A method for preparing a titanium dioxide hole blocking layer for large-area perovskite cells

Abstract

The present invention discloses a method for preparing a titanium dioxide hole blocking layer for a large-area perovskite solar cell. The method uses n-butyl titanate as a titanium source, and generates an N- and F-co-doped titanium dioxide film by a mixed hydrolysis method with nitric acid and 3-fluoropropanol. The titanium dioxide hole blocking layer surface is interface-modified using 3-mercaptopropionic acid or mercaptoacetic acid to form the titanium dioxide hole blocking layer of the perovskite solar cell. The method generates the N- and F-co-doped titanium dioxide film by a mixed hydrolysis method with nitric acid and 3-fluoropropanol, thereby ensuring that the large-area hole blocking layer film does not have holes and maintaining high photovoltaic performance of the solar cell.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and in particular to a method for preparing a titanium dioxide hole blocking layer for large-area perovskite solar cells. Background Art

[0002] Organic-inorganic hybrid perovskite solar cells have achieved remarkable progress in recent years, with their photoelectric conversion efficiency increasing from 3.8% in 2009 to 25.6% today. The classic nip-structured organic-inorganic hybrid perovskite solar cell consists of FTO / hole-blocking layer / mesoporous TiO2 layer / MAPbI3 / electron-blocking layer / Au. FTO is fluorine-doped SnO2, and MAPbI3 is the organic-inorganic hybrid perovskite thin film. The hole-blocking layer, also known as the electron-transporting layer, is a key component of perovskite solar cells, playing the crucial role of blocking holes and transporting electrons. As a thin film, the hole-blocking layer is prone to holes when fabricated over large areas. If used in solar cell assembly, this can lead to increased leakage current and even short circuits. Therefore, the conductivity and density of the hole-blocking layer significantly impact the photovoltaic performance of solar cells. Common hole-blocking layer materials include titanium dioxide, tin dioxide, zinc oxide, and some conductive polymers. Titanium dioxide is the most common hole-blocking layer due to its low cost and ease of preparation. Therefore, how to prepare a large-area, highly conductive, and highly dense titanium dioxide hole blocking layer plays an important role in accelerating the commercialization of perovskite solar cells.

[0003] Existing hole blocking layer films used in perovskite solar cells have the following problems:

[0004] (1) The effective area of ​​the hole blocking layer film is small, which hinders the commercialization of perovskite solar cells. Currently, most of the hole blocking layer films studied in perovskite solar cells are titanium dioxide or tin dioxide films with a size of 0.09 cm 2 about.

[0005] (2) The effective area of ​​the hole blocking layer exceeds 1 cm 2 For products with this structure, a thicker mesoporous titanium dioxide layer needs to be added to the film surface to prevent leakage current and improve contact with the light absorption layer. This is equivalent to increasing the length of the electron transmission path, which is not conducive to electron transmission.

[0006] (3) To increase the conductivity of the hole blocking layer film, the titanium dioxide hole blocking layer is doped with metal cations such as Li + , K + 、Ag + Mg 2+ 、Y 3+ 、La3+ Progress has been made in various aspects, but there is less research on non-metallic anion doping. Anion doping can also increase the carrier concentration and indirectly improve the conductivity. There is no report on the application of N and F co-doping methods using hydrolysis and spin coating to titanium dioxide hole blocking layers.

[0007] In theory, the thinner the hole-blocking layer film is, the better, as it is conducive to transmitting electrons and blocking holes. However, large-area perovskite solar cells require a large-area hole-blocking layer film. Large-area hole-blocking layer films are prone to defects such as holes, which are not conducive to the normal operation of solar cells and may even cause battery short circuits.

[0008] Therefore, a method for preparing a titanium dioxide hole blocking layer for large-area perovskite solar cells is proposed to solve the above problems. Summary of the Invention

[0009] A hole-blocking layer with high conductivity and close interface contact plays an important role in improving the photovoltaic performance of perovskite solar cells. To this end, TiO2 is selected as the hole-blocking layer. By co-doping with N and F, modifying the interface of the hole-blocking layer, and optimizing the number of hole-blocking layers, it is possible to ensure that large-area hole-blocking layer films do not have holes and maintain high photovoltaic performance of solar cells. In addition, to further reduce costs, the present invention uses carbon electrodes to replace traditional precious metal electrodes, eliminating the mesoporous layer and electron-blocking layer. The present invention spin-coats 1, 2, and 3 layers of N and F co-doped titanium dioxide thin films on the FTO surface, respectively, and then uses 3-mercaptopropionic acid (MPA) or thioglycolic acid (TGA) to modify the interface of the film surface to prepare a large-area, highly conductive, highly dense, and closely interfaced titanium dioxide hole-blocking layer film.

[0010] This invention provides a method for preparing a titanium dioxide hole-blocking layer for large-area perovskite solar cells. By co-doping with nitrogen and fluorine, modifying the hole-blocking layer interface, and optimizing the number of hole-blocking layer layers, the method ensures that the large-area hole-blocking layer film is free of holes and maintains high photovoltaic performance. This large-area, highly conductive, and dense titanium dioxide hole-blocking layer provides a low-cost, large-area assembly method for carbon-electrode perovskite solar cells (structured as FTO / TiO2 / MAPbI3 / C).

[0011] The present invention specifically comprises the following steps:

[0012] Step 1: Dissolve 5-8 μL of 4-8 mol / L concentrated nitric acid and 5-10 μL of 3-fluoropropanol in 2 mL of ultra-dry isopropyl alcohol to form a 0.02-0.03 mol / L nitric acid-3-fluoropropanol mixed solution. Slowly add the mixed solution dropwise to a predetermined volume of n-butyl titanate-isopropyl alcohol solution while stirring. Stir thoroughly to ensure uniform mixing and hydrolysis, thereby obtaining a precursor solution.

[0013] Step 2: Pipette 100-250 μL of the precursor mixed solution obtained in step 1 onto the cleaned conductive glass surface and prepare a thin film by spin coating. After the spin coating is completed, place it on a hot plate at 450-550°C and fully heat it. After cooling to room temperature, a layer of N and F co-doped titanium dioxide hole blocking layer thin film with a film thickness of 50-60 nm is obtained;

[0014] Step 3: Pipette 100-300 μL of 0.5-1.5% by volume 3-mercaptopropionic acid or thioglycolic acid ethanol solution and drop it onto the surface of the titanium dioxide hole blocking layer film obtained in step 2 for surface modification, followed by freeze drying in a vacuum freeze dryer for 2 hours.

[0015] Step 4: Repeat steps 2-3 to obtain N and F co-doped titanium dioxide hole blocking layer films with different numbers of layers.

[0016] The present invention uses n-butyl titanate as a titanium source, and hydrolyzes it with nitric acid and 3-fluoropropanol to produce a nitrogen- and fluorine-codoped titanium dioxide film. The nitrogen- and fluorine-codoping elements are derived from 4-8 mol / L concentrated nitric acid and 3-fluoropropanol. In step 3, the titanium dioxide hole-blocking layer is modified with 3-mercaptopropionic acid or mercaptoacetic acid. This creates a high density of PbS bonds at the TiO2 / MAPbI3 interface, enhancing interfacial contact. Furthermore, PbS is a semiconductor material with a similar band gap and energy level to MAPbI3.

[0017] The area of ​​the large-area perovskite cell is ≥1 cm 2 It is a flat perovskite solar cell composed of an electric carbon electrode and a hole-free transport layer. Currently, most perovskite solar cells studied use titanium dioxide or tin dioxide thin films with a size of 0.09 cm. 2 The effective area of ​​the hole blocking layer film is more than 1cm 2Products require adding a thicker mesoporous titanium dioxide layer on the film surface to avoid leakage current and improve the contact degree with the light absorption layer. This is equivalent to increasing the path length of electron transmission, which is not conducive to electron transmission. However, the present invention generates N and F co-doped titanium dioxide films through the mixed hydrolysis method of nitric acid and 3-fluoropropanol, ensuring that the large-area hole blocking layer film does not have holes and maintaining the high photovoltaic performance of the solar cell.

[0018] The method for preparing the mixed solution of nitric acid and 3-fluoropropanol in step 1 of the present invention is as follows: 5 to 8 μL of 4 to 8 mol / L concentrated nitric acid and 5 to 10 μL of 3-fluoropropanol are respectively pipetted and dissolved in 2 mL of ultra-dry isopropyl alcohol to form a mixed solution of nitric acid and 3-fluoropropanol with a concentration of 0.02 to 0.03 mol / L;

[0019] The preparation method of the n-butyl titanate-isopropanol solution is as follows: 100-300 μL of n-butyl titanate is dissolved in 2 mL of ultra-dry isopropanol to prepare the n-butyl titanate-isopropanol solution with a concentration of 0.15 mmol / L-0.45 mmol / L.

[0020] In order to remove insoluble matter in the precursor mixed solution, before step 2, the prepared precursor mixed solution is filtered using an organic filter membrane with a pore size of 0.22 μm.

[0021] In step 2, the thin film is prepared by spin coating using a spin coater, and the spin coating process parameters are: speed 2000-3000 r / min, time 30-60 s; in step 3, the spin coating process parameters are: speed 2000-3000 r / min, time 30-60 s.

[0022] In step 4, a titanium dioxide hole blocking layer thin film co-doped with N and F is obtained, with the number of layers being 1, 2 or 3.

[0023] The beneficial effects of the present invention are:

[0024] 1. The present invention uses n-butyl titanate as a titanium source and generates N and F co-doped titanium dioxide thin films by a mixed hydrolysis method of nitric acid and 3-fluoropropanol, which solves the problem that the effective area of ​​the hole blocking layer film exceeds 1 cm in the prior art. 2 When manufacturing a thin film, it is necessary to add a thicker mesoporous titanium dioxide layer on the surface of the film. In order to avoid leakage current and improve the contact degree with the light absorption layer, the path length of electron transmission is increased, which is not conducive to the transmission of electrons. It ensures that there are no holes in the large-area hole blocking layer film and maintains the high photovoltaic performance of the solar cell, which is conducive to accelerating its commercialization process.

[0025] 2. The present invention uses 3-mercaptopropionic acid or thioglycolic acid to perform interface modification on the surface of the titanium dioxide hole blocking layer, which can form a certain density of PbS bonds at the TiO2 / MAPbI3 interface, thereby enhancing the interfacial contact. In addition, PbS is also a semiconductor material with a similar band gap and energy level to MAPbI3.

[0026] 3. It is applicable to photovoltaic devices such as inorganic perovskite solar cells and organic-inorganic hybrid perovskite solar cells. It has a wide range of applications, a simple preparation process, is easy to operate, and is not highly dependent on special equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 Schematic diagram of the preparation process of a titanium dioxide hole blocking layer;

[0028] Figure 2 XRD patterns of films with different numbers of titanium dioxide hole-blocking layers;

[0029] Figure 3 Surface morphology and cross-sectional morphology of thin films with different numbers of titanium dioxide hole-blocking layers;

[0030] Figure 4 UV-visible absorption spectra and Tauc plots of TiO2 films with different numbers of hole-blocking layers;

[0031] Figure 5 XPS full spectrum of TiO2 films with different numbers of hole-blocking layers;

[0032] Figure 6 Ti 2p and O1s fine spectra of TiO2 films with different numbers of hole-blocking layers;

[0033] Figure 7 Full XPS spectrum of organic-inorganic hybrid perovskite solar cells based on different numbers of titanium dioxide hole blocking layers;

[0034] Figure 8 Fine spectra of Pb4f and I 3d in organic-inorganic hybrid perovskite solar cells with different numbers of TiO2 hole-blocking layers;

[0035] Figure 9 Current-voltage curves of organic-inorganic hybrid perovskite solar cells based on different numbers of titanium dioxide hole blocking layers; DETAILED DESCRIPTION

[0036] The following will be combined with the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the embodiments described are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0037] In this embodiment, in addition to specifically describing the preparation method of the titanium dioxide hole blocking layer for large-area perovskite solar cells, in order to perform performance testing on the titanium dioxide hole blocking layer for large-area perovskite cells prepared by the present invention and to more clearly illustrate the technical scheme and technical effects of the present invention, the etching and cleaning of FTO conductive glass, the preparation of the organic-inorganic hybrid perovskite light absorption layer, and the scraping implementation method of the carbon electrode are also specifically given.

[0038] Example 1

[0039] Preparation method of titanium dioxide hole blocking layer for large-area perovskite cell, wherein the area of ​​the large-area perovskite cell is ≥1cm 2 The invention relates to a flat perovskite solar cell composed of an electric carbon electrode and a hole-free transport layer. The preparation method of the titanium dioxide hole blocking layer of a large-area perovskite cell comprises the following steps:

[0040] Step 1: Slowly add a 0.026 mol / L mixed solution of nitric acid and 3-fluoropropanol dropwise to the n-butyl titanate-isopropanol solution under stirring, and stir thoroughly to mix the solution evenly and allow hydrolysis to occur, thereby obtaining a precursor solution A.

[0041] The preparation method of n-butyl titanate-isopropanol solution is as follows: 300 μL of n-butyl titanate is dissolved in 2 mL of ultra-dry isopropanol to prepare a n-butyl titanate-isopropanol solution with a concentration of 0.45 mmol / L;

[0042] The preparation method of the nitric acid and 3-fluoropropanol mixed solution is as follows: 6.5 μL of 8 mol / L concentrated nitric acid and 8 μL of 3-fluoropropanol are respectively pipetted and dissolved in 2 mL of ultra-dry isopropyl alcohol to form a nitric acid and 3-fluoropropanol mixed solution with a concentration of 0.026 mol / L.

[0043] Step 2 Step 1 Filter the prepared precursor solution A with an organic filter membrane with a pore size of 0.22μm to remove insoluble matter in the solution, transfer 200μL of precursor solution A and drop it on the cleaned conductive glass surface, and use a spin coater to prepare a thin film by spin coating. The spin coating process parameters are: speed 3000r / min, time 60s. After spin coating is completed, place it on a heating plate at 500℃ and heat for 30min. After cooling to room temperature, a layer of N and F co-doped titanium dioxide hole blocking layer film can be obtained with a film thickness of 50-60nm.

[0044] Step 3: Pipette 200 μL of a 1% volume ratio 3-mercaptopropionic acid or thioglycolic acid ethanol solution and drop it on the surface of the titanium dioxide hole blocking layer film obtained in step 2 above to perform surface modification by spin coating. The spin coating process parameters are: speed 3000 r / min, time 60 s, and then freeze-dry in a vacuum freeze dryer for 2 hours.

[0045] Step 4: Repeat steps 2-3 to obtain 1, 2, and 3 layers of N and F co-doped titanium dioxide hole blocking layer films, respectively.

[0046] like Figure 1 The figure shows a schematic diagram of the preparation process of a titanium dioxide hole blocking layer of the present invention.

[0047] Example 2

[0048] A method for preparing a titanium dioxide hole blocking layer for a large-area perovskite cell comprises the following steps:

[0049] Step 1: Slowly add a 0.020 mol / L mixed solution of nitric acid and 3-fluoropropanol dropwise to the n-butyl titanate-isopropanol solution under stirring, and stir thoroughly to mix the solution evenly and hydrolyze it to obtain a precursor mixed solution B;

[0050] The preparation method of n-butyl titanate-isopropyl alcohol solution is as follows:

[0051] 100 μL of n-butyl titanate was dissolved in 2 mL of ultra-dry isopropyl alcohol to prepare a n-butyl titanate-isopropyl alcohol solution with a concentration of 0.15 mmol / L.

[0052] The preparation method of the nitric acid and 3-fluoropropanol mixed solution is as follows:

[0053] Pipette 5 μL of 8 mol / L concentrated nitric acid and 6.5 μL of 3-fluoropropanol separately and dissolve them in 2 mL of ultra-dry isopropanol to form a mixed solution of nitric acid and 3-fluoropropanol with a concentration of 0.020 mol / L.

[0054] Step 2: Filter the prepared precursor mixed solution B through an organic filter membrane with a pore size of 0.22 μm to remove insoluble matter in the solution, pipette 200 μL of the precursor mixed solution B and drop it on the cleaned conductive glass surface. Use a spin coater to prepare a thin film by spin coating. The spin coating process parameters are: speed 2000 r / min, time 30 s. After the spin coating is completed, place it on a hot plate at 500 ° C and heat it for 60 min. After cooling to room temperature, a layer of N and F co-doped titanium dioxide hole blocking layer film with a film thickness of 50-60 nm is obtained.

[0055] Step 3: Pipette 100 μL of a 1% volume ratio 3-mercaptopropionic acid or thioglycolic acid ethanol solution and drop it on the surface of the titanium dioxide hole blocking layer film obtained in step 2 above to perform surface modification by spin coating. The spin coating process parameters are: speed 2000 r / min, time 30 s, and then freeze-dry in a vacuum freeze dryer for 2 hours.

[0056] Step 4: Repeat steps 2-3 to obtain 1, 2, and 3 layers of N and F co-doped titanium dioxide hole blocking layer films, respectively.

[0057] Example 3

[0058] A method for preparing a titanium dioxide hole blocking layer for a large-area perovskite cell comprises the following steps:

[0059] Step 1: Slowly add a 0.03 mol / L mixed solution of nitric acid and 3-fluoropropanol dropwise to the n-butyl titanate-isopropanol solution under stirring, and stir thoroughly to mix the solution evenly and hydrolyze it to obtain a precursor mixed solution C;

[0060] The preparation method of n-butyl titanate-isopropyl alcohol solution is as follows:

[0061] 200 μL of n-butyl titanate was dissolved in 2 mL of ultra-dry isopropyl alcohol to prepare a n-butyl titanate-isopropyl alcohol solution with a concentration of 0.3 mmol / L.

[0062] The preparation method of the nitric acid and 3-fluoropropanol mixed solution is as follows:

[0063] Pipette 7.5 μL of 8 mol / L concentrated nitric acid and 9.5 μL of 3-fluoropropanol separately and dissolve them in 2 mL of ultra-dry isopropanol to form a mixed solution of nitric acid and 3-fluoropropanol with a concentration of 0.03 mol / L.

[0064] Step 2 Step 1 The prepared solution precursor mixed solution C is filtered with an organic filter membrane with a pore size of 0.22 μm to remove insoluble matter in the solution, 200 μL of the precursor mixed solution C is pipetted and dropped on the clean conductive glass surface, and a thin film is prepared by spin coating using a spin coater. The spin coating process parameters are: speed 2500 r / min, time 40 s. After the spin coating is completed, it is placed on a hot plate at 500 ° C and heated for 30 min. After cooling to room temperature, a layer of N and F co-doped titanium dioxide hole blocking layer film is obtained, and the film thickness is 50-60 nm;

[0065] Step 3: Pipette 300 μL of a 1% volume ratio 3-mercaptopropionic acid or thioglycolic acid ethanol solution and drop it on the surface of the titanium dioxide hole blocking layer film obtained in step 2 above to perform surface modification by spin coating. The spin coating process parameters are: speed 2500 r / min, time 40 s, and then freeze-dry in a vacuum freeze dryer for 2 hours.

[0066] Step 4: Repeat steps 2-3 to obtain 1, 2, and 3 layers of N and F co-doped titanium dioxide hole blocking layer films, respectively.

[0067] The structure of the organic-inorganic hybrid perovskite solar cell is FTO / hole blocking layer / mesoporous TiO2 layer / MAPbI3 / electron blocking layer / electrode. In order to perform performance tests on the titanium dioxide hole blocking layer for large-area perovskite cells prepared by the present invention and to more clearly illustrate the technical solution and technical effects of the present invention, a preparation method for other structures of perovskite cells made by using the titanium dioxide hole blocking layer of the perovskite cell of Example 1 of the present invention is also specifically given, including the etching and cleaning of FTO conductive glass, the preparation of the MAPbI3 organic-inorganic hybrid perovskite light absorption layer, and the implementation method of carbon electrode scraping. The details are as follows:

[0068] This embodiment provides a method for cleaning the conductive glass in step 2. The specific process of etching and cleaning the FTO conductive glass is as follows:

[0069] (1) Use a glass cutter to cut the FTO conductive glass into 1.5 cm × 2.0 cm glass blocks. Use polyimide tape to protect the unetched portion. Evenly spread zinc powder on the unprotected portion, and then add 6 mol / L hydrochloric acid solution.

[0070] (2) After the reaction is fully completed, rinse with deionized water, remove the polyimide tape, and soak in a 2 mol / L potassium dichromate concentrated sulfuric acid solution for 24 hours to remove any organic matter that may exist on the surface of the conductive glass.

[0071] (3) Soak in 18 mol / L NaOH solution for 24 hours to remove the acidic substances remaining on the surface of the conductive glass.

[0072] (4) After a large amount of water washing, the conductive glass is wiped clean with anhydrous ethanol and placed in a beaker. Deionized water and detergent are added and ultrasonically cleaned in an ultrasonic cleaning machine for 30 minutes. Then, it is rinsed with deionized water and ultrasonically cleaned with deionized water for another 30 minutes.

[0073] (5) Finally, the sample was cleaned with a saturated solution of NaOH in anhydrous ethanol for 30 min, rinsed with anhydrous ethanol after ultrasonication, and freeze-dried for 3 hours in a dust-free drying box.

[0074] The preparation process of the MAPbI3 organic-inorganic hybrid perovskite light absorption layer also given in this embodiment is as follows:

[0075] The organic-inorganic hybrid perovskite light absorption layer is prepared by a two-step method. First, a PbI2(DMSO) thin film is prepared, then an isopropanol solution of methylammonium iodide is prepared, and finally the isopropanol solution of methylammonium iodide is deposited on the PbI2(DMSO) thin film and annealed to form a perovskite film.

[0076] (1) Preparation of PbI2 (DMSO) thin film: 1.46 g of PbI2 was added in batches to a mixed solution (1 mL) of DMF and DMSO in a volume ratio of 4:1. The solution was magnetically stirred at 70°C for 7 h until completely dissolved. The complex solution was filtered through a polytetrafluoroethylene organic filter membrane with a pore size of 0.22 μm. The precursor solution was spin-coated on the titanium dioxide hole blocking layer at 3000 rpm for 30 s. After spin-coating, the mixture was placed in a vacuum dryer for 2 h to completely evaporate the excess DMF, resulting in a PbI2 (DMSO) thin film.

[0077] (2) Preparation of methylammonium iodide-isopropanol solution: Dissolve 0.4253 g of methylammonium iodide powder in 5 mL of ultra-dry isopropanol and stir at room temperature until dissolved to obtain 0.535 mol·L -1 The ultra-dry isopropanol solution of methylammonium iodide was filtered through a 0.22 μm polytetrafluoroethylene organic filter membrane and then set aside.

[0078] (3) Preparation of organic-inorganic hybrid perovskite film: 100 μL, 0.535 mol·L -1 A methylammonium iodide-isopropanol solution was dripped onto the PbI2(DMSO) film and allowed to sit for 30 seconds. The excess methylammonium iodide-isopropanol solution was then removed by a spin coater at 5000 rpm for 30 seconds. The film was then heated on a 100°C hotplate for 30 minutes to convert it into a perovskite film. After cooling to room temperature, 200 μL of isopropanol was dripped onto the perovskite film surface and the excess methylammonium iodide was removed at 3000 rpm for 30 seconds.

[0079] This embodiment also provides the carbon electrode scraping process as follows:

[0080] Use a doctor blade to apply 0.5 mL of conductive carbon slurry to the surface of the perovskite film. The effective area of ​​the cell is 1 cm. 2 , anneal at 100℃ for 10min and set aside.

[0081] Then, the titanium dioxide hole blocking layer obtained in Example 1 was tested. The titanium dioxide hole blocking layer prepared in Example 1 and the etching and cleaning of FTO conductive glass, the preparation of MAPbI3 organic-inorganic hybrid perovskite light absorption layer, and the implementation steps of carbon electrode scraping were tested. The following is the effective area of ​​the titanium dioxide hole blocking layer of 1 cm 2Characterization data of titanium dioxide thin films with different numbers of layers and data for the assembly of organic-inorganic hybrid perovskite solar cells based on carbon electrodes without hole transport layers. (a) A perovskite cell with a single N and F co-doped titanium dioxide hole blocking layer; (b) A perovskite cell with a two-layer N and F co-doped titanium dioxide hole blocking layer; and (c) A perovskite cell with a three-layer N and F co-doped titanium dioxide hole blocking layer.

[0082] like Figure 2 The XRD patterns of films with different numbers of titanium dioxide hole blocking layers show that the number of titanium dioxide hole blocking layers has no effect on the crystal structure.

[0083] Figure 3 The surface morphology and cross-sectional morphology of thin films with different numbers of titanium dioxide hole blocking layers are shown in Figure 2.

[0084] Figure 4 UV-visible absorption spectra and Tauc plots of thin films with different numbers of titanium dioxide hole blocking layers.

[0085] Figure 5 This is the full XPS spectrum of titanium dioxide films with different numbers of hole blocking layers.

[0086] Figure 6 The Ti 2p and O1s fine spectra of TiO2 films with different numbers of hole-blocking layers.

[0087] Figure 7 This is the full XPS spectrum of organic-inorganic hybrid perovskite solar cells based on different numbers of titanium dioxide hole blocking layers.

[0088] Figure 8 Fine spectra of Pb4f and I 3d based on organic-inorganic hybrid perovskite solar cells with different numbers of titanium dioxide hole blocking layers.

[0089] Depend on Figures 4 to 8 It can be seen that the signal intensity of the N and F co-doped titanium dioxide hole blocking layer is higher than that of the three layers.

[0090] Figure 9 The current-voltage curves of organic-inorganic hybrid perovskite solar cells based on different numbers of titanium dioxide hole blocking layers.

[0091] Table 1 is a table of the photoelectric conversion efficiency of organic-inorganic hybrid perovskite solar cells based on different numbers of titanium dioxide hole blocking layers.

[0092] Table 1 Photovoltaic conversion efficiency of organic-inorganic hybrid perovskite solar cells based on different numbers of titanium dioxide hole blocking layers

[0093]

[0094] Depend on Figure 9 As shown in Table 1, when the number of the titanium dioxide hole blocking layer is one, the photoelectric conversion efficiency is the highest, and when the number of the titanium dioxide hole blocking layer is three, the filling factor reaches the maximum.

[0095] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or replace some or all of the technical features therein with equivalents. However, these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for preparing a titanium dioxide hole blocking layer for a large-area perovskite cell, characterized in that: The following steps are involved: Step 1: Pipette 5 to 8 μL of 4 to 8 mol / L concentrated nitric acid and 5 to 10 μL of 3-fluoropropanol, respectively, and dissolve them in 2 mL of ultra-dry isopropanol to form a mixed solution of nitric acid and 3-fluoropropanol with a concentration of 0.02 to 0.03 mol / L; slowly add the mixed solution dropwise to a certain volume of n-butyl titanate-isopropanol solution under stirring, and stir thoroughly to mix the solution evenly and hydrolyze it to obtain a precursor mixed solution; Step 2: Pipette 100-250 μL of the precursor mixed solution obtained in step 1 onto the cleaned conductive glass surface and prepare a thin film by spin coating. After the spin coating is completed, place it on a hot plate at 450-550°C and fully heat it. After cooling to room temperature, a layer of N and F co-doped titanium dioxide hole blocking layer thin film with a film thickness of 50-60 nm is obtained; Step 3: Pipette 100-300 μL of a 0.5-1.5% by volume ethanol solution of 3-mercaptopropionic acid or thioglycolic acid and drop it onto the surface of the titanium dioxide hole blocking layer film obtained in step 2 above for surface modification, and then fully dry the titanium dioxide hole blocking layer film by vacuum freeze drying; Step 4: Repeat steps 2-3 to obtain N and F co-doped titanium dioxide hole blocking layer films with different numbers of layers.

2. The method for preparing a titanium dioxide hole blocking layer for a large-area perovskite cell according to claim 1, characterized in that: The area of ​​the large-area perovskite cell is ≥1 cm 2 , is a flat perovskite solar cell consisting of an electric carbon electrode and a hole-free transport layer.

3. The method for preparing a titanium dioxide hole blocking layer for a large-area perovskite cell according to claim 1, characterized in that: The preparation method of the n-butyl titanate-isopropanol solution is as follows: 100-300 μL of n-butyl titanate is dissolved in 2 mL of ultra-dry isopropanol to prepare the n-butyl titanate-isopropanol solution with a concentration of 0.15 mmol / L-0.45 mmol / L.

4. The method for preparing a titanium dioxide hole blocking layer for a large-area perovskite cell according to claim 1, characterized in that: The preparation method of the nitric acid and 3-fluoropropanol mixed solution is as follows: 5 to 8 μL of 4 to 8 mol / L concentrated nitric acid and 5 to 10 μL of 3-fluoropropanol are respectively pipetted and dissolved in 2 mL of ultra-dry isopropyl alcohol to form a nitric acid and 3-fluoropropanol mixed solution with a concentration of 0.02 to 0.03 mol / L.

5. The method for preparing a titanium dioxide hole blocking layer for a large-area perovskite cell according to claim 1, characterized in that: Before step 2, the prepared precursor mixed solution is filtered through an organic filter membrane with a pore size of 0.22 μm to remove insoluble matter in the solution.

6. The method for preparing a titanium dioxide hole blocking layer for a large-area perovskite cell according to claim 1, characterized in that: In step 2, a thin film is prepared by spin coating using a spin coater, and the spin coating process parameters are: speed 2000-3000 r / min, time 30-60 s; in step 3, the surface of the titanium dioxide hole blocking layer film is surface modified by spin coating, and the spin coating process parameters are: speed 2000-3000 r / min, time 30-60 s, followed by cold drying in a vacuum freeze dryer for 2 hours.

7. The method for preparing a titanium dioxide hole blocking layer for a large-area perovskite cell according to claim 1, characterized in that: In step 4, a titanium dioxide hole blocking layer thin film co-doped with N and F is obtained, with the number of layers being 1, 2 or 3.

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