CN113336772A

CN113336772A - Hole transport material and synthesis method and application thereof

Info

Publication number: CN113336772A
Application number: CN202110429279.5A
Authority: CN
Inventors: 姜月; 伍业辉; 龚志明; 王茹; 高进伟
Original assignee: South China Normal University
Current assignee: South China Normal University
Priority date: 2021-04-21
Filing date: 2021-04-21
Publication date: 2021-09-03
Anticipated expiration: 2041-04-21
Also published as: CN113336772B

Abstract

The invention discloses a hole transport material, in particular to a hole transport material taking dithieno [3,2-b:2',3' -d ] pyrrole as a core and carbazole as an end group, and also discloses a synthesis process of the hole transport material, application of the hole transport material in preparation of a perovskite solar cell, and the perovskite solar cell prepared by using the hole transport material. The hole transport material has higher glass transition temperature, proper HOMO energy level and moderate optical band gap, and the prepared perovskite solar cell device has the highest photoelectric conversion efficiency of more than 18 percent; the synthetic method has simple steps and low preparation cost.

Description

Hole transport material and synthesis method and application thereof

Technical Field

The invention belongs to the technical field of hole transport materials, particularly relates to a hole transport material and a synthesis method and application thereof, and particularly relates to a hole transport material taking dithieno [3,2-b:2',3' -d ] pyrrole as a core and carbazole as an end group, and a synthesis method and application thereof.

Background

At present, excessive development and use of non-renewable energy sources represented by fossil energy causes increasingly serious problems such as energy exhaustion and environmental deterioration. The solar energy has the outstanding advantages of cleanness, no pollution, huge total radiation amount, no regional limitation and the like, and is widely concerned by researchers.

A third generation novel solar cell comprising: the organic solar cell (OPVs), the dye-sensitized solar cell (DSSCs), the quantum dot solar cell (QSCs), the Perovskite Solar Cell (PSCs) and the like, the preparation process is simple, the solution-soluble processing is adopted, the cost is low, and the excellent application prospect is shown. Among them, since 2009, with ten years of development, the Photoelectric Conversion Efficiency (PCE) of Perovskite Solar Cells (PSCs) has increased from the first 3.8% to the present 25.5%, becoming one of the most competitive photovoltaic technologies in the current new energy field.

As shown in fig. 1, the perovskite solar cell device is composed of five parts, namely a transparent conductive electrode, an electron transport layer, a perovskite light absorption layer, a hole transport layer and a metal back electrode. The hole transport material is one of the key materials of the perovskite solar cell, and mainly plays roles in extracting and transporting holes, blocking electrons and inhibiting accumulation and recombination at a carrier interface in a device. The ideal hole transport layer should have: (1) excellent hole mobility and conductivity; (2) the matched energy level (3) has excellent dissolving capacity and film-forming property; (4) high thermal stability, photochemical stability, and high hydrophobicity; (5) low commercial production cost and the like.

Common hole transport materials include three major classes of materials, inorganic, polymeric, and small molecules. Among them, the small molecule hole transport material has various structures and can be processed by solution, and is the most competitive hole transport layer material. 2,2',7,7' -tetra [ N, N-di (4-methoxyphenyl) amino ] -9,9' -spirobifluorene (Spiro-OMeTAD) is the most widely used small molecule hole transport layer at present. However, the Spiro-OMeTAD synthesis route is complicated and high in cost, which severely limits the commercial application (ACS appl. Mater. interfaces.2015,7(21): 11107-11116.). Therefore, designing and developing new and efficient organic small molecule hole transport materials become one of the research hotspots in the industry.

Disclosure of Invention

The first purpose of the invention is to provide a hole transport material, in particular to a hole transport material which takes dithieno [3,2-b:2',3' -d ] pyrrole as a core and carbazole as an end group, and the hole transport material has good stability, low price, easy regulation and good hole transport performance.

The second objective of the present invention is to provide a method for synthesizing the above hole transport material, especially a hole transport material using dithieno [3,2-b:2',3' -d ] pyrrole as a core and carbazole as an end group, wherein the method has advantages of simple process and low overall preparation cost.

The third purpose of the invention is to provide the application of the hole transport material, in particular to the application of the hole transport material taking dithieno [3,2-b:2',3' -d ] pyrrole as a core and carbazole as a terminal group in the aspect of perovskite solar cells.

The first object of the present invention can be achieved by the following technical solutions:

a hole transport material, especially a hole transport material with dithieno [3,2-b:2',3' -d ] pyrrole as core and carbazole as end group, its structural formula is as follows:

specifically, R is different alkyl chains and is n-hexyl or 2-ethylhexyl respectively, and the structural formula of R is as follows:

specifically, X is different side chain atoms or groups, and is respectively a hydrogen atom, an alkoxy group or a halogen atom, specifically a hydrogen atom, a methoxy group or a fluorine atom, and the specific structural formula of X is as follows:

x is H, OMe or F.

The specific structural formula of the hole transport material taking dithieno [3,2-b:2',3' -d ] pyrrole as a core and carbazole as a terminal group is TM-I-TM-VI, which is shown in figure 2.

The hole transport material of the invention introduces different side chain adjusting molecules on the mother nucleus to accumulate, and introduces the hole extracting capability of the adjusting molecules with different substituent groups on the carbazole end group.

The synthesis method of the hole transport material with dithieno [3,2-b:2',3' -d ] pyrrole as the core and carbazole as the end group is recommended to be prepared by the following method, specifically.

The second object of the present invention can be achieved by the following technical means: the synthesis method of the hole transport material comprises the following steps:

(1) mixing a 3-bromo-9-phenyl-9-H-carbazole derivative and diboron pinacol ester, adding an organic solvent for dissolving, then adding a catalyst a and an alkali a, and fully mixing and reacting under the protection of nitrogen to generate the 9-phenyl-3- (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborane-2-yl) -9H-carbazole derivative;

(2) selecting a 2, 6-dibromo-4-hydro-dithiophene [3,2-b:2',3' -d ] pyrrole derivative and the 9-phenyl-3- (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborane-2-yl) -9H-carbazole derivative prepared in the step (1), adding an organic solvent for dissolving, then adding a catalyst b and an alkali b, and reacting under the protection of nitrogen to generate a target product;

(3) after the reaction is finished, water and dichloromethane are used for extraction in sequence, an organic phase is collected, and the hole transport material taking dithieno [3,2-b:2',3' -d ] pyrrole as a core and carbazole as an end group is obtained after drying, filtering, chromatography and concentration.

Further, the method for synthesizing the hole transport material comprises the following steps:

(1) mixing a 3-bromo-9-phenyl-9-H-carbazole derivative and diboron pinacol ester, adding an organic solvent for dissolving, adding a catalyst a and an alkali a, and fully mixing and reacting under the protection of nitrogen to generate the 9-phenyl-3- (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborane-2-yl) -9H-carbazole derivative;

the synthetic route is as follows:

wherein the 3-bromo-9-phenyl-9-H-carbazole derivative is 3-bromo-9- (4-phenyl) -9H-carbazole, 3-bromo-9- (4-methoxyphenyl) -9H-carbazole, or 3-bromo-9- (4-fluorophenyl) -9H-carbazole;

the 9-phenyl-3- (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborane-2-yl) -9H-carbazole derivative is 9- (4-phenyl) -3- (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborane-2-yl) -9H-carbazole, 9- (4-methoxyphenyl) -3- (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborane-2-yl) -9H-carbazole or 9- (4-fluorophenyl) -3- (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborane-2-yl) -9H-carbazole;

(2) selecting a 2, 6-dibromo-4-hydro-dithiophene [3,2-b:2',3' -d ] pyrrole derivative and a 9-phenyl-3- (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborane-2-yl) -9H-carbazole derivative, adding an organic solvent for dissolving, adding a catalyst b and an alkali b, and carrying out Suzuki coupling reaction under the protection of nitrogen (A. tetrahedron Lett.1979,36, 3437-;

the synthetic route is as follows:

specifically, R is different alkyl chains and is respectively n-hexyl or 2-ethylhexyl, and the structural formula of R is as follows:

specifically, X is different side chain atoms or groups, specifically hydrogen atoms, methoxy groups or fluorine atoms, and the specific structural formula of X is as follows:

x is H, OMe or F;

wherein the 2, 6-dibromo-4-hydro-dithieno [3,2-b:2',3' -d ] pyrrole derivative is 2, 6-dibromo-4- (2-ethylhexyl) -4H-dithieno [3,2-b:2,3-d ] pyrrole or 2, 6-dibromo-4- (2-hexyl) -4H-dithieno [3,2-b:2',3' -d ] pyrrole;

In the above-mentioned method for synthesizing a hole transport material having dithieno [3,2-b:2',3' -d ] pyrrole as a core and carbazole as a terminal group:

preferably, the organic solvent in the steps (1) to (2) is anhydrous 1, 4-dioxane, and the reaction is carried out in a Schlenk reaction tube.

Preferably, the molar ratio of the 3-bromo-9-phenyl-9-H-carbazole derivative to the pinacol diboron in the step (1) is 1 (1.5-2).

Preferably, in step (1), the catalyst a is dichloro [1,1' -bis (diphenylphosphino) ferrocene]Palladium (Pd (dppf) Cl₂) The amount relationship between the 3-bromo-9-phenyl-9-H-carbazole derivative and the amount of the compound is (0.02-0.1): 1.

preferably, the base a in the step (1) is potassium acetate (AcOK), and the amount relation of the base a and the pinacol ester diboron is (2-3): 1.

preferably, the reaction temperature of the mixing reaction in the step (1) is 90-110 ℃, and the reaction time is 16-20 hours.

Preferably, the 3-bromo-9-phenyl-9-H-carbazole derivative in step (1) is 3-bromo-9- (4-phenyl) -9H-carbazole, 3-bromo-9- (4-methoxyphenyl) -9H-carbazole, or 3-bromo-9- (4-fluorophenyl) -9H-carbazole.

Preferably, the 9-phenyl-3- (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborane-2-yl) -9H-carbazole derivative in the step (1) is 9- (4-phenyl) -3- (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborane-2-yl) -9H-carbazole, 9- (4-methoxyphenyl) -3- (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborane-2-yl) -9H-carbazole or 9- (4-fluorophenyl) -3- (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborolan-2-yl) -9H-carbazole

Preferably, the molar ratio of the 2, 6-bis-bromo-4-hydro-dithieno [3,2-b:2',3' -d ] pyrrole derivative to the 9-phenyl-3- (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborolan-2-yl) -9H-carbazole derivative in step (2) is 1 (2-3).

Preferably, the 2, 6-dibromo-4-hydro-dithieno [3,2-b:2',3' -d ] pyrrole derivative in step (2) is 2, 6-dibromo-4- (2-ethylhexyl) -4H-dithieno [3,2-b:2,3-d ] pyrrole or 2, 6-dibromo-4- (2-hexyl) -4H-dithieno [3,2-b:2',3' -d ] pyrrole.

Preferably, the catalyst b in step (2) is tris (dibenzylideneacetone) dipalladium (Pd)₂dba₃) With 2, 6-dibromo-4-hydro-dithiophene [3,2-b:2',3' -d]The amount of the pyrrole derivative is (0.02-0.1): 1.

preferably, the base b in step (2) is potassium phosphate trihydrate (K)₃PO₄·3H₂O) in a mass relationship with 9-phenyl-3- (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborolan-2-yl) -9H-carbazole derivative of (2 to 3): 1.

preferably, the reaction temperature in the step (2) is 100-120 ℃, and the reaction time is 16-20 hours.

The third object of the present invention can be achieved by the following means: the application of the hole transport material in the perovskite solar cell.

The hole transport material taking dithieno [3,2-b:2',3' -d ] pyrrole as a core and carbazole as an end group has higher glass transition temperature and higher hole mobility, so the hole transport material can be used as a hole transport material of a perovskite solar cell.

The invention also provides a perovskite solar cell which is structurally composed of a transparent substrate layer, an electron transport layer, a perovskite active layer, a hole transport layer, a hole blocking layer and a metal electrode layer from bottom to top, wherein the hole transport layer is mainly prepared from the hole transport material which takes dithieno [3,2-b:2',3' -d ] pyrrole as a core and carbazole as an end group.

Preferably, in the perovskite solar cell, the transparent substrate layer is fluorine-doped tin oxide conductive glass (FTO).

Preferably, the electron transport layer of the perovskite solar cell is made of tin dioxide, and the thickness of the electron transport layer is 20-40 nm.

Preferably, in the perovskite solar cell, the material of the perovskite active layer is methylamine lead iodide, and the chemical structural general formula of the perovskite active layer is CH₃NH₃PbI₃The thickness is 350-450 nm.

Preferably, in the perovskite solar cell, the hole transport layer is made of compounds TM-I-TM-VI (shown in figure 2) and has a thickness of 150-200 nm.

Preferably, the perovskite solar cell is characterized in that the metal electrode layer is made of silver and has a thickness of 80-100 nm.

The invention has the following advantages:

(1) compared with a Spiro-OMeTAD material, the hole transmission synthesis method taking dithieno [3,2-b:2',3' -d ] pyrrole as a core and carbazole as an end group is simple, the preparation cost is low, and the material has high glass transition temperature and appropriate HOMO energy level, so that the material can be used as a hole transmission material of a perovskite solar cell;

(2) the hole transport material has higher hole mobility, and can obtain higher open-circuit voltage (V) when being used in the perovskite solar cell_OC) Short-circuit current (J)_SC) And Fill Factor (FF), ultimately higher Photoelectric Conversion Efficiency (PCE) is achieved, with TM-ii and TM-iii based devices achieving photoelectric conversion efficiencies in excess of 18%.

Drawings

FIG. 1 is a schematic diagram of a perovskite solar cell of the background art;

FIG. 2 shows the chemical structures of some of the organic hole transport materials TM-I, TM-II, TM-III, TM-IV, TM-V, TM-2, TM-3, and TM-4 of the present invention;

FIG. 3 is the NMR spectrum of the organic hole transporting material TM-I in example 3: (¹H NMR)；

FIG. 4 is the NMR spectrum of the organic hole transporting material TM-I in example 3: (¹³C NMR)；

FIG. 5 is a high resolution mass spectrum of the organic hole transporting material TM-I of example 3;

FIG. 6 is the NMR spectrum of the organic hole transporting material TM-II in example 4: (¹H NMR)；

FIG. 7 is the NMR spectrum of the organic hole transporting material TM-II in example 4 ((C))¹³C NMR)；

FIG. 8 is a MALDI-TOF mass spectrum of the organic hole transporting material TM-II of example 4;

FIG. 9 shows the NMR spectra of the organic hole transporting material TM-III in example 5: (¹H NMR)；

FIG. 10 shows the NMR spectrum of the organic hole transporting material TM-III in example 5 (C:)¹³C NMR)；

FIG. 11 shows the NMR spectra of the organic hole transporting material TM-III in example 5: (¹⁹F NMR)；

FIG. 12 is a high resolution mass spectrum of the organic hole transporting material TM-III of example 5;

FIG. 13 shows the NMR spectra of the organic hole transporting materials TM-IV in example 6: (¹H NMR)；

FIG. 14 is the NMR spectrum of carbon atom of the organic hole transporting material TM-IV in example 6 ((C))¹³C NMR)；

FIG. 15 is a high resolution mass spectrum of the organic hole transport material TM-IV of example 6;

FIG. 16 is the NMR spectrum of the organic hole transporting material TM-V in example 7 (H¹H NMR)；

FIG. 17 is the NMR spectrum of the organic hole transporting material TM-V in example 7 (C¹³C NMR)；

FIG. 18 is a high resolution mass spectrum of the organic hole transporting material TM-V of example 7;

FIG. 19 is a NMR spectrum of TM-VI as an organic hole transporting material in example 8¹H NMR)；

FIG. 20 is the NMR spectrum of carbon (C) for the organic hole transporting material TM-VI in example 8¹³C NMR)；

FIG. 21 shows organic holes in example 8Nuclear magnetic resonance fluorine spectrum of transmission material TM-VI: (¹⁹F NMR)；

FIG. 22 is a high resolution mass spectrum of the organic hole transporting material TM-VI of example 8;

FIG. 23 is a Cyclic Voltammogram (CV) for the organic hole transport materials TM-I-TM-VI of examples 3-8, wherein A is TM-I, B is TM-II, C is TM-III, D is TM-IV, E is TM-V, and F is TM-VI;

FIG. 24 is an ultraviolet-visible spectrum absorption spectrum (UV-vis) of films and solutions of the organic hole transport materials TM-I-TM-VI of examples 3-8, wherein A is TM-I, B is TM-II, C is TM-III, D is TM-IV, E is TM-V, and F is TM-VI;

FIG. 25 is a thermogravimetric plot (TGA) of the organic hole transport materials TM-I-TM-VI of examples 3-8, wherein A is TM-I, B is TM-II, C is TM-III, D is TM-IV, E is TM-V, and F is TM-VI;

FIG. 26 is a Differential Scanning Calorimetry (DSC) curve of the organic hole transporting materials TM-I-TM-VI of examples 3-8, wherein A is TM-I, B is TM-II, C is TM-III, D is TM-IV, E is TM-V, and F is TM-VI;

fig. 27 is the perovskite solar cell device structure in example 9;

FIG. 28 is a J-V characteristic curve of a device based on different hole transport materials in example 9.

Detailed Description

The present invention will be further illustrated with reference to the following specific examples, but the present invention is not limited to the following examples. The process is conventional unless otherwise specified, and the starting materials are commercially available from the open literature.

Example 1: synthesis of 9- (4-methoxyphenyl) -3- (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborolan-2-yl) -9H-carbazole (intermediate 1)

Synthetic route of intermediate 1:

to a 50mL Schlenk reaction tubeThe compound 3-bromo-9- (4-methoxyphenyl) -9H-carbazole (1.72g, 4.89mmol), pinacol diboron ester (1.86g, 7.34mmol), Pd (dppf) Cl₂(73mg, 0.1mmol), potassium acetate (1.4g, 14.67mmol) and anhydrous 1, 4-dioxane (20mL), followed by three additional purges, under nitrogen at 90 ℃ for 16 h.

After the reaction, the reaction solution was cooled to room temperature, 50mL of water was added to the reaction solution, the aqueous phase was extracted three times with dichloromethane, and the organic phase was purified over anhydrous Na₂SO₄After drying, the solvent was removed by distillation under reduced pressure. The crude product was purified by column chromatography (petroleum ether: ethyl acetate 10: 1 as eluent) to afford intermediate 1(1.27g, 65%) as a white solid.

Example 2: synthesis of 9- (4-fluorophenyl) -3- (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborane-2-yl) -9H-carbazole (intermediate 2)

Synthetic route of intermediate 2:

to a 50mL Schlenk reaction tube was added the compound 3-bromo-9- (4-fluorophenyl) -9H-carbazole (2.18g, 6.13mmol), pinacol diboron (2.32g, 9.20mmol), Pd (dppf) Cl₂(90mg, 0.12mmol), potassium acetate (1.8g, 18.39mmol) and anhydrous 1, 4-dioxane (30mL), followed by three additional purges, under nitrogen at 90 ℃ for 16 h.

After the reaction, the reaction solution was cooled to room temperature, 50mL of water was added to the reaction solution, the aqueous phase was extracted three times with dichloromethane, and the organic phase was purified over anhydrous Na₂SO₄After drying, the solvent was removed by distillation under reduced pressure. The crude product was purified by column chromatography (petroleum ether: ethyl acetate 25: 1 as eluent) to afford intermediate 2(2g, 84% yield) as a white solid;

example 3: 4- (2-ethylhexyl) -2, 6-bis (9-phenyl-9H-carbazol-3-yl) -4H-dithio [3,2-b: synthesis and characterization of 2',3' -d ] pyrrole (TM-I)

Synthetic route of TM-I:

to a 50mL Schlenk reaction tube was added the compound 2, 6-dibromo-4- (2-ethylhexyl) -4H-dithieno [3,2-b:2,3-d]Pyrrole (170mg, 0.38mmol), 9- (4-hydro) -phenyl-3- (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborane-2-yl) -9H-carbazole (280mg, 0.76mmol), Pd (PPh)₃)₄(9mg，0.008mmol)，K₃PO₄·3H₂O (404mg, 1.52mmol) and 1, 4-dioxane (5mL) were reacted under nitrogen at 100 ℃ for 16 h.

After the reaction, the reaction solution was cooled to room temperature, 50mL of water was added to the reaction solution, the aqueous phase was extracted three times with dichloromethane, and the organic phase was purified over anhydrous Na₂SO₄After drying, the solvent was removed by distillation under reduced pressure. The crude product was purified by column chromatography (petroleum ether: dichloromethane ═ 2: 1 as eluent) to give TM-i (200mg, yield 68%) as a yellow solid.

Nuclear magnetic resonance hydrogen spectrum of organic hole transport material TM-I (¹H NMR is shown in FIG. 3, nuclear magnetic resonance carbon spectrum: (¹³C NMR) as shown in fig. 4, the nuclear magnetic resonance characterization data is as follows:¹H NMR(600MHz,C₆D₆):8.64(d,J＝1.8Hz,2H),8.02(dd,J₁＝7.2Hz,J₂＝1.2Hz,2H),7.83(dd,J₁＝8.4Hz,J₂＝1.2Hz,2H),7.37(s,2H),7.29-7.26(m,6H),7.24-7.20(m,2H),7.18-7.16(m,6H),7.14-7.13(m,2H),3.90-3.80(m,2H),2.03-1.98(m,1H),1.35-1.15(m,8H),0.86(t,J＝7.2Hz,3H),0.78(t,J＝7.2Hz,3H).¹³C NMR(150MHz,C₆D₆) 145.49,143.16,141.59,140.44,137.63,129.66,128.66,127.13,126.95,126.29,124.50,124.34,123.61,120.70,120.30,117.44,114.50,110.30,109.93,106.53,50.99,40.31,30.56,28.47,24.03,23.05,13.96 and 10.52, the structure of the material TM-I can be determined by the peak positions and the number of hydrogens corresponding to them. The high resolution mass spectrum of the organic hole transport material TM-I is shown in FIG. 5, and the structural correctness is further confirmed by mass spectrum.

Then the material books are alignedThe properties of the material were characterized by the HOMO level of TM-I of-5.16 eV as measured by Cyclic Voltammetry (CV) as shown in Panel A of FIG. 23; as shown in FIG. 24, graph A, the maximum absorption peak in the solution state was at 402nm, the absorption band edge was 500nm, and the optical band gap was 2.48eV, as measured by ultraviolet-visible absorption spectroscopy (UV-Vis), indicating that the HOMO level of the material TM-I was matched to the level of the perovskite. FIG. 25 is a thermogravimetric plot of the material at 422 deg.C for the thermal decomposition temperature, and FIG. 26 is a differential scanning calorimetry plot of the material at T, the glass transition temperature of TM-I_gAnd the temperature is 91 ℃, which shows that the material TM-I has good thermal property.

Example 4: 4- (2-ethylhexyl) -2, 6-bis (9- (4-methoxyphenyl) -9H-carbazol-3-yl) -4H-dithio [3,2-b: synthesis and characterization of 2',3' -d ] pyrrole (TM-II)

Synthetic route of TM-II:

to a 50mL Schlenk reaction tube was added the compound 2, 6-dibromo-4- (2-ethylhexyl) -4H-dithieno [3,2-b:2,3-d]Pyrrole (225mg, 0.5mmol), intermediate 1(415mg, 1.0mmol), Pd (PPh)₃)₄(11mg，0.01mmol)，K₃PO₄·3H₂O (532mg, 2.0mmol) and 1, 4-dioxane (5mL) were reacted under nitrogen at 100 ℃ for 16 hours.

After the reaction, the reaction solution was cooled to room temperature, 50mL of water was added to the reaction solution, the aqueous phase was extracted three times with dichloromethane, and the organic phase was purified over anhydrous Na₂SO₄After drying, the solvent was removed by distillation under reduced pressure. The crude product was purified by column chromatography (petroleum ether: dichloromethane ═ 2: 1 as eluent) to give TM-ii (310mg, yield 72%) as a yellow solid.

Nuclear magnetic resonance hydrogen spectrum of organic hole transport material TM-II (¹H NMR As shown in FIG. 6, nuclear magnetic resonance carbon Spectroscopy: (¹³C NMR) as shown in fig. 7, the nuclear magnetic resonance characterization data is as follows:¹H NMR(600MHz,C₆D₆):8.68(d,J＝1.8Hz,2H),8.06(d,J＝7.8Hz,2H),7.88(dd,J₁＝8.4Hz,J₂＝1.8Hz,2H),7.38(s,2H),7.35-7.29(m,6H),7.26-7.23(m,2H),7.09-7.07(m,4H),6.78-6.75(m,4H),3.92-3.83(m,2H),3.32(s,6H),2.03-1.99(m,1H),1.37-1.15(m,8H),0.86(t,J＝7.2Hz,3H),0.78(t,J＝7.2Hz,3H).¹³C NMR(150MHz,C₆D₆) 158.98,145.48,143.25,142.15,141.00,130.11,128.46,128.40,126.26,124.48,124.12,123.41,120.72,120.09,117.48,114.97,114.47,110.26,109.90,106.49,54.72,51.00,40.31,30.56,28.47,23.06,13.97 and 10.53, the structure of the material TM-II can be determined by the peak positions and the number of hydrogens corresponding to them. MALDI-TOF mass spectrometry of the organic hole transport material TM-II is shown in FIG. 8, and the structural correctness is further confirmed by mass spectrometry.

The material property is characterized, as shown in a B diagram in FIG. 23, the HOMO energy level of TM-II is-5.14 eV measured by Cyclic Voltammetry (CV); as shown in B of FIG. 24, the maximum absorption peak in the solution state was at 402nm, the absorption band edge was 457nm, and the optical band gap was 2.71eV, as measured by ultraviolet-visible absorption spectroscopy (UV-Vis), indicating that the HOMO level of the material TM-II was matched to the perovskite level. FIG. 25, panel B, is a thermogravimetric analysis curve of a material having a thermal decomposition temperature at 435 ℃; FIG. 26B is a differential scanning calorimetry curve of a material, the glass transition temperature T of TM-II_gThe temperature is 101 ℃, which shows that the material TM-II has good thermal property.

Example 5: 4- (2-ethylhexyl) -2, 6-bis (9- (4-fluorophenyl) -9H-carbazol-3-yl) -4H-dithio [3,2-b: synthesis and characterization of 2',3' -d ] pyrrole (TM-III)

Synthetic route of TM-III:

to a 50mL Schlenk reaction tube was added the compound 2, 6-dibromo-4- (2-ethylhexyl) -4H-dithieno [3,2-b:2,3-d]Pyrrole (225mg, 0.5mmol), intermediate 2(387mg, 1.0mmol), Pd (PPh)₃)₄(11mg，0.01mmol)，K₃PO₄·3H₂O(532mg，2.0mmol) and 1, 4-dioxane (5mL) at 100 ℃ under nitrogen for 16 hours.

After the reaction, the reaction solution was cooled to room temperature, 50mL of water was added to the reaction solution, the aqueous phase was extracted three times with dichloromethane, and the organic phase was purified over anhydrous Na₂SO₄After drying, the solvent was removed by distillation under reduced pressure. The crude product was purified by column chromatography (petroleum ether: dichloromethane ═ 2: 1 as eluent) to give TM-iii (282mg, yield 70%) as a yellow solid.

Nuclear magnetic resonance hydrogen spectrum of organic hole transport material TM-III (¹H NMR As shown in FIG. 9, nuclear magnetic resonance carbon Spectroscopy: (¹³C NMR is shown in FIG. 10, nuclear magnetic resonance fluorine spectrum: (¹⁹F NMR) as shown in fig. 11, the nuclear magnetic resonance characterization data is as follows:¹H NMR(600MHz,DMSO-d6):8.59(s,2H),8.36(d,J＝7.8Hz,2H),7.77(s,4H),7.60-7.55(m,8H),7.48-7.46(m,2H),7.41-7.37(m,4H),7.35-7.32(m,2H),4.27-4.26(m,2H),2.60(s,6H),2.15-2.10(m,1H),1.41-1.21(m,8H),0.93(t,J＝7.2Hz,3H),0.85(t,J＝7.2Hz,3H).¹³C NMR(150MHz,DMSO-d6):145.65,141.94,141.24,139.96,138.45,133.83,128.08,127.75,127.70,127.15,124.29,123.81,121.33,120.77,117.11,112.94,110.71,110.31,108.04,51.13,40.28,30.28,28.15,23.79,23.15,15.19,14.37,10.97.¹⁹f NMR (564MHz, DMSO-d6):113.66, which corresponds to the peak position and the number of hydrogens, can determine the structure of the material TM-III. The high resolution mass spectrum of the organic hole transport material TM-III is shown in FIG. 12, and the structural correctness is further confirmed by mass spectrum.

The material property is characterized, and as shown in a C diagram in FIG. 23, the HOMO energy level of TM-III is-5.17 eV by Cyclic Voltammetry (CV); as shown in FIG. 24, C, the maximum absorption peak in the solution state was measured by ultraviolet-visible absorption spectroscopy (UV-Vis) at 401nm, the absorption band edge was 465nm, and the optical band gap was 2.66eV, indicating that the HOMO level of the material TM-III was matched to the level of the perovskite. FIG. 25, C is a thermogravimetric analysis curve of the material with a thermal decomposition temperature at 426 deg.C, and FIG. 26, C is a differential scanning calorimetry curve of the material with a glass transition temperature T of TM-III_gAt 103 ℃ indicating that the material TM-III is goodThermal properties.

Example 6: 4-hexyl-2, 6-bis (9-phenyl-9H-carbazol-3-yl) -4H-dithio [3,2-b: synthesis and characterization of 2',3' -d ] pyrrole (TM-IV)

Synthetic route of TM-IV:

to a 50mL Schlenk reaction tube was added the compound 2, 6-dibromo-4-hexyl-4H-thieno [3,2-b:2',3' -d]Pyrrole (210mg, 0.5mmol), 9-phenyl-3- (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborolan-2-yl) -9H-carbazole (369mg, 1.0mmol), Pd (PPh)₃)₄(11mg，0.01mmol)，K₃PO₄·3H₂O (532mg, 2.0mmol) and 1, 4-dioxane (5mL) were reacted under nitrogen at 100 ℃ for 16 hours.

After the reaction, the reaction solution was cooled to room temperature, 50mL of water was added to the reaction solution, the aqueous phase was extracted three times with dichloromethane, and the organic phase was purified over anhydrous Na₂SO₄After drying, the solvent was removed by distillation under reduced pressure. The crude product was purified by column chromatography (petroleum ether: dichloromethane ═ 2: 1 as eluent) to give TM-iv (200mg, 53% yield) as a yellow solid.

Nuclear magnetic resonance hydrogen spectrum of organic hole transport material TM-IV (¹H NMR is shown in FIG. 13, nuclear magnetic resonance carbon spectrum: (¹³C NMR) as shown in fig. 14, the nuclear magnetic resonance characterization data is as follows:¹H NMR(600MHz,DMSO-d6):8.62(s,2H),8.36(d,J＝8.4Hz,2H),7.83(s,2H),7.79-7.77(m,2H),7.72-7.70(m,4H),7.67-7.65(m,4H),7.58-7.55(m,2H),7.49-7.46(m,2H),7.42-7.39(m,4H),7.35-7.33(m,2H),4.38(t,J＝7.2Hz,3H),1.96-1.91(m,2H),1.41-1.26(m,6H),0.85(t,J＝7.2Hz,3H).¹³c NMR (150MHz, DMSO-d6):156.56,145.37,141.97,141.19,139.90,137.17,130.73,128.28,128.14,127.17,127.14,124.29,123.87,123.16,121.33,120.82,117.13,112.98,110.72,110.32,108.02,43.95,31.39,30.44,26.54,22.61,14.39, and the structure of the material TM-IV can be determined by the peak positions and the number of hydrogens corresponding to them. MALDI-TOF mass spectrometry of organic hole transport materials TM-IV asThe accuracy of the structure is further demonstrated by mass spectrometry, as shown in figure 15.

The material itself was characterized by the HOMO level of TM-IV measured by Cyclic Voltammetry (CV) as-5.11 eV as shown in graph D of FIG. 23; as shown in graph D of FIG. 24, the maximum absorption peak in the solution state was at 402nm, the absorption band edge was 506nm, and the optical band gap was 2.45eV, as measured by ultraviolet-visible absorption spectroscopy (UV-Vis), indicating that the HOMO level of the material TM-IV was matched to the level of the perovskite. FIG. 25, Panel D, is a thermogravimetric analysis curve of a material having a thermal decomposition temperature of 416 deg.C; FIG. 26, Panel D, is a differential scanning calorimetry curve for the material, the glass transition temperature T of the material TM-IV_gThe temperature is 104 ℃, which shows that the material TM-IV has good thermal property.

Example 7: 4-hexyl-2, 6-bis (9- (4-methoxyphenyl) -9H-carbazol-3-yl) -4H-dithio [3,2-b: synthesis and characterization of 2',3' -d ] pyrrole (TM-V)

Synthetic route of TM-V:

to a 50mL Schlenk reaction tube was added the compound 2, 6-dibromo-4-hexyl-4H-thieno [3,2-b:2',3' -d]Pyrrole (187mg, 0.44mmol), intermediate 1(350mg, 0.89mmol), Pd (PPh)₃)₄(11mg，0.01mmol)，K₃PO₄·3H₂O (532mg, 2.0mmol) and 1, 4-dioxane (5mL) were reacted under nitrogen at 100 ℃ for 16 hours.

After the reaction, the reaction solution was cooled to room temperature, 50mL of water was added to the reaction solution, the aqueous phase was extracted three times with dichloromethane, and the organic phase was purified over anhydrous Na₂SO₄After drying, the solvent was removed by distillation under reduced pressure. The crude product was purified by column chromatography (petroleum ether: dichloromethane ═ 1: 1 as eluent) to give TM-v (250mg, yield 70%) as a yellow solid.

NMR spectrum of organic hole transport material TM-V ()¹H NMR As shown in FIG. 16, nuclear magnetic resonance carbon Spectroscopy: (¹³C NMR) Nuclear magnetic resonance as shown in FIG. 17Vibration characterization data are as follows:¹H NMR(600MHz,DMSO-d6):8.60(s,2H),8.34(d,J＝7.2Hz,2H),7.82-7.75(m,4H),7.56-7.54(m,4H),7.47-7.44(m,2H),7.34-7.30(m,6H),7.25-7.23(m,4H),4.38(s,2H),3.90(s,6H),1.96-1.91(m,2H),1.41-1.33(m,4H),1.32-1.24(m,2H),0.86(t,J＝7.8Hz,3H).¹³c NMR (150MHz, DMSO-d6):159.11,145.32,142.04,141.68,140.40,129.64,128.68,127.05,124.23,123.60,122.89,121.25,117.09,115.85,112.88,110.71,110.24,107.89,55.97,47.08,31.39,30.44,26.54,22.62,14.39, corresponding to which by peak position and number of hydrogens, the structure of the material TM-V can be determined. The high resolution mass spectrum of the organic hole transport material TM-v is shown in fig. 18, and the structural correctness is further demonstrated by mass spectrometry.

The material itself was characterized by a HOMO level of-5.14 eV, as measured by Cyclic Voltammetry (CV), as shown in Panel E of FIG. 23; as shown in FIG. 24, graph E, the maximum absorption peak in the solution state was at 404nm, the absorption band edge was 465nm, and the optical band gap was 2.66eV, as measured by ultraviolet-visible absorption spectroscopy (UV-Vis), indicating that the HOMO level of the material TM-V matches the energy level of the perovskite. FIG. 25, E, is a thermogravimetric analysis curve of the material with a thermal decomposition temperature of 436 deg.C, and FIG. 26, E, is a differential scanning calorimetry curve of the material with a glass transition temperature T of TM-V_g106 ℃ indicates that the material TM-V has good thermal performance.

Example 8: 2, 6-bis (9- (4-fluorophenyl) -9H-carbazol-3-yl) -4-hexyl-4H-dithio [3,2-b: synthesis and characterization of 2',3' -d ] pyrrole (TM-VI)

Synthetic route of TM-VI:

to a 50mL Schlenk reaction tube was added the compound 2, 6-dibromo-4-hexyl-4H-thieno [3,2-b:2',3' -d]Pyrrole (210mg, 0.5mmol), intermediate 2(387mg, 1.0mmol), Pd (PPh)₃)₄(11mg，0.01mmol)，K₃PO₄·3H₂O (532mg, 2.0mmol) and 1, 4-dioxane (5mL) under nitrogen 1The reaction was carried out at 00 ℃ for 16 hours.

After the reaction, the reaction solution was cooled to room temperature, 50mL of water was added to the reaction solution, the aqueous phase was extracted three times with dichloromethane, and the organic phase was purified over anhydrous Na₂SO₄After drying, the solvent was removed by distillation under reduced pressure. The crude product was purified by column chromatography (petroleum ether: dichloromethane ═ 2: 1 as eluent) to give TM-vi (240mg, yield 61%) as a yellow solid.

Nuclear magnetic resonance hydrogen spectrum of organic hole transport material TM-VI (¹H NMR As shown in FIG. 19, nuclear magnetic resonance carbon Spectroscopy: (¹³C NMR is shown in FIG. 20, nuclear magnetic resonance fluorine spectrum: (¹⁹F NMR) as shown in fig. 21, the nuclear magnetic resonance characterization data is as follows:¹H NMR(600MHz,DMSO-d6):8.61(s,2H),8.36(d,J＝7.8Hz,2H),7.83(s,2H),7.78(d,J＝8.4Hz,2H),7.73-7.69(m,4H),7.56-7.52(m,4H),7.49-7.46(m,2H),7.39-7.33(m,6H),4.38(t,J＝7.2Hz,3H),1.96-1.91(m,2H),1.41-1.26(m,6H),0.86(t,J＝7.2Hz,3H).¹³C NMR(150MHz,DMSO-d6):162.39,160.76,145.36,141.94,141.38,140.11,133.42,129.57,128.17,127.19,124.30,123.79,123.07,121.32,120.84,117.68,117.53,117.12,112.97,110.63,110.22,108.04,47.09,31.39,30.44,26.54,22.61,14.39.¹⁹f NMR (564MHz, DMSO-d6):113.67, which corresponds to the peak position and the number of hydrogens, can determine the structure of the material TM-VI. The high resolution mass spectrum of the organic hole transport material TM-VI is shown in FIG. 22, and the structural correctness is further confirmed by mass spectrum.

The material property is characterized, and as shown in a graph F in FIG. 23, the HOMO energy level of TM-VI is measured to be-5.16 eV by Cyclic Voltammetry (CV); as shown in graph F in FIG. 24, the maximum absorption peak in the solution state was found to be 404nm by ultraviolet-visible absorption spectroscopy (UV-Vis), the absorption band edge was 520nm, and the optical band gap was 2.38eV, indicating that the HOMO level of the material TM-VI matches the energy level of the perovskite. FIG. 25 is a thermogravimetric plot of the material at 414 deg.C for the thermal decomposition temperature, and FIG. 26 is a differential scanning calorimetry plot of the material at T, the glass transition temperature of TM-VI_gThe temperature is 104 ℃, which shows that the material TM-VI has good thermal performance.

Example 9: perovskite solar cells are prepared on the basis of hole transport materials TM-I-TM-VI.

(1) Preparing a hole transport layer solution: respectively dissolving the hole transport materials TM-I-TM-VI and the Spiro-OMeTAD prepared in the embodiments 3-8 in chlorobenzene at a concentration of 0.06mol/L, and stirring for 4-12 hours at normal temperature;

(2) preparing an electron transport layer: spin-coating 0.1mol/L tin oxide sol on FTO conductive glass by adopting a spin-coating method, wherein the spin-coating process comprises the following steps: 500r/min 3s, then 3000r/min 30s, and then annealing at 100 ℃ for 60 minutes to obtain an electron transport layer, wherein the thickness of the electron transport layer is 30 nm;

(3) preparing a perovskite active layer: lead iodide and iodomethylamine with the mass ratio of 1: 0.8-1.15 are mixed and stirred in a solvent of N-N-dimethylformamide and dimethyl sulfoxide with the volume ratio of 4:1 for 12 hours to prepare perovskite precursor liquid. And (3) spin-coating the perovskite precursor liquid on the surface coated with the electron transport layer in the step (2) by adopting a spin-coating method, wherein the spin-coating process comprises the following steps: 800r/min 3s, then 4000r/min 30s, and 400 microliter of chlorobenzene is dripped in the spin coating process to be used as an anti-solvent, and then annealing is carried out for 15 minutes at 100 ℃ to obtain a perovskite light absorption layer, wherein the thickness of the perovskite light absorption layer is 450 nm;

(4) preparing a hole transport layer: respectively spin-coating the prepared hole transport layer solution in the step (1) on the surface coated with the perovskite layer by adopting a spin-coating method, wherein the spin-coating process is 500r/min 3s, and then 5000r/min 30s, so as to prepare a hole transport layer, wherein the thickness of the hole transport layer is 180 nm;

(5) and (3) silver electrode evaporation: arranging a silver electrode on the surface of the hole transport layer by adopting a thermal evaporation method, wherein the thickness of the silver electrode is 80 nm; the rate of thermal evaporation is

The thermal evaporation time was 10 min.

The perovskite solar cell prepared has the structure that: FTO/SnO₂/CH₃NH₃PbI₃(ii)/HTL/Ag as shown in FIG. 27. The illumination intensity is 100mW/cm²AM1.5 under simulated sunlight, based on different spaceVarious photovoltaic parameters of devices made of hole transport materials TM-I-TM-VI are shown in the following table 1, J-V characteristic curves of the devices are shown in a graph 28, and differences of conversion efficiencies of perovskite solar cells prepared based on different hole transport materials are found, which shows that accumulation of different side chain adjustable molecules is introduced on a parent nucleus, hole extraction capacity of adjustable molecules with different substituent groups is introduced on a carbazole end group, and compared with TM-I, TM-II and TM-III, a conjugated system is increased by introducing electron groups with lone pairs on side chains, and the charge transport performance of the materials is improved. Among them, devices based on TM-II and TM-III showed photoelectric conversion efficiency > 18% (18.12% and 18.02%), which is close to spiro-OMeTAD (19.98%), and have huge application potential.

TABLE 1 photovoltaic parameters of devices based on different hole transport materials

It should be noted that the above-mentioned are only non-limiting embodiments of the present invention and any modification or change by a person skilled in the art within the meaning and range equivalent to the technical solution of the present invention should be considered to be included in the protection scope of the present invention.

Claims

1. A hole transport material characterized in that the hole transport material has the following structural formula:

wherein R is n-hexyl or 2-ethylhexyl; x is a hydrogen atom, an alkoxy group or a halogen atom.

2. A method for synthesizing a hole transport material according to claim 1, comprising the steps of:

3. The method for synthesizing a hole transport material according to claim 2, wherein: in the step (1), the molar ratio of the 3-bromo-9-phenyl-9-H-carbazole derivative to the pinacol ester diboron is 1: (1.5-2); the 3-bromo-9-phenyl-9-H-carbazole derivative is 3-bromo-9- (4-phenyl) -9H-carbazole, 3-bromo-9- (4-methoxyphenyl) -9H-carbazole, or 3-bromo-9- (4-fluorophenyl) -9H-carbazole, and the 9-phenyl-3- (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborolan-2-yl) -9H-carbazole derivative is 9- (4-phenyl) -3- (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborolan-2-yl) -9H-carbazole, 9- (4-methoxyphenyl) -3- (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborane-2-yl) -9H-carbazole or 9- (4-fluorophenyl) -3- (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborane-2-yl) -9H-carbazole.

4. The method for synthesizing a hole transport material according to claim 2, wherein: in the step (1), the catalyst a is dichloro [1,1' -bis (diphenylphosphino) ferrocene]Palladium (Pd (dppf) Cl₂) The amount relationship between the 3-bromo-9-phenyl-9-H-carbazole derivative and the amount of the compound is (0.02-0.1): 1; in the step (1), the alkali a is potassium acetate (AcOK), and the quantitative relation between the alkali a and the pinacol ester diboron is (2-3): 1.

5. the method of synthesizing a hole transport material according to claim 2, wherein: in the step (2), the molar ratio of the 2, 6-dibromo-4-hydrogen-dithiophene [3,2-b:2',3' -d ] pyrrole derivative to the 9-phenyl-3- (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborane-2-yl) -9H-carbazole derivative is 1 (2-3); the 2, 6-dibromo-4-hydro-dithieno [3,2-b:2',3' -d ] pyrrole derivative is 2, 6-dibromo-4- (2-ethylhexyl) -4H-dithieno [3,2-b:2,3-d ] pyrrole or 2, 6-dibromo-4- (2-hexyl) -4H-dithieno [3,2-b:2',3' -d ] pyrrole.

6. The method for synthesizing a hole transport material according to claim 2, wherein: in the step (2), the catalyst b is tris (dibenzylidene) acetone dipalladium (Pd)₂dba₃) With 2, 6-dibromo-4-hydro-dithiophene [3,2-b:2',3' -d]The amount of the pyrrole derivative is (0.02-0.1): 1; the alkali b in the step (2) is potassium phosphate trihydrate (K)₃PO₄·3H₂O) in a mass relationship with 9-phenyl-3- (4,4,5, 5-tetramethyl-1, 3, 2-dioxaborolan-2-yl) -9H-carbazole derivative of (2 to 3): 1.

7. the method for synthesizing a hole transport material according to claim 2, wherein: in the steps (1) to (2), the organic solvent is anhydrous 1, 4-dioxane, and the reaction is carried out in a Schlenk reaction tube; the reaction temperature of the mixing reaction in the step (1) is 90-110 ℃, and the reaction time is 16-20 hours; the reaction temperature of the reaction in the step (2) is 100-120 ℃, and the reaction time is 16-20 hours.

8. Use of the hole transport material of claim 1 in a perovskite solar cell.

9. The perovskite solar cell is characterized in that the perovskite solar cell is respectively provided with a transparent substrate layer, an electron transport layer, a perovskite active layer, a hole transport layer, a hole barrier layer and a metal electrode layer from bottom to top: the hole transport layer is mainly made of the hole transport material which takes dithieno [3,2-b:2',3' -d ] pyrrole as a core and carbazole as an end group in claim 1.

10. The trans-perovskite solar cell of claim 9, wherein: the transparent substrate layer is fluorine-doped tin oxide conductive glass (FTO); the electron transmission layer is made of tin dioxide and has the thickness of 20-40 nm; the perovskite active layer is made of methylamine lead iodide, and the general formula of the chemical structure of the perovskite active layer is CH₃NH₃PbI₃The thickness is 350-450 nm; the thickness of the hole transport layer is 150-200 nm, the material of the metal electrode layer is silver, and the thickness is 80-100 nm.