A uniformly oriented quasi-single crystal perovskite film and its preparation method and application

Abstract

The present invention relates to the field of perovskite solar cells, and discloses a uniformly oriented quasi-single crystal perovskite film and its preparation method and application. The preparation method comprises: using at least one of N,N-dimethylpropylene urea, methylphenyl sulfoxide, and ethylsulfinylethane as a solvent additive and N,N-dimethylformamide to prepare an organic mixed solvent, dissolving lead iodide and cesium iodide and / or rubidium chloride in the organic mixed solvent and then coating, heating, to obtain a lead iodide film; depositing an organic amine salt solution on the lead iodide film, and annealing to obtain a perovskite film. The present invention reduces the reactivity of the lead iodide precursor by introducing solvent additives with different coordination abilities, effectively delaying the kinetic process of the perovskite formation reaction, thereby promoting the full reaction of the organic amine salt and the lead iodide intermediate phase, and effectively solving the problems of residual lead iodide impurities and poor crystallization quality in the perovskite film in the traditional two-step method.

Description

Technical Field

[0001] The present invention relates to the field of perovskite solar cells, and in particular to a uniformly oriented quasi-single crystal perovskite film and a preparation method and application thereof. Background Art

[0002] Organic-inorganic hybrid perovskite materials, with their extensive chemical tunability and excellent semiconductor properties, have become a representative material for the third generation of novel solar cells. The certified power conversion efficiency of single-junction devices constructed using this material has significantly increased from an initial 3.8% to 26.7%. The preparation process of perovskite thin films is a key factor in determining the film's crystalline quality and phase composition, directly impacting the solar cell's power conversion efficiency and long-term operational stability. Perovskite thin film preparation methods are primarily categorized into one-step and two-step methods. The one-step method deposits a perovskite precursor solution directly onto a substrate to complete film formation. The two-step method, on the other hand, first deposits a uniform lead iodide (PbI2) thin film on the substrate. The perovskite film is then formed by spin coating or immersion in an organic amine salt solution (AX, such as formamidine iodide, FAI) to react with the PbI2. The two-step method offers excellent process controllability, film uniformity, and compatibility with vacuum processes, thus holding significant potential for the industrialization of perovskite solar cells.

[0003] Although the two-step method has significant advantages, it still has the problem of uncontrollable precursor reaction, resulting in poor film crystallization quality and random orientation, which ultimately affects the photoelectric conversion efficiency and long-term stability of the device. Existing strategies usually introduce additive molecules into the lead iodide precursor solution to generate a low-dimensional perovskite phase on the surface of the perovskite grains to achieve the purpose of passivating the grain boundaries and prevent the perovskite from decomposing under operating conditions. However, this method still has the problem of introducing additives that affect the crystallization quality of the perovskite, and such additives will induce the formation of low-dimensional perovskites, resulting in the obstruction of carrier transport inside the perovskite, further limiting the carrier transport efficiency and device performance improvement. Therefore, the preparation process of the traditional two-step perovskite film needs to be further improved. The present invention regulates the two-step reaction by introducing a volatile solvent as an additive. Such additives can be completely volatilized during the perovskite annealing process, and the crystallization properties of the perovskite film can be non-destructively regulated without introducing impurities, thereby achieving the controllable construction of a uniformly oriented quasi-single-crystalline perovskite film. Based on this active layer preparation technology, high-efficiency and high-stability perovskite solar cell preparation is achieved. Summary of the Invention

[0004] In the traditional two-step perovskite film preparation process, excess lead iodide is often converted into a low-dimensional perovskite phase by introducing organic amine salts or amino acid additives. However, the carrier mobility of low-dimensional perovskite materials is usually significantly lower than that of bulk perovskite, resulting in limited carrier transport within the film and hindering the efficient extraction of carriers at the device interface. In addition, there is a strong coordination effect between these additives and lead iodide, which easily competes with the perovskite formation reaction, thereby significantly reducing the crystallization quality of the film and limiting further improvement of device performance. In order to solve the problem of film crystallization quality caused by the uncontrollable reaction between lead iodide and formamidine iodide, the present invention proposes a strategy to slow down the subsequent AX+PbI2 reaction kinetics by introducing volatile solvent additives with different coordination abilities to coordinate with lead iodide. This method aims to improve the crystallinity of perovskite polycrystalline films, regulate the orientation of polycrystalline films, and achieve efficient preparation of pure phase quasi-single crystal structure perovskite films to promote interface carrier extraction, thereby significantly improving the performance and stability of perovskite solar cells.

[0005] To achieve the above objectives, the present invention provides a method for preparing a uniformly oriented quasi-single-crystalline perovskite film, which comprises the following steps:

[0006] S1. Using at least one of N,N-dimethylpropylene urea, methylphenyl sulfoxide, and ethanesulfenyl ethane as a solvent additive, the solvent additive is mixed with N,N-dimethylformamide to prepare an organic mixed solvent, and lead iodide and cesium iodide and / or rubidium chloride are dissolved in the organic mixed solvent to obtain a lead iodide solution, wherein the molar ratio of the solvent additive to lead iodide is preferably 0.3-1.3:1; adopting a coating film-forming method, first coating the lead iodide solution, and then heating the solution at 50-75°C to obtain a lead iodide thin film; the coating process is any one of spin coating, blade coating, and spray coating.

[0007] S2. Dissolving at least one of formamidine iodide, methylammonium chloride, and methylammonium iodide in an isopropyl alcohol solvent to obtain an organic amine salt solution; depositing the organic amine salt solution on the lead iodide film to obtain a brown perovskite film, and then annealing the film at 135-150° C. to remove solvent additives and improve the perovskite crystallization quality, thereby obtaining a uniformly oriented quasi-single crystal perovskite film.

[0008] As a further preferred technical solution of the present invention, in step S1, the heating treatment time is 0.5-2 min.

[0009] As a further preferred technical solution of the present invention, in step S2, the annealing treatment time is 5-20 min.

[0010] As a further preferred technical solution of the present invention, in step S1, the molar ratio of the solvent additive to lead iodide is 0.3-1.3:1, and more preferably 0.5:1.

[0011] As a further preferred technical solution of the present invention, the dosage ratio of each component in the lead iodide solution is: 1 mL of organic mixed solvent, 1.5 mmol of lead iodide, 0.05 mmol of cesium iodide or 0.05 mmol of rubidium chloride.

[0012] According to another aspect of the present invention, the present invention also provides a uniformly oriented quasi-single-crystalline perovskite film, which is prepared by the above method.

[0013] According to another aspect of the present invention, the present invention also provides an application of a uniformly oriented quasi-single-crystalline perovskite film in a perovskite solar cell. The perovskite solar cell includes a transparent conductive substrate, and a tin dioxide electron transport layer, a perovskite active layer, a quasi-two-dimensional perovskite passivation layer, a hole transport layer and a metal electrode arranged in sequence on the transparent conductive substrate, or a hole transport layer, a quasi-two-dimensional perovskite passivation layer, a perovskite active layer, a tin dioxide electron transport layer and a metal electrode arranged in sequence on the transparent conductive substrate; wherein the perovskite active layer is a uniformly oriented quasi-single-crystalline perovskite film prepared according to the above-mentioned preparation method, and the transparent conductive substrate is a glass substrate coated with fluorine-doped tin oxide (FTO) or indium-doped tin oxide (ITO).

[0014] As a further preferred technical solution of the present invention, the quasi-two-dimensional perovskite passivation layer is obtained by coating an isopropanol solution of an aromatic and alkylamine salt into a film, wherein the chemical structural formula of the aromatic and alkylamine salt is AX, where A is one of phenylethylamine, amphetamine, phenbutylamine, n-hexylamine, and n-octylamine cations, and X is I - Br - 、Cl - One of them.

[0015] Compared with the prior art, the present invention can achieve the following beneficial effects:

[0016] In this two-step perovskite film preparation process, the present invention introduces solvent additives with varying coordination abilities to reduce the reactivity of the lead iodide precursor, effectively slowing the kinetics of the perovskite formation reaction and promoting a full reaction between the organic amine salt and the lead iodide intermediate phase. This method effectively slows the reaction rate of the two-step process and enables the orientation control of the perovskite polycrystalline film, successfully producing uniformly oriented quasi-single-crystalline perovskite films (hereinafter referred to as perovskite films), significantly enhancing interfacial carrier transport and extraction. Single-junction, small-area perovskite solar cells prepared using this method have a certified photoelectric conversion efficiency exceeding 26.8%. Furthermore, the operational stability of the packaged device at 85°C and 50% relative humidity is significantly improved.

[0017] The two-step perovskite film preparation process of the present invention effectively solves the problems of residual lead iodide impurities and poor crystallization quality in perovskite films produced by the traditional two-step method. By introducing a solvent additive, not only can the crystallization quality of the final film be improved, but the solvent additive can also be completely volatilized during the annealing process, avoiding the introduction of other impurities. This provides an innovative solution for the controllable preparation of pure, quasi-single-crystalline perovskite films with uniform orientation. The perovskite films prepared using this method have been successfully applied to high-performance, high-stability perovskite solar cells, significantly improving the device's fill factor while exhibiting excellent operational stability under harsh conditions (such as high temperature and high humidity environments). BRIEF DESCRIPTION OF THE DRAWINGS

[0018] The present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0019] Figure 1 3 are the morphologies of the perovskite films of the control example and examples 1 to 3.

[0020] Figure 2 Wide-angle X-ray scattering of the perovskite films of the comparative example and examples 1 to 3 at slightly incident angles.

[0021] Figure 3 The reverse sweep current-voltage curves and device parameters of the battery devices of the comparative example and examples 1 to 3 are shown.

[0022] Figure 4 The steady-state efficiency output of the battery devices of the control example and examples 1 to 3 at 85° C. and 50% relative humidity.

[0023] Figure 5 The figures are efficiency statistics of a series of devices prepared by changing the ratio of solvent additives according to the control example and Example 3.

[0024] The purpose, features and advantages of the present invention will be further described with reference to the accompanying drawings and in conjunction with the embodiments. DETAILED DESCRIPTION

[0025] The following describes the specific embodiments of the present invention in detail with reference to the accompanying drawings. It should be understood that the specific embodiments described herein are only used to illustrate and explain the present invention and are not intended to limit the present invention.

[0026] Unless otherwise defined, the technical terms used in the following examples have the same meanings as commonly understood by those skilled in the art to which this invention belongs. The experimental reagents used in the following examples, unless otherwise specified, are conventional biochemical reagents; the experimental methods described, unless otherwise specified, are conventional methods.

[0027] Example 1:

[0028] The preparation method of the perovskite solar cell provided in this embodiment is as follows:

[0029] Step 1: Cleaning the transparent conductive substrate:

[0030] The glass substrate coated with fluorine-doped tin oxide (FTO) was ultrasonically cleaned with glass cleaner, deionized water and ethanol for 15 minutes respectively; then plasma cleaning was performed for 10 minutes and set aside.

[0031] Step 2: Preparation of tin dioxide electron transport layer:

[0032] The tin dioxide nanoparticle colloidal solution is deposited on a transparent conductive substrate by a spin coating method, or the tin dioxide electron transport layer is prepared by a chemical bath deposition method.

[0033] Step 3: Preparation of active layer (perovskite film) based on a two-step method:

[0034] First, solution preparation:

[0035] 1.5 mmol of lead iodide (PbI2) and 0.05 mmol of cesium iodide (CsI) were uniformly dissolved in an organic mixed solvent of 90 μL of N,N-dimethylpropylene urea and 910 μL of N,N-dimethylformamide, and heated and stirred until fully dissolved to obtain a lead iodide solution;

[0036] Dissolve 0.5 mmol formamidine iodide (FAI) and 0.2 mmol methylammonium chloride (MACl) in 1 mL of isopropanol and stir until fully dissolved to obtain an organic amine salt solution.

[0037] Then, the perovskite film was prepared in two steps:

[0038] (1) The substrate obtained in step 2 was transferred to the inside of the glove box, 20 μL of lead iodide solution was pipetted onto the substrate, and the solution was spin-coated at an acceleration of 2000 rpm / s and a rotation speed of 2000 rpm for 30 s. After the spin coating process was stopped, the wet film was transferred to a 70 °C hot plate for annealing for 40 s to obtain a lead iodide film.

[0039] (2) The lead iodide film was cooled to room temperature, and 100 μL of organic amine salt solution was transferred onto the lead iodide film. The film was then spin-coated at an acceleration of 2000 rpm / s and a rotation speed of 2000 rpm for 30 s. After the spin coating process was stopped, the film was quickly transferred to an air environment with a relative humidity of ~35% and annealed on a hot plate at 150 °C for 10 min.

[0040] Step 4: Preparation of quasi-two-dimensional perovskite passivation layer:

[0041] Pipette 100 μL of 10 mM phenbutamine hydrobromide in isopropanol onto the active layer prepared in step 3 and spin coat at 4000 rpm / s for 30 s.

[0042] Step 5: Preparation of hole transport layer:

[0043] (1) Dissolve 72.3 mg of 2,2',7,7'-tetrakis[N,N-di(4-methoxyphenyl)amino]-9,9'-spirobifluorene (Spiro-OMeTAD) in 1 mL of chlorobenzene; add 30 μL of tetra-tert-butylpyridine (tBP) and 36 μL of 260 mg / mL lithium bis(trifluoromethylsulfonyl)imide (LiTFSI) in acetonitrile to prepare a mixed solution;

[0044] (2) Pipette 30 μL of the mixed solution and spin the gel at 4000 rpm / s for 30 s.

[0045] Step 6: Metal electrode deposition:

[0046] Vacuum evaporation method was used to deposit 5×10 -4 Under a vacuum degree of Pa, a gold electrode with a thickness of 80 nm was evaporated at a rate of 2 Å / s, and the preparation of the perovskite solar cell device was finally completed.

[0047] Example 2:

[0048] The only difference from Example 1 is that the solvent additive used to prepare the lead iodide solution is different, that is, 90 μL of N,N-dimethylpropylene urea in Example 1 is replaced with 100 μL of methyl phenyl sulfoxide, and then mixed with 900 μL of N,N-dimethylformamide to obtain 1 mL of organic mixed solvent.

[0049] Example 3:

[0050] The only difference from Example 1 is that the solvent additive used to prepare the lead iodide solution is different, that is, 90 μL of N,N-dimethylpropylene urea in Example 1 is replaced by 80 μL of ethanesulfenylethane, and mixed with 920 μL of N,N-dimethylformamide to obtain 1 mL of organic mixed solvent.

[0051] Comparative Example:

[0052] As a control experiment for the above three groups of examples, the only difference from Example 1 is that the solvent additive used to prepare the lead iodide solution is different, that is, 90 μL of N,N-dimethylpropylene in Example 1 is replaced with 60 μL of dimethyl sulfoxide, and mixed with 940 μL of N,N-dimethylformamide to obtain 1 mL of mixed solvent.

[0053] The perovskite films prepared in Examples 1 to 3 and the comparative example were characterized as follows:

[0054] Scanning electron microscopy (SEM) film morphology Figure 1 As shown in the figure, the perovskite grain size of the control example is small and the crystal quality is poor. The lead iodide particles of Example 1 are significantly reduced compared with the control example, and the grain size of Example 2 is further improved compared with Example 1. The average grain size of Example 3 is about 1.5 μm and is uniform, which shows the best effect.

[0055] Wide-angle X-ray scattering of thin films at slight incidence Figure 2 As shown in the figure, it can be seen that the film of the control example clearly has a lead iodide diffraction peak (q = 0.9 Å -1 ), and the perovskite polycrystalline film has no obvious orientation; in Example 1, the lead iodide diffraction peak intensity decreases, and the (100) diffraction peak (q = 1.0 Å -1 ) intensity is improved, which proves that the crystallinity of the film is improved; in Example 2, the lead iodide diffraction peak disappears completely, and the perovskite (100) diffraction peak shows a dominant orientation; in Example 3, the lead iodide diffraction peak disappears completely, and the film has a uniform orientation.

[0056] The photoelectric conversion efficiency and stability of the perovskite solar cell devices prepared in Examples 1 to 3 and the comparative example were tested as follows:

[0057] Under AM1.5G sunlight, the test mask area is 0.064 cm 2 , test device forward and reverse sweep current-voltage characteristic curve ( Figure 3 ), and test the device operation stability in an environmental chamber with 50% relative humidity and 85°C ( Figure 4 ). Comparison shows that compared with the control example, the device fill factor of Example 1 is significantly improved, and the device stability is also improved; the device fill factor of Example 2 is further improved, and the device efficiency attenuation is reduced to 5% after 1000 hours of aging test at 85°C and 50% humidity; Example 3 wins the championship with a device efficiency of 27.05%, and after 1000 hours of aging test at 85°C and 50% humidity, the device efficiency does not show significant attenuation.

[0058] In order to further demonstrate the beneficial technical effects of the present invention, based on the technical solution of Example 3, the amount ratio of the solvent additive (ethylsulfinylethane) used to prepare the lead iodide solution was changed, and the photoelectric conversion efficiency of the finally prepared series of perovskite solar cell devices was tested. The specific parameters and test results are shown in Table 1 and Figure 5 shown.

[0059] Table 1

[0060]

[0061] Analysis of the data in Table 1 shows that the amount of solvent additive (ethanesulfenylethane) is less than 1.3 times that of lead iodide, significantly improving the photovoltaic performance of battery devices. This effectively addresses the issues of residual lead iodide impurities and poor crystal quality in perovskite films, which affect battery performance in the traditional two-step process. Extensive experiments have determined a molar ratio of solvent additive to lead iodide of 0.3-1.3:1, with a molar ratio of 0.5:1 achieving optimal results.

[0062] Although specific embodiments of the present invention are described above, those skilled in the art should understand that these are merely examples and that various changes or modifications may be made to the embodiments without departing from the principles and essence of the present invention. The scope of protection of the present invention is limited only by the appended claims.

Claims

1. A method for preparing a uniformly oriented quasi-single-crystalline perovskite film, characterized in that: It consists of the following steps: S1. Using methyl phenyl sulfoxide as a solvent additive, mixing the solvent additive with N,N-dimethylformamide to prepare an organic mixed solvent, dissolving lead iodide and cesium iodide and / or rubidium chloride in the organic mixed solvent to obtain a lead iodide solution, wherein the molar ratio of the solvent additive to the lead iodide is 0.3-1.3:1; A coating film-forming method is adopted, wherein the lead iodide solution is coated and then subjected to a heating treatment to obtain a lead iodide film; S2, dissolving at least one of formamidine iodide, methylammonium chloride, and methylammonium iodide in isopropyl alcohol solvent to obtain an organic amine salt solution; depositing the organic amine salt solution on the lead iodide film, and then annealing at 135-150° C. to obtain a uniformly oriented quasi-single-crystalline perovskite film; In step S1, the heating treatment temperature is 50-75° C., and the heating treatment time is 0.5-2 min.

2. The method for preparing a uniformly oriented quasi-single-crystalline perovskite thin film according to claim 1, wherein: In step S2, the annealing treatment time is 5-20 min.

3. The method for preparing a uniformly oriented quasi-single-crystalline perovskite thin film according to claim 1, wherein: The dosage of each component in the lead iodide solution is: 1 mL of organic mixed solvent, 1.5 mmol of lead iodide, 0.05 mmol of cesium iodide or 0.05 mmol of rubidium chloride.

4. A uniformly oriented quasi-single-crystalline perovskite film, characterized in that: The method according to any one of claims 1 to 3 is used for preparation.

5. Use of the uniformly oriented quasi-single-crystalline perovskite film according to claim 4 in perovskite solar cells.

6. The use according to claim 5, characterized in that The perovskite solar cell includes a transparent conductive substrate, and a tin dioxide electron transport layer, a perovskite active layer, a quasi-two-dimensional perovskite passivation layer, a hole transport layer and a metal electrode arranged in sequence on the transparent conductive substrate, or a hole transport layer, a quasi-two-dimensional perovskite passivation layer, a perovskite active layer, a tin dioxide electron transport layer and a metal electrode arranged in sequence on the transparent conductive substrate, wherein the perovskite active layer is a uniformly oriented quasi-single crystal perovskite film.

7. The use according to claim 6, characterized in that The quasi-two-dimensional perovskite passivation layer is obtained by coating an isopropyl alcohol solution of aromatic and alkylamine salts, wherein the chemical structure of the aromatic and alkylamine salts is AX, wherein A is one of phenylethylamine, amphetamine, phenbutylamine, n-hexylamine, and n-octylamine cations, and X is I - Br - 、Cl - One of them.

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