Indole compound as well as preparation method and application thereof

Abstract

The invention relates to an indole compound as well as a preparation method and application thereof. The indole compound has a molecular structure represented by a general formula (1) or a general formula (2): # imgabs0 # (1) and # imgabs1 # (2), in which each R1 is selected from one of a hydrogen atom, a halogen atom, a cyano group, a C1-C6 alkoxy group and a C1-C10 alkyl group; and each R2 is selected from one of a substituted or unsubstituted aryl group and a substituted or unsubstituted heteroaryl group. The indole compound has excellent hole transport capability, and by connecting aryl or heteroaryl with an indole unit, the energy level structure is optimized, good energy level matching with a perovskite material is realized, the hole extraction performance is improved, the dipole moment of the compound is improved, the formation of a built-in electric field is facilitated, and the photoelectric conversion efficiency is further improved. The cyano phosphonic acid group or the cyano carboxylic acid group enables the compound to form a strong acting force with the perovskite material, so that the wettability is improved, and the interface stability can be enhanced.

Description

Technical Field

[0001] The present invention relates to the field of photovoltaic technology, and in particular to an indole compound and a preparation method and application thereof. Background Art

[0002] As the third generation of photovoltaic cells, perovskite solar cells have a theoretical photoelectric conversion efficiency of up to 31%, and the current highest photoelectric efficiency has exceeded 26.1%. However, perovskite solar cells still have problems such as poor stability and difficulty in large-scale preparation, resulting in their commercial development far behind traditional crystalline silicon cells.

[0003] In perovskite solar cells, a hole transport layer is usually set on one side of the perovskite light absorption layer to play an important role in hole extraction and transportation and electron blocking. However, traditional hole transport materials have problems such as insufficient stability and poor wettability with the substrate. Summary of the invention

[0004] Based on this, it is necessary to provide an indole compound and a preparation method and application thereof to solve the problems of insufficient stability and poor wettability with substrates of traditional hole transport materials.

[0005] The scheme of the present invention is as follows:

[0006] An indole compound having a molecular structure represented by general formula (1) or general formula (2):

[0007] (1)

[0008] (2),

[0009] Among them, each R 1 One selected from the group consisting of a hydrogen atom, a halogen atom, a cyano group, a C1~C6 alkoxy group, and a C1~C10 alkyl group;

[0010] Each R 2 One selected from a substituted or unsubstituted aryl group, and a substituted or unsubstituted heteroaryl group.

[0011] In one embodiment, each R 2 In the above-mentioned formula, the number of ring atoms of the aryl group is 6 to 30.

[0012] In one embodiment, each R 2 In the above, the aromatic group is one of benzene, biphenyl, naphthalene, anthracene, phenanthrene, pyrene, diphenylene and triphenylene.

[0013] In one embodiment, each R 2 Selected from one of the following groups:

[0014] ,

[0015] Among them, each R 3 One selected from the group consisting of a hydrogen atom, a halogen atom, a cyano group, a C1~C6 alkoxy group, and a C1~C10 alkyl group;

[0016] * represents the binding point.

[0017] In one embodiment, each R 2 In the above, the number of ring atoms of the heteroaryl group is 5 to 30; and / or

[0018] The heteroaryl group contains at least one heteroatom of O and S.

[0019] In one embodiment, each R 2 In the above, the heteroaryl group is one of furan, benzofuran, thiophene, benzothiophene, thienothiophene, furanopyrrole, furanofuran, and thienofuran.

[0020] In one embodiment, each R 2 Selected from one of the following groups:

[0021] ,

[0022] Among them, each R 4 One selected from the group consisting of a hydrogen atom, a halogen atom, a cyano group, a C1~C6 alkoxy group, and a C1~C10 alkyl group;

[0023] * represents the binding point.

[0024] A method for preparing the indole compound comprises the following steps:

[0025] Step S1, taking compound A, compound B and a first catalyst to react in a first solvent to prepare an intermediate C;

[0026] Step S2, reacting the intermediate C, diethyl cyanomethyl phosphate and the second catalyst in a second solvent to prepare an intermediate D;

[0027] Step S3, taking the intermediate D and trimethylsilyl bromide to react in a third solvent, adding methanol to the reaction product after drying, and then adding water dropwise until the reaction liquid becomes a white suspension, and continuing the reaction to obtain an indole compound represented by the general formula (1);

[0028] Alternatively, in step S4, intermediate C, cyanoacetic acid and a third catalyst are reacted in a fourth solvent to prepare an indole compound represented by general formula (2);

[0029] Wherein, the molecular structure of the compound A is shown in general formula (3):

[0030] (3),

[0031] In general formula (3), R 1 One selected from the group consisting of a hydrogen atom, a halogen atom, a cyano group, a C1~C6 alkoxy group, and a C1~C10 alkyl group;

[0032] The molecular structure of the compound B is shown in general formula (4):

[0033] (4),

[0034] In general formula (4), R 2 One selected from substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl;

[0035] The molecular structure of the intermediate C is shown in general formula (5):

[0036] (5);

[0037] The molecular structure of the intermediate D is shown in general formula (6):

[0038] (6).

[0039] In one embodiment, in step S1, the first catalyst includes cuprous iodide and potassium carbonate, and the molar ratio of the compound A, the compound B, cuprous iodide and potassium carbonate is 1:(2-3):(1.5-2):(3-4);

[0040] In one embodiment, in step S1, the reaction temperature is 100° C. to 110° C., and the reaction time is 16-24 hours.

[0041] In one embodiment, in step S2, the second catalyst is piperidine;

[0042] In one embodiment, in step S2, the molar ratio of the intermediate C to diethyl cyanomethyl phosphate is 1: (2-2.5);

[0043] In one embodiment, in step S2, the reaction temperature is 90-100° C., and the reaction time is 16-24 hours.

[0044] In one embodiment, in step S3, the molar ratio of intermediate D to trimethylsilyl bromide is 1:(2-3);

[0045] In one embodiment, in step S3, the reaction temperature is 25-40° C., and the reaction time is 12-16 hours.

[0046] In one embodiment, in step S4, the third catalyst is piperidine;

[0047] In one embodiment, in step S4, the molar ratio of the intermediate C to cyanoacetic acid is 1: (1.1-2);

[0048] In one embodiment, in step S4, the reaction temperature is 70-80° C., and the reaction time is 12-16 hours.

[0049] Application of the indole compound described in any of the above embodiments as a hole transport material.

[0050] A solar cell comprises a substrate, a hole transport layer, a perovskite light absorption layer, an electron transport layer and an electrode layer which are stacked in sequence, wherein the hole transport layer comprises the indole compound described in any one of the above embodiments.

[0051] In one embodiment, the perovskite light absorbing layer comprises a perovskite material ABX 3 ; wherein A includes one or more of cesium ion, rubidium ion, potassium ion, methylamine ion, formamidine ion, methylenediamine ion, benzamidine cation and guanidinium cation; B includes one or more of lead ion, copper ion, zinc ion, gallium ion, tin ion and calcium ion; X includes one or more of fluoride ion, chloride ion, bromide ion, iodide ion, thiocyanate ion, tetrafluoroborate ion, hexafluorophosphate ion, formate ion and acetate ion.

[0052] The material of the electron transport layer includes one or more of zinc oxide, tin oxide, titanium dioxide, strontium titanate, zinc stannate, zirconium dioxide, aluminum oxide, tungsten trioxide, cesium oxide, cadmium sulfide, cadmium selenide, barium stannate, niobium pentoxide, fullerene and fullerene derivatives.

[0053] Compared with the traditional scheme, the above-mentioned indole compounds have the following beneficial effects:

[0054] The above-mentioned indole compounds use indole units as the parent core, have excellent hole transport capabilities, and are constructed by connecting aromatic or heteroaromatic groups to indole units to construct a rigid skeleton, thereby optimizing the energy level structure of the compound, achieving good energy level matching with the perovskite material, improving the hole extraction performance, and increasing the dipole moment of the compound, which is conducive to the formation of a built-in electric field, thereby improving the photoelectric conversion efficiency. By connecting cyanophosphonic acid groups or cyanocarboxylic acid groups to indole units, the compound can form a strong force with the perovskite material, improve its wettability with the perovskite material, improve the uniformity of film formation, and facilitate the preparation of large-area perovskite solar cells, and enhance the interface stability between the perovskite light absorption layer and the hole transport layer, thereby improving the stability of the battery operation.

[0055] When R 1 When selected from halogen atoms, cyano groups, C1~C6 alkoxy groups, and C1~C10 alkyl groups, it can improve its wettability with perovskite materials, improve film formation uniformity, and facilitate the preparation of large-area perovskite solar cells. BRIEF DESCRIPTION OF THE DRAWINGS

[0056] FIG. 1 is a schematic structural diagram of a solar cell according to an embodiment. DETAILED DESCRIPTION

[0057] In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the relevant drawings. The preferred embodiments of the present invention are shown in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. The purpose of providing these embodiments is to make the understanding of the disclosure of the present invention more thorough and comprehensive.

[0058] It should be noted that when an element is referred to as being "disposed on" another element, it may be directly on the other element or there may be a central element. When an element is considered to be "connected to" another element, it may be directly connected to the other element or there may be a central element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are for illustrative purposes only and do not represent the only implementation method.

[0059] In the description of the present invention, it should be understood that the terms "first" and "second" are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number or order of the indicated technical features.

[0060] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which the present invention belongs. The terms used herein in the specification of the present invention are only for the purpose of describing specific embodiments and are not intended to limit the present invention. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0061] Unless otherwise specified or incompatible herewith, the terms and phrases used herein shall have the following meanings:

[0062] The term "alkyl" refers to a saturated hydrocarbon containing primary carbon atoms, secondary carbon atoms, tertiary carbon atoms, quaternary carbon atoms, or a combination thereof. Phrases containing this term, for example, "C1-C9 alkyl" refers to an alkyl group containing 1 to 9 carbon atoms, each occurrence of which can be independently C1 alkyl, C2 alkyl, C3 alkyl, C4 alkyl, C5 alkyl, C6 alkyl, C7 alkyl, C8 alkyl or C9 alkyl. Alkyl groups can be straight-chain or branched. Suitable examples include, but are not limited to, methyl (Me, -CH 3 ), ethyl (Et, -CH 2 CH 3 ), 1-propyl (n-Pr, n-propyl, -CH 2 CH 2 CH 3 ), 2-propyl (i-Pr, i-propyl, -CH (CH 3 ) 2 ), 1-butyl (n-Bu, n-butyl, -CH 2 CH 2 CH 2 CH 3 ), 2-methyl-1-propyl (i-Bu, i-butyl, -CH 2 CH(CH 3 ) 2 ), 2-butyl (s-Bu, s-butyl, -CH (CH 3 )CH 2 CH 3 ), 2-methyl-2-propyl (t-Bu, t-butyl, -C(CH 3 ) 3 ), 1-pentyl (n-pentyl, -CH 2 CH 2 CH 2 CH 2 CH 3 ), 2-pentyl (-CH(CH 3 )CH 2 CH 2 CH 3 ), 3-pentyl (-CH(CH 2 CH 3 ) 2 ), 2-methyl-2-butyl (-C(CH 3 ) 2 CH 2 CH 3 ), 3-methyl-2-butyl (-CH(CH 3 )CH(CH 3 ) 2 ), 3-methyl-1-butyl (-CH 2 CH2 CH(CH 3 ) 2 ), 2-methyl-1-butyl (-CH 2 CH(CH 3 )CH 2 CH 3 )、1-hexyl (-CH 2 CH 2 CH 2 CH 2 CH 2 CH 3 ), 2-hexyl (-CH(CH 3 )CH 2 CH 2 CH 2 CH 3 )、3-hexyl(-CH(CH 2 CH 3 )(CH 2 CH 2 CH 3 ))、2-methyl-2-pentyl (-C(CH 3 ) 2 CH 2 CH 2 CH 3 ), 3-methyl-2-pentyl (-CH(CH 3 )CH(CH 3 )CH 2 CH 3 ), 4-methyl-2-pentyl (-CH(CH 3 )CH 2 CH(CH 3 ) 2 ), 3-methyl-3-pentyl (-C(CH 3 )(CH 2 CH 3 ) 2 ), 2-methyl-3-pentyl (-CH(CH 2 CH 3 )CH(CH 3 ) 2 )、2,3-dimethyl-2-butyl (-C(CH 3 ) 2 CH(CH 3 ) 2 )、3,3-dimethyl-2-butyl (-CH(CH 3 )C(CH 3 ) 3 and octyl (-(CH 2 ) 7 CH 3 ).

[0063] The term "alkoxy" refers to a group having an -O-alkyl group, i.e., an alkyl group as defined above connected to a core structure via an oxygen atom. Phrases containing this term, for example, "C1-C9 alkoxy" means that the alkyl portion contains 1 to 9 carbon atoms, and each occurrence may be independently C1 alkoxy, C4 alkoxy, C5 alkoxy, C6 alkoxy, C7 alkoxy, C8 alkoxy or C9 alkoxy. Alkoxy groups may be straight-chain or branched. Suitable examples include, but are not limited to, methoxy (-O-CH 3 or -OMe), ethoxy (-O-CH 2 CH 3 or -OEt) and tert-butyloxy (-OC(CH 3 ) 3 or -OtBu).

[0064] "Aryl" refers to an aromatic hydrocarbon group derived from an aromatic ring compound by removing a hydrogen atom, which can be a monocyclic aromatic group, a condensed aromatic group, or a polycyclic aromatic group. For polycyclic rings, at least one is an aromatic ring system. For example, "C5-C20 aromatic group" refers to an aromatic group containing 5 to 20 carbon atoms, and each occurrence can be independently C5 aromatic group, C6 aromatic group, C10 aromatic group, C14 aromatic group, C18 aromatic group, C20 aromatic group, etc. Suitable examples include, but are not limited to, benzene, biphenyl, naphthalene, anthracene, phenanthrene, pyrene, perylene, triphenylene, and their derivatives.

[0065] "Heteroaryl" means that at least one carbon atom in an aryl group is replaced by a non-carbon atom, and the non-carbon atom may be an N atom, an O atom, an S atom, etc. For example, "C3-C10 heteroaryl" means a heteroaryl group containing 3 to 10 carbon atoms, and each occurrence may be independently C3 heteroaryl, C4 heteroaryl, C5 heteroaryl, C6 heteroaryl, C7 heteroaryl, C8 heteroaryl, etc. Suitable examples include, but are not limited to, furan, benzofuran, thiophene, benzothiophene, pyrrole, pyrazole, triazole, imidazole, oxazole, oxadiazole, thiazole, tetrazole, indole, carbazole, pyrroloimidazole, pyrrolopyrrole, thienopyrrole, thienothiophene, furanopyrrole, furanofuran, thienofuran, benzisoxazole, benzisothiazole, benzimidazole, pyridine, pyrazine, pyridazine, pyrimidine, triazine, quinoline, isoquinoline, o-naphthylidene, quinoxaline, phenanthridine, primidine, quinazoline, and quinazolinone.

[0066] "Halogen" or "halo" refers to F, Cl, Br or I.

[0067] In the present invention, the single bond connecting the substituent runs through the corresponding ring, indicating that the substituent can be connected to any optional position of the ring, and the number of the substituent is not limited to only one, and multiple substituents can be connected to any optional position of the ring. For example, Medium R 3 It can be connected to any substitutable position of the benzene ring, and R 3 It is not limited to just one, there can also be two, three, four or five.

[0068] The indole compounds provided by the present invention have a molecular structure represented by the general formula (1) or the general formula (2):

[0069] (1)

[0070] (2).

[0071] Among them, each R 1 One selected from a hydrogen atom, a halogen atom, a cyano group, a C1~C6 alkoxy group, and a C1~C10 alkyl group.

[0072] Each R 2 One selected from a substituted or unsubstituted aryl group, and a substituted or unsubstituted heteroaryl group.

[0073] When R 1 When selected from one of halogen atoms, cyano groups, C1~C6 alkoxy groups, and C1~C10 alkyl groups, it can improve the wettability of the compound with the perovskite material, improve the uniformity of film formation, and is conducive to the preparation of large-area perovskite solar cells.

[0074] When R 1 When selected from halogen atoms and cyano groups, on the one hand, halogen atoms and cyano groups have lone pairs of electrons, which can enhance the coordination ability of the compound with the perovskite material and improve the performance of hole extraction; on the other hand, halogen atoms and cyano groups are electron-withdrawing groups, which can regulate the molecular dipole moment, which is beneficial to the formation of a built-in electric field, thereby improving the conversion efficiency.

[0075] Each R 2 One selected from substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl. By connecting the aryl or heteroaryl to the indole molecule, the energy level structure of the compound is optimized, a good energy level match with the perovskite material is achieved, the hole extraction performance is improved, and the dipole moment of the compound is increased, which is conducive to the formation of a built-in electric field, thereby improving the conversion efficiency.

[0076] Each R 2 In the embodiment, the number of ring atoms of the aryl group is preferably 6 to 30. Specifically, the number of ring atoms of the aryl group may be 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 or 30. Further, the number of ring atoms of the aryl group is preferably 6 to 20.

[0077] The aryl group is, for example, one of benzene, biphenyl, naphthalene, anthracene, phenanthrene, pyrene, perylene and triphenylene.

[0078]

[0079] Among them, each R 3 One selected from hydrogen atom, halogen atom, cyano group, C1~C6 alkoxy group, C1~C10 alkyl group. * represents the binding site.

[0080] Each R 2 In the heteroaryl group, the number of ring atoms is preferably 5 to 30. Specifically, the number of ring atoms may be 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29 or 30. Further, the number of ring atoms of the heteroaryl group is preferably 5 to 15.

[0081] In some examples, the heteroaryl group contains at least one heteroatom of O and S. The introduction of atoms having lone electron pairs such as O and S improves the wettability of the compound with the perovskite material and improves the quality of the perovskite film.

[0082] The heteroaryl group is, for example, one of furan, benzofuran, thiophene, benzothiophene, thienothiophene, furanopyrrole, furanofuran, and thienofuran.

[0083] In some examples, the substituent on the aryl group is selected from one of a halogen atom, a cyano group, a C1-C6 alkoxy group, and a C1-C10 alkyl group. Further, the substituent on the aryl group is selected from one of a halogen atom and a cyano group.

[0084] In some examples, the substituent on the heteroaryl group is selected from one of a halogen atom, a cyano group, a C1-C6 alkoxy group, and a C1-C10 alkyl group. Further, the substituent on the heteroaryl group is selected from one of a halogen atom and a cyano group.

[0085] In some examples, R 2 Selected from one of the following groups:

[0086]

[0087] Among them, each R 4 One selected from hydrogen atom, halogen atom, cyano group, C1~C6 alkoxy group, C1~C10 alkyl group. * represents the binding site.

[0088] As a substituent on an aryl or heteroaryl group, R 3When selected from one of halogen atoms, cyano groups, C1~C6 alkoxy groups, and C1~C10 alkyl groups, it can improve the wettability of the compound with the perovskite material, improve the uniformity of film formation, and is conducive to the preparation of large-area perovskite solar cells.

[0089] When R 3 When selected from halogen atoms and cyano groups, on the one hand, halogen atoms and cyano groups have lone pairs of electrons, which can enhance the coordination ability of the compound with the perovskite material and improve the performance of hole extraction; on the other hand, halogen atoms and cyano groups are electron-withdrawing groups, which can regulate the molecular dipole moment, which is beneficial to the formation of a built-in electric field, thereby improving the conversion efficiency.

[0090] The above-mentioned indole compounds use indole units as the parent core, have excellent hole transport capabilities, and are constructed by connecting aromatic or heteroaromatic groups to indole units to construct a rigid skeleton, thereby optimizing the energy level structure of the compound, achieving good energy level matching with the perovskite material, improving the hole extraction performance, and increasing the dipole moment of the compound, which is conducive to the formation of a built-in electric field, thereby improving the photoelectric conversion efficiency. By connecting cyanophosphonic acid groups or cyanocarboxylic acid groups to indole units, the compound can form a strong force with the perovskite material, improve its wettability with the perovskite material, improve the uniformity of film formation, and facilitate the preparation of large-area perovskite solar cells, and enhance the interface stability between the perovskite light absorption layer and the hole transport layer, thereby improving the stability of the battery operation.

[0091] When R 1 When selected from halogen atoms, cyano groups, C1~C6 alkoxy groups, and C1~C10 alkyl groups, it can improve its wettability with perovskite materials, improve film formation uniformity, and facilitate the preparation of large-area perovskite solar cells.

[0092] Furthermore, the present invention also provides a method for preparing any of the above-mentioned indole compounds.

[0093] For the indole compound represented by the general formula (1), the method comprises the following steps:

[0094] Step S1, taking compound A, compound B and a first catalyst to react in a first solvent to prepare an intermediate C;

[0095] Step S2, reacting the intermediate C, diethyl cyanomethyl phosphate and piperidine in a second solvent to prepare an intermediate D;

[0096] Step S3, taking the intermediate D and trimethylsilyl bromide to react in a third solvent, the reaction product is spin-dried and methanol is added, and then water is added dropwise until the reaction liquid becomes a white suspension, and the reaction is continued to obtain an indole compound represented by the general formula (1).

[0097] Wherein, the molecular structure of compound A is shown in general formula (3):

[0098] (3),

[0099] In general formula (3), R 1 One selected from the group consisting of a hydrogen atom, a halogen atom, a cyano group, a C1~C6 alkoxy group, and a C1~C10 alkyl group;

[0100] The molecular structure of compound B is shown in general formula (4):

[0101] (4),

[0102] In general formula (4), R 2 One selected from substituted or unsubstituted aryl, substituted or unsubstituted heteroaryl;

[0103] The molecular structure of intermediate C is shown in general formula (5):

[0104] (5);

[0105] The molecular structure of intermediate D is shown in general formula (6):

[0106] (6).

[0107] For the indole compound represented by the general formula (2), the intermediate C can be prepared by the above step S1, and then:

[0108] Step S4, taking the intermediate C, cyanoacetic acid and the third catalyst to react in a fourth solvent to prepare an indole compound represented by the general formula (2).

[0109] The chemical reaction formula of the above reaction is as follows.

[0110]

[0111]

[0112] In some examples, in step S1, the reaction is carried out under a protective atmosphere, such as one or more of an inert gas such as argon and nitrogen.

[0113] In some examples, in step S1, the molar ratio of compound A to compound B is 1:(2-3), specifically 1:2, 1:2.1, 1:2.2, 1:2.3, 1:2.4, 1:2.5, 1:2.6, 1:2.7, 1:2.8, 1:2.9, 1:3, etc.

[0114] In some examples, in step S1, the first catalyst includes cuprous iodide (CuI) and potassium carbonate (K 2 CO 3 ). Further, the molar ratio of compound A, compound B, cuprous iodide and potassium carbonate is 1:(2-3):(1.5-2):(3-4).

[0115] In some examples, in step S1 , the first solvent is selected from at least one of toluene (PhMe), N,N-dimethylformamide (DMF), and tetrahydrofuran (THF).

[0116] In some examples, in step S1, the reaction temperature is 100°C-110°C, specifically 100°C, 101°C, 102°C, 103°C, 104°C, 105°C, 106°C, 107°C, 108°C, 109°C, 110°C, etc. The reaction time is 16-24 hours.

[0117] In some examples, in step S1, the reaction is quenched by a DCM / water system. After the reaction is completed, the product is purified. The purification can be performed by column chromatography.

[0118] In some examples, step S1 specifically includes:

[0119] Under a protective atmosphere, compound A, cuprous iodide and potassium carbonate are dissolved in a first solvent, the gas is evacuated to remove dissolved oxygen, and compound B is added, and the mixture is refluxed at 100°C to 110°C for 16-24 hours; after the reaction is completed, the mixture is quenched with a DCM / water system, purified by column chromatography after quenching, and dried to obtain intermediate C. The molar ratio of compound A, compound B, cuprous iodide and potassium carbonate is 1:(2-3):(1.5-2):(3-4).

[0120] In some examples, in step S2, the reaction is carried out under a protective atmosphere, such as one or more of an inert gas such as argon and nitrogen.

[0121] In some examples, in step S2, the second catalyst may be piperidine.

[0122] In some examples, in step S2, the molar ratio of intermediate C to diethyl cyanomethyl phosphate is 1:(2-2.5), specifically 1:2, 1:2.05, 1:2.1, 1:2.15, 1:2.2, 1:2.25, 1:2.3, 1:2.35, 1:2.4, 1:2.45, 1:2.5, etc.

[0123] In some examples, in step S2, the second solvent is selected from at least one of toluene, N,N-dimethylformamide, and tetrahydrofuran.

[0124] In some examples, in step S2, the reaction temperature is 90-100° C. and the reaction time is 16-24 hours.

[0125] In some examples, in step S2, the reaction is quenched by a DCM / water system. After the reaction is completed, the product is purified. Purification can be performed by column chromatography.

[0126] In some examples, step S2 specifically includes:

[0127] Under a protective atmosphere, intermediate C and diethyl cyanomethyl phosphate are dissolved in a second solvent, a second catalyst is added, and the mixture is refluxed at 90-100° C. for 16-24 hours; the mixture is quenched with a DCM / water system, and then purified by column chromatography and dried to obtain intermediate D.

[0128] In some examples, in step S3, the reaction is carried out under a protective atmosphere, such as one or more of an inert gas such as argon and nitrogen.

[0129] In step S3, the molar ratio of the intermediate D to trimethylsilyl bromide is 1:(2-3), for example, 1:2, 1:2.1, 1:2.2, 1:2.3, 1:2.4, 1:2.5, 1:2.6, 1:2.7, 1:2.8, 1:2.9, 1:3, etc.

[0130] In some examples, in step S3, the third solvent is selected from at least one of 1,4-dioxane and dichloromethane (DCM).

[0131] In some examples, in step S3, the reaction temperature is 25-40° C. The reaction time is 12-16 hours. After water is added dropwise until the reaction liquid becomes a white suspension, the reaction time is continued for 6-8 hours.

[0132] In some examples, step S3 specifically includes:

[0133] Under a protective atmosphere, the intermediate D is dissolved in a third solvent, trimethylsilyl bromide is added dropwise, and the reaction is carried out at 25°C for 12-16 hours. The reaction product is dried by spin drying, methanol is added, and water is added dropwise until the reaction liquid becomes a white suspension, and the reaction is continued for 6-8 hours. After the reaction is completed, the indole compound represented by the general formula (1) is obtained by filtering and washing.

[0134] In some examples, in step S4, the reaction is carried out under a protective atmosphere, such as one or more of an inert gas such as argon and nitrogen.

[0135] In some examples, in step S4, the third catalyst may be piperidine.

[0136] In some examples, in step S4, the molar ratio of intermediate C to cyanoacetic acid is 1:(1.1-2), specifically 1:1.1, 1:1.11, 1:1.12, 1:1.13, 1:1.14, 1:1.15, 1:1.16, 1:1.17, 1:1.18, 1:1.19, 1:1.2, etc.

[0137] In some examples, in step S4, the reaction temperature is 70-80° C. and the reaction time is 12-16 hours.

[0138] In some examples, in step S4, the fourth solvent is selected from at least one of toluene and acetic acid.

[0139] In some examples, in step S4, the reaction is quenched by a DCM / water system. After the reaction is completed, the product is purified. Purification can be performed by column chromatography.

[0140] In some examples, step S4 specifically includes:

[0141] Under a protective atmosphere, the intermediate C and cyanoacetic acid are dissolved in a fourth solvent, a third catalyst is added, and the mixture is refluxed at 70-80° C. for 12-16 hours. The reaction is quenched with a DCM / water system, and after quenching, the mixture is purified by column chromatography and dried to obtain an indole compound represented by the general formula (2).

[0142] The present invention also provides the use of the indole compound as a hole transport layer.

[0143] The invention also provides a solar cell.

[0144] As shown in FIG. 1 , a solar cell according to an embodiment includes a substrate 110 , a hole transport layer 120 , a perovskite light absorption layer 130 , an electron transport layer 140 , and an electrode layer 150 , which are stacked in sequence.

[0145] The perovskite light absorbing layer 130 includes a perovskite material (ABX 3 ). Wherein, A is a monovalent cation, including but not limited to one or more of cesium ion, rubidium ion, potassium ion, methylamine ion, formamidinium ion, methylenediamine ion, benzamidinium cation and guanidinium cation. B is a divalent cation, including but not limited to one or more of lead ion, copper ion, zinc ion, gallium ion, tin ion and calcium ion. X is a monovalent anion, including but not limited to one or more of fluoride ion, chloride ion, bromide ion, iodide ion, thiocyanate ion, tetrafluoroborate ion, hexafluorophosphate ion, formate ion and acetate ion.

[0146] Optionally, the thickness of the perovskite light absorbing layer 130 may be 0.1 μm to 10 μm, and more specifically, for example, 0.1 μm, 0.5 μm, 1 μm, 2 μm, 4 μm, 6 μm, 8 μm, 10 μm, etc.

[0147] The material of the substrate 110 can be a conductive oxide, for example, it can be but not limited to one or more of indium tin oxide (ITO), aluminum-doped zinc oxide (AZO), indium-doped zinc oxide (IZO), fluorine-doped tin oxide (FTO), indium tungsten oxide (IWO), indium cerium oxide (ICO) and the like.

[0148] Optionally, the material of the electron transport layer 140 may be, but is not limited to, ZnO (zinc oxide), SnO 2 (tin oxide), TiO 2 (TiO2), SrTiO 3 (Strontium titanate), Zn 2 SnO 4 (Zinc stannate), ZrO 2 (Zirconium dioxide), Al 2 O 3 (aluminum oxide), WO 3 (Tungsten trioxide), CeO x (cesium oxide), CdS (cadmium sulfide), CdSe (cadmium selenide), BaSnO 3 (barium stannate), Nb 2 O 5 (niobium pentoxide), C 60 (fullerene), PCBM (fullerene derivative) or more thereof.

[0149] In one example, the thickness of the electron transport layer is 1 nm to 30 nm. Further, in one example, the thickness of the electron transport layer is 5 nm to 20 nm. In some specific examples, the thickness of the electron transport layer is 2 nm, 5 nm, 8 nm, 12 nm, 15 nm, 18 nm, 20 nm, 22 nm, 25 nm, 27 nm, 29 nm, 30 nm, etc.

[0150] Optionally, the material of the electrode layer 150 may be, but is not limited to, one or more of metals such as Au, Ag, and Cu.

[0151] The solar cell 100 may be a single-layer perovskite cell or a tandem cell, wherein the tandem cell may be, for example, a perovskite / crystalline silicon tandem cell, a full perovskite tandem cell, a perovskite / organic tandem cell, a perovskite / CIGS tandem cell, a perovskite / CdTe tandem cell, a perovskite / GaAs tandem cell, etc.

[0152] The following specific examples are provided to further illustrate the present invention. The present invention provides the following specific examples for a better understanding of the present invention, but is not limited to the specific implementation methods, and does not limit the content and protection scope of the present invention.

[0153] Example 1

[0154] The synthesis routes of the indole compounds IN-1 and IN-2 provided in this example are shown in the following reaction formula.

[0155]

[0156] The preparation method of indole compounds IN-1 and IN-2 comprises the following steps:

[0157] Synthesis of intermediate C1: Under nitrogen protection, compound A1 (5-bromoindole-3-carboxaldehyde, 448 mg, 2.0 mmol), CuI (381 mg, 4.0 mmol), and potassium carbonate (672 mg, 6.0 mmol) were dissolved in toluene (20 mL), and the dissolved oxygen was removed by exhausting. Subsequently, compound B1 (1,3-difluoro-5-iodobenzene, 480 mg, 4.0 mmol) was added to the above solution and refluxed at 100°C for 24 hours. After the reaction was completed, it was quenched with a DCM / water system, and after removing the solvent, it was purified by column chromatography and dried to obtain intermediate C1 (610 mg, 1.82 mmol) with a yield of 91%.

[0158] Synthesis of intermediate D1: Under nitrogen protection, intermediate C1 (503 mg, 1.5 mmol) and diethyl cyanomethylphosphonate (531 mg, 3.0 mmol) were dissolved in toluene (20 mL), piperidine (2 mL) was added, and refluxed for 16 hours. The mixture was quenched with a DCM / water system, the solvent was removed, and the intermediate D1 (622 mg, 1.3 mmol) was obtained after column chromatography and drying, with a yield of 84%.

[0159] Synthesis of indole compound IN-1: Under nitrogen protection, intermediate D1 (495 mg, 1.0 mmol), trimethylsilyl bromide (1.53 g, 10.0 mmol) and 1,4-dioxane (15 mL) were added to a 100 mL round-bottom flask in sequence and reacted for 12 hours. After spin drying, methanol (10 mL) was added thereto, and deionized water was added dropwise until the reaction solution became a white suspension, and the reaction was continued for 7 hours. After the reaction was completed, the mixture was filtered, washed with deionized water, and the obtained solid was dissolved in THF after being drained, and then dropped into petroleum ether, filtered, and washed with petroleum ether to obtain indole compound IN-1 (364 mg, 0.83 mmol) with a yield of 83%.

[0160] The experimental data of H NMR spectrum of the prepared indole compound IN-1 are as follows:

[0161] 1 HNMR(500MHz,Chloroform-d)δ9.09(s,2H),8.56(s,1H),8.23(s,1H),7.98(d,J=1.7Hz,1H),7.64(d,J=8.0Hz,1H), 7.54(dd,J=8.1,2.0Hz,1H),7.15–7.09(m,2H),6.81(tt,J=8.1,2.2Hz,1H).HRMS(ESI / Q-TOF,m / z):Calcdfor[M+H] + C 17 H 11 F 2 N 2 O 3 P + :438.9580, found:438.9574. The molecular ion peak of the mass spectrum is 438.9574, which is consistent with the theoretical value [M+H] + C 17 H 11 F 2 N 2 O 3 P + =438.9580 is consistent.

[0162] Synthesis of indole compound IN-2: Under nitrogen protection, the intermediate C1 (503 mg, 1.5 mmol) and cyanoacetic acid (255 mg, 3.0 mmol) were dissolved in toluene (20 mL), piperidine (2 mL) was added, and the mixture was refluxed for 16 hours. The mixture was quenched with a DCM / water system, the solvent was removed, and the mixture was purified by column chromatography and dried to obtain indole compound IN-2 (443 mg, 1.1 mmol) with a yield of 71%.

[0163] The experimental data of H NMR spectrum of the prepared indole compound IN-2 are as follows:

[0164] 1 HNMR(500MHz,Chloroform-d)δ8.32(s,1H),8.28(s,1H),7.99(d,J=1.8Hz,1H),7.68(d,J=8.1Hz,1H),7.54( dd,J=8.1,1.8Hz,1H),7.15–7.09(m,2H),6.81(tt,J=8.1,2.2Hz,1H).HRMS(ESI / Q-TOF,m / z):Calcdfor[M+H] + C18 H 10 F 2 N 2 O 2 + :402.9815, found:402.981. The molecular ion peak of the mass spectrum is 402.981, which is consistent with the theoretical value [M+H] + C 18 H 10 F 2 N 2 O 2 + =402.9815 is consistent.

[0165] Example 2

[0166] The synthesis routes of the indole compounds IN-3 and IN-4 provided in this example are shown in the following reaction formula.

[0167]

[0168] The preparation method of indole compounds IN-3 and IN-4 comprises the following steps:

[0169] The synthesis of indole compound IN-3 was basically the same as the synthesis steps of compound IN-1 in Example 1, except that compound A1 (5-bromoindole-3-carboxaldehyde) in Example 1 was replaced by compound A2 (5-methoxyindole-3-carboxaldehyde), and compound B1 (1,3-difluoro-5-iodobenzene) was replaced by compound B2 (2-iodothiophene), and the total yield was 61%.

[0170] The experimental data of H NMR spectrum of the prepared indole compound IN-3 are as follows:

[0171] 1 HNMR(500MHz,Chloroform-d)δ9.09(s,2H),8.55(s,1H),8.28(s,1H),7.44(dd,J=4.8,1.6Hz,1H),7.33–7.28(m,2H),7. 20(s,0H),7.02(dd,J=4.9,3.9Hz,1H),6.94(dd,J=8.1,1.8Hz,1H),3.83(s,2H).HRMS(ESI / Q-TOF,m / z):Calcdfor[M+H] + C 16 H 14 N 2 O 4 PS +:361.0334, found:361.0329. The molecular ion peak of the mass spectrum is 361.0329, which is consistent with the theoretical value [M+H] + C 16 H 14 N 2 O 4 PS + =361.0334 is consistent.

[0172] The synthesis of indole compound IN-4 was basically the same as the synthesis steps of indole compound IN-2 in Example 1, except that compound A1 (5-bromoindole-3-carboxaldehyde) in Example 1 was replaced by compound A2 (5-methoxyindole-3-carboxaldehyde), and compound B1 (1,3-difluoro-5-iodobenzene) was replaced by compound B2 (2-iodothiophene), and the total yield was 54%.

[0173] The experimental data of H NMR spectrum of the prepared indole compound IN-4 are as follows:

[0174] 1 HNMR(500MHz,Chloroform-d)δ8.33(d,J=16.9Hz,2H),7.44(dd,J=4.8,1.6Hz,1H),7.33–7.28(m,2H),7.14(s,1 H),7.02(dd,J=4.9,3.9Hz,1H),6.94(dd,J=8.1,1.8Hz,1H),3.83(s,3H).HRMS(ESI / Q-TOF,m / z):Calcdfor[M+H] + C 17 H 13 N 2 O 3 S + :325.0569, found:325.0563. The molecular ion peak of the mass spectrum is 325.0563, which is consistent with the theoretical value [M+H] + C 17 H 13 N 2 O 3 S + =325.0569 is consistent.

[0175] Application Examples

[0176] The indole compounds prepared in the above embodiments are respectively applied as hole transport materials in perovskite solar cells.

[0177] Specifically, the preparation process of perovskite solar cells includes the following steps:

[0178] Step 1: ultrasonically clean the TCO conductive glass with deionized water, acetone and isopropanol for 15 minutes respectively, and then put it into a drying oven to dry at 75° C. Then, the dried TCO conductive glass is placed in a UV ozone machine for 5 minutes to remove organic impurities on its surface and optimize its surface wettability to obtain a substrate.

[0179] Step 2: dissolve 1.5 mg of an indole compound in 1 mL of ethanol to obtain an organic hole transport material solution.

[0180] Step 3, take 30 μL of the organic hole transport material solution prepared in step 2, add it dropwise on the substrate obtained in step 1, spin coat it at 5000 rpm for 30 seconds, then place the substrate coated with the above solution on a hot stage, heat and anneal it at 100°C for 10 minutes to form a hole transport layer with a thickness of about 3 nm.

[0181] Step 4: 722.08 mg of lead iodide (PbI 2 )、238.50mg iodine methylamine (CH 3 NH 3 I) was dissolved in 1 mL of N,N-dimethylformamide (DMF) and stirred at room temperature until completely dissolved to obtain a perovskite precursor solution.

[0182] Step 5. In a nitrogen glove box, take 30 μL of the perovskite precursor solution prepared in step 4, and add it dropwise onto the hole transport layer obtained in step 3. First, spin coat it at 1000 rpm for 10 seconds, and then spin coat it at 5000 rpm for 30 seconds. During this process, quickly add 125 μL of chlorobenzene after 25 seconds. Then, place it on a hot stage and heat and anneal it at 100°C for 40 minutes to form a perovskite light absorption layer with a thickness of about 350 nm.

[0183] Step 6, dissolve 20 mg of methanefullerene phenyl-C61-butyric acid methyl ester (PCBM) in 1 mL of chlorobenzene and stir at room temperature to obtain [6,6]-phenyl-C61-butyric acid methyl ester solution.

[0184] Step 7: Take 30 μL of the [6,6]-phenyl-C61-butyric acid methyl ester solution prepared in step 6, drop it on the perovskite light absorption layer obtained in step 5, and spin coat it at 3000 rpm for 60 s to form an electron transport layer with a thickness of about 30 nm.

[0185] Step 8, dissolving 0.5 mg of 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) in 1 mL of isopropanol, stirring at room temperature, to obtain an interface barrier material solution.

[0186] Step 9, take 40 μL of the interface barrier material solution prepared in step 8 and drop it on the electron transport layer obtained in step 7, and spin coat it at 5000 rpm for 35 seconds to form an interface barrier layer with a thickness of about 6 nm.

[0187] Step 10: transfer the product obtained in step 9 to a vacuum coating apparatus, and set the vacuum degree to 3×10 -4 Pa, and 100nm thick metallic silver was evaporated to form an electrode layer.

[0188] Comparative experiment

[0189] The perovskite solar cell of this comparative experiment uses a carbazole-based hole transport material 2PACz to replace the indole compound used in the aforementioned perovskite solar cell, and the remaining steps and materials are consistent with the preparation process of the aforementioned perovskite solar cell.

[0190] The performance of the perovskite solar cell prepared above was tested, and the test results are shown in Table 1.

[0191] Table 1 Performance parameters of perovskite solar cells using different hole transport materials

[0192]

[0193] It can be seen from the test results in Table 1 that the conversion efficiency of the perovskite solar cell prepared by using the indole compound of the present invention as the hole transport material is significantly improved compared with the traditional carbazole-based hole transport material 2PACz, and the short-circuit current, open-circuit voltage and fill factor are also improved to a certain extent.

[0194] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0195] The above-mentioned embodiments only express several implementation methods of the present invention, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for ordinary technicians in this field, several variations and improvements can be made without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent of the present invention shall be subject to the attached claims.

Claims

1. An indole compound, characterized in that It has a molecular structure represented by general formula (1) or general formula (2): （1）、 （2）， wherein each R1 is selected from one of a hydrogen atom, a halogen atom, a cyano group, a C1~C6 alkoxy group, and a C1~C10 alkyl group; Each R2 is selected from a substituted or unsubstituted aryl group, and a substituted or unsubstituted heteroaryl group.

2. The indole compound according to claim 1, characterized in that In each R2, the number of ring atoms of the aryl group is 6 to 30.

3. The indole compound according to claim 2, characterized in that In each R2, the aryl group is one of benzene, biphenyl, naphthalene, anthracene, phenanthrene, pyrene, perylene and triphenylene.

4. The indole compound according to claim 2, characterized in that Each R2 is selected from one of the following groups: ， wherein each R3 is selected from one of a hydrogen atom, a halogen atom, a cyano group, a C1-C6 alkoxy group, and a C1-C10 alkyl group; * represents the binding point.

5. The indole compound according to claim 1, characterized in that In each R2, the number of ring atoms of the heteroaryl group is 5 to 30; and / or In each R2, the heteroaryl group contains at least one heteroatom selected from O and S.

6. The indole compound according to claim 5, characterized in that In each R2, the heteroaryl group is one of furan, benzofuran, thiophene, benzothiophene, thienothiophene, furanopyrrole, furanofuran, and thienofuran.

7. The indole compound according to claim 5, characterized in that Each R2 is selected from one of the following groups: ， wherein each R4 is selected from one of a hydrogen atom, a halogen atom, a cyano group, a C1-C6 alkoxy group, and a C1-C10 alkyl group; * represents the binding point.

8. A method for preparing an indole compound according to any one of claims 1 to 7, characterized in that: The following steps are involved: Step S1, taking compound A, compound B and a first catalyst to react in a first solvent to prepare an intermediate C; Step S2, reacting the intermediate C, diethyl cyanomethyl phosphate and the second catalyst in a second solvent to prepare an intermediate D; Step S3, taking the intermediate D and trimethylsilyl bromide to react in a third solvent, adding methanol to the reaction product after drying, and then adding water dropwise until the reaction liquid becomes a white suspension, and continuing the reaction to obtain an indole compound represented by the general formula (1); Alternatively, in step S4, intermediate C, cyanoacetic acid and a third catalyst are reacted in a fourth solvent to prepare an indole compound represented by general formula (2); Wherein, the molecular structure of the compound A is shown in general formula (3): （3）， The molecular structure of the compound B is shown in general formula (4): （4）， The molecular structure of the intermediate C is shown in general formula (5): （5）； The molecular structure of the intermediate D is shown in general formula (6): （6）。 9. The preparation method according to claim 8, characterized in that: The preparation method meets at least one of the following characteristics (1) to (2): (1) In step S1, the first catalyst comprises cuprous iodide and potassium carbonate, and the molar ratio of the compound A, the compound B, cuprous iodide and potassium carbonate is 1:(2-3):(1.5-2):(3-4); (2) In step S1, the reaction temperature is 100°C to 110°C, and the reaction time is 16 to 24 hours.

10. The preparation method according to claim 8, characterized in that: The preparation method meets at least one of the following characteristics (1) to (3): (1) In step S2, the second catalyst is piperidine; (2) In step S2, the molar ratio of the intermediate C to diethyl cyanomethyl phosphate is 1: (2-2.5); (3) In step S2, the reaction temperature is 90-100°C and the reaction time is 16-24 hours.

11. The preparation method according to claim 8, characterized in that: The preparation method meets at least one of the following characteristics (1) to (2): (1) In step S3, the molar ratio of intermediate D to trimethylsilyl bromide is 1:(2-3); (2) In step S3, the reaction temperature is 25-40° C., and the reaction time is 12-16 hours.

12. The preparation method according to claim 8, characterized in that: The preparation method meets at least one of the following characteristics (1) to (3): (1) In step S4, the third catalyst is piperidine; (2) In step S4, the molar ratio of the intermediate C to cyanoacetic acid is 1:(1.1-2); (3) In step S4, the reaction temperature is 70-80°C and the reaction time is 12-16 hours.

13. Use of the indole compound according to any one of claims 1 to 7 as a hole transport material.

14. A solar cell, characterized in that: The invention comprises a substrate, a hole transport layer, a perovskite light absorption layer, an electron transport layer and an electrode layer which are stacked in sequence, wherein the hole transport layer comprises the indole compound according to any one of claims 1 to 7.

15. The solar cell according to claim 14, wherein: The solar cell meets at least one of the following characteristics (1) to (2): (1) The perovskite light absorption layer comprises a perovskite material ABX3; wherein A comprises one or more of cesium ions, rubidium ions, potassium ions, methylamine ions, formamidine ions, methylenediamine ions, benzamidine cations and guanidinium cations; B comprises one or more of lead ions, copper ions, zinc ions, gallium ions, tin ions and calcium ions; X comprises one or more of fluoride ions, chloride ions, bromide ions, iodide ions, thiocyanate ions, tetrafluoroborate ions, hexafluorophosphate ions, formate ions and acetate ions; (2) The material of the electron transport layer includes one or more of zinc oxide, tin oxide, titanium dioxide, strontium titanate, zinc stannate, zirconium dioxide, aluminum oxide, tungsten trioxide, cesium oxide, cadmium sulfide, cadmium selenide, barium stannate, niobium pentoxide, fullerene and fullerene derivatives.

Images