Mixed solvent and application thereof in preparation of perovskite solar cell

Abstract

The invention discloses a mixed solvent and an application thereof in preparation of a perovskite solar cell, the mixed solvent comprises a solvent A and a solvent B, the solvent A is N, N-dimethylacetamide, and the solvent B is one of N, N-dimethyl propenylurea, N-methyl pyrrolidone, 1, 3-dimethyl-2-imidazolinone and 1, 4-butyrolactone. Through the low-toxicity mixed solvent provided by the invention, a compact, uniform and flat perovskite film can be formed on the surface of a conductive layer, and interface contact and pinhole defects are improved; the mixed solvent provided by the invention can form a stable perovskite intermediate phase in the spin coating process, the processing time window of the preparation process is improved, and the reproducibility and stability of the perovskite solar cell are improved.

Description

Technical Field

[0001] The present invention relates to the technical field of perovskite solar cells, and particularly to a mixed solvent and its application in the preparation of perovskite solar cells. Background Art

[0002] Perovskite solar cells are a new photovoltaic technology that uses semiconductor materials with a perovskite crystal structure as the main light absorption layer to achieve efficient photoelectric conversion. Currently, the preparation of highly efficient perovskite solar cells mainly relies on an "antisolvent-assisted" coating process, which is achieved by dropping an antisolvent that is poorly soluble in the perovskite material during the spin-coating of the thin film. This method can quickly remove the perovskite solvent, rapidly reach a supersaturated state, and promote the rapid nucleation of perovskite crystals, thereby solving the problem of the mismatch between the nucleation and growth rates, improving the uniformity of the thin film, and reducing pore defects. However, the requirement for precisely controlling the dropping speed and time of the antisolvent limits its reproducibility and scalability in large-scale production. In addition, the use of traditional antisolvents, such as chlorobenzene, raises concerns about economic and environmental costs due to their potential toxicity and negative impacts on the environment and health.

[0003] To address these issues, researchers in this field are exploring various alternative technologies, such as solvent engineering, stepwise processing, air blowing, vacuum flash drying, and infrared rapid heating. In particular, a one-step spin-coating method without an antisolvent shows great potential due to its cost-effectiveness, ease of operation, and good reproducibility. In the traditional antisolvent-assisted process, a mixed solvent combination of dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) is widely used. However, this combination faces challenges in the solvent-free process, mainly because the high boiling point of DMF may lead to a decrease in the nucleation rate, thereby affecting the morphology of the perovskite thin film. To overcome these challenges, researchers have proposed two main strategies: one is to use solvents with lower boiling points, such as 2-methoxyethanol (2-OME), 2-methoxyethane (2-ME), acetonitrile (ACN), etc., to increase the nucleation rate of perovskite; the other is to use additives that can strongly coordinate with the perovskite components to slow down the crystal growth rate, thereby extending the nucleation time window and achieving high-quality perovskite thin films. For example, a method of adding N-methyl-2-pyrrolidone (NMP) and lead chloride (PbCl 2 ) to the perovskite precursor solution. This method utilizes PbI 2The strong interaction with NMP inhibits the formation of non-photoreactive intermediates between the perovskite components and DMF, successfully achieving the preparation of high-quality perovskite thin films without the use of an antisolvent. In many previous literatures, the solvent combination of dimethylformamide (DMF) and N-methyl-2-pyrrolidone (NMP) has been widely used in the field of perovskite solar cell (PSC) manufacturing without an antisolvent. Due to its high polarity and solubility, DMF performs excellently in dissolving perovskite materials, and the strong interaction between NMP and PbI 2 contributes to promoting the crystal growth process.

[0004] However, the environmental impact and potential toxicity problems of these solvents have attracted wide attention, prompting researchers to search for new solutions to replace these traditional solvents, with the aim of reducing the negative environmental impact while maintaining the high performance in perovskite solar cell manufacturing. Summary of the Invention

[0005] In view of the above deficiencies of the prior art, the present invention provides a mixed solvent and its application in the preparation of perovskite solar cells, so as to solve the problems that although high-quality perovskite thin films can be obtained using existing solvents, they still have environmental impact and potential toxicity.

[0006] The technical solutions adopted by the present invention to solve the above technical problems are as follows:

[0007] In the first aspect of the present invention, a mixed solvent is provided. The mixed solvent includes solvent A and solvent B. Solvent A is N,N-dimethylacetamide, and solvent B is one of N,N-dimethylallylurea, N-methylpyrrolidone, 1,3-dimethyl-2-imidazolidinone, and 1,4-butyrolactone

[0008] Preferably, the mass ratio of solvent A to solvent B is (6 - 40):1.

[0009] In the second aspect of the present invention, an application of the above mixed solvent in the preparation of perovskite solar cells is provided.

[0010] In the third aspect of the present invention, a method for preparing a perovskite solar cell is provided. The preparation method includes the step of preparing a perovskite thin film, and the step of preparing the perovskite thin film includes:

[0011] Dissolving the perovskite material in the above mixed solvent to obtain a perovskite precursor solution;

[0012] Coating the perovskite precursor solution on the surface of the conductive layer and annealing to obtain the perovskite thin film.

[0013] Preferably, in the perovskite precursor solution, the mass ratio of the perovskite material to the mixed solvent is (1.2 - 2):1.

[0014] Preferably, the perovskite material is a lead-based ABX 3 compound, where A is one of formamidinium ions, formamidinium / cesium mixed ions, B is lead ions, and X is iodide ions, bromide ions or chloride ions.

[0015] Preferably, the material of the conductive layer is one of fluorine-doped tin oxide (FTO), indium tin oxide (ITO), aluminum zinc oxide (AZO).

[0016] Preferably, the coating method is spin coating, the rotation speed of spin coating is 4000 - 9000 revolutions per minute, and the spin coating time is 40 - 80 seconds.

[0017] In the fourth aspect of the present invention, a perovskite solar cell is provided, and the perovskite solar cell is prepared by the above preparation method.

[0018] Preferably, the structure of the perovskite solar cell is a normal structure, an inverted structure, a mesoporous structure or a carbon electrode structure.

[0019] Beneficial effects:

[0020] The present invention discloses a mixed solvent and its application in the preparation of perovskite solar cells. Taking the mixed solvent composed of N,N-dimethylacetamide (DMAc) and N,N-dimethylpropylurea (DMPU) as an example, compared with the traditional DMF and NMP solvent combinations, the mixed solvent of the present invention can prepare perovskite solar cells with higher photoelectric conversion efficiency and better stability, while reducing toxicity and processing costs. Through comparative detection by scanning electron microscopy (SEM), it is found that the perovskite thin film prepared using the DMAc / DMPU mixed solvent is flatter and has larger grain size than that prepared using the DMF / NMP solvent. In addition, the test results of in-situ fluorescence emission spectroscopy show that compared with the NMP solvent, the perovskite precursor solution containing DMPU can form a more suitable solvent-perovskite intermediate phase during the one-step spin coating process without an antisolvent, which helps to produce a stable and high-quality perovskite thin film through subsequent annealing heating. The low-toxic mixed solvent provided by the present invention not only improves the quality of the perovskite thin film, enhances its stability, but also improves the interfacial contact between the perovskite and the substrate, and finally realizes a perovskite solar cell with high efficiency and good stability. Description of the drawings

[0021] Figure 1 is a path diagram for preparing a perovskite thin film in a preferred embodiment of the present invention;

[0022] Figure 2 is a schematic structural diagram of an inverted planar heterojunction perovskite solar cell prepared in Example 1 of the present invention;

[0023] Figure 3 Morphology comparison diagram of the perovskite thin film prepared in Example 1 of the present invention and the perovskite thin film prepared in Comparative Example 1;

[0024] Figure 4 Roughness comparison of the perovskite thin film prepared in Example 1 of the present invention and the perovskite thin film prepared in Comparative Example 1;

[0025] Figure 5 The I-V curve of the perovskite solar cell prepared in Example 1 of the present invention. Detailed implementation manners

[0026] The present invention provides a mixed solvent and its application in the preparation of perovskite solar cells. To make the objectives, technical solutions and effects of the present invention clearer and more definite, the present invention is further described in detail below. It should be understood that the specific embodiments described herein are only used to explain the present invention and are not used to limit the present invention.

[0027] An embodiment of the present invention provides a mixed solvent, the mixed solvent includes solvent A and solvent B, the solvent A is N,N-dimethylacetamide, and the solvent B is one of N,N-dimethylallylurea, N-methylpyrrolidone, 1,3-dimethyl-2-imidazolidinone, and 1,4-butyrolactone.

[0028] Using the mixed solvent provided by the embodiment of the present invention can obtain a perovskite thin film with a lower defect state density, higher flatness, and larger grain size, and the corresponding perovskite solar cell has higher photoelectric conversion efficiency and stability. The reason why the mixed solvent of the embodiment of the present invention can achieve a high-quality perovskite thin film is (taking N,N-dimethylallylurea (DMPU) and N,N-dimethylacetamide (DMAc) as examples), DMPU has a stronger interaction with the perovskite component PbI 2 and DMAc has a suitable perovskite dissolution ability and a small difference in evaporation rate from DMPU. The dissolution ability of DMAc for the perovskite component CsI is weaker than that of the traditional perovskite solvent DMF, which is beneficial to the formation of a stable solvent-perovskite intermediate phase during the spin-coating process, and finally a high-quality perovskite thin film is obtained through high-temperature annealing. In addition, the mixed solvent provided by the embodiment of the present invention can also prepare high-efficiency perovskite solar cells with different components through an anti-solvent-free process. This green solvent combination is also expected to be widely used in optoelectronic device fields such as perovskite light-emitting diodes, organic solar cells, organic light-emitting diodes, and field-effect transistors. Moreover, the mixed solvent provided by the embodiment of the present invention has obvious low toxicity and low cost while having the above excellent properties.

[0029] In some embodiments, the mass ratio of the solvent A to the solvent B is (6 - 40):1.

[0030] When the mass ratio is greater than 40:1, the perovskite film formed has more pinholes; when the mass ratio is less than 6:1, N,N-dimethylacetamide / N,N-dimethylpropyleneurea / perovskite cannot form a brownish-black intermediate phase within 60 seconds, and the film formation after annealing is poor.

[0031] In some preferred embodiments, the mass ratio of the solvent A to the solvent B is 15:1.

[0032] An embodiment of the present invention provides an application of the above-mentioned mixed solvent in the preparation of perovskite solar cells.

[0033] An embodiment of the present invention provides a method for preparing a perovskite solar cell. The preparation method includes the following steps for preparing a perovskite film, as shown Figure 1 (taking DMPU and DMAc as examples):

[0034] Dissolve the perovskite material in the above-mentioned mixed solvent to obtain a perovskite precursor solution;

[0035] Coat the perovskite precursor solution on the surface of the conductive layer, and perform spin coating, blade coating or slot die coating treatment, and then anneal to obtain the perovskite film.

[0036] In some preferred embodiments, the steps for preparing the perovskite film are as follows:

[0037] Spin coat the prepared perovskite precursor solution on a conductive glass substrate at a speed of 4000 - 9000 revolutions per minute for 40 - 80 seconds;

[0038] Then heat the obtained film at 100 - 150 °C for 30 minutes.

[0039] In some preferred embodiments, the optimal rotation speed is 6000 revolutions per minute, the optimal spin coating time is 60 seconds, and the optimal heating temperature is 150 °C.

[0040] In some embodiments, the preparation method includes the following steps for preparing a perovskite film:

[0041] Dissolve the perovskite material in the above-mentioned mixed solvent to obtain a perovskite precursor solution;

[0042] Coat the perovskite precursor solution on the surface of the conductive layer covered with a self-assembled monolayer, and perform spin coating, blade coating or slot die coating treatment, and then anneal to obtain the perovskite film.

[0043] In some embodiments, in the perovskite precursor solution, the mass ratio of the perovskite material to the mixed solvent is (1.2 - 2):1.

[0044] In some preferred embodiments, in the perovskite precursor solution, the mass ratio of the perovskite material to the mixed solvent is 1.266:1.

[0045] In some embodiments, the perovskite material is a lead-based ABX 3 compound, wherein A is one of formamidinium ions, formamidinium / cesium mixed ions, B is lead ions, and X is iodide ions, bromide ions or chloride ions.

[0046] In some embodiments, the material of the conductive layer is one of fluorine-doped tin oxide (FTO), indium tin oxide (ITO), aluminum zinc oxide (AZO).

[0047] An embodiment of the present invention provides a perovskite solar cell, and the perovskite solar cell is prepared by using the above preparation method.

[0048] In some embodiments, the structure of the perovskite solar cell is a normal structure, an inverted structure, a mesoporous structure or a carbon electrode structure.

[0049] The technical solutions in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments, and are only used to illustrate the present invention without any limitation to the present invention. All other embodiments obtained by those of ordinary skill in the art based on the embodiments of the present invention without creative efforts shall fall within the protection scope of the present invention.

[0050] Example 1

[0051] The preparation of a perovskite solar cell (the schematic structural diagram is as Figure 2 shown) includes the following steps:

[0052] (1) Cleaning the transparent conductive substrate FTO: The etched transparent conductive substrate FTO is ultrasonically treated in a cleaning agent, deionized water, absolute ethanol, acetone, and isopropanol for 15 minutes in sequence, taken out, dried with clean air, put into an oven, dried at 120 °C for 1 hour, and treated with ultraviolet / ozone for 30 minutes;

[0053] (2) Preparing a self-assembled monolayer (SAM): Prepare a solution of Me-PhpPACz, spin-coat the solution on the transparent conductive substrate ITO prepared in step (1) at a rotation speed of 3000 revolutions per minute for 30 seconds, and anneal the obtained film in nitrogen at 100 °C for 10 minutes;

[0054] (3) Preparation of perovskite light-absorbing layer (perovskite thin film): Dissolve 242 mg of FAI, 50 mg of CsI, 44 mg of PbCl 2 and 740 mg of PbI 2 in 0.9 mL of a mixed solvent (mass ratio of DMAc / DMPU is 15:1) to prepare a perovskite precursor solution. Spin-coat the prepared perovskite precursor solution on the single-molecule self-assembled layer prepared in step (2) by one-step spin-coating method. The spinning speed is 6000 revolutions per minute and the time is 60 seconds. Immediately after spin-coating, anneal the perovskite thin film at 150 °C for 0.5 hours.

[0055] (4) Preparation of electron transport layer: Deposit C60 on the surface of the perovskite light-absorbing layer prepared in step (3) under a vacuum of 1×10 -6 Pa.

[0056] (5) Preparation of silver electrode: Evaporate and deposit to prepare a silver electrode under a vacuum of 1×10 -6 Pa at a rate, control the electrode thickness to be about 100 nm, and obtain a perovskite solar cell with an effective area of 0.1 cm 2 .

[0057] Comparative Example 1

[0058] The preparation of a perovskite solar cell is basically the same as that of Example 1, except that: in step (3), the mixed solvent (DMAc / DMPU) is replaced by a traditional solvent (DMF / NMP).

[0059] Performance comparison test

[0060] For the perovskite thin films in the perovskite solar cells prepared in Example 1 and Comparative Example 1, the morphology comparison diagram is shown in Figure 3 , and the roughness comparison diagram is shown in Figure 4 .

[0061] Test the perovskite solar cell prepared in Example 1 under the test conditions: spectral distribution AM1.5G, light intensity 100 mW / cm 2 , AAA solar simulator (Beijing Zhuoli Hanguang Co., Ltd.), and measure the J-V curve with a Keithly2400 digital source meter.

[0062] The test results are shown in Figure 5 , and the best photovoltaic conversion efficiency parameters obtained are: open-circuit voltage 1.165 V, short-circuit current density 24.40 mA / cm 2 , fill factor 82.81%, and conversion efficiency 23.54%.

[0063] The performance diagrams of the perovskite solar cells prepared in Example 1 and Comparative Example 1 are shown in Table 1 below:

[0064] Table 1

[0065]

[0066] It should be understood that the application of the present invention is not limited to the above examples. For those of ordinary skill in the art, improvements or transformations can be made according to the above description, and all such improvements and transformations should fall within the protection scope of the appended claims of the present invention.

Claims

1. A mixed solvent, characterized in that: The mixed solvent comprises solvent A and solvent B, wherein solvent A is N,N-dimethylacetamide, and solvent B is one of N,N-dimethylpropylene urea, N-methylpyrrolidone, 1,3-dimethyl-2-imidazolidinone, and 1,4-butyrolactone.

2. The mixed solvent according to claim 1, characterized in that The mass ratio of the solvent A to the solvent B is (6-40):

1.

3. Use of the mixed solvent according to claim 1 in preparing perovskite solar cells.

4. A method for preparing a perovskite solar cell, characterized in that: The preparation method comprises the steps of preparing a perovskite film, and the steps of preparing a perovskite film comprise: Dissolving the perovskite material in the mixed solvent of claim 1 to obtain a perovskite precursor solution; The perovskite precursor solution is coated on the surface of the conductive layer, and the perovskite film is obtained after annealing.

5. The method for preparing a perovskite solar cell according to claim 4, characterized in that: In the perovskite precursor solution, the mass ratio of the perovskite material to the mixed solvent is (1.2-2):

1.

6. The method for preparing a perovskite solar cell according to claim 4, characterized in that: The perovskite material is a lead-based ABX3 compound, wherein A is one of a formamidine ion and a mixed ion of formamidine and cesium, B is a lead ion, and X is an iodine ion, a bromide ion or a chloride ion.

7. The method for preparing a perovskite solar cell according to claim 4, characterized in that: The material of the conductive layer is one of fluorine-doped tin oxide, indium tin oxide, and aluminum zinc oxide.

8. The method for preparing a perovskite solar cell according to claim 4, characterized in that: The coating method is spin coating, the spin coating speed is 4000-9000 rpm, and the spin coating time is 40-80 seconds.

9. A perovskite solar cell, characterized in that: The perovskite solar cell is prepared by the preparation method described in claim 4.

10. The perovskite solar cell according to claim 9, characterized in that: The structure of the perovskite solar cell is a regular structure, a reverse structure, a mesoporous structure or a carbon electrode structure.

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