Middle tunneling layer structure of laminated photovoltaic cell and preparation method and application of middle tunneling layer structure

Abstract

The embodiment of the invention provides an intermediate tunneling layer structure of a laminated photovoltaic cell and a preparation method and application of the intermediate tunneling layer structure. The middle tunneling layer structure of the laminated photovoltaic cell comprises a heavily-doped PN structure serving as a tunneling junction. The heavily-doped PN structure comprises a first N-type heavily-doped layer, a second N-type heavily-doped layer, a second P-type heavily-doped layer and a first P-type heavily-doped layer which are stacked; the doping concentration of the first N-type heavily doped layer is lower than that of the second N-type heavily doped layer. According to the technical scheme of the embodiment of the invention, the doping concentration of the first N-type heavily doped layer is designed to be lower than that of the second N-type heavily doped layer, and the second N-type heavily doped layer has higher carrier concentration and lower resistance, so that the resistance of the whole tunneling layer is further reduced, and the conductivity of the tunneling layer is improved; moreover, the higher carrier concentration can also improve the transmission rate of electrons, accelerate the transmission speed of carriers in the tunneling layer, and reduce the current loss, thereby improving the response speed and performance of the device.

Description

Technical Field

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

[0002] Among photovoltaic cells, the main commercialized solar cells are silicon solar cells, which currently occupy the mainstream position in the market share. However, the conversion efficiency of single-junction solar cells is limited by the Shockley~Queisser (S~Q) efficiency limit. In order to further reduce the cost of photovoltaic systems, it is currently urgent to further develop low-cost and high-efficiency solar cells.

[0003] Tandem solar cells provide a good technical path to further improve the efficiency of single-junction silicon solar energy. Photovoltaic tandem cells combine cells with different bandgap widths to broaden the solar spectrum absorption range, and use the solar spectrum in segments through different sub-cells to improve the utilization rate of solar energy and achieve an increase in the conversion efficiency of photovoltaic cells.

[0004] In the perovskite / crystalline silicon tandem cell technology, the top perovskite solar cell is integrated with the bottom crystalline silicon cell through a tunneling layer structure. The intermediate tunneling layer acts as a connecting layer, and plays a dual optical and electrical coupling role in the tandem cell structure, which plays a vital role in achieving high-efficiency tandem photovoltaic cells. At present, metal oxide materials such as IZO are generally used as tunneling layers. Metal oxide materials have good light transmittance in the visible light range, but may have poor light transmittance in the infrared region. Due to the lack of optical and electrical optimization, the light absorption of metal oxides such as IZO in the IR region increases, which in turn affects the photoelectric conversion efficiency of the bottom crystalline silicon cell. Therefore, it is urgent to develop a tunneling layer suitable for perovskite / crystalline silicon tandem cell devices with broad application prospects.

[0005] It should be noted that the above content is not necessarily prior art, nor is it intended to limit the scope of patent protection of this application. Summary of the invention

[0006] The embodiments of the present application provide a stacked photovoltaic cell intermediate tunneling layer structure and a preparation method and application thereof to solve or alleviate one or more of the technical problems raised above.

[0007] In a first aspect, an embodiment of the present application provides a stacked photovoltaic cell intermediate tunneling layer structure, wherein the stacked photovoltaic cell intermediate tunneling layer structure includes a heavily doped PN structure as a tunneling junction; the heavily doped PN structure includes a first N-type heavily doped layer, a second N-type heavily doped layer, a second P-type heavily doped layer, and a first P-type heavily doped layer that are stacked; The doping concentration of the first N-type heavily doped layer is lower than the doping concentration of the second N-type heavily doped layer.

[0008] Optionally, materials of the first N-type heavily doped layer and the second N-type heavily doped layer include one or more of ICO, IWO, IZO and ITO.

[0009] Optionally, the doping elements of the first N-type heavily doped layer and the second N-type heavily doped layer respectively and independently include one of titanium, magnesium, gallium and chromium.

[0010] Optionally, the thickness of the first N-type heavily doped layer is 5-50 nm; The thickness of the second N-type heavily doped layer is 1-5 nm; The thickness of the second N-type heavily doped layer is smaller than the thickness of the first N-type heavily doped layer.

[0011] In a second aspect, an embodiment of the present application provides a method for preparing an intermediate tunneling layer structure of a stacked photovoltaic cell, the preparation method comprising: The RPD deposition method is used to obtain the middle tunneling layer structure of the stacked photovoltaic cell.

[0012] Optionally, a first N-type heavily doped layer of the middle tunneling layer structure of the stacked photovoltaic cell is obtained by RPD deposition method; At a temperature of 20~25°C and a vacuum degree of 1~10E ~4 Torr, when the sputtering current is 120-180A, the first mixed gas is introduced to form the first N-type heavily doped layer; At a temperature of 20~25°C and a vacuum degree of 1~10E ~4 Torr, and when the sputtering current is 120-180 A, the second mixed gas is introduced to form the second N-type heavily doped layer.

[0013] Optionally, the first mixed gas includes silane, hydrogen and phosphine, and the ratio of the special gas flow rate of the hydrogen in the first mixed gas is 0-0.5%; the special gas flow rate of the first mixed gas is 50-200 sccm; The second mixed gas includes silane, hydrogen and phosphine, the ratio of the special gas flow rate of hydrogen in the second mixed gas is 0.5-5%, and the special gas flow rate of the second mixed gas is 50-200 sccm; The special gas flow rate of hydrogen in the second N-type heavily doped layer is greater than the special gas flow rate of hydrogen in the first N-type heavily doped layer.

[0014] In a third aspect, an embodiment of the present application provides a perovskite / crystalline silicon tandem photovoltaic cell structure, wherein the perovskite / crystalline silicon tandem photovoltaic cell structure contains the above-mentioned tandem photovoltaic cell intermediate tunneling layer structure.

[0015] Optionally, the perovskite / crystalline silicon laminated photovoltaic cell structure comprises a top sub-cell unit, a bottom sub-cell unit and a laminated photovoltaic cell intermediate tunneling layer structure; the laminated photovoltaic cell intermediate tunneling layer structure is arranged between the top sub-cell unit and the bottom sub-cell unit; The top sub-battery unit is a wide bandgap perovskite top sub-battery unit; The base battery cell is a narrow bandgap crystalline silicon base battery cell; The top of the base battery unit is connected to the middle tunneling layer structure of the laminated photovoltaic cell; The heavily doped layer at the place where the middle tunneling layer structure of the stacked photovoltaic cell is connected to the bottom battery unit and the top of the bottom battery unit are both N-type or P-type.

[0016] In a fourth aspect, an embodiment of the present application provides a photovoltaic cell, wherein the photovoltaic cell contains the above-mentioned stacked photovoltaic cell intermediate tunneling layer structure or the above-mentioned perovskite / crystalline silicon stacked photovoltaic cell structure.

[0017] The above technical solution adopted in the embodiment of the present application may have the following advantages: The use of a heavily doped PN structure is beneficial to reducing the optical absorption of the middle tunneling layer, ensuring the optical utilization of the bottom battery, and further improving the open circuit voltage and short circuit current of the stacked photovoltaic cell; the doping concentration of the first N-type heavily doped layer is lower than the doping concentration of the second N-type heavily doped layer, and the second N-type heavily doped layer has a higher carrier concentration and a lower resistance, further reducing the resistance of the entire tunneling layer and improving its conductivity; and a higher carrier concentration can also increase the transmission rate of electrons, speed up the transmission speed of carriers in the tunneling layer, and reduce current losses; at the same time, the design of two heavily doped layers can ensure that holes can be exhausted, thereby improving the FF of the battery, and then improving the response speed and performance of the device. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In the accompanying drawings, unless otherwise specified, the same reference numerals throughout the multiple drawings represent the same or similar parts or elements. These drawings are not necessarily drawn to scale. It should be understood that these drawings only depict some embodiments disclosed in the present application and should not be regarded as limiting the scope of the present application.

[0019] Figure 1 It is a schematic diagram of the structure of the perovskite / crystalline silicon tandem photovoltaic cell provided in the embodiment of the present application.

[0020] Description of reference numerals: 11. First carrier transport layer; 12. Perovskite light absorption layer; 13. Second carrier transport layer; 21. Second P-type heavily doped layer; 22. First P-type heavily doped layer; 23. First N-type heavily doped layer; 24. Second N-type heavily doped layer; 31. P-type non- / microcrystalline silicon layer; 32. First amorphous silicon layer; 33. Silicon substrate; 34. Second amorphous silicon layer; 35. N-type non- / microcrystalline silicon layer; 4. Transparent conductive glass; 5. Electrode. DETAILED DESCRIPTION

[0021] Embodiments of the present application are described in detail below, and examples of the embodiments are shown in the accompanying drawings. In the accompanying drawings, for clarity, the sizes of layers, regions, elements and their relative sizes may be exaggerated. Wherein the same or similar reference numerals throughout represent the same or similar elements or elements with the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain the present application, and cannot be understood as limitations on the present application. It should be noted that, in the absence of conflict, the embodiments in the present application and the features in the embodiments can be combined with each other.

[0022] It should be understood that when an element or layer is referred to as "on ...", "adjacent to ...", "connected to" or "coupled to" other elements or layers, it can be directly on, adjacent to, connected to or coupled to other elements or layers, or there can be intervening elements or layers. On the contrary, when an element is referred to as "directly on ...", "directly adjacent to ...", "directly connected to" or "directly coupled to" other elements or layers, there is no intervening element or layer. It should be understood that although the terms first, second, third, etc. can be used to describe various elements, components, regions, layers and / or parts, these elements, components, regions, layers and / or parts should not be limited by these terms. These terms are only used to distinguish one element, component, region, layer or part from another element, component, region, layer or part. Therefore, without departing from the teachings of the present disclosure, the first element, component, region, layer or part discussed below can be represented as the second element, component, region, layer or part. And when the second element, component, region, layer or part is discussed, it does not indicate that the present application discloses the existence of the first element, component, region, layer or part.

[0023] In this application, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection or an indirect connection through an intermediate medium, it can be the internal connection of two elements or the interaction relationship between two elements, unless otherwise clearly defined. For ordinary technicians in this field, the specific meanings of the above terms in this application can be understood according to specific circumstances.

[0024] It should be noted that the terms "first", "second", etc. in the specification and claims of the present application and the above-mentioned drawings are used to distinguish similar objects, and are not necessarily used to describe a specific order or sequence. It should be understood that the terms used in this way can be interchangeable where appropriate, so that the embodiments of the present application described herein can be implemented in an order other than those illustrated or described herein, for example. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions, for example, a process, method, system, product or device that includes a series of steps or units is not necessarily limited to those steps or units that are clearly listed, but may include other steps or units that are not clearly listed or inherent to these processes, methods, products or devices.

[0025] In the present application, when it comes to a numerical interval (i.e., a numerical range), unless otherwise specified, the distribution of the optional numerical values ​​in the numerical interval is considered to be continuous, and includes the two numerical endpoints (i.e., the minimum and maximum values) of the numerical interval, and each numerical value between the two numerical endpoints. Unless otherwise specified, when the numerical interval only refers to an integer in the numerical interval, it includes the two endpoint integers of the numerical range, and each integer between the two endpoints, which is equivalent to directly listing each integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be merged. In other words, unless otherwise specified, the numerical range disclosed in the present application should be understood to include any and all sub-ranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, a percentage, a ratio, etc. "Numerical interval" allows for broadly including quantitative intervals such as percentage intervals, ratio intervals, and ratio intervals.

[0026] The following provides an explanation of the terms used in this application.

[0027] Heavily doped layer: The concentration of doping elements is greater than 10 20 / cm 3 .

[0028] Hereinafter, exemplary embodiments according to the present application will be described in more detail with reference to the accompanying drawings. It should be noted that these exemplary embodiments can be implemented in many different forms and should not be construed as being limited to the embodiments described herein.

[0029] An embodiment of the present application provides an intermediate tunneling layer structure of a stacked photovoltaic cell, wherein the intermediate tunneling layer structure of the stacked photovoltaic cell includes a heavily doped PN structure serving as a tunneling junction; the heavily doped PN structure includes a first N-type heavily doped layer, a second N-type heavily doped layer, a second P-type heavily doped layer, and a first P-type heavily doped layer arranged in a stacked manner; wherein the doping concentration of the first N-type heavily doped layer is lower than the doping concentration of the second N-type heavily doped layer.

[0030] In this embodiment, the use of a heavily doped PN structure is beneficial to reducing the optical absorption of the intermediate tunneling layer, ensuring the optical utilization of the underlying battery, and further improving the open circuit voltage and short circuit current of the stacked photovoltaic cell; the doping concentration of the first N-type heavily doped layer is lower than the doping concentration of the second N-type heavily doped layer, and the second N-type heavily doped layer has a higher carrier concentration and a lower resistance, further reducing the resistance of the entire tunneling layer and improving its conductivity; and a higher carrier concentration can also increase the transmission rate of electrons, speed up the transmission speed of carriers in the tunneling layer, and reduce current losses, thereby improving the response speed and performance of the device.

[0031] In an optional embodiment, the first N-type heavily doped layer and the second N-type heavily doped layer are made of the same material, which is easy to prepare and the homojunction of the same material is easier to achieve material stability; on the other hand, the first N-type heavily doped layer and the second N-type heavily doped layer have a high matching property, which helps to reduce lattice defects and interface reflections, improve electron transmission efficiency, and the first N-type heavily doped layer and the second N-type heavily doped layer are made of the same material to form a homojunction, which can promote more efficient electron transmission and reduce the loss of electrons in the tunneling layer, thereby improving the efficiency of photovoltaic cells. It should be noted that when a heterojunction is formed in a battery, the heterojunction can increase the resistance to electron transmission, affect carrier behavior, form interface defects, and reduce material compatibility, thereby reducing the photoelectric conversion efficiency and device performance.

[0032] In an optional embodiment, the materials of the first N-type heavily doped layer and the second N-type heavily doped layer respectively and independently include one or more of ICO, IWO, IZO and ITO.

[0033] In this embodiment, ICO, IWO, IZO and ITO all have good optical transparency (high transmittance), which allows light to pass through and reach the underlying crystalline silicon cell, which helps to improve the photoelectric conversion efficiency; at the same time, it maintains good electrical conductivity, thereby ensuring the light absorption and electrical performance of the underlying crystalline silicon cell, promoting the comprehensive recombination of holes and electrons, and thus improving the efficiency of the stacked cell. In addition, the top layer of the base cell unit (crystalline silicon cell) is an amorphous silicon / microcrystalline silicon layer, and the first N-type heavily doped layer is in direct contact with the amorphous silicon / microcrystalline silicon layer. The energy level of the first N-type heavily doped layer matches the energy level of the amorphous silicon / microcrystalline silicon layer, and reduces interface defects and electron scattering, thereby reducing the potential barrier of electron transmission and improving the efficiency of electron transmission. It should be noted that the ICO, IWO, IZO and ITO materials selected in the embodiment of the present application have higher conductivity and lower resistivity, which can reduce the impedance of electron transmission, thereby reducing the potential barrier required for electron transmission.

[0034] In an optional embodiment, the doping elements of the first N-type heavily doped layer and the second N-type heavily doped layer both include one of titanium, magnesium, gallium and chromium.

[0035] In this embodiment, doping with Ti (titanium) can improve the electrical properties of the first N-type heavily doped layer and the second N-type heavily doped layer. Ti doping can increase the carrier concentration of the material, thereby improving the conductivity, and at the same time can improve the stability and durability of the material; doping with Mg (magnesium) is used to optimize the optical properties of the first N-type heavily doped layer and the second N-type heavily doped layer, reduce the refractive index, and improve the transparency, and at the same time can improve the optical uniformity and transmission performance; doping with Ga (gallium) can adjust the band gap and stabilize the carrier concentration; doping with Cr (chromium) can change the optical properties and color of the first N-type heavily doped layer and the second N-type heavily doped layer, and by introducing an absorption band, the optical absorption characteristics of the first N-type heavily doped layer and the second N-type heavily doped layer are changed, thereby adjusting their color and transmittance.

[0036] In an optional embodiment, the thickness of the first N-type heavily doped layer is 5~50nm (for example, 5nm, 30nm, 50nm); the thickness of the second N-type heavily doped layer is 1~5nm (for example, 1nm, 3nm, 5nm); the thickness of the second N-type heavily doped layer is less than the thickness of the first N-type heavily doped layer.

[0037] In this embodiment, the thickness of the first N-type heavily doped layer is greater than that of the second N-type heavily doped layer, which can reduce the resistance of the entire tunneling layer, reduce the loss of resistance, and help improve the efficiency of the device; in addition, the large thickness of the first N-type heavily doped layer can increase the amount of electrons injected into the perovskite layer, thereby increasing the carrier concentration in the perovskite layer, thereby improving the electron transmission and photoelectric conversion efficiency of the perovskite layer; at the same time, by increasing the thickness of the first N-type heavily doped layer, the interface matching between the perovskite layer and the crystalline silicon layer can be improved, reducing interface reflection and electron recombination, thereby improving the photoelectric conversion efficiency of the optoelectronic device. It should be noted that the carrier concentration in the second N-type heavily doped layer is relatively high, but because its thickness is lower than that of the first N-type heavily doped layer, the higher carrier concentration will not affect the transmittance of the film in the infrared region. In addition, in the heavily doped PN structure as a tunnel junction, the holes in the first P-type heavily doped layer and the second P-type heavily doped layer will penetrate into the first N-type heavily doped layer and the second N-type heavily doped layer to combine with electrons and be gradually consumed. As the depth of the holes in the first N-type heavily doped layer and the second N-type heavily doped layer increases, the more holes are consumed until they are exhausted. Therefore, when the thickness of the first N-type heavily doped layer is greater than the thickness of the second N-type heavily doped layer, it can be ensured that the holes are exhausted, thereby improving the battery FF.

[0038] The embodiment of the present application can also provide a method for preparing the middle tunneling layer structure of a stacked photovoltaic cell, the preparation method comprising: adopting the RPD deposition method to obtain the middle tunneling layer structure of the stacked photovoltaic cell. The preparation method provided by the present application is compatible with the existing crystalline silicon solar cell production line, has a simple process, and has a low production cost, which is conducive to reducing the cost per kilowatt-hour of photovoltaic cells. In addition, the use of RPD technology for deposition preparation, without electric field to accelerate ions, can basically achieve non-destructive preparation, thereby reducing the thickness of the spacer layer.

[0039] In an optional embodiment, the first N-type heavily doped layer of the middle tunneling layer structure of the stacked photovoltaic cell is obtained by RPD deposition; during the deposition of the first N-type heavily doped layer, the temperature is 20-25°C (for example, 20°C, 23°C, 25°C), and the vacuum degree is 1-10E ~4 Torr (e.g. 10E ~4 , 1), the sputtering current is 120~180A (for example, 120A, 160A, 180A); the first mixed gas introduced, the special gas flow rate of the first mixed gas is 50~200sccm (for example, 50sccm, 120sccm, 200sccm); wherein, the first mixed gas includes silane, hydrogen and phosphine, and the ratio of the special gas flow rate of hydrogen in the first mixed gas is 0~0.5% (for example, 0, 0.2%, 0.5%).

[0040] The second N-type heavily doped layer of the middle tunneling layer structure of the stacked photovoltaic cell is obtained by RPD deposition; during the deposition of the second N-type heavily doped layer, the temperature is 20-25°C (e.g., 20°C, 23°C, 25°C), and the vacuum degree is 1-10E ~4 Torr (e.g. 10E ~4 , 1), the sputtering current is 120~180A (for example, 120A, 160A, 180A); the second mixed gas introduced, the special gas flow rate of the second mixed gas is 50~200sccm (for example, 50sccm, 120sccm, 200sccm); wherein the second mixed gas includes silane, hydrogen and phosphine, and the ratio of the special gas flow rate of hydrogen in the second mixed gas is 0.5~1.5% (for example, 0.5%, 1%, 1.5%).

[0041] The special gas flow rate of hydrogen in the second N-type heavily doped layer is greater than the special gas flow rate of hydrogen in the first N-type heavily doped layer.

[0042] In this embodiment, during the preparation of the first N-type heavily doped layer, when the hydrogen gas flow rate is lower than the range of 0-0.5%, the hydrogen content in the deposited layer is insufficient, making the deposited first N-type heavily doped layer structure too dense; it also causes more hydrogen defects in the first N-type heavily doped layer, thereby affecting its crystallinity and mechanical properties. At the same time, hydrogen also participates in the hydrogenation reaction during the deposition process, and also reduces the deposition rate and the quality of the first N-type heavily doped layer; when the hydrogen content is higher than the range of 0-0.5%, the deposited material has a higher hydrogen content, thereby affecting the physical and chemical properties of the material, and also causes the first N-type heavily doped layer to have too much hydrogen content, forming hydrides, thereby affecting the optical, electrical and structural properties of the first N-type heavily doped layer. In addition, it will also reduce the deposition rate and prolong the deposition time, thereby increasing production costs. The special gas flow rate of hydrogen in the second N-type heavily doped layer is greater than the special gas flow rate of hydrogen in the first N-type heavily doped layer. Hydrogen enters the second N-type heavily doped layer in the form of hydrogen atoms and exists in the form of gap defects, which will provide additional carriers, thereby improving the carrier mobility.

[0043] like Figure 1 As shown, the embodiment of the present application also provides a perovskite / crystalline silicon laminated photovoltaic cell structure, the perovskite / crystalline silicon laminated photovoltaic cell structure contains any of the above laminated photovoltaic cell intermediate tunneling layer structures, the perovskite / crystalline silicon laminated photovoltaic cell structure includes a top sub-cell unit, a laminated photovoltaic cell intermediate tunneling layer structure and a bottom cell unit stacked from top to bottom, and transparent conductive glass 4 is respectively arranged on the other side of the top sub-cell unit and the bottom cell unit, and connected to an electrode 5; The top sub-battery unit includes a first carrier transport layer 11, a perovskite light absorption layer 12, and a second carrier transport layer 13 which are stacked in sequence from far away to close to the tunnel layer structure; the bottom sub-battery unit includes a P-type non- / microcrystalline silicon layer 31, a first amorphous silicon layer 32, a silicon substrate 33, a second amorphous silicon layer 34, and an N-type non- / microcrystalline silicon layer 35 which are stacked in sequence from far away to close to the tunnel layer structure.

[0044] The following specific examples further illustrate the present application, but should not be construed as limiting the present application. Without departing from the spirit and substance of the present application, modifications or replacements made to the methods, steps or conditions of the present application are within the scope of the present application.

[0045] [Example 1] like Figure 1As shown, an embodiment of the present application discloses a perovskite / crystalline silicon stacked photovoltaic cell structure, the perovskite / crystalline silicon stacked photovoltaic cell structure includes a top cell unit stacked from top to bottom, a middle tunneling layer structure of the stacked photovoltaic cell and a bottom cell unit, transparent conductive glass 4 is respectively arranged on the other side of the top cell unit and the bottom cell unit, and an electrode 5 is connected; the middle tunneling layer structure of the stacked photovoltaic cell includes a first N-type heavily doped layer 23, a second N-type heavily doped layer 24, a second P-type heavily doped layer 21 and a first P-type heavily doped layer 22 stacked in sequence from bottom to top.

[0046] Among them, the top battery cell is a wide-bandgap perovskite top battery cell, and the bottom battery cell is a narrow-bandgap crystalline silicon bottom battery cell.

[0047] The top sub-battery unit includes a first carrier transport layer 11, a perovskite light absorption layer 12, and a second carrier transport layer 13 which are stacked in sequence from away from the tunnel layer structure to close to it; the bottom sub-battery unit includes a P-type non- / microcrystalline silicon layer 31, a first amorphous silicon layer 32, a silicon substrate 33, a second amorphous silicon layer 34, and an N-type non- / microcrystalline silicon layer 35 which are stacked in sequence from away from the tunnel layer structure to close to it; the first N-type heavily doped layer 23 is connected to the N-type non- / microcrystalline silicon layer 35 of the bottom sub-battery unit, and the first P-type heavily doped layer 22 is connected to the second carrier transport layer 13 of the top sub-battery unit.

[0048] The specific preparation method of the middle tunneling layer structure of the stacked photovoltaic cell is as follows: According to the structure of the perovskite / crystalline silicon stacked photovoltaic cell, the first N-type heavily doped layer 23, the second N-type heavily doped layer 24, the second P-type heavily doped layer 21 and the first P-type heavily doped layer 22 are sequentially deposited by the RPD deposition method. The specific method is as follows: Step S1: Under the conditions that the substrate gas is an argon atmosphere, the temperature is 25°C, and the vacuum degree is 10E~4Torr, the sputtering current is set to 160A, and a first mixed gas is introduced. The special gas flow rate of the first mixed gas is 100sccm. The first mixed gas includes silane, hydrogen and phosphine. The ratio of the special gas flow rate of hydrogen to the first mixed gas is 0.5%. The first N-type heavily doped layer 23 is deposited on the N-type non- / microcrystalline silicon layer 35 of the base battery unit; Step S2: Under the conditions that the substrate gas is an argon atmosphere, the temperature is 25° C., and the vacuum degree is 10E~4Torr, the sputtering current is set to 160A, and a second mixed gas is introduced. The special gas flow rate of the second mixed gas is 100 sccm. The second mixed gas includes silane, hydrogen, and phosphine. The ratio of the special gas flow rate of hydrogen to the second mixed gas is 5%, and a second N-type heavily doped layer 24 is deposited on the first N-type heavily doped layer 23; Step S3: Under the conditions that the substrate gas is an argon atmosphere, the temperature is 25° C., and the vacuum degree is 0.5 Pa, the sputtering current is set to 160A, and a third mixed gas is introduced. The total gas flow of the third mixed gas is 200 sccm. The third mixed gas includes silane, hydrogen, and phosphine. The ratio of the special gas flow of hydrogen to the third mixed gas is 0.5%. The second P-type heavily doped layer 21 is deposited on the second N-type heavily doped layer 24 of the base battery unit; Step S4: Under the conditions that the substrate gas is an argon atmosphere, the temperature is 25° C., and the vacuum degree is 0.5 Pa, the sputtering current is set to 160A, and the fourth mixed gas is introduced. The total gas flow of the fourth mixed gas is 200 sccm. The fourth mixed gas includes silane, hydrogen, and phosphine. The ratio of the special gas flow of hydrogen to the fourth mixed gas is 0.5%. The first P-type heavily doped layer 22 is deposited on the second P-type heavily doped layer of the base battery unit; Among them, the thickness of the first N-type heavily doped layer 23 is 5nm, and the material is ICO with the doping element Ce. The thickness of the second N-type heavily doped layer 24 is 1nm, and the material is ICO. The thickness of the first P-type heavily doped layer 22 is 5nm, and the thickness of the second P-type heavily doped layer 21 is 20nm.

[0049] The doping concentration of the first N-type heavily doped layer 23 is less than the doping concentration of the second N-type heavily doped layer 24. The doping concentration of the first P-type heavily doped layer 22 is less than the doping concentration of the second P-type heavily doped layer 21, and the doping concentration of the second P-type heavily doped layer 21 is less than the doping concentration of the first N-type heavily doped layer 23.

[0050] [Example 2]~[Example 5] The intermediate tunneling layer structures of the laminated photovoltaic cells of Examples 2 to 3 were prepared by referring to the preparation method of Example 1, except that: In Example 2, the thickness of the first N-type heavily doped layer 23 is 25 nm, and the material is IWO with W as the doping element. The thickness of the second N-type heavily doped layer 24 is 3 nm, and the material is IWO with W as the doping element.

[0051] In Example 3, the thickness of the first N-type heavily doped layer 23 is 50 nm, and the material is IWO with W as the doping element. The thickness of the second N-type heavily doped layer 24 is 5 nm, and the material is IWO with W as the doping element.

[0052] In Example 4, during the preparation of the first N-type heavily doped layer 23, the ratio of the special gas flow rate of hydrogen to the first mixed gas is 0; during the preparation of the second N-type heavily doped layer 24, the ratio of the special gas flow rate of hydrogen to the second mixed gas is 0.5%.

[0053] In Example 5, during the preparation of the first N-type heavily doped layer 23, the ratio of the special gas flow rates of hydrogen to the first mixed gas is 0.25%; during the preparation of the second N-type heavily doped layer 24, the ratio of the special gas flow rates of hydrogen to the second mixed gas is 2%.

[0054] [Comparative Example 1] Referring to the perovskite / crystalline silicon laminated photovoltaic cell structure of Example 1, the perovskite / crystalline silicon laminated photovoltaic cell structure of Comparative Example 1 is different only in that: The tunneling layer made of ITO is used to replace the stacked first N-type heavily doped layer 23 , the second N-type heavily doped layer 24 , the second P-type heavily doped layer 21 and the first P-type heavily doped layer 22 .

[0055] The following is a performance test of the perovskite / crystalline silicon stacked photovoltaic cells provided in Examples 1 to 5 of the present application and Comparative Example 1, so as to obtain the open circuit voltage Voc, fill factor FF, short circuit current density Jsc, and photoelectric conversion efficiency PCE of the corresponding cell devices, and the test results are shown in Table 1.

[0056] Table 1 Performance test results of perovskite / crystalline silicon tandem photovoltaic cells of Examples 1 to 5 and Comparative Example 1

[0057] It can be seen from Table 1 that compared with Comparative Example 1, the open circuit voltage Voc, fill factor FF, short circuit current density Jsc, and photoelectric conversion efficiency PCE of the perovskite / crystalline silicon stacked photovoltaic cells of Examples 1 to 5 of the present application are significantly improved, which indicates that the intermediate tunneling layer structure of the stacked photovoltaic cells in Examples 1 to 5 of the present application is conducive to reducing the optical absorption of the intermediate tunneling layer, ensuring the optical utilization of the underlying battery, and further improving the open circuit voltage and short circuit current of the stacked photovoltaic cell; in addition, the doping concentration of the first N-type heavily doped layer is lower than the doping concentration of the second N-type heavily doped layer, and the second N-type heavily doped layer has a higher carrier concentration and a lower resistance, which further reduces the resistance of the entire tunneling layer and improves its conductive performance; In Examples 1 to 5, the materials of the first N-type heavily doped layer and the second N-type heavily doped layer are the same, which is convenient for preparation and the homojunction of the same material is more likely to achieve material stability; on the other hand, the first N-type heavily doped layer and the second N-type heavily doped layer of the same material have high matching properties, which helps to reduce lattice defects and interface reflections, improve electron transmission efficiency, and form a homojunction between the two layers. The homojunction can promote more efficient electron transmission and reduce the loss of electrons in the tunneling layer, thereby improving the efficiency of the photovoltaic cell; In embodiments 1 to 5, the thickness of the first N-type heavily doped layer is greater than the thickness of the second N-type heavily doped layer, which can reduce the resistance of the entire tunneling layer, reduce resistance loss, and help improve device efficiency.

[0058] It should be noted that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", "clockwise", "counterclockwise", "axial", "radial", "circumferential", etc. are only for the convenience of describing the present application and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present application. The orientation words "inside" and "outside" refer to the inside and outside relative to the outline of each component itself. For example, if the device in the accompanying drawings is inverted, the device described as "above other devices or structures" or "above other devices or structures" will be positioned as "below other devices or structures" or "below other devices or structures". Therefore, the exemplary term "above..." can include both "above..." and "below..." orientations. The device can also be positioned in other different ways (rotated 90 degrees or in other orientations), and the spatial relative descriptions used here are interpreted accordingly.

[0059] It should also be noted that "one embodiment", "another embodiment", "embodiment", etc. mentioned in this application refer to the specific features, structures or characteristics described in conjunction with the embodiment included in at least one embodiment generally described in this application. The same expression appearing in multiple places in the specification does not necessarily refer to the same embodiment. Further, when describing a specific feature, structure or characteristic in conjunction with any embodiment, it is claimed that the realization of such feature, structure or characteristic in conjunction with other embodiments also falls within the scope of this application.

[0060] In the above embodiments, the description of each embodiment has its own emphasis. For parts that are not described in detail in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.

[0061] It should also be noted that the above are only preferred embodiments of the present application, and the patent protection scope of the present application is not limited thereto. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly used in other related technical fields, are also included in the patent protection scope of the present application.

Claims

1. A middle tunneling layer structure of a laminated photovoltaic cell, characterized in that: The middle tunneling layer structure of the stacked photovoltaic cell includes a heavily doped PN structure as a tunneling junction; the heavily doped PN structure includes a first N-type heavily doped layer, a second N-type heavily doped layer, a second P-type heavily doped layer and a first P-type heavily doped layer stacked; The doping concentration of the first N-type heavily doped layer is lower than the doping concentration of the second N-type heavily doped layer.

2. The intermediate tunneling layer structure of the laminated photovoltaic cell according to claim 1, characterized in that: The materials of the first N-type heavily doped layer and the second N-type heavily doped layer respectively and independently include one or more of ICO, IWO, IZO and ITO.

3. The intermediate tunneling layer structure of the laminated photovoltaic cell according to claim 1, characterized in that: The doping elements of the first N-type heavily doped layer and the second N-type heavily doped layer respectively and independently include one of titanium, magnesium, gallium and chromium.

4. The intermediate tunneling layer structure of the laminated photovoltaic cell according to claim 1, characterized in that: The thickness of the first N-type heavily doped layer is 5-50 nm; The thickness of the second N-type heavily doped layer is 1-5 nm; The thickness of the second N-type heavily doped layer is smaller than the thickness of the first N-type heavily doped layer.

5. A method for preparing the intermediate tunneling layer structure of the laminated photovoltaic cell according to any one of claims 1 to 4, characterized in that: include: The RPD deposition method is used to obtain the middle tunneling layer structure of the stacked photovoltaic cell.

6. The method for preparing the middle tunneling layer structure of the laminated photovoltaic cell according to claim 5, characterized in that: The RPD deposition method is used to obtain the middle tunneling layer structure of the stacked photovoltaic cell, including: At a temperature of 20~25°C and a vacuum degree of 1~10E ~4 Torr, when the sputtering current is 120-180A, the first mixed gas is introduced to form the first N-type heavily doped layer; At a temperature of 20~25°C and a vacuum degree of 1~10E ~4 Torr, and when the sputtering current is 120-180 A, the second mixed gas is introduced to form the second N-type heavily doped layer.

7. The method for preparing the intermediate tunneling layer structure of the laminated photovoltaic cell according to claim 6, characterized in that: The first mixed gas includes silane, hydrogen and phosphine, and the ratio of the special gas flow rate of the hydrogen in the first mixed gas is 0-0.5%; the special gas flow rate of the first mixed gas is 50-200 sccm; The second mixed gas includes silane, hydrogen and phosphine, the ratio of the special gas flow rate of hydrogen in the second mixed gas is 0.5-5%, and the special gas flow rate of the second mixed gas is 50-200 sccm; The special gas flow rate of hydrogen in the second N-type heavily doped layer is greater than the special gas flow rate of hydrogen in the first N-type heavily doped layer.

8. A perovskite / crystalline silicon laminated photovoltaic cell structure, characterized in that: The perovskite / crystalline silicon tandem photovoltaic cell structure contains the tandem photovoltaic cell intermediate tunneling layer structure as described in any one of claims 1 to 4.

9. The perovskite / crystalline silicon tandem photovoltaic cell structure according to claim 8, characterized in that: include: A top battery unit, a stacked photovoltaic cell middle tunneling layer structure, and a bottom battery unit are stacked in sequence; The top sub-battery unit is a perovskite top sub-battery unit; The base battery unit is a crystalline silicon base battery unit; The top of the base battery unit is connected to the middle tunneling layer structure of the stacked photovoltaic cell.

10. A photovoltaic cell, characterized in that: The photovoltaic cell contains the intermediate tunneling layer structure of the stacked photovoltaic cell as described in any one of claims 1 to 4 or the perovskite / crystalline silicon stacked photovoltaic cell structure as described in any one of claims 8 to 9.

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