Method for simulating efficiency of microscale thick film perovskite device with substrate lift-off and applications

Abstract

This invention provides a method and application for improving the efficiency of micron-scale thick-film perovskite devices by simulating a substrate. A simulated substrate is constructed using a liquid-phase three-step spin coating method, and a micron-scale thick-film perovskite is prepared on the simulated substrate. This method can effectively continue the stress applied to the substrate, thereby restoring the stress that disappeared in the thick film. As a result, the micron-scale perovskite thick film of this solution has extremely high conductivity and photoelectric conversion efficiency when applied to optoelectronic devices.

Description

Technical Field

[0001] This invention relates to the field of solar cells, and in particular to a method and application for improving the efficiency of micron-scale thick-film perovskite devices by simulating substrates. Background Technology

[0002] Perovskite solar cells are solar cells that utilize perovskite-type organometal halide semiconductors as light-absorbing materials. They can convert and store solar energy into usable electrical energy. Specifically, when a perovskite solar cell is exposed to sunlight, the perovskite layer first absorbs photons, generating electron-hole pairs. Unrecombined electrons and holes are collected by the electron transport layer and hole transport layer, respectively. That is, electrons travel from the perovskite layer to the isoelectronic transport layer and are finally collected by ITO (inductively coupled plasma), while holes travel from the perovskite layer to the hole transport layer and are finally collected by the metal electrode, thus forming a current.

[0003] Currently, the main methods for preparing perovskite films (layers) include liquid-phase and gas-phase methods. The liquid-phase method involves dissolving the perovskite precursor material entirely in a solvent and then preparing the perovskite layer using methods such as spin coating, blade coating, screen printing, and spray pyrolysis. Thick-film perovskite is an important means to improve the photoelectric conversion efficiency of optoelectronic devices and is also crucial for its integration with silicon solar cells. Current technologies utilize various additives to significantly improve the performance of perovskite solar cells, but the thickness of perovskite films is generally limited to 400-600 nanometers. For example, the film thickness reported by South Korean scientist Seok in *Nature Materials* in 2014 was approximately 400 nanometers. The thickness of perovskite films prepared using these methods is difficult to reach 1 micrometer, indicating a limitation in the thickness of perovskite films.

[0004] Increasing the thickness of perovskite films not only presents technological challenges, but also increases defect density and reduces carrier diffusion length, thus affecting the photoelectric conversion efficiency of the device. In other words, ensuring that carrier diffusion is not affected by the thickness is crucial for improving the performance of perovskite solar cells. However, despite significant improvements in carrier diffusion length, current thick-film devices have not achieved improved photoelectric conversion efficiency. In other words, current perovskite film materials still cannot simultaneously achieve both increased film thickness and improved photoelectric conversion efficiency. Summary of the Invention

[0005] The purpose of this invention is to provide a method and application for improving the efficiency of micron-scale thick-film perovskite devices by simulating a substrate. This method utilizes a simulated substrate to increase the thickness of the micron-scale perovskite thick film to a thickness of more than 2 micrometers, while restoring the stress within the thick film to maintain good carrier diffusion performance within the micron-scale perovskite thick film. It can be applied to single-junction or multi-junction solar cell optoelectronic devices and also has extremely high open-circuit voltage and photoelectric conversion efficiency.

[0006] To achieve the above objectives, firstly, this technical solution provides a method for improving the efficiency of micron-scale thick-film perovskite devices by simulating substrates, comprising the following steps:

[0007] Preparation of perovskite precursor solution:

[0008] PbX2 and CsX were dissolved in a first precursor solvent and stirred until completely dissolved to obtain a first precursor solution; AX was dissolved in a second precursor solvent and stirred until completely dissolved to obtain a second precursor solution; AX and BM were dissolved in a third precursor solvent and stirred until completely dissolved to obtain a third precursor solution.

[0009] Preparation of micron-scale perovskite thick films:

[0010] The first precursor solution, the second precursor solution, and the third precursor solution were spin-coated onto the substrate in stages. After spin-coating, the substrate was heated in stages to obtain a micron-sized perovskite thick film.

[0011] The substrate for this solution can be selected from one of the following: FTO, ITO, n-Si, p-Si, CIGS flexible or rigid substrates. In one embodiment of this solution, the substrate is ITO with SnO2.

[0012] In the preparation step of the perovskite precursor solution, site A uses a mixed ratio of MA (methylamine ion), FA (formamidinium ion), and Cs (cesium ion); X is the same I (iodine), Br (bromine), Cl (chlorine) or different I, Br, Cl halide ions.

[0013] In some embodiments, AX is selected as FAI, MACL, FABr, MABr, FACl, MAI, CsI, or CsCl. In some preferred embodiments, AX is selected as FAI and MACL, wherein the ratio of FAI to MACL ranges from 1:1 to 1:4, preferably 1:1.

[0014] In some embodiments, BM is selected as benzalamide hydrochloride, or it may be selected as phenacetamidine hydrochloride or methoxybenzalamide hydrochloride. Of course, in addition to benzalamide hydrochloride, BM may also be selected as benzalamide bromate and hydroiodide; in addition to phenacetamidine hydrochloride, BM may also be selected as phenacetamidine bromate and hydroiodide.

[0015] BM, as an additive in perovskite precursor solutions, significantly enhances the carrier diffusion length. However, despite increasing the carrier diffusion length, the photoelectric conversion efficiency of micron-sized thick-film perovskites remains unchanged. Research revealed that this is because the stress on the lattice substrate is restricted after heating, preventing complete shrinkage and resulting in increased relative lattice distortion near the substrate. Specifically, for example... Figure 4 As shown, Figure 4 This is a schematic diagram of a traditional perovskite thick-film substrate. The arrows in the diagram indicate the lattice near the substrate. In perovskites, the lattice framework is mainly composed of Pb-X forming an octahedral structure, and its band structure is also formed by the coupling of Pb p orbitals and Is orbitals. However, due to stress-induced distortion, the relative positions and distances of Pb-I in thick-film perovskites change. This inevitably leads to changes in the band structure of the perovskite, which in turn causes stress to alter the effective mass of the thick-film perovskite, thereby reducing the carrier concentration and resulting in an overall decrease in the conductivity of the film.

[0016] The first, second, and third precursor solvents are the same or different solvents that can dissolve perovskite materials, such as DMF, DMSO, γ-butyrolactone, IPA, and CB.

[0017] Specifically, in some embodiments, the first precursor solvent is selected as a mixture of DMSO and DMF, wherein the ratio of DMSO to DMF ranges from 9:1 to 8:2, preferably 9:1. The corresponding PbX2 is selected as PbI2, PbBr2, or PbCl2.

[0018] In some embodiments, the second precursor solvent is selected as a good solvent capable of dissolving the second precursor, such as IPA (isopropanol), CB (chlorobenzene), or both. AX and BM are dissolved in the third precursor solvent and stirred evenly in a magnetic stirrer at room temperature. Similarly, PbX2 is dissolved in the first precursor solvent and stirred evenly in a magnetic stirrer at room temperature.

[0019] In some embodiments, the third precursor is selected as a good solvent capable of dissolving the third precursor, such as IPA (isopropanol), CB (chlorobenzene), or a combination of both.

[0020] The ratio between the first precursor solvent and the second precursor solvent is in the range of 1:1 to 40:49, preferably 1:1.

[0021] It is worth mentioning that this scheme constructs the simulated substrate by spin-coating the first precursor solution, the second precursor solution, and the third precursor solution onto the substrate in a stepwise manner. The structure of the simulated substrate is as follows: Figure 5As shown in the figure, the area outlined in the diagram represents the simulated substrate. The simulated substrate obtained using this method is a perovskite composed of components contained in the second precursor solution. The lattice within this perovskite layer is subjected to stress, has a thickness of approximately several hundred nanometers, and exhibits a uniform and homogeneous lattice distribution. The advantage of this approach is that it allows the applied stress on the substrate to be sustained, thus ensuring that the prepared thick film maintains the same stress level as the thin film (<1 μm).

[0022] This method involves staged heating after spin coating to obtain a thick perovskite film. The specific staged heating steps are as follows: heating at a first temperature for a first time, followed by heating at a second temperature for a second time, wherein the first time is shorter than the second time, and the first temperature is lower than the second temperature. This allows the perovskite film to nucleate slowly first, and then grow uniformly. In the embodiments of this method, the first temperature is 85-95℃, preferably 90℃; the second temperature is 140-160℃, preferably 157℃.

[0023] Compared to existing technologies, this method uses BM as an additive in the perovskite precursor solution, employing BM as a dopant material for the perovskite layer to prepare thick-film perovskite with a thickness of up to 2 μm. Compared to traditional methods for fabricating thick-film devices, the thick-film perovskite prepared using a simulated substrate method significantly increases the carrier concentration. This results in perovskite solar cell devices exhibiting extremely high conductivity. This invention is simple to operate, highly effective, and reproducible, making it suitable for large-scale commercial production in the photovoltaic industry.

[0024] Secondly, this solution provides a micron-scale thick-film perovskite device prepared by the above method.

[0025] The micron-scale thick-film perovskite devices prepared by the above methods have a film thickness greater than 2 micrometers, high crystal quality, and a photoluminescence transient fluorescence lifetime of up to 20 μs. When applied to optoelectronic devices, they achieve a photoelectric conversion efficiency as high as 23.5%.

[0026] Furthermore, the perovskite thick film prepared by this method can be applied to various optoelectronic devices to leverage their photoelectric conversion performance. For example, this method provides a perovskite solar cell, specifically, it can be used in forward-biased perovskite cells, including the perovskite film prepared by the above method. It can also be used in reverse-biased perovskite cells. Exemplarily, this method provides a single-junction optoelectronic device using the aforementioned micron-scale perovskite thick film. Exemplarily, this method provides a two-terminal stacked device using the aforementioned micron-scale perovskite thick film. Exemplarily, this method provides a four-terminal stacked device using the aforementioned micron-scale perovskite thick film.

[0027] Compared to existing technologies, this technical solution has the following characteristics and beneficial effects: As the perovskite film thickness increases, the stress in the corresponding film gradually disappears, which alters the film structure and thus affects the photoelectric conversion efficiency of the thick perovskite film. This solution fundamentally solves the problem caused by the thickening of the perovskite film by using a three-step spin-coating method to restore the stress in the thick perovskite film, restoring its structure to the structure corresponding to the thin film. Based on this, the carrier concentration is increased to improve conductivity, thereby improving the photoelectric conversion efficiency of the thick perovskite film. Attached Figure Description

[0028] Figure 1 This is a thickness map of the perovskite thick film prepared in Example 1 of this scheme, measured by a profilometer, wherein the thickness of the perovskite thick film is 2.05 μm.

[0029] Figure 2 This is a thickness diagram of the perovskite thick film prepared in control group 5 of this scheme, measured by a profilometer, in which the thickness of the perovskite thick film is 1.36 μm.

[0030] Figure 3 The graph shows the photoelectric conversion efficiency of the perovskite film applied to the SnO2 electron transport layer on the ITO substrate, which is the control group and the example of this scheme.

[0031] Figure 4 This is a schematic diagram of the substrate lattice of a traditional perovskite thick film.

[0032] Figure 5 This is a schematic diagram of the simulated substrate structure of the perovskite thick film prepared by the three-step spin coating method of this scheme. Detailed Implementation

[0033] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention are within the scope of protection of the present invention.

[0034] Those skilled in the art should understand that, in the disclosure of this invention, the terms "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, the above terms should not be construed as limiting this invention.

[0035] It is understood that the term "a" should be understood as "at least one" or "one or more", that is, in one embodiment, the number of an element can be one, while in another embodiment, the number of the element can be multiple, and the term "a" should not be understood as a limitation on the number.

[0036] Example 1

[0037] Micron-scale perovskite thick films were prepared using a simulated substrate method.

[0038] 1) At room temperature, PbI2 was dissolved in DMSO and DMF (solvent ratio 4:1) to prepare a mixed solution with a concentration of 2M, and stirred on a magnetic stirrer until completely dissolved;

[0039] 2) At room temperature, dissolve FAI (100 mg) and MACl (20 mg) in IPA (2 mL) and stir on a magnetic stirrer until completely dissolved;

[0040] 3) At room temperature, dissolve FAI (100 mg), MACl (20 mg), and benzalkonium hydrochloride (6 mg) in IPA (1 mL) and stir on a magnetic stirrer until completely dissolved;

[0041] 4) The above-mentioned clear solution was spin-coated onto an ITO substrate with a SnO2 electron transport layer using a liquid phase spin-coating method. After spin-coating, the substrate was heated at 90°C for 1 minute, followed by heating at 150°C for 10 minutes.

[0042] Control group:

[0043] In control group 1, micron-sized perovskite thick films were prepared using a two-step method, with the first precursor solution concentration being 2.0 M.

[0044] The difference between Example 1 and Control Group 1 is that no second precursor solution was prepared, and a two-step liquid-phase spin coating method was used.

[0045] 1) At room temperature, PbI2 was dissolved in DMSO and DMF (solvent ratio 4:1) to prepare a mixed solution with a concentration of 2.0M, and stirred on a magnetic stirrer until completely dissolved;

[0046] 2) At room temperature, dissolve FAI (140 mg), MACl (22.75 mg), and benzalkonium hydrochloride (7 mg) in IPA (1 mL) and stir on a magnetic stirrer until completely dissolved;

[0047] 3) The above-mentioned clear solution was spin-coated onto an ITO substrate with a SnO2 electron transport layer using a two-step liquid phase spin-coating method. After spin-coating, the substrate was heated at 90°C for 1 minute, followed by heating at 150°C for 10 minutes.

[0048] Effect detection:

[0049] (1) Thickness testing of perovskite thick films:

[0050] This method utilizes a profilometer to observe the perovskite films obtained in Example 1 and Control Group 1, such as... Figures 1 to 2 As shown, Figure 1 The image shows an electron microscope image of the perovskite film from Example 1. Figure 2 The image shows an electron microscope image of the perovskite film corresponding to control group 1. It can be seen from the image that the thickness of the micron-sized perovskite film obtained in Example 1 of this scheme is above 2 μm, while the thickness of the micron-sized perovskite film obtained in control group 1 is below 2 μm.

[0051] The thicknesses of the perovskite thick films obtained in Example 1 and Control Group 1 are shown in Table 1 below:

[0052] Table 1. Thickness of perovskite films

[0053] Example 1 2.05μm Control group 5 1.36μm

[0054] It is evident that, after adding the second precursor solution and employing the three-step spin coating method, the thickness of the perovskite thick film significantly increased.

[0055] (2) Photoelectric conversion efficiency test:

[0056] The photoelectric conversion test was conducted using an AAA-grade solar simulator, with a test step of 30ms and an effective area of ​​0.1cm². 2 The bias voltage ranges from -0.2V to 1.2V or from 1.2V to -0.2V. The photoelectric conversion efficiency of experimental group 1 and control group 1 is... Figure 3 As shown in Table 2:

[0057] Table 2 Photoelectric Conversion Efficiency

[0058] Photoelectric conversion efficiency Control group 1 10.88％ Example 1 21.90％

[0059] It can be seen that the photoelectric conversion efficiency of Example 1 of this scheme is much higher than that of Control Group 1. Combined with the results of the film thickness test, it can be seen that the perovskite thick film of this scheme has the advantages of both film thickness and high photoelectric conversion efficiency.

[0060] This invention is not limited to the preferred embodiments described above. Anyone can derive other products in various forms under the guidance of this invention. However, regardless of any changes in shape or structure, any technical solution that is the same as or similar to this application falls within the protection scope of this invention.

Claims

1. A method of simulating the efficiency of a substrate lifted microscale thick film perovskite device, characterized by, Includes the following steps: Preparation of perovskite precursor solution: PbX2 and CsX were dissolved in the first precursor solvent and stirred until completely dissolved to obtain the first precursor solution. Dissolve AX in the second precursor solvent and stir until completely dissolved to obtain the second precursor solution; AX and BM were dissolved in the third precursor solvent and stirred until completely dissolved to obtain the third precursor solution. Preparation of micron-scale perovskite thick films: The first precursor solution, the second precursor solution, and the third precursor solution were spin-coated onto the substrate in stages. After spin-coating, the substrate was heated in stages to obtain a micron-sized perovskite thick film. Site A uses a mixed ratio of MA, FA, and Cs; X is the same I, Br, Cl or different I, Br, Cl halide ions; BM is benzamide hydrochloride, benzamide bromate, hydroiodide, phenylacetamidine hydrochloride, phenylacetamidine bromate, hydroiodide or methoxybenzoamide hydrochloride.

2. The method of simulating the efficiency of a microscale thick film perovskite device with a lifted substrate according to claim 1, wherein, The substrate is one of the following: FTO, ITO, n-Si, p-Si, CIGS, or a flexible or rigid substrate.

3. The method of simulating the efficiency of a micron-scale thick film perovskite device with a lifted substrate according to claim 1, wherein, The steps of the phased heating are as follows: after heating at a first temperature for a first time, heating at a second temperature for a second time, wherein the first time is shorter than the second time and the first temperature is lower than the second temperature.

4. A micro-scale thick film perovskite device, characterized in that, The device was prepared using the method described in any one of claims 1-3 to improve the efficiency of micron-scale thick-film perovskite devices with simulated substrates.

5. The micrometer-scale thick film perovskite device of claim 4, wherein, The micron-scale perovskite thick film has a thickness greater than 2 microns and a photoluminescence transient fluorescence lifetime of 20 μs.

6. A unijunction photovoltaic device characterized by The micron-scale thick-film perovskite device described in claim 4 above is applied.

7. A two-terminal stacked device, characterized by, The micron-scale thick-film perovskite device described in claim 4 above is applied.

8. A four-terminal stacked device, characterized by, The micron-scale thick-film perovskite device described in claim 4 above is applied.

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