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

Abstract

The application relates to the technical field of photoelectric devices, in particular to a stacked solar cell, a preparation method thereof and a photovoltaic module. The stacked solar cell comprises a bottom cell and a first charge transport layer which are arranged in a stack, the bottom cell has a first textured structure, the first charge transport layer is arranged on the surface of the first textured structure to form a second textured structure, the second textured structure has a valley bottom and a peak tip, a perovskite light-absorbing layer is arranged on the side of the first charge transport layer away from the bottom cell, a spacing layer is arranged between the first charge transport layer and the perovskite light-absorbing layer and covers at least part of the valley bottom of the second textured structure, the spacing layer comprises a spacing material with a melting point of 90 DEG C to 170 DEG C, and the spacing material comprises at least one functional group selected from a phosphonic acid group, a biguanide group and a triazine group. The stacked solar cell can prevent the decomposition of the valley bottom metal halide, effectively passivate the interface defects, and improve the photoelectric conversion efficiency and long-term stability of the cell.

Description

Technical Field

[0001] This application relates to the field of optoelectronic device technology, specifically to tandem solar cells and their fabrication methods, and photovoltaic modules. Background Technology

[0002] Single-junction solar cells are limited by the Shockley-Queisser efficiency limit, creating an inherent bottleneck in improving photoelectric conversion performance. Tandem solar cells, by stacking sub-cells with different bandgap sizes in series, can utilize the full solar spectrum in a segmented manner, reducing energy loss of photogenerated carriers and thus overcoming the efficiency bottleneck of single-junction solar cells. In particular, introducing a pyramidal textured surface structure into tandem solar cells can suppress interface light reflection, enhance light-harvesting capabilities, and significantly improve the device's light absorption efficiency.

[0003] Perovskite solar cells possess advantages such as tunable bandgap, high light absorption coefficient, low-temperature fabrication capability, and excellent spectral matching performance with various bottom solar cells, making them the preferred choice for top solar cells. Currently, mainstream technologies use crystalline silicon bottom solar cells with a pyramidal textured surface as a substrate to fabricate perovskite top solar cells. When using a two-step process to prepare the perovskite absorbing layer, an inorganic metal halide precursor is first coated / deposited to construct an inorganic metal halide framework on the pyramidal textured surface. Then, an organic precursor solution is coated onto the surface of the inorganic metal halide framework, followed by an annealing reaction to generate a complete perovskite absorbing layer.

[0004] However, this process has significant drawbacks: the pyramidal textured surface has obvious steric hindrance at the valley bottom, hindering the deep penetration of the organic precursor solution. This results in insufficient reaction between the inorganic metal halide precursor and the organic precursor at the valley bottom, leading to the formation of inorganic residual phases. Simultaneously, the difference in solvent drying rates between the peaks and valleys of the textured surface exacerbates the uneven crystallization of the perovskite film and the problem of residual inorganic metal halide precursors at the valley bottom. The residual inorganic metal halide precursors are prone to decomposition and induce interface defects, causing a decrease in the photoelectric conversion efficiency of the tandem solar cell and a deterioration in its long-term operational stability. Summary of the Invention

[0005] Based on this, this application provides a tandem solar cell, its fabrication method, and a photovoltaic module. The tandem solar cell of this application can prevent the decomposition of the valley-bottom inorganic metal halide precursor and effectively passivate interface defects, which is beneficial to improving the photoelectric conversion efficiency and long-term stability of the cell.

[0006] A first aspect of this application provides a tandem solar cell, comprising: a bottom cell and a first charge transport layer stacked together, the bottom cell having a first textured structure, the first charge transport layer being disposed on the surface of the first textured structure to form a second textured structure; the second textured structure having valleys and peaks.

[0007] A perovskite light-absorbing layer is disposed on the side of the first charge transport layer away from the bottom cell.

[0008] A spacer layer is disposed between the first charge transport layer and the perovskite light-absorbing layer and covers at least a portion of the valley bottom of the second textured structure;

[0009] The spacer layer comprises a spacer material with a melting point of 90°C to 170°C; the spacer material comprises at least one functional group selected from phosphonic acid group, biguanide group and triazine group.

[0010] In some embodiments, the spacer material comprises at least one of compounds having a structure as shown in formulas (I) to (IV): , , , ,

[0011] Where n1 is any integer between 1 and 6; X is F, Cl, Br, or I; n2 is any integer between 1 and 6; Ar is C6 to C 12 Aromatic group; each time R1 appears, it is independently a C6 to C8 alkyl group.

[0012] In some embodiments, n1 is any integer between 3 and 5.

[0013] In some embodiments, X is Cl, and n2 is any integer between 1 and 3.

[0014] In some of these embodiments, Ar is phenyl.

[0015] In some of these embodiments, R1 is independently 2-ethylhexyl each time it appears.

[0016] In some embodiments, the spacer layer comprises a material with a melting point of 90°C to 150°C.

[0017] In some embodiments, the ratio of the thickness of the spacer layer to the pile depth of the second pile structure is 1:(80-100).

[0018] In some embodiments, the first charge transport layer is a hole transport layer.

[0019] In some embodiments, the perovskite light-absorbing layer comprises a perovskite structural material with the general structural formula ABX3; wherein A comprises at least one selected from cesium ions, rubidium ions, lithium ions, sodium ions, potassium ions, thallium ions, ammonium ions, methylamine ions, ethylammonium ions, dimethylamine ions, trimethylammonium ions, tetramethylammonium ions, formamidinium ions, methylformamidinium ions, ethylammonium ions, and guanidine ions; B comprises at least one selected from lead ions, tin ions, and germanium ions; and X comprises at least one selected from bromide ions, iodide ions, and chloride ions.

[0020] In some embodiments, the tandem solar cell further includes a second charge transport layer, a transparent conductive layer, and electrode grid lines sequentially disposed on the surface of the perovskite light-absorbing layer away from the spacer layer.

[0021] In some embodiments, the bottom battery includes:

[0022] A silicon substrate having a first surface and a second surface disposed opposite to each other;

[0023] An n-type window layer and a composite layer are sequentially disposed on the first surface; wherein, the first surface has a velvety structure, the n-type window layer is conformally covered on the first surface, and the composite layer conformally covers the surface of the n-type window layer, thereby forming the first velvety structure;

[0024] A p-type window layer and a back field electrode are sequentially disposed on the second surface.

[0025] A second aspect of this application provides a method for fabricating a tandem solar cell, comprising:

[0026] A bottom battery is provided, the bottom battery having a first textured surface structure;

[0027] A first charge transport layer is prepared on the surface of the first textured structure to form a second textured structure; the second textured structure has valleys and peaks.

[0028] Forming a spacer layer that covers at least part of the valley bottom of the second velvet structure;

[0029] A perovskite light-absorbing layer is formed on the side of the first charge transport layer away from the bottom cell. The perovskite light-absorbing layer covers the spacer layer and the portion of the second textured structure not covered by the spacer layer. The spacer layer comprises a spacer material with a melting point of 90°C to 170°C. The spacer material comprises at least one functional group selected from phosphonic acid, biguanide, and triazine groups.

[0030] In some embodiments, the spacer material comprises at least one of compounds having a structure as shown in formulas (I) to (IV): , , , ;

[0031] Where n1 is any integer between 1 and 6; X is F, Cl, Br, or I; n2 is any integer between 1 and 6; Ar is C6 to C 12 Aromatic group; each time R1 appears, it is independently a C6 to C8 alkyl group.

[0032] In some embodiments, the step of forming the spacer layer covering at least a portion of the valley floor of the second velvet structure includes:

[0033] A spacer material solution is applied to the surface of the second velvet structure and annealed to obtain a spacer layer covering at least a portion of the valley bottom of the second velvet structure; the spacer material solution includes spacer material and solvent.

[0034] In some embodiments, the mass concentration of the spacer material in the spacer material solution is 1 mg / mL to 4 mg / mL.

[0035] In some embodiments, the solvent of the spacer material solution includes at least one of ethanol, isopropanol, n-butanol, dimethylformamide, and dimethyl sulfoxide.

[0036] In some embodiments, the annealing temperature is greater than or equal to the melting point of the spacer material.

[0037] In some embodiments, the step of forming a perovskite light-absorbing layer on the side of the first charge transport layer away from the bottom cell includes:

[0038] A metal halide solution is coated on the side of the first charge transport layer away from the bottom cell to obtain a metal halide framework layer. The metal halide framework layer covers the spacer layer and the portion of the second textured structure not covered by the spacer layer.

[0039] An organic halide solution is coated onto the side of the metal halide framework layer facing away from the first charge transport layer, and then annealed to obtain a perovskite light-absorbing layer.

[0040] Optionally, the metal halide in the metal halide solution has a chemical formula including at least one of AlX and BX, and the organic halide in the organic halide solution has a chemical formula of A2X, wherein A1 includes at least one of cesium ion, rubidium ion, lithium ion, sodium ion, potassium ion and thallium ion; A2 includes at least one of ammonium ion, methylamine ion, ethylammonium ion, dimethylamine ion, trimethylammonium ion, tetramethylammonium ion, formamidine ion, methylformamidine ion, ethylamidine ion and guanidine ion; B includes at least one of lead ion, tin ion and germanium ion; and X includes at least one of bromide ion, iodide ion and chloride ion.

[0041] In some embodiments, the annealing temperature is 90°C to 170°C.

[0042] A third aspect of this application provides a photovoltaic module, including a tandem solar cell as described in any one of the first aspects of this application or a tandem solar cell prepared by any one of the preparation methods of the second aspect of this application.

[0043] The tandem solar cell provided in this application has at least the following beneficial effects:

[0044] The tandem solar cell provided in this application has a spacer layer between the valley bottom of the second textured structure and the perovskite light-absorbing layer. The spacer material contains functional groups such as phosphonic acid groups, biguanide groups, and triazine groups, which can coordinate and bind or hydrogen bond with the oxygen vacancies, dangling bonds, and other defect sites enriched in the valley bottom of the pyramid structure, effectively filling the interface defects. At the same time, these functional groups can be directionally adsorbed in the valley bottom region, blocking excessive contact between the perovskite light-absorbing layer and the first charge transport layer, reducing interface stress and non-radiative charge recombination, achieving precise passivation of the valley bottom region, and reducing the interface defect density.

[0045] On the other hand, the melting point of the spacer material is 90℃~170℃, which is compatible with the annealing temperature when preparing the perovskite light-absorbing layer. When preparing the perovskite light-absorbing layer, the spacer material melts and coats the unreacted metal halides at the bottom of the second textured structure, thus avoiding the decomposition of metal halides in the tandem solar cell.

[0046] On the other hand, the aforementioned spacer layer has good compatibility with the first charge transport layer and the perovskite light-absorbing layer, which is beneficial to improving the photoelectric conversion efficiency and long-term stability of the tandem solar cell. Attached Figure Description

[0047] To more clearly illustrate the technical solutions in the embodiments of this application or the prior art, the drawings used in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0048] Figure 1 This is a schematic diagram of the structure of a tandem solar cell provided as an example of this application.

[0049] Figure 2This is a structural flowchart of a method for fabricating a tandem solar cell provided in an example of this application; wherein (a) is a structural schematic diagram of the second textured structure in step S30, in which the spacer material solution 410 is coated on the surface of the first charge transport layer; wherein (b) is a structural schematic diagram of the spacer material melting and sliding down to the bottom of the second textured structure after annealing to form a spacer layer 400; wherein (c) is a structural schematic diagram of the metal halide framework layer 310 formed in step S41; and wherein (d) is a structural schematic diagram of the spacer layer solidifying and forming a perovskite light-absorbing layer after the annealing process is completed.

[0050] Figure 3 The images show scanning electron microscope (SEM) images of the first charge transport layer surface having a second textured surface structure formed in step (2) of Embodiment 1 of this application, and scanning electron microscope (SEM) images of the spacer layer covering the valleys of the second textured surface structure of the first charge transport layer surface after the spacer layer has been cured in step (3) of Embodiment 1; wherein, Figure 2 A and C are scanning electron microscope images of the second textured surface of the first charge transport layer formed in step (2) of Example 1. Figure 2 b and d are scanning electron microscope images of the valley of the second textured structure on the surface of the first charge transport layer after the spacer layer is cured in step (3) of Example 1.

[0051] Explanation of reference numerals in the attached figures

[0052] 10-Taped solar cell; 100-Base cell; 200-First charge transport layer; 210-Self-assembled monolayer; 220-Transition metal oxide layer; 300-Perovskite light-absorbing layer; 400-Spacer layer; 500-Second charge transport layer; 600-Transparent conductive layer; 700-Electrode grid line; 800-Buffer layer; 900-Passivation layer; 910-Antireflection layer; 110-Silicon substrate; 120-n-type window layer; 130-Composite layer; 140-p-type window layer; 150-Back field electrode; 151-Transparent electrode layer; 152-Metal electrode layer; 160-First intrinsic hydrogenated amorphous silicon passivation layer; 170-Second intrinsic hydrogenated amorphous silicon passivation layer; 410-Spacer material solution; 310-Metal halide framework layer. Detailed Implementation

[0053] The following detailed description, in conjunction with specific embodiments, provides a more complete and clear account of the tandem solar cell 10, its fabrication method, and the photovoltaic module. This application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a more thorough and complete understanding of the disclosure of this application.

[0054] Perovskite-crystalline silicon tandem solar cells represent a crucial technological approach to overcoming the theoretical efficiency limits of single-junction cells and achieving high-efficiency photovoltaic devices. Their photoelectric performance is closely related to the control of the surface morphology of the crystalline silicon substrate. The crystalline silicon substrate comprises a silicon substrate, which is texturized to form a pyramidal three-dimensional morphology, enhancing light capture capabilities through multiple light reflections and scattering. Simultaneously, the pyramidal structure obtained by conformally shaping the crystalline silicon substrate can induce the directional crystallization of the perovskite light-absorbing layer, improving the uniformity of the thin film coverage. Therefore, crystalline silicon substrates with pyramidal structures are widely used in perovskite-crystalline silicon tandem solar cells.

[0055] Perovskite top solar cells often employ a two-step solution method to prepare the perovskite absorbing layer. This involves first depositing or coating a metal halide framework layer (e.g., lead halide, cesium halide), then coating it with an organic halide solution, followed by annealing to allow the organic halide to react with the metal halide and form perovskite. However, the valleys of the pyramidal textured surface exhibit significant steric hindrance, leading to insufficient penetration of the organic halide solution into the metal halide framework layer. After annealing, incomplete metal halide reaction occurs at the valleys of the pyramidal textured surface, resulting in the formation of metal halide residues, particularly lead halide. Furthermore, the inconsistent solvent evaporation rates between the valleys and the pyramidal slopes further exacerbate the uneven crystallization of the perovskite absorbing layer and the presence of localized metal halide residues.

[0056] Taking lead iodide (PbI2) residue as an example, the residual PbI2 enriched at the bottom of the pyramid structure is prone to decomposition under light and thermal stress, producing free iodide ions and uncoordinated lead ions. Free iodide ions are highly mobile and easily migrate along grain boundaries, corroding the transport layer and electrodes, forming deep-level non-radiative recombination centers; uncoordinated lead ions disrupt the integrity of the perovskite lattice, exacerbating ion migration and defect recombination. These problems significantly increase the interface defect density, hinder efficient charge transport, induce perovskite lattice distortion and phase separation, and severely degrade the photoelectric conversion efficiency and long-term operational stability of tandem solar cells, constraining the key technological bottleneck for improving the efficiency and industrial application of perovskite-crystalline silicon tandem solar cells.

[0057] Based on this, see Figure 1 In a first aspect, this application provides a tandem solar cell 10, comprising: a bottom cell 100 and a first charge transport layer 200 stacked together. The bottom cell 100 has a first textured structure, and the first charge transport layer 200 is disposed on the surface of the first textured structure to form a second textured structure, the second textured structure having valleys and peaks. A perovskite light-absorbing layer 300 is disposed on the side of the first charge transport layer 200 away from the bottom cell 100. A spacer layer 400 is disposed between the first charge transport layer 200 and the perovskite light-absorbing layer 300 and covers at least a portion of the valleys of the second textured structure.

[0058] The spacer layer 400 comprises a spacer material with a melting point of 90°C to 170°C. The spacer material includes at least one functional group selected from phosphonic acid, biguanide, and triazine groups. In this application, "phosphonic acid" refers to... "Biguanidin" refers to... "Triazine" refers to In this context, a single-bond-through-the-ring indicates that the single bond can connect to any site on the ring, and the connection site is not limited to one. Furthermore, "triazine" refers to... In this application, the "perovskite light-absorbing layer 300" covers the spacer layer 400 and the pyramid structure.

[0059] The tandem solar cell 10 provided in this application includes a spacer layer 400 disposed at the valley bottom of the second textured structure of the first charge transport layer 200. The spacer layer 400 comprises a material with a melting point of 90°C to 170°C and contains functional groups such as phosphonic acid groups, biguanide groups, and triazine groups. During the annealing of the perovskite light-absorbing layer 300, the spacer layer 400 in the valley bottom metal halide residue region melts and coats the unconverted metal halides at the valley bottom, inhibiting the decomposition of the metal halides. Simultaneously, the aforementioned functional groups can form coordination bonds with free halide anions or metal cations, effectively fixing easily migrating halide anions or metal cations, alleviating ion migration and grain boundary corrosion, and repairing perovskite lattice defects.

[0060] Furthermore, the aforementioned functional groups can coordinate with or form hydrogen bonds with defect sites such as oxygen vacancies and dangling bonds enriched at the valley bottom of the pyramid structure, effectively filling interface defects. Simultaneously, the material of the aforementioned barrier layer can prevent excessive contact between the perovskite light-absorbing layer 300 and the first charge transport layer 200, reducing interfacial stress and non-radiative charge recombination, achieving precise passivation of the valley bottom region, and reducing the density of interface defects. Moreover, the aforementioned spacer layer 400 exhibits good compatibility with the charge transport layer and the perovskite light-absorbing layer 300, which is beneficial for improving the photoelectric conversion efficiency and long-term stability of the tandem solar cell 10.

[0061] As an example, the spacer material includes at least one of the compounds having the structures shown in formulas (I) to (IV): , , , .

[0062] Where n1 is any integer between 1 and 6. For example, n1 includes, but is not limited to, 1, 2, 3, 4, 5, or 6.

[0063] X is F, Cl, Br, or I. n2 is any integer between 1 and 6. n2 includes, but is not limited to, 1, 2, 3, 4, 5, or 6.

[0064] Ar is C6~C12 Aromatic group. In this application, "aromatic group" refers to an aromatic hydrocarbon group derived from an aromatic ring compound by removing one hydrogen atom. It can be a monocyclic aryl, a fused-ring aryl, or a polycyclic aryl; for polycyclic rings, at least one is an aromatic ring system. Phrases containing this term include, for example, "C6-C6..." 12 "Aromatic group" refers to an aryl group containing 6 to 12 carbon atoms. Each time it appears, it can be independently a C6 aryl group, a C6 aryl group, or a C6 aryl group. 10 Aryl, C 12 Aryl group. Suitable examples include, but are not limited to: benzene, biphenyl, and naphthalene.

[0065] Each instance of R1 is independently a C6-C8 alkyl group. In this application, "alkyl" refers to a saturated hydrocarbon group containing a primary (normal) carbon atom, or a secondary carbon atom, or a tertiary carbon atom, or a quaternary carbon atom, or a combination thereof. Phrases containing this term, such as "C6-C8 alkyl," refer to alkyl groups containing 6-8 carbon atoms. Suitable examples include, but are not limited to, 1-hexyl (normal hexyl, -CH2CH2CH2CH2CH2CH3), 2-hexyl (-CH(CH3)CH2CH2CH2CH3), 3-hexyl (-CH(CH2CH3)(CH2CH2CH3)), 2-methyl-2-pentyl (-C(CH3)2CH2CH2CH3), 3-methyl-2-pentyl (-CH(CH3)CH(CH3)CH2CH3), and 4-methyl-2-pentyl (-CH(CH3)CH2 CH(CH3)2), 3-methyl-3-pentyl (-C(CH3)(CH2CH3)2), 2-methyl-3-pentyl (-CH(CH2CH3)CH(CH3)2), 2,3-dimethyl-2-butyl (-C(CH3)2CH(CH3)2), 3,3-dimethyl-2-butyl (-CH(CH3)C(CH3)3, octyl (-(CH2)7CH3) or 2-ethylhexyl (-CH2CH2(CH2CH3)CH2CH2CH2CH3).

[0066] The spacer layer 400 with structures of formulas (I) to (IV) provided in this application contains phosphonic acid group, biguanide group, and triazine group functional groups, respectively. Its molecular structure is controllable and its melting point is adapted to the annealing conditions of perovskite. After heating, it can accurately spread and coat residual metal halides at the bottom of the pyramid structure. At the same time, through coordination and binding of corresponding functional groups with free ions and lattice defect sites, it can efficiently fix easily migrating ions and passivate interface defects. It also has good compatibility with the interface of perovskite light-absorbing layer 300 and charge transport layer, which can effectively suppress nonradiative recombination, relieve interface stress, and significantly improve the photoelectric conversion efficiency and long-term working stability of perovskite-crystalline silicon tandem solar cell 10.

[0067] In some examples, n1 is any integer between 3 and 5. Further, n1 is either 3 or 5. As an example, n1 is 3, and the spacer material is 4-phosphonobutyric acid. As an example, n1 is 5, and the spacer material is 6-phosphonohexanoic acid. .

[0068] In some examples, X is Cl. n2 is any integer between 1 and 3. Further, n2 is 1. As an example, n2 is 1, and the spacer material is chloromethylphosphoric acid. .

[0069] In some of these examples, Ar is phenyl. As an example, the spacer material is 1-phenylbiguanide. .

[0070] In some of these examples, R1 is independently 2-ethylhexyl each time it appears. As an example, the spacer material is octyltriazinone. .

[0071] Furthermore, the spacer material includes 4-phosphonobutyric acid. 6-phosphonohexanoic acid chloromethylphosphoric acid 1-Phenylan Octyltriazinone At least one of the above. Furthermore, the spacer layer 400 with the above-mentioned specific structure has a melting point adapted to the perovskite annealing process, which can accurately coat the residual metal halide at the bottom of the valley; and can efficiently fix migrating ions and passivate interface defects.

[0072] Furthermore, the spacer layer 400 comprises a material with a melting point of 90°C to 150°C.

[0073] To ensure that the spacer layer 400 is concentrated in the valley region of the pyramid, effectively coating and passivating residual divalent metal halides without over-covering the pyramid protrusions, thus guaranteeing normal charge transport between the perovskite light-absorbing layer 300 and the charge transport layer, in some examples, the ratio of the thickness of the spacer layer 400 to the texture depth of the second textured structure is 1:(80-100).

[0074] In this application, "thickness of spacer layer 400" refers to the vertical film thickness of spacer layer 400 itself, measured at the valley bottom of the second textured structure. "Textured depth of the second textured structure" refers to the vertical distance from the valley bottom to the peak of the second textured structure.

[0075] As an example, the ratio of the thickness of the spacer layer 400 to the pile depth of the second pile structure includes, but is not limited to, 1:80, 1:82, 1:85, 1:88, 1:90, 1:92, 1:95, 1:98 or 1:100, or any two of the above point values ​​as endpoint values ​​within the range.

[0076] In some of these examples, the first charge transport layer 200 is a hole transport layer. The hole transport layer comprises a self-assembled monolayer 210.

[0077] As an example, the material of the self-assembled monolayer 210 generally includes anchoring groups, alkyl bridges, and terminal groups. The alkyl bridges connect the anchoring groups and the terminal groups.

[0078] The anchoring group contains polar atoms such as oxygen, phosphorus, and sulfur, and exists in the form of active functional groups such as phosphonic acid group (-PO(OH)2), carboxyl group (-COOH), hydroxyl group (-OH), and thiol group (-SH).

[0079] Terminal groups include carbazole, dibenzocarbazole, acridine, phenothiazine, or phenyl groups. These terminal groups have a conjugated structure, and their π-electron clouds can compensate for the charge of halogen vacancies in the perovskite absorbing layer 300, thereby filling the shallow energy level defects caused by halogen vacancies. Among these, the nitrogen atoms in nitrogen-containing terminal groups such as carbazole, dibenzocarbazole, acridine, and phenothiazine contain lone pairs of electrons, which can interact with uncoordinated divalent cations (e.g., lead ions, Pb) on the surface of the perovskite absorbing layer 300. 2+ This process forms coordination bonds, thereby passivating deep-level defects caused by uncoordinated divalent cations. Substituents can be further introduced onto the terminal group. These substituents can regulate the electron cloud density of the terminal group, enhancing its coordination strength with uncoordinated divalent cations and improving defect passivation efficiency. Simultaneously, the substituents can form coordination bonds with uncoordinated divalent cations on the surface of the perovskite light-absorbing layer 300, or occupy halogen vacancies through their own electronegativity and lone pair electrons, achieving charge compensation and space filling at defect sites, thus effectively suppressing grain boundary defects. Exemplarily, the substituents include at least one of halogen substituents, alkyl groups, alkoxy groups, benzene substituents, and bis(4-methoxyphenyl)amino groups.

[0080] Alkyl bridges are the "backbone" connecting anchor groups and terminal groups, and are typically composed of saturated carbon chains. The length of the alkyl bridge directly determines the spatial distance between the anchor group and the terminal group, and its chain length and chemical properties further affect the molecular order, conductivity, and steric hindrance of the self-assembled monolayer 210 material.

[0081] For example, self-assembled monolayer materials may include, but are not limited to, [2-(9H-carbazole-9-yl)ethyl]phosphonic acid (2PACz, CAS No. 20999-38-6), [2-(3,6-dimethyl-9H-carbazole-9-yl)ethyl]phosphonic acid (Me-2PACz, CAS No. 2996161-30-7), [2-(3,6-dimethoxy-9H-carbazole-9-yl)ethyl]phosphonic acid (MeO-2PACz, CAS No. 2377770-18-6), and [2-(3,6-diphenyl-9H-carbazole-9-yl)ethyl]phosphonic acid (Ph-2PACz, CAS No. 3085827-62). -6), [2-(3,6-diiodo-9H-carbazole-9-yl)ethyl]phosphonic acid (I-2PACz, CAS No. 3026275-69-1), [2-(3,6-dibromo-9H-carbazole-9-yl)ethyl]phosphonic acid (Br-2PACz, CAS No. 2762888-11-7), [2-(3,6-dichloro-9H-carbazole-9-yl)ethyl]phosphonic acid (Cl-2PACz, CAS No. 3036926-72-1), [2-(3,6-difluoro-9H-carbazole-9-yl)ethyl]phosphonic acid (F-2PACz, CAS No. 3036926-69-6), [2-(7H-diphenyl]phosphonic acid... [2-(9H-9'-phenyl-3,3'-di-carbazole-9-yl)ethyl]phosphoric acid (2PADCB, CAS No. 2882156-61-6), [2-(9H-9'-phenyl-3,3'-di-carbazole-9-yl)ethyl]phosphoric acid (2PABCz), [4-(9H-carbazole-9-yl)butyl]phosphoric acid (4PACz, CAS No. 20999-36-4), [4-(3,6-dimethyl-9H-carbazole-9-yl)butyl]phosphonic acid (Me-4PACz, CAS No. 2747959-96-0), [4-(3,6-dimethoxy-9H-carbazole-9-yl)butyl]phosphonic acid (MeO-4PACz, CAS No. 2922526) -56-3), [4-(3,6-diphenyl-9H-carbazole-9-yl)butyl]phosphoric acid (Ph-4PACz, CAS No. 2814500-04-2), [4-(3,6-diiodo-9H-carbazole-9-yl)butyl]phosphonic acid (I-4PACz, CAS No. 3026275-67-9), [4-(3,6-dibromo-9H-carbazole-9-yl)butyl]phosphonic acid (Br-4PACz, CAS No. 2996161-28-3), [4-(3,6-dichloro-9H-carbazole-9-yl)butyl]phosphonic acid (Cl-4PACz, CAS No. 3026275-66-8), [4-(3,[6-Difluoro-9H-carbazole-9-yl)butyl]phosphonic acid (F-4PACz, CAS No. 3026275-65-7), [4-[3-bromo-6-(4-methoxyphenyl)-9H-carbazole-9-yl]butyl]phosphonic acid (BrMeOPh-4PACz, CAS No. 3053380-37-0), [4-(3,6-di-tert-butyl-9H-carbazole-9-yl)butyl]phosphonic acid (tBu-4PACz, CAS No. 3023627-39-3), [4-(7H-dibenzocarbazole-7-yl)butyl]phosphonic acid (4PADCB, CAS No. 2882156-63-8), [2-(9H-9`-phenyl-3,3`- At least one of the following: [dicarbazole-9-yl)butyl]phosphonic acid (4PABCz, CAS No. 2922526-56-3), [4-(2,7-dibromo-9,9-dimethylacridin-10(9H)-yl)butyl]phosphonic acid (2Br-4DMAcPA / DMAcPA, CAS No. 2971088-37-4), [2-(3,7-dibromo-10H-phenthiazin-10-yl)ethyl]phosphonic acid (Br-2EPT, CAS No. 2826271-17-2), and [2-(4-(bis(4-methoxyphenyl)amino)phenyl)-1-cyanovinyl]phosphonic acid (MPA-CPA, CAS No. 2212003-31-9).

[0082] Furthermore, the hole transport layer also includes a transition metal oxide layer 220, wherein a self-assembled monolayer 210 is disposed between the transition metal oxide layer 220 and the perovskite light-absorbing layer 300.

[0083] In some embodiments, the transition metal oxide layer 220 is made of at least one of nickel oxide, copper oxide, cobalt tetroxide, and ferric oxide. The transition metal oxide material can be prepared using methods such as solution deposition, physical vapor deposition (PVD), atomic layer deposition (ALD), and inkjet printing. The transition metal oxide layer 220 is disposed between the bottom cell 100 and the self-assembled monolayer 210.

[0084] The anchoring groups of the self-assembled monolayer material can form covalent or coordinate bonds with metal ions and hydroxyl groups on the surface of the transition metal oxide layer 220, achieving dense and uniform film formation. The terminal groups of the self-assembled monolayer material can compensate for the charge of halogen vacancies in the perovskite absorber layer 300 through conjugated π electron clouds, and can also form coordinate bonds with uncoordinated cations on the surface of the perovskite absorber layer 300, achieving dual passivation of interface defects. At the same time, it can precisely adjust the interface energy level matching, reduce the hole extraction barrier, and suppress nonradiative recombination at the interface.

[0085] Further, the preparation process of the self-assembled monolayer 210 can be as follows: The material of the self-assembled monolayer 210 is mixed with a solvent and stirred until completely dissolved to obtain a self-assembled monolayer solution. The concentration of the self-assembled monolayer material in the self-assembled monolayer solution can be 0.1 mg / mL to 3 mg / mL. The solvent is selected from at least one of ethanol, isopropanol, and methanol. The self-assembled monolayer solution is coated to obtain a wet film; then, it is heated and annealed at a temperature of 80℃ to 120℃ for 5 min to 20 min to form the self-assembled monolayer 210 (SAM). For example, the coating process of the self-assembled monolayer solution includes spin coating, blade coating, slot coating, and inkjet printing.

[0086] The thickness of the hole transport layer can range from 0.5 nm to 100 nm.

[0087] In some examples, the thickness of the self-assembled monolayer 210 can be 0.5 nm to 5 nm. For example, the thickness of the self-assembled monolayer 210 can be 0.5 nm, 1 nm, 1.5 nm, 2 nm, 2.5 nm, 3 nm, 3.5 nm, 4 nm, 4.5 nm, 5 nm, or a range between any two of the aforementioned values.

[0088] In some examples, the thickness of the transition metal oxide layer 220 can be 5 nm to 30 nm. Exemplarily, the thickness of the transition metal oxide layer 220 can be 5 nm, 10 nm, 12 nm, 15 nm, 20 nm, 25 nm, 30 nm, or a range between any two of the aforementioned values. Transition metal oxides possess excellent stability and a high work function, providing good hole transport channels and electron blocking capabilities.

[0089] In some examples, the perovskite light-absorbing layer 300 comprises a perovskite structure. The general structural formula of the perovskite structure is ABX3, where A includes cesium ions (Cs). + ), rubidium ions (Rb + Lithium ion (Li) + Sodium ions (Na) + ), potassium ions (K) + ), thallium ions (Tl) + ), ammonium ions (NH4) + ), Methylamine ion (MA) (CH3NH3) + ), ethylammonium ion (CH3CH2NH3) + ), dimethylamine ion ((CH3)2NH2) + ), trimethylammonium ion ((CH3)3NH + ), tetramethylammonium ion ((CH3)4N + ), formamidinium ion (FA) (HC(NH2)2+ ), Methylformamidinium ion (CH3C(NH2) 2+ Acetamidinium ion (H3C2(NH2)) 2+ ) and guanidine ions (C(NH2) 3+ B includes at least one of the following: lead ions (Pb). 2+ ), Tin ions (Sn) 2+ ) and germanium ions (Ge 2+ X includes at least one of the following: bromide ions (Br₂). - ), iodide ions (I - ) and chloride ions (Cl - X includes at least one of the following. X also includes thiocyanate ions (SCN). - ), thiocyanate ion (SCN) - It can partially replace halide anions to reduce carrier recombination, prevent halogen migration, suppress photo-induced phase separation, regulate band gap, and improve crystallization.

[0090] Furthermore, the general structural formula of perovskite-structured materials can be Cs x FA y MA 1-x-y Pb(Br z I 1-z )3, where 0≤x≤0.3, 0≤x+y≤1, 0≤z≤0.4.

[0091] For example, the molecular formula of perovskite structure materials can be FAPbI3, MAPbI3, CsPbI3, Cs 0.05 FA 0.8 MA 0.15 PbI3 or Cs 0.24 MA 0.02 FA 0.74 Pb(Br 0.24 I 0.76 3.

[0092] In some examples, the tandem solar cell 10 further includes a second charge transport layer 500, a transparent conductive layer 600, and electrode grid lines 700 sequentially disposed on the surface of the perovskite light-absorbing layer 300 away from the spacer layer 400.

[0093] In some examples, the second charge transport layer 500 is an electron transport layer. Further, the thickness of the electron transport layer can be 3 nm to 50 nm. For example, the thickness of the electron transport layer can be 3 nm, 5 nm, 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, or a range between any two of the aforementioned values.

[0094] Furthermore, the electron transport layer material includes fullerene-based electron transport materials. Fullerene-based electron transport materials include at least one selected from C60, fullerene C70, methyl (6,6)-phenyl-C61-butyrate (PCBM), and 4-(1',5'-dihydro-1'-methyl-2'H-(5,6)fullerene-C60-In-(1,9-c)pyrrole-2'-yl)benzamine chloride (CPMAC). Preparation processes include vacuum evaporation, spin coating, inkjet printing, doctor blade coating, slot coating, dip coating, spray coating, drop coating, and roll-to-roll printing. Vacuum evaporation is preferred, and the evaporation rate can be 0.05–0.1 nm / s.

[0095] Furthermore, the electron transport layer material also includes inorganic metal oxide materials. Inorganic metal oxide materials include at least one of tin oxide, titanium oxide, and zinc oxide. Preparation processes include sol-gel methods, atomic layer deposition (ALD), chemical vapor deposition (CVD, including plasma-enhanced chemical vapor deposition (PECVD), metal-organic chemical vapor deposition (MOCVD), etc.), physical vapor deposition (PVD, including magnetron sputtering, thermal evaporation, pulsed laser deposition (PLD)), spray pyrolysis, solution spin coating, electrochemical deposition, and chemical bath deposition, among which atomic layer deposition (ALD) is preferred.

[0096] The specific process for preparing the electron transport layer of inorganic metal oxide materials by atomic layer deposition (ALD) includes: alternating introduction of a metal precursor and an oxygen source under a gas pressure of 0.05 Torr to 1.5 Torr. The flow rate of the metal precursor introduced in each cycle can be 10 sccm to 100 sccm, and the pulse duration of the metal precursor introduction in each cycle can be 100 ms to 300 ms. The flow rate of the oxygen source introduced in each cycle can be 10 sccm to 100 sccm, and the pulse duration of the oxygen source introduction in each cycle can be 100 ms to 300 ms.

[0097] Electron transport layers of inorganic metal oxide materials are prepared using atomic layer deposition (ALD). The growth rate of the inorganic metal oxide can range from 0.03 nm / cycle to 0.2 nm / cycle, with the required number of cycles depending on the type of metal precursor, oxygen source, and process temperature. It is important to note that during the alternating introduction of the metal precursor and oxygen source, the metal precursor is introduced first.

[0098] Materials for the electron transport layer also include inorganic silicon materials. Inorganic silicon materials include at least one of n-type monocrystalline silicon, n-type polycrystalline silicon, and n-type amorphous silicon. The fabrication processes mainly include low-pressure chemical vapor deposition (LPCVD), plasma-enhanced chemical vapor deposition (PECVD), atomic layer deposition (ALD), magnetron sputtering, thermal diffusion (such as phosphorus diffusion), ion implantation, sol-gel methods, and electron beam evaporation.

[0099] Materials for the electron transport layer also include inorganic salts. These include barium stannate (BSO), lanthanum-doped barium stannate (LBSO), and titanium tin oxide (TiSnO). x ) and tin-zinc oxide (SnZnO) x At least one of the following: sol-gel method, nanoparticle dispersion method, atomic layer deposition (ALD), chemical vapor deposition (CVD, including plasma-enhanced chemical vapor deposition (PECVD)), physical vapor deposition (PVD, including magnetron sputtering, pulsed laser deposition (PLD), electron beam evaporation), spray pyrolysis, solution spin coating, electrochemical deposition, chemical bath deposition, and magnetron sputtering-annealing combined method.

[0100] The material of the electron transport layer can be a single material among the above-mentioned inorganic metal oxide materials, organic materials, inorganic silicon materials, and inorganic salt materials, or it can be a combination of multiple materials.

[0101] Furthermore, when the second charge transport layer 500 is an electron transport layer, a buffer layer 800 can also be provided on the side of the electron transport layer away from the perovskite light-absorbing layer 300. The material of the buffer layer 800 includes at least one of tin oxide, molybdenum oxide, titanium oxide, zinc oxide, zirconium oxide, magnesium oxide, and 2,9-dimethyl-4,7-biphenyl-1,10-o-diazaphenanthroline (also known as bath copper or BCP).

[0102] Furthermore, the thickness of the buffer layer 800 can be from 1 nm to 50 nm. Among them, when the material of the buffer layer 800 is zirconium oxide, magnesium oxide or 2,9-dimethyl-4,7-biphenyl-1,10-o-diazaphenanthroline (bath copper spirit), the thickness can be from 1 nm to 10 nm.

[0103] In some of these examples, the transparent conductive layer 600 is made of materials including, but not limited to, indium tin oxide (ITO), indium zinc oxide (IZO), indium tungsten oxide (IWO), fluorine-doped tin oxide (FTO), aluminum-doped zinc oxide (AZO), antimony-doped tin oxide (ATO), and gallium-doped zinc oxide (GZO), and is prepared by methods including, but not limited to, magnetron sputtering (PVD) and reactive plasma deposition (RPD).

[0104] Furthermore, the thickness of the transparent conductive layer 600 can be from 10 nm to 100 nm. For example, the thickness of the transparent conductive layer 600 can be 10 nm, 20 nm, 30 nm, 40 nm, 50 nm, 60 nm, 70 nm, 80 nm, 90 nm, 100 nm, or any range between the aforementioned values. The transparent conductive layer 600, deposited on the electron transport layer, is a thin film that is both conductive and transparent. It is used to laterally collect charge carriers and transport them to the electrode grid lines 700, and also reduces the reflection of incident light on the solar cell surface, increasing the absorption of light by the solar cell. The electrode grid lines 700 are used to efficiently collect and extract the charge carriers transported by the transparent conductive layer 600. The transparent conductive layer 600 and the electrode grid lines 700 together constitute the high-efficiency current collection and extraction system of the solar cell.

[0105] Furthermore, the material of the electrode grid line 700 includes at least one of gold (Au), silver (Ag), aluminum (Al), copper (Cu), chromium (Cr), titanium (Ti), nickel (Ni), platinum (Pt), and palladium (Pd); preferably silver, copper, or aluminum.

[0106] Furthermore, the thickness of the electrode grid line 700 can be from 10 μm to 120 μm. For example, the thickness of the electrode grid line 700 can be 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, or a range between any two of the aforementioned values.

[0107] In some of these examples, a passivation layer 900 is also provided between the perovskite light-absorbing layer 300 and the second charge transport layer 500.

[0108] For example, the thickness of the passivation layer 900 can be 2 nm to 8 nm. The passivation layer 900 includes 1,3-diaminopropane dihydrohalide. The passivation material of the passivation layer 900 includes at least one of methylamine iodide (MAI), benzylamine hydroiodide (PMAI), 4-fluorobenzylamine hydroiodide (pF-PMAI), formamidinium iodide (FAI), phenylethylamine iodide (PEAI), 2-(4-fluorophenyl)ethylamine hydroiodide (pF-PEAI), 1,3-diaminopropane dihydroiodide (PDAI2), ethylenediamine dihydroiodide (EDAI), butylamine iodide (BAI), hexylamine bromide (HABr), choline iodide (ChI), and sodium 4-phenylbutyrate (4-PBA).

[0109] Furthermore, the passivation layer 900 can be prepared by: mixing a passivating material with a solvent to obtain a passivation solution, wherein the concentration of the passivating material in the passivation solution is 0.3 mg / mL to 1 mg / mL; coating the passivation solution onto the surface of the perovskite absorbing layer 300; and annealing at a temperature of 80℃ to 120℃ for 5 to 30 minutes to obtain the passivation layer 900. Isopropanol can be used as the solvent for the passivation solution. The passivating material, sodium 4-phenylbutyrate (4-PBA), can be wet-formed on the perovskite absorbing layer 300 to form the passivation layer 900, and can also be incorporated into the perovskite precursor solution as a bulk passivating agent to repair internal defects in the perovskite absorbing layer 300 and optimize the film quality of the perovskite absorbing layer 300.

[0110] In some examples, an antireflection layer 910 is further provided on the surface of the transparent conductive layer 600 away from the second charge transport layer 500, and the electrode gate line 700 is in contact with the transparent conductive layer 600. As an example, the material of the antireflection layer 910 includes, but is not limited to, at least one of magnesium fluoride, silicon nitride, and aluminum oxide.

[0111] In some of these examples, the base cell 100 is selected from crystalline silicon base cells, CIGS thin-film base cells, cadmium telluride thin-film base cells, III V thin-film base cells, or perovskite base cells. Crystalline silicon base cells include at least one of heterojunction (HJT) cells, tunnel oxide passivated contact (TOPCon) cells, and passivated emitter and back contact (PERC) cells.

[0112] In some examples, the bottom cell 100 includes: a silicon substrate 110 having a first surface and a second surface disposed opposite to each other, and an n-type window layer 120 and a composite layer 130 sequentially disposed on the first surface. The first surface has a textured structure, the n-type window layer 120 conformally covers the first surface, and the composite layer 130 conformally covers the surface of the n-type window layer 120, forming a first textured structure; and a p-type window layer 140 and a back field electrode 150 sequentially disposed on the second surface.

[0113] In this application, "preservation of shape" means that the covering layer can completely follow the shape of the substrate and fit the surface of the substrate; and the overall shape after covering is basically consistent with the substrate, without obvious structural deformation.

[0114] The silicon substrate 110 absorbs light and generates charge carriers (holes and electrons). The p-type window layer 140 and the n-type window layer 120 form a PN junction, generating a built-in electric field to separate electrons and holes. The back field electrode 150 is used to collect and output photocurrent, and at the same time reflects the long-wavelength light that is not absorbed by the bottom cell 100 back to the bottom cell 100 to improve light utilization.

[0115] In some examples, the thickness of the silicon substrate 110 can be 80 μm to 220 μm. Exemplarily, the thickness of the silicon substrate 110 can be 80 μm, 85 μm, 90 μm, 95 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm, 150 μm, 160 μm, 170 μm, 180 μm, 190 μm, 200 μm, 210 μm, 220 μm, or a range between any two of the aforementioned values.

[0116] In some examples, the material of the n-type window layer 120 includes n-type hydrogenated nanocrystalline silicon (n-nc-Si:H) and n-type hydrogenated nanocrystalline silicon oxide (n-nc-SiO). x n-type hydrogenated amorphous silicon (na-Si:H), n-type hydrogenated amorphous silicon oxide (na-SiO) x At least one of n-type hydrogenated amorphous silicon-carbon (na-SiC:H) and n-type hydrogenated nanocrystalline silicon (n-nc-Si:H) or n-type hydrogenated nanocrystalline silicon-oxygen (n-nc-SiO) is preferred. x :H).

[0117] Furthermore, the thickness of the n-type window layer 120 can be 5nm to 30nm. For example, the thickness of the n-type window layer 120 can be 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, or a range between any two of the aforementioned values.

[0118] In some examples, the composite layer 130 may be made of a transparent conductive oxide. The transparent conductive oxide includes at least one of indium tin oxide (ITO), indium zinc oxide (IZO), tungsten-doped indium oxide (IWO), zirconium-doped indium oxide (IZrO), fluorine-doped tin oxide (FTO), aluminum-doped zinc oxide (AZO), antimony-doped tin oxide (ATO), and gallium-doped zinc oxide (GZO). Methods for preparing the transparent conductive oxide include, but are not limited to, magnetron sputtering (PVD) and reactive plasma deposition (RPD).

[0119] Furthermore, the thickness of the transparent conductive oxide composite layer 130 can be from 2 nm to 20 nm. For example, the thickness of the transparent conductive oxide composite layer 130 can be 2 nm, 3 nm, 4 nm, 5 nm, 6 nm, 7 nm, 8 nm, 9 nm, 10 nm, 11 nm, 12 nm, 13 nm, 14 nm, 15 nm, 16 nm, 17 nm, 18 nm, 19 nm, 20 nm, or a range between any two of the aforementioned values.

[0120] Furthermore, the material of the composite layer 130 can also be a tunneling junction, including an oxide tunneling junction or a silicon-based tunneling junction. For example, the oxide tunneling junction can be a NiOx / TiOx bilayer oxide tunneling junction, wherein the thickness of NiOx can be 2–10 nm, and the thickness of TiOx can be 2–10 nm.

[0121] For example, a silicon-based tunneling junction can be n + -Si / p + -Si tunnel junction, where n + The thickness of -Si can be 2nm to 15nm, p + The thickness of -Si can be 2nm to 15nm.

[0122] In some examples, the material of the p-type window layer 140 includes p-type hydrogenated nanocrystalline silicon (p-nc-Si:H) and p-type hydrogenated nanocrystalline silicon oxide (p-nc-SiO). x p-type hydrogenated amorphous silicon (pa-Si:H), p-type hydrogenated nanocrystalline silicon-carbon (p-nc-SiC:H), p-type hydrogenated amorphous silicon-oxygen (pa-SiO) x At least one of p-type hydrogenated nanocrystalline silicon (p-nc-Si:H) or p-type hydrogenated nanocrystalline silicon oxide (p-nc-SiO) is preferred. x :H).

[0123] Furthermore, the thickness of the p-type window layer 140 can be 5nm to 30nm. For example, the thickness of the p-type window layer 140 can be 5nm, 10nm, 15nm, 20nm, 25nm, 30nm, or a range between any two of the aforementioned values.

[0124] In some examples, the back electrode 150 includes a transparent electrode layer 151 and a metal electrode layer 152 disposed sequentially. The transparent electrode layer 151 is located between the metal electrode layer 152 and the p-type window layer 140. The transparent electrode layer 151 reduces the interfacial contact resistance, allowing photogenerated carriers to flow out smoothly, so as to uniformly conduct current to the metal electrode layer 152; the metal electrode layer 152 efficiently collects and extracts photogenerated carriers, and reflects unused long-wavelength photons back into the bottom cell 100 for secondary absorption.

[0125] Furthermore, the thickness of the transparent electrode layer 151 can be from 15 nm to 60 nm. For example, the thickness of the transparent electrode layer 151 can be 15 nm, 20 nm, 25 nm, 30 nm, 35 nm, 40 nm, 45 nm, 50 nm, 55 nm, 60 nm, or a range between any two of the aforementioned values. The material of the transparent electrode layer 151 includes at least one of indium tin oxide (ITO), indium zinc oxide (IZO), tungsten-doped indium oxide (IWO), zirconium-doped indium oxide (IZrO), fluorine-doped tin oxide (FTO), aluminum-doped zinc oxide (AZO), antimony-doped tin oxide (ATO), and gallium-doped zinc oxide (GZO).

[0126] Furthermore, the thickness of the metal electrode layer 152 can be 0.1–35 μm. For example, the thickness of the metal electrode layer 152 can be 0.1 μm, 0.5 μm, 1 μm, 2 μm, 5 μm, 10 μm, 15 μm, 20 μm, 25 μm, 30 μm, 35 μm, or a range between any two of the aforementioned values.

[0127] Furthermore, the material of the metal electrode layer 152 includes at least one of copper (Cu), aluminum (Al), silver (Ag), gold (Au), and silver-clad copper, wherein aluminum is suitable for metal electrode layers that cover the entire p-type window layer, and silver, copper, and silver-clad copper are suitable for patterned metal electrode layers.

[0128] Furthermore, the back electrode 150 also includes an adhesion layer disposed between the metal electrode layer 152 and the transparent electrode layer 151. This adhesion layer serves to adhere the metal electrode layer 152 to the transparent electrode layer 151 and also prevents metal atoms in the metal electrode layer 152 from diffusing into the transparent electrode layer 151 and the p-type window layer 140. The adhesion layer is made of at least one of titanium (Ti), chromium (Cr), nickel (Ni), and cobalt (Co), preferably titanium, chromium, or a composite structure of titanium and chromium. The thickness of the adhesion layer is 5 nm to 20 nm.

[0129] Furthermore, the back electrode 150 also includes an optical matching layer, which is disposed between the transparent electrode layer 151 and the metal electrode layer 152. The refractive index of the optical matching layer is lower than that of the transparent electrode layer 151. The transparent electrode layer 151, the optical matching layer, and the metal electrode layer 152 constitute an interference-type back reflection structure, which improves back reflection efficiency and light utilization through optical interference effect. Furthermore, the material of the optical matching layer includes at least one selected from silicon oxide, aluminum oxide, silicon nitride, sodium fluoride, lithium fluoride, silver fluoride, and calcium fluoride.

[0130] In some examples, a first intrinsic hydrogenated amorphous silicon passivation layer 160 is further disposed between the silicon substrate 110 and the p-type window layer 140. A second intrinsic hydrogenated amorphous silicon passivation layer 170 is further disposed between the silicon substrate 110 and the n-type window layer 120. The thicknesses of the first intrinsic hydrogenated amorphous silicon passivation layer 160 and the second intrinsic hydrogenated amorphous silicon passivation layer 170 are each independently 2 nm to 8 nm.

[0131] A second aspect of this application provides a method for fabricating a tandem solar cell 10, comprising the following steps:

[0132] S10, a bottom battery 100 is provided, the bottom battery 100 having a first velvety structure.

[0133] S20. A first charge transport layer 200 is prepared on the surface of the first textured structure to form a second textured structure. The second textured structure has valleys and peaks.

[0134] S30, forming a spacer layer 400 that covers at least part of the valley bottom of the second velvet structure.

[0135] S40, a perovskite light-absorbing layer 300 is formed on the side of the first charge transport layer 200 away from the bottom cell 100, the perovskite light-absorbing layer 300 covering the spacer layer 400 and the portion of the second textured structure not covered by the spacer layer 400.

[0136] The spacer layer 400 comprises a spacer material with a melting point of 90°C to 170°C. The spacer material comprises at least one functional group selected from phosphonic acid group, biguanide group, and triazine group.

[0137] In some of these examples, the spacer material comprises at least one of the compounds having the structures shown in Formulas (I) to (IV): , , , .

[0138] Where n1 is any integer between 1 and 6; X is F, Cl, Br, or I; n2 is any integer between 1 and 6; Ar is C6 to C 12 Aromatic group; each time R1 appears, it is independently a C6 to C8 alkyl group.

[0139] Understandably, the types of the aforementioned spacer materials are the same as those in the first aspect of this application, so they will not be described again here.

[0140] In steps S10 and S20, the structure and properties of the bottom battery 100 and the first charge transport layer 200 are the same as those in the first aspect of this application, so they will not be described again here.

[0141] In some examples, step S30, forming a spacer layer 400 that at least covers the valley bottoms of the second velvet structure, includes: applying a spacer material solution 410 to the surface of the second velvet structure and annealing to obtain a spacer layer 400 covering at least a portion of the valley bottoms of the second velvet structure. For example, the spacer material solution 410 comprises a spacer material and a solvent. The solvent includes at least one selected from ethanol, isopropanol, n-butanol, dimethylformamide, and dimethyl sulfoxide.

[0142] In some examples, the mass concentration of the spacer material in the spacer material solution 410 is from 1 mg / mL to 4 mg / mL. As examples, the mass concentration of the spacer material includes, but is not limited to, 1 mg / mL, 1.5 mg / mL, 1.8 mg / mL, 2 mg / mL, 2.5 mg / mL, 2.8 mg / mL, 3 mg / mL, 3.5 mg / mL, 3.8 mg / mL, or 4 mg / mL, or any two of the above values ​​as endpoints. In some examples, the annealing temperature is greater than or equal to the melting point of the spacer material. For example, the annealing temperature is from 90°C to 170°C. Further, the annealing time is from 5 min to 20 min. Even further, the annealing temperature is from 90°C to 150°C.

[0143] In some of these examples, see Figure 2 In step S40, the step of forming a perovskite light-absorbing layer 300 on the side of the first charge transport layer 200 away from the bottom cell 100 includes:

[0144] S41. A metal halide solution is coated on the side of the first charge transport layer 200 away from the bottom cell 100 to obtain a metal halide framework layer 310. The metal halide framework layer 310 covers the spacer layer 400 and the part of the second textured structure not covered by the spacer layer 400.

[0145] S42. An organic halide solution is coated on the side of the metal halide framework layer 310 facing away from the first charge transport layer 200, and then annealed to obtain a perovskite light-absorbing layer 300.

[0146] Optionally, in step S41, the chemical formula of the metal halide in the metal halide solution includes at least one of AlX and BX. The chemical formula of the organic halide in the organic halide solution is A2X. Wherein, A1 includes at least one of cesium ions, rubidium ions, lithium ions, sodium ions, potassium ions, and thallium ions. A2 includes at least one of ammonium ions, methylamine ions, ethylammonium ions, dimethylamine ions, trimethylammonium ions, tetramethylammonium ions, formamidine ions, methylformamidine ions, ethylamidine ions, and guanidine ions. B includes at least one of lead ions, tin ions, and germanium ions. X includes at least one of bromide ions, iodide ions, and chloride ions.

[0147] Furthermore, step S40, forming the perovskite light-absorbing layer 300 on the side of the first charge transport layer 200 away from the bottom cell 100, includes: vacuum evaporating AlX and BX on the side of the spacer layer 400 away from the first charge transport layer 200 to prepare a metal halide framework layer 310; wherein the evaporation rates of AlX and BX are each independently 0.01 nm / s to 0.3 nm / s. An organic halide solution is coated onto the surface of the metal halide framework layer 310 on the side opposite to the first charge transport layer 200 to form an organic halide wet film, followed by annealing to obtain the perovskite light-absorbing layer 300.

[0148] By precisely controlling the vacuum evaporation rate to prepare the metal halide framework layer 310, and combining it with the organic halide solution coating-annealing process, the perovskite composition and crystal quality can be precisely controlled. This, along with the spacer layer 400, reduces residual metal halides at the bottom of the valley, thereby improving the film uniformity and the photoelectric performance of the battery.

[0149] In some examples, the annealing temperature in step S42 is 90–170 °C. Further, the annealing temperature is 90 °C–150 °C. In some examples, the annealing temperature is greater than or equal to the melting point of the spacer material.

[0150] See Figure 2 In the preparation method provided in this application, in step S30, a schematic diagram of the second textured structure is shown below, where the spacer material solution 410 is coated onto the surface of the first charge transport layer 200. Figure 2 As shown in (a), annealing is performed. Since the annealing temperature matches the melting point of the spacer material, the spacer material melts and slides down to the bottom of the second textured surface valley. The corresponding structural diagram is shown below. Figure 2 As shown in (b). After annealing, the spacer material solidifies as the temperature decreases, resulting in spacer layer 400. In the subsequent step S40, a metal halide framework layer 310 is formed, and the corresponding structural diagram is shown below. Figure 2 As shown in (c), during the annealing process, when the metal halide reacts with the organic halide to form the perovskite light-absorbing layer 300, the spacer material melts and coats the incompletely converted metal halide at the bottom of the valley. After the annealing process is completed, a composite structure is formed in which the spacer layer 400 is located between the first charge transport layer 200 and the perovskite light-absorbing layer 300 and covers at least part of the valley bottom of the second textured structure. The corresponding structural schematic diagram is shown below. Figure 2 As shown in (d).

[0151] Because the melting point of the spacer material is compatible with the annealing temperature during the preparation of the perovskite light-absorbing layer 300, and because the spacer material has good thermal stability and chemical inertness, the spacer layer 400 exhibits excellent compatibility with the first charge transport layer 200 and the perovskite light-absorbing layer 300. During further annealing of the metal halide framework layer 310 and the organic halide wet film, the unreacted metal halides at the valley bottom of the second textured structure are coated by the molten spacer layer 400. The selection and placement of this spacer layer 400 prevents the decomposition of the valley bottom metal halides. Furthermore, the spacer layer 400 can coordinate and bond with free halide anions, lead ions, and other cations through phosphonate, biguanide, and triazine functional groups in its molecules, thereby fixing migrating ions, passivating valley bottom interface defects, inhibiting ion migration and grain boundary corrosion, and reducing non-radiative recombination. Simultaneously, it prevents excessive contact between the perovskite and the charge transport layer, alleviates interfacial stress, and improves the charge transport efficiency and long-term operational stability of the tandem solar cell.

[0152] Furthermore, the preparation method provided in this application is simple, highly operable, and suitable for large-scale industrial production, showing promising prospects for industrial application.

[0153] In a third aspect, this application provides a photovoltaic module, including a tandem solar cell 10 according to any one of the first aspects of this application or a tandem solar cell 10 prepared by any one of the preparation methods of the second aspect of this application.

[0154] The following detailed embodiments illustrate this application in more detail. It should also be understood that the following embodiments are for further explanation only and should not be construed as limiting the scope of protection of this application. Any non-essential improvements and adjustments made by those skilled in the art based on the above description of this application fall within the scope of protection of this application. The specific process parameters, etc., in the following embodiments are merely examples within a suitable range; that is, those skilled in the art can make appropriate selections within the range based on the description herein, and are not necessarily limited to the specific values ​​in the embodiments below.

[0155] Example 1

[0156] (1) A crystalline silicon bottom cell is provided, comprising an n-type monocrystalline silicon substrate (silicon substrate 110) with a thickness of 100 μm, wherein a first intrinsic hydrogenated amorphous silicon passivation layer 160 with a thickness of 5 nm, a p-type hydrogenated nanocrystalline silicon window layer (p-type window layer 140) with a thickness of 10 nm, an indium tin oxide (ITO) transparent electrode layer 151 with a thickness of 20 nm and a silver electrode layer with a thickness of 5 μm are sequentially deposited on the back side (backlight side / second surface) of the n-type monocrystalline silicon substrate, and a second intrinsic hydrogenated amorphous silicon passivation layer 170 with a thickness of 5 nm, an n-type hydrogenated nanocrystalline silicon window layer (n-type window layer 120) with a thickness of 10 nm and an indium tin oxide (ITO) composite layer 130 with a thickness of 10 nm are sequentially deposited on the front side (light-facing side / first surface) of the n-type monocrystalline silicon substrate. The n-type monocrystalline silicon substrate has a pyramid-shaped textured surface structure on both the back and front sides. The second intrinsic hydrogenated amorphous silicon passivation layer 170, the n-type hydrogenated nanocrystalline silicon window layer, and the indium tin oxide (ITO) composite layer 130 sequentially cover the pyramid-shaped textured surface structure on the front side of the n-type monocrystalline silicon substrate, thus giving the crystalline silicon bottom cell a first textured surface structure.

[0157] Using a spin coater, ethanol was spin-coated onto the indium tin oxide (ITO) composite layer 130 on the front side of the crystalline silicon bottom cell at a speed of 3000 rpm for 30 s, repeated twice, and then heat-treated at 200 ℃ for 10 min to complete the cleaning.

[0158] (2) Preparation of hole transport layer: The crystalline silicon bottom cell is placed in a sputtered nickel oxide (NiO) layer. x The mask is placed in a magnetron sputtering apparatus and evacuated to a vacuum of 7 × 10⁻⁶. -4 Below Pa, select the radio frequency magnetron sputtering mode, adjust the power to 200W, set the argon flow rate to 30sccm, and sputter for 1 min 50 s to form a 15 nm thick nickel oxide (NiO) layer on the indium tin oxide (ITO) composite layer 130. x The layer is a transition metal oxide layer 220;

[0159] The self-assembled monolayer material [2-(9H-carbazole-9-yl)ethyl]phosphonic acid (2PACz) was mixed with anhydrous ethanol and stirred until completely dissolved to obtain a self-assembled monolayer solution with a concentration of 1 mg / mL. The self-assembled monolayer solution was spin-coated onto a nickel oxide layer at a spin speed of 3000 rpm for 30 s. Then, it was heated and annealed on a hot plate at 100℃ for 10 min to form a self-assembled monolayer 210 with a thickness of 1 nm.

[0160] A hole transport layer is formed by combining a transition metal oxide layer 220 and a self-assembled monolayer 210. The hole transport layer is disposed on the surface of the first textured structure to form a second textured structure.

[0161] (3) Preparation of spacer layer 400: providing 6-phosphonohexanoic acid A spacer material solution 410 (6-phosphonohexanoic acid at a mass concentration of 2 mg / mL, solvent: ethanol, melting point of 6-phosphonohexanoic acid approximately 100 °C) was spin-coated onto the surface of the second textured structure of the hole transport layer. A first annealing treatment was then performed at 100 °C for 10 min to form a spacer layer 400 at the valley of the second textured structure. After the first annealing, the spacer layer 400 was cured, and the ratio of the thickness of the spacer layer 400 to the texture depth of the second textured structure was 1:90.

[0162] (4) Preparation of perovskite light-absorbing layer 300: PbI2 and CsBr are vacuum-deposited on the side of hole transport layer away from bottom cell 100 to prepare inorganic framework layer. The metal halide framework layer 310 covers the spacer layer 400 and the part of the second textured structure not covered by the spacer layer 400. The deposition rate of PbI2 is 0.2 nm / s and the deposition rate of CsBr is 0.01 nm / s.

[0163] MAI solution was spin-coated onto the metal halide framework layer 310 at a spin speed of 3000 rpm for 300 s; then, a second annealing treatment was performed at 150 °C for 30 min to obtain a perovskite light-absorbing layer 300; the perovskite light-absorbing layer 300 covered the spacer layer 400 and the portion of the second textured structure not covered by the spacer layer 400.

[0164] (5) Preparation of passivation layer 900: Passivation material PDAI2 (1,3-diaminopropane dihydroiodate, CAS No.: 120675-53-8) was mixed with isopropanol to obtain a passivation solution. The concentration of PDAI2 in the passivation solution was 1 mg / mL. The passivation solution was coated on the surface of perovskite light-absorbing layer 300 and annealed at 65 °C for 5 minutes to obtain a passivation layer 900 with a thickness of 2 nm.

[0165] (6) Fabrication of the electron transport layer: A 20 nm thick C layer was deposited on the passivation layer 900 using a vacuum evaporation process. 60 Electron transport layer, deposition rate 0.5 Å / s.

[0166] (7) Preparation of buffer layer 800: Atomic layer deposition was used to prepare the buffer layer 800 on a C14-C ... 60 Tin oxide (SnO) with a thickness of 10 nm was prepared on the electron transport layer. x 800 buffer layer.

[0167] (8) Fabrication of transparent conductive layer 600: Radio frequency magnetron sputtering was used to fabricate the transparent conductive layer 600 on tin oxide (SnO). xA 100 nm thick transparent conductive layer of indium zinc oxide (IZO) 600 was deposited on the buffer layer 800. The sputtering power was controlled at 300 W, the chamber pressure at 0.6 Pa, the argon flow rate at 20 sccm, the 5% argon-oxygen mixed flow rate at 5 sccm, and the sputtering time at 100 s.

[0168] (9) Preparation of electrode grid line 700: Silver paste with a thickness of 8 μm and a width of 50 μm and silver busbar with a thickness of 1.5 μm and a width of 1.5 mm are prepared by screen printing process, silver paste is coated on indium zinc oxide (IZO) transparent conductive layer 600 to prepare silver fine grid with a thickness of 8 μm and a width of 50 μm and silver busbar with a thickness of 1.5 μm and a width of 1.5 mm. The fine grid and the busbar constitute silver electrode grid line 700.

[0169] (10) Preparation of antireflection layer: A lithium fluoride antireflection layer 910 with a thickness of 100 nm was deposited on the silver electrode grid line 700 and the indium zinc oxide (IZO) transparent conductive layer 600 not covered by the silver electrode grid line 700 to obtain a perovskite / crystalline silicon tandem cell with a deposition rate of 1 Å / s.

[0170] Example 2

[0171] Example 2 is basically the same as Example 1, the main difference being that the spacer material in step (3) of Example 2 is 4-phosphonobutyric acid. (Melting point approximately 127–129 °C) Replace 6-phosphonohexanoic acid in Example 1, and the temperature of the second annealing treatment in step (4) of Example 2 is 130 °C. The ratio of the thickness of the spacer layer 400 to the texture depth of the second textured structure is 1:80.

[0172] Example 3

[0173] Example 3 is basically the same as Example 1, the main difference being that the spacer material in step (3) of Example 3 is 1-phenylbiguanide. (Melting point approximately 135–140 °C) Replace 6-phosphonohexanoic acid in Example 1, and the second annealing temperature in step (4) of Example 3 is 140 °C. The ratio of the thickness of the spacer layer 400 to the texture depth of the second textured structure is 1:100.

[0174] Example 4

[0175] Example 4 is basically the same as Example 1, the main difference being that in step (3) of Example 4, the mass concentration of the spacer material in the spacer material solution 410 is 4 mg / mL. The ratio of the thickness of the spacer layer 400 to the surface depth of the second textured structure is 1:50.

[0176] Comparative Example 1

[0177] Comparative Example 1 is basically the same as Example 1, except that Comparative Example 1 does not include step (3), and Comparative Example 1 directly prepares a perovskite light-absorbing layer 300 on the surface of the hole transport layer.

[0178] Comparative Example 2

[0179] Comparative Example 2 is basically the same as Example 1, the main difference being that the temperature of the first annealing treatment in step (3) of Comparative Example 2 is 60 °C. At this time, 6-phosphonohexanoic acid cannot melt and slide to the bottom of the second textured structure, but instead adheres to the peaks, sidewalls and bottoms of the second textured structure, making the effective contact area between the subsequently formed perovskite layer and the hole transport layer smaller.

[0180] Comparative Example 3

[0181] Comparative Example 3 is basically the same as Example 1, except that in step (3) of Comparative Example 3, 2-phenylethylamine hydroiodide is used to replace 6-phosphonohexanoic acid in Example 1. The melting point of phenylethylamine hydroiodide is about 267 °C. In the temperature environment of 100 °C in the first annealing treatment, phenylethylamine hydroiodide is difficult to melt and slide to the bottom of the second textured structure. Instead, it adheres to the peak, sidewall and bottom of the second textured structure, making the effective contact area between the perovskite layer and the hole transport layer formed later smaller. At the same time, it is difficult to melt at 150 °C in the second annealing treatment to effectively coat the unreacted PbI2.

[0182] In Example 1, the scanning electron microscope image of the hole transport layer surface with a second textured surface formed in step (2) is shown below. Figure 3 As shown in A and C. Example 1, after step (3) of curing the spacer layer 400, a scanning electron microscope image of the valley of the pyramid structure on the surface of the hole transport layer covered by the spacer layer 400 is shown below. Figure 3 As shown in b and d. From Figure 3 As can be seen from the comparison, in step (3) of this application, after the first annealing treatment, the spacer material can melt and slide to the bottom of the pyramid structure. As the first annealing ends, the spacer layer 400 is solid and covers the bottom of the pyramid.

[0183] The perovskite-crystalline silicon tandem solar cells 10 prepared in the above embodiments and comparative examples were subjected to efficiency tests and high-temperature and high-humidity aging tests (85°C, 85%RH) for 480 hours. The test results are shown in Table 1.

[0184] Table 1

[0185]

[0186] In Comparative Example 1, no spacer layer 400 was introduced at the valley bottom of the second textured structure of the hole transport layer. In Comparative Example 2, the first annealing temperature was below 60 °C, and the spacer material could not melt and slide to the valley bottom of the second textured structure. At this time, the spacer material partially filled the valley bottom of the second textured structure and partially adhered to the sidewalls and peaks of the second textured structure. This resulted in insufficient effective contact area between the perovskite light-absorbing layer 300 and the second textured structure, increased interfacial series resistance, hindered carrier extraction, and intensified nonradiative recombination at the interface, leading to a significant decrease in the cell open-circuit voltage, fill factor, and photoelectric conversion efficiency. Comparative Example 3 used a high-melting-point material (2-phenylethylamine hydroiodate, melting point 267 °C) as the spacer material. During the first annealing treatment at 100 °C, the 2-phenylethylenediamine hydroiodate did not melt and slide to the bottom of the second textured structure. Therefore, it partially filled the bottom of the second textured structure and partially adhered to the sidewalls and peaks of the second textured structure. This also resulted in insufficient effective contact area between the perovskite light-absorbing layer 300 and the second textured structure, increased interfacial series resistance, hindered carrier extraction, and intensified non-radiative recombination at the interface, leading to a significant decrease in the cell's open-circuit voltage, fill factor, and photoelectric conversion efficiency. As shown in Table 1, Comparative Examples 1 to 3 could not effectively improve the cell efficiency. If the spacer material is not annealed at a temperature above its melting point to allow it to slide to the bottom of the second textured structure, the spacer material attached to the sidewalls and peaks of the second textured structure will fill the interface between the perovskite light-absorbing layer 300 and the hole transport layer. This will result in an insufficient contact area between the perovskite light-absorbing layer 300 and the second textured structure, hindering carrier transport, increasing the interface charge transfer resistance, raising the device series resistance, and significantly reducing the short-circuit current density and fill factor. Ultimately, this will lead to a decrease in the efficiency and performance degradation of the tandem solar cell 10.

[0187] In Examples 1 to 4 of this application, 6-phosphonohexanoic acid, 4-phosphonobutyric acid, and 1-phenylbiguanide were used as spacer layers 400, all of which improved device performance. Data from Examples 1 and 4 show that the optimal concentration of the spacer material solution 410 is approximately 2–3 mg / mL. In Example 4, the concentration of the spacer material solution 410 was 4 mg / mL, and the ratio of the thickness of the spacer layer 400 to the texture depth of the second textured structure was <1:80. This means that the spacer layer 400 accumulated slightly more at the valley bottom of the pyramid, affecting carrier transport and causing a decrease in open-circuit voltage increase, a slight decrease in short-circuit cell density and fill factor, resulting in a slightly lower overall cell efficiency improvement compared to Examples 1 to 3. Furthermore, if the concentration of the spacer material solution 410 is too low, the ratio of the spacer layer 400 to the texture depth of the second textured structure will be >1:100, meaning that the deposition of the spacer layer 400 at the valley bottom of the second textured structure is insufficient, leading to inadequate coating of residual metal halides, especially lead halides, and insufficient interface passivation.

[0188] The high temperature and high humidity aging test data in Table 1 further corroborate that the insulating spacer passivation layer 900 filled at the bottom of the second textured structure can isolate water and oxygen, bind mobile halogen anions, alleviate the decomposition and degradation of metal halides, and significantly improve the long-term service stability of perovskite / crystalline silicon tandem solar cells.

[0189] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0190] The embodiments described above are merely illustrative of several implementation methods of this application, intended to facilitate a detailed understanding of the technical solutions of this application, but should not be construed as limiting the scope of protection of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the scope of protection of this application. It should be understood that technical solutions obtained by those skilled in the art based on the technical solutions provided in this application through logical analysis, reasoning, or limited experimentation are all within the scope of protection of the appended claims. Therefore, the scope of protection of this patent application should be determined by the content of the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. A tandem solar cell, characterized in that, include: A bottom battery and a first charge transport layer are stacked together. The bottom battery has a first textured structure, and the first charge transport layer is disposed on the surface of the first textured structure to form a second textured structure. The second textured structure has valleys and peaks. A perovskite light-absorbing layer is disposed on the side of the first charge transport layer away from the bottom cell; A spacer layer is disposed between the first charge transport layer and the perovskite light-absorbing layer and covers at least a portion of the valley bottom of the second textured structure; The spacer layer comprises a spacer material with a melting point of 90°C to 170°C; the spacer material comprises at least one functional group selected from phosphonic acid group, biguanide group and triazine group.

2. The tandem solar cell according to claim 1, characterized in that, The spacer material includes at least one of the compounds having the structures shown in Formulas (I) to (IV): , , , ; Where n1 is any integer between 1 and 6; X is F, Cl, Br, or I; n2 is any integer between 1 and 6; Ar is C6 to C 12 Aromatic group; each time R1 appears, it is independently a C6 to C8 alkyl group.

3. The tandem solar cell according to claim 2, characterized in that, n1 is any integer between 3 and 5; and / or, X is Cl, n2 is any integer between 1 and 3; and / or, Ar is phenyl; and / or, Each time R1 appears, it is independently 2-ethylhexyl.

4. The tandem solar cell according to any one of claims 1 to 3, characterized in that, The spacer layer comprises a material with a melting point of 90°C to 150°C; and / or, The ratio of the thickness of the spacer layer to the pile depth of the second pile structure is 1:(80-100).

5. The tandem solar cell according to any one of claims 1 to 3, characterized in that, The first charge transport layer is a hole transport layer; and / or, The perovskite light-absorbing layer comprises a perovskite structural material with the general structural formula ABX3; wherein, A comprises at least one selected from cesium ions, rubidium ions, lithium ions, sodium ions, potassium ions, thallium ions, ammonium ions, methylamine ions, ethylammonium ions, dimethylamine ions, trimethylammonium ions, tetramethylammonium ions, formamidinium ions, methylformamidinium ions, ethylammonium ions, and guanidine ions; B comprises at least one selected from lead ions, tin ions, and germanium ions; and X comprises at least one selected from bromide ions, iodide ions, and chloride ions. And / or, The tandem solar cell further includes a second charge transport layer, a transparent conductive layer, and electrode grid lines, which are sequentially disposed on the surface of the perovskite light-absorbing layer away from the spacer layer.

6. The tandem solar cell according to any one of claims 1 to 3, characterized in that, The bottom battery includes: A silicon substrate having a first surface and a second surface disposed opposite to each other; An n-type window layer and a composite layer are sequentially disposed on the first surface; wherein, the first surface has a velvety structure, the n-type window layer is conformally covered on the first surface, and the composite layer conformally covers the surface of the n-type window layer, thereby forming the first velvety structure; A p-type window layer and a back field electrode are sequentially disposed on the second surface.

7. A method for fabricating a tandem solar cell, characterized in that, include: A bottom battery is provided, the bottom battery having a first textured surface structure; A first charge transport layer is prepared on the surface of the first textured structure to form a second textured structure; The second velvet structure has valleys and peaks; Forming a spacer layer that covers at least part of the valley bottom of the second velvet structure; A perovskite light-absorbing layer is formed on the side of the first charge transport layer away from the bottom cell, and the perovskite light-absorbing layer covers the portion of the spacer layer and the second textured structure that is not covered by the spacer layer; The spacer layer comprises a spacer material with a melting point of 90°C to 170°C; the spacer material comprises at least one functional group selected from phosphonic acid group, biguanide group and triazine group.

8. The method for preparing a tandem solar cell according to claim 7, characterized in that, The spacer material includes at least one of the compounds having the structures shown in Formulas (I) to (IV): , , , ; Where n1 is any integer between 1 and 6; X is F, Cl, Br, or I; n2 is any integer between 1 and 6; Ar is C6 to C 12 Aromatic group; each time R1 appears, it is independently a C6 to C8 alkyl group.

9. The method for preparing a tandem solar cell according to claim 7 or 8, characterized in that, The step of forming a spacer layer covering at least part of the valley floor of the second velvet structure includes: A spacer material solution is applied to the surface of the second velvet structure and annealed to obtain a spacer layer covering at least a portion of the valley bottom of the second velvet structure; the spacer material solution includes spacer material and solvent.

10. The method for preparing a tandem solar cell according to claim 9, characterized in that, In the spacer material solution, the mass concentration of the spacer material is 1 mg / mL to 4 mg / mL; and / or, The solvent for the spacer material solution includes at least one selected from ethanol, isopropanol, n-butanol, dimethylformamide, and dimethyl sulfoxide; and / or, The annealing temperature is greater than or equal to the melting point of the spacer material.

11. The method for preparing a tandem solar cell according to claim 7 or 8, characterized in that, The step of forming a perovskite light-absorbing layer on the side of the first charge transport layer away from the bottom cell includes: A metal halide solution is coated on the side of the first charge transport layer away from the bottom cell to obtain a metal halide framework layer. The metal halide framework layer covers the spacer layer and the portion of the second textured structure not covered by the spacer layer. An organic halide solution is coated on the side of the metal halide framework layer away from the first charge transport layer, and then annealed to obtain a perovskite light-absorbing layer. Optionally, the metal halide in the metal halide solution has a chemical formula including at least one of AlX and BX, and the organic halide in the organic halide solution has a chemical formula of A2X, wherein A1 includes at least one of cesium ion, rubidium ion, lithium ion, sodium ion, potassium ion and thallium ion; A2 includes at least one of ammonium ion, methylamine ion, ethylammonium ion, dimethylamine ion, trimethylammonium ion, tetramethylammonium ion, formamidine ion, methylformamidine ion, ethylamidine ion and guanidine ion; B includes at least one of lead ion, tin ion and germanium ion; and X includes at least one of bromide ion, iodide ion and chloride ion.

12. The method for preparing a tandem solar cell according to claim 11, characterized in that, The annealing temperature is 90℃~170℃.

13. A photovoltaic module, characterized in that, The tandem solar cell includes the tandem solar cell according to any one of claims 1 to 6 or the tandem solar cell prepared by any one of claims 7 to 12.

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