Intermediate connection layer structure, preparation method thereof and laminated solar cell

Abstract

The invention relates to the technical field of photovoltaic cells, in particular to an intermediate connection layer structure, a preparation method thereof and a laminated solar cell. The middle connecting layer structure comprises a tunnel junction which comprises a p-type heavily-doped silicon layer and a p-type lightly-doped silicon layer which are sequentially stacked, and the surface of the p-type lightly-doped silicon layer is provided with hydroxyl; and the self-assembled monomolecular layer is formed by reacting a self-assembled monomolecular layer material with hydroxyl on the surface of the p-type lightly doped silicon layer, and the self-assembled monomolecular layer is arranged on the surface of the p-type lightly doped silicon layer. According to the intermediate connection layer structure provided by the invention, the self-assembled monomolecular material reacts with the hydroxyl group on the surface of the p-type lightly doped silicon layer in the tunnel junction to form the self-assembled monomolecular layer, so that negative charges are fixed on the surface of the p-type lightly doped silicon layer, a field passivation effect is generated, carrier recombination on the surface is reduced, the loss of carriers is reduced, and the performance of the device is improved. And the electric leakage phenomenon caused by the incompact thin film is inhibited, so that the device performance of the laminated solar cell is improved.

Description

Technical Field

[0001] The present application relates to the technical field of photovoltaic cells, and particularly to an intermediate connection layer structure, a preparation method thereof, and a tandem solar cell. Background Art

[0002] As a clean energy source with rich resources and no need for transportation, solar energy is expected to become an alternative to traditional fossil fuels. The development of solar energy collection and conversion technologies has gradually become the focus of research. Photovoltaic devices can directly convert solar energy into electrical energy, which is one of the most effective ways to utilize solar energy.

[0003] With the continuous development of photovoltaic technology, the efficiency of single-crystalline silicon cells is approaching the theoretical upper limit. To further improve the energy conversion efficiency of photovoltaic cells and further break through the thermal relaxation loss of single-junction cells, the concept of multi-junction cells has been proposed. Currently, stacking a wide-bandgap perovskite cell on a crystalline silicon cell can achieve an energy conversion efficiency of 33.9%, far exceeding that of current single-crystalline silicon cells (26.81%), demonstrating the excellent performance advantages of tandem cells.

[0004] The intermediate connection layer plays a connecting role between the crystalline silicon cell and the perovskite cell, and plays a dual optical and electrical coupling role in the tandem cell structure, which is crucial for achieving high-efficiency tandem photovoltaic cells.

[0005] In traditional technologies, a transparent conductive oxide (TCO) layer or a PN junction tunneling layer is used as the intermediate connection layer.

[0006] However, when using a TCO layer as the intermediate connection layer, since perovskite is usually prepared by a multi-step wet process, on the one hand, it is impossible to ensure the denseness of the film layer, and a large number of holes often occur; on the other hand, the TCO layer has infrared parasitic absorption, which affects the optical absorption of the bottom crystalline silicon cell. If a traditional PN junction tunneling layer is used as the intermediate connection layer, although the tunneling efficiency of carriers is solved, the traditional PN junction tunneling layer is usually formed by using materials with a high doping density, which is likely to cause the upper interface material of the tandem cell to form a good ohmic contact with the tunneling layer through the porous perovskite layer, and will also lead to a reduction in the efficiency of the tandem cell. Summary of the Invention

[0007] Based on this, it is necessary to provide an intermediate connection layer structure, a preparation method thereof, and a tandem solar cell, which can improve the optical absorption rate of the bottom cell, reduce the loss of carriers, and inhibit the leakage phenomenon caused by the non-denseness of the film while ensuring the charge transfer rate, thereby improving the device performance of the tandem solar cell.

[0008] A first aspect of the present application provides an intermediate connection layer structure, which includes: a tunneling junction, including a p-type heavily doped silicon layer and a p-type lightly doped silicon layer stacked in sequence, and the surface of the p-type lightly doped silicon layer has hydroxyl groups; and a self-assembled monolayer, formed by the reaction of a self-assembled monolayer material with the hydroxyl groups on the surface of the p-type lightly doped silicon layer, and the self-assembled monolayer is disposed on the surface of the p-type lightly doped silicon layer.

[0009] In some embodiments, the self-assembled monolayer material is selected from at least one of oxygen-containing organic acids and oxygen-containing inorganic acids.

[0010] In some embodiments, the self-assembled monolayer material has a first end group, and the first end group reacts with the hydroxyl groups on the surface of the p-type lightly doped silicon layer to form a self-assembled monolayer. The first end group includes at least one of trisilanol groups, phosphate groups, acetate groups, borate groups, sulfonate groups, carboxyl groups, catechol, phenol, mercapto groups, and mercaptoacetyl groups.

[0011] In some embodiments, the first end group is obtained by hydrolysis of a first end group precursor, and the first end group precursor is selected from at least one of 3-methoxysilyl, 3-ethoxysilyl, 3-chlorosilyl, and trimethyl phosphate.

[0012] In some embodiments, the self-assembled monolayer material further has a second end group, and the second end group is located on the side away from the surface of the p-type lightly doped silicon layer. The second end group includes at least one of phenyl, naphthyl, anthracenyl, phenanthryl, pyrenyl, chrysenyl, and perylenyl.

[0013] In some embodiments, the self-assembled monolayer material further has a second end group, and the second end group is located on the side away from the surface of the p-type lightly doped silicon layer. The second end group includes at least one of trifluoromethyl, sulfonate group, thiourea group, guanidine group, biguanide group, amino group, ether bond, carbonyl group, methoxy group, mercapto group, benzylamine group, and choline group.

[0014] In some embodiments, the doping concentration of the p-type heavily doped silicon layer is greater than or equal to 10 19 cm -3 and the doping concentration of the p-type lightly doped silicon layer is less than or equal to 10 19 cm -3 .

[0015] In some embodiments, the total thickness of the tunneling junction is less than or equal to 200 nm.

[0016] In some embodiments, in the tunneling junction, the p-type heavily doped silicon layer is a microcrystalline silicon layer or an amorphous silicon layer, and the p-type lightly doped silicon layer is a microcrystalline silicon layer or an amorphous silicon layer.

[0017] The second aspect of the present application provides a method for preparing an intermediate connection layer structure, and the preparation method includes the following steps: S1, preparing a tunneling junction, where the tunneling junction includes a p-type heavily doped silicon layer and a p-type lightly doped silicon layer stacked in sequence; S2, performing hydroxylation treatment on the surface of the p-type lightly doped silicon layer so that the surface of the p-type lightly doped silicon layer has hydroxyl groups; S3, reacting a self-assembled monolayer material with the hydroxyl groups on the surface of the p-type lightly doped silicon layer to form a self-assembled monolayer on the surface of the p-type lightly doped silicon layer, thereby obtaining an intermediate connection layer structure.

[0018] The third aspect of the present application provides a tandem solar cell, which includes a bottom cell, an intermediate connection layer structure, and a top cell stacked in sequence; the bottom cell includes a crystalline silicon cell, and the top cell includes a perovskite cell; the intermediate connection layer structure is the intermediate connection layer structure provided by the first aspect above or the intermediate connection layer structure prepared by the preparation method provided by the second aspect above.

[0019] In some embodiments, the self-assembled monolayer is in contact with the perovskite cell, and the tunneling junction is in contact with the crystalline silicon cell.

[0020] Compared with the traditional technology, the present application has at least the following beneficial effects: For the intermediate connection layer structure provided by the present application, on the one hand, a composite structure with a tunneling junction and a self-assembled monolayer is used to replace the traditional TCO layer or PN junction tunneling layer. By utilizing the doping concentration gradient formed by the p-type heavily doped silicon layer and the p-type lightly doped silicon layer, the surface work function is effectively reduced. Thus, while promoting charge transport, infrared parasitic absorption is reduced, and further, the optical absorption rate of the bottom cell is increased; on the other hand, a self-assembled monolayer is formed by reacting a self-assembled monolayer material with the hydroxyl groups on the surface of the p-type lightly doped silicon layer in the tunneling junction, thereby fixing negative charges on the surface of the p-type lightly doped silicon layer, generating a field passivation effect, reducing surface carrier recombination, reducing carrier loss, and further improving the device performance of the tandem solar cell; furthermore, the composite structure composed of the tunneling junction and the self-assembled monolayer is not easily in ohmic contact with the top TCO of the solar cell in the case of pinholes or defects in the perovskite film, suppressing the leakage phenomenon caused by the non-dense film. Description of the Drawings

[0021] Figure 1 It is a schematic structural diagram of an intermediate connection layer structure in an embodiment of the present application.

[0022] Figure 2 It is a schematic flowchart of a method for preparing an intermediate connection layer structure in an embodiment of the present application.

[0023] Reference numerals: 1, intermediate connection layer structure; 10, tunneling junction; 11, p-type heavily doped silicon layer; 12, p-type lightly doped silicon layer; 20, self-assembled monolayer. Detailed Embodiments

[0024] Reference will now be made in detail to embodiments of the present application, one or more examples of which are described below. Each example is provided by way of explanation and not limitation of the present application. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made to the present application without departing from the scope or spirit of the present application. For example, features illustrated or described as part of one embodiment can be used in another embodiment to yield a still further embodiment.

[0025] Accordingly, it is intended that the present application cover such modifications and variations that fall within the scope of the appended claims and their equivalents. Other objects, features, and aspects of the present application are disclosed in the following detailed description or are apparent therefrom. Those of ordinary skill in the art should understand that this discussion is only a description of exemplary embodiments and is not intended to limit the broader aspects of the present application.

[0026] In the present application, among the technical features described in an open-ended manner, there are included closed technical solutions composed of the listed features, as well as open technical solutions including the listed features.

[0027] In the present application, regarding numerical ranges, unless otherwise specified, the above numerical ranges are considered continuous and include the minimum and maximum values of the range, as well as each value between such minimum and maximum values. Further, when the range refers to integers, it includes each integer between the minimum and maximum values of the range. In addition, when multiple ranges are provided to describe features or characteristics, the ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all sub-ranges subsumed therein.

[0028] If there is no special instruction, all embodiments and optional embodiments of the present application can be combined with each other to form new technical solutions.

[0029] If there is no special instruction, all technical features and optional technical features of the present application can be combined with each other to form new technical solutions.

[0030] If there is no special instruction, all steps of the present application can be carried out in sequence or randomly, preferably in sequence. For example, the method includes steps (a) and (b), which means that the method can include steps (a) and (b) carried out in sequence, or can also include steps (b) and (a) carried out in sequence. For example, when it is mentioned that the method may further include step (c), it means that step (c) can be added to the method in any order. For example, the method can include steps (a), (b), and (c), or can also include steps (a), (c), and (b), or can also include steps (c), (a), and (b), etc.

[0031] If there is no special explanation, the "include" and "comprising" mentioned in this application are open-ended or closed-ended. For example, the "include" and "comprising" may mean that other components not listed may also be included or only the listed components may be included or only the listed components may be included.

[0032] If not specifically stated, in this application, the term "or" is inclusive. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, any of the following conditions satisfies the condition "A or B": A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0033] Combination Figure 1 As shown, the first aspect of the present application provides an intermediate connection layer structure 1, which includes a tunneling junction 10 and a self-assembled monolayer 20. The tunneling junction 10 includes a p-type heavily doped silicon layer 11 and a p-type lightly doped silicon layer 12 stacked in sequence, and the surface of the p-type lightly doped silicon layer 12 has hydroxyl groups. The self-assembled monolayer 20 is formed by the reaction of the self-assembled monolayer material with the hydroxyl groups on the surface of the p-type lightly doped silicon layer 12, and the self-assembled monolayer 20 is arranged on the surface of the p-type lightly doped silicon layer 12.

[0034] The intermediate connection layer structure 1 provided in the present application, on the one hand, adopts a composite structure having a tunneling junction 10 and a self-assembled monolayer 20 to replace the traditional TCO layer or PN junction tunneling layer, and utilizes the doping concentration gradient formed by the p-type heavily doped silicon layer and the p-type lightly doped silicon layer to effectively reduce the surface work function, thereby promoting charge transfer while reducing infrared parasitic absorption, thereby improving the optical absorption rate of the bottom battery; on the other hand, the self-assembled monolayer material reacts with the hydroxyl group on the surface of the p-type lightly doped silicon layer 12 in the tunneling junction 10 to form the self-assembled monolayer 20, thereby fixing negative charges on the surface of the p-type lightly doped silicon layer 12, generating a field passivation effect, thereby reducing the surface carrier recombination, reducing the loss of carriers, and thereby improving the device performance of the stacked solar cell; furthermore, the composite structure composed of the tunneling junction 10 and the self-assembled monolayer 20 is not easy to form ohmic contact with the top TCO of the solar cell when the perovskite film has pinholes or is poor, thereby suppressing the leakage phenomenon caused by the loose film.

[0035] In some embodiments, the self-assembled monolayer material is selected from at least one of an oxygen-containing organic acid and an oxygen-containing inorganic acid. For example, the oxygen-containing organic acid may be malic acid, tartaric acid, citric acid or oxalic acid; the oxygen-containing inorganic acid may be phosphoric acid, acetylphosphoric acid, hypophosphorous acid, metaphosphoric acid, phosphorous acid, sulfuric acid, carbonic acid, boric acid, perchloric acid, perbromic acid or periodic acid.

[0036] In some other embodiments, the self-assembled monolayer material has a first end group, which is connected to the hydroxyl groups on the surface of the p-type lightly doped silicon layer 12 through chemical bonding. The first end group includes at least one of trisilanol group, phosphate group, carboxyl group, mercapto group and mercaptoacetyl group. In this way, by utilizing the property that the first end group reacts with the hydroxyl groups on the surface of the p-type lightly doped silicon layer 12, a stable connection between the self-assembled monolayer 20 and the surface of the p-type lightly doped silicon layer 12 is achieved, negative charges are fixed on the surface of the p-type lightly doped silicon layer 12, a field passivation effect is generated, thereby reducing the surface carrier recombination, reducing the loss of carriers, and suppressing the leakage phenomenon caused by the non-dense thin film, and further improving the device performance of the tandem solar cell.

[0037] In some of these embodiments, the first end group of the self-assembled monolayer material is obtained by hydrolysis of a first end group precursor, and the first end group precursor is selected from at least one of 3-methoxysilyl group, 3-ethoxysilyl group, 3-chlorosilyl group and trimethyl phosphate. For example, in actual industrial production applications, since the trisilanol group will undergo self-polymerization, generally 3-methoxysilyl group, 3-ethoxysilyl group or 3-chlorosilyl group is used as the first end group precursor. After these groups are hydrolyzed into trisilanol groups during the process, the trisilanol groups react with the hydroxyl groups on the substrate surface as the first end group. Similarly, trimethyl phosphate can also be used as the first end group precursor to hydrolyze and generate phosphate groups.

[0038] In some of these embodiments, the self-assembled monolayer material further has a second end group, which is located on the side far from the surface of the p-type lightly doped silicon layer 12. The second end group includes at least one of phenyl group, naphthyl group, anthracenyl group, phenanthryl group, pyrenyl group, chrysenyl group and perylenyl group. In this way, the second end group is a polycyclic benzene group, and these groups can induce the formation of π-π stacking effect when common triphenylamine groups or carbazole groups in the subsequent hole transport material are deposited, so that these triphenylamine groups or carbazole groups grow pointing to the bottom interface, thereby promoting the effective transport of holes from the tunneling junction to the hole transport material, and further reducing the interface resistance, thus further improving the device performance of the tandem solar cell.

[0039] In some of these embodiments, the self-assembled monolayer material further has a second end group, which is located on the side far from the surface of the p-type lightly doped silicon layer 12. The second end group includes at least one of trifluoromethyl group, sulfonic acid group, thiourea group, guanidine group, biguanide group, amine group, ether bond, carbonyl group, oxygen atom, sulfur atom, benzylamine group and choline group. In this way, by utilizing the coordination effect of the second end group with the perovskite material, the defects on the perovskite surface are passivated, and the non-radiative recombination is reduced, thereby further improving the device performance of the tandem solar cell.

[0040] In some of these embodiments, the second end group and the first end group can be connected by an alkyl chain of varying lengths (0 - 8 carbons) to form a self-assembled monolayer material in this way.

[0041] It can be understood that if a conventional self-assembled monolayer material is used to prepare a self-assembled single-molecule material layer, since the conventional self-assembled monolayer material generally has a carbazole group or a triphenylamine group, the steric hindrance is relatively large, resulting in that the first end group cannot fully react with the substrate surface to form a complete coverage, and cannot play a comprehensive role in fixing negative charges, and a more comprehensive field passivation effect cannot be formed. In contrast, by using the self-assembled monolayer material provided in the above embodiments of the present application, it reacts with the hydroxyl groups on the surface of the p-type lightly doped silicon layer 12, realizing a stable connection between the self-assembled monolayer 20 and the surface of the p-type lightly doped silicon layer 12, fixing negative charges on the surface of the p-type lightly doped silicon layer 12, generating a field passivation effect, thereby reducing the surface carrier recombination, reducing the carrier loss, and suppressing the leakage phenomenon caused by the non-dense film, and further improving the device performance of the tandem solar cell.

[0042] In some of these embodiments, the doping concentration of the p-type heavily doped silicon layer 11 is greater than or equal to 10 19 cm -3 , and the doping concentration of the p-type lightly doped silicon layer 12 is less than or equal to 10 19 cm -3 . Further, the doping concentration of the p-type heavily doped silicon layer 11 is greater than or equal to 5 * 10 19 cm -3 , and the doping concentration of the p-type lightly doped silicon layer 12 is less than or equal to 10 18 cm -3 .

[0043] In some of these embodiments, the total thickness of the tunneling junction 10 is less than or equal to 200 nm. Within the above thickness range, the thickness of the tunneling junction 10 is relatively thin, which can improve the carrier transport rate and reduce the parasitic absorption, and further improve the device performance of the tandem solar cell.

[0044] In some of these embodiments, in the tunneling junction 10, the p-type heavily doped silicon layer 11 is a microcrystalline silicon layer or an amorphous silicon layer, and the p-type lightly doped silicon layer 12 is a microcrystalline silicon layer or an amorphous silicon layer. In this way, by selecting microcrystalline silicon or amorphous silicon as the materials of the p-type heavily doped silicon layer 11 and the p-type lightly doped silicon layer 12, and utilizing the excellent film-forming properties and adjustable electrical properties of microcrystalline silicon or amorphous silicon, the preparation of a high-quality tunneling junction is realized, thereby improving the charge transport efficiency and device performance of the tandem solar cell.

[0045] Further, in the tunneling junction 10, the p-type heavily doped silicon layer 11 is a hydrogenated microcrystalline silicon layer or a hydrogenated amorphous silicon layer, and the p-type lightly doped silicon layer 12 is a hydrogenated microcrystalline silicon layer or a hydrogenated amorphous silicon layer. In this way, by utilizing the passivation effect of hydrogen atoms on the surface and internal defects of the silicon material, the non-radiative recombination centers in the tunneling junction are significantly reduced, thereby increasing the carrier lifetime and tunneling efficiency, and further improving the device performance of the tandem solar cell.

[0046] The second aspect of the present application provides a method for preparing an intermediate connection layer structure. As Figure 2 shown, the preparation method includes the following steps: S1. Prepare a tunneling junction, which includes a p-type heavily doped silicon layer and a p-type lightly doped silicon layer stacked in sequence. S2. Hydroxylate the surface of the p-type lightly doped silicon layer so that the surface of the p-type lightly doped silicon layer has hydroxyl groups. S3. The self-assembled monolayer material reacts with the hydroxyl groups on the surface of the p-type lightly doped silicon layer to form a self-assembled monolayer on the surface of the p-type lightly doped silicon layer, obtaining the intermediate connection layer structure.

[0047] In some embodiments, step S1 specifically includes the following steps: S11. Prepare the tunneling junction by a deposition process.

[0048] The present application does not limit the deposition process. Exemplarily, the deposition process can be plasma-enhanced chemical vapor deposition (PECVD), hot-wire chemical vapor deposition (HWCVD), or magnetron sputtering.

[0049] In some embodiments, in step S11, the temperature of the deposition process is 150°C to 240°C. Exemplarily, the temperature of the deposition process can be, but is not limited to, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, 220°C, 230°C, 240°C.

[0050] In some embodiments, in step S11, the gas source of the deposition process is a mixed gas of silane, doping source, and carbon dioxide.

[0051] In some specific embodiments, the doping source is borane.

[0052] Further, in step S11, the gas source of the deposition process further includes hydrogen.

[0053] The present application does not limit the hydroxylation treatment method, as long as the surface of the p-type lightly doped silicon layer can have hydroxyl groups. For example, the hydroxylation treatment can be, but is not limited to, plasma treatment, treatment with ozone in air, hydrogen peroxide treatment, or dilute hydrochloric acid treatment.

[0054] In some embodiments, in step S2, the hydroxylation treatment is plasma treatment.

[0055] In some of these embodiments, the gas for plasma treatment is water vapor. Thus, by ionizing water vapor through a high-frequency electric field, hydroxyl radicals (OH·) are generated and then attached, thereby forming a silica layer rich in hydroxyl groups on the surface of the p-type lightly doped silicon layer, providing reliable connection sites for subsequent firm bonding with self-assembled monolayer materials.

[0056] In some of these embodiments, during plasma treatment, the temperature of the p-type lightly doped silicon layer is controlled to be 80°C to 220°C. Exemplarily, during plasma treatment, the temperature of the p-type lightly doped silicon layer can be, but is not limited to, 80°C, 90°C, 100°C, 110°C, 120°C, 130°C, 140°C, 150°C, 160°C, 170°C, 180°C, 190°C, 200°C, 210°C, 220°C. Controlling the temperature of the p-type lightly doped silicon layer (i.e., the substrate for plasma treatment) within the above range can avoid damage to the substrate by the plasma and at the same time accelerate the attachment rate of hydroxyl groups on the substrate surface.

[0057] In some of these embodiments, the gas for plasma treatment is carbon dioxide and hydrogen. Thus, through a high-frequency electric field, reactive oxygen atoms and hydrogen atoms generated by plasma excitation are utilized to form a silica layer rich in hydroxyl groups on the surface of the p-type lightly doped silicon layer, providing reliable connection sites for subsequent firm bonding with self-assembled monolayer materials.

[0058] In some of these embodiments, when the gas for plasma treatment is carbon dioxide and hydrogen, carbon dioxide and hydrogen alternately perform plasma treatment on the surface of the p-type lightly doped silicon layer in sequence.

[0059] In some other embodiments, in step S2, when the gas for plasma treatment is carbon dioxide and hydrogen, carbon dioxide and hydrogen simultaneously perform plasma treatment on the surface of the p-type lightly doped silicon layer.

[0060] In some of these embodiments, step S3 specifically includes the following steps: S31. Deposit self-assembled monolayer materials by chemical vapor deposition.

[0061] In some of these embodiments, in step S31, the deposition temperature of the chemical vapor deposition method is greater than or equal to 80°C.

[0062] In some of these embodiments, step S3 specifically includes the following steps: S32. Form a self-assembled monolayer on the surface of the p-type lightly doped silicon layer by wet method.

[0063] In some of these embodiments, step S32 specifically includes the following steps: S321. Immerse the p-type lightly doped silicon layer in a solution containing a self-assembled monolayer material, such that the self-assembled monolayer material reacts with the hydroxyl groups on the surface of the p-type lightly doped silicon layer to form a self-assembled monolayer.

[0064] In some of these embodiments, in step S321, the temperature of the solution is greater than or equal to 60 °C.

[0065] In some of these embodiments, step S32 specifically includes the following steps: S322. Coat the solution containing the self-assembled monolayer material on the surface of the p-type lightly doped silicon layer, and anneal the p-type lightly doped silicon layer, such that the self-assembled monolayer material reacts with the hydroxyl groups on the surface of the p-type lightly doped silicon layer to form a self-assembled monolayer.

[0066] The third aspect of the present application provides a tandem solar cell, which includes a bottom cell, an intermediate connection layer structure, and a top cell that are sequentially stacked. The bottom cell includes a crystalline silicon cell, and the top cell includes a perovskite cell. The intermediate connection layer structure is the intermediate connection layer structure provided in the first aspect above or the intermediate connection layer structure prepared by the preparation method provided in the second aspect above.

[0067] In some of these embodiments, the self-assembled monolayer is in contact with the perovskite cell, and the tunneling junction is in contact with the crystalline silicon cell.

[0068] In some of these embodiments, the perovskite cell includes a hole transport layer, a perovskite layer, and an electron transport layer that are sequentially stacked in a direction from close to far from the intermediate connection layer structure.

[0069] In some of these embodiments, the hole transport layer is another self-assembled monolayer. The other self-assembled monolayer material in the other self-assembled monolayer is selected from conventional self-assembled monolayer materials that can play a role in hole extraction. However, conventional self-assembled monolayer materials generally have a carbazole group or a triphenylamine group, with a large steric hindrance and a weak energy level modification effect.

[0070] In some of these embodiments, the crystalline silicon cell includes one of a passivated emitter and rear contact cell (PERC cell), a tunnel oxide passivated contact cell (TOPCon cell), a heterojunction with intrinsic thin layer solar cell (HJT cell), and an interdigitated back contact cell (IBC cell).

[0071] In some of these embodiments, the tandem solar cell is used alone or multiple of them are combined to form a photovoltaic module. Exemplarily, in the photovoltaic module, multiple tandem and / or parallel tandem solar cells may be included. Among them, multiple tandem solar cells may be arranged at intervals or stacked in a shingled form.

[0072] In some of these embodiments, the photovoltaic module is used to supply electrical energy to a photovoltaic system. The photovoltaic system can be applied in a photovoltaic power station, such as a ground power station, a rooftop power station, a water surface power station, etc., or can also be applied to equipment or devices that use solar energy for power generation, such as a user solar power supply, a solar street lamp, a solar vehicle, a solar building, and so on. Of course, it can be understood that the application scenarios of the photovoltaic system are not limited to this, that is to say, the photovoltaic system can be applied in all fields that require solar power generation. Taking a photovoltaic power generation system network as an example, the photovoltaic system can include a photovoltaic array, a combiner box, and an inverter. The photovoltaic array can be an array combination of multiple photovoltaic modules. For example, multiple photovoltaic modules can form multiple photovoltaic arrays. The photovoltaic array is connected to the combiner box, and the combiner box can collect the current generated by the photovoltaic array. After the collected current flows through the inverter and is converted into alternating current required by the mains power grid, it is connected to the mains network to achieve solar power supply.

[0073] The present application will be further described below in conjunction with specific embodiments and comparative examples.

[0074] For those not specified in the embodiments, the techniques or conditions described in the literature in this field or according to the product specifications are followed. For reagents or instruments not specified by the manufacturer, they are all conventional products that can be obtained through commercial procurement.

[0075] Example 1

[0076] Intermediate connection layer structure: The intermediate connection layer structure includes a tunneling junction and a self-assembled monolayer.

[0077] S1. Using a crystalline silicon cell as a substrate, a p-type heavily doped amorphous silicon layer and a p-type lightly doped amorphous silicon layer are sequentially deposited by PECVD to prepare a tunneling junction.

[0078] Among them, the deposition temperature is 190 °C; the gas sources of the p-type heavily doped amorphous silicon layer and the p-type lightly doped amorphous silicon layer are a mixed gas of silane, borane, carbon dioxide, and hydrogen; the doping concentration of the p-type heavily doped silicon layer is 5×10 19 cm -3 , and the doping concentration of the p-type lightly doped silicon layer is 5×10 17 cm -3 ; the total thickness of the tunneling junction is 160 nm.

[0079] S2. The substrate material is placed in a CVD chamber, and water vapor is introduced for plasma treatment. The water vapor is ionized by a high-frequency electric field, thereby forming hydroxyl groups on the surface of the p-type lightly doped amorphous silicon layer.

[0080] Among them, the temperature of the p-type lightly doped silicon layer is controlled to be 160 °C.

[0081] S3. Immerse the p-type lightly doped silicon layer in a phosphoric acid solution containing self-assembled monolayer material. Phosphoric acid reacts with the hydroxyl groups on the surface of the p-type lightly doped silicon layer to form a self-assembled monolayer, obtaining an intermediate connection layer structure.

[0082] Tandem solar cell: The tandem solar cell includes a bottom cell, an intermediate connection layer structure, and a top cell stacked in sequence. The bottom cell includes a crystalline silicon cell, and the top cell includes a perovskite cell.

[0083] The structure of the crystalline silicon cell is an n-type heavily doped amorphous silicon layer, an intrinsic amorphous silicon layer, a single-crystalline silicon layer, an intrinsic amorphous silicon layer, a p-type heavily doped hydrogenated amorphous silicon layer, and a TCO layer stacked in sequence in the direction from close to far from the intermediate connection layer structure. Among them, the doping concentrations of the n-type and p-type heavily doped hydrogenated amorphous silicon layers are 5*10 19 cm -3 .

[0084] The structure of the perovskite cell is a hole transport layer ((2-(9H-carbazol-9-yl)ethyl)phosphonic acid), a perovskite layer (Cs 0.2 FA 0.8 PbI 0.8 Br 0.2 ), an electron transport layer (C60), a buffer layer (SnO x ), and a TCO layer (IZO) stacked in sequence in the direction from close to far from the intermediate connection layer structure.

[0085] Example 2

[0086] The preparation method of the intermediate connection layer structure and the tandem solar cell in this example is basically the same as that in Example 1. The difference is that in step S3, the p-type lightly doped silicon layer is immersed in a solution containing the self-assembled monolayer material first end group precursor 3-aminopropyltrimethoxysilane. After hydrolysis, 3-aminopropyltrimethoxysilane generates trisilanol groups, and the trisilanol groups react with the hydroxyl groups on the surface of the p-type lightly doped silicon layer to form a self-assembled monolayer, obtaining an intermediate connection layer structure.

[0087] Among them, the first end group of the self-assembled monolayer material is trisilanol groups, and the second end group is amino groups.

[0088] Example 3

[0089] The preparation method of the intermediate connection layer structure and the tandem solar cell in this example is basically the same as that in Example 1. The difference is that in step S3, the self-assembled monolayer material is acetylphosphoric acid.

[0090] Example 4

[0091] The intermediate connection layer structure and the preparation method of the stacked solar cell in this embodiment are basically the same as those in Embodiment 1, except that: S2. Put the substrate material into the CVD chamber, alternately introduce carbon dioxide and hydrogen for plasma treatment, and ionize water vapor through a high-frequency electric field, so as to form hydroxyl groups on the surface of the p-type lightly doped amorphous silicon layer.

[0092] Among them, the temperature of the p-type lightly doped silicon layer is controlled at 160 °C.

[0093] Embodiment 5

[0094] The intermediate connection layer structure and the preparation method of the stacked solar cell in this embodiment are basically the same as those in Embodiment 1, except that: the structure of the perovskite cell is a structure without a hole transport layer, and the structure of the perovskite cell is a perovskite layer (Cs 0.2 FA 0.8 PbI 0.8 Br 0.2 ), an electron transport layer (C60), a buffer layer (SnO x ), and a TCO layer (IZO) stacked in sequence in the direction from close to far from the intermediate connection layer structure.

[0095] Embodiment 6

[0096] The intermediate connection layer structure and the preparation method of the stacked solar cell in this embodiment are basically the same as those in Embodiment 1, except that: a self-assembled monolayer material is grown on the surface of the p-type lightly doped silicon layer by using the CVD method.

[0097] Comparative Example 1

[0098] Intermediate connection layer structure: Using a crystalline silicon cell as the substrate, a p-type heavily doped amorphous silicon layer and a p-type lightly doped amorphous silicon layer are sequentially deposited by PECVD to prepare a tunneling junction, which is the intermediate connection layer structure.

[0099] Among them, the deposition temperature is 190 °C; the gas sources of the p-type heavily doped amorphous silicon layer and the p-type lightly doped amorphous silicon layer are a mixed gas of silane, borane, carbon dioxide and hydrogen; the doping concentration of the p-type heavily doped silicon layer is 5*10 19 cm -3 ; the doping concentration of the p-type lightly doped silicon layer is 5*10 17 cm -3 ; the total thickness of the tunneling junction is 160 nm.

[0100] Stacked solar cell: The stacked solar cell includes a bottom cell, an intermediate connection layer structure and a top cell stacked in sequence. The bottom cell includes a crystalline silicon cell, and the top cell includes a perovskite cell.

[0101] The structure of the crystalline silicon cell is an n-type heavily doped amorphous silicon layer, an intrinsic amorphous silicon layer, a single crystal silicon layer, an intrinsic amorphous silicon layer, a p-type heavily doped hydrogenated amorphous silicon layer, and a TCO layer stacked in sequence in the direction from close to far away from the intermediate connection layer structure. Among them, the doping concentrations of the n-type and p-type heavily doped hydrogenated amorphous silicon layers are 5*10 19 cm -3 .

[0102] The structure of the perovskite cell is a hole transport layer ((2-(9H-carbazol-9-yl)ethyl)phosphonic acid), a perovskite layer (Cs 0.2 FA 0.8 PbI 0.8 Br 0.2 ), an electron transport layer (C 60 ), a Buffer layer (SnO x ), and a TCO layer (IZO), stacked in sequence in the direction from close to far away from the intermediate connection layer structure.

[0103] Comparative Example 2

[0104] Intermediate connection layer structure: Using the crystalline silicon cell as the substrate, a 10 nm IZO thin film is deposited by PVD method, and the obtained TCO layer is used as the intermediate connection layer structure.

[0105] Stacked solar cell: The stacked solar cell includes a bottom cell, an intermediate connection layer structure, and a top cell stacked in sequence. The bottom cell includes a crystalline silicon cell, and the top cell includes a perovskite cell.

[0106] The structure of the crystalline silicon cell is an n-type heavily doped amorphous silicon layer, an intrinsic amorphous silicon layer, a single crystal silicon layer, an intrinsic amorphous silicon layer, a p-type heavily doped hydrogenated amorphous silicon layer, and a TCO layer stacked in sequence in the direction from close to far away from the intermediate connection layer structure. Among them, the doping concentrations of the n-type and p-type heavily doped hydrogenated amorphous silicon layers are 5*10 19 cm -3 .

[0107] The structure of the perovskite cell is a hole transport layer ((2-(9H-carbazol-9-yl)ethyl)phosphonic acid), a perovskite layer (Cs 0.2 FA 0.8 PbI 0.8 Br 0.2 ), an electron transport layer (C 60 ), a Buffer layer (SnO x ), and a TCO layer (IZO), stacked in sequence in the direction from close to far away from the intermediate connection layer structure.

[0108] Performance test

[0109] The solar cells prepared in the above embodiments and comparative examples were placed in a solar simulator (manufacturer: Wavelabs). Under the irradiation of one sun intensity, a bias voltage (Vp, the bias voltage range was -0.1 to 2 V) was applied to the device using a test source meter, and the output current of the device was measured to obtain the bias voltage-current density curve.

[0110] Open-circuit voltage (Voc): The terminal voltage when the cell is not connected to a load, that is, the bias voltage value when the current density in the bias voltage-current density curve is 0 mA·cm -2 at this time.

[0111] Short-circuit current density (Jsc): The output current when the cell is short-circuited per unit area, that is, the current density when the bias voltage is 0 V in the bias voltage-current density curve.

[0112] Fill factor (FF): FF = max(Vp×Jsc), where Vp is the bias voltage and Jsc is the short-circuit current density.

[0113] Shunt resistance (Rsh): The estimated value is determined according to the slope of the IV curve near the short-circuit current point.

[0114] Photovoltaic cell efficiency (PCE): PCE = Voc×Jsc×FF.

[0115] The test results of the above performances are shown in Table 1.

[0116] Table 1

[0117] Group Voc (V) <![CDATA[Jsc (mA·cm -2 )]]> FF (%) <![CDATA[Rsh (ohm·cm 2 )]]> PCE (%) Example 1 1.97 20.4 0.82 9.80E+03 33.0 Example 2 1.96 20.5 0.784 1.12E+04 31.5 Example 3 1.97 20.5 0.79 1.34E+04 31.9 Example 4 1.95 20.5 0.78 9.96E+03 31.2 Example 5 1.95 20.6 0.76 8.63E+04 30.5 Example 6 1.98 20.5 0.78 9.74E+04 31.7 Comparative Example 1 1.88 20.3 0.75 1.27E+04 28.6 Comparative Example 2 1.95 20.5 0.82 4.23E+03 32.8

[0118] As shown in Table 1, by comparing Examples 1 to 6 and Comparative Examples 1 to 2, it can be seen that the intermediate connection layer structure provided in the present application can ensure the charge transfer rate while improving the optical absorption rate of the bottom cell and reducing the carrier loss. From the significant increase in the shunt resistance, it can be found that the novel tunneling layer structure can suppress the leakage phenomenon caused by the non-dense perovskite film, thereby improving the photoelectric conversion efficiency of the tandem solar cell.

[0119] The technical features of the above embodiments can be combined arbitrarily. For the sake of brevity of description, 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, it should be considered as the scope recorded in this specification.

[0120] The above-described embodiments merely represent several implementation manners of the present application. The description thereof is relatively specific and detailed, but it should not be construed as a limitation to the patent scope of the present application. It should be noted that for those of ordinary skill in the art, without departing from the technical concept of the present application, several modifications and improvements can still be made, and these all fall within the protection scope of the present application. Therefore, the protection scope of the present application shall be subject to the appended claims.

Claims

1. An intermediate connection layer structure, characterized in that, Comprising: A tunneling junction, including a p-type heavily doped silicon layer and a p-type lightly doped silicon layer stacked in sequence, and the surface of the p-type lightly doped silicon layer has hydroxyl groups; And A self-assembled monolayer, formed by the reaction of a self-assembled monolayer material with the hydroxyl groups on the surface of the p-type lightly doped silicon layer, and the self-assembled monolayer is disposed on the surface of the p-type lightly doped silicon layer.

2. The intermediate connection layer structure according to claim 1, characterized in that, The self-assembled monolayer material is selected from at least one of oxygen-containing organic acids and oxygen-containing inorganic acids.

3. The intermediate connection layer structure according to claim 1, wherein The self-assembled monolayer material has a first end group, and the first end group reacts with the hydroxyl groups on the surface of the p-type lightly doped silicon layer to form the self-assembled monolayer. The first end group includes at least one of trisilanol groups, phosphate groups, acetate groups, borate groups, sulfonate groups, carboxyl groups, catechol, phenol, mercapto groups, and mercaptoacetyl groups.

4. The intermediate connection layer structure according to claim 3, wherein The first end group is obtained by hydrolysis of a first end group precursor, and the first end group precursor is selected from at least one of 3-methoxysilyl, 3-ethoxysilyl, 3-chlorosilyl, and trimethyl phosphate.

5. The intermediate connection layer structure according to claim 3, characterized in that, The self-assembled monolayer material further has a second end group, and the second end group is located on the side away from the surface of the p-type lightly doped silicon layer. The second end group satisfies at least one of the following conditions: (1) The second end group includes at least one of phenyl, naphthyl, anthracenyl, phenanthryl, pyrenyl, chrysenyl, and perylenyl; (2) The second end group includes at least one of trifluoromethyl, sulfonate group, thiourea group, guanidine group, biguanide group, amino group, ether bond, carbonyl group, methoxy group, mercapto group, hydroxyl group, benzylamine group, and choline group.

6. The intermediate connection layer structure according to any one of claims 1 to 4, characterized in that, The doping concentration of the p-type heavily doped silicon layer is greater than or equal to 10 19 cm -3 , and the doping concentration of the p-type lightly doped silicon layer is less than or equal to 10 19 cm -3 .

7. The intermediate connection layer structure according to any one of claims 1 to 4, characterized in that, The tunneling junction satisfies at least one of the following conditions: (1) The total thickness of the tunneling junction is less than or equal to 200 nm; (2) In the tunneling junction, the p-type heavily doped silicon layer is a microcrystalline silicon layer or an amorphous silicon layer, and the p-type lightly doped silicon layer is a microcrystalline silicon layer or an amorphous silicon layer.

8. A method for preparing an intermediate connection layer structure, characterized in that, Including the following steps: S1. Prepare a tunneling junction, and the tunneling junction includes a p-type heavily doped silicon layer and a p-type lightly doped silicon layer stacked in sequence; S2. Perform hydroxylation treatment on the surface of the p-type lightly doped silicon layer so that the surface of the p-type lightly doped silicon layer has hydroxyl groups; S3. The self-assembled monolayer material reacts with the hydroxyl groups on the surface of the p-type lightly doped silicon layer to form a self-assembled monolayer on the surface of the p-type lightly doped silicon layer, and an intermediate connection layer structure is obtained.

9. A laminated solar cell, characterized in that, Including a bottom cell, an intermediate connection layer structure, and a top cell stacked in sequence; The bottom cell includes a crystalline silicon cell, and the top cell includes a perovskite cell; The intermediate connection layer structure is the intermediate connection layer structure according to any one of claims 1 to 7 or the intermediate connection layer structure prepared by the preparation method of claim 8.

10. The stacked solar cell according to claim 9, characterized in that, The self-assembled monolayer is in contact with the perovskite cell, and the tunneling junction is in contact with the crystalline silicon cell.

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