Hole transport material and preparation method and application thereof

Abstract

The invention discloses a hole transport material and a preparation method and application thereof, and relates to the technical field of solar cells. Aiming at the problems of poor wettability, unmatched energy level distribution and the like of the existing polymer hole transport materials Poly-TPD and PTAA, a spirobifluorene unit is utilized to replace a polytriarylated amine structure or is embedded into the polytriarylated amine structure to form the polymer hole transport material, and the spirobifluorene unit is introduced into the traditional polytriarylated amine structures such as Poly-TPD and PTAA to form the polymer hole transport material. Original linear molecules can be connected into a three-dimensional network structure through four binding sites of the spirobifluorene unit, the stability of HTL molecules is better facilitated, meanwhile, the molecular stacking condition is adjusted, energy level arrangement is optimized, the hole extraction and transmission capacity of HTL to perovskite is improved, interface charge recombination is inhibited, and the perovskite performance is improved. The photovoltaic performance of the device and the battery stability can be obviously improved.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and more particularly, to a hole transporting material, a preparation method thereof, and an application thereof. Background Art

[0002] Due to the dense material structure, organic polymer HTMs usually exhibit good inherent optical, thermal, and chemical stabilities. There are various proven effective HTMs, such as poly[bis(4-phenyl)](2,4,6-trimethylphenyl)amine (PTAA) and poly[bis(4-phenyl)](4-n-butylphenyl)amine (Poly-TPD).

[0003] However, due to the strong hydrophobicity of the existing hole transporting materials PTAA and Poly-TPD, when preparing the perovskite layer on the PTAA or Poly-TPD layer, the perovskite precursor solution is difficult to wet and spread, resulting in a lower crystallinity of the perovskite layer and a poor buried interface. Some doping or surface modification techniques will increase the cost and complexity of the battery preparation process and potential stability problems. In addition, there is a large gap between the energy level distribution of the compound itself and the perovskite layer, which limits the further improvement of the battery efficiency.

[0004] Therefore, there is an urgent need to modify the existing hole transporting materials to further improve the performance of perovskite or related tandem solar cells.

[0005] In view of this, the present invention is specifically proposed. Summary of the Invention

[0006] The purpose of the present invention is to provide a hole transporting material, a preparation method thereof, and an application thereof, aiming to improve the performance and stability of perovskite or related tandem solar cells.

[0007] The present invention is implemented as follows:

[0008] In a first aspect, the present invention provides a hole transporting material, in which the structural unit in poly(triarylamine) is replaced by a spirobifluorene unit or embedded in the poly(triarylamine) structure to form a three-dimensional network structure;

[0009] The spirobifluorene unit is:

[0010]

[0011] It should be noted that in the present invention, a three-dimensional intermediate coupling group spirobifluorene is introduced into traditional poly(triarylamine) structures such as Poly-TPD and PTAA, which can connect the original linear molecules into a three-dimensional network structure with better stability. By combining the two, a polymer hole transporting material with more excellent performance is prepared.

[0012] In an alternative embodiment, the spirobifluorene unit replaces a structural unit in the poly(triarylamine) or is embedded in the poly(triarylamine) structure to form a three-dimensional network structure, and the specific structure is a copolymer structure formed by randomly connecting arylamine structural units, spirobifluorene structural units, and biphenyl structural units;

[0013] Among them, the arylamine structural unit is:

[0014]

[0015] R in the arylamine structural unit 1 、R 2 、R 3 、R 4 、R 5 are each independently selected from C1-C6 alkyl or H;

[0016] The biphenyl structural unit is:

[0017]

[0018] Preferably, the structure of the hole transport material is:

[0019]

[0020] The values of n, m, and y are all integers greater than 1.

[0021] In an alternative embodiment, the spirobifluorene unit replaces a structural unit in the poly(triarylamine) or is embedded in the poly(triarylamine) structure to form a three-dimensional network structure, and the specific structure is a copolymer structure formed by randomly connecting triarylamine structural units and spirobifluorene structural units;

[0022] Among them, the triarylamine structural unit is:

[0023]

[0024] R in the triarylamine structural unit 1 、R 2 、R 3 、R 4 、R 5 are each independently selected from C1-C6 alkyl or H.

[0025] Second, the present invention also provides a preparation method of a hole transport material, including: carrying out a polymerization reaction using an aniline compound, a halogen-containing spirobifluorene, and a halogen-containing biphenyl compound as raw materials.

[0026] In an alternative embodiment, the aniline compound is 4-butylaniline or 2,4,6-trimethylaniline;

[0027] and / or, the halogen-containing spirobifluorene is 2,2',7,7'-tetrabromo-9,9'-spirobifluorene;

[0028] and / or, the halogen-containing biphenyl compound is 4,4'-diiodobiphenyl or 4,4'-dibromobiphenyl;

[0029] And / or, the molar ratio of the aniline compound to the halogen-containing spirobifluorene is 1:(0.025-0.25).

[0030] In an optional embodiment, the method comprises: mixing an organic solvent, an aniline compound, a halogen-containing spirobifluorene, a halogen-containing biphenyl compound, an organic base, a palladium catalyst and an organic phosphine ligand, reacting the mixture at 115° C.-135° C. for 15 h-30 h, and then performing an end-capping treatment.

[0031] In an optional embodiment, the organic base is sodium tert-butoxide, and the molar ratio of the aniline compound to the organic base is 1:(2.5-3.5);

[0032] And / or, the palladium catalyst is tris(dibenzylideneacetone)dipalladium, and the molar ratio of the aniline compound to the palladium catalyst is 1:(0.003-0.010);

[0033] and / or, the organic phosphine ligand is tri-tert-butylphosphine, and the molar ratio of the aniline compound to the organic phosphine ligand is 1:(0.01-0.05);

[0034] And / or, the end-capping process includes: first adding an aniline compound and continuing to react at 115° C.-135° C. for 3 h-8 h, cooling, adding bromobenzene and continuing to react at 115° C.-135° C. for 3 h-8 h, and cooling.

[0035] In an optional embodiment, it also includes: after the end-capping treatment, treating with a mixed solvent formed by water and an organic solvent, then performing solid-liquid separation to obtain a solid material, washing the solid material, then dissolving the solid material again to remove the palladium, and then isolating the target product again.

[0036] In an optional embodiment, the mixed solvent is obtained by mixing acetone and water in a volume ratio of (8.0-9.5): 1:

[0037] And / or, the solid material is dissolved again with chloroform, and then palladium-removing silica gel is added for treatment, the solid silica gel is removed by solid-liquid separation, and a concentrated solution is obtained after evaporation and concentration, and the target product is obtained by ethyl acetate precipitation and solid-liquid separation, and the target product is washed and dried.

[0038] In a third aspect, the present invention further provides a method for preparing a hole transport material, comprising: carrying out a polymerization reaction using a halogen-containing triphenylamine compound and a halogen-containing spirobifluorene as raw materials.

[0039] In an alternative embodiment, the halogen-containing triphenylamine compound is 4-butyl-4',4''-dibromotriphenylamine or 2,4,6-trimethyl-4',4''-dibromotriphenylamine;

[0040] and / or, the halogen-containing spirobifluorene is 2,2',7,7'-tetrabromo-9,9'-spirobifluorene;

[0041] and / or, the molar ratio of the halogen-containing triphenylamine compound to the halogen-containing spirobifluorene is 1:(0.01 - 0.5).

[0042] In an alternative embodiment, an organic solvent, a catalyst, a ligand, a halogen-containing triphenylamine compound, and a halogen-containing spirobifluorene are mixed and reacted at 70°C - 90°C for 12 h - 20 h.

[0043] In an alternative embodiment, the catalyst is bis(1,5-cyclooctadiene)nickel(0), and the molar ratio of the halogen-containing triphenylamine compound to bis(1,5-cyclooctadiene)nickel(0) is 1:(0.8 - 3.0);

[0044] and / or, the ligand includes 2,2'-bipyridine and 1,5-cyclooctadiene, and the molar ratio of the halogen-containing triphenylamine compound, 2,2'-bipyridine, and 1,5-cyclooctadiene is 1:(1.0 - 4.0):(0.8 - 3.5);

[0045] and / or, further comprising: cooling after the reaction of the halogen-containing triphenylamine compound and the halogen-containing spirobifluorene is completed, then diluting with an organic solvent, and then washing successively with a hydrochloric acid solution, water, a sodium bicarbonate solution, and water, drying the obtained organic phase and then concentrating, and precipitating the concentrated solution with ethyl acetate to obtain a solid product.

[0046] Fourthly, the present invention provides an application of the hole transport material of the foregoing embodiments in the preparation of single-junction or tandem solar cells.

[0047] The present invention has the following beneficial effects: The present invention uses a spirobifluorene unit to replace or embed in the poly(triphenylamine) structure to form a polymeric hole transport material. By introducing a spirobifluorene unit into traditional poly(triphenylamine) structures such as Poly-TPD and PTAA, the four binding sites of the spirobifluorene unit can connect the originally linear molecules into a three-dimensional network structure, which is more conducive to the stability of HTL molecules. At the same time, the molecular packing is adjusted, the energy level arrangement is optimized, the hole extraction and transport ability of HTL for perovskite is improved, and the interfacial charge recombination is inhibited, which can significantly improve the photovoltaic performance and battery stability of the device.

[0048] The preparation method of the hole transport material provided by the present invention is simple and easy to implement. The hole transport material can be prepared only by one-step polymerization reaction, and the subsequent separation steps are also convenient to operate. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention, and thus should not be regarded as limiting the scope. For those of ordinary skill in the art, other related drawings can be obtained based on these drawings without creative efforts.

[0050] Figure 1 It is a synthetic route diagram provided for the embodiments of the present invention (the product structural formula serves as a schematic illustration and is only used to explain the reaction principle, and the structural formula is not limited to Figure 1 );

[0051] Figure 2 It is a test diagram of the aromatic region part of the 2H-NMR for the implementation case;

[0052] Figure 3 It is the thermogravimetric diagram of Comparative Case 1, Implementation Case 2, and Implementation Case 6 at N 2 ;

[0053] Figure 4 It is the energy level distribution diagram of the hole layer, perovskite, and electron transport layer;

[0054] Figure 5 It is the contact angle of the solvent of the perovskite precursor solution on the Poly-TPD and PTPD-S-10% films; (a) represents Poly-TPD, and (b) represents PTPD-S-10%;

[0055] Figure 6 It is the SEM diagram of the perovskite on the Poly-TPD and PTPD-S-10% films; (a) represents Poly-TPD, and (b) represents PTPD-S-10%;

[0056] Figure 7 It is the battery performance of different implementation cases; (a) represents PCE (photovoltaic cell efficiency), (b) represents V OC (open circuit voltage), (c) represents J SC (short circuit current density), and (d) represents FF (fill factor);

[0057] Figure 8 It is the battery performance parameters of Comparative Case 1, Comparative Case 2, and Implementation Case 2; (a) represents V OC (open circuit voltage), (b) represents J SC (short circuit current density), (c) represents FF (fill factor), and (d) represents PCE (photovoltaic cell efficiency);

[0058] Figure 9Battery performance parameters for different concentrations and compared with Comparative Case 1; (a) represents V OC (open circuit voltage), (b) represents J SC (short circuit current density), (c) represents FF (fill factor), (d) represents PCE (photovoltaic cell efficiency);

[0059] Figure 10 Performance parameters of Comparative Case 1 and Example 2 in the tandem cell; (a) represents V OC (open circuit voltage), (b) represents J SC (short circuit current density), (c) represents FF (fill factor), (d) represents PCE (photovoltaic cell efficiency);

[0060] Figure 11 Is the stability test data graph of the encapsulated tandem cell aged under the conditions of 85% humidity and 85 °C. Detailed implementation mode

[0061] To make the objectives, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below. Those not specified in the embodiments are carried out according to conventional conditions or conditions recommended by the manufacturer. Those reagents or instruments not specified by the manufacturer can be obtained as conventional products through commercial purchase.

[0062] Generally speaking, spiro molecules usually have the following advantages: (1) They are amorphous at room temperature, and the isotropic physical properties ensure the uniformity of hole transport, and the glass transition temperature (Tg) is relatively high, which helps to obtain a stable thin film; (2) The non-planar spiro structure makes the intermolecular interaction weak, has good solubility, is easy to be prepared into a film by solution method, and can better fill the perovskite layer; (3) The strong rigid conjugate system of such molecules can reduce the aggregation of molecules during the film formation process to form a smooth amorphous film morphology, and form good mutual contact with the perovskite layer; (4) The HOMO energy level can basically match well with the valence band of perovskite through molecular modification, etc.

[0063] The inventor creatively introduces a three-dimensional intermediate coupling group, spirobifluorene, into traditional poly(triarylamine) structures such as Poly-TPD and PTAA, which can connect the original linear molecules into a three-dimensional network structure, and a polymer hole transport material with more excellent performance can be prepared by combining the two.

[0064] The embodiments of the present invention provide a hole transport material, which is formed by replacing the structural unit in poly(triarylamine) with a spirobifluorene unit or embedding the spirobifluorene unit into the poly(triarylamine) structure to form a three-dimensional network structure; the spirobifluorene unit is:

[0065]

[0066] Specifically, the structure of the hole transporting material can be a three-dimensional network structure formed by replacing a certain number of spirobifluorene units with poly(triphenylamine) structures such as Poly-TPD and PTAA, or can be a three-dimensional network structure formed by embedding a certain number of spirobifluorene units into poly(triphenylamine) structures such as Poly-TPD and PTAA.

[0067] In some embodiments, the structure of the hole transporting material is a copolymer structure (hereinafter referred to as "the first structure") formed by randomly connecting arylamine structural units, spirobifluorene structural units, and biphenyl structural units, which can be a random copolymer or a regularly arranged copolymer. Among them, the arylamine structural unit is:

[0068]

[0069] R in the arylamine structural unit 1 、R 2 、R 3 、R 4 、R 5 are each independently selected from C1-C6 alkyl or H;

[0070] The structure of the spirobifluorene structural unit refers to the above.

[0071] The biphenyl structural unit is:

[0072]

[0073] In a preferred embodiment, the structure of the hole transporting material is:

[0074]

[0075] The values of n, m, and y are all integers greater than 1. Since it is a cross-linked compound, the values of n, m, and y can be the same or different, and can independently be 2, 5, 8, 10, 20, 30, 40, etc.

[0076] In another embodiment, its structure is a copolymer structure (hereinafter referred to as "the second structure") formed by randomly connecting triarylamine structural units and spirobifluorene structural units, which can be a random copolymer or a regularly arranged copolymer. Among them, the triarylamine structural unit is:

[0077]

[0078] R in the triarylamine structural unit 1 、R 2 、R 3 、R 4 、R 5 are each independently selected from C1-C6 alkyl or H;

[0079] The structure of the spirobifluorene structural unit is referred to above.

[0080] The "*" in the above structure represents the binding site.

[0081] Regarding the "first structure":

[0082] An embodiment of the present invention provides a method for preparing a hole transporting material. Using an aniline compound, a halogen-containing spirobifluorene, and a halogen-containing biphenyl compound as raw materials for a polymerization reaction to prepare a polymer that meets the first structure. The main steps are as follows (Steps S11 - S13):

[0083] S11. Polymerization reaction

[0084] To achieve the polymerization of the three monomer materials, an organic base, a catalyst, and an organic phosphine ligand need to be introduced. The specific steps are as follows: Mix an organic solvent, an aniline compound, a halogen-containing spirobifluorene, a halogen-containing biphenyl compound, an organic base, a palladium catalyst, and an organic phosphine ligand, and react under the conditions of 115°C - 135°C for 15h - 30h. By controlling the reaction temperature and time to repeat the reaction, the molecular weight of the obtained product is more suitable.

[0085] Specifically, the temperature of the polymerization reaction can be 115°C, 120°C, 125°C, 130°C, 135°C, etc., and the reaction time can be 15h, 20h, 24h, 28h, 30h, etc. After the reaction is completed, cool to room temperature (such as 25°C) and then perform subsequent end-capping treatment.

[0086] In some embodiments, the aniline compound can be 4-butylaniline, but is not limited thereto. The halogen-containing spirobifluorene can be 2,2",7,7"-tetrabromo-9,9"-spirobifluorene, but is not limited thereto; the halogen-containing biphenyl compound can be 4,4'-diiodobiphenyl, but is not limited thereto. Figure 1 For the reaction schematic diagram of the preferred embodiment, one-step polymerization is carried out using 4-butylaniline, 2,2",7,7"-tetrabromo-9,9"-spirobifluorene, and 4,4'-diiodobiphenyl, so that the arylamine structural unit is randomly connected to the spirobifluorene structural unit and / or the biphenyl structural unit to form a copolymer structure, and the product is a random copolymer.

[0087] Further, the molar ratio of the aniline compound to the halogen-containing biphenyl compound is 1:(0.50-0.95), such as 1:0.50, 1:0.55, 1:0.60, 1:0.65, 1:0.70, 1:0.75, 1:0.80, 1:0.85, 1:0.90, 1:0.95, etc. The molar ratio of the aniline compound to the halogen-containing spirobifluorene is 1:(0.025-0.25), such as 1:0.025, 1:0.030, 1:0.050, 1:0.080, 1:0.100, 1:0.150, 1:0.200, 1:0.250, etc. The molar ratio of the three monomers within this range can further improve the transmission performance and stability of the device. To ensure the degree of polymerization of the polymer, the above two molar ratios have a certain corresponding relationship. For example, when the molar ratio of the aniline compound to the halogen-containing biphenyl compound is 1:0.5, the molar ratio of the aniline compound to the halogen-containing spirobifluorene is adjusted to 1:0.25. Specifically, the molar ratio of the total halogen reaction sites to aniline (since the aniline reaction sites themselves are two) can be controlled to be 2:1.

[0088] In some embodiments, the type of organic solvent is not limited, and can be an organic solvent without halogen such as o-xylene and toluene. The organic base can be sodium tert-butoxide, but is not limited thereto, and the molar ratio of the aniline compound to the organic base is 1:(2.5-3.5), such as 1:2.5, 1:2.8, 1:3.0, 1:3.2, 1:3.5, etc. The palladium catalyst can be tris(dibenzylideneacetone)dipalladium, but is not limited thereto, and the molar ratio of the aniline compound to the palladium catalyst is 1:(0.003-0.010), such as 1:0.003, 1:0.005, 1:0.008, 1:0.010, etc. The organic phosphine ligand is tri-tert-butylphosphine, but not limited thereto, and the molar ratio of the aniline compound to the organic phosphine ligand is 1:(0.01-0.05), such as 1:0.01, 1:0.02, 1:0.03, 1:0.04, 1:0.05, etc. By adjusting the amount of each raw material, the polymerization reaction is promoted to be fully carried out and the utilization rate of the raw materials is improved.

[0089] S12, end-capping treatment

[0090] After the reaction in step S11 is completed, a capping treatment is performed to cap the halogen and amine groups, and the capping method is not limited.

[0091] In some embodiments, the capping process includes: first adding an aniline compound (such as 4-butylaniline) and continuing the reaction at 115°C - 135°C (such as 115°C, 120°C, 125°C, 130°C, 135°C, etc.) for 3h - 8h (such as 3h, 4h, 5h, 6h, 7h, 8h, etc.) to achieve the capping of halogens such as bromine. After cooling, add bromobenzene and continue the reaction at 115°C - 135°C (such as 115°C, 120°C, 125°C, 130°C, 135°C, etc.) for 3h - 8h (such as 3h, 4h, 5h, 6h, 7h, 8h, etc.), and then cool to achieve the capping of amino groups.

[0092] Furthermore, the amounts of the aniline compound and bromobenzene added are not limited and can be slightly excessive. For example, the molar ratio of the aniline compound added during the polymerization reaction to the aniline compound added during the capping can be 1:(0.06 - 0.08); the molar ratio of the aniline compound added during the polymerization reaction to the bromobenzene added during the capping can be 1:(0.15 - 0.25).

[0093] S13. Separation and purification

[0094] After the capping treatment, it is treated with a mixed solvent formed by water and an organic solvent, and then solid-liquid separation is carried out to obtain a solid material. The solid material is washed, and then the solid material is dissolved again for palladium removal treatment, and the target product is separated again. Through steps such as washing and palladium removal, impurities affecting the material properties are removed.

[0095] In some embodiments, the mixed solvent formed by water and an organic solvent can be a mixture of acetone and water in a volume ratio of (8.0 - 9.5):1. Adding the mixed solvent can quickly precipitate the polymer, and then solid-liquid separation is carried out by means such as filtration. The volume ratio of acetone to water can be 8.0:1, 8.5:1, 9.0:1, 9.5:1, etc.

[0096] In some embodiments, the solid material can be redissolved with chloroform, and then palladium-removing silica gel is added for treatment. Solid-liquid separation is carried out to remove the solid silica gel, and a concentrated solution is obtained after evaporation and concentration. The target product is precipitated with ethyl acetate and solid-liquid separated. The target product is washed and dried to obtain the final product. Specifically, stir with palladium-removing silica gel at room temperature overnight, remove the solid palladium-removing silica gel, and then perform rotary evaporation under reduced pressure to obtain a concentrated solution. Add ethyl acetate to the concentrated solution to precipitate the polymer. After filtration, the filter cake is washed with ethyl acetate, the light yellow filter cake is collected, and dried in a vacuum drying oven.

[0097] Regarding the "second structure":

[0098] An embodiment of the present invention provides a method for preparing a hole transporting material. A polymerization reaction is carried out using a halogen-containing triphenylamine compound and a halogen-containing spirobifluorene as raw materials. The main steps are as follows (Steps S21 - S23):

[0099] S21. Ingredients preparation

[0100] Provide a halogen-containing triphenylamine compound and a halogen-containing spirobifluorene. The halogen-containing triphenylamine compound can be 4-butyl-4',4''-dibromotriphenylamine or 2,4,6-trimethyl-4',4''-dibromotriphenylamine, but is not limited thereto; the halogen-containing spirobifluorene can be 2,2',7,7'-tetrabromo-9,9'-spirobifluorene, but is not limited thereto.

[0101] Furthermore, the molar ratio of the halogen-containing triphenylamine compound to the halogen-containing spirobifluorene is 1:(0.01 - 0.5), such as 1:0.01, 1:0.02, 1:0.03, 1:0.04, 1:0.05, 1:0.10, 1:0.20, 1:0.30, 1:0.40, 1:0.50, etc. When the molar ratio of the two is within the above range, the performance of the hole transporting material can be further improved.

[0102] This reaction needs to be carried out in the presence of a catalyst and a ligand. The catalyst can be bis(1,5-cyclooctadiene)nickel, but is not limited thereto; the molar ratio of the halogen-containing triphenylamine compound to bis(1,5-cyclooctadiene)nickel is 1:(0.8 - 3.0), such as 1:0.8, 1:1.0, 1:1.5, 1:2.0, 1:2.5, 1:3.0, etc. The ligand includes 2,2-bipyridine and 1,5-cyclooctadiene, but is not limited thereto; the molar ratio of the halogen-containing triphenylamine compound, 2,2-bipyridine and 1,5-cyclooctadiene is 1:(1.0 - 4.0):(0.8 - 3.5), such as 1:1.0:0.8, 1:2.0:1.5, 1:3.0:2.0, 1:4.0:3.5, etc.

[0103] S22. Polymerization reaction

[0104] Mix the organic solvent, catalyst, ligand, halogen-containing triphenylamine compound and halogen-containing spirobifluorene in proportion, and react at 70°C - 90°C for 12h - 20h to complete the polymerization reaction.

[0105] Specifically, the reaction temperature can be 70°C, 75°C, 80°C, 85°C, 90°C, etc.; the reaction time can be 12h, 15h, 18h, 20h, etc. The type of the organic solvent is not limited and can be toluene, but is not limited thereto.

[0106] S23. Post-treatment

[0107] After the reaction of the halogen-containing triphenylamine compound and the halogen-containing spirobifluorene is completed, the mixture is cooled to room temperature, diluted with an organic solvent (such as toluene), and then washed with hydrochloric acid solution, water, sodium bicarbonate solution and water in sequence to obtain an organic phase. The obtained organic phase is dried and then concentrated, and then the concentrated solution is precipitated with ethyl acetate to obtain a solid product.

[0108] Specifically, the drying method is not limited, and anhydrous sodium sulfate can be used for drying; the concentration method is not limited, and rotary evaporation can be used for evaporation concentration.

[0109] The hole transport material provided in the embodiment of the present invention can be further prepared to obtain a stacked solar cell. The improvement of the hole transport material can improve the photovoltaic performance of the device and the stability of the cell.

[0110] The features and performance of the present invention are further described in detail below in conjunction with the embodiments.

[0111] Example 1 (Synthesis of PTPD-S-5%)

[0112] This embodiment provides a method for preparing a hole transport material, the steps are as follows:

[0113] In a nitrogen glove box, add 149.3 mg (1.00 mmol) of 4-butylaniline, 15.9 mg (0.025 mmol) of 2,2',7,7'-tetrabromo-9,9'-spirobifluorene, 385.7 mg (0.95 mmol) of 4,4'-diiodobiphenyl, 296.4 mg (3.08 mmol) of sodium tert-butoxide, 4.5 mg (0.005 mmol) of tri(dibenzylideneacetone)dipalladium, and 20 μL (0.02 mmol) of a 1M toluene solution of tri-tert-butylphosphine to 10 mL of o-xylene. Heat and stir at 125°C for 24 h. Cool to room temperature, add 10.0 mg (0.067 mmol) of 4-butylaniline, and continue to heat and stir at 125°C for 5 h. Cool to room temperature, add 30.0 mg (0.191 mmol) of bromobenzene, and continue to heat and stir at 125°C for 5 h. Cool to room temperature, add 100mL acetone: water = 9: 1 solvent, a light yellow precipitate is generated, filter, wash the filter cake with acetone and water in turn, collect the light yellow filter cake, add 20mL chloroform to dissolve, add 200mg palladium-removing silica gel, stir at room temperature overnight, filter to remove solids except for silica gel, reduce pressure and rotary evaporation, and concentrate the solution. Add 20mL ethyl acetate to precipitate, filter, wash the filter cake with ethyl acetate, and collect the light yellow filter cake. Dry in a vacuum drying oven to obtain 265.3mg product PTPD-S-5%, yield 88.5%. GPC (chloroform phase): Mw = 19674, PDI = 2.65. According to nuclear magnetic hydrogen spectrum analysis, the replacement of biphenyl by spirobifluorene is about 5%, which is not much different from the feed ratio, proving that the spirobifluorene unit is successfully introduced into the polymer according to the molecular design ratio.

[0114] Example 2 (Synthesis of PTPD-S-10%)

[0115] Referring to the synthesis procedure of Example 1, the only difference is that the feeding amounts of 2,2',7,7'-tetrabromo-9,9'-spirobifluorene and 4,4'-diiodobiphenyl are adjusted to: 31.5 mg (0.05 mmol) of 2,2',7,7'-tetrabromo-9,9'-spirobifluorene and 365.4 mg (0.90 mmol) of 4,4'-diiodobiphenyl, respectively. 284.6 mg of the product PTPD-S-10% is obtained, with a yield of 94.9%. GPC (chloroform phase): Mw = 32143, PDI = 4.2. Through 1H NMR analysis, the replacement of biphenyl by spirobifluorene is about 9%, which is not much different from the feeding ratio.

[0116] Example 3 (Synthesis of PTPD-S-20%)

[0117] Referring to the synthesis procedure of Example 1, the only difference is that the feeding amounts of 2,2',7,7'-tetrabromo-9,9'-spirobifluorene and 4,4'-diiodobiphenyl are adjusted to: 63.3 mg (0.10 mmol) of 2,2',7,7'-tetrabromo-9,9'-spirobifluorene and 324.8 mg (0.80 mmol) of 4,4'-diiodobiphenyl, respectively. 273.8 mg of the product PTPD-S-20% is obtained, with a yield of 91.2%. GPC (chloroform phase): Mw = 60228, PDI = 4.9. Through 1H NMR analysis, the replacement of biphenyl by spirobifluorene is about 19%, which is not much different from the feeding ratio.

[0118] Example 4 (Synthesis of PTPD-S-30%)

[0119] Referring to the synthesis procedure of Example 1, the only difference is that the feeding amounts of 2,2',7,7'-tetrabromo-9,9'-spirobifluorene and 4,4'-diiodobiphenyl are adjusted to: 94.9 mg (0.15 mmol) of 2,2',7,7'-tetrabromo-9,9'-spirobifluorene and 284.4 mg (0.70 mmol) of 4,4'-diiodobiphenyl, respectively. 257.6 mg of the product PTPD-S-30% is obtained, with a yield of 85.7%. GPC (chloroform phase): Mw = 99946, PDI = 5.61. Through 1H NMR analysis, the replacement of biphenyl by spirobifluorene is about 30%, which is not much different from the feeding ratio.

[0120] Example 5 (Synthesis of PTPD-S-40%)

[0121] Referring to the synthesis steps of Example 1, the only difference is that the feeding amounts of 2,2',7,7'-tetrabromo-9,9'-spirobifluorene and 4,4'-diiodobiphenyl are adjusted to: 126.6 mg (0.2 mmol) of 2,2',7,7'-tetrabromo-9,9'-spirobifluorene and 243.8 mg (0.60 mmol) of 4,4'-diiodobiphenyl, respectively. 260.8 mg of product PTPD-S-40% was obtained with a yield of 86.6%. GPC (chloroform phase): Mw = 119250, PDI = 4.9. Analysis by 1H NMR showed that the replacement of biphenyl by spirobifluorene was about 41%, which was not much different from the feeding ratio.

[0122] Example 6 (Synthesis of PTPD-S-50%)

[0123] Referring to the synthesis steps of Example 1, the only difference is that the feeding amounts of 2,2',7,7'-tetrabromo-9,9'-spirobifluorene and 4,4'-diiodobiphenyl are adjusted to: 158.1 mg (0.25 mmol) of 2,2',7,7'-tetrabromo-9,9'-spirobifluorene and 203 mg (0.50 mmol) of 4,4'-diiodobiphenyl, respectively. 270.0 mg of product PTPD-S-50% was obtained with a yield of 89.6%. GPC (chloroform phase): Mw = 150794, PDI = 4.8. Analysis by 1H NMR showed that the replacement of biphenyl by spirobifluorene was about 50%, which was not much different from the feeding ratio.

[0124] Example 7

[0125] In a nitrogen glove box, 192.5 mg (0.7 mmol) of bis(1,5-cyclooctadiene)nickel, 148.0 mg (0.94 mmol) of 2,2'-bipyridine, 86.0 mg (0.80 mmol) of 1,5-cyclooctadiene, 206.6 mg (0.45 mmol) of 4-butyl-4',4''-tribromo triphenylamine, and 31.6 mg (0.05 mmol) of 2,2',7,7'-tetrabromo-9,9'-spirobifluorene were added to 10 mL of toluene. The temperature was raised to 80 °C and reacted for 16 h, and then cooled to room temperature. It was diluted with 50 mL of toluene and washed with dilute hydrochloric acid (mass fraction 10%), water, saturated sodium bicarbonate aqueous solution, and water respectively to obtain an organic phase. The organic phase was dried with anhydrous sodium sulfate, concentrated by rotary evaporation, and precipitated with ethyl acetate to obtain 121.2 mg of product. For Example 7, the yield was 80.6%. GPC (chloroform phase): Mw = 15135, PDI = 3.8.

[0126] Comparative Example 1

[0127] Commercially available Poly-TPD was provided.

[0128] Comparative Example 2

[0129] Provide a simple doped 2,2',7,7'-tetrakis(diphenylamino)-9,9'-spirobifluorene small molecule, specifically as follows: Calculate according to the spirobifluorene doping ratio in Example 2 with the best battery performance. Prepare a solution of a hole transport material of 1.8 mg / mL of Poly-TPD + 0.33 mg / mL of 2,2',7,7'-tetrakis(diphenylamino)-9,9'-spirobifluorene in chlorobenzene as the hole transport material according to the molar ratio of Poly-TPD (calculated as monomer) to 2,2',7,7'-tetrakis(diphenylamino)-9,9'-spirobifluorene of 9:0.5.

[0130] Test Example 1

[0131] Test the performance of the hole transport materials provided by each example and comparative example for perovskite solar cells. The test methods and results are as follows:

[0132] Preparation of the battery: Prepare a battery with the structure: ITO glass / hole transport layer / Cs0.22FA0.78Pb(I0.865Br0.135)3 / C60 / BCP / Cu. The specific preparation method is as follows:

[0133] ① Substrate preparation: Ultrasonically clean the etched ITO substrate with detergent, deionized water, acetone, and isopropanol for 15 minutes each, dry it in a nitrogen atmosphere, and then treat it with ultraviolet ozone for 30 minutes to remove organic impurities on the surface of the ITO substrate.

[0134] ② Hole transport layer preparation; The materials of Examples 1-6 are respectively dissolved in CB solvent to prepare a 2 mg / mL solution. Comparative Example 1 dissolves Poly-TPD in a mixed solvent of chlorobenzene to prepare a 2 mg / ml solution, and Comparative Example 2. Coat each solution on the surface of the ITO substrate and anneal it to dry.

[0135] ③ Perovskite layer preparation: Deposit a perovskite layer by spin-coating a 1.4 M Cs0.22FA0.78Pb(I0.865Br0.135)3 DMF:DMSO (4:1) precursor solution at 3000 rpm for 25 s on the hole transport layer, and treat the perovskite film by the air extraction method, and anneal it at 100 °C for 10 min to obtain the perovskite layer.

[0136] ④ Electron transport layer preparation: Electron transport layer preparation: Evaporate a 20 nm thick C60 layer as the electron transport layer at a rate of 0.1 Å / s by thermal evaporation. Subsequently, continue to evaporate a 5 nm thick BCP at a rate of 0.1 Å / s.

[0137] ⑤ Electrode preparation: Deposit a 100 nm thick copper electrode in a vacuum chamber under a high vacuum condition of 5×10 -4 Pa to obtain a structure as Figure 1The battery shown

[0138] Test results:

[0139] Figure 2 For the aromatic region part of the 2H-NMR in Example 2, through analysis and calculation, the substitution of spirobifluorene for biphenyl is about 9%, which is not much different from the feeding ratio. This is mainly due to the poor peak shape of the polymer nuclear magnetic resonance hydrogen spectrum and certain errors in integral attribution. The same conclusion is also presented in other examples.

[0140] Figure 3 The thermogravimetric results show that the stability of the example is improved compared with that of the comparative example poly-TPD.

[0141] Figure 4 The energy levels obtained from the tests show that the energy level distribution of the example is more matched. The HOMO energy level of PTPD-S-10% is -5.31 eV, which is about 40 meV lower than that of Poly-TPD and closer to the valence band top energy level of perovskite. This well-matched HOMO energy level will be more conducive to hole transfer, thereby improving the battery performance. Although the LUMO energy level of PTPD-S-10% is -2.37 eV, slightly lower than -2.31 eV of Poly-TPD, it is much higher than the conduction band low energy level of perovskite, which will be conducive to blocking unnecessary electron transfer from the perovskite layer to the hole transport layer.

[0142] Figure 5 It can be seen that the contact angle of PTPD-S-10% is smaller.

[0143] Figure 6 It can be seen that the perovskite grains of PTPD-S-10% are larger.

[0144] Figure 7 It can be seen that: the efficiency is the highest when doped with 10%. As the doping ratio of spirobifluorene increases, the V of the device OC and FF both show a trend of first increasing and then decreasing, but J SC shows a decreasing trend. Eventually, the PCE also shows a trend of first increasing and then decreasing. When the doping substitution ratio is 10%, that is, when using PTPD-S-10% as the hole transport layer, the battery device has the highest PCE (20.01%) and average PCE (20.56 ± 0.28%). Therefore, PTPD-S-10% is used as the hole transport layer for subsequent research.

[0145] Figure 8Comparing with the simple doping of 2,2',7,7'-tetrakis(diphenylamino)-9,9'-spirobifluorene small molecule, it can be seen from the results that: for the simple doping of 2,2',7,7'-tetrakis(diphenylamino)-9,9'-spirobifluorene, compared with pure Poly-TPD, it can slightly increase Voc and FF, but due to the decrease of J SC eventually leads to a slight decrease in PCE. For PTPD-S-10% doped by copolymerization, compared with Poly-TPD, V OC has a greater increase, and FF slightly increases. Although J SC still shows a downward trend, the decrease amplitude is smaller than that of the simple doping of 2,2',7,7'-tetrakis(diphenylamino)-9,9'-spirobifluorene, resulting in a PCE higher than that of the Poly-TPD sample. Finally, using PTPD-S-10% as the hole battery device has the best PCE (20.92%) and the highest average PCE (21.50±0.26%) higher than the best PCE (21.84%) and the highest average PCE (21.38±0.42%) of Poly and the best PCE (21.79%) and the highest average PCE (21.29±0.30%) of the simple doping of 2,2',7,7'-tetrakis(diphenylamino)-9,9'-spirobifluorene.

[0146] Figure 9 For different concentrations and comparison cases, it can be seen that: with the increase of the concentration of PTPD-S-10%, the Voc of the battery has a slight improvement effect. J SC and FF both show a trend of first increasing and then decreasing. Among them, J SC reaches the maximum average J SC (20.72±0.14) at 1.0mg / mL, while FF reaches the highest average FF (84.16±0.69) at 1.5mg / mL. The PCE also shows a trend of first increasing and then decreasing. At 1.0mg / mL, it has the best PCE (22.65%) and the highest average PCE (22.24±0.26%) higher than the best PCE (22.30%) and the highest average PCE (21.94±0.26%) of the comparison case 1.

[0147] Figure 10 For the data of the stacked battery, it can be seen that the implementation case 2 has the best PCE (30.46%) and the highest average PCE (29.32±0.74%) higher than the best PCE (29.27%) and the highest average PCE (28.81±0.40%) of the comparison case 1.

[0148] Figure 11To encapsulate the stability data of the stacked battery during aging at 85% humidity and 85°C. After 712 hours, Example 2 retained 79% of the initial battery efficiency, while Comparative Example 1 only retained 59% of the initial battery efficiency. The improvement in battery stability can be attributed to the use of Example 2 of the present invention.

[0149] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention can have various changes and modifications. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A hole transport material, characterized in that: The spirobifluorene unit replaces the structural unit in the polytriarylamine or is embedded in the polytriarylamine structure to form a three-dimensional network structure; The spirobifluorene unit is:

2. The hole transport material according to claim 1, characterized in that The spirobifluorene unit replaces the structural unit in the polytriarylamine or is embedded in the polytriarylamine structure to form a three-dimensional network structure, and the specific structure is a copolymer compound structure formed by randomly connecting the aromatic amine structural unit, the spirobifluorene structural unit and the biphenyl structural unit; Wherein, the aromatic amine structural unit is: R1, R2, R3, R4, and R5 in the aromatic amine structural unit are independently selected from C1-C6 alkyl or H; The biphenyl structural unit is: Preferably, the structure of the hole transport material is: The values ​​of n, m, and y are all integers greater than 1.

3. The hole transport material according to claim 1, characterized in that The spirobifluorene unit replaces the structural unit in the polytriarylamine or is embedded in the polytriarylamine structure to form a three-dimensional network structure, and the specific structure is a copolymer compound structure formed by randomly connecting the triarylamine structural unit and the spirobifluorene structural unit; Wherein, the triarylamine structural unit is: R1, R2, R3, R4 and R5 in the triarylamine structural unit are independently selected from C1-C6 alkyl or H.

4. A method for preparing the hole transport material according to claim 1 or 2, characterized in that: include: The polymerization reaction is carried out using aniline compounds, halogen-containing spirobifluorene and halogen-containing biphenyl compounds as raw materials.

5. The preparation method according to claim 4, characterized in that: The aniline compound is 4-butylaniline or 2,4,6-trimethylaniline; and / or, the halogen-containing spirobifluorene is 2,2',7,7'-tetrabromo-9,9'-spirobifluorene; And / or, the halogen-containing biphenyl compound is 4,4'-diiodobiphenyl or 4,4'-dibromobiphenyl; And / or, the molar ratio of the aniline compound to the halogen-containing spirobifluorene is 1:(0.025-0.25).

6. The preparation method according to claim 5, characterized in that: include: The organic solvent, the aniline compound, the halogen-containing spirobifluorene, the halogen-containing biphenyl compound, the organic base, the palladium catalyst and the organic phosphine ligand are mixed, reacted at 115° C.-135° C. for 15 h-30 h, and then end-capping treatment is performed.

7. The preparation method according to claim 6, characterized in that: The organic base is sodium tert-butoxide, and the molar ratio of the aniline compound to the organic base is 1:(2.5-3.5); And / or, the palladium catalyst is tris(dibenzylideneacetone)dipalladium, and the molar ratio of the aniline compound to the palladium catalyst is 1:(0.003-0.010); And / or, the organic phosphine ligand is tri-tert-butylphosphine, and the molar ratio of the aniline compound to the organic phosphine ligand is 1:(0.01-0.05); And / or, the end-capping process includes: first adding the aniline compound and continuing to react at 115°C-135°C for 3h-8h, cooling, adding bromobenzene and continuing to react at 115°C-135°C for 3h-8h, and cooling.

8. The preparation method according to claim 6, characterized in that: Also includes: After the end-capping treatment, the mixture is treated with a mixed solvent formed by water and an organic solvent, and then the solid-liquid separation is performed to obtain a solid material. The solid material is washed, and then the solid material is dissolved again to remove the palladium, and the target product is separated again.

9. The preparation method according to claim 8, characterized in that: The mixed solvent is obtained by mixing acetone and water in a volume ratio of (8.0-9.5):1: And / or, the solid material is dissolved again with chloroform, and then palladium-removing silica gel is added for treatment, and the solid silica gel is removed by solid-liquid separation, and a concentrated solution is obtained after evaporation and concentration, and the target product is obtained by ethyl acetate precipitation and solid-liquid separation, and the target product is washed and dried.

10. A method for preparing the hole transport material according to claim 1 or 3, characterized in that: include: The polymerization reaction is carried out using a halogen-containing triphenylamine compound and a halogen-containing spirobifluorene as raw materials.

11. The preparation method according to claim 10, characterized in that: The halogen-containing triphenylamine compound is 4-butyl-4',4"-dibromotriphenylamine or 2,4,6-trimethyl-4',4"-dibromotriphenylamine; and / or, the halogen-containing spirobifluorene is 2,2',7,7'-tetrabromo-9,9'-spirobifluorene; And / or, the molar ratio of the halogen-containing triphenylamine compound to the halogen-containing spirobifluorene is 1:(0.01-0.5).

12. The preparation method according to claim 11, characterized in that: An organic solvent, a catalyst, a ligand, the halogen-containing triphenylamine compound and the halogen-containing spirobifluorene are mixed and reacted at 70° C.-90° C. for 12 h-20 h.

13. The preparation method according to claim 12, characterized in that: The catalyst is bis(1,5-cyclooctadiene)nickel, and the molar ratio of the halogen-containing triphenylamine compound to bis(1,5-cyclooctadiene)nickel is 1:(0.8-3.0); and / or, the ligand comprises 2,2-bipyridine and 1,5-cyclooctadiene, and the molar ratio of the halogen-containing triphenylamine compound, 2,2-bipyridine and 1,5-cyclooctadiene is 1:(1.0-4.0):(0.8-3.5); And / or, it also includes: cooling after the reaction of the halogen-containing triphenylamine compound and the halogen-containing spirobifluorene is completed, then diluting with the organic solvent, and then washing with hydrochloric acid solution, water, sodium bicarbonate solution and water in sequence, drying the obtained organic phase and then concentrating it, and precipitating the concentrated solution with ethyl acetate to obtain a solid product.

14. Use of the hole transport material according to any one of claims 1 to 3 or the hole transport material prepared by the preparation method according to any one of claims 4 to 13 in preparing single-junction or stacked solar cells.

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