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; a first doped conductive region and a second doped conductive region, the first doped conductive region and the second doped conductive region are alternately arranged on the back surface of the semiconductor substrate, and the doping types of the first doped conductive region and the second doped conductive region are opposite; a first carrier selection layer and a second carrier selection layer, wherein the first carrier selection layer and the second carrier selection layer are respectively arranged on the first doped conductive region and the second doped conductive region; the first carrier selection layer and the second carrier selection layer respectively have hole selectivity and electron selectivity; and the passivation layer is arranged on the first carrier selection layer and the second carrier selection layer. According to the utility model, the photoelectric conversion efficiency of the back contact cell can be 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, which improves the photoelectric conversion efficiency of the cell by respectively arranging carrier selection layers with different selectivities on the doping layers of different doping types of the back-contact 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 first doped conductive region and a second doped conductive region, wherein the first doped conductive region and the second doped conductive region are alternately arranged on the back side of the semiconductor substrate, and the first doped conductive region and the second doped conductive region have opposite doping types;

[0006] a first carrier selection layer and a second carrier selection layer, wherein the first carrier selection layer and the second carrier selection layer are respectively disposed on the first doped conductive region and the second doped conductive region; the first carrier selection layer and the second carrier selection layer have hole selectivity and electron selectivity, respectively;

[0007] A passivation layer is provided on the first carrier selection layer and the second carrier selection layer.

[0008] As an improvement of the above scheme, when the first doped conductive region is an N-type doped conductive region, the first carrier selection layer has electron selectivity, and the first carrier selection layer is one or more of a titanium oxide layer, a cesium oxide layer, a cesium iodide layer, a cesium bromide layer, a cesium fluoride layer, a rubidium fluoride layer, a europium fluoride layer, and a yttrium fluoride layer.

[0009] As an improvement of the above scheme, the second doped conductive region is a P-type doped conductive region, the second carrier selection layer has hole selectivity, and the second carrier selection layer is one or more of a molybdenum oxide layer, a tungsten oxide layer, a tin oxide layer, and a vanadium oxide layer.

[0010] As an improvement of the above solution, the thickness of the first carrier selection layer is D1, the thickness of the second carrier selection layer is D2, and D1≤D2.

[0011] As an improvement of the above solution, D1 and D2 satisfy the following relationship: D2 = (2.3-2.8) D1.

[0012] As an improvement of the above solution, the D1 is 1 nm to 5 nm.

[0013] As an improvement of the above solution, the D2 is 5nm to 10nm.

[0014] As an improvement of the above solution, the back contact cell further includes an isolation region, and the isolation region is located between the first doped conductive region and the second doped conductive region.

[0015] As an improvement to the above solution, a passivation layer is provided on the isolation region.

[0016] As an improvement of the above solution, the 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.

[0017] As an improvement of the above solution, the back contact cell further includes a first electrode and a second electrode, and the first electrode and the second electrode are respectively arranged on the first carrier selection layer and the second carrier selection layer.

[0018] As an improvement of the above solution, the first doped conductive region includes a first tunneling layer and a first polarity doped layer, and the second doped conductive region includes a second tunneling layer and a second polarity doped layer, and the doping types of the first polarity doped layer and the second polarity doped layer are opposite.

[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 first polarity doped layer and the second polarity 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 utility model has the following beneficial effects: by respectively arranging the first carrier selection layer and the second carrier selection layer on the first doped conductive region and the second doped conductive region of the back contact solar cell, the first carrier selection layer and the second carrier selection layer respectively have hole selectivity and electron selectivity, which can achieve low minority carrier recombination and effective majority carrier transport, and form high resistance to electrons and low resistance to holes or high resistance to holes and low resistance to electrons on the surfaces of the first doped conductive region and the second doped conductive region, respectively, thereby allowing holes to pass through easily while blocking electrons, or allowing electrons to pass through easily while blocking holes, thereby improving the efficiency of the solar cell. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 This is a schematic structural diagram of the back contact battery cell provided by the present invention;

[0025] Figure 2 The utility model provides a schematic diagram of a physical model of selective contact of carriers in a back contact cell. DETAILED DESCRIPTION

[0026] 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.

[0027] 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.

[0028] 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.

[0029] like Figure 1 As 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 side 11 and a back side 12 that are arranged opposite to each other.

[0030] The first doped conductive regions 13 and the second doped conductive regions 14 are alternately arranged on the back surface 12 of the semiconductor substrate 1. The first doped conductive regions 13 and the second doped conductive regions 14 have opposite doping types. It is understood that the first doped conductive regions 13 can have the opposite or the same doping type as the semiconductor substrate 1.

[0031] A first carrier selection layer 15 and a second carrier selection layer 16 are provided. The first carrier selection layer 15 is provided on the first doped conductive region 13, and the second carrier selection layer 16 is provided on the second doped conductive region 14. The first carrier selection layer 15 and the second carrier selection layer 16 have hole selectivity and electron selectivity, respectively. In existing back-contact cells, an aluminum oxide layer is typically provided on both the first doped conductive region 13 and the second 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 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 battery. In the present application, the first carrier selection layer 15 and the second carrier selection layer 16 have hole selectivity and electron selectivity, respectively. The carrier selection layer with hole selectivity can transport holes and block electrons, and the carrier selection layer with electron selectivity can transport electrons and block holes, thereby blocking holes or electrons accordingly for different types of doped conductive regions.

[0032] It is understood that when the semiconductor substrate is an N-type silicon substrate, the first doped conductive region may be an N-type doped conductive region, the second doped conductive region may be a P-type doped conductive region, the N-type doped conductive region is provided with a first carrier selection layer with electron selectivity, allowing electrons to pass easily while blocking holes, and the P-type doped conductive region is provided with a second carrier selection layer with hole selectivity, allowing holes to pass easily while blocking electrons. Alternatively, when the semiconductor substrate is an N-type silicon substrate, the first doped conductive region may be a P-type doped conductive region, the second doped conductive region may be an N-type doped conductive region, the P-type doped conductive region is provided with a first carrier selection layer with hole selectivity, allowing holes to pass easily while blocking electrons, and the P-type doped conductive region is provided with a second carrier selection layer with electron selectivity, allowing electrons to pass easily while blocking holes.

[0033] A passivation layer 17 is provided on the first carrier selection layer 15 and the second carrier selection layer 16. Specifically, the passivation layer 17 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 carbonitride oxide layer, and is not specifically limited here. The thickness of the passivation layer 17 is 40 μm to 80 μm, and exemplarily is 45 μm, 50 μm, 55 μm, 60 μm, 65 μm, or 70 μm, but is not limited thereto.

[0034] like Figure 2 As shown, where E Fnand E Fp are the quasi-Fermi levels of electrons and holes, respectively, and the quasi-Fermi level splitting (E Fn -E Fp ), which determines the implicit open circuit voltage (iV oc ). Quasi-Fermi level gradient and is the electron current density J n and hole current density J p The thermodynamic driving force of and It is expressed as follows, where n and p are the electron concentration and hole concentration, respectively, and μ n and μ p are the electron mobility and hole mobility, σ n and σ p are the electron conductivity and hole conductivity respectively. When the electron current density J n and hole current density J p When the holes reach the carrier selection layer with hole selectivity, the hole conductivity σ p It is high for holes or low hole resistance, the hole current density J p Easily pass through, opposite electronic conductivity σ n It is low for electrons or high electron resistance, and the electron current density J n is blocked. Accordingly, when the electron current density J n and hole current density J p When the electrons reach the carrier selection layer with electron selectivity at the same time, the electron current density J n Easily pass, hole current density J p Therefore, the carrier-selective contact is selective for only one conductivity type of carrier, allowing only one conductivity type of carrier to pass through. This means that the conductivity at the contact is high for one conductivity type of carrier and low for the other, or in other words, there is conductivity asymmetry. In other words, the carrier-selective layer on the solar cell is not only responsible for collecting carriers of different conductivity types, but also acts as a semi-permeable membrane. One carrier-selective layer transports electrons and blocks holes, while the other carrier-selective layer transports holes and blocks electrons.

[0035] Specifically, when the first carrier selection layer 15 with electron selectivity contacts the doped conductive material on the first doped conductive region, the fixed charge is positive, and the conduction band and valence band of silicon at the interface bend downward, which is conducive to the transmission of electrons to the interface and blocks the transmission of holes; when the second carrier selection layer 16 with hole selectivity contacts the doped conductive material on the second doped conductive region, the fixed charge is negative, and the conduction band and valence band of silicon at the interface bend upward, which is conducive to the transmission of holes to the interface and blocks the transmission of electrons.

[0036] The electron-selective first carrier selection layer 15 may be one or more of a titanium oxide layer, a cesium oxide layer, a cesium iodide layer, a cesium bromide layer, a cesium fluoride layer, a rubidium fluoride layer, a europium fluoride layer, or a yttrium fluoride layer, without specific limitation. The mobility of the first carrier selection layer 15 matches the energy level of silicon, thereby achieving good electron transfer efficiency.

[0037] The hole-selective second carrier-selective layer 16 can be one or more of a molybdenum oxide layer, a tungsten oxide layer, a tin oxide layer, and a vanadium oxide layer, without specific limitation. The second carrier-selective layer 16 has excellent hole-transport properties. The first and second carrier-selective layers 15, 16 can be deposited by atomic layer deposition, chemical vapor deposition, or other coating methods.

[0038] The carrier selection layer is used to field-passivate the backlight side of the semiconductor substrate, forming an electric field at the interface between the two. This electric field reduces the concentration of free electrons or holes at the interface, thereby reducing the carrier recombination rate. Based on this, the carrier selection layer can be selected based on the doping type of the semiconductor substrate in the actual application scenario. This ensures that the carrier selection layer has a high passivation effect and can also improve the applicability of the back-contact solar cell in different application scenarios.

[0039] In a preferred embodiment, the thickness D1 of the first carrier selection layer 15 is less than or equal to the thickness D2 of the second carrier selection layer 16. Preferably, the ratio of the thickness D1 of the first carrier selection layer 15 to the thickness D2 of the second carrier selection layer 16 is 2.3 to 2.8. Controlling the ratio of the thickness D1 of the first carrier selection layer 15 to the thickness D2 of the second carrier selection layer 16 within a specific range can further improve the photoelectric conversion efficiency of the back-contact solar cell.

[0040] Specifically, the thickness D1 of the first carrier selection layer 15 is 1 nm to 5 nm, exemplified by, but not limited to, 2 nm, 2.5 nm, 3 nm, 3.5 nm, 4 nm, or 4.5 nm. If the thickness D1 of the first carrier selection layer 15 is less than 1 nm, it is difficult to form a good electron-selective contact. If the thickness D1 of the first carrier selection layer 15 is greater than 5 nm, it is not conducive to the high-speed migration of electrons with low mobility.

[0041] The thickness D2 of the second carrier selection layer 16 is 5 nm to 10 nm, exemplarily 6 nm, 7 nm, 8 nm, 8.5 nm, 9 nm, or 9.5 nm, but is not limited thereto. If the thickness D2 of the second carrier selection layer 16 is less than 5 nm, it is difficult to form a good hole-selective contact. If the thickness D2 of the second carrier selection layer 16 is greater than 10 nm, the fill factor is reduced, leading to interfacial recombination and a decrease in open-circuit voltage.

[0042] Optionally, the width H1 of the first carrier selection layer 15 is greater than or equal to the width H2 of the second carrier selection layer 16. Preferably, the width H1 of the first carrier selection layer 15 is greater than the width H2 of the second carrier selection layer 16, which is beneficial to the balance of hole transmission and electron transmission. If the width H1 of the first carrier selection layer 15 is less than the width H2 of the second carrier selection layer 16, it is easy to cause low hole collection efficiency and cause interfacial recombination of holes and electrons. Preferably, the ratio of the width H1 of the first carrier selection layer 15 to the width H2 of the second carrier selection layer 16 is 1.2 to 1.7. Controlling the ratio of the width H1 of the first carrier selection layer 15 to the width H2 of the second carrier selection layer 16 within a specific range can further improve the photoelectric conversion efficiency of the back contact cell. Specifically, the width H1 of the first carrier selection layer 15 is 2 mm to 15 mm, and is exemplarily 3 mm, 5 mm, 8 mm, 10 mm, 12 mm, or 14 mm, but is not limited thereto. The width H2 of the second carrier selection layer 16 is 1.5 mm to 10 mm, and is exemplarily 2 mm, 4 mm, 6 mm, 7 mm, 8 mm, or 9 mm, but is not limited thereto.

[0043] In order to avoid short circuits, the first doped conductive region 13 and the second 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 18, which is located between the first doped conductive region 13 and the second doped conductive region 14. The spaced first doped conductive region 13 and the second doped conductive region 14 can prevent the first doped conductive region 13 and the second doped conductive region 14 from contacting each other and causing a short circuit. The formation of the isolation region 18 can be assisted by isolation using laser isolation, chemical isolation, graphic masking, etc.

[0044] Optionally, the passivation layer 17 can be formed only on the first doped conductive region 13 and the second doped conductive region 14. Alternatively, the passivation layer 17 can also cover the first doped conductive region 13, the second doped conductive region 14, and the isolation region 18. 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 17, the passivation layer 17 can be obtained without patterning at least a portion of the passivation material. This can simplify the manufacturing process of the back contact cell, reduce the manufacturing difficulty of the back contact cell, and simultaneously reduce the manufacturing cost of the back contact cell. Specifically, the passivation layer 17 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, and is not specifically limited here. The thickness of the passivation layer 17 is 40 μm to 80 μm, and is exemplarily 45 μm, 50 μm, 55 μm, 60 μm, 65 μm or 70 μm, but is not limited thereto.

[0045] The back contact cell further includes a first electrode 21 and a second electrode 22 , which are disposed on the first carrier selection layer 15 and the second carrier selection layer 16 , respectively.

[0046] The materials of the first electrode 21 and the second electrode 22 can be one or more of gold, silver, aluminum, and graphene. The first electrode 21 and the second electrode 22 are made of materials with good electrical conductivity, which can better conduct current from the back-contact cell. Specifically, when exposed to light, the semiconductor substrate 1 acts as a light absorption layer, generating electron-hole pairs. The first carrier selection layer 15 has an electron-selective effect, and electrons are conducted away by the corresponding first electrode 21. The second carrier selection layer 16 has a hole-selective effect, and holes are conducted away by the corresponding second electrode 22. The electrons and holes are separated by the solar cell, generating a potential difference between the first electrode 21 and the second electrode 22, that is, generating a voltage, thereby converting light energy into electrical energy.

[0047] In a preferred embodiment, the first doped conductive region 13 includes a first tunneling layer 131 and a first polarity doped layer 132, and the second doped conductive region 14 includes a second tunneling layer 141 and a second polarity doped layer 142. The doping types of the first polarity doped layer 132 and the second polarity doped layer 142 are opposite. The first tunneling layer 131 and the second tunneling layer 141 mainly play the role of interface passivation and the role of transporting carriers, so that carriers are collected through the tunneling layer 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.

[0048] 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 first polarity doped layer 132 and the second polarity 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.

[0049] Correspondingly, an embodiment of the present invention also provides a solar cell string, including the above-mentioned back contact cells, each solar cell string includes a plurality of back contact cells connected in series, and the plurality of back contact cells can be partially overlapped to form a solar cell 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 overlapped areas, and the back contact cells are simply overlapped together. Optionally, the back contact cells are electrically connected in the form of a whole piece or multiple pieces. The overlapping areas of adjacent back contact cells in the solar cell string are provided with series welding strips to fixedly connect the adjacent back contact cells, and the series welding strips connect the adjacent back contact cells in series. Different solar cell strings are obtained by series and / or parallel connection.

[0050] Accordingly, embodiments of the present invention further provide a battery assembly comprising the aforementioned solar cell string. The battery assembly may further comprise a metal frame, a backsheet, photovoltaic glass, and an adhesive film. The adhesive film may be interposed between the front and back surfaces of the solar cell string, the photovoltaic glass, the backsheet, and the like. The adhesive film may be a transparent colloid with excellent light transmittance and aging resistance, such as EVA film or POE film. The adhesive film may be selected based on actual conditions and is not specifically limited herein.

[0051] Photovoltaic glass covers the front of the solar cell string. Ultra-clear glass, for example, boasts high light transmittance and transparency, along with superior physical, mechanical, and optical properties. For example, ultra-clear glass can achieve a light transmittance exceeding 92%, protecting the solar cell string while minimizing its efficiency. Furthermore, an adhesive film bonds the photovoltaic glass to the solar cell string, providing a sealed, insulated seal against water and moisture.

[0052] The backsheet can be attached to the back of the solar cell string, providing protection and support for the string. It features reliable insulation, water resistance, and aging resistance. It can be made of tempered glass, organic glass, aluminum alloy TPT composite film, and other materials, depending on the specific situation and not specifically limited here. The backsheet, solar cell string, film, and photovoltaic glass are assembled on a metal frame, which serves as the primary external support structure for the entire battery assembly, providing stable support and installation.

[0053] 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.

[0054] The present invention will be further described below with specific embodiments:

[0055] Example 1

[0056] This embodiment provides a back-contact solar cell, comprising:

[0057] The N-type silicon substrate has a front side and a back side that are opposite to each other.

[0058] 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.

[0059] A first carrier selection layer with electron selectivity and a second carrier selection layer with hole selectivity, the first carrier selection layer is arranged on the N-type doped conductive region, and the second carrier selection layer is arranged on the P-type doped conductive region; the first carrier selection layer is a titanium oxide layer with a thickness of 8nm, and the second carrier selection layer is a vanadium oxide layer with a thickness of 8nm.

[0060] The isolation region is arranged between the N-type doped conductive region and the P-type doped conductive region.

[0061] The passivation layer is arranged on the first carrier selection layer, the second carrier selection layer and the isolation region.

[0062] Example 2

[0063] This embodiment provides a back-contact solar cell, comprising:

[0064] The N-type silicon substrate has a front side and a back side that are opposite to each other.

[0065] 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.

[0066] A first carrier selection layer with electron selectivity and a second carrier selection layer with hole selectivity, the first carrier selection layer is arranged on the N-type doped conductive region, and the second carrier selection layer is arranged on the P-type doped conductive region; the first carrier selection layer is a cesium oxide layer with a thickness of 1nm, and the second carrier selection layer is a tungsten oxide layer with a thickness of 10nm.

[0067] The isolation region is arranged between the N-type doped conductive region and the P-type doped conductive region.

[0068] The passivation layer is arranged on the first carrier selection layer, the second carrier selection layer and the isolation region.

[0069] Example 3

[0070] This embodiment provides a back-contact solar cell, comprising:

[0071] The N-type silicon substrate has a front side and a back side that are opposite to each other.

[0072] 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.

[0073] A first carrier selection layer with electron selectivity and a second carrier selection layer with hole selectivity, the first carrier selection layer is arranged on the N-type doped conductive region, and the second carrier selection layer is arranged on the P-type doped conductive region; the first carrier selection layer is a rubidium fluoride layer with a thickness of 3nm, and the second carrier selection layer is a molybdenum oxide layer with a thickness of 7.5nm.

[0074] The isolation region is arranged between the N-type doped conductive region and the P-type doped conductive region.

[0075] The passivation layer is arranged on the first carrier selection layer, the second carrier selection layer and the isolation region.

[0076] Performance tests were performed on the back-contact cells of Examples 1 to 3, and the energy conversion efficiencies of the back-contact cells obtained were 9.25% to 11.82%.

[0077] 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.

[0078] 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 first doped conductive region and a second doped conductive region, wherein the first doped conductive region and the second doped conductive region are alternately arranged on the back side of the semiconductor substrate, and the first doped conductive region and the second doped conductive region have opposite doping types; a first carrier selection layer and a second carrier selection layer, wherein the first carrier selection layer and the second carrier selection layer are respectively disposed on the first doped conductive region and the second doped conductive region; The first carrier selection layer and the second carrier selection layer have hole selectivity and electron selectivity respectively; A passivation layer is provided on the first carrier selection layer and the second carrier selection layer.

2. The back contact solar cell according to claim 1, wherein: When the first doped conductive region is an N-type doped conductive region, the first carrier selection layer has electron selectivity, and the first carrier selection layer is one or more of a titanium oxide layer, a cesium oxide layer, a cesium iodide layer, a cesium bromide layer, a cesium fluoride layer, a rubidium fluoride layer, a europium fluoride layer, and a yttrium fluoride layer.

3. The back contact solar cell according to claim 2, wherein: The second doped conductive region is a P-type doped conductive region, the second carrier selection layer has hole selectivity, and the second carrier selection layer is one or more of a molybdenum oxide layer, a tungsten oxide layer, a tin oxide layer, and a vanadium oxide layer.

4. The back contact solar cell according to claim 3, wherein: The thickness of the first carrier selection layer is D1, the thickness of the second carrier selection layer is D2, and D1≤D2.

5. The back contact solar cell according to claim 4, wherein: The D1 and D2 satisfy the following relationship: D2 = (2.3-2.8) D1.

6. The back contact solar cell according to claim 4, wherein: The D1 is 1 nm to 5 nm.

7. The back contact solar cell according to claim 4, wherein: The D2 is 5nm to 10nm.

8. The back contact solar cell according to claim 1, wherein: The back-contact cell further includes an isolation region located between the first doped conductive region and the second doped conductive region.

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

10. The back contact solar cell according to claim 1, wherein: The 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.

11. The back contact solar cell according to claim 1, wherein: The back contact cell further includes a first electrode and a second electrode, wherein the first electrode and the second electrode are respectively disposed on the first carrier selection layer and the second carrier selection layer.

12. The back contact solar cell according to claim 1, wherein: The first doped conductive region includes a first tunneling layer and a first polarity doped layer, and the second doped conductive region includes a second tunneling layer and a second polarity doped layer. The first polarity doped layer and the second polarity doped layer have opposite doping types.

13. The back contact solar cell according to claim 12, 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 first polarity doped layer and the second polarity doped layer are one or more of a doped polycrystalline silicon layer, a doped amorphous silicon layer, and a doped microcrystalline silicon layer.

14. A battery string, characterized in that: The invention comprises a back contact cell according to any one of claims 1 to 13.

15. A battery assembly, characterized in that: Comprising the battery string as claimed in claim 14.

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

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