Back contact battery piece, battery string, battery assembly and photovoltaic system

Abstract

The utility model discloses a back contact battery piece, a battery string, a battery assembly and a photovoltaic system, the back contact battery piece comprises a semiconductor substrate, and the semiconductor substrate is provided with a front surface and a back surface which are oppositely arranged; p-type doped conductive regions and N-type doped conductive regions, wherein the P-type doped conductive regions and the N-type doped conductive regions are alternately arranged on the back surface of the semiconductor substrate; a first passivation layer and a second passivation layer, the first passivation layer is arranged on the P-type doped conductive region, and the second passivation layer is arranged on the first passivation layer and the N-type doped conductive region; the first passivation layer is a hole selection layer. According to the utility model, obstruction to electron transmission of the N-type region of the back contact cell can be reduced, so that the photoelectric conversion efficiency of the back contact cell is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of solar cells, and in particular to a back-contact cell sheet, a cell string, a cell assembly and a photovoltaic system. Background Art

[0002] The emitter and base electrodes of back-contact solar cells are both located on the back of the cell, reducing shading and improving photoelectric conversion efficiency. To reduce electron-hole pair recombination on the silicon wafer surface and thus reduce the interface state density, a passivation layer needs to be deposited on the N-type and P-type regions on the back of the cell. Existing passivation layers are generally composite films composed of aluminum oxide and silicon nitride. After annealing, the aluminum oxide layer has a high concentration of fixed negative charge at the interface and releases hydrogen during deposition, saturating dangling bonds at the interface, thereby reducing surface recombination and improving minority carrier lifetime. Although the aluminum oxide layer has a significant field passivation effect on the surface of the P-type region, when passivating the surface of the highly doped N-type region, it causes the N-type region surface to invert, resulting in a decrease in the electron collection efficiency of the N-type region and an increase in recombination in the electrode region, thereby reducing the efficiency of the cell. Utility Model Content

[0003] The technical problem to be solved by the present invention is to provide a back-contact cell, a cell string, a cell assembly and a photovoltaic system, in which a hole selection layer is only provided on the P-type doped region of the back-contact cell to improve the photoelectric conversion efficiency of the cell.

[0004] In order to solve the above technical problems, the utility model provides a back contact solar cell, comprising a semiconductor substrate, wherein the semiconductor substrate has a front surface and a back surface arranged opposite to each other;

[0005] A P-type doped conductive region and an N-type doped conductive region, wherein the P-type doped conductive region and the N-type doped conductive region are alternately arranged on the back surface of the semiconductor substrate;

[0006] a first passivation layer and a second passivation layer, wherein the first passivation layer is disposed on the P-type doped conductive region, and the second passivation layer is disposed on the first passivation layer and the N-type doped conductive region; and the first passivation layer is a hole selection layer.

[0007] As an improvement of the above solution, the first passivation layer is an aluminum oxide layer and / or a titanium oxide layer.

[0008] As an improvement of the above solution, the thickness of the first passivation layer is smaller than the thickness of the second passivation layer.

[0009] As an improvement of the above solution, the thickness of the first passivation layer is 1 nm to 10 nm.

[0010] As an improvement of the above solution, the thickness of the second passivation layer is 20 μm to 80 μm.

[0011] As an improvement of the above solution, the second passivation layer is one or more of an intrinsic amorphous silicon layer, an intrinsic polycrystalline silicon layer, an intrinsic nanocrystalline silicon layer, an intrinsic mixed crystal silicon layer, a silicon oxide layer, a silicon oxynitride layer, a silicon nitride layer, and a carbon nitride silicon oxide layer.

[0012] As an improvement of the above solution, the back-contact battery further includes an isolation region, and the isolation region is located between the P-type doped conductive region and the N-type doped conductive region.

[0013] As an improvement to the above solution, a third passivation layer is provided on the isolation region.

[0014] As an improvement of the above solution, the third passivation layer includes the first passivation layer and the second passivation layer.

[0015] As an improvement of the above solution, the surface of the third passivation layer is flush with the surface of the second passivation layer.

[0016] As an improvement of the above solution, the surface of the third passivation layer is concave toward the semiconductor substrate relative to the surface of the second passivation layer.

[0017] As an improvement of the above solution, the back-contact battery further includes a positive electrode and a negative electrode, the positive electrode is connected to the P-type doped conductive region, and the negative electrode is connected to the N-type doped conductive region.

[0018] As an improvement of the above solution, the P-type doped conductive region includes a first tunneling layer and a P-type doped layer, and the N-type doped conductive region includes a second tunneling layer and an N-type doped layer.

[0019] As an improvement of the above scheme, the first tunneling layer and the second tunneling layer are one or more of a silicon oxide layer, an aluminum oxide layer, a titanium oxide layer, a zinc oxide layer, an intrinsic amorphous silicon layer, an intrinsic polycrystalline silicon layer, an intrinsic nanocrystalline silicon layer, and an intrinsic mixed crystal silicon layer; the P-type doped layer and the N-type doped layer are one or more of a doped polycrystalline silicon layer, a doped amorphous silicon layer, and a doped microcrystalline silicon layer.

[0020] Correspondingly, the present invention also provides a battery string comprising the above-mentioned back-contact battery sheet.

[0021] Correspondingly, the present invention also provides a battery assembly, including the above-mentioned battery string.

[0022] Correspondingly, the present invention also provides a photovoltaic system, including the battery assembly as described above.

[0023] The implementation of the present invention has the following beneficial effects: by providing a first passivation layer on the P-type doped conductive region of the back contact battery cell, the first passivation layer has hole selectivity and can form a high resistance to electrons and a low resistance to holes, allowing holes to pass through easily while blocking electrons. The first passivation layer is not provided on the N-type doped conductive region, avoiding the first passivation layer from hindering the electron transmission in the N-type doped conductive region, thereby improving the efficiency of the battery. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic structural diagram of a back-contact cell provided in Example 1 of the present utility model;

[0025] Figure 2 This is a schematic structural diagram of a back-contact cell provided in Example 3 of the present utility model;

[0026] Figure 3 This is a schematic structural diagram of the back contact cell provided in Example 4 of the present utility model. DETAILED DESCRIPTION

[0027] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below with reference to the accompanying drawings and embodiments. Examples of the embodiments are shown in the accompanying drawings, in which 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 invention, and are not to be construed as limiting the present invention. In addition, it should be understood that the specific embodiments described herein are only used to explain the present invention and are not intended to limit the present invention.

[0028] In the description of the present invention, it should be understood that the terms "length", "width", "up", "down", "left", "right", "horizontal", "top", "bottom", etc., indicating the orientation or position relationship, are based on the orientation or position relationship shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying 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 invention.

[0029] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of the technical features being referred to. Thus, a feature defined as "first" or "second" may explicitly or implicitly include one or more of the described features. In the description of this utility model, "plurality" means two or more, unless otherwise specifically defined.

[0030] like Figure 1As shown, an embodiment of the present invention provides a back-contact cell, comprising a semiconductor substrate 1, wherein the semiconductor substrate 1 has a front surface 11 and a back surface 12 that are relatively arranged. The front surface 11 of the semiconductor substrate 1 can be a plane or a velvet surface. In a preferred embodiment, the front surface 11 of the semiconductor substrate 1 is a velvet surface, which has a light-trapping effect and can reduce the reflectivity of the front surface, so that more light is refracted from the front surface 11 into the semiconductor substrate 1 and absorbed and utilized by the semiconductor substrate 1, thereby improving the photoelectric conversion efficiency of the back-contact cell. The front surface 11 of the semiconductor substrate 1 is also provided with a front passivation layer. The back surface 12 of the semiconductor substrate 1 can be a plane or a velvet surface. In a preferred embodiment, the back surface 12 of the semiconductor substrate 1 is a plane, and the back surface 12 of the semiconductor substrate 1 is relatively flat, which is conducive to improving the formation quality of the P-type doped conductive region 13 and the N-type doped conductive region 14 formed on the back surface 12 of the semiconductor substrate 1.

[0031] The P-type doped conductive region 13 and the N-type doped conductive region 14 are alternately arranged on the back surface 12 of the semiconductor substrate 1 .

[0032] A first passivation layer 15 and a second passivation layer 16 are provided. The first passivation layer 15 is provided on the P-type doped conductive region 13, and the second passivation layer 16 is provided on the first passivation layer 15 and the N-type doped conductive region 14. The first passivation layer 15 is a hole selection layer. In existing back-contact cells, an aluminum oxide layer is typically provided on both the P-type doped conductive region 13 and the N-type doped conductive region 14. After annealing, the aluminum oxide layer has a high concentration of fixed negative charge at the interface and releases hydrogen during deposition, saturating dangling bonds at the interface, thereby reducing surface recombination and increasing minority carrier lifetime. Although the aluminum oxide layer has a significant field passivation effect on the surface of the P-type region, when passivating the surface of the highly doped N-type region, it causes the surface of the N-type region to invert, resulting in a decrease in the electron collection efficiency of the N-type region and an increase in recombination in the electrode region, thereby reducing the efficiency of the battery. In the present application, a first passivation layer 15 is provided on the P-type doped conductive region 14. The first passivation layer 15 is used to perform field passivation on the back surface 12 of the semiconductor substrate 1, forming an electric field at the interface between the two. The electric field is used to reduce the concentration of free electrons or holes at the interface, thereby achieving the purpose of reducing the carrier recombination rate. The first passivation layer 15 has hole selectivity. The fixed charge of the first passivation layer 15 with hole selectivity is negative. The conduction band and valence band of silicon at the interface are bent, which is conducive to the transmission of holes to the interface and blocks the transmission of electrons. The first passivation layer 15 is not provided on the N-type doped conductive region 14 to avoid the first passivation layer 15 hindering the electron transmission of the N-type doped conductive region 14, thereby improving the efficiency of the battery.

[0033] Optionally, the first passivation layer 15 may be an aluminum oxide layer and / or a titanium oxide layer. The first passivation layer 15 may be formed by a coating method such as atomic layer deposition or chemical vapor deposition. Both aluminum oxide and titanium oxide have excellent hole selectivity. The hole-selective transmission characteristics of the first passivation layer 15 are utilized to reduce recombination in the electrode region, thereby improving battery efficiency.

[0034] The second passivation layer 16 can be one or more of an intrinsic amorphous silicon layer, an intrinsic polycrystalline silicon layer, an intrinsic nanocrystalline silicon layer, an intrinsic mixed crystal silicon layer, a silicon oxide layer, a silicon oxynitride layer, a silicon nitride layer, and a silicon carbonitride oxide layer, and is not specifically limited here.

[0035] In a preferred embodiment, the thickness of the first passivation layer 15 is less than the thickness of the second passivation layer 16. Since the first passivation layer 15 acts as a carrier selective contact, the thickness of the first passivation layer 15 is relatively small to avoid electron-hole recombination at the interface of the first passivation layer 15 caused by excessive thickness. The second passivation layer 16 needs to be thick enough to ensure good passivation performance of the back contact battery.

[0036] Specifically, the thickness of the first passivation layer 15 is 1 nm to 10 nm, exemplified by, but not limited to, 2 nm, 3 nm, 5 nm, 6 nm, 8 nm, or 9 nm. If the thickness of the first passivation layer 15 is less than 1 nm, it is difficult to form a good hole-selective contact. If the thickness of the first passivation layer 15 is greater than 10 nm, the fill factor is reduced, leading to interfacial recombination and a decrease in open-circuit voltage. Preferably, the thickness of the first passivation layer 15 is 5 nm to 10 nm.

[0037] The thickness of the second passivation layer 16 is 20 μm to 80 μm, and is exemplarily 30 μm, 40 μm, 50 μm, 60 μm, 65 μm, or 70 μm, but is not limited thereto. If the thickness of the second passivation layer 16 is less than 20 μm, the passivation effect may not be achieved well. If the thickness of the second passivation layer 16 is greater than 80 μm, it will not significantly improve battery performance and will increase the overall thickness of the battery, which is not conducive to cost reduction.

[0038] The back contact cell also includes a positive electrode 21 and a negative electrode 22, which are respectively arranged on the first passivation layer 15 and the second passivation layer 16. The materials of the positive electrode 21 and the negative electrode 22 can be one or more of gold, silver, aluminum, and graphene. The positive electrode 21 and the negative electrode 22 are made of materials with good conductivity, which can better guide the current from the back contact cell. Specifically, when exposed to light, the semiconductor substrate 1 acts as a light absorption layer to generate electron-hole pairs. The first passivation layer 15 has a hole selection effect. The holes are guided by the corresponding negative electrode 22, and the electrons are guided by the corresponding positive electrode 21. The electrons and holes are separated by the solar cell, so that a potential difference is generated between the positive electrode 21 and the negative electrode 22, that is, a voltage is generated, thereby converting light energy into electrical energy.

[0039] In a preferred embodiment, the P-type doped conductive region 13 includes a first tunneling layer 131 and a P-type doped layer 132, and the N-type doped conductive region 14 includes a second tunneling layer 141 and an N-type doped layer 142. The P-type doped layer 132 and the N-type doped layer 142 have opposite doping types. The first tunneling layer 131 and the second tunneling layer 141 primarily serve as interface passivation and carrier transport, allowing carriers to be collected through the tunneling layers according to the tunneling effect. It should be noted that only one of the first tunneling layer 131 and the second tunneling layer 141 can be provided, or both can be provided. The size, thickness, and material of the first tunneling layer 131 and the second tunneling layer 141 can also be determined according to actual needs and are not specifically limited.

[0040] Optionally, the first tunneling layer 131 and the second tunneling layer 141 may be one or more of a silicon oxide layer, an aluminum oxide layer, a titanium oxide layer, a zinc oxide layer, an intrinsic amorphous silicon layer, an intrinsic polycrystalline silicon layer, an intrinsic nanocrystalline silicon layer, or an intrinsic mixed crystal silicon layer. The thickness of the first tunneling layer 131 and the second tunneling layer 141 is 0.1 nm to 5 nm, which provides excellent tunneling passivation performance without affecting carrier absorption. The P-type doped layer 132 and the N-type doped layer 142 may be one or more of a doped polycrystalline silicon layer, a doped amorphous silicon layer, or a doped microcrystalline silicon layer.

[0041] Optionally, the width of the first tunneling layer 131 is greater than or equal to the width of the second tunneling layer 141. Preferably, the width of the first tunneling layer 131 is greater than the width of the second tunneling layer 141, which is beneficial to the balance of hole transport and electron transport. If the width of the first tunneling layer 131 is less than the width of the second tunneling layer 141, it is easy to cause low hole collection efficiency and cause interfacial recombination of holes and electrons. Specifically, the width of the first tunneling layer 131 is 2mm to 15mm, and exemplarily is 3mm, 5mm, 8mm, 10mm, 12mm or 14mm, but not limited thereto. The width of the second tunneling layer 141 is 1.5mm to 10mm, and exemplarily is 2mm, 4mm, 6mm, 7mm, 8mm or 9mm, but not limited thereto.

[0042] In order to avoid short circuits, the P-type doped conductive region 13 and the N-type doped conductive region 14 of the back contact cell can be electrically insulated by setting a spacer, a dielectric layer or an insulating layer to ensure that the back contact cell does not leak electricity, reduce the recombination of carriers, and thus improve the photoelectric conversion efficiency. In a preferred embodiment, the back contact cell also includes an isolation region 17, and the isolation region 17 is located between the P-type doped conductive region 13 and the N-type doped conductive region 14. The spaced P-type doped conductive region 13 and the N-type doped conductive region 14 can prevent the P-type doped conductive region 13 and the N-type doped conductive region 14 from contacting and causing a short circuit. The formation of the isolation region 17 can be assisted by isolation using laser isolation, chemical isolation, graphic mask, etc.

[0043] Optionally, a third passivation layer is provided on the isolation region 17, and the third passivation layer can be one or more of an intrinsic amorphous silicon layer, an intrinsic polycrystalline silicon layer, an intrinsic nanocrystalline silicon layer, an intrinsic mixed crystal silicon layer, a silicon oxide layer, a silicon nitride oxide layer, a silicon nitride layer, and a carbon nitride silicon oxide layer, and is not specifically limited here. The thickness of the third passivation layer is 20μm to 80μm, and is exemplarily 30μm, 40μm, 50μm, 60μm, 65μm or 70μm, but is not limited thereto. Optionally, the third passivation layer can be made of the same material as the second passivation layer 16 and deposited on the surface of the N-type doped conductive region 14, the first passivation layer 15 and the isolation region 17 at one time, that is, the third passivation layer completely covers the isolation region 17, and the surface of the third passivation layer is flush with the surface of the second passivation layer. In this case, the passivation layer 17 covers the entire back side of the back contact cell. Accordingly, after the back side of the back contact cell is covered with the passivation material used to manufacture the passivation layer, the passivation layer can be obtained without patterning at least part of the passivation material, thereby simplifying the manufacturing process of the back contact cell, reducing the manufacturing difficulty of the back contact cell, and at the same time reducing the manufacturing cost of the back contact cell.

[0044] In a preferred embodiment, the third passivation layer includes a first passivation layer 15 and a second passivation layer 16. That is, a passivation layer structure identical to that on the P-type doped conductive region 13 is deposited on the isolation region 17. During the fabrication process, the passivation layer structure on the isolation region 17 can be fabricated simultaneously with the formation of the passivation layer structure on the P-type doped conductive region 13. The surface of the third passivation layer is recessed toward the silicon substrate relative to the surface of the second passivation layer. This provides a good passivation effect on the isolation region 17 and a simple fabrication process.

[0045] Correspondingly, an embodiment of the present invention also provides a battery string, including the above-mentioned back-contact battery cells, each battery string includes a plurality of back-contact battery cells connected in series, and the plurality of back-contact battery cells can be partially overlapped to form a battery string, and the contact areas between the overlaps are not conductively connected, that is, there is no need to set conductive glue or other adhesives between the overlapping areas, and the back-contact battery cells are simply overlapped together. Optionally, the back-contact battery cells are electrically connected in the form of a whole piece or multiple pieces. The overlapping areas of adjacent back-contact battery cells in the battery string are provided with series welding strips to fixedly connect the adjacent back-contact battery cells, and the series welding strips connect the adjacent back-contact battery cells in series. Different battery strings are obtained by series and / or parallel connection.

[0046] Correspondingly, an embodiment of the present invention further provides a battery assembly, comprising a first cover plate, a first adhesive film, at least one of the above-mentioned battery strings, a second adhesive film, and a second cover plate stacked in sequence.

[0047] Specifically, the first cover plate is usually made of a material with high light transmittance and strong weather resistance, including but not limited to glass and polycarbonate. Its main function is to protect the sensitive components inside the battery assembly from the external environment, while providing the necessary mechanical support to ensure the structural integrity of the battery assembly.

[0048] The first adhesive film is located between the first cover plate and the battery string, primarily serving as a bonding and sealing mechanism to prevent delamination or leakage during long-term use of the battery assembly. Materials for the first adhesive film include, but are not limited to, ethylene vinyl acetate (EVA) and polyolefin (POE).

[0049] The second adhesive film is located between the battery string and the second cover plate, and has a similar function to the first adhesive film, mainly serving as bonding and sealing.

[0050] The second cover plate is usually made of weather-resistant materials, including but not limited to aluminum plates and backplane films. Its main function is to protect the back of the battery assembly from the influence of the external environment and provide additional mechanical support. It can also serve as an insulating layer for the battery assembly to ensure safe use.

[0051] The battery assembly is formed by sequentially laying a first cover plate, a first adhesive film, a plurality of battery strings, a second adhesive film, and a second cover plate, followed by a lamination process. The lamination process includes preheating, pressurized heating, and cooling and curing. Its purpose is to tightly bond the multiple stacked component materials under high temperature and high pressure to form an integrated structure. The present invention does not specifically limit the lamination process.

[0052] Correspondingly, the embodiment of the present invention also provides a photovoltaic system. The photovoltaic system composed of battery components 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 can be understood that the application scenarios of the photovoltaic system are not limited to this. In other words, the photovoltaic system can be used in all fields that require the use of 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 battery components. For example, multiple battery components 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.

[0053] The present invention will be further described below with specific embodiments:

[0054] Example 1

[0055] This embodiment provides a back-contact solar cell, comprising:

[0056] The N-type silicon substrate has a front side and a back side that are opposite to each other.

[0057] The N-type doped conductive region and the P-type doped conductive region are alternately arranged on the back side of the N-type silicon substrate.

[0058] A first passivation layer and a second passivation layer, the first passivation layer is arranged on the P-type doped conductive region, and the second passivation layer is arranged on the first passivation layer and the N-type doped conductive region; the first passivation layer is an aluminum oxide layer with a thickness of 11nm, and the second passivation layer is a silicon oxynitride layer with a thickness of 15μm.

[0059] The isolation region is arranged between the N-type doped conductive region and the P-type doped conductive region. A third passivation layer is arranged on the isolation region, and a surface of the third passivation layer is flush with a surface of the second passivation layer.

[0060] Example 2

[0061] This embodiment provides a back-contact solar cell, comprising:

[0062] The N-type silicon substrate has a front side and a back side that are opposite to each other.

[0063] The N-type doped conductive region and the P-type doped conductive region are alternately arranged on the back side of the N-type silicon substrate.

[0064] A first passivation layer and a second passivation layer, the first passivation layer is arranged on the P-type doped conductive region, and the second passivation layer is arranged on the first passivation layer and the N-type doped conductive region; the first passivation layer is an aluminum oxide layer with a thickness of 11nm, and the second passivation layer is a silicon oxynitride layer with a thickness of 15μm.

[0065] The isolation region is arranged between the N-type doped conductive region and the P-type doped conductive region. A third passivation layer is arranged on the isolation region, and a surface of the third passivation layer is flush with a surface of the second passivation layer.

[0066] Example 3

[0067] This embodiment provides a back-contact solar cell, comprising:

[0068] The N-type silicon substrate has a front side and a back side that are opposite to each other.

[0069] The N-type doped conductive region and the P-type doped conductive region are alternately arranged on the back side of the N-type silicon substrate.

[0070] A first passivation layer and a second passivation layer, the first passivation layer is arranged on the P-type doped conductive region, and the second passivation layer is arranged on the first passivation layer and the N-type doped conductive region; the first passivation layer is a titanium oxide layer with a thickness of 8nm, and the second passivation layer is a silicon oxynitride layer with a thickness of 30μm.

[0071] The isolation region is arranged between the N-type doped conductive region and the P-type doped conductive region. A third passivation layer is arranged on the isolation region. The third passivation layer is a silicon oxynitride layer with a thickness of 30 μm.

[0072] Example 4

[0073] This embodiment provides a back-contact solar cell, comprising:

[0074] The N-type silicon substrate has a front side and a back side that are opposite to each other.

[0075] The N-type doped conductive region and the P-type doped conductive region are alternately arranged on the back side of the N-type silicon substrate.

[0076] A first passivation layer and a second passivation layer, the first passivation layer is arranged on the P-type doped conductive region, and the second passivation layer is arranged on the first passivation layer and the N-type doped conductive region; the first passivation layer is a titanium oxide layer with a thickness of 8nm, and the second passivation layer is a silicon oxynitride layer with a thickness of 30μm.

[0077] An isolation region is provided between the N-type doped conductive region and the P-type doped conductive region. A third passivation layer is provided on the isolation region. The third passivation layer includes a first passivation layer and a second passivation layer. The first passivation layer is a titanium oxide layer with a thickness of 8 nm. The second passivation layer is a silicon oxynitride layer with a thickness of 30 μm.

[0078] Performance tests were performed on the back-contact cells of Examples 1 to 4, and the energy conversion efficiencies of the back-contact cells obtained were 9.12% to 10.69%.

[0079] In the above embodiments, the descriptions of each embodiment have their own emphasis. For parts that are not described in detail in a certain embodiment, please refer to the relevant descriptions of other embodiments. In the description of this specification, the descriptions with reference to the terms "some embodiments", "illustrative embodiments", "examples", "specific examples", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiments or examples are included in at least one embodiment or example of the present application. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner.

[0080] The above is a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the principles of the present invention. These improvements and modifications are also considered to be within the scope of protection of the present invention.

Claims

1. A back contact solar cell, characterized in that: The semiconductor substrate comprises a front surface and a back surface which are opposite to each other; A P-type doped conductive region and an N-type doped conductive region, wherein the P-type doped conductive region and the N-type doped conductive region are alternately arranged on the back surface of the semiconductor substrate; a first passivation layer and a second passivation layer, wherein the first passivation layer is provided on the P-type doped conductive region, and the second passivation layer is provided on the first passivation layer and the N-type doped conductive region; The first passivation layer is a hole selection layer.

2. The back contact solar cell according to claim 1, wherein: The first passivation layer is an aluminum oxide layer and / or a titanium oxide layer.

3. The back contact solar cell according to claim 1, wherein: The thickness of the first passivation layer is smaller than the thickness of the second passivation layer.

4. The back contact solar cell according to claim 1, wherein: The thickness of the first passivation layer is 1 nm to 10 nm.

5. The back contact solar cell according to claim 1, wherein: The thickness of the second passivation layer is 20 μm to 80 μm.

6. The back contact solar cell according to claim 1, wherein: The second passivation layer is one or more of an intrinsic amorphous silicon layer, an intrinsic polycrystalline silicon layer, an intrinsic nanocrystalline silicon layer, an intrinsic mixed crystal silicon layer, a silicon oxide layer, a silicon oxynitride layer, a silicon nitride layer, and a silicon carbon nitride oxide layer.

7. The back contact solar cell according to claim 1, wherein: The back-contact cell further includes an isolation region located between the P-type doped conductive region and the N-type doped conductive region.

8. The back contact solar cell according to claim 7, wherein: A third passivation layer is provided on the isolation region.

9. The back contact solar cell according to claim 8, wherein: The third passivation layer includes the first passivation layer and the second passivation layer.

10. The back contact solar cell according to claim 8, wherein: A surface of the third passivation layer is flush with a surface of the second passivation layer.

11. The back contact solar cell according to claim 8, wherein: The surface of the third passivation layer is concave toward the semiconductor substrate relative to the surface of the second passivation layer.

12. The back contact solar cell according to claim 1, wherein: The back-contact battery further includes a positive electrode and a negative electrode, wherein the positive electrode is connected to the P-type doped conductive region, and the negative electrode is connected to the N-type doped conductive region.

13. The back contact solar cell according to claim 1, wherein: The P-type doped conductive region includes a first tunneling layer and a P-type doped layer, and the N-type doped conductive region includes a second tunneling layer and an N-type doped layer.

14. The back contact solar cell according to claim 13, wherein: The first tunneling layer and the second tunneling layer are one or more of a silicon oxide layer, an aluminum oxide layer, a titanium oxide layer, a zinc oxide layer, an intrinsic amorphous silicon layer, an intrinsic polycrystalline silicon layer, an intrinsic nanocrystalline silicon layer, and an intrinsic mixed crystal silicon layer; the P-type doped layer and the N-type doped layer are one or more of a doped polycrystalline silicon layer, a doped amorphous silicon layer, and a doped microcrystalline silicon layer.

15. A battery string, characterized in that: The invention comprises a back contact cell according to any one of claims 1 to 14.

16. A battery assembly, characterized in that: Comprising the battery string as claimed in claim 15.

17. A photovoltaic system, characterized in that: Comprising the battery assembly as claimed in claim 16.

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