Continuous reaction preparation method and application of perovskite thin film

Abstract

The invention provides a continuous reaction preparation method of a perovskite film, which comprises the following steps: 1) preparing a first precursor solution, and forming a first precursor layer on a substrate through a liquid phase deposition mode, the first precursor solution comprising lead-containing halide; (2) under the condition that the first precursor layer is still in a low crystallization state or is not completely crystallized and still keeps reaction activity, a second precursor solution is introduced, and the second precursor solution comprises at least two organic halogenated ammonium salts; and 3) carrying out thermal annealing treatment on the film layer after the second precursor solution is introduced, so that the first precursor layer reacts with the second precursor solution, and the perovskite thin film is formed through conversion. According to the preparation method of the perovskite thin film provided by the invention, through the continuous reaction, uniform film formation and efficient conversion of the perovskite thin film can be realized under the condition that an independent drying step is not introduced, the interface defect density is reduced, and the crystallization quality and photoelectric property of the thin film are improved.

Description

Technical Field

[0001] This invention belongs to the field of optoelectronic functional materials and thin film preparation technology, and relates to a continuous reaction preparation method for thin films for photovoltaic / optoelectronic devices. Background Technology

[0002] Perovskite materials, due to their excellent light absorption, long carrier diffusion length, and solution-processable properties, have shown broad application prospects in fields such as solar cells, photodetectors, and light-emitting devices. With the development of fabrication processes, solution methods have become the mainstream approach for perovskite thin film preparation due to their advantages such as low temperature, low cost, and suitability for large-area fabrication. Existing solution preparation methods for perovskite thin films mainly include one-step deposition and two-step deposition methods.

[0003] The two-step method typically includes: first, forming a lead halide precursor film on a substrate and then annealing it to obtain a highly crystalline lead halide film; then introducing an inorganic / organic ammonium halide solution onto the lead halide film and generating a perovskite film through an annealing process. This method expands the preparation process of perovskite films to some extent, but it still generally has the following shortcomings: (1) After the lead halide precursor is dried or crystallized, its film is too dense and the crystallinity of the lead halide crystal is high, which limits the subsequent full reaction with the organic ammonium halide; (2) The interface reaction between the precursor layer and the organic salt layer is limited, which easily produces unreacted residues and interface defects, affecting the photoelectric performance and stability of the device.

[0004] Therefore, there is an urgent need for a new method for preparing perovskite thin films to overcome the problem of limited reaction window in the traditional two-step method, and to achieve more complete reaction control and higher quality perovskite thin films. Summary of the Invention

[0005] The purpose of this invention is to provide a continuous reaction preparation method for perovskite thin films. By immediately introducing an organic ammonium halide salt solution while the first precursor layer is still in a low-crystallinity state and a high-reactivity stage, continuous reaction control is achieved. This method can effectively avoid the problems of dense structure and limited diffusion of organic ammonium salt caused by drying and solidification of the precursor in the traditional two-step method. It expands the reaction window, achieves more complete conversion reaction and crystal nucleus growth control, thereby improving the crystallization quality of the thin film, reducing the interface defect density, and enhancing the performance of perovskite thin films and related optoelectronic devices.

[0006] This invention provides a continuous reaction preparation method for perovskite thin films, comprising the following steps:

[0007] 1) Prepare a first precursor solution and form a first precursor layer on a substrate by liquid phase deposition, wherein the first precursor solution contains lead halide;

[0008] 2) While the first precursor layer is still in a low-crystallinity state or in a state that is not fully crystallized and still has reactivity, a second precursor solution is introduced, wherein the second precursor solution contains at least two organic ammonium halide salts.

[0009] 3) The film layer after the introduction of the second precursor solution is subjected to thermal annealing treatment, so that the first precursor layer reacts with the second precursor solution to form a perovskite film.

[0010] Furthermore, in step 2), the second precursor solution is introduced earlier than the solvent removal or crystallization of the first precursor layer.

[0011] Furthermore, the organic ammonium halide salt includes an organic ammonium salt for providing A-site cations and a halogen-regulating salt for controlling crystal phase stability or crystallization kinetics.

[0012] Furthermore, the organic ammonium salt includes formamidinium salt and / or methylammonium salt, and the halogen regulating salt includes ammonium bromide salt and / or ammonium chloride salt.

[0013] Furthermore, the molar concentration of the organic ammonium salt is 0.05M to 2M, and the molar concentration of the halogen-controlled salt is 0.001M to 1M.

[0014] Furthermore, the organic ammonium salt is one or more of formamidinium hydroiodate (FAI), methyl ammonium bromide (MABr), or methyl ammonium chloride (MACl).

[0015] Furthermore, the molar concentration of FAI is 0.05~0.8M, the molar concentration of MABr is 0.05~0.3M, and the molar concentration of MACl is 0.1~0.3M.

[0016] Furthermore, the second precursor solution comprises FAI, MABr, and MACl in a molar concentration ratio of 1:(0.01~0.3):(0.01~0.3).

[0017] Furthermore, the solvent of the second precursor solution is a polar organic solvent containing hydroxyl groups, selected from alcohols, glycols and their mixtures with other polar solvents, preferably alcohol solvents, and more preferably isopropanol.

[0018] Furthermore, the liquid phase deposition method described in step 1) includes spin coating, blade coating, spray coating, slot coating, slot coating, or a combination of the above methods.

[0019] Furthermore, the thermal annealing process includes single-step annealing, staged annealing, or annealing under a controlled atmosphere.

[0020] Furthermore, the annealing temperature of the heat annealing treatment is 80~160℃, and the annealing time is 5~30 minutes.

[0021] Further, the molar concentration of the first precursor solution is 0.5~2.0 M, the lead halide is lead iodide, and the solvent of the first precursor solution is a polar organic solvent, including but not limited to N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), γ-butyrolactone (GBL), N-methylpyrrolidone (NMP), or a mixture of any two or more thereof, preferably containing a mixture of DMF and DMSO, with a volume ratio of (4~19):1, preferably (4~9):1. The present invention also provides a perovskite thin film, which is prepared by the above-described preparation method.

[0022] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0023] This invention discloses a continuous reaction preparation method for perovskite thin films. While the first precursor layer is still in a low-crystallinity state or not fully crystallized and still retains reactivity, a second precursor solution is introduced in a timely manner, followed by thermal annealing. This allows the first precursor layer and the second precursor solution to react, forming a perovskite thin film. Unlike the traditional two-step method that requires drying and crystallizing the first precursor layer (lead halide) before a secondary reaction, this invention avoids the problem of subsequent reaction being hindered by the densification of the first precursor layer (lead halide). Through this continuous reaction preparation method, uniform film formation and efficient conversion of perovskite thin films can be achieved without introducing a separate drying step, reducing interface defect density and improving film crystallinity and photoelectric properties. Perovskite thin films prepared using this method can be applied to optoelectronic devices such as solar cells. Specifically, it has the following significant advantages:

[0024] (1) By introducing organic ammonium halide salts into the stage where the lead halide precursor still maintains low crystallinity and high reactivity, the ion exchange and diffusion kinetics are enhanced, the reaction window is broadened, and the full conversion of the precursor is promoted.

[0025] (2) The continuous reaction process improves the contact conditions of each component, reduces the density of interface defects between the precursor layer and the organic salt layer, and improves the compactness and crystallization uniformity of the film.

[0026] (3) No separate drying step is required, simplifying the process and facilitating large-scale preparation and industrial application;

[0027] (4) By reducing the density of interface defects and improving the uniformity of film formation, the perovskite thin film prepared by the method of the present invention helps to obtain good photoelectric properties. Attached Figure Description

[0028] To more clearly illustrate the technical solutions of the embodiments of the present invention, the drawings used in the description of the embodiments of the present invention 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.

[0029] Figure 1 Flowchart of continuous reaction preparation of perovskite thin films

[0030] Figure 2 The image shows the SEM image of lead iodide in the first precursor layer without annealing treatment in Example 1.

[0031] Figure 3 The image shows the SEM image of the perovskite film annealed by the continuous preparation method in Example 1.

[0032] Figure 4 SEM images of highly crystalline lead iodide films prepared by the conventional two-step method for comparison;

[0033] Figure 5 SEM images of perovskite films prepared by the conventional two-step method are shown for comparison.

[0034] Figure 6 XRD patterns of lead iodide in the first precursor layer of Example 1 and Comparative Example;

[0035] Figure 7 XRD patterns of the perovskite films prepared in Example 1 and the comparative example;

[0036] Figure 8 SEM images of the perovskite films prepared for repeatability testing;

[0037] Figure 9 The efficiency results of the perovskite thin film prepared for repeatability testing in solar cell devices. Detailed Implementation

[0038] To make the technical problems to be solved, the technical solutions, and the beneficial effects of the present invention clearer, the present invention will be further described in detail below with reference to embodiments and accompanying drawings. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention. The present invention will be specifically described below with reference to specific embodiments.

[0039] The present invention provides a continuous reaction preparation method for perovskite thin films, comprising the following steps:

[0040] 1) Prepare a first precursor solution, and then deposit the first precursor solution on a substrate by liquid phase deposition to form a first precursor layer, wherein the first precursor solution contains lead halide;

[0041] 2) While the first precursor layer is still in a low-crystallization state or in a stage where it is not fully crystallized and can react with the subsequently introduced organic ammonium halide salt at the interface, a second precursor solution is introduced, wherein the second precursor solution contains two or more organic ammonium halide salts.

[0042] 3) The film layer after the introduction of the second precursor solution is subjected to thermal annealing or other equivalent energy treatment, so that the first precursor layer reacts with the second precursor solution to form a high-quality perovskite film.

[0043] The thickness of the first precursor layer can be controlled by controlling the deposition rate, i.e., the deposition rate can be adjusted according to the film thickness.

[0044] Steps 1) and 2) are completed through a continuous liquid phase deposition process, and no independent drying or curing steps are introduced between the two steps.

[0045] Specifically, in step 2), the second precursor solution is introduced earlier than the solvent removal or crystallization of the first precursor layer.

[0046] Specifically, the organic ammonium halide salt includes an organic ammonium salt and a halogen-regulated salt, wherein the organic ammonium salt is used to provide an A-site cation, and the halogen-regulated salt is used to regulate the crystal phase stability or crystallization kinetics.

[0047] Specifically, the organic ammonium salt includes formamidinium salt and / or methylammonium salt, and the halogen regulating salt includes ammonium bromide salt and / or ammonium chloride salt.

[0048] Specifically, the molar concentration of the organic ammonium salt is 0.05M to 2M, and the molar concentration of the halogen-controlled salt is 0.001M to 1M.

[0049] Specifically, the organic ammonium salt is one or more of FAI, MABr, or MACl.

[0050] Specifically, the molar concentration of FAI is 0.05~0.8M, the molar concentration of MABr is 0.05~0.3M, and the molar concentration of MACl is 0.1~0.3M. By controlling their molar concentrations, the perovskite crystal structure and optical properties can be tuned.

[0051] Preferably, the second precursor solution comprises FAI, MABr, and MACl in a molar concentration ratio of 1:(0.01~0.3):(0.01~0.3).

[0052] Specifically, the solvent of the second precursor solution is a polar organic solvent containing hydroxyl groups, selected from alcohols, glycols and their mixtures with other polar solvents, preferably alcohols, and more preferably isopropanol.

[0053] Specifically, the liquid phase deposition method described in step 1) includes spin coating, blade coating, spray coating, slot coating, slot coating, or a combination of the above methods.

[0054] Specifically, the thermal annealing process includes single-step annealing, staged annealing, or annealing under a controlled atmosphere.

[0055] Specifically, the annealing temperature of the thermal annealing treatment is 80~160℃, and the annealing time is 5~30 minutes. The annealing temperature and annealing time can be optimized according to the film thickness and substrate material to obtain the best crystal growth and film uniformity. Specifically, the molar concentration of the first precursor solution is 0.5~2.0 M, the lead halide is lead iodide, and the solvent of the first precursor solution is a polar organic solvent, including but not limited to N,N-dimethylformamide (DMF), dimethyl sulfoxide (DMSO), γ-butyrolactone (GBL), N-methylpyrrolidone (NMP), or any mixture of two or more thereof, preferably containing a mixed solvent of DMF and DMSO, with a volume ratio of (4~19):1, preferably (4~9):1. This invention also provides a perovskite film, which is prepared by the above-described preparation method.

[0056] The embodiments of the present invention also provide the application of the above-described perovskite thin film in the fabrication of solar cell devices.

[0057] The following description is based on specific embodiments:

[0058] Example 1

[0059] Lead iodide (PbI2) was dissolved in a mixed solvent of N,N-dimethylformamide and dimethyl sulfoxide to prepare a first precursor solution with a molar concentration of 1.5 M. The first precursor solution was then spin-coated onto a pretreated conductive glass substrate to form a first precursor layer (PbI2 wet film). Its SEM image is shown below. Figure 2 As shown, the XRD pattern is as follows Figure 6 As shown, it can be seen that the lead iodide in the first precursor layer is not completely crystallized in this state.

[0060] FAI, MABr, and MACl were dissolved in IPA to prepare a second precursor solution with a molar ratio of 1:0.154:0.235. The second precursor solution was spin-coated immediately while the first precursor layer was still in a state of being partially dry and still reactive.

[0061] After spin coating, the resulting film was subjected to thermal annealing at 150°C for 15 minutes to allow the lead halide to react with the organic ammonium halide to form a perovskite film. The SEM images at this stage are shown below. Figure 3 As shown, PbI2 in this state is highly crystalline, and the resulting perovskite film is uniform and dense. The XRD pattern is shown below. Figure 7 As shown, the prepared perovskite film has almost no residual lead iodide, indicating that high-quality perovskite films can be prepared through continuous reaction.

[0062] Comparative Example

[0063] The difference from Example 1 is that, after the first precursor layer is completely dried, the SEM image is as follows: Figure 4 As shown, the XRD pattern is as follows Figure 6 As shown, the first precursor layer, lead iodide, has completed crystallization and stabilization in this state. The SEM image of the perovskite film formed by spin-coating the second precursor solution is shown below. Figure 5 As shown, through Figure 3 and Figure 5 The comparison shows that the perovskite film prepared in Example 1 has higher density and crystal uniformity, as shown in the XRD pattern. Figure 7 As shown, the prepared perovskite film still has a large amount of residue and has not been completely converted into perovskite.

[0064] Repeatability testing:

[0065] Based on Example 1, perovskite films of different thicknesses were prepared by adjusting the molar concentration of the first precursor lead iodide solution (1.1M, 1.3M, 1.5M, 1.7M). SEM images are shown below. Figure 8 As shown, when used in solar cell devices, the efficiency results are as follows: Figure 9 As shown. (Through) Figure 8 The SEM images show that the continuous reaction preparation process can achieve a uniform, dense perovskite thin film structure with large grain characteristics. Figure 9 The device efficiency data shown indicates that battery devices with good and nearly identical performance can still be prepared using first precursor solutions of different molar concentrations, proving that the perovskite thin film prepared in this invention has good adaptability and repeatability.

[0066] It should be noted that the various embodiments in this specification are described in a progressive manner, with each embodiment focusing on the differences from other embodiments. The same or similar parts between the various embodiments can be referred to each other.

[0067] The above description is merely a description of preferred embodiments of the present invention and is not intended to limit the scope of the present invention in any way. Any changes or modifications made by those skilled in the art based on the above disclosure shall fall within the scope of protection of the claims.

Claims

1. A continuous reaction preparation method for perovskite thin films, characterized in that, Includes the following steps: 1) Prepare a first precursor solution, and then deposit the first precursor solution on a substrate by liquid phase deposition to form a first precursor layer, wherein the first precursor solution contains lead halide; 2) While the first precursor layer is still in a low-crystallinity state or in a state that is not fully crystallized and has reactivity, a second precursor solution is introduced, wherein the second precursor solution contains at least two organic ammonium halide salts. 3) The film layer after the introduction of the second precursor solution is subjected to thermal annealing treatment, so that the first precursor layer reacts with the second precursor solution to form a perovskite film.

2. The continuous reaction preparation method for a perovskite thin film according to claim 1, characterized in that, In step 2), the second precursor solution is introduced earlier than the solvent removal or crystallization of the first precursor layer.

3. The continuous reaction preparation method for a perovskite thin film according to claim 1, characterized in that, The organic ammonium halide salts include organic ammonium salts and halogen-regulated salts.

4. The continuous reaction preparation method for a perovskite thin film according to claim 3, characterized in that, The organic ammonium salt includes formamidinium salt and / or methylammonium salt, and the halogen regulating salt includes ammonium bromide salt and / or ammonium chloride salt.

5. A continuous reaction preparation method for a perovskite thin film according to claim 3 or 4, characterized in that, The organic ammonium salt includes one or more of the following: 0.05-0.8 M formamidin hydroiodate, 0.05-0.3 M methylammonium bromide, or 0.1-0.3 M methylammonium chloride; And / or, the second precursor solution comprises formamidin hydroiodide, methylammonium bromide and methylammonium chloride in a molar ratio of 1:(0.01~0.3):(0.01~0.3); And / or, the solvent of the second precursor solution is a polar organic solvent containing hydroxyl groups.

6. The continuous reaction preparation method for a perovskite thin film according to claim 1, characterized in that, The liquid phase deposition method described in step 1) includes spin coating, blade coating, spray coating, slot coating, slot coating, or a combination of the above methods.

7. The continuous reaction preparation method for a perovskite thin film according to claim 1, characterized in that, The thermal annealing process includes single-step annealing, graded annealing, or annealing under a controlled atmosphere.

8. A continuous reaction preparation method for a perovskite thin film according to claim 1 or 7, characterized in that, The annealing temperature for the heat annealing process is 80~160℃, and the annealing time is 5~30 minutes.

9. The continuous reaction preparation method for a perovskite thin film according to claim 1, characterized in that, The molar concentration of the first precursor solution is 0.5~2.0 M, the lead halide is lead iodide, and the solvent of the first precursor solution includes N,N-dimethylformamide, dimethyl sulfoxide, γ-butyrolactone, N-methylpyrrolidone or any two or more of these. And / or, the solvent of the first precursor solution is a mixed solvent of DMF and DMSO in a volume ratio of (4~19):

1.

10. A perovskite thin film, characterized in that, The perovskite thin film is prepared by the preparation method according to any one of claims 1-9.

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