Method for preparing perovskite solar cell based on fused salt doped Spiro-OMeTAD hole transport layer

Abstract

The invention discloses a method for preparing a perovskite solar cell based on a fused salt doped Spiro-OMeTAD hole transport layer, and the method comprises the steps: dissolving lead iodide and formamidine iodide in a mixed solvent of N, N-dimethylformamide and dimethyl sulfoxide according to a molar ratio of (0.8-1.5): 1 to prepare an FAPbI3 perovskite precursor solution; the method comprises the following steps: mixing cyclohexylamine trifluoroacetic acid and 4-tert-butylpyridine according to a molar ratio of 1: (8-14), dissolving the mixture in a 70-110 mg / mL Spiro-OMeTAD chlorobenzene solution, adding an acetonitrile solution of LiTFSi, and stirring at normal temperature to obtain a hole transport material Spiro-OMeTAD solution; spin-coating the FTO substrate with an electron transport layer material, spin-coating the electron transport layer with the FAPbI3 perovskite precursor solution, and annealing to form a perovskite thin film; the method comprises the following steps: spin-coating an ammonium butyrate iodide solution on a perovskite thin film to obtain an interface modification layer, spin-coating a hole transport material Spiro-OMeTAD solution on the interface modification layer to obtain a cyclohexylamine trifluoroacetic acid doped Spiro-OMeTAD hole transport layer, and evaporating an interface modification layer and a metal electrode on the Spiro-OMeTAD hole transport layer.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of photoelectricity, and particularly relates to a method for preparing a perovskite solar cell based on doping of a Spiro-OMeTAD hole transport layer by using a molten salt. BACKGROUND

[0002] With the continuous development of society, the environmental problems caused by traditional fossil energy have attracted more and more attention, and the development of clean energy is imminent. With the increasing demand of human beings for clean energy, solar power generation has been paid more and more attention. At present, the mainstream solar power generation device on the market is mainly a silicon-based solar cell, but the expensive raw materials have become a bottleneck for its development, which greatly limits the industrialized production of the silicon-based solar cell.

[0003] The perovskite solar cell has the characteristics of simple manufacturing and low cost, and since 2009, its photoelectric conversion efficiency has rapidly increased from 3.8% to 26.1%. Although Spiro-OMeTAD has become the most commonly used hole transport material in the perovskite solar cell and has shown good performance. However, in order to promote the commercial application of the perovskite solar cell, the device stability and service life need to be further improved. In the structure of the formal perovskite solar cell, the position of the hole transport material layer is above the perovskite thin film, which can effectively physically isolate the perovskite active layer and the external environment (air moisture, etc.), and is one of the most critical parts of determining the stability of the perovskite solar cell.

[0004] At present, the research on Spiro-OMeTAD mainly focuses on improving the stability and hydrophobicity, and the research on ionic liquids is relatively less. Moreover, the currently used dopant components contain hygroscopic lithium salt and movable ions Li + , which seriously affects the stability of the solar cell device. SUMMARY

[0005] The embodiment of the application provides a method for preparing a perovskite solar cell based on doping of a Spiro-OMeTAD hole transport layer by using a molten salt, which comprises the following steps:

[0006] Lead iodide and formamidinium iodide are dissolved in a mixed solvent of N,N-dimethylformamide and dimethyl sulfoxide to prepare a FAPbI3 perovskite precursor solution according to a molar ratio of (0.8-1.5):1;

[0007] Cyclohexylamine trifluoroacetate and 4-tert-butylpyridine are mixed according to a molar ratio of 1:(8-14) and then dissolved in a 70-110 mg / mL Spiro-OMeTAD chlorobenzene solution, and a LiTFSi acetonitrile solution is added, and the mixture is stirred at room temperature to obtain a hole transport material Spiro-OMeTAD solution;

[0008] Electron transport layer material was spin-coated onto an FTO substrate, and FAPbI3 perovskite precursor solution was spin-coated onto the electron transport layer. The mixture was then annealed to form a perovskite thin film.

[0009] An interface modification layer was obtained by spin-coating a butylammonium iodide solution onto a perovskite thin film, and a hole transport material Spiro-OMeTAD solution was then spin-coated onto the interface modification layer to obtain a cyclohexylamine trifluoroacetic acid-doped Spiro-OMeTAD hole transport layer. Finally, an interface modification layer and a metal electrode were deposited on the Spiro-OMeTAD hole transport layer by vapor deposition.

[0010] The volume ratio of N,N-dimethylformamide to dimethyl sulfoxide is (7-12):1, preferably 9:1. Specifically, N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) are prepared as a solvent at a volume ratio of 9:1; lead iodide and formamidinium iodide are added to the solvent at a molar ratio of 1.1:1 to obtain a concentration of 800-1000 mg / mL, and the solution is stirred and dissolved at a temperature below 5°C for 3-6 hours.

[0011] The concentration of the FAPbI3 perovskite precursor solution was 800-1000 mg / mL. The molar ratio of cyclohexylamine trifluoroacetic acid and 4-tert-butylpyridine was 1:(10-12). Cyclohexylamine trifluoroacetic acid was prepared by stirring cyclohexylamine and trifluoroacetic acid at a low temperature of -16°C for 2 hours.

[0012] Preferably, the concentration of the Spiro-OMeTAD chlorobenzene solution is 85-90 mg / mL. The concentration of the LiTFSi acetonitrile solution is 40-150 mg / mL. This invention employs a spin-coating and annealing method in an N2 atmosphere, specifically: the substrate temperature is set to 50-100℃, the spin-coating conditions are 1200-1500 r / min, and after spin-coating for 10-15 seconds, spin-coating is performed for 30-40 seconds at 4000-5000 r / min, while simultaneously adding diethyl ether as an anti-solvent. After spin-coating, annealing is performed at 100-150℃ for 10-20 minutes.

[0013] Furthermore, it also includes: the electron transport layer is SnO2, and after spin-coating SnO2, it is annealed at 120-180℃ for 20-50 min. Specifically, the spin-coating conditions are 4000-5000 r / min, spin-coating for 30-40 s, and after spin-coating, annealing at 130-150℃ for 30-40 min.

[0014] Specifically, after spin-coating the FAPbI3 perovskite precursor solution, a stable perovskite film is obtained by gradient annealing at 150-170℃ for 5-10 min, wherein the annealing cooling rate is 80-100℃ / min.

[0015] Specifically, the interface modification layer on the perovskite film is ammonium iodide. Specifically, butylamine iodide is dissolved in isopropanol to prepare a concentration of 3-5 mg / ml, and stirred at room temperature for 2-5 hours at a speed of 200-400 rpm. The solution is then spin-coated onto the perovskite film at a speed of 4000-5000 rpm for 20-30 seconds.

[0016] Specifically, the interface modification layer on the Spiro-OMeTAD transport layer is MoO3, and the metal electrode is Ag. MoO3 is deposited on the hole transport layer with a thickness of 2-10 nm, preferably 5 nm; the thickness of the Ag metal electrode is 50-150 nm, preferably 100 nm.

[0017] The Spiro-OMeTAD hole transport layer film prepared by this invention, by introducing cyclohexylamine trifluoroacetic acid molten salt as a dopant, significantly improves its stability and carrier mobility, resulting in a FAPbI3 perovskite solar cell with excellent energy conversion efficiency, which is beneficial for its industrialization. Furthermore, compared to traditional methods that only dope with lithium salt and TBP, the use of cyclohexylamine trifluoroacetic acid molten salt and the modulation of molecular stacking between Spiro-OMeTAD significantly enhance the interaction between cyclohexylamine trifluoroacetic acid and Spiro-OMeTAD, greatly improving the hole mobility of the Spiro-OMeTAD hole transport layer and further enhancing device performance. Attached Figure Description

[0018] To more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying 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.

[0019] Figure 1 This is a structural diagram of the FAPbI3 perovskite solar cell device prepared according to the present invention;

[0020] Figure 2 This is a SEM image of the cyclohexylamine trifluoroacetic acid-doped Spiro-OMeTAD hole transport layer film prepared in Example 1 of this invention;

[0021] Figure 3 This is a SEM image of the Spiro-OMeTAD hole transport layer film prepared in comparison.

[0022] Figure 4 These are the JV curves of the solar cells prepared in Examples 1-3 and the comparative examples of the present invention. Detailed Implementation

[0023] To enable those skilled in the art to better understand the present invention, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings.

[0024] Example 1

[0025] 1. The etched FTO conductive glass was sequentially ultrasonicated for 15 minutes each in ethanol, ultrapure water with cleaning agent, ultrapure water, and ethanol. After drying with nitrogen, it was placed in a 100°C oven for 30 minutes to obtain a clean FTO substrate.

[0026] 2. Mix lead iodide and formamidinium iodide in a molar ratio of 1.1:1 and dissolve them in a mixed solvent of N,N-dimethylformamide (DMF) and dimethyl sulfoxide (DMSO) (DMF to DMSO volume ratio 9:1) to prepare a FAPbI3 perovskite precursor solution. Stir and dissolve the solution at 5°C for 3-6 hours.

[0027] 3. Mix cyclohexylamine trifluoroacetic acid and 4-tert-butylpyridine at a molar ratio of 1:10 and dissolve them in a chlorobenzene solution of 90 mg / mL Spiro-OMeTAD. Then add a acetonitrile solution of 520 mg / mL LiTFSi and stir at room temperature for 1 hour to prepare a hole transport material Spiro-OMeTAD solution.

[0028] 4. Dissolve 5 mg of ammonium iodide in 1 mL of isopropanol solution, and stir the solution at room temperature at 300 rpm for 5 hours to obtain perovskite thin film interface modification material.

[0029] 5. Treat the FTO substrate with ultraviolet ozone for 15 minutes, drop 45 μL of electron transport material SnO2 onto the FTO substrate, spin coat it into a film using a spin coater at a speed of 4000 r / min for 30 s, and then anneal it at 150℃ for 30 minutes to obtain the electron transport layer.

[0030] 6. Place the FTO conductive substrate with the electron transport layer spin-coated onto a hot spin coater at a substrate temperature of 100°C and preheat for 5 minutes. Spin-coat the FAPbI3 titanium dioxide precursor solution onto the electron transport layer in an N2 atmosphere, using diethyl ether as a desolvent. After gradient annealing at 150°C for 10 minutes, a smooth and dense perovskite film is obtained.

[0031] 7. The interface modification material, ammonium iodide, is spin-coated onto the perovskite thin film at a speed of 3000 rpm for 30 seconds to form an ammonium iodide interface modification layer. Spiro-OMeTAD solution is then spin-coated onto the interface modification layer at the same speed of 3000 rpm for 30 seconds to form a hole transport layer. Using vacuum evaporation, 5 nm of MoO3 is deposited on the hole transport layer, followed by the deposition of a 100 nm Ag metal electrode to obtain the perovskite solar cell.

[0032] For the fabrication methods of perovskite solar cells in Examples 2-3 and the comparative examples below, please refer to Example 1.

[0033] Table 1. Molar ratio of cyclohexylamine trifluoroacetic acid and 4-tert-butylpyridine in the examples and comparative examples

[0034] Example 1 1:10 Example 2 1:11 Example 3 1:12 Comparative Example Undoped

[0035] like Figure 1 The diagram shown is a structural diagram of the perovskite solar cell prepared in Example 1. Figure 2 and Figure 3 The images show surface test patterns of the hole transport layer films prepared in Example 1 and the comparative example, respectively. Figure 2 and Figure 3 It can be seen that the hole transport layer film prepared in Example 1 has a dense, flat surface without defects, and Example 1 is significantly better than the comparative example.

[0036] The solar cells prepared in Examples 1-3 were tested under standard test conditions (AM1.5 G illumination), as shown in Table 2. Figure 4 (control is a comparative example, 1, 2, 3 are examples 1, 2, 3), where the optimal ratio is 1:11 (example 2). The energy conversion efficiency of this battery device is 24.29%, the open-circuit voltage is 1.18V, and the short-circuit current is 25.75mA / cm. 2 The fill factor is 79.93%, while the comparative power conversion efficiency is 21.94%, the open-circuit voltage is 1.10V, and the short-circuit current is 25.30mA / cm. 2 The fill factor is 78.61%. It can be seen that Example 1 is significantly better than the comparative example.

[0037] Table 2 Performance comparison between Spiro-OMeTAD devices with different doping ratios and undoped devices

[0038]

[0039]

[0040] Obviously, the above embodiments are merely illustrative examples for clear explanation and are not intended to limit the implementation. Those skilled in the art will recognize that other variations or modifications can be made based on the above description. It is neither necessary nor possible to exhaustively list all possible implementations here. However, obvious variations or modifications derived therefrom are still within the scope of protection of this invention.

[0041] The above description is only a partial embodiment of the present invention. It should be noted that for those skilled in the art, several improvements and modifications can be made without departing from the principle of the present invention, and these improvements and modifications should also be considered within the scope of protection of the present invention.

Claims

1. A method for fabricating perovskite solar cells based on a molten salt-doped Spiro-OMeTAD hole transport layer, characterized in that, include: A FAPbI3 perovskite precursor solution was prepared by dissolving lead iodide and formamidinium iodide in a molar ratio of (0.8–1.5):1 in a mixed solvent of N,N-dimethylformamide and dimethyl sulfoxide. Cyclohexylamine trifluoroacetic acid and 4-tert-butylpyridine were mixed at a molar ratio of 1:(8-14) and dissolved in a chlorobenzene solution of 70-110 mg / mL Spiro-OMeTAD. An acetonitrile solution of LiTFSi was added and stirred at room temperature to obtain a hole transport material Spiro-OMeTAD solution. Electron transport layer material was spin-coated onto an FTO substrate, and FAPbI3 perovskite precursor solution was spin-coated onto the electron transport layer. The mixture was then annealed to form a perovskite thin film. An interface modification layer was obtained by spin-coating a butylammonium iodide solution onto a perovskite thin film, and a hole transport material Spiro-OMeTAD solution was then spin-coated onto the interface modification layer to obtain a cyclohexylamine trifluoroacetic acid-doped Spiro-OMeTAD hole transport layer. Finally, an interface modification layer and a metal electrode were deposited on the Spiro-OMeTAD hole transport layer by vapor deposition.

2. The method according to claim 1, characterized in that, The volume ratio of N,N-dimethylformamide to dimethyl sulfoxide is (7-12):

1.

3. The method according to claim 1, characterized in that, The concentration of the FAPbI3 perovskite precursor solution is 800-1000 mg / mL.

4. The method according to claim 1, characterized in that, The molar ratio of cyclohexylamine trifluoroacetic acid to 4-tert-butylpyridine is 1:(10-12).

5. The method according to claim 1, characterized in that, The concentration of Spiro-OMeTAD chlorobenzene solution is 85-90 mg / mL.

6. The method according to claim 1, characterized in that, The concentration of the acetonitrile solution of LiTFSi is 40-150 mg / mL.

7. The method according to claim 1, characterized in that, Also includes: The electron transport layer is SnO2. After spin-coating SnO2, it is annealed at 120-180℃ for 20-50 min.

8. The method according to claim 1, characterized in that, After spin-coating with FAPbI3 perovskite precursor solution, a stable perovskite film was obtained by gradient annealing at 150-170℃ for 5-10 min. The annealing cooling rate was 100℃ / min.

9. The method according to claim 1, characterized in that, The interface modification layer on the perovskite film is ammonium iodide.

10. The method according to claim 1, characterized in that, The interface modification layer on the Spiro-OMeTAD transport layer is MoO3, and the metal electrode is Ag.

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