Perovskite photovoltaic film based on self-migration 1D seed growth method and preparation method thereof

Abstract

The invention relates to a perovskite photovoltaic thin film based on a self-migration 1D seed growth method and a preparation method thereof, and the preparation method comprises the steps: S1, adding a proper amount of BMIMX into a PbI2 precursor solution, and preparing an EMIMX-PbI2 precursor solution; the BMIMX is one or more of BMIMCl, BMIMBr or BMIMI, and the BMIMX is one or more of BMIMCl, BMIMBr and BMIMI; s2, a crystal nucleus is introduced into the EMIMX-PbI2 precursor solution, and a PbI2 layer is prepared; and S3, depositing an FAI / MAI solution on the PbI2 layer, and heating and annealing to obtain the perovskite photovoltaic thin film. The crystallinity of the perovskite photovoltaic thin film is effectively improved, the bottom burying defect of the perovskite thin film is obviously reduced, 1D PVK is formed on the surface in the perovskite crystallization process, and the stability, the short-circuit current, the open-circuit voltage, the filling factor and the photoelectric conversion efficiency of a solar cell are obviously improved. The method is simple, practical, low in cost and easy to popularize, and has great reference significance for improving the photovoltaic performance of the perovskite photovoltaic film.

Description

Technical Field

[0001] The present invention relates to the technical field of solar cells, and in particular to a perovskite photovoltaic film based on a self-migrating 1D seed growth method and a preparation method thereof. Background Art

[0002] Perovskite solar cells are considered one of the most promising new solar cells due to their high photoelectric conversion efficiency, low manufacturing cost and great potential for low-temperature manufacturing. Since perovskite solar cells were first proposed in 2009, their photoelectric conversion efficiency has increased from the initial 3.8% to 26.7%.

[0003] The rapid development of perovskite solar cells in such a short period of time is attributed to the use of perovskite-type (ABX3) organic metal halide semiconductors (A:CH3NH 3+ CH3(NH2) 2+ ;Cs + , B:Pb 2+ ;Sn 2+ ;Ge 2+ , X:Cl - Br - ;I - ; SCN - ) as a light-absorbing material. In the field of high-efficiency perovskite solar cells, CH3NH3PbI3 (MAPbI3) is the most commonly used photovoltaic layer material. Although the efficiency of MAPbI3-based perovskite solar cells can reach 20%, they will decompose when in contact with water and oxygen. At the same time, light stability and thermal stability are also urgent problems that need to be solved for the industrialization of perovskite solar cells. Through the device packaging process, the contact between perovskite materials and water and oxygen can be greatly avoided, effectively alleviating the water and oxygen instability of perovskites. However, light stability and thermal stability cannot be improved by the packaging process.

[0004] Most efficient perovskite films are prepared by anti-solvent one-step deposition. The anti-solvent one-step deposition method is to mix and dissolve all the components of the perovskite in a high-boiling polar solvent to form a precursor solution, add anti-solvent during the film coating process, and then use thermal annealing to promote the crystallization growth of the film. Although this method is simple in process, the processing window is narrow, making the film crystallization difficult to control, the reproducibility is poor, and there is a problem of toxic solvent volatilization, which is not conducive to the preparation of large-area uniform films. In addition, there are also some scenarios that are prepared by a two-step deposition method. The two-step method mainly includes the following steps: first prepare a lead iodide (PbI2) layer, and then deposit an organic cationic component on the surface of the inorganic component, so that the two components react under certain conditions, and finally form a perovskite film. This method decomposes the perovskite film formation process into two steps, which is beneficial to the control of the nucleation and crystallization of perovskite. Compared with the two, the anti-solvent one-step deposition method is not suitable for large-scale industrialization, and the two-step deposition method is more suitable for large-scale linear coating technology. However, the existing two-step deposition method has many buried defects in the prepared perovskite film, resulting in the stability and photoelectric conversion efficiency of the final solar cell failing to meet expectations. Summary of the invention

[0005] In the process of implementing the present invention, the inventors found that the growth process of perovskite grains basically conforms to the crystal formation model, which is mainly divided into three stages: (1) medium supersaturation stage or supercooling stage; (2) nucleation stage, that is, crystal nucleus formation stage; (3) crystal growth stage. Among them, only when the particle size of the grain is large enough can it become a crystal nucleus. The growth process of the grain can be explained by the relationship diagram between Gibbs free energy and particle size (Gr diagram). G=Gs+Gv, Gs is the surface free energy, which increases with the increase of particle size r. Gv is the volume free energy, which decreases with the increase of particle size r. As Figure 1 , when the crystal grain size exceeds the zero-boundary radius r*, its relative Gibbs free energy ΔG < 0, and the subsequent growth process will occur automatically. During the growth of perovskite, the perovskite grains need to overcome the nucleation Gibbs free energy and grow into crystal nuclei. Therefore, by introducing crystal nuclei from the outside, more crystal nuclei can be provided for the growth process of perovskite, thereby promoting the growth of perovskite and obtaining higher quality perovskite films.

[0006] In view of this, the present invention provides a perovskite photovoltaic film based on a self-migrating 1D seed growth method and a preparation method thereof. The perovskite photovoltaic film for FAPbI3-based perovskite solar cells is prepared by a two-step deposition method. By adding an appropriate amount of ionic liquid to a PbI2 precursor solution (with DMF / DMSO as a solvent), a seed crystal is introduced into the solution, and the BMIMPbI3 seeds are introduced into the PbI2 film, which provides a crystal nucleus for the subsequent perovskite layer growth process, and migrates to the perovskite surface during the subsequent perovskite crystallization process, thereby effectively improving the stability, short-circuit current, open-circuit voltage, fill factor and photoelectric conversion efficiency of the solar cell.

[0007] The specific plan is as follows:

[0008] A method for preparing a perovskite photovoltaic film based on a self-migrating 1D seed growth method, comprising:

[0009] S1, adding an appropriate amount of ionic liquid to a PbI2 precursor solution to prepare an EMIMX-PbI2 precursor solution; the ionic liquid is one or more of BMIMCl, BMIMBr or BMIMI;

[0010] S2, introducing crystal nuclei into the EMIMX-PbI2 precursor solution to prepare a PbI2 layer;

[0011] S3, depositing FAI / MAI solution on the PbI2 layer and heating and annealing to obtain a perovskite photovoltaic film.

[0012] Preferably, step S2 specifically includes:

[0013] S21, spin coating the EMIMX-PbI2 precursor solution containing the BMIMPbI3 seed solution on the substrate, and heating and annealing to obtain a PbI2 layer.

[0014] Preferably, in step S21, the annealing temperature is 135°C to 150°C, and the annealing time is 10 min to 15 min.

[0015] Preferably, the solvent of the PbI2 precursor solution is a mixed solvent of dimethylformamide (DMF) / dimethyl sulfoxide (DMSO), and in the DMF / DMSO mixed solvent, the solvent volume ratio of DMF to DMSO is 9:1.

[0016] Preferably, the concentration of the BMIMPbI3 seed solution is 0.075M mol / L.

[0017] Preferably, when the ionic liquid is added to the PbI2 precursor solution, the volume ratio of the ionic liquid to the entire mixed solution is 1% to 5%; and the concentration of the PbI2 precursor solution is 1M to 2M.

[0018] Preferably, in step S3, the annealing temperature is 50° C. to 70° C., and the annealing time is 45 s to 1 min.

[0019] Preferably, the FAI / MAI solution is a mixed solution of iodoformamidine FAI and iodomethylamine MAI, wherein the mass ratio of FAI is 0% to 100%, preferably 50% to 90%.

[0020] Preferably, the total concentration of the FAI / MAI solution is 2 mg / mL to 200 mg / mL, preferably 50 mg / mL to 100 mg / mL.

[0021] The embodiment of the present invention further provides a perovskite photovoltaic film, which is prepared by the above-mentioned preparation method.

[0022] Compared with the existing two-step deposition method for preparing FAMAPbI3 perovskite photovoltaic thin film, the present invention has the following advantages:

[0023] (1) The present invention introduces BMIMPbI3 seeds into the PbI2 film to provide nuclei for the growth of perovskite photovoltaic films, promote the growth of perovskite grains, and improve the quality of perovskite photovoltaic films. The improvement in the quality of perovskite photovoltaic films reduces the recombination of electron-hole pairs and the grain boundary defects of perovskite grains, and the Cl- therein effectively promotes the crystallization of perovskite, forming 1D PVK on the perovskite surface. The perovskite solar cell prepared based on the self-migration 1D seed growth method significantly improves its short-circuit current, open-circuit voltage and fill factor. The perovskite solar cell prepared by this method has achieved better photovoltaic performance, and its photoelectric conversion efficiency has increased by about 3%;

[0024] (2) The present invention successfully achieves a two-step deposition method to prepare a 1D perovskite photovoltaic film on the surface by introducing BMIMPbI3 seeds into the PbI2 film. This method improves the quality of the perovskite photovoltaic film by introducing BMIMPbI3 seeds and crystal nuclei, and at the same time, forms 1D PVK on the surface of the perovskite photovoltaic film, thereby improving the light stability of the perovskite photovoltaic film;

[0025] (3) The process of the present invention is simple and can meet the requirements of large-scale industrialization. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings required for use in the embodiments are briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without creative work.

[0027] Figure 1 This is the relationship between the Gibbs free energy of the grain growth process and the particle size (Gr diagram).

[0028] Figure 2 This is the planar SEM image of the PbI2 thin film prepared by the traditional two-step deposition method.

[0029] Figure 3 A planar SEM image of a PbI2 film prepared by the preparation method provided in an embodiment of the present invention.

[0030] Figure 4 This is a planar SEM image of the perovskite photovoltaic film prepared by the traditional two-step deposition method.

[0031] Figure 5 A planar SEM image of a perovskite photovoltaic film prepared by the preparation method provided in an embodiment of the present invention.

[0032] Figure 6 This is a planar SEM image of the buried interface of the perovskite photovoltaic film prepared by the traditional two-step deposition method.

[0033] Figure 7 A planar SEM image of the buried interface of the perovskite photovoltaic film prepared by the preparation method provided in an embodiment of the present invention.

[0034] Figure 8 This is the cross-sectional SEM image of the FAMAPbI3-based perovskite photovoltaic film prepared by the traditional two-step deposition method.

[0035] Fig. 9 This is a cross-sectional SEM image of the perovskite photovoltaic film prepared by the preparation method provided in the embodiment.

[0036] Fig.10 JV (current density-voltage) curve of FAMAPbI3-based perovskite photovoltaic film as a solar cell device.

[0037] Fig.11 To test the stability of FAMAPbI3-based perovskite photovoltaic films as solar cell devices. DETAILED DESCRIPTION

[0038] To make the purpose, technical scheme and advantages of the embodiments of the present invention clearer, the technical scheme in the embodiments of the present invention will be clearly and completely described below. The described embodiments are only a part of the embodiments of the present invention, rather than all the embodiments. Based on the embodiments in the present invention, all other embodiments obtained by ordinary technicians in the field without making creative work are within the scope of protection of the present invention. If the specific conditions are not specified in the embodiments, they are carried out according to the normal conditions or the conditions recommended by the manufacturer. If the manufacturer is not specified in the reagents or instruments used, they are all conventional products that can be purchased commercially.

[0039] The present invention will be further described in detail by enumerating examples below. The following examples are only used to further illustrate the present invention and are not intended to limit the scope of protection of the present invention. Some non-essential improvements and adjustments made by those skilled in the art based on the above content of the present invention all belong to the scope of protection of the present invention. The specific process parameters in the following embodiments are only examples suitable for the parameter range, and those skilled in the art can select the range according to the above text, and are not necessarily limited to the specific process parameter values ​​in the following embodiments.

[0040] Embodiment 1:

[0041] (1) Spin coating a PbI2 precursor solution containing a BMIMPbI3 seed solution on a substrate; the volume ratio of the BMIMPbI3 seeds in the PbI2 precursor solution is 5% of the entire mixed solution; the solvent of the PbI2 precursor solution is a DMF / DMSO mixed solvent, the volume ratio of the DMF solvent is 80%, and the concentration of the PbI2 precursor solution is 1M.

[0042] (2) heating and annealing at 50°C for 45s to obtain a PbI2 layer;

[0043] (3) Spin coating the FAI / MAI solution on the PbI2 layer; wherein the FAI / MAI solution is a mixed solution of iodoformamidine (FAI) and iodomethylamine (MAI), wherein the mass ratio of FAI is 0%, and the total concentration of the FAI / MAI solution is 50 g / mL.

[0044] (4) Heating and annealing at 135°C for 5 min to obtain a perovskite light absorption layer, i.e., a perovskite photovoltaic film.

[0045] See also Figure 2 and Figure 3 , Figure 2 This is the SEM image of the PbI2 thin film prepared by the traditional two-step deposition method. Figure 3 This is a planar SEM image of the PbI2 film prepared by the preparation method provided in this embodiment.

[0046] See also Figure 4 and Figure 5 , Figure 4 This is a planar SEM image of the perovskite photovoltaic film prepared by the traditional two-step deposition method. Figure 5 From the planar SEM image of the perovskite photovoltaic film prepared by the preparation method provided in this embodiment, it can be seen that the surface of the perovskite photovoltaic film prepared by the self-migrating 1D seed growth method has obvious 1D PVK.

[0047] See also Figure 6 and Figure 7 , Figure 6 This is a planar SEM image of the buried interface of the perovskite photovoltaic film prepared by the traditional two-step deposition method. Figure 7 The plane SEM image of the buried interface of the perovskite photovoltaic film prepared by the preparation method provided in the embodiment of the present invention. It can be seen that the defects of the buried interface of the perovskite photovoltaic film prepared by the self-migrating 1D seed growth method are significantly reduced.

[0048] See also Figure 8 and Fig. 9 , Figure 8 This is the cross-sectional SEM image of the FAMAPbI3-based perovskite photovoltaic film prepared by the traditional two-step deposition method. Fig. 9 This is a cross-sectional SEM image of a perovskite photovoltaic film prepared by the preparation method provided in the embodiment. It can be seen that the FAMAPbI3-based perovskite photovoltaic film prepared by the self-migrating 1D seed growth method has better crystal integrity.

[0049] See also Fig.10 , Fig.10 The JV (current density-voltage) curve of the FAMAPbI3-based perovskite photovoltaic film as a solar cell device. It can be seen that the perovskite photovoltaic film using the self-migration 1D seed growth method has a better photoelectric conversion efficiency than the perovskite solar cell prepared by the traditional process, and the photoelectric conversion efficiency is increased from 21.88% to 24.38%.

[0050] See also Fig.11 , Fig.11 This is a stability test of FAMAPbI3-based perovskite photovoltaic films as solar cell devices. It can be seen that the perovskite solar cells using the self-migrating 1D seed growth method have better stability than the perovskite solar cells prepared by the traditional process.

[0051] Embodiment 2:

[0052] (1) Spin coating a PbI2 precursor solution containing a BMIMPbI3 seed solution on a substrate; wherein the concentration is 0.075 M, and the volume ratio of the BMIMPbI3 seeds in the PbI2 precursor solution is 5% of the entire mixed solution; wherein the solvent of the PbI2 precursor solution is a DMF / DMSO mixed solvent, the volume ratio of the DMF solvent is 100%, and the concentration is 2 M.

[0053] (2) annealing at 120°C for 5 min to obtain a PbI2 layer;

[0054] (3) Spin coating the FAI / MAI solution on the PbI2 layer; wherein the FAI / MAI solution is a mixed solution of iodoformamidine (FAI) and iodomethylamine (MAI), wherein the mass ratio of FAI is 100%, and the total concentration of the FAI / MAI solution is 100 g / mL.

[0055] (4) Heating and annealing at 180°C for 30 min obtains a perovskite light absorption layer, i.e., a perovskite photovoltaic film.

[0056] Embodiment 3:

[0057] (1) Spin coating a PbI2 precursor solution containing a BMIMPbI3 seed solution on a substrate; wherein the concentration is 0.075 M, and the volume ratio of the BMIMPbI3 seeds in the PbI2 precursor solution is 5% of the entire mixed solution; wherein the solvent of the PbI2 precursor solution is a DMF / DMSO mixed solvent, the volume ratio of the DMF solvent is 90%, and the concentration of the PbI2 precursor solution is 1.5 M.

[0058] (2) annealing at 85°C for 3 min to obtain a PbI2 layer;

[0059] (3) Spin coating the FAI / MAI solution on the PbI2 layer; wherein the FAI / MAI solution is a mixed solution of iodoformamidine (FAI) and iodomethylamine (MAI), wherein the mass ratio of FAI is 50%, and the total concentration of the FAI / MAI solution is 75 g / mL.

[0060] (4) Heating and annealing at 160°C for 30 min obtains a ternary mixed cation perovskite light absorption layer, i.e., a perovskite photovoltaic film.

[0061] The embodiments described above are part of the embodiments of the present invention, rather than all of the embodiments. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention claimed for protection, but merely represents selected embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Claims

1. A method for preparing a perovskite photovoltaic film based on a self-migrating 1D seed growth method, characterized in that: include: S1, adding an appropriate amount of ionic liquid to a PbI2 precursor solution to prepare an EMIMX-PbI2 precursor solution; the ionic liquid is one or more of BMIMCl, BMIMBr or BMIMI; S2, introducing crystal nuclei into the EMIMX-PbI2 precursor solution to prepare a PbI2 layer; S3, depositing FAI / MAI solution on the PbI2 layer and heating and annealing to obtain a perovskite photovoltaic film.

2. The method for preparing a perovskite photovoltaic thin film based on a self-migrating 1D seed growth method according to claim 1, characterized in that: Step S2 specifically includes: S21, spin coating the EMIMX-PbI2 precursor solution containing the BMIMPbI3 seed solution on the substrate, and heating and annealing to obtain a PbI2 layer.

3. The method for preparing a perovskite photovoltaic thin film based on a self-migrating 1D seed growth method according to claim 2, characterized in that: In step S21, the annealing temperature is 135°C to 150°C, and the annealing time is 10 min to 15 min.

4. The method for preparing a perovskite photovoltaic thin film based on a self-migrating 1D seed growth method according to claim 1, characterized in that: The solvent of the PbI2 precursor solution is a mixed solvent of dimethylformamide (DMF) / dimethyl sulfoxide (DMSO), and in the DMF / DMSO mixed solvent, the solvent volume ratio of DMF to DMSO is 9:

1.

5. The method for preparing a perovskite photovoltaic thin film based on a self-migrating 1D seed growth method according to claim 2, characterized in that: The concentration of the BMIMPbI3 seed solution is 0.075M mol / L.

6. The method for preparing a perovskite photovoltaic thin film based on a self-migrating 1D seed growth method according to claim 1, characterized in that: When the ionic liquid is added to the PbI2 precursor solution, the volume ratio of the ionic liquid to the entire mixed solution is 1% to 5%; the concentration of the PbI2 precursor solution is 1M to 2M.

7. The method for preparing a perovskite photovoltaic thin film based on a self-migrating 1D seed growth method according to claim 1, characterized in that: In step S3, the annealing temperature is 50°C to 70°C, and the annealing time is 45s to 1min.

8. The method for preparing a perovskite photovoltaic thin film based on a self-migrating 1D seed growth method according to claim 1, characterized in that: The FAI / MAI solution is a mixed solution of iodoformamidine FAI and iodomethylamine MAI, wherein the mass ratio of FAI is 0% to 100%, preferably 50% to 90%.

9. The method for preparing a perovskite photovoltaic thin film based on a self-migrating 1D seed growth method according to claim 1, characterized in that: The total concentration of the FAI / MAI solution is 2 mg / mL to 200 mg / mL, preferably 50 mg / mL to 100 mg / mL.

10. A perovskite photovoltaic film, characterized in that: The method is described in any one of claims 1 to 9.

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