Methylamine-free perovskite thin film with high thermal stability and preparation method thereof

Abstract

The invention discloses a methylamine-free perovskite thin film with high thermal stability and a preparation method of the methylamine-free perovskite thin film. The perovskite thin film is prepared from an FAPbI3 perovskite precursor solution doped with 2-(methylsulfonyl) ethylamine hydrochloride. A proper amount of 2-(methylsulfonyl) ethylamine hydrochloride is added into the perovskite precursor solution, the compact and uniform FAPbI3 perovskite thin film with photovoltaic activity is obtained under the condition that methylamine ions are not introduced, the thin film has excellent thermal stability, the service life of a perovskite solar cell can be prolonged, and the service life of the perovskite solar cell is prolonged. And the positive significance is realized on the commercialized application of the perovskite battery.

Description

Technical Field

[0001] This invention belongs to the field of semiconductor device technology, specifically relating to a thermally stable methylamine-free perovskite thin film and its preparation method. Background Technology

[0002] Solar energy technology is currently undergoing a structural upgrade centered on perovskite materials. Breakthroughs in efficiency improvement, large-scale production, and expanded application scenarios are posing a systemic challenge to monocrystalline silicon technology. However, the long-term stability of perovskite solar cells is still inferior to that of traditional crystalline silicon cells, limiting their commercial application and promotion.

[0003] Formamidinium lead iodide (FAPbI3) perovskite films are a typical high-performance perovskite film. The photovoltaic active phase (α phase) of FAPbI3 perovskite films is thermodynamically unstable at room temperature and spontaneously transforms into the non-photovoltaic active phase (δ phase), thus losing its photoelectric conversion performance. This kinetic process is influenced by the defect density in the film; the more defects, the faster and easier the phase transition occurs. A common approach is to introduce formamidinium cations (FA) with a higher ionic radius than the perovskite composition into the film. + Smaller methylamine cations (MA) + Doping with methylamine ions can reduce the tolerance factor (τ) of the structure, thereby stabilizing the photovoltaic active phase at room temperature. However, methylamine ions have poor stability and are prone to decomposition above 150°C, forming methylamine and volatilizing, leading to film degradation. Furthermore, methylamine ion doping increases the band gap of perovskite materials, reducing spectral absorption and hindering high efficiency. Therefore, a methylamine-free perovskite film is being prepared... + Highly thermally stable FAPbI3 perovskite films are of great significance for improving the lifespan of perovskite solar cells.

[0004] This invention introduces 2-(methanesulfonyl)ethylamine hydrochloride (AEMSCl, CAS: 104458-24-4) into FAPbI3 perovskite films, achieving the desired effect without introducing any MA. + Under these conditions, high-quality perovskite thin films can be obtained, which exhibit better thermal stability and are beneficial to narrowing the lifespan gap between perovskite solar cells and crystalline silicon solar cells. Summary of the Invention

[0005] The technical problem to be solved by the present invention is to address the above-mentioned deficiencies in the prior art by providing a methylamine-free perovskite thin film with high thermal stability and its preparation method. The perovskite thin film has few surface defects and high thermal stability.

[0006] The first aspect of the present invention provides a thermally stable non-methylamine perovskite thin film, which is prepared from a FAPbI3 perovskite precursor solution doped with 2-(methylsulfonyl)ethylamine hydrochloride.

[0007] According to the above scheme, the thermally stable non-methylamine perovskite film has an α phase, a dense and smooth surface, and a grain size of 500 nm to 2 μm.

[0008] According to the above scheme, the thickness of the thermally stable non-methylamine perovskite film is 500~800nm.

[0009] The second aspect of the present invention provides a method for preparing the above-mentioned thermally stable methylamine-free perovskite thin film: 2-(methylsulfonyl)ethylamine hydrochloride is added to the FAPbI3 perovskite precursor solution, and the thermally stable methylamine-free perovskite thin film is prepared using the process conditions for preparing FAPbI3 thin films.

[0010] According to the above plan, the specific steps are as follows: 1) Lead iodide (PbI2), formamidine hydroiodide (FAI) and 2-(methanesulfonyl)ethylamine hydrochloride were dissolved in a mixed solvent to obtain a perovskite precursor solution containing 2-(methanesulfonyl)ethylamine hydrochloride; 2) The perovskite precursor solution containing 2-(methylsulfonyl)ethylamine hydrochloride obtained in step 1) is coated onto the substrate and then annealed to obtain a methylamine-free perovskite film with high thermal stability.

[0011] According to the above scheme, the molar ratio of lead iodide to formamidin hydroiodate in step 1) is 1~1.1:1.

[0012] According to the above scheme, the amount of 2-(methylsulfonyl)ethylamine hydrochloride added in step 1) is 5 to 20 mol of the molar amount of formamidin hydroiodide.

[0013] According to the above scheme, the mixed solvent in step 1) is a mixture of 1,3-dimethyl-2-imidazolinone and 2-methoxyethanol in a volume ratio of 1:6 or a mixture of 1,3-dimethyl-2-imidazolinone and N,N-dimethylformamide (DMF) in a volume ratio of 1:5.

[0014] According to the above scheme, the concentration of formamidinium hydroiodate in the perovskite precursor solution containing 2-(methylsulfonyl)ethylamine hydrochloride in step 1) is 1~2 mol / L.

[0015] According to the above scheme, step 2) is a spin coating method, with a spin coating speed of 3000~5000 rpm, a spin coating time of 30~60 seconds, and a spin coating thickness of 600~800 nm.

[0016] According to the above scheme, the substrate in step 2) is an FTO or ITO substrate with an electron transport layer or a hole transport layer.

[0017] According to the above scheme, the electron transport layer is one of tin oxide film, titanium oxide film, and zinc oxide film, and the hole evoked layer is one of [4-(7H-dibenzo[c,g]carbazole-7-yl)butyl]phosphoric acid, [2-(3,6-dimethyl-9H-carbazole-9-yl)ethyl]phosphonic acid, and (4-(3,6-dimethyl-9H-carbazole-9-yl)butyl)phosphonic acid.

[0018] According to the above scheme, the annealing process conditions for step 2) are as follows: under the protection of an inert atmosphere, first heat at 80~120℃ for 5~20 minutes, then raise the temperature to 150℃ and heat for 10~20 minutes.

[0019] A third aspect of the present invention provides a perovskite solar cell containing a methylamine-free perovskite thin film with high thermal stability as described above.

[0020] According to the above scheme, the structure of the perovskite solar cell, from top to bottom, is a transparent conductive substrate, an electron transport layer, a perovskite layer, a hole transport layer, and a metal electrode; or a transparent conductive substrate, a hole transport layer, a perovskite layer, an electron transport layer, a buffer layer, and a metal electrode; the perovskite layer is the above-mentioned thermally stable methylamine-free perovskite thin film.

[0021] The beneficial effects of this invention are as follows: 1. By adding an appropriate amount of 2-(methanesulfonyl)ethylamine hydrochloride to the perovskite precursor solution, a dense, uniform, and photovoltaic-active FAPbI3 perovskite film is obtained without introducing methylamine ions. This film exhibits excellent thermal stability, which can improve the lifespan of perovskite solar cells and has positive significance for promoting the commercial application of perovskite solar cells. 2. The preparation method of this invention is simple, requires no additional steps, and is easy to industrialize. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the process for preparing FAPbI3 perovskite thin films in Example 1 of the present invention; Figure 2 Scanning electron microscope images of the perovskite films prepared in Example 1, Comparative Example 1, and Comparative Example 2; Figure 3 Comparison of X-ray diffraction patterns of the perovskite films prepared in Example 1 and Comparative Example 1; Figure 4 The perovskite solar cells prepared in Example 1 and Comparative Example 1 JV curve; Figure 5The X-ray diffraction comparison images of the perovskite thin films prepared in Example 1 and Comparative Example 2 before and after heating are shown. Figure 6 The perovskite solar cells prepared in Example 1 and Comparative Example 2 are before and after aging tests. JV curve. Detailed Implementation

[0023] To enable those skilled in the art to better understand the technical solution of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings.

[0024] Example 1 A thermally stable methylamine-free perovskite thin film is prepared by the following specific steps: 1) The ITO substrate (2.5cm×2.5cm) was ultrasonically cleaned with pure water, ethanol and isopropanol for 15 minutes in sequence, and then treated with ultraviolet ozone cleaning machine for 25 minutes. Then, an ethanol solution of (4-(3,6-dimethyl-9H-carbazole-9-yl)butylphosphonic acid (concentration of 1mg / mL) was spin-coated onto the ITO substrate and annealed at 100℃ for 5 minutes to obtain a substrate with a hole transport layer for later use. 2) Weigh 1 mmol of FAI and 1 mmol of lead iodide, add 5% of the molar amount of 2-(methanesulfonyl)ethylamine hydrochloride, add to a mixed solvent of 1,3-dimethyl-2-imidazolinone / 2-methoxyethanol (v:v=1:6), shake until completely dissolved to obtain a perovskite precursor solution with a FAI concentration of 1.4 mol / L. 3) Spin-coat the perovskite precursor solution obtained in step 2) onto the substrate obtained in step 1). The spin-coating speed is 4500 rpm and the spin-coating time is 45 seconds. Then, place it in a nitrogen glove box for annealing treatment. First, heat at 120°C for 10 minutes, and then heat at 150°C for 10 minutes to obtain FAPbI3 perovskite film. The thickness of the perovskite film is about 700 nm and the band gap is about 1.5 eV.

[0025] A schematic diagram of the process for preparing the FAPbI3 perovskite thin film in this embodiment is shown below. Figure 1 As shown. The surface morphology of the obtained FAPbI3 perovskite film is as follows. Figure 2 As shown in the left figure, without methylamine ion doping, the addition of 2-(methylsulfonyl)ethylamine hydrochloride yields a dense and smooth perovskite film, with most grains ranging from 1 to 2 μm in size. X-ray diffraction (XRD) results ( Figure 3 As shown, the perovskite thin film obtained in this embodiment has a crystalline phase that is photovoltaic active, which is an α phase.

[0026] In this embodiment, 25 nm C atoms were sequentially deposited on the surface of the FAPbI3 perovskite thin film.60 A pin-structured perovskite solar cell is obtained by using an electron transport layer, a 7nm copper bath (buffer layer), and a 100nm silver electrode.

[0027] The perovskite solar cell with a pin structure obtained in this embodiment JV Curves Figure 4 As shown, the reverse scanning efficiency reached 25.39%, and the forward scanning efficiency reached 25.11%, proving that the addition of 2-(methanesulfonyl)ethylamine hydrochloride to the FAPbI3 perovskite precursor solution in this embodiment prepared a high-quality FAPbI3 film with low defect density.

[0028] Comparative Example 1 A methylamine-free FAPbI3 thin film was prepared in a manner different from that of Example 1, except that 2-(methylsulfonyl)ethylamine hydrochloride was not added; the remaining steps were the same as in Example 1. A pin-structured perovskite solar cell was then fabricated using the same method as in Example 1.

[0029] The surface morphology of the perovskite thin film prepared in this comparative example is as follows: Figure 2 As shown in the figure, the perovskite film prepared in this comparative example has a rough surface, contains voids, and has a small grain size, with most not exceeding 1 μm. XRD results ( Figure 3 The results showed that the obtained perovskite film still contained the non-photovoltaic active δ-phase, and had not completely transformed into the photovoltaic active α-phase. Due to the presence of the non-photovoltaic phase and the poor morphology, the corresponding perovskite solar cell device had extremely low efficiency. Figure 4 ).

[0030] Comparative Example 2 A methylamine ion-doped perovskite thin film differs from the methylamine-free FAPbI3 thin film in Example 1 in that it incorporates methylamine hydrochloride. Methylamine hydrochloride is a commonly used perovskite additive used to assist crystallization and promote phase transitions. All other steps are the same as in Example 1. This comparative example is used to verify the difference in thermal stability compared to Example 1.

[0031] In this comparative example, the perovskite solution was prepared by weighing 1 mmol of FAI, 1 mmol of lead iodide, and 20% of the molar amount of FAI in methylamine hydrochloride, adding them to a mixed solvent of 1,3-dimethyl-2-imidazolinone / 2-methoxyethanol (v:v=1:6), shaking until completely dissolved to obtain a perovskite precursor solution with a FAI concentration of 1.4 M.

[0032] The surface morphology of the perovskite thin film prepared in this comparative example is as follows: Figure 2As shown on the right, the addition of methylamine hydrochloride makes the film denser, increases the grain size to about 1 μm, and fabricates a pin-structured perovskite solar cell using the same method as in Example 1.

[0033] The perovskite films of Example 1 and this comparative example were placed in a nitrogen atmosphere and heated at 150°C for 10 hours. The XRD patterns of the two films before and after heating were compared with those before heating. Figure 5 As shown, the addition of methylamine hydrochloride in Comparative Example 2 completely transformed the film into the α phase. However, after heating at 150°C for 10 hours, a strong lead iodide peak was generated in the film of Comparative Example 2. This is because the perovskite phase rich in methylamine ions degraded, the methylamine volatilized, and lead iodide remained in the film. In contrast, the perovskite film of Example 1, after heating at 150°C for 10 hours, only generated a very small amount of lead iodide, and its high-temperature thermal stability was significantly better than that of the perovskite film of Comparative Example 2.

[0034] The perovskite solar cells with pin structures prepared in Example 1 and this comparative example were subjected to aging tests, and were heated and aged at 85°C for 100 hours in a nitrogen glove box. The results before and after the aging tests for both types of cells are shown below. JV Curve Figure 6 After aging tests, the efficiency of the battery in Example 1 changed from 25.05% (reverse scan) and 24.36% (forward scan) to 24.70% (reverse scan) and 23.16% (forward scan), while the efficiency of the battery prepared in this comparative example decreased from 24.67% (reverse scan) and 24.54% (forward scan) to 18.17% (reverse scan) and 16.98% (forward scan). It is evident that the battery in Example 1 exhibits better thermal stability.

[0035] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.

Claims

1. A methylamine-free perovskite thin film with high thermal stability, characterized in that, It was prepared from a FAPbI3 perovskite precursor solution doped with 2-(methylsulfonyl)ethylamine hydrochloride.

2. The thermally stable non-methylamine perovskite thin film according to claim 1, characterized in that, The thermally stable non-methylamine perovskite film has an α phase, a dense and smooth surface, and a grain size of 500 nm to 2 μm.

3. The thermally stable non-methylamine perovskite thin film according to claim 1, characterized in that, The thermally stable non-methylamine perovskite film has a thickness of 500~800 nm.

4. A method for preparing a thermally stable, methylamine-free perovskite thin film according to any one of claims 1-3, characterized in that, 2-(methylsulfonyl)ethylamine hydrochloride was added to the FAPbI3 perovskite precursor solution, and a methylamine-free perovskite film with high thermal stability was prepared using the process conditions for preparing FAPbI3 films.

5. The method for preparing a thermally stable, methylamine-free perovskite thin film according to claim 4, characterized in that, The specific steps are as follows: 1) Dissolve lead iodide, formamidin hydroiodide and 2-(methanesulfonyl)ethylamine hydrochloride in a mixed solvent to obtain a perovskite precursor solution containing 2-(methanesulfonyl)ethylamine hydrochloride; 2) The perovskite precursor solution containing 2-(methylsulfonyl)ethylamine hydrochloride obtained in step 1) is coated onto the substrate and then annealed to obtain a methylamine-free perovskite film with high thermal stability.

6. The method for preparing a thermally stable, methylamine-free perovskite thin film according to claim 5, characterized in that, In step 1), the molar ratio of lead iodide to formamidinium hydroiodate is 1~1.1:1; in step 1), the amount of 2-(methanesulfonyl)ethylamine hydrochloride added is 5~20 mol% of the molar amount of formamidinium hydroiodate; in step 1), the mixed solvent is a mixture of 1,3-dimethyl-2-imidazolinone and 2-methoxyethanol at a volume ratio of 1:6 or a mixture of 1,3-dimethyl-2-imidazolinone and N,N-dimethylformamide at a volume ratio of 1:5; in step 1), the concentration of formamidinium hydroiodate in the perovskite precursor solution containing 2-(methanesulfonyl)ethylamine hydrochloride is 1~2 mol / L.

7. The method for preparing a thermally stable, methylamine-free perovskite thin film according to claim 5, characterized in that, Step 2) The coating method is spin coating, the spin coating speed is 3000~5000 rpm, the spin coating time is 30~60 seconds, and the spin coating thickness is 600~800 nm; Step 2) The substrate is an FTO or ITO substrate with an electron transport layer or a hole transport layer.

8. The method for preparing a thermally stable, methylamine-free perovskite thin film according to claim 7, characterized in that, The electron transport layer is one of tin oxide film, titanium oxide film, and zinc oxide film, and the hole evoked layer is one of [4-(7H-dibenzo[c,g]carbazole-7-yl)butyl]phosphoric acid, [2-(3,6-dimethyl-9H-carbazole-9-yl)ethyl]phosphonic acid, and (4-(3,6-dimethyl-9H-carbazole-9-yl)butyl)phosphonic acid.

9. The method for preparing a thermally stable, methylamine-free perovskite thin film according to claim 5, characterized in that, Step 2) Annealing process conditions are as follows: under inert atmosphere protection, first heat at 80~120℃ for 5~20 minutes, then heat to 150℃ for 10~20 minutes.

10. A perovskite solar cell comprising a methylamine-free perovskite thin film with high thermal stability as described in any one of claims 1-3.

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