Hole transport material and synthesis method thereof, perovskite solar cell and preparation method thereof

Abstract

The invention provides a hole transport material and a synthesis method thereof, and a perovskite solar cell and a preparation method thereof. The general formula of the chemical structure of the hole transport material is shown as a formula 1, wherein R is alkyl with the carbon atom number of 1-6. The perovskite solar cell prepared from the hole transport material is high in photoelectric conversion efficiency and basically free of attenuation, and has good device stability and photoelectric conversion efficiency.

Description

Technical Field

[0001] This invention relates to hole transport materials and their synthesis methods, as well as inverted perovskite solar cells containing the hole transport materials and their preparation methods. Background Technology

[0002] Compared to nip-structured (NIP) perovskite solar cells, pin-structured (PIN) perovskite solar cells offer advantages such as stronger thermal and light stability, fewer interface defects, lower sintering temperatures, and higher low-light response. Currently, the hole transport materials used in the market for pin-structured perovskite solar cells are primarily self-assembled monolayers (SAMs). However, SAMs have high synthesis costs and poor stability, thus limiting the development of pin-structured perovskite solar cells. Furthermore, the photoelectric conversion efficiency of other existing hole transport materials needs further improvement. Summary of the Invention

[0003] In order to solve the above-mentioned technical problems in the prior art, the purpose of this invention is to provide a hole transport material and a method for synthesizing the same, including an inverse perovskite solar cell of the hole transport material and a method for preparing it.

[0004] The objective of this invention is mainly achieved through the following technical solutions:

[0005] In a first aspect, the present invention provides a hole transport material for use in inverted (pin) perovskite solar cells, the general chemical structure of which is shown in Formula 1:

[0006] Formula 1

[0007] In Formula 1, R is an alkyl group having 1 to 6 carbon atoms.

[0008] Optionally, R in Formula 1 is methyl, ethyl, n-propyl, n-butyl, n-pentyl, or n-hexyl.

[0009] In a second aspect, the present invention provides a method for synthesizing hole transport materials, used for synthesizing hole transport materials in the first aspect, the method comprising the following steps:

[0010] The hole transport material is obtained by reacting a mixture of N1-(4-aminophenyl)-N1-(4-alkoxyphenyl)benzene-1,4-diamine, halothiophene, catalyst, organophosphine, and organic solvent.

[0011] Optionally, the molar ratio of the N1-(4-aminophenyl)-N1-(4-alkoxyphenyl)phenyl-1,4-diamine to the halothiophene is 1:3 to 1:7; and / or,

[0012] The molar ratio of N1-(4-aminophenyl)-N1-(4-alkoxyphenyl)phenyl-1,4-diamine to the catalyst is 1:0.2 to 1:0.4; and / or,

[0013] The molar ratio of the N1-(4-aminophenyl)-N1-(4-alkoxyphenyl)phenyl-1,4-diamine to the organophosphine is 1:1 to 1:3; and / or,

[0014] The reaction temperature is 105~140℃, and the reaction time is 5~15h.

[0015] Optionally, the catalyst is a palladium-based catalyst; and / or,

[0016] The organic solvent is toluene or xylene; and / or

[0017] The organophosphine is tri-tert-butylphosphine, triphenylphosphine, or tricyclohexylphosphine.

[0018] Optionally, the reaction raw materials may also include alkoxides.

[0019] Optionally, the molar ratio of the N1-(4-aminophenyl)-N1-(4-alkoxyphenyl)phenyl-1,4-diamine to the alkoxide is 1:2 to 1:3; and / or,

[0020] The alkoxide is a tert-butanol.

[0021] Thirdly, the present invention provides an inverted perovskite solar cell, comprising a conductive substrate, a hole transport layer, a perovskite light-absorbing layer, an electron transport layer and a top electrode stacked sequentially, wherein the hole transport layer comprises the hole transport material provided in the first aspect.

[0022] Optionally, the thickness of the hole transport layer is 30~70 nm; preferably, the thickness of the hole transport layer is 40~60 nm.

[0023] Optionally, the hole transport layer is prepared by the following method: the hole transport layer is prepared by spin-coating an organic solution of the hole transport material onto the surface of the conductive substrate, followed by heating and annealing to obtain the hole transport layer. The spin-coating speed is 2500–3500 rpm, the spin-coating time is 20–40 s, the spin-coating acceleration is 2500–3500 rpm / s, the mass-volume concentration of the hole transport material in the organic solution is 0.5–2 mg / mL, the heating and annealing temperature is 90–120 °C, and the heating and annealing time is 10–15 min.

[0024] Compared with the prior art, the present invention can achieve at least one of the following beneficial effects:

[0025] A) The hole transport material provided by this invention can replace existing SAMs materials. The hole transport material of this invention is based on a triphenylamine group. Since triphenylamine is a p-type semiconductor, it is more inclined towards holes, which is beneficial for hole transport; the nitrogen atom itself has a lone pair of electrons and mainly plays a role in charge transport in the molecule, and the introduction of the nitrogen atom further facilitates charge transport; the oxygen atom in the alkoxy group itself has a lone pair of electrons and mainly plays a role in charge transport in the molecule, and the introduction of the oxygen atom also facilitates charge transport. The introduction of di(thiophene-3-yl)amino further promotes the hyperconjugated structure of the triphenylamine structure, further contributing to hole transport. Therefore, perovskite solar cells prepared using the hole transport material of this invention have high photoelectric conversion efficiency with virtually no degradation, exhibiting good device stability and photoelectric conversion efficiency.

[0026] B) The method for synthesizing hole transport materials provided by the present invention uses N1-(4-aminophenyl)-N1-(4-alkoxyphenyl)benzene-1,4-diamine as a raw material. Under the catalysis of the catalytic system, the hole transport material can be synthesized in one step. The synthesis is simple and the cost of the raw materials is low, which helps to reduce the industrialization cost of perovskite solar cell production in the later stage.

[0027] Other features and advantages of the invention will be set forth in the description which follows, and will be apparent in part from the description, or may be learned by practicing the invention. The objects and other advantages of the invention may be realized and obtained by means of the structures particularly pointed out in the written description and the accompanying drawings. Attached Figure Description

[0028] The accompanying drawings are for illustrative purposes only and are not intended to limit the invention. Throughout the drawings, the same reference numerals denote the same parts.

[0029] Figure 1 This is a diagram illustrating the synthesis process of the hole transport material of the present invention;

[0030] Figure 2 This is a schematic diagram of the inverted perovskite solar cell of the present invention;

[0031] Figure 3 This is a comparison chart of the cell performance of the inverted perovskite solar cells prepared in Comparative Example 1 and Example 3.

[0032] Figure Labels

[0033] 1-Conductive substrate; 2-Hole transport layer; 3-Perovskite light-absorbing layer; 4-Electron transport layer; 5-Top electrode. Detailed Implementation

[0034] Preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, which form part of the present invention and, together with the embodiments of the present invention, serve to illustrate the principles of the present invention.

[0035] In a first aspect, the present invention provides a hole transport material as shown in Formula 1:

[0036] Formula 1

[0037] The chemical name of the hole transport material is N1-(4-(di(thiophen-3-yl)amino)phenyl)-N1-(4-alkoxyphenyl)benzene-1,4-diamine. In Formula 1, R is an alkyl group, and the number of carbon atoms in the alkyl group is less than or equal to 6.

[0038] From the perspective of electron transport, R is selected from alkyl groups, including methyl, ethyl, n-propyl, n-butyl, n-pentyl, or n-hexyl. When R is methyl, the hole transport material of the present invention is N1-(4-(di(thiophen-3-yl)amino)phenyl)-N1-(4-methoxyphenyl)-N4,N4-di(thiophen-3-yl)phenyl-1,4-diamine (hereinafter sometimes simply referred to as "PhPzSN").

[0039] Compared with existing technologies, the hole transport material provided by this invention can replace existing SAMs materials. The hole transport material of this invention is based on a triphenylamine group to construct the molecule. Since triphenylamine is a p-type semiconductor, it is more inclined towards holes, which is beneficial for hole transport; the nitrogen atom itself has a lone pair of electrons and mainly plays a role in charge transport in the molecule, and the introduction of the nitrogen atom further facilitates charge transport; the oxygen atom in the alkoxy group itself has a lone pair of electrons and mainly plays a role in charge transport in the molecule, and the introduction of the oxygen atom also facilitates charge transport. The introduction of di(thiophene-3-yl)amino further promotes the hyperconjugated structure of the triphenylamine structure, further contributing to hole transport. Therefore, perovskite solar cells prepared using the hole transport material of this invention have high photoelectric conversion efficiency with virtually no degradation, exhibiting good device stability and photoelectric conversion efficiency.

[0040] A second aspect of the present invention provides a method for synthesizing a hole transport material, used for synthesizing the hole transport material of the first aspect of the present invention. The synthesis method includes the following steps:

[0041] Step 1: Weigh and mix the reaction raw materials to obtain a raw material mixture. The reaction raw materials include N1-(4-aminophenyl)-N1-(4-alkoxyphenyl)benzene-1,4-diamine, halothiophene (e.g., 3-bromothiophene or 3-chlorothiophene), catalyst (preferably palladium-based catalyst, more preferably palladium acetate), and organophosphorus (preferably tri-tert-butylphosphine, triphenylphosphine, or tricyclohexylphosphine, more preferably tri-tert-butylphosphine); and

[0042] Step 2: The raw material mixture is mixed with an organic solvent (e.g., toluene or xylene) and then reacted to obtain a hole transport material.

[0043] like Figure 1 As shown, in the synthesis method of the hole transport material of the present invention, N1-(4-aminophenyl)-N1-(4-alkoxyphenyl)phenyl-1,4-diamine and halothiophene are used as raw materials. In the presence of a catalyst and organophosphorus compounds, the hydrogen atom in the amino group is replaced by the thiophene group, thereby synthesizing the hole transport material of the present invention, N1-(4-(di(thiophene-3-yl)amino)phenyl)-N1-(4-alkoxyphenyl)phenyl-1,4-diamine. In this reaction, N1-(4-aminophenyl)-N1-(4-alkoxyphenyl)phenyl-1,4-diamine serves as the reactant, providing the main molecular structure. Halothiophene participates in the reaction as a reaction ligand. The catalyst accelerates the reaction. The organophosphorus compounds provide an alkaline environment for the reaction, promoting the forward reaction.

[0044] Compared with the prior art, the hole transport material synthesis method provided by the present invention uses N1-(4-aminophenyl)-N1-(4-alkoxyphenyl)benzene-1,4-diamine as the synthesis raw material. Under the catalysis of the catalytic system, the hole transport material can be synthesized in one step. The synthesis is simple and the cost of the synthesis raw materials is low, which helps to reduce the industrialization cost of perovskite solar cell production in the later stage.

[0045] In one embodiment, in order to control the reaction yield, the molar ratios of the various raw materials in the above-mentioned reaction raw materials are as follows:

[0046] The molar ratio of N1-(4-aminophenyl)-N1-(4-alkoxyphenyl)benzene-1,4-diamine to halothiophene can be 1:3 to 1:7, preferably 1:4 to 1:6; the molar ratio of N1-(4-aminophenyl)-N1-(4-alkoxyphenyl)benzene-1,4-diamine to catalyst can be 1:0.2 to 1:0.4; the molar ratio of N1-(4-aminophenyl)-N1-(4-alkoxyphenyl)benzene-1,4-diamine to tri-tert-butylphosphine can be 1:1 to 1:3.

[0047] In one embodiment, in order to control the reaction rate, in step 2, the reaction temperature can be 105~140℃, preferably 110~125℃, and the reaction time can be 5~15h, preferably 7~11h.

[0048] Considering that byproducts (i.e., hydrogen bromide or hydrogen iodide) will be generated during the above reaction process, in order to consume the byproducts and promote the reaction, the reactants also include an alkoxide that can react with hydrogen halides. Thus, by adding the alkoxide, it can react with the generated byproducts, consume the byproducts, and promote the forward reaction. Preferably, the alkoxide that can react with hydrogen halides can be a tert-butoxide, more preferably potassium tert-butoxide or sodium tert-butoxide.

[0049] In order to improve the reaction yield of alkoxide and byproduct, the molar ratio of N1-(4-aminophenyl)-N1-(4-alkoxyphenyl)benzene-1,4-diamine to alkoxide in the reaction raw materials can be 1:2~3.

[0050] A third aspect of the present invention provides an inverted perovskite solar cell. For example... Figure 2 As shown, in one embodiment, the inverted perovskite solar cell of the present invention includes a conductive substrate 1, a hole transport layer 2, a perovskite light-absorbing layer 3, an electron transport layer 4, and a top electrode 5 stacked sequentially, wherein the hole transport layer 2 is prepared from the hole transport material provided in the first aspect of the present invention.

[0051] In one embodiment, in the inverted perovskite solar cell of the present invention, the thickness of the hole transport layer 2 can be 30-70 nm, preferably 40-60 nm (e.g., 45 nm, 50 nm, or 55 nm). When the thickness of the hole transport layer 2 is within the above range, it is beneficial for carrier transport. On the other hand, when the thickness of the hole transport layer 2 is outside the above range, it may affect carrier transport, thereby causing energy level mismatch. The thickness of the hole transport layer 2 and other layers of the inverted perovskite solar cell can be measured by imaging the inverted perovskite solar cell with a scanning electron microscope (SEM).

[0052] Compared with the prior art, the beneficial effects of the inverted perovskite solar cell provided by the present invention are basically the same as the beneficial effects of the hole transport material provided in the first aspect of the present invention, and will not be described in detail here.

[0053] The inverted perovskite solar cell of the present invention can be fabricated by the following method. In one embodiment, the fabrication method of the inverted perovskite solar cell of the present invention includes the following steps:

[0054] Step a: Provide a conductive substrate;

[0055] Step b: Coat the surface of the conductive substrate with an organic solution of the hole transport material to form a hole transport layer;

[0056] Step c: Form a perovskite light-absorbing layer on the hole transport layer;

[0057] Step d: Forming an electron transport layer on the perovskite light-absorbing layer; and

[0058] Step e: Fabricate a top electrode on the surface of the electron transport layer to obtain an inverted perovskite solar cell.

[0059] Compared with the prior art, the beneficial effects of the method for preparing the inverted perovskite solar cell provided by the present invention are basically the same as those of the inverted perovskite solar cell provided in the second aspect of the present invention, and will not be elaborated here.

[0060] The following will describe in detail the various steps of the inverted perovskite solar cell of the present invention.

[0061] There are no particular limitations on the specific type of conductive substrate in step a; any conductive substrate commonly used in the art can be used. In one embodiment, an FTO (Fluorine-doped Tin Oxide) conductive glass substrate can be used.

[0062] In one embodiment, the method for forming the hole transport layer 2 in step b may include the following steps:

[0063] The hole transport material PhPzSN of the first aspect of the present invention was dissolved in an organic solvent and coated onto an FTO conductive glass substrate by spin coating. The coated FTO conductive glass substrate was then transferred to a heating stage for heating and annealing, followed by cooling to obtain the hole transport layer 2.

[0064] In one embodiment, in the above-mentioned heating annealing process, the heating annealing temperature is 90-120°C and the heating annealing time is 10-15 min.

[0065] In one embodiment, isopropanol can be used as an organic solvent to dissolve the hole transport material PhPzSN of the first aspect of the present invention. In one embodiment, the mass-volume concentration of PhPzSN in the PhPzSN solution can be 0.5~2 mg / mL; the spin-coating speed of the PhPzSN solution can be 3000~4000 rpm, the spin-coating time can be 30~40 s, and the spin-coating acceleration can be 3000~4000 rpm / s.

[0066] It is understood that the above step b includes a step of synthesizing hole transport materials. For the synthesis of hole transport materials, the method for synthesizing hole transport materials provided in the second aspect of the present invention can be used, which will not be described in detail here.

[0067] To ensure the cleanliness of the conductive substrate, the following step a' is added between steps a and b: the conductive substrate 1 is sequentially subjected to cleaning water, water cleaning, organic solvent (e.g., acetone) cleaning, drying (e.g., nitrogen purging and drying), and ultraviolet ozone treatment (UVO). The cleaning water consists of a cleaning solution (e.g., acetone and water (e.g., deionized water) with a volume ratio of 1:40 to 1:60. The UV ozone cleaning treatment time is 20 to 30 minutes.

[0068] In one embodiment, the method for forming the perovskite light-absorbing layer 3 in step c may include the following steps:

[0069] Step c-1: Mix the perovskite precursor raw material with an organic solvent and stir to obtain a precursor solution;

[0070] Step c-2: Spin-coating the precursor solution obtained in step c-1 onto the surface of hole transport layer 2;

[0071] Step c-3: The conductive substrate 1 with the precursor solution spin-coated is transferred to a heating stage for heating and annealing, and then cooled to obtain a perovskite light-absorbing layer.

[0072] In one embodiment, in step c-1 above, the composition of the perovskite precursor raw material may include methyl ammonium chloride (MACl), lead iodide (PbI2), and methyl iodide (FAI), wherein the mass ratio of methyl ammonium chloride, lead iodide, and methyl iodide is (3-4):(70-72):(23-25), the composition of the organic solvent includes N,N-dimethylformamide (DMF) and / or dimethyl sulfoxide (DMSO), preferably the composition of the organic solvent includes N,N-dimethylformamide and dimethyl sulfoxide, the volume ratio of the two is 5:1 to 10:1, the stirring temperature is 20-30°C, and the stirring time is 5-12 h.

[0073] In one embodiment, in step c-3, the heating annealing temperature is 90-120°C, and the heating annealing time is 10-120 min.

[0074] In one embodiment, in order to improve spin coating efficiency and quality, the spin coating of the precursor solution in step c-3 above includes at least two stages (e.g., a first spin coating and a second spin coating). Preferably, the spin coating speed, spin coating time, and spin coating acceleration of the second spin coating are all greater than those of the first spin coating.

[0075] In one embodiment, in step c-2 above, the spin coating speed for the first spin coating is 900–1050 rpm, the spin coating time is 8–12 s, and the spin coating acceleration is 900–1050 rpm / s; the spin coating speed for the second spin coating is 4500–5500 rpm, the spin coating time is 15–45 s, and the spin coating acceleration is 4500–5500 rpm / s. In the final stage of the second spin coating, an antisolvent is slowly added dropwise to induce perovskite crystallization. Preferably, the antisolvent is added dropwise during the last 5 to 20 seconds of the second spin coating. The antisolvent includes anisole or ethyl acetate, preferably anisole. There is no specific limitation on the amount of antisolvent used, as long as sufficient crystallization of the perovskite is achieved.

[0076] In one embodiment, the electron transport layer 4 in step d above can be formed by methods such as vapor deposition. In one embodiment, the material used to form the electron transport layer 4 can be a carbon material (e.g., fullerene (C4)). 60 In one embodiment, the thickness of the electron transport layer 4 can be 20-30 nm.

[0077] For purposes such as defect state passivation, energy level modulation, and suppression of ion migration, preferably, in one embodiment, step c' is further included between step c and step d: forming a passivation layer 3' on the surface of the perovskite light-absorbing layer 3.

[0078] In one implementation, the method for forming the passivation layer 3' in step c' may include the following steps:

[0079] Step c'-1: Dissolve the passivation layer precursor material in an organic solvent to obtain a passivation layer precursor solution;

[0080] Step c'-2: Spin-coating the passivation layer precursor solution obtained in step c'-1 onto the surface of the perovskite light-absorbing layer 3.

[0081] Step c'-3: Transfer the conductive substrate 1, which is spin-coated with the passivation layer precursor solution, to a heating stage for heating and annealing to obtain the passivation layer.

[0082] In one embodiment, in step c'-1 above, the passivation layer precursor raw material may include 1,3-diaminopropane dihydroiodide (PDADI), the organic solvent may be isopropanol, and the mass-volume concentration of the passivation layer precursor solution may be 0.5~2 mg / mL.

[0083] In one embodiment, in step c'-3, the heating annealing temperature is 90-120°C, and the heating annealing time is 10-15 min.

[0084] In one embodiment, in step e above, the top electrode 5 is formed by vapor deposition. In one embodiment, the material forming the top electrode 5 can be a material commonly used for top electrodes in perovskite solar cells (e.g., Ag), and the thickness of the top electrode 4 can be 50~150 nm.

[0085] For the purpose of blocking hole backflow and reducing interfacial recombination, in one embodiment, preferably, a step d' is included between step d and step e: forming a hole blocking layer 4' on the surface of the electron transport layer 4. In one embodiment, the material used to form the hole blocking layer 4' can be BCP (Bathocuproine, chemical name 2,9-dimethyl-4,7-diphenyl-1,10-phenanthroline), and the thickness of the hole blocking layer 4' can be 3~8 nm.

[0086] Example

[0087] The hole transport material and its synthesis method of the present invention, including the inverse perovskite solar cell of the hole transport material and its preparation method, will be described in detail below through specific embodiments. However, the following embodiments are not intended to limit the scope of the present invention.

[0088] The main reagents used in each embodiment and comparative example are shown below:

[0089] 3-Bromothiophene (Shanghai Jizhi Biochemical Technology Co., Ltd.);

[0090] Palladium acetate (Shanghai Yuanye Biotechnology Co., Ltd.);

[0091] tert-tert-butylphosphine (Shanghai Jizhi Biochemical Technology Co., Ltd.);

[0092] Potassium tert-butoxide (Shanghai Yuanye Biotechnology Co., Ltd.)

[0093] Example 1: Synthesis of PhPzSN

[0094] Weigh 1 g of N1-(4-aminophenyl)-N1-(4-methoxyphenyl)phenyl-1,4-diamine and mix it with 2.67 g of 3-bromothiophene (5 equivalents), 35 mg of palladium acetate (0.28 equivalents), 2.65 g of tri-tert-butylphosphine (2.0 equivalents), and 1.65 g of potassium tert-butoxide (2.5 equivalents). Add 100 mL of toluene as solvent and react at 120 °C for 8 h to obtain 1.66 g of product N1-(4-(di(thiophen-3-yl)amino)phenyl)-N1-(4-methoxyphenyl)-N4,N4-di(thiophen-3-yl)phenyl-1,4-diamine (PhPzSN).

[0095] Example 2: Synthesis of PhPzSN-3

[0096] Weigh 1 g of N1-(4-aminophenyl)-N1-(4-propoxyphenyl)phenyl-1,4-diamine and mix it with 2.67 g of 3-bromothiophene (5 equivalents), 45 mg of palladium acetate (0.36 equivalents), 2.65 g of tri-tert-butylphosphine (2.0 equivalents), and 1.65 g of potassium tert-butoxide (2.5 equivalents). Add 100 mL of toluene as solvent and react at 120 °C for 10 h to obtain 1.54 g of product N1-(4-(di(thiophen-3-yl)amino)phenyl)-N1-(4-propoxyphenyl)-N4,N4-di(thiophen-3-yl)phenyl-1,4-diamine (PhPzSN-3).

[0097] Example 3: Fabrication of an inverted perovskite solar cell

[0098] Step a: Provide an FTO conductive glass substrate.

[0099] Step a': The FTO conductive glass substrate was cleaned sequentially with a glass cleaning solution of 1:50 (volume ratio), deionized water, and acetone. After cleaning, the FTO conductive glass substrate was dried with dry nitrogen gas. After drying, the conductive glass substrate was cleaned with ultraviolet ozone for 20 minutes.

[0100] Step b: Weigh 2 mg of PhPzSN obtained in Example 1 and dissolve it in 1 mL of isopropanol solution to prepare a solution with a concentration of 2 mg / mL; spin-coat the obtained solution onto the FTO conductive glass substrate obtained in step a' using a spin-coating method with a spin-coating speed of 3500 rpm, a spin-coating time of 35 s, and a spin-coating acceleration of 3500 rpm / s; after spin-coating, transfer the FTO glass to a heating stage and anneal at 100 °C for 12 min, and then cool to room temperature to obtain a hole transport layer with a thickness of 48 nm.

[0101] Step c: Dissolve 40 mg MACl, 857 mg PbI2, and 293 mg FAI in 1 mL DMF / DMSO (volume ratio 6:1) and stir at room temperature (25 °C) for 8 h. After stirring, spin-coat the precursor solution onto the FTO conductive glass substrate treated in step b. Two spin-coatings were then performed: the first spin-coating was performed at 1000 rpm for 10 s with an acceleration of 1000 rpm / s; the second spin-coating was performed at 5000 rpm for 20 s with an acceleration of 5000 rpm / s. During the last 10 seconds of the second spin-coating, 120 μL of the antisolvent anisole was slowly added dropwise. After spin-coating, the FTO conductive glass substrate was annealed on a hot plate at 110 °C for 20 min, followed by cooling to obtain the perovskite light-absorbing layer.

[0102] Step c': Weigh 1 mg of 1,3-diaminopropane dihydroiodide (PDADI) and dissolve it in 1 mL of isopropanol solution to prepare a solution with a concentration of 1 mg / mL. Spin-coat this solution onto the perovskite light-absorbing layer of the FTO conductive glass substrate obtained in step c) at a spin speed of 3000 rpm for 30 s with an acceleration of 3000 rpm / s. After spin-coating, transfer the FTO conductive glass substrate to a heating stage and anneal at 100°C for 12 min. After cooling, a passivation layer is obtained.

[0103] Step d: Deposit 25 nm (rate 0.5 nm / s) of fullerene onto the passivation layer of the FTO conductive glass substrate obtained in step c' to obtain an electron transport layer.

[0104] Step d': A 6 nm (rate 0.3 nm / s) BCP is deposited on the electron transport layer of the FTO conductive glass substrate obtained in step d to obtain a hole blocking layer.

[0105] Step e: Deposit 100 nm (rate 1 nm / s) of Ag on the hole blocking layer of the FTO conductive glass substrate obtained in step d' as the top electrode, and obtain an inverted perovskite solar cell.

[0106] Example 4

[0107] Step a: Provide an FTO conductive glass substrate.

[0108] Step a': The FTO conductive glass substrate was cleaned sequentially with a glass cleaning solution of 1:60 (volume ratio), deionized water, and acetone. After cleaning, the FTO conductive glass substrate was dried with dry nitrogen gas. After drying, the conductive glass substrate was cleaned with ultraviolet ozone for 25 minutes.

[0109] Step b: Weigh 1.8 mg of PhPzSN obtained in Example 1 and dissolve it in 1 mL of isopropanol solution to prepare a solution with a concentration of 1.8 mg / mL; spin-coat the obtained solution onto the FTO conductive glass substrate obtained in step a' using a spin-coating method with a spin-coating speed of 3800 rpm, a spin-coating time of 33 s, and a spin-coating acceleration of 3800 rpm / s; after spin-coating, transfer the FTO glass to a heating stage and anneal it at 110 °C for 15 min, and then cool it to room temperature to obtain a hole transport layer with a thickness of 51 nm.

[0110] Step c: Dissolve 40 mg MACl, 857 mg PbI2, and 293 mg FAI in 1 mL DMF / DMSO (volume ratio 6:1) and stir at room temperature (25 °C) for 7 h. After stirring, spin-coat the precursor solution onto the FTO conductive glass substrate treated in step b. Two spin-coatings were then performed: the first spin-coating was performed at 1000 rpm for 10 s with an acceleration of 1000 rpm / s; the second spin-coating was performed at 4500 rpm for 35 s with an acceleration of 4500 rpm / s. During the last 10 seconds of the second spin-coating, 120 μL of the antisolvent anisole was slowly added dropwise. After spin-coating, the FTO conductive glass substrate was annealed on a hot plate at 110 °C for 20 min, followed by cooling to obtain the perovskite light-absorbing layer.

[0111] Step c': Weigh 1 mg of 1,3-diaminopropane dihydroiodide (PDADI) and dissolve it in 1 mL of isopropanol solution to prepare a solution with a concentration of 1 mg / mL. Spin-coat this solution onto the perovskite light-absorbing layer of the FTO conductive glass substrate obtained in step c) at a spin speed of 3000 rpm for 30 s with an acceleration of 3000 rpm / s. After spin-coating, transfer the FTO conductive glass substrate to a heating stage and anneal at 100°C for 12 min. After cooling, a passivation layer is obtained.

[0112] Step d: A fullerene layer of 28 nm (rate 0.5 nm / s) is deposited on the passivation layer of the FTO conductive glass substrate obtained in step c' to obtain an electron transport layer.

[0113] Step d': A 5 nm (rate 0.3 nm / s) BCP is deposited on the electron transport layer of the FTO conductive glass substrate obtained in step d to obtain a hole blocking layer.

[0114] Step e: Deposit 90 nm (rate 1 nm / s) of Ag on the hole blocking layer of the FTO conductive glass substrate obtained in step d' as the top electrode, and obtain an inverted perovskite solar cell.

[0115] Example 5

[0116] Except for using the hole transport material obtained in Example 2 as the hole transport layer, an inverted perovskite solar cell was prepared by the same method as in Example 3.

[0117] Comparative Example 1

[0118] Except that [2-(3,6-dimethoxy-9H-carbazole-9-yl)ethyl]phosphonic acid (MeO-4PACz) was used as the hole transport material and the mass-volume concentration of the MeO-4PACz isopropanol solution used for spin coating was 1 mg / mL, the inverted perovskite solar cell was prepared by the same method as in Example 3.

[0119] Comparative Example 2

[0120] Except for using the compound represented by Formula 2 as the hole transport layer, an inverted perovskite solar cell was prepared by the same method as in Example 3.

[0121] Formula 2

[0122] Comparative Example 3

[0123] Except for using the compound represented by Formula 3 as the hole transport layer, an inverted perovskite solar cell was prepared by the same method as in Example 3.

[0124] Formula 3

[0125] The performance of the inverted perovskite solar cells prepared in Example 3 and Comparative Example 1 was tested, and the test results are shown in [reference needed]. Figure 3 The photovoltaic performance parameters of the inverted perovskite solar cells prepared in Examples 3-5 and Comparative Examples 1-3 are shown in Table 1.

[0126]

[0127] from Figure 3 It can be seen that the inverted perovskite solar cell prepared in Example 3 (the hole transport material is the PhPzSN of the present invention) has significantly better cell performance than the inverted perovskite solar cell of Comparative Example 1 (the hole transport material is the prior art SAM (MeO-4PACz)).

[0128] On the other hand, as can be seen from Table 1, compared with Comparative Examples 1-3 using various hole transport materials of the prior art, the inverted perovskite solar cells prepared using the hole transport materials of the present invention in Examples 3-5 all show significant improvements in photovoltaic performance parameters such as short-circuit current density, open-circuit voltage, fill factor, and photoelectric conversion efficiency.

[0129] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any changes or substitutions that can be easily conceived by those skilled in the art within the scope of the technology disclosed in the present invention should be included within the scope of protection of the present invention.

Claims

1. A hole transport material, characterized in that, For use in inverted perovskite solar cells, the general chemical structure of the hole transport material is shown in Formula 1: Formula 1 In Formula 1, R is an alkyl group having 1 to 6 carbon atoms.

2. The hole transport material according to claim 1, characterized in that, R is methyl, ethyl, n-propyl, n-butyl, n-pentyl, or n-hexyl.

3. A method for synthesizing a hole transport material, characterized in that, For the synthesis of the hole transport material as described in claim 1 or 2, the synthesis method includes the following steps: The hole transport material is obtained by reacting a mixture of N1-(4-aminophenyl)-N1-(4-alkoxyphenyl)benzene-1,4-diamine, halothiophene, catalyst, organophosphine, and organic solvent.

4. The method for synthesizing hole transport materials according to claim 3, characterized in that, The molar ratio of the N1-(4-aminophenyl)-N1-(4-alkoxyphenyl)phenyl-1,4-diamine to the halothiophene is 1:3 to 1:7; and / or, The molar ratio of N1-(4-aminophenyl)-N1-(4-alkoxyphenyl)phenyl-1,4-diamine to the catalyst is 1:0.2 to 1:0.4; and / or, The molar ratio of the N1-(4-aminophenyl)-N1-(4-alkoxyphenyl)phenyl-1,4-diamine to the organophosphine is 1:1 to 1:3; and / or, The reaction temperature is 105~140℃, and the reaction time is 5~15h.

5. The method for synthesizing hole transport materials according to claim 3 or 4, characterized in that, The reaction raw materials also include alkoxides.

6. The method for synthesizing hole transport materials according to claim 5, characterized in that, The molar ratio of the N1-(4-aminophenyl)-N1-(4-alkoxyphenyl)phenyl-1,4-diamine to the alkoxide is 1:2 to 1:3; and / or, The alkoxide is a tert-butanol.

7. The method for synthesizing hole transport materials according to claim 3 or 4, characterized in that, The catalyst is a palladium-based catalyst; and / or, The organic solvent is toluene or xylene; and / or The organophosphine is tri-tert-butylphosphine, triphenylphosphine, or tricyclohexylphosphine.

8. A reverse-structure perovskite solar cell, comprising a conductive substrate, a hole transport layer, a perovskite light-absorbing layer, an electron transport layer, and a top electrode stacked sequentially, characterized in that, The hole transport layer comprises the hole transport material as described in claim 1 or 2.

9. The inverted perovskite solar cell according to claim 7, characterized in that, The thickness of the hole transport layer is 30~70 nm, preferably 40~60 nm.

10. The inverted perovskite solar cell according to claim 8 or 9, characterized in that: The hole transport layer is prepared by the following method: an organic solution of the hole transport material is spin-coated onto the surface of the conductive substrate, followed by a heating annealing treatment to obtain the hole transport layer. The spin-coating speed is 3000–4000 rpm, the spin-coating time is 30–40 s, the spin-coating acceleration is 3000–4000 rpm / s, the mass-volume concentration of the hole transport material in the organic solution is 0.5–2 mg / mL, the heating annealing temperature is 90–120℃, and the heating annealing time is 10–15 min.

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