the perovskite layer, significantly suppressing nonradiative recombination loss at the interface, thereby simultaneously improving the open circuit voltage and fill factor.

[0019] In terms of interface morphology and wettability control, the three-dimensional spatial structure of the molecule and the tunability of its terminal groups enable it to optimize the interaction with the surface of transparent conductive substrates such as indium tin oxide, forming a dense and uniform monomolecular capping layer. This layer can also regulate the surface wetting behavior of the perovskite precursor solution, induce the perovskite crystals to grow in a preferred direction, and finally obtain a high-quality perovskite active layer with low defect density.

[0020] In terms of device stability, the self-assembled monolayer forms a stable chemical bond with the substrate through anchoring groups such as phosphonic acid groups, which constitutes an effective physical and chemical barrier layer. This not only prevents direct contact between the perovskite components and the bottom electrode, inhibits ion migration and electrode corrosion side reactions at the interface, but also enhances the long-term working stability of the entire device under thermal, optical and environmental stress.

[0021] In summary, the dibenzofuran-carbazole compound provided by this invention, when used as a self-assembled monolayer material in the hole transport layer, achieves multiple benefits including energy level matching, defect passivation, morphology regulation, and enhanced stability. It is a key interface material for improving the overall performance of inverted perovskite solar cells. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the structure of the perovskite solar cell provided by the present invention, wherein 1 is a metal electrode, 2 and 3 are electron transport layers, 4 is a perovskite light-absorbing layer, 5 is a hole transport layer, and 6 is a conductive substrate.

[0023] Figure 2 The JV curves are for application embodiments and comparative examples of the present invention. Figure 3 The NMR spectrum of the dibenzofuran-carbazole compound (compound 1) prepared in Example 1 of this invention is shown. Figure 4 The NMR spectrum of the dibenzofuran-carbazole compound (compound 2) prepared in Example 2 of this invention is shown. Figure 5 The NMR spectrum of the dibenzofuran-carbazole compound (compound 3) prepared in Example 3 of this invention is shown. Figure 6 The NMR spectrum of the dibenzofuran-carbazole compound (compound 4) prepared in Example 4 of this invention is shown. Detailed Implementation

[0024] To enable those skilled in the art to better understand and implement the technical solutions of this invention, the invention is further described below with reference to specific embodiments. However, the embodiments are not intended to limit the invention. Unless otherwise specified, the following test methods and detection methods are conventional methods; unless otherwise specified, the reagents and raw materials are commercially available.

[0025] Existing hole transport layer materials for perovskite solar cells are mainly carbazole derivatives. Although carbazole compounds possess strong electron-donating capabilities and large π-conjugated systems, existing carbazole-based SAM materials generally suffer from defects such as loose molecular stacking, uneven coverage, and weak resistance to solvent desorption. Under high temperature and high humidity environments, molecular shedding easily occurs, leading to substrate exposure and accelerated perovskite layer decomposition, resulting in severe efficiency degradation of the cell under harsh conditions. To address these technical problems, this invention provides a dibenzofuran-carbazole-based compound and its preparation method, as well as a perovskite solar cell.

[0026] The technical solution of the present invention will be described in detail below.

[0027] This invention provides a dibenzofuran-carbazole compound with the following general structural formula: or Wherein, L1, L2, and L3 are each independently a C0-C4 alkylene group. The dibenzofuran-carbazole compound provided in subsequent embodiments of this invention is... , , , The above-mentioned dibenzofuran-carbazole compounds are named Compound 1 to Compound 4, respectively.

[0028] The aforementioned dibenzofuran-carbazole compound represents the first application of a dibenzofuran-carbazole derivative with a specific fused ring and linker structure as a self-assembled monolayer material in the hole transport interface of an inverted perovskite solar cell. In terms of device performance, this material achieves highly efficient synergy between energy level matching, charge extraction, and interface passivation through its unique molecular structure. Its dibenzofuran-carbazole fused ring structure ensures high intrinsic hole mobility and optimized energy level positions, resulting in better alignment between its highest occupied molecular orbital energy level and the valence band top of the perovskite active layer, significantly reducing the energy barrier for hole extraction. Simultaneously, the abundant phosphorus-oxygen bonds in the molecule act as highly efficient Lewis base sites, strongly interacting with uncoordinated lead ions and halogen vacancies on the perovskite lower surface, achieving deep interface defect passivation and effectively suppressing non-radiative recombination. Based on this self-assembled monolayer inverse perovskite solar cell, a comprehensive and significant improvement in photoelectric performance is achieved. The photoelectric conversion efficiency, particularly the open-circuit voltage which determines voltage loss and the fill factor reflecting the internal carrier transport and collection capabilities, are all substantially improved. Experimental data show that devices using the material of this invention consistently achieve a maximum photoelectric conversion efficiency exceeding 25%, demonstrating the outstanding potential of this material in realizing high-efficiency photovoltaic devices.

[0029] In terms of process adaptability and industrialization potential, this self-assembled monolayer material exhibits significant advantages. From a material synthesis perspective, its preparation route is clear, the involved organic synthesis reactions are mature, and the post-processing and purification methods are relatively simple, facilitating standardized and reproducible synthesis production. From a device fabrication perspective, its self-assembly film formation process is extremely simple, requiring only immersion of the substrate in a diluted solution or spin coating to form a uniform and dense monolayer at low temperatures, completely avoiding the high-temperature annealing process required for traditional hole transport materials, greatly reducing process complexity and energy consumption. This characteristic makes it highly compatible with the low-temperature, all-solution processing flow of inverted perovskite solar cells, especially suitable for advanced device structures sensitive to temperature, such as flexible substrates and tandem solar cells. Furthermore, since the self-assembled monolayer covers the substrate with a single-molecule thickness, material consumption is extremely low, providing a significant cost control advantage in large-scale production, laying a solid foundation for its future commercial applications.

[0030] The present invention also provides a method for preparing the above-mentioned dibenzofuran-carbazole compound, comprising the following steps: Using compounds of formula 3 and formula 4 as starting materials, the compounds were dissolved in an organic solvent (1,4-dioxane) at room temperature and coupled under the action of a base and a catalyst to attach carbazole to dibenzofuran, yielding compound 5. Using compound 5 and an lipid compound as starting materials, the mixture was refluxed at 130℃–160℃ to yield compound 6. Using compound 6 and trimethylbromosilane of formula 7 as starting materials, a substitution reaction was carried out at room temperature in an organic solvent (1,4-dioxane). The solvent was removed under reduced pressure, and then hydrolysis was carried out in a mixed solution of methanol and water at a volume ratio of 1:1.2–1.8 to yield dibenzofuran-carbazole compound of formula 1. The synthetic route is as follows: .

[0031] Alternatively, using compounds of formula 8 and formula 4 as starting materials, they are dissolved in an organic solvent (1,4-dioxane) at room temperature and coupled under the action of a base and a catalyst to attach carbazole to dibenzofuran, yielding compound 9; using compound 9 and an lipid compound as starting materials, a reflux reaction is carried out at 130℃–160℃ to yield compound 10; using compound 10 and trimethylbromosilane of formula 7 as starting materials, a substitution reaction is carried out at room temperature in an organic solvent (1,4-dioxane), the solvent is removed under reduced pressure, and then hydrolysis is carried out in a mixed solution of methanol and water with a volume ratio of 1:1.2–1.8 to yield dibenzofuran-carbazole compound of formula 2. The synthetic route is as follows: Among them, L1, L2, and L3 are each independently C0 to C4 alkylene groups.

[0032] It should be noted that the molar ratio of the compound of Formula 3 to the compound of Formula 4 is 1:2 to 10; the molar ratio of the compound of Formula 8 to the compound of Formula 4 is 1:2 to 10; the molar ratio of the compound of Formula 5 to the lipid compound is 1:2 to 5; the molar ratio of the compound of Formula 9 to the lipid compound is 1:2 to 5; the molar ratio of the compound of Formula 6 to the trimethylbromosilane of Formula 7 is 1:2 to 5; and the molar ratio of the compound of Formula 10 to the trimethylbromosilane of Formula 7 is 1:2 to 5.

[0033] In subsequent embodiments of the present invention, the lipid compounds used are selected from diethyl 2-bromoethylphosphonate or triethyl phosphite; the organic solvent is 1,4-dioxane.

[0034] The present invention also provides an inverted perovskite solar cell, which is provided from bottom to top with a conductive substrate, a hole transport layer, a perovskite light-absorbing layer, an electron transport layer and a metal electrode, wherein the hole transport layer is a self-assembled monolayer material of the dibenzofuran-carbazole compound applied to the hole transport interface.

[0035] It should be noted that the hole transport layer is prepared as follows: Under a nitrogen atmosphere, a dibenzofuran-carbazole compound is dissolved in an organic solvent (anhydrous ethanol or isopropanol) to obtain a coating solution with a concentration of 0.5 mg / mL to 6 mg / mL. The coating solution is then spin-coated onto a conductive substrate at a speed of 1000 rpm to 5000 rpm and annealed at 100℃ to 150℃ to obtain the hole transport layer. Alternatively, a pre-cleaned and treated transparent conductive substrate (such as ITO) is immersed in the coating solution and allowed to stand at 25℃ to 80℃ for 1 h to 24 h, allowing molecules to self-assemble on the surface of the conductive substrate through the anchoring groups of phosphonic acid groups to form a monolayer. The substrate is then rinsed with a suitable solvent and dried to obtain the hole transport layer.

[0036] The method for preparing the inverted perovskite solar cell of the present invention includes the following steps: S1, Glass Cleaning: Patterned indium tin oxide (ITO) conductive glass with a surface resistivity of 15 Ω / sq was used as the substrate. The glass was ultrasonically cleaned sequentially in aqueous solutions containing detergent, deionized water, acetone, and anhydrous ethanol, each for 15 minutes. After cleaning, it was dried with high-purity nitrogen and treated in a UV-ozone generator for 15 minutes to enhance surface hydrophilicity and remove organic contaminants, resulting in a transparent conductive substrate 6, denoted as ITO.

[0037] S2, Preparation of SAM: In a nitrogen-atmospheric glove box, the compound of Formula 1 or Formula 2 of the present invention is dissolved in anhydrous ethanol to prepare a solution with a concentration of 0.5 mg / mL to 6 mg / mL. The solution is filtered through a 0.22 μm polytetrafluoroethylene filter. 100 μL of the solution is pipetted onto the transparent conductive substrate 1 and spin-coated at 3000 rpm for 30 s. After spin-coating, the substrate is removed and annealed on a hot plate at 100 °C for 10 minutes to obtain an ITO substrate modified with SAM, which is the hole transport layer 5, denoted as ITO / SAM.

[0038] S3, Preparation of perovskite solution: In a glove box, dissolve 1.1 mol / L PbI2, 0.2 mol / L MABr, 0.2 mol / L PbBr2, 1 mol / L FAI, and 0.06 mol / L CsI in 1250 μL of a mixed solution of N,N-dimethylformamide and dimethyl sulfoxide in a volume ratio of 4:1. After shaking at room temperature for 3 h, a precursor solution of 1.2 mol / L to 1.5 mol / L is obtained. Filter the solution through a 0.22 μm polytetrafluoroethylene filter for later use.

[0039] Preparation of the perovskite film: ITO / SAM was fixed in a spin coater, and 80 μL of the above precursor solution was added dropwise. The spin coater was first rotated at 1500 rpm for 10 s, and then 400 μL of anhydrous diethyl ether was rapidly added as a reverse solvent 15 s before the end of the spin coat. The spin coater was then rotated at 5000 rpm for 30 s. After spin coating, the wet film was immediately transferred to a hot plate at 110 °C and annealed for 30 min to form a uniform perovskite polycrystalline film, which is the perovskite light-absorbing layer 4.

[0040] S4, Deposition of the electron transport layer: The perovskite light-absorbing layer 4 is transferred to a high-vacuum thermal evaporation apparatus, where the vacuum level is below 5 × 10⁻⁶. -4 Under the condition of Pa, a 25 nm thick C60 layer was deposited at a deposition rate of 0.8 Å / s. Subsequently, the sample was transferred to an atomic layer deposition apparatus, and a 10 nm thick tin oxide film was deposited at 100 °C using tetra(dimethylamino)tin and water as precursors to form a C60 / SnO2 bilayer electron transport structure, i.e., electron transport layers 2 and 3.

[0041] S5, Fabrication of the metal electrode: Covered by a mask, under a vacuum level below 5 × 10⁻⁶. -4 Under the condition of Pa, a 100 nm thick silver electrode is deposited by vapor deposition, and the effective area of ​​the cell is defined as 0.04 cm². 2 That is, metal electrode 1 is obtained.

[0042] The invention will now be described in detail through the following embodiments and comparative examples.

[0043] Example 1 A dibenzofuran-carbazole compound, with the following structural formula: .

[0044] The preparation method of the above-mentioned dibenzofuran-carbazole compound includes the following steps: Synthesis of S1, Intermediate 1: 4-Bromodibenzofuran (60.71 mmol), carbazole-3-borate pinacol ester (63.74 mmol), sodium hydroxide (121.41 mmol), tetrakis(triphenylphosphine)palladium (1.82 mmol), dioxane (120 mL), and deionized water (30 mL) were added to a reaction flask. The gas was purged with nitrogen, and the mixture was heated to 90 °C for 18 h. After the reaction was complete, the solvent was concentrated, and the mixture was extracted with ethyl acetate and water. The extract was dried over anhydrous sodium sulfate (Na₂SO₄), and the solvent was concentrated under reduced pressure. The product was then separated by column chromatography using petroleum ether and dichloromethane in a 5:1 volume ratio as eluents. The product yield was 77%. The synthetic route is as follows: .

[0045] Synthesis of S2, Intermediate 2: Under nitrogen protection, NaH (35.99 mmol), anhydrous DMF 24 mL, and Intermediate 1 (18 mmol) were dissolved in 36 mL of DMF and reacted at 10 °C for 1.5 h. Then, diethyl 2-bromoethylphosphonate (35.99 mmol) was added dropwise. After the addition was complete, the reaction was heated for 3 h. After the reaction was completed, the solvent was removed under reduced pressure, and the reaction mixture was extracted with water and ethyl acetate. The mixture was dried over anhydrous sodium sulfate (Na2SO4). Finally, the product was separated by column chromatography using petroleum ether and ethyl acetate in a volume ratio of 1:6. The product yield was 73%. The synthetic route is as follows: .

[0046] Synthesis of S3, Compound 1: Intermediate 2 (11.05 mmol) and 1,4-dioxane (44 mL) were added to a reaction flask. Trimethylbromosilane (66.33 mmol) was added dropwise under nitrogen protection. The substitution reaction was carried out at 25 °C for 24 h. After the reaction was completed, the solvent was removed under reduced pressure, and 22 mL of methanol was added to dissolve the solid. Then, 35 mL of water was added dropwise, and the solid crystallized for 1 h. The solid was filtered at 20 °C and dried under vacuum. The product was washed with deionized water and dried in a vacuum oven at 65 °C for 16 h. Finally, 3.07 g of solid was obtained, with a yield of 63%. The synthetic route is as follows: .

[0047] NMR data for compound 1 above: 1 H NMR (400 MHz, DMSO-d6) δ 8.15 (ddt, J= 8.0,4.6, 0.8 Hz, 2H), 8.06 (dd, J = 9.2, 0.8 Hz, 1H), 8.00 (t, J = 1.5 Hz, 1H), 7.95 (dd, J = 9.2, 0.7 Hz, 1H), 7.80 (dd, J = 6.8, 1.5 Hz, 1H), 7.53-7.28 (m, 8H), 4.36 (t, J = 7.9 Hz, 2H), 2.27 (dt, J = 11.9, 8.0 Hz, 2H).

[0048] Example 2 A dibenzofuran-carbazole compound, with the following structural formula: .

[0049] The preparation method of the above-mentioned dibenzofuran-carbazole compound includes the following steps: Synthesis of S1, Intermediate 1: 4-Bromodibenzofuran (60.71 mmol), carbazole-3-borate pinacol ester (63.74 mmol), sodium hydroxide (121.41 mmol), tetrakis(triphenylphosphine)palladium (1.82 mmol), dioxane (120 mL), and deionized water (30 mL) were added to a reaction flask. The gas was purged with nitrogen, and the mixture was heated to 90 °C for 18 h. After the reaction was complete, the solvent was concentrated, and the mixture was extracted with ethyl acetate and water. The extract was dried over anhydrous sodium sulfate (Na₂SO₄), and the solvent was concentrated under reduced pressure. The product was then separated by column chromatography using petroleum ether and dichloromethane in a 5:1 volume ratio as eluents. The product yield was 77%. The synthetic route is as follows: .

[0050] Synthesis of S2, Intermediate 2: Under nitrogen protection, NaH (35.99 mmol), anhydrous DMF 24 mL, and Intermediate 1 (18 mmol) were dissolved in 36 mL of DMF. The solution was then added dropwise to the reaction mixture at 15 °C. After the addition was complete, the reaction mixture was kept at 10 °C for 1.5 h. Then, 1,4-dibromobutane (35.99 mmol) was added dropwise at a controlled temperature. After the addition was complete, the reaction mixture was heated for 3 h. The reaction mixture was then extracted with water and ethyl acetate, dried over anhydrous sodium sulfate (Na2SO4), and finally separated by column chromatography using petroleum ether and ethyl acetate in a volume ratio of 10:1 as eluents. The product yield was 71.5%. The synthetic route is as follows: .

[0051] Synthesis of S3, Intermediate 3: Under nitrogen protection, intermediate 2 (12.81 mmol) was added to a reaction flask, followed by triethyl phosphite (128.1 mmol). The reaction was heated for 16 h. After the reaction was completed, the solvent was removed, and the product was separated by column chromatography (n-hexane / ethyl acetate = 1:2). The product yield was 82%. The synthetic route is as follows: .

[0052] Synthesis of S4, Compound 2: Intermediate 3 (10.08 mmol) and 1,4-dioxane (42 mL) were added to a reaction flask. Trimethylbromosilane (60.5 mmol) was added dropwise under nitrogen protection. The substitution reaction was carried out at 25 °C for 24 h. After the reaction was completed, the solvent was removed under reduced pressure, and 21 mL of methanol was added to dissolve the solid. Then, 32 mL of water was added dropwise, and the solid crystallized for 1 h. The solid was filtered at 20 °C and dried under vacuum. The product was washed with deionized water and dried in a vacuum oven at 65 °C for 16 h. Finally, 2.79 g of solid was obtained, with a yield of 59%. The synthetic route is as follows: .

[0053] NMR data for compound 2 above: 1 H NMR (400 MHz, DMSO-d6) δ 8.19-8.12 (m, 2H),8.06 (dd, J = 9.2, 0.8 Hz, 1H), 8.00 (t, J = 1.6 Hz, 1H), 7.95 (dd, J = 9.2, 0.7Hz, 1H), 7.90 (dd, J = 6.4, 1.4 Hz, 1H), 7.80 (dd, J = 6.8, 1.5 Hz, 1H), 7.49 (dd, J = 8.2, 1.3 Hz, 3H), 7.49-7.43 (m, 1H), 7.46-7.35 (m, 2H), 7.35-7.29 (m,1H), 4.14 (t, J = 5.1 Hz, 2H), 1.87 (dtd, J = 11.9, 9.3, 0.9 Hz, 2H), 1.84-1.75(m, 2H), 1.72-1.62 (m, 2H).

[0054] Example 3 A dibenzofuran-carbazole compound, with the following structural formula: .

[0055] The preparation method of the above-mentioned dibenzofuran-carbazole compound includes the following steps: Synthesis of S1, Intermediate 1: 4,6-Dibromodibenzofuran (82.83 mmol), carbazole-3-borate pinacol ester (182.22 mmol), sodium hydroxide (289.89 mmol), tetrakis(triphenylphosphine)palladium (4.14 mmol), dioxane (243 mL), and deionized water (81 mL) were added to a reaction flask. The gas was purged with nitrogen, and the mixture was heated to 90 °C for 18 h. After the reaction was complete, the solvent was concentrated, and the mixture was extracted with ethyl acetate and water. The extract was dried over anhydrous sodium sulfate (Na₂SO₄), and the solvent was concentrated under reduced pressure. The product was then separated by column chromatography using petroleum ether and dichloromethane (volume ratio 10:1) as eluents. The product yield was 43%. The synthetic route is as follows: .

[0056] Synthesis of S2, Intermediate 2: Under nitrogen protection, NaH (60.17 mmol), anhydrous DMF (24 mL), and intermediate 1 (12.03 mmol) dissolved in 36 mL of DMF were added to a reaction flask. The reaction was allowed to proceed for 1.5 h. Then, diethyl 2-bromoethylphosphonate (36.10 mmol) was added dropwise at 15 °C. After the addition was complete, the reaction was heated for 3 h. After the reaction was completed, the solvent was removed under reduced pressure, and the reaction mixture was extracted with water and ethyl acetate. The mixture was dried over anhydrous sodium sulfate (Na2SO4). Finally, the product was separated by column chromatography using petroleum ether and ethyl acetate in a volume ratio of 1:10. The product yield was 41.6%. The synthetic route is as follows: .

[0057] Synthesis of S3, Compound 3: Intermediate 2 (5.01 mmol) and 1,4-dioxane (35 mL) were added to a reaction flask. Trimethylbromosilane (30.04 mmol) was added dropwise under nitrogen protection. The substitution reaction was carried out at 25 °C for 24 h. After the reaction was completed, the solvent was removed under reduced pressure, and 23 mL of methanol was added to dissolve the solid. Then 40 mL of water was added dropwise, and the solid crystallized for 1 h. The solid was filtered at 20 °C and dried under vacuum. The product was washed with deionized water and dried in a vacuum oven at 65 °C for 16 h. Finally, 1.72 g of solid was obtained, with a yield of 48%. The synthetic route is as follows: .

[0058] NMR data for compound 3 above: 1 H NMR (400 MHz, DMSO-d6) δ 8.15 (dt, J = 8.0, 0.8 Hz, 2H), 8.05 (d, J= 9.2 Hz, 2H), 8.02-7.98 (m, 2H), 7.96 (dd, J = 9.2, 0.7Hz, 2H), 7.54-7.41 (m, 10H), 7.36-7.28 (m, 2H), 4.36 (t, J = 7.9 Hz, 4H), 2.27(dt, J = 11.9, 8.0 Hz, 4H).

[0059] Example 4 A dibenzofuran-carbazole compound, with the following structural formula: .

[0060] The preparation method of the above-mentioned dibenzofuran-carbazole compound includes the following steps: Synthesis of S1, Intermediate 1: 4,6-Dibromodibenzofuran (82.83 mmol), carbazole-3-borate pinacol ester (182.22 mmol), sodium hydroxide (289.89 mmol), tetrakis(triphenylphosphine)palladium (4.14 mmol), dioxane (243 mL), and deionized water (81 mL) were added to a reaction flask. The gas was purged with nitrogen, and the mixture was heated to 90 °C for 18 h. After the reaction was complete, the solvent was concentrated, and the mixture was extracted with ethyl acetate and water. The extract was dried over anhydrous sodium sulfate (Na₂SO₄), and the solvent was concentrated under reduced pressure. The product was then separated by column chromatography using petroleum ether and dichloromethane (volume ratio 10:1) as eluents. The product yield was 43%. The synthetic route is as follows: .

[0061] Synthesis of S2, Intermediate 2: Under nitrogen protection, NaH (80.23 mmol) and 32 mL of anhydrous DMF were added to a reaction flask. Intermediate 1 (16.05 mmol) was dissolved in 48 mL of DMF and then added dropwise to the reaction mixture at 15 °C. After the addition was complete, the reaction mixture was kept at 10 °C for 1.5 h. Then, 1,4-dibromobutane (80.23 mmol) was added dropwise at 15 °C. After the addition was complete, the reaction mixture was heated for 3 h. After the reaction was completed, the reaction mixture was extracted with water and ethyl acetate, dried over anhydrous sodium sulfate (Na2SO4), and finally separated by column chromatography using petroleum ether and ethyl acetate in a volume ratio of 10:1 as eluents. The product yield was 35.2%. The synthetic route is as follows: .

[0062] Synthesis of S3, Intermediate 3: Under nitrogen protection, intermediate 2 (5.20 mmol) and triethyl phosphite (52.04 mmol) were added to a reaction flask. The system became clear, and the reaction was heated for 16 h. After the reaction was completed, the solvent was removed by concentration, and the reaction product was separated by column chromatography using hexane and ethyl acetate in a volume ratio of 1:4 as eluents. The product yield was 56%. The synthetic route is as follows: .

[0063] Synthesis of S4, compound 4: Intermediate 3 (2.91 mmol) and 1,4-dioxane (20 mL) were added to a reaction flask, and trimethylbromosilane (17.46 mmol) was added dropwise under nitrogen protection. The substitution reaction was carried out at 25 °C for 24 h. After the reaction was completed, the solvent was removed under reduced pressure, and 15 mL of methanol was added to dissolve the solid. Then 18 mL of water was added dropwise, and the solid crystallized for 1 h. The solid was filtered at 20 °C and dried under vacuum. The product was washed with deionized water and dried in a vacuum oven at 65 °C for 16 h. Finally, 0.90 g of solid was obtained, with a yield of 40%. The synthetic route is as follows: .

[0064] NMR data for compound 4 above: 1 H NMR (400 MHz, DMSO-d6) δ 8.18-8.12 (m, 2H),8.05 (d, J = 9.3 Hz, 2H), 8.02-7.98 (m, 2H), 7.96 (dd, J = 9.2, 0.7 Hz, 2H), 7.90(dd, J = 6.5, 1.6 Hz, 2H), 7.54-7.49 (m, 4H), 7.52-7.45 (m, 2H), 7.45 (t, J = 9.1Hz, 2H), 7.36-7.29 (m, 2H), 4.14 (t, J = 5.1 Hz, 4H), 1.92-1.75 (m, 8H), 1.72-1.62 (m, 4H).

[0065] Application Example 1 A method for fabricating an inverted perovskite solar cell includes the following steps: S1, Glass Cleaning: Patterned indium tin oxide (ITO) conductive glass with a surface resistivity of 15 Ω / sq and a thickness of 2.2 mm was used as the substrate. The glass was ultrasonically cleaned sequentially in aqueous solutions containing detergent, deionized water, acetone, and anhydrous ethanol, each for 15 minutes. After cleaning, the glass was dried with high-purity nitrogen and then treated in a UV-ozone generator for 15 minutes to enhance surface hydrophilicity and remove organic contaminants.

[0066] S2, Preparation of SAM: In a nitrogen-atmospheric glove box, the compound prepared as in Example 1 was dissolved in anhydrous ethanol to prepare a solution with a concentration of 3 mg / mL, which was then filtered through a 0.22 μm polytetrafluoroethylene filter. 100 μL of the above solution was pipetted onto the bottom electrode and spin-coated at 3000 rpm for 30 s. After spin-coating, the substrate was removed and annealed on a 100°C hot plate for 10 minutes to obtain an ITO substrate modified with SAM, denoted as ITO / SAM, with a thickness of 30 nm.

[0067] S3, Preparation of perovskite solution: In a glove box, dissolve 1.1 mol / L PbI2, 0.2 mol / L MABr, 0.2 mol / L PbBr2, 1 mol / L FAI, and 0.06 mol / L CsI in 1250 μL of a mixed solution of N,N-dimethylformamide and dimethyl sulfoxide in a volume ratio of 4:1. After shaking at room temperature for 3 h, a 1.2-1.5 M precursor solution is obtained, which is then filtered through a 0.22 μm polytetrafluoroethylene filter for later use.

[0068] Preparation of S4 perovskite film: An ITO / SAM substrate was fixed on a spin coater, and 80 μL of the above precursor solution was added dropwise. The spin coater was first rotated at 1500 rpm for 10 seconds, and then 400 μL of anhydrous diethyl ether was rapidly added as an antisolvent 15 seconds before the end of the spin coat. The spin coater was then rotated at 5000 rpm for 30 seconds. After spin coating, the wet film was immediately transferred to a 110°C hot plate for annealing for 30 minutes to form a uniform perovskite polycrystalline film with a thickness of 550 nm.

[0069] S5, Deposition of the electron transport layer: The above sample is transferred to a high-vacuum thermal evaporation apparatus, where the vacuum level is below 5 × 10⁻⁶. -4 Under the condition of Pa, a 25 nm thick C60 layer was deposited at a deposition rate of 0.8 Å / s. Subsequently, the sample was transferred to an atomic layer deposition apparatus, and a 10 nm thick tin oxide film was deposited at 100°C using tetra(dimethylamino)tin and water as precursors to form a C60 / SnO2 bilayer electron transport structure.

[0070] S6, Fabrication of the metal electrode: Covered by a mask, under a vacuum level below 5 × 10⁻⁶. -4Under the condition of Pa, a 100 nm thick silver electrode is deposited by vapor deposition, and the effective area of ​​the cell is defined as 0.04 cm².

[0071] Application Example 2 Compared with Application Example 1, the difference is that in S2, compound 2 prepared in Example 2 is used as the material of the hole transport layer, and compound 2 prepared in Example 2 is mixed with anhydrous ethanol to obtain a coating solution with a concentration of 2.5 mg / mL.

[0072] Application Example 3 Compared with Application Example 1, the difference is that in S2, compound 3 prepared in Example 3 is used as the material of the hole transport layer, and compound 3 prepared in Example 3 is mixed with anhydrous ethanol to obtain a coating solution with a concentration of 2 mg / mL.

[0073] Application Example 4 Compared with Application Example 1, the difference is that in S2, compound 4 prepared in Example 4 is used as the material of the hole transport layer, and compound 4 prepared in Example 4 is mixed with anhydrous ethanol to obtain a coating solution with a concentration of 1 mg / mL.

[0074] Application Comparative Example 1 Compared with Application Example 1, the difference is that in S2, conventional Me-4PACz is used as the material for the hole transport layer. Me-4PACz is mixed with anhydrous ethanol to obtain a coating solution with a concentration of 1.5 mg / mL. 100 μL of the coating solution is taken onto the bottom electrode using a pipette and spin-coated at 3000 rpm for 30 s. After spin-coating, it is annealed on a hot plate at 100°C for 10 min and then naturally cooled to obtain the hole transport layer.

[0075] The performance of the inverted perovskite solar cells prepared in the above application examples and application comparison example 1 was tested, and the results are shown in Table 1 below.

[0076] Table 1 Performance of the perovskite solar cell of the present invention From Table 1 and Figure 2 As can be seen, in Application Examples 1 to 3, after using the dibenzofuran-carbazole compound provided by this invention as the SAM layer material, all key parameters are superior to those of Application Comparative Example 1, especially the photoelectric conversion efficiency, which increased from 22.02% to 23.26%. Therefore, the dibenzofuran-carbazole compound, an organic small molecule material provided by this invention, can significantly improve the photoelectric conversion efficiency of perovskite solar cells.

[0077] Obviously, those skilled in the art can make various modifications and variations to this invention without departing from its spirit and scope. Therefore, if these modifications and variations fall within the scope of the claims of this invention and their equivalents, this invention also intends to include these modifications and variations.

Claims

1. A dibenzofuran-carbazole compound, characterized in that, The general structural formula of dibenzofuran-carbazole compounds is: or ; Among them, L1, L2, and L3 are each independently C0 to C4 alkylene groups.

2. The dibenzofuran-carbazole compound according to claim 1, characterized in that, L1, L2, and L3 are each independently a C1-C4 straight-chain alkylene group.

3. The dibenzofuran-carbazole compound according to claim 1, characterized in that, The dibenzofuran-carbazole compound is any one of the following structural formulas: , , , .

4. A method for preparing the dibenzofuran-carbazole compound according to claim 1, characterized in that, Includes the following steps: Using compounds of formula 3 and formula 4 as starting materials, the compounds are dissolved in an organic solvent at room temperature and coupled under the action of a base and a catalyst to attach carbazole to dibenzofuran, yielding compound 5. Using compound 5 and an lipid compound as starting materials, the mixture is refluxed at 130℃–160℃ to yield compound 6. Using compound 6 and trimethylbromosilane of formula 7 as starting materials, a substitution reaction is carried out in an organic solvent at room temperature, followed by hydrolysis in an aqueous methanol solution to yield dibenzofuran-carbazole compound of formula 1. The synthetic route for dibenzofuran-carbazole compound of formula 1 is as follows: ； Alternatively, using compounds of formula 8 and formula 4 as starting materials, they are dissolved in an organic solvent at room temperature and coupled under the action of a base and a catalyst to attach carbazole to dibenzofuran, yielding compound 9; using compound 9 and an lipid compound as starting materials, a reflux reaction is carried out at 130℃–160℃ to yield compound 10; using compound 10 and trimethylbromosilane of formula 7 as starting materials, a substitution reaction is carried out in an organic solvent at room temperature, followed by hydrolysis in an aqueous methanol solution to yield dibenzofuran-carbazole compound of formula 2. The synthetic route for dibenzofuran-carbazole compound of formula 2 is as follows: ； Among them, L1, L2, and L3 are each independently C0 to C4 alkylene groups.

5. The method for preparing the dibenzofuran-carbazole compound according to claim 4, characterized in that, The molar ratio of the compound of Formula 3 to the compound of Formula 4 is 1:2 to 10; the molar ratio of the compound of Formula 8 to the compound of Formula 4 is 1:2 to 10.

6. The method for preparing the dibenzofuran-carbazole compound according to claim 4, characterized in that, The molar ratio of the compound of Formula 5 to the lipid compound is 1:2 to 5; the molar ratio of the compound of Formula 9 to the lipid compound is 1:2 to 5.

7. The method for preparing the dibenzofuran-carbazole compound according to claim 4, characterized in that, The molar ratio of the compound of Formula 6 to the trimethylbromosilane of Formula 7 is 1:2 to 5; the molar ratio of the compound of Formula 10 to the trimethylbromosilane of Formula 7 is 1:2 to 5.

8. The method for preparing the dibenzofuran-carbazole compound according to claim 4, characterized in that, The lipid compound is selected from diethyl 2-bromoethylphosphonate or triethyl phosphite; the organic solvent is 1,4-dioxane.

9. A reverse perovskite solar cell, comprising, from bottom to top, a conductive substrate, a hole transport layer, a perovskite light-absorbing layer, an electron transport layer, and a metal electrode, characterized in that, The hole transport layer is a self-assembled monolayer material made of the dibenzofuran-carbazole compound as described in claim 1 or 2.

10. The inverted perovskite solar cell according to claim 9, characterized in that, The hole transport layer is prepared by dissolving a dibenzofuran-carbazole compound in ethanol under a nitrogen atmosphere to obtain a coating solution with a concentration of 0.5 mg / mL to 6 mg / mL. The coating solution is then spin-coated onto a conductive substrate at a speed of 1000 rpm to 5000 rpm and annealed at 100°C to 150°C to obtain the hole transport layer.

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