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

Abstract

The present application relates to the technical field of photovoltaic cells, and in particular to an intermediate connection layer structure and a preparation method thereof, and a stacked solar cell. The intermediate connection layer structure includes: a tunnel junction, including a p-type heavily doped silicon layer and a p-type lightly doped silicon layer stacked in sequence, the surface of the p-type lightly doped silicon layer having hydroxyl groups; and a self-assembled monolayer, 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, the self-assembled monolayer being arranged on the surface of the p-type lightly doped silicon layer. The intermediate connection layer structure provided by the present application, wherein the self-assembled monolayer material reacts with the hydroxyl groups on the surface of the p-type lightly doped silicon layer in the tunnel junction to form a self-assembled monolayer, thereby fixing negative charges on the surface of the p-type lightly doped silicon layer, generating a field passivation effect, thereby reducing surface carrier recombination, reducing carrier loss, and suppressing leakage caused by the non-density of the film, thereby improving the device performance of the stacked solar cell.

Description

Technical Field

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

[0002] As a clean energy source that is abundant and requires no transportation, solar energy holds promise as a viable alternative to traditional fossil fuels. The development of solar energy collection and conversion technologies has become a research focus. Photovoltaic devices, which directly convert solar energy into electricity, are one of the most efficient ways to utilize solar energy.

[0003] With the continuous advancement of photovoltaic technology, the efficiency of single-crystal silicon cells is approaching its theoretical upper limit. To further improve the energy conversion efficiency of photovoltaic cells and overcome the thermal relaxation losses of single-junction cells, the concept of multi-junction cells has been proposed. Currently, stacking wide-bandgap perovskite cells on crystalline silicon cells can achieve an energy conversion efficiency of 33.9%, far exceeding the current single-crystal silicon cell (26.81%) and demonstrating the outstanding performance advantages of stacked cells.

[0004] The intermediate connecting 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 stacked cell structure, which plays a vital role in achieving high-efficiency stacked photovoltaic cells.

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

[0006] However, using a TCO layer as the intermediate interconnect layer, because perovskites are typically prepared using a multi-step wet process, can't guarantee film density, often resulting in numerous voids. Furthermore, the TCO layer exhibits parasitic infrared absorption, which impacts the optical absorption of the underlying crystalline silicon cell. Using a traditional PN junction tunneling layer as the intermediate interconnect layer solves the tunneling efficiency issue, but these layers are typically formed from highly doped materials. This can easily lead to poor ohmic contact between the interface material in the tandem cell and the tunneling layer through the porous perovskite layer, similarly reducing the efficiency of the tandem cell. Summary of the Invention

[0007] Based on this, it is necessary to provide an intermediate connection layer structure and its preparation method, and a stacked solar cell, which can ensure the charge transfer rate while improving the optical absorption rate of the bottom cell, reducing the loss of carriers, and suppressing the leakage phenomenon caused by the non-density of the film, thereby improving the device performance of the stacked solar cell.

[0008] The first aspect of the present application provides an intermediate connecting layer structure, which includes: a tunnel junction, including a p-type heavily doped silicon layer and a p-type lightly doped silicon layer stacked in sequence, the surface of the p-type lightly doped silicon layer having hydroxyl groups; and a self-assembled monolayer, 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, and the self-assembled monolayer is arranged 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 an oxygen-containing organic acid and an oxygen-containing inorganic acid.

[0010] In some embodiments, the self-assembled monolayer material has a first end group, which reacts with a hydroxyl group on the surface of the p-type lightly doped silicon layer to form a self-assembled monolayer, and the first end group includes at least one of a trisilanol group, a phosphate group, an acetate group, a borate group, a sulfonic acid group, a carboxylic acid group, catechol, phenol, a thiol group, and a thioacetyl group.

[0011] In some embodiments, the first end group is obtained by hydrolyzing 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, which is located on a side away from the surface of the p-type lightly doped silicon layer, and the second end group includes at least one of a phenyl group, a naphthyl group, an anthracenyl group, a phenanthrenyl group, a pyrene group, a chrysene group, and a perylene group.

[0013] In some embodiments, the self-assembled monolayer material further has a second end group, which is located on a side away from the surface of the p-type lightly doped silicon layer, and the second end group includes at least one of a trifluoromethyl group, a sulfonic acid group, a thiourea group, a guanidine group, a biguanidine group, an amino group, an ether bond, a carbonyl group, a methoxy group, a mercapto group, a benzylamine group, and a 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 , 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 tunnel junction, the heavily p-type doped silicon layer is a microcrystalline silicon layer or an amorphous silicon layer, and the lightly p-type 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 connecting layer structure, which includes the following steps: S1, preparing a tunnel junction, the tunnel junction including a p-type heavily doped silicon layer and a p-type lightly doped silicon layer stacked in sequence; S2, hydroxylating 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 to obtain an intermediate connecting layer structure.

[0018] The third aspect of the present application provides a stacked 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 in the first aspect above or the intermediate connection layer structure prepared by the preparation method provided in 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 conventional technologies, the present application has at least the following beneficial effects: the intermediate connection layer structure provided by the present application, on the one hand, adopts a composite structure having a tunneling junction and a self-assembled monolayer to replace the conventional 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 absorptivity of the bottom cell; on the other hand, the self-assembled monolayer 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 in the tunneling junction, thereby fixing negative charges on the surface of the p-type lightly doped silicon layer, generating a field passivation effect, thereby reducing surface carrier recombination and reducing carrier loss, thereby improving the device performance of the stacked solar cell; furthermore, the composite structure composed of the tunneling junction and the self-assembled monolayer 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 leakage caused by the non-density of the film. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 Schematic diagram of the structure of the intermediate connecting layer in one embodiment of the present application.

[0022] Figure 2 Schematic diagram of the process for preparing the intermediate connecting layer structure in one embodiment of the present application.

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

[0024] References to embodiments of the present application will now be provided in detail, one or more examples of which are described below. Each example is provided to illustrate, not to limit, the present application. Indeed, it will be apparent to those skilled in the art that various modifications and variations may 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 may be used in another embodiment to produce further embodiments.

[0025] Therefore, it is intended that this application covers 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 or are apparent from the following detailed description. Those skilled in the art will appreciate that this discussion is merely a description of exemplary embodiments and is not intended to limit the broader aspects of the present application.

[0026] In this application, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0027] In this application, when referring to numerical ranges, unless otherwise specified, the numerical ranges are considered continuous and include the minimum and maximum values of the range, as well as every value between such minimum and maximum values. Further, when a range refers to an integer, every integer between the minimum and maximum values of the range is included. In addition, when multiple ranges are provided to describe a feature or characteristic, the ranges can be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges subsumed therein.

[0028] Unless otherwise specified, all embodiments and optional embodiments of the present application can be combined with each other to form a new technical solution.

[0029] Unless otherwise specified, all technical features and optional technical features of this application can be combined with each other to form a new technical solution.

[0030] Unless otherwise specified, all steps of the present application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), which means that the method may include steps (a) and (b) performed sequentially, or may include steps (b) and (a) performed sequentially. For example, it is mentioned that the method may also include step (c), which means that step (c) may be added to the method in any order, for example, the method may include steps (a), (b) and (c), or may include steps (a), (c) and (b), or may include steps (c), (a) and (b), etc.

[0031] Unless otherwise specified, the terms "include" and "comprising" used in this application may be open-ended or closed-ended. For example, "include" and "comprising" may mean that other components not listed may also be included or that only the listed components are included.

[0032] Unless otherwise specified, the term "or" is used in this application to be inclusive. For example, the phrase "A or B" means "A, B, or both A and B." More specifically, the condition "A or B" is satisfied if any of the following conditions are met: 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] Combine Figure 1 As shown, the first aspect of the present application provides an intermediate connecting 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, which are stacked in sequence. 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. The self-assembled monolayer 20 is disposed 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 absorptivity of the bottom cell; on the other hand, the self-assembled monolayer material reacts with the hydroxyl groups 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 surface carrier recombination and reducing carrier loss, 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; and 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 other embodiments, the self-assembled monolayer material has a first end group that is chemically bonded to a hydroxyl group on the surface of the p-type lightly doped silicon layer 12. The first end group includes at least one of a trisilanol group, a phosphate group, a carboxyl group, a thiol group, and a thioacetyl group. Thus, by utilizing the property of the first end group reacting with the hydroxyl group 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, and negative charges are fixed on the surface of the p-type lightly doped silicon layer 12, resulting in a field passivation effect. This reduces surface carrier recombination, reduces carrier loss, and suppresses leakage caused by film imperfections, thereby improving the device performance of the stacked solar cell.

[0037] In some 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, 3-ethoxysilyl, 3-chlorosilyl and trimethyl phosphate. For example, in actual industrial production applications, since trisilanol groups can self-polymerize, 3-methoxysilyl, 3-ethoxysilyl or 3-chlorosilyl groups are generally used as first end group precursors. After these groups are hydrolyzed into trisilanol groups during the process, the trisilanol groups are used as first end groups to react with hydroxyl groups on the substrate surface. Similarly, trimethyl phosphate can also be used as a first end group precursor, which is hydrolyzed to generate a phosphate group.

[0038] In some embodiments, the self-assembled monolayer material further comprises a second end group, which is located on a side away from the surface of the p-type lightly doped silicon layer 12. The second end group comprises at least one of a phenyl group, a naphthyl group, an anthracenyl group, a phenanthrenyl group, a pyrene group, a chrysene group, and a perylene group. Thus, the second end group is a polyphenyl ring group, which can induce a π-π stacking effect during the subsequent deposition of triphenylamine groups or carbazole groups commonly found in hole transport materials. This causes these triphenylamine groups or carbazole groups to grow toward the bottom interface, thereby promoting efficient hole transport from the tunneling junction to the hole transport material, thereby reducing the interfacial resistance and further improving the device performance of the stacked solar cell.

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

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

[0041] It is understandable that if a conventional self-assembled monolayer material is used to prepare a self-assembled monolayer material layer, since conventional self-assembled monolayer materials generally have carbazole groups or triphenylamine groups, the steric hindrance is large, resulting in the first end group being unable to fully react with the substrate surface to form complete coverage, unable to fully fix the negative charge, and unable to form a more comprehensive field passivation effect. In contrast, the self-assembled monolayer material provided in the above-mentioned embodiment of the present application is used to react with the hydroxyl groups on the surface of the p-type lightly doped silicon layer 12, thereby achieving 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 surface carrier recombination, reducing carrier loss, and suppressing leakage caused by the non-density of the film, thereby improving the device performance of the stacked solar cell.

[0042] In some embodiments, the doping concentration of the p-type heavily doped silicon layer 11 is greater than or equal to 10 19 cm -3 , the doping concentration of the p-type lightly doped silicon layer 12 is less than or equal to 10 19 cm -3 Furthermore, the doping concentration of the p-type heavily doped silicon layer 11 is greater than or equal to 5*10 19 cm -3 , 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 embodiments, the total thickness of the tunnel junction 10 is less than or equal to 200 nm. Within the above thickness range, the thin thickness of the tunnel junction 10 can increase the carrier transmission rate and reduce parasitic absorption, thereby further improving the device performance of the tandem solar cell.

[0044] In some embodiments, in the tunnel junction 10, the heavily p-type doped silicon layer 11 is a microcrystalline silicon layer or an amorphous silicon layer, and the lightly p-type doped silicon layer 12 is a microcrystalline silicon layer or an amorphous silicon layer. Thus, by selecting microcrystalline silicon or amorphous silicon as the material for the heavily p-type doped silicon layer 11 and the lightly p-type doped silicon layer 12, and utilizing the excellent film-forming properties and tunable electrical properties of microcrystalline silicon or amorphous silicon, a high-quality tunnel junction is fabricated, thereby improving the charge transfer efficiency and device performance of the tandem solar cell.

[0045] Furthermore, in tunnel junction 10, p-type heavily doped silicon layer 11 is a hydrogenated microcrystalline silicon layer or a hydrogenated amorphous silicon layer, and p-type lightly doped silicon layer 12 is a hydrogenated microcrystalline silicon layer or a hydrogenated amorphous silicon layer. This significantly reduces non-radiative recombination centers in the tunnel junction by utilizing the passivation effect of hydrogen atoms on surface and internal defects in the silicon material, thereby increasing 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 connecting layer structure, such as Figure 2 As shown, the preparation method includes the following steps: S1. Preparing a tunnel junction, the tunnel junction comprising a p-type heavily doped silicon layer and a p-type lightly doped silicon layer stacked in sequence. S2. Hydroxylating the surface of the p-type lightly doped silicon layer to impart hydroxyl groups to the surface of the p-type lightly doped silicon layer. 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 connecting layer structure.

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

[0048] The present application does not limit the deposition process. For example, the deposition process may be plasma enhanced chemical vapor deposition (PECVD), hot filament 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. For example, the temperature of the deposition process may be, but is not limited to, 150° C., 160° C., 170° C., 180° C., 190° C., 200° C., 210° C., 220° C., 230° C., or 240° C.

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

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

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

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

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

[0055] In some embodiments, the plasma treatment gas is water vapor. The high-frequency electric field ionizes the water vapor, generating hydroxyl radicals (OH·) that then attach to the surface of the p-type lightly doped silicon layer, forming a hydroxyl-rich silicon oxide layer. This provides reliable connection sites for subsequent strong bonding with the self-assembled monolayer material.

[0056] In some embodiments, during plasma treatment, the temperature of the p-type lightly doped silicon layer is controlled to be between 80°C and 220°C. For example, during plasma treatment, the temperature of the p-type lightly doped silicon layer may 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, or 220°C. Controlling the temperature of the p-type lightly doped silicon layer (i.e., the plasma-treated substrate) within the above range can prevent plasma damage to the substrate and accelerate the attachment rate of hydroxyl groups to the substrate surface.

[0057] In some embodiments, the plasma treatment gases are carbon dioxide and hydrogen. Thus, through the high-frequency electric field, plasma excitation generates active oxygen and hydrogen atoms, forming a hydroxyl-rich silicon oxide layer on the surface of the p-type lightly doped silicon layer, providing reliable connection sites for subsequent strong bonding with the self-assembled monolayer material.

[0058] In some embodiments, when the plasma treatment gases are carbon dioxide and hydrogen, the carbon dioxide and hydrogen are alternately used in sequence to perform plasma treatment on the surface of the p-type lightly doped silicon layer.

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

[0060] In some embodiments, step S3 specifically includes the following steps: S31, depositing a self-assembled monolayer material using chemical vapor deposition.

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

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

[0063] In some embodiments, step S32 specifically includes the following steps: S321, immersing the p-type lightly doped silicon layer in a solution containing a self-assembled monolayer material, so 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 embodiments, in step S321, the temperature of the solution is greater than or equal to 60°C.

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

[0066] A third aspect of the present application provides a tandem solar cell comprising a bottom cell, an intermediate connection layer structure, and a top cell stacked in sequence. The bottom cell comprises a crystalline silicon cell, and the top cell comprises 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 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 embodiments, the perovskite cell includes a hole transport layer, a perovskite layer, and an electron transport layer stacked in sequence in a direction from close to far away from the intermediate connecting layer structure.

[0069] In some embodiments, the hole transport layer is another self-assembled monolayer. The other self-assembled monolayer materials are conventional self-assembled monolayer materials that can perform hole extraction. However, conventional self-assembled monolayer materials generally have carbazole groups or triphenylamine groups, which have large steric hindrance and weak energy level modification effects.

[0070] In some embodiments, the crystalline silicon cell includes one of a passivated emitter and back contact cell (PERC cell), a tunneling oxide passivated contact cell (TOPCon cell), a crystalline silicon heterojunction solar cell (HJT cell), and an interlayer back contact cell (IBC cell).

[0071] In some embodiments, a photovoltaic module may be composed of a single or multiple tandem solar cells. For example, a photovoltaic module may include multiple tandem solar cells connected in series and / or in parallel. The multiple tandem solar cells may be arranged in an intermittent pattern or stacked in a shingled format.

[0072] In some embodiments, photovoltaic modules are used to provide electrical energy for photovoltaic systems. Photovoltaic systems can be used in photovoltaic power stations, such as ground power stations, rooftop power stations, water surface power stations, etc., and can also be used in equipment or devices that use solar energy to generate electricity, such as user solar power supplies, solar street lights, solar cars, solar buildings, etc. Of course, it is understandable that the application scenarios of photovoltaic systems are not limited to this, that is, photovoltaic systems can be used in all fields that require solar energy to generate electricity. Taking the photovoltaic power generation system network as an example, the photovoltaic system may include a photovoltaic array, a junction 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 junction box. The junction box can converge the current generated by the photovoltaic array. The converged current flows through the inverter to be converted into the alternating current required by the mains power grid and then connected to the mains power network to achieve solar power supply.

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

[0074] If no specific techniques or conditions are specified in the examples, the experiments were carried out according to the techniques or conditions described in the literature in the field or according to the product instructions. All reagents or instruments used without specifying the manufacturer are commercially available conventional products.

[0075] Example 1

[0076] Intermediate connecting layer structure: The intermediate connecting 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 using the PECVD method to prepare a tunnel junction.

[0078] The deposition temperature is 190°C; the gas source for the p-type heavily doped amorphous silicon layer and the p-type lightly doped amorphous silicon layer is a mixture 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 tunnel junction is 160 nm.

[0079] S2. Place the substrate material in a CVD chamber, introduce water vapor into the chamber for plasma treatment, and ionize the water vapor through a high-frequency electric field to form hydroxyl groups on the surface of the p-type lightly doped amorphous silicon layer.

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

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

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

[0083] The structure of the crystalline silicon solar 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 from close to far away from the intermediate connection layer structure. Among them, the doping concentration of the n-type and p-type heavily doped hydrogenated amorphous silicon layers is 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 )、electron transport layer(C60)、buffer layer(SnO x ) and TCO layer (IZO).

[0085] Example 2

[0086] The intermediate connecting layer structure and the preparation method of the stacked solar cell in this embodiment are basically the same as those in Example 1, except that: in step S3, the p-type lightly doped silicon layer is immersed in a solution containing 3-aminopropyltrimethoxysilane, the first end group precursor of the self-assembled monolayer material, and 3-aminopropyltrimethoxysilane is hydrolyzed to form trisilanol groups. 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 to obtain the intermediate connecting layer structure.

[0087] The first end group of the self-assembled monolayer material is a trisilanol group, and the second end group is an amino group.

[0088] Example 3

[0089] The preparation method of the intermediate connection layer structure and the stacked solar cell in this embodiment is basically the same as that in Example 1, except that: in step S3, the self-assembled monolayer material is acetyl phosphate.

[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 Example 1, except that: S2, the substrate material is placed in a CVD chamber, and carbon dioxide and hydrogen are alternately introduced into the chamber for plasma treatment, and 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.

[0092] The temperature of the p-type lightly doped silicon layer is controlled to be 160°C.

[0093] Example 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 Example 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 structure in which the perovskite layers (Cs) are stacked in sequence in the direction from close to far away from the intermediate connection layer structure. 0.2 FA 0.8 PbI 0.8 Br 0.2 )、electron transport layer(C60)、buffer layer(SnO x ) and TCO layer (IZO).

[0095] Example 6

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

[0097] Comparative Example 1

[0098] Intermediate connection layer structure: Using crystalline silicon cells as the substrate, the PECVD method is used to deposit a p-type heavily doped amorphous silicon layer and a p-type lightly doped amorphous silicon layer in sequence to prepare a tunnel junction, which is the intermediate connection layer structure.

[0099] The deposition temperature is 190°C; the gas source for the p-type heavily doped amorphous silicon layer and the p-type lightly doped amorphous silicon layer is a mixture 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 tunnel junction is 160 nm.

[0100] Tandem solar cell: A tandem solar cell comprises a bottom cell, an intermediate connection layer structure and a top cell stacked in sequence, wherein the bottom cell comprises a crystalline silicon cell and the top cell comprises a perovskite cell.

[0101] The structure of the crystalline silicon solar 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 from close to far away from the intermediate connection layer structure. Among them, the doping concentration of the n-type and p-type heavily doped hydrogenated amorphous silicon layers is 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 )、Electron Transport Layer(C 60 ), Buffer layer (SnO x ) and TCO layer (IZO).

[0103] Comparative Example 2

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

[0105] Tandem solar cell: A tandem solar cell comprises a bottom cell, an intermediate connection layer structure and a top cell stacked in sequence, wherein the bottom cell comprises a crystalline silicon cell and the top cell comprises a perovskite cell.

[0106] The structure of the crystalline silicon solar 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 from close to far away from the intermediate connection layer structure. Among them, the doping concentration of the n-type and p-type heavily doped hydrogenated amorphous silicon layers is 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 )、Electron Transport Layer(C 60 ), Buffer layer (SnO x ) and TCO layer (IZO).

[0108] Performance Testing

[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 sunlight intensity, a bias voltage (Vp, bias voltage range is -0.1~2V) was applied to the device using a test source meter and the device output current was measured to obtain a bias voltage-current density curve.

[0110] Open circuit voltage (Voc): The terminal voltage of the cell when there is no load, that is, the current density in the bias-current density curve is 0 mA cm -2 The bias value at .

[0111] Short-circuit current density (Jsc): The output current per unit area of the battery cell when it is short-circuited, that is, the current density when the bias voltage is 0V in the bias-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 based on 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 performance 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, a comparison of Examples 1-6 and Comparative Examples 1-2 demonstrates that the intermediate connection layer structure provided by this application ensures a high charge transfer rate while improving the optical absorption rate of the bottom cell and reducing carrier loss. The significant improvement in shunt resistance indicates that the novel tunneling layer structure can suppress leakage caused by the looseness of the perovskite film, thereby improving the photoelectric conversion efficiency of the tandem solar cell.

[0119] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0120] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the present application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the technical concept of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present application shall be determined by the appended claims.

Claims

1. An intermediate connection layer structure, characterized in that: include: A tunnel junction comprising a p-type heavily doped silicon layer and a p-type lightly doped silicon layer stacked in sequence, wherein the surface of the p-type lightly doped silicon layer has hydroxyl groups; as well as A self-assembled monolayer is formed by reacting a self-assembled monolayer material with a hydroxyl group 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; The self-assembled monolayer material is selected from at least one of oxygen-containing organic acids and oxygen-containing inorganic acids; Alternatively, the self-assembled monolayer material has a first end group, which reacts with the hydroxyl group on the surface of the p-type lightly doped silicon layer to form the self-assembled monolayer, and the first end group includes at least one of a trisilanol group, a phosphate group, an acetate group, a borate group, a sulfonic acid group, a carboxylic acid group, catechol, phenol, a thiol group and a thioacetyl group.

2. The intermediate connection layer structure according to claim 1, characterized in that: The first end group is obtained by hydrolyzing a first end group precursor, and the first end group precursor is at least one selected from 3-methoxysilyl, 3-ethoxysilyl, 3-chlorosilyl and trimethyl phosphate.

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

4. The intermediate connection layer structure according to any one of claims 1 to 3, characterized in that: The doping concentration of the p-type heavily doped silicon layer is greater than or equal to 5*10 19 cm -3 The doping concentration of the p-type lightly doped silicon layer is less than or equal to 10 18 cm -3 .

5. The intermediate connection layer structure according to any one of claims 1 to 3, characterized in that: The tunnel junction satisfies at least one of the following conditions: (1) The total thickness of the tunnel junction is less than or equal to 200 nm; (2) In the tunnel 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.

6. A method for preparing an intermediate connecting layer structure, characterized in that: The following steps are involved: S1. preparing a tunnel junction, wherein the tunnel junction comprises a p-type heavily doped silicon layer and a p-type lightly doped silicon layer stacked in sequence; S2. performing a 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 to obtain an intermediate connecting layer structure; The self-assembled monolayer material is selected from at least one of oxygen-containing organic acids and oxygen-containing inorganic acids; Alternatively, the self-assembled monolayer material has a first end group, which reacts with the hydroxyl group on the surface of the p-type lightly doped silicon layer to form the self-assembled monolayer, and the first end group includes at least one of a trisilanol group, a phosphate group, an acetate group, a borate group, a sulfonic acid group, a carboxylic acid group, catechol, phenol, a thiol group and a thioacetyl group.

7. A stacked solar cell, characterized in that: It includes a bottom battery, an intermediate connection layer structure and a top battery stacked in sequence; The bottom cell comprises a crystalline silicon cell, and the top cell comprises a perovskite cell; The intermediate connecting layer structure is the intermediate connecting layer structure according to any one of claims 1 to 5 or the intermediate connecting layer structure prepared by the preparation method according to claim 6.

8. The tandem solar cell according to claim 7, characterized in that: The self-assembled monolayer is in contact with the perovskite cell, and the tunnel junction is in contact with the crystalline silicon cell.

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