Method for improving buried bottom interface of perovskite / crystalline silicon tandem solar cell top cell

Abstract

The application discloses a method for improving a buried bottom interface of a top cell of a perovskite / crystalline silicon laminated solar cell. The method first deposits an ultrathin lead iodide layer above a hole transport layer, then forms a two-dimensional perovskite through a liquid phase reaction of the ultrathin lead iodide layer and organic cation halides with cross-linkable functional groups. Finally, a cross-linking reaction is induced by heating and / or ultraviolet irradiation, so that the two-dimensional perovskite is firmly attached to the buried bottom interface, thereby forming a stable double-layer heterojunction with the upper three-dimensional perovskite layer. The formation of the two-dimensional / three-dimensional perovskite heterojunction can passivate defects at the buried bottom interface, and can also adjust the crystallization growth process of the upper three-dimensional perovskite, thereby improving the photoelectric properties of the entire laminated solar cell, especially bringing obvious gain effect in open-circuit voltage and fill factor. The method is suitable for crystalline silicon bottom cells with different textured structures, and is expected to promote the industrialization process of perovskite / crystalline silicon laminated solar cells.

Description

Technical Field

[0001] This invention belongs to the field of solar cell technology, specifically relating to a method for improving the buried interface of the top cell in a perovskite / crystalline silicon tandem solar cell. By preparing a stable two-dimensional / three-dimensional heterojunction, the open-circuit voltage and fill factor of the perovskite / crystalline silicon tandem solar cell are simultaneously improved. Background Technology

[0002] Perovskite solar cells have become a promising thin-film photovoltaic technology due to their high light absorption coefficient, long carrier diffusion length, ability to be fabricated using both solution processing and vacuum methods, and tunable bandgap. Their efficiency has reached an astonishing 25.7%, approaching that of crystalline silicon solar cells.

[0003] Perovskite / crystalline silicon tandem solar cells have garnered significant attention due to their lower material costs and high conversion efficiency, utilizing perovskite as the top cell and crystalline silicon as the bottom cell. The price of silicon and perovskite makes them cost-effective for power generation systems. According to the Shockley-Quiser constraint, the maximum theoretical conversion efficiency of a single-junction silicon solar cell is 33.5%, while that of a tandem perovskite / crystalline silicon solar cell can theoretically reach 45.1%. From a practical perspective, the potential conversion efficiency of perovskite / silicon tandem solar cells is estimated to exceed 34%. Results from the Helmholtz Centre for Materials and Energy in Berlin (HZB) in 2023 show a record of 32.5%, and this record is expected to be broken further.

[0004] Traditional methods for suppressing nonradiative recombination through interface optimization involve spin-coating large volumes of organic amines, such as phenylethylamine iodide and n-butylamine bromide, onto the surface of the perovskite solar cell (the interface between the perovskite and electron transport layer). This forms a two-dimensional perovskite bilayer heterojunction to passivate surface defects in the three-dimensional perovskite, achieving high open-circuit voltage and long-term stability. However, this method results in a mismatch in the work function between the perovskite and electron transport layer, and the quantum well structure between the two-dimensional perovskites is stabilized solely by van der Waals forces, leading to device stability that still falls short of expectations. More importantly, when placed at the buried interface, it is easily damaged during the liquid-phase preparation of the upper three-dimensional perovskite layer. For these reasons, among the numerous interface optimization methods, there are few reports on the optimization of the buried interface (hole transport layer and perovskite interface) in perovskite solar cells, and even fewer studies on improving the buried interface of the top cell in perovskite / crystalline silicon tandem solar cells. Summary of the Invention

[0005] To overcome the shortcomings of the prior art, the present invention provides a method for improving the buried interface of the top cell of a perovskite / crystalline silicon tandem solar cell, which forms a two-dimensional / three-dimensional perovskite through covalent bonds formed by cross-linking, thereby forming a more stable two-dimensional / three-dimensional perovskite heterojunction.

[0006] The perovskite / crystalline silicon tandem solar cell of this invention consists of three parts: a crystalline silicon bottom cell, an intermediate indium tin oxide composite layer, and a perovskite top cell. A stable two-dimensional / three-dimensional perovskite heterojunction is formed at the buried interface of the perovskite top cell. Both the two-dimensional and three-dimensional perovskite layers in the stable heterojunction are prepared using a vacuum-assisted two-step method to match the surface texture of the crystalline silicon bottom cell. The surface texture of the crystalline silicon bottom cell is a pyramidal texture with dimensions of 0.5 to 5 micrometers. The perovskite top cell is prepared in the following order: nickel oxide hole transport layer, stable two-dimensional / three-dimensional perovskite heterojunction, lithium fluoride passivation layer, fullerene electron transport layer, tin dioxide protective layer, front indium tin oxide transparent electrode, front silver grid electrode, and magnesium fluoride antireflection layer. The specific preparation process of the stable two-dimensional / three-dimensional perovskite heterojunction includes the following steps:

[0007] (1) At the buried interface of the perovskite top solar cell, an ultrathin lead iodide film with a thickness of 2-10 nm is first deposited using vacuum technology. Then, it is reacted with an organic cationic halide with crosslinkable functional groups in the liquid phase to form a two-dimensional perovskite. Subsequently, a crosslinking treatment is completed by heating and / or ultraviolet irradiation for 10 to 30 minutes to convert the two-dimensional perovskite into a stable two-dimensional perovskite. The crosslinkable functional group is an alkenyl or oxetane-containing compound. Preferably, the organic cationic halide is 4-vinylbenzylamine iodate or 3-oxetane ethylamine iodate.

[0008] (2) Lead iodide and cesium bromide were co-deposited on the surface of the prepared stable two-dimensional perovskite using vacuum technology to obtain a mixed inorganic compound layer. The deposition rate ratio of co-evaporated lead iodide and cesium bromide was between 1:0.04 and 1:0.10, resulting in a total thickness of 500-800 nm. Then, it was reacted with formamidinium halide in the liquid phase to form a three-dimensional perovskite. After annealing and heating, the preparation of the stable two-dimensional / three-dimensional perovskite heterojunction was completed.

[0009] The liquid-phase formation processes for the two-dimensional and three-dimensional perovskites in the two steps include any one of spin coating, coating, blade coating, and spray coating. The organic solvent is an alcohol solvent, preferably ethanol or isopropanol. In step (2), the annealing of the three-dimensional perovskite is carried out by heat treatment. The sample after the liquid-phase reaction is completed is quickly placed on a hot stage at 150°C and annealed for 20-40 minutes in an environment with a relative humidity of about 50% to complete the preparation of the heterojunction.

[0010] Mechanism of the invention:

[0011] The buried interface in the top cell of a perovskite / crystalline silicon tandem solar cell has many defects. We propose a method to improve the buried interface of the top cell of a perovskite / crystalline silicon tandem solar cell. This method first deposits an ultrathin lead iodide layer above the hole transport layer, and then reacts it with an organic cationic halide with crosslinkable functional groups in a liquid phase to form a two-dimensional perovskite. Finally, a crosslinking reaction is carried out by heating and / or ultraviolet irradiation, which makes the two-dimensional perovskite firmly attached to the buried interface, resistant to damage by subsequent solution preparation processes, thus forming a stable bilayer heterojunction with the upper three-dimensional perovskite layer. The formation of perovskite heterojunctions can passivate defects at the interface and optimize carrier transport at the buried interface of the top cell. At the same time, the strong interaction between two-dimensional and three-dimensional perovskites at the heterojunction acts as a nucleation site, regulating the crystallization process of three-dimensional perovskite and changing the morphology of the upper perovskite, thereby affecting the performance of the entire device. This greatly improves the open-circuit voltage and fill factor of perovskite / crystalline silicon tandem solar cells. Due to the stable two-dimensional / three-dimensional heterojunction, the stability of tandem solar cells is also significantly improved.

[0012] Compared with the prior art, the beneficial effects of the present invention are:

[0013] 1) This invention provides a method for improving the buried interface of the top cell of a perovskite / crystalline silicon tandem solar cell. A crosslinkable two-dimensional perovskite layer prepared by a vacuum-assisted two-step method is introduced between the perovskite and the hole transport layer. The crosslinked two-dimensional perovskite is not easily damaged by the preparation process of the upper three-dimensional perovskite, and forms a stable two-dimensional / three-dimensional heterostructure with the upper perovskite.

[0014] 2) This invention provides an effective improvement scheme for the buried interface of the top cell in perovskite / crystalline silicon tandem solar cells. In the top cell fabricated by the two-step method, it is easy to generate many defects at its buried interface, which leads to a decrease in the open-circuit voltage and stability of the tandem cell. This improvement method can form a very stable two-dimensional and three-dimensional heterojunction to passivate the defects of the perovskite layer, while optimizing the crystallization and morphology of the upper three-dimensional perovskite, thereby affecting the performance of the entire device and greatly improving the open-circuit voltage and stability of perovskite / crystalline silicon tandem solar cells. Attached Figure Description

[0015] Figure 1This is a schematic diagram of the structure of the fully textured perovskite / crystalline silicon tandem solar cell of the present invention; the names of each part are as follows: 10, back silver electrode; 20, back indium tin oxide transparent electrode; 30, back p-type amorphous silicon; 40, back intrinsic amorphous silicon; 50, micron-scale textured intrinsic monocrystalline silicon wafer; 60, front intrinsic amorphous silicon; 70, front n-type amorphous silicon; 80, ITO composite layer; 90, nickel oxide hole transport layer; 100, two-dimensional perovskite layer; 110, three-dimensional perovskite layer; 120, passivation layer; 130, electron transport layer; 140, protective layer; 150, front indium tin oxide transparent electrode; 160, front silver grid electrode; 170, antireflection layer MgF2.

[0016] Figure 2 These are scanning electron microscope (SEM) images of the three-dimensional perovskite surfaces of the top solar cells prepared in Example 1 and Comparative Example 1 of this invention.

[0017] Figure 3 These are the IV characteristic curves of the perovskite / crystalline silicon tandem solar cells prepared in Example 1 and Comparative Example 1 of this invention under AM1.5G illumination. Detailed Implementation

[0018] The present invention will now be described in further detail with reference to the accompanying drawings and specific embodiments. The following embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0019] Example 1

[0020] This embodiment provides a method for improving the buried interface of the top cell in a perovskite / crystalline silicon tandem solar cell. The method is applicable to the buried interface of the top cell in a vacuum-assisted two-step perovskite tandem solar cell.

[0021] Please see Figure 1 The present invention is a perovskite / crystalline silicon tandem solar cell, which, from bottom to top, comprises a crystalline silicon bottom cell, an intermediate indium tin oxide composite layer, and a vacuum-assisted two-step perovskite top cell.

[0022] The above-mentioned method for fabricating perovskite / crystalline silicon tandem solar cells includes the following steps:

[0023] 1) Fabrication of crystalline silicon bottom cells: A commercially available 3-micron textured intrinsic monocrystalline silicon wafer 50 (resistance 1-3Ω, 150 microns) is selected. Using a plasma-enhanced chemical vapor deposition (PECVD) device, 5nm of back-side intrinsic amorphous silicon 40 and 10nm of back-side p-type amorphous silicon 30 are deposited sequentially on the back side of the intrinsic monocrystalline silicon wafer. Then, 5nm of front-side intrinsic amorphous silicon 60 and 10nm of front-side n-type amorphous silicon 70 are deposited sequentially on the front side of the intrinsic monocrystalline silicon wafer. Intrinsic amorphous silicon is obtained by introducing SiH4 and H2 into the reaction chamber of the device under the action of plasma. During the deposition of p-type amorphous silicon, B2H6 gas needs to be introduced in addition, and during the deposition of n-type amorphous silicon, PH3 gas needs to be introduced in addition. Next, a 100nm indium tin oxide transparent electrode 20 (indium oxide to tin oxide mass ratio of 97:3) is deposited on the p-type amorphous silicon back side of the silicon wafer using a physical vapor deposition device. Then, a 200nm silver electrode is deposited on the indium tin oxide transparent electrode 20 using a thermal evaporation vacuum deposition device to obtain the back silver electrode 10, thereby completing the fabrication of the crystalline silicon bottom cell.

[0024] 2) Composite layer preparation: The composite layer is made of ITO. The wafer is placed in a mask and physical vapor deposition is used. The mask is placed on a carrier plate and the carrier plate is inserted into the cavity to deposit a 20nm transparent oxide as the ITO composite layer 80 connecting the two cells.

[0025] 3) Hole transport layer fabrication: The material used is nickel oxide, which is prepared by magnetron sputtering and has a thickness of 10 nm.

[0026] 4) Preparation of a robust 2D / 3D heterojunction perovskite light-absorbing layer: 5 nm of lead iodide was deposited on the aforementioned nickel oxide hole transport layer 90 using a thermal evaporation vacuum deposition apparatus at a deposition rate of [missing information]. A 3 mg / ml solution of 4-vinylbenzylamine (VBAI) was prepared using a 1:1 volume ratio of chlorobenzene and isopropanol as solvents. This solution was spin-coated onto the lead iodide layer from the previous step at a spin-coating speed of 4000 rpm for 20 seconds. After spin-coating, the layer was annealed at 100°C for 1 minute, followed by UV crosslinking treatment at 70°C for 15 minutes to obtain the two-dimensional perovskite layer 100. The upper three-dimensional perovskite layer 110 was then prepared using a vacuum-assisted two-step method, consisting of three main components. The process involves several steps. The first step is the preparation of the organic amine solution. Using an electronic balance, formamidinium iodide (FAI), formamidinium bromide (FABr), and formamidinium chloride (FACl) are weighed and dissolved in an ethanol solution at a ratio of 3:1:1, resulting in a concentration of 0.65 M. This is a pure formamidinium organic amine salt system. The second step is the preparation of the inorganic layer. Using a thermal evaporation apparatus with two evaporation sources (left and right), the evaporation rate of lead iodide needs to be stable at 1.0 Å / s, and the evaporation rate of cesium bromide needs to be stable at 0.1 Å / s. The third step involves transferring the sample to a nitrogen-protected glove box. Using a pipette, 200 μL of the organic amine solution is dropped onto the surface of the inorganic layer. After standing for 15 seconds, it is rotated at 4000 rpm for 30 seconds. Then, it is removed from the glove box and annealed at 150°C for 30 minutes in an environment with 50% humidity to obtain a two-dimensional / three-dimensional heterojunction perovskite light-absorbing layer. Figure 2 The scanning electron microscope (SEM) image of the three-dimensional perovskite surface of the top solar cell in Example 1 shows high-quality crystallization of the perovskite grains and good textured surface coverage. Compared with Control Example 1, the formation of a two-dimensional / three-dimensional perovskite heterojunction effectively improves the crystallinity quality of the upper three-dimensional perovskite film.

[0027] 5) The passivation layer 120 is made of LiF, and the electron transport layer is made of C. 60 After annealing, the sample was placed in a specific mask, and a 1 nm layer of LiF was first deposited as a passivation layer at a deposition rate of 0.12 Å / s, followed by the deposition of a 20 nm layer of C. 60 As electron transport layer 130, the deposition rate is 0.15 Å / s.

[0028] 6) The silicon wafer with the electron transport layer deposited is placed in an atomic layer deposition (ALD) apparatus. Through alternating purging with tin and water sources, a layer-by-layer SnO2 molecular layer is formed. Finally, after 100 cycles, a SnO2 protective layer 140 with a thickness of approximately 14 nm, i.e., perovskite, is obtained during the sputtering process. Subsequently, a 100 nm thick indium tin oxide transparent electrode (indium oxide to tin oxide mass ratio of 97:3) is deposited on the SnO2 surface using physical vapor deposition.

[0029] 7) Finally, using a thermal evaporation vacuum deposition apparatus, a 200 nm thick front silver gate electrode 160 is deposited on the front indium tin oxide transparent electrode 150 from step (6). (The gate electrode consists of a main gate and a fine gate, with the effective area of ​​the main gate being 1 cm².) 2 The main gate contains four fine gates, each 7 mm long, evenly distributed within the main gate, and a 100 nm thick antireflection layer MgF2170. Figure 3 The IV characteristic curves of the tandem solar cell in Example 1 under AM1.5G illumination show that the open-circuit voltage is 1.79V, the fill factor is 75.10%, and the photoelectric conversion efficiency is 26.69%. Compared with Control Example 1, the open-circuit voltage and fill factor of the tandem cell are significantly improved.

[0030] Compare with Example 1

[0031] The fabrication method of non-two-dimensional / three-dimensional heterojunction perovskite / crystalline silicon tandem solar cells includes the following steps:

[0032] The above-mentioned method for fabricating perovskite / crystalline silicon tandem solar cells includes the following steps:

[0033] 1) Fabrication of crystalline silicon bottom cells: Commercially available 3-micron textured intrinsic monocrystalline silicon wafers (resistance 1-3Ω, 150 microns) are selected. 5nm intrinsic amorphous silicon and 10nm p-type amorphous silicon are deposited sequentially on the back side of the intrinsic monocrystalline silicon wafer using plasma-enhanced chemical vapor deposition equipment. Then, 5nm intrinsic amorphous silicon and 10nm n-type amorphous silicon are deposited sequentially on the front side of the intrinsic monocrystalline silicon wafer. Intrinsic amorphous silicon is obtained by introducing SiH4 and H2 into the reaction chamber of the equipment under the action of plasma. During the deposition of p-type amorphous silicon, B2H6 gas needs to be introduced additionally, and during the deposition of n-type amorphous silicon, PH3 gas needs to be introduced additionally. Next, a 100nm indium tin oxide transparent electrode (indium oxide to tin oxide mass ratio of 97:3) is deposited on the p-type amorphous silicon back side of the silicon wafer using a physical vapor deposition device. Then, a 200nm silver electrode is deposited on the indium tin oxide transparent electrode using a thermal evaporation vacuum deposition device to obtain the back electrode, thus completing the fabrication of the crystalline silicon bottom cell.

[0034] 2) Composite layer preparation: The composite layer is made of ITO. The wafer is placed in a mask and physical vapor deposition is used. The mask is placed on a carrier plate and the carrier plate is inserted into the cavity to deposit a 20nm transparent oxide as the composite layer connecting the two cells.

[0035] 3) Hole transport layer fabrication: The material used is nickel oxide, which is prepared by magnetron sputtering and has a thickness of 10 nm.

[0036] 4) Vacuum-assisted two-step preparation of upper perovskite: This mainly consists of three steps. The first step is the preparation of the organic amine solution. Using an electronic balance, formamidinium iodide (FAI), formamidinium bromide (FABr), and formamidinium chloride (FACl) are weighed and dissolved in an ethanol solution at a ratio of 3:1:1, with a concentration of 0.65M. This is a pure formamidinium organic amine salt system. The second step is the preparation of the inorganic layer. Using a thermal evaporation device with two evaporation sources, the evaporation rate of lead iodide needs to be stable at 1.0 Å / s, and the evaporation rate of cesium bromide needs to be stable at 0.1 Å / s. The third step involves transferring the sample to a nitrogen-protected glove box, using a pipette to add 200 μL of organic amine solution to the surface of the inorganic layer, allowing it to stand for 15 seconds, then rotating it at 4000 rpm for 30 seconds, and finally removing it from the glove box. The sample is then heated and annealed at 150°C for 30 minutes in an environment with 50% humidity to obtain a two-dimensional / three-dimensional heterojunction perovskite light-absorbing layer.

[0037] 5) The passivation layer is LiF, and the electron transport layer is C. 60 After annealing, the sample was placed in a specific mask, and a 1 nm layer of LiF was first deposited as a passivation layer at a deposition rate of 0.12 Å / s, followed by the deposition of a 20 nm layer of C. 60 As an electron transport layer, the deposition rate is 0.15 Å / s.

[0038] 6) The silicon wafer with the electron transport layer deposited is placed in an atomic layer deposition (ALD) apparatus. Through alternating purging with tin and water sources, a layer-by-layer SnO2 molecular layer is formed. Finally, after 100 cycles, a SnO2 protective layer with a thickness of approximately 14 nm, i.e., the perovskite layer during the sputtering process, is obtained. Subsequently, a 100 nm thick indium tin oxide transparent electrode (indium oxide to tin oxide mass ratio of 97:3) is deposited on the SnO2 surface using physical vapor deposition.

[0039] 7) Finally, a thermal evaporation vacuum deposition apparatus is used to deposit a 200 nm thick front-side silver gate electrode on the indium tin oxide transparent electrode from step (6). (The gate electrode consists of a main gate and a fine gate, with the effective area of ​​the main gate being 1 cm².) 2 The main gate contains four fine gates, each 7 mm long, evenly distributed within the main gate, and a 100 nm thick anti-reflection layer of MgF2. Figure 3 The IV characteristic curve of the tandem solar cell in Example 1 under AM1.5G illumination shows that the open-circuit voltage is 1.75V, the fill factor is 69.71%, and the photoelectric conversion efficiency is 25.02%.

[0040] The above embodiments are merely some preferred embodiments of the present invention, used only to illustrate the principles and improvements of the present invention, and should not be used to limit the scope of patent protection of the present invention. Those skilled in the art, outside the spirit and scope of the invention, can make various changes, improvements, and refinements to the present invention. The additional functions in these improvements can be individual or combined in any way, and these changes, improvements, and refinements should also be considered within the scope of protection of this patent.

Claims

1. A method for improving the buried interface of the top cell in a perovskite / crystalline silicon tandem solar cell, wherein the perovskite / crystalline silicon tandem solar cell comprises three parts: a crystalline silicon bottom cell, an intermediate indium tin oxide composite layer, and a perovskite top cell, characterized in that: The improvement method involves forming a stable two-dimensional / three-dimensional perovskite heterojunction at the buried interface of the perovskite top cell. Both the two-dimensional and three-dimensional perovskite layers in the stable two-dimensional / three-dimensional perovskite heterojunction are prepared using a vacuum-assisted two-step method to match the surface texture of the crystalline silicon bottom cell. Specifically, the method includes the following steps: (1) At the buried interface of the perovskite top cell, a thin lead iodide film with a thickness of 2-10 nm is first deposited using vacuum technology. Then, it is reacted with an organic cationic halide with crosslinkable functional groups in the liquid phase to form a two-dimensional perovskite. Then, the crosslinking process is completed by heating and / or ultraviolet irradiation for 10 to 30 minutes to convert the two-dimensional perovskite into a stable two-dimensional perovskite. (2) Lead iodide and cesium bromide were co-deposited on the surface of the prepared stable two-dimensional perovskite using vacuum technology to obtain a mixed inorganic compound layer. Then, it was reacted with formamidine halide in the liquid phase to form a three-dimensional perovskite. After annealing and heating, the preparation of the stable two-dimensional / three-dimensional perovskite heterojunction was completed.

2. The method for improving the buried interface of the top cell in a perovskite / crystalline silicon tandem solar cell according to claim 1, characterized in that, The surface morphology of the crystalline silicon bottom cell is a pyramidal textured surface with a size of 0.5 to 5 micrometers.

3. The method for improving the buried interface of the top cell in a perovskite / crystalline silicon tandem solar cell according to claim 1, characterized in that, In step (1), the crosslinkable functional group is an alkenyl or oxetane, and the organic cationic halide is 4-vinylbenzylamine iodate or 3-oxetane ethylamine iodate.

4. The method for improving the buried interface of the top cell in a perovskite / crystalline silicon tandem solar cell according to claim 1, characterized in that, In step (2), a mixed inorganic compound layer is deposited, and the deposition rate ratio of lead iodide and cesium bromide is between 1:0.04 and 1:0.10, resulting in a mixed inorganic compound layer with a total thickness of 500-800 nm.

5. The method for improving the buried interface of the top cell in a perovskite / crystalline silicon tandem solar cell according to claim 1, characterized in that, The liquid phase formation process of two-dimensional and three-dimensional perovskites in steps (1) and (2) includes any one of spin coating, coating, blade coating and spray coating; in the liquid phase reaction, the organic cationic halides and formamidinium halides are dissolved in an organic solvent, which is an alcohol solvent, and the alcohol solvent is selected as ethanol or isopropanol.

6. The method for improving the buried interface of the top cell in a perovskite / crystalline silicon tandem solar cell according to claim 1, characterized in that, In step (2), the annealing of the three-dimensional perovskite is carried out by heat treatment. The sample after the liquid phase reaction is completed is quickly placed on a hot stage at 150°C and annealed for 20 to 40 minutes in an environment with a relative humidity of about 50% to complete the preparation of the heterojunction.

7. The method for improving the buried interface of the top cell in a perovskite / crystalline silicon tandem solar cell according to claim 1, characterized in that, The fabrication sequence of the perovskite top solar cell is as follows: nickel oxide hole transport layer, stable two-dimensional / three-dimensional perovskite heterojunction, lithium fluoride passivation layer, fullerene electron transport layer, tin dioxide protective layer, front indium tin oxide transparent electrode, front silver grid line electrode, and magnesium fluoride antireflection layer.

8. A perovskite / crystalline silicon tandem solar cell prepared by the improved method according to any one of claims 1 to 7.

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