Titanium dioxide thin film modified by levodopa molecule, preparation method thereof and application thereof in perovskite solar cell

Abstract

The application belongs to the technical field of solar cell preparation, and relates to a levodopa molecule modified titanium dioxide film, a preparation method thereof and application thereof in a perovskite solar cell. The levodopa molecule is used to introduce a molecular interface layer in the perovskite and the titanium dioxide, passivate defects in the perovskite and the titanium dioxide, improve photoelectric conversion efficiency, and strengthen working stability and storage stability. The levodopa molecule modified titanium dioxide film prepared by the application can also be applied in the preparation of a perovskite solar cell. The perovskite solar cell is made of a conductive substrate, an electron transport layer, a perovskite layer, a hole transport layer and a metal electrode layer arranged from bottom to top, wherein the electron transport layer is the levodopa molecule modified titanium dioxide film.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of solar cell preparation, and relates to a levodopa molecule modified titanium dioxide film, a preparation method thereof and application thereof in a perovskite solar cell. BACKGROUND

[0002] Traditional fossil energy cannot meet the increasing energy demand of mankind due to its problems such as small reserves, high pollution and low conversion rate, so the utilization and development of renewable energy have gradually become one of the key research and development targets; solar energy is an important part of green renewable energy due to its characteristics of universal existence, abundant reserves and clean harmlessness, in order to realize long-term and efficient utilization of solar energy, people have developed various material solar cells, and perovskite solar cells have developed rapidly in recent years, and the photoelectric conversion efficiency has caught up with commercial monocrystalline silicon solar cells within ten years, and there is still much potential for development in various performances of the cell.

[0003] For perovskite solar cells, efficiency and stability are the two most important properties; the perovskite layer is excited by light to generate excitons, and the excitons are further separated into electron-hole pairs, which migrate to both ends by the electron transport layer and the hole transport layer, respectively, to generate a potential difference, and form a loop under an external circuit.

[0004] At present, the spin coating method is widely used for preparing perovskite films, and has the advantages of simplicity, speed and low cost, but the micro-morphology of titanium dioxide is very sensitive to the spin coating process, a rough titanium dioxide surface not only causes uneven growth of perovskite grains, resulting in a large number of pinholes and defects, but also causes partial contact between the perovskite layer and the conductive substrate, resulting in short circuit of the device; in addition, under the working state of the cell, titanium dioxide is excited by ultraviolet light to generate superoxide radicals and positively charged holes, and the free Pb ions and I ions in the perovskite layer also move directionally under the action of an electric field, which together generate a non-optically active phase PbI2 at the interface, affecting the photoelectric conversion efficiency of the device. SUMMARY

[0005] In view of the above technical deficiencies, the present application provides a levodopa molecule modified titanium dioxide film, a preparation method thereof and application thereof in a perovskite solar cell, wherein the levodopa molecule is used to introduce a molecular interface layer in the perovskite and titanium dioxide, passivate defects in the perovskite and titanium dioxide, improve the photoelectric conversion efficiency, and strengthen the working stability and storage stability.

[0006] To solve the above technical problems, the technical scheme adopted by the present application is as follows:

[0007] A preparation method of a levodopa molecule modified titanium dioxide film, comprising the following steps:

[0008] (1) preparing a titanium dioxide colloidal solution;

[0009] (2) depositing the conductive substrate in the titanium dioxide colloidal solution of step (1) to obtain a one-stage deposited substrate;

[0010] (3) taking out the one-stage deposited substrate of step (2) from the titanium dioxide colloidal solution, then adding levodopa molecules into the titanium dioxide colloidal solution and mixing uniformly to obtain a mixed solution, and depositing the one-stage deposited substrate in the mixed solution to obtain a two-stage deposited substrate;

[0011] wherein the mass ratio of the levodopa molecules to the volume of the titanium dioxide colloidal solution of step (2) is 0.2-0.6 mg:1 mL;

[0012] (4) annealing the two-stage deposited substrate of step (3) after washing to obtain a levodopa molecule-modified titanium dioxide thin film.

[0013] Preferably, the titanium dioxide colloidal solution in step (1) is prepared according to the following steps: dissolving titanium tetrachloride in water, reacting at 0-60℃ for 15 min to obtain a titanium dioxide colloidal solution;

[0014] wherein the concentration of titanium tetrachloride in the titanium dioxide colloidal solution is 150-250 mmol / L.

[0015] Preferably, the conductive substrate in step (2) is selected from a conductive FTO substrate, an ITO substrate, and a PEN conductive film.

[0016] The conductive substrate in step (2) is subjected to washing treatment before use, and the treatment method is: sequentially using glass cleaning solution, deionized water, acetone, and ethanol for ultrasonic cleaning, then drying, and then using ultraviolet ozone cleaning treatment.

[0017] Preferably, the deposition conditions of step (2) and step (3) are both: depositing at 70±5℃ for 20-60 min.

[0018] Preferably, the annealing treatment conditions of step (4) are: treating at 100-150℃ for 1-3 h.

[0019] The present application also protects the levodopa molecule-modified titanium dioxide thin film prepared by the preparation method.

[0020] The present application also protects the application of the levodopa molecule-modified titanium dioxide thin film in preparing a perovskite solar cell, and the perovskite solar cell is made of a conductive substrate, an electron transport layer, a perovskite layer, a hole transport layer, and a metal electrode layer arranged from bottom to top.

[0021] The electron transport layer is a titanium dioxide thin film modified with the L-DOPA molecule, and the metal electrode layer is a gold electrode layer or a silver electrode layer.

[0022] Preferably, the perovskite solar cell is prepared according to the following steps:

[0023] Step 1, Preparation of the perovskite layer: The perovskite precursor solution is dropped onto the electron transport layer, and then an antisolvent is added under high-speed rotation. Then, annealing is performed to obtain the perovskite layer.

[0024] Step 2, Preparation of hole transport layer: Spin-coating hole transport material spiro-OMeTAD onto the perovskite layer described in Step 1 to obtain the hole transport layer;

[0025] Step 3, Fabrication of perovskite solar cells: Metal is deposited on the hole transport layer described in Step 2 to obtain perovskite solar cells.

[0026] Preferably, the perovskite precursor solution in step 1 is selected from FAPbI3 perovskite precursor solution or CsFAMA ternary perovskite precursor solution, and the concentration of the perovskite precursor solution is 1.5-1.7 mol / mL.

[0027] The perovskite layer described in step 1 is prepared according to the following steps: Under spin coating conditions, the perovskite precursor solution is drop-coated onto the electron transport layer in batches. An antisolvent is added 10-15 seconds before the spin coating is finished, and then the layer is annealed at 120-140℃ for 10-60 minutes.

[0028] The antisolvent is selected from ethyl acetate, chlorobenzene, chloroform, diethyl ether, and toluene, and the volume ratio of the perovskite precursor solution to the antisolvent is 1-2:10.

[0029] Preferably, the thickness of the hole transport layer in step 2 is 150-250 nm, the evaporation rate in step 3 is 0.4 nm / s, and the thickness of the metal coating in step 3 is 80-120 nm.

[0030] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0031] (1) The present invention uses a two-step deposition method to successfully introduce L-DOPA molecules into the front surface and interface of titanium dioxide, forming a very thin monomolecular modification layer at the interface, and enhancing the crystallinity of titanium dioxide in the bulk phase; in addition, the purpose of using the two-step deposition method is to obtain a more flat and dense titanium dioxide film, which enhances the charge transport efficiency of perovskite solar cells and prepares devices with higher photoelectric conversion efficiency.

[0032] (2) The application can passivate the defects of the lower interface of titanium dioxide and perovskite after introducing levodopa molecules between the electron transport layer and the perovskite layer, so that the prepared perovskite solar cell has good photoelectric conversion efficiency, and the light stability is further enhanced. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 Structure schematic diagram of the perovskite solar cell modified by the levodopa molecules of the application embodiment 1-4;

[0034] Figure 2 AFM comparison diagram of the titanium dioxide thin film prepared by the application embodiment 1 and the comparative example 1, wherein, (a) is the AFM image of the comparative example 1; (b) is the AFM image of the embodiment 1; (c) is the roughness curve of a certain section of the comparative example 1 and the embodiment 1;

[0035] Figure 3 J-V curve comparison diagram of the FAPbI3 type perovskite solar cell prepared by the application embodiment 1 and the comparative example 1, wherein, the left graph is the J-V curve and the efficiency parameter of the comparative example 1; the right graph is the J-V curve and the efficiency parameter of the embodiment 1;

[0036] Figure 4 Steady-state output efficiency comparison diagram of the FAPbI3 type perovskite solar cell prepared by the application embodiment 1 and the comparative example 1;

[0037] Figure 5 Stability comparison diagram of the FAPbI3 type perovskite solar cell prepared by the application embodiment 1 and the comparative example 1 in air;

[0038] Figure 6 Working stability comparison diagram of the FAPbI3 type perovskite solar cell prepared by the application embodiment 1 and the comparative example 1;

[0039] Figure 7 J-V curve comparison diagram of the CsFAMA perovskite solar cell prepared by the application embodiment 2 and the comparative example 2, wherein, the left graph is the J-V curve and the efficiency parameter of the comparative example 2, and the right graph is the J-V curve and the efficiency parameter of the embodiment 2.

[0040] BRIEF DESCRIPTION OF DRAWINGS

[0041] 1, conductive substrate; 2, electron transport layer; 3, perovskite layer; 4, hole transport layer; 5, metal electrode layer. DETAILED DESCRIPTION

[0042] The specific embodiments of the present application are described in detail below, but it should be understood that the scope of protection of the present application is not limited by the specific embodiments. Based on the examples in the present application, all other examples obtained by those of ordinary skill in the art without creative labor are within the scope of protection of the present application. The experimental methods described in the embodiments of the present application are conventional methods unless otherwise specified.

[0043] A levodopa molecule modified perovskite solar cell, the specific structure is as shown in Figure 1 The conductive substrate 1, the electron transport layer 2, the perovskite layer 3, the hole transport layer 4 and the metal electrode layer 5 are sequentially arranged from bottom to top, the electron transport layer 2 is a levodopa molecule modified titanium dioxide film; several examples are provided below to provide several different levodopa molecule modified perovskite solar cells.

[0044] Example 1

[0045] A preparation method of a perovskite solar cell, the perovskite solar cell is a levodopa molecule modified perovskite solar cell, comprising the following steps:

[0046] (1) Preparation of the electron transport layer:

[0047] S1, the conductive FTO substrate is sequentially cleaned by glass cleaning solution, deionized water, acetone and ethanol for 15 min, and then dried, treated by ultraviolet ozone cleaning machine;

[0048] S2, 850 μL of titanium tetrachloride is added to 40 mL of ultrapure water, and a titanium dioxide colloid solution is obtained after sufficient reaction;

[0049] S3, the cleaned conductive FTO substrate is placed in the titanium dioxide colloid solution and deposited at 70°C for 30 min to obtain a first deposition substrate; the first deposition substrate is taken out of the titanium dioxide colloid solution, 16 mg of levodopa molecule is added to the titanium dioxide colloid solution and mixed uniformly to obtain a mixed solution, the first deposition substrate is placed in the mixed solution and continues to be deposited at 70°C for 20 min; after the reaction is completed, the glass substrate is cleaned repeatedly with ultrapure water and anhydrous ethanol, and then annealed at 130°C for 1 h to obtain a dense levodopa molecule modified titanium dioxide film with a thickness of about 20 nm, which is the electron transport layer;

[0050] (2) Preparation of the perovskite layer:

[0051] S1, in a nitrogen glove box, a 1.6 moL / L lead iodide formamidinate (FAPbI3) perovskite precursor solution was prepared: 234 mg CH3NH3I, 775 mg PbI2, 18 mg MABr, 22 mg MACl, 21 mg CsI were mixed in a small glass bottle, then 800 μL dimethylformamide and 200 μL dimethyl sulfoxide were added, a rotor was added and placed on a stirring table, heated and stirred at 55°C for 2 h, the undissolved impurities were filtered with a 0.22 μm organic filter head, and a 1.6 moL / L FAPbI3 perovskite precursor solution was obtained;

[0052] S2, 20 μL of the FAPbI3 perovskite precursor solution was taken and added dropwise to the titanium dioxide film of step (1), and the surface was completely infiltrated, and spin-coated at a speed of 4000 r / min for 40 s, and 200 μL of ethyl acetate was extracted dynamically spin-coated to the surface in the last 12 s, and finally annealed at 130°C for 10 min, to obtain a perovskite layer;

[0053] (3) Preparation of a hole transport layer: a 200 nm thick hole transport layer Spiro-OMeTAD was spin-coated on the perovskite layer prepared in step (2) at a speed of 4000 r / min for 30 s, to obtain a hole transport layer;

[0054] (4) An area of 0.05 cm 2 , a thickness of 100 nm Au electrode was evaporated on the hole transport layer of step (3) using a molecular vacuum coating instrument, and the evaporation rate was 0.4 nm / s, to obtain a levodopa molecule modified FAPbI3 perovskite solar cell.

[0055] Example 2

[0056] A preparation method of a perovskite solar cell, the perovskite solar cell being a levodopa molecule modified perovskite solar cell, comprising the following steps:

[0057] The preparation steps (1) and (3) of Example 1 are the same, except that the preparation method of the perovskite layer in step (2) is:

[0058] S1, in an argon glove box, a 1.25 moL / L Cs 0.05 FA 0.81 MA 0.14 PbI 2.55 Br 0.45A (CsFAMA) ternary perovskite precursor solution: 16.2 mg CH3NH3I, 173.5 mg HC(=NH)NH3I, 19.9 mg CH3NH3Br, 494.1 mg PbI2, and 65.4 mg PbBr2 were mixed in a brown reagent bottle, then 800 μL dimethylformamide and 200 μL dimethyl sulfoxide were added, a rotor was added and placed on a stirring table, heated and stirred at 55°C for 2 h, and the undissolved impurities were filtered with a 0.22 μm organic filter head to obtain a 1.25 moL / L (CsFAMA) ternary perovskite precursor solution;

[0059] S2, 20 μL of the CsFAMA ternary perovskite precursor solution was dropped onto the titanium dioxide film, first spin-coated at a low speed of 2000 rpm for 10 s, then spin-coated at a high speed of 4000 rpm for 30 s, and immediately added 200 μL of ethyl acetate solution when the high-speed spin-coating remained for 12 s, and finally annealed at 130°C for 1 h to obtain a perovskite layer:

[0060] The preparation method of the hole transport layer in step (4) is as follows:

[0061] A layer of Ag electrode with an area of 0.05 cm 2 , a thickness of 100 nm was evaporated on the hole transport layer by using a molecular vacuum coating instrument, and the evaporation rate was 0.4 nm / s, thereby obtaining a levodopa molecule modified CsFAMA ternary perovskite solar cell.

[0062] Example 3

[0063] The preparation method of the perovskite solar cell is a levodopa molecule modified perovskite solar cell, which comprises the following steps:

[0064] (1) Preparation of the electron transport layer:

[0065] S1, the conductive FTO substrate was sequentially cleaned with glass cleaning solution, deionized water, acetone, and ethanol for 15 min, then dried, and treated with a UV-ozone cleaning machine;

[0066] S2, 700 μL of titanium tetrachloride was added to 40 mL of ultrapure water, and a titanium dioxide colloid solution was obtained after sufficient reaction;

[0067] S3, the cleaned conductive FTO substrate is put into the titanium dioxide colloid solution and deposited for 60 minutes at 65°C to obtain a deposited substrate; the deposited substrate is taken out of the titanium dioxide colloid solution, 8 mg of levodopa molecules are added into the titanium dioxide colloid solution and mixed uniformly to obtain a mixed solution, the deposited substrate is placed in the mixed solution and continues to be deposited for 60 minutes at 65°C; after the reaction is completed, the glass substrate is taken out, washed repeatedly with ultrapure water and anhydrous ethanol, and then annealed at 100°C for 3 hours to obtain a dense levodopa molecule modified titanium dioxide film with a thickness of about 20 nm, which is an electron transport layer;

[0068] (2) Preparation of the perovskite layer:

[0069] S1, a 1.6 moL / L lead iodide formamidinium (FAPbI3) perovskite precursor solution is prepared in a nitrogen glove box: 234 mg of CH3NH3I, 775 mg of PbI2, 18 mg of MABr, 22 mg of MACl, and 21 mg of CsI are mixed in a small glass bottle, then 800 μL of dimethylformamide and 200 μL of dimethyl sulfoxide are added, a rotor is added and placed on a stirring table, heated and stirred at 55°C for 2 hours, the undissolved impurities are filtered with a 0.22 μm organic filter to obtain a 1.6 moL / L FAPbI3 perovskite precursor solution;

[0070] S2, 20 μL of the FAPbI3 perovskite precursor solution is taken and dropped onto the titanium dioxide film prepared in step (1), and the surface is completely infiltrated, and then spin-coated at a speed of 4000 r / min for 40 s, and in the last 15 s, 200 μL of ethyl acetate is extracted for dynamic spin coating on the surface, and finally annealed at 120°C for 10 minutes to obtain a perovskite layer;

[0071] (3) Preparation of the hole transport layer: a 250 nm thick hole transport layer Spiro-OMeTAD is spin-coated on the perovskite layer prepared in step (2) at a speed of 4000 r / min for 30 s to obtain a hole transport layer;

[0072] (4) An area of 0.05 cm 2 , a thickness of 80 nm Au electrode is evaporated on the hole transport layer prepared in step (3) by using a molecular vacuum coating instrument, and the evaporation rate is 0.4 nm / s to obtain a levodopa molecule modified FAPbI3 perovskite solar cell.

[0073] Example 4

[0074] A preparation method of a perovskite solar cell, the perovskite solar cell being a levodopa molecule modified perovskite solar cell, comprising the following steps:

[0075] (1) Preparation of the electron transport layer:

[0076] S1, the conductive FTO substrate was sequentially cleaned by glass cleaning solution, deionized water, acetone, and ethanol for 15 min, and then dried, and treated by a UV-ozone cleaning machine;

[0077] S2, 1000 μL of titanium tetrachloride was added to 40 mL of ultrapure water, and a titanium dioxide colloidal solution was obtained after sufficient reaction;

[0078] S3, the cleaned conductive FTO substrate was placed in the titanium dioxide colloidal solution and deposited at 75°C for 20 min to obtain a first deposition substrate; the first deposition substrate was taken out of the titanium dioxide colloidal solution, and 24 mg of levodopa molecules were added to the titanium dioxide colloidal solution and mixed uniformly to obtain a mixed solution; the first deposition substrate was placed in the mixed solution and continued to be deposited at 75°C for 20 min; after the reaction was completed, the glass substrate was cleaned repeatedly with ultrapure water and anhydrous ethanol, and then annealed at 150°C for 1 h to obtain a dense levodopa molecule modified titanium dioxide film with a thickness of about 20 nm, which was the electron transport layer;

[0079] (2) Preparation of the perovskite layer:

[0080] S1, a 1.6 moL / L lead iodide formamidinium (FAPbI3) perovskite precursor solution was prepared in a nitrogen glove box: 234 mg of CH3NH3I, 775 mg of PbI2, 18 mg of MABr, 22 mg of MACl, and 21 mg of CsI were mixed in a small glass bottle, then 800 μL of dimethylformamide and 200 μL of dimethyl sulfoxide were added, a rotor was added and placed on a stirring table, heated and stirred at 55°C for 2 h, and then filtered with a 0.22 μm organic filter to remove undissolved impurities, to obtain a 1.6 moL / L FAPbI3 perovskite precursor solution;

[0081] S2, 20 μL of the FAPbI3 perovskite precursor solution was added dropwise to the titanium dioxide film prepared in step (1), and the surface was completely infiltrated; the solution was spin-coated at a speed of 4000 r / min for 40 s, and 200 μL of ethyl acetate was extracted dynamically to the surface in the last 10 s; finally, the perovskite layer was obtained by annealing at 140°C for 10 min;

[0082] (3) Preparation of the hole transport layer: a 150 nm thick hole transport layer Spiro-OMeTAD was spin-coated on the perovskite layer prepared in step (2) at a speed of 4000 r / min for 30 s, to obtain the hole transport layer;

[0083] (4) A layer of area 0.05 cm2 Au electrode with a thickness of 120 nm, and the evaporation rate was 0.4 nm / s, thereby obtaining the levodopa molecule modified FAPbI3 perovskite solar cell.

[0084] Comparative Example 1

[0085] A preparation method of a perovskite solar cell, which is the same in structure as that of Example 1, except that the electron transport layer in Comparative Example 1 is not modified, and the preparation of the electron transport layer comprises the following steps:

[0086] The preparation steps are the same as those of Example 1, except that 850 μL of titanium tetrachloride is added to 40 mL of ultrapure water, and a titanium dioxide colloidal solution is obtained after sufficient reaction, the conductive FTO substrate is sequentially cleaned with glass cleaning solution, deionized water, acetone, and ethanol, and then dried, treated with an ultraviolet ozone cleaning machine, and then placed in the titanium dioxide colloidal solution, and deposited at 70°C for 50 min; after the reaction is completed, the glass substrate is repeatedly cleaned with ultrapure water and anhydrous ethanol, and then annealed at 130°C for 1 h, thereby obtaining a dense titanium dioxide film with a thickness of about 20 nm, which is the electron transport layer.

[0087] Comparative Example 2

[0088] A preparation method of a perovskite solar cell, which is the same in structure as that of Example 2, except that the electron transport layer in Comparative Example 2 is not modified, and the preparation of the electron transport layer comprises the following steps:

[0089] The preparation steps are the same as those of Example 2, except that 850 μL of titanium tetrachloride is added to 40 mL of ultrapure water, and a titanium dioxide colloidal solution is obtained after sufficient reaction, the conductive FTO substrate is sequentially cleaned with glass cleaning solution, deionized water, acetone, and ethanol, and then dried, treated with an ultraviolet ozone cleaning machine, and then placed in the titanium dioxide colloidal solution, and deposited at 70°C for 50 min; after the reaction is completed, the glass substrate is repeatedly cleaned with ultrapure water and anhydrous ethanol, and then annealed at 130°C for 1 h, thereby obtaining a dense titanium dioxide film with a thickness of about 20 nm, which is the electron transport layer.

[0090] In order to evaluate the levodopa molecule modified perovskite solar cell prepared by the present application, the performance of the perovskite solar cells of Examples 1-2 and Comparative Examples 1-2 was detected, and the specific results are shown in Table 1. Figures 2 to 7 .

[0091] Figure 2 Atomic force microscopic images (AFM) of the levodopa molecule modified titanium dioxide prepared in step S1 of Example 1 and the unmodified titanium dioxide prepared in Comparative Example 1; Figure 2The data show that the levodopa molecule modified titanium dioxide surface prepared in Example 1 is smoother, with an average roughness RMS = 12.13 nm, and the unmodified titanium dioxide has an average roughness RMS = 20.88 nm.

[0092] Figure 3 Current-voltage curve of the levodopa molecule modified FAPbI3 perovskite solar cell prepared in Example 1 and the unmodified FAPbI3 perovskite solar cell prepared in Comparative Example 1; Figure 3 The data show that the highest photoelectric conversion efficiency of the solar cell prepared in Example 1 is 23.28%, and the highest efficiency of the unmodified FAPbI3 cell is 21.91%.

[0093] Figure 4 Steady-state output efficiency of the levodopa molecule modified FAPbI3 perovskite solar cell prepared in Example 1 and the unmodified FAPbI3 perovskite solar cell prepared in Comparative Example 1; Figure 4 It can be seen that the steady-state output efficiency of the solar cell prepared in Example 1 can reach 22.44%, while the steady-state output efficiency of the unmodified solar cell in the comparative example is 20.7%.

[0094] Figure 5 Stability curve of the levodopa molecule modified FAPbI3 perovskite solar cell prepared in Example 1 and the unmodified FAPbI3 perovskite solar cell prepared in Comparative Example 1 under the condition of relative humidity of 25%; from Figure 5 The data show that Example 1 still has 94% of the initial efficiency after 23 weeks of storage at 25°C and 25% relative humidity, while the unmodified solar cell in Comparative Example 1 has only 70% of the initial efficiency after the same time.

[0095] Figure 6 Light stability curve of the levodopa molecule modified FAPbI3 perovskite solar cell prepared in Example 1 and the unmodified FAPbI3 perovskite solar cell prepared in Comparative Example 1; from Figure 6 It can be seen that Example 1 still has 90% of the initial efficiency after 28 hours of continuous work under simulated sunlight with intensity of 0.23 Sμn, while Comparative Example 1 has only 81% of the initial efficiency under the same conditions.

[0096] Figure 7 Current-voltage curve of the levodopa molecule modified ternary ion CsFAMAPbI3 perovskite solar cell prepared in Example 2 and the unmodified ternary ion CsFAMAPbI3 perovskite solar cell prepared in Comparative Example 2; Figure 7Data show that the efficiency of the modified CsFAMAPbI3 perovskite solar cell is up to 21.06% under the method, and the efficiency of the perovskite solar cell without modification in the comparative example 2 is up to 19.44%.

[0097] In conclusion, the present application introduces levodopa molecules between the perovskite layer and the electron transport layer, improves the performance of the titanium dioxide in the electron transport layer, provides sites for perovskite nucleation, passivates the lower interface defects of the perovskite, and improves the extraction and transport capacity of the electron transport layer for the perovskite photo-generated carriers, compared with the unmodified perovskite solar cell, has higher photoelectric conversion efficiency and longer stability.

[0098] Obviously, those skilled in the art can make various modifications and variations to the present application without departing from the spirit and scope of the present application. Thus, if these modifications and variations of the present application belong to the scope of the claims of the present application and their equivalent technologies, the present application also intends to include these modifications and variations. The above-described embodiments are only preferred embodiments of the present application, and the protection scope of the present application is not limited thereto. The equivalent substitutions or transformations made by those skilled in the art on the basis of the present application are within the protection scope of the present application, and the protection scope of the present application is subject to the claims.

Claims

1. A method for preparing a titanium dioxide thin film modified with L-DOPA molecules, characterized in that, Includes the following steps: (1) Preparation of titanium dioxide colloidal solution; (2) A conductive substrate is deposited in the titanium dioxide colloidal solution of step (1) to obtain a section of deposited substrate; (3) Take out one section of the deposition substrate from the titanium dioxide colloidal solution in step (2), then add levodopa molecules to the titanium dioxide colloidal solution, mix evenly to obtain a mixture, and deposit one section of the deposition substrate in the mixture to obtain a second section of the deposition substrate; The mass ratio of levodopa molecules to the volume ratio of the titanium dioxide colloidal solution in step (2) is 0.2-0.6 mg: 1 mL. (4) After cleaning the two-stage deposition substrate in step (3), annealing is performed to obtain a titanium dioxide film modified with L-DOPA molecules; The titanium dioxide colloidal solution in step (1) is prepared according to the following steps: titanium tetrachloride is dissolved in water and reacted at 0-60℃ for 15 min to obtain titanium dioxide colloidal solution; The concentration of titanium tetrachloride in the titanium dioxide colloidal solution is 150-250 mmol / L.

2. The method for preparing L-DOPA-modified titanium dioxide thin films according to claim 1, characterized in that, The conductive substrate in step (2) is selected from conductive FTO substrate, ITO substrate, and PEN conductive film; The conductive substrates in step (2) are all cleaned before use. The cleaning method is as follows: ultrasonic cleaning is performed sequentially with glass cleaning fluid, deionized water, acetone and ethanol, followed by drying, and then ultraviolet ozone cleaning.

3. The method for preparing L-DOPA-modified titanium dioxide thin films according to claim 1, characterized in that, The deposition conditions for both steps (2) and (3) are: deposition at 70±5℃ for 20-60 min.

4. The method for preparing L-DOPA-modified titanium dioxide thin films according to claim 1, characterized in that, The annealing conditions for step (4) are: annealing at 100-150℃ for 1-3 hours.

5. A titanium dioxide thin film modified with L-DOPA molecules prepared by the preparation method according to any one of claims 1-4.

6. The application of the L-DOPA molecule-modified titanium dioxide thin film according to claim 5 in the preparation of perovskite solar cells, characterized in that, The perovskite solar cell is made of a conductive substrate (1), an electron transport layer (2), a perovskite layer (3), a hole transport layer (4), and a metal electrode layer (5) arranged sequentially from bottom to top; The electron transport layer (2) is a titanium dioxide film modified with the L-DOPA molecule, and the metal electrode layer (5) is a gold electrode layer or a silver electrode layer.

7. The application according to claim 6, characterized in that, The perovskite solar cell is prepared according to the following steps: Step 1, preparation of perovskite layer (3): The perovskite precursor solution is dropped onto the electron transport layer (2), and then an antisolvent is added under high-speed rotation. Then, annealing is performed to obtain the perovskite layer (3). Step 2, Preparation of hole transport layer (4): Spin-coating hole transport material spiro-OMeTAD onto the perovskite layer (3) in step 1 to obtain the hole transport layer (4). Step 3, Preparation of perovskite solar cells: Metal is deposited on the hole transport layer (4) of step 2 to obtain perovskite solar cells.

8. The application according to claim 7, characterized in that, The perovskite precursor solution in step 1 is selected from FAPbI3 perovskite precursor solution or CsFAMA ternary perovskite precursor solution, and the concentration of the perovskite precursor solution is 1.5-1.7 mol / mL. The perovskite layer (3) described in step 1 is prepared according to the following steps: Under rotation conditions, the perovskite precursor solution is dropped onto the electron transport layer (2) in batches. An anti-solvent is added 10-15s before the end of spin coating, and then annealed at 120-140℃ for 10-60min. The antisolvent is selected from ethyl acetate, chlorobenzene, chloroform, diethyl ether, and toluene, and the volume ratio of the perovskite precursor solution to the antisolvent is 1-2:

10.

9. The application according to claim 7, characterized in that, The thickness of the hole transport layer in step 2 is 150-250 nm, and the thickness of the metal coating in step 3 is 80-120 nm.

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