A method for preparing large-area tin-based narrow-bandgap perovskite thin films based on solvent engineering

Abstract

This invention discloses a method for preparing large-area tin-based narrow-bandgap perovskite thin films based on solvent engineering, as well as the narrow-bandgap perovskite thin films, single-junction narrow-bandgap perovskite modules, and all-perovskite stacked modules prepared thereby. This invention uses a pyridine-containing mixed solvent system, in which pyridine and divalent tin ions have a stronger coordination interaction, effectively forming a strong electron donor-acceptor complex intermediate phase, and regulating the crystal growth process by altering the thermodynamic process. Furthermore, pyridine has a high saturated vapor pressure, and combined with an innovative vacuum-assisted annealing method, the perovskite phase transformation rate is adjusted by changing the kinetic process. Finally, a uniform and dense narrow-bandgap perovskite thin film with a corresponding thickness of 10.4 cm⁻¹ is obtained. 2 The all-perovskite tandem solar module achieved a photoelectric conversion efficiency of 22.9%.

Description

Technical Field

[0001] This invention belongs to the field of perovskite solar cell technology, specifically relating to a method for preparing large-area tin-based narrow bandgap perovskite thin films and a method for preparing devices based on solvent engineering. Background Technology

[0002] Over the past decade, the photoelectric conversion efficiency (PCE) of single-junction perovskite solar cells has rapidly increased to over 26%, gradually approaching the upper limit of the Shockley-Queisser theory. To overcome the efficiency limitations of single-junction solar cells, researchers have developed and constructed multi-junction tandem solar cell technology. By stacking absorber layers with different band gaps, they can fully utilize the solar spectrum and reduce thermal losses, thereby further improving PCE efficiency. Among these technologies, all-perovskite tandem solar cells are expected to become the preferred choice for future photovoltaic applications due to their low cost, high PCE efficiency, and continuous production capabilities.

[0003] Currently, the most advanced all-perovskite stacked devices have achieved efficiencies exceeding 30%. However, they are typically fabricated using spin-coating techniques and have relatively small device sizes (effective area ~0.1 cm²). 2 To date, only a few studies have begun to attempt to apply high-throughput solution preparation technologies (including blade coating, roll-to-roll coating, and slot coating) to the production of large-area all-perovskite solar modules. However, although this technology has been widely used in the preparation of single-junction perovskite solar modules (~1.5 eV), it has been found in practice that it is difficult to directly transfer to the production of all-perovskite tandem solar modules. This is mainly because wide-bandgap and narrow-bandgap perovskite films have their own unique crystallization kinetics, making them incompatible with current solvent systems. This problem is more pronounced in tin-based narrow-bandgap perovskites, which are prone to rapid crystallization. The underlying mechanism is that, compared to lead ions (whose ionic radius is smaller due to lanthanide contraction), divalent tin ions have a larger ionic radius and lower electronegativity. This results in weaker coordination ability of tin ions with solvents (such as dimethyl sulfoxide and N-methyl-2-pyrrolidone), making it difficult to form an effective mesophase to finely regulate the crystallization process of perovskite. Furthermore, these coordination solvents have low saturated vapor pressures, making them easily trapped at the perovskite buried interface during annealing and ultimately forming voids. These two challenges severely hinder the preparation of high-quality, large-area, narrow-bandgap perovskite films. Summary of the Invention

[0004] To overcome the shortcomings of existing technologies, this invention develops a pyridine-containing mixed solvent system for the preparation of narrow-bandgap perovskite thin films. Pyridine exhibits stronger coordination with divalent tin ions, effectively forming a strong electron donor-acceptor complex mesophase, thereby modulating the crystal growth process by altering the thermodynamics. Furthermore, pyridine possesses a high saturated vapor pressure, and combined with an innovative vacuum-assisted annealing method, the perovskite phase transformation rate is adjusted by modifying the kinetics. Ultimately, a uniform and dense narrow-bandgap perovskite thin film with a corresponding thickness of 10.4 cm⁻¹ is obtained. 2 The all-perovskite tandem solar module achieved a photoelectric conversion efficiency of 22.9%.

[0005] In one aspect, the present invention provides a method for preparing a narrow bandgap perovskite thin film, comprising:

[0006] S1: Press FA 0.8 Cs 0.2 Pb 0.5 Sn 0.5 In a molar ratio of I3, formamidine iodide (FAI), cesium iodide (CsI), tin iodide (SnI2), lead iodide (PbI2), tin fluoride (SnF2), and lead thiocyanate (Pb(SCN)2) were dissolved in a mixed solvent of DMF (N,N-dimethylformamide) / DMSO (dimethyl sulfoxide) / pyridine. The solution was stirred at room temperature for 3 hours and then filtered to obtain a narrow bandgap perovskite precursor solution.

[0007] S2: A narrow bandgap perovskite precursor solution is coated onto the substrate to form a wet film;

[0008] S3: Vacuum anneal the wet film at 100-105℃ and 10-100Pa pressure for 10 minutes to obtain a narrow bandgap perovskite film.

[0009] In some embodiments, in S1, the volume ratio of DMF:DMSO:pyridine in the mixed solvent is 85%:(15%-5%):(0-10%), and the volume of pyridine is not zero, preferably 85%:5%:10%. In this invention, selecting pyridine solvent, which has high saturated vapor pressure and high coordination ability, to largely replace and reduce the amount of DMSO used is beneficial for forming a large amount of mesophase, thereby slowing down the crystallization rate of narrow-bandgap perovskites and reducing the likelihood of DMSO being "captured" by the lower interface. Ultimately, the film quality and the efficiency of the corresponding device are thus significantly improved.

[0010] In some embodiments, in S2, the substrate is cleaned before coating. A transparent ITO (indium tin oxide) conductive glass substrate is selected as the substrate. After being cleaned with detergent, it is ultrasonically cleaned in deionized water, acetone and isopropanol for 15 minutes each. After ultrasonic cleaning, it is dried with nitrogen gas. Finally, it is treated with ultraviolet ozone for about 30 minutes.

[0011] In some embodiments, in S2, a blade coating machine is used for coating, with the gap between the blade coating machine and the substrate set to 60 μm and the coating speed to 1 mm / s. -1 The nitrogen gas knife pressure is 60 psi.

[0012] In a second aspect, the present invention provides a narrow bandgap perovskite thin film obtained by the above preparation method.

[0013] In a third aspect, the present invention provides a method for preparing a single-junction narrow-bandgap perovskite module, comprising:

[0014] (1) At a base temperature of 45℃, with a speed of 5 mm s -1 The conductive poly(3,4-ethylenedioxythiophene)-poly(p-phenylene sulfonic acid) (PEDOT:PSS) solution was coated onto the cleaned substrate at a certain speed, and then annealed in air at 120°C for 10 minutes to prepare the hole transport layer.

[0015] (2) The narrow bandgap perovskite precursor solution is coated on the substrate treated in step (1), and vacuum annealed to obtain a narrow bandgap perovskite film.

[0016] (3) Using thermal evaporation technology to convert C 60 BCP and Ag were deposited on the substrate after step (2) to obtain a single-junction narrow-bandgap perovskite module.

[0017] In a fourth aspect, the present invention provides a method for fabricating an all-perovskite multilayer device, comprising:

[0018] Step 1: Press FA 0.8 Cs 0.2 Pb 0.5 Sn 0.5 In a molar ratio of I3, formamidine iodide (FAI), cesium iodide (CsI), tin iodide (SnI2), lead iodide (PbI2), tin fluoride (SnF2), and lead thiocyanate (Pb(SCN)2) were dissolved in a mixed solvent of DMF (N,N-dimethylformamide) / DMSO (dimethyl sulfoxide) / pyridine. The solution was stirred at room temperature for 3 hours and then filtered to obtain a narrow bandgap perovskite precursor solution.

[0019] Step 2: Press FA 0.7 Cs 0.3 Pb(I 0.6 Br 0.4 In a molar ratio of 3, FAI, CsI, PbI2 and PbBr2 were dissolved in a mixed solvent of DMF / DMSO, stirred at room temperature for 3 hours, and filtered to obtain a wide-bandgap perovskite precursor solution.

[0020] Step 3: Cleaning the transparent conductive glass substrate;

[0021] Step 4: NiO X Nickel oxide was coated onto a transparent conductive glass substrate by spin coating, transferred to a heating stage at 150°C and annealed for 15 minutes. After cooling to room temperature, a hole transport layer was obtained.

[0022] Step 5: Coat the wide-bandgap perovskite precursor solution onto the substrate treated in Step 4 to form a wet film. Vacuum anneal the wet film at 100-105℃ and 10-100Pa pressure for 10 minutes to obtain a wide-bandgap perovskite thin film.

[0023] Step Six: In the C vapor deposition 60 Subsequently, the substrate processed in step five was transferred to an atomic layer deposition (ALD) system (NCE-200R) to deposit a dense 15 nm SnO2 (tin oxide) film using tetra(dimethylamino)tin (iv) and deionized water as precursors at 95 °C. Then, 1 nm Au (gold) clusters were deposited on the SnO2 layer, followed by deposition at a substrate temperature of 45 °C at a speed of 5 mm / s. -1 The PEDOT:PSS solution (diluted with isopropanol at a volume ratio of 1:2) was coated onto the above layer at a certain speed, and then annealed in air at 100°C for 10 minutes to form a "tunneling knot".

[0024] Step 7: Coat the narrow bandgap perovskite precursor solution onto the substrate treated in Step 6 to form a wet film. Vacuum anneal the wet film at 100-105℃ and 10-100Pa pressure for 10 minutes to obtain a narrow bandgap perovskite thin film.

[0025] Step 8: Using thermal evaporation technology to remove C 60 BCP and Ag are deposited on the substrate obtained after step seven to form a fully perovskite stacked module device.

[0026] In some embodiments, in step one, the volume ratio of DMF:DMSO:pyridine in the mixed solvent is 85%:(15%-5%):(0-10%) and the volume of pyridine is not 0, preferably 85%:5%:10%.

[0027] In some embodiments, in step two, the volume ratio of DMF / DMSO in the mixed solvent is 60%:40%.

[0028] In some embodiments, in step three, a transparent ITO conductive glass substrate is selected as the substrate, and after being washed with detergent, it is ultrasonically cleaned in deionized water, acetone and isopropanol for 15 minutes each; after ultrasonic cleaning, it is dried with nitrogen gas; finally, the transparent conductive glass substrate is treated with ultraviolet ozone for about 30 minutes.

[0029] In a fifth aspect, the present invention provides an all-perovskite stacked device obtained by the above-described preparation method.

[0030] In some embodiments, the photoelectric conversion efficiency of the all-perovskite stacked device is 22.9%.

[0031] Technical effect

[0032] This invention suppresses the crystallization rate of narrow-bandgap perovskites through solvent engineering based on high coordination interactions. Thanks to its strong electron pair donor ability, pyridine can effectively coordinate with divalent tin ions to form an intermediate phase, thereby suppressing rapid heterogeneous nucleation during crystallization. The crystal quality and photoelectric properties of the narrow-bandgap perovskite films prepared based on the coordination solvent were investigated using X-ray diffraction (XRD), scanning Kelvin probe force microscopy (KPFM), and conductive atomic force microscopy (C-AFM). It can be seen that the addition of pyridine can effectively improve the crystallinity of the narrow-bandgap perovskite films while reducing the defect density.

[0033] This invention selects a coordination solvent with high saturated vapor pressure and constructs a vacuum-assisted annealing process for rapid solvent extraction. Combining the high saturated vapor pressure of pyridine with vacuum-assisted annealing effectively accelerates the solvent extraction rate. This prevents solvent residue at the bottom interface and the formation of voids. Comparison of scanning electron microscopy (SEM) images of narrow-bandgap perovskite films prepared based on different solvent systems shows that the voids in the bottom film disappear after the addition of pyridine.

[0034] This invention improves the quality of perovskite thin films, thereby enhancing the overall photovoltaic performance of the corresponding devices. The photoelectric conversion efficiency of narrow bandgap perovskite solar cells and their modules is significantly improved. Ultimately, this invention yields an all-perovskite solar photovoltaic module (10.4 cm²) with an efficiency of 22.9%. 2 ). Attached Figure Description

[0035] Figure 1 This demonstrates a general approach to improving the quality of narrow bandgap perovskite thin films through coordination solvent engineering.

[0036] Figure 2 This is a schematic diagram of the vacuum-assisted annealing process;

[0037] Figure 3 The states of SnI2 powder in different solvent systems are shown;

[0038] Figure 4 Photographs of narrow bandgap perovskite precursor solutions after N2-assisted blade coating processes are shown in different solvent systems.

[0039] Figure 5The interaction between pyridine and Sn was shown. 2+ Fourier transform infrared spectra of interactions between ions;

[0040] Figure 6 XRD patterns of narrow bandgap perovskite films obtained by different preparation methods;

[0041] Figure 7 Cross-sectional SEM images of narrow bandgap perovskites prepared under different solvent systems;

[0042] Figure 8 The photoelectric properties of narrow bandgap perovskite thin films prepared based on different solvent systems are shown;

[0043] Figure 9 Photograph of a large-area narrow-bandgap perovskite thin film prepared by N2-assisted blade coating process;

[0044] Figure 10 The current-voltage (JV) curves of narrow bandgap perovskite solar cells prepared based on different proportions of pyridine are shown.

[0045] Figure 11 The images show physical photos of narrow bandgap modules, photovoltaic performance diagrams of single-junction narrow bandgap and tandem modules. Detailed Implementation

[0046] The preferred embodiments of the present invention are described below with reference to the accompanying drawings to make the technical content clearer and easier to understand. The present invention can be embodied in many different forms, and the scope of protection of the present invention is not limited to the embodiments mentioned herein.

[0047] Example 1: Fabrication of a single-junction narrow-bandgap perovskite module

[0048] (1) Narrow bandgap perovskite (FA) 0.8 Cs 0.2 Pb 0.5 Sn 0.5 I3) Preparation of precursor solution

[0049] 289.0 mg of FAI, 109.2 mg of CsI, 391.1 mg of SnI2, 484.0 mg of PbI2, 16.0 mg of SnF2, and 5.2 mg of Pb(SCN)2 were dissolved in 1 mL of a mixed solvent of DMF / DMSO / pyridine (volume ratio 85%:5%:10%) to obtain a narrow bandgap perovskite (FAI). 0.8 Cs 0.2 Pb 0.5 Sn 0.5 I3) precursor solution.

[0050] (2) Cleaning of transparent conductive glass substrate

[0051] After etching, the transparent ITO conductive glass substrate was cleaned with dish soap and then transferred to a cleaning tray. It was then ultrasonically cleaned sequentially with deionized water, acetone, and isopropanol for 15 minutes each. After ultrasonic cleaning, it was dried with nitrogen gas and set aside. Finally, it was treated with ultraviolet ozone for approximately 30 minutes to serve as the substrate.

[0052] (3) Preparation of hole transport layer

[0053] At a coating machine temperature of 45℃, with a coating speed of 5mm / s -1 The PEDOT:PSS solution (diluted with isopropanol at a volume ratio of 1:2) was coated onto the cleaned substrate at a certain speed, and then annealed in air at 120°C for 10 minutes to form a hole transport layer.

[0054] (4) Blade coating of narrow bandgap perovskite thin films

[0055] The gap between the blade coating machine and the substrate treated in step (3) was set to 60 μm, and the coating speed was 1 mm / s. -1 A nitrogen knife pressure of 60 psi was used to coat a narrow-bandgap perovskite precursor solution onto a substrate to form a wet film. Subsequently, vacuum annealing was performed at 100°C and 10-100 Pa for 10 minutes to obtain a narrow-bandgap perovskite film. This procedure can also be applied to groove coating, spraying, or vapor deposition of perovskite. Here, to address the difficulty of effectively extracting solvents with low saturated vapor pressure using traditional annealing methods, this invention innovatively employs vacuum-assisted annealing, i.e., annealing is performed at a vacuum of 10-100 Pa using a hot stage at 105°C. Figure 2 As shown, it can reduce the vacuum level to 10-100 Pa in a short time (<3s). This allows solvents such as DMF / DMSO to be quickly extracted from the wet film, reducing the porosity of the perovskite interface and further improving the film quality.

[0056] (5) Preparation of single-junction narrow bandgap perovskite modules

[0057] 20nm C was removed using thermal evaporation technology. 60 A single-junction narrow bandgap perovskite module was fabricated by depositing 5nm BCP and 120nm Ag on the substrate after step (4).

[0058] Figure 1 This invention presents a comprehensive approach to improving the quality of narrow-bandgap perovskite films through coordination solvent engineering. The invention selects pyridine solvent, which has high saturated vapor pressure and high coordination ability, to largely replace and reduce the amount of DMSO used. This facilitates the formation of a large amount of mesophase, thereby slowing down the crystallization rate of narrow-bandgap perovskites and reducing the likelihood of DMSO being "captured" by the lower interface. Ultimately, the film quality and the efficiency of the corresponding devices are significantly improved.

[0059] This application compares and analyzes products with different D N The coordination ability of a solvent (the ability to donate electron pairs) is a factor in its coordinating power. For example... Figure 3 As shown, when 1.0 mol / L SnI2 powder was added to DMSO and pyridine respectively, SnI2 exhibited simple dissolution in DMSO (e.g., ...). Figure 3 (as shown in a). However, in pyridine (as shown in a). Figure 3 As shown in b), due to their strong coordination ability, a yellow SnI2·pyridine complex was formed.

[0060] Comparative Example 1: Fabrication of a single-junction narrow-bandgap perovskite module

[0061] The single-junction narrow bandgap perovskite module was prepared using the same method as in Example 1, except that in step (1), DMSO / DMF solvent (volume ratio 15%:85%) was used as the solvent for the narrow bandgap perovskite precursor solution.

[0062] Figure 4 The images show photographs of narrow-bandgap perovskite precursor solutions after N2-assisted blade coating processes in different solvent systems. It can be seen that in Comparative Example 1, the precursor based on DMSO / DMF solvent rapidly crystallizes and directly transforms into a black perovskite phase (e.g., after N2-assisted blade coating process, without annealing) in a Comparative Example 1. Figure 4 (as shown in a). This is mainly due to DMSO and Sn. 2+ Weak coordination between ions resulted in insufficient formation of an intermediate phase. And as... Figure 4 As shown in Example 1, high D N When pyridine is added to the solvent system, it forms a uniform brown film after passing through an N2-assisted blade coating process, corresponding to the pyridine-induced mesophase.

[0063] This invention utilizes Fourier transform infrared (FTIR) to confirm the interaction between pyridine and Sn. 2+ Strong electron donor-acceptor interactions between ions ( Figure 5 ).like Figure 5 As shown, 1042cm -1 The absorption peak at 1068 cm⁻¹ is attributed to the stretching vibration of S=O(ν(S=O)) in DMSO, and no significant shift of this absorption peak was found in the FTIR spectrum of DMSO·SnI₂. Conversely, in the spectrum of SnI₂·pyridine, the absorption peak related to the stretching vibration of CN(ν(CN)) in pyridine shifts from 1068 cm⁻¹. -1 Displaced to 1064cm -1 Furthermore, at 1003cm -1 and 1006cm -1 A new signal was detected at the site, corresponding to pyridine and Sn. 2+Ion coordination-induced bending vibrations of the pyridine skeleton. These findings confirm that, compared to DMSO, pyridine exhibits greater flexibility with Sn. 2+ Ions exhibit stronger electron donor-acceptor interactions.

[0064] XRD patterns of narrow bandgap perovskite films prepared by different methods (using DMF / DMSO as solvent, using DMF / pyridine / DMSO as solvent, and using DMF / pyridine / DMSO as solvent with vacuum-assisted annealing) are shown below. Figure 6 As shown, compared to perovskite films prepared using DMSO solvent, the addition of pyridine enhances the intensity of all characteristic XRD diffraction peaks in the narrow-bandgap perovskite, indicating an improvement in the crystallinity of the narrow-bandgap perovskite. Vacuum-assisted annealing (VA) further improves the crystallinity of the narrow-bandgap perovskite.

[0065] Figure 7 These are cross-sectional SEM images of narrow-bandgap perovskites prepared in different solvent systems. Samples were prepared under vacuum-assisted annealing by default. Figure 7 As shown in Figure a, some voids were still observed at the bottom of the perovskite film prepared using DMSO solvent. This is because DMSO molecules are trapped at the perovskite bottom interface and have difficulty escaping, ultimately leading to film damage. After the addition of pyridine (such as... Figure 7 (as shown in b) a dense, uniform perovskite crystal with a highly columnar structure was obtained.

[0066] This invention utilizes scanning Kelvin probe force microscopy and conductive atomic force microscopy to investigate the photoelectric properties of narrow bandgap perovskite thin films prepared based on different solvent systems. Figure 8 ).like Figure 8 As shown in 8a and 8b, the narrow bandgap perovskite film prepared using DMSO solvent exhibits a wide contact surface potential distribution of 40 mV and a wide leakage current distribution of ~4.2 pA, along with a high leakage current of ~12.0 pA. This highly non-uniform distribution of surface charge and leakage current is mainly attributed to the high density of active defects in the perovskite film. Conversely, as Figure 8 As shown in c and 8d, after the addition of pyridine, the wide contact surface potential distribution, wide leakage current distribution, and leakage current of the perovskite film were significantly reduced to approximately ~20 mV, ~3.5 pA, and ~7.2 pA, respectively. This indicates that the addition of pyridine can significantly improve the quality of narrow bandgap perovskite films while greatly reducing the defect density.

[0067] Figure 9 The invention demonstrates the preparation of a large-area narrow-bandgap perovskite thin film using an N2-assisted blade coating process, indicating that the process of the present invention can prepare high-quality, large-area narrow-bandgap perovskite thin films.

[0068] Example 2

[0069] Single-junction narrow-bandgap perovskite modules were prepared using the same method as in Example 1, except that in step (1), different proportions of pyridine (based on a mixed solvent of 100 vol%, DMF accounts for 85 vol%, pyridine accounts for 0-10 vol%, and DMSO accounts for 15%-5%) were used as solvents for the narrow-bandgap perovskite precursor solution.

[0070] The current-voltage (JV) curve of the fabricated single-junction narrow-bandgap perovskite module is shown in Figure 1. Figure 10 As shown.

[0071] For the reference narrow-bandgap perovskite solar cell (pyridine volume 0), its power conversion efficiency (PCE) is 18.5%, open-circuit voltage (VOC) is 0.814V, and short-circuit current (JSC) is 30.2mAcm. -2 The fill factor (FF) was 75.2%. In the mixed solvent system, all photovoltaic parameters, including PCE, VOC, JSC, and FF, were significantly enhanced as the pyridine ratio increased from 0 to 10 vol%.

[0072] Adding 10 vol% pyridine to the DMSO-DMF solvent system yielded optimal PCE, VOC, JSC, and FF, with PEC at 22.0%, VOC at 0.853 V, and JSC at 32.5 mA / cm². -2 FF was 79.2%.

[0073] However, the presence of excess pyridine (which further increases its proportion in the mixed solvent to 13 vol% and 15 vol%) leads to poor photovoltaic performance of narrow bandgap perovskite solar cells.

[0074] Example 3: Preparation of an all-perovskite stacked module

[0075] Step 1: Narrow bandgap perovskite (FA) 0.8 Cs 0.2 Pb 0.5 Sn 0.5 I3) Preparation of precursor solution

[0076] 289.0 mg of FAI, 109.2 mg of CsI, 391.1 mg of SnI2, 484.0 mg of PbI2, 16.0 mg of SnF2, and 5.2 mg of Pb(SCN)2 were dissolved in 1 mL of a mixed solvent of DMF / DMSO / pyridine (volume ratio 85%:5%:10%) to obtain a narrow bandgap perovskite (FAI). 0.8 Cs 0.2 Pb 0.5 Sn 0.5 I3) precursor solution.

[0077] Step 2, Wide-bandgap perovskite (FA)0.7 Cs 0.3 Pb(I 0.6 Br 0.4 3) Preparation of precursor solution

[0078] 192.6 mg of FAI, 124.8 mg of CsI, 295.0 mg of PbI₂, and 352.3 mg of PbBr₂ were dissolved in 1 mL of a mixed solvent of DMF / DMSO (volume ratio 60%:40%) to obtain a wide-bandgap perovskite (FA). 0.7 Cs 0.3 Pb(I 0.6 Br 0.4 3) Precursor solution;

[0079] All perovskite precursor solutions were stirred at room temperature for 3 hours and then filtered through a 0.22 μm polytetrafluoroethylene (PTFE) membrane before use.

[0080] Step 3: Cleaning the transparent conductive glass substrate

[0081] After etching, the transparent ITO (indium tin oxide) conductive glass substrate was cleaned with detergent and transferred to a cleaning tray. It was then ultrasonically cleaned sequentially with deionized water, acetone, and isopropanol for 15 minutes each. After ultrasonic cleaning, it was dried with N2 and set aside. Finally, it was treated with ultraviolet ozone for approximately 30 minutes to serve as the substrate.

[0082] Step 4: Preparation of Hole Transport Materials

[0083] 10 mg / mL NiO X Nickel oxide was applied to the substrate by spin coating at 4000 rpm for 30 seconds. It was then transferred to a heating stage at 150°C and annealed for 15 minutes to form a hole transport layer. It was then allowed to cool to room temperature before use.

[0084] Step 5: Blade Coating of Wide-Bandwidth Perovskite Thin Film

[0085] The gap between the blade coating machine and the substrate treated in step four was set to 30 μm, and the coating speed was 3 mm / s. -1 A wide-bandgap perovskite precursor solution is coated onto a substrate and a wet film is formed using an N2 knife at a pressure of 60 psi. Subsequently, it is vacuum annealed at 100°C and 10-100 Pa for 10 minutes to form a wide-bandgap perovskite thin film. This process can also be applied to trench coating, spraying, or vapor deposition of perovskites.

[0086] Step Six: Preparation of Tunnel Junction

[0087] 20nm C evaporation 60Subsequently, the substrate treated in step five was transferred to the ALD system, where a dense 15 nm SnO2 film was deposited at 95 °C using tetra(dimethylamino)tin (iv) and deionized water as precursors. Then, 1 nm Au (gold) clusters were deposited on the SnO2 layer, followed by coating at 45 °C with a speed of 5 mm / s. -1 The PEDOT:PSS solution (diluted with isopropanol at a volume ratio of 1:2) was coated onto the above layer at a certain speed, and then annealed in air at 100°C for 10 minutes to form a "tunneling junction".

[0088] Step 7: Blade Coating of Narrow Bandgap Perovskite Thin Films

[0089] The gap between the blade coating machine and the substrate treated in step six was set to 60 μm, and the coating speed was 1 mm / s. -1 A narrow-bandgap perovskite precursor solution is coated onto a substrate and a wet film is formed using an N2 knife at a pressure of 60 psi. Subsequently, it is vacuum annealed at 100 °C and 10-100 Pa for 10 minutes to form a narrow-bandgap perovskite thin film. This process can be applied to groove coating, spraying, or vapor deposition of perovskite.

[0090] Step 8: Fabrication of stacked module devices

[0091] 20nm C was removed using thermal evaporation technology. 60 5 nm BCP and 120 nm Ag were deposited on the substrate obtained after step seven.

[0092] Etching of all-perovskite tandem photovoltaic micromodules

[0093] The transparent ITO conductive glass substrate, hole transport layer / wide bandgap perovskite film / tunneling junction / narrow bandgap perovskite film / electron transport layer, and Ag (silver) electrode were etched using a laser scribing machine (GT-LS150-G) to form patterns P1, P2, and P3. The widths of P1, P2, and P3 in the sub-cells are 6.7 mm, 30 μm, 120 μm, and 100 μm, respectively. The effective area of ​​the module is 10.4 cm². 2 .

[0094] Physical photos of narrow bandgap modules, photovoltaic performance diagrams of single-junction narrow bandgap and tandem modules are shown below. Figure 11 As shown. Figure 11 As shown in Figure a, the mini-module consists of four sub-units. The width of each sub-unit and the dead zone are designed to be 6.7 mm and 0.35 mm, respectively, resulting in a corresponding geometric factor of 94.7%. A mask is placed on top for component testing, with an effective area of ​​10.4 cm². 2The narrow-bandgap perovskite mini-module exhibits a PCE of 16.3%, a VOC of 3.25V, an ISC of 72.6mA, and an FF of 71.7% under reverse scanning, and displays negligible hysteresis. Figure 11 b).

[0095] The fabricated all-perovskite tandem mini-module exhibits a high PCE of 22.9%, a VOC of 8.10V, an ISC of 37.0mA, and an FF of 79.5% under reverse scanning. Figure 11 c and Table 1).

[0096] Table 1: Photovoltaic performance of single-junction narrow-bandgap, wide-bandgap modules and corresponding multilayer modules

[0097] Battery Type Open circuit voltage [V] Short-circuit current [mA] Fill factor [%] efficiency[%] Narrow bandgap module 3.25 72.6 71.7 16.3 Wide bandgap module 5.13 40.6 79.2 15.9 Stacked modules 8.10 37.0 79.5 22.9

[0098] (Note: The device structure of the narrow (wide) bandgap module is: ITO electrode layer / hole transport layer / narrow (wide) bandgap perovskite film / electron transport layer / Ag electrode; the device structure of the stacked module is: ITO electrode layer / hole transport layer / wide bandgap perovskite film / tunnel junction / narrow bandgap perovskite film / electron transport layer / Ag electrode)

[0099] The preferred embodiments of the present invention have been described in detail above. It should be understood that those skilled in the art can make numerous modifications and variations based on the concept of the present invention without creative effort. Therefore, all technical solutions that can be obtained by those skilled in the art based on the concept of the present invention through logical analysis, reasoning, or limited experimentation on the basis of existing technology should be within the scope of protection defined by the claims.

Claims

1. A method for preparing a narrow bandgap perovskite thin film, comprising: S1: Press FA 0.8 Cs 0.2 Pb 0.5 Sn 0.5 In a molar ratio of I3, formamidine iodide, cesium iodide, tin iodide, lead iodide, tin fluoride, and lead thiocyanate were dissolved in a mixed solvent of N,N-dimethylformamide (DMF) / dimethyl sulfoxide (DMSO) / pyridine. The solution was stirred at room temperature for 3 hours and then filtered to obtain a narrow bandgap perovskite precursor solution. S2: A narrow bandgap perovskite precursor solution is coated onto the substrate to form a wet film; S3: Vacuum anneal the wet film at 100-105℃ and 10-100 Pa pressure for 10 minutes to obtain a narrow bandgap perovskite film.

2. The preparation method according to claim 1, wherein, In S1, the volume ratio of DMF:DMSO:pyridine in the mixed solvent is 85%:(15%-5%):(0-10%), and the volume of pyridine is not 0.

3. The preparation method according to claim 1, wherein, In step S2, the substrate is cleaned before coating. A transparent ITO conductive glass substrate is selected as the substrate. After being cleaned with detergent, it is ultrasonically cleaned in deionized water, acetone and isopropanol for 15 minutes each. After ultrasonic cleaning, it is dried with nitrogen gas. Finally, it is treated with ultraviolet ozone for 30 minutes.

4. The preparation method according to claim 1, wherein, In S2, a blade coating machine is used for coating, with the gap between the blade coating machine and the substrate set to 60 μm and the coating speed to 1 mm / s. -1 The nitrogen gas knife pressure is 60 psi.

5. A narrow bandgap perovskite thin film obtained by the preparation method according to any one of claims 1-4.

6. A method for fabricating a single-junction narrow-bandgap perovskite module, comprising: (1) At a coating machine temperature of 45℃, with a speed of 5 mm / s -1 The conductive poly(3,4-ethylenedioxythiophene)-poly(p-phenylene sulfonic acid) solution (PEDOT:PSS) was coated onto the cleaned substrate at a certain speed, and then annealed in air at 120°C for 10 minutes to prepare the hole transport layer. (2) The narrow bandgap perovskite precursor solution of claim 1 is coated on the substrate treated in step (1), and vacuum annealed to obtain a narrow bandgap perovskite film. (3) Fullerene C is processed by thermal evaporation technology 60 2,9-Dimethyl-4,7-diphenyl-1,10-phenanthroline (BCP) and silver (Ag) were deposited on the substrate treated in step (2) to obtain a single-junction narrow-bandgap perovskite module.

7. A method for fabricating an all-perovskite multilayer device, comprising: Step 1: Press FA 0.8 Cs 0.2 Pb 0.5 Sn 0.5 The molar ratio of I3 was used to dissolve formamidine iodide, cesium iodide, tin iodide, lead iodide, tin fluoride and lead thiocyanate in a mixed solvent of DMF / DMSO / pyridine, stirred at room temperature for 3 hours, and filtered to obtain a narrow bandgap perovskite precursor solution. Step 2: Press FA 0.7 Cs 0.3 Pb(I 0.6 Br 0.4 In a molar ratio of 3, FAI, CsI, PbI2 and PbBr2 were dissolved in a mixed solvent of DMF / DMSO, stirred at room temperature for 3 hours, and filtered to obtain a wide-bandgap perovskite precursor solution. Step 3: Cleaning the transparent conductive glass substrate; Step 4: Apply nickel oxide onto the transparent conductive glass substrate cleaned in Step 3 using spin coating, transfer it to a heating stage at 150°C and anneal for 15 minutes. After cooling to room temperature, a hole transport layer is obtained. Step 5: Coat the wide-bandgap perovskite precursor solution onto the substrate treated in Step 4 to form a wet film. Vacuum anneal the wet film at 100-105℃ and 10-100 Pa pressure for 10 minutes to obtain a wide-bandgap perovskite thin film. Step Six: After C60 evaporation, the substrate treated in Step Five is transferred to the ALD system. Using tetra(dimethylamino)tin (iv) and deionized water as precursors, a dense 15 nm SnO2 film is deposited at 95°C. Then, 1 nm Au clusters are deposited on the SnO2 layer, and finally, the coating is applied at 45°C with a coating speed of 5 mm / s. -1 The PEDOT:PSS solution was applied to the treated substrate at a high speed and then annealed in air at 100°C for 10 minutes to form a "tunneling junction". Step 7: Coat the narrow bandgap perovskite precursor solution onto the substrate treated in Step 6 to form a wet film. Vacuum anneal the wet film at 100-105℃ and 10-100 Pa pressure for 10 minutes to obtain a narrow bandgap perovskite thin film. Step 8: Using thermal evaporation technology to remove C 60 BCP and Ag are deposited on the substrate obtained after step seven to form a fully perovskite stacked module device.

8. The preparation method according to claim 7, wherein, In step six, the PEDOT:PSS solution is diluted with isopropanol at a volume ratio of 1:

2.

9. The preparation method according to claim 7, wherein, In step one, the volume ratio of DMF:DMSO:pyridine in the mixed solvent is 85%:(15%-5%):(0-10%), and the volume of pyridine is not 0.

10. A fully perovskite stacked device obtained by the preparation method according to any one of claims 7-9.

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