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

Abstract

The application relates to a perovskite photovoltaic film based on a self-migration 1D seed growth method and a preparation method thereof, and the preparation method comprises the following steps: S1, adding appropriate BMIMX into a PbI2 precursor solution to prepare an EMIMX-PbI2 precursor solution; the BMIMX is one or more of BMIMCl, BMIMBr or BMIMI; S2, introducing a crystal nucleus into the EMIMX-PbI2 precursor solution to prepare a PbI2 layer; and S3, depositing a FAI / MAI solution on the PbI2 layer and heating and annealing to obtain a perovskite photovoltaic film. The application effectively improves the crystallinity of the perovskite photovoltaic film, the buried bottom defect of the perovskite film is obviously reduced, 1D PVK is formed on the surface in the perovskite crystallization process, and the stability, short-circuit current, open-circuit voltage, fill factor and photoelectric conversion efficiency of the solar cell are obviously improved. The application is simple and practical, low in cost, 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 the potential for low-temperature fabrication. Since their initial proposal in 2009, perovskite solar cells have seen their photoelectric conversion efficiency increase from an 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 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 through the packaging process.

[0004] Most high-efficiency perovskite films are prepared by the antisolvent one-step deposition method. The antisolvent one-step deposition method is to mix and dissolve all the components of the perovskite in a high-boiling point polar solvent to form a precursor solution. The antisolvent is then added dropwise during the film coating process, and thermal annealing is used to promote the crystallization growth of the film. Although this method is simple, the processing window is narrow, making the film crystallization difficult to control and the reproducibility poor. There is also the 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 use a two-step deposition method for preparation. 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. The two components are allowed to react under certain conditions to finally form a perovskite film. This method decomposes the perovskite film formation process into two steps, which is beneficial to achieve control over the nucleation and crystallization of the perovskite. Compared with the two, the antisolvent 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-bound radius r*, its relative Gibbs free energy ΔG is less than 0, and the subsequent growth process occurs automatically. During the perovskite growth process, the perovskite grains need to overcome the nucleation Gibbs free energy to grow into crystal nuclei. Therefore, by introducing crystal nuclei from outside, it is possible to provide more crystal nuclei for the perovskite growth process, 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 the 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 (using DMF / DMSO as a solvent), a crystal seed 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. In the subsequent perovskite crystallization process, the crystal nucleus migrates to the perovskite surface, 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 thin film based on a self-migrating 1D seed growth method, comprising:

[0009] S1, adding an appropriate amount of ionic liquid to the 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 the 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 an EMIMX-PbI2 precursor solution containing a 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 the volume ratio of DMF to DMSO in the DMF / DMSO mixed solvent 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 seconds to 1 minute.

[0019] Preferably, the FAI / MAI solution is a mixed solution of iodomethanesulfonate (FAI) and iodomethanesulfonate (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] An embodiment of the present invention further provides a perovskite photovoltaic film, which is prepared using the above-mentioned preparation method.

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

[0023] (1) The present invention introduces BMIMPbI3 seeds into the PbI2 film to provide crystal 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 this self-migrating 1D seed growth method significantly improves its short-circuit current, open-circuit voltage and fill factor. The perovskite solar cell prepared by this method obtains more excellent photovoltaic performance, and its photoelectric conversion efficiency is improved by about 3%;

[0024] (2) The present invention successfully achieved 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 introducing crystal nuclei. At the same time, it 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 following briefly introduces the drawings required for use in the embodiments. It should be understood that the following drawings only illustrate certain embodiments of the present invention and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without paying any creative work.

[0027] Figure 1 The relationship between Gibbs free energy and particle size during the grain growth process (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 This is a planar SEM image of a PbI2 thin 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 This is a planar SEM image of the 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 This is 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] Figure 9 This is a cross-sectional SEM image of the perovskite photovoltaic film prepared by the preparation method provided in the embodiment.

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

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

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

[0039] The present invention will be further described in detail below by way of examples. The following examples are intended only to further illustrate the present invention and are not intended to limit the scope of protection of the present invention. Any non-essential improvements and adjustments made by those skilled in the art based on the above disclosure of the present invention fall within the scope of protection of the present invention. The specific process parameters in the following embodiments are merely examples within a suitable parameter range, and those skilled in the art can select a range based on the above text, and are not necessarily limited to the specific process parameter values ​​in the following embodiments.

[0040] Example 1:

[0041] (1) A PbI2 precursor solution containing a BMIMPbI3 seed solution was spin-coated on a substrate; the volume ratio of the BMIMPbI3 seeds in the PbI2 precursor solution was 5%; the solvent of the PbI2 precursor solution was a DMF / DMSO mixed solvent, the volume ratio of the DMF solvent was 80%, and the concentration of the PbI2 precursor solution was 1 M.

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

[0043] (3) Spin-coating a FAI / MAI solution on the PbI2 layer; wherein the FAI / MAI solution is a mixed solution of iodomethane (FAI) and iodomethane (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 using 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 This is 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. It can be seen that the defects of the buried interface of the perovskite photovoltaic film prepared using the self-migrating 1D seed growth method are significantly reduced.

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

[0049] See also Figure 10 , Figure 10 The JV (current density-voltage) curve of a FAMAPbI3-based perovskite photovoltaic film used as a solar cell device shows that the perovskite photovoltaic film grown using the self-migrating 1D seeding method has a significantly better photoelectric conversion efficiency than perovskite solar cells prepared using traditional processes, with the photoelectric conversion efficiency increasing from 21.88% to 24.38%.

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

[0051] Example 2:

[0052] (1) A PbI2 precursor solution containing a BMIMPbI3 seed solution was spin-coated on a substrate; wherein the concentration was 0.075 M, and the volume ratio of the BMIMPbI3 seeds in the PbI2 precursor solution was 5% of the total mixed solution; wherein the solvent of the PbI2 precursor solution was a DMF / DMSO mixed solvent, the volume ratio of the DMF solvent was 100%, and the concentration was 2 M.

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

[0054] (3) Spin-coating a FAI / MAI solution on the PbI2 layer; wherein the FAI / MAI solution is a mixed solution of iodomethane (FAI) and iodomethane (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 to obtain a perovskite light absorption layer, i.e., a perovskite photovoltaic film.

[0056] Example 3:

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

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

[0059] (3) Spin-coating a FAI / MAI solution on the PbI2 layer; wherein the FAI / MAI solution is a mixed solution of iodomethane (FAI) and iodomethane (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 some, but not all, of the embodiments of the present invention. The detailed description of the embodiments of the present invention is not intended to limit the scope of the invention as claimed, but rather merely represents selected embodiments of the present invention. All other embodiments derived by persons of ordinary skill in the art based on the embodiments of the present invention without inventive effort are also within the scope of protection of the present invention.

Claims

1. A method for preparing perovskite photovoltaic thin films based on self-migrating 1D seed growth method, characterized in that: include: S1, adding an appropriate amount of ionic liquid to the 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 an EMIMX-PbI2 precursor solution to obtain a PbI2 layer; wherein the method specifically comprises: S21, spin coating an EMIMX-PbI2 precursor solution containing a BMIMPbI3 seed solution on a substrate, and heating and annealing to obtain a PbI2 layer; S3, depositing a FAI / MAI solution on the PbI2 layer and heating and annealing it to obtain a perovskite photovoltaic film; the FAI / MAI solution is a mixed solution of iodomethane FAI and iodomethane MAI.

2. The method for preparing a perovskite photovoltaic thin film based on the self-migrating 1D seed growth method according to claim 1, 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.

3. The method for preparing a perovskite photovoltaic thin film based on the 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) and dimethyl sulfoxide (DMSO). In the DMF / DMSO mixed solvent, the solvent volume ratio of DMF to DMSO is 9:

1.

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

5. The method for preparing a perovskite photovoltaic thin film based on the 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.

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: In step S3 , the annealing temperature is 50° C. to 70° C., and the annealing time is 45 seconds to 1 minute.

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 the FAI / MAI solution, the mass ratio of FAI is 0% to 100%.

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 total concentration of the FAI / MAI solution is 2 mg / mL to 200 mg / mL.

9. A perovskite photovoltaic film, characterized in that: The method is described in any one of claims 1 to 8.

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