Carbazole and thiophene compounds, methods of making, and applications as undoped hole transport materials in perovskite solar cells

Abstract

This invention discloses a carbazothiophene compound, its preparation method, and its application as a doped hole transport material in perovskite solar cells. A carbazothiophene small molecule hole transport material is described, and its application in perovskite solar cells is also described. One carbazothiophene compound has the chemical structure shown in Formula I: in Formula I, R1, R2, and R3 may be the same or different, and each is -C. n H 2n+1 One of the two; n is any integer from 1 to 18. The synthesis method of this carbazothiophene compound is simple. When used as a hole transport material, it still has a high hole mobility without doping. After strategically adjusting the substituents of the compound, the battery device under the condition of no doping additives has a high photoelectric conversion efficiency and excellent humidity stability and thermal stability.

Description

Technical Field

[0001] This invention belongs to the field of photovoltaic materials and relates to novel hole transport materials in solar cells. Specifically, it designs a carbazole-thiophene compound and its preparation method, and its application as an undoped hole transport material in perovskite solar cells. Background Technology

[0002] Perovskite photovoltaics is currently the fastest-growing photoelectric conversion technology, with laboratory efficiencies exceeding 26%, comparable to commercial silicon-based solar cells, but with production costs far lower than those of silicon-based solar cells (https: / / www.nrel.gov / pv / Cell-efficiency.html, 2021). The photogenerated exciton separation energy of perovskite materials is below 0.025 eV, which is less than the 0.3 eV required by other types of solar cells (such as dye-sensitized solar cells and organic solar cells) (Kojima A, Teshima K, Shirai Y, et al. Organometal Halide Perovskites as Visible-Light Sensitizers for Photovoltaic Cells [J]. Journal of the American Chemical Society, 2009, 131(17): 6050-6051). Although photogenerated excitons within perovskite materials dissociate into free electrons and holes at room temperature, these separated electrons and holes need to be efficiently extracted to improve photoelectric conversion efficiency. Organic small-molecule hole transport materials are favored by researchers due to their high tunability of energy levels and structure, good reproducibility, and relatively easy purification. However, perovskite materials with organic small-molecule hole transport also exhibit low hole mobility, requiring p-doping to improve it. Nevertheless, additives in traditional hole transport materials often exacerbate the deliquescence of perovskite materials, which is detrimental to the long-term stability of perovskite solar cell devices.

[0003] Therefore, the development of efficient and inexpensive undoped hole transport materials is of great significance to the long-term stability and industrialization of perovskite solar cell devices. Summary of the Invention

[0004] To address the issue of low hole mobility in organic small molecule hole transport materials requiring doping, and the fact that traditional doping additives in hole transport materials often exacerbate the deliquescence of perovskite materials, thus negatively impacting the long-term stability of perovskite solar cell devices, this invention provides a carbazothiophene compound, its preparation method, and its application as an undoped hole transport material in perovskite solar cells. The carbazothiophene compound has a simple synthesis method, and when used as a hole transport material, it maintains high hole mobility without doping. The resulting solar cell device exhibits high photoelectric conversion efficiency and excellent humidity and thermal stability without the need for doping additives.

[0005] The first aspect of the present invention is to provide a carbazothiophene compound having the chemical structure shown in Formula I:

[0006]

[0007] In Equation I, R1, R2, and R3 may be the same or different, and each is -C. n H 2n+1 , One of them; n is any integer from 1 to 18.

[0008] The inventors of this invention discovered through research that introducing a rigid conjugated structure into the molecular structure of small-molecule hole transport materials is beneficial for improving the inter-molecule π-π stacking, thereby constructing charge transport channels and increasing the hole mobility of the material. This invention, using carbazole cyclization on thiophene oxide as the core, designed an undoped hole transport material with a high degree of conjugation and successfully applied it in perovskite solar cells.

[0009] As mentioned above, the energy level structure of carbazothiophene compounds can be regulated by introducing alkyl or alkoxy groups; the Π-Π stacking of carbazothiophene compounds can be regulated by introducing alkyl or alkoxy-substituted benzene rings.

[0010] According to the present invention, the substituted alkyl moiety (i.e. -C) in R1, R2, and R3 n H 2n+1 , C in n H 2n+1 ) can be C1-C 18 It can be a straight-chain alkyl group or a branched alkyl group.

[0011] According to the present invention, preferably, the substituted alkyl chain moieties of R1, R2, and R3 are C5-C. 12 The alkyl group, for example, can have 5, 6, 7, 8, 9, 10, 11, or 12 carbon atoms.

[0012] Through the inventors' research, it was discovered that the groups corresponding to R1, R2, and R3, compared to individual alkyl chains (-C), n H 2n+1 When the substituent is an alkyl-substituted benzene ring At this time, the conjugated system of the compound is further extended, exhibiting stronger π-π interactions, which is conducive to intermolecular stacking and the formation of charge transport channels; compared with alkyl-substituted benzene rings, when the substituent is alkoxy-substituted benzene ring... At that time, due to the stronger electron-donating ability of the alkoxy group, the compound exhibits a higher HOMO energy level. Therefore, R1 is... Preferably, R1 is And / or, R2 and R3 are each Preferably, each is Most preferably, R1, R2, and R3 are all alkoxy-substituted benzene rings. The target compound has a more matched energy level structure and stronger charge transport capability.

[0013] The second aspect of the present invention is to provide a method for preparing the carbazothiophene compound (i.e., the compound shown in Formula I) as described in the first aspect, comprising oxidizing, dehydrogenating and cyclizing the carbazothiophene compound shown in Formula II to obtain a reaction product containing the carbazothiophene compound, wherein the oxidant is ferric chloride or dichlorocyanobenzoquinone.

[0014] When the oxidant is ferric chloride, the reaction temperature is 50-70℃ and the reaction time is 3.5-4.5h.

[0015]

[0016] In Equation II, R1, R2, and R3 are each -C n H 2n+1 , One of them;

[0017] R1, R2, and R3 may be the same or different, and n is any integer from 1 to 18 for each of them; preferably:

[0018] R1 is Preferably, R1 is And / or,

[0019] R2 and R3 are each... Preferably, each is And / or,

[0020] n can be any integer from 5 to 12.

[0021] According to the present invention, preferably, the value of n in R1, R2 and R3 is 5 to 12.

[0022] Research has shown that when the molecule of Formula II is fused into a ring, the molecule of Formula I is obtained. The molecule of Formula I has a higher hole mobility than the molecule of Formula II. When used as a hole transport material in perovskite solar cells, it can achieve a high photoelectric conversion efficiency without the need for doping additives.

[0023] According to the present invention, when the oxidant is ferric chloride, it is necessary to control the reaction temperature and time. Maintaining the reaction temperature above 40°C can significantly accelerate the reaction rate; however, when the reaction temperature exceeds 70°C, side reactions gradually increase, making subsequent separation and purification difficult. When the reaction time is extended to more than 8 hours, the system becomes darker, and side reactions gradually increase, which is not conducive to subsequent separation and purification.

[0024] According to the present invention, the compound represented by the target product formula I is prepared by using reaction one or reaction two:

[0025] The reaction one includes: dissolving the carbazole-substituted thiophene compound (shown in Formula II) in the solvent to obtain solution one, dissolving ferric chloride in nitromethane to obtain solution two, and adding solution two to solution one to mix and react;

[0026] The second reaction comprises: dissolving the carbazole-substituted thiophene compound (shown in Formula II) and dichlorocyanobenzoquinone in dichloromethane, and adding methanesulfonic acid dropwise to the above solution to catalyze the reaction.

[0027] According to the present invention, the reaction one includes: dissolving the carbazole-substituted thiophene compound in the solvent to obtain solution one, dissolving ferric chloride in nitromethane to obtain solution two, and adding solution two to solution one and mixing to carry out the reaction.

[0028] According to reaction one of the present invention, preferably, the conditions of reaction one include:

[0029] In reaction one, the molar ratio of ferric chloride to the carbazole-substituted thiophene compound is 1.8-2.8, preferably 2.0-2.2, and most preferably, 2.2 equivalents of ferric chloride are added.

[0030] According to reaction one of the present invention, preferably, the solvent in reaction one is selected from at least one of dichloromethane, chloroform, and chlorobenzene. These reaction solvents have high solubility for the raw materials. Most preferably, dichloromethane, which is relatively inexpensive, is selected.

[0031] According to reaction one of the present invention, preferably, the amount of nitromethane used is 20-30 mL relative to 1 g of ferric chloride.

[0032] As an example, the preparation method of the compound of formula I provided by the present invention includes reaction one:

[0033] Method 1: Dissolve the thiophene containing two adjacent carbazole-substituted compounds (as shown in Formula II) in dichloromethane or chloroform solvent. Other sites on the thiophene or carbazole may also be modified by other substituents. Dissolve ferric chloride in nitromethane, and then slowly add this ferric chloride solution dropwise to the carbazole-substituted thiophene solution at 50-70°C. After stirring for 3.5-4.5 hours, the reaction is complete, and the crude product is obtained by filtration. The crude product is then purified by recrystallization using a mixed solvent. The good solvent can be dichloromethane or chloroform, and the bad solvent can be ethanol or methanol, preferably a dichloromethane and ethanol system. Preferably, the volume ratio of the bad solvent to the good solvent is (2-5):1.

[0034] According to the present invention, the second reaction comprises: dissolving the carbazole-substituted thiophene compound and dichlorocyanobenzoquinone in dichloromethane, and adding methanesulfonic acid dropwise to the above solution to catalyze the reaction.

[0035] According to reaction two of the present invention, preferably, the molar ratio of dichlorodicyanobenzoquinone to carbazole-substituted thiophene compound in reaction two is 1.0-2.5, more preferably 1.6-2.0.

[0036] According to reaction 2 of the present invention, preferably, the amount of methanesulfonic acid added is such that the pH of the reaction system is 0-5, preferably 2-3.

[0037] According to the second reaction of the present invention, preferably, the second reaction is carried out under heating conditions, preferably at 20-60°C, and more preferably at 35-45°C.

[0038] According to the second reaction of the present invention, preferably, the reaction time is 0-12h, more preferably 7-8h.

[0039] As an example, Method 2: Dissolve the thiophene containing two adjacent carbazole-substituted compounds as shown in Formula II in dichloromethane or chloroform solvent, wherein other sites on the thiophene or carbazole may also be modified, and add methanesulfonic acid dropwise to the above solution to catalyze the reaction, wherein the amount of methanesulfonic acid added is such that the pH of the reaction system is 0-5, preferably 2-3.

[0040] According to the present invention, preparation can be carried out using either reaction one or reaction two. The preparation using reaction two has the following advantages:

[0041] (1) Ferric chloride is hygroscopic and difficult to store, while dichlorocyanobenzoquinone is relatively stable and easy to store.

[0042] (2) The preparation of reaction 2 uses the pure organic compound dichlorocyanobenzoquinone, which will not introduce potential impurities such as Fe2O3 in the subsequent processing, which is beneficial to subsequent separation and purification.

[0043] (3) The reaction of dichlorocyanobenzoquinone is easier to control.

[0044] According to the present invention, preferably, the method further includes a step of purifying the reaction products obtained from reaction one and / or reaction two to obtain a purified target product; preferably, the purification step includes: first filtering the reaction products to obtain a crude product, and then using a mixed solvent to recrystallize and purify the crude product.

[0045] More preferably, the mixed solvent comprises a good solvent and a bad solvent; even more preferably, the good solvent is selected from at least one of dichloromethane, chloroform, and chlorobenzene, and the bad solvent is selected from ethanol and / or methanol. This invention utilizes recrystallization to purify compounds, greatly reducing the difficulty and cost of separation and purification. Preferably, the volume ratio of the bad solvent to the good solvent is (2-5):1.

[0046] According to the present invention, as an example, a specific thiophene containing two carbazole-substituted groups at the ortho position as shown in Formula II can be synthesized by the following method: when R1, R2, and R3 in the target product are different from those in the above reaction formula, the target substituents can be changed to the corresponding groups here.

[0047]

[0048] As an example, and more specifically, the ortho-substituted thiophene containing two carbazoles as shown in Formula II is prepared by the following method:

[0049] 2-Bromo-9H-carbazole was dissolved in THF, and then KOH and freshly prepared copper powder were added to the solution. The mixture was stirred until dissolved, and then a bromoalkane compound (e.g., 4-bromohexyloxybenzene) was added. The reaction was carried out under nitrogen protection and stirred at 180°C for 8 hours. After the reaction was complete, it was quenched with a large amount of water, the organic phase was extracted with DCM, and the mixture was purified by silica gel flash chromatography. The solvent was dried by rotary evaporation to obtain compound 1.

[0050] Compound 1 was dissolved in freshly distilled THF under low-temperature nitrogen protection. Then, n-BuLi (n-hexane solution) was added dropwise to the solution, and stirring continued. Isopropanol pinacol borate was added to the mixture, and stirring continued. After the reaction was complete, it was quenched with a large amount of water, the organic phase was extracted with DCM, and purified on silica gel. The solvent was dried by rotary evaporation to obtain compound 2.

[0051] Compound 2, 2,3-dibromothiophene, K₂CO₃, and Pd(PPh₃)₄ were dissolved in DMF under N₂ protection, and the mixture was then heated and stirred overnight. After the reaction was completed, it was quenched with a large amount of water, the organic phase was extracted with DCM, and purified on a silica gel column. After drying the solvent by rotary evaporation, compound 3 was obtained.

[0052] Compound 3 was dissolved in freshly distilled THF and stirred at -78°C under N2 protection. Then, n-BuLi (n-hexane solution) was added dropwise to the mixture. The mixture was stirred at -78°C, and isopropanol pinacol boronic acid ester was added. Stirring continued overnight. After the reaction was complete, purification was performed on a silica gel column. After drying the solvent by rotary evaporation, compound 4 was obtained.

[0053] Under N2 protection, compound 4, bromoalkyl-substituted benzene (e.g.) K₂CO₃ and Pd(PPh₃)₄ were dissolved in DMF. The mixture was then heated overnight. After the reaction was complete, the mixture was purified on a silica gel column. The solvent was dried by rotary evaporation to give compound (a), namely the ortho-substituted thiophene containing two carbazoles.

[0054] The specific dosage and preparation conditions in the synthesis method of ortho-carbazole-substituted thiophene shown in Formula II above can be referred to the conditions in Example 1 of this invention, including but not limited to specific point values.

[0055] A third aspect of the present invention is to provide the application of the carbazothiophene compound described in the first aspect or the carbazothiophene compound prepared by the preparation method described in the second aspect as a hole transport material; preferably,

[0056] Application of the carbazothiophene compounds as undoped hole transport materials.

[0057] According to the present invention, when the carbazothiophene compound is used as a hole transport material, it is not doped with additives, and the doping additives include, but are not limited to, one or more of lithium salts (including but not limited to Li-TFSI), t-BP, and cobalt salts (including but not limited to FK209).

[0058] In the above, Li-TFSI is lithium bis(trifluoromethanesulfonyl)imide, t-BP is 4-tert-butylpyridine, and FK209 refers to [tris(2-(1H-pyrazol-1-yl)-4-tert-butylpyridine)cobalt(III)tris[bis(trifluoromethane)sulfonylimide].

[0059] According to the present invention, preferably, the carbazothiophene compound is used as a hole transport layer in a perovskite solar cell, and preferably, the thickness of the hole transport layer is 20-40 nm.

[0060] According to the present invention, preferably, the hole transport layer is prepared by spin coating or blade coating of the carbazole-thiophene compound dissolved in a solvent. The solvent includes, but is not limited to, chlorobenzene.

[0061] A fourth aspect of the present invention is to provide a perovskite solar cell device, comprising a hole transport layer and a perovskite layer;

[0062] The hole transport layer contains the carbazothiophene compound described in the first aspect or the carbazothiophene compound prepared by the preparation method described in the second aspect, and the hole transport layer is not doped with any additives.

[0063] According to the present invention, preferably, the perovskite layer has an ABX3 crystal configuration, wherein A is MA. + or FA + B is Pb 2+ ;X is I - or Br - More preferably, the perovskite layer is at least one of MAPbI3, FAPbI3, MAPbBr3, and FAPbBr3.

[0064] According to the present invention, the doping additives include, but are not limited to, one or more of lithium salts such as Li-TFSI, t-BP, and cobalt salts such as FK209; and / or,

[0065] According to the present invention, preferably, the thickness of the hole transport layer is 20-40 nm; and / or,

[0066] According to the present invention, preferably, the hole transport layer is prepared by dissolving the carbazothiophene compound in a solvent and then spin-coating or blade-coating.

[0067] The carbazothiophene products synthesized using the above technical solutions are used as hole transport materials in perovskite solar cells. The cell device includes a counter electrode, a hole transport layer, a perovskite layer, an electron transport layer, and a conductive substrate. That is, the perovskite solar cell device also includes a counter electrode, an electron transport layer, and a conductive substrate.

[0068] In the perovskite solar cell device described above, preferably, the counter electrode is a conductive material, preferably at least one of gold, silver, copper, and carbon.

[0069] Preferably, in the perovskite solar cell device described above, the electron transport layer is at least one of titanium dioxide, tin dioxide, and zinc oxide.

[0070] In the perovskite solar cell device described above, preferably, the conductive substrate is at least one of fluorine-doped tin oxide and indium tin oxide.

[0071] Preferably, in the perovskite solar cell device described above, the hole transport layer is made of a carbazole-thiophene-based undoped hole transport material synthesized using the above technical solution, with a thickness of 20-40 nm.

[0072] As described above, this invention overcomes the traditional strategy of using noble metals to catalyze carbon-carbon coupling to improve the conjugation degree of materials. Instead, it uses carbazole-thiophene-based small molecule hole transport materials in perovskite solar cells, thus reducing production costs. This invention provides an undoped carbazole-thiophene-based small molecule hole transport material, assembled into a perovskite solar cell structure comprising a conductive substrate, an electron transport layer, a perovskite active layer, a hole transport layer, and a counter electrode. This results in high photoelectric conversion efficiency and excellent device stability, demonstrating very promising application prospects.

[0073] This invention utilizes ferric chloride or DDQ (dichlorocyanobenzoquinone) to catalyze the "carbon-carbon coupling" enhancement of carbazole conjugation, yielding a small-molecule carbazole-thiophene compound that improves the hole mobility of the material. Taking advantage of the excellent hole transport properties of this conjugated carbazole, it is applied to the hole transport layer of perovskite solar cells.

[0074] Compared with the prior art, the present invention has the following advantages:

[0075] (1) A high hole mobility is a necessary condition for undoped hole transport materials; carbazole and thiophene molecules are important components of p-type organic semiconductors. In this invention, ferric chloride or DDQ is used as an oxidant to efficiently catalyze the cyclization of carbazole substituted at the ortho position on thiophene, thereby improving the hole mobility of the material by forming a rigid conjugated aromatic ring and constructing a p-type organic semiconductor material with a high hole mobility.

[0076] (2) The synthesized hole transport material can be purified by recrystallization, which is convenient to operate. When this material is used as a hole transport material for perovskite solar cells, the battery device can achieve high photoelectric conversion efficiency without the need for additives, and has excellent humidity stability. Attached Figure Description

[0077] Figure 1 The UV-Vis absorption spectrum of the compound described in this invention is shown in dichloromethane solution or spin-coated onto a glass substrate.

[0078] Figure 2 The cyclic voltammetry curves of the compounds described in this invention in dichloromethane are shown.

[0079] Figure 3 The figure shows the hole mobility test curve of the single-carrier device of the compound described in this invention.

[0080] Figure 4 The thermogravimetric analysis curves of the compounds described in this invention are shown.

[0081] Figure 5This is a schematic diagram of a battery device structure in which the compound described in this invention is used as a hole transport material.

[0082] Figure 6 This represents the JV curve scanned after the compound described in this invention is assembled into a battery device.

[0083] Figure 7 The graphs show the stability test and water contact angle test results of the compound described in this invention assembled into a battery device.

[0084] Figure 8 This is a synthetic route diagram of one of the compounds of this invention.

[0085] In the attached figures, (a) refers to compound (a), (b) refers to compound (b), and (f) refers to compound (f). Detailed Implementation

[0086] The present invention will now be described in detail with reference to the accompanying drawings and embodiments. It should be noted that the following embodiments are only used to further illustrate the present invention and should not be construed as limiting the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the content of the present invention are still within the scope of protection of the present invention.

[0087] The present invention will be described in detail below with reference to specific embodiments, so that those skilled in the art can better understand the present invention, but the present invention is not limited thereto.

[0088] All experimental reagents used in the following examples were purchased from Anaiji Chemical Co., Ltd., and were used directly unless otherwise specified.

[0089] In the following embodiments, -C6H 13 It refers to straight-chain alkyl-C6H 13 .

[0090] Example 1

[0091] The synthetic route for carbazole-thiophene-type undoped organic hole transport materials is as follows:

[0092]

[0093] Compound 1:

[0094] 0.859 g of 2-bromo-9H-carbazole was dissolved in 25 mL of THF, and then 0.215 g of KOH and 0.1 g of freshly prepared copper powder were added to the solution. After stirring for 1 hour, 0.9 g of 4-bromohexyloxybenzene was added, and the mixture was stirred at 180 °C under nitrogen protection for 8 hours. After the reaction was complete, it was quenched with a large amount of water, and the organic phase was extracted with 50 mL of DCM. The mixture was then purified by silica gel flash chromatography with a PE:DCM ratio of 10:1 as the eluent. After the solvent was dried by rotary evaporation, a colorless oil was obtained with a yield of 1.3 g (90%). High-resolution mass spectrometry analysis: C 24 H 24 BrNO,[M] + Exact Mass=421.1,found 422.1([M+H] + Nuclear magnetic resonance spectroscopy analysis: 1 H NMR(500MHz,Chloroform)δ7.82(s,16H),7.65(s,16H),7.54(dd,J=20.2,3.5Hz,66H),7.28(s,17H),7.20(s,16H),7.13(d,J=1.4 Hz,5H),7.12–6.97(m,44H),3.99–3.95(m,31H),1.78–1.74(m,27H),1.41–1.37(m,24H),1.37–1.24(m,70H),1.01–0.97(m,47H).

[0095] Compound 2

[0096] Under nitrogen protection at -78°C, 1.221 g of compound 1 was dissolved in freshly distilled THF. Then, 1.5 mL of n-BuLi (2.5 M, n-hexane solution) was added dropwise, and stirring was continued for 2 hours. 0.868 g of isopropanol pinacol borate was added to the mixture, and stirring was continued for 8 hours. After the reaction was complete, it was quenched with a large amount of water, and the organic phase was extracted with 50 mL of DCM. Purification was performed on silica gel using PE:DCM = 8:1 as the eluent. The solvent was dried by rotary evaporation to give a colorless oil (compound 2). The yield was 1.26 g (90%). High-resolution mass spectrometry analysis: C 31 H 40 BrNO3,[M] + Exact Mass=485.3, found 486.3([M+H] + ).

[0097] Compound 3:

[0098] Compound 2 (0.97 g), 0.24 g 2,3-dibromothiophene, 1.345 g K₂CO₃, and 0.018 g Pd(PPh₃)₄ were dissolved in 35 mL DMF under N₂ protection. The mixture was then heated to 110 °C and stirred overnight. After the reaction was complete, it was quenched with a large amount of water, and the organic phase was extracted with 50 mL DCM. Purification was performed on a silica gel column using PE:DCM = 13:1 as the eluent. After drying the solvent by rotary evaporation, a colorless oil (compound 3) was obtained, with a yield of 0.69 g (90%). High-resolution mass spectrometry analysis: C 52 H 50 N₂O₂S, [M] + Exact Mass=766.36,found-766.36([M] + MALDI-TOF nuclear magnetic resonance spectroscopy analysis: 1 H NMR(500MHz,Chloroform)δ8.14(d,J=3.6Hz,3H),7.96(d,J=34.7Hz,3H),7.88 (s,1H),7.79(s,3H),7.70(d,J=11.7Hz,2H),7.65–7.58(m,4H),7.58–7.48(m, 8H),7.27–7.22(m,3H),7.19–7.15(m,3H),7.10–6.96(m,6H),3.98–3.94(m,6H ),1.76–1.72(m,5H),1.55–1.38(m,5H),1.38–1.27(m,13H),1.01–0.97(m,9H).

[0099] Compound 4:

[0100] 0.76 g of compound 3 was dissolved in 30 mL of freshly distilled THF and stirred at -78 °C under N2 protection. Then, 0.7 mL of n-BuLi (2.5 M, n-hexane solution) was added dropwise to the mixture. After stirring at -78 °C for 2 hours, 0.372 g of isopropanol pinacol boronic acid ester was added, and stirring continued overnight. After the reaction was complete, purification was performed on a silica gel column using PE:DCM = 5:1 as the eluent. After rotary evaporation to dry the solvent, white crystals (i.e., compound 4) were obtained, with a yield of 0.845 g (95%). High-resolution mass spectrometry analysis: C 58 H 61 BN2O4S,[M] + Exact Mass=892.4,found 892.4([M] + MALDI-TOF).

[0101] Compound (a):

[0102] Under N2 protection, 0.89 g of compound 4, 0.26 g of 1-bromo-4-hexylbenzene, 1.345 g of K2CO3, and 0.018 g of Pd(PPh3)4 were dissolved in 30 mL of DMF. The mixture was then heated at 110 °C overnight. After the reaction was complete, the mixture was purified on a silica gel column using PE:DCM = 10:1 as the eluent. After drying the solvent by rotary evaporation, a pale yellow powder (i.e., compound (a)) was obtained, with a yield of 0.848 g (90%). High-resolution mass spectrometry analysis: C 64 H 66 N₂O₃S, [M] + Exact Mass=942.48,found942.48([M] + MALDI-TOF nuclear magnetic resonance spectroscopy analysis: 1 H NMR(500MHz,Chloroform)δ8.16(s,2H),8.09(s,2H),7.99(d,J=15.5Hz,4H),7.93 (s,2H),7.80(d,J=14.9Hz,4H),7.71–7.65(m,4H),7.65–7.60(m,6H),7.60–7.44(m ,10H),7.28–7.24(m,4H),7.22–7.18(m,4H),7.17–7.00(m,12H),4.01–3.94(m,12 H),1.80–1.74(m,11H),1.42–1.38(m,9H),1.35–1.31(m,23H),1.01–0.97(m,17H).

[0103] Compound (b):

[0104] 0.94 g of compound (a) was dissolved in 30 mL of dichloromethane and heated to 60 °C. Then, 0.47 g of ferric chloride was dissolved in 10 mL of nitromethane and added dropwise to a round-bottom flask. The reaction mixture was stirred at 60 °C for 4 hours, and a pale yellow solid precipitated. The solid precipitate was collected by filtration and placed in a beaker. Then, 5 mL of dichloromethane was added to dissolve the solid, and 20 mL of ethanol was slowly added along the wall of the beaker. After standing for 3 days, 0.8 g of yellow crystals (i.e., compound (b)) precipitated, with a yield of 87%. High-resolution mass spectrometry analysis: C 64 H 64 N₂O₃S, [M]⁺ = 940.46, -940.46 was found ([M]⁺, MALDI-TOF). Nuclear magnetic resonance spectroscopy analysis: 1H NMR(500MHz,Chloroform)δ9.37(d,J=1.9Hz,2H),8.71(d,J=9.7Hz,2H),8.62(s,1H),7.88(d,J=1.3Hz,2H),7.69(dd,J=1.4,0.5Hz,4H),7.63–7.56(m,4H) ,7.31–7.27(m,2H),7.24–7.20(m,2H),7.14–7.04(m,6H),4.04–3.98(m,6H), 1.80–1.75(m,5H),1.41–1.37(m,4H),1.37–1.30(m,12H),1.01–0.97(m,9H).

[0105] Following the synthesis method of compound (b) in Example 1, by using the molar ratio of ferric chloride to the carbazole-substituted thiophene compound, the amount of solvent, nitromethane, reaction temperature, and reaction time as described in this invention, and by changing the specific synthesis conditions of compound (b) in Example 1, the target product compound (b) can also be obtained. Under the preferred conditions described in this invention, the yield of the target product compound (b) is higher.

[0106] Example 2

[0107] The energy level structure, hole mobility properties and thermal stability of the hole transport material (b) synthesized in Example 1 and (a) as a reference were tested.

[0108] The energy level structure was detected by calculating the oxidation potential of the HOMO energy level of the material using electrochemical cyclic voltammetry; the band gap width of the material was calculated using the absorption edge of the ultraviolet-visible absorption spectrum.

[0109] The hole mobility property is detected by fabricating a single-carrier device and using the space charge confinement current method.

[0110] The thermal stability is tested using a differential scanning calorimeter and a thermogravimetric analyzer.

[0111] The results show that the UV-Vis absorption spectra of the hole transport material (b) and the reference (a) in dichloromethane solution are as follows: Figure 1 As shown. According to the formula: E g =1240 / λ edge The band gaps of hole transport material (b) and reference (a) are 2.7 eV and 3.1 eV, respectively. The relatively narrower band gap of (b) is consistent with its higher degree of conjugation.

[0112] From the cyclic voltammetry curve (e.g.) Figure 2The first oxidation potential of the hole transport material (b) and the reference (a) were calculated to be -5.2 eV and -5.37 eV, respectively (taking...). A hole-single-carrier device was assembled, and the hole mobility of the hole transport material (b) and the reference (a) was calculated to be 6.9 × 10⁻⁶ using the space charge-limited current method and the Mott–Gurney formula. -4 cm 2 V -1 With 5.9×10 -5 cm 2 V -1 (like Figure 3 ).

[0113] The hole mobility of the hole transport material (b) after cyclic oxidation with ferric chloride is an order of magnitude higher than that of the reference material (a) before cyclic oxidation, indicating that cyclic oxidation with ferric chloride is an effective strategy to improve the hole mobility of the material, because it enhances the π-π interaction between molecules. The thermal stability of the material was tested under nitrogen conditions using differential scanning calorimetry and thermogravimetric analysis. The results showed that the phase transition temperature of the reference material (a) before cyclic oxidation was 40℃, while the phase transition temperature of the hole transport material (b) after cyclic oxidation increased to 159℃ (e.g., ...). Figure 4 Furthermore, the experiment revealed that the reference material (a) before ring formation began to change from a solid to a liquid state upon heating to around 50°C, while the hole transport material (b) after ring formation remained unchanged even after heating to 150°C. This result is consistent with the differential scanning calorimetry results. Simultaneously, the thermal decomposition temperature of the material increased from 357°C before ring formation to 420°C after ring formation. The test results demonstrate that cyclic formation via ferric chloride oxidation to enhance rigidity is an effective method for improving the thermal stability of materials.

[0114] Example 3

[0115] The hole transport material (b) prepared in Example 1 was assembled with the reference (a) into a perovskite solar cell. The device structure used was FTO / c-TiO2 / (FAPbI3). 0.85 (MAPbBr3) 0.15 / HTM / Au (e.g.) Figure 5 The compound can be used, but is not limited to, this single battery structure as a hole transporter.

[0116] The fabrication process for the aforementioned perovskite solar cell device is as follows:

[0117] (1) Cleaning of FTO conductive glass

[0118] Four-fifths of the FTO conductive glass was covered with tape. The exposed area was etched using a 2M hydrochloric acid solution with zinc powder. After etching, the glass surface was rinsed with water to remove any residue. After removing the tape, the glass surface was wiped with a cotton ball soaked in surfactant and rinsed clean with water. The pre-cleaned FTO was neatly arranged on a Teflon rack. The rack was then ultrasonically cleaned in a detergent solution, deionized water, acetone, and isopropanol for 30 minutes each, then dried with N2. Before use, it was cleaned with O2 plasma for 3 minutes.

[0119] (2) Preparation of titanium dioxide dense layer

[0120] Diisopropyl di(acetylacetonate)titanate was diluted with ethanol at a volume ratio of 1:20 to prepare a titanium precursor solution, which was then filtered through a 0.22 μm polytetrafluoroethylene (PTFE) membrane before use. The cleaned conductive glass was placed on a plate furnace and heated to 450 °C. One-fifth of the FTO conductive surface was covered with glass, and then the prepared titanium precursor solution was spray-pyrolyzed to deposit a film approximately 30 nm thick. After cooling to room temperature, the film was transferred to a muffle furnace and annealed at a programmed temperature of 500 °C for 1 hour.

[0121] (3) Preparation of perovskite layer

[0122] A mixed solution of PbI₂ (1.1 M), FAI (1.0 M), PbBr₂ (0.2 M), and MABr (0.2 M) was prepared using a DMF:DMSO mixture of 4:1 (V:V). After magnetic stirring at 60 °C for 2 h, the solution was filtered through a 0.22 μm PTFE membrane before use. A coating was applied using a spin coater. 50 μL of the perovskite precursor solution was dropped onto an O₂ plasma-treated titanium dioxide film. The spin coater was operated at 1000 rpm / 10 s, 4000 rpm / 30 s, and then 130 μL of chlorobenzene was rapidly dropped as an anti-solvent to promote perovskite crystallization at the 15-second countdown. After the spin coater stopped, the film was transferred to a 100 °C heating stage for annealing for 30 min, resulting in a black, mirror-like perovskite film.

[0123] (4) Preparation of hole transport layer

[0124] 10mg mL -1 A chlorobenzene solution of hole transport material (b) was spin-coated onto the perovskite layer at 2000 rpm for 30 seconds and then dried at 70°C for 1 minute. Simultaneously, 10 mg / mL of [unclear text - likely a specific chemical formula] was applied. -1 The reference (a) was prepared under the same conditions as a comparison.

[0125] (5) Deposition of gold on the electrode

[0126] Use a knife to scrape away a portion of the perovskite film to expose the FTO conductive surface. Place the film in a custom-shaped photomask at a 5×10mm diameter. -4 A gold counter electrode with a thickness of 80 nanometers was deposited under vacuum conditions of Pa.

[0127] The battery device prepared by the above method achieves a performance of 100mW cm⁻¹. -2 JV tests were conducted under simulated sunlight intensity, and the results are referenced. Figure 6 V oc =1.08V, J sc =24.4mA cm -2 FF = 67%, PCE = 17.6%. Under the same conditions, reference (a) only achieved a photoelectric conversion efficiency of 6.6% (Voc = 0.83V, J). sc =18.2mA cm -2 ,FF = 43.5%.

[0128] The stability test of the battery device based on hole transport material (b) is as follows (e.g. Figure 7 Because no hygroscopic additives were used, the unencapsulated battery device retained 90% of its initial efficiency after being stored at 80% relative humidity (-25℃) for 170 hours; the results indicate that this undoped carbazole-thiophene hole transport material plays an important role in improving the stability of the device.

[0129] Example 4

[0130] Carbazole-thiophene compounds were prepared according to the method in Example 1, except that DDQ was used as a fused-ring oxidant.

[0131] Compound (b):

[0132] 0.94 g of compound (a) and 0.59 g of DDQ were dissolved in 30 mL of dichloromethane. The pH was adjusted to 2 by adding methanesulfonic acid, and the mixture was heated to 45 °C and reacted for 8 h. After the reaction was complete, the mixture was quenched with a large amount of water. The mixture was extracted with DCM and purified on a silica gel column using PE:DCM = 5:1 as the eluent. The solvent was dried by rotary evaporation to obtain a pale yellow powder with a yield of 0.895 g (95%). High-resolution mass spectrometry and nuclear magnetic resonance spectroscopy analysis confirmed that the obtained product was the target product shown in formula (b).

[0133]

[0134] A comparison of Examples 4 and 1 shows that both methods can yield the target product. The yield is higher when the target product is prepared using DDQ.

[0135] It has been confirmed that, following the method of Example 4, by adjusting the molar ratio of dichlorodicyanobenzoquinone to carbazole-substituted thiophene compounds as described in this invention, and by modifying the amount of methanesulfonic acid added, the pH of the reaction system, the heating temperature, and the reaction time, and by changing the specific conditions in Example 4, the target product can be obtained. Under the preferred parameters described in this invention, the yield of the target product is even higher (e.g., Example 4).

[0136] Example 5

[0137]

[0138] Prepared under the same conditions as in Example 1 according to the above reaction formula, except that the alkoxy-substituted phenyl group in Example 1 was replaced with an alkyl-substituted phenyl group, resulting in a novel compound (d). High-resolution mass spectrometry and nuclear magnetic resonance spectroscopy analysis revealed that the obtained product was the target product shown in formula (d).

[0139] Compared to compound (b), compound (d) has a relatively lower HOMO energy level, while compound (b) has a higher HOMO energy level. Compound (b) is more conducive to the extraction of charge from the perovskite light-absorbing layer to the hole transport layer. Therefore, the photoelectric conversion efficiency of the perovskite solar cell based on compound (b) is higher than that of the perovskite solar cell based on compound (d) under the same conditions.

[0140] Example 6

[0141]

[0142] Prepared under the same conditions as in Example 1 according to the above reaction formula, in this example, the alkoxy-substituted phenyl group in Example 1 was replaced with an alkyl group, yielding a novel compound (f). High-resolution mass spectrometry and nuclear magnetic resonance spectroscopy analysis revealed that the obtained product was the target product shown in formula (f). Compared to compound (b), compound (f) has a relatively low degree of conjugation, which is unfavorable for the formation of intermolecular π-π stacking, while compound (b) is more favorable for the formation of intermolecular π-π stacking. Therefore, as... Figure 3 As shown, the hole mobility based on compound (b) is higher than that based on compound (f). And as... Figure 6 As shown, under the same conditions, the battery device based on compound (f) has an efficiency of only 15.8% (Voc = 0.99V, J). sc =23.3mA cm -2 (FF = 68%), the perovskite solar cells based on compound (b) have higher efficiency.

[0143] A comparison of Examples 1, 5, and 6 shows that by changing the substituents on the carbazole-thiophene core, the energy level positions and packing patterns of the target hole transport material can be adjusted, thereby affecting the compound's performance as a hole transport material. When R1, R2, and R3 in Formula I are... When R1, R2, and R3 are alkyl groups, they exhibit better performance as hole transport materials compared to alkyl groups. When used as a hole transport material, compared to alkyl or It has further improved performance.

[0144] Comparative Example 1

[0145] In Example 1, the reaction conditions of compound (a) were changed to those of compound (b), and the mixture was stirred at room temperature for the same time (4 h), resulting in almost no product (b) being formed.

[0146] Comparative Example 2

[0147] In Example 1, changing the reaction conditions from compound (a) to compound (b), setting the reaction temperature to 100°C and stirring for the same time for 4 hours resulted in an increase in side reactions, making subsequent separation and purification difficult.

[0148] Comparative Example 3

[0149] In Example 1, the reaction conditions of compound (a) to compound (b) were changed. The reaction time was extended to 12 hours at 60°C. The system became darker and the side reactions gradually increased, which was not conducive to subsequent separation and purification.

[0150] As can be seen from Comparative Examples 1-3, this reaction is sensitive to temperature and time. Too low a temperature results in almost no product formation; too high a temperature leads to an increase in byproducts. Too short a reaction time results in too low a yield; too long a reaction time increases side reactions and makes separation and purification difficult.

[0151] Comparative Example 4

[0152] If the solvent nitromethane used in the synthesis of compound (b) in Example 1 is replaced with ethanol, the target product cannot be obtained. It is speculated that this is because ferric chloride has a stronger oxidizing power in nitromethane than in ethanol.

[0153] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A carbazothiophene compound having the chemical structure shown in Formula I: In Equation I, R1, R2, and R3 may be the same or different, and each is -C. n H 2n+1 , One of them; n is any integer from 1 to 18.

2. The carbazothiophene compound according to claim 1, characterized in that: R1 is And / or, R2 and R3 are each... And / or, n can be any integer from 5 to 12.

3. The carbazothiophene compound according to claim 1, characterized in that: R1 is And / or, R2 and R3 are each...

4. A method for preparing a carbazothiophene compound according to any one of claims 1-3, comprising oxidizing, dehydrogenating and cyclizing a carbazothiophene compound represented by formula II to obtain a reaction product containing the carbazothiophene compound, wherein the oxidant is ferric chloride or dichlorocyanobenzoquinone; When the oxidant is ferric chloride, the reaction temperature is 50-70℃ and the reaction time is 3.5-4.5h. In Formula II, R1, R2 and R3 each correspond to R1, R2 and R3 in the carbazothiophene compound according to any one of claims 1-3.

5. The preparation method according to claim 4, characterized in that, The preparation method employs either reaction one or reaction two. The first reaction includes: dissolving the carbazole-substituted thiophene compound in a solvent to obtain solution one, dissolving ferric chloride in nitromethane to obtain solution two, and adding solution two to solution one and mixing to carry out the reaction; The second reaction comprises: dissolving the carbazole-substituted thiophene compound and dichlorocyanobenzoquinone in dichloromethane, and adding methanesulfonic acid dropwise to the above solution to catalyze the reaction.

6. The preparation method according to claim 5, characterized in that, The conditions for reaction one include: In reaction one, the molar ratio of ferric chloride to the carbazole-substituted thiophene compound is 1.8-2.8; and / or, The solvent is selected from at least one of dichloromethane, chloroform, and chlorobenzene; and / or, The amount of nitromethane used is 20-30 mL relative to 1 g of ferric chloride.

7. The preparation method according to claim 5, characterized in that, The conditions for reaction one include: In reaction one, the molar ratio of ferric chloride to the carbazole-substituted thiophene compound is 2-2.

2.

8. The preparation method according to claim 5, characterized in that, The conditions for reaction two include: In reaction two, the molar ratio of dichlorocyanobenzoquinone to carbazole-substituted thiophene compounds is 1.0-2.5; and / or, The amount of methanesulfonic acid added is such that the pH of the reaction system is 0-5; and / or, The second reaction is carried out under heating conditions; and / or the time for the second reaction is 0.5-12 h.

9. The preparation method according to claim 5, characterized in that, The conditions for reaction two include: In reaction two, the molar ratio of dichlorocyanobenzoquinone to carbazole-substituted thiophene compounds is 1.6-2; and / or, The amount of methanesulfonic acid added is such that the pH of the reaction system is 2-3; and / or, The second reaction is carried out under heating conditions, at 20-60°C; and / or, the second reaction takes 7-8 hours.

10. The preparation method according to claim 5, characterized in that, The conditions for reaction two include: The second reaction is carried out under heating conditions, at 35-45°C.

11. The preparation method according to any one of claims 5-10, characterized in that: It also includes the step of purifying the reaction products obtained from reaction one and / or reaction two to obtain the target product.

12. The preparation method according to claim 11, characterized in that: The purification steps include: first filtering the reaction product to obtain a crude product, and then using a mixed solvent to recrystallize and purify the crude product.

13. The preparation method according to claim 12, characterized in that: The mixed solvents include both benign and undesirable solvents.

14. The preparation method according to claim 13, characterized in that: The benign solvent is selected from at least one of dichloromethane, chloroform, and chlorobenzene, and the undesirable solvent is selected from ethanol and / or methanol.

15. The use of any carbazothiophene compound according to any one of claims 1-3 as a hole transport material.

16. The application according to claim 15, characterized in that: The application refers to the use of the carbazothiophene compounds as undoped hole transport materials.

17. The application according to claim 15 or 16, characterized in that: When the carbazothiophene compounds are used as hole transport materials, no doping additives are used; and / or, The carbazothiophene compounds are used as hole transport layers in perovskite solar cells; and / or The hole transport layer is prepared by dissolving the carbazole-thiophene compound in a solvent and then spin-coating or blade-coating it.

18. The application according to claim 15 or 16, characterized in that: The carbazothiophene compound is used as a hole transport layer in perovskite solar cells, and the thickness of the hole transport layer is 20-40 nm.

19. A perovskite solar cell device, comprising a hole transport layer and a perovskite layer; The hole transport layer contains a carbazothiophene compound as described in any one of claims 1-3, and the hole transport layer is not doped with any additives.

20. The perovskite solar cell device according to claim 19, characterized in that: The perovskite layer has an ABX3 crystal configuration, where A is MA. + or FA + B is Pb 2+ ;X is I - or Br - ; and / or, The hole transport layer has a thickness of 20-40 nm; and / or, The hole transport layer is prepared by dissolving the carbazole-thiophene compound in a solvent and then spin-coating or blade-coating it.

21. The perovskite solar cell device according to claim 19, characterized in that: The perovskite layer is at least one of MAPbI3, FAPbI3, MAPbBr3, and FAPbBr3.

22. The perovskite solar cell device according to any one of claims 19-21, characterized in that: The perovskite solar cell device also includes a counter electrode, an electron transport layer, and a conductive substrate.

23. The perovskite solar cell device according to claim 22, characterized in that: The counter electrode is made of a conductive material; and / or, The electron transport layer is at least one of titanium dioxide, tin dioxide, and zinc oxide; and / or, The conductive substrate is at least one of fluorine-doped tin oxide and indium tin oxide.

24. The perovskite solar cell device according to claim 22, characterized in that: The counter electrode is at least one of gold, silver, copper, and carbon.

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