Perovskite tandem solar cell and preparation method therefor

Abstract

The present application relates to the technical field of solar cells. Disclosed are a perovskite tandem solar cell and a preparation method therefor. The perovskite tandem solar cell comprises: a bottom cell structure (1), a composite layer (2) disposed on one side of the bottom cell structure (1), and a top cell structure (3) disposed on the composite layer (2), wherein the top cell structure (3) comprises a first carrier transport layer (31), a charge collection structure (32), a perovskite absorption layer (33) and a second carrier transport layer (34) which are disposed in sequence; the first carrier transport layer (31) is of a first conductivity type; the charge collection structure (32) is of a second conductivity type, and comprises a plurality of doped layers (321, 322, 323), the doping concentrations of which increase progressively; the perovskite absorption layer (33) covers the charge collection structure (32); and the second carrier transport layer (34) is of the second conductivity type. The charge collection structure (32) absorbs carriers generated in the perovskite absorption layer (33), so as to reduce carrier recombination in the perovskite absorption layer (33); moreover, the plurality of doped layers (321, 322, 323), the doping concentrations of which gradually decrease from top to bottom, significantly increase the movement velocity of free charges, thereby ultimately improving the photoelectric conversion efficiency of the perovskite tandem solar cell.

Description

Perovskite tandem solar cells and their fabrication methods

[0001] Cross-reference to related applications

[0002] This application claims priority to Chinese Patent Application No. 202411742602.4, filed on November 29, 2024, entitled "Perovskite Tandem Solar Cell and Method for Preparing the Same", the entire contents of which are incorporated herein by reference. Technical Field

[0003] This application relates to the field of solar cell technology, specifically to a perovskite tandem solar cell and its fabrication method. Background Technology

[0004] A solar cell is a device that converts light energy into electrical energy. In recent years, perovskite solar cells have received increasing attention due to their environmentally friendly and high-efficiency characteristics. Perovskite solar cells can be divided into single-junction solar cells and multi-junction tandem solar cells. Single-junction solar cells have limited absorption of sunlight within a limited wavelength range, resulting in low conversion efficiency. Therefore, more and more research is being conducted on multi-junction tandem solar cells. Multi-junction tandem solar cells mainly consist of two parts: a top cell with a wider bandgap, responsible for absorbing short-wavelength light energy; and a bottom cell with a narrower bandgap, responsible for absorbing long-wavelength light energy, thereby reducing energy loss.

[0005] In related multi-junction tandem solar cell structures, if two sub-cells are connected by a middle composite layer, the multi-junction tandem solar cell is a monolithic tandem solar cell with two ends (2T). If the two sub-cells each contain positive and negative electrodes and are connected only by mechanical stacking, the multi-junction tandem solar cell is a multilithic tandem solar cell with four ends (4T). However, since the commercial production of 4T tandem solar cells requires additional equipment, and the cell fabrication is complex and economically inefficient, monolithic tandem solar cells with two ends are becoming a hot research topic.

[0006] However, in monolithic perovskite / crystalline silicon tandem solar cells made using crystalline silicon, the current density of the crystalline silicon bottom cell is much higher than that of the perovskite top cell. Since the top and bottom cells of the 2T structure tandem solar cell are connected in series, the currents of the two sub-cells must be consistent. The side with the lower current determines the final output current. Therefore, the 2T structure perovskite / crystalline silicon tandem solar cell can only generate a current that matches the side with the lower current density (i.e., the perovskite cell). The current mismatch between the top and bottom cells will lead to a decrease in current density and will also affect the fill factor (FF), thereby causing a decrease in photoelectric conversion efficiency. Summary of the Invention

[0007] In view of this, this application provides a perovskite tandem solar cell and its fabrication method to solve the problem of reduced current density caused by current mismatch between the top and bottom cells in existing perovskite tandem solar cells, which affects the fill factor and photoelectric conversion efficiency.

[0008] In a first aspect, this application provides a perovskite tandem solar cell, comprising: a bottom cell structure, a composite layer, and a top cell structure, wherein the composite layer is disposed on one side surface of the bottom cell structure; the top cell structure is disposed on the side of the composite layer opposite to the bottom cell structure; the top cell structure includes a first carrier transport layer, a charge collection structure, a perovskite absorber layer, and a second carrier transport layer disposed sequentially, wherein the first carrier transport layer is of a first conductivity type; the charge collection structure is of a second conductivity type opposite to the first conductivity type, and extends from the side closer to the bottom cell structure to the side farther away from the bottom cell structure, and the charge collection structure includes multiple doped layers stacked in ascending order of doping concentration; the perovskite absorber layer covers the charge collection structure; and the second carrier transport layer is of the first conductivity type.

[0009] Beneficial effects: In the perovskite tandem solar cell of this application, a charge collection structure with gradually decreasing doping concentration from the light-receiving side downwards is provided on the carrier transport layer of the top cell structure near the bottom cell structure. A perovskite absorber layer is then covered on the charge collection structure. This allows electrons and holes generated in the perovskite absorber layer to move towards the first and second carrier transport layers on the upper and lower sides of the perovskite absorber layer, respectively, based on the attraction of the carrier transport layers with different conductivity types on the upper and lower sides. Furthermore, they also move towards the first carrier transport layer near the bottom cell structure, i.e., at the bottom of the perovskite absorber layer. The resulting charge collection structure collects the same type of charge in the perovskite absorber layer as the first carrier transport layer, maximizing charge collection capability, reducing carrier recombination in the perovskite absorber layer, and increasing the current density of the perovskite top cell. Furthermore, because the charge collection structure has multiple doped layers with gradually decreasing doping concentration from top to bottom, it greatly improves the movement speed of free charges, thereby optimizing current formation and ultimately improving the photoelectric conversion efficiency of the perovskite tandem solar cell. Moreover, the charge collection structure is located inside the perovskite absorber layer, has a simple structure, does not increase the thickness of the tandem cell, and ensures reliability and stability.

[0010] In one alternative embodiment, the number of doped layers in the charge collection structure ranges from 2 to 5.

[0011] Beneficial effects: Within the thickness range of the perovskite absorber layer, setting 2 to 5 doped layers helps to maximize the absorption of free charges at various thicknesses of the perovskite absorber layer, and causes the absorbed free charges to move rapidly from the high concentration side to the low concentration side, reducing carrier recombination in the perovskite absorber layer, and ultimately increasing the current density of the perovskite absorber layer.

[0012] In one alternative implementation, the maximum doping concentration among the multiple doped layers is 10. -21 cm 3 The minimum doping concentration in multiple doped layers is greater than or equal to the doping concentration of the bottom cell structure.

[0013] Beneficial effect: Limits the maximum doping concentration to 10. -21 cm 3 To ensure that the charge collection structure can maximize the collection of charge carriers generated in the perovskite absorber layer; the minimum doping concentration is higher than that of the bottom cell structure in order to ensure that the collected charge carriers can flow efficiently to the bottom cell structure side, thereby increasing the charge flow velocity and improving the photoelectric conversion efficiency.

[0014] In one alternative implementation, the number of charge collection structures ranges from 2 to 10.

[0015] Beneficial effects: Setting the charge collection structure to 2 to 10 can ensure sufficient collection of charge carriers at each position on the plane of the perovskite absorption layer, while avoiding setting too many to reduce the light-receiving area and affect the current density and photoelectric conversion efficiency.

[0016] In one alternative embodiment, the width of the charge collection structure ranges from 1 μm to 10 μm, and the height ranges from 1 μm to 100 μm.

[0017] Beneficial effects: If the width of the charge collection layer is too large, it will reduce the light-receiving area of ​​the bottom cell structure, thus affecting the effective absorption of sunlight. Therefore, limiting the width of the charge collection layer to between 1 μm and 10 μm can ensure sufficient absorption of charge carriers within the plane range of the perovskite absorption layer, while also ensuring that the bottom cell structure has a sufficient light absorption area. Setting the height of the charge collection structure between 1 μm and 100 μm can achieve complete coverage of the charge collection structure by the perovskite absorption layer, and the perovskite absorption layer has a complete light-receiving surface on the top layer, thereby improving the light absorption capacity.

[0018] In one alternative embodiment, the top battery structure further includes a transparent conductive layer disposed on the side surface of the second carrier transport layer opposite to the bottom battery structure.

[0019] Beneficial effects: The transparent conductive layer can serve as the transparent electrode in the perovskite top cell structure. Sunlight enters from the transparent electrode side. The transparent electrode is placed on the second carrier transport layer, which not only increases the light-receiving area, but also helps to collect the current on the second carrier transport layer side, thereby improving the photoelectric conversion efficiency of the perovskite tandem solar cell.

[0020] In one alternative embodiment, the top battery structure further includes a protective layer disposed on the side surface of the transparent conductive layer opposite to the bottom battery structure.

[0021] Beneficial effects: The protective layer of this application can protect the transparent conductive layer and reduce the reflection of sunlight on the light-receiving side, so that more sunlight is absorbed by the perovskite absorption layer, thereby improving the light absorption of the perovskite tandem solar cell and thus improving the power generation efficiency.

[0022] In one optional embodiment, it further includes: a first electrode and a second electrode, wherein the first electrode is disposed on the side surface of the bottom battery structure opposite to the composite layer, and the second electrode is disposed on the side surface of the protective layer opposite to the bottom battery structure.

[0023] Beneficial effects: The first and second electrodes serve as the positive and negative electrodes of the perovskite tandem solar cell, respectively, allowing the current generated in the tandem cell to be extracted and utilized.

[0024] Secondly, this application also provides a method for preparing a perovskite tandem solar cell, comprising:

[0025] Provide a bottom battery structure;

[0026] A composite layer is formed on one side surface of the bottom battery structure;

[0027] A top cell structure is formed on the surface of the composite layer facing away from the bottom cell structure. The top cell structure includes a first carrier transport layer, a charge collection structure, a perovskite absorber layer, and a second carrier transport layer arranged sequentially. The first carrier transport layer is of a first conductivity type. The charge collection structure is of a second conductivity type opposite to the first conductivity type and extends from the side closer to the bottom cell structure to the side farther away from the bottom cell structure. The charge collection structure includes multiple doped layers stacked with increasing doping concentration. The perovskite absorber layer covers the charge collection structure. The second carrier transport layer is of the first conductivity type.

[0028] Beneficial Effects: In the fabrication method of the perovskite tandem solar cell of this application, a composite layer is first formed on the bottom cell structure, and then a first carrier transport layer of the top cell structure is formed on the composite layer. Next, a charge collection structure with gradually decreasing doping concentration from the light-receiving side downwards is formed on the first carrier transport layer of the top cell structure near the bottom cell structure. Then, a perovskite absorber layer is covered on the charge collection structure. This allows electrons and holes generated in the perovskite absorber layer to move towards the first carrier transport layer on the upper and lower sides of the perovskite absorber layer according to the attraction of the carrier transport layers with different conductivity types on the upper and lower sides of the perovskite absorber layer. While the carrier transport layer and the second carrier transport layer move, a charge collection structure is formed on the first carrier transport layer near the bottom cell structure, that is, at the bottom of the perovskite absorber layer. This structure collects the same type of charge in the perovskite absorber layer as the first carrier transport layer, maximizing charge collection and reducing carrier recombination in the perovskite absorber layer, thus increasing the current density of the perovskite top cell. Furthermore, because the charge collection structure has multiple doped layers with gradually decreasing doping concentration from top to bottom, it greatly improves the movement speed of free charges, thereby optimizing current formation and ultimately improving the photoelectric conversion efficiency of the perovskite tandem solar cell.

[0029] In one alternative embodiment, a top battery structure is formed on the surface of the composite layer facing away from the bottom battery structure, including:

[0030] A first carrier transport layer is formed on the surface of the composite layer away from the bottom battery structure, and the first carrier transport layer is of a first conductivity type.

[0031] A charge collection structure is formed on the first carrier transport layer. The charge collection structure is a second type of conductivity opposite to the first type of conductivity, and extends from the side closer to the bottom cell structure to the side farther away from the bottom cell structure. The charge collection structure includes multiple doped layers stacked together with increasing doping concentration.

[0032] A perovskite absorption layer is formed on the first carrier transport layer, and the perovskite absorption layer covers the charge collection structure.

[0033] A second carrier transport layer is formed on the surface of the perovskite absorber layer away from the bottom cell structure. The second carrier transport layer is of the first conductivity type.

[0034] A transparent conductive layer is formed on the surface of the second carrier transport layer on the side opposite to the bottom battery structure.

[0035] A protective layer is formed on the surface of the transparent conductive layer that is opposite to the bottom battery structure;

[0036] After forming the top battery structure on the side of the composite layer away from the bottom battery structure, the method further includes: forming a first electrode on the side of the bottom battery structure away from the composite layer, and forming a second electrode on the side of the protective layer away from the bottom battery structure.

[0037] Beneficial effects: The process of forming the top cell structure does not change the conventional perovskite cell fabrication process. Only after the first carrier donation and transport layer, a charge collection structure is first set up before covering the perovskite absorber layer. The process steps are simple. The charge collection structure is formed inside the top cell structure, which has a high-efficiency protection function, ensuring efficient collection and transport of charge, and improving the service life and power generation efficiency of the perovskite tandem cell. Attached Figure Description

[0038] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0039] Figure 1 is a schematic diagram of the structure of a perovskite tandem solar cell according to an embodiment of this application;

[0040] Figure 2 is a schematic flowchart of a method for fabricating a perovskite tandem solar cell according to an embodiment of this application;

[0041] Figure 3 is a schematic diagram of the bottom battery structure according to an embodiment of this application;

[0042] Figure 4 is a schematic diagram of the structure after a composite layer is provided on the bottom battery structure according to an embodiment of this application;

[0043] Figure 5 is a schematic diagram of the structure after a composite layer is provided on the bottom battery structure according to an embodiment of this application;

[0044] Figure 6 is a schematic diagram of the structure after the top battery structure is provided on the composite layer according to an embodiment of this application;

[0045] Figure 7 is a schematic diagram of another process for fabricating a perovskite tandem solar cell according to an embodiment of this application.

[0046] Explanation of reference numerals in the attached figures: 1. Bottom cell structure; 2. Composite layer; 3. Top cell structure; 31. First carrier transport layer; 32. Charge collection structure; 321. First doped layer; 322. Second doped layer; 323. Third doped layer; 33. Perovskite absorber layer; 34. Second carrier transport layer; 35. Transparent conductive layer; 36. Protective layer; 4. First electrode; 5. Second electrode. Detailed Implementation

[0047] The present application will be further described in detail below with reference to the accompanying drawings and embodiments. It is understood that the specific embodiments described herein are merely illustrative of the present application and not intended to limit it. It should also be noted that, for ease of description, only the parts relevant to the present application are shown in the drawings, not all structures. In the following description, descriptions of well-known structures and technologies are omitted to avoid unnecessarily obscuring the concepts of the present application. The accompanying drawings show various structural schematic diagrams according to embodiments of the present application. These drawings are not drawn to scale, and some details are enlarged for clarity and may be omitted. The shapes of the various regions and layers shown in the drawings, as well as their relative sizes and positional relationships, are merely exemplary and may deviate in practice due to manufacturing tolerances or technical limitations. Furthermore, those skilled in the art can design regions / layers with different shapes, sizes, and relative positions as needed. In the context of this application, when a layer / element is referred to as being "on" another layer / element, the layer / element may be directly on the other layer / element, or there may be an intermediate layer / element between them. Additionally, if one layer / component is "above" another layer / component in one orientation, then when the orientation is reversed, that layer / component can be "below" that other layer / component.

[0048] In related multi-junction tandem solar cell structures, if two sub-cells are connected by a middle composite layer, the multi-junction tandem solar cell is a monolithic tandem solar cell with two ends (2T). In monolithic perovskite / crystalline silicon tandem solar cells made using crystalline silicon, the current density of the crystalline silicon bottom cell is much higher than that of the perovskite top cell. Since the top and bottom cells of the 2T tandem solar cell are in series, the currents of the two sub-cells must be consistent. The side with the lower current determines the final output current. Therefore, the 2T perovskite / crystalline silicon tandem solar cell can only generate a current that matches the side with the lower current density (i.e., the perovskite cell). The current mismatch between the top and bottom cells will lead to a decrease in current density and will also affect the fill factor (FF), thereby causing a decrease in photoelectric conversion efficiency.

[0049] To overcome this drawback, related technologies have made improvements by designing complex structures for the composite layer connecting the top and bottom cells, or for the perovskite absorber layer itself. However, this greatly increases the manufacturing cost, and the complex structures of the composite layer and the perovskite absorber layer increase the thickness of the stacked cell, posing a challenge to its stability. Therefore, a perovskite stacked cell structure is needed that is simple in structure, can extract the charge form present in the perovskite absorber layer with maximum efficiency, and maximizes the current density of the perovskite absorber layer used as the top cell.

[0050] Based on this, referring to Figure 1, this embodiment provides a perovskite tandem solar cell, including: a bottom cell structure 1, a composite layer 2, and a top cell structure 3. The composite layer 2 is disposed on one side surface of the bottom cell structure 1; the top cell structure 3 is disposed on the side of the composite layer 2 away from the bottom cell structure 1; the top cell structure 3 includes a first carrier transport layer 31, a charge collection structure 32, a perovskite absorber layer 33, and a second carrier transport layer 34 arranged sequentially. The first carrier transport layer 31 is of a first conductivity type; the charge collection structure 32 is of a second conductivity type opposite to the first conductivity type, and extends from the side closer to the bottom cell structure 1 to the side farther away from the bottom cell structure 1. The charge collection structure 32 includes multiple doped layers stacked with increasing doping concentration; the perovskite absorber layer 33 covers the charge collection structure 32; the second carrier transport layer 34 is of the first conductivity type.

[0051] Specifically, the aforementioned bottom cell structure 1 is a crystalline silicon bottom cell, which can be one of the following: a passivated emitter and rear cell (PERC), a tunnel oxide passivated contact (TOPCon), or a silicon heterojunction (SHJ). In this embodiment, it is a TOPCon cell. The composite layer 2 is a transparent conductive oxide (TCO) layer, which can be an indium tin oxide (ITO), an indium zinc oxide (IZO), or an aluminum-doped zinc oxide (ACO) film. The composite layer 2 is a type of oxidant (AZO). Its thickness is set between 50 nm and 500 nm, and its sheet resistance is set between 1.0 × 10⁻⁴ Ω / cm and 1.0 × 10⁻³ Ω / cm. The composite layer 2 allows for smooth current flow between the top cell structure 3 and the bottom cell structure 1. Free charges in the top cell structure 3 and the bottom cell structure 1 recombine at the composite layer 2, and then generate free charges again in the composite layer 2. The top cell structure 3 is specifically a perovskite top cell. In the first carrier transport layer 31 and the second carrier transport layer 34, one is an electron transport layer (ETL), and the other is a hole transport layer (HTL). The thickness of both the electron transport layer and the hole transport layer is set between 20 nm and 100 nm. The electron transport layer can be titanium dioxide (TiO₂), tin dioxide (SnO₂), zinc oxide (ZnO), a C60 derivative (Phenyl-C61-Butyric Acid Methyl Ester, abbreviated as PCBM), or C60. 60One of them; the hole transport layer can be nickel oxide (NiO). x One of the following: poly[bis4-phenyl)(2,4,6-trimethylphenyl)amine (PTAA), 2,2',7,7'-tetratetra[n,n-di(4-methoxyphenyl)amino]-9,9'-spirodifluorene (Sprio-OMeTAD), and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT); (electro) The charge collection structure 32 has the same conductivity type as the first carrier transport layer 31 below it, which is close to the bottom cell structure 1. That is, if the first carrier transport layer 31 is an electron transport layer, then the charge collection structure 32 is an electron collection structure formed by phosphorus doping; if the first carrier transport layer 31 is a hole transport layer, then the charge collection structure 32 is a hole collection structure formed by boron doping. The doping concentration of the multiple doped layers of the charge collection structure 32 gradually decreases from top to bottom with the light-receiving surface as the reference. The perovskite absorption layer 33 can be one of methylammonium lead iodide (MAPbI3), formamidinium lead iodide (FAPbI3), mixed cation perovskite, and 2D / 3D halide perovskite. When sunlight enters the perovskite absorption layer 33, excitons are generated, and the excitons are separated to generate electrons and holes.

[0052] When the top cell structure 3 is a nip structure, the first carrier transport layer 31 is a hole transport layer, the second carrier transport layer 34 is an electron transport layer, and the charge collection structure 32 is a hole-type collection structure. Specifically, it can be obtained by doping polycrystalline silicon with different concentrations of boron to achieve maximum hole collection. When the top cell structure 3 is a pin structure, the first carrier transport layer 31 is an electron transport layer, the second carrier transport layer 34 is a hole transport layer, and the charge collection structure 32 is an electron-type collection structure. Specifically, it can be obtained by doping polycrystalline silicon with different concentrations of phosphorus to achieve maximum electron collection.

[0053] In this embodiment of the perovskite tandem solar cell, a charge collection structure 32 with gradually decreasing doping concentration from the light-receiving side is provided on the carrier transport layer of the top cell structure 3 near the bottom cell structure 1. A perovskite absorber layer 33 is then covered on the charge collection structure 32. This allows electrons and holes generated in the perovskite absorber layer 33 to move towards the first carrier transport layer 31 and the second carrier transport layer 34 on the upper and lower sides of the perovskite absorber layer 33, respectively, based on the attraction of the carrier transport layers with different conductivity types on the upper and lower sides of the perovskite absorber layer 33. Furthermore, they also move towards the first carrier transport layer 31 near the bottom cell structure 1, i.e., on the perovskite absorber layer 33. At the bottom, the charge collection structure 32 collects the same type of charge as the first carrier transport layer 31 in the perovskite absorber layer 33, maximizing the charge collection capability, reducing carrier recombination in the perovskite absorber layer 33, and improving the current density of the perovskite top cell. Furthermore, because the charge collection structure 32 has multiple doped layers with gradually decreasing doping concentration from top to bottom, it greatly improves the movement speed of free charges, thereby optimizing current formation and ultimately improving the photoelectric conversion efficiency of the perovskite tandem solar cell. Moreover, the charge collection structure 32 is located inside the perovskite absorber layer 33, with a simple structure that does not increase the thickness of the tandem cell, ensuring reliability and stability.

[0054] The number of doped layers in the charge collection structure 32 described above ranges from 2 to 5.

[0055] Referring to Figure 1, this embodiment uses a charge collection structure 32 with three doped layers as an example. From the bottom cell structure 1 to the top cell structure 3, the charge collection structure 32 includes a first doped layer 321, a second doped layer 322, and a third doped layer 323, with the doping concentration of the first doped layer 321, the second doped layer 322, and the third doped layer 323 gradually increasing. Within the thickness range of the perovskite absorber layer 33, 2 to 5 doped layers are provided, which helps to maximize the absorption of free charges on each thickness of the perovskite absorber layer 33 and allows the absorbed free charges to move rapidly from the high concentration side to the low concentration side, reducing carrier recombination in the perovskite absorber layer 33 and ultimately increasing the current density of the perovskite absorber layer 33.

[0056] In one embodiment, the maximum doping concentration in the plurality of doped layers of the charge collection structure 32 is 10. - 21 cm 3 The minimum doping concentration in the multiple doped layers is greater than or equal to the doping concentration of the bottom cell structure 1.

[0057] In the multiple doped layers of the charge collection structure 32, excessively high doping concentrations can actually hinder the collection of charges from the perovskite absorber layer 33. Therefore, the maximum doping concentration is limited to 10.- 21 cm 3 This ensures that the charge collection structure 32 can maximize the collection of charge carriers generated in the perovskite absorber layer 33; the minimum doping concentration is higher than the doping concentration of the bottom cell structure 1 in order to ensure that the collected charge carriers can flow efficiently to the bottom cell structure 1 side, thereby increasing the charge flow rate and improving the photoelectric conversion efficiency.

[0058] As shown in Figure 1, in this embodiment of the perovskite tandem solar cell, the number of charge collection structures 32 is set to multiple, specifically 2 to 10.

[0059] Specifically, multiple layers of initial doped material can be sequentially formed on the first carrier transport layer 31 using methods such as low-pressure vapor deposition or plasma-enhanced chemical vapor deposition. Then, the initial doped material is locally removed using a patterned mask to form multiple charge collection structures 32 with multiple doped layers. The number of charge collection structures 32 can be set to 2 to 10, ensuring sufficient collection of carriers at all locations on the plane of the perovskite absorption layer 33 while avoiding excessive structures that would reduce the light-receiving area and affect current density and photoelectric conversion efficiency.

[0060] Furthermore, the width of each of the above-mentioned charge collection structures 32 ranges from 1 μm to 10 μm, and the height ranges from 1 μm to 100 μm.

[0061] If the width of the charge collection layer is too large, it will reduce the light-receiving area of ​​the bottom cell structure 1, thus affecting the effective absorption of sunlight. Therefore, the width of the charge collection layer is limited to between 1 μm and 10 μm, which can ensure sufficient absorption of charge carriers within the plane range of the perovskite absorption layer 33, and also ensure that the bottom cell structure has a sufficient light-receiving area. Since the thickness of the perovskite absorption layer 33 is set between 300 nm and 600 nm, the height of the charge collection structure 32 is set between 1 μm and 100 μm, which can achieve complete coverage of the charge collection structure 32 by the perovskite absorption layer 33, and the perovskite absorption layer 33 has a complete light-receiving surface on the top layer, thereby improving the light absorption capacity.

[0062] Based on the above scheme, the top cell structure 3 of the perovskite tandem solar cell in this embodiment further includes a transparent conductive layer 35, which is disposed on the side surface of the second carrier transport layer 34 away from the bottom cell structure 1.

[0063] In this embodiment, the transparent conductive layer 35 can be a transparent conductive oxide (TCO) layer, such as indium tin oxide (ITO), indium zinc oxide (IZO), or aluminum-doped zinc oxide (AZO), to serve as the transparent electrode of the perovskite top cell structure 3. The thickness of the transparent conductive layer 35 is set between 50 nm and 500 nm, and the sheet resistance is set at 1.0 × 10⁻⁶. -4 Ω / cm~1.0×10 - 3 Between Ω / cm. Sunlight enters from the transparent electrode side. The transparent electrode, located on the second carrier transport layer 34, not only increases the light-receiving area but also helps to collect the current on the second carrier transport layer 34 side, thereby improving the photoelectric conversion efficiency of the perovskite tandem solar cell.

[0064] In one embodiment, the top battery structure 3 further includes a protective layer 36, which is disposed on the side surface of the transparent conductive layer 35 facing away from the bottom battery structure 1.

[0065] Specifically, the protective layer 36 can be one or more of silicon dioxide (SiO2), titanium dioxide (TiO2), aluminum oxide (Al2O3), parylene, polyethylene terephthalate (PET), or polymethyl methacrylate (PMMA); the thickness of the protective layer 36 ranges from 10 nm to 600 nm. In this embodiment, the protective layer 36 can protect the transparent conductive layer 35 and reduce the reflection of sunlight on the light-receiving side, allowing more sunlight to be absorbed by the perovskite absorption layer 33, thereby improving the light absorption of the perovskite tandem solar cell and thus increasing the power generation efficiency.

[0066] Referring to Figure 1, the perovskite tandem solar cell of this embodiment also includes a first electrode 4 and a second electrode 5. The first electrode 4 is disposed on the side surface of the bottom cell structure 1 away from the composite layer 2, and the second electrode 5 is disposed on the side surface of the protective layer 36 away from the bottom cell structure 1.

[0067] The first electrode 4 and the second electrode 5 are metal electrodes, specifically one or more highly conductive metal materials such as gold (Au), silver (Ag), aluminum (Al), or copper (Cu). The thickness of the first electrode 4 and the second electrode 5 is set to 60 nm to 120 nm. The first electrode 4 and the second electrode 5 serve as the positive and negative electrodes of the perovskite tandem solar cell, respectively, to extract and utilize the current generated in the tandem cell.

[0068] Referring to Figures 2 to 6, this embodiment also provides a method for fabricating a perovskite tandem solar cell, used to prepare the above-mentioned perovskite solar tandem cell. Figure 2 is a schematic flowchart of the fabrication method of the perovskite tandem solar cell, which includes the following steps:

[0069] Step S201, provide bottom battery structure 1.

[0070] As shown in Figure 3, exemplarily, the bottom cell structure 1 is a crystalline silicon bottom cell, specifically one of the following: a passivated emitter and rear cell (PERC), a tunnel oxide passivated contact (TOPCon), or a silicon heterojunction (SHJ). In this embodiment, it is a TOPCon cell. The specific fabrication process of the bottom cell structure 1 is well known in the art and will not be described in detail here.

[0071] In step S202, a composite layer 2 is formed on one side surface of the bottom battery structure 1.

[0072] As shown in Figure 4, exemplarily, the composite layer 2 can be a transparent conductive oxide (TCO) layer formed by methods such as magnetron sputtering, evaporation, or atomic layer deposition (ALD). Specifically, the composite layer 2 can be one of indium tin oxide (ITO), indium zinc oxide (IZO), or aluminum-doped zinc oxide (AZO). The thickness of the composite layer 2 is set between 50 nm and 500 nm, and the sheet resistance is set between 1.0 × 10⁻⁴ Ω / cm and 1.0 × 10⁻³ Ω / cm. The composite layer 2 allows for smooth current flow between the top battery structure 3 and the bottom battery structure 1. The free charges of the top battery structure 3 and the bottom battery structure 1 recombine at the composite layer 2, and after recombination, free charges are generated again in the composite layer 2.

[0073] As shown in Figure 5, in step S203, a top cell structure 3 is formed on the surface of the composite layer 2 facing away from the bottom cell structure 1. The top cell structure 3 includes a first carrier transport layer 31, a charge collection structure 32, a perovskite absorber layer 33, and a second carrier transport layer 34 arranged sequentially. The first carrier transport layer 31 is of a first conductivity type; the charge collection structure 32 is of a second conductivity type opposite to the first conductivity type, and extends from the side closer to the bottom cell structure 1 to the side farther away from the bottom cell structure 1. The charge collection structure 32 includes multiple doped layers stacked with increasing doping concentration; the perovskite absorber layer 33 covers the charge collection structure 32; and the second carrier transport layer 34 is of the first conductivity type.

[0074] The top cell structure 3 is specifically a perovskite top cell, in which the first carrier transport layer 31 and the second carrier transport layer 34 are, respectively, an electron transport layer (ETL) and a hole transport layer (HTL). The electron transport layer and the hole transport layer can be deposited by methods such as spin coating, ALD or spray thermal decomposition, and their thicknesses are set in the range of 20nm to 100nm. The electron transport layer can be one of titanium dioxide (TiO2), tin dioxide (SnO2), zinc oxide (ZnO), a C60 derivative (Phenyl-C61-Butyric Acid Methyl Ester, abbreviated as PCBM), or C60; the hole transport layer can be one of nickel oxide (NiOx), poly[bis4-phenyl)(2,4,6-trimethylphenyl)amine (abbreviated as PTAA), 2,2',7,7'-tetratetra[n,n-bis(4-methoxyphenyl)amino]-9,9'-spirodifluorene (abbreviated as Sprio-OMeTAD), or poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate, abbreviated as PEDOT). The fabrication process of the charge collection structure 32 specifically includes: firstly, forming multiple layers of initial doped material on the first carrier transport layer 31 sequentially through low-pressure vapor deposition, atomic layer deposition, plasma-enhanced chemical vapor deposition, etc.; then, locally removing the initial doped material through a patterned mask to form multiple charge collection structures 32 with multiple doped layers. The conductivity type of the charge collection structure 32 is the same as that of the first carrier transport layer 31 below it, which is close to the bottom battery structure 1. That is, if the first carrier transport layer 31 is an electron transport layer, the charge collection structure 32 corresponds to an electron collection structure formed by phosphorus doping. For example, phosphorus doping can use dopants such as phosphine (PH3) and phosphorus oxychloride (POCl3); if the first carrier transport layer 31 is a hole transport layer, the charge collection structure 32 is a hole collection structure formed by boron doping. For example, boron doping can use doping gases such as diborane (B2H6), boron trifluoride (BF3), and boron trichloride (BCl3). The multiple doped layers of the charge collection structure 32 gradually decrease in doping concentration from top to bottom, with the light-receiving surface as the reference. The perovskite absorber layer 33 can be one of methylammonium lead iodide (MAPbI3), formamidinium lead iodide (FAPbI3), mixed cation perovskite, and 2D / 3D halide perovskite, and can be formed by methods such as spin coating, vacuum evaporation, or ALD.

[0075] In the fabrication method of the perovskite tandem solar cell in this embodiment, a composite layer 2 is first formed on the bottom cell structure 1, and then a first carrier transport layer 31 of the top cell structure 3 is formed on the composite layer 2. Next, a charge collection structure 32 with gradually decreasing doping concentration from the light-receiving side is formed on the first carrier transport layer 31 of the top cell structure 3 near the bottom cell structure 1. Then, a perovskite absorption layer 33 is covered on the charge collection structure 32. This allows electrons and holes generated in the perovskite absorption layer 33 to move towards the first carrier transport layer 31 on the top cell structure 3 near the bottom cell structure 1, according to the attraction of the different conductivity types of the carrier transport layers on the upper and lower sides of the perovskite absorption layer 33. As the charge transport layer 31 and the second charge transport layer 34 move, a charge collection structure 32 is formed on the first charge transport layer 31 near the bottom cell structure 1, that is, at the bottom of the perovskite absorber layer 33. This structure collects the same type of charge in the perovskite absorber layer 33 as in the first charge transport layer 31, maximizing charge collection and reducing carrier recombination in the perovskite absorber layer 33, thereby increasing the current density of the perovskite top cell. Furthermore, because the charge collection structure 32 has multiple doped layers with gradually decreasing doping concentration from top to bottom, it greatly improves the movement speed of free charges, thereby optimizing current formation and ultimately improving the photoelectric conversion efficiency of the perovskite tandem solar cell.

[0076] Referring to Figure 7, in one embodiment, step S203, forming a top battery structure 3 on the surface of the composite layer 2 facing away from the bottom battery structure 1, includes:

[0077] In step S2031, a first carrier transport layer 31 is formed on the surface of the composite layer 2 facing away from the bottom battery structure 1. The first carrier transport layer 31 is of a first conductivity type.

[0078] In this embodiment, the first carrier transport layer 31 can be an electron transport layer or a hole transport layer deposited by methods such as spin coating, ALD, or spray thermal decomposition, and the thickness of the first carrier transport layer 31 is set between 20nm and 100nm.

[0079] In step S2032, a charge collection structure 32 is formed on the first carrier transport layer 31. The charge collection structure 32 is a second conductivity type opposite to the first conductivity type and extends from the side closer to the bottom cell structure 1 to the side farther away from the bottom cell structure 1. The charge collection structure 32 includes multiple doped layers stacked together with increasing doping concentration.

[0080] The fabrication process of the charge collection structure 32 specifically includes: firstly, forming multiple layers of initial doped material on the first carrier transport layer 31 sequentially through low-pressure vapor deposition, atomic layer deposition, plasma-enhanced chemical vapor deposition, etc.; then, locally removing the initial doped material through a patterned mask to form multiple charge collection structures 32 with multiple doped layers. The conductivity type of the charge collection structure 32 is the same as that of the first carrier transport layer 31 below it, which is close to the bottom battery structure 1. That is, if the first carrier transport layer 31 is an electron transport layer, the charge collection structure 32 corresponds to an electron collection structure formed by phosphorus doping. For example, phosphorus doping can use dopants such as phosphine (PH3) and phosphorus oxychloride (POCl3); if the first carrier transport layer 31 is a hole transport layer, the charge collection structure 32 is a hole collection structure formed by boron doping. For example, boron doping can use doping gases such as diborane (B2H6), boron trifluoride (BF3), and boron trichloride (BCl3). The doping concentration of the multiple doped layers of the charge collection structure 32 gradually decreases from top to bottom, with the light-receiving surface as the reference.

[0081] In step S2033, a perovskite absorption layer 33 is formed on the first carrier transport layer 31, and the perovskite absorption layer 33 covers the charge collection structure 32.

[0082] The perovskite absorber layer 33 can be one of methylammonium lead iodide (MAPbI3), formamidinium lead iodide (FAPbI3), mixed cation perovskite, and 2D / 3D halide perovskite, and can be formed by spin coating, vacuum evaporation, or ALD.

[0083] In step S2034, a second carrier transport layer 34 is formed on the surface of the perovskite absorber layer 33 facing away from the bottom cell structure 1. The second carrier transport layer 34 is of the first conductivity type.

[0084] In this embodiment, the second carrier transport layer 34 can be an electron transport layer or a hole transport layer deposited by methods such as spin coating, ALD, or spray thermal decomposition, and the thickness of the second carrier transport layer 34 is set between 20nm and 100nm.

[0085] In the first carrier transport layer 31 and the second carrier transport layer 34, one of them is an electron transport layer (ETL), and the other is a hole transport layer (HTL). The electron transport layer can be one of titanium dioxide (TiO2), tin dioxide (SnO2), zinc oxide (ZnO), a C60 derivative (Phenyl-C61-Butyric Acid Methyl Ester, abbreviated as PCBM), or C60; the hole transport layer can be one of nickel oxide (NiOx), poly[bis4-phenyl)(2,4,6-trimethylphenyl)amine (abbreviated as PTAA), 2,2',7,7'-tetratetra[n,n-bis(4-methoxyphenyl)amino]-9,9'-spirodifluorene (abbreviated as Sprio-OMeTAD), or poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate, abbreviated as PEDOT).

[0086] In step S2035, a transparent conductive layer 35 is formed on the side surface of the second carrier transport layer 34 facing away from the bottom battery structure 1.

[0087] In this embodiment, the transparent conductive layer 35 can be a transparent conductive oxide (TCO) layer formed by methods such as magnetron sputtering, evaporation, and ALD, such as indium tin oxide (ITO), indium zinc oxide (IZO), or aluminum-doped zinc oxide (AZO), to serve as the transparent electrode of the perovskite top cell structure 3. The thickness of the transparent conductive layer 35 is set between 50 nm and 500 nm, and the sheet resistance is set at 1.0 × 10⁻⁶. -4 Ω / cm~1.0×10 -3 Between Ω / cm. Sunlight enters from the transparent electrode side. The transparent electrode, located on the second carrier transport layer 34, not only increases the light-receiving area but also helps to collect the current on the second carrier transport layer 34 side, thereby improving the photoelectric conversion efficiency of the perovskite tandem solar cell.

[0088] Step S2036: A protective layer 36 is formed on the surface of the transparent conductive layer 35 facing away from the bottom battery structure 1.

[0089] Specifically, the protective layer 36 can be formed by methods such as spin coating, sol-gel method, vacuum evaporation method, and ALD. The material of the protective layer 36 can be one or more of silicon oxide (SiO2), titanium oxide (TiO2), aluminum oxide (Al2O3), parylene, polyethylene terephthalate (PET), or polymethyl methacrylate (PMMA). The thickness of the protective layer 36 ranges from 10 nm to 600 nm. In this embodiment, the protective layer 36 can protect the transparent conductive layer 35 and reduce the reflection of sunlight on the light-receiving side, allowing more sunlight to be absorbed by the perovskite absorption layer 33, improving the light absorption of the perovskite tandem solar cell, thereby improving the power generation efficiency.

[0090] Referring to Figure 7, after forming the top battery structure 3 on the side of the composite layer 2 facing away from the bottom battery structure 1 in step S203 above, the method further includes:

[0091] In step S204, a first electrode 4 is formed on the surface of the bottom battery structure 1 facing away from the composite layer 2, and a second electrode 5 is formed on the surface of the protective layer 36 facing away from the bottom battery structure 1.

[0092] The first electrode 4 and the second electrode 5 are metal electrodes, specifically one or more of gold (Au), silver (Ag), aluminum (Al), or copper (Cu). The thickness of the first electrode 4 and the second electrode 5 is set to 60 nm to 120 nm. The first electrode 4 and the second electrode 5 serve as the positive and negative electrodes of the perovskite tandem solar cell, respectively, to extract and utilize the current generated in the tandem cell.

[0093] Further functional descriptions of the above modules are the same as those in the corresponding embodiments described above, and will not be repeated here.

[0094] The above description does not provide detailed explanations of the technical aspects of each layer's patterning, etching, etc. However, those skilled in the art should understand that various technical means can be used to form layers and regions of the desired shape. Furthermore, to form the same structure, those skilled in the art can also design methods that are not entirely identical to those described above. Additionally, although various embodiments have been described above, this does not mean that the measures in the various embodiments cannot be used advantageously in combination.

[0095] Although embodiments of this application have been described in conjunction with the accompanying drawings, those skilled in the art can make various modifications and variations without departing from the spirit and scope of this application, and such modifications and variations all fall within the scope defined by the appended claims.

Claims

1. A perovskite tandem solar cell, characterized in that, include: Bottom battery structure; A composite layer is disposed on one side surface of the bottom battery structure; A top cell structure is disposed on the side of the composite layer opposite to the bottom cell structure. The top cell structure includes a first carrier transport layer, a charge collection structure, a perovskite absorber layer, and a second carrier transport layer arranged sequentially. The first carrier transport layer has a first conductivity type. The charge collection structure has a second conductivity type opposite to the first conductivity type and extends from the side closer to the bottom cell structure to the side farther away from the bottom cell structure. The charge collection structure includes multiple doped layers stacked with increasing doping concentration. The perovskite absorber layer covers the charge collection structure. The second carrier transport layer has the first conductivity type.

2. The perovskite tandem solar cell according to claim 1, characterized in that, The number of doped layers in the charge collection structure ranges from 2 to 5.

3. The perovskite tandem solar cell according to claim 2, characterized in that, The maximum doping concentration among the plurality of doped layers is 10. -21 cm 3 The minimum doping concentration among the plurality of doped layers is greater than or equal to the doping concentration of the bottom battery structure.

4. The perovskite tandem solar cell according to claim 1, characterized in that, The number of charge collection structures ranges from 2 to 10.

5. The perovskite tandem solar cell according to claim 1, characterized in that, The width of the charge collection structure ranges from 1 μm to 10 μm, and the height ranges from 1 μm to 100 μm.

6. The perovskite tandem solar cell according to any one of claims 1-5, characterized in that, The top battery structure also includes: A transparent conductive layer is disposed on the surface of the second charge carrier transport layer on the side opposite to the bottom battery structure.

7. The perovskite tandem solar cell according to claim 6, characterized in that, The top battery structure also includes: A protective layer is disposed on the surface of the transparent conductive layer that faces away from the bottom battery structure.

8. The perovskite tandem solar cell according to claim 7, characterized in that, Also includes: A first electrode and a second electrode are provided, wherein the first electrode is disposed on the side surface of the bottom battery structure opposite to the composite layer, and the second electrode is disposed on the side surface of the protective layer opposite to the bottom battery structure.

9. A method for preparing a perovskite tandem solar cell, used to prepare the perovskite tandem solar cell according to any one of claims 1-8, characterized in that, include: Provide a bottom battery structure; A composite layer is formed on one side surface of the bottom battery structure; A top cell structure is formed on the surface of the composite layer facing away from the bottom cell structure. The top cell structure includes a first carrier transport layer, a charge collection structure, a perovskite absorber layer, and a second carrier transport layer arranged sequentially. The first carrier transport layer has a first conductivity type. The charge collection structure has a second conductivity type opposite to the first conductivity type and extends from the side closer to the bottom cell structure to the side farther away from the bottom cell structure. The charge collection structure includes multiple doped layers stacked with increasing doping concentration. The perovskite absorber layer covers the charge collection structure. The second carrier transport layer has the first conductivity type.

10. The method for preparing a perovskite tandem solar cell according to claim 9, characterized in that, The formation of a top battery structure on the surface of the composite layer opposite to the bottom battery structure includes: A first carrier transport layer is formed on the surface of the composite layer opposite to the bottom battery structure, and the first carrier transport layer is of a first conductivity type. A charge collection structure is formed on the first carrier transport layer. The charge collection structure is a second conductivity type opposite to the first conductivity type and extends from the side closer to the bottom cell structure to the side farther away from the bottom cell structure. The charge collection structure includes multiple doped layers stacked together with increasing doping concentration. A perovskite absorption layer is formed on the first carrier transport layer, and the perovskite absorption layer covers the charge collection structure. A second carrier transport layer is formed on the surface of the perovskite absorber layer opposite to the bottom cell structure, and the second carrier transport layer is of a first conductivity type. A transparent conductive layer is formed on the surface of the second charge carrier transport layer that is away from the bottom battery structure; A protective layer is formed on the surface of the transparent conductive layer that is opposite to the bottom battery structure. After forming a top battery structure on the surface of the composite layer opposite to the bottom battery structure, the method further includes: forming a first electrode on the surface of the bottom battery structure opposite to the composite layer, and forming a second electrode on the surface of the protective layer opposite to the bottom battery structure.

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