A tin-lead perovskite solar cell without tin fluoride and its fabrication method

Abstract

This invention relates to a tin-lead perovskite solar cell without tin fluoride and its fabrication method. The perovskite layer of the tin-lead perovskite solar cell incorporates a surface passivating agent, which is one or more lead salts such as lead fluoride, lead bromide, lead chloride, and lead oxalate. Applying this surface passivation strategy to tin-lead perovskite solar cells avoids the dependence of high-efficiency tin-lead perovskite solar cells on tin fluoride additives, suppresses the perovskite deprotonation reaction caused by tin fluoride, and thus effectively improves the photothermal stability of the tin-lead perovskite solar cell.

Description

Technical Field

[0001] This invention relates to the field of tin-lead perovskite solar cell technology, and more particularly to high-quality tin-lead perovskite thin films without tin fluoride additives and their preparation methods. Background Technology

[0002] Tin-lead perovskite solar cells possess the highest theoretical efficiency for a single cell, but their poor photothermal stability currently limits their application prospects. Stannous fluoride (Sfluoride) is an indispensable component in high-efficiency SFDs, suppressing the formation of tetravalent tin and tin vacancies. However, under heating or illumination, Sfluoride undergoes a severe deprotonation reaction with the perovskite components, generating numerous formamidinium vacancy defects and unfavorable band bending. Simultaneously, the deprotonation product, hydrofluoric acid, is highly corrosive, significantly corroding both the ITO anode and the metal cathode. Therefore, if Sfluoride could be replaced to avoid the deprotonation reaction and corrosive product formation under photothermal conditions, while maintaining the thin film crystal quality and the formation of tetravalent tin / tin vacancies, the photothermal stability of SFDs could be significantly improved without reducing the photoelectric conversion efficiency. Summary of the Invention

[0003] Based on this, the purpose of this invention is to address the limitation of tin fluoride additives on photothermal stability in tin-lead perovskite, and to provide a tin fluoride-free, low-defect tin-lead perovskite solar cell and its preparation method. This method can suppress the generation of tetravalent tin and tin vacancies, and avoid deprotonation degradation reaction under photothermal conditions. When applied to perovskite cells, it can significantly improve their photothermal stability.

[0004] The specific technical solution for achieving the objective of this invention is as follows:

[0005] A method for fabricating a tin-lead perovskite solar cell without tin fluoride, the method comprising the following steps:

[0006] Step 1: Select a substrate, first use a cleaning agent to sonicate for 10-30 minutes to remove surface grease and organic matter, then sonicate with deionized water, acetone and isopropanol for 10-30 minutes each, blow dry with nitrogen, and then treat with ozone plasma for 15-30 minutes before use.

[0007] Step 2: On the treated substrate, a hole transport layer is deposited using a solution spin-coating method. The hole transport layer is a P3CT-Cs material layer, which is formed by spin-coating with a methanol solution of P3CT-Cs with a concentration of 0.2-1.0 mg / ml. The spin coater speed is 2000-5000 rpm, the time is 30-60 seconds, and the thickness is 5-10 nm.

[0008] Step 3: Prepare a tin-lead perovskite thin film layer on the hole transport layer, specifically as follows:

[0009] 3.1: Preparation of tin-lead perovskite precursor solution: Dissolve 1.20-1.30 mmol FAI, 0.30-0.45 mmol CsI, 0.75-0.90 mmol SnI2, 0.75-0.90 mmol PbI2 and 0.02-0.05 mmol GuaSCN in a mixed solvent of 600 μl N,N-dimethylimide and 200 μl dimethyl sulfoxide, add 20-60 mg of metallic lead powder, and stir overnight at room temperature;

[0010] 3.2: The tin-lead perovskite precursor solution was deposited on the P3CT-Cs hole transport layer by solution spin coating. The spin coating speed was 800-1500 rpm for 5-15 seconds, then 3500-5000 rpm for 40-70 seconds. 200-400 μL of chlorobenzene antisolvent was dropped between 5-10 seconds after the end of the second spin coating.

[0011] Then anneal at 110-130 ℃ for 10-15 minutes to form a tin-lead perovskite thin film;

[0012] 3.3 After surface passivation of the tin-lead perovskite film, an anhydrous isopropanol solution of 0.5-1.5 mg / ml of metallic lead salt surface passivating agent was deposited on the tin-lead perovskite film by spin coating at a speed of 4000-5000 rpm for 20-30 seconds, followed by annealing at 90-100 ℃ for 3-5 minutes; the metallic lead salt is one of lead fluoride, lead bromide, lead chloride, and lead oxalate.

[0013] Step 4: An electron transport layer is fabricated on the post-treated tin-lead perovskite thin film. A C60 layer with a thickness of 20-40 nm is deposited by vacuum evaporation. Then, a BCP layer with a thickness of 5-8 nm is deposited on the C60 layer by vacuum evaporation. Finally, a LiF layer with a thickness of 1-3 nm is deposited on the BCP layer by vacuum evaporation.

[0014] Step 5: Deposit a layer of silver as an electrode on the electron transport layer using vacuum evaporation, with a thickness of 80-150 nm; thus obtaining the tin-lead perovskite solar cell without fluoride.

[0015] A tin-lead perovskite solar cell without tin fluoride, prepared by the above method, wherein the tin-lead perovskite thin film layer is free of tin fluoride additives, and the chemical passivation and field effect passivation of the surface passivating agent reduces film defects and improves carrier extraction rate; the surface passivating agent forms stable ionic bonds and interfacial dipole interactions with the surface of the tin-lead perovskite thin film, ensuring the durability of the cell under photothermal conditions.

[0016] The tin-lead perovskite battery of the present invention is characterized by replacing the stannous fluoride additive in the precursor solution with lead fluoride post-treatment. Within the battery operating temperature range, lead fluoride is less prone to deprotonation reaction with organic amine components, thus avoiding perovskite degradation caused by the deprotonation reaction between stannous fluoride and organic amines. At the same time, it avoids the generation of corrosive products and effectively inhibits the generation of tetravalent tin and tin vacancy defects in the thin film.

[0017] This invention relates to a tin-lead perovskite solar cell and its fabrication method. The perovskite layer of the tin-lead perovskite solar cell incorporates a surface passivating agent, which is one or more metal salts such as lead fluoride, lead bromide, lead chloride, and lead oxalate. Applying this surface passivation strategy to tin-lead perovskite solar cells can avoid the dependence of high-efficiency tin-lead perovskite solar cells on stannous fluoride additives, suppress the perovskite deprotonation reaction caused by stannous fluoride, and thus effectively improve the photothermal stability of the tin-lead perovskite solar cell. Attached Figure Description

[0018] Figure 1 This is a schematic diagram of the structure of the tin-lead perovskite solar cell of the present invention;

[0019] Figure 2 A schematic diagram of the thermal stability of perovskite thin films containing stannous fluoride additives and lead fluoride passivating agents.

[0020] Figure 3 A schematic diagram showing the changes in band structure of a perovskite thin film before and after degradation, containing stannous fluoride additives and lead fluoride passivating agents.

[0021] Figure 4 This is a schematic diagram of the carrier transport performance of a tin-lead perovskite battery, a control group, and a tin-containing tin fluoride additive and a lead fluoride passivator, according to the present invention.

[0022] Figure 5 The diagram shows the IV curves and photothermal stability of the tin-lead perovskite battery with lead fluoride passivator, which is the control group of this invention. Detailed Implementation

[0023] The following will provide a detailed description of the tin-lead perovskite solar cell and its preparation method provided by the present invention.

[0024] The tin-lead perovskite precursor solution provided by this invention does not contain tin fluoride additives, but instead uses lead salt surface passivators.

[0025] The concentration of the lead salt surface passivating agent solution is 0.5-3.0 mg / ml. When used in perovskite solar cells, considering the improvement effect of the post-treatment material on cell efficiency and stability, the concentration of the post-treatment material is preferably 0.5-1.5 mg / ml.

[0026] In ABX3 type organic-inorganic hybrid perovskite materials, A is an organic amine cation or a cesium metal cation, and B is Pb. 2+ Sn 2+ 、Ge 2+ Cation, where X is a halide anion or SCN - Anion. Preferably, A is CH3NH3. + HC(NH2) 2+ and Cs + B is Pb 2+ and Sn 2+ X is I - Since the perovskite bandgap is 1.22 eV when the molar ratio of tin to lead is 1:1, exhibiting the highest theoretical efficiency for a single cell, the tin-lead perovskite material is further preferably Cs. 0.2 FA 0.8 Pb 0.5 Sn 0.5 I3.

[0027] The surface passivating agent is one or more of metallic lead salts such as lead fluoride, lead bromide, lead chloride, and lead oxalate. Lead fluoride has better solubility in perovskite antisolvents such as isopropanol, making selective control and solution preparation easier. Furthermore, fluoride ions can effectively suppress the formation of tetravalent tin and tin vacancy defects on the film surface, which is beneficial to improving battery efficiency. Therefore, lead fluoride is preferably the preferred surface passivating agent.

[0028] See Figure 1 The tin-lead perovskite solar cell of the present invention includes a substrate 1, a hole transport layer 2, a tin-lead perovskite thin film 3, an electron transport layer 4, and a metal electrode 5 stacked together.

[0029] The material of the substrate 1 is not limited and can be any one of glass, silicon wafer, or stainless steel sheet. ITO is a metallic compound with high visible spectral transmittance and excellent electrical conductivity; therefore, the substrate 1 is preferably ITO conductive glass.

[0030] The hole transport layer 2 is a poly[3-(cesium butyrate)thiophene] (P3CT-Cs) material layer with a thickness of 5-15 nm. Compared with the commonly used PEDOT:PSS hole transport layer (HOMO = -5.0 eV), the HOMO level of P3CT-Cs is -5.08 eV, which is closer to the valence band (-5.31 eV) of the prepared tin-lead perovskite, effectively avoiding energy loss due to energy level mismatch. The preferred thickness of P3CT-Cs is 8 nm, and its chemical structure is as follows:

[0031]

[0032] The tin-lead perovskite thin film 3 has a precursor solution free of tin fluoride additives. The film is formed using a solution spin-coating combined with anti-solvent extraction. Considering the influence of perovskite layer thickness on light absorption and bulk recombination, a thickness of 800-1300 nm is preferred.

[0033] For the post-treatment of the tin-lead perovskite film, considering the passivation effect of fluoride ions on tetravalent tin and tin vacancy defects, and the strong binding effect of lead ions and fluoride ions to avoid the deprotonation reaction of fluoride ions with organic ammonium salts, lead fluoride is preferred for post-treatment of the perovskite film. Considering the ease of implementation of solution spin coating, solution spin coating is preferred. Furthermore, considering the good solubility of lead fluoride in isopropanol and its non-damage to the underlying perovskite layer, isopropanol is preferred as the solvent. Too high a lead fluoride concentration will affect carrier transport, while too low a concentration will result in insignificant defect passivation; therefore, a concentration of 0.5-1.5 mg / ml is preferred.

[0034] The electron transport layer 4 comprises a C60 layer and a BCP layer stacked sequentially. The C60 layer has a thickness of 30-40 nm, the BCP layer has a thickness of 6-10 nm, the LiF layer has a thickness of 1-3 nm, and the electron transport layer 4 has a thickness of 37-53 nm. The C60, BCP, and LiF layers are all prepared by vacuum evaporation, a method that ensures a denser and more uniform film. Preferably, their thicknesses are 30 nm, 6 nm, and 1 nm, respectively.

[0035] The thickness of the electrode 5 is 100-300 nm, and the material is not limited, but considering the cost and work function of metal, the preferred electrode is a silver electrode, and the preferred thickness is 100 nm.

[0036] The following will further illustrate the tin-lead perovskite thin film, tin-lead perovskite battery, and their preparation method through specific embodiments.

[0037] Example

[0038] like Figure 1 As shown, the tin-lead perovskite solar cell comprises a substrate 1, a hole transport layer 2, a tin-lead perovskite thin film 3, a surface passivation layer 4, an electron transport layer 5, and a metal electrode 6, which are stacked sequentially. The fabrication method is as follows:

[0039] Using ITO conductive glass as substrate 1, the substrate is first ultrasonically cleaned with ITO cleaning agent for 15 min to remove surface grease and organic matter. Then, it is ultrasonically cleaned with deionized water, acetone and isopropanol for 15 min each. After being dried with nitrogen, it is treated with ozone plasma for 20 min before use.

[0040] Hole transport layer 2 was deposited on the treated ITO conductive glass using a solution spin coating method. Hole transport layer 2 was a P3CT-Cs material layer, formed by spin coating with a methanol solution of P3CT-Cs at a concentration of 0.5 mg / ml. The spin coating machine speed was 4000 rpm for 30 seconds, and the thickness was 8 nm.

[0041] A tin-lead perovskite thin film 3 is prepared on the hole transport layer 2, and the specific method is as follows:

[0042] Tin-lead perovskite precursor solution: Dissolve 1.20 mmol FAI, 0.30 mmol CsI, 0.75 mmol SnI2, 0.75 mmol PbI2 and 0.02 mmol GuaSCN in a mixed solvent of 600 μl N,N-dimethylimide and 200 μl dimethyl sulfoxide, add 20 mg lead powder, and stir overnight at room temperature;

[0043] Tin-lead perovskite precursor solution was deposited on the P3CT-Cs hole transport layer using a solution spin coating method. The spin coating speed was initially 1000 rpm for 5 seconds, then 4000 rpm for 50 seconds. 300 μL of chlorobenzene antisolvent was dropped 5 seconds after the second spin coating ended.

[0044] Then anneal at 130 °C for 5 minutes to form a tin-lead perovskite thin film;

[0045] The tin-lead perovskite film was post-treated by spin-coating a 1.0 mg / ml isopropanol solution of lead fluoride onto the tin-lead perovskite film at a spin speed of 4000-5000 rpm for 20-30 seconds, followed by annealing at 90-100 °C for 3-5 minutes.

[0046] An electron transport layer 5 was fabricated on the post-treated tin-lead perovskite thin film layer 4. A C60 layer with a thickness of 30 nm was deposited by vacuum evaporation. Then, a BCP layer with a thickness of 6 nm was deposited on the C60 layer by vacuum evaporation. Finally, a LiF layer with a thickness of 1 nm was deposited on the BCP layer by vacuum evaporation.

[0047] A 100 nm thick layer of silver was deposited as electrode 6 on the electron transport layer using vacuum evaporation. (See also...) Figure 1 This is a schematic diagram of a fluorine-free tin-lead perovskite solar cell.

[0048] Figure 2This is a schematic diagram illustrating the thermal stability of the perovskite thin film containing stannous fluoride additive and lead fluoride passivator of the present invention. In the figure, (a) is the thermogravimetric spectrum of formamidine, a mixture of formamidine and stannous fluoride, and a mixture of formamidine and lead fluoride; (b) is the scanning electron microscope morphology of the perovskite thin film containing stannous fluoride additive and lead fluoride passivator after degradation at 85°C for one week; (c) and (d) are the proportions of deprotonated N in the perovskite thin film containing stannous fluoride additive and lead fluoride passivator before degradation and after degradation at 85°C for one week, respectively (N 1s XPS spectrum).

[0049] Figure 3 This is a schematic diagram showing the changes in the band structure of the perovskite thin film containing tin fluoride additive and lead fluoride passivator before and after degradation according to the present invention. (a)-(c) show the band structure of the perovskite thin film containing tin fluoride before degradation (a) and after degradation at 85°C for one week (c); (d)-(f) show the band structure of the perovskite thin film containing lead fluoride before degradation (d) and after degradation at 85°C for one week (f).

[0050] Figure 4 This diagram illustrates the carrier transport performance of the control group, the tin-lead perovskite battery containing tin fluoride additive, and the lead fluoride passivator of this invention. (a) shows the fluorescence quantum yield of the control group, the tin-lead perovskite battery containing tin fluoride additive, and the lead fluoride passivator; (b)-(c) show the transient absorption spectra of the control group (b), the tin-lead perovskite battery containing tin fluoride additive (c), and the lead fluoride passivator (d), respectively.

[0051] Figure 5 The diagram shows the IV curves and photothermal stability of the tin-lead perovskite battery with lead fluoride passivator, which are the control group and the control group of the present invention. (a) shows the IV curves of the tin-lead perovskite battery with lead fluoride passivator; (b) shows the external quantum efficiency of the tin-lead perovskite battery with lead fluoride passivator; (c)-(d) show the maximum power output stability of the tin-lead perovskite battery with lead fluoride passivator under continuous illumination at 65°C (c) and 85°C (d), respectively.

Claims

1. A method for fabricating a tin-lead perovskite solar cell without tin fluoride, characterized in that, The preparation method includes the following steps: Step 1: Select a substrate, first use a cleaning agent to sonicate for 10-30 minutes to remove surface grease and organic matter, then sonicate with deionized water, acetone and isopropanol for 10-30 minutes each, blow dry with nitrogen, and then treat with ozone plasma for 15-30 minutes before use. Step 2: On the treated substrate, a hole transport layer is deposited using a solution spin coating method. The hole transport layer is a P3CT-Cs material layer, which is formed by spin coating with a methanol solution of P3CT-Cs with a concentration of 0.2-1.0 mg / ml. The spin coater speed is 2000-5000 rpm, the time is 30-60 seconds, and the thickness is 5-10 nm. Step 3: Prepare a tin-lead perovskite thin film layer on the hole transport layer, specifically as follows: 3.1: Preparation of tin-lead perovskite precursor solution: Dissolve 1.20-1.30 mmol FAI, 0.30-0.45 mmol CsI, 0.75-0.90 mmol SnI2, 0.75-0.90 mmol PbI2 and 0.02-0.05 mmol GuaSCN in a mixed solvent of 600 μl N,N-dimethylimide and 200 μl dimethyl sulfoxide, add 20-60 mg of metallic lead powder, and stir overnight at room temperature; 3.2: The tin-lead perovskite precursor solution was deposited on the P3CT-Cs hole transport layer by solution spin coating. The spin coating speed was 800-1500 rpm for 5-15 seconds, then 3500-5000 rpm for 40-70 seconds. 200-400 μL of chlorobenzene antisolvent was dropped between 5-10 seconds after the end of the second spin coating. Then anneal at 110-130 ℃ for 10-15 minutes to form a tin-lead perovskite thin film; 3.3 After surface passivation of the tin-lead perovskite film, an anhydrous isopropanol solution of 0.5-1.5 mg / ml of metallic lead salt surface passivating agent was deposited on the tin-lead perovskite film by spin coating at a speed of 4000-5000 rpm for 20-30 seconds, followed by annealing at 90-100 ℃ for 3-5 minutes; the metallic lead salt is one of lead fluoride, lead bromide, lead chloride, and lead oxalate. Step 4: An electron transport layer is fabricated on the post-treated tin-lead perovskite thin film. A C60 layer with a thickness of 20-40 nm is deposited by vacuum evaporation. Then, a BCP layer with a thickness of 5-8 nm is deposited on the C60 layer by vacuum evaporation. Finally, a LiF layer with a thickness of 1-3 nm is deposited on the BCP layer by vacuum evaporation. Step 5: Deposit a layer of silver as an electrode on the electron transport layer using vacuum evaporation, with a thickness of 80-150 nm; thus obtaining the tin-lead perovskite solar cell without fluoride.

2. A tin-lead perovskite solar cell without fluoride tin was prepared by the method of claim 1.

3. The tin-lead perovskite solar cell without tin fluoride according to claim 2, characterized in that, The tin-lead perovskite thin film layer, which is free of tin fluoride additives, reduces film defects and improves carrier extraction rate through chemical passivation and field effect passivation of the surface passivating agent; the surface passivating agent forms stable ionic bonds and interfacial dipole interactions with the surface of the tin-lead perovskite thin film, ensuring the durability of the battery under photothermal conditions.

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