Preparation method and application of 1-ethyl-3-methylimidazole acetate modified low-temperature titanium dioxide nano material

Abstract

The invention discloses a preparation method and application of a 1-ethyl-3-methylimidazole acetate modified low-temperature titanium dioxide nano material, and belongs to the technical field of solar cell preparation. The preparation method of the 1-ethyl-3-methylimidazole acetate modified low-temperature titanium dioxide mesoporous layer comprises the following steps: mixing 1-ethyl-3-methylimidazole acetate and an organic solvent to obtain a mixed solution; and spin-coating the titanium dioxide mesoporous layer with the mixed solution, and carrying out first calcination to obtain the 1-ethyl-3-methylimidazole acetate modified low-temperature titanium dioxide mesoporous layer. Compared with an unmodified low-temperature titanium dioxide mesoporous layer, when the low-temperature titanium dioxide mesoporous layer modified by the 1-ethyl-3-methylimidazole acetate solution is used as an electron transport layer material of a perovskite solar cell (PSCs), the overall performance of a device can be improved.

Description

Technical Field

[0001] The present invention belongs to the technical field of solar cell preparation, and more specifically relates to a preparation method and application of a low-temperature titanium dioxide nanomaterial modified with 1-ethyl-3-methylimidazolium acetate. Background Art

[0002] Solar energy is a common and currently mature renewable energy source. After being proposed in 2009, perovskite solar cells (PSCs) have developed rapidly. After only more than a decade of research, the efficiency of perovskite solar cells has reached 26.7%, and their performance can be comparable to that of crystalline silicon solar cells under laboratory conditions. Compared with crystalline silicon solar cells, the new PSCs have a simpler manufacturing process, lower cost, and higher theoretical photoelectric conversion efficiency, and have become one of the important battery systems.

[0003] The structure of perovskite solar cells is mainly divided into a mesoscopic structure and a planar structure. There is an obvious hysteresis effect during the measurement of the planar structure, and the test results of the photoelectric conversion efficiency are inaccurate; while the mesoscopic structure means that the electron transport layer material is a mesoporous material. Currently, the research focus of this type of structure is on using mesoporous TiO 2 As the electron transport layer, compared with other semiconductor materials, they have the advantages of high carrier mobility, high specific surface area, large pore volume, adjustable pore size and morphology, etc. When used as a mesoporous layer, it needs to be heat-treated at a high temperature (450 °C) to decompose the impurities remaining in the mesoporous layer. However, the problems brought by high-temperature preparation are the increase in manufacturing cost and the limitation of the development of flexible devices. The method of preparing the TiO 2 mesoporous layer requires heating the reactants to a relatively high temperature, and maintaining such a high temperature requires a large amount of energy input. The high-temperature heating makes the energy cost account for a relatively large proportion in the entire production cost. In order to withstand the high-temperature environment, special high-temperature-resistant reaction vessels and heating equipment are required. These devices are not only expensive themselves, but also will have certain losses during long-term high-temperature operation. For example, the lining material of the high-temperature furnace will be damaged due to repeated thermal expansion and contraction and needs to be replaced regularly, which also increases the cost of equipment maintenance and update. Therefore, there is a problem of high cost. On the other hand, due to the common defects in titanium dioxide being oxygen vacancy defects, these oxygen vacancies will become charge trapping centers, making electrons easily trapped and difficult to be transmitted smoothly, hindering charge transmission. The perovskite material itself may also have defects, and the defects will interact with the defects of titanium dioxide at the interface, further increasing the charge recombination probability at the interface and reducing the transmission of effective charges. Therefore, there is a problem of blocked interfacial charge transmission. Therefore, it is of great significance to develop a low-temperature titanium dioxide mesoporous layer with a simple process, low cost, and capable of improving the surface quality of the electron transport layer to solve the problem of blocked interfacial charge transmission. Summary of the Invention

[0004] The object of the present invention is to provide a preparation method and application of a 1-ethyl-3-methylimidazolium acetate modified low-temperature titanium dioxide nanomaterial, so as to solve the problems of high cost and blocked interfacial charge transport existing when preparing a TiO 2 mesoporous layer, and realize the preparation of a perovskite solar cell device with excellent performance.

[0005] To achieve the above object, the present invention provides the following solutions:

[0006] One of the technical solutions of the present invention: Provide a preparation method of a 1-ethyl-3-methylimidazolium acetate modified low-temperature titanium dioxide mesoporous layer, including the following steps:

[0007] Mix 1-ethyl-3-methylimidazolium acetate and an organic solvent to obtain a mixed solution; spin-coat the mixed solution on the titanium dioxide mesoporous layer, and obtain the 1-ethyl-3-methylimidazolium acetate modified low-temperature titanium dioxide mesoporous layer after the first calcination.

[0008] The present invention uses 1-ethyl-3-methylimidazolium acetate (EMIMAc) to modify the low-temperature titanium dioxide mesoporous layer. Due to the interaction between the Ti atoms in TiO 2 and the EMIMAc ligand, the -COO- group combines with TiO 2 to promote the defect passivation on the surface of the TiO 2 film. Compared with the unmodified TiO 2 film, the oxygen vacancies in the TiO 2 film modified by EMIMAc are reduced, the deep trap states of TiO 2 are inhibited, and the effective improvement of the TiO 2 film quality is achieved.

[0009] In addition, the amino group with a single electron pair in EMIMAc forms a Pb-N bond on the perovskite crystal of the perovskite solar cell. At the same time, there will be a coordination interaction between the imidazole ring and the Pb 2+ defects. In addition, after adding EMIMAc, there is an interaction between the imidazole ring and the PbI 3- defects. The interaction force between I and the strongly electronegative Pb 2+ is reduced, so that the binding force between the modified layer and the perovskite layer is increased. In addition, the EMIMAc organic small molecule can also adhere to the low-temperature titanium dioxide mesoporous layer skeleton, significantly improving the interfacial binding resistance between the low-temperature titanium dioxide mesoporous layer and the perovskite film. Thereby, the charge recombination loss is largely inhibited, the problem of blocked interfacial charge transport is solved, and the overall performance of the device is effectively improved.

[0010] Preferably, the preparation of the titanium dioxide mesoporous layer includes the following steps:

[0011] Mix nano-titanium dioxide, terpineol and ethyl cellulose to obtain a colloid; dilute the colloid with an organic solvent to obtain a mesoporous layer precursor solution; spin-coat the mesoporous layer precursor solution on a substrate formed with dense layer titanium dioxide, and after the second calcination, form the titanium dioxide mesoporous layer with a thickness of 150-200 nm.

[0012] Compared with the existing low-temperature preparation scheme of titanium dioxide mesoporous layer, the present invention modifies the low-temperature titanium dioxide mesoporous layer with 1-ethyl-3-methylimidazolium acetate (EMIMAc), so that titanium dioxide does not require complex high-temperature reaction equipment and special reaction conditions, reducing the requirements for production equipment and investment costs. At the same time, the process flow of this method is relatively simple, easy to operate and control, reducing the labor cost in the production process and further improving the economy of production. Moreover, this green material of ionic liquid has good chemical stability and recyclability and can be recycled and reused. This greatly reduces the use cost of ionic liquid and further improves the economy of the whole production process. Therefore, the preparation method described in the present invention significantly reduces the preparation cost and solves the problems existing in the prior art.

[0013] Preferably, the mass ratio of the nano-titanium dioxide, terpineol and ethyl cellulose is 1:2:4.

[0014] Preferably, the dosage ratio of the colloid to the organic solvent is 1 g: 8.5-10 mL.

[0015] Preferably, the temperature of the second calcination is 100-150 °C, and the time of the second calcination is 10-40 min.

[0016] Preferably, the preparation of the substrate formed with dense layer titanium dioxide includes the following steps:

[0017] Spin-coat the dense layer titanium dioxide precursor solution on an FTO glass substrate, and after the third calcination, form a dense layer titanium dioxide with a thickness of 50-60 nm, that is, obtain the substrate formed with dense layer titanium dioxide.

[0018] Preferably, the dense layer titanium dioxide precursor solution includes Triton, glacial acetic acid, tetrabutyl titanate and an organic solvent; the volume ratio of the Triton, glacial acetic acid, tetrabutyl titanate and the organic solvent is 3:4:1:40.

[0019] Preferably, the temperature of the third calcination is 400-500 °C, and the time of the third calcination is 10-40 min.

[0020] The present invention does not have a specific limitation on the type of the organic solvent involved, as long as it can dissolve the raw materials to ensure the smooth progress of the reaction. The organic solvent involved is preferably ethanol.

[0021] Preferably, the dosage ratio of the 1-ethyl-3-methylimidazolium acetate to the organic solvent is 1 to 20 mg:1 mL.

[0022] Preferably, the spin coating amount of the mixed solution is 0.0133 to 0.26 g / cm 2 .

[0023] Preferably, the temperature of the first calcination is 50 to 100 °C, and the time of the first calcination is 5 to 10 min.

[0024] The overall performance of the present invention can be regulated by controlling the addition amount of 1-ethyl-3-methylimidazolium acetate, the thickness of the modification layer, and the calcination parameters. An appropriate addition amount can ensure the surface properties of low-temperature mesoporous titanium dioxide, decompose the residual impurities on the surface, make the electron transport layer more conducive to electron capture and transfer, reduce the recombination of electrons and holes, improve the electron transport characteristics of the electron transport layer, and improve the photoelectric conversion efficiency of perovskite; an appropriate modification layer thickness can regulate the energy band structure of titanium dioxide, which is beneficial to electron transition; and appropriate calcination parameters can make the modification layer more uniformly dispersed on the surface of mesoporous titanium dioxide, so that 1-ethyl-3-methylimidazolium acetate can better interact with the mesoporous layer and the perovskite layer. However, exceeding this range will cause the surface of titanium dioxide to be overly covered, hinder electron transition, and reduce the electron transport efficiency.

[0025] The second technical solution of the present invention: Provide a 1-ethyl-3-methylimidazolium acetate modified low-temperature titanium dioxide mesoporous layer prepared by the above preparation method.

[0026] The third technical solution of the present invention: Provide the application of the above 1-ethyl-3-methylimidazolium acetate modified low-temperature titanium dioxide mesoporous layer in the preparation of perovskite solar cells.

[0027] The fourth technical solution of the present invention: Provide a perovskite solar cell, which includes an FTO glass substrate, a dense layer of titanium dioxide, a 1-ethyl-3-methylimidazolium acetate modified low-temperature titanium dioxide mesoporous layer, a perovskite layer, a hole transport layer, and a counter electrode arranged in sequence.

[0028] The fifth technical solution of the present invention: Provide the preparation method of the above perovskite solar cell, including the following steps:

[0029] Successively arrange a dense layer of titanium dioxide, a 1-ethyl-3-methylimidazolium acetate modified low-temperature titanium dioxide mesoporous layer, a perovskite layer, a hole transport layer, and a counter electrode on the FTO glass substrate to obtain the perovskite solar cell.

[0030] The present invention discloses the following technical effects:

[0031] 1. The present invention improves the defects of the TiO material itself caused by the low-temperature preparation of the titanium dioxide mesoporous layer and the problem of charge transport with the light-absorbing layer by introducing a green and environmentally friendly imidazolium-based ionic liquid, thereby increasing the mobility of carriers in the material and further enhancing the electron transport performance of the mesoporous perovskite solar cell prepared at low temperature using it as a raw material, while improving the photoelectric conversion efficiency of the device. 2 3. When the low-temperature titanium dioxide mesoporous layer modified by the 1-ethyl-3-methylimidazolium acetate solution of the present invention is used as the electron transport layer material of a perovskite solar cell (PSCs), the overall performance of the device can be improved compared to the unmodified low-temperature titanium dioxide mesoporous layer.

[0032] 2. The preparation process of the present invention is simple, and the obtained perovskite solar cell (PSCs) has good photoelectric conversion efficiency and low cost, which promotes the development of high-quality perovskite solar cells and has double significance of good economic benefits and high environmental benefits.

[0033] 3. The preparation process of the present invention is simple, and the obtained perovskite solar cell (PSCs) has good photoelectric conversion efficiency and low cost, which promotes the development of high-quality perovskite solar cells and has double significance of good economic benefits and high environmental benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] Figure 1 FIG. 1 is a schematic structural diagram of the perovskite solar cell (PSCs) of the present invention, where 1 is an FTO glass substrate, 2 is a dense titanium dioxide layer and a low-temperature titanium dioxide mesoporous layer, 3 is a 1-ethyl-3-methylimidazolium acetate (EMIMAc) modification layer, 4 is a perovskite layer, 5 is a hole transport layer, and 6 is a counter electrode;

[0035] Figure 2 FIG. 2 is an XPS spectrum of N element of the low-temperature titanium dioxide mesoporous layer with different concentrations of 1-ethyl-3-methylimidazolium acetate (EMIMAc) interface modification prepared in Example 1 and Comparative Examples 2-4 and the unmodified low-temperature titanium dioxide mesoporous layer prepared in Comparative Example 1;

[0036] Figure 3 FIG. 3 is an XPS spectrum of different elements in the 1-ethyl-3-methylimidazolium acetate (EMIMAc) interface-modified low-temperature titanium dioxide mesoporous layer and perovskite layer prepared in Example 1 and the unmodified low-temperature titanium dioxide mesoporous layer and perovskite layer prepared in Comparative Example 1, where a is the XPS spectrum of O, b is the XPS spectrum of Ti, c is the XPS spectrum of Pb, and d is the XPS spectrum of I;

[0037] Figure 4 FIG. 4 is a photoluminescence spectrum of the low-temperature titanium dioxide mesoporous layer with different concentrations of 1-ethyl-3-methylimidazolium acetate (EMIMAc) interface modification prepared in Example 1 and Comparative Examples 2-4 and the unmodified low-temperature titanium dioxide mesoporous layer prepared in Comparative Example 1;

[0038] Figure 5 Photovoltaic conversion efficiency comparison chart of perovskite solar cells (PSCs) prepared in Example 1 and Comparative Examples 1-4;

[0039] Figure 6 Incident monochromatic light-photovoltaic conversion efficiency comparison chart of perovskite solar cells (PSCs) prepared in Example 1 and Comparative Example 1. Detailed implementation manners

[0040] Now, various exemplary implementation manners of the present invention will be described in detail. This detailed description should not be considered as a limitation of the present invention, but should be understood as a more detailed description of certain aspects, characteristics, and implementation manners of the present invention.

[0041] It should be understood that the terms described in the present invention are only for describing specific implementation manners and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Any intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges can be independently included or excluded from the range.

[0042] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. All documents mentioned in this specification are incorporated by reference to disclose and describe the methods and / or materials related to the documents. In case of conflict with any incorporated document, the content of this specification shall prevail.

[0043] Without departing from the scope or spirit of the present invention, various improvements and changes can be made to the specific implementation manners of the present invention specification, which are obvious to those skilled in the art. Other implementation manners obtained from the present invention specification are obvious to those skilled in the art. The present invention specification and examples are only exemplary.

[0044] Regarding the terms "comprising", "including", "having", "containing", etc. used herein, they are all open-ended terms, meaning including but not limited to.

[0045] The raw materials used in the examples and comparative examples of the present invention are all commercially available products without special limitations.

[0046] The structural schematic diagram of the perovskite solar cell (PSC) prepared in the example of the present invention is as Figure 1 shown Figure 1Among them, 1 is the FTO glass substrate, 2 is the dense titanium dioxide layer and the low-temperature titanium dioxide mesoporous layer, 3 is the 1-ethyl-3-methylimidazolium acetate (EMIMAc) modification layer, 4 is the perovskite layer, 5 is the hole transport layer, and 6 is the counter electrode.

[0047] Example 1

[0048] This example provides a method for preparing a mesoscopic perovskite solar cell, and the steps are as follows:

[0049] (1) Preparation of the dense titanium dioxide layer: Measure 0.5 g of Triton, 5 mL of absolute ethanol, 0.5 mL of glacial acetic acid, and 0.125 mL of tetrabutyl titanate, mix them evenly to obtain the precursor solution of the dense titanium dioxide layer; then use a spin coater to spin-coat the precursor solution of the dense titanium dioxide layer onto the FTO glass substrate (1.5 cm × 1.5 cm, thickness 2.2 mm), and then put it into a muffle furnace for calcination. The calcination temperature is 450 °C and the time is 30 min, thus forming the dense titanium dioxide layer (thickness 50 nm).

[0050] (2) Preparation of the 10 mg / mL EMIMAc interface-modified low-temperature titanium dioxide mesoporous layer:

[0051] Weigh 1 g of nano-titanium dioxide, grind it into powder in a mortar, transfer it to a beaker and add 2 g of terpineol, heat and stir at 60 °C and add 4 g of ethyl cellulose, and ball-mill it with a ball mill at room temperature for 5 h to obtain a white colloidal substance; then weigh 1 g of the white colloidal substance, add 8.5 mL of absolute ethanol for dilution to obtain the precursor solution of the titanium dioxide mesoporous layer; finally, set the spin coater parameters with a rotation speed of 5000 r / min and a time of 20 s during spin coating. Take 70 μL of the precursor solution of the titanium dioxide mesoporous layer, drop it onto the dense titanium dioxide layer prepared in step (1), and wait for it to flow and cover evenly, then turn on the spin coater; after spin coating, put the above-mentioned FTO coated with the titanium dioxide layer into a muffle furnace and calcine it at 130 °C for 30 min to obtain the mesoscopic PSCs titanium dioxide mesoporous layer (thickness 150 nm);

[0052] Mix 10 mg of 1-ethyl-3-methylimidazolium acetate (EMIMAc) and 1 mL of absolute methanol and stir evenly to obtain solution A. Take 30 μL of solution A and spin-coat it onto the mesoscopic PSCs titanium dioxide mesoporous layer, and the spin coating amount is 0.133 g / cm 2 , and calcine it at 70 °C for 5 min to make EMIMAc play its role, thus forming the EMIMAc interface modification layer.

[0053] (3) Preparation of perovskite layer: Weigh 18.12 mg of ammonium methyl bromide, 150.368 mg of formamidinium hydroiodide, 56.44 mg of lead bromide, 423.192 mg of lead iodide, 640 μL of N,N-dimethylformamide, and 160 μL of dimethyl sulfoxide, and mix them evenly to obtain a perovskite precursor solution; then, using ethyl acetate as an antisolvent, spin-coat the perovskite precursor solution onto the EMIMAc interfacial modification layer prepared in step (2); the rotation speed during the spin-coating process is set to 3000 r / min, the time is 30 s, and the acceleration is 1000 r / min; 200 μL of ethyl acetate is dropped onto the spin-coated surface 5 s before the end of spin-coating, and after spin-coating, it is heated at 100 °C for 30 min to obtain a perovskite layer (with a thickness of 300 nm). The above process is carried out in a glove box.

[0054] (4) Preparation of inorganic hole transport layer: Weigh 72.3 mg of Spiro-OMeTAD, 1 mL of anhydrous chlorobenzene, 28.8 μL of 4-tert-butylpyridine, and 18 μL of lithium bis(trifluoromethanesulfonyl)imide solution, and mix them evenly to obtain a hole transport layer precursor solution; then, spin-coat the hole transport layer precursor solution onto the perovskite layer prepared in step (3) and dry it naturally to obtain an inorganic hole transport layer (with a thickness of 200 nm). The spin-coating speed is 4000 r / min, the spin-coating time is 30 s, and the spin-coating acceleration is 3000 r / min.

[0055] (5) Preparation of counter electrode: Place the device with the hole transport layer prepared in step (4) into a mask plate, and use the vacuum evaporation method to evaporate a layer of Ag metal counter electrode (with a thickness of 50 nm) under a vacuum of 6.0×10 -4 Pa to obtain a mesoscopic perovskite solar cell (PSCs) product.

[0056] Comparative Example 1

[0057] The difference from Example 1 is that in step (2), the modification process of "1-ethyl-3-methylimidazolium acetate (EMIMAc)" is omitted, and the others are the same as in Example 1.

[0058] Comparative Example 2

[0059] The difference from Example 1 is that step (2) is different. Specifically:

[0060] Preparation of 1 mg / mL EMIMAc interfacial modification low-temperature titanium dioxide mesoporous layer:

[0061] Weigh 1 g of nano-titanium dioxide, grind it into powder in a mortar, transfer it to a beaker, add 2 g of terpineol, heat and stir at 60 °C, add 4 g of ethyl cellulose, and ball-mill at room temperature for 5 h to obtain a white colloidal substance; then weigh 1 g of the white colloidal substance, add 8.5 mL of absolute ethanol for dilution to obtain a titanium dioxide mesoporous layer precursor solution; finally, set the spin coater parameters, with a rotation speed of 5000 r / min and a time of 20 s during spin coating. Take 70 μL of the titanium dioxide mesoporous layer precursor solution, drop it onto the dense layer of titanium dioxide prepared in step (1), and after it spreads evenly, start the spin coater; after spin coating, put the above-mentioned FTO coated with a titanium dioxide layer into a muffle furnace and calcine at 130 °C for 30 min to obtain a mesoscopic PSCs titanium dioxide mesoporous layer (with a thickness of 150 nm);

[0062] Mix 1 mg of 1-ethyl-3-methylimidazolium acetate (EMIMAc) and 1 mL of absolute methanol and stir evenly to obtain solution A. Take 30 μL of solution A and spin coat it onto the mesoscopic PSCs titanium dioxide mesoporous layer, with a spin coating amount of 0.0133 g / cm 2 , and calcine at 70 °C for 5 min to make EMIMAc play its role, that is, to form an EMIMAc interfacial modification layer.

[0063] Others are the same as in Example 1.

[0064] Comparative Example 3

[0065] The difference from Example 1 is: step (2) is different, specifically:

[0066] Preparation of a 5 mg / mL EMIMAc interfacial modification low-temperature titanium dioxide mesoporous layer:

[0067] Weigh 1 g of nano-titanium dioxide, grind it into powder in a mortar, transfer it to a beaker, add 2 g of terpineol, heat and stir at 60 °C, add 4 g of ethyl cellulose, and ball-mill at room temperature for 5 h to obtain a white colloidal substance; then weigh 1 g of the white colloidal substance, add 8.5 mL of absolute ethanol for dilution to obtain a titanium dioxide mesoporous layer precursor solution; finally, set the spin coater parameters, with a rotation speed of 5000 r / min and a time of 20 s during spin coating. Take 70 μL of the titanium dioxide mesoporous layer precursor solution, drop it onto the dense layer of titanium dioxide prepared in step (1), and after it spreads evenly, start the spin coater; after spin coating, put the above-mentioned FTO coated with a titanium dioxide layer into a muffle furnace and calcine at 130 °C for 30 min to obtain a mesoscopic PSCs titanium dioxide mesoporous layer (with a thickness of 150 nm);

[0068] 5 mg of 1-ethyl-3-methylimidazolium acetate (EMIMAc) was mixed with 1 mL of anhydrous methanol and stirred evenly to obtain solution A. 30 μL of solution A was spin-coated onto the mesoscopic PSCs titanium dioxide mesoporous layer, and the spin-coating amount was 0.0667 g / cm 2 , and it was calcined at 70 °C for 5 min to make EMIMAc play its role, that is, an EMIMAc interfacial modification layer was formed.

[0069] Others are the same as in Example 1.

[0070] Comparative Example 4

[0071] The difference from Example 1 is that step (2) is different. Specifically:

[0072] Preparation of 20 mg / mL EMIMAc interfacial modification low-temperature titanium dioxide mesoporous layer:

[0073] Weigh 1 g of nano-titanium dioxide, grind it into powder in a mortar, transfer it to a beaker and add 2 g of terpineol. Heat and stir at 60 °C and add 4 g of ethyl cellulose, and ball-mill it in a ball mill at room temperature for 5 h to obtain a white colloidal substance; then weigh 1 g of the white colloidal substance, add 8.5 mL of anhydrous ethanol for dilution to obtain a titanium dioxide mesoporous layer precursor solution; finally, set the spin coater parameters, the rotation speed during spin coating is 5000 r / min, the time is 20 s, take 70 μL of the titanium dioxide mesoporous layer precursor solution, drop it onto the dense layer titanium dioxide prepared in step (1), and after it flows and spreads evenly, turn on the spin coater; after spin coating, put the above-mentioned FTO coated with titanium dioxide layer into a muffle furnace and calcine it at 130 °C for 30 min to obtain a mesoscopic PSCs titanium dioxide mesoporous layer (thickness is 150 nm);

[0074] 20 mg of 1-ethyl-3-methylimidazolium acetate (EMIMAc) was mixed with 1 mL of anhydrous methanol and stirred evenly to obtain solution A. 30 μL of solution A was spin-coated onto the mesoscopic PSCs titanium dioxide mesoporous layer, and the spin-coating amount was 0.26 g / cm 2 , and it was calcined at 70 °C for 5 min to make EMIMAc play its role, that is, an EMIMAc interfacial modification layer was formed.

[0075] Others are the same as in Example 1.

[0076] Comparative Example 5

[0077] The difference from Example 1 is that the ionic liquid used in step (2) is different. Specifically:

[0078] Mix an amount of N-methylimidazole equal to that of "1-ethyl-3-methylimidazolium acetate (EMIMAc)" in Example 1 with 1 mL of anhydrous methanol and stir evenly to obtain Solution B. Take 30 μL of Solution B and spin-coat it onto the mesoscopic PSCs titanium dioxide mesoporous layer, with a spin-coating amount of 0.133 g / cm 2 , and calcine it at 70 °C for 5 min to make it work, that is, to form an EMIMAc interfacial modification layer.

[0079] Other conditions are the same as in Example 1.

[0080] After testing, the photoelectric conversion efficiency (PCE) of the battery product obtained in this comparative example is 15.06%.

[0081] Comparative Example 6

[0082] The difference from Example 1 is as follows: Step (2) is different. Specifically:

[0083] Use the common method in the prior art to prepare the titanium dioxide mesoporous layer. The steps are as follows:

[0084] Using rutile-phase titanium dioxide nanoparticles with a particle size of 30 nm as raw materials, add 1.5 g of polymethyl methacrylate (pore-forming agent), 30 g of terpineol (solvent), and 1.4 g of polyvinyl alcohol (binder) to mix and make a slurry. Set the spin coater parameters with a rotation speed of 5000 r / min and a time of 20 s during spin coating. Take 70 μL of the prepared slurry and drop it onto the dense layer titanium dioxide obtained in step (1). After it spreads evenly, turn on the spin coater; after spin coating, first cure the above-mentioned FTO coated with a titanium dioxide layer on a hot stage at 80 °C for 10 min, and then sinter it at 300 °C for 0.5 h to form a titanium dioxide mesoporous layer.

[0085] Other conditions are the same as in Example 1.

[0086] After testing, the photoelectric conversion efficiency (PCE) of the battery product obtained in this comparative example is 15.28%.

[0087] Effect verification:

[0088] 1. Use an X-ray photoelectron spectrometer to detect the different concentrations of 1-ethyl-3-methylimidazolium acetate (EMIMAc) interfacial modification low-temperature titanium dioxide mesoporous layers prepared in Example 1 and Comparative Examples 2-4, as well as the unmodified low-temperature titanium dioxide mesoporous layer prepared in Comparative Example 1. The obtained results are as Figure 2 and Figure 3 shown.

[0089] Figure 2XPS spectra of N element for low-temperature titanium dioxide mesoporous layers with different concentrations of 1-ethyl-3-methylimidazolium acetate (EMIMAc) prepared in Example 1 and Comparative Examples 2-4, and for the low-temperature titanium dioxide mesoporous layer without interface modification prepared in Comparative Example 1 Figure 2 In 2 +20 mM EMIMAc represents Comparative Example 4, TiO 2 +10 mM EMIMAc represents Example 1, TiO 2 +5 mM EMIMAc represents Comparative Example 3, TiO 2 +1 mM EMIMAc represents Comparative Example 2, TiO 2 represents Comparative Example 1; Figure 3 XPS spectra of different elements in the 1-ethyl-3-methylimidazolium acetate (EMIMAc) interface-modified low-temperature titanium dioxide mesoporous layer and perovskite layer prepared in Example 1, and in the low-temperature titanium dioxide mesoporous layer and perovskite layer without interface modification prepared in Comparative Example 1. Among them, a is the XPS spectrum of O, b is the XPS spectrum of Ti, c is the XPS spectrum of Pb, and d is the XPS spectrum of I.

[0090] From Figure 2 and Figure 3 it can be seen that the XPS spectral intensity of the N peak can reflect the presence of nitrogen element in the sample and observe whether 1-ethyl-3-methylimidazolium acetate (EMIMAc) is deposited on the surface of mesoporous titanium dioxide. And Figure 3 In a and b of 2 the XPS spectra are for observing how the embedded organic small molecules act on the surface of TiO 2 and perovskite, showing the O and Ti peaks on the untreated and treated surfaces. Compared with the original TiO 2 , due to the interaction between the Ti atoms in TiO 2 and the IL ligand, the interaction between EMIMAc and the TiO - film is confirmed by the shift of the Ti 2p peak. The binding between the -COO 2 group and TiO 2 results in defect passivation of the TiO 2 (mesoporous titanium dioxide) film. The O1s peak at 530.0 eV can be attributed to the Ti-O bond, while the O1s shoulder peak at 531.4 eV can be attributed to the reduction of oxygen vacancies in the mp-TiO 2 (mesoporous titanium dioxide) film after EMIMAc treatment compared with the original mp-TiO 2 (mesoporous titanium dioxide) film. This indicates that EMIMAc can passivate oxygen vacancy defects, thereby improving the quality of the mp-TiO Figure 3It can be seen from Figures c and d that the amino group with a single electron pair in EMIMAc forms a Pb-N bond on the perovskite crystal. The Pb 4f spectrum shows two characteristic peaks at 138.5 eV and 143.3 eV, corresponding to the spin-orbit splitting of the Pb 4f 7 / 2 and 4f 5 / 2 components respectively. The obtained signals are respectively shifted to lower binding energies of 138.3 eV and 143.1 eV, confirming the coordination interaction between the imidazole ring and Pb 2+ defects. In addition, the I 3d spectrum shifts from 619.3 eV to 618.2 eV, indicating the interaction between the imidazole ring and PbI 3- defects and the decrease in the interaction force between I and strongly electronegative Pb 2+ defects.

[0091] 2. The fluorescence spectrometer was used to detect the different concentrations of 1-ethyl-3-methylimidazolium acetate (EMIMAc) interface-modified low-temperature titanium dioxide mesoporous layers prepared in Example 1 and Comparative Examples 2-4, as well as the unmodified low-temperature titanium dioxide mesoporous layer prepared in Comparative Example 1. The obtained results are as Figure 4 shown.

[0092] Figure 4 Figure 19 is the photoluminescence spectra of the different concentrations of 1-ethyl-3-methylimidazolium acetate (EMIMAc) interface-modified low-temperature titanium dioxide mesoporous layers prepared in Example 1 and Comparative Examples 2-4, as well as the unmodified low-temperature titanium dioxide mesoporous layer prepared in Comparative Example 1. Figure 4 In it, perovskite / TiO 2 represents Comparative Example 1, perovskite / 1 mM EMIMAc / TiO 2 represents Comparative Example 2, perovskite / 5 mM EMIMAc / TiO 2 represents Comparative Example 3, perovskite / 10 mM EMIMAc / TiO 2 represents Example 1, perovskite / 20 mM EMIMAc / TiO 2 represents Comparative Example 4.

[0093] It can be Figure 4 seen that by observing the photoluminescence spectrum of the combination of the perovskite light absorption layer and the electron transport layer, the PL spectrum shows a weakening trend, indicating that the electron transport layer can effectively extract and transport the photo-generated carriers generated by the perovskite layer, reducing the recombination of carriers.

[0094] 3. Performance evaluation of the perovskite solar cells (PSCs) prepared in Example 1 and Comparative Examples 1-4: Using a solar light simulator (100 mW / cm 2, irradiate the PSCs under AM1.5G, and at the same time use the Keithley system to measure the J-V characteristic curve and obtain their photoelectric conversion efficiency. The results are as Figure 5 shown.

[0095] Figure 5 Figure for comparing the photoelectric conversion efficiency of perovskite solar cells (PSCs) prepared in Example 1 and Comparative Examples 1-4. Figure 5 In it, 20 mg / mL EMIMAc represents Comparative Example 4, 10 mg / mL EMIMAc represents Example 1, 5 mg / mL EMIMAc represents Comparative Example 3, 1 mg / mL EMIMAc represents Comparative Example 2, and 0 mg / mL EMIMAc represents Comparative Example 1.

[0096] It can be seen from Figure 5 that the PSCs prepared with a TiO₂ mesoporous layer modified with 10 mg / mL EMIMAc have a higher photoelectric conversion efficiency than the PSCs prepared with other TiO₂, indicating that the interfacial modification between the perovskite and the charge transport layer (electron transport layer and hole transport layer) can improve the photoelectric conversion efficiency, reduce the charge recombination at the interface, and promote the smooth transport of carriers.

[0097] 4. Compare the incident monochromatic light-electron conversion efficiency of the perovskite solar cells (PSCs) prepared in Example 1 and Comparative Example 1: Use the solar cell quantum efficiency test system (550 nm) to irradiate the PSCs with green light, and use the IPCE test system to measure the IPCE and obtain the incident monochromatic light-electron conversion efficiency. The results are as Figure 6 shown.

[0098] Figure 6 Figure for comparing the incident monochromatic light-electron conversion efficiency of the perovskite solar cells (PSCs) prepared in Example 1 and Comparative Example 1. Figure 6 In it, IPCE-EMIMAc+perovskite represents Example 1, and IPCE-perovskite represents Comparative Example 1.

[0099] It can be seen from Figure 6 that compared with the PSCs prepared with the unmodified TiO₂ mesoporous layer in Comparative Example 1, the PSCs prepared with the TiO₂ mesoporous layer modified with 10 mg / mL EMIMAc have a higher current density and monochromatic photoelectric conversion efficiency.

[0100] 5. Detect the photovoltaic parameters (photoelectric conversion efficiency (PCE), open circuit voltage (V oc ), short circuit current density (J sc ), fill factor (FF)) of the perovskite solar cells (PSCs) prepared in Example 1 and Comparative Examples 1-4. The results are as follows:

[0101] The photovoltaic parameters of the PSCs prepared with a TiO₂ mesoporous layer modified with 10 mg / mL EMIMAc in Example 1 were: V oc = 1.09 V, J sc = 27.65 mA / cm 2 , FF = 0.66, PCE = 19.85%.

[0102] The photovoltaic parameters of the PSCs prepared with an unmodified TiO₂ mesoporous layer in Comparative Example 1 were: V oc = 1.07 V, J sc = 23.86 mA / cm 2 , FF = 0.57, PCE = 14.52%.

[0103] The photovoltaic parameters of the PSCs prepared with a TiO₂ mesoporous layer modified with 1 mg / mL EMIMAc in Comparative Example 2 were: V oc = 1.04 V, J sc = 27.18 mA / cm 2 , FF = 0.58, PCE = 16.10%.

[0104] The photovoltaic parameters of the PSCs prepared with a TiO₂ mesoporous layer modified with 5 mg / mL EMIMAc in Comparative Example 3 were: V oc = 1.06 V, J sc = 27.45 mA / cm 2 , FF = 0.63, PCE = 17.37%.

[0105] The photovoltaic parameters of the PSCs prepared with a TiO₂ mesoporous layer modified with 20 mg / mL EMIMAc in Comparative Example 4 were: V oc = 1.01 V, J sc = 22.65 mA / cm 2 , FF = 0.57, PCE = 15.22%.

[0106] From the above photovoltaic parameters, it can be seen that the PSCs prepared in the examples of the present invention have relatively high photoelectric conversion efficiency (PCE), open circuit voltage (V oc ), short circuit current density (J sc ) and fill factor (FF) values, indicating that the PSCs obtained in the present invention have better performance in energy conversion and more practical value; they have strong light absorption ability, and the generation and transmission processes of photo-generated carriers are relatively efficient; the ohmic loss and carrier recombination loss inside the battery are relatively small, and the battery can more effectively convert photo-generated carriers into output current and voltage, and the overall performance and energy conversion efficiency of the battery are relatively high.

[0107] In addition, comparing the photoelectric conversion efficiency data of the battery products obtained in Example 1, Comparative Example 5, and Comparative Example 6, it can be seen that the photoelectric conversion efficiency of the battery products obtained after replacing the ionic liquid decreases, and the PSCs prepared in Example 1 of the present invention have a high photoelectric conversion efficiency (PCE); compared with the common titanium dioxide mesoporous layer in the prior art, when the low-temperature titanium dioxide mesoporous layer modified with 1-ethyl-3-methylimidazolium acetate solution is used as the electron transport layer material of perovskite solar cells (PSCs), the photoelectric conversion efficiency (PCE) of the device can be significantly improved.

[0108] The various embodiments in this specification are described in a progressive manner. Each embodiment focuses on the differences from other embodiments. For the same and similar parts among the various embodiments, reference may be made to each other.

[0109] The above description of the disclosed embodiments enables those skilled in the art to implement or use the present invention. Various modifications to these embodiments will be obvious to those skilled in the art, and the general principles defined herein can be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but will be accorded the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A method for preparing a low-temperature titanium dioxide mesoporous layer modified with 1-ethyl-3-methylimidazolium acetate, characterized in that: The steps include: 1-ethyl-3-methylimidazolium acetate and an organic solvent are mixed to obtain a mixed solution; the mixed solution is spin-coated on a titanium dioxide mesoporous layer, and after a first calcination, a low-temperature titanium dioxide mesoporous layer modified with 1-ethyl-3-methylimidazolium acetate is obtained.

2. The preparation method according to claim 1, characterized in that: The preparation of the titanium dioxide mesoporous layer comprises the following steps: Mixing nano titanium dioxide, pine alcohol and ethyl cellulose to obtain a colloid; diluting the colloid with an organic solvent to obtain a mesoporous layer precursor solution; spin-coating the mesoporous layer precursor solution on a substrate forming a dense layer of titanium dioxide, and performing a second calcination to form the titanium dioxide mesoporous layer with a thickness of 150 to 200 nm; The mass ratio of the nano titanium dioxide, pineol and ethyl cellulose is 1:2:4; The dosage ratio of the colloid and the organic solvent is 1g:8.5-10mL; The temperature of the second calcination is 100-150° C., and the time of the second calcination is 10-40 minutes.

3. The preparation method according to claim 2, characterized in that: The preparation of the matrix for forming a dense layer of titanium dioxide comprises the following steps: Spin-coating a dense layer titanium dioxide precursor solution on a FTO glass substrate, and performing a third calcination to form a dense layer titanium dioxide with a thickness of 50 to 60 nm, thereby obtaining the matrix for forming the dense layer titanium dioxide; The dense layer titanium dioxide precursor solution comprises Triton, glacial acetic acid, tetrabutyl titanate and an organic solvent; the volume ratio of Triton, glacial acetic acid, tetrabutyl titanate and the organic solvent is 3:4:1:40; The temperature of the third calcination is 400-500° C., and the time of the third calcination is 10-40 minutes.

4. The preparation method according to claim 1, characterized in that: The usage ratio of the 1-ethyl-3-methylimidazole acetate and the organic solvent is 1-20 mg:1 mL.

5. The preparation method according to claim 1, characterized in that: The spin coating amount of the mixed solution is 0.0133-0.26 g / cm 2 .

6. The preparation method according to claim 1, characterized in that: The temperature of the first calcination is 50-100° C., and the time of the first calcination is 5-10 minutes.

7. A low-temperature titanium dioxide mesoporous layer modified with 1-ethyl-3-methylimidazolium acetate prepared by the preparation method according to any one of claims 1 to 6.

8. Use of the low-temperature titanium dioxide mesoporous layer modified with 1-ethyl-3-methylimidazolium acetate according to claim 7 in the preparation of perovskite solar cells.

9. A perovskite solar cell, characterized in that: The perovskite solar cell comprises an FTO glass substrate, a dense layer of titanium dioxide, a low-temperature titanium dioxide mesoporous layer modified by 1-ethyl-3-methylimidazole acetate, a perovskite layer, a hole transport layer and a counter electrode which are arranged in sequence.

10. The method for preparing a perovskite solar cell according to claim 9, characterized in that: The steps include: A dense layer of titanium dioxide, a low-temperature titanium dioxide mesoporous layer modified by 1-ethyl-3-methylimidazole acetate, a perovskite layer, a hole transport layer and a counter electrode are sequentially arranged on a FTO glass substrate to obtain the perovskite solar cell.

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