Stacked solar cell and method of manufacturing the same, photovoltaic module

Abstract

The application relates to the photovoltaic technology field, in particular to a laminated solar cell, a preparation method thereof and a photovoltaic module, wherein the laminated solar cell comprises a silicon cell and a perovskite cell which are arranged in layers; the perovskite cell comprises an organic hole transport layer, a perovskite absorption layer and an electron transport layer which are arranged in layers on one side of the silicon cell; a metal oxide layer is arranged on the side of the silicon cell facing the organic hole transport layer; the organic hole transport layer is arranged on the metal oxide layer; and the material of the organic hole transport layer comprises a 1,2-bisphosphonic acid derivative based on a rigid aromatic skeleton. In the technical scheme, the bisphosphonic acid group in the 1,2-bisphosphonic acid derivative based on the rigid aromatic skeleton can be combined with metal atoms in the metal oxide layer to form a stable chelate structure, the combination strength of the organic hole transport layer and the silicon cell is enhanced, the contact uniformity between the silicon cell and the perovskite absorption layer is improved, and the photoelectric performance of the laminated solar cell is improved.

Description

Technical Field

[0001] This invention relates to the field of photovoltaic technology, and in particular to tandem solar cells and their preparation methods, as well as photovoltaic modules. Background Technology

[0002] Organic-inorganic hybrid perovskite materials have attracted much attention from industry and academia due to their excellent photoelectric properties and low-cost preparation methods, and are considered to be the next generation of photovoltaic cell materials. In less than 15 years, the efficiency of monolayer perovskite solar cells has exceeded 26%, gradually approaching the highest efficiency of the current mainstream monocrystalline silicon cells (approximately 26.8%).

[0003] In recent years, with the continuous improvement of photoelectric conversion efficiency of tandem perovskite solar cells and their excellent radiation resistance, which is far lower than that of traditional crystalline silicon cells, they have shown good adaptability to the space environment and are regarded as the next generation of core energy technology for space photovoltaics.

[0004] During the research process, the inventors discovered that existing perovskite-Si tandem solar cells have problems such as uneven contact between the Si cell and the perovskite absorber layer, which affects the improvement of the photoelectric performance of perovskite-Si tandem solar cells. Summary of the Invention

[0005] This application proposes a tandem solar cell and its fabrication method, as well as a photovoltaic module, which helps to improve the contact uniformity between the silicon cell and the perovskite absorber layer, thereby enhancing the photoelectric performance of the tandem solar cell.

[0006] In a first aspect, embodiments of this application provide a tandem solar cell, including a silicon cell and a perovskite cell stacked together, wherein the perovskite cell includes an organic hole transport layer, a perovskite absorber layer and an electron transport layer stacked on one side of the silicon cell; The silicon cell has a metal oxide layer disposed on the side facing the organic hole transport layer, and the organic hole transport layer is disposed on the metal oxide layer. The material of the organic hole transport layer includes a 1,2-bisphosphonic acid derivative based on a rigid aromatic framework.

[0007] In some embodiments, the 1,2-bisphosphonic acid derivative based on a rigid aromatic skeleton includes at least one of 1,2-phenylene diphosphonic acid and its derivatives and 4-(9H-carbazole-9-yl)phenyl-1,2-bisphosphonic acid and its derivatives.

[0008] In some embodiments, the metal oxide layer is an inorganic hole transport layer.

[0009] In some embodiments, the material of the inorganic hole transport layer includes at least one of nickel oxide, cuprous oxide, cobalt oxide, molybdenum oxide, tungsten oxide, vanadium oxide, cuprous thiocyanate, nickel sulfide, molybdenum sulfide, and tungsten sulfide.

[0010] In some embodiments, the thickness of the inorganic hole transport layer is 1~10 nm.

[0011] In some embodiments, the tandem solar cell further includes a first electrode and a second electrode, wherein the first electrode is disposed on the side of the silicon cell facing away from the perovskite cell, and the second electrode is disposed on the side of the perovskite cell facing away from the silicon cell, and the second electrode is a first transparent conductive layer, or the second electrode is a metal layer.

[0012] In some embodiments, the second electrode is a first transparent conductive layer, and the metal oxide layer is an interconnect layer disposed between the silicon cell and the perovskite cell; or... The second electrode is a metal layer, the metal oxide layer is a second transparent conductive layer, and the silicon cell includes a silicon substrate and the second transparent conductive layer, which is disposed on the side of the silicon substrate facing the perovskite cell.

[0013] In some embodiments, the thickness of the first transparent conductive layer is 5~40 nm.

[0014] In some embodiments, the thickness of the interconnect layer is 10~30nm.

[0015] In some embodiments, the thickness of the metal layer is 0.7~1µm and the width is 0.6~0.9µm.

[0016] In some embodiments, the thickness of the second transparent conductive layer is 30~50nm.

[0017] In some embodiments, the interconnect layer includes a third transparent conductive layer, a metal layer, and a fourth transparent conductive layer stacked together, the perovskite solar cell being disposed on the side of the fourth transparent conductive layer opposite to the metal layer, and the materials of the third and fourth transparent conductive layers include indium tin oxide.

[0018] In some embodiments, the material of the second transparent conductive layer includes indium tungsten oxide.

[0019] In some embodiments, the electron transport layer is a single-layer film or a composite film of at least one material selected from tin oxide, titanium oxide, zinc oxide, zirconium oxide, indium oxide, aluminum-doped zinc oxide, C60, C70, PCBM, lithium chloride, and cesium carbonate.

[0020] In some embodiments, the thickness of the organic hole transport layer is 1~10 nm.

[0021] In some embodiments, the thickness of the perovskite absorber layer is 400~600 nm.

[0022] In some embodiments, the thickness of the electron transport layer is 10~20 nm.

[0023] In some embodiments, the silicon cell is selected from any one of HJT, TOPCon, IBC, HJT-IBC, and TOPCon-IBC.

[0024] In some embodiments, the silicon cell has a textured structure on the side facing the perovskite solar cell, and the perovskite solar cell is disposed on the textured structure.

[0025] Secondly, embodiments of this application propose a method for fabricating a tandem solar cell, comprising the following steps: Prepare a hole transport layer precursor solution, wherein the hole transport layer precursor solution comprises a 1,2-bisphosphonic acid derivative based on a rigid aromatic skeleton. A silicon cell is provided, wherein a metal oxide layer is disposed on one side of the silicon cell, and a hole transport layer precursor solution is coated on the metal oxide layer to form a hole transport layer on the metal oxide layer. A perovskite absorber layer, an electron transport layer, and a second electrode are sequentially disposed on the side of the hole transport layer facing away from the silicon cell.

[0026] Thirdly, embodiments of this application propose a photovoltaic module, including a tandem solar cell as described in the first aspect, or a tandem solar cell prepared by the preparation method described in the second aspect.

[0027] Compared with the prior art, this technical solution has at least the following technical advantages: In this application, the organic hole transport layer material of the tandem solar cell includes a 1,2-bisphosphonic acid derivative based on a rigid aromatic framework. The bisphosphonic acid in this structure can combine with metal atoms in the metal oxide layer to form a chelate structure, enhancing the bonding strength between the organic hole transport layer and the silicon cell. Unlike conventional bisphosphonic acid molecular structures, the bisphosphonic acid molecular structure in this application employs a rigid aromatic ring framework, with bisphosphonic acid groups attached to adjacent substitution sites on the aromatic ring. This allows the spatial positions and distances of the coordinating atoms (phosphonic acid oxygens) in the phosphonic acid groups to be pre-fixed at the optimal coordination geometry, enhancing the chelating and anchoring effect of the bisphosphonic acid molecular structure. This further strengthens the bonding strength between the organic hole transport layer and the silicon cell, improves the contact uniformity between the silicon cell and the perovskite absorber layer, and enhances the photoelectric performance of the tandem solar cell. The technical solution of this application overcomes the problems of thickness sensitivity and insufficient coverage of traditional carbazole-based organic hole transport layer materials. The organic hole transport layer material used not only has excellent anchoring effect with its substrate (metal oxide layer), but also has good buried passivation effect, optimizes the energy level matching between it and the perovskite absorber layer, improves the spreadability of the perovskite absorber layer precursor solution, and makes the tandem solar cell have good stability, carrier extraction capability and better photoelectric conversion efficiency. Attached Figure Description

[0028] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0029] Figure 1 This is a schematic diagram of the structure of a perovskite solar cell in one embodiment of this application; Figure 2 This is a schematic diagram of the process flow for the fabrication method of the perovskite solar cell of this application.

[0030] Figure label: Detailed Implementation To better understand the technical solution of the present invention, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0031] It should be understood that the described embodiments are merely some, not all, of the embodiments of the present 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.

[0032] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0033] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0034] All numerical values ​​or expressions relating to component amounts, process conditions, etc., used in this application shall be understood to be modified with “about” in all cases. All ranges relating to the same component or property include endpoints, which may be combined independently. Since these ranges are continuous, they include every value between the minimum and maximum values. It should also be understood that any numerical range referenced in this application is intended to include all subranges within that range.

[0035] Unless otherwise specified, the raw materials and equipment used in this application are commonly used in the field; unless otherwise specified, the methods used in this application are conventional methods in the field.

[0036] In this embodiment, the photovoltaic module includes a laminate and a frame, with the frame mounted on the edge of the laminate. Specifically, the laminate includes photovoltaic glass, a first encapsulating film, a cell layer, a second encapsulating film, and a backsheet stacked sequentially; or, the laminate includes first photovoltaic glass, a first encapsulating film, a cell layer, a second encapsulating film, and second photovoltaic glass stacked sequentially. The cell layer includes multiple parallel cell strings, each cell string including multiple cells connected in series. Each cell can be a whole cell or a cut piece of a whole cell.

[0037] In this embodiment of the application, at least some of the cells are tandem solar cells 100.

[0038] Please see Figure 1 In this embodiment of the application, the tandem solar cell 100 includes a silicon cell 110 and a perovskite cell stacked together. The perovskite cell includes an organic hole transport layer 150, a perovskite absorber layer 160, and an electron transport layer 170 stacked on one side of the silicon cell 110. A metal oxide layer is disposed on the side of the silicon cell 110 facing the organic hole transport layer 150. The organic hole transport layer 150 is disposed on the metal oxide layer. The material of the organic hole transport layer 150 includes a 1,2-bisphosphonic acid derivative based on a rigid aromatic framework.

[0039] In the embodiments of this application, the bisphosphonic acid groups in the 1,2-bisphosphonic acid derivative structure based on the rigid aromatic skeleton are respectively connected to the adjacent substitution sites of the aromatic ring. The bisphosphonic acid groups can coordinate with metal atoms to form a stable chelate structure, which can be a five-membered ring or a six-membered ring.

[0040] In the embodiments of this application, it should be noted that the metal oxide layer refers to a film structure that includes metal oxides, and not just a film structure composed of metal oxides.

[0041] In this application, the organic hole transport layer 150 of the tandem solar cell 100 is made of a 1,2-bisphosphonic acid derivative based on a rigid aromatic framework. The bisphosphonic acid groups in this structure can combine with metal atoms in the metal oxide layer to form a chelate structure, enhancing the bonding strength between the organic hole transport layer 150 and the silicon cell 110. Unlike conventional bisphosphonic acid molecular structures, the bisphosphonic acid molecular structure in this application employs a rigid aromatic ring framework, with bisphosphonic acid groups respectively attached to adjacent substitution sites on the aromatic ring. This allows the spatial positions and distances of the coordinating atoms (phosphonic acid oxygens) in the phosphonic acid groups to be pre-fixed at the optimal coordination geometry, enhancing the chelating and anchoring effect of the bisphosphonic acid molecular structure. This further strengthens the bonding strength between the organic hole transport layer 150 and the silicon cell 110, improves the contact uniformity between the silicon cell 110 and the perovskite absorber layer 160, and enhances the photoelectric performance of the tandem solar cell 100. This application's technical solution overcomes the problems of thickness sensitivity and insufficient coverage of traditional carbazole-based organic hole transport layer materials. The organic hole transport layer 150 material used not only has excellent anchoring effect with its substrate (metal oxide layer), but also has good buried passivation effect, optimizing the energy level matching with the perovskite absorber layer 160, and improving the spreadability of the perovskite absorber layer precursor solution. This results in the tandem solar cell 100 having good stability, carrier extraction capability, and better photoelectric conversion efficiency. This application's technical solution is not only applicable to small-area tandem solar cells 100, but also suitable for large-area tandem solar cells 100, making its application more widespread.

[0042] In the embodiments of this application, the bisphosphonic acid groups in the 1,2-bisphosphonic acid derivative structure based on the rigid aromatic skeleton are respectively connected to the adjacent substitution sites of the aromatic ring, and the bisphosphonic acid groups can chelate with metal atoms to form a stable seven-membered ring structure.

[0043] It should be noted that, according to the strain theory, seven-membered rings are considered medium to large rings in chemistry and are generally less stable than five- or six-membered rings. However, because the ligand skeleton in this application is a rigid aromatic ring, fixing the distance and angle between C1 and C2 (the carbon atoms directly connected to the phosphonic acid group), the conformation of the seven-membered ring is highly restricted, with almost no flexibility. This, in turn, increases its pre-organization, making the chelate very stable.

[0044] In some embodiments, the 1,2-bisphosphonic acid derivatives based on a rigid aromatic framework include at least one of 1,2-phenylene diphosphonic acid and its derivatives, and 4-(9H-carbazole-9-yl)phenyl-1,2-bisphosphonic acid and its derivatives. These structures are insensitive to substrate roughness and can effectively chelate and anchor with the metal oxide layer on the silicon cell 110; they also exhibit stronger anchoring synergy through the competition among phosphonic acid groups. Simultaneously, they can improve the wettability of the perovskite absorber layer 160 precursor solution by regulating surface energy, promoting uniform nucleation of the perovskite absorber layer 160, optimizing energy level matching, and reducing interfacial barriers. Furthermore, the conjugated structures in these structures can enhance hole mobility, and the phosphonic acid groups can passivate interfacial defects and suppress nonradiative recombination, further improving the overall performance of the tandem solar cell 100.

[0045] In some embodiments, the silicon cell 110 can be selected from any one of HJT (heterojunction silicon cell), TOPCon (tunneling oxide passivated contact cell), IBC (interdigitated back contact cell), HJT-IBC, and TOPCon-IBC. HJT-IBC cells combine the technologies of HJT and TOPCon cells, while TOPCon-IBC cells combine the technologies of TOPCon and IBC cells, both possessing the advantages of no metal obstruction on the front side (an advantage of IBC) and excellent surface passivation (an advantage of HJT / TOPCon).

[0046] In some embodiments, the silicon cell 110 has a textured structure on the side facing the perovskite solar cell, and the perovskite solar cell is disposed on the textured structure. The textured structure can reduce the direct reflectivity of light from more than 30% on a flat surface to less than 10%, allowing more light to enter the tandem solar cell 100.

[0047] In the above embodiments, the texture structure can be pyramidal, inverted pyramidal, V-groove / channel, or nanoscale needle-like, pore-like, etc., which can be selected by those skilled in the art according to actual application requirements.

[0048] In some embodiments, the thickness of the organic hole transport layer 150 is 0.5 nm to 1 nm, specifically 0.5 nm, 0.6 nm, 0.7 nm, 0.8 nm, 0.9 nm, 1 nm, or any value between them. Those skilled in the art can adjust it according to actual application requirements. By controlling the thickness of the organic hole transport layer within this range, it is beneficial to achieve a delicate balance between interface passivation, efficient transport, and optical transparency.

[0049] In some embodiments, the perovskite solar cell further includes an inorganic hole transport layer 140, which is a metal oxide layer. In the tandem solar cell 100 provided in this embodiment, the hole transport structure uses the stability and high mobility of inorganic materials as the "skeleton" and the excellent interface passivation and energy level tunability of organic materials as the "finishing touches," thus combining the advantages of high hole mobility and strong interface stability.

[0050] In some embodiments, the inorganic hole transport layer 140 is made of at least one of nickel oxide, cuprous oxide, cobalt oxide, molybdenum oxide, tungsten oxide, vanadium oxide, cuprous thiocyanate, nickel sulfide, molybdenum sulfide, and tungsten sulfide. These materials exhibit good hole transport performance and stability.

[0051] In some embodiments, the thickness of the inorganic hole transport layer 140 is 1~10 nm, specifically 1 nm, 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, or any value between them. A suitable thickness of the inorganic hole transport layer 140 ensures effective hole transport while avoiding increased resistance and light absorption loss caused by an excessively thick inorganic hole transport layer 140. Since the 1,2-bisphosphonic acid derivative material based on a rigid aromatic framework in this application has a stronger chelating and anchoring effect than the traditional organic hole transport layer 150 material, the thickness of the inorganic hole transport layer 140 in this application can be set to be narrower, further reducing the increased resistance and light absorption loss caused by the inorganic hole transport layer 140.

[0052] In this embodiment, the main material of the perovskite absorber layer 160 is a perovskite compound, such as methylammonium lead iodide (CH3NH3PbI3). This type of material has excellent light absorption and photoelectric conversion properties, and it is in close contact with the organic hole transport layer 150. The good interface properties help to effectively extract and transport holes; together with the electron transport layer 170, it achieves effective separation and transport of electrons and holes.

[0053] In some embodiments, the thickness of the perovskite absorber layer 160 is 500~700 nm, specifically 500 nm, 550 nm, 600 nm, 650 nm, 700 nm or any value between them, which can be adjusted by those skilled in the art according to actual application requirements.

[0054] In some embodiments, the thickness of the electron transport layer 170 is 15~20nm, specifically 15nm, 16nm, 17nm, 18nm, 19nm, 20nm or any value between them, which can be adjusted by those skilled in the art according to actual application requirements.

[0055] In some embodiments, the electron transport layer 170 is a single-layer film or a composite film of at least one material selected from tin oxide, titanium oxide, zinc oxide, zirconium oxide, indium oxide, aluminum-doped zinc oxide, C60, C70, PCBM, lithium chloride, and cesium carbonate.

[0056] In one specific embodiment, the electron transport layer 170 includes a C60 layer, a tin oxide layer (SnO2), and an indium zinc oxide (IZO) layer, which are stacked sequentially from the inside to the outside on the side of the perovskite absorber layer 160 facing away from the organic hole transport layer 150. The C60 (fullerene) layer has a high electron affinity, which matches well with the energy levels of the perovskite absorber layer 160, forming an extremely low electron extraction barrier, facilitating efficient electron extraction. Furthermore, the small molecular structure of C60 can effectively fill and passivate defect states (such as lead dangling bonds and iodine vacancies) on the perovskite surface and at grain boundaries, significantly reducing non-radiative recombination losses at the interface and increasing the open-circuit voltage. The tin oxide layer has a lower (more negative) energy level than the C60 layer and a good work function match with the IZO layer, forming a "downhill" energy level gradient from C60 to SnO2 and then to IZO. This drives electrons to be "pushed" towards the electrode, greatly promoting the directional flow of electrons. Furthermore, the SnO2 layer has strong hole-blocking capabilities and prevents upper metal (such as Ag) atoms from diffusing downwards and damaging the perovskite layer. The robust IZO (zinc-doped indium oxide) layer acts as a "sacrificial buffer layer," able to withstand process damage and protect the core functional layers (from the C60 layer to the SnO2 layer).

[0057] In the above specific embodiments, in the electron transport layer 170, the thickness of the C60 layer is 10~20nm, specifically 10nm, 15nm, 20nm or any value between them; the thickness of the tin oxide layer (SnO2) is 10~30nm, specifically 10nm, 15nm, 20nm, 25nm, 30nm or any value between them; the thickness of the indium zinc oxide (IZO) layer is 30~50nm, specifically 30nm, 35nm, 40nm, 45nm, 50nm or any value between them.

[0058] In this embodiment, the tandem solar cell 100 can be either a formal structure or an inverted structure.

[0059] When the tandem solar cell 100 is in its formal structure, during operation, light is incident from the side of the perovskite cell facing away from the silicon cell 110, passing through both the perovskite and silicon cells 110. The light is first absorbed by the wide-bandgap perovskite (high-energy photons), and the transmitted low-energy long-wavelength photons are then absorbed by the bottom silicon cell 110. Its optical design focuses on maximizing the transmittance of the perovskite layer and tunneling layer for long wavelengths, and utilizing the silicon back electrode for reflection.

[0060] When the tandem solar cell 100 is in an inverted structure, during operation, light is incident from the side of the silicon cell 110 away from the perovskite cell, passing through both the silicon cell 110 and the perovskite cell. The light is first absorbed by the narrow bandgap silicon (partially low-energy photons), and the transmitted high-energy short-wavelength photons are then absorbed by the top perovskite, and finally reflected back into the device by the top metal electrode for secondary absorption.

[0061] In this embodiment of the application, the tandem solar cell 100 further includes a first electrode 190 and a second electrode 180. The first electrode 190 is disposed on the side of the silicon cell 110 facing away from the perovskite cell, and the second electrode 180 is disposed on the side of the perovskite cell facing away from the silicon cell 110.

[0062] In this embodiment, the first electrode 190 is a metal layer, referred to as the first metal layer 190, and the first electrode 190 is the metallized grid line of the silicon cell 110; the specific structural design of the second electrode 180 can be determined according to whether the tandem solar cell 100 is a formal structure or an inverted structure.

[0063] In some embodiments, the tandem solar cell 100 is a formal structure, the second electrode 180 is a transparent conductive film, referred to as the first transparent conductive layer; the tandem solar cell 100 also includes an interconnect layer (also called an independent tunnel junction), the interconnect layer being disposed between the silicon cell 110 and the perovskite cell.

[0064] In the above embodiments, the material of the first transparent conductive layer can be selected from a variety of options.

[0065] In some embodiments, the material of the first transparent conductive layer includes at least one of indium tin oxide, fluorine-doped tin oxide, tungsten-doped indium oxide, aluminum / gallium zinc oxide, etc.

[0066] In some embodiments, the thickness of the first transparent conductive layer is 10~40nm, specifically 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm or any value between them.

[0067] Based on the above embodiments, in some specific embodiments, the interconnect layer is a metal oxide layer, or the side of the interconnect layer facing the organic hole transport layer 150 contains a metal oxide. The 1,2-bisphosphonic acid derivative based on a rigid aromatic framework in the organic hole transport layer 150 can form a chelate structure with the metal atoms in the interconnect layer.

[0068] Based on the above embodiments, in some other specific embodiments, the perovskite solar cell includes an inorganic hole transport layer 140, which is a metal oxide layer, disposed on an interconnect layer, and an organic hole transport layer 150 disposed on the inorganic hole transport layer 140.

[0069] In some embodiments, the interconnect layer includes a third transparent conductive layer, a metal layer (denoted as the third metal layer) and a fourth transparent conductive layer stacked together, with the perovskite solar cell disposed on the side of the fourth transparent conductive layer facing away from the third metal layer, and the fourth transparent conductive layer being a metal oxide layer.

[0070] In some embodiments, the materials of the third and fourth transparent conductive layers include indium tin oxide.

[0071] In some embodiments, the thickness of the third transparent conductive layer is 10~40nm, specifically 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm or any value between them.

[0072] In some embodiments, the thickness of the fourth transparent conductive layer is 10~40nm, specifically 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm or any value between them.

[0073] In some embodiments, the material of the third metal layer includes at least one of gold, silver, copper, etc.

[0074] In some embodiments, the thickness of the third metal layer is 1 to 3 nm, specifically 1 nm, 2 nm, 3 nm or any value between them.

[0075] In some embodiments, the total thickness of the interconnect layer is 10~40nm, specifically 10nm, 15nm, 20nm, 25nm, 30nm, 35nm, 40nm or any value between them.

[0076] Please see Figure 1 In some embodiments, the tandem solar cell 100 has an inverted structure, with both the first electrode 190 and the second electrode 180 being metal layers. A third electrode, a transparent conductive film, is also disposed on the side of the silicon cell 110 facing the tandem solar cell 100. This third electrode is a second transparent conductive layer 130, which is part of the overall structure of the silicon cell 110. That is, the silicon cell 110 includes a silicon substrate and a second transparent conductive layer 130, with the second transparent conductive layer 130 disposed on the side of the silicon substrate facing the perovskite cell. Specifically, the first electrode 190 is referred to as the first metal layer 190, for example, an Ag layer; the second electrode 180 is referred to as the second metal layer 180, for example, an Ag layer. In the above embodiments, the thickness of the first metal layer 190 is 0.7~1um, specifically 0.7um, 0.8um, 0.9um, 1um or any value between them.

[0077] In the above embodiments, the thickness of the second metal layer 180 is 0.7~1um, specifically 0.7um, 0.8um, 0.9um, 1um or any value between them.

[0078] In the above embodiments, the first metal layer 190 and the second metal layer 180 are strip structures. The width of the first metal layer 190 is 0.5~1um, and / or the width of the second metal layer 180 is 0.6~0.9um, specifically 0.6um, 0.7um, 0.8um, 0.9um or any value between them.

[0079] Based on the above embodiments, in some specific embodiments, the second transparent conductive layer 130 is a metal oxide layer. The 1,2-bisphosphonic acid derivative based on a rigid aromatic framework in the organic hole transport layer 150 can form a chelate structure with the metal atoms in the second conductive layer.

[0080] Based on the above embodiments, in some other specific embodiments, the perovskite solar cell includes an inorganic hole transport layer 140, which is a metal oxide layer, disposed on the second transparent conductive layer 130, and an organic hole transport layer 150 disposed on the inorganic hole transport layer 140.

[0081] In the above embodiments, the material of the second transparent conductive layer 130 can be selected from a variety of options.

[0082] In some embodiments, the material of the second transparent conductive layer 130 includes indium tungsten oxide.

[0083] In some embodiments, the thickness of the second transparent conductive layer 130 is 30~50nm, specifically 30nm, 35nm, 40nm, 45nm, 50nm or any value between them.

[0084] It should be noted that in the above embodiments, the interconnect layer is also essentially a transparent conductive structure, but the interconnect layer is the "connector in series," while the second transparent conductive layer 130 is the "tentacle of the silicon cell 110 itself." They are fundamentally different in their electrical affiliation, optical role, and structural position in the device.

[0085] Please see Figure 2 In this embodiment of the application, the method for fabricating the tandem solar cell 100 includes the following steps: S10. Prepare an organic hole transport layer precursor solution, wherein the organic hole transport layer precursor solution includes a 1,2-bisphosphonic acid derivative based on a rigid aromatic skeleton. S20. A silicon cell 110 is provided, and a metal oxide layer is disposed on one side of the silicon cell 110. An organic hole transport layer precursor solution is coated on the metal oxide layer to form an organic hole transport layer 150 on the metal oxide layer. S30. A perovskite absorber layer 160, an electron transport layer 170, and a second electrode 180 are sequentially disposed on the side of the organic hole transport layer 150 facing away from the silicon cell 110.

[0086] In some embodiments, step S10 specifically includes: mixing an organic hole transport material, including a 1,2-bisphosphonic acid derivative based on a rigid aromatic skeleton, with a first solvent to prepare an organic hole transport layer 150 precursor solution of 0.7~1.3 mg / L.

[0087] In the above embodiments, the first solvent may be selected from at least one of alcohol ether organic solvents such as ethanol and isopropanol.

[0088] In some embodiments, in step S20, after coating the hole transport layer precursor solution onto the metal oxide layer, a first annealing treatment is also required. The hole transport layer precursor solution is dried by the annealing treatment to obtain an organic hole transport layer 150 thin film.

[0089] In some embodiments, the temperature of the first annealing treatment is 100–140°C, and the duration of the first annealing treatment is 8–15 min. Within this temperature range, organic hole transport materials, including 1,2-bisphosphonic acid derivatives based on rigid aromatic skeletons, can acquire sufficient energy to move and interact more fully. The reaction between the phosphonic acid groups and the metal sites of the metal oxide layer is more active, which helps to form stronger chemical bonds, thereby enhancing the anchoring effect. An appropriate annealing temperature can promote a more ordered molecular arrangement in the organic hole transport layer 150, forming a denser and more uniform film structure. This structural optimization helps to reduce defects and porosity inside the film, making the contact between the organic hole transport layer 150 and the substrate (metal oxide layer) tighter, further improving the anchoring effect.

[0090] In some embodiments, in step S20, the organic hole transport layer 150 precursor solution is coated onto the metal oxide layer using a spin coating method. The spin coating method has a rotation speed of 4000~5000 rpm and a duration of 20~30 seconds.

[0091] In the above embodiments, the spreading and film formation process of the organic hole transport layer 150 precursor solution on the metal oxide layer surface can be effectively controlled within a rotation speed range of 4000~5000 rpm. A suitable rotation speed allows the mixed solution to be uniformly distributed on the substrate surface, forming a film of uniform thickness. This uniform film thickness helps ensure consistent distribution of the organic hole transport layer 150 material across the metal oxide layer surface, enabling the phosphonic acid groups to fully contact and react with the active sites on the substrate surface, thereby enhancing the overall anchoring effect.

[0092] In some embodiments, in step S20, the temperature of the first annealing treatment is 110~130°C, the duration of the first annealing treatment is 9~12 min, the rotation speed of the spin coating method is 4200~4500 rpm, and the duration is 22~27 seconds.

[0093] In some embodiments, the specific steps of S30 include: S31. Prepare perovskite precursor solution; S32. The perovskite absorber layer 160 precursor solution is coated on the surface of the organic hole transport layer 150 and subjected to a second annealing treatment to obtain the perovskite absorber layer 160. S33. An electron transport layer 170 is deposited on the surface of the perovskite absorber layer 160; S34. A second electrode 180 is disposed on the surface of the electron transport layer 170.

[0094] In some embodiments, step S31 includes: uniformly mixing CsI, PbI2, PbBr2, FAI and MAI in a second solvent according to a certain molar ratio to prepare a perovskite absorber layer 160 precursor solution.

[0095] In the above embodiments, the second solvent may be selected from at least one of DMF, DMSO, etc.

[0096] In some embodiments, in step S32, a spin coating method is used to coat the perovskite absorber layer 160 precursor solution onto the surface of the organic hole transport layer 150. The spin coating method has a rotation speed of 3000~5000 rpm and a duration of 20~30 seconds, which can make the perovskite precursor solution uniformly coated on the organic hole transport layer 150.

[0097] At a rotation speed of 3000-5000 rpm, the perovskite absorber layer 160 precursor solution can be uniformly spread on the surface of the organic hole transport layer 150 with appropriate centrifugal force, forming a thin film of uniform thickness. The uniformly coated perovskite absorber layer 160 precursor solution can form good interfacial contact with the organic hole transport layer 150, which is beneficial to the effective transport of holes from the perovskite absorber layer 160 to the organic hole transport layer 150, thereby improving the photoelectric conversion efficiency of the tandem solar cell 100.

[0098] In some embodiments, in step S32, the temperature of the second annealing treatment is 90~100°C, and the duration of the second annealing treatment is 8~15 min.

[0099] By controlling the temperature and duration of the second annealing treatment within the aforementioned range, sufficient crystallization of the perovskite absorber layer 160 precursor can be ensured, avoiding excessive crystal growth or other adverse reactions. This also helps to obtain a perovskite absorber layer 160 with moderate grain size and fewer defects, thereby improving the overall performance of the perovskite solar cell.

[0100] In some embodiments, the specific steps of S33 include: A C60 thin film was deposited on the perovskite absorber layer 160 using a vapor deposition machine. Then, an ALD device was used to deposit a SnO2 film on the C60 film; An IZO layer was deposited on the surface of a SnO2 thin film using magnetron sputtering.

[0101] In this embodiment, the first electrode 190 is a metal layer; the second electrode 180 can be a metal layer or a transparent conductive film.

[0102] In some embodiments, the tandem solar cell 100 is the formal structure, and the specific steps of S34 include: forming a transparent conductive film on the surface of the electron transport layer 170, which is the second electrode 180.

[0103] In some embodiments, the tandem solar cell 100 has an inverted structure, and the specific steps of S34 include: depositing metal onto the surface of the electron transport layer 170 to prepare the second electrode 180.

[0104] The fabrication method of the tandem solar cell 100 in this application has the advantages of simple fabrication process, low raw material cost, and suitability for industrial production. The molecular structure of the 1,2-bisphosphonic acid derivative based on a rigid aromatic framework in the organic hole transport layer 150 not only has excellent anchoring effect with its substrate (metal oxide layer), but also has good buried passivation effect, optimizing the energy level matching with the perovskite absorber layer 160 (PVK), and improving the spreadability of the perovskite absorber layer 160 precursor solution. This results in the tandem solar cell 100 exhibiting good stability, carrier extraction capability, and superior photoelectric conversion efficiency. The tandem solar cell 100 prepared by this method has good structural stability and can be stored outdoors for 1000 hours with a cell degradation of less than 1%. The present application will be further described below through specific embodiments and comparative examples, but the present application is not limited to these specific examples.

[0105] Example 1 (1) Preparation of inorganic hole transport layer: Provide 1cm A 1cm silicon substrate is used to deposit a nickel oxide thin film (inorganic hole transport layer) on the silicon substrate to obtain a Si / inorganic hole transport layer composite layer, wherein the thickness of the inorganic hole transport layer is 5nm.

[0106] (2) Preparation of organic hole transport layer: Weigh 1 mg of 1,2-phenylene diphosphonic acid, dissolve it in 2 mL of ethanol solution, add a magnetic stir bar, stir overnight to dissolve it, and obtain an organic hole transport layer precursor solution.

[0107] In a glove box, an appropriate amount of hole transport layer precursor solution is uniformly dropped onto the surface of the inorganic hole transport layer of the composite layer in step (1), spin-coated at 4500 rpm for 250 seconds, annealed at 120°C for 10 minutes, and then cooled to room temperature to obtain a Si / inorganic hole transport layer / organic hole transport layer composite layer, wherein the thickness of the organic hole transport layer is 5 nm.

[0108] (3) Preparation of perovskite absorber layer: CsI, PbI2, PbBr2, FAI and MAI were uniformly mixed in DMF and DMSO according to a certain molar ratio to prepare a perovskite absorber layer precursor solution. A perovskite absorber layer was deposited on the surface of the composite layer obtained in step (2) above using a nitrogen air knife device: the perovskite absorber layer precursor solution was spread all over the surface of the organic hole transport layer and scraped at a speed of 10 cm / s. After coating, it was annealed at 95°C for 10 minutes to obtain a composite layer of Si / inorganic hole transport layer / organic hole transport layer / perovskite absorber layer, wherein the thickness of the perovskite absorber layer is 500 nm.

[0109] (4) Preparation of electron transport layer: C60 thin film was deposited on the surface of perovskite absorber layer of Si / inorganic hole transport layer / organic hole transport layer / perovskite absorber layer composite layer using a vapor deposition machine; then SnO2 thin film was deposited on C60 thin film using an ALD device; then IZO thin film was deposited on SnO2 thin film using magnetron sputtering technology; a composite layer of Si / inorganic hole transport layer / organic hole transport layer / perovskite absorber layer / C60 layer / SnO2 layer / IZO layer was obtained, wherein the thickness of C60 layer is 15nm, the thickness of SnO2 layer is 15nm, and the thickness of IZO layer is 35nm.

[0110] (5) Electrode preparation: The composite layer obtained in step (5) is placed in a vacuum evaporation chamber, and Ag (1000nm) is deposited on the IZO layer to obtain a tandem solar cell.

[0111] Example 2 The difference from Example 1 is that in step (2), 1,2-phenylene diphosphonic acid in Example 1 is replaced with 4-(9H-carbazole-9-yl)phenyl-1,2-bisphosphonic acid.

[0112] Example 3 The difference from Example 1 is that in step (1), the thickness of the inorganic hole transport layer is 10 μm.

[0113] Example 4 The difference from Example 1 is that in step (1), the thickness of the inorganic hole transport layer is 1 μm.

[0114] Comparative Example 1 The difference from Example 1 is that in step (2), 1,2-phenylene diphosphonic acid in Example 1 is replaced with 2pacz ([2-(9H-carbazole-9-yl)ethyl]phosphonic acid).

[0115] Comparative Example 2 The difference from Example 1 is that in step (2), 1,2-phenylene diphosphonic acid in Example 1 is replaced with MEO-2PACZ ([2-(3,6-dimethoxy-9H-carbazole-9-yl)ethyl]phosphonic acid).

[0116] Comparative Example 3 The difference from Example 1 is that in step (2), the 1,2-phenylene diphosphonic acid in Example 1 is replaced with ME-4PACZ ([4-(3,6-dimethyl-9H-carbazole-9-yl)butyl]phosphonic acid).

[0117] Performance testing: The power of the tandem solar cell devices prepared in the above embodiments and comparative examples was adjusted to 100 mW / cm². 2 To simulate the AM 1.5G radiation standard, the current and voltage values ​​of the devices were read by a computer connected to a Keithley 2450 power meter. Before measuring the JV curve, the light intensity was calibrated using a Newport standard silicon cell 91150, with the device in forward and reverse scan mode at a scan rate of 0.05 V / s. The open-circuit voltage (Voc), short-circuit current (Jsc), fill factor (FF), and power conversion efficiency (PCE) of each tandem solar cell device were obtained. The specific test results are shown in Table 1 below. Table 1. Performance test results of each embodiment and comparative example analyze: By comparing Examples 1-4 with Comparative Examples 1-2, it can be demonstrated that, compared to existing monophosphate organic hole transport materials, organic hole materials based on rigid aromatic frameworks of 1,2-bisphosphonic acid derivatives are more effective in enhancing the bonding strength between the organic hole transport layer and the silicon cell, improving the contact uniformity between the silicon cell and the perovskite absorber layer, and thus enhancing the photoelectric performance of tandem solar cells. Furthermore, unlike conventional bisphosphonic acid molecular structures, the chelation and anchoring effect of organic hole materials based on rigid aromatic frameworks of 1,2-bisphosphonic acid derivatives can further enhance the bonding strength between the organic hole transport layer and the silicon cell, thereby improving the photoelectric performance of tandem solar cells. The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A tandem solar cell, characterized in that, The invention includes a silicon cell and a perovskite cell stacked together. The perovskite cell includes an organic hole transport layer, a perovskite absorber layer, and an electron transport layer stacked on one side of the silicon cell. The silicon cell has a metal oxide layer disposed on the side facing the organic hole transport layer. The organic hole transport layer is disposed on the metal oxide layer, and the material of the organic hole transport layer includes a 1,2-bisphosphonic acid derivative based on a rigid aromatic framework.

2. The tandem solar cell as described in claim 1, characterized in that, The 1,2-bisphosphonic acid derivatives based on rigid aromatic skeletons include at least one of 1,2-phenylene bisphosphonic acid and its derivatives and 4-(9H-carbazole-9-yl)phenyl-1,2-bisphosphonic acid and its derivatives.

3. The tandem solar cell as described in claim 1, characterized in that, The metal oxide layer is an inorganic hole transport layer.

4. The tandem solar cell as described in claim 3, characterized in that, The material of the inorganic hole transport layer includes at least one of nickel oxide, cuprous oxide, cobalt oxide, molybdenum oxide, tungsten oxide, vanadium oxide, cuprous thiocyanate, nickel sulfide, molybdenum sulfide, and tungsten sulfide.

5. The tandem solar cell as described in claim 3, characterized in that, The thickness of the inorganic hole transport layer is 1~10nm.

6. The tandem solar cell as described in claim 1, characterized in that, The tandem solar cell further includes a first electrode and a second electrode. The first electrode is disposed on the side of the silicon cell facing away from the perovskite cell, and the second electrode is disposed on the side of the perovskite cell facing away from the silicon cell. The second electrode is a first transparent conductive layer, or the second electrode is a metal layer.

7. The tandem solar cell as described in claim 6, characterized in that, The second electrode is a first transparent conductive layer, and the metal oxide layer is an interconnect layer disposed between the silicon cell and the perovskite cell; or, The second electrode is a metal layer, the metal oxide layer is a second transparent conductive layer, and the silicon cell includes a silicon substrate and the second transparent conductive layer, which is disposed on the side of the silicon substrate facing the perovskite cell.

8. The tandem solar cell as described in claim 7, characterized in that, It also includes at least one of the following features: (1) The thickness of the first transparent conductive layer is 5~40nm; (2) The thickness of the interconnect layer is 10~30nm; (3) The thickness of the metal layer is 0.7~1um and the width is 0.6um~0.9um; (4) The thickness of the second transparent conductive layer is 30~50nm.

9. The tandem solar cell as described in claim 7, characterized in that, The interconnect layer includes a third transparent conductive layer, a metal layer, and a fourth transparent conductive layer stacked together. The perovskite solar cell is disposed on the side of the fourth transparent conductive layer facing away from the metal layer. The materials of the third and fourth transparent conductive layers include indium tin oxide.

10. The tandem solar cell as claimed in claim 7, characterized in that, The material of the second transparent conductive layer includes indium tungsten oxide.

11. The tandem solar cell according to any one of claims 1-10, characterized in that, The electron transport layer is a single-layer film or a composite film of at least one material selected from tin oxide, titanium oxide, zinc oxide, zirconium oxide, indium oxide, aluminum-doped zinc oxide, C60, C70, PCBM, lithium chloride, and cesium carbonate.

12. The tandem solar cell according to any one of claims 1-10, characterized in that, It also includes at least one of the following features: (1) The thickness of the organic hole transport layer is 1~10 nm; (2) The thickness of the perovskite absorber layer is 400~600 nm; (3) The thickness of the electron transport layer is 10~20nm; (4) The silicon cell is selected from any one of HJT, TOPCon, IBC, HJT-IBC, and TOPCon-IBC.

13. The tandem solar cell according to any one of claims 1-10, characterized in that, The silicon cell has a textured structure on the side facing the perovskite solar cell, and the perovskite solar cell is disposed on the textured structure.

14. A method for preparing a tandem solar cell, characterized in that, Includes the following steps: Prepare a hole transport layer precursor solution, wherein the hole transport layer precursor solution comprises a 1,2-bisphosphonic acid derivative based on a rigid aromatic skeleton. A silicon cell is provided, wherein a metal oxide layer is disposed on one side of the silicon cell, and a hole transport layer precursor solution is coated on the metal oxide layer to form a hole transport layer on the metal oxide layer. A perovskite absorber layer, an electron transport layer, and a second electrode are sequentially disposed on the side of the hole transport layer facing away from the silicon cell.

15. A photovoltaic module, characterized in that, This includes the tandem solar cell as described in any one of claims 1-13, or the tandem solar cell prepared by the preparation method as described in claim 14.

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