Method for realizing mechanical planarization of surface of perovskite thin film through blade coating and preparation method of perovskite solar cell

Abstract

The invention belongs to the technical field of large-area photovoltaic cells, and particularly relates to a method for realizing mechanical planarization of the surface of a perovskite thin film through blade coating and a preparation method of a perovskite solar cell. The method comprises the following steps: firstly, preparing an initial perovskite layer by adopting a blade coating, gas quenching and annealing process, and then dropwise adding an alcohol auxiliary solution to carry out blade coating, gas quenching and annealing treatment again to flatten the surface of the initial perovskite layer so as to obtain a final perovskite thin film layer; the uniformity and smoothness of the upper surface of the thin film are effectively improved through the dropwise adding of the auxiliary solution and the synergistic effect of the two times of blade coating, gas quenching and annealing processes. When the perovskite solar cell is applied to the perovskite solar cell, the carrier transmission efficiency between a perovskite light absorption layer and an electron transmission layer is effectively improved; the moisture absorbed by the thin film in the blade coating process is reduced, and the damage of the moisture to the perovskite thin film in the subsequent annealing process is reduced, so that the overall performance of the perovskite solar cell is effectively improved.

Description

Technical Field

[0001] This invention belongs to the field of large-area photovoltaic cell technology, specifically relating to a method for achieving mechanical planarization of the surface of perovskite thin films through scraping and a method for preparing perovskite solar cells. Background Technology

[0002] Organic-inorganic hybrid perovskite solar cells (PSCs), the third generation of photovoltaic solar cells, are considered one of the most promising photovoltaic technologies due to their high efficiency, low-cost solution processability, and tunable bandgap. In recent years, the best power conversion efficiency (PCE) of single-junction PSCs has reached 27%. Although the best photoelectric conversion efficiency of perovskite solar cells prepared by the blade coating method is only 23%, compared to traditional solution methods, the blade coating method has significant advantages in terms of industrial adaptability and process control flexibility due to its high material utilization, low equipment cost, ability to achieve square meter-level uniform film formation, and compatibility with existing printing technologies (such as flexographic printing) and fewer barriers to mass production. These advantages make the blade coating method the preferred technology for moving perovskite solar cells from the laboratory to commercialization, and it is expected to dominate perovskite production processes in the future.

[0003] However, the open-circuit voltage (V) of solar cells currently fabricated by the blade coating method is... OC The photoelectric conversion efficiency is still below its theoretical limit, which may be due to the difficulty in achieving a microscopically smooth upper surface during the coating process, leading to poor contact between the perovskite film and the electron transport layer, resulting in poor energy level alignment and consequently a large Vo. OC The loss of energy and the eventual reduction in efficiency prevent the efficient conversion of solar energy into electricity, which is a problem that urgently needs to be solved. Summary of the Invention

[0004] In view of this, the present invention proposes a method for mechanically planarizing the surface of perovskite thin films by scraping and a method for preparing perovskite solar cells, in order to solve the problem in the prior art that the surface of the perovskite light-absorbing layer is uneven and rough due to a large number of defects, which hinders carrier transport and leads to a significant reduction in turn-on voltage and efficiency.

[0005] To solve the above problems, the present invention adopts the following technical solution:

[0006] A method for achieving mechanical planarization of perovskite film surface by scraping includes the following steps:

[0007] A perovskite precursor solution was coated onto a substrate and then subjected to gas quenching and annealing to form an initial thin film.

[0008] The initial film was subjected to physical and mechanical planarization to obtain a perovskite film with a smooth surface.

[0009] Furthermore, the process of coating a perovskite precursor solution onto a substrate and then performing gas quenching and annealing to form the initial thin film includes:

[0010] The perovskite precursor solution is dropped onto the substrate, and a doctor blade with an integrated air knife is used to coat the substrate at a speed of 2.5-4 mm / s, with the distance between the doctor blade and the substrate controlled at 500-3000 μm. Then, the air knife following the doctor blade is controlled to blow the substrate at a pressure not exceeding 0.2 MPa, thereby simultaneously completing the formation of the wet film and the vapor phase quenching treatment to obtain the perovskite precursor wet film.

[0011] The wet perovskite precursor film was placed on a hot stage and subjected to hot annealing at 100-150℃ for 15-30 minutes to crystallize and transform it into the initial perovskite film.

[0012] The process of physically and mechanically planarizing the initial perovskite film to obtain the final perovskite film includes:

[0013] An auxiliary solution is dropped onto a substrate, and a scraping device with an integrated air knife is used to control the distance between the scraper and the substrate to be 500-1500 μm, and the scraping is performed at a speed of 5-8 mm / s. Immediately afterwards, the air knife following the scraper is controlled to blow away the substrate at a pressure not exceeding 0.2 MPa, thereby simultaneously completing the scraping of the auxiliary solution and the vapor phase quenching treatment, and obtaining a perovskite film after physical and mechanical planarization treatment.

[0014] Furthermore, the auxiliary solution includes alcohols such as ethanol, propanol, and butanol, with n-butanol being preferred.

[0015] A perovskite thin film is prepared by the above-described method of mechanically planarizing the surface of the perovskite thin film through a blade coating process.

[0016] A method for fabricating a perovskite solar cell, comprising:

[0017] S1. A hole transport layer is formed on ITO transparent conductive glass;

[0018] S2. A perovskite thin film is prepared on the hole transport layer using a perovskite thin film preparation method based on scraping and post-planarization, so as to serve as a perovskite light-absorbing layer.

[0019] S3. Prepare an electron transport layer on the perovskite light-absorbing layer;

[0020] S4. A metallic conductive layer is formed on the electron transport layer to obtain a perovskite solar cell.

[0021] Furthermore, the implementation process of step S1 includes:

[0022] ITO transparent conductive glass pretreatment: ITO transparent conductive glass is cleaned with acetone and ethanol in sequence, followed by ultraviolet ozone treatment for 10~30 minutes;

[0023] Preparation of [4-(7H-dibenzocarbazole-7-yl)butyl]phosphonic acid solution: [4-(7H-dibenzocarbazole-7-yl)butyl]phosphonic acid was dissolved in ethanol to obtain a [4-(7H-dibenzocarbazole-7-yl)butyl]phosphonic acid solution with a concentration of 0.5 mg / mL;

[0024] Hole transport layers were prepared on pretreated ITO transparent conductive glass using a solution of [4-(7H-dibenzocarbazole-7-yl)butyl]phosphonic acid.

[0025] Furthermore, the electron transport layer has a multilayer structure, consisting of lithium fluoride (LiF) and a carbon 60 layer (C). 60 A wide bandgap semiconductor consisting of layers of 2,9-dimethyl-4,7-biphenyl-1,10-phenanthroline (BCP) stacked from bottom to top.

[0026] Furthermore, the total thickness of the electron transport layer is 10~50nm.

[0027] Furthermore, the conductive metal layer is made of gold (Au) or silver (Ag).

[0028] A perovskite solar cell includes, from bottom to top, an ITO transparent conductive glass, a hole transport layer, a perovskite light-absorbing layer, an electron transport layer, and a metal electrode layer; the perovskite light-absorbing layer is a perovskite thin film layer prepared by a perovskite thin film preparation method based on top coating and post-planarization.

[0029] The perovskite thin film preparation method provided by this invention first uses a "scraping + gas quenching + annealing" process to obtain an initial perovskite layer. Then, an auxiliary solution (alcohol) is added dropwise, and the "scraping + gas quenching + annealing" process is repeated to planarize the surface, resulting in the final perovskite thin film layer. Through the synergistic effect of the addition of the auxiliary solution and the two "scraping + gas quenching + annealing" processes, the uniformity and smoothness of the film surface are effectively improved. When applied to perovskite solar cells, it effectively improves the carrier transport efficiency between the perovskite light-absorbing layer and the electron transport layer. Furthermore, due to the low polarity of alcohols, it can prevent moisture from entering the perovskite film during the scraping process, and its evaporation rate effectively controls the contact time between the film and air, comprehensively reducing the moisture absorbed by the film during scraping and minimizing moisture damage to the perovskite film during subsequent annealing, thereby effectively improving the overall performance of the perovskite solar cell.

[0030] Compared with the prior art, the present invention has at least the following beneficial effects:

[0031] 1. The perovskite solar cell of the present invention can improve the yield of perovskite cells, obtain high open-circuit voltage and better cell conversion efficiency, and is more conducive to the large-area application and long-term use of cells.

[0032] 2. The present invention benefits from the smooth and uniform upper surface of the perovskite light-absorbing layer, which optimizes the interface contact between the perovskite layer and the electron transport layer. This helps to offset the negative impact of the lithium fluoride passivation layer on the stability of the device. Attached Figure Description

[0033] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0034] Figure 1 The diagram shows the structure of the perovskite solar cells prepared in Examples 1 to 3.

[0035] Figure 2 This is a schematic diagram of the coating and annealing process of the perovskite light-absorbing layer and its physical and mechanical planarization in the perovskite solar cells prepared in Examples 1 to 3.

[0036] Figure 3 Atomic force microscopy (AFM) images of the perovskite thin films obtained in comparative examples 1 to 3;

[0037] Figure 4 Scanning electron microscope (SEM) images of the perovskite films obtained in comparative examples 1 to 3.

[0038] Figure 5 The XRD patterns of the perovskite films obtained in comparative examples and Examples 1 to 3 are shown.

[0039] Figure 6 Box plots showing the open-circuit voltage, short-circuit current, fill factor, and photoelectric conversion efficiency of the perovskite solar cells obtained in comparative examples 1 to 3. Detailed Implementation

[0040] To further understand the present invention, preferred embodiments are described below with reference to examples, wherein the accompanying drawings constitute a part of the present invention and are used together with the invention to illustrate the principles of the invention. However, it should be understood that these descriptions are only for further illustrating the features and advantages of the invention and are not intended to limit the scope of the claims. All raw materials used in the present invention are not particularly limited in their source and can be purchased commercially or prepared according to conventional methods known to those skilled in the art.

[0041] This invention provides a method for mechanically planarizing the surface of a perovskite thin film using a blade coating process. The method includes: coating a perovskite precursor solution onto a substrate, followed by gas quenching and annealing to form an initial thin film; and using an alcohol as an auxiliary solution to perform physical-mechanical planarization on the initial thin film to obtain the perovskite thin film. Applying this method to perovskite solar cells can improve the yield, achieve higher open-circuit voltage, and enhance cell conversion efficiency, thus facilitating commercial applications and long-term use. Specific process steps will be described in detail during the perovskite solar cell fabrication process.

[0042] like Figure 1 As shown, this embodiment provides a perovskite solar cell comprising, from bottom to top, a substrate, a conductive layer, a hole transport layer, a perovskite light-absorbing layer, an electron transport layer, and a conductive electrode layer. The perovskite light-absorbing layer is prepared using the aforementioned perovskite thin film preparation method based on a blade-coated surface physical-mechanical planarization process. To better extract the charge carriers generated by the perovskite layer under light irradiation, the thickness of the hole transport layer is 20 nm to 40 nm. To facilitate electron transport, the electron transport layer is made of a wide bandgap semiconductor. In addition to fullerene (C60), its derivatives (PCBM) can also be used as the electron transport layer material. The electron transport layer may include multiple stacked transport layers, with a total thickness of 10 to 50 nm.

[0043] Example 1:

[0044] A perovskite solar cell includes the following steps:

[0045] Step S1: Cleaning the ITO glass substrate: First, ultrasonically clean with acetone for 15 minutes, then ultrasonically clean with ethanol for 15 minutes.

[0046] Step S2: Dry the cleaned ITO glass substrate in an oven, and then treat it with ultraviolet ozone (UV) for 20 minutes.

[0047] Step S3, for illustrative purposes, defines the [4-(7H-dibenzocarbazole-7-yl)butyl]phosphonic acid solution as a 4PADCB solution. A certain amount of 4PADCB is weighed and dissolved in anhydrous ethanol to prepare a 0.5 mg / mL 4PADCB solution. 75 μL of the 4PADCB solution is spin-coated onto the ITO glass substrate obtained in step S2 at 3000 rpm for 30 s. Subsequently, it is annealed on a hot plate at 100 °C for 10 min to obtain the hole transport layer.

[0048] Step S4: Prepare a perovskite thin film on the hole transport layer to serve as a perovskite light-absorbing layer. Specifically:

[0049] Preparation of perovskite precursor solution:

[0050] Weigh out 187.79 mg of FAI, 80.02 mg of CsI, 500.20 mg of PbI2, 115.57 mg of PbBr2, 4.72 mg of MACl, 19.49 mg of PbCl2 and 14.23 mg of DPSO; dissolve the weighed substances in 1 mL of a mixed solvent and stir for 12 h to prepare a perovskite precursor solution, wherein the mixed solvent is composed of DMF and NMP, and the volume ratio of DMF to NMP is 19:1;

[0051] Preparation of perovskite thin films:

[0052] 20 μL of perovskite precursor solution was dropped onto the hole transport layer. The gap between the scraper and the hole transport layer in the integrated air knife was adjusted to 1260 μm, the scraper speed was 3 mm / s, and the air knife pressure was 0.1 MPa for scraping. After scraping, the product was placed on a hot table for annealing at 150 °C for 20 min to obtain the initial thin film layer.

[0053] Secondary coating process: 20 μL of ethanol is dropped into the gap between the perovskite film and the doctor blade. The doctor blade gap and air knife pressure remain unchanged. The doctor blade speed is adjusted to 6 mm / s for secondary coating process. After the coating is completed, annealing is performed at 100℃ for 5 min to obtain the final perovskite film layer, i.e., the perovskite light-absorbing layer.

[0054] Step S5: Sequentially deposit 1 nm of lithium fluoride (LiF), 10 nm of C60 and 15 nm of BCP on the surface of the perovskite layer by vacuum thermal evaporation to obtain the electron transport layer.

[0055] Step S6: Fabricate an electrode layer on the electron transport layer. Silver is deposited on the surface of the electron transport layer using vacuum thermal evaporation through a photomask, with a thickness of 120 nm, to obtain the desired result. Figure 1 The complete inverted perovskite solar cell is shown.

[0056] Example 2:

[0057] The perovskite solar cell prepared in this embodiment follows a similar preparation process to that in Example 1, except that in step 4, during the secondary coating process, 20 μL of propanol is dropped into the gap between the perovskite film and the doctor blade; all other steps are identical. This results in an inverse wide-bandgap perovskite solar cell.

[0058] Example 3:

[0059] The perovskite solar cell prepared in this embodiment follows a similar preparation process to that in Example 1, except that in step 4, during the secondary coating process, 20 μL of butanol is added dropwise into the gap between the perovskite film and the doctor blade; all other steps are identical. This results in an inverse wide-bandgap perovskite solar cell.

[0060] Table 1. Performance of wide-bandgap perovskite solar cells prepared in the examples and comparative examples.

[0061]

[0062] As shown in Table 1, Example 3 exhibits the highest open-circuit voltage and photoelectric conversion efficiency, and demonstrates a higher open-circuit voltage and higher photoelectric conversion efficiency compared to Comparative Example 1, along with a high fill factor. This proves that the perovskite surface and electron transport layer achieve better contact and carrier transport after secondary coating with n-butanol.

[0063] Figure 1 The diagram shows the structure of the inverted perovskite solar cells prepared in Examples 1 to 3. The overall structure can be clearly seen from the diagram. Figure 2 These are schematic diagrams illustrating the coating process and physical-mechanical planarization process of the perovskite light-absorbing layer in the inverted perovskite solar cells prepared in Examples 1 to 3. Figure 1 and Figure 2 The preparation of the perovskite thin film and the secondary coating process can be clearly seen in the image.

[0064] AFM analysis was performed on the perovskite layers of the devices prepared in Examples 1 to 3 and Comparative Example 1. The results are as follows: Figure 3 As shown, compared to the comparative example, the addition of alcohols resulted in a reduced thickness and more uniform thickness of the perovskite film. Among several alcohols, n-butanol was the optimal auxiliary solution. Using n-butanol (nBA) for secondary coating for physical-mechanical planarization yielded the best results due to its low polarity and appropriate evaporation rate. The low polarity of n-butanol hinders the penetration of moisture into the perovskite film during coating, while its moderate evaporation rate regulates the contact time between the film and air. This synergistic effect reduces water absorption during coating, thereby mitigating the destructive effects of moisture on the perovskite film during subsequent annealing (such as inducing decomposition to form lead iodide or even creating pores). This method effectively suppresses the adverse effects of atmospheric moisture on perovskite film preparation, significantly improving the quality and uniformity of perovskite films on large-area glass substrates. Furthermore, the secondary coating process further optimizes the surface uniformity of the film and reduces its surface roughness, thereby effectively improving the open-circuit voltage and photoelectric conversion efficiency of perovskite solar cell devices.

[0065] The films prepared in the comparative examples and Examples 1 to 3 were characterized by XRD, and the results are as follows: Figure 5As shown; compared with the comparative example, after secondary coating and polishing with n-butanol, the characteristic peak of lead iodide at 12.8° in Example 3 was significantly lower than that of the characteristic peak of perovskite phase at 14.2°, indicating that the perovskite film had better crystallinity after secondary coating and polishing, and reduced the formation of lead iodide phase, thus improving the crystallinity quality of the perovskite film.

[0066] Performance analyses were performed on the perovskite solar cell devices prepared in the first to third studies, respectively, and the results are as follows: Figure 6 As shown, after the perovskite thin film undergoes a secondary coating process with n-butanol, the perovskite solar cell device exhibits significant improvements in open-circuit voltage, short-circuit current, fill factor, and photoelectric conversion efficiency.

[0067] The above description is merely a specific embodiment of this patent, enabling those skilled in the art to understand or implement this application. Various modifications to the embodiments will be readily apparent to those skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of this application. Therefore, this application is not to be limited to the embodiments shown herein, but is to be accorded the widest scope consistent with the principles and novel features claimed herein.

Claims

1. A method for achieving mechanical planarization of the surface of a perovskite thin film by scraping, characterized in that, Includes the following steps: A perovskite precursor solution was coated onto a substrate and then subjected to gas quenching and annealing to form an initial thin film. The initial film was subjected to physical and mechanical planarization to obtain a perovskite film with a smooth surface.

2. The method for achieving mechanical planarization of perovskite film surface by scraping as described in claim 1, characterized in that... The process of coating a perovskite precursor solution onto a substrate and then performing gas quenching and annealing to form the initial thin film includes: The perovskite precursor solution is dropped onto the substrate, and a scraping device with an integrated air knife is used to control the distance between the scraper and the substrate to be 500-3000 μm, and the scraping is performed at a speed of 2.5-4 mm / s. Then, the air knife following the scraper is controlled to blow the film at a pressure not exceeding 0.2 MPa, thereby simultaneously completing the formation of the wet film and the vapor phase quenching treatment to obtain the perovskite precursor wet film. The wet perovskite precursor film was placed on a hot stage and subjected to hot annealing at 100-150℃ for 15-30 minutes to crystallize and transform it into the initial perovskite film. The process of physically and mechanically planarizing the initial perovskite film to obtain the final perovskite film includes: An auxiliary solution is dropped onto a substrate, and a scraping device with an integrated air knife is used to control the distance between the scraper and the substrate to be 500-1500 μm, and the scraping is performed at a speed of 5-8 mm / s. Immediately afterwards, the air knife following the scraper is controlled to blow away the substrate at a pressure not exceeding 0.2 MPa, thereby simultaneously completing the scraping of the auxiliary solution and the vapor phase quenching treatment, and obtaining a perovskite film after physical and mechanical planarization treatment.

3. The method for achieving mechanical planarization of perovskite film surface by scraping as described in claim 2, characterized in that, The auxiliary solution includes alcohols such as ethanol, propanol, and butanol, with n-butanol being preferred.

4. A perovskite thin film, which is prepared by a method for mechanically planarizing the surface of a perovskite thin film by a blade coating as described in any one of claims 1 to 3.

5. A method for preparing a perovskite solar cell, characterized in that, include: S1. A hole transport layer is formed on ITO transparent conductive glass; S2. Using the method of mechanical planarization of the perovskite film surface by scraping as described in any one of claims 1 to 3, a perovskite film is prepared on the hole transport layer to serve as a perovskite light-absorbing layer. S3. Prepare an electron transport layer on the perovskite light-absorbing layer; S4. A metallic conductive layer is formed on the electron transport layer to obtain a perovskite solar cell.

6. The method for preparing a perovskite solar cell as described in claim 5, characterized in that, The implementation process of step S1 includes: ITO transparent conductive glass pretreatment: ITO transparent conductive glass is cleaned with acetone and ethanol in sequence, followed by ultraviolet ozone treatment for 10~30 minutes; Preparation of [4-(7H-dibenzocarbazole-7-yl)butyl]phosphonic acid solution: [4-(7H-dibenzocarbazole-7-yl)butyl]phosphonic acid was dissolved in ethanol to obtain a [4-(7H-dibenzocarbazole-7-yl)butyl]phosphonic acid solution with a concentration of 0.5 mg / mL; Hole transport layers were prepared on pretreated ITO transparent conductive glass using a solution of [4-(7H-dibenzocarbazole-7-yl)butyl]phosphonic acid.

7. The method for preparing a perovskite solar cell as described in claim 5, characterized in that, The electron transport layer is a multilayer structure, consisting of a wide bandgap semiconductor formed by stacking lithium fluoride, a carbon 60 layer, and a 2,9-dimethyl-4,7-biphenyl-1,10-phenanthroline layer from bottom to top.

8. The method for preparing a perovskite solar cell as described in claim 7, characterized in that, The total thickness of the electron transport layer is 10~50nm.

9. The method for preparing a perovskite solar cell as described in claim 5, characterized in that, The metallic conductive layer is made of gold or silver.

10. A perovskite solar cell, characterized in that, It includes, from bottom to top, an ITO transparent conductive glass, a hole transport layer, a perovskite light-absorbing layer, an electron transport layer, and a metal electrode layer; the perovskite light-absorbing layer is the perovskite thin film as described in claim 4.

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