A large-area perovskite tandem cell preparation method based on inkjet printing

Abstract

The application relates to a large-area perovskite laminated cell preparation method based on inkjet printing, which sequentially comprises the following steps: depositing a transparent conductive composite layer and a hole transport layer on a crystalline silicon bottom cell with an industrial textured structure; depositing an FAI pre-deposition layer on the above-mentioned hole transport layer; depositing an inorganic skeleton layer on the FAI pre-deposition layer through vacuum evaporation; depositing an organic salt solution on the inorganic skeleton layer to form a perovskite light-absorbing layer; performing annealing treatment on the thin film after the perovskite light-absorbing layer is deposited, and sequentially depositing a passivation layer, an electron transport layer, a transparent electrode layer, a metal electrode layer and an anti-reflection layer, so as to obtain a perovskite laminated cell. The FAI pre-deposition layer printed in advance can precisely fill the bottom interface, in-situ reaction is caused by substrate heating when PbI2 is subsequently evaporated, the limitation of natural diffusion of the organic salt is avoided, and residual PbI2 is completely eliminated.

Description

Technical Field

[0001] This invention relates to the field of perovskite solar cell technology, and in particular to a method for fabricating large-area perovskite tandem solar cells based on inkjet printing. Background Technology

[0002] Crystalline silicon / perovskite tandem solar cells combine the high stability of crystalline silicon with the high photoelectric conversion efficiency of perovskite, making them a research hotspot in the photovoltaic field. Industrial-grade crystalline silicon substrates commonly employ textured structures (pyramid height 2-5 μm) to enhance light absorption efficiency, but the uneven morphology of the textured surface poses a challenge to the uniform preparation of the perovskite layer.

[0003] The preparation of perovskite layers commonly employs a two-step method: first, an inorganic framework layer (such as PbI2, CsBr, etc.) is vacuum thermally evaporated; then, an organic salt (such as FAI, MAI, etc.) is deposited using methods such as spin coating, slot coating, or inkjet printing. Spin coating utilizes centrifugal force to allow the organic salt to penetrate to the bottom of the inorganic framework layer, enabling a thorough reaction with PbI2. However, it is limited by small areas (≤100 cm²). 2 This approach cannot meet the demands of large-area industrial fabrication. Inkjet printing, as a non-contact large-area fabrication technology, relies solely on the natural diffusion of organic salts. This can lead to insufficient diffusion at the buried interface of the textured silicon substrate, resulting in unreacted PbI2 residue. This residual PbI2 forms deep-level defects, hindering charge transport, reducing the open-circuit voltage and fill factor of the tandem solar cell, and accelerating the degradation of the perovskite layer, severely impacting the cell's stability and lifespan. Existing improvement schemes mostly focus on optimizing organic salt concentration or printing parameters, but do not address the diffusion limitation problem at the reaction mechanism level. Some schemes use high-temperature annealing to promote diffusion, but high temperatures can easily lead to the failure of the passivation layer on the crystalline silicon substrate. Therefore, developing a method for fabricating large-area tandem solar cells that is compatible with industrial textured crystalline silicon substrates and can fundamentally solve the problem of incomplete PbI2 reaction at the buried interface is key to promoting the industrialization of this technology.

[0004] In view of the above-mentioned shortcomings, the designer actively researched and innovated in order to create a method for preparing large-area perovskite tandem solar cells based on inkjet printing, making it more valuable for industrial applications. Summary of the Invention

[0005] To address the aforementioned technical problems, the present invention aims to provide a method for fabricating large-area perovskite tandem solar cells based on inkjet printing.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A method for fabricating large-area perovskite tandem solar cells based on inkjet printing includes the following steps: Step 1: Sequentially deposit a transparent conductive composite layer and a hole transport layer on a crystalline silicon bottom cell with an industrial textured surface; Step 2: On the hole transport layer described above, a FAI pre-deposit layer is deposited by inkjet printing. The FAI pre-deposit layer serves as a precursor for subsequent reactions, used to fill the textured structure and construct reaction sites. Step 3: On the FAI pre-deposited layer, an inorganic framework layer containing PbI2 is deposited by vacuum evaporation; Step 4: On the inorganic framework layer, an organic salt solution is deposited by inkjet printing to form a perovskite light-absorbing layer; Step 5: Anneal the thin film after depositing the perovskite light-absorbing layer, and then deposit a passivation layer, an electron transport layer, a transparent electrode layer, a metal electrode layer and an antireflection layer in sequence to obtain a perovskite tandem solar cell.

[0007] As a further improvement of the present invention, the crystalline silicon bottom cell is a heterocrystalline silicon cell or a TOPCon cell; the hole transport layer is any one or a combination of two or more of poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine], nickel oxide, Spiro-TTB, PEDOT-PSS, or self-contained monolayer.

[0008] As a further improvement of the present invention, the FAI pre-deposited layer is formed by dissolving FAI in a n-butanol solution, depositing it by inkjet printing, and then annealing it.

[0009] As a further improvement of the present invention, the inkjet printing speed is 180~220mm / s, and after printing, it is annealed on a hot plate at 80~120℃ for 8~12min.

[0010] As a further improvement of the present invention, the inorganic framework layer is a co-evaporated inorganic salt film of PbI2 and CsBr, which is deposited by co-evaporation using a vacuum evaporation deposition device.

[0011] As a further improvement of the present invention, the evaporation rate ratio of PbI2 to CsBr is 8~12:1, and the evaporation thickness of PbI2 is 200~400nm.

[0012] As a further improvement of the present invention, the organic salt solution in step 4 is a mixed solution containing at least one of FAI, FABr, MAI and MACl, and the solvent is n-butanol.

[0013] As a further improvement of the present invention, the annealing process in step 5 includes a vacuum flash evaporation step and a laser annealing step; the vacuum flash evaporation is carried out for 10 to 20 seconds under a vacuum of 8 to 12 Pa within 8 to 12 seconds; the laser annealing is carried out by surface laser irradiation, the annealing temperature is 100 to 150°C, the annealing time is 30 to 60 seconds, and after the annealing is completed, it is taken out and cooled naturally.

[0014] As a further improvement of the present invention, the passivation layer material is any one or a combination of two or more of phenylethyl ammonium iodide, piperazine monoiodide, piperazine iodide, oleylamine iodide, phenylethyl ammonium bromide, oleylamine chloride, ethylenediamine iodide, propylenediamine iodide, and lithium fluoride, and is deposited by inkjet printing; the electron transport layer is C 60 It is any one or a combination of two or more of PCBM, zinc oxide, tin oxide, and titanium oxide, and is obtained by vacuum evaporation or atomic layer deposition.

[0015] As a further improvement of the present invention, the metal electrode layer is any one or a combination of two or more of Au, Ag, Cu, and Al; the antireflection layer is any one of LiF and MgF2.

[0016] By means of the above-described solution, the present invention has at least the following advantages: This invention completely solves the problem of incomplete PbI2 reaction at the substrate interface: the pre-deposited FAI layer printed by inkjet printing can accurately fill the substrate interface. During the subsequent PbI2 evaporation, the substrate heating triggers an in-situ reaction, avoiding the limitations of natural diffusion of organic salts, and the residual PbI2 is completely eliminated.

[0017] This invention is suitable for large-area industrial suede substrates: using inkjet printing technology, it can achieve uniform coating of large-area industrial-grade suede substrates, overcoming the area limitations of spin coating processes, and the printing parameters can be precisely controlled by the program to meet mass production requirements.

[0018] This invention improves the performance of tandem solar cells: the defect density at the buried interface of the perovskite layer is reduced, the photoelectric conversion efficiency of the tandem solar cells is improved, and the open-circuit voltage is increased.

[0019] The invention has strong process compatibility: the entire process does not require the introduction of special equipment, inkjet printing and vacuum evaporation can be seamlessly integrated into existing industrial production lines, and the pretreatment and passivation processes meet the mass production standards of crystalline silicon cells.

[0020] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the following are preferred embodiments of the present invention described in detail with reference to the accompanying drawings. Attached Figure Description

[0021] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0022] Figure 1This is a schematic diagram of the structure of the perovskite / crystalline silicon tandem solar cell prepared by the present invention; Figure 2 This is a SEM image of the perovskite buried interface without a deposited FAI pre-deposited layer. Figure 3 This is a schematic diagram of the SEM morphology of the perovskite buried interface of the FAI pre-deposited layer. Figure 4 XRD comparison images of perovskite films with and without FAI pre-deposited layers; Figure 5 This is a SEM image of the perovskite thin film with FAI pre-deposited layer on an industrial textured crystalline silicon substrate. Detailed Implementation

[0023] The specific embodiments of the present invention will be described in further detail below with reference to the accompanying drawings and examples. The following examples are for illustrative purposes only and are not intended to limit the scope of the invention.

[0024] To enable those skilled in the art to better understand the present invention, the technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. The components of the embodiments of the present invention described and shown in the accompanying drawings can generally be arranged and designed in various different configurations. Therefore, the following detailed description of the embodiments of the present invention provided in the accompanying drawings is not intended to limit the scope of the claimed invention, but merely to illustrate selected embodiments of the invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0025] The purpose of this invention is to overcome the defects of the prior art and provide a method for fabricating large-area industrial textured crystalline silicon / perovskite tandem solar cells based on inkjet printing. By inkjet printing a pre-deposited FAI layer on the buried interface of the textured crystalline silicon substrate before evaporating the inorganic framework layer, the buried interface is filled in advance and reaction sites are constructed to ensure the full reaction between PbI2 and FAI in the subsequent process, thereby achieving efficient and stable fabrication of large-area tandem solar cells.

[0026] The technical solution of the present invention is as follows: To achieve the above-mentioned objectives, the present invention adopts the following technical solution: A method for fabricating large-area perovskite tandem solar cells based on inkjet printing includes the following steps: Step 1: Prepare a transparent conductive composite layer on the bottom cell by magnetron sputtering or deposition; Step 2: Prepare a hole transport layer on the conductive substrate layer processed in Step 1 above; Step 3: Prepare a FAI pre-deposited layer on the substrate treated in Step 2 above; Step 4: Prepare an inorganic framework layer on the substrate treated in Step 3 above; Step 5: Prepare an organic salt solution on the substrate treated in Step 4 above; Step 6: Flash evaporate the thin film prepared in Step 5 above, and then perform laser annealing; Step 7: Prepare a passivation layer on the thin film treated in Step 6 above; Step 8: Prepare an electron transport layer on the thin film prepared in Step 7 above; Step 9: Prepare a transparent electrode layer on the thin film prepared in Step 8 above; Step 10: Prepare a metal electrode layer on the thin film prepared in Step 9 above; Step 11: Prepare an antireflection layer on the thin film prepared in Step 10 above to obtain a large-area industrial textured crystalline silicon / perovskite tandem solar cell based on inkjet printing.

[0027] Furthermore, the bottom cell mentioned in step 1 can be either a heterocrystalline silicon cell or a TOPCON cell.

[0028] Furthermore, the hole transport layer material described in step 2 may be, but is not limited to, any one or more of poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine] (PTAA), nickel oxide (NiOx), Spiro-TTB, PEDOT-PSS, or self-contained monolayers (SAMs).

[0029] Furthermore, in step 3, FAI is dissolved in a n-butanol solution.

[0030] Furthermore, the passivation layer material in step 7 can be any one or more of the following materials: phenylethyl ammonium iodide, piperazine monoiodide, piperazine iodide, oleylamine iodide, phenylethyl ammonium bromide, oleylamine chloride, ethylenediamine iodide, propylenediamine iodide, and lithium fluoride.

[0031] Furthermore, the electron transport layer material described in step 8 is C. 60 Any one or more of the following materials: PCBM, zinc oxide, tin oxide, and titanium oxide.

[0032] Furthermore, the metal electrode described in step 10 can be any one or more of the following materials: Au, Ag, Cu, and Al.

[0033] Furthermore, the antireflection layer described in step 11 can be either LiF or MgF2.

[0034] A schematic diagram of the fabricated perovskite / crystalline silicon tandem solar cell is shown below. Figure 1As shown, the structure includes a bottom cell crystalline silicon cell (S200), a transparent conductive composite layer (S201), a hole transport layer NiOx (S202), a self-contained monomolecular layer (SAM) (S203), a perovskite light-absorbing layer (S204), a passivation layer (S205), an electron transport layer (S206), a hole blocking layer (S207), a transparent electrode layer (S208), and a metal electrode layer (S209).

[0035] Embodiment 1 of the present invention: This embodiment describes a method for fabricating a large-area industrial textured silicon / perovskite tandem solar cell based on inkjet printing. Using a heterocrystalline silicon solar cell as the substrate, NiOx and self-assembled monolayers (SAM) serve as the hole transport layer. PbI2 and CsBr are deposited as the inorganic salt framework. A mixed solution of formamidine iodide (FAI), formamidine bromide (FABr), methylamine iodide (MAI), and methylamine chloride (MACl) is coated to form the perovskite light-absorbing layer. Piperazine monoiodide (PiPl) serves as the passivation layer. 60 The electron transport layer is composed of SnO2 as the hole blocking layer, and ITO and Cu are used as the back electrode. The specific steps are as follows: Step 1: An intermediate composite layer ITO is prepared on the n-side of a heterocrystalline silicon substrate using a vacuum sputtering deposition (PVD) system. After fixing the sample on the substrate holder, it is fed into the deposition chamber through the transmission system of the equipment. After reaching the set vacuum level, the sputtering process is performed. The sputtering power is set to 1KW, the gas mixture is 9:1 argon-oxygen, and the thickness of ITO is 20nm, thus obtaining the intermediate composite layer (i.e., the transparent conductive composite layer). Step 2: On the surface of the intermediate composite layer ITO prepared in Step 1, a hole transport layer NiOx is prepared by vacuum sputtering deposition equipment (PVD). The sputtering power is 1KW, the thickness of NiOx is 13nm, and the process temperature is 200℃ to obtain the NiOx hole transport layer. Step 3: The surface of the NiOx hole transport layer prepared in Step 2 is inkjet printed with an ethanol-dissolved MeO-4PACz self-assembled monolayer as the hole transport layer. The nozzle is 1 mm away from the substrate and the printing speed is 200 mm / s. After printing, it is annealed on a hot stage at 100℃ for 10 min to obtain the MeO-4PACz hole transport layer. Step 4: Print the surface of the MeO-4PACz hole transport layer prepared in Step 3 with butanol-dissolved FAI by inkjet printing. The nozzle is 1 mm above the substrate and the printing speed is 200 mm / s. After printing, anneal on a hot stage at 100°C for 10 min to obtain the FAI layer.

[0036] Step 5: Weigh a certain amount of PbI2 and CsBr and add them to different evaporation crucibles. Use a beam source evaporation device to co-evaporate PbI2 and CsBr. The evaporation rate ratio of PbI2 to CsBr is 10:1. Stop evaporating PbI2 when the thickness is 300 nm. Prepare an inorganic salt film co-evaporated with PbI2 and CsBr.

[0037] Step 6: Weigh out 3.5g of formamidine iodide (FAI), 2.5g of formamidine bromide, 1g of methylamine iodide, and 0.8g of methylamine chloride, and dissolve them in 100mL of n-butanol to prepare an organic salt solution. Then, fill the ink supply system of the inkjet printer with the prepared organic salt ink, set the printing parameters to 1mm above the substrate, and a printing speed of 350mm / s, and begin printing. Immediately after printing, transfer the wet film to a height of 400mm and purge it with a nitrogen air knife at a pressure of 0.8MPa and a purging speed of 200mm / s.

[0038] Step 7: Transfer the dried perovskite film obtained in Step 6 to a laser annealing apparatus for annealing. The laser is a surface laser with a maximum power of 9KW. Set the pre-annealing parameters to 70℃ and 20s; then set the annealing parameters to 120℃ and 30-60s. After annealing, remove the film and allow it to cool naturally to obtain the rapidly pretreated perovskite film.

[0039] Step 8: Weigh 50 mg of piperazine monoiodine powder and add 100 mL of isopropanol solvent in a glove box under inert gas protection. Shake to fully dissolve the powder to obtain a passivation layer precursor solution with a concentration of 0.5 mg / m. After the precursor solution is completely dissolved by shaking, inkjet printing of the piperazine monoiodine solution passivation layer is performed on the surface of the wide bandgap film prepared in Step 7. The printing parameters are set as follows: printing height of 1 mm and printing speed of 200 mm / s. After inkjet printing is completed, the film is immediately transferred to a hot plate preheated to 100°C for annealing treatment for 5 min to obtain the perovskite passivation layer.

[0040] Step 9: On the surface of the piperazine monoiodine passivation layer obtained in Step 8, C is prepared using vacuum evaporation technology. 60 Electron transport layer; the sample to be processed is fixed on the adapter mask, and the vacuum degree is maintained at 6×10 -4 In a vacuum environment of Pa, using a linear evaporation source as the deposition carrier and controlling the deposition rate at 0.15 Å / s, a C deposition layer with a thickness of approximately 20 nm was formed. 60 Thin film, i.e., the electron transport layer is made.

[0041] Step 10: On the electron transport layer surface obtained in Step 9 above, a hole blocking layer SnO2 is prepared by atomic layer deposition (ALD). The sample is sent into the process vacuum chamber, the chamber temperature is set to a stable 80°C, the tin source is TDMASn, the oxygen source is pure water, the outlet temperature is 65°C, and the number of purging cycles is 80 times to prepare the hole blocking layer.

[0042] Step 11: A transparent conductive electrode, ITO, is fabricated on the hole-blocking layer obtained in Step 10 using a vacuum sputtering deposition (PVD) system. After fixing the sample on a substrate holder, it is fed into the deposition chamber via the equipment's transmission system. Once the set vacuum level is reached, the sputtering process is performed. The sputtering power is set to 1 kW, using an argon-oxygen mixture (oxygen content 10%), and the ITO thickness is 20 nm, thus obtaining a transparent ITO electrode. Subsequently, a silver grid is fabricated by screen printing. The silver paste is cured at 100°C, finally yielding a large-area industrial textured crystalline silicon / perovskite tandem solar cell based on inkjet printing.

[0043] Embodiment 2 of the present invention: This embodiment describes a method for fabricating a large-area industrial textured silicon / perovskite tandem solar cell based on inkjet printing. Using a TOPCON silicon solar cell as the substrate, NiOx and self-assembled monolayers (SAM) serve as the hole transport layer. PbI2 and CsBr are deposited as the inorganic salt framework. A mixed solution of formamidine iodide (FAI), formamidine bromide (FABr), methylamine iodide (MAI), and methylamine chloride (MACl) is coated to form the perovskite light-absorbing layer. Piperazine monoiodide (PiPl) serves as the passivation layer. 60 The electron transport layer is composed of SnO2 as the hole blocking layer, and ITO and Cu are used as the back electrode. The specific steps are as follows: Step 1: An intermediate composite layer ITO is prepared on the n-side of the TOPCON crystalline silicon bottom cell using a vacuum sputtering coating equipment (PVD). After fixing the sample on the substrate holder, it is fed into the coating chamber through the transmission system of the equipment. After reaching the set vacuum level, the sputtering process is performed. The sputtering power is set to 1KW, the gas mixture is 9:1 argon-oxygen, and the thickness of ITO is 20nm, thus obtaining the intermediate composite layer. Step 2: On the surface of the intermediate composite layer ITO prepared in Step 1, a hole transport layer NiOx is prepared by vacuum sputtering deposition equipment (PVD). The sputtering power is 1KW, the thickness of NiOx is 13nm, and the process temperature is 200℃ to obtain the NiOx hole transport layer. Step 3: The surface of the NiOx hole transport layer prepared in Step 2 is inkjet printed with an ethanol-dissolved MeO-4PACz self-assembled monolayer as the hole transport layer. The nozzle is 1 mm away from the substrate and the printing speed is 200 mm / s. After printing, it is annealed on a hot stage at 100℃ for 10 min to obtain the MeO-4PACz hole transport layer. Step 4: Print the surface of the MeO-4PACz hole transport layer prepared in Step 3 with butanol-dissolved FAI by inkjet printing. The nozzle is 1 mm above the substrate and the printing speed is 200 mm / s. After printing, anneal on a hot stage at 100°C for 10 min to obtain the FAI layer.

[0044] Step 5: Weigh a certain amount of PbI2 and CsBr and add them to different evaporation crucibles. Use a beam source evaporation device to co-evaporate PbI2 and CsBr. The evaporation rate ratio of PbI2 to CsBr is 10:1. Stop evaporating PbI2 when the thickness is 300 nm. Prepare an inorganic salt film co-evaporated with PbI2 and CsBr.

[0045] Step 6: Weigh out 3.5g of formamidine iodide (FAI), 2.5g of formamidine bromide, 1g of methylamine iodide, and 0.8g of methylamine chloride, and dissolve them in 100mL of n-butanol to prepare an organic salt solution. Then, fill the ink supply system of the inkjet printer with the prepared organic salt ink, set the printing parameters to 1mm from the printhead to the substrate, and a printing speed of 350mm / s, and begin printing.

[0046] Step 7: Place the perovskite wet film obtained in Step 6 in a vacuum flash evaporation furnace; the parameters for vacuum flash evaporation are set as follows: evaporation to 10 Pa within 10 s, and a total flash evaporation time of 15 s. After flash evaporation, a dry perovskite film is obtained. The dried perovskite film is then transferred to a laser annealing apparatus for annealing. The laser is a surface laser with a maximum power of 9 kW. Pre-annealing parameters are set: temperature 70℃, time 20 s; then annealing parameters are set: temperature 120℃, annealing time 30-60 s. After annealing, the film is removed and allowed to cool naturally, thus obtaining the rapidly pretreated perovskite film.

[0047] Step 8: Weigh 50 mg of piperazine monoiodine powder and add 100 mL of isopropanol solvent in a glove box under inert gas protection. Shake to fully dissolve the powder to obtain a passivation layer precursor solution with a concentration of 0.5 mg / m. After the precursor solution is completely dissolved by shaking, inkjet printing of the piperazine monoiodine solution passivation layer is performed on the surface of the wide bandgap film prepared in Step 7. The printing parameters are set as follows: printing height of 1 mm and printing speed of 200 mm / s. After inkjet printing is completed, the film is immediately transferred to a hot plate preheated to 100°C for annealing treatment for 5 min to obtain the perovskite passivation layer.

[0048] Step 9: On the surface of the piperazine monoiodine passivation layer obtained in Step 8, a C60 electron transport layer is prepared using vacuum evaporation technology; the sample to be processed is fixed on a matching mask, and the vacuum degree is maintained at 6×10 -4In a vacuum environment of Pa, using a linear evaporation source as the deposition carrier and controlling the deposition rate at 0.15 Å / s, a C deposition layer with a thickness of approximately 20 nm was formed. 60 Thin film, i.e., the electron transport layer is made.

[0049] Step 10: On the electron transport layer surface obtained in Step 9 above, a hole blocking layer SnO2 is prepared by atomic layer deposition (ALD). The sample is sent into the process vacuum chamber, the chamber temperature is set to a stable 80°C, the tin source is TDMASn, the oxygen source is pure water, the outlet temperature is 65°C, and the number of purging cycles is 80 times to prepare the hole blocking layer.

[0050] Step 11: A transparent conductive electrode, ITO, is fabricated on the hole-blocking layer obtained in Step 10 using a vacuum sputtering deposition (PVD) system. After fixing the sample on a substrate holder, it is fed into the deposition chamber via the equipment's transmission system. Once the set vacuum level is reached, the sputtering process is performed. The sputtering power is set to 1 kW, using an argon-oxygen mixture (oxygen content 10%), and the ITO thickness is 20 nm, thus obtaining a transparent ITO electrode. Subsequently, a silver grid is fabricated by screen printing. The silver paste is cured at 100°C, finally yielding a large-area industrial textured crystalline silicon / perovskite tandem solar cell based on inkjet printing.

[0051] The core improvements of Embodiments 1 and 2 above are briefly described as follows: I. Improvements to the "FAI pre-deposition layer" step: Existing technologies generally follow the sequence of "hole layer → perovskite layer" and have never deposited FAI separately before evaporating PbI2.

[0052] This invention transforms FAI from a "reactant" (the second step in a two-step process) into a "pre-reaction site," altering its functional positioning and deposition timing within the process flow.

[0053] Those skilled in the art generally believe that FAI should be deposited after PbI2 to avoid decomposition or volatilization of FAI during high-temperature vapor deposition. This invention, however, goes against this conventional wisdom, breaking this technical bias.

[0054] In summary, "In the prior art, FAI has always appeared as a 'post-deposit' in the reaction with PbI2. This invention is the first to propose using FAI as a 'pre-deposit layer,' a technical approach that overturns the inherent understanding of the two-step process sequence in the field and overcomes the technical problem that 'FAI is easily decomposed during the vapor deposition process.'"

[0055] II. Synergistic improvement of the two-step process of "FAI pre-deposition layer + vacuum evaporation of PbI2": The conventional sequence is to first evaporate PbI2 → then deposit FAI solution (FAI needs to diffuse into the bottom of the PbI2 layer) → the reaction is incomplete in the pits on the textured surface.

[0056] In this invention, FAI is deposited first, followed by PbI2 evaporation (the heat during evaporation triggers an in-situ reaction between FAI and PbI2) → the reaction occurs at the location of FAI and does not rely on diffusion.

[0057] Synergistic effect: The FAI layer acts as a "reaction anchor point" to ensure that PbI2 reacts immediately upon arrival, completely eliminating the PbI2 residue at the buried interface caused by diffusion limitation in traditional processes.

[0058] Using a FAI pre-deposit layer alone (without PbI2 evaporation) cannot form perovskites; evaporating PbI2 alone (without FAI pre-deposit) will result in PbI2 residue. Only by combining the two in this order can the effect of "zero PbI2 residue at the interface" be achieved.

[0059] In summary, the combination of the FAI pre-deposition layer and the subsequent PbI2 evaporation is not a simple superposition of two conventional steps. The two processes form a synergistic mechanism of "anchoring before reaction," solving the long-standing problem of "limited diffusion at the textured substrate interface" that has plagued existing technologies. This synergistic effect goes beyond the simple summation of the effects of each step alone.

[0060] 3. Synergistic dual-printing process of "inkjet printing of FAI pre-deposited layer + inkjet printing of organic salt solution": Conventional method: In the two-step method, the inorganic layer is deposited by vapor deposition, and the organic layer is deposited by spin coating (small area) or slot coating / inkjet printing (large area). However, when printing the organic layer, the solution needs to pass through the already deposited PbI2 layer to reach the bottom.

[0061] In this invention, two inkjet printing processes (first printing a FAI pre-deposited layer, then printing an organic salt solution) are combined with PbI2 vapor deposition to form an alternating "printing-vapor deposition-printing" structure.

[0062] Synergistic effect: The first printed FAI layer forms a dense coating after annealing, providing a reaction substrate for subsequent PbI2; the organic salt solution printed in the second layer only needs to react with the surface PbI2, without the need for deep diffusion.

[0063] If only one printing is used (mixing precursors), the precise layering reaction of FAI and PbI2 cannot be achieved; if two printings are used but PbI2 is not evaporated in between, the perovskite structure cannot be formed.

[0064] In summary, this invention employs alternating inkjet printing and vacuum evaporation to form a sandwich structure consisting of a "FAI anchoring layer—PbI2 reaction layer—organic salt supplementary layer." This alternating deposition method allows each printing step to perform a different function, both serving the core objective of "eliminating incomplete reactions at the source," rather than simply repeating the same operation.

[0065] IV. Parameter Selection: 1. FAI Solvent: Conventionally, high-boiling-point solvents such as DMF and DMSO are used (for spin coating or slot coating); this invention uses n-butanol (low boiling point, suitable for inkjet printing). n-Butanol is not a conventional choice for FAI solvent in the field of inkjet printing perovskites. Its low boiling point and moderate surface tension make it suitable for rapid drying before vapor deposition, avoiding affecting the quality of subsequent vapor deposition.

[0066] 2. Annealing method: Conventional methods use hot-stage annealing (100-150℃, 5-15min); this invention uses vacuum flash evaporation + laser annealing. Vacuum flash evaporation can quickly remove the solvent, and laser annealing can achieve selective heating, avoiding thermal damage to the passivation layer of the crystalline silicon substrate. The combination of the two forms a "two-step rapid annealing" strategy, which is a specific optimization for industrial textured crystalline silicon substrates.

[0067] 3. PbI2:CsBr evaporation rate ratio: Conventionally, PbI2 is deposited alone or co-evaporated with MAI; in this invention, it is 10:1 (PbI2:CsBr). This ratio is optimized for FAI pre-deposited layers. The introduction of CsBr can adjust the perovskite band gap, but excessive CsBr will affect the reaction kinetics.

[0068] In summary, the process parameters of this invention (such as FAI solvent selection, annealing method, and evaporation rate ratio) are not conventional choices in the field, but rather synergistic optimizations based on the innovative step of FAI pre-deposition. These parameters form a "dependent relationship," collectively serving to solve the specific technical problem of "incomplete reaction at the textured surface-buried interface," and cannot be separated into independent, limited-number experimental optimizations.

[0069] V. Overall Coordination and Improvement of the Technical Steps of the Invention: 1. Breakthrough in understanding the technical problem: While existing technologies may recognize the problem of PbI2 residue, they generally attribute it to "insufficient diffusion," and solutions revolve around "promoting diffusion." This invention is the first to recognize that the root cause of the problem lies in "missing reaction sites," thus proposing a solution of "pre-constructing reaction sites."

[0070] 2. Disruptive Technological Approach: Existing technologies have always been within the framework of "PbI2 first, then organic salt" (such as additives, ion exchange, and optimized printing parameters). This invention breaks out of this framework, changing the deposition order of reactants, which constitutes a path innovation.

[0071] 3. Non-linear growth in performance: As shown in Table 1 below, after adding the FAI pre-deposition layer, PCE increased from 22.3% to 24.6% (an increase of 10.3%), and FF increased from 70.25% to 75.31% (an increase of 7.2%). This performance leap is not the result of simply adding the effects of each step, but rather a "1+1>2" effect produced synergistically by the FAI pre-deposition layer and subsequent steps.

[0072] 4. Breakthrough in Industrial Applicability: Existing technologies for solving interface problems (such as spin-coating passivation layers and optimized diffusion) are mostly limited to small-area applications in the laboratory. This invention uses inkjet printing to achieve large-area uniform preparation of FAI pre-deposited layers, realizing a leap from laboratory to industrial mass production.

[0073] VI. Result Verification: The final battery parameters obtained through JV testing are shown in Table 1: Table 1: Comparison of parameters of perovskite thin film devices with and without FAI pre-deposition layer Figure 2 and Figure 3 SEM images of the buried interface of wide-bandgap perovskite films on glass substrates with and without FAI pre-deposited layers are shown.

[0074] like Figure 2 There is a very obvious presence of lead iodide at the perovskite subsurface interface without a FAI pre-deposited layer. For example... Figure 3 After optimization of the FAI pre-deposition layer, lead iodide was significantly eliminated at the perovskite buried interface.

[0075] Figure 4 XRD comparison images of wide-bandgap perovskite films on glass substrates with and without FAI pre-deposited layers. To verify the SEM results, the XRD images clearly show that the perovskite films with pre-deposited FAI layers ( Figure 4 The image above the center showed no obvious XRD characteristic peak of PbI2 (12.6°) after testing, unlike inkjet-printed perovskite films without a pre-deposited FAI layer. Figure 4 The lower center of the graph shows a clear XRD characteristic peak for PbI2. This indicates that the pre-deposited FAI layer can be improved by optimizing the FAI layer. + The reaction kinetics with PbI2 promote the complete reaction of the perovskite precursor, effectively suppress the residual PbI2 impurities, and ultimately improve the phase purity and crystal quality of the perovskite film.

[0076] Figure 5 SEM images of perovskite thin films with FAI pre-deposited layers on industrial textured silicon substrates, from... Figure 5 It can be seen that the perovskite-buried interface significantly eliminates lead iodide.

[0077] In the description of this invention, it should be understood that the terms "center," "longitudinal," "lateral," "upper," "lower," "front," "rear," "left," "right," "vertical," "horizontal," "top," "bottom," "inner," and "outer," etc., indicating orientations or positional relationships based on the orientations or positional relationships shown in the accompanying drawings, are used only for the convenience of describing the invention and for simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation of the invention. Furthermore, the terms "first," "second," etc., are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implying the number of indicated technical features. Thus, a feature defined with "first," "second," etc., may explicitly or implicitly include one or more of that feature. In the description of this invention, unless otherwise stated, "a plurality of" means two or more.

[0078] In the description of this invention, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art will understand the specific meaning of the above terms in this invention based on the specific circumstances.

[0079] The above description is merely a preferred embodiment of the present invention and is not intended to limit 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 technical principles 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 large-area perovskite tandem solar cells based on inkjet printing, characterized in that, The steps are as follows: Step 1: Sequentially deposit a transparent conductive composite layer and a hole transport layer on a crystalline silicon bottom cell with an industrial textured surface; Step 2: On the hole transport layer described above, a FAI pre-deposit layer is deposited by inkjet printing. The FAI pre-deposit layer serves as a precursor for subsequent reactions, used to fill the textured structure and construct reaction sites. Step 3: On the FAI pre-deposited layer, an inorganic framework layer containing PbI2 is deposited by vacuum evaporation; Step 4: On the inorganic framework layer, an organic salt solution is deposited by inkjet printing to form a perovskite light-absorbing layer; Step 5: Anneal the thin film after depositing the perovskite light-absorbing layer, and then deposit a passivation layer, an electron transport layer, a transparent electrode layer, a metal electrode layer and an antireflection layer in sequence to obtain a perovskite tandem solar cell.

2. The method for fabricating large-area perovskite tandem solar cells based on inkjet printing as described in claim 1, characterized in that, The crystalline silicon base cell is a heterocrystalline silicon cell or a TOPCon cell; the hole transport layer is any one or a combination of two or more of poly[bis(4-phenyl)(2,4,6-trimethylphenyl)amine], nickel oxide, Spiro-TTB, PEDOT-PSS, or self-contained monolayers.

3. The method for fabricating large-area perovskite tandem solar cells based on inkjet printing as described in claim 1, characterized in that, The FAI pre-deposited layer is formed by dissolving FAI in a n-butanol solution, depositing it through inkjet printing, and then annealing it.

4. The method for fabricating large-area perovskite tandem solar cells based on inkjet printing as described in claim 3, characterized in that, The inkjet printer has a printing speed of 180~220mm / s, and after printing, it is annealed on a hot plate at 80~120℃ for 8~12 minutes.

5. The method for fabricating large-area perovskite tandem solar cells based on inkjet printing as described in claim 1, characterized in that, The inorganic framework layer is a co-evaporated inorganic salt film of PbI2 and CsBr, which is deposited by vacuum evaporation equipment.

6. The method for fabricating large-area perovskite tandem solar cells based on inkjet printing as described in claim 5, characterized in that, The evaporation rate ratio of PbI2 to CsBr is 8~12:1, and the evaporation thickness of PbI2 is 200~400nm.

7. The method for fabricating large-area perovskite tandem solar cells based on inkjet printing as described in claim 1, characterized in that, The organic salt solution in step 4 is a mixed solution containing at least one of FAI, FABr, MAI and MACl, and the solvent is n-butanol.

8. The method for fabricating large-area perovskite tandem solar cells based on inkjet printing as described in claim 1, characterized in that, The annealing process in step 5 includes a vacuum flash evaporation step and a laser annealing step; the vacuum flash evaporation is performed by evacuating to a vacuum of 8-12 Pa within 8-12 s and processing for 10-20 s; the laser annealing is performed by surface laser irradiation, the annealing temperature is 100-150℃, the annealing time is 30-60 s, and after annealing, it is taken out and allowed to cool naturally.

9. The method for fabricating a large-area perovskite tandem solar cell based on inkjet printing as described in claim 1, characterized in that, The passivation layer material is any one or a combination of two or more of phenylethyl ammonium iodide, piperazine monoiodide, piperazine iodide, oleylamine iodide, phenylethyl ammonium bromide, oleylamine chloride, ethylenediamine iodide, propylenediamine iodide, and lithium fluoride, and is deposited by inkjet printing; the electron transport layer is C 60 It is any one or a combination of two or more of PCBM, zinc oxide, tin oxide, and titanium oxide, and is obtained by vacuum evaporation or atomic layer deposition.

10. The method for fabricating a large-area perovskite tandem solar cell based on inkjet printing as described in claim 1, characterized in that, The metal electrode layer is any one or a combination of two or more of Au, Ag, Cu, and Al; the antireflection layer is any one of LiF and MgF2.

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