Fused benzothiadiazole derivatives, methods for their preparation, hole transport materials, hole transport layers, perovskite cells

Abstract

The application discloses a fused benzothiadiazole derivative, a preparation method thereof, a hole transport material, a hole transport layer and a perovskite battery, and belongs to the technical field of battery materials.The fused benzothiadiazole derivative can be applied as a hole transport material, contains a fused benzothiadiazole unit in a mother nucleus, has a large conjugate core, and has a D-A-D type molecular structure, so that the intermolecular interaction can be strengthened, and the extraction of holes can be promoted.In addition, the fused benzothiadiazole derivative also contains a phosphate group, so that a self-assembled monolayer can be formed in the form of a bidentate bond or a tridentate bond on a transparent conductive glass to improve the contact between the hole transport layer and an ITO interface.Further, the fused benzothiadiazole derivative also contains rich heteroatoms such as sulfur, nitrogen and oxygen, can be used as a Lewis base to passivate free lead iodine ions at the interface, so that the loss caused by charge recombination can be reduced, and the performance of an inverted perovskite solar cell can be improved.

Description

Technical Field

[0001] This invention relates to the field of battery materials technology, and in particular to a fused benzothiadiazole derivative and its preparation method, hole transport materials, hole transport layers, and perovskite batteries. Background Technology

[0002] With the vigorous development of mineral energy resources, energy shortages and environmental pollution problems have become increasingly serious, thus necessitating the development of clean and renewable energy sources.

[0003] Perovskite solar cells have gradually become the most promising new generation of photovoltaic power generation technology due to their advantages such as high efficiency, low cost and flexibility. Today, the highest efficiency of single-junction devices has reached more than 25%, showing an extremely broad prospect for industrialization.

[0004] The charge extraction and transfer between the hole transport layer and the perovskite layer has a crucial impact on the performance of PSCs devices. Therefore, the selection and use of hole transport materials are particularly important to improve the performance of perovskite solar cells. Hole transport materials can be classified into inorganic materials (including NiO, CuI, CuSCN, etc.), organic polymer materials (including PTAA, PEDOT:PSS, P3HT, etc.), and organic small molecule materials (including Spiro-OMeTAD, MeO-2PACz, etc.). Compared with inorganic hole transport materials, the biggest advantage of organic hole transport materials is that energy levels can be adjusted and molecular energization can be achieved through molecular design modification. The mainstream hole transport materials used in inverted devices are usually polymers PTAA and PEDOT:PSS, but they have problems such as high cost, poor superhydrophobic wettability, and corrosiveness and hygroscopicity, which can damage the perovskite layer and thus affect the stability and electrochemical performance of the cell. Moreover, the aforementioned hole transport materials are unable to improve the interfacial contact between the perovskite and ITO conductive layers, optimize the energy level arrangement between adjacent layers, improve the carrier mobility of the device, increase the short-circuit current and fill factor, thus limiting the large-scale application of such materials. Summary of the Invention

[0005] To address the aforementioned technical problems, this invention proposes a fused benzothiadiazole derivative and its preparation method, a hole transport material, a hole transport layer, and a perovskite battery.

[0006] To achieve the above objectives, the first aspect of the present invention provides a fused benzothiadiazole derivative having the following structural formula:

[0007]

[0008] A second aspect of the present invention provides a method for preparing the fused benzothiadiazole derivative as described above, comprising the following steps:

[0009] Preparation of intermediate 6: Intermediate 5 and triethyl phosphite were mixed to obtain a mixed solution, and the mixed solution was subjected to reflux reaction to obtain a reaction mixture. The reaction mixture was cooled, crystallized, filtered, and washed to obtain intermediate 6.

[0010] Preparation of fused benzothiadiazole derivative: The intermediate 6 was dissolved in a nonpolar solvent and trimethylbromosilane was added dropwise to react and obtain a reaction mixture. A poor solvent was added to the reaction mixture and stirred and evaporated to concentrate. Then, a solvent was added dropwise until the reaction product in the reaction mixture was dissolved. Then, the mixture was stirred, filtered, washed with water, and dried to obtain the fused benzothiadiazole derivative.

[0011] The intermediate 5 has the following structural formula:

[0012]

[0013] The intermediate 6 has the following structural formula:

[0014]

[0015] In some embodiments of the present invention, in the step of preparing intermediate 6:

[0016] The reflux reaction is carried out in a vacuum inert atmosphere;

[0017] And / or, the reaction temperature of the reflux reaction is 120°C to 180°C;

[0018] And / or, the reflux reaction time is 14h to 18h;

[0019] And / or, monitor the degree of reaction of the reflux reaction using a spot plate test;

[0020] And / or, the reaction mixture is cooled to 20°C to 30°C;

[0021] And / or, the crystallization step includes: adding a poor solvent to the reaction mixture, the poor solvent including at least one of petroleum ether, ethanol, and methanol;

[0022] And / or, the cleaning step includes: cleaning with a poor solvent, the poor solvent including at least one of petroleum ether, ethanol, and methanol;

[0023] And / or, the solid-liquid ratio of intermediate 5 and triethyl phosphite is (1g~3g) / (10ml~20ml).

[0024] In some embodiments of the present invention, in the step of preparing the fused benzothiadiazole derivative:

[0025] The molar ratio of intermediate 6 to trimethylbromosilane is (1:10) to (1:20);

[0026] And / or, the nonpolar solvent includes at least one of anhydrous 1,4-dioxane, tetrahydrofuran, and pyridine;

[0027] And / or, the reaction temperature is 20℃~30℃;

[0028] And / or, the reaction time is 20h to 30h;

[0029] And / or, the undesirable solvent includes at least one of methanol, ethanol, and petroleum ether;

[0030] And / or, the stirring time is 12h to 24h;

[0031] And / or, the reaction is carried out under a vacuum inert atmosphere;

[0032] And / or, add the undesirable solvent in multiple portions.

[0033] In some embodiments of the present invention, the method for preparing the fused benzothiadiazole derivative further includes the following steps:

[0034] Preparation of intermediate 1: Dilute nitric acid was added dropwise to a mixed solution of 4,7-dibromobenzothiazolium and sulfuric acid to react and obtain a reaction mixture. The reaction mixture was added to water and filtered to obtain a precipitate. The precipitate was washed and crystallized to obtain intermediate 1 (4,7-dibromo-5-nitrobenzothiazolium).

[0035] Preparation of intermediate 2: The intermediate 1, organic solvent and catalyst are mixed to obtain a mixed solution. The mixed solution is degassed and refluxed and stirred to obtain a reaction mixture. The reaction mixture is extracted and collected to obtain an organic phase. The organic phase is dried, concentrated and purified to obtain intermediate 2 (4,7-dibromo-2,2-dinitrodibenzothiazole).

[0036] Preparation of intermediate 3: Intermediate 2 is mixed with organic solvent and tin powder and adjusted to acidity. The mixture is stirred at 80℃~90℃ to obtain a reaction mixture. The reaction mixture is poured into sodium hydroxide solution and extracted with an extractant to obtain an organic phase. The organic phase is washed, dried, concentrated, purified and separated to obtain intermediate 3 (4,7-dibromo-2,2-diaminobisbenzothiadiazole).

[0037] Preparation of intermediate 4: Intermediate 3 and phosphoric acid were mixed and stirred at 100℃~140℃ to obtain a reaction mixture. The reaction mixture was poured into water and filtered to collect intermediate 4 (2,7-dibromo-carbazole[3,4-c:5,6-c]bis[1,2,5]thiadiazole).

[0038] Preparation of intermediate 5: Intermediate 4, 1,2-dibromobutane, tetrabutylammonium bromide and alkaline aqueous solution are mixed and heated to obtain a reaction mixture. The reaction mixture is cooled, washed with water, extracted, dried, concentrated and purified to obtain intermediate 5.

[0039] In some embodiments of the present invention, in the step of preparing intermediate 1:

[0040] The temperature of the dilute nitric acid is 0℃~5℃;

[0041] And / or, the reaction time is 20 min to 40 min;

[0042] And / or, the filtrate is crystallized in an ethanol solution;

[0043] And / or, the solid-liquid ratio of the 4,7-dibromobenzothiazole and dilute nitric acid is in the range of (10g~25g) / (50ml~100ml);

[0044] And / or, the solid-liquid ratio of the 4,7-dibromobenzothiazole and sulfuric acid is in the range of (10g~25g) / (30ml~100ml).

[0045] In some embodiments of the present invention, in the step of preparing intermediate 2:

[0046] The organic solvent includes at least one of dimethylformamide, tetrahydrofuran, chlorobenzene, and chloroform;

[0047] And / or, the catalyst comprises copper;

[0048] And / or, the reaction time is 1 h to 4 h;

[0049] And / or, the reaction mixture is extracted with an extractant to collect an organic phase, the extractant comprising a mixed solution of dichloromethane and deionized water;

[0050] And / or, the organic phase is dried and concentrated using a desiccant, all of which include anhydrous magnesium sulfate;

[0051] And / or, the purification method includes silica gel column chromatography, recrystallization or filtration;

[0052] And / or, the molar ratio of the intermediate 1 to the catalyst is (1:2) to (1:5).

[0053] In some embodiments of the present invention, in the step of preparing intermediate 3:

[0054] The molar ratio of the intermediate 2 and the tin powder is (1:1) to (1:5);

[0055] And / or, the organic solvent includes at least one of alcohol, isopropanol, DMF (dimethylformamide), and DMSO (dimethyl sulfoxide);

[0056] And / or, adjust to acidity with an acid regulator, said acid regulator including at least one of hydrochloric acid, sulfuric acid, and nitric acid;

[0057] And / or, the stirring reaction time is 2h to 6h;

[0058] And / or, the extractant includes at least one of diethyl ether, ethyl acetate, dichloromethane, and chloroform;

[0059] And / or, the mass concentration of the sodium hydroxide is 3% to 8%;

[0060] And / or, drying and concentration are carried out using a desiccant, said desiccant including anhydrous magnesium sulfate;

[0061] And / or, the purification and separation methods include silica gel column chromatography, recrystallization, or filtration.

[0062] In some embodiments of the present invention, in the step of preparing intermediate 4:

[0063] The solid-liquid ratio of intermediate 3 and phosphoric acid is (1g~5g) / (50ml~100ml);

[0064] And / or, the reaction mixture is poured into water at 0-5°C and filtered to collect intermediate 4;

[0065] And / or, the stirring reaction time is 10h to 15h.

[0066] In some embodiments of the present invention, in the step of preparing intermediate 5:

[0067] The solid-liquid ratio of intermediate 4 and 1,2-dibromobutane is (0.5g~3g) / (5ml~15ml);

[0068] And / or, the molar ratio of intermediate 4 to tetrabutylammonium bromide is in the range of (4:1) to (6:1);

[0069] And / or, the temperature of the heating reaction is 60°C to 80°C;

[0070] And / or, the heating reaction time is 12h to 24h;

[0071] And / or, monitor the extent of the heating reaction using a spot plate reaction;

[0072] And / or, the alkaline solution includes a potassium hydroxide solution;

[0073] And / or, the reaction mixture is cooled to 20°C to 30°C;

[0074] And / or, extraction is performed using an extractant, said extractant including dichloromethane;

[0075] And / or, drying is performed using a desiccant, said desiccant including anhydrous magnesium sulfate;

[0076] And / or, the purification method includes silica gel column chromatography, recrystallization, or filtration.

[0077] In some embodiments of the present invention, the structural formulas of intermediate 1, intermediate 2, intermediate 3, and intermediate 4 are as follows:

[0078]

[0079] A third aspect of the present invention provides a hole transport material, the hole transport material comprising the fused benzothiadiazole derivative as described above.

[0080] A fourth aspect of the present invention provides a hole transport layer, the hole transport layer comprising the hole transport material as described above.

[0081] A fifth aspect of the present invention provides a perovskite solar cell, the perovskite solar cell comprising a hole transport layer as described above.

[0082] In some embodiments of the present invention, the perovskite solar cell further includes a glass substrate, a perovskite light-absorbing layer, an electron transport layer, a hole-blocking layer, and / or an electrode layer.

[0083] The beneficial effects that this invention can achieve are:

[0084] The fused benzothiadiazole derivative of this invention can be used as a hole transport material. Its core contains fused benzothiadiazole units, possessing a large conjugated core and a DAD-type molecular structure, which enhances intermolecular interactions and thus promotes hole extraction. Furthermore, the fused benzothiadiazole derivative also contains phosphate groups, allowing it to form self-assembled monolayers on transparent conductive glass via bidentate or tripentate bonds. This improves the contact between the hole transport layer and the ITO interface, optimizes the energy level arrangement between adjacent layers, increases carrier mobility, and enhances short-circuit current and fill factor. Moreover, the fused benzothiadiazole derivative contains abundant heteroatoms such as sulfur, nitrogen, and oxygen, which can act as Lewis bases to passivate free lead-iodide ions at the interface, thereby reducing losses due to charge recombination and improving the performance of inverted perovskite solar cells. This provides a valuable reference for the design and synthesis of hole transport materials for high-efficiency perovskite solar cells. Attached Figure Description

[0085] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art are 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 the structures shown in these drawings without creative effort.

[0086] Figure 1 The figure shows the performance test results of a perovskite solar cell according to an embodiment of the present invention.

[0087] The realization of the objective, functional features and advantages of the present invention will be further explained in conjunction with the embodiments and with reference to the accompanying drawings. Detailed Implementation

[0088] It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

[0089] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0090] In this invention, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Therefore, a feature defined with "first" or "second" may explicitly or implicitly include at least one of that feature. Furthermore, the technical solutions of the various embodiments can be combined with each other, but only on the basis of being achievable by those skilled in the art. If the combination of technical solutions is contradictory or impossible to implement, such a combination of technical solutions should be considered non-existent and not within the scope of protection claimed by this invention.

[0091] The first aspect of this invention provides a fused benzothiadiazole derivative having the following chemical structural formula:

[0092]

[0093] The fused benzothiadiazole derivative of the present invention can be used as a hole transport material to prepare the hole transport layer of perovskite solar cells. It can improve the interfacial contact between the perovskite and ITO conductive layers, optimize the energy level arrangement between adjacent layers, improve the carrier mobility of the device, increase the short-circuit current and fill factor, thereby improving the performance of the perovskite solar cell device.

[0094] Specifically, the fused benzothiadiazole derivative of this invention contains fused benzothiadiazole units in its core, possesses a large conjugated core, and has a DAD-type molecular structure, which can enhance intermolecular interactions and thus promote hole extraction. Furthermore, the fused benzothiadiazole derivative also contains phosphate groups, allowing it to form a self-assembled monolayer on transparent conductive glass in the form of didentate or tridentate bonds to improve the contact between the hole transport layer and the ITO interface, optimize the energy level arrangement between adjacent layers, improve the carrier mobility of the device, and increase the short-circuit current and fill factor. Further, the fused benzothiadiazole derivative also contains abundant heteroatoms such as sulfur, nitrogen, and oxygen, which can act as Lewis bases to passivate free lead-iodide ions at the interface, thereby reducing losses caused by charge recombination and improving the performance of inverted perovskite solar cells.

[0095] This invention does not limit the amount of fused benzothiadiazole derivatives used in the preparation of hole transport layers. The amount can be controlled according to actual needs. Fused benzothiadiazole derivatives can be used as hole transport materials to prepare fused benzothiadiazole derivative hole transport layers, or they can be mixed with other materials to form hole transport materials to prepare hole transport layers containing fused benzothiadiazole derivatives. The hole transport layers prepared in both ways can obtain the beneficial effects brought by fused benzothiadiazole derivatives.

[0096] A second aspect of the present invention provides a method for preparing the above-mentioned fused benzothiadiazole derivative, comprising the following steps:

[0097] Preparation of intermediate 6: Intermediate 5 and triethyl phosphite were mixed to obtain a mixed solution. The mixed solution was refluxed to obtain a reaction mixture. The reaction mixture was cooled, crystallized, filtered, and washed to obtain intermediate 6.

[0098] Preparation of fused benzothiadiazole derivatives: Intermediate 6 was dissolved in a nonpolar solvent and trimethylbromosilane was added dropwise to react and obtain a reaction mixture. A poor solvent was added to the reaction mixture and stirred and evaporated to concentrate. Then, solvent was added dropwise until the reaction product in the reaction mixture was dissolved. Then, the mixture was stirred, filtered, washed with water, and dried to obtain the fused benzothiadiazole derivatives.

[0099] Intermediate 5 has the following structural formula:

[0100]

[0101] Intermediate 6 has the following structural formula:

[0102]

[0103] It should be noted that intermediate 5 can be obtained by purchase or prepared by a preparation method commonly used in this field.

[0104] The following explains the steps for preparing intermediate 6.

[0105] This step can be carried out in a vacuum inert atmosphere, including a nitrogen atmosphere. This can promote the reaction and avoid the influence of air on the reaction, such as causing lower yield or more impurities.

[0106] In some embodiments, the reflux reaction is carried out in an iron sand bath.

[0107] In some embodiments, the reflux reaction temperature is 120°C to 180°C, and can be any temperature value within the range of 120°C to 180°C, such as 120°C, 125°C, 130°C, 135°C, 140°C, 145°C, 150°C, 155°C, 160°C, 165°C, 170°C, 175°C, or 180°C. At these reaction temperatures, it is beneficial to promote the reaction between intermediate 5 and triethyl phosphite, thereby increasing the reaction rate and yield.

[0108] The reaction time of the reflux reaction in this invention is preferably such that the reaction is complete. In some embodiments, the reaction time can be 14h to 18h, for example, any time value within the range of 14h to 18h, such as 14h, 15h, 16h, 17h, 18h, etc. Under the above time conditions, it is beneficial to promote the complete reaction of the reactants and improve the yield.

[0109] In some embodiments, the degree of reaction of the reflux reaction can be monitored using a spot plate reaction to determine whether the reaction has been completed. If the reaction has been completed, the reaction can be quenched and the next step can be performed.

[0110] In this step, after the reflux reaction is completed, a reaction mixture is obtained. It is understood that the reaction mixture contains not only the target product intermediate 6, but may also contain impurities and solvents. Therefore, the reaction mixture needs to be purified to obtain the target product intermediate 6.

[0111] The reaction mixture obtained after the reaction is at a high temperature. Therefore, it can be cooled to 20°C to 30°C before proceeding with subsequent crystallization, filtration, and washing steps.

[0112] In some embodiments, the crystallization step includes: adding a poor solvent to the reaction mixture to precipitate the reaction product using the poor solvent, wherein the poor solvent includes at least one of petroleum ether, ethanol, and methanol, and the reaction product in the reaction mixture has poor compatibility with the aforementioned poor solvent, allowing the reaction product to precipitate smoothly, which is beneficial to improving the yield of intermediate 6.

[0113] In some embodiments, after the reaction mixture is added to a poor solvent, crystallization is carried out under low temperature conditions, such as -5°C to 5°C.

[0114] The amount of unsuitable solvent used in the crystallization step of this invention can be adjusted according to the content of the reaction mixture to achieve the purpose of crystallizing the target product.

[0115] In some embodiments, the cleaning step includes cleaning with a poor solvent. Cleaning with a poor solvent can improve the precipitation rate of the reaction product and dissolve excess impurities, thereby improving the purity and yield of the reaction product.

[0116] In some embodiments, the unsuitable solvent for the cleaning step includes at least one of petroleum ether, ethanol, and methanol.

[0117] In some embodiments, the solid-liquid ratio of intermediate 5 and triethyl phosphite is (1g-3g) / (10ml-20ml), which can be 1.739g / 10.4ml. Under the above ratio conditions, it is beneficial to promote the complete reaction of the reactants, reduce resource waste, and improve the purity of the target product.

[0118] In some embodiments, the reflux reaction can be carried out in a reaction tube.

[0119] The following explains the steps for preparing fused benzothiadiazole derivatives.

[0120] In this step, intermediate 6 can be dissolved in a nonpolar solvent to react and obtain the reaction product fused benzothiadiazole derivative. Trimethylbromosilane has an activating and damping effect on the groups in intermediate 6. It can use its own silicon group to replace the active hydrogen atom in intermediate 6, increase the solubility of intermediate 6 in nonpolar solvent, thereby promoting the reaction and increasing the yield of the target product.

[0121] In some embodiments, the molar ratio of intermediate 6 to trimethylbromosilane is (1:10) to (1:20), for example, it can be any ratio in the range of (1:10) to (1:20) such as 1:10, 1:11, 1:12, 14:13, 1:15, 1:18, 1:19, 1:20, etc.

[0122] In some embodiments, the nonpolar solvent includes at least one of anhydrous 1,4-dioxane, tetrahydrofuran, and pyridine. Intermediate 6 is readily soluble in the above-mentioned nonpolar solvents to react and obtain the reaction product, a fused benzothiadiazole derivative. Among these, anhydrous 1,4-dioxane exhibits good solubility for intermediate 6.

[0123] In some embodiments, this step is carried out under a vacuum inert atmosphere, including a nitrogen atmosphere. This promotes the reaction and avoids the influence of air on the reaction, such as causing lower yields of the target product or increased impurities.

[0124] In some embodiments, the reaction can be carried out at room temperature, that is, the reaction temperature can be 20℃ to 30℃, such as any temperature value in the range of 20℃ to 30℃, such as 20℃, 22℃, 24℃, 25℃, 28℃, 30℃, etc.

[0125] In some embodiments, the reaction time is 20h to 30h, which can be any time value in the range of 20h to 30h, such as 20h, 22h, 24h, 25h, 26h, 28h, 30h, etc.

[0126] In this step, after the reaction is completed, a reaction mixture is obtained. It is understood that the reaction mixture contains not only the target product fused benzothiadiazole derivative, but may also contain impurities and solvents. Therefore, the reaction mixture needs to be purified to obtain the target product fused benzothiadiazole derivative.

[0127] In this step, the target product, a fused benzothiadiazole derivative, is first precipitated from the reaction mixture using a poor solvent. In some embodiments, the poor solvent includes at least one of methanol, ethanol, and petroleum ether.

[0128] In some embodiments, after adding a poor solvent to the reaction mixture, stirring is performed to accelerate the precipitation of the target product. The stirring time can be 12h to 24h.

[0129] In some embodiments, after the target product is precipitated and concentrated by evaporation using a poor solvent, a solvent is added dropwise to dissolve the target product, thereby reducing its solubility in the poor solvent and facilitating its precipitation. The solvents include, but are not limited to, water. In this embodiment, after adding the solvent, the dissolution of the target product can be determined by observing whether the solution becomes transparent. When the solution becomes turbid and no longer transparent, the target product has dissolved.

[0130] In some embodiments, the undesirable solvent may be added in multiple stages to improve the precipitation rate of the target product.

[0131] In some embodiments, the method for preparing fused benzothiadiazole derivatives further includes the following steps:

[0132] Preparation of intermediate 1: Dilute nitric acid was added dropwise to a mixed solution of 4,7-dibromobenzothiazolium and sulfuric acid to obtain a reaction mixture. The reaction mixture was added to water and filtered to obtain a precipitate. The precipitate was washed and crystallized to obtain intermediate 1 (4,7-dibromo-5-nitrobenzothiazolium).

[0133] Preparation of intermediate 2: The intermediate 1, organic solvent and catalyst are mixed to obtain a mixed solution. The mixed solution is degassed and refluxed and stirred to obtain a reaction mixture. The reaction mixture is extracted and collected to obtain an organic phase. The organic phase is dried, concentrated and purified to obtain intermediate 2 (4,7-dibromo-2,2-dinitrodibenzothiazole).

[0134] Preparation of intermediate 3: Intermediate 2 is mixed with organic solvent and tin powder and adjusted to acidity. The mixture is stirred at 80℃~90℃ to obtain a reaction mixture. The reaction mixture is poured into sodium hydroxide solution and extracted with an extractant to obtain an organic phase. The organic phase is washed, dried, concentrated, purified and separated to obtain intermediate 3 (4,7-dibromo-2,2-diaminobisbenzothiadiazole).

[0135] Preparation of intermediate 4: Intermediate 3 and phosphoric acid were mixed and stirred at 100℃~140℃ to obtain a reaction mixture. The reaction mixture was poured into water and filtered to collect intermediate 4 (2,7-dibromo-carbazole[3,4-c:5,6-c]bis[1,2,5]-thiadiazole).

[0136] Preparation of intermediate 5: Intermediate 4, 1,2-dibromobutane, tetrabutylammonium bromide and alkaline aqueous solution are mixed and heated to obtain a reaction mixture. The reaction mixture is cooled, washed with water, extracted, dried, concentrated and purified to obtain intermediate 5.

[0137] The steps for preparing intermediate 1 are explained below.

[0138] In some embodiments, the temperature of dilute nitric acid is 0℃~5℃, which can be any temperature value in the range of 0℃~5℃, such as 0℃, 1℃, 2℃, 3℃, 4℃, 5℃, etc. Under these temperature conditions, it is beneficial to reduce the formation of by-products.

[0139] In some embodiments, the reaction time is 20 min to 40 min, for example, it can be any time value in the range of 20 min to 40 min, such as 20 min, 25 min, 30 min, 35 min, 40 min, etc.

[0140] In some embodiments, the filtrate is crystallized in an ethanol solution.

[0141] In some embodiments, the solid-liquid ratio of 4,7-dibromobenzothiazole and dilute nitric acid ranges from (10g to 25g) to (50ml to 100ml), and can be 15g / 60ml.

[0142] In some embodiments, the solid-liquid ratio of 4,7-dibromobenzothiazole and sulfuric acid ranges from (10g to 25g) to (30ml to 100ml), and can be 15g / 30ml.

[0143] The steps for preparing intermediate 2 are explained below.

[0144] In this step, degassing the reaction system before the reaction can reduce the risk that water and oxygen, acting as oxidants, may react with reaction intermediates to produce byproducts, thereby reducing the yield of the target product. In some embodiments, nitrogen can be used for degassing.

[0145] This step does not limit the type of organic solvent, including at least one of dimethylformamide, tetrahydrofuran, chlorobenzene, and chloroform. In some embodiments, dimethylformamide is used as the organic solvent, and dissolving the reactants with dimethylformamide is beneficial to improving the yield of the target product.

[0146] This step does not limit the container used for the reaction, including but not limited to round-bottom flasks. In some embodiments, the reaction vessel may be purged with nitrogen before the reactants are added to initiate the reaction.

[0147] In this step, the catalyst includes copper, which can catalyze the reaction of intermediate 1 to obtain intermediate 2.

[0148] In some embodiments, the stirring and reflux reaction time is 1h to 4h, which can be any time value among 1h to 4h, such as 1h, 2h, 3h, 4h, etc.

[0149] In this step, after the reaction is completed, a reaction mixture is obtained. It is understood that the reaction mixture contains not only the target product intermediate 2, but may also contain impurities and solvents. Therefore, the reaction mixture needs to be purified to obtain the target product intermediate 2.

[0150] In some embodiments, the reaction mixture is extracted with an extractant to obtain an organic phase, the extractant comprising a mixed solution of dichloromethane and deionized water, wherein the deionized water quenches the reaction, and the dichloromethane primarily extracts the product to obtain the organic phase.

[0151] In some embodiments, the organic phase is dried and concentrated using a desiccant, including anhydrous magnesium sulfate.

[0152] In some embodiments, the purification method includes silica gel column chromatography, recrystallization, or filtration.

[0153] In some embodiments, the molar ratio of intermediate 1 to catalyst is (1:2) to (1:5), and can be any ratio in the range of (1:2) to (1:5), such as 1:2, 1:2.5, 1:3, 1:3.5, 1:4, 1:4.5, 1:5, etc.

[0154] The steps for preparing intermediate 3 are explained below.

[0155] The organic solvent in this step can dissolve intermediate 2. Intermediate 2 and tin powder can react under acidic heating conditions to generate intermediate 3. In some embodiments, the organic solvent includes, but is not limited to, alcohol.

[0156] In some embodiments, the molar ratio of intermediate 2 to tin powder is (1:1) to (1:5). For example, it can be 1:1, 1:1.2, 1:1.4, 1:1.8, 1:2, 1:3, 1:4, 1:4.3, 1:4.4, 1:4.5, or 1:5. Under these molar ratio conditions, the reactants can react more completely, increasing the yield of the target product.

[0157] In some embodiments, the reaction system can be adjusted to acidity using an acid regulator, which includes at least one of hydrochloric acid, sulfuric acid, and nitric acid.

[0158] This step does not limit the stirring reaction time. In some embodiments, the stirring reaction time is 2h to 6h, which can be any time value from 2h to 6h, such as 2h, 3h, 4h, 5h, 6h, etc.

[0159] In this step, after the reaction is completed, a reaction mixture is obtained. It is understood that the reaction mixture contains not only the target product intermediate 3, but may also contain impurities and solvents. Therefore, the reaction mixture needs to be purified to obtain the target reaction product intermediate 3.

[0160] This step involves dissolving the target product intermediate 3 in the reaction mixture into a sodium hydroxide solution. It should be noted that since the dissolution of sodium hydroxide solution is exothermic, it is advisable to prepare the sodium hydroxide solution and allow it to cool to room temperature before use. This reduces the risk of the sodium hydroxide solution becoming too hot and affecting the target product intermediate 3. Specifically, after preparing the sodium hydroxide solution, allow it to stand for 30 minutes and cool to room temperature before pouring the reaction mixture into the sodium hydroxide solution.

[0161] In some embodiments, the mass concentration of the sodium hydroxide solution is 3% to 8%, which can be any mass concentration in the range of 3% to 8%, such as 3%, 4%, 5%, 6%, 7%, 8%, etc., so that the target product intermediate 3 in the reaction mixture can be dissolved in the sodium hydroxide solution in large quantities.

[0162] In some embodiments, the extractant includes at least one of diethyl ether, ethyl acetate, dichloromethane, and chloroform.

[0163] In some embodiments, the organic phase can be washed with sodium bicarbonate solution before subsequent drying, concentration, and purification, which can improve the purity of the target product.

[0164] In some embodiments, drying and concentration are carried out using a desiccant, which includes, but is not limited to, anhydrous magnesium sulfate.

[0165] This step does not limit the purification and separation method. In some embodiments, the purification and separation methods include silica gel column chromatography, recrystallization, or filtration.

[0166] The steps for preparing intermediate 4 are explained below.

[0167] In this step, phosphoric acid can act as an electrophile to attack the amino group on intermediate 4, causing it to detach and form a ring. This allows the final product, a fused benzothiadiazole derivative, to possess a phosphate group. When used to prepare the hole transport layer of a perovskite solar cell, it can form a self-assembled monolayer on a transparent conductive glass in the form of didentate or tridentate bonds to improve the contact between the hole transport layer and the ITO interface, optimize the energy level arrangement between adjacent layers, improve the carrier mobility of the device, and increase the short-circuit current and fill factor.

[0168] In some embodiments, the solid-liquid ratio of intermediate 3 and phosphoric acid is (1g~5g) / (50ml~100ml), which can be 2g / 50ml.

[0169] In this step, after the reaction is completed, a reaction mixture is obtained. It is understood that the reaction mixture contains not only the target product intermediate 4, but may also contain impurities and solvents. Therefore, the reaction mixture needs to be purified to obtain the target product intermediate 4.

[0170] In this step, the target product and some impurities in the resulting reaction mixture are poorly soluble in water. Therefore, adding water to the reaction mixture is beneficial for the precipitation of the target product.

[0171] In some embodiments, the reaction mixture can be poured into water at 0–5°C and filtered to collect intermediate 4. Cold water at 0–5°C helps to reduce the loss of the target product intermediate 4 during the filtration and collection process.

[0172] This step does not limit the stirring reaction time and can be adjusted according to the amount of reactants. In some embodiments, the stirring reaction time is 10h to 15h, and the stirring reaction time can be any time value within the range of 10h to 15h, such as 10h, 11h, 12h, 13h, 14h, 15h, etc.

[0173] In this step, the reverse temperature is 100℃~140℃, which can be any temperature value in the range of 100℃~140℃, such as 100℃, 110℃, 120℃, 130℃, 140℃, etc.

[0174] The following explains the steps for preparing intermediate 5.

[0175] In some embodiments, the solid-liquid ratio of intermediate 4 and 1,2-dibromobutane is (0.5g~3g) / (5ml~15ml), which can be 1.787g / 9.7ml.

[0176] In some embodiments, the molar ratio of intermediate 4 to tetrabutylammonium bromide is in the range of (4:1) to (6:1), and can be any value in the range of (4:1) to (6:1), such as 4:1, 5:1, 6:1, etc.

[0177] In some embodiments, the temperature of the heating reaction is 60°C to 80°C, which can be any temperature value in the range of 60°C to 80°C, such as 60°C, 65°C, 70°C, 75°C, 80°C, etc. Under the above reaction temperature conditions, it is beneficial to promote the reaction between intermediate 4 and 1,2-dibromobutane.

[0178] This step does not limit the heating reaction time. In some embodiments, the heating reaction time is 12h to 24h; it can be any time value in the range of 12h to 24h, such as 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h, 24h.

[0179] In some embodiments, a spot plate reaction can be used to monitor the progress of the heating reaction in order to determine whether the reaction has been completed.

[0180] In some embodiments, the alkaline solution includes a potassium hydroxide solution, wherein the mass concentration of the potassium hydroxide solution may be 50%.

[0181] In some embodiments, the reaction mixture is cooled to 20°C to 30°C, i.e., cooled to room temperature. This can be any temperature value within the range of 20°C to 30°C, such as 20°C, 22°C, 25°C, 28°C, or 30°C, which is more conducive to the operation of subsequent steps.

[0182] In some embodiments, extraction is performed using an extractant, including dichloromethane.

[0183] In some embodiments, drying is performed using a desiccant, which includes, but is not limited to, anhydrous magnesium sulfate;

[0184] In some embodiments, the purification method includes silica gel column chromatography, recrystallization, or filtration.

[0185] In some embodiments, purification is performed using silica gel column chromatography, wherein the eluent may include petroleum ether and dichloromethane in a volume ratio of 3:1.

[0186] The target product intermediate 5 obtained in this step is a yellow powder with the following structural formula:

[0187]

[0188] The structural formulas of intermediate 1, intermediate 2, intermediate 3, and intermediate 4 prepared in this invention are as follows:

[0189]

[0190] In some embodiments, the synthetic route for preparing the final product, the fused benzothiadiazole derivative, from intermediate 1 according to the present invention is as follows:

[0191]

[0192] It should be noted that when using the fused benzothiadiazole derivative of the present invention as a hole transport material, the method for preparing the hole transport layer is not limited. Commonly used methods for preparing hole transport layers in this technical field can be selected, such as spin coating, vapor deposition, etc.

[0193] Before preparing the hole transport layer, the fused benzothiadiazole derivative can be dissolved in an organic solvent to obtain a fused benzothiadiazole derivative solution. In some embodiments, the organic solvent includes, but is not limited to, chlorobenzene, and the mass concentration of the fused benzothiadiazole derivative solution can be adjusted according to actual needs.

[0194] It should be noted that intermediates 1 to 5 can all be purchased commercially or prepared using techniques commonly used in the field. The final product, fused benzothiadiazole derivative, can be prepared by using intermediates 1, 2, 3, 4, or 5 as initial reaction raw materials according to the preparation method described above in this invention.

[0195] A third aspect of the present invention provides a hole transport material comprising the fused benzothiadiazole derivative of the present invention as described above, having at least the same beneficial effects as the fused benzothiadiazole derivative, which will not be repeated here.

[0196] A fourth aspect of the present invention provides a hole transport layer comprising the hole transport material of the present invention as described above, having at least the same beneficial effects as the fused benzothiadiazole derivative, which will not be repeated here.

[0197] The fifth aspect of the present invention provides a perovskite solar cell comprising the hole transport layer of the present invention as described above, having at least the same beneficial effects as the fused benzothiadiazole derivative, which will not be repeated here.

[0198] In some embodiments, the perovskite solar cell of the present invention further includes a glass substrate, a perovskite light-absorbing layer, an electron transport layer, and / or an electrode layer.

[0199] The technical solution of the present invention will be further described in detail below with reference to specific embodiments. It should be understood that the following specific embodiments are only used to explain the present invention and are not intended to limit the present invention.

[0200] Example 1

[0201] The steps for preparing the fused benzothiadiazole derivative in this embodiment are as follows:

[0202] Preparation of Intermediate 1: Dilute nitric acid (60 ml) was slowly added dropwise to a sulfuric acid solution (30 ml) containing 4,7-dibromobenzothiazole (15.0 g), and the reaction was carried out at 0 °C to obtain a reaction mixture. After the reaction mixture was allowed to stand at room temperature for 0.5 h, it was poured into 500 ml of ice water, the precipitate was filtered off, and the filtrate was washed three times with water. Then, ethanol solution was added to crystallize the mixture to obtain Intermediate 1 (7.5 g, 0.02 mol), with a yield of 29.0%.

[0203] Preparation of intermediate 2: 5 g of intermediate 1 (15.0 mmol) and 5 g of copper (37.6 mmol) were added to a round-bottom flask purged with nitrogen. 100 ml of dimethylformamide (DMF) was injected to obtain the reaction system. The reaction system was degassed with N2 and then heated under reflux with stirring for 2 h to obtain the reaction mixture. After the reaction mixture was cooled, it was extracted with dichloromethane and deionized water to collect the organic phase. Then, it was dried and concentrated with anhydrous magnesium sulfate to obtain the crude product. The crude product was purified by silica gel column chromatography to obtain yellow crystals, which were the target product intermediate 2 (5.8 g, yield 70%). The silica gel column chromatography used a mixture of n-hexane and dichloromethane as the eluent: n-hexane / dichloromethane = 10 / 1 (v / v).

[0204] Preparation of intermediate 3: Intermediate 2 (5g, 9.69mmol), tin powder (20 equal parts, 5g total), 20ml hydrochloric acid, and 100ml ethanol were added to a round-bottom flask. The mixture was stirred at 80℃ for 4h to obtain a reaction mixture. The reaction mixture was poured into a 5% NaOH solution (250ml) at 0℃~5℃ and extracted three times with diethyl ether to obtain the diethyl ether phase. The diethyl ether phase was washed with sodium bicarbonate solution and dried and concentrated with anhydrous magnesium sulfate to obtain the crude product. The crude product was then purified by silica gel column chromatography to obtain the target product intermediate 3 (3.32g, yield 50%). The eluent used for silica gel column chromatography was as follows: hexane / dichloromethane = 10 / 1 (v / v).

[0205] Preparation of intermediate 4: Intermediate 3 (2g, 4.38mmol) and 50ml of phosphoric acid were added to a round-bottom flask and stirred at 130℃ for 12h to obtain a reaction mixture. The reaction mixture was then poured into cold water at 0℃~5℃, filtered and collected to obtain intermediate 4.

[0206] Preparation of Intermediate 5: Intermediate 4 (1.787 g, 4.05 mmol), 1,2-dibromobutane (9.7 ml), tetrabutylammonium bromide (260.2 mg, 0.81 mmol), and 2.2 ml of 50% potassium hydroxide aqueous solution were added sequentially to a 100 ml reaction tube. The mixture was then heated to 70 °C and reacted overnight. The reaction was monitored by TLC and quenched when complete to obtain the reaction mixture. The reaction mixture was cooled to room temperature, washed with water, and extracted with dichloromethane to obtain the organic phase. The organic phase was dried with anhydrous magnesium sulfate and then purified by silica gel column chromatography to obtain a yellow powder, which was the target product intermediate 5 (1.773 g, yield 76%), denoted as CBTBr-C4Br. The eluent used for silica gel column chromatography was: petroleum ether / dichloromethane = 3:1 (v / v).

[0207] Preparation of intermediate 6: Intermediate 5 (1.739 g, 3.02 mmol) and 10.4 ml of triethyl phosphite were added to a 100 ml reaction tube. The tube was evacuated and purged with nitrogen several times. Then, the tube was placed in an iron sand bath and refluxed at 160 °C for 16 h. The reaction was quenched after TLC to confirm that the reaction was complete, and the reaction mixture was obtained. After the reaction mixture was cooled to room temperature, 200 ml of petroleum ether was introduced. The mixture was crystallized at low temperature and filtered to obtain a crude product. The crude product was washed with petroleum ether to obtain a white powder, which was the target product intermediate 6 (1.549 g, yield 81%), denoted as CBBr-C4P.

[0208] Preparation of fused benzothiadiazole derivative: Intermediate 6 (1.425 g, 2.25 mmol) was dissolved in 15 mL of anhydrous 1,4-dioxane under a nitrogen atmosphere, and trimethylbromosilane (3.0 mL, 22.52 mmol) was added dropwise. The reaction was carried out at room temperature for 24 h. Then, 2 mL of methanol was added and stirring was continued for 3 h. Part of the solvent was removed by rotary evaporation, and 8 mL of methanol was added. Then, 15 mL of distilled water was added dropwise until the solution was opaque. After stirring overnight, the solution was filtered, washed with water, and dried to obtain a white solid. This white solid was the target product, fused benzothiadiazole derivative (0.948 g, 73%), denoted as CBTBr-C4PA.

[0209] Application examples

[0210] Application Example: Using the fused benzothiadiazole derivative obtained in Example 1 as a hole transport material, a perovskite solar cell was prepared. The preparation method is as follows:

[0211] Step 1: Cleaning the ITO conductive glass

[0212] Remove the protective film from the ITO conductive glass, and first use deionized water with detergent for ultrasonic cleaning. Then, place it in deionized water, acetone, and isopropanol in sequence for ultrasonic treatment for 20 minutes. Then, use a hot air gun to dry the cleaned ITO conductive glass substrate and place it in an ultraviolet ozone treatment machine for ozone treatment for 20 minutes. Then, cool it to room temperature for later use.

[0213] Step 2: Preparation of the hole transport layer

[0214] The fused benzothiadiazole derivative obtained in Example 1 was dissolved in a chlorobenzene solution and shaken until fully dissolved to obtain a concentration of 0.8 mg / ml. -1A condensed benzothiadiazole derivative chlorobenzene solution was prepared. An ITO conductive glass substrate was placed on a spin coater under a nitrogen atmosphere in a glove box. 50 μl of the condensed benzothiadiazole derivative chlorobenzene solution was added dropwise using a pipette. Then, a spin coating program with a speed of 3000 rpm and a time of 30 s was started. After spin coating was completed, the substrate was placed on a hot stage at 100°C for 30 min of heat annealing to remove the chlorobenzene, thus obtaining the hole transport layer.

[0215] Step 3: Preparation of the perovskite active layer

[0216] A mixture of 19.8 mg CsI, 16.2 mg MABr, 20.3 mg MACl, 224.4 mg FAI, and 742.2 mg PbI2 powders was dissolved in 1 mL of anhydrous DMF / DMSO (4 / 1, v / v) mixture solvent and stirred at 60 °C for 2 hours to obtain a perovskite precursor solution with the composition Cs 0.05 FA 0.85 MA 0.1 Pb(I 0.97 Br 0.03)3 and a concentration of 1.61 mol·L⁻¹. -1 .

[0217] A one-step method was used to prepare perovskite films. Chlorobenzene was used as the anti-solvent. 50 μl of the perovskite precursor solution was spin-coated onto the hole transport layer. The first spin-coating program was started at 1000 rpm for 10 s and the second spin-coating program was started at 5000 rpm for 30 s. 100 μl of chlorobenzene solution was added dropwise between 20 s and 25 s after the second program started. The sample was then placed on a hot plate at 150 °C and annealed for 10 min to form the perovskite active layer.

[0218] Step 4: Fabrication of the functional layer and its metal electrode layer

[0219] Inside a glove box, the ITO conductive glass substrate, after being processed in steps 1 to 4, is placed in a metal vacuum evaporation deposition chamber, and C layers with a thickness of 35 nm are sequentially deposited under vacuum conditions. 60 The process involved a 7nm thick BCP hole-blocking layer, a 100nm thick Ag electrode layer, and finally, a complete electrode with an area of ​​0.06cm². 2 Perovskite solar cell devices.

[0220] Performance testing

[0221] Under standard sunlight (AM 1.5G) irradiation, the perovskite solar cell prepared according to Example 1 was subjected to device performance testing. The current density-voltage curve of the perovskite solar cell is shown below. Figure 1 As shown.

[0222] The fused benzothiadiazole derivative of this invention is used as the hole transport material to prepare the hole transport layer of a perovskite solar cell device. The fused benzothiadiazole derivative core contains fused benzothiadiazole units, possesses a large conjugated core, and has a DAD-type molecular structure, which can enhance intermolecular interactions and thus promote hole extraction. Furthermore, the fused benzothiadiazole derivative also contains phosphate groups, which can form a self-assembled monolayer on transparent conductive glass in the form of bidentate or tripentate bonds to improve the contact between the hole transport layer and the ITO interface, optimize the energy level arrangement between adjacent layers, improve the carrier mobility of the device, and increase the short-circuit current and fill factor. Further, the fused benzothiadiazole derivative also contains abundant heteroatoms such as sulfur, nitrogen, and oxygen, which can act as Lewis bases to passivate free lead-iodide ions at the interface, thereby reducing losses caused by charge recombination and improving the performance of the inverted perovskite solar cell. Specifically, from Figure 1 It can be seen that the open-circuit voltage Voc of the obtained perovskite solar cell device is 1.13V, and the short-circuit current is 24.25mA / cm. -2 With a fill factor of 74.99% and a photoelectric conversion efficiency of 20.70%, the fused benzothiadiazole derivative of this invention exhibits superior hole transport performance, demonstrating the feasibility of the invention. The fused benzothiadiazole derivative, a hole transport material based on fused benzothiadiazole units, has great application potential in wide-bandgap perovskite solar cell devices.

[0223] The above are merely preferred embodiments of the present invention and do not limit the patent scope of the present invention. Any equivalent structural or procedural transformations made based on the content of the present invention's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A fused benzothiadiazole derivative, characterized in that, The fused benzothiadiazole derivative has the following structural formula: 。 2. A method for preparing the fused benzothiadiazole derivative according to claim 1, characterized in that, Includes the following steps: Preparation of intermediate 6: Intermediate 5 and triethyl phosphite were mixed to obtain a mixed solution, and the mixed solution was subjected to reflux reaction to obtain a reaction mixture. The reaction mixture was cooled, crystallized, filtered, and washed to obtain intermediate 6. Preparation of fused benzothiadiazole derivative: The intermediate 6 was dissolved in a nonpolar solvent and trimethylbromosilane was added dropwise to react and obtain a reaction mixture. A poor solvent was added to the reaction mixture and stirred and evaporated to concentrate. Then, a solvent was added dropwise until the reaction product in the reaction mixture was dissolved. Then, the mixture was stirred, filtered, washed with water, and dried to obtain the fused benzothiadiazole derivative. The intermediate 5 has the following structural formula: ， The intermediate 6 has the following structural formula: 。 3. The method for preparing the fused benzothiadiazole derivative according to claim 2, characterized in that, In the step of preparing intermediate 6: The reflux reaction is carried out in a vacuum inert atmosphere; The reflux reaction temperature is 120℃~180℃; The reflux reaction time is 14h~18h; The degree of reaction of the reflux reaction was monitored using a spot plate test. The reaction mixture was cooled to 20°C~30°C; The crystallization step includes: adding a poor solvent to the reaction mixture, wherein the poor solvent includes at least one of petroleum ether, ethanol, and methanol; The cleaning step includes: cleaning with a poor solvent, wherein the poor solvent includes at least one of petroleum ether, ethanol, and methanol; The solid-liquid ratio of intermediate 5 and triethyl phosphite is (1g~3g) / (10ml~20ml).

4. The method for preparing the fused benzothiadiazole derivative according to claim 2, characterized in that, In the step of preparing the fused benzothiadiazole derivative: The molar ratio of intermediate 6 to trimethylbromosilane is (1:10) to (1:20). The nonpolar solvent includes at least one of anhydrous 1,4-dioxane, tetrahydrofuran, and pyridine; The reaction temperature is 20℃~30℃; The reaction time is 20h~30h; The unsuitable solvents include at least one of methanol, ethanol, and petroleum ether; The stirring time is 12h~24h; The reaction was carried out under a vacuum inert atmosphere; The undesirable solvent is added in multiple batches.

5. The method for preparing the fused benzothiadiazole derivative according to claim 2, characterized in that, The method for preparing the fused benzothiadiazole derivative further includes the following steps: Preparation of Intermediate 1: Dilute nitric acid was added dropwise to a mixed solution of 4,7-dibromobenzothiadiazole and sulfuric acid to obtain a reaction mixture. The reaction mixture was then added to water and filtered to obtain a precipitate. The precipitate was washed and crystallized to obtain Intermediate 1 (4,7-dibromo-5-nitrobenzothiadiazole), which has the following structural formula: ； Preparation of intermediate 2: Intermediate 1, organic solvent, and catalyst are mixed to obtain a mixed solution. The mixed solution is degassed and refluxed with stirring to obtain a reaction mixture. The reaction mixture is extracted and collected to obtain an organic phase. The organic phase is dried, concentrated, and purified to obtain intermediate 2 (4,7-dibromo-2,2-dinitrodibenzothiadiazole). Intermediate 2 has the following structural formula: ； Preparation of intermediate 3: Intermediate 2 is mixed with an organic solvent and tin powder and adjusted to acidity. The mixture is stirred at 80℃~90℃ to obtain a reaction mixture. The reaction mixture is poured into a sodium hydroxide solution and extracted with an extractant to obtain an organic phase. The organic phase is washed, dried, concentrated, purified, and separated to obtain intermediate 3 (4,7-dibromo-2,2-diaminobisbenzothiadiazole). Intermediate 3 has the following structural formula: ； Preparation of intermediate 4: Intermediate 3 and phosphoric acid were mixed and reacted at 100℃~140℃ to obtain a reaction mixture. The reaction mixture was poured into water and filtered to collect intermediate 4 (2,7-dibromo-carbazole[3,4-c:5,6-c]bis[1,2,5]-thiadiazole), which has the following structural formula: ； Preparation of intermediate 5: Intermediate 4, 1,2-dibromobutane, tetrabutylammonium bromide and alkaline aqueous solution are mixed and heated to obtain a reaction mixture. The reaction mixture is cooled, washed with water, extracted, dried, concentrated and purified to obtain intermediate 5.

6. The method for preparing the fused benzothiadiazole derivative according to claim 5, characterized in that, In the step of preparing intermediate 1: The temperature of the dilute nitric acid is 0℃~5℃; The reaction time is 20 min to 40 min; The solid-liquid ratio of the 4,7-dibromobenzothiadiazole and dilute nitric acid is in the range of (10g~25g) / (50ml~100ml); The solid-liquid ratio of the 4,7-dibromobenzothiadiazole and sulfuric acid is in the range of (10g~25g) / (30ml~100ml).

7. The method for preparing the fused benzothiadiazole derivative according to claim 5, characterized in that, In the step of preparing intermediate 2: The organic solvent includes at least one of dimethylformamide, tetrahydrofuran, chlorobenzene, and chloroform; The catalyst includes copper; The reaction time is 1 hour to 4 hours. The reaction mixture was extracted with an extractant, and the organic phase was collected. The extractant included a mixed solution of dichloromethane and deionized water. The organic phase was dried and concentrated using desiccants, all of which included anhydrous magnesium sulfate. The purification methods include silica gel column chromatography, recrystallization, or filtration. The molar ratio of intermediate 1 to the catalyst is (1:2) to (1:5).

8. The method for preparing the fused benzothiadiazole derivative according to claim 5, characterized in that, In the step of preparing intermediate 3: The molar ratio of intermediate 2 to tin powder is (1:1) to (1:5); The organic solvent includes at least one of alcohol, isopropanol, DMF (dimethylformamide), and DMSO (dimethyl sulfoxide); The solution is adjusted to acidity using an acid regulator, wherein the acid regulator includes at least one of hydrochloric acid, sulfuric acid, and nitric acid. The stirring reaction time is 2h~6h; The extractant includes at least one of diethyl ether, ethyl acetate, dichloromethane, and chloroform; The mass concentration of the sodium hydroxide is 3% to 8%; The material is dried and concentrated using a desiccant, which includes anhydrous magnesium sulfate. The purification and separation methods include silica gel column chromatography, recrystallization, or filtration.

9. The method for preparing the fused benzothiadiazole derivative according to claim 5, characterized in that, In the step of preparing intermediate 4: The solid-liquid ratio of intermediate 3 and phosphoric acid is (1g~5g) / (50ml~100ml). The reaction mixture was poured into water at 0-5°C and filtered to collect intermediate 4. The stirring reaction time is 10h~15h.

10. The method for preparing the fused benzothiadiazole derivative according to claim 6, characterized in that, In the step of preparing intermediate 5: The solid-liquid ratio of intermediate 4 and 1,2-dibromobutane is (0.5g~3g) / (5ml~15ml). The molar ratio of intermediate 4 to tetrabutylammonium bromide is in the range of (4:1) to (6:1). The temperature of the heating reaction is 60℃~80℃; The heating reaction time is 12h~24h; The extent of the heating reaction was monitored using a spot plate test. The alkaline aqueous solution includes potassium hydroxide solution; The reaction mixture was cooled to 20°C~30°C; Extraction is performed using an extractant, said extractant including dichloromethane; Drying is performed using a desiccant, which includes anhydrous magnesium sulfate; The purification methods include silica gel column chromatography, recrystallization, or filtration.

11. A hole transport material, characterized in that, The hole transport material includes the fused benzothiadiazole derivative of claim 1.

12. A hole transport layer, characterized in that, The hole transport layer comprises the hole transport material of claim 11.

13. A perovskite battery, characterized in that, The perovskite solar cell includes the hole transport layer as described in claim 12.

14. The perovskite solar cell according to claim 13, characterized in that, The perovskite solar cell further includes a glass substrate, a perovskite light-absorbing layer, an electron transport layer, a hole-blocking layer, and / or an electrode layer.

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