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 chemical structural general formula of the hole transport material is as shown in the formula 1. 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 fabrication 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. For pin-structured perovskite solar cells, the hole transport materials currently used in the market are mainly self-assembled monolayers (SAMs). However, SAMs have high synthesis costs and poor stability, thus limiting the development of pin-structured perovskite solar cells. In addition, existing technologies have developed hole transport materials with dihydrophenazine as the main structure, which can improve the mobility of the hole transport layer. However, the synthesis methods of existing dihydrophenazine compounds are still relatively complex, leading to increased costs. Furthermore, the photoelectric conversion efficiency and stability of existing dihydrophenazine compounds still need 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 a second aspect, the present invention provides a method for synthesizing hole transport materials, characterized in that the method is used for synthesizing the hole transport material as described in claim 1, the synthesis method comprising the following steps:

[0008] A hole transport material is obtained by reacting a mixture of 10-(2-bromoethyl)-10H-phenoxazine, 5,10-dihydrophenazine, a catalyst, an organophosphorus compound, and an organic solvent.

[0009] Optionally, the molar ratio of 5,10-dihydrophenazine to 10-(2-bromoethyl)-10H-phenoxazine is 1:1 to 1:5, preferably 1:2 to 1:4; and / or,

[0010] The molar ratio of 5,10-dihydrophenazine to the catalyst is 1:0.1 to 1:0.3; and / or,

[0011] The molar ratio of 5,10-dihydrophenazine to the organophosphine is 1:1 to 1:3, preferably 1:1.5 to 1:2.5; and / or,

[0012] The reaction temperature is 105~140℃ and the reaction time is 5~15h; preferably, the reaction temperature is 110~130℃ and the reaction time is 7~10h.

[0013] Optionally, the catalyst is a palladium-based catalyst; and / or,

[0014] The organic solvent is toluene or xylene; and / or

[0015] The organophosphine is tri-tert-butylphosphine, triphenylphosphine, or tricyclohexylphosphine.

[0016] Optionally, the reaction raw materials may also include alkoxides.

[0017] Optionally, the molar ratio of the 5,10-dihydrophenazine to the alkoxide is 1:2 to 1:3; and / or,

[0018] The alkoxide is a tert-butoxide, preferably potassium tert-butoxide or sodium tert-butoxide.

[0019] 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.

[0020] Optionally, 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 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 annealing temperature is 90–120 °C, and the heating annealing time is 10–15 min.

[0021] Optionally, the thickness of the hole transport layer is 30~70 nm, preferably 40~60 nm.

[0022] Optionally, it further includes a passivation layer disposed between the perovskite light-absorbing layer and the electron transport layer; and / or,

[0023] It also includes a hole blocking layer disposed between the electron transport layer and the top electrode.

[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 has a large conjugated system and a stable structure, thus possessing suitable HOMO energy levels and low LUMO energy levels, high hole mobility and conductivity, excellent stability, and low processing costs. Therefore, perovskite solar cells fabricated using the hole transport material of this invention are beneficial for hole transport, thereby improving the hole transport effect of perovskite solar cells, exhibiting good stability, high photoelectric conversion efficiency with virtually no degradation, and demonstrating good device stability and photoelectric conversion efficiency.

[0026] B) The method for synthesizing hole transport materials provided by the present invention uses 5,10-dihydrophenazine and 10-(2-bromoethyl)-10H-phenoxazine as raw materials. Under the catalysis of the catalytic system, the hole transport materials 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 5,10-bis(2-(10H-phenoxazine-10-yl)ethyl)-5,10-dihydrophenazine (hereinafter sometimes simply referred to as "CzCoEt").

[0038] Compared with existing technologies, the hole transport material provided by this invention can replace existing SAMs materials. The hole transport material of this invention has a large conjugated system and a stable structure, thus possessing suitable HOMO energy levels and low LUMO energy levels, high hole mobility and conductivity, excellent stability, and low processing costs. Therefore, perovskite solar cells fabricated using the hole transport material of this invention are beneficial for hole transport, thereby improving the hole transport performance of perovskite solar cells, exhibiting good stability, high photoelectric conversion efficiency with virtually no degradation, and good device stability and photoelectric conversion efficiency.

[0039] 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:

[0040] Step 1: Weigh and mix the reaction raw materials to obtain a raw material mixture, wherein the reaction raw materials include 5,10-dihydrophenazine, 10-(2-bromoethyl)-10H-phenoxazine, a catalyst (preferably a palladium-based catalyst, more preferably palladium acetate), and an organophosphorus (preferably tri-tert-butylphosphine, triphenylphosphine, or tricyclohexylphosphine, more preferably tri-tert-butylphosphine); and

[0041] 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.

[0042] like Figure 1As shown, in the synthesis method of the hole transport material of the present invention, 5,10-bis(2-(10H-phenoxazine-10-yl)ethyl)-5,10-dihydrophenazine is synthesized using 5,10-dihydrophenazine and 10-(2-bromoethyl)-10H-phenoxazine as raw materials in the presence of a catalyst and an organophosphorus compound. In this reaction, 5,10-dihydrophenazine serves as the reactant, providing the main molecular structure. 10-(2-bromoethyl)-10H-phenoxazine participates in the reaction as a ligand. The catalyst effectively accelerates the reaction. The organophosphorus compound provides an alkaline environment for the reaction, promoting the forward reaction.

[0043] Compared with the prior art, the hole transport material synthesis method provided by the present invention uses 5,10-dihydrophenazine and 10-(2-bromoethyl)-10H-phenoxazine as raw materials. 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.

[0044] 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:

[0045] The molar ratio of 5,10-dihydrophenazine to 10-(2-bromoethyl)-10H-phenoxazine is 1:1 to 1:5, preferably 1:2 to 1:4; and / or, the molar ratio of 5,10-dihydrophenazine to the catalyst is 1:0.1 to 1:0.3; and / or, the molar ratio of 5,10-dihydrophenazine to organophosphine is 1:1 to 1:3, preferably 1:1.5 to 1:2.5.

[0046] In one embodiment, in order to control the reaction rate, in step 2, the reaction temperature can be 105~140℃, preferably 110~130℃, and the reaction time can be 5~15h, preferably 7~10h.

[0047] In one embodiment, in step 2, the ratio of the raw material mixture to the organic solvent, i.e., the concentration of the raw material mixture in the reaction system, is not particularly limited, as long as it can be ensured that the raw material mixture can be fully dissolved.

[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 5,10-dihydrophenazine to alkoxide in the reaction raw materials can be 1:2 to 1:3.

[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. 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 not within 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 a hole transport precursor solution to form a hole transport layer. The hole transport precursor solution includes at least the hole transport material provided in any of the above embodiments.

[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 details the steps of the method for preparing 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 CzCoEt 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 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 CzCoEt of the first aspect of the present invention. In one embodiment, the mass-volume concentration of CzCoEt in the CzCoEt solution can be 0.5~2 mg / mL; the spin-coating speed of the CzCoEt solution can be 2500~3500 rpm, the spin-coating time can be 20~40 s, and the spin-coating acceleration can be 2500~3500 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 included between steps a and b: the conductive substrate 1 is sequentially cleaned with cleaning water, cleaned with water, cleaned with an organic solvent (e.g., acetone), dried, and treated with ultraviolet ozone (UVO). The cleaning water consists of cleaning solution (e.g., acetone) and water (e.g., deionized water), with a volume ratio of cleaning solution to water of 1:40 to 1:60. Drying is performed by nitrogen purging. The UVO 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-2 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 anti-solvent is slowly added dropwise to induce perovskite crystallization. Preferably, the anti-solvent is added dropwise during the last 5 to 20 seconds of the second spin coating. The anti-solvent includes anisole or ethyl acetate, preferably anisole. The amount of anti-solvent used is not specifically limited 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 as follows:

[0089] 5,10-Dihydrophenazine (Shanghai Yuanye Biotechnology 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 CzCoEt

[0094] Weigh 1 g of 5,10-dihydrophenazine and mix it with 3.98 g of 10-(2-bromoethyl)-10H-phenoxazine (2.5 equivalents), 25 mg of palladium acetate (0.2 equivalents), 2.22 g of tri-tert-butylphosphine (2.0 equivalents), and 1.54 g of potassium tert-butoxide (2.5 equivalents). Add 80 mL of toluene solvent and react at 120 °C for 8 h to obtain 2.64 g of product 5,10-bis(2-(10H-phenoxazine-10-yl)ethyl)-5,10-dihydrophenazine (CzCoEt).

[0095] Example 2: Synthesis of CzCoEt

[0096] Weigh 1 g of 5,10-dihydrophenazine and mix it with 4.46 g of 10-(2-bromoethyl)-10H-phenoxazine (2.8 equivalents), 30 mg of palladium acetate (0.24 equivalents), 2.44 g of tri-tert-butylphosphine (2.2 equivalents), and 1.72 g of potassium tert-butoxide (2.8 equivalents). Add 80 mL of toluene solvent and react at 120 °C for 8 h to obtain 2.73 g of product 5,10-bis(2-(10H-phenoxazine-10-yl)ethyl)-5,10-dihydrophenazine (CzCoEt).

[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 1 mg of CzCoEt obtained in Example 1 and dissolve it in 1 mL of isopropanol solution to prepare a solution with a concentration of 1 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 3000 rpm, a spin-coating time of 30 s, and a spin-coating acceleration of 3000 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 47 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 a spin-coating 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 0.9 mg of CzCoEt obtained in Example 1 and dissolve it in 1 mL of isopropanol solution to prepare a solution with a concentration of 0.9 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 3200 rpm, a spin-coating time of 35 s, and a spin-coating acceleration of 3200 rpm / s; after spin-coating, transfer the FTO glass to a heating stage and anneal it at 110 °C for 10 min, and then cool it to room temperature to obtain a hole transport layer with a thickness of 53 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: Deposit 28 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.

[0113] Step d': A 5 nm thick BCP (rate 0.3 nm / s) 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 CzCoEt of the present invention) has significantly better cell performance than the inverted perovskite solar cell of Comparative Example 1 (the hole transport material is SAM (MeO-4PACz) of the prior art).

[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.

2. A method for synthesizing a hole transport material, characterized in that, The method for synthesizing the hole transport material as described in claim 1 includes the following steps: A hole transport material is obtained by reacting a mixture of 10-(2-bromoethyl)-10H-phenoxazine, 5,10-dihydrophenazine, a catalyst, an organophosphorus compound, and an organic solvent.

3. The method for synthesizing hole transport materials according to claim 2, characterized in that, The molar ratio of 5,10-dihydrophenazine to 10-(2-bromoethyl)-10H-phenoxazine is 1:1 to 1:5; and / or, The molar ratio of 5,10-dihydrophenazine to the catalyst is 1:0.1 to 1:0.3; and / or, The molar ratio of 5,10-dihydrophenazine to the organophosphine is 1:1 to 1:3; and / or, The reaction temperature is 105~140℃, and the reaction time is 5~15h.

4. The method for synthesizing hole transport materials according to claim 2 or 3, characterized in that, The reaction raw materials also include alkoxides.

5. The method for synthesizing hole transport materials according to claim 4, characterized in that, The molar ratio of the 5,10-dihydrophenazine to the alkoxide is 1:2 to 1:3; and / or, The alkoxide is a tert-butanol.

6. The method for synthesizing hole transport materials according to claim 2 or 3, 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.

7. 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 includes the hole transport material as described in claim 1.

8. The inverted perovskite solar cell according to claim 7, 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 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 annealing temperature is 90–120 °C, and the heating annealing time is 10–15 min.

9. The inverted perovskite solar cell according to claim 7 or 8, 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 7, characterized in that, It also includes a passivation layer disposed between the perovskite light-absorbing layer and the electron transport layer; and / or, It also includes a hole blocking layer disposed between the electron transport layer and the top electrode.

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